JP5044789B2 - Fixing apparatus, image forming apparatus, fixing method, and image forming method - Google Patents

Description

  The present invention relates to a fixing device provided in an image forming apparatus such as a copying machine, a facsimile machine, a printer, and the like, and provided with a plurality of heat generating means for generating heat by receiving power supply from a commercial power source and an auxiliary power source charged thereby. The present invention relates to such an image forming apparatus, a fixing method using such a plurality of heating means, and an image forming method using these.

  2. Description of the Related Art Image forming apparatuses such as copying machines, facsimile machines, and printers are known that include a fixing device for fixing a toner image on a sheet of paper or the like on which a toner image as a fixed image is formed.

  The fixing device has a heating roller that is rotationally driven and a pressure roller that is pressed against the heating roller and is driven to rotate by the heating roller, and a sheet is fed to the nip formed by both rollers by the rotation of both rollers. A so-called roller pair type fixing device that passes and heat-presses to fix the toner image, an endless fixing belt, a heating roller and a fixing roller around which the fixing belt is wound, and the fixing roller via the fixing belt. The pressure roller or the like is a constituent element, and the sheet is passed through the nip formed by the fixing belt and the pressure roller by the rotation of the fixing belt and the pressure roller, and the toner image is fixed by heating and pressing. A so-called belt-type fixing device is known.

  As described in [Patent Document 1] to [Patent Document 5], the heating roller has a heater for heating the sheet, and the temperature is increased by the heat generated by the heater. Yes. Such heaters are known to have a plurality of configurations as described in [Patent Document 1] to [Patent Document 5] for various purposes. In the fixing device described in [1] to [Patent Document 3], for the purpose of quickly increasing the temperature of the heating roller, etc., a commercial power source and an auxiliary power source charged thereby are used for power supply to a plurality of heaters. Used.

  The fixing devices described in [Patent Document 1] and [Patent Document 2] have a plurality of heaters having different heat generation distributions in the sheet width direction, and adjust the temperature distribution of the heating roller in the sheet width direction. Is possible.

  Specifically, the fixing device described in [Patent Document 1] includes a plurality of heaters that are supplied with electric power by a commercial power source, and these heaters have different heat generation distributions in the width direction of the sheet. The fixing device described in Patent Document 2 includes a plurality of heaters that are supplied with power by an auxiliary power source, and these heaters have different heat generation distributions in the sheet width direction.

JP 2003-084221 A JP 2004-095525 A Japanese Patent Laying-Open No. 2005-092186 JP 63-280283 A Japanese Patent No. 3492820

  However, it is preferable that the heaters supplied with power by the commercial power supply and the heaters supplied with power by the auxiliary power supply have different heat generation distributions in the sheet width direction.

  The present invention relates to a fixing device which is a plurality of heat generating means that generate heat by receiving power supply from a commercial power source and an auxiliary power source charged thereby, and each of the fixing devices has different heat generation distributions in the width direction of the sheet. It is an object of the present invention to provide an image forming apparatus such as a copying machine, a facsimile, or a printer provided with the apparatus, a fixing method using such a plurality of heat generating means, and an image forming method using these.

In order to achieve the above object, according to the first aspect of the present invention, there is provided a first heat generating means for generating heat by receiving power from a commercial power source, and a second for generating heat by receiving power from an auxiliary power source charged by the commercial power source. Heat generating means, temperature detecting means for detecting the temperature of the first heat generating means and the second heat generating means, and the first heat generating means and the second heat generating means based on the temperature detected by the temperature detecting means. And a first heating unit and a second heating unit that have different heat generation distributions in the width direction of the sheet, respectively, in the fixing device that fixes the image on the sheet. The second heat generating unit has a built-in electric double layer capacitor, and the auxiliary power source is charged by a commercial power source, or the second heat generating unit is provided by the auxiliary power source. Electric power A switching means for switching between supply and supply, the target detection temperature Ta in the first heat generation means and the target detection temperature Tb in the second heat generation means are in a relationship of Ta> Tb, and during standby, The temperature detected by the temperature detection means by switching the power supply to the first heat generation means in a state where the power supply to the second heat generation means is stopped by the switching means and the auxiliary power supply is charged. When the sheet passing is started while keeping between Ta and the detected temperature Tb, power is supplied to the first heat generating means, and power supply to the second heat generating means is started by the switching means. The temperature detected by the temperature detecting means before the elapse of the time for shutting off the same power supply determined according to the amount of decrease due to the elapse of time of power supply from the first to the second heat generating means is the detected temperature. Once the temperature falls below Tb and reaches the same detection temperature Tb, the switching means stops power supply to the second heat generation means and charges the auxiliary power supply. After that, the temperature detection means detects the passage of paper. When the detected temperature is equal to or higher than the detected temperature Tb, the temperature detected by the temperature detecting means is maintained between the detected temperature Ta and the detected temperature Tb by switching the power supply to the first heat generating means, Only when the temperature detected by the temperature detecting means falls below the detected temperature Tb, the switching means supplies power to the second heat generating means .

  According to a second aspect of the present invention, in the fixing device according to the first aspect, a plurality of the temperature detecting means are disposed at different positions in the width direction of the sheet.

  According to a third aspect of the present invention, in the fixing device according to the second aspect, the plurality of heat generating portions include a central heat generating portion having a heat generation distribution biased toward a central portion in the width direction of the sheet, and an end portion in the width direction of the sheet. The temperature detecting means is provided in correspondence with the central temperature detecting means and the edge heat generating section. And an end temperature detecting means.

  According to a fourth aspect of the present invention, in the fixing device according to the third aspect, the control unit determines a ratio of power supply from the auxiliary power source to each of the plurality of heat generating units provided in the second heat generating unit. The center temperature detecting means is changed according to the difference between the target detected temperature and the actual detected temperature, and the difference between the target detected temperature and the actual detected temperature in the end temperature detecting means, To do.

  According to a fifth aspect of the present invention, in the fixing device according to any one of the first to fourth aspects, the control unit is configured such that the width of the sheet for fixing the image is the first heat generation unit and the second heat generation unit. When the width is smaller than the width, power is supplied to only the heat generating portions corresponding to the sheet passing region among the plurality of heat generating portions provided in the first heat generating means and the second heat generating means to generate heat. Features.

According to a sixth aspect of the present invention, in the fixing device according to any one of the first to fifth aspects, the auxiliary power source is switched to the auxiliary power source when the switching unit is switched to charge the auxiliary power source with a commercial power source. It has a charging means for charging the electric double layer capacitor by adjusting the voltage of the power supplied from the commercial power source to the auxiliary power source and rectifying from AC to DC .

  A seventh aspect of the present invention is an image forming apparatus having the fixing device according to any one of the first to sixth aspects.

According to an eighth aspect of the present invention, there is provided a first heat generating means for generating heat by receiving power supply from a commercial power source, a second heat generating means for generating heat by receiving power supply from an auxiliary power source charged by the commercial power source, Temperature detecting means for detecting the temperatures of the heat generating means and the second heat generating means, and the power supply to the first heat generating means and the second heat generating means is controlled based on the temperature detected by the temperature detecting means. In the fixing method for fixing an image on a sheet using a control unit, each of the first heat generating unit and the second heat generating unit includes a plurality of heat generating portions having different heat generation distributions in the sheet width direction. The second heat generating means incorporates an electric double layer capacitor, and switches between charging the auxiliary power supply with a commercial power supply or supplying power to the second heat generating means with the auxiliary power supply. Using the switching means, the target detection temperature Ta in the first heat generation means and the target detection temperature Tb in the second heat generation means are in a relationship of Ta> Tb. The temperature detected by the temperature detection means by switching the power supply to the first heat generation means in a state where the power supply to the heat generation means is stopped and the auxiliary power supply is charged is detected temperature Ta and the detection temperature Tb. When the sheet passing is started, power is supplied to the first heat generating means, and power supply to the second heat generating means is started by the switching means, and the second heat generating means is supplied from the auxiliary power source. After the temperature detected by the temperature detecting means once falls below the detected temperature Tb before the time for shutting off the same power supply determined according to the amount of decrease due to the time of power supply to the When the detected temperature Tb is reached, the switching means stops power supply to the second heat generating means and charges the auxiliary power source. During the subsequent sheet passing, the temperature detected by the temperature detecting means is the detected temperature. When the temperature is equal to or higher than Tb, the temperature detected by the temperature detecting means is maintained between the detected temperature Ta and the detected temperature Tb by switching the power supply to the first heat generating means, and is detected by the temperature detecting means. Only when the temperature falls below the detected temperature Tb, the switching means supplies power to the second heat generating means .

  According to a ninth aspect of the present invention, an image is formed by using the fixing device according to any one of the first to sixth aspects, the image forming apparatus according to the seventh aspect, or the fixing method according to the eighth aspect. There is an image forming method to be performed.

The present invention includes a first heat generating unit that generates heat upon receiving power supply from a commercial power source, a second heat generating unit that generates heat upon receiving power supply from an auxiliary power source charged by the commercial power source, Temperature detecting means for detecting the temperature of the second heat generating means, and control means for controlling power supply to the first heat generating means and the second heat generating means based on the temperature detected by the temperature detecting means. A fixing device for fixing an image on a sheet, wherein each of the first heat generating means and the second heat generating means includes a plurality of heat generating portions having different heat distributions in the width direction of the sheet , The second heat generating means has a built-in electric double layer capacitor, and switching means for switching between charging the auxiliary power source with a commercial power source or supplying power to the second heat generating unit with the auxiliary power source. The target detection temperature Ta in the first heat generation means and the target detection temperature Tb in the second heat generation means have a relationship of Ta> Tb, and the second heat generation means is set by the switching means during standby. The temperature detected by the temperature detection means between the detection temperature Ta and the detection temperature Tb by switching the power supply to the first heat generation means in a state where the power supply to the auxiliary power supply is stopped and the auxiliary power supply is charged. When the sheet passing is started, power is supplied to the first heat generating means, and power supply to the second heat generating means is started by the switching means, and power from the auxiliary power source to the second heat generating means is started. The temperature detected by the temperature detection means once falls below the detection temperature Tb before the passage of time for shutting off the same power supply determined according to the amount of decrease due to the passage of the supply time, and then the detection temperature T Is reached, the power supply to the second heat generating means is stopped by the switching means, and the auxiliary power supply is charged. During the subsequent sheet passing, the temperature detected by the temperature detecting means is equal to or higher than the detected temperature Tb. In some cases, the temperature detected by the temperature detecting means is kept between the detected temperature Ta and the detected temperature Tb by switching the power supply to the first heat generating means, and the temperature detected by the temperature detecting means is because and performs power supply to the second heat generating means by said switching means only when below the detection temperature Tb, it is possible to heat the appropriate heating unit according to the size of the sheet, also auxiliary It is possible to efficiently supply power from the power source and suppress or prevent heating due to excessive power supply to the first heat generating means and the second heat generating means. In addition, it is possible to provide a fixing device that can reduce wasteful power consumption and obtain an energy saving effect and can perform good fixing.

  If a plurality of the temperature detection means are arranged at different positions in the width direction of the sheet, it is possible to perform high-precision control to generate heat from an appropriate heat generating part according to the sheet size, and wasteful power consumption It is possible to provide a fixing device that can obtain an energy saving effect by further reducing the image quality and can perform better fixing.

  The plurality of heat generating portions include a central heat generating portion having a heat generation distribution biased toward a central portion in the width direction of the sheet, and an end heat generating portion having a heat generation distribution biased to an end portion in the width direction of the sheet, If the detecting means includes a central temperature detecting means provided corresponding to the central heat generating part and an end temperature detecting means provided corresponding to the end heat generating part, the heat generating part is arranged. High-accuracy temperature detection is performed by the temperature detection means arranged so as to correspond to the installation position. It is possible to provide a fixing device that can reduce power consumption and obtain an energy saving effect and can perform better fixing.

  The control means determines the ratio of power supply from the auxiliary power source to each of the plurality of heat generating parts provided in the second heat generating means, as a target detected temperature and an actual detected temperature in the central temperature detecting means. If the temperature is changed according to the difference between the target temperature detected by the end temperature detecting means and the actual detected temperature, the temperature is set so as to correspond to the position where the heat generating portion is set. By detecting the temperature with high accuracy by the detection means, it is possible to control the heat generation appropriately according to the size of the sheet, so that the control can be performed with higher accuracy, and wasteful power consumption can be further reduced to obtain an energy saving effect. In addition, it is possible to provide a fixing device capable of making the temperature distribution in the width direction of the sheet uniform and performing better fixing.

  When the width of the sheet for fixing the image is smaller than the width of the first heat generating unit and the second heat generating unit, the control unit includes the plurality of units provided in each of the first heat generating unit and the second heat generating unit. If the power is supplied only to the heat generating part corresponding to the sheet passing area to generate heat, the appropriate heat generating part can be heated according to the size of the sheet, and wasteful power consumption is achieved. It is possible to provide a fixing device that can reduce the energy saving effect and can perform good fixing.

  Since the present invention is an image forming apparatus having the fixing device according to any one of claims 1 to 6, the image forming apparatus includes the fixing device that exhibits the above-described effects, and an appropriate heat generating portion according to the size of the sheet. An image forming apparatus capable of generating heat and reducing wasteful power consumption to obtain an energy saving effect, and capable of performing good fixing and good image formation thereby. Can do.

The present invention includes a first heat generating unit that generates heat upon receiving power supply from a commercial power source, a second heat generating unit that generates heat upon receiving power supply from an auxiliary power source charged by the commercial power source, Temperature detecting means for detecting the temperature of the second heat generating means, and control means for controlling power supply to the first heat generating means and the second heat generating means based on the temperature detected by the temperature detecting means. In the fixing method used to fix an image on a sheet, each of the first heat generating means and the second heat generating means includes a plurality of heat generating portions having different heat distributions in the width direction of the sheet . The second heat generating means incorporates an electric double layer capacitor, and is a switching means for switching between charging the auxiliary power source with a commercial power supply or supplying power to the second heat generating means with the auxiliary power source. The target detection temperature Ta in the first heat generation means and the target detection temperature Tb in the second heat generation means have a relationship of Ta> Tb, and the standby means switches to the second heat generation means during standby. The temperature detected by the temperature detection means is switched between the detection temperature Ta and the detection temperature Tb by switching the power supply to the first heat generation means in a state where the power supply of the auxiliary power supply is charged with the power supply of the auxiliary power supply being stopped. When the sheet passing is started, power is supplied to the first heat generating means and power is supplied to the second heat generating means by the switching means, and power is supplied from the auxiliary power source to the second heat generating means. The temperature detected by the temperature detecting means once falls below the detected temperature Tb before the time for shutting off the same power supply determined according to the amount of decrease due to the elapse of time, and then the detected temperature T Is reached, the power supply to the second heat generating means is stopped by the switching means, and the auxiliary power supply is charged. During the subsequent sheet passing, the temperature detected by the temperature detecting means is equal to or higher than the detected temperature Tb. In some cases, the temperature detected by the temperature detecting means is kept between the detected temperature Ta and the detected temperature Tb by switching the power supply to the first heat generating means, and the temperature detected by the temperature detecting means is because and performs power supply to the second heat generating means by said switching means only when below the detection temperature Tb, it is possible to heat the appropriate heating unit according to the size of the sheet, also auxiliary It is possible to efficiently supply power from the power source and suppress or prevent heating due to excessive power supply to the first heat generating means and the second heat generating means. In addition, it is possible to provide a fixing method capable of reducing wasteful power consumption and obtaining an energy saving effect and capable of performing good fixing.

  According to another aspect of the present invention, there is provided an image forming method for forming an image using the fixing device according to any one of claims 1 to 6, the image forming device according to claim 7, or the fixing method according to claim 8. Therefore, using the fixing device that exhibits each of the above-described effects, the image forming device that exhibits the above-described effects, or the fixing method that exhibits the above-described effects, the size of the sheet can be reduced while performing good fixing and good image formation thereby. Accordingly, it is possible to heat an appropriate heat generating part, and it is possible to obtain an energy saving effect by reducing wasteful power consumption, and to perform good fixing and good image formation by this. A forming method can be provided.

  FIG. 1 shows a fixing device according to an embodiment to which the present invention is applied and an image forming apparatus having the same. An image forming apparatus 30 shown in FIG. 1 is a digital copying machine, which is a combined machine of a facsimile and a laser printer. The image forming apparatus 30 may be another copier, a facsimile, a printer such as a laser beam printer, or a complex machine of these.

  The image forming apparatus 30 forms an image on the sheet material 2 which is a sheet as a sheet-like recording medium. As the sheet material 2, special sheets such as cardboard and OHP sheets can be used in addition to plain paper. The image forming apparatus 30 can form images on the sheet material 2 having various sizes. The image forming apparatus 30 forms a single color image, but may be capable of forming a color image.

  From above, the image forming apparatus 30 includes a document reading unit 32 as an optical reading system, a writing device 33 as an optical writing system that is a laser optical system, an image forming unit 34 as an image forming system, and a sheet material 2. A double-sided device 42 that reverses the sheet material 2 on which the toner image is formed on one side in the image forming unit 34 and sends it again to the image forming unit 34, and a sheet material 2 feeding device A feeding device 100 which is a paper feeding device.

  The image forming apparatus 30 is also arranged on the upstream side of the image forming unit 34 in the conveyance path of the sheet material 2 indicated by reference numeral 37, and a registration roller 6 that sends the sheet material 2 toward the image forming unit 34 at a predetermined timing. And a roller pair type fixing device 38 for fixing the toner image on the sheet material 2 to the sheet material 2 disposed on the downstream side of the image forming unit 34 in the conveyance path 37.

  The image forming apparatus 30 also selects a discharge branch claw 51 that selects whether the sheet material 2 on which the toner image is fixed by the fixing device 38 is discharged out of the main body 31 of the image forming apparatus 30 or sent to the double-sided device 42. A sheet discharge roller pair 39 having a sheet discharge roller 39a and a sheet discharge roller 39b for discharging the sheet material 2 on which the toner image has been fixed by the fixing device 38 to the outside of the main body 31; A sheet discharge tray 40 as a sheet discharge unit for stacking the sheet material 2 discharged by the discharge roller pair 39 and a control unit (not shown) as a control unit for controlling the overall operation of the image forming apparatus 30. Yes.

  The image forming unit 34 is an image carrier that is a drum-shaped latent image carrier, and rotates in the clockwise direction in FIG. A charging device 56 as a charging unit for charging the photosensitive drum 35 and a developing unit as a developing unit for developing the electrostatic latent image on the photosensitive drum 35 into a visible image. Device 36.

  The image forming unit 34 also transfers a toner image obtained by developing the electrostatic latent image on the photosensitive drum 35 by the developing device 36 along the direction A from the photosensitive drum 35 to the sheet material 2. A transfer device 59 serving as a transfer means, and the transfer device 59 to transfer a toner image on the photosensitive drum 35 to the sheet material 2 and then to expose foreign matters such as residual toner and paper dust remaining on the photosensitive drum 35. And a cleaning device 50 as a cleaning means for removal from the body drum 35.

  Although not shown, the document reading unit 32 includes a document placement table, a light source for scanning the document placed on the document placement table, and an optical path conversion reflecting mirror, and reflects light from the document. Is incident on an optical element such as a CCD via a reading optical system, and is output to the control unit as image information which is image data of a document by the optical element.

  The writing device 33 includes a polygon mirror 57, a semiconductor laser (not shown) that performs irradiation according to the image information of the document input to the control unit, and a reflecting mirror and an imaging lens (not shown) that form an imaging optical system. The scanning light L emitted from the semiconductor laser and reflected by the polygon mirror 57 is irradiated to a position between the charging device 56 and the developing device 36 on the photosensitive drum 35 so as to form an electrostatic latent image. It has become.

  The semiconductor laser is controlled to emit light based on an image signal from the control unit. In the control unit, not only the image information from the document reading unit 32 but also image data and a facsimile apparatus when used as a printer. The drive control of the semiconductor laser is performed by an image signal corresponding to the image data when used as a laser.

  The reversing device 42 includes a reverse conveyance path 41 that is a path through which the sheet material 2 enters by branching by the paper discharge branch claw 51, a double-sided tray 43 that stacks the sheet material 2 conveyed through the reverse conveyance path 41, A double-sided conveyance path 44 that is a path for feeding the sheet material 2 from the tray 43 toward the image forming unit 34 is provided.

  The feeding device 100 includes a cassette 11 on which the sheet material 2 is stacked, a spring (not shown) as an urging unit that urges the cassette 11 upward, and the uppermost sheet material 2 among the sheet materials 2 stacked on the cassette 11. A separation roller 8 that separates the sheet material 2 one by one from the feeding roller 4 and feeds it to the image forming unit 34; A spring 5 as an urging means for urging the member 8 toward the feeding roller 4 and a sheet material 2 fed by the feeding roller 4 and the separating member 8 are conveyed toward the image forming unit 34. The conveyance roller pair 7 is provided.

  The sheet feeding device 100 can feed the sheet material 2 with either the center reference or the one-side reference. In this embodiment, it is assumed that the sheet material 2 is fed with the center reference. The paper feeding device 100 is configured to detect whether the sheet material 2 is fed based on the central reference or the one-side reference, and the size of the sheet material 2, and transmits these pieces of information to the control unit. .

  As shown in FIG. 2, the fixing device 38 includes a heating roller 61 as a fixing roller that heats the sheet material 2 and is rotationally driven in the direction of arrow B by a motor as a drive source (not shown) and conveys the sheet material 2 by rotation. The pressure roller 62 is pressed against the heating roller 61 and is rotated in the direction of the arrow C following the heating roller 61 to convey the sheet material 2 together with the heating roller 61, and a first roller disposed inside the heating roller 61. The heater 63 which is a main heating element as a heating means, the heater 64 which is an auxiliary heating element as a second heating means, and a support plate 60 which integrally supports the heaters 63 and 64 are provided.

  The fixing device 38 also covers a guide plate 65 as a guide member that guides the sheet material 2 to the nip portion 81 where the heating roller 61 and the pressure roller 62 are in pressure contact with each other, and covers the heating roller 61 and the support plate 60. It has an upper cover 66 that is supported, and a lower cover 67 that covers the pressure roller 62 and supports the guide plate 65.

  As shown in FIG. 3, the fixing device 38 also supplies power to the main power supply device 82 as a main power source that supplies power to the heater 63 in order to cause the heater 63 to generate heat, and to supply power to the heater 64 in order to cause the heater 64 to generate heat. An auxiliary power supply 83 as an auxiliary power supply that is charged by the main power supply 82, and a main switch 84 that is a relay circuit for switching whether to supply power from the main power supply 82 to the heater 63. ing.

  The fixing device 38 is also supplied with power from the main power supply device 82 as a charging device for charging the auxiliary power supply device 83. The charging device 85 charges the auxiliary power supply device 83 with the charging device 85 or the auxiliary power supply device 83. It has a switch 86 as a relay circuit as switching means for switching whether the power supply 83 supplies power to the heater 64.

  The fixing device 38 also has an auxiliary power supply control means 87 for controlling the auxiliary power supply device 83 and the temperature of the surface of the heating roller 61 constituting the heating unit for heating the sheet material 2 in order to detect the temperature of the heaters 63 and 64. And temperature detecting means 88 for detecting.

  Although not shown, the heating roller 61 is a thin roller having a thin cylindrical cored bar and a release layer formed of PFA or PTFE on the surface of the cored bar. The diameter of the metal core of the heating roller 61 is 16 mm or more and 40 mm or less, and the thickness of the metal core is 0.25 mm or more and 0.6 mm or less. In this embodiment, the cored bar of the heating roller 61 is made of an aluminum alloy and has a diameter of 30 mm and a wall thickness of 0.5 mm. A material having a small specific heat and a high thermal conductivity is preferable, and metals such as iron, copper, stainless steel, and aluminum such as STKM11 and STKM12 can be used in addition to an aluminum alloy.

  Although not shown, the pressure roller 62 is made of an elastic layer having an outer diameter of 25 mm to 30 mm and a thickness of 5 mm to 7 mm, and a fluororesin having a thickness of 30 μm to 80 μm on the elastic layer. And a layer covering the tube. In the present embodiment, the elastic layer is a sponge layer having an outer diameter of 25 mm and a thickness of 5 mm using sponge time rubber having a small heat capacity, and the thickness of the fluororesin layer is 50 μm.

  As described above, the heating roller 61 and the pressure roller 62 are each designed to shorten the warm-up time due to the reduction in heat capacity, that is, the rise time when the power is turned on or the time from the standby state in the energy saving mode to the return. .

  When the sheet material 2 moves from the right side to the left side in FIG. 2, an image formed by toner carried on the surface, that is, a toner image is fixed at the nip portion 81. At this time, a direction perpendicular to the paper surface in FIG. 2 is referred to as a width direction of the sheet material 2. Hereinafter, the width direction of the sheet material 2 is simply referred to as the width direction.

  The heating roller 61 and the pressure roller 62 are long in the width direction, and have a width larger than the width of the sheet material 2 usable in the image forming apparatus 30 in the width direction. Since the sheet material 2 is fed on the basis of the center, the center of the sheet material 2 in the width direction coincides with the centers of the heating roller 61 and the pressure roller 62. When the paper is fed on the one-side basis, one edge of the sheet material 2 passes through a fixed position in the vicinity of the end portions of the heating roller 61 and the pressure roller 62.

  Although not shown, the heaters 63 and 64 are longer than the width of the heating roller 61 in the width direction and are disposed in a manner penetrating the heating roller 61. The support plate 60 is disposed outside the respective end portions of the heating roller 61 in the region where the heating roller 61 extends in the width direction, and supports the end portions of the heaters 63 and 64 at this position. is doing. The heaters 63 and 64 are arranged in the vertical direction, the heater 63 is located on the upper side, and the heater 64 is located on the lower side. Therefore, the heater 64 is disposed at a position closer to the nip portion 81, which is the passage position of the sheet material 2, than the heater 63.

  In this embodiment, the heaters 63 and 64 are infrared heaters and are provided inside the heating roller 61. However, the heaters 63 and 64 may be a planar heating element integrated with the heating roller 61 or an IH system. The heating element may be used. An external heating method may be used.

  The main power supply device 82 is supplied with power from a commercial power supply and has a well-known configuration. For example, the power supplied from an outlet or the like is adjusted to an appropriate voltage according to the heater 63, the charging device 85, and the like. Etc.

  The auxiliary power supply device 83 has a built-in chargeable / dischargeable capacitor. This capacitor is composed of an electric double layer capacitor or the like, and unlike the secondary battery, has an excellent characteristic because it does not involve a chemical reaction. That is, when a general nickel-cadmium battery or the like is used as a secondary battery for the auxiliary power supply device 83, a long time of several tens of minutes to several hours is required even if quick charging is performed. When a capacitor is used for the power supply device 83, rapid charging of about several minutes is possible.

  Therefore, by using the capacitor, even when the standby state and the heating state, that is, the power supply state are repeated, it is possible to reliably supply power from the auxiliary power supply 83 at the time of power supply, and to shorten the heating roller 61. It can be raised to a predetermined temperature in time.

  In addition, since the nickel-cadmium battery has an allowable number of repetitions of charge / discharge of about 500 to 1000 times, it has a short life for use in the auxiliary power supply device 83 for heating the heating roller 61, and the labor and cost of replacement are low. In the auxiliary power supply 83, by using an electric double layer capacitor, the allowable number of repetitions of charging / discharging is several million times or more, and deterioration due to repeated charging / discharging is small. Thus, there is no need for liquid replacement or replenishment, so that almost no maintenance is required, and it can be used stably for a long time.

  An electric double layer capacitor does not have a dielectric, and uses the absorption and desorption reactions (charging and discharging) of the ion adsorbing layer of the electric double layer in which the charge of ions or solvent molecules formed at the solid electrode and solution interface is concentrated. It has excellent features such as strong resistance to repeated charge and discharge, long life, no maintenance, environmental friendliness, and high charge and discharge efficiency. Recently, the capacitance is tens of thousands of F and the energy density is several. A large capacity of 10 wh / kg has been developed, and the capacity is being increased further.

The main switch 84 turns on / off the power supplied from the main power supply device 82 to the heater 63.
The charging device 85 has a function of adjusting the voltage according to the auxiliary power supply device 83 with the power supplied from the main power supply device 82 and rectifying from AC to DC, and charges the capacitor.

  The temperature detection means 88 is disposed in contact with or non-contact with the surface of the heating roller 61 and outputs a detection signal to the control unit. As the temperature detection means 88, a thermistor of the type that contacts the heating roller 61, a non-contact type thermistor that does not form a scratch on the heating roller 61, and a non-contact type thermopile are appropriately selected and used. For example, when the temperature detecting means 88 is a thermistor, the output value is converted into a temperature by the control unit.

  The auxiliary power supply control unit 87 is configured by a part of the control unit, and controls the power supply to the heater 64 based on the temperature detected by the temperature detection unit 88. The control unit controls the power supply to the heaters 63 and 64 by driving the main power supply device 82 and the main switch 84 based on the temperature detected by the temperature detecting means 88. The control unit includes a CPU, a memory such as a ROM and a RAM, and a timer. A target detection temperature that should be detected by the temperature detection unit 88, that is, a set temperature, is stored in the ROM. The actual detected temperature detected by the temperature detecting means 88 is compared with the set temperature, and based on this, on / off control of the heaters 63 and 64 is performed as will be described later.

The basic operation of the fixing device 38 will be described.
During standby, the charging device 85 is connected to the auxiliary power supply device 83 by the switch 86, and the capacitor of the auxiliary power supply device 83 is charged.

  When the temperature of the heating roller 61 is raised, the main switch 84 is turned on to supply power from the main power supply 82 to the heater 63, and at the same time, the switch 86 is switched to supply power from the auxiliary power supply 83 to the heater 64 for heating. A large amount of power is supplied to the roller 61. Thus, when heating of the heating roller 61 is started, since a large amount of power is supplied to the heating roller 61 from both the main power supply device 82 and the auxiliary power supply device 83, the heating roller 61 is brought to a predetermined temperature in a short time. stand up.

  When the auxiliary power supply control unit 87 detects that a predetermined time has elapsed since the auxiliary power supply 83 supplied power to the heater 64 and started heating, the auxiliary power supply control means 87 detects the auxiliary power supply. The electric power supplied from 83 to the heater 64 is cut off to prevent overheating of the heating roller 61 and maintained at a predetermined temperature. As with the discharge characteristics shown in FIG. 4, the power supplied from the auxiliary power supply 83 to the heater 64 decreases as time passes after the supply is started.

  A time for cutting off the power supplied from the auxiliary power supply device 83 to the heater 64 is determined according to the amount of decrease in the supplied power, and is supplied from the auxiliary power supply device 83 to the heater 64 when the supplied power decreases to some extent. Shut off the power. Therefore, deterioration of each component of the surrounding circuit and electromagnetic noise that occur when shutting off while supplying a large amount of electric power are prevented. In FIG. 4, the horizontal axis indicates time, and the vertical axis indicates power amount or voltage.

  The sheet material 2 to which the toner image has been transferred is conveyed to the nip portion 81, and the toner is heated and melted by the heating roller 61 heated to a constant temperature by the heaters 63 and 64, thereby fixing the toner image on the sheet material 2. Therefore, electric power is supplied to the heaters 63 and 64 from the main power supply device 82 and the auxiliary power supply device 83, respectively, and the temperature of the heating roller 61 is raised. The constant temperature includes a temperature range having a predetermined width suitable for fixing.

  At this time, the auxiliary power supply control means 87 performs on / off control of the power supply from the auxiliary power supply device 83 based on the above-described time and the temperature detected by the temperature detection means 88, so that the temperature of the heating roller 61 is increased. Is controlled to keep the fixing temperature, that is, the temperature of the heating roller 61 at a constant temperature or to show a required temperature change. As a result, the toner is stably heated and melted, and a high-quality toner image is fixed on the sheet material 2.

  At this time, power is supplied from the main power supply device 82 and the auxiliary power supply device 83 to the heaters 63 and 64 built in the heating roller 61 to raise the temperature of the heating roller 61, so that the surface temperature of the heating roller 61 is fixed to a predetermined level. It rises quickly to temperature.

  Since the image forming apparatus 30 is configured as described above, the writing device 33 scans the scanning light on the photosensitive drum 35 charged by the charging device 56 based on the image data read by the document reading unit 32. A latent image is formed by irradiating L, and the developing device 36 makes the latent image a visible image with toner.

  The sheet material 2 is fed from the cassette 11 by the feeding roller 4, and the sheet material 2 is well separated one by one by cooperation with the separating member 8, and only one sheet material 2 is conveyed by the conveying roller pair 7. The image is conveyed to the image forming unit 34 through the path 37, is timed by the registration roller 6, and is sent out between the photosensitive drum 35 and the transfer device 59 so that a visible image, that is, a toner image on the photosensitive drum 35 is obtained. The image is transferred onto the sheet material 2 by the transfer device 59. After the transfer, the photosensitive drum 35 is cleaned by the cleaning device 50 and is again charged by the charging device 56.

  The sheet material 2 to which the toner image has been transferred while being in close contact with the photosensitive drum 35 is separated from the photosensitive drum 35 by the curvature of the photosensitive drum 35, conveyed to the fixing device 38, and fixed, and discharged. When the paper is conveyed to the paper discharge roller pair 39 through 51, it is discharged to the external paper discharge tray 40 by the paper discharge roller pair 39.

  When the double-sided image is formed and the image is formed only on one side, the sheet material 2 is conveyed from the reverse conveyance path 41 toward the double-sided device 42 by the paper discharge branch claw 51 and temporarily stored in the double-sided tray 43. After that, the direction of travel is reversed, and the image is formed again on the back surface from the double-sided conveyance path 44 to the image forming unit 34, and passes through the fixing device 38, the paper discharge branch claw 51, and the paper discharge roller pair 39. 40 is discharged.

  The fixing device 38 supplies power to the heaters 63 and 64 from the main power supply device 82 and the auxiliary power supply device 83, so that the fixing device 38 can be quickly turned on when the heaters 63 and 64 are turned on during the image formation. When the warm-up is completed and fixing is performed, the heaters 63 and 64 are appropriately turned on, so that the temperature of the heating roller 61 is always maintained at a temperature suitable for fixing and good fixing is performed. . As a result, image formation by the image forming apparatus 30 is favorably performed.

  In order to perform the fixing operation in the fixing device 38 and the image forming operation in the image forming apparatus 30 by this, the heater 63 in the fixing device 38 generates heat different from each other in the width direction as shown in FIG. The heater 64 has a plurality of heat generating parts 64a and 64b having different heat distributions in the width direction.

  The heat generating portions 63a and 64a function as a central heat generating portion having a heat generation distribution biased toward the center portion in the width direction, and the heat generating portions 63b and 64b are used as both end heat generating portions having a heat generation distribution biased at both end portions in the width direction. It functions. The controller can heat the heat generating part 63a, the heat generating part 64a, the heat generating part 63b, and the heat generating part 64b independently by turning on / off a relay circuit (not shown).

  The plurality of heat generating parts constituting the heaters 63 and 64 may be three or more instead of two like the heat generating parts 63a and 63b and the heat generating parts 64a and 64b. For example, each of the heat generating parts 63b and 64b may be configured to be separated into two end heat generating parts having a heat generation distribution biased to each end in the width direction.

  Also, in this embodiment, emphasizing the paper passing with the central reference, the plurality of heat generating parts are configured by the central heat generating part and the end heat generating part, but when emphasizing the paper passing with the one side reference is important. A plurality of heat generating portions may be configured by a heat generating portion having a heat generation distribution biased toward the reference end portion and a heat generation portion having a heat generation distribution biased toward the other end portion and the central portion.

A heat generating part having a flat heat generation distribution over the entire sheet passing area may be used together with the heat generating part having an uneven heat generation distribution.
As described above, by combining various heat generation distributions of the plurality of heat generating portions, it is possible to adapt to various conditions such as the size in the width direction of the sheet material 2, that is, the sheet width, the type of the sheet material 2, and the like.

  The temperature detection means 88 corresponds to the heat generation distributions of the heat generating parts 63a and 63b and the heat generating parts 64a and 64b in the width direction, and the center temperature detection means is located at different positions in the width direction, that is, at the center and end in the width direction. 88a and end temperature detecting means 88b.

  Detection signals from the central temperature detecting means 88a and the end temperature detecting means 88b are transmitted to the control unit. The ROM of the control unit stores a target detection temperature that should be detected by each of the center temperature detection means 88a and the end temperature detection means 88b when the sheet material 2 passes through the nip portion 81 and includes a timing at which the sheet material 2 passes. ing. The controller causes the heat generating parts 63a and 64a to generate heat until the actual detected temperature detected by the central temperature detecting means 88a reaches the target detected temperature, and the actual detected temperature detected by the end temperature detecting means 88b is the target. The heat generating parts 63b and 64b are caused to generate heat until the detected temperature is reached.

  As described above, by disposing a plurality of temperature detecting means 88 at different positions in the width direction, the temperature distribution in the width direction of the heating roller 61 can be grasped in more detail and detected with higher accuracy. Further, such different positions correspond to the arrangement positions of the plurality of heat generating parts 63a and 63b and the heat generating parts 64a and 64b constituting the heaters 63 and 64, so the heat generating parts 63a and 63b and the heat generating parts 64a and 64b are provided. This control is appropriately performed, high-precision fixing and high-precision image formation are performed, and wasteful power consumption is suppressed, so that an energy saving effect is obtained.

  Here, when the sheet passing width as the width of the sheet material 2 is smaller than the maximum width in which the heater 63 and the heater 64 are disposed in the width direction and the heating roller 61 can be heated, for example, a postcard, A5 vertical width, When the B5 vertical width sheet is passed, as shown in FIG. 6A, if all of the heat generating parts 63a and 63b and the heat generating parts 64a and 64b are heated, the sheet has the sheet passing width at the center. Although the material 2 is kept at an appropriate temperature in order to take heat away, the temperature becomes excessive at both ends, and an end temperature rise state occurs.

  Therefore, the control unit determines whether the heat generation units 63a and 63b and the heat generation units 64a and 64b are in accordance with the central reference or one-side reference sheet feed and the sheet material 2 size information transmitted from the paper supply device 100. In this case, only the heat generating part 63a and the heat generating part 64a are heated as shown in FIG.

  Thus, when the width | variety of the sheet material 2 is smaller than the width | variety of the heaters 63 and 64, a control part is the sheet | seat material 2 of the some heat generating parts 63a and 63b and the heat generating parts 64a and 64b with which these were equipped. By supplying electric power only to the heat generating portion corresponding to the passage area to generate heat, the temperature distribution of the heating roller 61 is kept uniform and appropriate throughout the width direction as shown in FIG.

  Note that such control is performed when the paper is being passed, and when the paper is not passed, such as during standby, the heat generating portion is maintained so that the temperature distribution of the heating roller 61 is kept uniform over the entire width direction. All of the heat generators 63a and 63b and / or the heat generating parts 64a and 64b are simultaneously heated, or the heat generating parts 63a and 64a and the heat generating parts 63b and 64b are alternately heated.

  The auxiliary power control means 87 determines the ratio of the power supply from the auxiliary power supply 83 to each of the heat generating parts 64a and 64b provided in the heater 64 and the target detected temperature in the central temperature detecting means 88a when the paper is passed. The change is made in accordance with the ratio between the difference between the actual detection temperature and the difference between the target detection temperature and the actual detection temperature in the end temperature detection means 88b.

  For example, when a sheet is passed, as shown in FIGS. 7B and 7C, when the ratio of power supply to each of the heat generating portions 64a and 64b, that is, the amount of power distribution is set to 50%, FIG. As shown in Fig. 4, the temperature at the center in the width direction has reached the target detection temperature, but the temperatures at both ends in the same direction have not reached the target detection temperature, and an end temperature drop state has occurred. Suppose that

  At this time, fixing quality may not be ensured, for example, fixing may not be performed well at both ends of the sheet material 2. In such a case, as shown in FIGS. 8B and 8C, the ratio of power supply to the heat generating part 64a is reduced from 50% to 25%, and the ratio of power supply to the heat generating part 64b is 50%. By increasing from% to 75%, the temperature distribution of the heating roller 61 is made uniform and appropriate throughout the width direction as shown in FIG. These values of 25% and 75% are merely examples, and the temperature distribution of the heating roller 61 is appropriately changed so as to be uniform and appropriate in the entire width direction, but the total is adjusted to be 100%. .

  The target detection temperature Ta of the heater 63 and the target detection temperature Tb of the heater 64 are stored as different values in the ROM of the control unit. Specifically, the former detected temperature Ta is higher. These detected temperatures Ta and Tb are used at least during paper feeding.

  As shown in FIG. 9, at the time of standby, in the example of FIG. 9, the power supply to the heater 63 is switched as needed, and the power supply to the heater 64 is maintained in a stopped state, so that the temperature of the heating roller 61 is increased. It keeps between detection temperature Ta and target detection temperature Tb.

  When paper feeding is started, power supply to the heater 64 is started, but when the actual detected temperature reaches the target detected temperature Tb, power supply to the heater 64 is stopped. In this case, it is assumed that the actual detected temperature has reached the target detected temperature Tb before the above-described predetermined time has elapsed. Thereafter, when the actual detection temperature is equal to or higher than Tb, the temperature of the heating roller 61 is kept between the target detection temperature Ta and the target detection temperature Tb by turning on / off the power supply to the heater 63, and the actual detection temperature. Only when the temperature falls below Tb, power is supplied to the heater 64.

  As described above, when the temperature of the heating roller 61 is significantly decreased at the initial stage of paper feeding, the heater 64 assists the power to avoid or suppress the temperature decrease of the heating roller 61 and assist the temperature increase of the heating roller 61. Since the temperature of the heating roller 61 is basically controlled by supplying power only to the heater 63 after the temperature of the heating roller 61 has been restored, the power stored in the auxiliary power supply device 83 is not wasted, so that an energy saving effect is achieved. Obtained and preferred. Note that the heater 63 may be controlled using the target detection temperatures Ta and Tb during standby, and the heaters 63 and 64 may be controlled in the same manner as during paper feeding.

  As described above, as a preferred embodiment of the present invention, the fixing device to which the present invention is applied, the image forming apparatus including the fixing device, the fixing method, and the image forming method using the same have been described. The present invention is not limited to the embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims, unless otherwise limited in the above description.

  For example, the fixing device may be a belt type fixing device instead of a roller pair type fixing device. As shown in FIG. 10, the belt-type fixing device includes an endless fixing belt 91 for conveying the sheet material 2 on which toner is fixed, a heating roller 61 and a fixing roller 92 around which the fixing belt 91 is wound. And a fixing device 94 having a pressure roller 62 disposed to face the fixing roller 92 via the fixing belt 91 and heaters 63 and 64 disposed inside the heating roller 61.

  In the fixing device 94, the toner image carried on the surface of the sheet material 2 is fixed at the nip portion 93 where the fixing belt 91 and the pressure roller 62 abut. The fixing device 94 is configured in the same manner as the fixing device 38 in other portions. The belt-type fixing device 94 and the image forming apparatus 30 including the same, the fixing method, and the image forming method using the fixing device 38, the image forming apparatus 30 including the fixing device 38, the fixing method, and the fixing method 38 are also provided. The same effects as the image forming method used are exhibited.

  The effects described in the embodiments of the present invention are only the most preferable effects resulting from the present invention, and the effects of the present invention are limited to those described in the embodiments of the present invention. is not.

1 is a schematic front view of a fixing device to which the present invention is applied and an image forming apparatus having the same. FIG. 2 is an enlarged schematic front view of the fixing device shown in FIG. 1. FIG. 2 is a schematic circuit block diagram of the fixing device shown in FIG. 1. FIG. 3 is a correlation diagram with time showing a discharge state of an auxiliary power source provided in the fixing device shown in FIG. 2. FIG. 3 is a circuit block diagram of a main part of the fixing device shown in FIG. 2. It is a conceptual diagram which shows one condition for making temperature distribution in the width direction of a sheet | seat uniform and appropriate. FIG. 9 is a conceptual diagram used in comparison with FIG. 8 for explaining another condition for making the temperature distribution in the width direction of the sheet uniform and appropriate. It is a conceptual diagram which shows the other conditions for making temperature distribution in the width direction of a sheet | seat uniform and appropriate. It is a conceptual diagram which shows an example of the transition of the aspect of the electric power feeding to these heat_generation | fever means, and actual detection temperature by the target detection temperature of a 1st, 2nd heat_generation | fever means mutually differing. It is the schematic of the fixing device of the other structure to which this invention is applied.

Explanation of symbols

2 Sheet 30 Image forming apparatus 38 Fixing device 63 First heat generating means 63a Central heat generating section 63b End heat generating sections 63a, 63b Plural heat generating sections provided in the first heat generating means 64 Second heat generating means 64a Central heat generating section 64b End heat generating parts 64a, 64b A plurality of heat generating parts provided in the second heat generating means 83 Auxiliary power supply 87 Control means (part)
88 Temperature detection means 88a Central temperature detection means 88b End temperature detection means 88a, 88b Multiple temperature detection means 94 Fixing device Ta Target detection temperature in the first heat generation means Tb Target detection temperature in the second heat generation means

Claims (9)

A first heat generating means for generating heat upon receiving power supply from a commercial power source;
Second heat generating means for generating heat by receiving power supply from an auxiliary power source charged by a commercial power source;
Temperature detecting means for detecting the temperature of the first heat generating means and the second heat generating means;
A fixing device that includes a control unit that controls power supply to the first heat generation unit and the second heat generation unit based on the temperature detected by the temperature detection unit, and fixes the image on the sheet;
Each of the first heat generating means and the second heat generating means includes a plurality of heat generating portions having different heat generation distributions in the width direction of the sheet ,
The second heat generating means incorporates an electric double layer capacitor,
Switching means for switching between charging the auxiliary power source with a commercial power source or supplying power to the second heat generating unit with the auxiliary power source;
The target detection temperature Ta in the first heat generation means and the target detection temperature Tb in the second heat generation means are in a relationship of Ta> Tb,
During standby, the power supply to the second heat generating means is stopped by the switching means, and the temperature detected by the temperature detecting means is switched by switching the power supply to the first heat generating means while charging the auxiliary power supply. Keeping between the detection temperature Ta and the detection temperature Tb, and when the sheet passing is started, power is supplied to the first heat generation means and power supply to the second heat generation means is started by the switching means, The temperature detected by the temperature detecting means before the lapse of time for shutting off the same power supply determined according to the amount of decrease in the power supply time from the auxiliary power source to the second heat generating means is detected. Once the temperature Tb is reached and the detected temperature Tb is reached, the switching means stops the power supply to the second heat generating means and charges the auxiliary power source. When the temperature detected by the means is equal to or higher than the detected temperature Tb, the temperature detected by the temperature detecting means is changed between the detected temperature Ta and the detected temperature Tb by switching the power supply to the first heat generating means. The fixing device is characterized in that power is supplied to the second heat generating means by the switching means only when the temperature detected by the temperature detecting means falls below the detected temperature Tb .   2. The fixing device according to claim 1, wherein a plurality of the temperature detecting means are disposed at different positions in the width direction of the sheet. The fixing device according to claim 2.
The plurality of heat generating portions include a central heat generating portion having a heat generation distribution biased at a central portion in the width direction of the sheet, and an end portion heat generating portion having a heat generation distribution biased at an end portion in the width direction of the sheet,
The temperature detecting means includes a central temperature detecting means provided corresponding to the central heat generating part, and an end temperature detecting means provided corresponding to the end heat generating part. . The fixing device according to claim 3.
The control means determines the ratio of power supply from the auxiliary power source to each of the plurality of heat generating parts provided in the second heat generating means, as a target detected temperature and an actual detected temperature in the central temperature detecting means. And a difference between the target detected temperature and the actual detected temperature in the end temperature detecting means. In the fixing device according to any one of claims 1 to 4,
When the width of the sheet for fixing the image is smaller than the width of the first heat generating unit and the second heat generating unit, the control unit includes the plurality of units provided in each of the first heat generating unit and the second heat generating unit. The fixing device is characterized in that power is supplied to only the heat generating portion corresponding to the sheet passage region to generate heat. In the fixing device according to any one of claims 1 to 5,
Connected to the auxiliary power source when the switching means is switched to charge the auxiliary power source by a commercial power source, adjusts the voltage for power supplied from the commercial power source to the auxiliary power source, and rectifies from AC to DC And a fixing means for charging the electric double layer capacitor .   An image forming apparatus comprising the fixing device according to claim 1. A first heat generating means for generating heat upon receiving power supply from a commercial power source;
Second heat generating means for generating heat by receiving power supply from an auxiliary power source charged by a commercial power source;
Temperature detecting means for detecting the temperature of the first heat generating means and the second heat generating means;
In a fixing method for fixing an image on a sheet using a control means for controlling power supply to the first heat generating means and the second heat generating means based on the temperature detected by the temperature detecting means,
Each of the first heat generating means and the second heat generating means includes a plurality of heat generating portions having different heat generation distributions in the width direction of the sheet ,
The second heat generating means incorporates an electric double layer capacitor,
Using a switching means for switching between charging the auxiliary power supply with a commercial power supply or supplying power to the second heat generating means with the auxiliary power supply,
The target detection temperature Ta in the first heat generation means and the target detection temperature Tb in the second heat generation means are in a relationship of Ta> Tb,
During standby, the power supply to the second heat generating means is stopped by the switching means, and the temperature detected by the temperature detecting means is switched by switching the power supply to the first heat generating means while charging the auxiliary power supply. Keeping between the detection temperature Ta and the detection temperature Tb, and when the sheet passing is started, power is supplied to the first heat generation means and power supply to the second heat generation means is started by the switching means, The temperature detected by the temperature detecting means before the lapse of time for shutting off the same power supply determined according to the amount of decrease in the power supply time from the auxiliary power source to the second heat generating means is detected. Once the temperature Tb is reached and the detected temperature Tb is reached, the switching means stops the power supply to the second heat generating means and charges the auxiliary power source. When the temperature detected by the means is equal to or higher than the detected temperature Tb, the temperature detected by the temperature detecting means is changed between the detected temperature Ta and the detected temperature Tb by switching the power supply to the first heat generating means. The fixing method is characterized in that power is supplied to the second heat generating means by the switching means only when the temperature detected by the temperature detecting means falls below the detected temperature Tb .   An image forming method for forming an image by using the fixing device according to claim 1, the image forming device according to claim 7, or the fixing method according to claim 8.

Images