JP2009210893A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which can suppress an increase in consumed power for an apparatus as a whole while preventing instability in power source voltage caused by energizing to an electric heater which is provided in the apparatus. <P>SOLUTION: The image forming apparatus includes: a fixing unit 15f with a heater lamp f3 as the electric heater, a power source voltage detection circuit 154 for detecting the power source voltage applied to the heater lamp f3 by an AC power source; a zero cross control circuit 155 for carrying out energizing control of the heater lamp 3f when a voltage drop ΔV which is calculated based on the detected power source voltage is less than a first reference value C1 indicating that the power source voltage is in a state of excessive load; and a phase control circuit 156 carrying out energizing control of the heater lamp 3f when the calculated voltage drop ΔV is equal to or more than the first reference value C1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus having a fixing device provided with an electric heater.

  2. Description of the Related Art An electrophotographic image forming apparatus such as a printer and a copying machine includes a fixing device for fixing a toner image transferred onto a recording paper through various processes to the recording paper with heat and pressure.

  In general, the fixing device includes an electric heater such as a halogen lamp that supplies heat for melting toner, and so-called zero cross control is adopted for energization control of such an electric heater.

  Here, the zero-cross control is a control method in which energization is performed in half-wave units by performing switching at the moment when the voltage of the AC power supply becomes close to zero (zero-cross point). According to the zero cross control, an inrush current at the time of switching can be prevented, and the generation of switching noise can be suppressed.

  However, since the ON / OFF switching of energization can be performed only in half-wave units according to zero cross control, there is a possibility that the power supply temporarily reaches an overload state due to energization of the electric heater. As a result, the power supply voltage becomes unstable, and there is a risk that problems such as flickering of fluorescent lamps in the same power supply environment may occur. As a countermeasure, a control method for switching at a predetermined phase angle (that is, phase control) is widely adopted. However, since phase control involves large switching noise, it is necessary to provide a dedicated noise filter. Here, since the noise filter generally consumes a large amount of power, executing the phase control increases the power consumption of the entire image forming apparatus. In order to suppress such an increase in power consumption, it is preferable to limit the execution of phase control to only the necessary scenes.

  In relation to this, the following Patent Document 1 proposes an image forming apparatus capable of switching between zero cross control and phase control in accordance with an operation mode such as a print mode / standby mode.

However, simply switching the control method according to the operation mode in this way will perform the phase control even when the power supply has not reached the overload state, and thus sufficiently suppress the increase in power consumption. It is not possible.
JP 2001-305905 A

  The present invention has been made in view of the above-described problems of the prior art, and the object of the present invention is to prevent power supply voltage from becoming unstable due to energization of an electric heater provided in the apparatus, An object of the present invention is to provide an image forming apparatus capable of suppressing an increase in power consumption of the entire apparatus.

  The above object of the present invention is achieved by the following means.

  (1) A fixing device provided with an electric heater, voltage drop detecting means for detecting a voltage drop of an AC power source applied to the electric heater, and the detected voltage drop means that the AC power source is in an overload state. When the detected voltage drop is greater than or equal to the first reference value, the energization control to the electric heater is performed when the detected voltage drop is equal to or greater than the first reference value. And an energization control unit that performs phase control.

  (2) The image forming apparatus according to (1), wherein the first reference value is 5%.

  (3) energization for stopping energization of the heater when the detected voltage drop is equal to or greater than a second reference value larger than the first reference value indicating that the AC power supply is in an overload state The image forming apparatus according to (1) or (2), further comprising a stopping unit.

  (4) Any one of the above (1) to (3), further comprising display means for displaying to the user that the energization stop means has stopped energization of the electric heater. The image forming apparatus described in 1.

  (5) The image forming apparatus according to (3) or (4), wherein the second reference value is 20%.

  (6) The above (1) to (1), further comprising a cooling device that is operated to cool the image forming apparatus when the energization control unit performs energization control on the electric heater by phase control. The image forming apparatus according to any one of (5).

  According to the image forming apparatus of the present invention, phase control with large power consumption is prevented while preventing the power supply voltage from becoming unstable by switching between zero cross control and phase control of the electric heater according to the magnitude of the voltage drop. Execution time can be minimized. As a result, it is possible to suppress an increase in power consumption of the entire image forming apparatus while preventing flickering of fluorescent lamps in the same power supply environment.

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

<First Embodiment>
FIG. 1 is a block diagram showing a configuration of a printer 1 as an image processing apparatus according to the first embodiment of the present invention. As shown in FIG. 1, the printer 1 includes a control unit 11, a storage unit 12, an operation unit 13, a printing unit 14, a power supply unit 15, and a communication interface 16, which are a bus 17 for exchanging signals. Are connected to each other.

  The control unit 11 is a CPU, and controls the above units and performs various arithmetic processes according to a program.

  The storage unit 12 stores a variety of programs and parameters in advance, a ROM that temporarily stores programs and data as a work area, stores various programs and parameters, or stores image data obtained by image processing, and the like. Consists of a hard disk or the like used for temporary storage.

  The operation unit 13 displays various types of information or a touch panel for inputting various settings, a numeric keypad for setting the number of copies, a start key for instructing start of operation, a stop key for instructing stop of operation, and various setting conditions at the initial stage. It consists of various fixed keys such as reset keys, display lamps and the like.

  The printing unit 14 prints and discharges the image data on a sheet of paper through the steps of charging, exposure, development, transfer, and fixing by electrophotography. Details of the printing unit 14 will be described later.

  The power supply unit 15 adjusts the voltage of the external AC power supply to a voltage necessary for driving each unit of the printer 1. Specifically, it has functions of transforming an AC voltage, converting it to a constant DC voltage, adjusting electric power by the AC voltage, and removing power supply noise. Details of the power supply unit 15 will be described later.

  The communication interface 16 is an interface for performing communication between the printer 1 and an external device. The communication interface 16 is a network interface based on a standard such as Ethernet (registered trademark), token ring, or FDDI, a serial interface such as USB or IEEE 1394, or a SCSI. A parallel interface such as IEEE 1284, various local connection interfaces such as a wireless communication interface such as Bluetooth, IEEE802.11, HomeRF, and IrDA, a telephone line interface for connecting to a telephone line, and the like are used.

  With the configuration described above, the printer 1 can perform print output on recording paper or the like based on a print job received from an external device. Normally, the control unit 11, the storage unit 12, and the communication interface 16 are mounted on the printer 1 as a printer controller for receiving a print job from an external device and generating image data that can be processed by the printing unit 14. (See FIG. 2).

  Next, the printing unit 14 of the printer 1 according to this embodiment will be described in more detail. FIG. 2 is a schematic diagram of the printer 1 according to the present embodiment, and mainly shows the printing unit 14.

  As shown in FIG. 2, the printing unit 14 forms an image on recording paper by an electrophotographic method, and includes a paper feeding unit 14a that accommodates and conveys the recording paper, and yellow (Y), magenta (M), and cyan. (C), a black (K) image forming portion 14b, an intermediate transfer unit 14c that forms a toner image on an intermediate transfer belt c1 described later, and a toner image formed on the intermediate transfer belt c1 is transferred to a recording sheet 2 Next transfer roller 14d, cleaning unit 14e that removes and collects toner adhering to the intermediate transfer belt c1, fixing device 14f that melts and adheres the toner image to the recording paper, and fixing the recording paper on which the toner image is fixed A paper discharge unit 14g that discharges and stores the paper outside the printer. Furthermore, the printer 1 according to the present embodiment includes a cooling fan 14h for cooling the inside of the apparatus.

  The paper feed unit 14a feeds the recording paper fed by the paper feed cassette a1, the paper feed roller a2 for feeding the recording paper from the paper feed cassette a1, and the recording paper fed by the paper feed roller a2 upward. A registration roller a3 for taking timing.

  The image forming unit 14b includes Y, M, C, and K developing devices b1, and each developing device b1 charges a photosensitive drum b11 made of a-Si (amorphous silicon) and the like, and the photosensitive drum b11. A charging unit b12 and an exposure unit b13 that exposes the charged photosensitive drum b11 to form an electrostatic latent image on the surface of the photosensitive drum b11 are provided. Each photosensitive drum b11 is rotatably provided in the direction of the arrow in the drawing.

  The intermediate transfer unit 14c is an intermediate transfer belt c1, a driving roller c2 and a driven roller c3 that stretch the intermediate transfer belt c1, and a transfer for transferring a toner image formed on the photosensitive drum b11 to the intermediate transfer belt c1. And a roller c4. The drive roller c2 is rotationally driven by a motor (not shown) or the like, the intermediate transfer belt c1 is rotated by the drive roller c2, and the driven roller c3 is rotated by the intermediate transfer belt c1. Further, the intermediate transfer belt c1 is pressed against each photosensitive drum b11 by the transfer roller c4.

  The secondary transfer roller 14d is disposed so as to sandwich the driven roller c3 and the intermediate transfer belt c1. The cleaning unit 14e includes a cleaning device e1 that removes toner attached to the intermediate transfer belt c1, and a toner storage box e2 that collects toner removed by the cleaning device e1.

  The fixing device 14f includes a pressure roller f1, a heating roller f2 facing the pressure roller f1, and a heater lamp f3 as an electric heater provided inside the heating roller f2. The pressure roller f1 is pressed against the heating roller f2 at a constant pressure, and forms a nip portion for sandwiching the recording paper at a contact portion with the heating roller f2. The heating roller f2 is rotationally driven by a motor (not shown) or the like with the surface heated to a constant temperature by the heater lamp f3. The heater lamp is a halogen lamp as an example. When the recording paper conveyed from the secondary transfer roller 14d passes through the nip portion, unfixed toner on the recording paper is melted and penetrated by heat and pressure in the nip portion, and the toner image is fixed on the recording paper.

  The paper discharge unit 14g includes a discharge roller g1 for feeding the recording paper conveyed from the fixing device 14f to the outside, and a paper discharge tray g2 for storing the recording paper fed by the discharge roller g1.

  The cooling fan 14h releases the heat in the printer 1 to the outside by the rotation of the fan. The cooling fan 14 h prevents the inside of the printer 1 from reaching an excessively high temperature due to heat generated by the printing unit 14 and the power supply unit 15.

  Next, the power supply unit 15 of the printer 1 according to this embodiment will be described in more detail. FIG. 3 is a block diagram illustrating a configuration of the power supply unit 15 of the printer 1 according to the present embodiment.

  As shown in FIG. 3, the power supply unit 15 includes a noise filter 151, a DC voltage generation unit 152, a zero cross detection circuit 153, a power supply voltage detection circuit 154, a zero cross control circuit 155, a phase control circuit 156, a phase A control noise filter 157.

  The noise filter 151 removes noise from the external AC power supply to which the power supply unit 15 is connected. The DC voltage generator 152 generates a constant DC voltage (+ 5V, + 24V, etc.) based on the AC voltage of the external AC power supply. The zero-cross detection circuit 153 is a circuit that detects a zero-cross point of the external AC power supply, and transmits a zero-cross signal to the control unit 11 when the zero-cross point is detected. The power supply voltage detection circuit 154 monitors the voltage of the external AC power supply and transmits a voltage monitor signal to the control unit 11. The zero cross control circuit 155 receives the zero cross control signal from the control unit 11 and executes the zero cross control of energization to the heater lamp f3. The phase control circuit 156 receives a phase control signal from the control unit 11 and executes phase control of energization to the heater lamp. The phase control noise filter 157 removes switching noise generated when the phase control circuit 156 switches the heater lamp f3 on / off.

  According to the zero-cross control circuit 156, switching is always performed in the vicinity of the voltage of the AC power supply being zero, so that an inrush current to the heater lamp f3 can be prevented and switching noise can be reduced. However, since the control by the zero cross control circuit 156 is always performed in half-wave units, there is a possibility that the AC power supply temporarily reaches an overload state due to energization of the heater lamp f3 and the power supply voltage becomes unstable. There is. Specifically, there is a possibility that problems such as flickering of fluorescent lamps in the same power supply environment may occur.

  Therefore, when the power supply voltage reaches an overload state, the printer 1 of the present embodiment performs energization control to the heater lamp f3 by the phase control circuit 156 instead of the zero cross circuit 155. The phase control circuit 156 can finely adjust the energization time to the heater lamp f3 by controlling the phase angle for switching. Therefore, by setting the energization time sufficiently small, the power supply to the heater lamp f3 can be slowed up and the power supply voltage can be prevented from becoming unstable.

  When the phase control circuit 156 is operated, it is necessary to operate the phase control noise filter 157 with large power consumption in order to eliminate switching noise. The printer 1 according to the present embodiment is as follows. By performing this process, the operation time of the phase control circuit 156 (and the phase control noise filter 157) can be minimized.

  Next, in the printer 1 according to this embodiment, an operation for controlling energization to the heater lamp f3 in the fixing device 14f will be described. FIG. 4 is a flowchart illustrating a processing procedure of the printer 1 according to the present embodiment.

  4 is stored as a control program in the storage unit 12, and is read out and executed by the control unit 11 when the operation is started.

  First, the printer 1 waits until energization of the heater lamp f3 is turned on (NO in S101). When turned on (YES in S101), the power supply voltage detection circuit 154 detects the voltage of the external AC power supply. (S102), and transmits a voltage monitor signal to the control unit (see FIG. 3). Then, the control unit 11 calculates a voltage drop ΔV at that time based on the received voltage monitor signal.

  FIG. 5 is a diagram illustrating an example of a voltage waveform when energization to the heater lamp f3 of the printer 1 connected to the external AC power supply of 100 V is switched on. The solid line 1) in the figure shows an example in which the voltage drop ΔV when the heater lamp f3 is turned on is less than 5%, and the dotted lines 2) and 3) indicate that ΔV is 5% or more and An example of 20% or more is shown. The magnitude of the voltage drop ΔV depends on the state of the load under the same power supply environment, the temperature of the heater lamp f3, and the like.

  Subsequently, the printer 1 determines whether or not the voltage drop ΔV is less than a certain reference value C1 indicating that the AC power supply is in an overload state (S103). In this example, the reference value C1 is 5%.

  Here, when ΔV <C1 (YES in S103), it is unlikely that the power supply voltage becomes unstable even if the zero cross control is performed (that is, there is a possibility that a problem such as flickering of a fluorescent lamp occurs). The control unit 11 transmits a zero cross control signal to the zero cross control circuit 155 (see FIG. 3). And the zero cross control circuit 155 which received the zero cross control signal from the control part 11 performs the zero cross control of electricity supply to the heater lamp f3 (S104).

  Note that the energization time to the heater lamp f3 at the time of executing the zero-cross control can be appropriately changed according to the status of the heater lamp f3 at that time. That is, when rapid heating of the heater lamp f3 is necessary for continuous printing or the like, it is possible to energize 100%, or because the printer 1 is in a standby state, etc. When heating is not necessary, it is possible to energize several half waves.

  Further, when ΔV ≧ C1 (NO in S103), that is, when the power supply is in an overload state, it is further determined whether or not the voltage drop ΔV is less than a certain reference value C2 indicating a significant overload state. Determination is made (S105). In this example, the reference value C2 is 20%.

  Here, when ΔV <C2 (YES in S105), a phase control signal is transmitted from the control unit 11 to the phase control circuit 156 to control the phase of the heater lamp f3 (see FIG. 3). And the phase control part 156 which received the phase control signal from the control part 11 performs phase control of the electricity supply to the heater lamp f3 (S106). Thus, by slowing up the power supplied to the heater lamp f3 by phase control, it is possible to prevent the AC voltage from becoming unstable and causing problems such as flickering of the fluorescent lamp.

  Note that the energization time to the heater lamp f3 at the time of phase control can be changed as appropriate according to the power supply environment at that time. In other words, when the voltage drop ΔV at that time is relatively small, the energization time can be lengthened, and otherwise, the energization time can be shortened. The recording unit 12 stores data related to an optimal control method corresponding to various power supply environments, and the control unit 11 instructs the phase control unit 156 about the optimal control method by referring to the data. It is possible (see FIG. 3).

  On the other hand, if ΔV ≧ C2 in S105 (NO in S105), it is determined that it is inappropriate to continue energizing the heater lamp f3, and the energization to the heater lamp f3 is switched off (S107). The process ends. At this time, it is preferable to display an error to the user through the operation unit 13.

  Subsequently, the printer 1 determines whether or not the energization to the heater lamp f3 is turned off (S108), and if it is turned off (YES in S108), the process is terminated as it is and is not turned off. (NO in S108), the steps after S102 are repeatedly executed until it is turned off.

  Next, the voltage waveform applied to the heater lamp f3 in the present embodiment will be described. FIG. 6 shows voltage waveforms after the energization of the heater lamp f3 is turned on in the printer 1 of the present embodiment, the zero cross signal from the Xerox detection circuit 153, and the phase control signal / phase control signal from the control unit 11. Shown with. FIG. 6 shows a voltage waveform when the voltage drop ΔV when the energization to the heater lamp f3 is turned on is 5% or more and less than 20% (see dotted line 2 in FIG. 5).

  As shown in the voltage waveform of FIG. 6, phase control for slowing up the power supplied to the heater lamp f3 is performed for a certain period after the energization of the heater lamp f3 is turned on (S106 in FIG. 4). ). This is because the voltage drop ΔV detected when the heater lamp f3 is turned on is 5% or more and less than 20% (NO in S102 and S103, YES in S104). When phase control is executed, a phase control noise filter 157 for removing switching noise is operating.

  When the power supply voltage becomes stable after a certain period of time and the voltage drop ΔV decreases to less than 5% (YES in S3), the phase control for the slow-up is terminated and normal zero cross control is performed (S104).

As described above, according to the present embodiment, it is possible to limit the execution of the phase control for energization control to the heater lamp f3 only to the necessary scene, and to minimize the operation time of the phase control circuit 156. it can. As a result, the operating time of the phase control noise filter 157 with high power consumption can be minimized, so that the flickering of the fluorescent lamp due to the unstable power supply voltage can be effectively prevented and the printer 1 as a whole. An increase in power consumption can be suppressed.
<Second Embodiment>
Subsequently, a second embodiment of the present invention will be described. Note that the configuration of the printer 1 according to the present embodiment is the same as that of the first embodiment described above, and a description thereof will be omitted. The difference from the first embodiment is that the cooling fan 14h is operated according to the control method of the heater lamp f3.

  FIG. 7 is a flowchart showing a processing procedure of the MFP 1 according to the present embodiment. Note that the algorithm shown in the flowchart of FIG. 7 is stored as a control program in the storage unit 12, and is read out and executed by the control unit 11 when the operation starts.

  First, the printer 1 waits until energization of the heater lamp f3 is turned on (NO in S201), and when turned on (YES in S102), the power supply voltage detection circuit 154 detects the voltage of the external AC power supply. (S202), and transmits a voltage monitor signal to the control unit (see FIG. 3). Then, the control unit 11 calculates a voltage drop ΔV at that time based on the received voltage monitor signal.

  Subsequently, the printer 1 determines whether or not the voltage drop ΔV is less than a certain reference value C1 indicating that the AC power supply is in an overload state (S203). In this example, the reference value C1 is 5%.

  Here, when ΔV <C1 (YES in S203), it is unlikely that the power supply voltage will be unstable even if zero cross control is performed (that is, the possibility of flickering of the fluorescent lamp is low). The control unit 11 transmits a zero cross control signal to the zero cross control circuit 155 (see FIG. 3). And the zero cross control circuit 155 which received the zero cross control signal from the control part 11 performs the zero cross control of electricity supply to the heater lamp f3 (S204).

  Subsequently, the printer 1 of the present embodiment stops the cooling fan 14h that is operating (S205). This is because the phase control noise filter 157 that generates a large amount of heat is not operating when the zero cross control is executed, and therefore it is considered that the possibility that the inside of the printer 1 will reach an excessively high temperature is low even if the cooling fan 14h is stopped. It is. Thus, the power consumption of the entire printer 1 can be reduced by shortening the unnecessary operation time of the cooling fan 14h.

  Further, when ΔV ≧ C1 (NO in S203), that is, when the power source is in an overload state, it is further determined whether or not the voltage drop ΔV is less than a certain reference value C2 indicating a significant overload state. Determination is made (S206). In this example, the reference value C2 is 20%.

  Here, if ΔV <C2 (YES in S206), a phase control signal is transmitted from the control unit 11 to the phase control circuit 156 in order to perform phase control of energization to the heater lamp f3 (see FIG. 3). . Then, the phase control circuit 156 that has received the phase control signal from the control unit 11 performs phase control of energization to the heater lamp f3 (S207). Thus, by slowing up the power supplied to the heater lamp f3 by phase control, it is possible to prevent the AC voltage from becoming unstable and causing problems such as flickering of the fluorescent lamp.

  Subsequently, the printer 1 of the present embodiment operates the cooling fan 14h that is stopped (S208). This is because the phase control noise filter 157 that generates a large amount of heat is in operation when the phase control is executed, and therefore, it is considered highly likely that the inside of the printer 1 will reach an excessively high temperature unless the cooling fan 14h is operated. .

  On the other hand, if ΔV ≧ C2 in S206 (NO in S206), it is determined that it is inappropriate to continue energizing the heater lamp f3, and the energization to the heater lamp f3 is switched off (S209). The process ends. At this time, it is preferable to display an error to the user through the operation unit 13.

  Subsequently, the printer 1 determines whether or not the energization to the heater lamp f3 is turned off (S210). When the power is turned off (YES in S210), the process is terminated as it is, and the printer 1 is not turned off. (S210: NO), the steps from S202 onward are repeatedly executed until it is turned off.

  As described above, the printer 1 of the present embodiment can switch the operation / stop of the cooling fan 14h according to the energization control method of the heater lamp f3. That is, in the present embodiment, the cooling fan 14h of the printer 1 is in a state as shown in Table 1 below when energization to the heater lamp f3 is on.

  As described above, when it is considered that the phase control noise filter 157 having a large amount of heat generation is not in operation and the possibility that the inside of the printer 1 reaches an excessively high temperature is low, the cooling fan 14h is automatically stopped. Thus, the power consumption of the entire printer 1 can be reduced.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims. For example, in the above-described embodiment, the printer has been described as an example of the image forming apparatus according to the present invention, but the present invention is not necessarily limited thereto. In other words, the image forming apparatus of the present invention may be anything as long as it has a heating type fixing device. For example, the image forming apparatus has a scan function, a print function, a copy function, and an e-mail print function. It may be a peripheral device (MFP Multiple Function Peripheral).

  The image forming apparatus according to the present invention can be realized by a dedicated hardware circuit for executing each procedure described above, or by a CPU executing a program describing each procedure described above. When the present invention is realized by the latter, the program for operating the image forming apparatus may be provided by a computer-readable recording medium such as a floppy (registered trademark) disk or a CD-ROM, or a network such as the Internet. May be provided online. In this case, the program recorded on the computer-readable recording medium is usually transferred and stored in a ROM, a hard disk or the like. Further, this program may be provided as, for example, a single application software, or may be incorporated in the software of the apparatus as one function of the image forming apparatus.

1 is a block diagram illustrating a configuration of a printer according to an embodiment of the present invention. FIG. 2 is a schematic diagram centering on a printing unit of a printer according to an embodiment of the present invention. FIG. 2 is a block diagram illustrating a configuration of a power supply unit of a printer according to an embodiment of the present invention. 5 is a flowchart illustrating a processing procedure of a printer according to an embodiment of the present invention. It is a figure which shows an example of the voltage waveform of AC power supply to which the printer which concerns on one Embodiment of this invention was connected. It is a figure which shows an example of the voltage waveform applied to the heater lamp of the printer which concerns on one Embodiment of this invention. It is a flowchart which shows the procedure of the process of the printer which concerns on other embodiment of this invention.

Explanation of symbols

1 printer,
11 Control unit,
14 Printing department,
14f fixing device,
14h cooling fan,
15 power supply,
151 noise filter,
152 DC voltage generator,
153 Zero cross detection circuit,
154 power supply voltage detection circuit,
155 Zero cross control circuit,
156 phase control circuit,
157 noise filter for phase control,
f1 pressure roller,
f2 heating roller,
f3 Heater lamp.

Claims (6)

A fixing device equipped with an electric heater;
Voltage drop detection means for detecting a voltage drop of an AC power source applied to the electric heater;
When the detected voltage drop is less than a first reference value indicating that the AC power supply is in an overload state, energization control to the electric heater is performed by zero cross control, and the detected voltage drop is An image forming apparatus comprising: an energization control unit that performs energization control on the electric heater by phase control when it is equal to or greater than one reference value.   The image forming apparatus according to claim 1, wherein the first reference value is 5%.   Energization stopping means for stopping energization of the electric heater when the detected voltage drop is equal to or greater than a second reference value greater than the first reference value indicating that the AC power supply is in an overload state; The image forming apparatus according to claim 1, further comprising:   The image forming apparatus according to claim 1, further comprising a display unit configured to display to the user that the energization stop unit has stopped energization of the electric heater. .   The image forming apparatus according to claim 3, wherein the second reference value is 20%.   6. The apparatus according to claim 1, further comprising a cooling device that is operated to cool the image forming apparatus when the energization control unit performs energization control on the electric heater by phase control. The image forming apparatus according to one.

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