JP2017090692A - Image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate damage by noise to each device that performs communication by using a communication line placed near a high voltage application part.SOLUTION: An image formation device includes: a converter for generating and outputting a first voltage V1; a high voltage power supply unit for outputting a second voltage based on voltage obtained by stepping up the first voltage; a unit for performing operation for printing a toner image by using the second voltage V2; a first device for performing communication; a second device attached to the unit for communicating with the first device via a communication line; and a ground connection circuit for connecting the communication line to the ground during a high voltage application period, i.e. a period when the high voltage power supply unit inputs the second voltage into the unit.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an image forming apparatus including a unit to which a high voltage is applied and to which a device that communicates with a main body is attached.

  An image forming apparatus using toner is provided with a developing device that develops the electrostatic latent image formed on the photosensitive drum with toner. For development with toner, an AC voltage having a peak-to-peak voltage of 1 kV or higher is applied to the developing device. Also, a voltage of several hundred volts or more may be applied to a charging device that charges the photosensitive drum or a transfer device that transfers a toner image on the photosensitive drum to a sheet or a transfer body. Patent Document 1 describes a technique for suppressing the influence of noise from these high voltage application portions on a communication line.

  Specifically, Patent Document 1 discloses a charging unit that charges a photosensitive drum, a developing unit that develops an electrostatic latent image on the photosensitive drum using toner, and the developed toner image is transferred to a recording sheet. A transfer unit, a power supply unit that outputs at least one of a charging voltage, a development voltage, and a transfer voltage, a serial communication communication line, a noise detection unit that detects noise generated in the communication line, and a power source when noise is detected An image forming apparatus including a voltage control unit that lowers the output voltage of the unit is described. With this configuration, communication errors are less likely to occur (Patent Document 1: Claim 1, paragraph [0005]).

JP 2007-310356 A

  An image forming apparatus that performs printing using toner may include a plurality of units such as a drum unit, a developing unit, and a charging unit. With use, deterioration of members included in each unit (for example, wear of the rotating body) proceeds. It is necessary to replace a unit that has reached the end of its life (exceeded its useful life).

  In order to be able to determine the replacement time of a unit, a device (memory) that stores determination information (information indicating how much of the unit has been used from the start of use) may be attached to the unit. The accumulated number of printed sheets and the accumulated operation time of the unit are stored as determination information. A master device that generates discrimination information is connected to a device attached to the unit via a communication line. The master device transmits the determination information generated via the communication line to the device to update the determination information. The master device determines that the unit whose determination information value has reached a predetermined lifetime value is the unit whose lifetime has ended.

  Here, in order to move the charged toner, a high voltage is applied to a unit constituting a portion (image forming portion) for forming and transferring a toner image. A portion that generates a high voltage, a portion to which a high voltage is applied, and a conductive wire that connects the high voltage generation portion and the high voltage application portion become a high-level noise generation source (electromagnetic radiation source).

  Since the device is attached to the unit, the communication line between the master device and the device is arranged near the noise generation source. The communication line is close to the noise source, and the emitted noise is strong because of the high voltage. As a result, there is a problem that large noise is superimposed on the communication line, the voltage input to each device exceeds the upper limit value of the input voltage in the specification, and each device may be damaged.

  Here, the image forming apparatus described in Patent Document 1 reduces the output voltage of the power supply unit at the time of noise detection, thereby suppressing the disturbance of the signal waveform due to the noise and making the communication error less likely to occur. However, suddenly strong noise (electromagnetic waves) is generated during the printing process (during high voltage application), so that there is a possibility that a voltage that can cause damage is input to each device. Therefore, the above problem cannot be solved.

  In view of the above-described problems of the prior art, the present invention eliminates damage caused by noise to each device that performs communication using a communication line arranged near a high voltage application portion.

  In order to solve the above problem, an image forming apparatus according to a first aspect includes a converter, a high-voltage power supply unit, a unit, a first device, a second device, and a ground connection circuit. The converter generates and outputs a first voltage. The high-voltage power supply unit receives the first voltage generated by the converter, boosts the first voltage at a predetermined magnification, and outputs a second voltage based on the boosted voltage. The unit receives the second voltage and performs an operation for printing a toner image using the second voltage. The first device performs communication. The second device is connected to the first device via a communication line to communicate with the first device, and is attached to the unit. The ground connection circuit connects the communication line to the ground during a high voltage application period in which the converter generates the first voltage and the high-voltage power supply unit inputs the second voltage to the unit.

  ADVANTAGE OF THE INVENTION According to this invention, the damage (failure, breakage | damage) by the noise with respect to each device which communicates using the communication line distribute | arranged to the position near a high voltage application part can be eliminated. Therefore, the life determination information is not lost, and it is possible to accurately determine the time when the life of the unit of the image forming apparatus is reached.

1 is a diagram illustrating an example of a printer according to an embodiment. 2 is a diagram illustrating an example of an image forming unit according to an embodiment. FIG. It is a figure which shows an example of the structure which applies a voltage to the developing roller which concerns on embodiment. It is a figure for demonstrating the 1st example of the ground connection circuit which concerns on embodiment. It is a figure which shows an example of the operation rate table for calculating an operation rate. It is a figure for demonstrating the 2nd example of the ground connection circuit which concerns on embodiment. It is a figure for demonstrating the 3rd example of the ground connection circuit which concerns on embodiment. 6 is a flowchart illustrating an example of a flow of life determination in the printer according to the embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. In the following description, the printer 100 will be described as an example of the image forming apparatus. However, each element such as configuration and arrangement described in this embodiment does not limit the scope of the invention and is merely an illustrative example.

(Outline of printer 100)
Next, an outline of the printer 100 according to the embodiment will be described with reference to FIG. FIG. 1 is a diagram illustrating an example of a printer 100 according to the embodiment.

  A control unit 1 (control board) is provided in the printer 100. The control unit 1 controls the operation of the printer 100. The control unit 1 includes a control circuit 10 (corresponding to a first device) and an image processing circuit 12. The control circuit 10 is an integrated circuit such as a CPU. The control circuit 10 controls each unit of the printer 100 based on a program and data stored in the storage unit 13. The control circuit 10 performs various arithmetic processes based on programs and data stored in the storage unit 13. The image processing circuit 12 performs image processing such as density conversion, enlargement, and reduction on the image data used for printing in accordance with the print setting contents (setting data) in the computer 200. The control unit 1 may be divided like a main control unit that performs overall control and image processing and an engine control unit that actually controls the printing unit 2.

  The storage unit 13 includes a ROM 14, a RAM 15, and an HDD 16. The storage unit 13 is a combination of nonvolatile and volatile storage devices. The storage unit 13 stores various data such as various programs and data for controlling the printer 100, setting data, and image data. The printer 100 also includes a display panel that displays the status of the printer 100, various messages, and various setting screens, and an operation panel 3 that includes a plurality of hard keys for setting operations.

  The printer 100 includes a printing unit 2. The printing unit 2 includes a paper feeding unit 2a, a conveying unit 2b, an image forming unit 2c, and a fixing unit 2d. The control unit 1 controls operations of the paper feeding unit 2a, the conveyance unit 2b, the image forming unit 2c, and the fixing unit 2d, and performs printing-related processing such as paper feeding, paper conveyance, toner image formation, transfer, and fixing. Control.

  When executing a print job, the paper feed unit 2a feeds the sheets one by one to the transport unit 2b. The transport unit 2b transports the paper supplied from the paper feed unit 2a. The image forming unit 2c forms a toner image based on the image data, and transfers the toner image to the conveyed paper. The fixing unit 2d fixes the toner image transferred to the paper. The transport unit 2b discharges the paper after toner fixing to the outside of the apparatus. The printed paper is discharged to a discharge tray (not shown).

  Further, the printer 100 is provided with a communication unit 17 including various sockets and chips for network 300 communication. The communication unit 17 is mounted on the substrate of the control unit 1 (may be a separate substrate). The communication unit 17 is communicably connected to a network 300 such as a LAN. The communication unit 17 can transmit and receive data via the network 300 and the computer 200 such as a PC or a server. The communication unit 17 receives print data (data including print contents such as image data and data including print setting data) transmitted from the computer 200. The control circuit 10 causes the image processing circuit 12 to perform image processing based on the printing data, and causes the printing unit 2 to perform printing based on the image data after the image processing.

(Image forming unit 2c)
Next, the image forming unit 2c according to the embodiment will be described with reference to FIG. FIG. 2 is a diagram illustrating an example of the image forming unit 2c according to the embodiment.

  As shown in FIG. 2, the image forming unit 2 c includes a photosensitive drum 21, a charging unit 22, an exposure unit 23, a developing unit 4, a transfer unit 24, and a cleaning unit 25. In the printer 100 of the present embodiment, the paper supplied from the paper supply unit 2a reaches the image forming unit 2c from below, and the image forming unit 2c sends the paper upward toward the fixing unit 2d (see FIG. 2). . The photosensitive drum 21 and the unit can be replaced independently. Replacing a unit that has reached the end of its life can greatly extend the overall life of the printer 100.

  The photosensitive drum 21 is rotationally driven at a predetermined peripheral speed by the driving force of the motor 2e (see FIG. 1). The photosensitive drum 21 is charged, exposed and developed, and carries a toner image on the peripheral surface (image carrier). The charging unit 22 charges the surface of the photosensitive drum 21 with a constant potential. The exposure unit 23 includes a polygon mirror 23a that reflects a semiconductor laser device (laser diode) and a polygon motor 23b that rotates the polygon mirror 23a. The exposure unit 23 irradiates the charged photosensitive drum 21 with an optical signal (laser light, shown by a broken line in FIG. 2) based on the image data, and scans and exposes the photosensitive drum 21. Thereby, an electrostatic latent image combined with the image data is formed on the peripheral surface of the photosensitive drum 21.

  The developing unit 4 (corresponding to a unit) accommodates toner therein. The developing unit 4 includes a developing roller 41 that carries toner. The developing unit 4 includes a stirring member 42 that stirs the toner. The developing roller 41 and the stirring member 42 are rotated by receiving the driving force of the motor 2e. The developing roller 41 faces the photosensitive drum 21 and the axes of the developing roller 41 are parallel to each other. A minute gap (gap) is provided between the developing roller 41 and the corresponding photosensitive drum 21. A thin layer of toner is formed on the peripheral surface of the developing roller 41. Then, a voltage for development is applied to the developing roller 41 (details will be described later). Further, a memory 8 (corresponding to a second device) for storing information on the developing unit 4 is attached to the bottom surface of the developing unit 4 (details will be described later). The cleaning unit 25 cleans the photosensitive drum 21. The cleaning unit 25 extends in the axial direction of the photosensitive drum 21 and rubs the surface of the photosensitive drum 21 to remove residual toner and the like.

(Voltage applied to developing roller 41)
Next, a configuration for applying a voltage to the developing roller 41 according to the embodiment will be described with reference to FIG. FIG. 3 is a diagram illustrating an example of a configuration for applying a voltage to the developing roller 41 according to the embodiment.

  As shown in FIG. 3, the printer 100 is provided with a DA converter 5 (corresponding to a converter), a high-voltage power supply unit 6, and a ground connection circuit 77 in addition to the control circuit 10 and the development unit 4 described above.

  The control circuit 10 transmits data indicating the magnitude of the voltage to be generated (voltage instruction data D1) to the DA converter 5 when a high voltage is applied to the developing roller 41 such as when a print job is executed. The DA converter 5 generates a voltage (first voltage V1) having a magnitude instructed from the control circuit 10 and outputs it. For example, the DA converter 5 generates and outputs a constant DC voltage.

  The first voltage V <b> 1 generated by the converter is input to the high voltage power supply unit 6. The high voltage power supply unit 6 includes a DC bias generation unit 61 and an AC bias generation unit 62. The DC bias generator 61 boosts the first voltage V1 to generate a developing DC voltage. The DC voltage for development is about several hundred volts (for example, 300 volts).

  The AC bias generator 62 generates a second voltage V <b> 2 that is an AC voltage to be applied to the developing roller 41. The AC bias generator 62 includes a booster circuit 63 and a switching circuit 64. The booster circuit 63 receives the first voltage V1 and boosts the first voltage V1 at a predetermined magnification. The booster circuit 63 is a circuit including a transformer 65. The switching circuit 64 includes a rectangular wave generating element 66 (a switching element such as a transistor) that performs switching to generate a rectangular wave, and a controller 67 that controls switching (ON / OFF) of the rectangular wave generating element 66.

  For example, a rectangular wave generating element 66 is provided between the output of the DA converter 5 and the booster circuit 63. The controller 67 turns on / off the rectangular wave generating element 66 at a predetermined duty ratio and a predetermined frequency. As a result, a rectangular wave having a predetermined duty ratio and a predetermined frequency is generated. Further, for example, a capacitor 68 for removing a DC component of the rectangular wave generated between the rectangular wave generating element 66 and the transformer 65 of the booster circuit 63 is provided. As a result, a rectangular wave from which a DC component is removed is input to the primary coil of the transformer 65 of the booster circuit 63. As a result, an AC voltage (second voltage V2) is output from the secondary side of the transformer 65 of the booster circuit 63. The peak-to-peak voltage of the second voltage V2 is 1 kV to several kV. The frequency of the second voltage V2 is up to several kHz (for example, 3 kHz). The high-voltage power supply unit 6 applies a voltage obtained by superimposing the second voltage V <b> 2 and the developing DC voltage to the developing roller 41.

  The developing unit 4 receives the second voltage V2 and the developing DC voltage. The developing unit 4 performs a developing operation for printing a toner image using the second voltage V2 and the developing DC voltage. Specifically, a voltage obtained by superimposing the second voltage V2 and the developing DC voltage is applied to the developing roller 41, and the toner on the peripheral surface of the developing roller 41 is caused to fly toward the photosensitive drum 21. As a result, the electrostatic latent image on the photosensitive drum 21 is developed with toner (toner is placed on the exposed portion).

  Further, as shown in FIG. 3, a memory 8 (corresponding to the second device) connected to the control circuit 10 (corresponding to the first device) via the communication line 9 and communicating with the control circuit 10 is attached to the developing unit 4. . The memory 8 is a nonvolatile storage device such as an EEPROM. In the present embodiment, the memory 8 is attached to the bottom surface of the developing unit 4 (see FIG. 2). However, the memory 8 may be attached to a place other than the bottom surface.

  The memory 8 indicates how much the developing unit 4 has been used from the start of use until the present time, and stores determination information i1 for determining whether or not the lifetime has expired. The memory 8 stores the number of sheets printed from the start of use to the present time (total number of printed sheets). It should be noted that information other than the number of printed sheets such as the cumulative time during which the voltage is applied to the developing roller 41 from the start of use to the present time may be stored in the memory 8 as the determination information i1. The memory 8 may store information indicating the origin of the developing unit 4 such as the date of manufacture, the manufacturing location, the serial number, the model number, and the corresponding model.

  As shown in FIG. 3, the control circuit 10 and the memory 8 are connected by a communication line 9. An I2C bus can be applied to a communication method between the control circuit 10 and the memory 8. A communication method other than the I2C bus may be used.

  As described above, the control circuit 10 and the memory 8 communicate with each other via the communication line 9 such as a flexible flat cable. Since the memory 8 is provided on the bottom surface of the developing unit 4, the communication line 9 is arranged near the developing unit 4 so as to connect the control circuit 10 and the bottom surface of the developing unit 4. The communication line 9 is routed in the vicinity of a strong noise source such as a high-voltage power supply unit 6, a development unit 4 (development roller 41), and a conductive wire for applying the output voltage of the high-voltage power supply unit 6 to the development roller 41.

  When the noise is superimposed and the voltage of the communication line 9 rises due to the short distance between the high-voltage power supply unit 6, the developing roller 41, and the conducting wire, and the noise generation source handles high voltage, the control connected to the communication line 9 There is a possibility that a large voltage exceeding the upper limit value (hereinafter referred to as “upper limit value”) of the input voltage in the specification may be inputted to the terminals of the circuit 10 and the memory 8. For example, when the voltage of the clock line or the data line rises due to noise, the voltage input to the terminal may become so large that the control circuit 10 or the memory 8 is broken.

  Therefore, the printer 100 is provided with a ground connection circuit 7. The ground connection circuit 7 connects the communication line 9 to the ground during a high voltage application period in which the DA converter 5 generates the first voltage V1 and the high voltage power supply unit 6 inputs the second voltage V2 to the developing unit 4. .

(First example of ground connection circuit 7)
Next, a first example of the ground connection circuit 7 according to the embodiment will be described with reference to FIG. FIG. 4 is a diagram for explaining a first example of the ground connection circuit 7 according to the embodiment.

  The ground connection circuit 7 of this example includes one transistor Tr1 (corresponding to a switching element). Hereinafter, an example in which an npn bipolar transistor is used as a transistor will be described. Note that other types of transistors such as MOSFETs may be used.

  The transistor Tr1 receives the first voltage V1 and is connected to the communication line 9 and the ground. Specifically, the first voltage V1 is input to the base. The collector is connected to the communication line 9. The source is connected to ground.

  During the high voltage application period (while applying the second voltage V2 to the developing roller 41, while the DA converter 5 outputs the first voltage V1, while applying the high voltage to the developing roller 41), the DA converter 5 is a transistor Continue to output a voltage that turns on Tr1. As a result, during the high voltage application period, the transistor Tr1 continues to connect the communication line 9 to the ground. On the other hand, when the DA converter 5 stops generating the first voltage V1, the voltage input to the base of the transistor Tr1 decreases. As a result, outside the high voltage application period, the transistor Tr1 is turned off and does not connect the communication line 9 and the ground.

  That is, the communication line 9 is connected to the ground during a period in which high-intensity noise is generated by the output of the second voltage V2 of the high-voltage power supply unit 6 and the voltage of the communication line 9 increased due to noise superposition may exceed the upper limit value. To do. Thereby, even if noise is superimposed, the voltage input to the control circuit 10 and the memory 8 can be prevented from exceeding the upper limit value.

(Second example of the ground connection circuit 7)
Next, a second example of the ground connection circuit 7 according to the embodiment will be described with reference to FIG. FIG. 5 is a diagram for explaining a second example of the ground connection circuit 7 according to the embodiment.

  The ground connection circuit 7 of this example includes one comparator COM and one transistor Tr2 (corresponding to a switching element). Hereinafter, an example in which an npn bipolar transistor is used as the transistor will be described (other types of transistors may be used).

In the comparator COM, the first voltage V1 is input to one input terminal (plus terminal). A reference voltage Vref having a predetermined magnitude is input to the other input terminal (minus terminal) of the comparator COM. Therefore, the comparator COM outputs High when the first voltage V1 is larger than the reference voltage Vref.

  The reference voltage generation unit 70 may be a circuit in which two resistors are connected in series between the power supply and the ground. In this case, the voltage between the resistors is extracted as the reference voltage Vref. Further, the reference voltage generation unit 70 may be a power supply circuit that outputs a voltage having a certain magnitude, such as a DCDC converter or a regulator. Further, the reference voltage generation unit 70 may be a circuit that outputs a constant voltage having a magnitude instructed to the control circuit 10 such as a DA converter.

  First, the density of the formed toner image varies depending on the magnitude of the peak-to-peak voltage of the second voltage V2. In general, the larger the peak-to-peak voltage of the second voltage V2, the easier the toner will fly, and the higher the density of the toner image. Since there are individual differences among the printers 100, the magnitude of the first voltage V1 is adjusted so that the density of an image to be formed is appropriate when shipped from the factory. As a result, the second voltage V2 is also adjusted. In addition, when the density decreases due to secular change, the magnitude of the first voltage V1 may be adjusted so that the density of an image formed during maintenance is appropriate. Thus, the magnitude of the first voltage V1 varies depending on the peak-to-peak voltage of the second voltage V2 to be output. In other words, the magnitude of the first voltage V <b> 1 is different for each printer 100. The control circuit 10 gives an instruction to the DA converter 5 to output the first voltage V1 having a magnitude determined by adjustment.

  The stronger the peak-to-peak voltage of the second voltage V2, the stronger noise (electromagnetic wave) is emitted from the noise source. If the peak-to-peak voltage of the second voltage V2 is small to some extent, even if communication is performed between the control circuit 10 and the memory 8 during the high voltage application period, the voltage of the communication line 9 increased due to noise superimposition is increased. It may fall below the upper limit of.

  Further, since the peak-to-peak voltage of the second voltage V2 is increased by the adjustment at the time of maintenance, the voltage of the communication line 9 that has increased due to noise superposition may exceed the upper limit value. In such a case, there may be no problem even if communication is performed between the control circuit 10 and the memory 8 during the high voltage application period before the peak-to-peak voltage of the second voltage V2 is raised.

  The second voltage V2 increases as the first voltage V1 increases. Therefore, when the first voltage V1 exceeds the reference voltage Vref and there is a high possibility that the voltage of the communication line 9 increased due to noise superposition exceeds the upper limit value, the transistor Tr2 Connects the communication line 9 to the ground.

  For example, the first voltage V1 in which the voltage of the communication line 9 that has risen due to noise superposition exceeds the upper limit value is confirmed by experiments, and the voltage value obtained by subtracting a predetermined margin from the confirmed first voltage V1 is determined as the reference voltage Vref. Can do.

  In this example, the output of the comparator COM is input to the base of the transistor Tr2. The collector of the transistor Tr2 is connected to the communication line 9. The source of the transistor Tr2 is connected to the ground. Then, during the high voltage application period, when the output level of the comparator COM is High (when it is highly likely that the upper limit value is exceeded), the transistor Tr2 connects the communication line 9 to the ground. On the other hand, when the output level of the comparator COM is Low (when it falls below the upper limit), the transistor Tr2 disconnects the communication line 9 from the ground.

  When the communication line 9 and the ground are connected, communication between the control circuit 10 and the memory 8 is impossible. However, in this example, when it is recognized that the control circuit 10 and the memory 8 are not damaged even when a high voltage is applied to the developing roller 41, the communication line 9 and the ground are not connected, and the control circuit 10 and the memory 8 are not connected. Make communication possible.

(Third example of the ground connection circuit 7)
Next, a third example of the ground connection circuit 7 according to the embodiment will be described with reference to FIG. FIG. 6 is a diagram for explaining a third example of the ground connection circuit 7 according to the embodiment.

  The ground connection circuit 7 of this example includes one transistor Tr3 (corresponding to a switching element). Hereinafter, an example in which an npn bipolar transistor is used as the transistor Tr3 will be described (other types of transistors may be used).

  The transistor Tr3 is connected to one output port of the control circuit 10, and is connected to the communication line 9 and the ground. Specifically, the collector is connected to the communication line 9. The source is connected to ground. The control circuit 10 is connected to the base. Since the control circuit 10 and the base are connected, the control circuit 10 turns on / off the transistor Tr3.

  In this example, the AD conversion circuit 10a is provided inside the control circuit 10 (or externally). The voltage of the communication line 9 is input to the AD conversion circuit 10a. The control circuit 10 recognizes the magnitude of the voltage of the communication line 9 based on the conversion result of the AD conversion circuit 10a (digital value indicating the potential of the communication line 9). That is, the control circuit 10 measures the potential of the communication line 9.

  When the control circuit 10 recognizes that the magnitude of the voltage of the communication line 9 has exceeded a predetermined threshold during the high voltage application period, the control circuit 10 connects the communication line 9 to the switching element until the end of the high voltage application period. Connect to ground. When it is recognized that the voltage of the communication line 9 that has risen due to noise superposition does not exceed the threshold value and does not exceed the upper limit value of the control circuit 10 or the memory 8, the communication line 9 is not connected to the ground, and control is performed even during a high voltage application period. Communication between the circuit 10 and the memory 8 is made possible.

  Here, the threshold value is the same as the upper limit value or smaller than the upper limit value. For example, the threshold value is made smaller than the upper limit value by a predetermined margin. The threshold value is set to be larger than the voltage when the clock and data are high. For example, when 3.3V is used for clock and data communication and the upper limit value is 3.6V, the threshold value is set to be larger than 3.3V and up to 3.6V. Thereby, during the high voltage application period, the communication line 9 can be connected to the ground before the control circuit 10 and the memory 8 are damaged by the voltage of the communication line 9 increased due to noise superposition.

(Unit life judgment)
Next, an example of a life determination flow in the printer 100 according to the embodiment will be described with reference to FIG. FIG. 7 is a flowchart illustrating an example of a life determination flow in the printer 100 according to the embodiment.

  In this description, an example will be described in which the control circuit 10 determines whether or not the life of the developing unit 4 has expired based on the determination information i1 stored in the memory 8 of the developing unit 4. A case will be described in which the cumulative number of printed sheets is stored in the memory 8 as the determination information i1.

  In the start of FIG. 7, the control circuit 10 stops the output of the first voltage V <b> 1 of the DA converter 5 and the high-voltage power supply unit 6 develops the second voltage V <b> 2 with the end of development as when the print job is completed. This is the point in time when the application to the unit 4 is stopped.

  First, the control circuit 10 transmits data indicating the number of prints of the completed print job to the memory 8 (step # 1). The memory 8 updates the value of the total number of printed sheets based on the received data (step # 2). Then, the control circuit 10 acquires data of the updated total number of printed sheets from the memory 8 (step # 3).

  The control circuit 10 determines whether or not the life of the developing unit 4 has expired (step # 4). Specifically, the control circuit 10 determines that the life of the developing unit 4 has expired when the cumulative number of printed sheets is a predetermined number of printed sheets and is equal to or longer than the life value that is the number of printed sheets that is considered to have expired. To do.

  If the lifetime has expired (Yes in step # 4), the control circuit 10 notifies that the lifetime of the developing unit 4 has expired (step # 5). For example, the control circuit 10 displays a message indicating that the life of the developing unit 4 has expired on a display panel (not shown) of the operation panel 3. Further, the control circuit 10 causes the communication unit 17 to transmit message data indicating that the life of the developing unit 4 has expired toward the computer 200 for managing the printer 100 connected via the network 300. Then, this flow ends (END). On the other hand, when the lifetime has not expired (No in step # 4), no notification is necessary, and thus this flow ends (end).

  In this way, the control circuit 10 transmits data for updating the determination information i1 stored in the memory 8 to the memory 8. The memory 8 updates the discrimination information i1 based on the received data. In addition, the control circuit 10 determines that a unit whose lifetime has reached the value of the determination information i1 stored in the memory 8 is a unit whose lifetime has been exhausted.

  As described above, the image forming apparatus (printer 100) according to the embodiment receives the first voltage V1 generated and output from the converter (DA converter 5) and the first voltage V1 generated by the converter. The voltage V1 is boosted at a predetermined magnification, and a high voltage power supply unit 6 that outputs a second voltage V2 based on the boosted voltage, and the second voltage V2 are input, and printing of a toner image is performed using the second voltage V2. A unit (developing unit 4) that performs an operation for the first device, a first device (control circuit 10) that performs communication, and a first device that is connected to the first device via a communication line 9 and that is attached to the unit. 2 devices (memory 8) and the communication line 9 during the high voltage application period, in which the converter generates the first voltage V1 and the high voltage power source 6 inputs the second voltage V2 to the unit. It includes a ground connection circuit 7 to be connected to the land, the.

  Thus, the communication line 9 can be connected to the ground in synchronization with the control for applying a high voltage to the unit (developing unit 4). Thereby, the noise superimposed on the communication line 9 due to the noise generated with the application of the high voltage to the unit flows into the ground. During the high voltage application period, the level of the communication line 9 can be kept at the ground level. Therefore, even if noise is superimposed and the voltage of the communication line 9 rises, a voltage exceeding the upper limit value of the input voltage in the specification is not input to the first device (control circuit 10) and the second device (memory 8). Further, in order to eliminate damage to the first device and the second device due to noise caused by high voltage application, it is not necessary to use an expensive shield member for preventing electromagnetic waves.

  The ground connection circuit 7 may include a switching element (transistor Tr1) connected to the communication line 9 and the ground while receiving the first voltage V1. Then, during the high voltage application period, the switching element connects the communication line 9 to the ground, and the communication line 9 and the ground are not connected outside the high voltage application period in which the converter (DA converter 5) stops generating the first voltage V1. Connection may be made. As a result, the converter generates the first voltage V1, and the high-voltage power supply unit 6 boosts the first voltage V1 and applies the second voltage V2 to the unit (developing unit 4). Can keep.

    The magnitude of the second voltage V2 output from the high-voltage power supply unit 6 depends on the amplitude (level) of the first voltage V1. The second voltage V2 (peak-to-peak voltage) increases as the first voltage V1 increases. That is, as the first voltage V1 is increased, the second voltage V2 is increased, noise is increased, and the amount of increase in the voltage of the communication line 9 when noise is superimposed is increased. On the other hand, when the first voltage V1 is relatively small and the second voltage V2 is also relatively small, the voltage of the communication line 9 may fall below the upper limit value of the input voltage in the specification even if noise is superimposed. . Therefore, the ground connection circuit 7 may include a comparator COM and a switching element (transistor Tr2). The comparator COM is high when the first voltage V1 is input to one input terminal, the reference voltage Vref having a predetermined magnitude is input to the other input terminal, and the first voltage V1 is higher than the reference voltage Vref. Is output. The switching element receives the output of the comparator COM and is connected to the communication line 9 and the ground. During the high voltage application period, the switching element connects the communication line 9 to the ground when the output level of the comparator COM is High. When the output level of the comparator COM is low, the communication line 9 and the ground may be disconnected.

  Thus, when the first voltage V1 exceeds the reference voltage Vref and it is recognized that the amount of increase in the voltage of the communication line 9 due to noise superposition is large (the control circuit 10 and the memory 8 exceed the upper limit value of the input voltage in the specification) When it is recognized that a magnitude voltage is input), the communication line 9 can be connected to ground during the period of high voltage application. In addition, when the first voltage V1 is lower than the reference voltage Vref and it is recognized that the amount of increase in the voltage of the communication line 9 due to noise superimposition is relatively small (the voltage input to the control circuit 10 and the memory 8 is input according to the specification). When it is recognized that the voltage is within the voltage range), the first device (control circuit 10) and the second device (memory 8) can be kept communicable without connecting the communication line 9 to the ground even during the high voltage application period. it can. Through an experiment, an average value of the first voltage V1 when the voltage input to the first device and the second device becomes the upper limit value can be obtained, and a voltage value smaller than the obtained average value can be set as the reference voltage Vref. .

  The magnitude of the second voltage V2 output from the high-voltage power supply unit 6 depends on the amplitude (level) of the first voltage V1. The second voltage V2 (peak-to-peak voltage) increases as the first voltage V1 increases. That is, as the first voltage V1 is increased, the second voltage V2 is increased, noise is increased, and the amount of increase in the voltage of the communication line 9 when noise is superimposed is increased. On the other hand, when the first voltage V1 and the second voltage V2 are also relatively small, the voltage of the communication line 9 may fall within the input voltage range in the specification even if noise is superimposed. Therefore, the ground connection circuit 7 may include a switching element (transistor Tr3). The switching element is connected to the first device (control circuit 10) and to the communication line 9 and the ground. When the first device recognizes the magnitude of the voltage of the communication line 9 and recognizes that the magnitude of the voltage of the communication line 9 has exceeded a predetermined threshold during the high voltage application period, Until the end, the communication line 9 may be connected to the switching element to the ground.

  As a result, the magnitude of the voltage of the communication line 9 exceeds a predetermined threshold value. If the voltage level of the communication line 9 increases as a result of noise superposition, the first device (control circuit 10) and the second device (memory 8) ), The communication line 9 can be kept at the ground level when it is recognized that a voltage exceeding the upper limit value of the input voltage in the specification is input. Further, when it is recognized that the amount of increase in the voltage of the communication line 9 due to noise superposition is relatively small (when it is recognized that the voltage input to the first device and the second device falls within the input voltage range in the specification) Even during the high voltage application period, the first device and the second device can be kept in communication with each other without connecting the communication line 9 to the ground. The threshold value is set larger than the voltage of the communication line 9 at the high level. Further, the threshold value is set to a value that is smaller than the upper limit value of the input voltage on the specifications of the first device and the second device, or a margin that is smaller than the upper limit value of the input voltage on the specifications.

  Further, the unit may be a developing unit 4 that includes a developing roller 41 that contains toner, carries the toner, and causes the toner to fly based on the second voltage V <b> 2 from the high-voltage power supply unit 6. In this case, the second device is a memory 8 that is attached to the developing unit 4 and stores information of the developing unit 4. Thereby, when a high voltage is applied to the developing unit 4 (developing unit 4), the memory 8 attached to the developing unit 4 (developing unit 4) is not broken by noise.

  Next, another embodiment will be described. In the above description of the embodiment, the developing unit 4 has been described as an example of a unit in which the memory 8 (second device) is provided. However, there is a case where a memory for determining that the lifetime has expired is attached to a unit other than the developing unit 4 such as the transfer unit 24 and the control circuit 10 and the memory are connected by a communication line. The high voltage power supply unit 6 is provided with a transfer voltage generating booster circuit, the voltage to be output by the control circuit 10 is instructed to another DA converter, and the generated voltage of the other DA converter is used to generate the transfer voltage of the high voltage power supply unit 6. In some cases, the booster circuit boosts the voltage at a predetermined magnification, and a transfer voltage (for example, several hundred to several kV) based on the boosted voltage is applied to the transfer unit 24. The transfer unit 24 performs an operation for transferring the toner image using the input transfer voltage. A ground connection circuit that connects the communication line between the control circuit 10 and the memory of the transfer unit to the ground during a high voltage application period in which the high voltage power supply unit 6 inputs a transfer voltage to the transfer unit 24 with respect to the transfer unit 24. May be provided. The ground connection circuit for the transfer unit 24 may be the same as that of the developing unit 4 and may be any one shown in FIGS.

  In addition, a memory for determining that the life of the charging unit 22 has expired may be attached, and the control circuit 10 and the memory may be connected by a communication line. The high voltage power supply unit 6 is provided with a charging voltage generating booster circuit, and the control circuit 10 instructs the other DA converter to output the voltage to be output, and the generated voltage of the other DA converter is used to generate the charged voltage of the high voltage power supply unit 6. In some cases, the boosting circuit boosts the voltage at a predetermined magnification, and a charging voltage (for example, about several hundred V to 1000 V) based on the boosted voltage is applied to the charging unit 22. The charging unit 22 performs an operation for forming a toner image (charging of the photosensitive drum 21) using the input charging voltage. The communication line between the control circuit 10 and the memory of the charging unit 22 is grounded during a high voltage application period in which another DA converter generates a voltage and the high-voltage power supply unit 6 inputs a charging voltage to the charging unit 22. A ground connection circuit may be provided to connect to the. The ground connection circuit for the charging unit 22 may be the same as that of the developing unit 4 and may be any one shown in FIGS.

  Although the embodiment of the present invention has been described, the scope of the present invention is not limited to this, and various modifications can be made without departing from the spirit of the invention.

  The present invention can be used in an image forming apparatus including a unit to which a high voltage is applied and a device that communicates with the main body side is attached.

100 Printer (image forming apparatus) 10 Control circuit (first device)
4 Developing Unit (Unit) 41 Developing Roller 5 DA Converter (Converter) 6 High Voltage Power Supply Unit 7 Ground Connection Circuit 8 Memory (Second Device)
9 communication line V1 first voltage V2 second voltage COM comparator Tr1 transistor (switching element)
Tr2 transistor (switching element)
Tr3 transistor (switching element)
Vref reference voltage

Claims (5)

A converter that generates and outputs a first voltage;
A high-voltage power supply unit that receives the first voltage generated by the converter, boosts the first voltage at a predetermined magnification, and outputs a second voltage based on the boosted voltage;
A unit that receives the second voltage and performs an operation for printing a toner image using the second voltage;
A first device for communication;
A second device connected to the first device connected to the first device via a communication line and attached to the unit;
A ground connection circuit for connecting the communication line to the ground during a high voltage application period in which the converter generates the first voltage and the high-voltage power supply unit inputs the second voltage to the unit. An image forming apparatus. The ground connection circuit includes a switching element that receives the first voltage and is connected to the communication line and the ground.
During the high voltage application period, the switching element connects the communication line to the ground, and disconnects the communication line from the ground outside the high voltage application period when the converter stops generating the first voltage. The image forming apparatus according to claim 1. The ground connection circuit includes a comparator and a switching element,
In the comparator, the first voltage is input to one input terminal, a reference voltage having a predetermined magnitude is input to the other input terminal, and High is set when the first voltage is larger than the reference voltage. Output,
The switching element receives the output of the comparator and is connected to the communication line and the ground. During the high voltage application period, the communication line is connected to the ground when the output level of the comparator is High. The image forming apparatus according to claim 1, wherein the communication line and the ground are disconnected when the output level of the comparator is low. The ground connection circuit includes a switching element,
The switching element is connected to the first device and connected to the communication line and the ground,
The first device recognizes the magnitude of the voltage of the communication line, and recognizes that the magnitude of the voltage of the communication line has exceeded a predetermined threshold during the high voltage application period. The image forming apparatus according to claim 1, wherein the communication line is connected to the ground until the end of the application period. The unit is a developing unit including a developing roller that accommodates toner, carries the toner, and causes the toner to fly based on the second voltage from the high-voltage power supply unit;
5. The image forming apparatus according to claim 1, wherein the second device is a memory that is attached to the developing unit and stores information on the developing unit. 6.

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