Image forming apparatus

Abstract

An image forming apparatus includes: an image forming section that forms an image on a sheet; a high-voltage power supply substrate that applies a high voltage to the image forming section on the basis of a supplied voltage and outputs a discharge detection signal by detecting an overcurrent flowing through the image forming section; a switching circuit that switches between supplying and stopping a voltage to the high-voltage power supply substrate; and first and second control units to which a discharge detection signal is input. The first control section performs: a first determination process for determining whether or not abnormal discharge has occurred in the image forming section on the basis of the discharge detection signal; and a first instruction process of instructing the switching circuit to stop supplying the voltage to the high-voltage power supply substrate when it is determined that the image forming portion has abnormal discharge. The second control section performs: a second determination process for determining whether or not abnormal discharge has occurred in the image forming section on the basis of the discharge detection signal; and a second instruction process of instructing the switching circuit to stop supplying the voltage to the high-voltage power supply substrate when it is determined that the image forming portion has abnormal discharge.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus having an image forming portion for forming an image on a sheet, and capable of determining whether abnormal discharge has occurred in the image forming portion. Background Art

[0002] The image forming apparatus described in Patent Document 1 counts the number of inputs when the charging voltage is higher than a predetermined reference value. The image forming apparatus determines whether abnormal discharge such as arc discharge has occurred based on the count value, and stops applying the charging voltage when abnormal discharge is determined to have occurred.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2010-197969 Summary of the invention

[0004] The structure for determining whether the above-mentioned abnormal discharge has occurred can be implemented by a hardware circuit, in which case a customized AS IC equipped with the hardware circuit is used; the same structure can also be implemented by software in a general-purpose SoC (System on a Chip). In this case, depending on the type of fault, it may not be possible to determine whether abnormal discharge has occurred.

[0005] An object of the present invention is to provide a technology capable of reliably determining whether abnormal discharge has occurred in an image forming portion even when a configuration for determining whether abnormal discharge has occurred in the image forming portion is implemented by software.

[0006] In order to achieve the above-mentioned object, the image forming device of the present invention includes: an image forming unit for forming an image on a sheet; a high-voltage power supply substrate for applying a high voltage to the image forming unit based on a supplied voltage, the high-voltage power supply substrate outputting a discharge detection signal by detecting that an overcurrent has flowed through the image forming unit; a switching circuit for switching between supplying and stopping the supply of the voltage to the high-voltage power supply substrate; a first control unit to which the discharge detection signal is input; and a second control unit for controlling the high voltage by outputting a control signal to the high-voltage power supply substrate, the second control unit being input with the discharge detection signal, the first control unit executing: The second control unit executes: a first judgment process, judging whether abnormal discharge has occurred in the image forming unit based on the input discharge detection signal; and a first instruction process, instructing the switching circuit to stop supplying the voltage to the high-voltage power supply substrate when it is judged in the first judgment process that abnormal discharge has occurred in the image forming unit, and the second control unit executes: a second judgment process, judging whether abnormal discharge has occurred in the image forming unit based on the input discharge detection signal; and a second instruction process, instructing the switching circuit to stop supplying the voltage to the high-voltage power supply substrate when it is judged in the second judgment process that abnormal discharge has occurred in the image forming unit.

[0007] The first control unit performs a first judgment process for judging whether abnormal discharge has occurred in the image forming unit based on the input discharge detection signal, and the second control unit also performs a second judgment process for judging whether abnormal discharge has occurred in the image forming unit based on the input discharge detection signal. Therefore, even if an abnormality occurs in the first control unit and the first judgment process cannot be performed, since the second control unit performs the second judgment process that is the same as the first judgment process, it is possible to judge whether abnormal discharge has occurred in the image forming unit. Similarly, even if an abnormality occurs in the second control unit and the second judgment process cannot be performed, the first control unit performs the first judgment process that is the same as the second judgment process, so it is possible to judge whether abnormal discharge has occurred in the image forming unit. In this way, even if an abnormality occurs in either the first control unit or the second control unit, it is possible to judge whether abnormal discharge has occurred in the image forming unit when the other one does not have an abnormality, so the judgment can be reliably performed. Therefore, when it is judged that abnormal discharge has occurred in the image forming unit, the switching circuit can be reliably instructed to stop supplying voltage to the high-voltage power supply substrate through the first indication process or the second indication process.

[0008] In the image forming device of the present invention, the first control unit counts the number of times the discharge detection signal is input in the first judgment process, and if the counted number is greater than a specified number, it is judged that abnormal discharge has occurred in the image forming unit, and first information indicating that the first control unit has judged that the abnormal discharge has occurred is set; the second control unit counts the number of times the discharge detection signal is input in the second judgment process, and if the counted number is greater than a specified number, it is judged that abnormal discharge has occurred in the image forming unit, and second information indicating that the second control unit has judged that the abnormal discharge has occurred is set.

[0009] Thus, in the first determination process executed by the first control unit and the second determination process executed by the second control unit, when the discharge detection signal is input more than a predetermined number of times, it is determined that abnormal discharge has occurred in the image forming unit, thereby improving the accuracy of determining the occurrence of abnormal discharge.

[0010] In the image forming apparatus of the present invention, after executing the first instruction processing, the first control unit determines whether the second information is set, and instructs the second control unit to initialize if the second information is not set.

[0011] When the first control unit executes the first instruction processing, the second control unit should set the second information. Therefore, if the second information is not set at this time, it is considered that some abnormality has occurred in the second control unit. Therefore, the first control unit can eliminate the abnormality of the second control unit by instructing the second control unit to initialize.

[0012] In the image forming apparatus of the present invention, the second control unit determines whether the first information is set after executing the second instruction process, and instructs the first control unit to initialize if the first information is not set.

[0013] When the second control unit executes the second instruction processing, the first control unit should set the first information, so if the first information is not set at this time, it is considered that some abnormality has occurred in the first control unit. Therefore, the second control unit can eliminate the abnormality of the first control unit by instructing the first control unit to initialize.

[0014] The image forming device of the present invention further includes an indication circuit, to which an indication of the first indication processing and an indication of the second indication processing are input, and when an indication of at least one of the indication of the first indication processing and the indication of the second indication processing is input, the indication circuit instructs the switching circuit to stop supplying the voltage to the high-voltage power supply substrate.

[0015] Thus, when at least one of the instructions of the first instruction processing and the instructions of the second instruction processing is input, the switching circuit is instructed to stop supplying voltage to the high-voltage power supply substrate. Therefore, even if an abnormality occurs in either the first control unit or the second control unit, if no abnormality occurs in the other unit, the switching circuit can be reliably instructed to stop supplying voltage to the high-voltage power supply substrate through the first instruction processing or the second instruction processing.

[0016] In the image forming device of the present invention, the first control unit outputs a deep sleep signal for causing the image forming device to shift to a deep sleep state when specified conditions are met, including when it is determined in the first judgment process that abnormal discharge has occurred in the image forming unit, and inputs the deep sleep signal to the indication circuit to replace the indication of the first indication process, and the indication circuit instructs the switching circuit to stop supplying the voltage to the high-voltage power supply substrate when at least one of the deep sleep signal and the indication of the second indication process is input.

[0017] Thus, since the instruction of the first instruction process is replaced with the deep sleep signal originally possessed by the image forming apparatus, the first instruction process can be omitted, and the output terminal for outputting the instruction of the first instruction process can be omitted.

[0018] The image forming apparatus of the present invention further includes a low voltage power supply circuit for supplying the voltage to the high voltage power supply substrate, and the deep sleep signal is a signal instructing the low voltage power supply circuit to supply a voltage lower than the voltage.

[0019] In this way, since the deep sleep signal is a signal originally possessed by the image forming apparatus, the first instruction process can be omitted by replacing the instruction of the first instruction process with the deep sleep signal, and the output terminal for outputting the instruction of the first instruction process can be omitted.

[0020] The image forming device of the present invention comprises an image forming unit including a photosensitive drum, a charger for charging the photosensitive drum, and an exposure unit for forming an electrostatic latent image on the photosensitive drum charged by the charger, wherein the abnormal discharge of the image forming unit is the abnormal discharge of the charger.

[0021] This makes it possible to reliably determine that abnormal discharge has occurred in the charger.

[0022] In the image forming apparatus of the present invention, the first control unit attempts to communicate with the second control unit after executing the first instruction process, and instructs the second control unit to initialize when the communication is impossible.

[0023] Thus, when the first control unit is operating normally, if the first control unit cannot communicate with the second control unit, it is considered that some abnormality has occurred in the second control unit. Therefore, the first control unit can eliminate the abnormality of the second control unit by instructing the second control unit to initialize.

[0024] In the image forming apparatus of the present invention, the second control unit attempts to communicate with the first control unit after executing the second instruction process, and instructs the first control unit to initialize when the communication is impossible.

[0025] Thus, when the second control unit is operating normally, if the second control unit cannot communicate with the first control unit, it is considered that some abnormality has occurred in the first control unit. Therefore, the second control unit can eliminate the abnormality of the first control unit by instructing the first control unit to initialize. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a cross-sectional view showing a schematic structure of a color laser printer according to a first embodiment of the present invention.

[0027] Figure 2 It is shown Figure 1 Block diagram of the control structure of a color laser printer.

[0028] Figure 3 It is shown Figure 2 A block diagram of a signal transmission path of a portion of the periphery of the main substrate.

[0029] Figure 4 It is shown that the Figure 2 Flowchart of the control process executed by the main control circuit on the main substrate.

[0030] Figure 5 It is shown that the Figure 2 Flowchart of the control processing performed by the sub-control circuit on the main substrate.

[0031] Figure 6 This is a block diagram showing a portion of signal transmission paths around a main substrate of a color laser printer according to a second embodiment of the present invention. DETAILED DESCRIPTION

[0032] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0033] (First Embodiment)

[0034] Figure 1 1 is a cross-sectional view showing a schematic structure of a color laser printer (hereinafter referred to as a printer) 1 according to a first embodiment of the present invention. The printer 1 is a so-called tandem laser printer that uses four colors of toner. Figure 1 As shown in FIG. 1 , the description is based on the direction from which the user using the printer 1 is viewed. Figure 1 The right side in the description is referred to as “front”, the left side is referred to as “rear”, the upper side is referred to as “upper”, the lower side is referred to as “lower”, the near front side is referred to as “left”, and the back side is referred to as “right”.

[0035] like Figure 1 As shown, the printer 1 includes a main body shell 2, a supply unit 10 and an image forming unit 20. The main body shell 2 is roughly box-shaped. The supply unit 10 and the image forming unit 20 are accommodated inside the main body shell 2. An ejection tray 5 is formed on the upper surface of the main body shell 2. The printer 1 ejects the sheets S with images formed thereon onto the ejection tray 5 in a stacked state. In addition, a front cover 2a is provided on the front surface of the main body shell 2. The front cover 2a is a cover for opening and closing an opening 2b formed on the front surface of the main body shell 2. The front cover 2a can be rotated to the front side, for example, around a rotating shaft 2c provided at the lower end, so as to be able to rotate from the front side to the front side. Figure 1 The position shown closing the opening 2b is rotated to a position leaving the opening 2b open (open).

[0036] The supply section 10 includes a supply tray 11 for accommodating sheets S, a pickup roller 12, a separation pad 13, a pressure plate 14, a positioning roller 15 and other rollers. The sheets S may be sheets of a size such as A4, but are not limited to paper media such as ordinary paper or thick paper, and may also be other recording media such as OHP sheets. The supply tray 11 is mounted on the lower part of the main body shell 2 in a removable manner. The pressure plate 14 is arranged in the supply tray 11. A shifting mechanism not shown is arranged below the pressure plate 14. The shifting mechanism shifts the pressure plate 14 to an inclined state with a higher front side before image formation. As a result, the sheets S accommodated in the supply tray 11 are brought close to the pickup roller 12 side through the pressure plate 14, separated one by one by the pickup roller 12 and the separation pad 13, and after the direction of the front end of the sheet S is aligned by the positioning roller 15, it is transported to the image forming section 20 by other rollers. The sheet S fed from the supply tray 11 is conveyed along the conveyance path R by the image forming unit 20 , the discharge roller 65 , and the like, and is discharged onto the discharge tray 5 .

[0037] The image forming unit 20 is disposed at a substantially central portion of the main body housing 2, and includes developing cartridges 30Y, 30M, 30C, 30K, an exposure unit 40, a transfer unit 50, and a fixing device 60. The developing cartridges 30Y, 30M, 30C, and 30K contain yellow, magenta, cyan, and black toners, respectively. The four developing cartridges 30Y to 30K are disposed from the front side to the rear side of the printer 1 in the order of the developing cartridges 30Y, 30M, 30C, and 30K. In addition, the developing cartridges 30Y to 30K can be taken out from the opening 2b of the main body housing 2 by opening the front cover 2a for replacement.

[0038] The developing cartridge 30K includes a photosensitive drum 31, a charger 32, a toner cartridge 33K, etc. The toner colors of the other developing cartridges 30C, 30M, and 30Y are different, and the other structures are the same as the developing cartridge 30K. Therefore, in the following description, the developing cartridge 30K is mainly described, and the description of the other developing cartridges 30C, 30M, and 30Y is appropriately omitted.

[0039] The charger 32 is, for example, a scorotron charger having a charging wire 32a and a grid portion 32b. In image formation, before an electrostatic latent image is formed on the surface of the photosensitive drum 31, the charger 32 uniformly charges the surface of the photosensitive drum 31 with positive charges. The device for charging the photosensitive drum 31 is not limited to a scorotron charger, but may be another device such as a roller-type charging roller. In addition, the polarity of charging the photosensitive drum 31 is not limited to positive charging, but may be negative charging.

[0040] The toner cartridge 33K includes a toner storage chamber 33a, an agitator 33e, a supply roller 33b, a developing roller 33f, a layer thickness limiting blade 33d, and the like. The toner storage chamber 33a stores black toner. The agitator 33e agitates the toner stored in the toner storage chamber 33a. The supply roller 33b is disposed in the toner storage chamber 33a and is driven by a process motor 111 (see FIG. 11 ) disposed in the main body housing 2. Figure 2 ) is rotated by the driving force transmitted by the supply roller 33b. The supply roller 33b supplies the toner supplied from the toner storage chamber 33a to the developing roller 33f. Figure 1 The developing roller 33f is arranged at the lower and oblique rear portion of the supply roller 33b and is in contact with the supply roller 33b. In addition, the developing roller 33f is arranged on the downstream side of the position of the charger 32 in the rotation direction of the photosensitive drum 31. The developing roller 33f is also rotated by transmitting the driving force from the processing motor 111. A positive voltage is applied to the roller shaft of the developing roller 33f. The colorant supplied to the developing roller 33f is carried on the developing roller 33f as the developing roller 33f rotates. The layer thickness limiting sheet 33d is arranged to be in pressure contact with the developing roller 33f from above, and the thickness of the colorant attached to the outer peripheral surface of the developing roller 33f is adjusted to a certain thickness. Figure 1 The toner cartridges 33C, 33M, and 33Y of other colors (cyan, magenta, and yellow) shown in the figure also have the same structure as the toner cartridge 33K.

[0041] The exposure unit 40 is disposed in the upper part of the main body housing 2 and is provided with a laser light source, a polygon mirror, a lens, a reflector, etc. (not shown). The laser beam emitted from the laser light source is deflected by the polygon mirror, etc. and then emitted from the exposure unit 40. The exposure unit 40 emits the laser beam to the surface of the photosensitive drum 31. Figure 1The light beam indicated by the single-dot chain line in the figure exposes the surface of the photosensitive drum 31. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 31. Due to the potential difference between the developing roller 33f and the electrostatic latent image formed on the photosensitive drum 31, the toner carried on the developing roller 33f moves to the electrostatic latent image on the photosensitive drum 31, thereby forming a toner image.

[0042] The transfer unit 50 is provided above the supply unit 10 and below the developer cartridge 30C. The transfer unit 50 conveys the sheet S supplied from the supply unit 10 to the discharge tray 5. The transfer unit 50 includes a driving roller 51, a driven roller 52, a conveying belt 53, a plurality of (four in this embodiment) transfer rollers 54, and the like. The conveying belt 53 is, for example, an endless belt, and is extended between the driving roller 51 located below the rear end side of the developer cartridge 30K and the driven roller 52 located below the front end side of the developer cartridge 30M.

[0043] Each of the plurality of transfer rollers 54 is disposed at a position corresponding to each photosensitive drum 31 in the vertical direction, sandwiching the sheet conveying surface 53A as the outer peripheral surface of the conveying belt 53, and contacts the conveying belt 53 from the back side of the sheet conveying surface 53A. A negative transfer voltage is applied to each of the plurality of transfer rollers 54 according to the conveying timing of the sheet S, so that the toner image carried on the surface of the photosensitive drum 31 is transferred to the sheet S conveyed on the sheet conveying surface 53A.

[0044] The fixing device 60 is disposed downstream of the position of the transfer unit 50 in the conveying direction. The fixing device 60 includes a heating roller 61 for heating the sheet S, a pressure roller 62 that sandwiches the sheet S with the heating roller 61, and a thermistor 63 (see Figure 2 The image forming unit 20 conveys the sheet S with the toner image transferred thereto to the fixing device 60. The fixing device 60 heat-fixes the toner image transferred thereto on the sheet S by conveying the sheet S between the heating roller 61 and the pressure roller 62. The sheet S with the image printed thereon is discharged to the discharge tray 5 by the discharge roller 65.

[0045] The thermistor 63 is provided near the heating roller 61 and detects the temperature of the heating roller 61. The thermistor 63 is provided to the main control circuit 101 (see Figure 2 ) outputs a signal corresponding to the detected temperature.

[0046] The fixing device 60 includes a heating roller 61 and a pressure roller 62, but is not limited thereto. For example, the fixing device may include a heater, a nip plate receiving radiant heat from the heater, a heating belt rotating around the nip plate, and a pressure roller.

[0047] In addition, the fixing device may also be configured to include a substrate having a heat pattern formed thereon, a belt rotating around the substrate, and a pressure roller, and the substrate and the belt are in contact with each other. In addition, the fixing device may also be configured to include a heating roller, a heater, and a pressure belt.

[0048] Next, refer to Figure 2 The control structure of the printer 1 is described. Figure 2 As shown, the printer 1 further includes a main control circuit 101, a ROM 102, a RAM 103, a nonvolatile memory 104, and a sub-control circuit 105. The main substrate 100 is provided with the main control circuit 101, the ROM 102, the RAM 103, the nonvolatile memory 104, the sub-control circuit 105, a DC-DC (direct current-direct current) converter 106, a main motor driver MD1, and a processing motor driver MD2.

[0049] The main control circuit 101 is composed of, for example, a general-purpose SoC having a CPU (not shown), and performs overall control of the various parts of the printer 1. The main control circuit 101 is electrically connected to the ROM 102, the RAM 103, the non-volatile memory 104, the sub-control circuit 105, the DC-DC converter 106, the main motor driver MD1, and the processing motor driver MD2. In addition, the main control circuit 101 is connected to the sub-control circuit 105 via a signal line L1. The signal line L1 is a signal line for transmitting data between the main control circuit 101 and the sub-control circuit 105. As a communication method, for example, UART (Universal As ynchronous Receive Transmitter) is used, but it is not limited to this method. In addition, a specific example of data transmitted through the signal line L1 will be described later. Figure 4 and Figure 5 The processing is described in .

[0050] The ROM 102 stores various control programs, various settings, and the like for controlling the printer 1 . Figure 4 The control processing programs are included in various control programs.

[0051] The RAM 103 is used as a work area for reading various control programs and a storage area for temporarily storing image data included in a job. The main control circuit 101 (CPU) stores the processing results in the RAM 103 or the nonvolatile memory 104 according to the control program read from the ROM 102 and the signals output from various sensors including the thermistor 63, and controls each part of the printer 1.

[0052] The main motor driver MD1 controls the driving voltage based on the control signal from the main control circuit 101, and outputs the driving voltage to the main motor 110, thereby controlling the driving of the main motor 110. The main motor 110 drives the heating roller 61, the pressure roller 62, and the roller group 120 of the fuser 60. The roller group 120 includes the pickup roller 12, the registration roller 15, the discharge roller 65, etc. The driving force of the main motor 110 is transmitted to the heating roller 61 and the roller group 120 via the gear group (not shown). That is, in order to indicate that the driving force of the main motor 110 is indirectly transmitted to the heating roller 61 and the roller group 120 via the gear group, Figure 2 In the figure, the main motor 110, the heating roller 61 and the roller group 120 are connected by dotted lines.

[0053] The process motor driver MD2 is also supplied with a control signal from the main control circuit 101. The process motor driver MD2 controls the driving voltage according to the control signal from the main control circuit 101, outputs the driving voltage to the process motor 111, and controls the driving of the process motor 111. The process motor 111 drives the four developing rollers 33f and the four photosensitive drums 31. The reason why the process motor 111 is connected with the developing rollers 33f and the photosensitive drums 31 by a dotted line is the same as the reason why the main motor 110 is connected with the heating roller 61 and the roller group 120 by a dotted line.

[0054] The low voltage power supply substrate 113 is connected to the DC-DC converter 106. The low voltage power supply substrate 113 includes an AC-DC (alternating current-direct current) converter (not shown), and converts the input AC voltage (e.g., commercial AC 100V) into a DC voltage (e.g., DC24V) through the AC-DC converter, and outputs it to the DC-DC converter 106 or the high voltage power supply substrate 112 (see Figure 3 The DC-DC converter 106 converts the input DC 24V into a lower DC voltage (eg DC 3.3V) and supplies the voltage to the main control circuit 101 and the sub-control circuit 105 as a power supply voltage.

[0055] The sub-control circuit 105 is composed of, for example, an MCU (microcontroller unit), and outputs a high-voltage control signal for controlling the high-voltage power supply substrate 112 to the high-voltage power supply substrate 112. The high-voltage power supply substrate 112 applies a high-voltage (for example, about 1 kV) charging voltage to the four charging devices 32 based on the DC24V supplied from the low-voltage power supply substrate 113. The value of the charging voltage is controlled based on the high-voltage control signal from the sub-control circuit 105.

[0056] Figure 3 FIG. 1 shows a transmission path of a portion of the signal around the main substrate 100. Figure 3As shown, the high-voltage power supply substrate 112 has an output terminal OUT31. When any of the four chargers 32 has an abnormal discharge such as over-discharge, a discharge detection signal is output from the output terminal OUT31. The discharge detection signal indicates that an abnormal discharge has occurred when it is H, and indicates that an abnormal discharge has not occurred when it is L, but the logic may be reversed. The output terminal OUT31 is connected to the input terminal IN2 of the sub-control circuit 105 via the signal line L5, and is connected to the input terminal IN1 of the main control circuit 101 via the signal line L6 branched from the signal line L5. Therefore, the main control circuit 101 can detect that an abnormal discharge has occurred in a certain charger 32 based on the discharge detection signal input to the input terminal IN1. Similarly, the sub-control circuit 105 can also detect that an abnormal discharge has occurred in a certain charger 32 based on the discharge detection signal input to the input terminal IN2.

[0057] The input terminal IN41 of the high voltage power source substrate 112 is connected to the output terminal OUT4 of the sub control circuit 105 via the signal line L7. The high voltage control signal is transmitted from the sub control circuit 105 to the high voltage power source substrate 112 via the signal line L7.

[0058] The main control circuit 101 has an output terminal OUT1, and when the specified conditions are met and the printer 1 is to be transferred to the deep sleep state, a D-SLEEP signal is output from the output terminal OUT1. The D-SLEEP signal, for example, indicates a transfer to the deep sleep state when it is L, and indicates not to transfer to the deep sleep state when it is H, but the logic can also be reversed. The output terminal OUT1 is connected to the input terminal IN11 of the low-voltage power supply substrate 113 via the signal line L2. Therefore, the low-voltage power supply substrate 113 can detect whether to transfer the printer 1 to the deep sleep state based on the D-SLEEP signal input to the input terminal IN11. When the D-SLEEP signal is H, that is, when the printer 1 is not transferred to the deep sleep state, the low-voltage power supply substrate 113 outputs DC24V from the output terminal OUT11; on the other hand, when the D-SLEEP signal is L, that is, when the printer 1 is transferred to the deep sleep state, a DC voltage lower than the voltage value of DC24V, such as DC 6V, is output from the output terminal OUT11.

[0059] Output terminal OUT11 is connected to input terminal IN21 of relay 108 via power line PL1. Output terminal OUT21 of relay 108 is connected to input terminal IN31 of high voltage power source substrate 112 via power line PL2. On / off of relay 108 is controlled by output of AND circuit 107.

[0060] On the input side of the AND circuit 107, the output terminal OUT2 of the main control circuit 101 is connected via the signal line L3, and the output terminal OUT3 of the sub-control circuit 105 is connected via the signal line L4. The main control circuit 101 outputs the HV_ENABLE1 signal for instructing the high-voltage power supply substrate 112 to output / stop the high voltage from the output terminal OUT2. Similarly, the sub-control circuit 105 also outputs the HV_ENABLE2 signal for instructing the high-voltage power supply substrate 112 to output / stop the high voltage from the output terminal OUT3. When the HV_ENABLE1 signal and the HV_ENABLE2 signal are H, it indicates that the high voltage is output to the high-voltage power supply substrate 112, and when they are L, it indicates that the high voltage is stopped. Therefore, the output of the AND circuit 107 becomes H when both the HV_ENABLE1 signal and the HV_ENABLE2 signal are H, and becomes L when at least one of the HV_ENABLE1 signal and the HV_ENABLE2 signal is L. Relay 108 is turned on when the output of AND circuit 107 is H, and is turned off when the output of AND circuit 107 is L. When both the main control circuit 101 and the sub-control circuit 105 instruct the high-voltage power supply substrate 112 to output a high voltage, relay 108 is turned on, and the high voltage is output from the high-voltage power supply substrate 112. When at least one of the main control circuit 101 and the sub-control circuit 105 instructs the high-voltage power supply substrate 112 to stop the high voltage, relay 108 is turned off, and the application of high voltage from the high-voltage power supply substrate 112 stops.

[0061] based on Figure 4 and Figure 5 The control process executed by the printer 1 configured as above will be described in detail.

[0062] Figure 4 1 shows the flow of the control process executed by the main control circuit 101. The program of this control process is stored in the ROM 102 as described above, and is read from the ROM 102 to the RAM 103 when the main control circuit 101 executes it. This control process starts when the sub-control circuit 105 starts applying a high voltage to the high-voltage power supply substrate 112, for example, when the main control circuit 101 receives a print job or a print command. In the following description of each process, the step is marked as "S".

[0063] exist Figure 4 In the embodiment, first, the main control circuit 101 (CPU) initializes the discharge count counter to "0" (S10). The discharge count counter is, for example, a software counter configured using a register (not shown) provided in the main control circuit 101, and has a function of measuring the time when the discharge detection signal input to the input terminal IN1 of the main control circuit 101 is H, that is, the time when any of the four chargers 32 has abnormal discharge.

[0064] Next, the main control circuit 101 monitors whether the discharge detection signal input to the input terminal IN1 is H or L every predetermined time (eg, 5 ms ec) (S12). This monitoring can be performed using, for example, an interrupt processing corresponding to an interrupt signal set to occur every predetermined time.

[0065] Then, the main control circuit 101 determines whether the discharge detection signal monitored every predetermined time is H (S14). In this judgment, when the discharge detection signal is H (S14: Yes), the main control circuit 101 increments the discharge number counter by "1" (S16), and determines whether the value of the incremented discharge number counter is below a predetermined threshold value (for example, 100 times) (S18). In this judgment, when the value of the discharge number counter is below a predetermined threshold value (S18: Yes), the main control circuit 101 determines whether the sub-control circuit 105 ends applying high voltage (S20). This judgment can be performed, for example, based on whether the printing process corresponding to the received print job or print command is completed.

[0066] In the judgment of S20, when the sub-control circuit 105 continues to apply the high voltage (S20: No), the main control circuit 101 returns the process to S12. On the other hand, when the sub-control circuit 105 stops applying the high voltage (S20: Yes), the main control circuit 101 ends the control process.

[0067] On the other hand, in the judgment of S14, when the discharge detection signal is L (S14: No), the main control circuit 101 decrements the discharge number counter by "1" (S22), and judges whether the value of the discharge number counter after decrement is less than "0", that is, whether it is a negative value (S24). In this judgment, if the value of the discharge number counter is a negative value (S24: Yes), the main control circuit 101 initializes the discharge number counter to "0" (S26), and then enters the process into S20. On the other hand, if the value of the discharge number counter is not a negative value (S24: No), the main control circuit 101 skips S26 and enters the process into S20.

[0068] On the other hand, in the judgment of S18, when the value of the discharge number counter exceeds the predetermined threshold value (S18: No), the main control circuit 101 sets the discharge flag in the register (S30). The discharge flag is a flag set when the main control circuit 101 judges that abnormal discharge has occurred in any of the four chargers 32. The register (area) in which the discharge flag is set and the register (area) used as the discharge number counter are of course different.

[0069] Next, the main control circuit 101 sets the HV_ENABLE1 signal to L (S32) and sets the D-SLEEP signal to L (S34). As a result, the HV_ENABLE1 signal of L is output from the output terminal OUT2, and the D-SLEEP signal of L is output from the output terminal OUT1. The low-voltage power supply substrate 113 to which the D-SLEEP signal of L is input from the input terminal IN11 outputs DC6V in the deep sleep state from the output terminal OUT11 instead of the normal DC24V as described above.

[0070] The main control circuit 101 attempts to communicate with the sub-control circuit 105 (S36). As a communication method, UART is used as described above in this embodiment, so the communication here is performed based on the communication protocol of UART. The main control circuit 101 determines whether communication is possible (S38). In this judgment, if communication is possible (S38: Yes), the main control circuit 101 determines whether the discharge flag of the register of the sub-control circuit 105 is in the set state (S40). Specifically, the main control circuit 101 inquires the sub-control circuit 105 through communication whether the discharge flag is set in the register of the sub-control circuit 105, and determines whether the discharge flag of the register of the sub-control circuit 105 is in the set state based on the answer from the sub-control circuit 105. In the judgment of S40, if the discharge flag of the register of the sub-control circuit 105 is in the set state (S40: Yes), the main control circuit 101 displays an error display indicating that abnormal discharge has occurred in one of the four chargers 32 on the display unit (not shown) of the printer 1 (S42), and then the control process ends.

[0071] On the other hand, in the judgment of S38, when communication is impossible (S38: No), the main control circuit 101 instructs the sub-control circuit 105 to reset (S44), and then ends the control process. In addition, in the judgment of S40, when the discharge flag of the register of the sub-control circuit 105 is not in the set state (S40: No), the main control circuit 101 causes the process to enter S44. Both the sub-control circuit 105 and the main control circuit 101 are configured to be able to input a reset instruction from the outside, and are reset when the reset instruction is input. Therefore, in S44, if the main control circuit 101 instructs the sub-control circuit 105 to reset, the sub-control circuit 105 is reset to the initial state. In S38, when it is judged that communication with the sub-control circuit 105 is impossible, the main control circuit 101 determines that some abnormality has occurred in the sub-control circuit 105, and instructs the sub-control circuit 105 to reset. Similarly, in S40, when it is determined that the discharge flag of the register of the sub-control circuit 105 is not set, the main control circuit 101 also determines that some abnormality has occurred in the sub-control circuit 105 and instructs the sub-control circuit 105 to reset. Figure 5 As described later, since the sub-control circuit 105 also performs the same processing as that of S12 to S30 in S52 to S70, when abnormal discharge occurs in any of the four chargers 32, a discharge flag should be set in the register of the sub-control circuit 105. In S40, when it is determined that the discharge flag of the register of the sub-control circuit 105 is not set, although the discharge flag should be set in the register of the sub-control circuit 105, since the discharge flag is not set in the register of the sub-control circuit 105, the main control circuit 101 determines that some abnormality has occurred in the sub-control circuit 105, and instructs the sub-control circuit 105 to reset.

[0072] Figure 5 FIG. 1 shows the flow of the control process executed by the sub-control circuit 105. The program of the control process is, for example, built into the sub-control circuit 105 and is executed only by the sub-control circuit 105. Figure 4 The control process is similar to that of , and starts when the sub-control circuit 105 starts applying high voltage to the high voltage power supply substrate 112.

[0073] exist Figure 5 In the process of S50 to S70, except for the process of S51, the process of Figure 4 The processing from S10 to S30 is the same. However, Figure 5In the embodiment, the discharge count counter is composed of a register of the sub-control circuit 105, and the discharge flag is set in the register of the sub-control circuit 105. In addition, the discharge detection signal represents the discharge detection signal input from the input terminal IN2 of the sub-control circuit 105. In S51, the sub-control circuit 105 starts Figure 4 There is no high voltage control in the control process, because the sub-control circuit 105 is responsible for the control of the high voltage power supply substrate 112 as described above.

[0074] In S72 after S70, the sub-control circuit 105 sets the HV_ENABLE2 signal to L. As a result, the HV_ENABLE2 signal of L is output from the output terminal OUT3. Then, the sub-control circuit 105 stops the high voltage control (S90), and then determines whether there is communication with the main control circuit 101 within a predetermined time (S92). In S92, it is possible to Figure 4 In S36 of the main control circuit 101, when the communication is possible, it is determined that there is communication, and when communication is not possible, it is determined that there is no communication. In the judgment of S92, when there is communication with the main control circuit 101 (S92: Yes), the sub-control circuit 105 ends the control processing. On the other hand, in the judgment of S92, when there is no communication with the main control circuit 101 (S92: No), the sub-control circuit 105 enters the processing into the next S76.

[0075] Each process from S76 to S84 is Figure 4 Compared with the processing of S36 to S44 of the embodiment, except that there is no display error processing of S42, they are basically the same. However, the difference is that in the processing of S36 to S44, the sub-control circuit 105 is used as the processing object, and in the processing of S76 to S84, the main control circuit 101 is used as the processing object. Thus, since the processing of S36 to S44 and the processing of S76 to S84 are roughly the same, the above description of the processing of S76 to S84 is omitted.

[0076] As described above, the printer 1 of this embodiment has: an image forming unit 20, which forms an image on a sheet S; a high-voltage power supply substrate 112, which applies a high voltage to the image forming unit 20 based on the supplied DC24V voltage, detects an overcurrent flowing in the image forming unit 20, and outputs a discharge detection signal; a relay 108, which switches the supply and stop of the DC24V voltage to the high-voltage power supply substrate 112; a main control circuit 101 to which the discharge detection signal is input; and a sub-control circuit 105, which controls the high voltage by outputting a control signal to the high-voltage power supply substrate 112, and to which the discharge detection signal is input.

[0077] The main control circuit 101 performs: a first judgment process (S18) for judging whether abnormal discharge has occurred in the image forming unit 20 based on the input discharge detection signal; and a first instruction process (S32) for instructing the relay 108 to stop supplying the DC24V voltage to the high-voltage power supply substrate 112 when it is judged in the first judgment process that abnormal discharge has occurred in the image forming unit 20 (S18: No). The sub-control circuit 105 performs: a second judgment process (S58) for judging whether abnormal discharge has occurred in the image forming unit 20 based on the input discharge detection signal; and a second instruction process (S72) for instructing the relay 108 to stop supplying the DC24V voltage to the high-voltage power supply substrate 112 when it is judged in the second judgment process that abnormal discharge has occurred in the image forming unit 20 (S58: No).

[0078] In the printer 1 of the present embodiment, the main control circuit 101 performs a first judgment process for judging whether abnormal discharge has occurred in the image forming unit 20 based on the input discharge detection signal, and the sub-control circuit 105 also performs a second judgment process for judging whether abnormal discharge has occurred in the image forming unit 20 based on the input discharge detection signal. Therefore, even if an abnormality occurs in the main control circuit 101 and the first judgment process cannot be performed, since the sub-control circuit 105 performs the second judgment process which is the same as the first judgment process, it is possible to judge whether abnormal discharge has occurred in the image forming unit 20. Similarly, even if an abnormality occurs in the sub-control circuit 105 and the second judgment process cannot be performed, the main control circuit 101 performs the first judgment process which is the same as the second judgment process, and thus it is possible to judge whether abnormal discharge has occurred in the image forming unit 20. In this way, even if an abnormality occurs in either the main control circuit 101 or the sub-control circuit 105, it is possible to judge whether abnormal discharge has occurred in the image forming unit 20 when no abnormality occurs in the other, and thus the judgment can be made reliably. Thus, when it is determined that abnormal discharge has occurred in the image forming unit 20 , the relay 108 can be reliably instructed to stop supplying voltage to the high-voltage power source substrate 112 through the first instruction process or the second instruction process.

[0079] In addition, in the first judgment process, the main control circuit 101 counts the number of times the discharge detection signal is input. If the count number is greater than the specified number, it is determined that abnormal discharge has occurred in the image forming unit 20, and the first information (discharge flag) indicating that the main control circuit 101 has determined that abnormal discharge has occurred is set. In the second judgment process, the sub-control circuit 105 counts the number of times the discharge detection signal is input. If the count number is greater than the specified number, it is determined that abnormal discharge has occurred in the image forming unit 20, and the second information (discharge flag) indicating that the sub-control circuit 105 has determined that abnormal discharge has occurred is set.

[0080] Therefore, in the first judgment process executed by the main control circuit 101 and the second judgment process executed by the sub-control circuit 105, when the discharge detection signal is input more than the specified number of times, it is judged that abnormal discharge has occurred in the image forming unit 20, which can improve the accuracy of judging the occurrence of abnormal discharge.

[0081] Furthermore, after executing the first instruction process, the main control circuit 101 determines whether the second information is set, and instructs the sub-control circuit 105 to perform initialization if the second information is not set.

[0082] When the main control circuit 101 executes the first instruction processing, the sub-control circuit 105 should set the second information, so if the second information is not set at this time, it is considered that some abnormality has occurred in the sub-control circuit 105. Therefore, the main control circuit 101 can eliminate the abnormality of the sub-control circuit 105 by instructing the sub-control circuit 105 to initialize.

[0083] Furthermore, after executing the second instruction process, the sub-control circuit 105 determines whether the first information is set, and instructs the main control circuit 101 to initialize if the first information is not set.

[0084] When the sub-control circuit 105 executes the second instruction processing, the main control circuit 101 should set the first information, so if the first information is not set at this time, it is considered that some abnormality has occurred in the main control circuit 101. Therefore, the sub-control circuit 105 can eliminate the abnormality of the main control circuit 101 by instructing the main control circuit 101 to initialize.

[0085] In addition, the printer 1 also includes an AND circuit 107, to which an indication of a first instruction processing and an indication of a second instruction processing are input. When an indication of at least one of the indication of the first instruction processing and the indication of the second instruction processing is input, the AND circuit 107 instructs the relay 108 to stop supplying a DC24V voltage to the high-voltage power supply substrate 112.

[0086] Therefore, when at least one of the instructions of the first instruction processing and the instructions of the second instruction processing is input, the relay 108 is instructed to stop supplying the DC24V voltage to the high-voltage power supply substrate 112. Therefore, even if an abnormality occurs in either the main control circuit 101 or the sub-control circuit 105, if an abnormality does not occur in the other side, the relay 108 can be reliably instructed to stop supplying voltage to the high-voltage power supply substrate 112 through the first instruction processing or the second instruction processing.

[0087] The image forming unit 20 includes a photosensitive drum 31 , a charger 32 for charging the photosensitive drum 31 , and an exposure unit 40 for forming an electrostatic latent image on the photosensitive drum 31 charged by the charger 32 . The abnormal discharge in the image forming unit 20 is the abnormal discharge of the charger 32 .

[0088] This makes it possible to reliably determine that abnormal discharge has occurred in the charger 32 .

[0089] Furthermore, after executing the first instruction process, the main control circuit 101 attempts to communicate with the sub-control circuit 105 , and when communication is not possible, instructs the sub-control circuit 105 to initialize.

[0090] Thus, when the main control circuit 101 is operating normally, if the main control circuit 101 cannot communicate with the sub-control circuit 105, it is considered that some abnormality has occurred in the sub-control circuit 105. Therefore, the main control circuit 101 can eliminate the abnormality of the sub-control circuit 105 by instructing the sub-control circuit 105 to initialize.

[0091] Furthermore, after executing the second instruction process, the sub-control circuit 105 attempts to communicate with the main control circuit 101 , and when communication is not possible, instructs the main control circuit 101 to initialize.

[0092] Thus, when the sub-control circuit 105 is operating normally, if the sub-control circuit 105 cannot communicate with the main control circuit 101, it is considered that some abnormality has occurred in the main control circuit 101. Therefore, the sub-control circuit 105 can eliminate the abnormality of the main control circuit 101 by instructing the main control circuit 101 to initialize.

[0093] (Second Embodiment)

[0094] Next, the second embodiment of the present invention will be described. This embodiment is different from the first embodiment in that only a portion of the wiring of the main substrate 100' is different, so the description will be centered on the different portions, and the description of other portions will be appropriately omitted. In addition, the hardware reference numerals of this embodiment are directly the same as those in the first embodiment. Figure 1 and Figure 2 The processing of this embodiment also directly uses the above-mentioned hardware reference numerals. Figure 4 and Figure 5 processing.

[0095] Figure 6 The transmission path of a part of the signal around the main substrate 100' of this embodiment is shown, which is different from that of the first embodiment. Figure 3 Corresponding. Compare Figure 6 and Figure 3 It is known that in Figure 6The output terminal OUT2 is omitted, and the output terminal OUT1 and the input side of the AND circuit 107 are directly connected via the signal line L2′. In addition, the output terminal OUT1 and the input terminal IN11 of the low-voltage power supply substrate 113 are connected via the signal line L2 as in the first embodiment. That is, in this embodiment, the D-SLEEP signal has two functions: the function of transferring to the deep sleep state and the function of the HV_ENABLE1 signal. In this way, the D-SLEEP signal can also be used as the HV_ENABLE1 signal because Figure 4 In S32 and S34 of FIG. 1 , the HV_ENABLE1 signal and the D-SLEEP signal are set to L. However, in the present embodiment, the main control circuit 101 does not output the HV_ENABLE1 signal, so the process of S32 is omitted.

[0096] As described above, the printer 1 of this embodiment has: an image forming unit, which forms an image on a sheet; a high-voltage power supply substrate, which applies a high voltage to the image forming unit 20 based on the supplied voltage, detects an overcurrent flowing in the image forming unit 20, and outputs a discharge detection signal; a switching circuit, which switches the supply and stop of the DC24V voltage to the high-voltage power supply substrate 112; a first control unit, to which the discharge detection signal is input; and a second control unit, which controls the high voltage by outputting a control signal to the high-voltage power supply substrate 112, and to which the discharge detection signal is input.

[0097] The main control circuit 101 performs: a first judgment process, based on the input discharge detection signal, to judge whether abnormal discharge has occurred in the image forming unit 20; and a first instruction process, when it is judged in the first judgment process that abnormal discharge has occurred in the image forming unit 20, to instruct the relay 108 to stop supplying the DC24V voltage to the high-voltage power supply substrate 112. The sub-control circuit 105 performs: a second judgment process, based on the input discharge detection signal, to judge whether abnormal discharge has occurred in the image forming unit 20; and a second instruction process, when it is judged in the second judgment process that abnormal discharge has occurred in the image forming unit 20, to instruct the relay 108 to stop supplying the DC24V voltage to the high-voltage power supply substrate 112.

[0098] In the printer 1 of the present embodiment, the main control circuit 101 performs a first judgment process for judging whether abnormal discharge has occurred in the image forming unit 20 based on the input discharge detection signal, and the sub-control circuit 105 also performs a second judgment process for judging whether abnormal discharge has occurred in the image forming unit 20 based on the input discharge detection signal. Therefore, even if an abnormality occurs in the main control circuit 101 and the first judgment process cannot be performed, since the sub-control circuit 105 performs the second judgment process which is the same as the first judgment process, it is possible to judge whether abnormal discharge has occurred in the image forming unit 20. Similarly, even if an abnormality occurs in the sub-control circuit 105 and the second judgment process cannot be performed, the main control circuit 101 performs the first judgment process which is the same as the second judgment process, and thus it is possible to judge whether abnormal discharge has occurred in the image forming unit 20. In this way, even if an abnormality occurs in either the main control circuit 101 or the sub-control circuit 105, it is possible to judge whether abnormal discharge has occurred in the image forming unit 20 when no abnormality occurs in the other, and thus the judgment can be made reliably. Thus, when it is determined that abnormal discharge has occurred in the image forming unit 20 , the relay 108 can be reliably instructed to stop supplying voltage to the high-voltage power source substrate 112 through the first instruction process or the second instruction process.

[0099] In addition, the printer 1 also includes an AND circuit 107, to which an indication of a first instruction processing and an indication of a second instruction processing are input. When an indication of at least one of the indication of the first instruction processing and the indication of the second instruction processing is input, the AND circuit 107 instructs the relay 108 to stop supplying a DC24V voltage to the high-voltage power supply substrate 112.

[0100] Therefore, when at least one of the instructions of the first instruction processing and the instructions of the second instruction processing is input, the relay 108 is instructed to stop supplying the DC24V voltage to the high-voltage power supply substrate 112. Therefore, even if an abnormality occurs in either the main control circuit 101 or the sub-control circuit 105, if an abnormality does not occur in the other side, the relay 108 can be reliably instructed to stop supplying voltage to the high-voltage power supply substrate 112 through the first instruction processing or the second instruction processing.

[0101] In addition, when specified conditions are met, including a determination in the first judgment process that abnormal discharge has occurred in the image forming unit 20, the main control circuit 101 outputs a DS LEE P signal for causing the printer 1 to shift to a deep sleep state, and inputs a D-SLEEP signal to the AND circuit 107 instead of the instruction of the first instruction process. When at least one of the D-SLEEP signal and the instruction of the second instruction process is input, the AND circuit 107 instructs the relay 108 to stop supplying the DC24V voltage to the high-voltage power supply substrate 112.

[0102] Thus, since the instruction of the first instruction process is replaced by the D-SLEEP signal originally provided by the printer 1, the first instruction process can be omitted, and the output terminal for outputting the instruction of the first instruction process can be omitted.

[0103] The printer 1 also includes a low voltage power board 113 that supplies a DC 24V voltage to the high voltage power board 112. The D-SLEEP signal is a signal that instructs the low voltage power board 113 to supply a DC 6V voltage that is lower than the DC 24V voltage.

[0104] Since the D-SLEEP signal is a signal originally possessed by the printer 1, the first instruction process can be omitted by replacing the instruction of the first instruction process with the D-SLEEP signal, and the output terminal for outputting the instruction of the first instruction process can be omitted.

[0105] The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the invention.

[0106] (1) In the above embodiments, a color laser printer is used as an example of an image forming device, but the image forming device is not limited to this and may be a monochrome laser printer. In addition, the image forming device is not limited to a printer and may be a multifunction machine or a copier.

[0107] (2) In the above-mentioned embodiments, the relay 108 is listed as a switching circuit for switching the supply and stop of the DC24V voltage to the high-voltage power supply substrate 112, but it is not limited to a relay with contacts. A circuit using a semiconductor such as FET may also be used, as long as the output of the AND circuit 107 can switch the supply and stop of the DC24V voltage to the high-voltage power supply substrate.

[0108] (3) In the above-mentioned embodiments, the discharge count counter and the discharge flag are configured and stored using the respective registers of the main control circuit 101 and the sub-control circuit 105, but the present invention is not limited thereto and they may be configured and stored using different storage areas on the RAM 103. In this case, in addition to the main control circuit 101, the sub-control circuit 105 may also access the storage area on the RAM 103 to read or write the stored contents.

[0109] (4) In the above embodiments, abnormal discharge such as overdischarge occurs in any one of the four chargers 32 , but the present invention is not limited to the charger 32 , and abnormal discharge in the path of the high-voltage power supply substrate 112 may be detected.

[0110] (5) In each of the above embodiments, Figure 4The control processing program is executed by reading the program stored in ROM 102 into RAM 103. Figure 5 The control processing program is to directly execute the program built into the sub-control circuit 105, but is not limited to this. Figure 5 The control processing program may be stored in the ROM 102, and the sub-control circuit 105 reads it out to the RAM 103 for execution. In addition, the control processing program stored in the ROM 102 may be directly executed without being read out to the RAM 103. The control processing program may be stored in the nonvolatile memory 104 instead of the ROM 102.

Claims

1. An image forming device, comprising: An image forming unit for forming an image on a sheet; a high voltage power source substrate for applying a high voltage to the image forming portion based on the supplied voltage, the high voltage power source substrate outputting a discharge detection signal by detecting that an overcurrent has flowed in the image forming portion; A switching circuit for switching between supplying and stopping supplying the voltage to the high voltage power supply substrate; a first control unit to which the discharge detection signal is input; as well as a second control unit configured to control the high voltage by outputting a control signal to the high voltage power supply substrate, the second control unit being input with the discharge detection signal, The first control unit performs: a first determination process of determining whether abnormal discharge has occurred in the image forming portion based on the input discharge detection signal; and a first instruction process of instructing the switching circuit to stop supplying the voltage to the high voltage power source substrate when it is determined in the first determination process that abnormal discharge has occurred in the image forming unit; The second control unit executes: a second determination process of determining whether abnormal discharge has occurred in the image forming portion based on the input discharge detection signal; and The second instruction process instructs the switching circuit to stop supplying the voltage to the high-voltage power source substrate when it is determined in the second determination process that abnormal discharge has occurred in the image forming portion.

2. The image forming apparatus according to claim 1, wherein: The first control unit counts the number of times the discharge detection signal is input in the first judgment process, and if the counted number is greater than a predetermined number, determines that abnormal discharge has occurred in the image forming unit, and sets first information indicating that the first control unit has determined that the abnormal discharge has occurred. The second control unit counts the number of times the discharge detection signal is input in the second judgment process, and if the counted number is greater than a specified number, determines that abnormal discharge has occurred in the image forming unit, and sets second information indicating that the second control unit has determined that the abnormal discharge has occurred.

3. The image forming apparatus according to claim 2, wherein: After executing the first instruction processing, the first control unit determines whether the second information is set, and instructs the second control unit to initialize if the second information is not set.

4. The image forming apparatus according to claim 2, wherein: After executing the second instruction process, the second control unit determines whether the first information is set, and instructs the first control unit to initialize if the first information is not set.

5. The image forming apparatus according to claim 1, wherein: It also includes an indication circuit, to which the indication of the first indication processing and the indication of the second indication processing are input, and when at least one of the indication of the first indication processing and the indication of the second indication processing is input, the indication circuit instructs the switching circuit to stop supplying the voltage to the high-voltage power supply substrate.

6. The image forming apparatus according to claim 5, wherein: The first control unit outputs a deep sleep signal for causing the image forming device to shift to a deep sleep state when a predetermined condition is satisfied, including when it is determined in the first determination process that abnormal discharge has occurred in the image forming unit. The deep sleep signal is input to the instruction circuit instead of the instruction of the first instruction processing, and the instruction circuit instructs the switching circuit to stop supplying the voltage to the high voltage power supply substrate when at least one of the deep sleep signal and the instruction of the second instruction processing is input.

7. The image forming apparatus according to claim 6, wherein: Also included is a low voltage power supply circuit for supplying the voltage to the high voltage power supply substrate, The deep sleep signal is a signal that instructs the low voltage power supply circuit to supply a voltage lower than the voltage.

8. The image forming apparatus according to claim 1, wherein: The image forming unit includes: Photosensitive drum; a charger for charging the photosensitive drum; and an exposure unit for forming an electrostatic latent image on the photosensitive drum charged by the charger, The abnormal discharge in the image forming section is abnormal discharge of the charger.

9. The image forming apparatus according to claim 1, wherein: After executing the first instruction process, the first control unit attempts to communicate with the second control unit, and if the communication is not possible, instructs the second control unit to initialize.

10. The image forming apparatus according to claim 1, wherein After executing the second instruction process, the second control unit attempts to communicate with the first control unit, and if the communication is not possible, instructs the first control unit to initialize.

Images