JP2016012050A - Fixation device and image forming apparatus comprising the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixation device capable of stopping a heating operation of a heating part when a fixation belt is damaged.SOLUTION: A fixation device 1 includes a fixation belt 3, a belt guide member 6, a heating part 7, a first temperature detection element TH1, a second temperature detection element TH2, and a heating stop part. The belt guide member 6 is disposed in an area counter to the heating part 7 and supports the inner peripheral surface of the fixation belt 3. The heating part 7 heats the fixation belt 3. The first temperature detection element TH1 detects a temperature of the fixation belt 3. The second temperature detection element TH2 contacts with an inner surface of the belt guide member 6 and detects a temperature of the belt guide member 6. The heating stop part stops a heating operation of the heating part 7 on the basis of the outputs of the first temperature detection element TH1 and/or the second temperature detection element TH2.

Description

  The present invention relates to a fixing device and an image forming apparatus including the same.

  As a fixing device for fixing a toner image formed on a recording medium such as paper or film, a fixing device employing a heat fixing method is generally used. The heat fixing method is a method for fixing a toner image by melting the toner by heat. Among the heat fixing methods, the heat roller method is most widely used because of its high thermal efficiency and high safety.

  A fixing device adopting a heat roller system includes a fixing roller. The fixing roller is generally made of a hollow cored bar. Generally, aluminum is used as the material for the hollow metal core. The fixing device adopting a heat roller system most commonly includes a halogen lamp as a heat source. A fixing device including a halogen lamp causes the temperature of the fixing roller to be a predetermined temperature by causing the halogen lamp to generate heat.

  However, the hot roller system has a problem that the temperature increase rate (temperature rise) of the fixing roller at the start of heating is slow. This leads to an increase in warm-up time. Therefore, in order to shorten the warm-up time, the fixing roller is made thinner. Thereby, the heat capacity of the fixing roller can be reduced, and the temperature increase rate of the fixing roller can be improved.

  However, the thinning of the fixing roller increases the amount of deflection at the central portion in the longitudinal direction of the fixing roller. When the amount of deflection increases, the nip pressure is weakened, which may cause a fixing failure. Therefore, the fixing roller needs to be thick. For this reason, the heat roller method has a limit in shortening the warm-up time.

  In order to solve such a problem, a fixing device using a fixing belt has been developed. A fixing device using a fixing belt is disclosed in Patent Document 1, for example. Specifically, the fixing device disclosed in Patent Document 1 includes an endless fixing belt, a sliding member fixedly disposed inside the fixing belt, and a pressure roller. The pressure roller is pressed against the sliding member via the fixing belt. As a result, the pressure roller and the sliding member form a nip portion via the fixing belt. The fixing device disclosed in Patent Document 1 directly heats the fixing belt by an induction heating method.

  In this way, a low heat capacity can be realized by employing a fixing belt as the heating member. Furthermore, high heating efficiency is realizable by employ | adopting an induction heating system. Accordingly, the warm-up time can be shortened. The pressure roller forms a nip portion together with a sliding member fixedly arranged inside the fixing belt. Therefore, the nip pressure is not weakened.

  Further, the fixing device disclosed in Patent Document 1 includes a belt guide member in order to stabilize the traveling track of the fixing belt. The belt guide member is fixed inside the fixing belt and applies a predetermined tension to the fixing belt. The belt guide member is disposed to face the induction heating coil. As a result, the belt guide member generates heat by a magnetic field (magnetic flux), and supplementarily heats the fixing belt.

  Furthermore, in the fixing device disclosed in Patent Document 1, a notch is formed in the belt guide member, and a temperature sensor is disposed in the notch. According to such a configuration, in the region where the temperature is highest in the circumferential direction of the fixing belt, the temperature of the fixing belt can be detected by bringing the temperature sensor into contact with the inner peripheral surface of the fixing belt.

JP 2009-223044 A

  However, the fixing device disclosed in Patent Document 1 cannot stop the heating operation by the heating unit when a defect occurs in the fixing belt, and the image forming apparatus falls into a dangerous state such as a fire. there is a possibility.

  For example, when the fixing belt is lost in a region other than the portion where the temperature is detected by the temperature sensor, the temperature sensor normally detects the temperature. Therefore, electric power is supplied to the induction heating coil in the same manner as normal. However, in the region where the fixing belt is missing, the heat of the belt guide member is not taken away by the fixing belt. For this reason, the belt guide member may cause abnormal heat generation. As a result, the image forming apparatus may fall into a dangerous state such as a fire.

  In addition, when a defect in the fixing belt occurs at a location where the temperature is detected by the temperature sensor, the temperature detected by the temperature sensor decreases. Therefore, electric power is supplied to the induction heating coil in order to increase the temperature detected by the temperature sensor, but the electric power is continuously supplied because the temperature detected by the temperature sensor does not increase. On the other hand, in the area where the fixing belt is missing, the heat of the belt guide member is not taken away by the fixing belt. For this reason, the belt guide member may cause abnormal heat generation. As a result, the image forming apparatus may fall into a dangerous state such as a fire.

  In view of the above problems, the present invention provides a highly secure fixing device capable of stopping a heating operation by a heating unit when a defect occurs in a fixing belt, and an image forming apparatus including the fixing device. Objective.

  The fixing device according to the present invention includes a fixing belt, a pressure member, a heating unit, a belt guide member, a first temperature detection element, a power control unit, at least one second temperature detection element, and a heating. And a stop unit. The pressure member contacts the outer peripheral surface of the fixing belt and rotates the fixing belt. The heating unit heats the fixing belt. The belt guide member is disposed in a region facing the heating unit and supports an inner peripheral surface of the fixing belt. The first temperature detecting element is in contact with the fixing belt and detects the temperature of the fixing belt. The power control unit controls power supplied to the heating unit based on a temperature detected by the first temperature detection element. The at least one second temperature detection element is in contact with the inner surface of the belt guide member and detects the temperature of the belt guide member. The heating stop unit stops a heating operation by the heating unit based on an output of the first temperature detection element and / or the at least one second temperature detection element.

  An image forming apparatus according to the present invention includes the above-described fixing device, an image forming unit, and a transport unit. The image forming unit forms a toner image on a recording medium. The transport unit transports the recording medium from the image forming unit to the fixing device. The fixing device fixes the toner image on the recording medium.

  According to the present invention, when a defect occurs in the fixing belt, the heating operation by the heating unit can be stopped. Accordingly, the safety of the fixing device and the image forming apparatus including the fixing device can be improved.

1 is a cross-sectional view illustrating a fixing device according to an embodiment of the present invention. FIG. 3 is a plan view showing the inside of the fixing belt according to the embodiment of the present invention. 1 is a plan view showing a fixing device according to an embodiment of the present invention. FIG. 2 is an enlarged plan view showing a part of a fixing belt according to an embodiment of the present invention. It is a top view which shows the pulse plate which concerns on embodiment of this invention. It is a figure which shows the rotation detection sensor which concerns on embodiment of this invention. FIG. 2 is a block diagram illustrating a part of the configuration of the fixing device according to the embodiment of the present invention. FIG. 3 is a plan view illustrating a first example in a state where a fixing belt according to an embodiment of the present invention is missing. FIG. 6 is a plan view illustrating a second example in a state where the fixing belt according to the embodiment of the present invention is missing. FIG. 10 is a plan view illustrating a third example in a state where the fixing belt according to the embodiment of the present invention is missing. 1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 6 is a diagram illustrating a part of a configuration of another example 1 of the fixing device according to the embodiment of the present invention. FIG. 8 is a diagram illustrating a part of the configuration of another example 2 of the fixing device according to the embodiment of the present invention. FIG. 10 is a diagram illustrating a part of a configuration of another example 3 of the fixing device according to the embodiment of the present invention.

  Hereinafter, embodiments of a fixing device and an image forming apparatus of the present invention will be described with reference to the drawings. However, in the drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated. Moreover, the material, dimension, etc. of each component shown by the following embodiment are examples, and are not specifically limited.

  FIG. 1 is a cross-sectional view showing a fixing device according to an embodiment of the present invention. The fixing device 1 according to the present embodiment heats and pressurizes an unfixed toner image on a sheet S (an example of a recording medium) to melt and fix the toner image on the sheet S.

  As shown in FIG. 1, the fixing device 1 includes a pressure roller 2 that is an example of a pressure member, an endless fixing belt 3, a pressure pad 4 that is an example of a sliding member, a support member 5, The belt guide member 6 includes an induction heating unit 7 that is an example of a heating unit, and a first thermistor TH1 that is an example of a first temperature detection element.

  The pressure roller 2 includes a metal core 21, an elastic layer 22 formed on the metal core 21, and a release layer 23 that covers the surface of the elastic layer 22. For example, the pressure roller 2 has an elastic layer 22 made of silicone rubber having a thickness of 2 mm to 5 mm on a stainless steel core bar 21, and PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) is formed on the elastic layer 22. ) And the like. When the pressure roller 2 has the release layer 23, the releasability between the pressure roller 2 and the paper S can be improved. The core metal 21 of the pressure roller 21 may be a cylindrical core metal.

  The pressure roller 2 is pressed against the pressing pad 4 via the fixing belt 3. As a result, the pressure roller 2 contacts the outer peripheral surface of the fixing belt 3, and the pressing pad 4 contacts the inner peripheral surface of the fixing belt 3.

  The fixing belt 3 has at least an induction heating layer containing a magnetic metal material. The induction heating layer of the fixing belt 3 generates heat by a magnetic field generated by the induction heating unit 7 (magnetic flux generated from the induction heating unit 7). For example, the fixing belt 3 is made of an induction heating layer made of electroformed nickel having a thickness of 30 μm to 50 μm, an elastic layer made of silicone rubber having a thickness of 50 μm to 500 μm, and a fluororesin such as PFA, in order from the inner peripheral side. The release layer is laminated. Since the fixing belt 3 has a release layer, the releasability between the fixing belt 3 and the toner image can be improved.

  The pressing pad 4 is fixed to the support member 5 inside the fixing belt 3 and faces the pressure roller 2 through the fixing belt 3. The surface of the pressing pad 4 on the pressure roller 2 side (the surface that contacts the inner peripheral surface of the fixing belt 3) is curved toward the pressure roller 2 at a downstream portion in the transport direction D of the paper S. . Due to this curved shape, the releasability between the sheet S and the fixing belt 3 is improved. Resin can be used for the material of the pressing pad 4. For example, as the material of the pressing pad 4, polyphenylene sulfide resin (PPS resin), liquid crystal polymer (LCP resin), or polyethylene terephthalate resin (PET resin) can be used.

  The support member 5 is fixedly disposed inside the fixing belt 3. The support member 5 is preferably a non-magnetic material and is made of, for example, SUS304 having a high Young's modulus. By selecting a non-magnetic material as the material of the support member 5, the magnetic flux generated from the induction heating unit 7 can be stably passed through the fixing belt 3.

  The belt guide member 6 is fixed to the support member 5 inside the fixing belt 3 and faces the induction heating unit 7 via the fixing belt 3. In the present embodiment, the belt guide member 6 has an arc-shaped cross section when viewed from the axial direction of the pressure roller 2. The belt guide member 6 supports the inner peripheral surface of the fixing belt 3 and stabilizes the traveling track of the fixing belt 3. A predetermined tension can be applied to the fixing belt 3 by the belt guide member 6. Preferably, a magnetic metal material (for example, an iron-based alloy) is used for the material of the belt guide material 6.

  As described above, the pressure roller 2 is pressed by the pressing pad 4 that is fixedly arranged inside the fixing belt 3. As a result, a nip portion N is formed at a location where the pressure roller 2 is pressed against the fixing belt 3. Further, when the pressure roller 2 rotates about the core metal 21 in the rotation direction R1, the fixing belt 3 rotates following the rotation direction R2. The running track of the fixing belt 3 is held by the belt guide member 6. When the sheet S is conveyed in the conveyance direction D and reaches the nip portion N, the sheet S is conveyed downstream by the pressure roller 2 and the fixing belt 3. When the sheet S passes through the nip portion N, the unfixed toner image on the sheet S is heated and pressurized, and the toner image is melted and fixed on the sheet S.

  Next, the induction heating unit 7 of the fixing device 1 will be described. The induction heating unit 7 includes a coil bobbin 71, an induction heating coil 72, a rotary core unit 73, an arched core unit 74, and a side core unit 75. The fixing device 1 employs an IH (Induction Heating) system using an induction heating system heat source, and directly heats the fixing belt 3.

  The coil bobbin 71 is disposed at a position spaced from the outer peripheral surface of the fixing belt 3 by a predetermined distance, and faces the belt guide member 6 through the fixing belt 3. For the material of the coil bobbin 71, a heat resistant resin such as an LCP resin (liquid crystal polymer), a PET resin (polyethylene terephthalate resin), or a PPS resin (polyphenylene sulfide resin) is preferably used in order to withstand heat radiation from the fixing belt 3. Is done.

  The induction heating coil 72 is a coil in which a conducting wire (for example, a litz wire) is wound a plurality of times along the axial direction of the pressure roller 2 and has a loop shape. The induction heating coil 72 is fixed to the coil bobbin 71 with a silicon adhesive or the like.

  The induction heating coil 72 is connected to a power supply circuit and generates an alternating magnetic flux (magnetic field) by a high-frequency current supplied from the power supply circuit. Due to this AC magnetic flux, an eddy current is generated in the induction heating layer of the fixing belt 3. When an eddy current is generated in the induction heating layer, Joule heat is generated due to the electrical resistance of the induction heating layer, and the fixing belt 3 generates heat. Further, since a magnetic metal material is used as the material of the belt guide member 6, an eddy current is also generated in the belt guide member 6, and the belt guide member 6 generates heat. Therefore, the belt guide member 6 can supplementarily heat the fixing belt 3. Therefore, even if heat is removed from the fixing belt 3 by the paper S, the temperature decrease of the fixing belt 3 can be suppressed.

  The high-frequency current supplied to the induction heating coil 72 is controlled based on a signal from the first thermistor TH1. The first thermistor TH1 contacts the inner peripheral surface of the fixing belt 3 in a region different from the region where the belt guide member 6 is disposed, and detects the temperature of the fixing belt 3 (the temperature of the inner peripheral surface). The first thermistor TH1 outputs a signal having a level (voltage value) corresponding to the detected temperature. Therefore, the temperature of the fixing belt 3 can be adjusted to a predetermined temperature by performing feedback control based on the signal from the first thermistor TH1. The first thermistor TH1 can be, for example, a detection element of a thermistor probe. In this case, the base end of the thermistor probe is supported by the support member 5.

  The rotary core 73, the arch core 74, and the side core 75 surround the outside of the induction heating coil 72. That is, the rotary core 73 faces the center of the loop-shaped induction heating coil 72. Arched core portions 74 are disposed on both sides of the rotary core portion 73, respectively. The arched core part 74 extends in an arch shape along the coil bobbin 71 with the rotary core part 73 side as a base end. Side core portions 75 are arranged in the vicinity of the end of each arched core portion 74.

  A magnetic material such as ferrite is used for the material of the rotary core 73, the arch core 74, and the side core 75. As a result, the magnetic flux generated from the induction heating coil 72 is guided to the rotary core portion 73, the arch type core portion 74, and the side core portion 75 and flows along the fixing belt 3. As a result, an eddy current is generated in the induction heating layer of the fixing belt 3 and the fixing belt 3 generates heat. Further, when a magnetic metal material is used as the material of the belt guide member 6, a part of the magnetic flux flows along the belt guide member 6. Therefore, an eddy current is generated in the belt guide member 6 and the belt guide member 6 generates heat.

  Further, the rotary core portion 73 has a rotation shaft 76 at its axis, and is rotatable about the rotation shaft 76. Further, the rotary core portion 73 has a magnetic shielding member 77 attached to the outer peripheral surface thereof, and the magnetic shielding member 77 partially covers the outer peripheral surface of the rotary core portion 73. When the driving force is transmitted to the rotating shaft 76 and the rotary core portion 73 rotates, the magnetic shielding member 77 partially enters the path of the magnetic flux generated from the induction heating coil 72. As a result, the path of the magnetic flux is partially shielded. For example, copper can be used as the material of the magnetic shielding member 77.

  FIG. 2 is a plan view showing the inside of the fixing belt 3, and the fixing belt 3, the induction heating unit 7, and the like are omitted. As shown in FIG. 2, the pressing pad 4, the support member 5, and the belt guide member 6 all extend in the axial direction of the pressure roller 2. Further, the fixing device 1 includes a drive gear 9 fixed to one end of the cored bar 21. The pressure roller 2 rotates when the driving force is transmitted to the driving gear 9.

  Further, the fixing device 1 includes two second thermistors TH2 (TH2a, TH2b) which are examples of the second temperature detection element. As shown in FIG. 1, the two second thermistors TH2 (TH2a, TH2b) both come into contact with the inner side surface of the belt guide member 6 and detect the temperature of the belt guide member 6. The second thermistors TH2a and TH2b each output a signal having a level (voltage value) corresponding to the detected temperature. Each of the second thermistors TH2a and TH2b can be, for example, a detection element of a thermistor probe. In this case, the base end of each thermistor probe is supported by the support member 5.

  As shown in FIG. 2, one second thermistor TH2a is disposed in one end region in the longitudinal direction of the fixing belt 3 (the axial direction of the pressure roller 2), and the other second thermistor TH2b is The fixing belt 3 is disposed at the other end region in the longitudinal direction. In this embodiment, when the longitudinal direction of the A5 size paper is made to coincide with the transport direction, the region (A5R) through which the A5 size paper passes through the fixing device 1 corresponds to the central region in the longitudinal direction of the fixing belt 3. The areas outside the central area correspond to end areas in the longitudinal direction of the fixing belt 3.

  The first thermistor TH1, one second thermistor TH2a, and the other second thermistor TH2b are arranged in different areas according to the sizes of various papers that can pass through the fixing device 1, respectively. In the present embodiment, the first thermistor TH1 is disposed in the central region (region A5R) in the longitudinal direction of the fixing belt 3. One second thermistor TH2a is disposed outside the region A5R and inside the region A4R. The area A4R is an area through which the A4 size sheet passes through the fixing device 1 when the longitudinal direction of the A4 size sheet coincides with the transport direction. The other second thermistor TH2b is arranged outside the area A4R and inside the area A4Y. The region A4Y is a region through which the A4 size sheet passes through the fixing device 1 when the direction orthogonal to the longitudinal direction of the A4 size sheet is matched with the transport direction. As described above, in the present embodiment, the two second thermistors TH2a and TH2b are respectively disposed in the end regions on both sides of the belt guide member 6 in the longitudinal direction. Further, the two second thermistors TH2a and TH2b are disposed at positions where the distances from the longitudinal center of the belt guide member 6 are different from each other.

  FIG. 3 is a plan view showing the fixing device 1. As shown in FIG. 3, the rotary core portion 73 extends in the axial direction of the pressure roller 2. In addition, the fixing device 1 includes a plurality of arched core portions 74. The plurality of arched core parts 74 are arranged at substantially equal intervals along the axial direction of the pressure roller 2. The side core portion 75 extends in the axial direction of the pressure roller 2.

  The fixing device 1 includes a plurality of magnetic shielding members 77. The plurality of magnetic shielding members 77 are arranged according to the sizes of various sheets that can pass through the fixing device 1. Further, the plurality of magnetic shielding members 77 are fixed to the rotary core unit 73 so that the region for shielding the path of the magnetic flux changes according to the rotational position of the rotary core unit 73. In the present embodiment, the magnetic shielding member 77a is disposed in the region from the end of the region A5R to the end of the region A4R, and the magnetic shielding member 77b is disposed in the region outside the end of the region A4R. Further, a rotational position where the magnetic shielding members 77a and 77b do not shield the magnetic flux path is set as the reference position in the rotational direction of the rotary core 73. Thus, when the rotary core 73 is rotated from the reference position, first, the magnetic flux path is shielded by the magnetic shielding member 77b in the outer region from the end of the region A4R. When the rotary core 73 is further rotated, the magnetic flux path is shielded in the outer region from the end of the region A5R by the magnetic shielding members 77a and 76b.

  Further, the fixing device 1 includes restriction members 10 a and 10 b attached to both ends of the fixing belt 3 in order to stabilize the traveling track of the fixing belt 3. While the fixing belt 3 is rotating, the end face of the fixing belt 3 comes into contact with the regulating members 10a and 10b, so that the displacement of the fixing belt 3 in the longitudinal direction is regulated. FIG. 4 is an enlarged plan view showing a part of the fixing belt 3. As shown in FIG. 4, in the present embodiment, the regulating member 10a has a U-shaped cross section, and one end of the fixing belt 3 is inserted into the regulating member 10a. Although not shown, the regulating member 10b has a U-shaped cross section, and the other end of the fixing belt 3 is inserted into the regulating member 10b.

  As shown in FIG. 3, rotating shafts 11a and 11b are fixed to the regulating members 10a and 10b, respectively. The regulating members 10a and 10b rotate around the rotation shafts 11a and 11b by the frictional force generated between the regulating members 10a and 10b, respectively. That is, the regulating members 10 a and 10 b rotate together with the fixing belt 3.

  Further, in the present embodiment, the regulating member 10a is a gear, and the fixing device 1 includes a gear 12 that meshes with many tooth portions formed on the peripheral surface of the regulating member 10a. The fixing device 1 also includes a central shaft 13 of the gear 12, a pulse plate 14 attached to an end of the central shaft 13, and a rotation detection sensor 15. When the fixing belt 3 rotates and the regulating member 10a is driven to rotate, the gear 12, the central shaft 13, and the pulse plate 14 rotate. The rotation detection sensor 15 outputs a signal corresponding to the rotation of the pulse plate 14 and the stop of the rotation. Therefore, based on the output of the rotation detection sensor 15, the rotation of the restricting member 10a and the stop of the rotation can be detected.

  FIG. 5 is a plan view showing the pulse plate 14. As shown in FIG. 5, the pulse plate 14 includes a disc portion 14a attached to the central shaft 13 and a plurality of blade portions 14b provided along the outer peripheral surface of the disc portion 14a. Each blade part 14b is erected in the radial direction of the disk part 14a. FIG. 6 is a diagram showing the rotation detection sensor 15. The rotation detection sensor 15 is a transmissive photo interrupter, and includes a light emitting unit 15a and a light receiving unit 15b that receives the light L emitted from the light emitting unit 15a. The rotation detection sensor 15 is disposed such that each blade 14b shown in FIG. 5 passes between the light emitting unit 15a and the light receiving unit 15b by the rotation of the disk unit 14a.

  According to such a configuration, when the regulating member 10a rotates and the pulse plate 14 rotates, each blade portion 14b passes between the light emitting portion 15a and the light receiving portion 15b one after another. As a result, the rotation detection sensor 15 generates a pulse signal. On the other hand, when the regulating member 10a does not rotate, each blade 14b does not move. Therefore, when any blade 15 is present between the light emitter 15a and the light receiver 15b, the light receiver 15b cannot receive the light L, and the blade 15 is not between the light emitter 15a and the light receiver 15b. When it does not exist, the light receiving unit 15b always receives the light L. As a result, no pulse signal is generated from the rotation detection sensor 15. Therefore, the rotation of the regulating member 10a and the stop of the rotation can be detected depending on whether or not a pulse signal is generated from the rotation detection sensor 15.

  FIG. 7 is a block diagram illustrating a part of the configuration of the fixing device 1. As shown in FIG. 7, the fixing device 1 further includes a control unit 16, a power supply circuit 17, and a motor 18. As the control unit 16, a control unit of an image forming apparatus equipped with the fixing device 1 can be used. Signals from the first thermistor TH1, the second thermistors TH2a and TH2b, and the rotation detection sensor 15 are input to the control unit 16, respectively.

  The power supply circuit 17 supplies a high frequency current (electric power) to the induction heating coil 72 (induction heating unit 7). The control unit 16 functions as a power control unit that controls the power supplied to the induction heating unit 7 based on the temperature detected by the first thermistor TH1. Specifically, the control unit 16 controls the supply of high-frequency current (power supply) to the induction heating coil 72 and the stop of the supply so that the temperature detected by the first thermistor TH1 becomes a predetermined temperature. . As a result, the temperature of the fixing belt 3 is adjusted to a predetermined temperature.

  The motor 18 drives the rotary core unit 73. That is, the rotary shaft 76 (see FIG. 1) of the rotary core 73 is rotated. The controller 16 drives the motor 18 based on the temperatures detected by the second thermistors TH2a and TH2b. Thereby, the rotational position of the rotary core 73 is controlled, and the heat generation distribution of the fixing belt 3 is adjusted.

  Furthermore, the control unit 16 also functions as a heating stop unit that stops the supply of electric power (high-frequency current) to the induction heating coil 72 (induction heating unit 7) and stops the heating operation by the induction heating unit 7.

  That is, the control unit 16 controls the operation of the power supply circuit 17 when any of the temperatures detected by the second thermistors TH2a and TH2b is equal to or higher than a preset temperature (first specified value), Supply of high-frequency current to the induction heating coil 72 (power supply) is stopped. Thereby, the heating operation by the induction heating unit 7 is stopped.

  Further, the control unit 16 determines that a difference between the temperature detected by the first thermistor TH1 and the temperature detected by the second thermistor TH2a or the second thermistor TH2b is a preset temperature difference (second specified value). When the above is reached, the operation of the power supply circuit 17 is controlled to stop the supply of high-frequency current (power supply) to the induction heating coil 72. Thereby, the heating operation by the induction heating unit 7 is stopped.

  Further, the control unit 16 stops the supply of high-frequency current (power supply) to the induction heating coil 72 in accordance with the signal from the rotation detection sensor 15. Specifically, when the rotation detection sensor 15 detects the rotation stop of the regulating member 10a, the control unit 16 controls the operation of the power supply circuit 17 to supply a high-frequency current to the induction heating coil 72 (power supply). Stop. Thereby, the heating operation by the induction heating unit 7 is stopped.

  Subsequently, a first operation of the fixing device 1 will be described with reference to FIGS. 1, 3, and 7. The first operation is an operation for adjusting the heat generation distribution of the fixing belt 3.

  For example, when a plurality of A4 size sheets S are continuously fed to the nip portion N of the fixing device 1 with the longitudinal direction thereof aligned with the transport direction D, the sheet S is fixed in the region A4R. The heat of the belt 3 is taken away. The control unit 16 controls the power supplied to the induction heating unit 7 based on the temperature detected by the first thermistor TH1 disposed in the region A4R. Thereby, the temperature of the fixing belt 3 is adjusted to a predetermined temperature in the region A4R.

  On the other hand, the area outside the area A4R is a non-sheet passing area through which the sheet S does not pass. For this reason, in the area outside the area A4R, the heat of the fixing belt 3 is not taken away by the sheet S, and the temperature of the fixing belt 3 rises (overheating). As a result, the temperature of the belt guide member 6 also increases in the region outside the region A4R.

  In the present embodiment, the temperature of the belt guide member 6 in the region outside the region A4R is detected by the second thermistor TH2b. When the temperature detected by the second thermistor TH2b is equal to or higher than a preset temperature (for example, 220 ° C.), the control unit 16 drives the motor 18 to move the rotary core unit 73 (rotating shaft 76). Rotate to a predetermined rotational position. As a result, the magnetic shielding member 77b enters the magnetic flux path formed in the region outside the region A4R, and reduces the magnetic flux density in the region outside the region A4R (non-sheet passing region). Thereby, the excessive temperature rise of the fixing belt 3 in the area outside the area A4R (non-sheet passing area) can be suppressed.

  Similarly, when the area outside the area A5R is a non-sheet passing area, the control unit 16 determines that the temperature detected by the second thermistor TH2a is equal to or higher than a preset temperature (for example, 220 ° C.). The motor 18 is driven to rotate the rotary core 73 (rotary shaft 76) to a predetermined rotational position. As a result, the magnetic shielding members 77a and 77b enter the magnetic flux path formed in the area (non-sheet passing area) outside the area A5R, and reduce the magnetic flux density in the non-sheet passing area. Thereby, the excessive temperature rise of the fixing belt 3 in the non-sheet passing area can be suppressed.

  As described above, the heat generation distribution of the fixing belt 3 can be adjusted by the magnetic shielding member 77 (77a, 77b). In the present embodiment, the heat generation distribution adjusting mechanism includes a control unit 16, a motor 18 (an example of a driving unit), a rotary core unit 73 (an example of a rotating body), and magnetic shielding members 77a and 77b.

  Next, the second operation of the fixing device 1 will be described with reference to FIGS. 1, 3, and 5 to 10. 8 to 10 are diagrams showing typical patterns of defects in the fixing belt 3. The second operation is an operation for stopping the heating operation by the induction heating unit 7 when a defect occurs in the fixing belt 3.

  As shown in FIG. 3, regulating members 10 a and 10 b are provided on both sides of the fixing belt 3. The regulating members 10 a and 10 b regulate the position of the fixing belt 3 in the longitudinal direction and stabilize the traveling track of the fixing belt 3. However, if the fixing belt 3 is biased to one of its longitudinal directions and continues to rotate while being in contact with one of the regulating members 10a and 10b, the fixing belt 3 breaks and finally the fixing belt 3 There is a possibility that a part or all of is lost. When the defect of the fixing belt 3 occurs, the belt guide member 6 may not be deprived of heat by the fixing belt 3 in the region where the defect occurs, and thus the belt guide member 6 may cause abnormal heat generation. As a result, the image forming apparatus equipped with the fixing device 1 may fall into a dangerous state such as a fire.

  On the other hand, in this embodiment, the defect of the fixing belt 3 is detected based on the temperatures detected by the first thermistor TH1, the second thermistor TH2a, and TH2b, and the heating operation by the induction heating unit 7 is stopped. Can be made.

  For example, FIG. 8 shows a state in which the regulating member 10b side of the fixing belt 3 is partially lost. In this case, the belt guide member 6 generates abnormal heat in a region where the fixing belt 3 is missing. In the present embodiment, the second thermistor TH2b detects the temperature of the portion of the belt guide member 6 on the regulating member 10b side, and the controller 16 first detects the temperature detected by the second thermistor TH2b. When the temperature is higher than a preset temperature (for example, 220 ° C.), the motor 18 is driven to reduce the magnetic flux density in the area outside the area A4R (non-sheet passing area). However, since the fixing belt 3 is missing, the temperature detected by the second thermistor TH2b does not decrease but rises further. When the temperature detected by the second thermistor TH2b becomes equal to or higher than a first specified value (for example, 250 ° C.), the control unit 16 stops the supply of high-frequency current (power supply) to the induction heating coil 72, and induces induction. The heating operation by the heating unit 7 is stopped.

  FIG. 9 shows a state where a portion of the fixing belt 3 on the side of the regulating member 10a is missing. Similarly, in this case, when the temperature detected by the second thermistor TH2a is equal to or higher than the first specified value, the control unit 16 stops the supply of high-frequency current (supply of power) to the induction heating coil 72 to induce induction. The heating operation by the heating unit 7 is stopped.

  In this embodiment, when the portion of the fixing belt 3 on the regulating member 10a side is lost, the regulating member 10a does not rotate, and the rotation detection sensor 15 detects the rotation stop of the regulating member 10a. When the control unit 16 determines to stop the rotation of the regulating member 10 a based on the signal from the rotation detection sensor 15, the control unit 16 stops the supply of high-frequency current (supply of power) to the induction heating coil 72 and causes the induction heating unit 7 to Stop the heating operation.

  FIG. 10 shows a state where the central region of the fixing belt 3 is missing. In this case, the temperature detected by the first thermistor TH1 does not increase or decreases. Therefore, electric power (high-frequency current) is supplied to the induction heating coil 72 in order to increase the detection temperature of the first thermistor TH1, but since the detection temperature of the first thermistor TH1 does not increase, the supply of electric power continues. Done. On the other hand, in a region where the fixing belt 3 is not broken, the second thermistors TH2a and TH2b normally detect the temperature of the belt guide member 6. Therefore, the difference between the temperature detected by the second thermistor TH2a and TH2b and the temperature detected by the first thermistor TH1 widens. When the difference between the detected temperature of the first thermistor TH1 and the detected temperature of the second thermistor TH2a or the second thermistor TH2b becomes equal to or higher than a second specified value (for example, 50 ° C.), the control unit 16 moves to the induction heating coil 72. The high-frequency current supply (power supply) is stopped, and the heating operation by the induction heating unit 7 is stopped.

  As described above, according to the fixing device 1 according to the present embodiment, when the defect occurs in the fixing belt 3, the heating operation by the induction heating unit 7 can be stopped. Therefore, the safety of the fixing device 1 and the image forming apparatus equipped with the fixing device 1 can be improved.

  Further, according to the fixing device 1 according to the present embodiment, it is possible to realize temperature control of the fixing belt 3 and detection of abnormal heat generation of the fixing belt 3 without forming a notch in the belt guide member 6. That is, the fixing device 1 can directly detect the temperature of the fixing belt 3 and adjust the temperature of the fixing belt 3 by the first thermistor TH1. The fixing device 1 can indirectly detect abnormal heat generation of the fixing belt 3 using the second thermistors TH2a and TH2b that detect the temperature of the belt guide member 6. On the other hand, when a notch is formed in the belt guide member and a temperature detection element such as a thermistor is arranged in the notch, temperature control of the fixing belt and detection of abnormal heat generation of the fixing belt 3 are performed. The magnetic flux density changes between the region where the notch is formed and the other region. For this reason, the temperature distribution in the longitudinal direction of the fixing belt becomes non-uniform. Therefore, according to this embodiment, since the belt guide member 6 does not have a notch, the temperature distribution in the longitudinal direction of the fixing belt 3 can be made uniform.

  Next, an example of the image forming apparatus 100 including the fixing device 1 will be described with reference to FIG. FIG. 11 is a diagram illustrating a schematic configuration of the image forming apparatus 100 according to the present embodiment. The image forming apparatus 100 is a monochrome copying machine.

  As shown in FIG. 11, the image forming apparatus 100 includes a paper feeding unit 101 disposed in a lower portion thereof, a paper transporting unit 102 disposed on the side of the paper feeding unit 101, and an upper side of the paper transporting unit 102. An image forming unit 103 disposed on the image forming unit 103, a fixing device 1 disposed on the discharge side of the image forming unit 103, and an image reading unit 104 disposed above the image forming unit 103 and the fixing device 1. I have. In addition, the image forming apparatus 100 includes a control unit 16. The control unit 16 controls the overall operation of the image forming apparatus 100. Further, as described with reference to FIGS. 1 to 10, the control unit 16 controls the power supplied to the induction heating unit 7, adjusts the heat distribution of the fixing belt 3, and fixes the fixing belt 3. It has a function of stopping the heating operation by the induction heating unit 7 when a defect occurs.

  The paper feed unit 101 includes a plurality of paper feed cassettes 105 that store paper S, which is a recording medium, and paper feed rollers 106 provided corresponding to the paper feed cassettes 105. When the sheet S is fed from the sheet feeding unit 101, one of the plurality of sheet feeding cassettes 105 is selected, and the sheet feeding roller 106 corresponding to the selected sheet feeding cassette 105 starts to rotate. As a result, the sheets S are sent out one by one from the selected sheet feeding cassette 105 to the sheet conveying unit 102.

  The paper S sent to the paper transport unit 102 is transported toward the image forming unit 103 via a paper transport path 107 provided in the paper transport unit 102. The image forming unit 103 forms a toner image on the paper S by an electrophotographic process. The image forming unit 103 includes a photosensitive drum 141 that is rotatably supported in the arrow direction of FIG. The image forming unit 103 includes a charging unit 142, an exposure unit 143, a developing unit 144, a transfer unit 145, a cleaning unit 146, and a charge removal unit 147 around the photosensitive drum 141 along the rotation direction.

  The charging unit 142 includes a charging wire to which a high voltage is applied, and a predetermined potential is applied to the surface of the photosensitive drum 141 by corona discharge from the charging wire. As a result, the surface of the photosensitive drum 141 is uniformly charged. Then, when light based on the image data of the original read by the image reading unit 104 is irradiated to the photosensitive drum 141 by the exposure unit 143, the surface potential of the photosensitive drum 141 is selectively attenuated, and the photosensitive drum. An electrostatic latent image is formed on the surface 141.

  Next, the developing unit 144 develops the electrostatic latent image on the surface of the photosensitive drum 141. As a result, a toner image is formed on the surface of the photosensitive drum 141. Then, the toner image is transferred by the transfer unit 145 to the paper S supplied between the photosensitive drum 141 and the transfer unit 145.

  The sheet S to which the toner image has been transferred is conveyed toward the fixing device 1 disposed downstream of the image forming unit 103 in the sheet conveying direction. In the fixing device 1, the paper S is heated and pressurized, and the toner image is melted and fixed on the paper S. Next, the sheet S on which the toner image is fixed is discharged onto the discharge tray 109 by the discharge roller pair 108.

  After the transfer of the toner image onto the paper S by the transfer unit 145, the toner remaining on the surface of the photoconductive drum 141 is removed by the cleaning unit 146, and the electric charge remaining on the surface of the photoconductive drum 141 is It is removed by the charge removal unit 147. The photosensitive drum 141 is charged again by the charging unit 142, and thereafter image formation is performed in the same manner.

  The embodiment of the present invention has been described above with reference to the drawings (FIGS. 1 to 11). However, the present invention is not limited to the above-described embodiment, and can be implemented in various modes without departing from the gist thereof.

  For example, in the embodiment of the present invention, the control unit 16 functions as a heating stop unit that stops the heating operation by the induction heating unit 7, but the present invention is not limited to this.

  FIG. 12 shows another configuration in which the heating operation by the induction heating unit 7 is stopped when a defect occurs in any one of the end regions in the longitudinal direction of the fixing belt 3. The configuration (heating stop unit) shown in FIG. 12 includes two comparators 31 and 32, an OR circuit 33, and a switch unit 34. As the switch unit 34, for example, a bidirectional thyristor (so-called triac) or a relay switch can be used.

  The comparator 31 compares the output voltage (corresponding to the detected temperature) of one second thermistor TH2a with the reference voltage VR1 (corresponding to the first specified value), and outputs the one second thermistor TH2a. When the voltage becomes equal to or higher than the reference voltage VR1, an H level signal is output.

  The comparator 32 compares the output voltage (corresponding to the detected temperature) of the other second thermistor TH2b with the reference voltage VR1 (corresponding to the first specified value), and outputs the other second thermistor TH2b. When the voltage becomes equal to or higher than the reference voltage VR1, an H level signal is output.

  When receiving an H level signal from at least one of the comparators 31 and 32, the OR circuit 33 generates a signal for opening the switch unit 34. As a result, the supply of power to the induction heating coil 72 is stopped, and the heating operation by the induction heating unit 7 is stopped.

  FIG. 13 shows another configuration in which the heating operation by the induction heating unit 7 is stopped when a defect occurs in the central region in the longitudinal direction of the fixing belt 3. The configuration (heating stop unit) illustrated in FIG. 13 includes two difference units 35 and 36, two comparators 37 and 38, an OR circuit 39, and a switch unit 40. As the switch unit 40, for example, a bidirectional thyristor (so-called triac) or a relay switch can be used.

  The differentiator 35 outputs the difference between the output voltage of the first thermistor TH1 and the output voltage of one second thermistor TH2a. The output voltage of the differentiator 35 indicates the difference between the temperature detected by the first thermistor TH1 and the temperature detected by one second thermistor TH2a.

  The differentiator 36 outputs the difference between the output voltage of the first thermistor TH1 and the output voltage of the other second thermistor TH2b. The output voltage of the differentiator 36 indicates the difference between the temperature detected by the first thermistor TH1 and the temperature detected by the other second thermistor TH2b.

  The comparator 37 compares the output voltage of the differentiator 35 with the reference voltage VR2 (corresponding to the second specified value), and outputs an H level signal when the output voltage of the differencer 35 becomes equal to or higher than the reference voltage VR2. .

  The comparator 38 compares the output voltage of the differentiator 36 with the reference voltage VR2 (corresponding to the second specified value), and outputs an H level signal when the output voltage of the differentiator 36 becomes equal to or higher than the reference voltage VR2. .

  When receiving an H level signal from at least one of the comparators 37 and 38, the OR circuit 39 generates a signal for opening the switch unit 40. As a result, the supply of power to the induction heating coil 72 is stopped, and the heating operation by the induction heating unit 7 is stopped.

  FIG. 14 shows another configuration in which the heating operation by the induction heating unit 7 is stopped when a defect occurs in either the longitudinal end region or the central region of the fixing belt 3. The configuration (heating stop unit) shown in FIG. 14 includes comparators 31 and 32 as in the configuration shown in FIG. 14 includes difference units 35 and 36 and comparators 37 and 38 as in the configuration shown in FIG. Furthermore, the configuration shown in FIG. 14 includes an OR circuit 41 having four input terminals that respectively receive outputs from the comparator 31, the comparator 32, the comparator 37, and the comparator 38, and a switch unit 42. As the switch unit 42, for example, a bidirectional thyristor (so-called triac) or a relay switch can be used. According to such a configuration, similarly to the configuration described with reference to FIGS. 12 and 13, the supply of power to the induction heating coil 72 can be stopped and the heating operation by the induction heating unit 7 can be stopped. .

  In the embodiment of the present invention, when the difference between the temperature detected by the first thermistor TH1 and the temperature detected by the second thermistor TH2a or the second thermistor TH2b is equal to or greater than the second specified value, the induction is performed. Although the structure which the heating operation by the heating part 7 stops was demonstrated, this invention is not limited to this.

  For example, the control unit 16 (heating stop unit) indicates that the gradient of temperature change (temperature change per unit time) detected by the first thermistor TH1 is equal to or less than a preset value (third specified value). When it is determined, the heating operation by the induction heating unit 7 may be stopped.

  That is, at the normal time when no defect occurs in the central region of the fixing belt 3, the detected temperature of the first thermistor TH 1 rises according to the electric power supplied to the induction heating coil 72. On the other hand, if the central region of the fixing belt 3 is lost, the detected temperature of the first thermistor TH1 does not rise as much as the supply amount even if power is supplied to the induction heating coil 72. Accordingly, when the central region of the fixing belt 3 is lost, the gradient of the temperature change detected by the first thermistor TH1 becomes smaller than that in the normal time. Therefore, the control unit 16 determines that a defect has occurred in the central region of the fixing belt 3 when the gradient of the change in the detected temperature of the first thermistor TH1 is not more than a third specified value (for example, 10 ° C.). Then, the heating operation by the induction heating unit 7 may be stopped.

  Further, for example, the control unit 16 (heating stop unit) may set one of the gradients (temperature change per unit time) of the temperature detected by the second thermistors TH2a and TH2b to a preset value (fourth regulation). Value) or higher, the heating operation by the induction heating unit 7 may be stopped.

  That is, when the central region of the fixing belt 3 is lost, the detected temperature of the first thermistor TH1 does not rise even when power is supplied to the induction heating coil 72, and thus the supply of power to the induction heating coil 72 is continued. Executed. As a result, the gradient of the temperature change detected by the second thermistors TH2a and TH2b becomes larger than that in the normal state. Therefore, the control unit 16 causes the defect in the central region of the fixing belt 3 when any of the temperature change gradients detected by the second thermistors TH2a and TH2b is equal to or higher than a fourth specified value (for example, 5 ° C.). It may be determined that the above has occurred, and the heating operation by the induction heating unit 7 may be stopped.

  In the embodiment of the present invention, two second thermistors TH2 are used, but one second thermistor TH2 may be used. When the defect of the fixing belt 3 is detected using the difference between the temperature detected by the first thermistor TH1 and the temperature detected by the second thermistor TH2, the second thermistor TH2 is the first in the longitudinal direction of the fixing belt 3. It is arranged at a position different from 1 thermistor TH1.

  In the embodiment of the present invention, the rotation stop of the regulating member 10a is detected and the heating operation by the induction heating unit 7 is stopped. Similarly, the rotation stopping of the regulating member 10b is detected and the induction heating unit 7 is stopped. The heating operation by may be stopped. That is, a gear is used as the restricting member 10b, a gear meshing with a large number of teeth formed on the peripheral surface of the restricting member 10b, a central axis of the gear, and a pulse attached to an end of the central axis A plate and a rotation detection sensor may be provided. Accordingly, it is possible to detect that the fixing belt 3 is defective on the regulating member 10b side based on the output of the rotation detecting sensor on the regulating member 10b side.

  In the embodiment of the present invention, the A5 size paper S is placed vertically, the A4 size paper S is placed vertically, and the A4 size paper S is placed horizontally, Although the longitudinal region of the fixing belt 3 is divided, the longitudinal region of the fixing belt 3 may be further finely divided by further increasing the types of sheets to be applied (including portrait and landscape orientation). In this case, the number of second thermistors TH2 for detecting the temperature of the belt guide member 6 is increased according to the number of divided areas, that is, according to the sizes of various sheets, and the second thermistors are detected. The mr TH2 is disposed at a position where the distances from the center in the longitudinal direction of the fixing belt 3 are different from each other. Further, a plurality of magnetic shielding members 77 are arranged according to the sizes of various papers. This makes it possible to finely adjust the heat generation distribution according to the sizes of various papers. In addition, it is possible to detect defects occurring in the fixing belt 3 with higher accuracy. If the purpose is to detect defects generated in the fixing belt 3 with higher accuracy, a plurality of second thermistors TH2 that are in contact with the inner surface of the belt guide member 6 are arranged at equal intervals. Also good.

  In the embodiment of the present invention, the heat distribution of the fixing belt 3 is adjusted by the magnetic shielding member 77 in order to lower the temperature of the non-sheet passing region of the fixing belt 3. When the plurality of sheets S are sequentially conveyed to the fixing device 1, the control unit 16 feeds the plurality of sheets S based on the temperatures detected by the second thermistors TH2a and TH2b, that is, a sheet feeding roller. The interval between the intermittent paper feeding operations 106 may be adjusted. Specifically, when one of the temperatures detected by the second thermistors TH2a and TH2b is equal to or higher than a preset temperature (for example, 220 ° C.), the interval between intermittent paper feeding operations by the paper feeding roller 106 is performed. The controller 16 may control the driving of the paper feed roller 106 so that is larger than normal. When the interval between intermittent sheet feeding operations by the sheet feeding roller 106 is increased, the heat in the central region of the fixing roller 3 is not easily taken away by the sheet S passing through the central region, and is detected by the first thermistor TH1. Temperature rises. Therefore, the control unit 16 performs control to lower the detected temperature of the first thermistor TH1. As a result, the temperature of the non-sheet passing area of the fixing belt 3 is lowered.

  Further, in the embodiment of the present invention, the magnetic shielding member 77 (76a, 77b), the rotating body (rotary core portion 73) having the magnetic shielding member 77 (76a, 77b) fixed to the peripheral surface thereof, and the rotation The heat generation distribution of the fixing belt 3 was adjusted by a drive unit (motor 18) for driving the body and a control unit (control unit 16) for controlling the drive unit. However, the mechanism for adjusting the heat distribution of the fixing belt 3 (heat generation distribution adjusting mechanism) is not limited to such a configuration. For example, the heat generation distribution adjusting mechanism may be a mechanism that overlaps a degaussing coil in a region where the magnetic flux is to be reduced, and energizes the degaussing coil to generate a magnetic flux that cancels out the magnetic flux generated from the induction heating coil 72. Further, the heat generation distribution adjusting mechanism may include a duct for sending air along the longitudinal direction of the fixing belt 2 and a fan for allowing air to flow into the duct. Or the structure provided with the divided | segmented induction heating coil may be sufficient as the heat_generation | fever distribution adjustment mechanism. That is, for example, a plurality of induction heating coils may be provided in accordance with the sizes of various papers, and the heat distribution of the fixing belt 3 may be adjusted by controlling energization of each induction heating coil.

  In the embodiment of the present invention, the case where the first specified value for stopping the heating operation by the induction heating unit 7 is higher than the temperature condition for operating the heat generation distribution adjusting mechanism has been described. The temperature condition for operating the heat distribution adjustment mechanism (for example, 220 ° C. or higher) may be the same. In this case, the temperature of the belt guide member 6 after a lapse of a certain time after the heat generation distribution adjusting mechanism is operated satisfies a temperature condition (for example, 220 ° C. or more) for operating the heat generation distribution adjusting mechanism, so that the induction heating unit 7 The heating operation may be stopped.

  Moreover, in this embodiment, although the pulse plate 14 in which the several blade | wing part 14b was provided along the outer peripheral surface of a disc (disk part 14a) was used, as a pulse plate 14, a some through-hole is provided in an outer peripheral part. A disk formed with may be used.

  In the embodiment of the present invention, the thermistor is shown as the temperature detection element. However, the temperature detection element is not limited to the thermistor, and for example, a thermocouple may be used.

  In the embodiment of the present invention, the paper S is shown as an example of the recording medium. However, the recording medium is not limited to the paper S, and may be a resin sheet such as a film.

  In the embodiment of the present invention, the image forming apparatus 100 is a monochrome copying machine. However, the present invention is not limited to this, and can be applied to an image forming apparatus including an IH fixing device. It can be applied to copiers, color printers, facsimiles, and multifunction machines.

  In addition, in order to make it easy to understand, the drawings schematically show each component as a main component. Accordingly, the thickness, length, and the like of each illustrated component are different from actual ones for the convenience of drawing.

  According to the present invention, when a defect occurs in the fixing belt, the heating operation by the heating unit can be stopped, and the present invention can be used for an image forming apparatus such as a copying machine, a printer, a facsimile machine, and a multifunction machine. This is particularly useful for an image forming apparatus having a fixing device of the type.

DESCRIPTION OF SYMBOLS 1 Fixing device 2 Pressure roller 3 Fixing belt 6 Belt guide member 7 Induction heating part 16 Control part TH1 1st thermistor TH2, TH2a, TH2b 2nd thermistor

Claims (12)

A fixing belt,
A pressure member that contacts the outer peripheral surface of the fixing belt and rotates the fixing belt;
A heating unit for heating the fixing belt;
A belt guide member disposed in a region facing the heating unit and supporting an inner peripheral surface of the fixing belt;
A first temperature detecting element that is in contact with the fixing belt and detects a temperature of the fixing belt;
A power control unit configured to control power supplied to the heating unit based on a temperature detected by the first temperature detection element;
At least one second temperature detecting element that is in contact with the inner surface of the belt guide member and detects the temperature of the belt guide member;
A fixing device comprising: a heating stop unit that stops a heating operation by the heating unit based on an output of the first temperature detection element and / or the at least one second temperature detection element.   The fixing device according to claim 1, further comprising a heat generation distribution adjusting mechanism that adjusts a heat generation distribution of the fixing belt based on a temperature detected by the at least one second temperature detection element.   3. The fixing device according to claim 1, wherein the heating stop unit stops a heating operation by the heating unit when a temperature detected by the at least one second temperature detection element is equal to or higher than a first specified value. . The at least one second temperature detection element is disposed at a position different from the first temperature detection element in the longitudinal direction of the fixing belt;
When the difference between the temperature detected by the first temperature detection element and the temperature detected by the at least one second temperature detection element is equal to or greater than a second specified value, the heating stop unit The fixing device according to claim 1, wherein the heating operation is stopped.   The heating stop unit stops the heating operation by the heating unit when the gradient of the temperature change detected by the first temperature detection element is a third specified value or less. The fixing device according to Item 1.   The heating stop unit stops a heating operation by the heating unit when a gradient of a temperature change detected by the at least one second temperature detection element is a fourth specified value or more. 4. The fixing device according to claim 1. The first temperature detecting element is disposed in a central region in a longitudinal direction of the fixing belt;
The fixing device according to claim 1, wherein the at least one second temperature detection element is disposed in one end region in a longitudinal direction of the belt guide member. A plurality of the second temperature detection elements;
The fixing device according to claim 1, wherein the plurality of second temperature detection elements are arranged in end regions on both sides in the longitudinal direction of the belt guide member.   9. The fixing device according to claim 8, wherein the plurality of second temperature detection elements are arranged at positions different from each other in a distance from a center in a longitudinal direction of the belt guide member. One or two regulating members that can abut one end surface of the fixing belt or both of the end surfaces and rotate with the rotation of the fixing belt;
One or two sensors for detecting the rotation stop of the one restricting member or the rotation stop of each of the two restricting members;
The fixing device according to claim 1, wherein the heating stop unit stops the heating operation by the heating unit in accordance with outputs from the one or two sensors. A fixing device according to any one of claims 1 to 10,
An image forming unit for forming a toner image on a recording medium;
A transport unit that transports the recording medium from the image forming unit to the fixing device;
The fixing device fixes the toner image on the recording medium.   When the plurality of recording media are sequentially conveyed to the fixing device, an interval at which the plurality of recording media are sequentially fed based on the temperature detected by the at least one second temperature detection element is set. The image forming apparatus according to claim 11, further comprising a control unit for adjustment.

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