Patent Publication Number: US-11036172-B2

Title: Image forming apparatus

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to an image forming apparatus including a plurality of AC receiving portions configured to receive power from an AC power source. 
     Description of the Related Art 
     In recent years, there have been demands in the market for a production printer, a multifunction peripheral, or another type of image forming apparatus adapted to use various kinds of recording sheets. Heat of a fixing unit is liable to be lost at the time of sheet passage depending on the thickness of the recording sheet, and it takes time to restore the temperature to that for fixing the next recording sheet, resulting in reduced productivity. In view of the above, there has been adopted a configuration in which a voltage of an AC power source is increased, and the number of power supplies to be supplied to the fixing heater is increased, to thereby shorten the temperature restoring time period. Further, there has been proposed an image forming apparatus including a power supply voltage determination device configured to distinguish, with high accuracy, voltage values of commercial power sources, which vary depending on foreign regions (Japanese Patent Application Laid-Open No. 2008-026175). 
     For example, an outlet for a general household in Japan has a power rating of 100 V and 15 A (1.5 kW), and a power cable therefor is widely distributed. As other power ratings, although electric work is required, single-phase 200 V and three-phase 200 V are also selectable. A power cable for 200 V can supply power up to 30 A (6 kW) depending on the type. However, as compared to a power cable for a general household, the power cable for 200 V has higher rated output and thus has a thicker cable diameter. The power cable for 200 V is also expensive because the cable has a less-distributed plug shape. 
     In view of the above, it is desired to supply power to the image forming apparatus through use of a plurality of inexpensive power cables for a general household without using the expensive power cable for 200 V. In this case, power can be supplied to a fixing device via an image forming device. However, when a supply unit configured to supply power from the image forming device to the fixing device is not appropriately connected, fixing of a toner image to the recording sheet by the fixing device may not be appropriately performed. 
     SUMMARY OF THE INVENTION 
     According to an embodiment of the present invention, there is provided an image forming apparatus, comprising: an image forming device including an image forming unit configured to form a toner image on a recording sheet; a fixing device including a fixing unit configured to fix the toner image to the recording sheet conveyed from the image forming device; a first AC receiving portion configured to receive power to be supplied from an AC power source to the image forming device via a first power cable; a second AC receiving portion configured to receive power to be supplied from the AC power source to the fixing unit via a second power cable; a third AC receiving portion, which is removably connected to the image forming device, and is configured to receive power to be supplied to the fixing unit via the first AC receiving portion; and a connection detecting portion configured to detect whether power is supplied from the third AC receiving portion to the fixing device, wherein the connection detecting portion is supplied with a voltage for an operation based on the power received from the AC power source via the second AC receiving portion, and wherein the image forming device detects whether the third AC receiving portion is connected to the image forming device based on a detection result of the connection detecting portion. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram for illustrating an image forming apparatus and a fixing apparatus. 
         FIG. 2  is a block diagram for illustrating a control unit for the image forming apparatus and the fixing apparatus. 
         FIG. 3  is a flow chart for illustrating connection detection of a third AC receiving portion. 
         FIG. 4  is a flow chart for illustrating a print operation. 
         FIG. 5  is a diagram for illustrating one housing including the image forming apparatus and the fixing apparatus. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
       FIG. 1  is a diagram for illustrating an image forming apparatus  100  and a fixing apparatus  300 . As illustrated in  FIG. 1 , the image forming apparatus  100  serving as an image forming device forms a toner image on a recording sheet P by a tandem-type intermediate transfer system in which image forming units  1   a ,  1   b ,  1   c , and  1   d  are arranged along an upper surface of an intermediate transfer belt  3 . The recording sheet P having the toner image formed thereon is conveyed to the fixing apparatus  300  serving as a fixing device. The fixing apparatus  300  fixes the toner image to the recording sheet P. In this manner, the image forming apparatus  100  and the fixing apparatus  300  form a full-color printer configured to form a full-color image on the recording sheet P. 
     The fixing apparatus  300  is housed in a housing  300   a  different and independent from a housing  100   a  of the image forming apparatus  100 . The fixing apparatus  300  is connected to the image forming apparatus  100  so as to be separable from the image forming apparatus  100 . However, the fixing apparatus  300  may be formed together with the image forming apparatus  100  in one housing  400  ( FIG. 5 ).  FIG. 5  is a diagram for illustrating one housing  400  including the image forming apparatus  100  and the fixing apparatus  300 . A combination of the image forming apparatus  100  and the fixing apparatus  300  is also referred to as “image forming apparatus”. 
     A feeding cassette  4  configured to receive the recording sheets P is provided at a lower portion of the image forming apparatus  100 . The feeding cassette  4  can be pulled out from a main body  30  of the image forming apparatus  100 . A user pulls out the feeding cassette  4  from the main body  30  to replenish the recording sheets P into the feeding cassette  4 , and pushes the feeding cassette  4  into the main body  30  again to mount the feeding cassette  4 . A separation roller  8  separates the recording sheets P fed from the feeding cassette  4  from each other to convey each recording sheet P to registration rollers  9 . A leading edge of the recording sheet P abuts against the stopped registration rollers  9 , and thus the recording sheet P briefly waits at the registration rollers  9 . The registration rollers  9  convey the recording sheet P to a secondary transfer portion T 2  so that a leading edge of a toner image formed on the intermediate transfer belt  3  matches the leading edge of the recording sheet P. 
     The image forming units  1   a ,  1   b ,  1   c , and  1   d  have substantially the same structure except that developing devices  51   a ,  51   b ,  51   c , and  51   d  of the respective image forming units  1   a ,  1   b ,  1   c , and  1   d  use toner of different colors. The image forming unit  1   a  forms a black toner image. The image forming unit  1   b  forms a cyan toner image. The image forming unit  1   c  forms a magenta toner image. The image forming unit  1   d  forms a yellow toner image. In the following, the image forming unit  1   a  is described, and description of the image forming units  1   b ,  1   c , and  1   d  is omitted. Unless particularly required, suffixes “a”, “b”, “c”, and “d” of the reference symbols are omitted. 
     The image forming unit  1  is configured as a replaceable unit integrally including a photosensitive drum  10 , a charging device  41 , and the developing device  51 . The photosensitive drum  10  includes a photosensitive layer having a negative charging polarity on an outer peripheral surface of an aluminum cylinder. A drive force is transmitted from a drive motor (not shown) to the photosensitive drum  10  so that the photosensitive drum  10  rotates at a predetermined rotation speed (process speed). The charging device  41  charges the surface of the photosensitive drum  10  to a uniform negative potential. 
     An exposure device  6  scans, by a rotary mirror of each color, a laser beam that is ON/OFF modulated based on scanning line image data obtained by loading an image of each color of yellow, magenta, cyan, and black to thereby form an electrostatic latent image on the uniformly-charged surface of the photosensitive drum  10  of the corresponding color. The developing device  51  causes toner of each color to adhere to the electrostatic latent image formed on the surface of the photosensitive drum  10  of each color to form the toner image of each color. 
     A primary transfer roller  2  presses the intermediate transfer belt  3  toward the photosensitive drum  10  to form a primary transfer portion T between the photosensitive drum  10  and the intermediate transfer belt  3 . When a positive DC voltage is applied to the primary transfer roller  2 , the negative toner image borne on the surface of the photosensitive drum  10  is transferred onto the intermediate transfer belt  3  passing through the primary transfer portion T. 
     An intermediate transfer unit  20  is arranged below the image forming unit  1 , and includes a support mechanism and a drive mechanism for the intermediate transfer belt  3 . The intermediate transfer belt  3  is looped around and supported by a tension roller  27 , a belt drive roller  26 , and a secondary transfer inner roller  25 , to thereby be driven by the belt drive roller  26  to rotate in an arrow R 2  direction. The intermediate transfer belt  3  is an endless belt member configured not to extend or contract. 
     Primary transfer rollers  2   a ,  2   b ,  2   c , and  2   d  are provided so as to correspond to the image forming units  1   a ,  1   b ,  1   c , and  1   d , respectively. The primary transfer rollers  2   a ,  2   b ,  2   c , and  2   d  are biased by springs toward the photosensitive drums  10   a ,  10   b ,  10   c , and  10   d , respectively, so that the intermediate transfer belt  3  abuts against the photosensitive drums  10   a ,  10   b ,  10   c , and  10   d . Thus, the primary transfer portion T for primarily transferring the toner image is formed. 
     A secondary transfer outer roller  22  abuts against the intermediate transfer belt  3  whose inner side surface is stretched by the secondary transfer inner roller  25 , to thereby form the secondary transfer portion T 2  between an outer side surface of the intermediate transfer belt  3  and the secondary transfer outer roller  22 . The secondary transfer inner roller  25  is provided in the intermediate transfer unit  20 . Meanwhile, the secondary transfer outer roller  22  is provided in the main body  30  of the image forming apparatus  100 . The secondary transfer inner roller  25  stretches the intermediate transfer belt  3  at the secondary transfer portion T 2  for secondarily transferring the toner image. When a positive DC voltage is applied to the secondary transfer outer roller  22  from a power source (not shown), an electric field for transferring the toner image is formed between the secondary transfer outer roller  22  and the secondary transfer inner roller  25  connected to a ground potential. 
     The recording sheet P having the toner image formed thereon is discharged through a discharge port  110  of the image forming apparatus  100  by a discharge belt  14  looped around and supported by discharge rollers  12  and  13 . The recording sheet P discharged through the discharge port  110  is received by a receiving port  310  of the fixing apparatus  300 . The discharge port  110  of the image forming apparatus  100  is communicated with the receiving port  310  of the fixing apparatus  300  so as to be separable therefrom. The fixing apparatus  300  includes a fixing unit  5 . The fixing unit  5  includes a fixing roller  5   a  and a pressure roller  5   b . The pressure roller  5   b  is pressurized to the fixing roller  5   a  to form a heating nip between the fixing roller  5   a  and the pressure roller  5   b . The fixing roller  5   a  and the pressure roller  5   b  include a fixing heater (first heating portion)  305   a  and a fixing heater (second heating portion)  305   b , respectively. In a process of conveying the recording sheet P while nipping the recording sheet P by the heating nip, the recording sheet P is heated and pressurized so that the toner image is melted, and thus a full-color image is fixed to the surface of the recording sheet P. The fixing roller  5   a  and the pressure roller  5   b  have a thermistor  15   a  and a thermistor  15   b , respectively, provided thereon to measure the temperatures of the fixing heaters  305   a  and  305   b.    
     The recording sheet P having the full-color image fixed thereon is discharged from the fixing apparatus  300  by discharge rollers  11  to be stacked on a discharge tray  7 . A post-processing apparatus may be connected in place of the discharge tray  7 . The image forming apparatus  100  includes a user interface (hereinafter referred to as “console portion”)  202  including an input/output interface. The user can operate the console portion  202  to give an instruction to perform a print operation as described above. The console portion  202  includes a display unit  203  configured to display indications to be shown to the user, such as states of the image forming apparatus  100  and the fixing apparatus  300 , information on, for example, the number of sheets to be subjected to image formation and whether or not the image formation is in progress, and occurrence of jamming and the location thereof. Further, the display unit  203  displays, to a serviceman, an indication of a cause of an operation failure for improving the efficiency of service work, and a guide indication of an initialization operation at the time of installation of the main body or replacement of the developing device, and receives the start of an operation. 
       FIG. 2  is a block diagram for illustrating a control unit  200  for the image forming apparatus  100  and the fixing apparatus  300 . In  FIG. 2 , power lines  600  to  602 ,  604  to  607 ,  609 , and  610  serving as AC power supply lines are indicated by the thickest lines. Power lines  603  and  611  to  613  serving as DC power supply lines are indicated by lines thinner than the AC power supply lines. Signal lines  700  to  705  serving as communication control lines of a CPU  104   a  are indicated by the thinnest lines. 
     First, connection of the power lines  600 ,  601 ,  602 , and  603  of the image forming apparatus  100  is described. Power is supplied to the image forming apparatus  100  from a commercial power source or other alternating-current power sources (AC power sources) through a power plug (hereinafter referred to as “first AC receiving portion”)  101  and the power line  600  serving as a first power cable. In  FIG. 2 , for the sake of easiness in description, one power line  600  is provided to the image forming apparatus  100 . However, the number of power cables of the image forming apparatus  100  is not limited to one. A plurality of power cables may be provided to the image forming apparatus  100 . 
     The power from the AC power source received via the first AC receiving portion  101  is supplied to a first power distribution portion  102  through the power line  600 . The power is supplied from the first power distribution portion  102  to an AC-DC power source  103  for image formation (first power source unit) through the power line  601 . Further, the power is supplied from the first power distribution portion  102  to a relay connector  132  through the power line  602 . The relay connector  132  of the image forming apparatus  100  is removably connected to a connector (hereinafter referred to as “third AC receiving portion”)  332  of the fixing apparatus  300 . The power from the AC power source is supplied from the third AC receiving portion  332  to the inside of the fixing apparatus  300  via the relay connector  132 . 
     The AC-DC power source  103  for image formation converts an alternating-current voltage (AC voltage) into a direct-current voltage (DC voltage) to generate the DC voltage. The AC-DC power source  103  for image formation supplies power from a DC power source to an image formation controller  106 , the CPU  104   a , and the console portion  202  through the power line  603 . The image formation controller  106  and the CPU  104   a  form a first controller. The power from the DC power source is supplied to each load (not shown) and sensors (not shown) via the image formation controller  106 . 
     Next, connection of the power lines  604  to  613  of the fixing apparatus  300  is described. Power is supplied to the fixing apparatus  300  from a commercial power source or other alternating-current power sources (AC power sources) through a power plug (hereinafter referred to as “second AC receiving portion”)  301  and the power line  604  serving as a second power cable. In  FIG. 2 , for the sake of easiness in description, one power line  604  is provided to the fixing apparatus  300 . However, the number of power cables of the fixing apparatus  300  is not limited to one. A plurality of power cables may be provided to the fixing apparatus  300 . 
     The power from the AC power source received from the second AC receiving portion  301  is supplied to a second power distribution portion  302  through the power line  604 . The power from the second AC receiving portion  301  is supplied from the second power distribution portion  302  to an AC-DC power source  303  for fixing (second power source unit) through the power line  605 . The power from the AC power source received from the second AC receiving portion  301  is supplied from the second power distribution portion  302  to a temperature adjustment controller  304  through the power line  606 . The power from the second AC receiving portion  301  is supplied from the temperature adjustment controller  304  to the fixing heater  305   a  through the power line  607 . The fixing heater  305   a  is built into the fixing roller  5   a  of the fixing unit  5  illustrated in  FIG. 1 . 
     The third AC receiving portion  332  is electrically connected to a connection detecting portion  308  by the power line  608 . The power from the AC power source received from the third AC receiving portion  332  is supplied to the connection detecting portion  308  through the power line  608 . The power from the third AC receiving portion  332  is supplied from the connection detecting portion  308  to the temperature adjustment controller  304  through the power line  609 . The power from the third AC receiving portion  332  is supplied from the temperature adjustment controller  304  to the fixing heater  305   b  through the power line  610 . The fixing heater  305   b  is built into the pressure roller  5   b  of the fixing unit  5  illustrated in  FIG. 1 . 
     The connection detecting portion  308  detects whether or not the third AC receiving portion  332  is connected to the relay connector  132  of the image forming apparatus  100 . The connection detecting portion  308  is only required to have a configuration capable of detecting that the power from the AC power source is supplied from the third AC receiving portion  332 , as in zero-cross detection of the AC voltage. A connection detection method of detecting whether or not the third AC receiving portion  332  is connected to the relay connector  132  is not limited the above-mentioned method, and other connection detection methods may be used. 
     The temperature adjustment controller  304  includes a mechanism (switch mechanism) for supplying and blocking the power from the AC power source, for example, a triac. The temperature adjustment controller  304  performs temperature adjustment control of controlling a period of supplying the power from the AC power source so that the fixing heaters  305   a  and  305   b  are brought to appropriate temperatures. In the embodiment, in addition to the fixing heater  305   a  of the fixing roller  5   a , the fixing heater  305   b  is provided to the pressure roller  5   b . Through use of the fixing heaters  305   a  and  305   b , a rising time period of the fixing temperature is shortened, and abrupt temperature drop at the time of sheet passage is suppressed. 
     The AC-DC power source  303  for fixing converts an alternating-current voltage (AC voltage) into a direct-current voltage (DC voltage). The AC-DC power source  303  for fixing supplies power from a DC power source to a fixing controller (second controller)  306  though the power line  611 . The power from the DC power source is further supplied to each load (not shown) and sensors (not shown) via the fixing controller  306 . The AC-DC power source  303  for fixing supplies the power from the DC power source to the temperature adjustment controller  304  through the power line  612 . The power from the DC power source supplied to the temperature adjustment controller  304  is used as power for temperature adjustment control. The AC-DC power source  303  for fixing supplies the power from the DC power source to the connection detecting portion  308  through the power line  613 . The power from the DC power source supplied to the connection detecting portion  308  is used as power for connection detection. 
     Next, connection of the signal lines  700  to  705  of the CPU  104   a  is described. The CPU  104   a  integrally controls the image forming apparatus  100  and the fixing apparatus  300 . The CPU  104   a  is connected to a ROM (memory unit)  104   b  so as to allow communication thereto or therefrom by the signal line  700 . The CPU  104   a  is connected to a RAM (memory unit)  104   c  so as to allow communication thereto or therefrom by the signal line  701 . The CPU  104   a  executes various sequences related to an image formation sequence determined in advance, in accordance with a program stored in the ROM  104   b . At this time, the CPU  104   a  stores required data into the RAM  104   c . The RAM  104   c  stores, for example, a setting value of a high voltage to be applied at the time of image formation, various kinds of data, and image formation instruction information from the console portion  202 . The RAM  104   c  is supplied with power from a battery (not shown) to store data even when the image forming apparatus  100  is powered off. 
     The CPU  104   a  is connected to the image formation controller  106  so as to allow communication thereto or therefrom by the signal line  702 . The CPU  104   a  performs drive of each load (for example, motor, solenoid, or clutch) of the image forming apparatus  100 , acquisition of information from the sensors, and image formation control (for example, high-voltage output control or drum drive control) via the image formation controller  106 . Further, the CPU  104   a  is connected to the console portion  202  so as to allow communication thereto or therefrom by the signal line  703 . 
     The CPU  104   a  is connected to a relay connector  131  by the signal line  704 . The relay connector  131  is connected to a connector  331  connected to the signal line  705  of the fixing apparatus  300 . The CPU  104   a  performs communication to/from the fixing apparatus  300  via the signal line  704 , the relay connector  131 , the connector  331 , and the signal line  705 . Further, the connector  331  is connected to the fixing controller  306 , the temperature adjustment controller  304 , and the connection detecting portion  308 , which are provided in the fixing apparatus  300 , via the signal line  705 . 
     The CPU  104   a  performs drive of each load in the fixing apparatus  300  and acquisition of information from the sensors via the fixing controller  306 . The CPU  104   a  controls the switch mechanism of the temperature adjustment controller  304  to control the power from the AC power source to be supplied to the fixing heaters  305   a  and  305   b  so that the fixing roller  5   a  and the pressure roller  5   b  are brought to target temperatures. The CPU  104   a  controls the temperature adjustment controller  304  based on temperature information of the thermistor  15   a  and the thermistor  15   b  ( FIG. 1 ) provided to the fixing roller  5   a  and the pressure roller  5   b , respectively, to thereby maintain the temperatures of the fixing roller  5   a  and the pressure roller  5   b  at target temperatures. The CPU  104   a  acquires a detection state of the connection detecting portion  308  configured to perform connection detection between the third AC receiving portion  332  and the relay connector  132 . 
     In the embodiment, a total value of power consumption of the image forming apparatus  100  and power consumption of the fixing apparatus  300  is set within a range of a total value of a rated voltage of the power line  600  of the first AC receiving portion  101  and a rated voltage of the power line  604  of the second AC receiving portion  301 . Almost all power consumed by the fixing apparatus  300  is consumed by the fixing heater  305   a . The power from the first AC receiving portion  101  is supplied via the image forming apparatus  100  to one fixing heater  305   b  of the plurality of fixing heaters  305   a  and  305   b  provided in the fixing apparatus  300 . In this manner, each of the power consumption of the image forming apparatus  100  and the power consumption of the fixing apparatus  300  can fall within a range of rated power consumption of an outlet for a general household. 
     The fixing apparatus  300  is supplied with power from the image forming apparatus  100  via the third AC receiving portion  332 . The image forming operation is executed under a state in which the relay connector  131  is connected to the connector  331  and further the relay connector  132  is connected to the third AC receiving portion  332 . In a case where the connector  331  is not connected to the relay connector  131 , the CPU  104   a  cannot communicate to/from the fixing apparatus  300 . Thus, the CPU  104   a  displays an error on the display unit  203  of the console portion  202  to urge the user or the serviceman to connect the connector  331 . 
     The third AC receiving portion  332  is connected to the connection detecting portion  308  via the power line  608 . The connection detecting portion  308  detects whether or not the third AC receiving portion  332  is connected to the relay connector  132 , and transmits a detection result to the CPU  104   a  via the signal line  705 . The CPU  104   a  can instantly detect the connection state between the relay connector  132  and the third AC receiving portion  332  based on the detection result of the connection detecting portion  308 . In a case where the third AC receiving portion  332  is not connected to the relay connector  132 , the CPU  104   a  receives a low-level signal from the connection detecting portion  308 . The CPU  104   a  displays an error on the display unit  203  of the console portion  202  to urge the user or the serviceman to connect the third AC receiving portion  332 . 
     Even when the fixing heater  305   b  is not heated, temperature adjustment control to a temperature that allows fixing is possible through use of the fixing heater  305   a  alone. However, there is a fear in that the temperature drop at the time when a sheet passes through the fixing apparatus may not be able to be suppressed, and the image quality may be reduced. In a case where the temperature drop occurs at the time of sheet passage, the fixing performance reduces from the middle of the successive printing, but it is difficult to detect the reduction in image quality. A plurality of fixing heaters may be provided to the fixing apparatus  300  to suppress the temperature drop at the time of sheet passage, but the power consumption of the fixing apparatus  300  may exceed the rated power consumption. In the embodiment, power from the second AC receiving portion  301  of the fixing apparatus  300  is supplied to one fixing heater  305   a  of the plurality of fixing heaters  305   a  and  305   b  provided to the fixing apparatus  300 . Power from the third AC receiving portion  332  is supplied to another fixing heater  305   b . In this case, in a case where the third AC receiving portion  332  is not connected to the relay connector  132 , power is not supplied to the fixing heater  305   b . Thus, the CPU  104   a  is configured to allow detection of connection of the third AC receiving portion  332  through use of the connection detecting portion  308 . 
     Next, with reference to  FIG. 3 , connection detection of the third AC receiving portion  332  to be executed by the CPU  104   a  is described.  FIG. 3  is a flow chart for illustrating the connection detection of the third AC receiving portion  332 . The CPU  104   a  executes the connection detection of the third AC receiving portion  332  in accordance with a program stored in the ROM  104   b . In a case where the connection detection is started, the CPU  104   a  determines whether or not a high-level connection detection signal being a logic signal is output from the connection detecting portion  308  (Step S 700 ). 
     In a case where the third AC receiving portion  332  is not connected to the relay connector  132 , the connection detecting portion  308  outputs a low-level signal. In a case where the third AC receiving portion  332  is connected to the relay connector  132 , the connection detecting portion  308  outputs a high-level signal. In a case where the connection detection signal is not high level (NO in Step S 700 ), the CPU  104   a  displays, on the display unit  203  of the console portion  202 , for example, a message of “please check connection between image forming apparatus and fixing apparatus” to urge the user or the serviceman to check the connection (Step S 701 ). The CPU  104   a  displays the above-mentioned message on the display unit  203  and stands by while the connection detection signal from the connection detecting portion  308  is low level. When the user or the serviceman connects the third AC receiving portion  332  to the relay connector  132 , the connection detection signal from the connection detecting portion  308  changes from low level to high level. 
     When the connection detection signal is high level (YES in Step S 700 ), the CPU  104   a  ends the connection detection. In a case where the connector  331  is not connected to the relay connector  131 , the CPU  104   a  cannot detect the connection detection signal from the connection detecting portion  308 . In this case, similarly to the case in which the third AC receiving portion  332  is not connected to the relay connector  132 , the CPU  104   a  detects that the connection detection signal is low level. Thus, the connection detection of the third AC receiving portion  332  involves connection detection of the connector  331 . 
     Next, with reference to  FIG. 4 , an operation performed after the power source is turned on is described.  FIG. 4  is a flow chart for illustrating the operation performed after the power source is turned on. The CPU  104   a  executes the print operation in accordance with the program stored in the ROM  104   b . When the image forming apparatus  100  is powered on, the CPU  104   a  is supplied with power and activated by the AC-DC power source  103  for image formation. The CPU  104   a  executes the connection detection illustrated in  FIG. 3  at the time of activation (Step S 800 ). The CPU  104   a  determines whether or not the print instruction is input (Step S 801 ). In a case where no print instruction is input (NO in Step S 801 ), the connection detection of Step S 800  is executed again. 
     In a case where the print instruction is input (YES in Step S 801 ), the CPU  104   a  executes printing via the image formation controller  106 , the fixing controller  306 , and the temperature adjustment controller  304  (Step S 802 ). In a case where the instructed printing is completed (YES in Step S 803 ), the processing returns to Step S 800 . 
     In the embodiment, as illustrated in  FIG. 4 , the CPU  104   a  executes the connection detection at the time of power activation or in a case where the print instruction is waited for. However, the timing to perform the connection detection is not limited thereto. For example, the CPU  104   a  may execute the connection detection during the print operation. Conversely, the CPU  104   a  may not execute the connection detection during a period in which the print instruction is waited for after the connection detection is performed at the time of power activation. Further, the connection detection may be executed when a detection mechanism configured to detect mechanical connection between the image forming apparatus  100  and the fixing apparatus  300  detects a change from non-connection to connection between the image forming apparatus  100  and the fixing apparatus  300 . Further, the connection between the image forming apparatus  100  and the fixing apparatus  300  may be determined by the CPU  104   a  based on communication establishment between the CPU  104   a  and the fixing controller  306  instead of detecting the mechanical connection between the image forming apparatus  100  and the fixing apparatus  300 , and then the connection detection may be executed. In the embodiment, the fixing heater  305   a  and the fixing heater  305   b  are provided to the fixing roller  5   a  and the pressure roller  5   b , respectively. However, the number of fixing heaters is not limited thereto. For example, a plurality of fixing heaters may be provided only to the fixing roller  5   a . Alternatively, a plurality of fixing heaters may be provided to each of the fixing roller  5   a  and the pressure roller  5   b.    
     Further, even when the image forming apparatus  100  and the fixing apparatus  300  are arranged in one housing  400 , the relay connector  132  and the third AC receiving portion  332  are provided in the housing  400 . 
     According to the embodiment, it is possible to detect whether or not the third AC receiving portion  332  configured to receive power from the AC power source supplied from the commercial power source to the fixing apparatus  300  via the image forming apparatus  100  is normally connected. 
     According to the embodiment, it is possible to detect whether or not connection is established so that power is normally supplied from the AC power source to the fixing device via a different power cable. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2019-188406, filed Oct. 15, 2019, which is hereby incorporated by reference herein in its entirety.