JP2019008094A - Separation state determination apparatus and separation state determination method - Google Patents

Abstract

To determine a state of use of a process cartridge without adding a new member.SOLUTION: A separation state determination apparatus includes: an image carrier; charging means of charging the image carrier; separation means of separating the image carrier from the charging means before use, and bringing them into contact with each other after use; and determination means which applies a first bias lower than that for charging the image carrier, to the charging means, and applies, when a separation state between the image carrier and the charging means determined from a value of a current flowing at that time is a predetermined separation state, a second bias larger than the first bias to the charging means, to determine a separation state between the image carrier and the charging means from a value of a current flowing in the charging means at that time.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an image forming apparatus such as a page printer or a copying machine using an electrophotographic system, and more particularly to an image forming apparatus having means for detecting whether a cartridge is installed or not and whether it is new or old.

  In an image forming apparatus such as a laser beam printer, an electrophotographic photosensitive member, a charging roller, a developing device, and the like are integrally accommodated in a cartridge container as a process cartridge, and are detachably disposed in a main body of the image forming apparatus. There are many that are. Such a process cartridge is intended to facilitate the replacement operation of the device by replacing the entire process cartridge when the internal device reaches the end of its life. Since there are many opportunities to attach / detach the process cartridge to / from the apparatus main body, it is necessary to detect and confirm whether or not the process cartridge is installed in the apparatus main body when forming an image.

  In addition, the life of the process cartridge is extended, and it is detected whether the process cartridge is new. If it is new, the image forming conditions change depending on the necessity of performing an initialization operation such as resetting the page counter and the frequency of use of the process cartridge. Need to be made.

  In view of these, Patent Document 1 discloses a technique for detecting whether a process cartridge is new or old by the work of a user or a service person as follows. That is, the manufacturing number is displayed with a barcode at a predetermined position of the process cartridge. Then, this is read by the bar code reader on the main body side to determine whether or not the process cartridge is new. Alternatively, the fact that the process cartridge has been replaced with a new one is stored in the main body by a button provided on the main body when the process cartridge is replaced during maintenance inspection.

JP-A-7-92752

  However, in the above-described prior art, when the manufacturing number is displayed on the barcode displayed on the process cartridge and the barcode is read by the barcode reader on the main body side, the barcode reader is necessary, which complicates the configuration and increases the cost. Invite.

  The present invention has been made in view of the above problems, and in a process cartridge having a member for separating a charging member and an image carrier in a new state, the charging member and the image carrier without adding a new member. An object of the present invention is to provide an image forming apparatus that can determine the separation state of the image forming apparatus.

  In order to achieve this object, the separation state determination device of the present invention includes an image carrier, a charging unit that charges the image carrier, and a state in which the image carrier and the charging unit are separated before the start of use. A separation means for bringing the image carrier and the charging means into contact with each other after the start of use, and a first bias lower than that for charging the image carrier to the charging means. When the result of determining the separation state between the image carrier and the charging unit from the value of the flowing current is determined to be a predetermined separation state, the charging unit is provided with a second bias larger than the first bias. And determining means for determining a separation state between the image carrier and the charging means from the value of the current applied to the charging means at that time.

  In the present invention, it is possible to determine the separation state between the charging member and the image carrier without adding a new member.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to a first embodiment of the present invention. It is a figure which shows the structure of the separation member which concerns on 1st Embodiment of this invention. FIG. 2A shows a state where the process cartridge is new and before use, and FIG. 2B shows a state where the process cartridge is used (after use is started). 1 is a diagram illustrating a configuration of a charging voltage generation circuit, a current detection circuit, and an engine controller of an image forming apparatus according to a first embodiment of the present invention. 4 is a flowchart showing a new and old process cartridge detection detection operation in the first embodiment of the present invention. 6 is a time chart showing a new and old process cartridge detection detection operation in the first embodiment of the present invention. 9 is a flowchart showing a new and old / uninstalled process cartridge detection operation in the second embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, what attached | subjected the same code | symbol in each drawing has the same structure or effect | action, The duplication description about these is abbreviate | omitted suitably. In addition, unless specifically stated otherwise, the scope of the present invention is limited to the scope of the present invention, unless otherwise specified, such as device configurations, components, component dimensions, materials, shapes, and other relative arrangements described in the following embodiments. It is not intended to be limited to.

<First Embodiment>
(Overall configuration of image forming apparatus)
FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus according to the first embodiment of the present invention. In this embodiment, a laser beam printer will be described as an example of the image forming apparatus.

  As shown in the figure, the image forming apparatus A has a photosensitive drum 100 as an image carrier for realizing an electrophotographic process, and a high pressure for placing a uniform charge necessary for the electrophotographic process on the photosensitive drum 100. A charging voltage generating circuit 500 that generates a voltage in which a DC voltage is superimposed on a sine wave, and a charging roller 700 that is a charging member for uniformly applying the charge of the charging voltage generating circuit 500 to the photosensitive drum 100. A laser scanner 300 for irradiating laser light on the photosensitive drum 100 according to image data to form an electrostatic latent image, the photosensitive drum 100 is disposed opposite to the photosensitive drum 100, carries toner, and is static on the photosensitive drum 100. A developing device 400 including a developing sleeve 410 that develops the electrostatic latent image, a transfer device 800 that transfers the toner image on the photosensitive drum 100 to the recording medium P, and after the transfer And a cleaning device 900 for removing the toner remaining on the optical drum 100 from the surface.

  The photosensitive drum 100, the charging roller 700, and the cleaning device 900 are provided in a process cartridge 200 that can be attached to and detached from the apparatus main body.

  The photosensitive drum 100 that is uniformly charged via the charging roller 700 is irradiated with laser light from the laser scanner 300 according to the image data to form an electrostatic latent image. The electrostatic latent image is developed by the developing device 400 to form a toner image, and transferred to the recording medium P by the transfer device 800. The recording medium P is conveyed to a fixing device 1000 including a heating roller 1010, and a toner image is fixed as a permanent image, and is further discharged to the outside of the image forming apparatus A.

  The process cartridge 200 is provided with a separation member 710 that separates the photosensitive drum 100 and the charging roller 700.

  FIG. 2 is a diagram illustrating a configuration of the separation member 710. FIG. 2A shows a state where the process cartridge 200 is new and before use, and FIG. 2B shows a state where the process cartridge 200 is being used (after the start of use).

  As shown in FIG. 2A, the charging roller 700 provided in the new process cartridge 200 is separated from the photosensitive drum 100 by a separating member 710. Before use, the charging roller 700 is kept separated from the photosensitive drum 100 by the separating member 710. When the photosensitive drum 100 rotates in the rotation direction, the separation member gear 730 is driven via the photosensitive drum gear 110, and the separation member 710 rotates about the rotation shaft 720. As a result, as shown in FIG. 2B, the charging roller 700 is configured to be separated from the separation member 710 and to come into contact with the photosensitive drum 100 (the separation is released).

  In this embodiment, the photosensitive drum 100 and the charging roller 700 are separated from each other by using the separation member 710. However, the mechanism for bringing the photosensitive drum 100 and the charging roller 700 into contact with each other from the separated state. Any shape is acceptable.

  FIG. 3 is a diagram illustrating a configuration of the charging voltage generation circuit 500, the current detection circuit 550, and the engine controller 600 (control unit) of the image forming apparatus A.

  In the figure, the output PRACC from the engine controller 600 is a square wave of about 200 Hz to 1000 Hz, and is determined by the process speed or the like. In this embodiment, it is a square wave with a frequency of 470 Hz, a duty of 50%, and Vpp of 5 V, and the level is converted to Vpp 24 V by the transistor 502 and the resistor 503. The operational amplifier 501 converts the square wave signal PRACC input from the engine controller 600 into a sine voltage of Vpp20V. The voltage input to the transformer 511 is converted into a voltage corresponding to the winding of the transformer 511 (a sine voltage of about 2 kVpp). A diode 509 and a capacitor 508 are a circuit for rectifying a sine voltage, and a DC voltage 510 is a DC power source for shifting the central value of the charged AC voltage. A capacitor 519 connected to the secondary side of the transformer 511 is a capacitor for extracting a part of the electric power transmitted to the charging roller 700, and is converted into a current voltage by a resistor 520. Thereafter, only a positive voltage is extracted by the diode 521, and is peak-charged by the operational amplifier 522, the capacitor 524, and the resistor 523, and is input to the A / D input port of the engine controller 600 as the signal CRGSNS. Further, an electrolytic capacitor 512 for charging / discharging is connected between the output side of the operational amplifier 501 and the primary side winding of the transformer 511. Therefore, the signal CRGSNS input from the capacitor 519 through the current detection circuit 550 to the A / D input port of the engine controller 600 has a voltage value reflecting the value of the current supplied to the charging roller 700.

  FIG. 4 is a flowchart showing the new / old and mounted / unmounted detection operation of the process cartridge 200.

  When the main power switch of the image forming apparatus A is turned on or the door is opened and closed (step S100), the process cartridge 200 is mounted, not mounted, old and new before the normal initial operation (front multiple rotation) is started. Detecting

  First, a voltage is applied from the charging voltage generation circuit 500 to the charging roller 700. The applied voltage at this time is less than the charging bias at the time of image formation, and more preferably a voltage Vs (first bias) smaller than the discharge start voltage Vth (step S101).

  A part of the current supplied to the charging roller 700 by the voltage Vs is supplied, and a voltage value signal CRGSNS indicating the current supplied to the charging roller 700 by the current detection circuit 550 is input to the A / D input port of the engine controller 600. The The engine controller 600 samples the signal CRGSNS input to this A / D input port (step S102). The signal CRGSNS is sampled every 40 msec, and an average value obtained by sampling 10 times is calculated as an average Ic value (step S103). Then, the usage status of the CRG is determined based on the average Ic value of the signal CRGSNS (step S104). If the result of step S104 is that the average Ic value of the signal CRGSNS is greater than or equal to the predetermined current value Iu (first current value) at the time of cartridge use in normal use stored in advance in the engine controller 600, the process cartridge It is determined that the cartridge 200 is in use (old product) (step S105). The predetermined current value Iu will be described later. Thereafter, image formation is started (step S113).

  On the other hand, if the average Ic value of the signal CRGSNS is less than a predetermined current value Iu stored in the engine controller 600 in advance during normal use (step S104), the applied voltage is increased to start discharging. A voltage Vb (second bias) equal to or higher than the voltage is applied (step S106).

  Next, the use state of the cartridge is determined based on the average Ic value of the signal CRGSNS (step S107). That is, if the average Ic value of the signal CRGSNS is less than a predetermined current Io (second current value) stored in the engine controller 600 in advance during normal use, whether the cartridge is not installed. (Forget to mount), even if it is mounted, it is determined that the mounted state is incomplete, and it is detected that there is no cartridge (step S108). Then, an error is notified to the user (step S109), and the operation is stopped.

  On the other hand, when the average Ic value of the signal CRGSNS is equal to or greater than the predetermined current Io stored in the engine controller 600 in advance during normal use, it is detected as an unused cartridge (new) (step S110). . The current Io is a minimum current value that can be detected when a cartridge in which the photosensitive drum 100 and the charging roller 700 are separated is inserted. In this case, thereafter, the usage amount count value of the process cartridge 200 stored in the storage unit is cleared (step S111). That is, the usage amount count value of the process cartridge 200 before replacement is reset to set the usage amount count value to “0”. Here, the usage amount count value counts how many recording media P have passed through the process cartridge 200, how long the photosensitive drum 100 has been rotated, and the like. These count values are accumulated and stored in a RAM (not shown) provided in the storage unit 620 as needed. With this function, the life of the photosensitive drum 100 is detected. When a new (unused) process cartridge 200 is mounted on the main body of the image forming apparatus 1, the usage amount count value of the process cartridge 200 that performs this life detection is reset.

  That is, the engine controller 600 has a RAM serving as storage means for storing usage information of the process cartridge 200. Then, the engine controller 600 determines that the process cartridge 200 is new (unused). In that case, the usage information of the process cartridge 200 stored in the RAM is reset.

  Thereafter, the process cartridge 200 is initialized (step S112). Here, the initialization operation of the process cartridge 200 is as follows. That is, when starting to use a new (unused) process cartridge 200, the deformation of the charging roller 700 is eliminated and the dust adhering to the surface of the photosensitive drum 100 is removed. For this purpose, the photosensitive drum 100 and the charging roller 700 are idly rotated without applying the charging bias voltage Vt. Alternatively, the surface of the photosensitive drum 100 is uniformly charged by the charging roller 700 to which the charging bias voltage Vt is applied. In addition, various initialization operations when starting to use a new (unused) process cartridge 200 are performed.

  In order to make the surface of the photosensitive drum 100 uniform before use, the photosensitive drum 100 performs an initialization operation in which the photosensitive drum 100 is rotationally driven by a driving unit (not shown) for a predetermined time.

  The charging bias voltage Vt is applied to the charging roller 700 by the charging voltage generation circuit 500 within the driving time of the photosensitive drum 100. Then, the surface of the photosensitive drum 100 is made uniform. Alternatively, the laser scanner 300 irradiates the surface of the photosensitive drum 100 with laser light. Thereby, the potential rising of the surface of the photosensitive drum 100 is improved.

  That is, the engine controller 600 serving as a control unit controls the initialization operation of the process cartridge 200. When the engine controller 600 determines that the process cartridge 200 is new (unused), the engine controller 600 performs an initialization operation for the process cartridge 200.

  Thereafter, the image forming process operation is started based on the input of the print start signal (step S113).

  FIG. 5 is a time chart showing an operation for detecting whether a process cartridge is new or old, mounted, or not mounted. The engine controller 600 performs cartridge old / new and presence / absence detection operations at a timing such as when the power is turned on or when the door is closed or when the power is stopped.

  The engine controller 600 outputs a signal PRACC to drive the charging voltage generation circuit 500 to supply a charging signal to the charging roller 700. While the charging voltage is being output, the A / D of the engine controller 600 is output. The sampling of the signal CRGSNS is repeated at the input port (step S102). And the average of the data sampled during 400 msec is taken, and it is set as the electric current value Ic.

  When the charging roller 700 and the photosensitive drum 100 are in contact with each other and a high charging bias is applied without applying rotational driving, memory (uneven charging) is caused in the photosensitive drum 100 and the subsequent image formation is affected. Use a value less than the charging bias at the time of image formation. Furthermore, by using a voltage that does not cause a discharge between the photosensitive drum 100 and the charging roller 700, it is possible to reliably prevent such image defects.

  The detected current Ic is compared with the specified current value Iu during 0 to 200 msec within 400 msec of the cartridge presence / absence detection operation (period X in FIG. 5) (step S104). Judgment is made, and a print waiting state is set (step S113). Thus, in the period X, when the voltage Vs is supplied to the charging roller 700, current flows only when “in use”, and when “new” and “none”, current does not flow. This is because the photosensitive drum 100 and the charging roller 700 are in contact only when “in use”. Therefore, the specified current value Iu is set to a value that can distinguish between the “in use” state and the “new” or “none” state. Thus, by comparing the detected current Ic with the specified current value Iu, it is determined whether the process cartridge 200 is in the “in use” state, “new” or “no” state.

  If Iu is not exceeded during 0 to 200 msec within 400 msec of the cartridge presence / absence detection operation, an applied voltage equal to or higher than the charging bias at the time of image formation is used after the detection voltage is 200 msec or later (period Y in FIG. 5). At this time, the photosensitive drum 100 and the charging roller 700 are separated from each other or the cartridge is not mounted (forgetting to mount). Therefore, the above-mentioned image defect does not occur even when a high charging bias is applied.

  The detection current Ic is compared with the specified current Io during 200 to 400 msec within a predetermined time of 400 msec of the cartridge presence / absence detection operation (step S107). If it is less than Io, it is determined that the cartridge is not loaded (step S108), and the user is notified using a display means (not shown) (step S108).

  When the voltage Vb is applied to the charging roller 700 in the period Y, the current flows in the case of “new”, even if the photosensitive drum 100 and the charging roller 700 are separated, depending on the principle of the capacitor. This is because a floating current flows between 100 and the charging roller 700. Therefore, the specified current Io is set to a value that can distinguish whether or not the floating current is flowing. Thus, by comparing the detection current Ic and the specified current Io, it can be determined whether the state is “new” or “no”.

  If the specified current Io is not exceeded during 200 to 400 msec within a predetermined time of 400 msec of the cartridge presence / absence detection operation, it is determined that the cartridge is a new cartridge (step S110). Then, CRG Count in the storage unit is cleared (step S111), and CGR initialization processing is executed (step S112). After the sampling is completed, PRACC is stopped.

  As described above, in the present embodiment, the input sampling of the signal CRGSNS is repeated from the output timing of the signal PRACC within the activation time of the cartridge old / old and mounted / unmounted detection operation, and the cartridge old / old, mounted / non-mounted determination is performed. Is possible.

Second Embodiment
Next, another embodiment of the present invention will be described with reference to the flowchart of FIG. In the first embodiment, the new / old and old / unmounted detection operations of the cartridge are performed in a state in which the motor driver is OFF, that is, in a state in which the photosensitive drum 100 is stopped. That is, the cartridge old / new and mounted / unmounted detection operations are performed while the photosensitive drum 100 is driven.

  As shown in FIG. 6, first, when the main power switch of the image forming apparatus A is turned on or the door is opened and closed (step S200), the motor driver is turned on (step S201), and the photosensitive drum 100 is turned on. The rotation drive is started (step S202).

  Then, a voltage is applied from the charging voltage generation circuit 500 to the charging roller 700. The applied voltage at this time is less than the charging bias at the time of image formation, and more preferably less than the discharge start voltage Vth (step S203).

  The engine controller 600 performs detection (measurement) of the current flowing through the charging roller 700 by this applied voltage by sampling the signal CRGSNS input to the A / D input port (step S204).

  The signal CRGSNS is sampled every 40 msec, and an average value obtained by sampling 10 times is calculated as an average Ic value (step S205). The usage status of the CRG is determined based on the average Ic value of the signal CRGSNS (step S206).

  If the average Ic value of the signal CRGSNS is equal to or higher than the specified current Iu stored in the engine controller 600 in advance during normal use, it is determined that the process cartridge 200 is CRG (old product) being used ( Step S207). Then, after that, image formation is started (step S113).

  When the average Ic value of the signal CRGSNS is less than the specified current Iu stored in the engine controller 600 in advance during normal use (step S206), the applied voltage is increased to a voltage equal to or higher than the discharge start voltage. Is applied (step S208).

  Next, the use state of the cartridge is determined based on the average Ic value of the signal CRGSNS (step S209). That is, if the average Ic value of the signal CRGSNS is less than a predetermined current value Io stored in the engine controller 600 during normal use, the cartridge is not mounted (forgotten to mount) or mounted. Even if it is determined that the mounted state is incomplete, it is detected that there is no cartridge (step S210). Then, an error is notified to the user (step S211), and the operation is stopped.

  On the other hand, if the average Ic value of the signal CRGSNS is greater than or equal to a predetermined current value Io stored in the engine controller 600 in advance during normal use, it is detected as unused CRG (new) (step S212). ) The usage amount count value of the process cartridge 200 stored in the storage unit is cleared (step S213). The current Io is a minimum current value detected when a cartridge in which the photosensitive drum 100 and the charging roller 700 are separated is inserted. The usage amount count value of the process cartridge 200 before replacement is reset to set the usage amount count value to “0”. Here, the usage amount count value counts how many recording media P have passed through the process cartridge 200, how long the photosensitive drum 100 has been rotated, and the like. These count values are accumulated and stored in a RAM (not shown) provided in the storage unit 620 as needed. With this function, the life of the photosensitive drum 100 is detected. When a new (unused) process cartridge 200 is mounted on the main body of the image forming apparatus 1, the usage amount count value of the process cartridge 200 that performs this life detection is reset.

  That is, the engine controller 600 has a RAM serving as storage means for storing usage information of the process cartridge 200. Then, the engine controller 600 determines that the process cartridge 200 is new (unused). In that case, the usage information of the process cartridge 200 stored in the RAM is reset.

  Thereafter, the process proceeds to step (step S214), and the process cartridge 200 is initialized. Here, the initialization operation of the process cartridge 200 is as follows. That is, when starting to use a new (unused) process cartridge 200, the deformation of the charging roller 700 is eliminated and the dust adhering to the surface of the photosensitive drum 100 is removed. For this purpose, the photosensitive drum 100 and the charging roller 700 are idly rotated without applying the charging bias voltage Vt. Alternatively, the surface of the photosensitive drum 100 is uniformly charged by the charging roller 700 to which the charging bias voltage Vt is applied. In addition, various initialization operations when starting to use a new (unused) process cartridge 200 are performed.

  In order to make the surface of the photosensitive drum 100 uniform before use, the photosensitive drum 100 performs an initialization operation in which the photosensitive drum 100 is rotationally driven by a driving unit (not shown) for a predetermined time.

  The charging bias voltage Vt is applied to the charging roller 700 by the charging voltage generation circuit 500 within the driving time of the photosensitive drum 100. Then, the surface of the photosensitive drum 100 is made uniform. Alternatively, the laser scanner 300 irradiates the surface of the photosensitive drum 100 with laser light. Thereby, the potential rising of the surface of the photosensitive drum 100 is improved.

  That is, the engine controller 600 serving as a control unit controls the initialization operation of the process cartridge 200. When the engine controller 600 determines that the process cartridge 200 is new (unused), the engine controller 600 performs an initialization operation for the process cartridge 200.

  Thereafter, the image forming process operation is started based on the input of the print start signal (step S215).

DESCRIPTION OF SYMBOLS 100 ... Photosensitive drum 200 ... Process cartridge 500 ... Charge voltage generation circuit 550 ... Current detection circuit 600 ... Engine controller 610 ... Memory | storage part 700 ... Charging roller 710 ... Separation member

Claims (10)

An image carrier;
Charging means for charging the image carrier;
A separation unit that puts the image carrier and the charging unit in a separated state before the start of use of the image carrier and the charging unit;
A first bias lower than that for charging the image carrier is applied to the charging means, and the result of determining the separation state between the image carrier and the charging means from the value of the current flowing at that time is a predetermined separation. When the state is determined, a second bias larger than the first bias is applied to the charging unit, and the image carrier and the charging unit are separated from the value of the current flowing through the charging unit at that time. Determining means for determining the state;
A separation state determination device characterized by comprising:   The first bias is a bias smaller than a bias applied to the charging unit when forming an image on the surface of the image carrier, and the magnitude of the second bias is an image on the surface of the image carrier. The separated state determination apparatus according to claim 1, wherein the separation state determination apparatus is equal to or greater than a bias applied to the charging unit during image formation.   The separated state determination apparatus according to claim 1, wherein the predetermined state is a state in which the image carrier and the charging unit are not in contact with each other. In the first step,
If the value of the current flowing between the image carrier and the charging unit is smaller than a threshold value, it is determined that the image carrier and the charging unit are not in contact with each other.
2. The apparatus according to claim 1, wherein when the value of a current flowing between the image carrier and the charging unit is equal to or greater than the threshold value, it is determined that the image carrier and the charging unit are in contact with each other. The separated state determination apparatus according to any one of claims 3 to 3.   In the second step, when the current flowing through the charging member is smaller than a second threshold different from the threshold, at least one of the image carrier and the charging unit is not mounted When the current flowing through the charging member is equal to or greater than the second threshold value, it is determined that the image carrier and the charging unit are mounted and separated. The separation state determination device according to claim 4.   In the second step, when it is determined that the image carrier and the charging unit are separated from each other, it is determined that the image carrier and the charging unit are not yet in use, and the image carrier is 6. The separated state determining apparatus according to claim 5, further comprising a step of resetting usage information of the body and the charging means.   In the second step, when it is determined that the image carrier and the charging unit are not yet in use, the image carrier and the charging unit further include an initialization process. The separated state determination apparatus according to claim 6.   In the second step, when it is determined that at least one of the image carrier and the charging unit is not attached, the method further includes a step of notifying the user of an error. The separation state determination device according to claim 5, wherein the separation state determination device is a separation state determination device.   9. The electric current flowing between the image carrier and the charging unit is measured by extracting a part of a charging bias signal supplied to the charging unit. The separation state determination device according to any one of the above. A determination method for determining a separation state between an image carrier and a charging unit for charging the image carrier,
A first bias lower than that for charging the image carrier is applied to the charging unit, and a separation state between the image carrier and the charging unit is determined based on a current value flowing through the charging unit at that time. 1 process,
When it is determined in the first step that the image carrier and the image carrier are in a predetermined separated state, a second bias larger than the first bias is applied to the charging member, A second step of determining a separation state between the image carrier and the charging unit from a value of a current flowing through the charging unit;
A separation state determination method characterized by comprising:

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