JP2015022221A - Image heating device, and image forming apparatus including the image heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image heating device that can suppress the sudden stop of the device even when an external heating member has large overshoot.SOLUTION: When detection means 75 has detected that a first rotating body 40 and an external heating member 83 are in a separation state, and temperature detection means 31 and 32 have detected that the external heating member is at an abnormal temperature that is higher than a predetermined target temperature, contact/separation means 90 shifts the first rotating body and the external heating member into a pressure-contact state.

Description

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

  As a fixing device (fixing device) mounted on an electrophotographic recording type copying machine or printer, a fixing device (fixing device) having a heating rotator and a pressure rotator which forms a nip portion in contact with the heating rotator is known. ing. The recording material carrying the unfixed toner image is heated while being conveyed in the nip portion, whereby the toner image is fixed on the recording material.

  Commercial combinations of rotating roller members, rotating roller members and endless belt members, or rotating endless belt members are also available as combinations of heating and pressure rotating members. Has been.

  The fixing device includes a heating source such as a halogen heater, a ceramic heater, or an induction heater that heats the heating rotator, and a temperature detection unit such as a thermistor that detects the temperature of the heating rotator. The fixing device further includes control means for controlling the heating source in accordance with the output from the temperature detection means so that the heating rotator has a predetermined control temperature (temperature control temperature). Here, the control means has a predetermined error detection temperature higher than the normal temperature control temperature in order to prevent damage to the components of the fixing device due to an abnormal temperature rise.

  In addition, the fixing device includes an energization interruption member such as a thermo switch that interrupts energization to the heating source when the temperature detection unit detects a temperature equal to or higher than the error detection temperature.

  In particular, in a fixing device having a configuration in which the heating rotator and the pressure rotator can be pressed or separated from each other, the heat capacity and the heat radiation amount of the heating rotator change due to the pressure contact or separation between the heating rotator and the pressure rotator. For this reason, there is a possibility that the error detection temperature cannot be detected in the separated state between the heating rotator and the pressure rotator.

  Patent Document 1 discloses a fixing device in which a threshold value of an error detection temperature is variable depending on whether a heating rotator and a pressure rotator are in a pressurized state or a pressure released state. In the fixing device disclosed in Patent Document 1, the second error temperature in the pressure release state is set lower than the first error detection temperature in the pressurization state, thereby reducing the pressure release state. However, the abnormality is detected more reliably.

  In Patent Document 2, when a predetermined error temperature is detected during heating of the recording material, the heat conduction from the heating rotator to the recording material is performed by releasing the pressure of the heating rotator and the pressure rotator. There is disclosed a fixing device which reduces the above-described problem.

JP 2007-212868 A JP 2008-176002 A

  Incidentally, the image forming apparatus is required to increase the speed of print output and to cope with recording materials such as cardboard and coated paper. In these cases, since the temperature drop of the nip portion when the recording material passes increases, heat is supplied from the surface of the heating rotator by a heating source in order to maintain the temperature of the nip portion at a predetermined temperature control temperature. A fixing device having an external heating means has been proposed.

  Here, when the surface of the heating rotator is maintained at a predetermined temperature control temperature, the heating rotation is performed at the timing of supplying and cutting off the power to the heating source and the timing at which the temperature detecting means detects the temperature of the heating rotator. Due to the heat capacity and heat dissipation of the body and the external heating means, a time lag will occur. For this reason, a temperature rise (hereinafter also referred to as overshoot) or a temperature decrease (hereinafter also referred to as undershoot) occurs in the heating rotator with respect to a predetermined temperature control temperature.

  Normally, in the standby state where the recording material is not heated, the heating rotator and the external heating means are separated from each other in order to reduce the power consumption in the standby state and extend the durability life of the heating rotator and the pressure rotator. Yes.

  In the fixing device configured to be able to press-contact or separate the heating rotator and the external heating unit, the external heating unit overshoots normally due to large changes in the heat capacity and the heat radiation amount of the external heating unit between the press-contact state and the separated state. It may be larger than that during temperature control. Therefore, even if the fixing device performs a predetermined heating operation in a normal state, the detected temperature of the temperature detecting unit is not equal to the above error due to overshoot of the external heating unit due to the pressure contact or separation between the heating rotating body and the external heating unit. The detected temperature may be exceeded.

  With respect to this problem, in the fixing devices as disclosed in Patent Document 1 and Patent Document 2, the energization cut-off member operates and the subsequent heating operation is impossible despite the normal attachment / detachment operation. There is a risk of becoming. On the other hand, when the error detection temperature is set high in anticipation of an increase in overshoot due to the pressure contact state or the separated state, the operation of the energization cutoff member due to an abnormal temperature rise is delayed.

  An object of the present invention is to provide an image heating apparatus capable of suppressing an unexpected stop of the apparatus even when the overshoot of the external heating member is large, and an image forming apparatus including the image heating apparatus. is there.

  Another object of the present invention is to provide an image heating apparatus capable of suppressing an unexpected stop of the apparatus even when the overshoot of the first rotating body is large, and an image forming apparatus including the image heating apparatus. It is to provide.

  (1) The configuration of the image heating apparatus according to the present invention for achieving the above object includes a first rotating body for heating a recording material carrying an image at a nip portion therebetween, and the first rotating body. An external heating member that contacts and heats the outer surface of the rotating body; a heating source that heats the external heating member; contact / separation means that contacts and separates the external heating member and the first rotating body; Detection means for detecting the pressure contact state and the separation state between the external heating member and the first rotating body, temperature detection means for detecting the temperature of the external heating member, and the external heating member so as to have a predetermined target temperature Control means for controlling energization to the heating source in accordance with the output of the temperature detection means, wherein the detection means detects that the separated state and the temperature The external heating member is detected by the detecting means. If it serial is higher abnormal temperature than the target temperature is detected, and wherein the shifting to the pressed state by the moving means.

  (2) Another configuration of the image heating apparatus according to the present invention for achieving the above object includes a first rotating body and a second rotating body for heating a recording material carrying an image at a nip portion therebetween, and the first rotating body. A heating source for heating one rotating body, contact / separation means for contacting / separating the first rotating body and the second rotating body, and pressure contact between the first rotating body and the second rotating body Detecting means for detecting the state and the separated state, temperature detecting means for detecting the temperature of the first rotating body, and output of the temperature detecting means so that the first rotating body has a predetermined target temperature. An image heating apparatus having a control means for controlling energization to the heating source, wherein the detection means detects that the separated state is detected, and the temperature detection means detects the first rotating body. Is detected as an abnormal temperature higher than the target temperature , And wherein the shifting to the pressed state by the moving means.

  (3) Another configuration of the image heating apparatus according to the present invention for achieving the above object includes: a first rotating body that heats a recording material carrying an image at a nip portion therebetween; A heat source that heats one rotating body, an external heat radiating member that contacts the outer surface of the first rotating body and radiates heat of the first rotating body, the external heat radiating member, and the first rotating body. Contact / separation means for contacting / separating, detection means for detecting the pressure contact state and separation state of the external heat radiating member and the first rotating body, and temperature detection means for detecting the temperature of the first heating body, An image heating apparatus comprising: control means for controlling energization to the heating source in accordance with an output of the temperature detection means so that the first rotating body has a predetermined target temperature, wherein the detection means By the temperature detecting means. When said external heating member is higher abnormal temperature than the target temperature is detected, and wherein the shifting to the pressed state by the moving means.

  (4) A configuration of an image forming apparatus according to the present invention for achieving the above object includes an image forming unit that forms an image on a recording material, and an image heating unit that heats the image formed on the recording material. In the image forming apparatus, the image heating unit is the image heating apparatus according to any one of (1) to (3).

  According to the present invention, it is possible to provide an image heating apparatus capable of suppressing an unexpected stop of the apparatus even when the overheating of the external heating member is large, and an image forming apparatus including the image heating apparatus. .

  According to the present invention, there is also provided an image heating apparatus capable of suppressing an unexpected stop of the apparatus even when the overshoot of the first rotating body is large, and an image forming apparatus including the image heating apparatus. Can be realized.

Sectional drawing showing schematic structure of an example of image forming apparatus 1 is a longitudinal central sectional view illustrating a schematic configuration of a fixing device according to a first embodiment. Explanatory drawing of the contact / separation means of the fixing roller and pressure roller of the fixing apparatus which concerns on Example 1, an external heating unit, and the contact / separation means of a fixing roller and an external heating unit FIG. 3 is an explanatory diagram illustrating the fixing device according to the first exemplary embodiment from the downstream side in the recording material conveyance direction. FIG. 5 is a diagram illustrating a state where the pressure roller and the external heating belt are separated from the fixing roller of the fixing device according to the first exemplary embodiment. FIG. 6 is a flowchart illustrating a procedure for detecting an abnormal temperature of the heating roller at the end of printing in the fixing device according to the first exemplary embodiment. Flowchart showing detection procedure of abnormal temperature of heating roller at end of printing in fixing device of first comparative example Flowchart showing detection procedure of abnormal temperature of heating roller at end of printing in fixing device of second comparative example 10 is a flowchart illustrating a procedure for detecting an abnormal temperature of the heating roller at the end of printing in the fixing device according to the second exemplary embodiment. Explanatory drawing of the structure for rotating a heating roller directly in the fixing device which concerns on Example 2. FIG. FIG. 10 is a longitudinal center sectional view illustrating a schematic configuration of a fixing device according to a third embodiment. FIG. 10 is a diagram illustrating a state in which the pressure roller is separated from the fixing roller of the fixing device according to the third embodiment. 9 is a flowchart illustrating a procedure for detecting an abnormal temperature of the fixing roller at the end of printing in the fixing device according to the third exemplary embodiment. 10 is a flowchart illustrating a procedure for detecting an abnormal temperature of the fixing roller at the end of printing in the fixing device according to the fourth exemplary embodiment. Longitudinal central sectional view showing schematic configuration of fixing apparatus according to Embodiment 5 FIG. 10 is a diagram illustrating a state in which the pressure roller is separated from the fixing roller of the fixing device according to the fifth exemplary embodiment and the external heat radiating roller is pressed against the fixing roller. 10 is a flowchart illustrating a procedure for detecting an abnormal temperature of the fixing roller at the end of printing in the fixing device according to the fifth exemplary embodiment. 10 is a flowchart illustrating a procedure for detecting an abnormal temperature of the fixing roller at the end of printing in the fixing device according to the sixth embodiment.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Although the preferred embodiment of the present invention is an example of the best embodiment of the present invention, the present invention is not limited by the following examples, and various other configurations are possible within the scope of the idea of the present invention. It is possible to replace this with a known configuration.

[Example 1]
(1) Image Forming Apparatus An image forming apparatus equipped with the image heating apparatus according to the present invention as a fixing device will be described with reference to FIG. FIG. 1 is a cross-sectional view illustrating a schematic configuration of an example of an image forming apparatus (full color printer in this embodiment) 100 using an electrophotographic recording technique.

  In the image forming apparatus 100, an image forming unit 101 that forms a toner image on a recording material P includes four image forming stations Pa, Pb, Pc, and Pd of yellow, magenta, cyan, and black. Each image forming station includes a photosensitive drum 1 as an image carrier, a charging member 2, a laser scanner 3, a developing device 4, and a cleaner 5 for cleaning the photosensitive drum. Each image forming station further includes a transfer member 6, a belt 7 that conveys the toner image transferred from the photosensitive drum 1 by the transfer member, and a secondary transfer member 8 that transfers the toner image from the belt to the recording material P. And a cleaner 10 for cleaning the belt 7. Since the operation of the image forming unit 101 described above is well known, detailed description thereof is omitted.

  The recording material P stored in the cassette 11 in the image forming apparatus 100 is fed one by one to the transport path 13 a by the rotation of the roller 12. The recording material P is conveyed to the secondary transfer nip portion formed by the belt 7 and the secondary transfer member 8 by the rotation of the roller 14. The recording material P on which the unfixed toner image is transferred to the first surface in the secondary transfer nip is sent to a fixing device 9 as an image heating unit, and the toner image is heated and fixed on the recording material by the fixing device. The recording material P exiting the fixing device 9 is sorted by the flapper 15 and discharged to the tray 17 in the case of single-sided printing.

  In the case of duplex printing, the recording material P exiting the fixing device 9 is distributed by the flapper 15 and guided to the conveyance path 13b. In the conveyance path 13b, the recording material P is switched back and conveyed to the conveyance path 13a. The recording material P is conveyed to the secondary transfer nip portion by the rotation of the roller 14. The recording material P on which the unfixed toner image is transferred to the second surface at the secondary transfer nip portion is sent to the fixing device 9, and the toner image is heated and fixed to the recording material by the fixing device. The recording material P exiting the fixing device 9 is distributed by the flapper 15 and discharged to the tray 17.

(2) Fixing device (image heating device) 9
FIG. 2 is a longitudinal central sectional view showing a schematic configuration of the fixing device 9. FIG. 3 is an explanatory view of the pressure contact / separation means 50 for the pressure roller of the fixing device 9, the external heating unit 80, and the pressure contact / separation means 90 for the external heating unit. FIG. 4 is an explanatory view showing the fixing device 9 shown in FIG. 3 from the downstream side in the recording material conveyance direction. FIG. 5 is a diagram illustrating a state in which the pressure roller and the external heating belt 83 are separated from the fixing roller 40 of the fixing device 9.

  The fixing device 9 includes a fixing roller 40 as a first rotating body, a pressure roller 41 as a second rotating body, and a first contact / separation unit 50 that presses or separates the fixing roller and the pressure roller. Have. Further, the fixing device 9 includes an external heating unit 80 as an external heating unit, and an external heating belt 83 as an external heating member of the external heating unit and a second contact / separation unit 90 that presses or separates the fixing roller 40. Have. The fixing roller 40, the pressure roller 41, and the external heating belt 83 are members that are long in a direction orthogonal to the recording material conveyance direction (hereinafter referred to as a longitudinal direction).

(2-1) Fixing roller (first rotating body) 40
The fixing roller 40 has a hollow cylindrical cored bar 40a made of aluminum and having a thickness of 3 mm. An elastic layer 40b made of heat-resistant silicone rubber is formed on the outer peripheral surface between the shaft portions 40a1 and 40a2 on both sides in the longitudinal direction of the core metal 40a. Further, on the outer peripheral surface of the elastic layer, heat-resistant fluororesin A release layer 40c having a thickness of 50 μm is formed.

  In the fixing roller 40, the shaft portions 40 a 1 and 40 a 2 of the core metal 40 a are rotatably supported by the pair of first side plates A 1 and A 2 of the fixing device 9. A halogen heater 60 as a heating source is disposed at the rotation center of the fixing roller 40, and this halogen heater is fixedly supported on side plates (not shown) disposed at both ends in the longitudinal direction of the cored bar 40a. A gear G1 is fixed to the shaft portion 40a1 of the cored bar 40a, and this gear is rotated by a motor M1 as a rotating means.

  On the upstream side of the nip portion N in the rotation direction of the fixing roller 40, a thermistor 30 as a temperature detecting means for detecting the temperature of the outer peripheral surface (outer surface) of the fixing roller is disposed in non-contact with the outer surface of the fixing roller.

(2-2) Pressure roller (second rotating body) 41
The pressure roller 41 arranged in parallel with the fixing roller 40 has a hollow cylindrical cored bar 41a made of aluminum and having a thickness of 5 mm. An elastic layer 41b made of heat-resistant silicone rubber is formed on the outer peripheral surface between the shaft portions 41a1 and 41a2 on both sides in the longitudinal direction of the metal core 41a. Further, on the outer peripheral surface of the elastic layer, heat-resistant fluororesin A release layer 41c having a thickness of 50 μm is formed. The shaft portions 41a1 and 41a2 of the cored bar 41a are rotatably supported by a pair of second side plates A3 and A4 of the fixing device 9.

(2-3) Contact / separation means 50
The structure of the contacting / separating means 50 will be described with reference to FIGS. The contact / separation means 50 includes a pair of cams 50a1 and 50a2 as contact / separation members, and a cam shaft 50b that connects these cams along the longitudinal direction of the pressure roller 41. Each of the cams 50a1 and 50a2 is formed in an elliptical shape having a large diameter portion and a small diameter portion as shown in FIG. The cam shaft 51 is rotatably supported by a pair of third side plates A5 and A6 of the fixing device 9. A gear G2 is fixed to the longitudinal end portion of the cam shaft 50b, and this gear is rotated by a motor M2 as a second rotating means.

  The contact / separation means 50 presses the pressure roller 41 against the fixing roller 40 to bring the pressure roller and the fixing roller into a pressure state (pressure contact state), and separates the pressure roller from the fixing roller to The fixing roller is in a pressure release state (separated state). When the recording material P carrying the unfixed toner image t is heated, the pressure roller 41 is pressed against the fixing roller 40 as shown in FIG. In the standby state of the fixing device 9 (when waiting for image formation), the pressure roller 41 is separated from the fixing roller 40 as shown in FIG.

  When the pressure roller 41 is brought into pressure contact with the fixing roller 40, the motor M2 rotates the cam shaft 50b via the gear G2, and rotates the cams 50a1 and 50a2 from the position indicated by the alternate long and short dash line to the position indicated by the solid line (FIG. 3). Then, by rotation of the cams 50a1 and 50a2, the bottom plate B1 between the side plates A3 and A4 is pushed up by the cam maximum diameter portions 50a11 and 50a21 in the vertical direction perpendicular to the generatrix direction of the fixing roller 40, and the outer peripheral surface (outer surface) of the pressure roller 41 ) To the outer surface of the fixing roller 40. As a result, the elastic layers 41b and 40b of the pressure roller 41 and the fixing roller 40 are crushed and elastically deformed, and a nip portion N (see FIG. 2) having a predetermined width is formed between the pressure roller outer surface and the fixing roller outer surface.

  In this embodiment, the nip portion N is formed by pressing the pressure roller 41 against the fixing roller 40 with a total pressure of about 784 N (about 80 kgf).

  When the pressure roller 41 is separated from the fixing roller 40, the motor M2 rotates the cam shaft 51 via the gear G2, and rotates the cams 50a1 and 50a2 from the position indicated by the solid line to the position indicated by the one-dot chain line (FIG. 3). The rotation of the cams 50a1 and 50a2 lowers the outer surface of the pressure roller 41 from the outer surface of the fixing roller 40 by lowering the bottom plate B1 in the vertical direction perpendicular to the generatrix direction of the fixing roller 40 while supporting the bottom plate B1 by the minimum diameter portions 50a12 and 50a22 of the cam. Separate (see FIG. 5).

(2-4) External heating unit 80
When the unfixed toner image t carried on the recording material P such as coated paper or thick paper is heat-fixed on the recording material at high speed, the thermal conductivity of the elastic layer 40b of the fixing roller 40 is low. The thermal response from the halogen heater 60 may not be in time for the amount of heat lost. For this reason, as shown in FIG. 2, an external heating unit 80 for heating the outer surface of the fixing roller 40 is arranged. The fixing roller 40 can receive heat supply from the external heating unit 80 as well as the halogen heater 60 disposed in the cored bar 40a. Therefore, the fixing roller 40 can keep the outer surface temperature of the fixing roller 40 constant even when the unfixed toner image carried on the coated paper or the thick paper is heated and fixed at high speed.

  The external heating unit 80 includes two hollow cylindrical heating rollers 81 and 82 as heating members, and an endless external heating belt 83 as an external heating member stretched around these heating rollers. The heating rollers 81 and 82 are long members in the longitudinal direction. The heating rollers 81 and 82 include halogen heaters 61 and 62 as heating sources, respectively.

  The outer peripheral surfaces (outer surfaces) of the heating rollers 81 and 82 are made of a metal cylindrical material such as a metal cylinder material such as aluminum, iron, or stainless steel having a high thermal conductivity, or a rubber or resin having high releasability. It is configured by coating the surface of a base layer (not shown). Flange (not shown) is fixed to both ends in the longitudinal direction of each of the heating rollers 81, 82, and each flange is a pair of fourth side plates A7, A8 of the fixing device 9 via a heat insulating bush having high heat resistance. Is rotatably supported. Halogen heaters 61 and 62 disposed at the rotation centers of the heating rollers 81 and 82 are fixedly supported by the flanges.

  Thermistors 31 and 32 as temperature detecting means for detecting the outer surface temperature of the heating roller are in contact with the outer surfaces of the heating rollers 81 and 82.

  The external heating belt 83 is a member that contacts the outer surface of the fixing roller 40 and heats the outer surface of the fixing roller. The external heating belt 83 has a base layer (not shown) made of a heat-resistant resin or a metal belt, and a release layer (not shown) made of a fluororesin formed on the outer surface of the base layer on the side in contact with the fixing roller 40. . The external heating belt 83 is stretched around heating rollers 81 and 82 to form a heating portion H together with the fixing roller 40. By stretching the external heating belt 44 on the heating rollers 81 and 82 in this way, it becomes possible to increase the width of the heating portion as compared with the case where the heating portion is formed only with these heating rollers, and the surface of the fixing roller 40 is moved. The higher-speed heating operation becomes possible.

(2-5) Contact / separation means 90
The structure of the contacting / separating means 90 will be described with reference to FIGS. The contact / separation means 90 includes a pair of cams 90a1 and 90a2 as contact / separation members, and a cam shaft 90b that connects these cams along the longitudinal direction of the fixing roller 40. The cams 90a1 and 90a2 are formed in an elliptical shape having a large diameter portion and a small diameter portion as shown in FIG. The cam shaft 90b is rotatably supported by the fourth side plates A7 and A8. A gear G3 is fixed to the longitudinal end of the cam shaft 90b, and this gear is rotated by a motor M3 as a third rotating means.

  The contact / separation means 90 presses the external heating belt 83 against the fixing roller 40 to bring the external heating belt and the fixing roller into a pressurized state (pressure contact state), and separates the external heating belt from the fixing roller to the external heating belt. The fixing roller is in a pressure release state (separated state). When heating the recording material P carrying the unfixed toner image t, the external heating belt 83 is pressed against the fixing roller 40 as shown in FIG. In the standby state of the fixing device 9, the external heating belt 83 is separated from the fixing roller 40 as shown in FIG. 6.

  When the external heating belt 83 is brought into pressure contact with the fixing roller 40, the motor M3 rotates the cam shaft 90b via the gear G3 and rotates the cams 90a1 and 90a2 from the position indicated by the alternate long and short dash line to the position indicated by the solid line (FIG. 3). Then, by rotating the cams 90a1 and 90a2, the bottom plate B2 between the side plates A7 and A8 is supported by the minimum diameter portions 90a11 and 90a21 of the cam while being lowered in the vertical direction perpendicular to the generatrix direction of the fixing roller 40. The outer surface is brought into pressure contact with the outer surface of the fixing roller. As a result, a heating portion H (see FIG. 2) having a predetermined width is formed between the outer surface of the external heating belt 83 and the outer surface of the fixing roller 40.

  In this embodiment, the heating portion H is formed by pressing the external heating belt 83 against the fixing roller 40 with a total pressure of about 78.4 N (about 8 kgf).

  When the external heating belt 83 is separated from the fixing roller 40, the motor M3 rotates the cam shaft 90b via the gear G3, and rotates the cams 90a1 and 90a2 from the position indicated by the solid line to the position indicated by the one-dot chain line (FIG. 3). As the cams 90a1 and 90a2 rotate, the bottom plate B1 is pushed up in the vertical direction perpendicular to the generatrix direction of the fixing roller 40 by the cam maximum diameter portions 90a12 and 90a22 to separate the outer surface of the external heating belt 83 from the outer surface of the fixing roller 40 (FIG. 5).

  In the fixing device 9 of the present embodiment, a photo sensor 75 as a detecting unit is disposed between the fixing roller 40 and the external heating belt 83 in order to detect the pressure contact state or the separation state between the fixing roller 40 and the external heating belt 83. (See FIG. 2). In the photosensor 75, when the light 75l emitted from the light emitting element 75a of the photosensor is not shielded by the external heating belt 83, the light receiving element 75b sends a high level signal (hereinafter referred to as H signal) to the rotation control circuit 71 described later. To output. The photo sensor 75 outputs a low level signal (hereinafter referred to as an L signal) to the rotation control circuit 71 when the light 75l emitted from the light emitting element 75a is blocked by the external heating belt 83. It has become.

(2-6) Heat-fixing processing operation The heat-fixing processing operation in the fixing device 9 of this embodiment will be described with reference to FIGS. 2, 4, and 5. Before the recording material P carrying the unfixed toner image t reaches the nip portion N, the control circuit 70 serving as a control means rotates the motor M2 to press the pressure roller 41 against the fixing roller 40 to thereby press the nip portion N. Form.

  Further, the control circuit 70 drives the motor M1 to rotate the fixing roller 40 in the arrow direction. The pressure roller 41 follows the rotation of the fixing roller 40 and rotates in the direction of the arrow.

  Next, the control circuit 70 energizes the halogen heaters 60, 61, 62 from an AC power source (not shown) through the thermo switch 20 as an energization cut-off member to turn on each halogen heater. The halogen heater 60 heats the fixing roller 40 from the inner surface side of the cored bar 40a. On the other hand, the halogen heater 61 heats the heating roller 81 from the inner surface side of the base layer, and the halogen heater 62 heats the heating roller 82 from the inner surface side of the base layer. These heating rollers 81 and 82 heat the external heating belt 83 from the inner surface side, whereby the external heating belt heats the fixing roller 40 from the outer surface side of the fixing roller.

  Next, the control circuit 70 adjusts the supply power (energization) to the halogen heater 60 so that the outer surface temperature of the fixing roller 40 detected by the thermistor 30 converges to a predetermined temperature control temperature (target temperature). The control circuit 70 controls the power supplied to the halogen heaters 61 and 62 (energization) based on the temperature information of the heating rollers 81 and 82 output from the thermistors 31 and 32, thereby adjusting the outer surface temperature of the heating rollers to a predetermined temperature. Adjust to temperature (target temperature).

  In the fixing device 9 of this embodiment, the temperature adjustment temperature of the fixing roller 40 is 170 ° C., and the temperature adjustment temperatures of the heating rollers 81 and 82 are equal to 200 ° C. That is, when the thermistor 30 detects a temperature higher than 170 ° C., the power supply to the halogen heater 60 is interrupted by the control circuit 70. When the thermistors 31 and 32 detect a temperature higher than 200 ° C., the power supply to the halogen heaters 61 and 62 is interrupted by the control circuit 70.

  The recording material P carrying the unfixed toner image t is introduced into the recording material passage region (see FIG. 4) of the nip portion N. The recording material P is nipped and conveyed at the nip portion N, and the heat of the fixing roller 40 and the pressure at the nip portion are applied to the unfixed toner image t, whereby the toner image is heated and fixed on the recording material. When the recording material P is discharged from the nip portion N, the fixing device 9 enters a standby state.

(2-7) Detection Procedure of Abnormal Temperature of Heating Rollers 81 and 82 at the End of Printing FIG. 6 shows a detection procedure of abnormal temperatures of the heating rollers 81 and 82 at the end of printing in the fixing device 9 of this embodiment.

  When the printing operation for one job of the image forming apparatus is completed (S101), the control circuit 70 determines that the external heating belt 83 and the fixing roller 40 are in a pressure contact state based on the L signal from the photosensor 75. The control circuit 70 rotates the motor M3 to separate the external heating belt 83 from the fixing roller 40. Further, the control circuit 70 stops the rotation drive of the motor M1 and stops the rotation of the fixing roller 40 (S102).

  Next, the control circuit 70 includes a detection temperature T (° C.) of the thermistors 31 and 32, a first abnormal temperature (220 ° C. in this embodiment) higher than the temperature control temperature of the heating rollers 81 and 82, Are compared (S103). When the detected temperature T is 220 ° C. or lower, the separated state between the external heating belt 83 and the fixing roller 40 is continued as a normal standby operation (S109). On the other hand, if the detected temperature T exceeds the first abnormal temperature 220 ° C., the process proceeds to S104.

  In S <b> 104, the control circuit 70 determines that the external heating belt 83 and the fixing roller 40 are in a separated state based on the H signal from the photosensor 75. The control circuit 70 rotationally drives the motor M 3 to press the external heating belt 83 against the fixing roller 40. Accordingly, the heat of the heating rollers 82 and 83 is transmitted from the external heating belt 83 to the fixing roller 40 through the heating unit H. That is, the amount of heat released from the heating rollers 82 and 83 is increased to reduce overshoot (temperature rise) of the external heating belt.

  Next, the control circuit 70 compares the detected temperature T with a return temperature lower than the first abnormal temperature and higher than the temperature adjustment temperature of the heating rollers 81 and 82 (in this embodiment, 215 ° C.). (S105). When the detected temperature T is equal to or lower than the return temperature 215 ° C., the control circuit 70 determines that the external heating belt 83 and the fixing roller 40 are in a pressure contact state based on the L signal from the photosensor 75. Then, the control circuit 70 drives the motor M3 to move the external heating belt 83 away from the fixing roller 40 (S107), and shifts to a normal standby operation (S109).

  On the other hand, when the detected temperature T exceeds the return temperature 215 ° C., the control circuit 70 determines the detected temperature T and a second abnormal temperature higher than the first abnormal temperature (230 ° C. in this embodiment). Are compared (S106). If the detected temperature T is equal to or lower than the second abnormal temperature 230 ° C., the process returns to S105. When the detected temperature T exceeds the second abnormal temperature 230 ° C., the control circuit 70 determines that this is an original error (S108), stops energization of the halogen heaters 61 and 62, and stops the heating operation by the halogen heater. To do.

  If the temperature exceeds 230 ° C., which is the second abnormal temperature, the external heating unit 50 and the thermistors 31 and 32 may be damaged due to high temperatures. Specifically, the external heating belt 83 may be deformed, or the thermistors 31 and 32 may fail. For this reason, it is desirable to set the second abnormal temperature below the heat resistance temperature of the fixing device to be applied.

  The first abnormal temperature is desirably set higher than the temperature control temperature of the heating rollers 81 and 82 and lower than the second abnormal temperature. Further, the return temperature is preferably higher than the temperature control temperature of the heating rollers 81 and 82 and lower than the first abnormal temperature. Furthermore, it is desirable that the second abnormal temperature is set lower than the operating temperature of the thermoswitch 20.

In the image forming apparatus equipped with the fixing device 9 of this embodiment, A3 size 350 g / cm ² thick paper carrying the unfixed toner image t as the recording material P is continuously passed through the nip portion N (continuously). Introduced). The maximum value of the detected temperature T (the overshoot temperature of the heating rollers 81 and 82) of the thermistors 31 and 32 immediately after the continuous paper passing was measured and found to be 226 ° C. For this reason, no error occurred and the printing operation could be continued.

  Further, assuming that the control circuit 70 is abnormal, the maximum power is continuously applied to the halogen heaters 61 and 62. When the detection temperature T of the thermistors 31 and 32 detects 230 ° C., the heating operation by the halogen heaters 61 and 62 is performed. Stopped. Even in this case, the external heating belt 83 and the thermistors 31 and 32 were not damaged by heat.

<Comparative example>
For the fixing device 9 of this embodiment, FIG. 7 shows a procedure for detecting abnormal temperatures of the heating rollers 81 and 82 at the end of printing in the fixing device of the first comparative example. FIG. 8 shows a procedure for detecting abnormal temperatures of the heating rollers 81 and 82 at the end of printing in the fixing device of the second comparative example. The fixing device of the present embodiment is different from the fixing device of the first comparative example and the fixing device of the second comparative example, except that the procedure for detecting the abnormal temperature of the heating rollers 81 and 82 at the end of printing is different. It has the same configuration as

  In the fixing device of the first comparative example shown in FIG. 7, when the printing operation of one job of the image forming apparatus is completed (S201), the control circuit 70 separates the external heating belt 83 from the fixing roller 40 by the contact / separation means 90. (S202). In S202, the control circuit 70 stops the rotation of the fixing roller 40.

  Thereafter, the control circuit 70 compares the detected temperature T of the thermistors 31 and 32 of the external heating unit 80 with the abnormal temperature (230 ° C. in the first comparative example) (S203). When the detected temperature T is 230 ° C. or lower, the normal standby operation is assumed (S205). If the detected temperature T exceeds 230 ° C., an error is determined (S204), and the heating operation of the external heating belt 83 by the halogen heaters 61 and 62 is stopped.

  In the fixing device of the second comparative example shown in FIG. 8, when the printing operation is completed (S301), the control circuit 70 separates the external heating belt 83 from the fixing roller 40 by the contact / separation means 90 (S302). In S302, the control circuit 70 stops the rotation of the fixing roller 40.

  Thereafter, the control circuit 70 compares the detected temperature T of the thermistors 31 and 32 of the external heating unit 80 with the abnormal temperature (240 ° C. in the second comparative example) (S303). When the detected temperature T is 240 ° C. or lower, the normal standby operation is assumed (S305). If the detected temperature T exceeds 240 ° C., an error is determined (S304), and the heating operation of the external heating belt 83 by the halogen heaters 61 and 62 is stopped.

In the image forming apparatus equipped with the fixing device of the first comparative example and the image forming apparatus equipped with the fixing device of the second comparative example, similarly to the image forming apparatus equipped with the fixing device of this embodiment, unfixed A3 size 350 g / cm ² thick paper carrying the toner image t was continuously passed. The maximum value of the detected temperature T (the overshoot temperature of the heating rollers 81 and 82) of the thermistors 31 and 32 immediately after continuous paper passing was measured and found to be 233 ° C. For this reason, in the image forming apparatus equipped with the fixing device of the first comparative example, although the printing operation ended normally, it was determined as an error and the printing operation could not be resumed.

  On the other hand, in the image forming apparatus equipped with the fixing device of the second comparative example, it was not determined that there was an error at the end of the printing operation, so the printing operation could be resumed.

  Further, similarly to the image forming apparatus equipped with the fixing device of the present embodiment, the maximum power is continuously applied to the halogen heaters 61 and 62 in consideration of the abnormality of the control circuit 70. Then, in the fixing device of the first comparative example, when the detection temperature T of the thermistors 31 and 32 detected 230 ° C., the heating operation by the halogen heaters 61 and 62 was stopped. At this time, the heating belt 83 and the thermistors 31 and 32 were not damaged by heat.

  On the other hand, in the fixing device of the second comparative example, when the detection temperature T of the thermistors 31 and 32 detected 240 ° C., the heating operation by the halogen heaters 61 and 62 was stopped. At this time, deformation of the heating belt 83 and failure of the thermistors 31 and 32 occurred.

  When the thermistors 31 and 32 detect the first abnormal temperature higher than the temperature control temperature of the heating rollers 81 and 82 in the separated state of the fixing roller 40 and the external heating belt 83, the fixing device 9 of the present embodiment The heating belt and the fixing roller are brought into a pressure contact state. By bringing the external heating belt 83 and the fixing roller 40 into a pressure contact state, the heat capacity and the heat radiation amount of the external heating belt can be increased. For this reason, even when the overheating of the external heating belt 83 heated by the halogen heaters 61 and 62 via the heating rollers 81 and 82 is large, an unnecessary high temperature error does not occur, and the apparatus is unexpected. Can be prevented.

  Further, the fixing device 9 of this embodiment separates the external heating belt from the fixing roller when the thermistors 31 and 32 detect the return temperature in the pressure contact state between the fixing roller 40 and the external heating belt 83. For this reason, since the pressure contact state between the fixing roller 40 and the external heating belt 83 is not maintained more than necessary during standby, the durability life of the fixing roller and the external heating belt can be extended.

  In the fixing device 9 of this embodiment, when the thermistors 31 and 32 detect the second abnormal temperature in the contact state between the fixing roller 40 and the external heating belt 83, the energization to the halogen heaters 61 and 62 is stopped. Stop the heating operation by the halogen heater. For this reason, power consumption can be reduced, and it can be avoided that the operation of the thermoswitch 20 is delayed due to an abnormal temperature rise.

[Example 2]
Another example of the fixing device 9 will be described. The fixing device 9 shown in the present embodiment has the same configuration as the fixing device of the first embodiment except that the detection procedure of the abnormal temperature of the heating rollers 81 and 82 at the end of printing in the fixing device 9 of the first embodiment is different. is there.

  FIG. 9 shows a procedure for detecting abnormal temperatures of the heating rollers 81 and 82 at the end of printing in the fixing device 9 of this embodiment.

  Since the processes of S401, S402, S403, and 409 are the same as S101, S102, S103, and S109 shown in FIG. 6, the description of S101, S102, S103, and S109 is used.

  In S404, the control circuit 70 determines that the external heating belt 83 and the fixing roller 40 are in a separated state based on the H signal from the photosensor 75. The control circuit 70 rotationally drives the motor M 3 to press the external heating belt 83 against the fixing roller 40. Furthermore, the control circuit 70 drives the motor M1 to start rotation of the fixing roller 40. Thereby, in the rotation state of the fixing roller 40, the external heating belt 83, and the heating rollers 82, 83, the heat of the heating rollers 82, 83 is transmitted from the external heating belt 83 to the fixing roller 40 through the heating unit H. Further, by rotating the fixing roller 40, the external heating belt 83, and the heating rollers 82, 83, the amount of heat released to the periphery of these members is increased, and the overshoot (temperature rise) of the external heating belt is reduced. Yes.

  Since the processes of S405 and S406 are the same as S105 and S106 shown in FIG. 6, respectively, the description of S105 and S106 is used.

  In step S <b> 407, the control circuit 70 determines that the external heating belt 83 and the fixing roller 40 are in a pressure contact state based on the L signal from the photosensor 75. The control circuit 70 rotates the motor M3 to separate the fixing roller 40 from the external heating belt 83. Further, the control circuit 70 stops the rotation of the motor M1 and stops the rotation of the fixing roller 40.

  In S408, the control circuit 70 determines that this is an original error, stops energization of the halogen heaters 61 and 62, and stops the heating operation by the halogen heater. Further, the control circuit 70 stops the rotation of the motor M1 and stops the rotation of the fixing roller 40.

In the image forming apparatus equipped with the fixing device 9 of this example, A3 size 350 g / cm ² thick paper carrying the unfixed toner image t as the recording material P was continuously passed through the nip portion N. The maximum value of the detected temperature T (the overshoot temperature of the heating rollers 81 and 82) of the thermistors 31 and 32 immediately after the continuous paper passing was measured and found to be 218 ° C. For this reason, no error occurred and the printing operation could be continued.

  Further, assuming that the control circuit 70 is abnormal, the maximum power is continuously applied to the halogen heaters 61 and 62. When the detection temperature T of the thermistors 31 and 32 detects 230 ° C., the heating operation by the halogen heaters 61 and 62 is performed. Stopped. Even in this case, the external heating belt 83 and the thermistors 31 and 32 were not damaged by heat.

  In the fixing device 9 of this embodiment, after the thermistors 31 and 32 detect the first abnormal temperature, the fixing roller, the external heating belt, and the heating rollers 81 and 82 are in a pressure contact state between the fixing roller 40 and the external heating belt 83. Rotates. By bringing the external heating belt 83 and the fixing roller 40 into a pressure contact state, the heat capacity of the external heating belt can be increased. Further, by rotating the fixing roller 40, the external heating belt 83, and the heating rollers 81 and 82, it is possible to increase the amount of heat dissipated around these members. For this reason, even when the overheating of the external heating belt 83 heated by the halogen heaters 61 and 62 via the heating rollers 81 and 82 is large, an unnecessary high temperature error does not occur, and the apparatus is unexpected. Can be prevented.

  In the fixing device 9 of this embodiment, after the thermistors 31 and 32 detect the first abnormal temperature, when the thermistors 31 and 32 detect the return temperature in the contact state between the fixing roller 40 and the external heating belt 83, Separate the fixing roller from the external belt. For this reason, the same effect as the fixing device 9 of the first embodiment can be obtained.

  In the fixing device 9 of the present embodiment, the thermistors 31 and 32 detect the first abnormal temperature, and then the thermistors 31 and 32 have the second abnormal temperature in the contact state between the fixing roller 40 and the external heating belt 83. When detected, the subsequent heating operation is stopped. For this reason, the same effect as the fixing device 9 of the first embodiment can be obtained.

  FIG. 10 shows a configuration for directly rotating the heating rollers 81 and 82. In the fixing device 9 of the present embodiment, the fixing roller 40 is rotated by the motor M1 and the heating rollers 81 and 82 are rotated indirectly, but the gear G fixed to the shaft portion 81a1 of the heating roller 81 as shown in FIG. May be directly rotated by a motor M4 as a fourth rotating means. In this case, in order to reduce the load on the motor M4, the gear G1 is fixed to the shaft portion 41a1 of the pressure roller 41, and the gear M1 is rotated by the motor M1.

[Example 3]
Another example of the fixing device 9 will be described. The fixing device 9 shown in this embodiment is different from the fixing device 9 of the first embodiment as follows.
1) Point excluding external heating unit 80 and contact / separation mechanism 90 2) Point where photo sensor 75 is arranged between fixing roller 40 and pressure roller 41 3) Detection target for detecting abnormal temperature at the end of printing The fixing device 9 of the present embodiment has the same configuration as the fixing device 9 of the first embodiment except for the above three points.

  FIG. 11 is a longitudinal center sectional view showing a schematic configuration of the fixing device 9 of the present embodiment. FIG. 12 is a diagram illustrating a state in which the pressure roller 41 is separated from the fixing roller 40 of the fixing device 9 according to the present exemplary embodiment.

  With reference to FIG. 11, the heat fixing processing operation of the fixing device 9 of this embodiment will be described. Before the recording material P carrying the unfixed toner image t reaches the nip portion N, the control circuit 70 rotates the motor M2, and presses the pressure roller 41 against the fixing roller 40 to form the nip portion N.

  Further, the control circuit 70 drives the motor M1 to rotate the fixing roller 40 in the arrow direction. The pressure roller 41 follows the rotation of the fixing roller 40 and rotates in the direction of the arrow.

  Next, the control circuit 70 energizes the halogen heater 60 from the AC power source (not shown) via the thermo switch 20 to turn on the halogen heater. The halogen heater 60 heats the fixing roller 40 from the inner surface side of the cored bar 40a.

  Next, the control circuit 70 adjusts the power supplied to the halogen heater 60 so that the outer surface temperature of the fixing roller 40 detected by the thermistor 30 converges to a predetermined temperature control temperature (target temperature).

  In the fixing device 9 of this embodiment, the temperature adjustment temperature of the fixing roller 40 is 170 ° C. That is, when the thermistor 30 detects a temperature higher than 170 ° C., the power supply to the halogen heater 60 is interrupted by the control circuit 70.

  The recording material P carrying the unfixed toner image t is introduced into the recording material passage region (see FIG. 4) of the nip portion N. The recording material P is nipped and conveyed at the nip portion N, and the heat of the fixing roller 40 and the pressure at the nip portion are applied to the unfixed toner image t, whereby the toner image is heated and fixed on the recording material. When the recording material P is discharged from the nip portion N, the fixing device 9 enters a standby state.

  FIG. 13 shows a procedure for detecting an abnormal temperature of the fixing roller 40 at the end of printing in the fixing device 9 of this embodiment.

  When the printing operation for one job of the image forming apparatus is completed (S501), the control circuit 70 determines that the pressure roller 41 and the fixing roller 40 are in a pressure contact state based on the L signal from the photosensor 75. Then, the control circuit 70 drives the motor M2 to move the pressure roller 41 away from the fixing roller 40 (see FIG. 12). Further, the control circuit 70 stops the rotation driving of the motor M1 and stops the rotation of the fixing roller 40 (S502).

  Next, the control circuit 70 compares the detected temperature T (° C.) of the thermistor 30 with the first abnormal temperature (in this embodiment, 220 ° C.) (S503). When the detected temperature T is 220 ° C. or lower, the separation state between the pressure roller 41 and the fixing roller 40 is continued as a normal standby operation (S509). On the other hand, if the detected temperature T exceeds the first abnormal temperature 220 ° C., the process proceeds to S504.

  In S504, the control circuit 70 determines that the pressure roller 41 and the fixing roller 40 are in a separated state based on the H signal from the photosensor 75. The control circuit 70 rotationally drives the motor M2 to press the pressure roller 41 against the fixing roller 40. As a result, the heat of the fixing roller 41 is transmitted to the pressure roller 41 through the nip portion N. That is, the heat release amount of the fixing roller 40 is increased, and the overshoot (temperature increase) of the fixing roller is reduced.

  Next, the control circuit 70 compares the detected temperature T with the return temperature (in this embodiment, 215 ° C.) (S505). When the detected temperature T is equal to or lower than the return temperature 215 ° C., the control circuit 70 determines that the pressure roller 41 and the fixing roller 40 are in a pressure contact state based on the L signal from the photosensor 75. Then, the control circuit 70 drives the motor M2 to move the pressure roller 41 away from the fixing roller 40 (S507), and shifts to a normal standby operation (S509).

  On the other hand, when the detected temperature T exceeds the return temperature 215 ° C., the control circuit 70 determines the detected temperature T and a second abnormal temperature higher than the first abnormal temperature (230 ° C. in this embodiment). Are compared (S506). If the detected temperature T is equal to or lower than the second abnormal temperature 230 ° C., the process returns to S505. When the detected temperature T exceeds the second abnormal temperature 230 ° C., the control circuit 70 determines that this is an original error (S508), stops energization of the halogen heater 60, and stops the heating operation by the halogen heater.

  When the thermistor 30 detects a first abnormal temperature higher than the temperature adjustment temperature of the fixing roller in the separated state between the pressure roller 41 and the fixing roller 40, the fixing device 9 of this embodiment And press. By bringing the pressure roller 41 and the fixing roller 40 into a pressure contact state, the heat capacity and the heat radiation amount of the fixing roller can be increased. For this reason, even when the overshoot of the fixing roller 40 heated by the halogen heater 60 is large, an unnecessary high temperature error does not occur, and the unexpected stop of the apparatus can be suppressed.

  In the fixing device 9 of this embodiment, when the thermistor 30 detects the return temperature in the contact state between the fixing roller 40 and the pressure roller 41 after the thermistor 30 detects the first abnormal temperature, the fixing roller 9 Separate the pressure rollers. For this reason, since the pressure contact state between the fixing roller 40 and the pressure roller 41 is not maintained more than necessary during standby, the durability life of the fixing roller and the pressure roller can be extended.

  Further, in the fixing device 9 of the present embodiment, after the thermistor 30 detects the first abnormal temperature, when the thermistor detects the second abnormal temperature in the contact state between the fixing roller 40 and the pressure roller 41, thereafter. Stop the heating operation. For this reason, power consumption can be reduced, and it can be avoided that the operation of the thermoswitch 20 is delayed due to an abnormal temperature rise.

[Example 4]
Another example of the fixing device 9 will be described. The fixing device 9 shown in the present embodiment has the same configuration as the fixing device of the third embodiment, except that the detection procedure of the abnormal temperature of the fixing roller 40 at the end of printing in the fixing device 9 of the third embodiment is different.

  FIG. 14 shows a procedure for detecting an abnormal temperature of the fixing roller 40 at the end of printing in the fixing device 9 of this embodiment.

  Since the processes of S601, S602, S603, and 609 are the same as S501, S502, S503, and 509 shown in FIG. 13, respectively, the description of S501, S502, S503, and S509 is cited.

  In S <b> 604, the control circuit 70 determines that the pressure roller 41 and the fixing roller 40 are in a separated state based on the H signal from the photosensor 75. The control circuit 70 rotationally drives the motor M2 to press the pressure roller 41 against the fixing roller 40. Furthermore, the control circuit 70 drives the motor M1 to start rotation of the fixing roller 40. Thereby, in the rotation state of the fixing roller 40 and the pressure roller 41, the heat of the fixing roller 40 is transmitted to the pressure roller 41 through the nip N. Further, by rotating the fixing roller 40 and the pressure roller 41, the amount of heat released to the periphery of these members is increased, and the overshoot (temperature increase) of the fixing roller is reduced.

  Since the processes of S605 and S606 are the same as S505 and S506 shown in FIG. 13, respectively, the description of S505 and S506 is cited.

  In S <b> 607, the control circuit 70 determines that the pressure roller 41 and the fixing roller 40 are in a pressure contact state based on the L signal from the photosensor 75. Then, the control circuit 70 drives and rotates the motor M <b> 2 to separate the pressure roller 41 from the fixing roller 40. Further, the control circuit 70 stops the rotation of the motor M1 and stops the rotation of the fixing roller 40.

  In S608, the control circuit 70 determines that the error is an original error, stops energization of the halogen heater 60, and stops the heating operation by the halogen heater. Further, the control circuit 70 stops the rotation of the motor M1 and stops the rotation of the fixing roller 40.

  In the fixing device 9 of the present embodiment, after the thermistor 30 detects the first abnormal temperature, the fixing roller 40 and the pressure roller 41 rotate in the pressure contact state between the pressure roller 41 and the fixing roller 40. By bringing the pressure roller 41 and the fixing roller 40 into a pressure contact state, the heat capacity of the fixing roller can be increased. Furthermore, the amount of heat released to the periphery of these members can be increased by rotating the pressure roller and the fixing roller. For this reason, even when the overshoot of the fixing roller 40 heated by the halogen heater 60 is large, an unnecessary high temperature error does not occur, and the unexpected stop of the apparatus can be suppressed.

  In the fixing device 9 of this embodiment, when the thermistor 30 detects the return temperature in the contact state between the fixing roller 40 and the pressure roller 41 after the thermistor 30 detects the first abnormal temperature, the fixing roller and the pressure are applied. Separate the rollers. For this reason, the same effect as the fixing device 9 of the third embodiment can be obtained.

  Further, in the fixing device 9 of the present embodiment, after the thermistor 30 detects the first abnormal temperature, when the thermistor detects the second abnormal temperature in the contact state between the fixing roller 40 and the pressure roller 41, thereafter. Stop the heating operation. For this reason, the same effect as the fixing device 9 of the third embodiment can be obtained.

[Example 5]
Another example of the fixing device 9 will be described. The fixing device 9 shown in this embodiment is different from the fixing device 9 of the first embodiment as follows.
1) A point in which an external heat radiation roller 85 as an external heat radiation member is used instead of the external heating unit 80 2) A point in which the external heat radiation roller 85 is pressed against or separated from the fixing roller 40 by using a contact / separation mechanism 90 2) External 4) The photo sensor 75 is disposed between the heat radiating roller 85 and the fixing roller 40. 4) The detection target for detecting the abnormal temperature at the end of printing is the fixing roller 40. The fixing device 9 of this embodiment has the above four points. Except for the fixing device 9 of the first embodiment.

  FIG. 15 is a longitudinal center sectional view showing a schematic configuration of the fixing device 9 of the present embodiment. FIG. 16 is a diagram illustrating a state in which the pressure roller 41 is separated from the fixing roller 40 of the fixing device 9 of the present exemplary embodiment and the external heat radiating roller 85 is in pressure contact with the fixing roller.

  The external heat radiation roller 85 is formed using a metal material having thermal conductivity. The external heat radiation roller 85 is a member that is long in the longitudinal direction, and the shaft portions on both sides in the longitudinal direction of the external heat radiation roller are rotatably supported by a pair of fourth side plates A7 and A8 (see FIG. 4) of the fixing device 9. .

  When the external heat dissipation roller 85 is brought into pressure contact with the fixing roller 40 by the contact / separation mechanism 90, the motor M3 rotates the cam shaft 90b via the gear G3, and the cams 90a1 and 90a2 (see FIG. 3) are moved from the position indicated by the one-dot chain line. Rotate to the position indicated by the solid line. Then, by rotating the cams 90a1 and 90a2, the bottom plate B2 between the side plates A7 and A8 is supported by the minimum diameter portions 90a11 and 90a21 of the cam while being lowered in the vertical direction perpendicular to the generatrix direction of the fixing roller 40. The outer peripheral surface (outer surface) is pressed against the outer surface of the fixing roller. As a result, a heat transfer pressure contact portion R (see FIG. 16) having a predetermined width is formed between the outer surface of the external heat radiating roller 85 and the outer surface of the fixing roller 40.

  When the external heat radiating roller 85 is separated from the fixing roller 40, the motor M3 rotates the cam shaft 90b via the gear G3 and rotates the cams 90a1 and 90a2 from the position indicated by the solid line to the position indicated by the alternate long and short dash line (FIG. 3). Then, by rotation of the cams 90a1 and 90a2, the bottom plate B1 is pushed up in the vertical direction perpendicular to the generatrix direction of the fixing roller 40 by the cam maximum diameter portions 90a12 and 90a22 to separate the outer surface of the external heat radiating roller 85 from the outer surface of the fixing roller 40 (FIG. 15).

  Since the heat fixing processing operation of the fixing device 9 of the present embodiment is the same as that of the fixing device 9 of the third embodiment, the description of the heat fixing processing operation of the fixing device 9 of the third embodiment is cited.

  FIG. 17 shows a procedure for detecting an abnormal temperature of the fixing roller 40 at the end of printing in the fixing device 9 of this embodiment.

  When the printing operation of one job of the image forming apparatus is completed (S701), the control circuit 70 determines that the external heat radiating roller 85 and the fixing roller 40 are in a pressure contact state based on the L signal from the photosensor 75. The control circuit 70 rotates the motor M3 to separate the fixing roller 40 and the external heat radiation roller 85 from each other. Further, the control circuit 70 stops the rotation of the motor M1 and stops the rotation of the fixing roller 40 (S702).

  Next, the control circuit 70 compares the detected temperature T (° C.) of the thermistor 30 with the first abnormal temperature (in this embodiment, 220 ° C.) (S703). When the detected temperature T is 220 ° C. or lower, the separated state between the external heat radiation roller 85 and the fixing roller 40 is continued as a normal standby operation (S709). On the other hand, if the detected temperature T exceeds the first abnormal temperature 220 ° C., the process proceeds to S704.

  In S <b> 704, the control circuit 70 determines that the external heat radiating roller 85 and the fixing roller 40 are in a separated state based on the H signal from the photosensor 75. The control circuit 70 rotationally drives the motor M3 to press-contact the fixing roller 40 and the external heat radiation roller 85. Thereby, the heat of the fixing roller 40 is transmitted to the external heat radiation roller 85 through the heat transfer pressure contact portion R. That is, the heat release amount of the fixing roller 40 is increased, and the overshoot (temperature increase) of the fixing roller is reduced.

  Next, the control circuit 70 compares the detected temperature T with the return temperature (in this embodiment, 215 ° C.) (S705). When the detected temperature T is equal to or lower than the return temperature 215 ° C., the control circuit 70 determines that the external heat radiating roller 85 and the fixing roller 40 are in a pressure contact state based on the L signal from the photosensor 75. Then, the control circuit 70 drives and rotates the motor M3 to separate the fixing roller 40 and the external heat radiation roller 85 (S707), and shifts to a normal standby operation (S709).

  On the other hand, when the detected temperature T exceeds the return temperature 215 ° C., the control circuit 70 determines the detected temperature T and a second abnormal temperature higher than the first abnormal temperature (230 ° C. in this embodiment). Are compared (S706). If the detected temperature T is equal to or lower than the second abnormal temperature 230 ° C., the process returns to S705. If the detected temperature T exceeds the second abnormal temperature 230 ° C., the control circuit 70 determines that this is an original error (S708), stops energization of the halogen heater 60, and stops the heating operation by the halogen heater.

  When the thermistor 30 detects the first abnormal temperature higher than the temperature adjustment temperature T in the separated state of the fixing roller 40 and the external heat dissipation roller 85, the fixing device 9 of the present embodiment connects the external heat dissipation roller and the fixing roller. Set to pressure contact. The heat transfer pressure contact portion R is formed by the external heat radiating roller 85 and the fixing roller 40, whereby the heat capacity and the heat radiation amount of the fixing roller 40 can be increased. For this reason, even when the overshoot of the fixing roller 40 heated by the halogen heater 60 is large, an unnecessary high temperature error does not occur, and the unexpected stop of the apparatus can be suppressed.

  In the fixing device 9 of this embodiment, when the thermistor 30 detects the return temperature in the contact state between the fixing roller 40 and the external heat radiation roller 85 after the thermistor 30 detects the first abnormal temperature, the fixing roller 9 Separate the heat dissipation roller. For this reason, since the pressure contact state between the fixing roller 40 and the external heat radiation roller 85 is not maintained more than necessary during standby, the durability life of the fixing roller and the external heat radiation roller 85 can be extended.

  In the fixing device 9 of this embodiment, when the thermistor 30 detects the second abnormal temperature in the contact state between the fixing roller 40 and the external heat radiation roller 85 after the thermistor 30 detects the first abnormal temperature, Subsequent heating operation is stopped. For this reason, power consumption can be reduced, and it can be avoided that the operation of the thermoswitch 20 is delayed due to an abnormal temperature rise.

[Example 6]
Another example of the fixing device 9 will be described. The fixing device 9 shown in the present embodiment has the same configuration as the fixing device of the fifth embodiment, except that the detection procedure of the abnormal temperature of the fixing roller 40 at the end of printing in the fixing device 9 of the fifth embodiment is different.

  FIG. 18 shows a procedure for detecting an abnormal temperature of the fixing roller 40 at the end of printing in the fixing device 9 of this embodiment.

  Since the processes of S801, S802, S803, and 809 are the same as S701, S702, S703, and S709 shown in FIG. 17, respectively, the description of S701, S702, S703, and S709 is cited.

  In step S804, the control circuit 70 determines that the external heat radiating roller 85 and the fixing roller 40 are in a separated state based on the H signal from the photosensor 75. The control circuit 70 rotationally drives the motor M3 to press the external heat radiation roller 85 against the fixing roller 40. Furthermore, the control circuit 70 drives the motor M1 to start rotation of the fixing roller 40. Thereby, in the rotation state of the fixing roller 40 and the external heat radiation roller 85, the heat of the fixing roller 40 is transmitted to the external heat radiation roller through the heat transfer pressure contact portion R. Further, by rotating the fixing roller 40 and the external heat radiating roller 85, the amount of heat radiated to the periphery of these members is increased, and the overshoot (temperature rise) of the fixing roller is reduced.

  Since the processes of S805 and S806 are the same as S705 and S706 shown in FIG. 17, respectively, the description of S705 and S706 is cited.

  In step S <b> 807, the control circuit 70 determines that the external heat radiating roller 85 and the fixing roller 40 are in a pressure contact state based on the L signal from the photosensor 75. The control circuit 70 rotates the motor M3 to separate the fixing roller 40 and the external heat radiation roller 85 from each other. Further, the control circuit 70 stops the rotation of the motor M1 and stops the rotation of the fixing roller 40.

  In S808, the control circuit 70 determines that this is an original error, stops energization of the halogen heater 60, and stops the heating operation by the halogen heater. Further, the control circuit 70 stops the rotation of the motor M1 and stops the rotation of the fixing roller 40.

  In the fixing device 9 of the present embodiment, after the thermistor 30 detects the first abnormal temperature, the external heat radiating roller 85 and the fixing roller 40 rotate in the pressure contact state between the fixing roller 40 and the external heat radiating roller 85. By bringing the external heat radiation roller 85 and the fixing roller 40 into a pressure contact state, the heat capacity of the fixing roller can be increased. Further, by rotating the fixing roller 40 and the external heat radiation roller 85, it is possible to increase the heat radiation amount to the surroundings of these members. For this reason, even when the overshoot of the fixing roller 40 heated by the halogen heater 60 is large, an unnecessary high temperature error does not occur, and the unexpected stop of the apparatus can be suppressed.

  Further, in the fixing device 9 of this embodiment, when the thermistor 30 detects the return temperature in the contact state between the fixing roller 40 and the external heat radiation roller 85 after the thermistor 30 detects the first abnormal temperature, the fixing roller and the external Separate the heat dissipation roller. For this reason, the same effect as that of the fixing device 9 of the fifth embodiment can be obtained.

  Further, in the fixing device 9 of this embodiment, after the thermistor 30 detects the first abnormal temperature, when the thermistor detects the second abnormal temperature in the contact state between the fixing roller 40 and the external heat radiation roller 85, the subsequent operation is performed. Stop the heating operation. For this reason, the same effect as that of the fixing device 9 of the fifth embodiment can be obtained.

  In the fixing device 9 of this embodiment, the fixing roller 40 is rotated by the motor M1 and the external heat radiating roller 85 is rotated indirectly. However, the gear fixed to the shaft (not shown) of the external heat radiating roller 85 is attached to the motor M4 ( You may make it rotate directly in FIG. In this case, in order to reduce the load on the motor M4, the gear G1 is fixed to the shaft portion 41a1 of the pressure roller 41, and the gear M1 is rotated by the motor M1.

[Other embodiments]
1) The image forming apparatus 100 on which the fixing devices 9 according to the first to sixth embodiments are mounted has the following configuration. After the second abnormal temperature continues for a predetermined time after the external heating belt of the fixing device and the fixing roller are shifted to the pressure contact state by the contact / separation means, image formation by the image forming unit is prohibited. .

  2) The image forming apparatus 100 on which the fixing devices 9 according to the first to sixth embodiments are mounted has the following configuration. After the external heating belt of the fixing device and the fixing roller are shifted to the pressure contact state by the contact / separation means, the detected temperature of the thermistor returns to the predetermined temperature control temperature of the heating roller within the predetermined time from the second abnormal temperature The image forming unit is allowed to form an image.

  3) In the fixing device 9 of each embodiment, the control circuit 70 responds to the outputs (output signals) of the thermistors 31 and 32 so that the outer surface temperature of the heating rollers 81 and 82 becomes a predetermined temperature control temperature (target temperature). The power supplied to the halogen heaters 61 and 62 is controlled. The thermistors 31 and 32 are not limited to the temperature detection of the heating rollers 81 and 82, and the outer surface temperature of the external conveyance belt may be detected by at least one thermistor. In accordance with the output (output signal) of the thermistor in the control circuit 70, the halogen heater 61, The power supplied to 62 may be controlled.

  4) The image heating device of the present invention is not limited to use as a fixing device in each embodiment, but is assumed to be a hypothetical fixing device that presupposes an unfixed toner image on a recording material, and reheats a recording material carrying a fixed toner image It is also effective as an image heating apparatus such as a surface modification apparatus for modifying the image surface properties such as the shine.

  5) The form of the first and second rotating bodies is not limited to the roller body, but may be another rotating body such as an endless belt body. In addition, the recording material member may be heated by another rotating body such as an endless belt that is in contact with a fixed or rotatable heating member. The external heating member may be only an external heating roller. Similarly, the pressure rotating body is not limited to the roller body, and may be in the form of another rotating body such as an endless belt body.

  6) As a heating source, not only a halogen heater but also a resistance heating element or an induction heating method may be used.

  7) The conditions for separating the external heating belt 83 and the fixing roller 40, the fixing roller 40 and the pressure roller 41, and the fixing roller 40 and the external heat radiation roller 85 are not limited to the end of the printing operation. For example, the present invention can be applied to all the separated conditions such as when the fixing device 9 is activated and when the printing operation is interrupted by each adjustment operation of the image forming apparatus 100.

30: Thermistor, 31, 32: Thermistor, 40: Fixing roller, 41: Pressure roller, 50: Pressure contact / separation means, 60: Halogen heater, 61, 62: Halogen heater, 70: Control circuit, 75: Photo sensor, 81, 82: heating roller, 83: external heating belt, 85: external heat radiation roller, 90: pressure contact / separation means, M1, M4: motor, P: recording material, t: unfixed toner image

Claims (21)

  First and second rotating bodies that heat a recording material carrying an image at a nip portion therebetween, an external heating member that contacts and heats the outer surface of the first rotating body, and the external heating member A heating source that heats the external heating member, contact / separation means that contacts and separates the external heating member and the first rotating body, and detection that detects a pressure contact state and a separation state of the external heating member and the first rotating body Means, temperature detecting means for detecting the temperature of the external heating member, and control means for controlling energization to the heating source in accordance with the output of the temperature detecting means so that the external heating member has a predetermined target temperature. An image heating apparatus comprising: a detecting unit that detects that the separated state is detected by the detecting unit; and that the temperature detecting unit detects that the external heating member has an abnormal temperature higher than the target temperature. If the previous Image heating apparatus, characterized in that shifting to the pressure contact state by moving means.   Rotating means for rotating the external heating member, the detecting means detecting that the separated state is detected, and the temperature detecting means is that the external heating member has an abnormal temperature higher than the target temperature. The image heating apparatus according to claim 1, wherein the rotation unit rotates the external heating member when detected.   After the temperature detection means detects the abnormal temperature, when the detection means detects the pressure contact state, the temperature detection means detects a return temperature that is lower than the abnormal temperature and higher than the target temperature. The image heating apparatus according to claim 1, wherein the contacting / separating unit separates the first rotating body and the external heating member.   After the temperature detection means detects the abnormal temperature, when the detection means detects the pressure contact state, if the temperature detection means detects an abnormal temperature higher than the abnormal temperature, the control means The image heating apparatus according to any one of claims 1 to 3, wherein energization to the heating source is stopped.   An image forming apparatus comprising: an image forming unit that forms an image on a recording material; and an image heating unit that heats an image formed on the recording material, wherein the image heating unit is any one of claims 1 to 4. An image forming apparatus according to claim 1.   After the transition to the pressure contact state by the contact / separation means of the image heating device, when an abnormal temperature higher than the abnormal temperature continues for a predetermined time, image formation by the image forming unit is prohibited. The image forming apparatus according to claim 5.   The image forming unit is allowed to form an image when the temperature is returned to the target temperature within a predetermined time after the transition to the pressure contact state by the contact / separation means of the image heating apparatus. The image forming apparatus according to claim 5 or 6.   First and second rotating bodies that heat a recording material carrying an image at a nip portion therebetween, a heating source that heats the first rotating body, the first rotating body, and the second rotation Contact / separation means for contacting / separating the body, detection means for detecting the pressure contact state and the separation state of the first rotating body and the second rotating body, and temperature for detecting the temperature of the first rotating body An image heating apparatus comprising: detection means; and control means for controlling energization to the heating source in accordance with an output of the temperature detection means so that the first rotating body has a predetermined target temperature, When the detection means detects that the separated state is detected, and the temperature detection means detects that the first rotating body has an abnormal temperature higher than the target temperature, the contact / separation is performed. The image is moved to the press-contact state by means of means. Apparatus.   A rotating unit that rotates the first rotating body, wherein the detecting unit detects the separated state, and the temperature detecting unit causes the first rotating body to have an abnormal temperature higher than the target temperature; The image heating apparatus according to claim 8, wherein the rotation unit rotates the first rotating body when it is detected that   After the temperature detection means detects the abnormal temperature, when the detection means detects the pressure contact state, the temperature detection means detects a return temperature that is lower than the abnormal temperature and higher than the target temperature. The image heating apparatus according to claim 8, wherein the contacting / separating unit separates the first rotating body and the second rotating body.   After the temperature detection means detects the abnormal temperature, when the detection means detects the pressure contact state, if the temperature detection means detects an abnormal temperature higher than the abnormal temperature, the control means The image heating apparatus according to any one of claims 8 to 10, wherein energization to the heating source is stopped.   An image forming apparatus comprising: an image forming unit that forms an image on a recording material; and an image heating unit that heats an image formed on the recording material, wherein the image heating unit is any one of claims 8 to 11. An image forming apparatus according to claim 1.   After the transition to the pressure contact state by the contact / separation means of the image heating device, when an abnormal temperature higher than the abnormal temperature continues for a predetermined time, image formation by the image forming unit is prohibited. The image forming apparatus according to claim 12.   The image forming unit is allowed to form an image when the temperature is returned to the target temperature within a predetermined time after the transition to the pressure contact state by the contact / separation means of the image heating apparatus. The image forming apparatus according to claim 12 or 13.   First and second rotating bodies that heat a recording material carrying an image at a nip portion therebetween, a heating source that heats the first rotating body, and an outer surface of the first rotating body An external heat radiating member for radiating heat of the first rotating body, contact / separation means for contacting and separating the external heat radiating member and the first rotating body, and the external heat radiating member and the first rotating body. Detection means for detecting the pressure contact state and the separation state, temperature detection means for detecting the temperature of the first rotating body, and output of the temperature detecting means so that the first rotating body has a predetermined target temperature. And a control means for controlling energization to the heating source in response to the detection of the separation state by the detection means and the first rotation by the temperature detection means. It is detected that the body has an abnormal temperature higher than the target temperature. If the, the image heating apparatus, characterized in that shifting to the pressed state by the moving means.   A rotating unit that rotates the first rotating body, wherein the detecting unit detects the separated state, and the temperature detecting unit causes the first rotating body to have an abnormal temperature higher than the target temperature; The image heating apparatus according to claim 15, wherein the rotation unit rotates the first rotating body when it is detected.   After the temperature detection means detects the abnormal temperature, when the detection means detects the pressure contact state, the temperature detection means detects a return temperature that is lower than the abnormal temperature and higher than the target temperature. The image heating apparatus according to claim 15, wherein the contacting / separating unit separates the first rotating body and the second rotating body.   After the temperature detection means detects the abnormal temperature, when the detection means detects the pressure contact state, if the temperature detection means detects an abnormal temperature higher than the abnormal temperature, the control means The image heating apparatus according to claim 15, wherein energization to the heating source is stopped.   An image forming apparatus comprising: an image forming unit that forms an image on a recording material; and an image heating unit that heats an image formed on the recording material, wherein the image heating unit is any one of claims 15 to 18. An image forming apparatus according to claim 1.   After the transition to the pressure contact state by the contact / separation means of the image heating device, when an abnormal temperature higher than the abnormal temperature continues for a predetermined time, image formation by the image forming unit is prohibited. The image forming apparatus according to claim 19.   The image forming unit is allowed to form an image when the temperature is returned to the target temperature within a predetermined time after the transition to the pressure contact state by the contact / separation means of the image heating apparatus. The image forming apparatus according to claim 19 or 20.