JP5031489B2 - High voltage power supply unit and image forming apparatus - Google Patents

Description

  The present invention corresponds to a photoreceptor unit including a DC high-voltage power supply and an AC high-voltage power supply that are applied to a charging roller with respective output voltages superimposed, and the charging roller and a photosensitive drum charged by the charging roller. The present invention relates to a high-voltage power supply unit provided in the same number and an image forming apparatus equipped with the high-voltage power supply unit.

  In a charging roller type image forming apparatus, a charging roller, which is output from a DC high voltage and an AC high voltage provided in a high voltage power supply unit driven by a control unit, is applied in contact with a photosensitive drum. Thus, the surface of the photosensitive drum is uniformly charged.

  In Patent Document 1, in the charging voltage control of the photosensitive drum, when the peak voltage value Vpp of the AC high voltage is increased, the charging voltage of the photosensitive drum increases in proportion to the peak voltage value Vpp. However, it is disclosed that when the voltage reaches about twice the charging start voltage by the DC high voltage, the charging potential is saturated, and the charging potential does not change even if the voltage is increased further.

  When the AC high voltage becomes higher than necessary, discharge products increase and adhere to the charging roller and the photosensitive drum, causing image deterioration and characteristic deterioration of the photosensitive drum. It is desirable to adjust the charging potential of the drum to the lowest value at which saturation of the charging potential is maintained. The control unit for adjusting the charging potential of the photosensitive drum is configured so that the charging roller is saturated in the same manner as the charging potential is saturated. The adjustment of the AC high voltage is executed based on the DC charging current flowing through the drum.

  By the way, in a tandem type image forming apparatus in which a photosensitive unit including a charging roller and a photosensitive drum is provided for each toner color, it is necessary to adjust a charging potential of the photosensitive drum, that is, a charging amount for each photosensitive unit. Yes, it is necessary to detect the DC charging current for each photoconductor unit.

  Therefore, in a low-speed machine that places importance on cost, the high-voltage power supply unit includes only one current detection unit that detects a current value after addition of the DC charging current for each photoconductor unit, and is based on the output signal of the current detection unit. The controller is configured to sequentially switch and adjust the AC high voltage applied to each charging roller one by one. That is, the control unit applies an AC high voltage only to the photosensitive unit to be adjusted to saturate the charging potential, and adjusts and adjusts the AC high voltage based on the DC charging current detected by the current detection unit. The AC high voltage of all the photoconductor units is adjusted by sequentially switching the objects and executing the adjustment. Therefore, although time is required for adjustment, only one current detection unit is required, and the component cost can be saved.

  Further, in a high-speed machine in which speed is more important than cost, the high-voltage power supply unit is provided with current detection units as many as the number of photosensitive units, and the control unit is configured to simultaneously adjust the AC high-voltage applied to each charging roller . That is, the control unit simultaneously applies an AC high voltage to all the photoreceptor units to saturate each charging potential, and each AC high voltage based on each DC charging current detected by each current detection unit. Is adjusted. Therefore, the charge amount adjustment of each photoconductor unit can be completed in a short time.

JP-A 63-149668

  By the way, if a high-voltage power supply unit is shared with a low-speed machine or a high-speed machine, it is possible to reduce the manufacturing cost due to the mass production effect, and furthermore, it is possible to realize a reduction in management cost and maintenance cost. It is considered that the total cost can be reduced rather than preparing the high voltage power supply unit for high speed and the high voltage power supply unit for high speed machine individually.

  However, as described above, since the control process of the control unit for the high-voltage power supply unit is different between the low-speed machine and the high-speed machine, for example, the high-voltage power supply unit that is common to devices equipped with the respective high-voltage power supply units For example, it is necessary to rewrite the software of the control unit, and there is a problem that the working efficiency is lowered and the total cost is increased. Therefore, it is difficult to share the high-voltage power supply unit.

  In view of the above-described problems, the object of the present invention can be driven in common from any of the control units that execute charge amount adjustment control of the photosensitive drum in different processes without rewriting software. Another object of the present invention is to provide a high-voltage power supply unit capable of reducing manufacturing costs due to mass production effects and management costs due to common parts, and an image forming apparatus equipped with the high-voltage power supply unit.

  In order to achieve the above-described object, the high voltage power supply unit according to the present invention is characterized in that the high voltage power supply unit is a DC high voltage power source that is applied to the charging roller with each output voltage superimposed thereon as described in claim 1 of the claims. A power source and an AC high-voltage power source, and a current detection unit for detecting a DC charging current flowing from the charging roller to the photosensitive drum, are provided in a number corresponding to the photosensitive unit including the charging roller and the photosensitive drum, and An addition circuit for adding the output signals of the current detection unit; a plurality of first output connectors for individually outputting the output signals from the respective current detection units; and a second output connector for outputting the output signal of the addition circuit. There is in point.

  According to the above-described configuration, for example, a control installed in a high-speed machine is configured to simultaneously receive output signals from the respective current detection units and simultaneously adjust the AC high voltage applied to each charging roller. The first output connector may be connected to the unit, and the output signal from each current detection unit is sequentially switched and received, and the AC high voltage applied to each charging roller is adjusted sequentially. For example, what is necessary is just to connect a 2nd output connector with respect to the control part mounted in the low speed machine. That is, the high-voltage power supply unit can be installed in common for both control units of the high-speed machine and the low-speed machine.

  The first characteristic configuration of the image forming apparatus according to the present invention is the simultaneous adjustment mode in which the charge amount adjustment control of each photoconductor unit is simultaneously executed based on each output signal of the current detection unit as described in claim 2. A charge amount adjusting unit that adjusts the charge amount in any one of the sequential adjustment modes that sequentially execute the charge amount adjustment control of each photoconductor unit based on the output signal of the adder circuit, and the first output connector Driven by the control unit having a connection state determination unit that determines whether or not connected, a mode switching unit that switches the charge amount adjustment control mode based on a determination result of the connection state determination unit, and The high voltage power supply unit according to claim 1 is provided.

  According to the above configuration, the control unit simultaneously adjusts the AC high voltage applied to each charging roller when the first output connector is connected. When the first output connector is disconnected for some reason, it takes time to adjust the AC high voltage applied to each charging roller. Quantity adjustment can be executed reliably.

  In the second feature configuration, as described in claim 3, in addition to the first feature configuration described above, the connection state determination unit is configured to output the first feature based on an output signal level output from each current detection unit. The point is to determine whether or not one output connector is connected.

  According to the above-described configuration, it is possible to determine whether or not the first output connector is connected by software without using parts that require an increase in cost and installation space.

  In the third feature configuration, as described in claim 4, in addition to the first feature configuration described above, the connection state determination unit corresponds to whether or not the first output connector is connected. It is in the point provided with the switch part which can be switched on and off.

  According to the configuration described above, it is possible to reliably determine whether or not the first output connector is connected by hardware having a simple configuration.

  As described above, according to the present invention, it is possible to drive in common from any of the control units that execute the charge amount adjustment control of the photosensitive drum in different processes without rewriting software or the like. It has become possible to provide a high-voltage power supply unit capable of reducing manufacturing costs due to mass production effects and management costs due to common parts, and an image forming apparatus equipped with the high-voltage power supply unit.

  A copier as an example of an image forming apparatus equipped with the high-voltage power supply unit of the present invention will be described below.

  As shown in FIG. 2, the tandem type copying machine 1 adopting the electrophotographic system includes an operation unit 10 on which a display unit including a liquid crystal screen, a start key for starting a copying operation, and the like are arranged, and a document feeding An image reading unit 12 that sequentially feeds documents placed on the table 11 and photoelectrically converts the document image to read it as image data, and image processing that converts the image data read by the image reading unit 12 into output image data The image forming unit 2 that forms a toner image on the basis of the output image data and transfers the toner image to a fed paper; and heat that heats and fixes the toner image transferred onto the paper. A fixing unit 14, a sheet storage unit 15 that stores a sheet on which a toner image is transferred by the image forming unit 2, a transport mechanism 16 that transports the sheet, a paper discharge unit 17 that discharges the sheet, Control the functional block Configured with a control unit 3 for executing the process as copy machine 1.

  The control unit 3 includes a CPU, a ROM that stores an operation program for the CPU, a RAM that serves as a work area, an input port that receives a signal from a sensor installed in each unit, and a control signal that is output to each unit. Output port. The CPU that executes the operation program stored in the ROM cooperates with the hardware related to the CPU, and constitutes a plurality of control blocks that control each part of the copying machine 1 including the image forming part 2.

  As shown in FIG. 1, the image forming unit 2 includes a high-voltage power supply unit 20 including a DC high-voltage power supply 22, an AC high-voltage power supply 21, a current detection unit 23, an adder circuit 24, and a connector unit 25, magenta (M), and cyan. For each toner color of (C), yellow (Y), and Bragg (K), a photosensitive unit including a charging roller 26 and a photosensitive drum 27 is provided. The DC high-voltage power supply 21, the AC high-voltage power supply 22, and the current detection units 23 are provided in a number corresponding to each photoconductor unit, and have the same hardware configuration for each photoconductor unit.

  Hereinafter, the DC high-voltage power supply 22, the AC high-voltage power supply 21, and the current detection unit 23 for one photoconductor unit will be described.

  As shown in FIG. 3, the DC high-voltage power supply 22 receives a pulse signal from a pulse signal generation unit 220 that outputs a pulse signal based on a DC voltage control signal input from the control unit 3 via the connector unit 25. Is input to the primary side, a high-voltage AC voltage is output from the secondary side, smoothed by a rectifier circuit including a diode 222 and a capacitor 223, and output to the secondary side of the AC high-voltage power supply 21 as a DC high-voltage.

  In the AC high voltage power supply 21, a pulse signal from a pulse signal generation unit 210 that outputs a pulse signal based on an AC voltage control signal input from the control unit 3 via the connector unit 25 is input to the primary side of the transformer 211. Then, an AC high voltage is generated on the secondary side, and is superimposed on the DC high voltage output from the DC high voltage power supply 22 and output to the charging roller 26.

  The current detection unit 23 includes a current-voltage conversion operational amplifier 230 and a voltage amplification operational amplifier 231. The inverting input terminal of the operational amplifier 230 is connected to the secondary side of the DC high-voltage power supply 22, and the non-inverting input terminal is connected to the connection node of the resistor 232 and the resistor 233 that divides the reference voltage Vref. A current flowing through the resistor 234, that is, a DC charging current Idc flowing from the charging roller 26 to the photosensitive drum 27 so as to equalize the voltage between the inverting input terminal and the inverting input terminal is converted into a voltage, amplified by the operational amplifier 231 and detected. It is output as a current output signal.

  As shown in FIG. 4, the adder circuit 24 includes an operational amplifier 240 whose non-inverting input terminal is grounded and each output signal of the current detection unit 23 is input to the inverting input terminal via resistors 241, 242, 243, and 244. The operational amplifier 240 outputs the output signal of the detected total current obtained by adding and inverting the output signals. Here, the adder circuit 24 may output the signal after inverting the polarity of the detected total current signal via an inverter.

  As shown in FIGS. 5, 6, and 7, the connector unit 25 includes a plurality of input connectors 250 to which a DC voltage control signal and an AC voltage control signal output from the control unit 3 for each photosensitive unit are input. Each of the connectors 250 includes a plurality of first output connectors 251 that individually output an output signal from each current detection unit 23 for each photoconductor unit, and a second output connector 252 that outputs an output signal of the adder circuit 25. , 251 and 252 are connected to an output port or an input port of the control unit 3 via a harness (not shown).

  In the following, the charge amount adjustment control of each photoconductor unit is configured to be executed sequentially based on the output signal of the adder circuit 24, for example, the charge amount adjustment of each photoconductor unit by the control unit 3 provided in the low speed machine. Control will be described.

  As illustrated in FIG. 5, the control unit 3 includes a plurality of charge amount adjustment units 30 that sequentially execute charge amount adjustment control of each photosensitive unit as a part of control blocks that control the image forming unit 2, and a second control unit 30. An AD conversion unit 31 is provided that converts an output signal that is an analog signal input from the adder circuit 24 via the output connector 252 into a digital signal and inputs the digital signal to each charge amount adjustment unit 30.

  Each charge amount adjustment unit 30 adjusts the timing of outputting the DC voltage control signal and the AC voltage control signal when the power to the copying machine 1 is turned on or when the charge amount in each photoconductor unit deviates from a predetermined charge amount. The charge amount adjustment control of each photoconductor unit is executed, and during the adjustment control of one charge amount adjustment unit 30, the other charge amount adjustment unit 30 outputs the AC voltage control signal. Stop.

  Therefore, only the current detection unit 23 corresponding to the photosensitive unit whose charge amount is being adjusted detects the DC charging current Idc flowing from the charging roller 26 to the photosensitive drum 27, and the adder circuit 24 outputs the DC charging current Idc. Only the signal is output, and the charge amount adjustment unit 30 executing adjustment control executes charge amount adjustment control based on the output signal received via the AD conversion unit 31.

  Each charge amount adjustment unit 30 is configured to sequentially execute charge amount adjustment control for each photoconductor unit in a preset order. When one charge amount adjustment unit 30 completes the charge amount adjustment, The charge amount adjustment unit 30 starts the charge amount adjustment control, and this is repeated until the charge amount adjustment for all the photoconductor units is completed.

  The charging amount adjustment control of each photoconductor unit is executed simultaneously based on each output signal of the current detection unit 23, for example, the charging of each photoconductor unit by the control unit 3 provided in the high speed machine, for example. The amount adjustment control will be described.

  As illustrated in FIG. 6, the control unit 3 includes a plurality of charge amount adjustment units 30 that execute charge amount adjustment control of each photoconductor unit as a part of control blocks for controlling the image forming unit 2, and a plurality of first control units. A plurality of AD conversion units 31 are provided that convert each output signal, which is an analog signal input from the current detection unit via one output connector 251, into a digital signal and input the digital signal to the corresponding charge amount adjustment unit 30.

  Each charge amount adjustment unit 30 adjusts the timing of outputting the DC voltage control signal and the AC voltage control signal when the power to the copying machine 1 is turned on or when the charge amount in each photoconductor unit deviates from a predetermined charge amount. Thus, the charge amount adjustment control of each photoconductor unit is executed, and the charge amount adjustment control is executed regardless of the adjustment control execution state of the other charge amount adjustment units 30.

  That is, each charge amount adjustment unit 30 can individually execute charge amount adjustment control based on the corresponding DC charging current Idc received via the corresponding AD conversion unit 31. That is, when the charge amount adjustment control is necessary for all the photoconductor units, each charge amount adjustment unit 30 can simultaneously execute the charge amount adjustment control of each photoconductor unit. When the charge amount adjustment control is required for the photosensitive unit, only the corresponding charge amount adjustment unit 30 executes the charge amount adjustment control at the same time. Therefore, the charge amount adjustment control of the photosensitive unit can be completed in a short time.

  In the following, a simultaneous adjustment mode in which the charge amount adjustment control of each photoconductor unit is simultaneously executed based on each output signal of the current detector 23, and a charge amount adjustment control of each photoconductor unit based on the output signal of the addition circuit 24. The charge amount adjustment control of each photoconductor unit by the control unit 3 configured to adjust the charge amount of each photoconductor unit in any one of the sequential adjustment modes that sequentially execute the above will be described.

  As shown in FIG. 7, the control unit 3 simultaneously performs charge amount adjustment control of each photoconductor unit based on each output signal of the current detection unit 23 as a partial control block for controlling the image forming unit 2. A charge amount adjustment unit 30 that adjusts the charge amount in any one of a simultaneous adjustment mode and a sequential adjustment mode that sequentially executes charge amount adjustment control of each photoconductor unit based on the output signal of the adder circuit 24; A connection state determination unit 32 for determining whether or not the output connector 251 is connected; a mode switching unit 33 for switching the charge amount adjustment control mode based on the determination result of the connection state determination unit 32; An output signal composed of an analog signal input from the adder circuit 24 via the output connector 252 and an analog signal input from the current detection unit via the plurality of first output connectors 251 Provided that the output signals to the connection state determining unit 32 into a digital signal, a plurality of AD conversion unit 31 to be input to the mode switching unit 33. The charge amount adjusting units 30 are provided in a number corresponding to each photoconductor unit.

  The connection state determination unit 32 is based on the level of the output signal from each current detection unit, that is, when the digital value of each output signal input from each AD conversion unit 31 does not change for a predetermined time, or is set in advance. When deviating from the range, it is determined that the first output connector 251 is not connected, and otherwise, it is determined that the first output connector 251 is connected.

  When the connection state determination unit 32 determines that the first output connector 251 is connected, the mode switching unit 33 switches the charge amount adjustment control mode to the simultaneous adjustment mode, and the connection state determination unit 32 determines the first output connector. If it is determined that 251 is not connected, the charge amount adjustment control mode is sequentially switched to the adjustment mode.

  Each charge amount adjustment unit 30 adjusts the timing of outputting the DC voltage control signal and the AC voltage control signal when the power to the copying machine 1 is turned on or when the charge amount in each photoconductor unit deviates from a predetermined charge amount. Thus, the charge amount adjustment control of each photoconductor unit is executed.

  When the charge amount adjustment control mode is the simultaneous adjustment mode, each charge amount adjustment unit 30 performs charge amount adjustment control based on the corresponding DC charging current Idc received via the corresponding AD conversion unit 31. Run each one separately. That is, when the charge amount adjustment control is necessary for all the photoconductor units, each charge amount adjustment unit 30 can simultaneously execute the charge amount adjustment control of each photoconductor unit. When the charge amount adjustment control is required for the photosensitive unit, only the corresponding charge amount adjustment unit 30 executes the charge amount adjustment control at the same time. Therefore, the charge amount adjustment control of the photosensitive unit can be completed in a short time.

  When the charge amount adjustment control mode is the sequential adjustment mode, each charge amount adjustment unit 30 sequentially executes charge amount adjustment control for each photoconductor unit in a preset order. When the charge amount adjustment is completed, the next charge amount adjustment unit 30 starts the charge amount adjustment control, and this is repeated until the charge amount adjustment for all the photoconductor units is completed. While the adjustment control of one charge amount adjustment unit 30 is being executed, the other charge amount adjustment unit 30 is configured to stop outputting the AC voltage control signal.

  Therefore, only the current detection unit 23 corresponding to the photosensitive unit whose charge amount is being adjusted detects the DC charging current Idc flowing from the charging roller 26 to the photosensitive drum 27, and the adding circuit 24 outputs an output signal corresponding to the DC charging current. The charge amount adjusting unit 30 that is only outputting the adjustment control and executing the adjustment control executes the charge amount adjustment control based on the output signal received via the AD conversion unit 31.

  Another embodiment will be described below.

  In the above-described embodiment, the connection state determination unit 32 has been described as determining whether or not the first output connector 251 is connected based on the value of the output signal input from the AD conversion unit 31. A switch unit that is switched on and off according to whether or not the first output connector 251 is connected is provided, and it is determined whether or not the first output connector 251 is connected based on the on / off state of the switch unit. You may do.

  For example, when the first output connector 251 is connected to the connector unit 25, the connector unit 25 includes a third output connector that outputs a pulled-up output signal, and the connection state determination unit 32 is input via a harness. When the level of the output signal of the third output connector is high, it may be determined that the first output connector 251 is connected. In this case, the third output connector and the harness serve as a switch portion. The output signal output from the third output connector is not limited to the one pulled up, and may be one that pulls down or outputs a predetermined level. Any device that determines whether or not the first output connector 251 is connected based on the level may be used.

  Further, for example, as shown in FIG. 8, six connection pins of the control unit 3 side plug of the harness connecting the first output connector 251 and the control unit 3 are configured, and two of them are input ports of the control unit 3. The connection state determination unit 32 determines that the first output connector 251 is connected by configuring the output signal that is pulled up and output from one of the two to be input to the control unit 3. It may be configured as follows. In this case, an output signal pulled up from the control unit 3 is output, and an input port that is turned back and input from a plug of the harness and a connection pin that turns back the output signal of the plug constitute a switch unit. Note that the output signal output from the control unit 3 is not limited to the one pulled up, but may be one that pulls down or outputs a predetermined level. Any method may be used as long as it can determine whether or not the first output connector 251 is connected.

  In the above-described embodiment, the copying machine 1 on which the high-voltage power supply unit 20 of the present invention is mounted has been described. However, the high-voltage power supply unit 20 is not mounted only on the copying machine, but other devices such as a multifunction machine and a printer. It may be mounted on a tandem type image forming apparatus employing an electrophotographic system.

  Each of the above-described embodiments is merely an example of the present invention, and the scope of the present invention is not limited by the description. The specific configuration of each part is appropriately selected within the scope of the effects of the present invention. It goes without saying that changes can be designed. Furthermore, you may comprise combining the above-mentioned several embodiment suitably.

Explanatory drawing of high voltage power supply unit External view of copier Illustration of AC high voltage power supply, DC high voltage power supply and current detector Illustration of adder circuit Illustration of control unit and connector unit Illustration of control unit and connector unit Illustration of control unit and connector unit Explanatory drawing of the harness which connects a control part and a 1st output connector in another embodiment

Explanation of symbols

20: High voltage power supply unit 21: AC high voltage power supply 22: DC high voltage power supply 23: Current detection unit 24: Adder circuit 25: First output connector, second output connector (connector unit)
26: Charging roller 27: Photosensitive drum

Claims (4)

  A DC high voltage power source and an AC high voltage power source that are applied to the charging roller with respective output voltages superimposed thereon, and a current detection unit that detects a DC charging current flowing from the charging roller to the photosensitive drum, the charging roller and the photoconductor As many as the number corresponding to the photosensitive unit provided with the drum, the addition circuit for adding the output signal of each current detection unit, a plurality of first output connectors for individually outputting the output signal from each current detection unit, A high voltage power supply unit comprising a second output connector for outputting an output signal of the adder circuit.   Simultaneous adjustment mode for simultaneously executing charge amount adjustment control of each photoconductor unit based on each output signal of the current detector, and charge amount adjustment control for each photoconductor unit sequentially based on the output signal of the adder circuit A charge amount adjustment unit that adjusts the charge amount in any of the sequential adjustment modes, a connection state determination unit that determines whether or not the first output connector is connected, and a determination result of the connection state determination unit An image forming apparatus comprising: a control unit having a mode switching unit that switches the charge amount adjustment control mode based on the control unit; and the high-voltage power supply unit that is driven by the control unit.   The image forming apparatus according to claim 2, wherein the connection state determination unit determines whether the first output connector is connected based on an output signal level output from each current detection unit.   The image forming apparatus according to claim 2, wherein the connection state determination unit includes a switch unit that can be switched on and off according to whether or not the first output connector is connected.

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