JP4404022B2 - Image forming apparatus - Google Patents

Description

The present invention relates to an image forming apparatus including a plurality of electrical components that receive power from a single power supply, and more particularly to an image forming apparatus that takes into account stabilization of the power supply voltage of the power supply.

  Conventionally, as a DC power source for various electronic devices such as laser printers, for example, a relatively low voltage (eg, 3.3V) stabilized output for power supply to a CPU or the like, a printer engine, a fan, etc. In some cases, a power supply having a drive system output with a relatively high voltage (for example, 24 V) for supplying power to a plurality of electrical components may be used. In addition, as this type of power supply, a switching power supply including a single transformer having the control system output and the drive system output on the secondary side may be used.

With this type of power supply, when the drive system output load is small and the control system output load is large, the drive system output voltage will increase if an attempt is made to stabilize the control system output voltage. There is. Therefore, in such a case, it has been proposed to increase the load of the drive system output by driving a load such as a fan to suppress the voltage increase of the drive system output (see, for example, Patent Document 1). ).
JP 11-196574 A

However, in order to suppress the voltage rise of the drive system output by driving a fan or the like as in the above technique, a voltage having a rated voltage higher than the original voltage of the drive system output is not used. Fans are destroyed when climbing. For this reason, it becomes necessary to use an expensive fan having a high rated voltage, which increases the manufacturing cost of the apparatus. In addition to the power supply having two outputs for the control system and the drive system as described above, when a plurality of electrical components are supplied with power from one power supply, the original power supply is prepared in preparation for voltage fluctuation. It was necessary to use an electrical component having a rated voltage higher than the voltage. Accordingly, the present invention provides an image forming apparatus having a plurality of electrical components that are supplied with power from a single power supply, and can vary the power supply voltage without using electrical components having a rated voltage higher than the original power supply voltage. It was made for the purpose of suppression.

The present invention has been made in order to achieve the above object, an image forming apparatus having a plurality of electrical components provided with a image forming means for forming an image on a recording medium, supplied with electric power from a single power supply, The power source includes a switching power source including one transformer having a stabilized output for a control system and a drive system output for supplying power to the plurality of electrical components. And a predetermined electric component whose rated current is larger than that of the cooling fan, and another electric component, wherein power is supplied from the output for the control system, and the predetermined electric component is supplied from the output for the drive system. not power is supplied to the goods and the electrical equipment with the exception of the cooling fan, the above-mentioned predetermined electrical equipment a first operation mode in which current-rated in the predetermined electrical component is energized, the output the control system Power supplied And an energization control means capable of executing a second operation mode in which a current for driving the cooling fan and the predetermined electrical component at full speed is energized from the drive system output. It is a feature.

In the present invention configured as described above, when the output voltage of the power supply may increase, that is, the power is supplied from the control system output of the power supply, and the predetermined electrical component is supplied from the drive system output. In the first operation mode in which power is not supplied to the electrical components other than the cooling fan, the energization control means energizes the predetermined electrical component with a current less than the rating of the predetermined electrical component. For this reason, the increase in the output voltage can be suppressed by increasing the power supply current flowing out from the power supply. In addition, since the current supplied to the predetermined electrical component is less than the rated value, the predetermined electrical component can be prevented from being destroyed even if the rated voltage of the predetermined electrical component is not so high. Further, since the current supplied to the predetermined electrical component is smaller than the rated value as described above, there is little influence on the image forming apparatus due to the energization, and the degree of freedom of selection of the predetermined electrical component is expanded. For this reason, an increase in output voltage can be suppressed more satisfactorily. Therefore, in the present invention, fluctuations in the power supply voltage can be suppressed without using an electrical component having a high rated voltage, and thus the manufacturing cost of the image forming apparatus can be reduced.

When the power supply is configured as described above, in the operation mode in which power is supplied from the control system output as described above and power is not supplied from the drive system output to the electrical components except for the predetermined electrical component and the cooling fan. It is known that the voltage of the drive system output is likely to increase because the current flowing from the drive system output is small despite the power supplied from the control system output. Therefore, in the present invention, in such a first operation mode, a current less than the above-mentioned rating is applied to a predetermined electrical component supplied with power from the drive system output, thereby increasing the voltage of the drive system output. Can be suppressed well. Further, as described above, there has been a conventional idea to drive the cooling fan to suppress the voltage increase of the drive system output. However, in the present invention, the rated current of the predetermined electrical component is the rating of the cooling fan. Since it is larger than the current, it is possible to more effectively suppress the drive system output voltage from rising. Further, in the first operation mode, the cooling fan may be energized so as to be driven at half speed.

In addition, as the output voltage of the drive system output tends to increase, the energization control means sets the current value of the current less than the rating that energizes the predetermined electrical component in the first operation mode to be larger. May be. For example, it is known that when an expansion memory is connected to the control system, the output voltage at the drive system output is likely to increase. Therefore, as the output voltage of the drive system output tends to increase, the current value less than the above rating is set larger to suppress the drive system output voltage from increasing more favorably. Can do.

Further, the number of the predetermined electrical components is not limited to one. For example, the predetermined electrical components include a plurality of the predetermined electrical components, and an abnormality detection unit that detects at least one abnormality among the plurality of predetermined electrical components. When the detecting unit detects an abnormality of the one predetermined electrical component, the energization control unit does not energize the one predetermined electrical component in the first operation mode, and does not apply the rating to the other predetermined electrical component. Less than a current may be applied. In this case, by not energizing the predetermined electrical component in which an abnormality has been detected, there is a further effect that the predetermined electrical component can be prevented from being damaged.

The upper SL predetermined electric component may be a transport driving device for conveying the recording medium through the image forming means.

In this case, when the current less than the rating is set to a current value at which the recording medium is not conveyed by the conveyance driving device, the following effects are further produced. That is, in this case, since the recording medium is not transported regardless of whether or not the current is supplied to the transport driving device, the operation of the image forming apparatus as an electronic apparatus is not affected as described above. It is possible to suppress a rise in the voltage of the drive system output. Further, in this case, energization of the current less than the rating to the transport driving device may be performed after temporarily stopping energization to the transport driving device.

The upper Kiga image forming unit includes a photosensitive member on which an electrostatic latent image is formed on the surface in accordance with the exposure, an exposure unit for scanning exposure of the surface of the photosensitive member in response to rotation of the polygon mirror, the photosensitive Developing means for developing a developer on an electrostatic latent image formed on the surface of the body, and transferring means for transferring the developer attached to the photosensitive member by the developing means to the recording medium. The predetermined electrical component may be a polygon driving device that rotationally drives the polygon mirror.

  In this case, the predetermined electrical component includes the polygon driving device and a transport driving device for transporting the recording medium through the image forming unit, and covers a transport path of the recording medium. A cover and an opening detection means for detecting the opening of the cover, and when the opening detection means detects the opening of the cover, the energization control means does not energize the transport drive device, and the polygon A current less than the above-mentioned rating may be applied to the driving device.

  In this type of image forming apparatus, when the cover is opened, the recording medium may be pulled by the user. If the recording medium is pulled while a current less than the above-mentioned rating is applied to the transport driving device, an unexpected load is applied to the transport driving device, which is not preferable. Therefore, in the present invention, when the opening detection unit detects the opening of the cover, the energization control unit does not energize the transport driving device, but energizes the polygon driving device with a current less than the rated value. For this reason, it is possible to prevent breakage of the transport driving means even better.

  Next, embodiments of the present invention will be described with reference to the drawings. As described below, the present embodiment is an application of the present invention to a so-called laser printer as an image forming apparatus.

1. FIG. 1 is a perspective view showing the appearance of a laser printer 1 according to the present embodiment. The laser printer 1 is installed with the upper side of the paper as the upper side in the direction of gravity, and usually the left front side of the paper is the front side. Used as.

  The housing 3 of the laser printer 1 is formed in a substantially box shape (a rectangular parallelepiped shape), and a recording medium discharged from the housing 3 after printing is placed on the upper surface side of the housing 3. A paper discharge tray 5 is provided. In the present embodiment, paper such as paper or an OHP sheet is assumed as the recording medium.

  Further, the paper discharge tray 5 is configured with an inclined surface 5a that is inclined so as to descend from the upper surface of the housing 3 toward the rear side, and printing is finished on the rear end side of the inclined surface 5a. A discharge unit 7 for discharging the recording medium is provided.

  The upper cover 9 formed in a substantially U-shape so as to surround the paper discharge tray 5 (inclined surface 5a) in the casing 3 includes a case where the laser printer 1 is connected to the network and a case where the laser printer 1 is disconnected from the network. Are provided, a line switch 1a for switching, a job cancel switch 1b for forcibly ending (interrupting) printing, and the like.

2. Internal Configuration of Laser Printer FIG. 2 is a longitudinal sectional view showing the internal configuration of the laser printer 1. The image forming unit 10 accommodated in the laser printer 1 constitutes an image forming unit that forms an image on a recording medium, and the feeder unit 20 is a conveying unit that supplies the recording medium to the image forming unit 10. It constitutes a part of

  The first discharge chute 30 and the second discharge chute 40 are turned approximately 180 ° so as to make a U-turn in the transport direction of the recording medium on which image formation has been completed in the image forming unit 10, and the recording medium is fixed to the fixing unit. It constitutes a guide member that guides to a discharge portion 7 provided above 90 (details will be described later).

  The forward / reverse switching mechanism 50 reverses the transport direction of the recording medium ejected from the image forming unit 10 and simultaneously discharges the recording medium whose transport direction is reversed to the image forming unit 10 side. The double-sided printing unit 60 constitutes a conveyance path for a recording medium whose conveyance direction is reversed by the forward / reverse switching mechanism 50.

2.1. Feeder unit The feeder unit 20 includes a paper feed tray 21 housed in the lowermost part of the housing 3, a paper feed roller 22 that is provided above the front end of the paper feed tray 21 and transports a recording medium to the image forming unit 10, In addition, the image forming apparatus includes a separation roller 23 and a separation pad 24 that separate the recording medium conveyed by the paper feeding roller 22 one by one. Then, the recording medium placed on the paper feed tray 21 is conveyed to the image forming unit 10 disposed substantially at the center in the housing 3 so as to make a U-turn on the front side in the housing 3. Is done.

  In addition, in the conveyance path of the recording medium from the paper feed tray 21 to the image forming unit 10, the image forming surface (printing surface) of the recording medium is attached to the outside of the top portion of the portion that turns in a substantially U shape. A paper dust removing roller 25 that removes paper dust and the like is disposed, and a counter roller 26 that presses the recording medium to be conveyed against the paper dust removing roller 25 is disposed inside the top portion.

  Further, at the entrance of the image forming unit 10 in the transport path from the paper feed tray 21 to the image forming unit 10, a resist composed of a pair of rollers that applies a transport resistance to the recording medium and adjusts the transport state of the recording medium. A roller 27 is provided.

2.2. Image Forming Unit The image forming unit 10 includes a scanner unit 70, a process cartridge 80, a fixing unit 90, and the like.

2.2.1. Scanner unit The scanner unit 70 is provided at an upper part in the housing 3 and constitutes an exposure unit that forms an electrostatic latent image on the surface of a photosensitive drum 81 to be described later. And a polygon mirror 72 driven by a polygon motor 450, an fθ lens 73, a reflecting mirror 74, a lens 75, and a reflecting mirror 76.

  Then, the laser beam based on the image data emitted from the laser light source is deflected by the polygon mirror 72, passes through the fθ lens 73, the optical path is turned back by the reflecting mirror 74, and further passes through the lens 75, and then reflected. When the optical path is bent downward by the mirror 76, it is irradiated onto the surface of the photosensitive drum 81 as a photosensitive member, and an electrostatic latent image is formed.

2.2.2. Process Cartridge The process cartridge 80 is detachably disposed in the housing 3 below the scanner unit 70. The process cartridge 80 includes a photosensitive drum 81, a charger 82, a transfer roller 83, and a development roller. It is composed of a cartridge 84 and the like.

  The photoconductive drum 81 extends along the longitudinal direction of the drum main body 81a at a cylindrical drum main body 81a formed by a positively chargeable photosensitive layer whose outermost layer is made of polycarbonate or the like, and the axis of the drum main body 81a. And a drum shaft 81b that rotatably supports the drum body 81a.

  The charger 82 charges the surface of the photosensitive drum 81 prior to the formation of the electrostatic latent image by the laser beam. The charger 82 is predetermined so as not to come into contact with the photosensitive drum 81 at the upper rear side of the photosensitive drum 81. The photosensitive drum 81 is disposed opposite to the photosensitive drum 81 with a gap. The charger 82 according to the present embodiment employs a scorotron charger that charges the surface of the photosensitive drum 81 substantially uniformly with positive charges using corona discharge.

  The transfer roller 83 is disposed so as to face the photosensitive drum 81 and rotates in conjunction with the rotation of the photosensitive drum 81, and when the recording medium passes near the photosensitive drum 81, the transfer roller 83 is attached to the photosensitive drum 81. By applying a charge opposite to the charged charge (in this embodiment, a negative charge) to the recording medium from the side opposite to the printing surface, the toner attached to the surface of the photosensitive drum 81 is printed on the recording medium. It constitutes a transfer means for transferring to the surface.

  The developing cartridge 84 includes a toner storage chamber 84a that stores toner, a toner supply roller 84b that supplies the toner to the photosensitive drum 81, a developing roller 84c, and the like.

  The toner stored in the toner storage chamber 84a is supplied to the developing roller 84c as a developing unit by the rotation of the toner supply roller 84b. Further, the toner supplied to the developing roller 84c is carried on the surface of the developing roller 84c, adjusted to have a predetermined thickness by the layer thickness regulating blade 84d and frictionally charged, and then in the scanner unit 70. The exposed surface of the photosensitive drum 81 is supplied.

2.2.3. Fixing Unit The fixing unit 90 is disposed downstream of the photosensitive drum 81 in the recording medium conveyance direction, and heats and melts the toner transferred to the recording medium for fixing. Specifically, the fixing unit 90 is disposed on the printing surface side of the recording medium to heat the toner, and is disposed on the opposite side of the heating roller 91 across the recording medium. A pressure roller 92 that presses the recording medium toward the heating roller 91 is provided.

  Incidentally, the heating roller 91 according to the present embodiment is composed of a metal tube whose surface is coated with a fluororesin, and a halogen lamp for heating in the metal tube. The metal roller shaft is covered with a roller made of a rubber material.

In the image forming unit 10 described above, an image is formed on a recording medium as follows.
In other words, the surface of the photosensitive drum 81 is uniformly positively charged by the charger 82 as it rotates, and then exposed by high-speed scanning of the laser beam emitted from the scanner unit 70. As a result, an electrostatic latent image corresponding to the image to be formed on the recording medium is formed on the surface of the photosensitive drum 81.

  Next, when the developing roller 84c rotates, the positively charged toner carried on the developing roller 84c is formed on the surface of the photosensitive drum 81 when it contacts the photosensitive drum 81. Of the electrostatic latent image, that is, the surface of the uniformly positively charged photosensitive drum 81, is supplied to the exposed portion where the potential is lowered by the laser beam. As a result, the electrostatic latent image on the photosensitive drum 81 is visualized, and a toner image by reversal development is carried on the surface of the photosensitive drum 81.

  Thereafter, the toner image carried on the surface of the photosensitive drum 81 is transferred to a recording medium by a transfer bias applied to the transfer roller 83. The recording medium to which the toner image has been transferred is conveyed to the fixing unit 90 and heated, and the toner transferred as the toner image is fixed to the recording medium, thereby completing the image formation.

2.3. First Discharge Chute In the laser printer 1 according to the present embodiment, the first discharge chute 30 is disposed on the rear end side in the housing 3 as shown in FIG. On the side, that is, in the vicinity of the first discharge chute 30, a rear cover 3b that opens and closes an opening 3a formed in the housing 3 is rotatably assembled.

  The first discharge chute 30 is disposed downstream of the fixing unit 90 in the transport direction in the transport direction of the recording medium, and the transport direction of the recording medium in which image formation has been completed in the image forming unit 10. Is rotated approximately 90 ° to guide the recording medium to the second discharge chute 40.

  The first discharge chute 30 is disposed on the downstream side in the recording medium conveyance direction from the front chute 31 disposed at a portion where the recording medium discharged from the fixing unit 90 first contacts, and the front chute 31. The outer chute 32 is provided. Each of the front chute 31 and the outer chute 32 is formed with a plurality of protruding front chute ribs 31a and outer chute ribs 32a extending along the recording medium conveyance direction. The ribs 31a and 32a are guided toward the second discharge chute 40 while being in contact with the leading ends of the ribs 31a and 32a. Further, the first discharge chute 30 is provided with a first paper discharge roller 34a, and a first pinch roller 34b is provided at a position facing the first paper discharge roller 34a on the fixing unit 90 side.

  The first paper discharge roller 34a is a transport roller that applies a transport force to the recording medium by rotating while contacting the recording medium, and the first pinch roller 34b is a first paper discharge sandwiching the recording medium. The recording medium is pressed toward the first paper discharge roller 34a from the side opposite to the roller 34a. For this reason, the recording medium discharged from the fixing unit 90 is conveyed to the second discharge chute 40 side so as to be sandwiched between the first discharge roller 34a and the first pinch roller 34b.

2.4. Second discharge chute The second discharge chute 40 is provided on the upper cover 9 with a predetermined gap 40a with respect to the first discharge chute 30, and the conveying direction is turned by approximately 90 ° by the first discharge chute 30. The recording medium is further turned by approximately 90 ° and guided to the discharge unit 7.

  Further, a gap 40a between the first discharge chute 30 and the second discharge chute 40 is a recording medium conveyance path (conveyance path indicated by a thick two-dot chain line) whose conveyance direction is reversed by the forward / reverse switching mechanism 50. Part of. Incidentally, in FIG. 2, a transport path indicated by a thick one-dot chain line indicates a transport path of a recording medium transported by the feeder unit 20.

2.5. Forward / reverse switching mechanism and double-sided printing unit The forward / reverse switching mechanism 50 switches the rotation direction of the second paper discharge roller 43 to discharge the recording medium conveyed from the first discharge chute 30 to the discharge unit 7 (paper discharge). The case of transporting to the tray 5) side and the case of transporting to the gap 40a side are switched. For example, the forward / reverse switching mechanism 50 uses a solenoid (not shown) to switch the number of gears that transmit a rotational force generated by a DC motor 440 (see FIG. 4), which will be described later, to the second paper discharge roller 43 to perform the second paper discharge. This is a mechanism for switching the rotation direction of the roller 43. The second pinch roller 43b disposed opposite to the second paper discharge roller 43 rotates in a manner to sandwich the recording medium in cooperation with the second paper discharge roller 43, so that the second recording roller and the second recording roller 43b are rotated. The contact surface pressure with the paper discharge roller 43 is increased.

  The duplex printing unit 60 has a plurality of guide ribs (not shown) formed in a protruding shape so as to extend in the conveyance direction (front-rear direction) of the recording medium, and contacts the recording medium while rotating. A plurality of rollers (not shown) for applying a conveyance force to the recording medium are provided, and the recording medium conveyed from the second paper discharge roller 43 through the gap 40a is conveyed to the image forming unit 10. .

2.6. Power Supply Unit A power supply unit 100 that supplies power to each unit of the laser printer 1 is disposed between the fixing unit 90 and the duplex printing unit 60. Next, the configuration of the power supply unit 100 will be described with reference to the circuit diagram of FIG. In addition, the power supply unit 100 is configured to simultaneously supply a voltage (24V in the present embodiment) supplied to various motors and the like and a voltage (3.3V in the present embodiment) supplied to a logic circuit that controls each unit. Output.

  As shown in FIG. 3, the power supply unit 100 includes, on the primary side of the transformer 200, a rectifier circuit 120 that rectifies current supplied from a commercial power supply 110 (AC100V), a smoothing capacitor 130, and a transformer 200. A switching element 140 that switches energization to the primary coil and an oscillation control circuit 150 that controls ON / OFF of the switching element 140 are provided.

  The oscillation control circuit 150 constitutes a photocoupler together with a secondary side photodiode 161 described later, and internally includes a phototransistor 160 that is turned on / off by receiving light emitted from the photodiode 161. In the present embodiment, the oscillation control circuit 150 assumes a self-excited configuration in which the switching element 140 oscillates at an oscillation frequency defined by ON / OFF of the phototransistor 160. A separately-excited configuration that controls the energization time to the primary side of the transformer 200 may be used. In the present embodiment, a flyback in which energy is accumulated in the transformer 200 when the switching element 140 is turned on and an electromotive force is generated on the secondary side when the switching element 140 on the primary side is turned off. The configuration of the method was adopted.

  On the secondary side of the transformer 200, a first output line 311 that outputs a voltage of 24V via a rectifier element 310 and a second output line 313 that outputs a voltage of 3.3V via a rectifier element 312 are provided. It has been. Since the voltage of 3.3V output to the second output line 313 is supplied to the logic circuit or the like as described above, it needs to be stabilized. Therefore, in the power supply unit 100, a photodiode 161 is connected between the second output line 313 and the ground line 314, and the output voltage of the second output line 313 is obtained by the photodiode 161 and the phototransistor 160 that constitutes the photocoupler. Feedback to the primary side.

  The photodiode 161 is turned on when the output of the second output line 313 becomes higher than a predetermined value and the shunt regulator 321 becomes conductive from the second output line 313 to the ground line 314. Note that the voltage of the second output line 313 at which the shunt regulator 321 becomes conductive can be finely adjusted by the variable resistor 330. In the self-excited type as in the present embodiment, when the photodiode 161 is lit, the oscillation frequency of the switching element 140 is increased, the amount of energization on the primary side of the transformer 200 is decreased, and the voltage on the secondary side is decreased. Is feedback controlled. On the other hand, when the voltage of the second output line 313 decreases, the photodiode 161 is turned off and the primary-side energization amount increases.

2.7. As shown in FIGS. 1 and 2, the laser printer 1 further includes a main fan 410 that cools the entire image forming unit 10 around the fixing unit 90 as a cooling fan. And a PS fan 420 that cools the power supply unit 100. As shown in FIG. 4, the main fan 410 and the PS fan 420 are connected to an ASIC (application specific integrated circuit) 500 incorporating a CPU together with a solenoid 430, a DC motor 440, and a polygon motor 450. Yes. Note that the solenoid 430 shown in FIG. 4 switches whether or not the rotational force generated by the DC motor 440 is transmitted to the paper feed roller 22. The DC motor 440 is configured as a transport driving device that drives various rollers including the second paper discharge roller 43 and the paper feed roller 22 described above, the photosensitive drum 81, and the like. The main fan 410, the PS fan 420, the solenoid 430, the DC motor 440, the polygon motor 450, and the like are supplied with power from the first output line 311 of the power supply unit 100.

  As shown in FIG. 4, the ASIC 500 is connected to the main fan 410 via the main fan drive circuit 411, and determines whether or not the aforementioned 24V is supplied to the main fan 410 via the main fan drive circuit 411. Switch. Similarly, the ASIC 500 is connected to the PS fan 420 via the PS fan drive circuit 421, and switches whether or not the aforementioned 24V is energized to the PS fan 420 via the PS fan drive circuit 421. Further, the ASIC 500 is connected to the solenoid 430 via the solenoid drive circuit 431, and switches whether or not the aforementioned 24V is energized to the solenoid 430 via the solenoid drive circuit 431.

  The ASIC 500 is connected to a DC motor 440 via a DC motor drive circuit 441, and a D / A conversion circuit 442 is also connected between the DC motor drive circuit 441 and the ASIC 500. The ASIC 500 directly inputs an ON / OFF signal for switching whether or not the aforementioned 24 V is supplied to the DC motor 440 to the DC motor drive circuit 441, while a PWM signal as a drive current control signal for the DC motor 440 is The signal is input to the DC motor drive circuit 441 through the D / A conversion circuit 442. Similarly, the ASIC 500 is connected to the polygon motor 450 via a polygon motor drive circuit 451, and a D / A conversion circuit 452 is also connected between the polygon motor drive circuit 451 and the ASIC 500. The ASIC 500 directly inputs an ON / OFF signal for switching whether or not to energize the aforementioned 24V to the polygon motor 450 to the polygon motor drive circuit 451, while receiving a PWM signal as a drive current control signal for the polygon motor 450, The data is input to the polygon motor drive circuit 451 via the D / A conversion circuit 452.

  The DC motor 440 is connected to a DC motor speed detection circuit 443 that detects the rotation speed, and the detection result is input to the ASIC 500. Further, the DC motor drive circuit 441 is connected to a DC motor drive current detection circuit 444 that detects the energization current, and the detection result is input to the ASIC 500. Similarly, a polygon motor speed detection circuit 453 is connected to the polygon motor 450, and a polygon motor drive current detection circuit 454 is connected to the polygon motor drive circuit 451. The detection results are input to the ASIC 500, respectively. Further, as shown by a broken line in FIG. 4, the ASIC 500 is configured such that a network board 501 and a DIMM 502 can be optionally mounted as an expansion memory.

3. Control in Laser Printer of Embodiment Next, processing executed by the ASIC 500 will be described. FIG. 5 is a flowchart showing processing executed by the ASIC 500. In the ASIC 500, this process is started when the laser printer 1 is powered on.

  When the process is started, first, in S1 (S represents a step: the same applies hereinafter), current control is performed with the standby current setting I = 3. In the present embodiment, four standby current settings I of 0, 1, 2, and 3 are prepared as shown in Table 1 below during standby (so-called standby mode) in which image formation is not performed. In any standby current setting I, the DC motor current DMI supplied to the DC motor 440 is set to such an extent that the DC motor 440 does not rotate, and the polygon motor current PMI supplied to the polygon motor 450 is The noise generated by the rotation is set to be 50 dB or less, which is an average office noise.

  That is, in S1, current control is performed via the DC motor drive circuit 441 and the polygon motor drive circuit 451 according to the standby current setting I = 3 with the largest amount of current. In subsequent S3, it is determined whether or not the network board 501 is mounted. If not (S2: N), it is determined whether or not the DIMM 502 is mounted in S3. When neither the network board 501 nor the DIMM 502 is mounted (S3: N), in S4, the standby current setting I = 0 with the smallest current amount is set in the memory.

  On the other hand, when the network board 501 is not mounted but the DIMM 502 is mounted (S3: Y), the standby current setting I = 1 with the second smallest amount of current is set in the memory at S5. If the network board 501 is mounted (S2: Y), it is determined in S6 whether the DIMM 502 is mounted. If both the network board 501 and the DIMM 502 are mounted (S6). : Y), in S8, the standby current setting I = 3 with the largest amount of current is set in the memory. Further, when the network board 501 is mounted but the DIMM 502 is not mounted (S6: N), the standby current setting I = 2 with the second largest amount of current is set in the memory at S9.

  As described above, when the standby current setting I is set in the memory in any of S4, S5, S8, and S9, the process proceeds to S10, and current control is performed with the set standby current setting I. In the subsequent S11, it is determined whether or not an image formation command has been issued. If there is no image formation command (S11: N), the process stands by in S11. When an image formation command is generated, for example, when data is input from the outside (S11: Y), a known image formation process by the image forming unit 10 is executed in S12. In subsequent S13, it is determined whether or not the image formation has been completed. If the image formation has not been completed (S13: N), the process proceeds to S12 again and the image formation process is continued.

  When the image formation is completed while the processes of S12 and S13 are repeated (S13: Y), the DC motor current DMI is controlled to 0A in S14. In any of the above-described standby current settings I, the DC motor current DMI is not 0 A. Therefore, if current control according to the standby current settings I is performed immediately after completion of image formation, it may take time to stop the DC motor 440. There is. Therefore, after the image formation is completed, the DC motor current DMI is once controlled to 0 A and the DC motor 440 is braked. In subsequent S15, after waiting for a predetermined time required for the DC motor 440 to stop, the process proceeds to S10 described above, and current control is performed with the standby current setting I set in the memory.

  FIG. 6 is an explanatory diagram illustrating a change in the energization state of each unit according to the above processing. 6 corresponds to the case where both the network board 501 and the DIMM 502 are mounted and the standby current setting I = 3 is set in the memory.

As shown in FIG. 6, in the print mode (corresponding to the second operation mode ) during execution of the image forming process, the main fan 410 (MAIN FAN), PS fan 420 (PS FAN), DC motor 440, polygon Since all the motors 450 are driven at full speed (ON), a large amount of current flows out from the first output line 311 (hereinafter referred to as 24V current). For this reason, the output voltage of the first output line 311 (hereinafter referred to as 24V voltage) is controlled to an appropriate value.

In the standby mode (corresponding to the first operation mode ) that waits until there is an image formation command in S11, the 24V voltage tends to increase, but in this embodiment, the increase is as follows. Can be suppressed. That is, as shown in FIG. 6, when the DC motor current DMI is set to 0 A (OFF) for a predetermined time required for the DC motor 440 to stop, the polygon motor 450 is still driven at full speed. For this reason, the fall of 24V current can be suppressed and the rise of 24V voltage can be suppressed. In the standby mode, since current control is performed with the standby current setting I = 3 in S10, the DC motor current DMI and the polygon motor current PMI are each energized by 0.1 A. Therefore, also in this case, the decrease in the 24V current can be suppressed, and the increase in the 24V voltage can be suppressed.

  Moreover, the DC motor current DMI and the polygon motor current PMI are less than the ratings of the DC motor 440 and the polygon motor 450, and as described above, the DC motor 440 does not rotate and the noise of the polygon motor 450 is also a problem. do not become. Therefore, the DC motor 440 and the polygon motor 450 can be prevented from being destroyed, and the laser printer 1 is externally similar to the conventional Steinby mode in which no power is supplied to them.

  Furthermore, it is known that when the network board 501 and the DIMM 502 are mounted on the ASIC 500, the 24V voltage is likely to rise. In this embodiment, the standby current setting I is changed according to the mounting state. Therefore, the increase in the 24V voltage can be suppressed more satisfactorily. Moreover, since the rated current of the DC motor 440 is larger than the rated current of the main fan 410 and the PS fan 420, the increase in the 24V voltage can be more efficiently suppressed.

  In the above embodiment, the DC motor 440 and the polygon motor 450 are the predetermined electrical components, the solenoid 430 is the other electrical components, the DC motor drive circuit 441, the polygon motor drive circuit 451, and the ASIC 500 are the energization control means. The power supply unit 100 corresponds to a switching power supply, the first output line 311 corresponds to a drive system output, and the second output line 313 corresponds to a control system output. The present invention is not limited to the above-described embodiment, and can be implemented in various forms without departing from the gist of the present invention. For example, in the above-described embodiment, in the standby mode, the main fan 410 and the PS fan 420 may be driven at half speed after the fixing unit 90 is cooled. In this case, noise in the standby mode is further improved. Can be reduced.

  The main fan 410 and the PS fan 420 may be driven at half speed by connecting the main fan 410 and the PS fan 420 to the first output line 311 via a constant voltage element such as a Zener diode or a resistor. According to this configuration, the output voltage of the first output line 311 is supplied to the main fan 410 and the PS fan 420 by being divided by the constant voltage element connected in series with the main fan 410 and the PS fan 420 or the resistor. Therefore, it becomes a half speed drive. At this time, even if the output voltage of the first output line 311 slightly increases, the divided voltage is applied to the main fan 410 and the PS fan 420, so that a voltage exceeding the rated voltage is not applied to them. Further, the present invention can be further implemented in various forms as follows.

4). Second Embodiment FIG. 7 is a block diagram showing a configuration of a control system in a second embodiment of the present invention. As shown in FIG. 7, the present embodiment is different from the above-described embodiment (first embodiment) in that a 24V voltage detection unit 510 that detects the voltage (24V voltage) of the first output line 311 is connected to the ASIC 500. Unlike the embodiment, others are configured similarly. Although not shown in FIG. 7, the network board 501 and the DIMM 502 can be mounted on the ASIC 500 also in this embodiment.

  Next, processing executed by the ASIC 500 in the present embodiment will be described. FIG. 8 is a flowchart showing processing executed by the ASIC 500. In the ASIC 500, this process is started when the laser printer 1 is powered on.

  When the process is started, first, in S1, the DC motor current DMI is controlled to 0.2A and the polygon motor current PMI is controlled to 0.1A. These current values are current values that can reliably suppress an increase in the 24V voltage in the standby mode. In subsequent S2, it is determined whether or not the 24V voltage (24V output) is equal to or higher than the lower limit of the appropriate range in the standby mode.

  When the 24V voltage is less than the lower limit, it can be seen that more current than necessary to suppress the increase in the 24V voltage is applied to the DC motor 440 and the like. Therefore, in this case (S2: N), it is determined in S3 whether or not the polygon motor current PMI is 0A. If PMI ≠ 0A (S3: N), the DC motor current DMI remains unchanged in S4. Thus, the polygon motor current PMI is corrected to decrease by 0.02A. If PMI = 0A (S3: Y), in S5, the polygon motor current PMI remains unchanged and the DC motor current DMI is corrected to decrease by 0.02A.

  As described above, when the polygon motor current PMI or the DC motor current DMI is corrected to decrease, the process again proceeds to S2, and the above process is repeated until the 24V voltage becomes equal to or higher than the lower limit. When the 24V voltage becomes equal to or higher than the lower limit (S2: Y), the process proceeds to S11, and the same processes as S11 to S15 in FIG. 5 are performed. That is, it waits until there is an image formation command (S11), and when an image formation command is generated (S11: Y), an image formation process is executed (S12). When the image formation is completed (S13: Y), the DC motor current DMI is controlled to 0A (S14), and after waiting for a predetermined time required for the DC motor 440 to stop (S15), the process is the same as S1 described above. Migrate to

  Also in this embodiment, similarly to the first embodiment, an increase in 24V voltage can be satisfactorily suppressed. In the present embodiment, since the energization current in the standby mode is suppressed to the necessary minimum based on the detection result of the 24V voltage detection unit 510, the power consumption can be further reduced.

5). Third Embodiment FIG. 9 is a block diagram showing a configuration of a control system in a third embodiment of the present invention. As shown in FIG. 9, in the present embodiment, a registration solenoid 460 for switching driving / stopping of the registration roller 27 is connected to the ASIC 500 via a registration solenoid drive circuit 461, and the above-described paper feed tray 21, rear cover. 3b and cover sensors 521, 522, and 523 as opening detection means for detecting opening and closing of the front cover 3c (both corresponding to the cover) shown in FIG. 1, and the recording medium immediately downstream of the fixing unit 90 Unlike the first embodiment, the other configuration is the same as that of the first embodiment in that a paper discharge sensor 524 for detecting presence or absence is connected to the ASIC 500. Although not shown in FIG. 9, the network board 501 and the DIMM 502 can be mounted on the ASIC 500 also in this embodiment.

  Next, processing executed by the ASIC 500 in the present embodiment will be described. FIGS. 10 and 11 are flowcharts showing processing executed by the ASIC 500. In the ASIC 500, this process is started when the laser printer 1 is powered on.

  When the process is started, first, in S1, the polygon motor current PMI is controlled to 0.1A, the DC motor current DMI is controlled to 0.1A, and the main fan 410 and the PS fan 420 are controlled to half speed. The configuration in which the main fan 410 and the PS fan 420 are driven at half speed is the same as that of the first embodiment in that the main fan 410 and the PS fan 420 are first connected via a constant voltage element such as a Zener diode or a resistor. What is necessary is just to connect to the output line 311. In subsequent S2, the system waits until an image formation command is issued. When an image formation command is generated (S2: Y), in S3, polygon motor 450, DC motor 440, main fan 410, and PS fan 420 are controlled to full speed, respectively. Then, a well-known image forming process is executed.

  In subsequent S4, it is determined whether or not a jam has been detected during image formation. If no jam has been detected (S4: N), it is determined in S5 whether or not image formation has been completed. If the image formation has not been completed (S5: N), the process proceeds to S4 again, and the image formation is continued while the processes of S4 and S5 are repeated. When image formation is completed (S5: Y), the process proceeds to S1 described above, the polygon motor current PMI is 0.1A, the DC motor current DMI is 0.1A, and the main fan 410 and the PS fan 420 are half speed. Respectively. As described above, also in the present embodiment, in the standby mode (during standby in S2), the polygon motor current PMI and the DC motor current DMI are controlled to 0.1 A, thereby suppressing an increase in 24V voltage.

  In the present embodiment, when a jam is detected during the loop processing of S4 and S5 (S4: Y), the following control is executed by the processing of S8 and subsequent steps. Note that various known methods can be used as a jam detection method. Here, as an example, a method for detecting a jam using the registration solenoid 460 and the paper discharge sensor 524 will be described.

  FIG. 12 is a flowchart showing an example of such a jam detection process. As shown in FIG. 12, in this process, first, in S41, it waits until there is an image formation command. If there is an image formation command (S41: Y), it waits in S42 that there is a paper feed command. To do. When a paper feed command is issued (S42: Y), in S43, the registration solenoid 460 is turned off in S44 after waiting for a predetermined time required for the recording medium to be conveyed to the vicinity of the registration roller 27. Is switched from ON to ON. As a result, the registration roller 27 is prohibited from rotating, and the leading end of the recording medium can be locked.

  Subsequently, after waiting for a predetermined time required for the registration roller 27 to adjust the recording medium conveyance state in S45, the registration solenoid 460 is switched from ON to OFF in S46. Then, normally, an image is formed on the recording medium and discharged to the paper discharge tray 5. Therefore, in subsequent S47, the apparatus waits for a predetermined time (for example, 5.79 seconds) sufficient for the recording medium to be discharged to the discharge tray 5, and in S48, the discharge sensor 524 is turned off (that is, the recording medium). Is not detected). If the paper discharge sensor 524 is OFF (S48: Y), it is determined that the recording medium has been normally discharged, and it is determined in S51 that there is no jam. Then, the process proceeds to S42 described above and the next paper feed command is issued. Wait until there is. On the other hand, if the paper discharge sensor 524 is not OFF (S48: N), it can be seen that a jam has occurred and the recording medium has not been discharged normally. To do.

  Returning to FIG. 10, when a jam is detected during image formation (S4: Y), the main fan 410 and the PS fan 420 are controlled at half speed in S8, and in step S9, the DC motor is controlled. The current DMI is controlled to 0A, and the polygon motor current PMI is controlled to 0.1A. In subsequent S10, after waiting for a predetermined time required for the DC motor 440 to stop, in S11, the DC motor 440 is reversely rotated for a predetermined time. This is a process for facilitating the work of taking out the jammed recording medium and eliminating the jam.

  After the reverse rotation for a predetermined time in S11, the DC motor current DMI is set to 0A again. In the subsequent S12, after waiting for a predetermined time necessary for the DC motor 440 to stop, the DC motor current DMI is 0.1A. Controlled. Then, as described above, since the DC motor 440 has a small energization amount, the DC motor 440 continues to be stationary. In S14, after waiting for a predetermined time necessary for the 24V voltage to stabilize, the main fan 410 and the PS fan 420 are driven at full speed in S15. At this time, since the increase in the 24V voltage is suppressed by the energization of the DC motor 440, even if the main fan 410 and the PS fan 420 are driven at full speed, no voltage exceeding the rating is applied to the fans. .

  In subsequent S16, it is determined whether or not a predetermined time required for cooling the fixing unit 90 has elapsed since the main fan 410 and the PS fan 420 were driven at full speed. If the predetermined time has not elapsed (S16: N), in S17, it is determined whether any cover open (cover open) is detected by any of the cover sensors 521 to 523, and the cover is opened. Is not detected (S17: N), the process proceeds to S16 described above. Thus, when the predetermined time elapses while the loop processing of S16 and S17 is repeated (S16: Y), the main fan 410 and the PS fan 420 are controlled at half speed in S20, and in the subsequent S21, the ASIC 500 is jammed. Error waiting state.

  On the other hand, when the cover open is detected before the predetermined time has elapsed after the main fan 410 and the PS fan 420 are driven at full speed (S17: Y), the process proceeds to S25, and the polygon motor current PMI is 0. .2A is controlled. Subsequently, after waiting for a predetermined time until the 24V voltage is stabilized in S26, the DC motor current DMI is controlled to 0A in S27. If the DC motor current DMI is controlled to 0.1 A or the like when the cover is open, an unexpected load may be applied to the DC motor 440 when the recording medium is pulled by the user. In this embodiment, therefore, DMI = 0A is controlled when the cover is opened. In addition, since the polygon motor current PMI is controlled to 0.2 A prior to this processing, the increase in the 24V voltage can be suppressed well.

  In subsequent S28, it is determined whether or not a predetermined time required for cooling the fixing unit 90 has elapsed since the main fan 410 and the PS fan 420 were driven at full speed. If the predetermined time has not elapsed (S28: N), it is determined in S29 whether all of the cover sensors 521 to 523 have detected that the cover is closed (cover closed). When the cover close is not detected, the process proceeds to S28 described above. If the predetermined time elapses while the processes of S28 and S29 are repeated (S28: Y), the main fan 410 and the PS fan 420 are controlled at half speed in S30, and the cover close is detected in subsequent S31. Wait until

  If a cover close is detected during the loop processing of S28, S29 or during the standby in S31 (S29: Y or S31: Y), the DC motor current is controlled to 0.1A in S32, and 24V in S33. After waiting for a predetermined time necessary for the voltage to stabilize, the polygon motor current PMI is controlled to 0.1 A in S34. In subsequent S35, it is determined whether or not a predetermined time required for cooling the fixing unit 90 has elapsed since the main fan 410 and the PS fan 420 were driven at full speed. If the predetermined time has passed (S35: Y), if the predetermined time has not passed (S35: N), wait until the predetermined time has passed in S35 (S35: Y). ), The process proceeds to S20 described above.

Next, FIG. 13 is a time chart showing a change in the energization state of each part according to the above processing. As shown in FIG. 13, until the jam at time t ₁ in the image formation is detected, the main fan 410, PS fan 420, DC motor 440, any polygon motor 450 is driven at full speed (S3) . When a jam is detected at time t ₁ (S4: Y), the DC motor 440 is reversed with braking by setting DMI = 0A (S11), and again with DMI = 0.1A with braking. As a result, the stationary state is maintained (S13).

When a predetermined time required for the 24V voltage to stabilize has elapsed from time t ₂ controlled to DMI = PMI = 0.1 A (S14: Y), the main fan 410 and the PS fan 420 are driven at full speed, and further predetermined When the time elapses and the fixing unit 90 is cooled (S16: Y), the main fan 410 and the PS fan 420 are driven at half speed.

As long as the cover is not opened, DMI = PMI = 0.1 A is maintained after time t ₂ , as indicated by a one-dot chain line in FIG. However, for example, the cover open at time t ₂ after the time t ₃ is to have been made, as shown by the solid line in FIG. 13, is a PMI = 0.2A (S25), are DMI = 0A (S27). Thus, by setting DMI = 0A when the cover is open, it is possible to satisfactorily prevent the DC motor 440 from being damaged even when the user pulls the recording medium for jam processing.

6). Further Embodiments Further, in each of the above embodiments, if the following interrupt processing is executed, it is possible to cope with an abnormality of the DC motor 440. FIG. 14 is a flowchart showing a process that is executed in response to an energization signal that instructs rotation of DC motor 440.

  In this process, first, in S71, it is determined whether or not a DC motor lock signal is detected within a predetermined time after the energization signal of the DC motor 440 is generated. The DC motor lock signal is a signal generated when the DC motor 440 reaches a predetermined number of revolutions. If there is no abnormality in the DC motor 440, the DC motor lock signal is detected within the predetermined time. Therefore, if an affirmative determination is made in S71, it is determined that there is no abnormality in the DC motor 440, and the routine proceeds to a normal process in S72.

  On the other hand, when the DC motor lock signal is not detected within the predetermined time (S71: N), the DC motor current DMI is controlled to 0A and the polygon motor current PMI is controlled to 0.2A in S73. That is, since there is a possibility that the DC motor 440 is abnormal, the energization to the DC motor 440 is stopped.

  Subsequently, after waiting for a predetermined time required for the 24V voltage to stabilize in S74, the main fan 410 and the PS fan 420 are driven at full speed in S75. Then, after waiting for a predetermined time required for cooling of the fixing unit 90 in S76, the main fan 410 and the PS fan 420 are driven at half speed in S77, and in S78, the ASIC 500 is switched to DC. Motor lock error standby status is entered.

  When there is a possibility that the DC motor 440 is abnormal by the above processing (S71: N), the DC motor 440 is not energized, and only the polygon motor 450 is energized to suppress the increase in 24V voltage. Can do. Therefore, damage to the DC motor 440 can be prevented even better.

  In the above process, S71 corresponds to the abnormality detection means. Furthermore, the present invention can also be applied to electronic equipment other than the image forming apparatus, and various forms other than the above can be considered as the predetermined electrical equipment and other electrical equipment.

1 is a perspective view illustrating an appearance of a laser printer to which the present invention is applied. It is a longitudinal cross-sectional view showing the internal structure of the laser printer. It is a circuit diagram showing the structure of the power supply unit of the laser printer. It is a block diagram showing the structure of the control system of the laser printer. It is a flowchart showing the process performed in the control system. It is explanatory drawing showing the change of the energization state of each part according to the process. It is a block diagram showing the structure of the control system in 2nd Embodiment. It is a flowchart showing the process performed in the control system. It is a block diagram showing the structure of the control system in 3rd Embodiment. It is a flowchart showing a part of process performed in the control system. It is a flowchart showing the continuation of the process performed in the control system. It is a flowchart showing an example of the jam detection process in the process. It is a time chart showing the change of the energization state of each part according to the processing. It is a flowchart showing the process which can be interrupted in each embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laser printer 10 ... Image formation part 20 ... Feeder part 21 ... Paper feed tray 27 ... Registration roller 70 ... Scanner part 72 ... Polygon mirror 80 ... Process cartridge 83 ... Transfer roller 84c ... Development roller 81 ... Photoconductor drum 90 ... Fixing Unit 100 ... power supply unit 140 ... switching element 150 ... oscillation control circuit 160 ... phototransistor 161 ... photodiode 200 ... transformer 311 ... first output line 313 ... second output line 410 ... main fan 411 ... main fan drive circuit 420 ... PS fan 421 ... PS fan drive circuit 430 ... solenoid 431 ... solenoid drive circuit 440 ... DC motor 441 ... DC motor drive circuit 442 ... D / A conversion circuit 443 ... DC motor speed detection circuit 444 ... DC motor drive current Detection circuit 450 ... polygon motor 451 ... polygon motor drive circuit 452 ... D / A conversion circuit 454 ... polygon motor drive current detection circuit 460 ... registration solenoid 461 ... registration solenoid driver circuit 500 ... ASIC
501 ... Network board 502 ... DIMM
510: 24V voltage detection unit 521: Cover sensor 524: Paper discharge sensor

Claims (9)

Provided with a image forming means for forming an image on a recording medium, an image forming apparatus having a plurality of electrical components supplied with electric power from a single power supply,
The power source is composed of a switching power source including one transformer having a stabilized output for a control system and an output for a drive system that supplies power to the plurality of electrical components.
As the plurality of electrical components, a cooling fan, a predetermined electrical component whose rated current is larger than the cooling fan, and further other electrical components are provided,
Power is supplied from the output the control system, and, from the output the drive system is not supplied power to the electrical equipment with the exception of the predetermined electric component and the cooling fan, the above-mentioned predetermined electrical component that predetermined electric a first operation mode in which current-rated goods is energized, the power from the output the control system is supplied, and driven at full speed to the cooling fan and the predetermined electrical component from the output the drive system An energization control means capable of executing a second operation mode in which a current to be energized is energized ,
An image forming apparatus comprising the image forming apparatus . 2. The image forming apparatus according to claim 1, wherein in the first operation mode, the cooling fan can be energized so as to be driven at half speed. The energization control means sets the current value of the current less than the rated value that energizes the predetermined electrical component in the first operation mode as the output voltage of the drive system output is more likely to increase. The image forming apparatus according to claim 1, wherein: A plurality of the predetermined electrical components and an abnormality detecting means for detecting at least one abnormality of the predetermined electrical components,
When the abnormality detecting unit detects an abnormality of the one predetermined electrical component, the energization control unit does not energize the one predetermined electrical component in the first operation mode, and does not apply the other predetermined electrical component to the other predetermined electrical component. The image forming apparatus according to claim 1, wherein a current less than the rating is applied. Upper Kisho constant electrical equipment, image forming apparatus according to any one of claims 1 to 4, characterized in that through said image forming means is a conveying drive for conveying the recording medium. 6. The image forming apparatus according to claim 5, wherein the current less than the rating is set to a current value at which the recording medium is not transported by the transport driving device . The image forming apparatus according to claim 6, wherein the energization of the current less than the rating to the conveyance driving device is performed after the energization to the conveyance driving device is once stopped. Upper Kiga image forming unit includes a photosensitive member on which an electrostatic latent image is formed on the surface in accordance with the exposure, an exposure unit for scanning exposure of the surface of the photosensitive member in response to rotation of the polygon mirror, of the photosensitive member A developing means for developing the developer by attaching the developer to the electrostatic latent image formed on the surface; and a transferring means for transferring the developer attached to the photosensitive member by the developing means to the recording medium,
The image forming apparatus according to claim 1, wherein the predetermined electrical component is a polygon driving device that rotationally drives the polygon mirror. The predetermined electrical component includes the polygon driving device and a transport driving device for transporting the recording medium through the image forming unit,
A cover that covers the conveyance path of the recording medium;
Opening detection means for detecting the opening of the cover;
With
The energization control unit does not energize the transport driving device and energizes the polygon driving device with a current less than the rating when the opening detecting unit detects the opening of the cover. 9. The image forming apparatus according to 8.

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