JP4982001B2 - Heating apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to, for example, a heating device for heating various materials and apparatuses, a fixing device using the same, and an image forming apparatus such as an electrophotographic copying machine, a printer, and a facsimile using the fixing device. The present invention relates to an improvement in efficiency of a heating device in a fixing device.

  In an image forming apparatus such as a copying machine, an image is formed on a recording medium such as plain paper or OHP, and an electrophotographic method is often employed because of high-speed image formation, image quality, cost, and the like. The electrophotographic method is a method in which a toner image is formed on a recording medium, and the formed toner image is fixed on the recording medium with heat and pressure. As the fixing method, the heat roller method is currently most frequently used from the viewpoint of safety and the like. In the heat roller method, a heat roller heated by a heat generating member such as a halogen heater and a pressure roller disposed opposite to the heat roller are pressed to form a mutual pressure contact portion called a nip portion, and a toner image is formed in the nip portion. Is heated and pressurized through the recording medium to which the toner has been transferred, thereby fixing the toner to the recording medium.

  In recent years, environmental problems have become important, and image forming apparatuses such as copiers and printers have been saving energy. What can not be ignored when considering the energy saving of this image forming apparatus is the power saving of the fixing device for fixing the toner to the recording medium. Therefore, to reduce the power consumption of the fixing device during standby of the image forming apparatus, the temperature of the heating roller is kept at a constant temperature slightly lower than the fixing temperature during standby, and immediately rises to a usable temperature during use. Many methods are employed so that the user does not wait for the temperature of the fixing roller to rise. In the case of this method, a certain amount of power must be supplied even when the fixing device is not used, thereby consuming extra energy. This standby energy consumption is said to correspond to approximately 70% to 80% of the energy consumption of the devices constituting the image forming apparatus.

  Accordingly, it has been desired to reduce energy consumption during standby and to further save power, and there is a demand for zero power supply when not in use. However, if energy consumption is reduced to zero during standby, the heating roller of the fixing device mainly uses a metal roller such as iron or aluminum and has a large heat capacity, so that the temperature rises to a usable temperature of about 180 ° C. Requires a long heating time of several minutes to several tens of minutes. Such a waiting time deteriorates the usability of the user, so that a heating method that consumes as little power as possible while rapidly rising from the standby state is desired.

  In order to shorten the heating time of the heating roller, it is clear that it is better to increase the input energy per unit time, that is, the rated power. In fact, in an image forming apparatus called a high-speed machine with a high printing speed, In many cases, the power supply voltage is 200V.

  However, in general offices in Japan, the commercial power supply is 100V, 15A, and it is necessary to carry out special work on the power-related equipment at the installation site in order to make it compatible with 200V. It's not an ideal solution.

  That is, as long as a commercial power supply of 100 V and 15 A is used, the maximum input energy is determined by the power supply even when the temperature of the heating roller is to be raised in a short time. When this happens, a voltage lower by a certain level is supplied to the heating roller to delay the temperature of the fixing device from falling, or the secondary battery, which is an auxiliary power supply, is charged when the fixing device is on standby, and the fixing device is started up. Sometimes power is supplied from the main power supply and the secondary or primary battery to shorten the rise time.

JP 2002-184554 A JP-A-2005-174777 JP 2003-29752 A JP 2005-174578 A

  However, the technique disclosed in Japanese Patent Application Laid-Open No. H10-228561 cannot provide sufficient power saving because it supplies a low voltage by a certain level to the fixing device even during standby. Moreover, the maximum supply power at the time of start-up is not mainly intended to be higher than the power supplied from the main power supply device.

  On the other hand, the fixing device disclosed in Patent Document 2 supplies power from a main power supply device and a secondary battery or a primary battery at the time of start-up. As a secondary power supply, a lead storage battery, a nickel cadmium battery, or a nickel metal hydride battery is generally used. I use it. Such a secondary battery has a property that the capacity deteriorates and decreases when charging and discharging are repeated, and the life is shortened as discharging is performed with a large current. There is also a phenomenon of capacity reduction due to the memory effect. Even if it is generally considered to have a long life with a large current, the number of charge / discharge cycles is about 500 to 1000 times. If 20 cycles of charge / discharge are repeated per day, the battery life will be reached in about one month. It will end up. Therefore, the replacement frequency of the battery is increased, so that much labor is required and the running cost such as the cost of the battery to be replaced is increased. Furthermore, in lead storage batteries, liquid sulfuric acid is used as the electrolyte, which is undesirable for office equipment.

  In addition, the load on the heating circuit built in the heating roller increases due to sudden current changes and inrush power when starting and stopping the supply of large power, and the input current is also applied to the peripheral circuits. There is also a problem that noise flows and flows. For this reason, it is not preferable to frequently turn on and off the power supply from the large-capacity auxiliary power supply device. In addition, if a large amount of power is supplied at once, there is a possibility that the supply will be excessive and the temperature of the heating circuit will rise too much.

  These points are improved to improve the power saving effect, reduce noise due to inrush current and sudden current change when supplying large power, shorten the rise time, and prevent the temperature from rising excessively. As the fixing device that can be used, a chargeable / dischargeable capacitor is used for the auxiliary power supply, the charger charges the capacitor of the auxiliary power supply with power supplied from the main power supply, and the switching device charges the auxiliary power supply. There has been proposed a device that switches the power supply from the auxiliary power supply to the auxiliary heating element and adjusts the amount of power supplied from the auxiliary power supply to the auxiliary heating element.

  The basic function of the capacitor in this configuration is to cause the auxiliary heater to generate heat with the electric power supplied from the capacitor, to shorten the time for the heating roller to rise to a predetermined temperature using this heat, and to reduce the fixing temperature when passing paper. The present invention aims to further reduce power consumption by supplying power more efficiently.

Among the heating devices of the present invention, the one according to claim 1 is
A main power supply device, an auxiliary power supply device, a heating unit that has a main heating element and an auxiliary heating element and heats a member to be heated, and a temperature detection unit that measures the temperature of the heating unit,
A heating device that generates heat by the power supplied from the main power supply device or the auxiliary power supply device,
The auxiliary power supply device includes a chargeable / dischargeable power storage device. The auxiliary power supply device controls the auxiliary power supply device to supply power to the auxiliary heating element to keep the heating unit at a set temperature, and the set temperature. Auxiliary power supply control means that can be made variable,
At paper passing start, depending on the state of the main heating element is powered from the main power supply, the heating device for changing the power supply control to the auxiliary heat generating element from said auxiliary power unit,
In the case where the temperature of the heating unit tends to increase due to the power supply signal to the main heating element being on at the start of paper feeding, the auxiliary power supply device starts after the first time has elapsed after the paper feeding starts. Power assistance to the auxiliary heating element,
When the temperature of the heating unit tends to decrease due to the power supply signal to the main heating element being off at the start of paper feeding, a second time shorter than the first time elapses after the paper feeding starts. It performs power assist to the auxiliary heat generating element from the auxiliary power unit from,
It is characterized by that.

Those according to the claim 2 is the heating apparatus according to claim 1, wherein the auxiliary power unit control means, the power supply time for the power assistance from the auxiliary power unit to the auxiliary heating element, said temperature sensing It changes according to the temperature of the said heating part measured by the means .

According to the third aspect of the present invention, in the heating device according to the first or second aspect, in place of power assistance to the auxiliary heating element after the second time has elapsed , The power supplement from the auxiliary power supply to the auxiliary heating element is performed .

  An image forming apparatus according to claim 4 has the heating device according to any one of claims 1 to 3.

  In the present invention, the necessary power is supplied by changing the power supply control from the auxiliary power supply device to the auxiliary heating element according to the state when the heating element supplied with power from the main power supply device starts to pass. Therefore, it becomes possible to save power more efficiently.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a schematic view around a fixing device in an embodiment of a heating device according to the present invention and an image forming apparatus using the same. The heating device 1 of this embodiment includes a heating unit 2, a main power supply device 3, an auxiliary power supply device 4, a main switch 5, a charger 6, and auxiliary power supply control means 8. In FIG. 1, the heating unit 2 composed of the main heating element 2a and the auxiliary heating element 2b is drawn outside the fixing roller 40. However, this is for convenience of illustration, and both the heating elements 2a, 2b Provided in the fixing roller 40.

  The overall configuration of the image forming apparatus according to the present invention is not shown, but it may be of any type as long as it is a well-known type of image forming apparatus that uses a heat fixing device. The illustrated fixing device includes a fixing roller 40 and a pressure roller 41, and it is desirable to form a release layer such as PFA or PTFE on the outermost layer of the fixing roller. The fixing roller 40 includes a heating unit 2 including a main heating element 2a made of, for example, a halogen heater and an auxiliary heating element 2b. The fixing roller 40 and the pressure roller 41 pass through the recording medium P on which the toner T is placed. Thus, a nip portion N to be pressurized and heated is formed.

  The heating unit 2 includes a main heating element 2a that generates heat by the electric power supplied from the main power supply device 3, and an auxiliary heating element 2b that generates heat by the electric power supplied from the auxiliary power supply device 4, and is a fixing roller that is a heated object. 40 is heated. Although not shown in detail, the main power supply device 3 is supplied with power from a commercial power supply in the image forming apparatus in which the heating device 1 is installed. The main power supply device 3 has a function of adjusting, for example, power supplied from an outlet or the like to a voltage corresponding to the heating unit 2. However, since the main power supply device 3 is well known, detailed illustration and description are omitted.

  The auxiliary power supply device 4 includes a chargeable / dischargeable capacitor C. The capacitor C is preferably an electric double layer capacitor, for example. Unlike a secondary battery, a capacitor such as an electric double layer capacitor has excellent characteristics because it does not involve a chemical reaction.

  That is, as already described, in the auxiliary power supply apparatus using a general nickel-cadmium battery as a secondary battery, a long time of several tens of minutes to several hours is required even if rapid charging is performed, but a capacitor is used. The auxiliary power supply 4 can be rapidly charged for several minutes, and when the standby state and the heating state are repeated within the same time, the auxiliary power supply device 4 using a capacitor can be used at the time of heating start-up. Electric power can be supplied from the auxiliary power supply 4 to the heating unit 2, and the heating unit 2 can be raised to a predetermined temperature in a short time. Further, since the nickel-cadmium battery has an allowable number of charge / discharge repetitions of about 500 to 1000 times, it has a short life as an auxiliary power supply for heating, and there is a problem in replacement labor and cost. The auxiliary power supply device 4 using a capacitor has an allowable number of repetitions of charge / discharge of several million times or more, is less deteriorated by repeated charge / discharge, and does not require liquid replacement or replenishment unlike a lead storage battery. Therefore, it requires little maintenance and 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, capacitance is tens of thousands of F, energy density is several. A large capacity of 10 wh / kg has been developed, and the capacity is being increased further.

  The main switch 5 turns on / off the power supplied from the main power supply device 3 to the main heating element 2a, and the charger 6 sets the voltage according to the auxiliary power supply device 4 with the power supplied from the main power supply device 3. The capacitor C is charged by adjusting and rectifying from AC to DC.

  The auxiliary power control means includes a switching device 7, a switch 9, and a CPU 10, and serves as a discharge control means 8a and a power supply control means 8b. The discharge control means 8a switches between charging of the auxiliary power supply 4 and power supply from the auxiliary power supply 4 to the auxiliary heating element 2b under conditions described later.

  The power supply control means 8b performs power supply control for turning on / off the power supplied from the auxiliary power supply device 4 to the auxiliary heating element 2b under the conditions set later which are set in advance. However, the configuration of the control means 8 shown in the drawing is merely an example showing only a portion that controls the heating unit 2, and various configurations such as a device that controls the entire image forming apparatus can be employed. Further, the connection form for controlling the auxiliary power supply 4 is not limited to the illustrated example.

  The basic operation of such a heating device 1 will be described. First, at the time of standby, the switching device 7 is switched and the charger 6 is connected to the auxiliary power supply device 4 to charge the capacitor C of the auxiliary power supply device 4. When heating the heating unit 2 with the heating device 1 in this state, the main switch 5 is turned on to supply power from the main power supply device 3 to the main heating element 2a, and at the same time, the switching device 7 is switched and the auxiliary power supply device 4 is switched. Electric power is supplied to the auxiliary heating element 2b, and a large amount of electric power is supplied to the heating unit 2. Thus, when heating of the heating unit 2 is started, a large amount of power is supplied from both the main power supply device 3 and the auxiliary power supply device 4 to the heating unit 2, so that the heating unit 2 is brought to a predetermined temperature in a short time. Can be launched.

  In addition, the auxiliary power supply control means receives auxiliary power from the auxiliary power supply device 4 when a predetermined time elapses after the auxiliary power supply device 4 supplies power to the auxiliary heating element 2b of the heating unit 2 and starts heating. The electric power supplied to the heating element 2b is cut off to prevent overheating of the heating unit 2 and maintained at a predetermined temperature. The power supplied from the auxiliary power supply 4 to the auxiliary heating element 2b decreases as time elapses after the supply is started. A time for cutting off the power supplied from the auxiliary power supply 4 to the auxiliary heating element 2b is determined in accordance with the reduction amount of the supplied power. When the supplied power is cut off, it is possible to prevent deterioration of each component of the surrounding circuit and electromagnetic noise that occur when cutting off in the state of supplying a large amount of power.

  The recording medium P to which the toner image T has been transferred is conveyed between the fixing roller 40 and the pressure roller 41, and the toner T is heated and melted by the fixing roller 40 heated to a constant temperature, so that the toner image is formed on the recording medium P as a toner image. Let it settle. Therefore, power is supplied from the main power supply device 3 and the auxiliary power supply device 4 to the main heating element 2a and the auxiliary heating element 2b included in the heating unit 2 of the fixing roller 40, thereby increasing the temperature of the fixing roller 40 and the auxiliary power supply. By controlling on / off of the power supplied from the device 4, the temperature of the fixing roller 40 is prevented from becoming too high, and the fixing temperature is kept at a constant temperature or a desired temperature, or a required temperature change is shown. Thus, the toner T is stably heated and melted, and a good quality toner image T is fixed on the recording medium P. Further, since the power is supplied from the main power supply device 3 and the auxiliary power supply device 4 to the main heating element 2a and the auxiliary heating element 2b of the heating unit 2 built in the fixing roller 40, the temperature of the fixing roller 40 is raised. The surface temperature of the toner can be quickly raised to a predetermined fixing temperature.

  A first example of control according to this embodiment is shown in FIG. In FIG. 2A, the heating element 2a signal is on until just before the start of paper passing, and therefore the temperature of the heating unit 2 is a line rising to the right. On the other hand, in FIG. 2B, since the heating element 2a signal is off immediately before the start of paper feeding, the temperature of the heating unit 2 is a downward-sloping line due to the effect of natural heat dissipation. In the case of FIG. 2A, since the heating unit 2 temperature tends to rise due to the heating element 2a signal being on at the start of paper feeding, there is no need for power assistance from the auxiliary power supply device even after paper feeding has started. The temperature of the heating unit 2 does not drop so much (or at least). In the case of FIG. 2B, since the temperature of the heating unit 2 tends to decrease, power is assisted from the auxiliary power supply device after the start of paper feeding to reduce / avoid the decrease in temperature of the heating unit 2. FIG. 2B shows a state in which the amount of auxiliary power is reduced by performing power assistance simultaneously with the start of paper feeding. In this way, the power supply control from the auxiliary power supply to the auxiliary heating element is changed according to the state of the heating element (energization or non-energization) at the start of paper feeding. As a result, power can be efficiently saved by supplying power only when necessary.

  A second example of control according to this embodiment is shown in FIG. In FIG. 3A, the heating element 2a signal is on until just before the start of paper feeding, and therefore the temperature of the heating unit 2 is a line rising to the right. On the other hand, in FIG. 3B, since the heating element 2a signal is off immediately before the start of paper feeding, the temperature of the heating unit 2 is a downward-sloping line due to the effect of natural heat dissipation. In the case of FIG. 3A, since the heating element 2a signal is on at the start of paper passing and the temperature of the heating unit 2 tends to rise, power is assisted from the auxiliary power supply device after a time t1 after the paper starts. However, even if there is such a time difference from the start of paper feeding to the start of power assistance, the temperature of the heating unit 2 does not drop so much. In the case of FIG. 3 (B), since the temperature of the heating unit 2 tends to decrease, electric power is assisted after a time t2 after the start of paper feeding to reduce / avoid the decrease in the temperature of the heating unit 2. When the heating element 2a signal is on at the start of paper feeding and the time t for starting power supplement is longer (t1> t2), more efficient power saving can be achieved. It is most desirable for t2 to be zero in order to obtain a high quality image by improving the fixability.

  FIG. 4 shows a third example of control according to this embodiment. In FIG. 4A, the heating element 2a signal is on until just before the start of paper passing, and therefore the temperature of the heating unit 2 is a line rising to the right. On the other hand, in FIG. 4B, since the heating element 2a signal is off immediately before the start of paper passing, the temperature of the heating unit 2 is a downward-sloping line due to the effect of natural heat dissipation. In the case of FIG. 4B, since the temperature of the heating unit 2 tends to increase due to the heating element 2a signal being on at the start of paper feeding, power supply is started from the auxiliary power supply device after the paper feeding starts and time ta The power supply is terminated after the elapse. Since the heating unit 2 temperature is originally high, the heating unit 2 temperature does not drop so much even if the time ta is not so long. In the case of FIG. 4B, since the temperature of the heating unit 2 tends to decrease, power supply is started from the auxiliary power supply device after the start of paper feeding and the power supply is ended after the elapse of time tb. In order to avoid a drop in temperature, it needs to be a long time. That is, when the heating element 2a signal is on at the start of paper feeding and the power assist time t is shorter (tb> ta), more efficient power saving can be achieved. In FIGS. 4A and 4B, power supply is started after a little time has elapsed from the start of paper feeding. However, the power supply is not limited to this, and power supply may be started simultaneously with the start of paper feeding. At this time, since the temperature drop of the heated portion can be reduced, a high quality image can be expected by improving the fixing property.

  FIG. 5 shows a fourth example of control according to this embodiment. In FIG. 5A, the heating element 2a signal is on until just before the start of paper passing, and therefore the temperature of the heating unit 2 is a line rising to the right. On the other hand, in FIG. 5B, since the heating element 2a signal is off immediately before the start of paper feeding, the temperature of the heating unit 2 is a downward-sloping line due to the effect of natural heat dissipation. In the case of FIG. 5A, since the heating element 2 temperature tends to rise due to the heating element 2a signal being on at the start of paper feeding, power supply is started from the auxiliary power supply device after the paper feeding starts, and the auxiliary power amount When the voltage reaches V1, power supply is terminated. Since the heating part 2 temperature is originally high, the heating part 2 temperature does not drop so much even if this V1 is not so large in capacity. In the case of FIG. 5B, since the temperature of the heating unit 2 tends to decrease, power supply is started from the auxiliary power supply device after the start of paper feeding, and the power supply ends when the auxiliary power amount reaches V2. This V2 needs to have a large capacity in order to avoid the temperature drop of the heating unit 2. That is, when the heating element 2a signal is on at the start of paper passing, the power consumption can be more efficiently reduced if the auxiliary power amount is smaller (V2> V1). In FIGS. 5A and 5B, power supply is started after a little time has elapsed from the start of paper feeding. However, this is not restrictive, and power supply may be started simultaneously with the start of paper feeding. At this time, since the temperature drop of the heated portion can be reduced, a high quality image can be expected by improving the fixing property.

  FIG. 6 shows a fifth example of control according to this embodiment. In FIG. 6 (A), the heating element 2a signal is on until just before the start of paper passing, so that the temperature of the heating unit 2 is a line rising to the right. On the other hand, in FIG. 6B, since the heating element 2a signal is off immediately before the start of paper feeding, the temperature of the heating unit 2 is a downward-sloping line due to the effect of natural heat dissipation. In the case of FIG. 6A, since the temperature of the heating unit 2 tends to increase due to the heating element 2a signal being on at the start of paper feeding, power supply is started from the auxiliary power supply device after the paper feeding starts and the heating unit 2 is started. Power supply is terminated when the temperature reaches Ta. Since the temperature of the heating unit 2 is originally high, the temperature of the heating unit 2 does not drop so much even if this Ta is not so low. In the case of FIG. 6B, since the temperature of the heating unit 2 tends to decrease, power supply is started from the auxiliary power supply after the start of paper feeding, and the power supply is terminated when the temperature of the heating unit 2 reaches Tb. This Tb needs to be set to a low value in order to avoid a drop in temperature of the heating unit 2 in order to earn time for assisting power as much as possible. That is, when the heating unit set temperature at which the power supply is stopped when the heating element 2a signal is on at the start of paper feeding is higher (Ta> Tb), more efficient power saving can be achieved. In FIGS. 6A and 6B, power supply is started after a little time has elapsed from the start of paper passing. However, the power supply is not limited to this, and power supply may be started simultaneously with the start of paper passing. At this time, since the temperature drop of the heated portion can be reduced, a high quality image can be expected by improving the fixing property.

  As described above, the auxiliary power supply device 4 in the embodiment of the present invention is the capacitor C, and the excellent characteristics of the capacitor are as described above. In the present invention, the heating element 2a fed from the main power supply device is Changing the power supply control from the auxiliary power supply device to the auxiliary heating element 2b according to the state (energization or non-energization) at the start of paper feeding (for example, the auxiliary heating element 2b when the heating element 2a is not energized) When the heating element 2a is energized, the auxiliary heating element 2b is not supplied with power, and the heating element supplied from the main power supply device is assisted according to the state at the start of paper feeding. By changing the power supply start timing by power supply control from the power supply device to the auxiliary heating element 2b, power is supplied more efficiently and power saving is achieved.

  Further, according to the state at the start of paper feeding of the heating element fed from the main power supply device, the power feeding time is changed by feeding control from the auxiliary power supply device to the auxiliary heating element 2b, thereby more efficiently feeding power and saving power. The heating unit set temperature at which the power supply is stopped by the power supply control from the auxiliary power supply device to the auxiliary heat generating element 2b is changed according to the state at the start of paper feeding of the heat generating element supplied from the main power supply device. However, power can be supplied more efficiently to save power. In addition, if an electric double layer capacitor is used as an auxiliary power supply device, as described above, there is little deterioration even if the number of times of charging / discharging is high, and furthermore, there is no need for liquid replacement or replenishment like lead-acid batteries. Since it can be used stably for a long period of time with little maintenance, it is possible to more efficiently save power.

Schematic of one embodiment of a heating device according to the present invention The figure which shows the 1st example of the control which concerns on a present Example The figure which shows the 2nd example of the control which concerns on a present Example The figure which shows the 3rd example of the control which concerns on a present Example The figure which shows the 4th example of the control which concerns on a present Example The figure which shows the 5th example of control which concerns on a present Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heating device 2 Heating part 2a Main heating element 2b Auxiliary heating element 3 Main power supply device 4 Auxiliary power supply device 5 Main switch 6 Charger 7 Switching device 8 Auxiliary power supply control means 8a Discharge control means 8b Power supply control means 9 Switch 10 CPU
40 Fixing roller 41 Pressure roller T Toner P Recording medium C Capacitor

Claims (4)

A main power supply device, an auxiliary power supply device, a heating unit that has a main heating element and an auxiliary heating element and heats a member to be heated, and a temperature detection unit that measures the temperature of the heating unit,
A heating device that generates heat by the power supplied from the main power supply device or the auxiliary power supply device,
The auxiliary power supply device includes a chargeable / dischargeable power storage device. The auxiliary power supply device controls the auxiliary power supply device to supply power to the auxiliary heating element to keep the heating unit at a set temperature, and the set temperature. Auxiliary power supply control means that can be made variable,
At paper passing start, depending on the state of the main heating element is powered from the main power supply, the heating device for changing the power supply control to the auxiliary heat generating element from said auxiliary power unit,
If the power supply signal to the main heating element is on at the start of paper passing and the temperature of the heating unit measured by the temperature detecting means tends to increase, after the first time has elapsed after the paper starts passing Power assistance from the auxiliary power supply to the auxiliary heating element;
If the power supply signal to the main heating element is off at the start of paper feeding and the temperature of the heating unit measured by the temperature detecting means tends to decrease, the second time shorter than the first time after the paper feeding starts. After the time elapses , power assistance from the auxiliary power supply to the auxiliary heating element is performed.
A heating device characterized by that. In the heating apparatus according to claim 1, wherein the auxiliary power unit control means, the assist from the power supply the power assist for feeding power time to the auxiliary heating element, the temperature of the heating unit measured by said temperature detecting means The heating apparatus is characterized by being changed according to the temperature. 3. The heating device according to claim 1, wherein , instead of substituting electric power to the auxiliary heating element after the second time has elapsed, the auxiliary power supply device transfers to the auxiliary heating element simultaneously with the start of sheet feeding. The heating apparatus characterized by performing the electric power assistance . An image forming apparatus comprising the heating device according to claim 1.