JP2010211093A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device and an image forming apparatus, wherein malfunction of an overheat preventing member according to overshoot of a heating element is never caused even when a main switch of an image forming apparatus body is off during printing operation or just after completion of printing operation, or even when carrying of a recording medium is stopped (jammed) during printing operation. <P>SOLUTION: The fixing device includes: the heating element 21 which is heated by receiving power supply from a first power source 61; the overheat preventing member 48 for interrupting the power supply from the first power source 61 when the temperature of the heating element 21 reaches a predetermined value; and a cooling means 50 which cools the preventing member 48. The cooling means 48 is operated only for a predetermined time, after the power supply from the first power source 61 is terminated or interrupted, by receiving power supply from a second power source 52 different from the first power source 61. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine thereof, and a fixing device installed therein, and more particularly, when a heating body is heated abnormally, The present invention relates to a fixing device and an image forming apparatus provided with an excessive temperature rise prevention member such as a thermostat for interrupting power supply.

  Conventionally, in an image forming apparatus such as a copying machine or a printer, there has been known a problem that a heating body of a fixing device overheats after a printing operation is completed (see, for example, Patent Document 1 and Patent Document 2). .)

Specifically, the fixing device is provided with a heating body (heating member) such as a heating roller heated by a heater, an electromagnetic induction heating device, or the like, and a fixing roller. In these fixing devices, during the printing operation (recording medium conveyance operation), the heating medium is deprived of heat by the recording medium via a fixing member such as a fixing belt and a fixing roller, so the temperature of the heating body is abnormal. It will never be expensive. However, immediately after the end of the printing operation, the heat transfer to the recording medium is suddenly stopped, so that the temperature of the heating body becomes abnormally high due to the heat accumulated in the core metal of the heating body ( This phenomenon is called “overshoot” after printing.)
In particular, such a problem is likely to occur immediately after the end of the continuous printing operation. Further, the higher the printing speed (CPM) of the image forming apparatus or the larger the basis weight of the recording medium to be conveyed, the more likely the problems described above occur.

On the other hand, conventionally, in a fixing device installed in an image forming apparatus such as a copying machine or a printer, the heating body rises abnormally in order to prevent thermal damage to the components of the fixing device due to overheating of the heating body. There is known a technique of installing an excessive temperature rise prevention member such as a thermostat for cutting off power supply from a power source to a heater when heated (see, for example, Patent Document 3).
Further, in Patent Document 3, for the purpose of causing the excessive temperature rise prevention member (over temperature rise prevention means) to function normally, the over temperature rise prevention member is cooled by the cooling means during normal heating operation, and the heating body Discloses a technique for stopping the operation of the cooling means when the temperature reaches a predetermined temperature.

In the conventional fixing device described above, when the main switch of the main body of the image forming apparatus is turned off during the printing operation or immediately after the completion of the printing operation, when the conveyance of the recording medium is stopped (jammed) during the printing operation, When a power failure occurs during or immediately after the end of the printing operation and power is not supplied to the image forming apparatus, an overshoot of the heating element may occur, which may cause the overheat prevention member to malfunction. It was.
In particular, in a recent fixing device in which the temperature rise efficiency of the heating body is increased by thinning the heating roller or adopting a heater having good rise characteristics, an excessive overheating temperature of the heating body is surely prevented. In many cases, the operating temperature of the temperature rise prevention member (thermostat) is set to be relatively low, and the malfunction of the excessive temperature rise prevention member at the time of overshooting described above is likely to occur.
If the above-described excessive temperature rise prevention member malfunctions during overshoot, the "down time" in which the image forming apparatus cannot be used without energizing the image forming apparatus until subsequent maintenance is performed by a service person. Has occurred.

  On the other hand, since the technique of Patent Document 3 described above is a technique that cools the excessive temperature rise prevention member by the cooling means during normal heating operation by supplying power from a power source that supplies power to the heater, the above-described problem is solved. I couldn't. That is, when the main switch of the image forming apparatus main body is turned off during the printing operation or immediately after the printing operation is completed, when the conveyance of the recording medium is stopped (jammed) during the printing operation, or during the printing operation or immediately after the printing operation is completed. When a power failure occurs and power is no longer supplied to the image forming apparatus, the cooling means cannot be operated, and the above-described excessive temperature rise prevention member malfunctions easily during overshoot. .

  The present invention has been made to solve the above-described problems. When the main switch of the image forming apparatus main body is turned off during the printing operation or immediately after the printing operation is completed, or the recording medium is conveyed during the printing operation. Even when the printer stops (jammed) or when power is not supplied to the image forming apparatus due to a power outage during printing operation or immediately after the printing operation is over, An object of the present invention is to provide a fixing device and an image forming apparatus in which a temperature rise prevention member does not malfunction.

  The fixing device according to the first aspect of the present invention is a fixing device that fixes a toner image on a recording medium, and is a heating body that is directly or indirectly heated by being supplied with electric power from a first power source. And an excessive temperature rise prevention member for cutting off power supply from the first power source when the temperature of the heating body reaches a predetermined value, and a cooling means for cooling the excess temperature rise prevention member. The cooling means is operated for a predetermined time after power is supplied from the second power source different from the first power source after the power supply from the first power source is terminated or interrupted.

  The fixing device according to a second aspect of the present invention is the fixing device according to the first aspect, wherein the cooling means operates when the operation of the apparatus is stopped.

  According to a third aspect of the present invention, in the fixing device according to the first or second aspect, the first power source is a commercial power source, and the second power source is connected to the image forming apparatus main body. The battery is installed in

  According to a fourth aspect of the present invention, in the fixing device according to the first or second aspect, the first power source is a commercial power source, and the second power source is connected to the image forming apparatus main body. And a rechargeable battery that is charged by the commercial power source.

  A fixing device according to a fifth aspect of the present invention is the fixing device according to any one of the first to fourth aspects, further comprising a temperature detecting means for detecting a temperature of the heating body, wherein the cooling means The operation is stopped when the temperature detected by the temperature detecting means falls below a predetermined value.

  A fixing device according to a sixth aspect of the present invention is the fixing device according to any one of the first to fifth aspects, further comprising a temperature detecting unit that detects a temperature of the heating body, and the cooling unit includes: The operation is started when the temperature detected by the temperature detection means becomes equal to or higher than a predetermined value A, and the operation is started when the temperature detected by the temperature detection means becomes equal to or higher than a predetermined value B greater than the predetermined value A. Is to stop.

  The fixing device according to a seventh aspect of the present invention is the fixing device according to any one of the first to sixth aspects, wherein the excessive temperature rise prevention member is a thermostat, and the cooling means is This is a cooling fan facing the thermostat.

  According to an eighth aspect of the present invention, there is provided a fixing device according to any one of the first to seventh aspects, wherein a fixing auxiliary roller and a heater electrically connected to the first power source are provided. A heating roller provided, a fixing belt stretched on the heating roller, and a pressure member that forms a nip portion that is pressed against the fixing auxiliary roller via the fixing belt to convey a recording medium, and The heating body is the heating roller or the fixing belt.

  An image forming apparatus according to a ninth aspect of the present invention includes the fixing device according to any one of the first to eighth aspects.

  In the present invention, after the power supply from the first power supply is terminated or interrupted, the cooling means is operated for a predetermined time by the power supply from the second power supply different from the first power supply to cool the excessive temperature rise prevention member. Yes. As a result, when the main switch of the image forming apparatus main body is turned off during the printing operation or immediately after the printing operation is finished, when the conveyance of the recording medium is stopped (jammed) during the printing operation, or during the printing operation or the printing operation is completed. Even when a power failure occurs immediately after the power is not supplied to the image forming apparatus, the overheating prevention member does not malfunction due to the overshoot of the heating body, and the fixing device, An image forming apparatus can be provided.

1 is an overall configuration diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. 2 is a configuration diagram illustrating a fixing device. FIG. 6 is a graph showing temperature fluctuations of the heating roller and the thermostat after the main switch of the image forming apparatus is turned off. It is a graph which shows the temperature fluctuation of a heating roller and a thermostat after turning off the main switch of the conventional image forming apparatus. 6 is a graph showing temperature fluctuations of a heating roller after a main switch of a conventional image forming apparatus is turned off. It is a graph which shows the temperature fluctuation of a heating roller and a thermostat when another control is performed. It is a graph which shows the temperature fluctuation of a heating roller and a thermostat when another control is performed. It is a block diagram which shows the fixing device in Embodiment 2 of this invention. It is a block diagram which shows the fixing device in Embodiment 3 of this invention. It is a block diagram which shows the fixing device in Embodiment 4 of this invention. It is a block diagram which shows the fixing device in Embodiment 5 of this invention. It is a block diagram which shows the fixing device in Embodiment 6 of this invention.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

Embodiment 1 FIG.
A first embodiment of the present invention will be described in detail with reference to FIGS.
First, the configuration and operation of the entire image forming apparatus will be described with reference to FIG.
In FIG. 1, reference numeral 1 denotes an apparatus main body of a tandem color copier as an image forming apparatus, 2 a writing unit that emits laser light based on input image information, and 3 an original conveying unit that conveys an original D to an original reading unit 4. 4 is a document reading unit that reads image information of the document D, 7 is a paper feeding unit that accommodates a recording medium P such as transfer paper, 9 is a registration roller that adjusts the conveyance timing of the recording medium P, and 11Y, 11M, and 11C. , 11BK are photosensitive drums on which toner images of respective colors (yellow, magenta, cyan, and black) are formed, 12 is a charging unit that charges the photosensitive drums 11Y, 11M, 11C, and 11BK, and 13 is each photosensitive drum. A developing unit that develops electrostatic latent images formed on 11Y, 11M, 11C, and 11BK, and a toner image formed on each of the photosensitive drums 11Y, 11M, 11C, and 11BK Transfer bias roller for transferring superimposed on the recording medium P (1 transfer bias roller), 15 denotes the photosensitive drums 11Y, 11M, 11C, cleaning unit for collecting the untransferred toner on 11BK, a.

  Reference numeral 16 denotes an intermediate transfer belt cleaning unit that cleans the intermediate transfer belt 17, 17 an intermediate transfer belt on which toner images of a plurality of colors are transferred and superimposed, and 18 a color toner image on the intermediate transfer belt 17 on the recording medium P. A secondary transfer bias roller 20 for transferring the toner image onto the recording medium P is a fixing device for fixing the toner image (unfixed image) on the recording medium P.

Hereinafter, an operation during normal color image formation in the image forming apparatus will be described.
First, the document D is transported from the document table in the direction of the arrow in the drawing by the transport rollers of the document transport unit 3 and placed on the contact glass 5 of the document reading unit 4. Then, the document reading unit 4 optically reads the image information of the document D placed on the contact glass 5.

  Specifically, the document reading unit 4 scans the image of the document D on the contact glass 5 while irradiating light emitted from an illumination lamp. Then, the light reflected by the document D is imaged on the color sensor via the mirror group and the lens. The color image information of the document D is read for each RGB (red, green, blue) color separation light by the color sensor, and then converted into an electrical image signal. Further, the image processing unit performs color conversion processing, color correction processing, spatial frequency correction processing, and the like based on the RGB color separation image signals to obtain yellow, magenta, cyan, and black color image information.

  Then, the image information of each color of yellow, magenta, cyan, and black is transmitted to the writing unit 2. The writing unit 2 emits laser light (exposure light) based on the image information of each color toward the corresponding photosensitive drums 11Y, 11M, 11C, and 11BK.

On the other hand, the four photosensitive drums 11Y, 11M, 11C, and 11BK are rotated clockwise in FIG. First, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK are uniformly charged at a portion facing the charging unit 12 (this is a charging process). Thus, a charged potential is formed on the photosensitive drums 11Y, 11M, 11C, and 11BK. Thereafter, the charged surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK reach the irradiation positions of the respective laser beams.
In the writing unit 2, laser light corresponding to the image signal is emitted from the four light sources corresponding to each color. Each laser beam passes through a separate optical path for each of the yellow, magenta, cyan, and black color components (this is an exposure process).

  Laser light corresponding to the yellow component is irradiated on the surface of the first photosensitive drum 11Y from the left side of the drawing. At this time, the yellow component laser light is scanned in the rotation axis direction (main scanning direction) of the photosensitive drum 11Y by a polygon mirror that rotates at high speed. Thus, an electrostatic latent image corresponding to the yellow component is formed on the photosensitive drum 11Y charged by the charging unit 12.

  Similarly, the laser beam corresponding to the magenta component is irradiated onto the surface of the second photosensitive drum 11M from the left side of the paper, and an electrostatic latent image corresponding to the magenta component is formed. The cyan component laser light is applied to the surface of the third photosensitive drum 11C from the left side of the paper, and an electrostatic latent image of the cyan component is formed. The black component laser beam is applied to the surface of the fourth photosensitive drum 11BK from the left side of the paper, and an electrostatic latent image of the black component is formed.

Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK on which the electrostatic latent images of the respective colors are formed reach positions facing the developing unit 13, respectively. Then, the respective color toners are supplied from the developing units 13 onto the photosensitive drums 11Y, 11M, 11C, and 11BK, and the latent images on the photosensitive drums 11Y, 11M, 11C, and 11BK are developed (development process). .)
Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK after the development process reach the facing portions of the intermediate transfer belt 17, respectively. Here, a transfer bias roller 14 is installed at each facing portion so as to contact the inner peripheral surface of the intermediate transfer belt 17. Then, the toner images of the respective colors formed on the photosensitive drums 11Y, 11M, 11C, and 11BK are sequentially superimposed and transferred onto the intermediate transfer belt 17 at the position of the transfer bias roller 14 (in the primary transfer process). is there.).

Then, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK after the transfer process reach positions facing the cleaning unit 15, respectively. Then, the untransferred toner remaining on the photosensitive drums 11Y, 11M, 11C, and 11BK is collected by the cleaning unit 15 (this is a cleaning process).
Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK pass through a neutralization unit (not shown), and a series of image forming processes on the photoconductive drums 11Y, 11M, 11C, and 11BK is completed.

On the other hand, the intermediate transfer belt 17 on which the toners of the respective colors on the photosensitive drums 11Y, 11M, 11C, and 11BK are transferred (carrying) are run in the clockwise direction in FIG. Reach the opposite position. Then, a color toner image carried on the intermediate transfer belt 17 is transferred onto the recording medium P at a position facing the secondary transfer bias roller 18 (secondary transfer step).
Thereafter, the surface of the intermediate transfer belt 17 reaches the position of the intermediate transfer belt cleaning unit 16. Then, the untransferred toner adhered on the intermediate transfer belt 17 is collected by the intermediate transfer belt cleaning unit 16, and a series of transfer processes in the intermediate transfer belt 17 is completed.

Here, the recording medium P transported between the intermediate transfer belt 17 and the secondary transfer bias roller 18 (secondary transfer nip) is transported from the paper supply unit 7 via the registration roller 9 and the like. It is a thing.
Specifically, the recording medium P fed by the paper feeding roller 8 from the paper feeding unit 7 that stores the recording medium P is guided to the registration roller 9 after passing through the conveyance guide. The recording medium P that has reached the registration roller 9 is conveyed toward the secondary transfer nip at the same timing.

Then, the recording medium P on which the full-color image is transferred is guided to the fixing device 20 by the transport belt. In the fixing device 20, the color image (toner) is fixed on the recording medium P at the nip between the fixing belt and the pressure roller.
Then, the recording medium P after the fixing step is discharged as an output image outside the apparatus main body 1 by a paper discharge roller, and a series of image forming processes is completed.
The image forming apparatus according to the first embodiment has a productivity of about 75 CPM when the conveyance speed (process linear speed) of the recording medium P is continuously about 352 mm / second and the A4-sized recording medium P is continuously conveyed in the horizontal direction. It is a high-speed machine set to.

Next, the configuration / operation of the fixing device 20 installed in the image forming apparatus main body 1 will be described in detail with reference to FIG.
As shown in FIG. 2, the fixing device 20 includes a fixing belt 21 as a heating body, a fixing auxiliary roller 22, a heating roller 23, a heater 25, a pressure roller 31 as a pressure member, and an excessive temperature rise prevention member (overtemperature rise). A thermostat 48 as a temperature preventing means), a cooling fan 50 as a cooling means, a temperature sensor 40 as a temperature detecting means, a separation plate 37, a guide plate 35, and the like.

Here, the fixing belt 21 (fixing member) as a heating body is an endless belt having a multilayer structure in which an elastic layer and a release layer are sequentially laminated on a base layer made of a resin material such as polyimide (perimeter is 70 mm). Is set to a degree.) The elastic layer of the fixing belt 21 is formed of an elastic material such as fluorine rubber, silicone rubber, or foamable silicone rubber. The release layer of the fixing belt 21 is made of PFA (tetrafluoroethylene bar fluoroalkyl vinyl ether copolymer resin) or the like. By providing the release layer on the surface layer of the fixing belt 21, the releasability (peelability) for the toner T (toner image) is ensured. The fixing belt 21 is stretched and supported by two roller members (a fixing auxiliary roller 22 and a heating roller 23), and travels in the direction of the arrow in FIG. The fixing belt 21 is supplied with power from a commercial power source 61 (commercial power source A) as a first power source and is indirectly heated. That is, the fixing belt 21 receives heat from the heating roller 23 heated by the radiant heat of the heater 25 supplied with power from the commercial power supply 61 and is heated.
By using the fixing belt 21 having a low heat capacity as the fixing member, the temperature rise characteristic of the apparatus is improved.

  The fixing auxiliary roller 22 is a roller member (an outer diameter is set to about 52 mm and a wall thickness is set to about 10 mm) in which an elastic layer 22b made of a foam material such as expandable silicone rubber is formed on a core metal 22a such as SUS304. And a nip portion is formed by contacting the pressure roller 31 as a pressure member via the fixing belt 21. By forming the elastic layer 22b from a foamed material, the nip width (nip amount) at the nip portion can be set relatively large, and the heat of the fixing belt 21 is difficult to transfer to the auxiliary fixing roller 22. The fixing auxiliary roller 22 rotates in the clockwise direction in FIG.

The heating roller 23 is a hollow roller member (cylindrical body) made of a metal material such as aluminum or stainless steel, and a heater 25 (heat source) is fixed inside the cylindrical body.
By setting the thickness of the heating roller 23 to 1 mm or less, the heat capacity is lowered and the temperature rise characteristic of the apparatus is improved (rise time is shortened). Here, the heating roller 23 in the first embodiment is made of aluminum, and has a thickness of 0.6 mm and an outer diameter of 35 mm.

The heater 25 (heating means) of the heating roller 23 is a halogen heater, and both ends thereof are fixed to a side plate (not shown) of the fixing device 20. Then, in a state where the main switch 62 of the image forming apparatus main body 1 is turned on, a control unit (apparatus main body control unit) 63 of the image forming apparatus main body 1 from the commercial power source 61 (commercial power source A) as the first power source, heater control Electric power is supplied to the heater 25 via the section 64. Then, the heating roller 23 is heated by the radiant heat from the heater 25 whose output is controlled by the heater control unit 64, and heat is further applied to the toner image T on the recording medium P from the surface of the fixing belt 21 heated by the heating roller 23. Added. That is, the fixing belt 21 and the heating roller 23 are indirectly heated by being supplied with electric power from the commercial power source 61 (first power source) (indirectly by the heater 25 supplied with electric power from the commercial power source 61. It will be heated.)
The output control of the heater 25 is performed based on the detection result of the belt surface temperature by the temperature sensor 40 (thermopile) as temperature detecting means that faces the surface of the fixing belt 21 in a non-contact manner. Specifically, the AC voltage is applied to the heater 25 for the energization time determined based on the detection result of the temperature sensor 40 as the temperature detecting means. By such output control of the heater 25, the temperature (fixing temperature) of the fixing belt 21 can be adjusted and controlled to a desired temperature (target control temperature).
Here, in the first embodiment, the heater 25 having a rated wattage of 1200 watts is used. Thus, by increasing the total wattage of the heater 25, the rise time (warming up time) of the apparatus can be shortened.

The pressure roller 31 as a pressure member mainly includes a cored bar 32 and an elastic layer 33 formed on the outer peripheral surface of the cored bar 32 via an adhesive layer. The elastic layer 33 of the pressure roller 31 is made of a material such as foamable silicone rubber, fluorine rubber, or silicone rubber. A thin release layer made of PFA or the like can be provided on the surface layer of the elastic layer 33.
The pressure roller 31 is pressed against the fixing auxiliary roller 22 via the fixing belt 21 by a pressure mechanism (not shown). In this way, a desired nip portion is formed between the pressure roller 31 and the fixing belt 21. In addition, the above-mentioned pressurization mechanism is comprised so that pressurization cancellation | release (or pressure reduction) can be performed.
In the first embodiment, a heater 34 is provided in the pressure roller 31 in order to improve the heating efficiency of the fixing belt 21. The output control of the heater 34 is performed based on the detection result of the temperature sensor 45 that detects the surface temperature of the pressure roller 31.

  In the fixing device according to the first embodiment, the control temperature of the heating roller 23 is set to 170 ° C. and the control temperature of the pressure roller 31 is set to 150 ° C. during standby (when operation is stopped). In addition, the set temperature of the heating roller 23 is set to 165 ° C. and the set temperature of the pressure roller 31 is set to 120 ° C. at the time of paper passing (during operation).

Referring to FIG. 2, guide plates 35 for guiding the conveyance of the recording medium P are respectively provided at the entrance side and the exit side of the contact portion (nip portion) between the fixing belt 21 and the pressure roller 31. It is arranged. The guide plate 35 is fixed to the side plate of the fixing device 20.
Further, a separation plate 37 is disposed in a position facing the outer peripheral surface of the fixing belt 21 and in the vicinity of the exit side of the nip portion. By installing the separation plate 37, it is possible to reduce a problem that the recording medium P after the fixing process is wound around the fixing belt 21 along the travel of the fixing belt 21.

The fixing device 20 configured as described above operates as follows.
When the main switch 62 of the apparatus main body 1 is turned on, an AC voltage is applied (powered) to the heater 25 from the commercial power supply 61 as the first power supply, and the fixing belt 21 (fixing auxiliary roller 22 and heating roller 23) and The pressure roller 31 starts to rotate in the direction of the arrow in FIG. The commercial power supply 61 is also a power supply source for devices other than the fixing device 20 installed in the image forming apparatus main body 1 (for example, an image forming unit, a paper feeding unit, a conveyance unit, etc.).
Thereafter, the recording medium P is fed from the paper supply unit 7 and the toners of the respective colors on the photosensitive drums 11Y, 11M, 11C, and 11BK are carried on the recording medium P as unfixed images. The recording medium P carrying the unfixed image T (toner image) is conveyed in the direction of the arrow Y10 in FIG. 2 and fed into the nip portion between the fixing belt 21 and the pressure roller 31 that are in a pressure contact state. The toner image T is fixed on the surface of the recording medium P by the heating by the fixing belt 21 and the pressing force of the fixing belt 21 (fixing auxiliary roller 22) and the pressure roller 31. Thereafter, the recording medium P sent out from the nip portion by the rotating fixing belt 21 and the pressure roller 31 is conveyed in the direction of the arrow Y11.

Hereinafter, the characteristic configuration and operation of the fixing device 20 according to the first embodiment will be described in detail.
Referring to FIG. 2, a thermostat 48 (non-contact type thermostat) as an excessive temperature rise prevention member is installed at a position facing the heating roller 23 with the fixing belt 21 interposed therebetween. This thermostat 48 (overheating prevention member) is used when the surface temperature of the fixing belt 21 (indirectly, the temperature of the heating roller 23) rises abnormally and reaches a predetermined value. This is for cutting off the power supply from the (first power source). Specifically, although illustration is omitted, the detected temperature of the thermostat 48 (overheating prevention member) is a predetermined value (the operating temperature, which is set to about 180 ° C. in the first embodiment). When it reaches, the electric circuit of the heater 25 is cut off.
In the first embodiment, the non-contact type thermostat 48 is used, but a contact type thermostat can also be used. In the first embodiment, the thermostat 48 is disposed at a position facing the heating roller 23 via the fixing belt 21, but the thermostat 48 directly faces (or contacts) the heating roller 23 (heating body). It can also be arranged in position.

Further, in the first embodiment, a cooling fan 50 is installed as a cooling means for cooling the thermostat 48 (overheating prevention member). A duct is provided in the vicinity of the cooling fan 50 (cooling means) so that the thermostat 48 can be efficiently cooled.
The cooling fan 50 includes a commercial power source 52 (commercial power source) as a second power source different from the commercial power source 61 (commercial power source A) as a first power source that is turned on / off by the main switch 62 of the image forming apparatus main body 1. Power is supplied from B) to operate. Specifically, after the power supply from the commercial power supply 61 as the first power supply is completed or interrupted, the cooling fan 50 is supplied with power from the commercial power supply 52 as the second power supply (separate power supply), and the fan control unit 51. The thermostat 48 is cooled by operating for a predetermined time (set to 60 seconds in the first embodiment).

  More specifically, when the main switch 62 of the image forming apparatus body 1 is turned off during the printing operation or immediately after the printing operation is completed, or when the conveyance of the recording medium P is stopped (jammed) during the printing operation, the image is displayed. The operation of the forming apparatus 1 (fixing apparatus 20) is stopped, and the power supply from the commercial power supply 61 as the first power supply to the apparatus main body control unit 63 is ended or interrupted. At this time, the energization to the heater control unit 64 is also terminated or interrupted, and the current sensor 65 detects the situation, and the fan control unit 51 is supplied with power by the commercial power source 52 as the second power source using the current sensor 65 as a trigger. The cooling fan 50 is operated via That is, after the operation of the image forming apparatus 1 (fixing apparatus 20) is stopped and the supply of power from the commercial power supply 61 as the first power supply is terminated or interrupted, the cooling fan 50 is activated and a predetermined temperature of the thermostat 48 is set. The cooling of the time is performed, and then the operation of the cooling fan 50 is stopped.

  With such a configuration and operation, when the main switch 62 of the image forming apparatus main body 62 is turned off during the printing operation or immediately after the printing operation is completed, or when the conveyance of the recording medium P is stopped (jammed) during the printing operation. Even if an overshoot of the heating roller 23 or the fixing belt 21 occurs (this is a phenomenon in which the temperature rises after the apparatus is stopped), the thermostat 48 is cooled by the cooling fan 50 for a predetermined time. Can be prevented from malfunctioning. If a malfunction of the thermostat 48 occurs, the apparatus is not defective due to overshoot, but the heater 25 circuit is shut off because the apparatus is defective. Until the image forming apparatus 1 is completed, downtime occurs.

FIG. 3 is a graph showing temperature fluctuations of the heating roller 23 and the thermostat 28 after the main switch 62 of the image forming apparatus 1 according to the first embodiment is turned off. FIG. 4 is a graph showing temperature fluctuations of the heating roller 23 and the thermostat 28 after the main switch of the conventional image forming apparatus (without the cooling fan 50) is turned off. 3 and 4 show the results of experiments conducted by the present inventors in order to confirm the effects described above.
3 and 4, the horizontal axis represents time, and the vertical axis represents temperature. In the figure, the solid line graph shows the temperature fluctuation of the heating roller 23, and the broken line graph shows the temperature fluctuation of the thermostat 48. The straight line indicated by the alternate long and short dash line is the operating temperature of the thermostat 48 (the temperature at which an abnormality is detected), and is set to about 180 ° C. That is, if the temperature of the thermostat 48 exceeds the operating temperature range indicated by the alternate long and short dash line after the main switch 62 is turned off (power off), the thermostat 48 malfunctions.
As shown in FIG. 3 and FIG. 4, overshoot of the heating roller 23 occurs after the power is turned off (paper feeding is stopped). As shown in FIG. 4, when the thermostat 48 is not cooled by the cooling fan 50, the thermostat 48 directly detects the temperature rise due to the overshoot of the heating roller 23, thereby increasing the temperature of the thermostat 48 itself. As a result, the temperature exceeded the operating temperature range indicated by the alternate long and short dash line, and the thermostat 48 malfunctioned. On the other hand, as shown in FIG. 3, when the thermostat 48 is cooled by the cooling fan 50 for a predetermined time (a range indicated by a double-headed arrow in the figure), the thermostat 48 is over the heating roller 23. Without directly detecting the temperature increase due to the chute, the temperature increase of the thermostat 48 itself is suppressed, and the temperature does not exceed the operating temperature range indicated by the alternate long and short dash line, thereby preventing the thermostat 48 from malfunctioning.

  FIG. 5 is a graph showing the temperature fluctuation of the heating roller 23 after the main switch 62 of the conventional image forming apparatus (with no cooling fan 50 installed) having a different printing speed (CPM) is turned off. It is. In FIG. 5, a graph Q1 shows a temperature fluctuation of the heating roller 23 in the image forming apparatus with a printing speed of 75 CPM, and a graph Q2 shows a temperature fluctuation of the heating roller 23 in the image forming apparatus with a printing speed of 40 CPM. From the result of FIG. 5, it can be seen that the effect of cooling the thermostat 48 by the cooling fan 50 described above is useful because the higher the speed of the image forming apparatus, the greater the degree of overshoot of the heating roller 23.

  As described above, the operation start timing of the cooling fan 50 is not triggered by the off signal of the main switch 62, but the current sensor 65 detects the stop of energization of the heater 25 and detects the detection signal. This is done using as a trigger. As a result, the conveyance of the recording medium P is stopped during the printing operation (jam) in addition to the case where the main switch 62 is turned off immediately after the printing operation is completed or the main switch 62 is forcibly turned off during the printing operation. Even in such a case, since the cooling fan 50 operates for a certain period of time to cool the thermostat 48, malfunction of the thermostat 48 due to overshoot of the heating roller 23 can be reliably prevented.

Here, in the control of the cooling fan 50 (cooling means) in the first embodiment, the temperature detected by the temperature sensor 40 (temperature detecting means) (the surface temperature of the fixing belt 21) becomes a predetermined value or less. In this case, the cooling fan 50 can be controlled to stop operating.
Specifically, energization of the heater 25 is stopped, and the temperature detected by the temperature sensor 40 exceeds a predetermined value (the temperature of the heating roller 23 is the temperature on the fixing belt 21 corresponding to 200 ° C.). If the thermostat 48 is malfunctioning due to overshoot, the cooling fan 50 is operated to cool the thermostat 48 for 60 seconds. On the other hand, the power supply to the heater 25 is stopped and the temperature detected by the temperature sensor 40 is equal to or lower than a predetermined value (the temperature on the fixing belt 21 corresponding to the temperature of the heating roller 23 of 200 ° C.). In such a case, the cooling of the thermostat 48 is stopped without operating the cooling fan 50, assuming that the overshoot is small and the thermostat 48 does not malfunction.

By performing such control, the cooling fan 50 is operated only when the thermostat 48 is in a malfunctioning state. Therefore, the thermostat is not consumed from the commercial power source 52 as the second power source. The effectiveness of preventing malfunctions of 48 can be enhanced.
FIG. 6 is a graph showing temperature fluctuations of the heating roller 23 and the thermostat 28 when such control is performed, and the components in the figure are the same as those in FIGS. 3 and 4 described above. In FIG. 6, a two-dot chain line S <b> 1 indicates the temperature (200 ° C.) of the heating roller 23, which is a threshold for operating / stopping the cooling fan 50. As shown in FIG. 6, when control is performed to idle the fixing device 20 for a predetermined time (for example, 200 seconds) after the paper is stopped, the heat of the heating roller 23 is fixed to the fixing belt 21 (idle driving). In other words, the overshoot of the heating roller 23 can be reduced. In such a case, since the temperature of the heating roller 23 does not easily reach the threshold value of 200 ° C., the operation of the cooling fan 50 is stopped by the control described above.
Here, the above-described control is performed by indirectly detecting the temperature of the heating roller 23 via the fixing belt 21 by the temperature sensor 40. On the other hand, it is also possible to perform the above-described control by installing a temperature detecting means at a position directly facing the heating roller 23 and directly detecting the temperature of the heating roller 23 by this temperature detecting means.

In the control of the cooling fan 50 (cooling means) in the first embodiment, the operation of the cooling fan 50 is started when the temperature detected by the temperature sensor 40 (temperature detecting means) becomes equal to or higher than the predetermined value A. The operation of the cooling fan 50 can also be controlled to stop when the temperature detected by the temperature sensor 40 exceeds a predetermined value B greater than the predetermined value A.
FIG. 7 is a graph showing temperature fluctuations of the heating roller 23 and the thermostat 28 when such control is performed when the control of the heater 25 runs out of control. 3 and 4 described in the above. In FIG. 7, a two-dot chain line S <b> 1 indicates the temperature (200 ° C.) of the heating roller 23 that becomes the first threshold value (predetermined value A) for operating / stopping the cooling fan 50, and a two-dot chain line S <b> 2 is the cooling fan 50. This shows the temperature (280 ° C.) of the heating roller 23 that becomes the second threshold value (predetermined value B) for the operation / stop of the. As shown in FIG. 7, when the energization sensor fails in the control circuit of the heater 25, it is determined that the heater 25 is not energized even though the heater 25 is actually energized. A “heater control runaway” occurs in which the lamp is lit continuously.
In such a case, as shown in FIG. 7, first, when the temperature of the heating roller 23 becomes equal to or higher than a predetermined value A (200 ° C.) after the paper feeding is stopped, the cooling fan 50 is operated and the thermostat 48 is temporarily turned on. The temperature drops. Thereafter, when the temperature of the heating roller 23 continues to rise due to the runaway of the heater control and the temperature of the heating roller 23 becomes equal to or higher than a predetermined value B (280 ° C.), the operation of the cooling fan 50 is stopped. Thereby, the abnormal temperature rise exceeding the range of the overshoot of the normal heating roller 23 is detected by the thermostat 48. Specifically, before the heating roller 23 reaches 450 ° C. (a temperature at which it is possible to sufficiently prevent problems such as ignition in the apparatus), the thermostat 48 is activated, Power supply is cut off.

  As described above, in the first embodiment, after the power supply from the commercial power supply 61 as the first power supply is terminated or interrupted, the power supply from the commercial power supply 52 as the second power supply different from the first power supply is performed. Thus, the cooling fan 50 (cooling means) is operated for a predetermined time to cool the thermostat 48 (overheating prevention member). Accordingly, even when the main switch 62 of the image forming apparatus main body 1 is turned off during the printing operation or immediately after the printing operation is finished, or even when the conveyance of the recording medium is stopped (jammed) during the printing operation, the heating roller 23 and the malfunction of the thermostat 48 due to the overshoot of the fixing belt 21 (heating member) can be suppressed.

Embodiment 2. FIG.
A second embodiment of the present invention will be described in detail with reference to FIG.
FIG. 8 is a configuration diagram illustrating the fixing device according to the second embodiment, and corresponds to FIG. 2 of the first embodiment. The second embodiment is that the battery 53 is used as the second power source for operating the cooling means 50, and the second commercial power source 52 is used as the second power source for operating the cooling means 50. This is different from Form 1.

  Similarly to the first embodiment, the fixing device 20 according to the second embodiment also has a fixing belt 21 (heating member), a fixing auxiliary roller 22, a heating roller 23, a heater 25, a pressure roller 31, and a thermostat 48 ( An excessive temperature rise prevention member), a cooling fan 50 (cooling means), a temperature sensor 40 (temperature detection means), and the like. Also in the second embodiment, the cooling fan 50 operates with power supplied from a second power source different from the commercial power source 61 as the first power source, and cools the thermostat 48 at a predetermined timing.

Here, in the second embodiment, a battery 53 that is replaceably installed in the image forming apparatus main body 1 is used as the second power source (separate power source). When the end or interruption of the energization of the heater 25 is detected, the cooling fan 50 is operated for 60 seconds by the power supply from the battery 53, and the thermostat 48 is cooled.
In particular, in the second embodiment, since the battery 53 is used as the second power source, a power failure occurs during the printing operation or immediately after the printing operation is finished, and power is not supplied to the image forming apparatus 1. In addition, the cooling fan 50 can be operated independently.

  As described above, in the second embodiment, after power supply from the commercial power supply 61 (first power supply) is terminated or interrupted, power supply from the battery 53 (second power supply) different from the commercial power supply 61 is performed. The cooling fan 50 (cooling means) is operated for a predetermined time to cool the thermostat 48 (overheating prevention member). Accordingly, when the main switch 62 of the image forming apparatus main body 1 is turned off during the printing operation or immediately after the printing operation is finished, when the conveyance of the recording medium is stopped (jammed) during the printing operation, or during the printing operation or the printing operation. Even when a power failure occurs immediately after the end of operation and power is not supplied to the image forming apparatus, the thermostat 48 malfunctions due to overshooting of the heating roller 23 and the fixing belt 21 (heating body). Can be suppressed.

Embodiment 3 FIG.
A third embodiment of the present invention will be described in detail with reference to FIG.
FIG. 9 is a configuration diagram illustrating the fixing device according to the third embodiment, and corresponds to FIG. 2 of the first embodiment. The third embodiment is different from the first embodiment in that a rechargeable battery 54 is used as a second power source for operating the cooling means 50.

  Similarly to the first embodiment, the fixing device 20 according to the third embodiment also has a fixing belt 21 (heating member), a fixing auxiliary roller 22, a heating roller 23, a heater 25, a pressure roller 31, and a thermostat 48 ( An excessive temperature rise prevention member), a cooling fan 50 (cooling means), a temperature sensor 40 (temperature detection means), and the like. Also in the third embodiment, the cooling fan 50 operates by being supplied with power from a second power source different from the commercial power source 61 as the first power source, and cools the thermostat 48 at a predetermined timing.

Here, in Embodiment 3, a rechargeable battery 54 (rechargeable battery) installed in the image forming apparatus main body 1 is used as the second power supply (separate power supply). The rechargeable battery 54 is a battery that can be charged by a commercial power supply 61. Specifically, when the capacity of the rechargeable battery 54 decreases, the rechargeable battery 54 is charged with electric power from the commercial power supply 61 via the charging device 55.
When the end or interruption of energization of the heater 25 is detected, the cooling fan 50 is operated for 60 seconds by the supply of power from the rechargeable battery 54, and the thermostat 48 is cooled.
In particular, in the third embodiment, since the rechargeable battery 54 is used as the second power source, power is not supplied to the image forming apparatus 1 due to a power failure during the printing operation or immediately after the end of the printing operation. Even if it exists, while being able to operate the cooling fan 50 independently, the replacement | exchange operation | work of a battery becomes unnecessary like the case where a normal battery is used as a 2nd power supply.

  As described above, in the third embodiment, the power from the rechargeable battery 54 (second power supply) different from the commercial power supply 61 after the power supply from the commercial power supply 61 (first power supply) is terminated or interrupted. By supplying, the cooling fan 50 (cooling means) is operated for a predetermined time to cool the thermostat 48 (overheating prevention member). Accordingly, when the main switch 62 of the image forming apparatus main body 1 is turned off during the printing operation or immediately after the printing operation is finished, when the conveyance of the recording medium is stopped (jammed) during the printing operation, or during the printing operation or the printing operation. Even when a power failure occurs immediately after the end of operation and power is not supplied to the image forming apparatus, the thermostat 48 malfunctions due to overshooting of the heating roller 23 and the fixing belt 21 (heating body). Can be suppressed.

Embodiment 4 FIG.
A fourth embodiment of the present invention will be described in detail with reference to FIG.
FIG. 10 is a configuration diagram illustrating the fixing device according to the fourth embodiment, and corresponds to FIG. 8 of the second embodiment. In the fourth embodiment, the fixing roller 230 is used as a fixing member, and the pressure pad 310 and the pressure belt 311 are used as pressure members. The fixing belt 21 is a fixing member. This is different from the second embodiment in which the pressure roller 31 is used as the pressure member.

  As shown in FIG. 10, the fixing device 20 according to the fourth embodiment includes a fixing roller 230 (fixing member) as a heating body, a heater 25, a pressure pad 310 (pressure member), and a pressure belt (pressure member). ), A reinforcing member 312, a thermostat 48 (overheating prevention member), a cooling fan 50 (cooling means), a temperature sensor (temperature detection means), and the like. Also in the fourth embodiment, the cooling fan 50 is supplied with electric power from a second power source (a battery 53 is used in the fourth embodiment) different from the commercial power source 61 as the first power source. The thermostat 48 is cooled at a predetermined timing.

Here, in the fourth embodiment, a fixing roller 230 is used as a fixing member. The fixing roller 230 is a roller member in which an elastic layer, a release layer, and the like are sequentially formed on a cored bar, and is rotated in a clockwise direction in FIG. 10 by a drive motor (not shown). A heater 25 is installed inside the fixing roller 230, and the fixing roller 230 as a heating body is heated by the radiant heat of the heater 25. A thermostat 48 as an excessive temperature rise prevention member is installed at a position facing the fixing roller 230.
A pressure pad 310 is brought into pressure contact with the fixing roller 230 via a pressure belt 311, so that a desired nip portion is formed between the members 230 and 310. The pressure pad 310 is held by the reinforcing member 312 without rotating, and the pressure belt 311 rotates counterclockwise in FIG. 10 by the frictional force with the fixing roller 230.

  As described above, also in the fourth embodiment, as in the second embodiment, after the power supply from the commercial power supply 61 (first power supply) is terminated or interrupted, the battery 53 ( By supplying power from the second power source), the cooling fan 50 (cooling means) is operated for a predetermined time to cool the thermostat 48 (overheating prevention member). Accordingly, when the main switch 62 of the image forming apparatus main body 1 is turned off during the printing operation or immediately after the printing operation is finished, when the conveyance of the recording medium is stopped (jammed) during the printing operation, or during the printing operation or the printing operation. Even when a power failure occurs immediately after the operation ends and power is no longer supplied to the image forming apparatus, the malfunction of the thermostat 48 due to the overshoot of the fixing roller 230 (heating member) is suppressed. Can do.

Embodiment 5 FIG.
A fifth embodiment of the present invention will be described in detail with reference to FIG.
FIG. 11 is a configuration diagram showing the fixing device according to the fifth embodiment, which corresponds to FIG. 8 of the second embodiment. In the fifth embodiment, the fixing film 240 is used as a fixing member and the ceramic heater 241 is used as a heating unit. The fixing belt 21 is used as a fixing member, and the heater 25 is a heating unit. This is different from the second embodiment in which is used.

  As shown in FIG. 11, the fixing device 20 according to the fifth embodiment includes a fixing film 240 (fixing member) as a heating body, a ceramic heater 241, a holding member 242, a pressure roller 31 (pressure member), and a thermostat 48. (Over temperature rise prevention member), cooling fan 50 (cooling means), temperature sensor (temperature detection means), and the like. Also in the fifth embodiment, the cooling fan 50 is supplied with electric power from a second power source (a battery 53 is used in the fifth embodiment) different from the commercial power source 61 as the first power source. The thermostat 48 is cooled at a predetermined timing.

Here, in the fifth embodiment, the fixing film 240 is used as the fixing member. The fixing film 240 is an endless film-like member having a single layer structure made of polyimide, polyamide, fluororesin, metal, or the like, and rotates in the clockwise direction in FIG. Inside the fixing film 240, a ceramic heater 241 that forms a nip portion by pressing against the pressure roller 31 through the fixing film 240 is installed. The ceramic heater 241 is held by a holding member 242 and is supplied with power from the commercial power supply 61. Then, the fixing film 240 as a heating body is heated by the ceramic heater 241. A thermostat 48 as an excessive temperature rise prevention member is installed at a position facing the fixing film 240.
The pressure roller 31 is rotated counterclockwise in FIG. 11 by a drive motor (not shown).

  As described above, also in the fifth embodiment, as in the second embodiment, after the power supply from the commercial power supply 61 (first power supply) is terminated or interrupted, the battery 53 ( By supplying power from the second power source), the cooling fan 50 (cooling means) is operated for a predetermined time to cool the thermostat 48 (overheating prevention member). Accordingly, when the main switch 62 of the image forming apparatus main body 1 is turned off during the printing operation or immediately after the printing operation is finished, when the conveyance of the recording medium is stopped (jammed) during the printing operation, or during the printing operation or the printing operation. Even when a power failure occurs immediately after the operation ends and power is no longer supplied to the image forming apparatus, the malfunction of the thermostat 48 due to the overshoot of the fixing film 240 (heating body) is suppressed. Can do.

Embodiment 6 FIG.
A sixth embodiment of the present invention will be described in detail with reference to FIG.
FIG. 12 is a configuration diagram showing the fixing device according to the sixth embodiment, which corresponds to FIG. 8 of the second embodiment. In the sixth embodiment, the fixing pad 250 that is pressed against the pressure roller 31 via the fixing belt 21 is used, and the auxiliary fixing roller 22 that is pressed against the pressure roller 31 via the fixing belt 21 is used. This is different from the second embodiment.

  As shown in FIG. 12, the fixing device 20 according to the sixth embodiment includes a fixing belt 21, a heating roller 23, a fixing pad 250, a heater 25, a pressure roller 31 (a pressure member), and a thermostat 48 (an excessive temperature rise prevention). Member), a cooling fan 50 (cooling means), a temperature sensor (temperature detection means), and the like. Also in the sixth embodiment, the cooling fan 50 is supplied with electric power from a second power source (a battery 53 is used in the sixth embodiment) different from the commercial power source 61 as the first power source. The thermostat 48 is cooled at a predetermined timing.

Here, in the sixth embodiment, the fixing belt 21 as a fixing member is stretched and supported by the heating roller 23 and the fixing pad 250. The fixing pad 250 has a sliding surface with the fixing belt 21 made of a low friction material, and is fixed to a side plate (not shown) of the fixing device 20. The fixing pad 250 is pressed against the pressure roller 31 via the fixing belt 21 to form a desired nip portion. A thermostat 48 as an excessive temperature rise prevention member is installed at a position facing the pressure roller 23 with the fixing belt 21 interposed therebetween.
The pressure roller 31 is rotated counterclockwise in FIG. 12 by a drive motor (not shown). As a result, the fixing belt 21 also travels in the direction of the arrow in the figure due to frictional resistance with the pressure roller 31.

  As described above, also in the sixth embodiment, as in the second embodiment, after the power supply from the commercial power supply 61 (first power supply) is terminated or interrupted, the battery 53 ( By supplying power from the second power source), the cooling fan 50 (cooling means) is operated for a predetermined time to cool the thermostat 48 (overheating prevention member). Accordingly, when the main switch 62 of the image forming apparatus main body 1 is turned off during the printing operation or immediately after the printing operation is finished, when the conveyance of the recording medium is stopped (jammed) during the printing operation, or during the printing operation or the printing operation. Even when a power failure occurs immediately after the end of operation and power is not supplied to the image forming apparatus, the thermostat 48 malfunctions due to overshooting of the heating roller 23 and the fixing belt 21 (heating body). Can be suppressed.

In each of the embodiments described above, the present invention is applied to the fixing device 20 that heats the heating body using the heater 25 or the ceramic heater 241, but the fixing device that heats the heating body by electromagnetic induction heating is used. Of course, the present invention can be applied. Even in that case, substantially the same effect as the present embodiment can be obtained.
In each of the above embodiments, the cooling fan 50 is installed in the fixing device 20, but the cooling fan 50 can be installed on the apparatus main body 1 side.
Further, in each of the above embodiments, the cooling fan 50 is used as a cooling means for cooling the heating body. However, the cooling means is not limited to this, and for example, heat that operates so as to be able to contact with and separate from the thermostat 48. A pipe or the like can also be used. Also in that case, the effect similar to each said embodiment can be acquired by performing the operation | movement (contact / separation operation | movement) of the heat pipe with respect to the thermostat 48 with a 2nd power supply.

  It should be noted that the present invention is not limited to the above-described embodiments, and within the scope of the technical idea of the present invention, the embodiments can be modified as appropriate in addition to those suggested in the embodiments. Is clear. In addition, the number, position, shape, and the like of the constituent members are not limited to the above embodiments, and can be set to a number, position, shape, and the like that are suitable for carrying out the present invention.

1 image forming apparatus body (apparatus body),
20 fixing device,
21 fixing belt,
22 fixing auxiliary roller,
23 Heating roller,
25, 34 heater,
31 Pressure roller (pressure member),
40 Temperature sensor (temperature detection means),
48 thermostat (over temperature prevention member),
50 cooling fan (cooling means),
52 second commercial power source (second power source),
53 battery (second power supply), 54 rechargeable battery (second power supply),
61 Commercial power supply (first power supply), P recording medium.

JP 2006-119430 A Japanese Patent Laid-Open No. 2005-37539 JP 2006-172781 A

Claims (9)

A fixing device for fixing a toner image on a recording medium,
A heating element that is directly or indirectly heated by power supplied from the first power source;
An excessive temperature rise prevention member for cutting off the power supply from the first power supply when the temperature of the heating body reaches a predetermined value;
A cooling means for cooling the overheating prevention member;
With
The fixing device is characterized in that, after the power supply from the first power source is completed or interrupted, the cooling unit is operated for a predetermined time with power supplied from a second power source different from the first power source.   The fixing device according to claim 1, wherein the cooling unit is activated when the operation of the apparatus is stopped. The first power source is a commercial power source,
The fixing device according to claim 1, wherein the second power source is a battery installed in the main body of the image forming apparatus. The first power source is a commercial power source,
The fixing device according to claim 1, wherein the second power source is a rechargeable battery that is installed in a main body of the image forming apparatus and is charged by the commercial power source. Temperature detecting means for detecting the temperature of the heating body,
The fixing device according to claim 1, wherein the cooling unit stops operation when a temperature detected by the temperature detection unit becomes a predetermined value or less. Temperature detecting means for detecting the temperature of the heating body,
The cooling means starts operation when the temperature detected by the temperature detecting means reaches a predetermined value A or higher, and the temperature detected by the temperature detecting means becomes equal to or higher than a predetermined value B greater than the predetermined value A. The fixing device according to any one of claims 1 to 5, wherein the operation is stopped when it becomes. The excessive temperature rise prevention member is a thermostat,
The fixing device according to claim 1, wherein the cooling unit is a cooling fan facing the thermostat. A fixing auxiliary roller, a heating roller in which a heater electrically connected to the first power source is provided, a fixing belt stretched around the fixing roller,
A pressure member that forms a nip portion to which the recording medium is conveyed in pressure contact with the fixing auxiliary roller via the fixing belt;
With
The fixing device according to claim 1, wherein the heating body is the heating roller or the fixing belt.   An image forming apparatus comprising the fixing device according to claim 1.

Images