JP2008216751A - Charging controller for image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charging controller for an image forming apparatus capable of controlling potential by charging of an image carrier so that fogging or irregular density may not be caused even when the image forming apparatus is used under low-temperature environment. <P>SOLUTION: The charging controller 9 for the image forming apparatus includes: a high voltage generation circuit 91 for applying oscillating voltage obtained by superposing DC voltage and AC voltage to a charging member 42 arranged in contact with or proximately to the image carrier 41; a current detection means 92 for detecting a DC current value between the image carrier 41 and the charging member 42; and a voltage control means 96 for controlling the AC voltage so that the detected DC current value may be maintained within a target current range. The controller includes an aging control means 95 for driving and rotating the image carrier 41 while holding the AC voltage and the DC voltage at a predetermined voltage set in advance. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a high voltage generating circuit for applying an oscillating voltage in which a DC voltage and an AC voltage are superimposed on a charging member arranged in contact with or close to an image carrier, and a direct current value between the image carrier and the charging member. The present invention relates to a charge control device for an image forming apparatus, comprising: a current detection unit that detects the voltage; and a voltage control unit that controls the AC voltage so that the detected DC current value is maintained in a target current range.

  In recent years, from the viewpoint of low pressure process, low ozone generation, low cost, etc., a charging member such as a roller type or a blade type is arranged in contact with or close to the surface of the image carrier, and a DC voltage and an AC voltage are applied to the charging member. A contact charging method in which the surface of an image carrier is uniformly charged by applying a superposed vibration voltage is becoming mainstream. Here, the vibration voltage is not limited to a sine wave, but may be any vibration waveform that changes periodically, such as a rectangular wave, a triangular wave, and a pulse wave.

  As a charging device that employs such a contact charging method, Patent Document 1 discloses that when the voltage value Vpp between peaks of an alternating voltage among vibration voltages is increased, the charging voltage of the image carrier increases in proportion thereto, In order to secure the uniformity of charging, the charging potential is saturated when the peak-to-peak voltage value Vpp reaches about twice the charging start voltage due to the DC voltage, and the charging potential does not change even if the voltage is increased further. It is necessary to apply an oscillating voltage having a peak-to-peak voltage more than twice the charging start voltage when applying a DC voltage determined by various characteristics of the image carrier, and the resulting charging voltage is the DC component of the applied voltage. It is disclosed that it depends on.

  Patent Document 2 discloses that there is no problem of degradation of the image carrier, toner fusion, image flow, etc. by always generating a constant amount of discharge regardless of variations in the resistance value of the charging member due to the environment and manufacturing. Discharge to the image carrier when a DC voltage is applied to the charging member, provided with means for measuring the AC current value flowing to the charging means via the image carrier for the purpose of achieving uniform charging. When the starting voltage is Vth, at the time of non-image formation, a current value when a peak-to-peak voltage less than twice the Vth of at least one point is applied to the charging unit and at least twice the Vth of at least two points A charging control method is disclosed in which the current value when the above peak-to-peak voltage is applied is measured, and the peak-to-peak voltage of the alternating voltage applied to the charging means during image formation is determined based on the measured alternating current value.

More specifically, the peak-to-peak voltage-alternating current obtained by connecting 0 to the current value when a peak-to-peak voltage less than twice the Vth of one point is applied to the charging means with D being a predetermined constant. By comparing the function fI1 (Vpp) with the peak-to-peak voltage-alternating current function fI2 (Vpp) obtained from the current value when the peak-to-peak voltage more than twice the Vth of at least two points is applied, fI2 The peak-to-peak voltage value at which (Vpp) −fI1 (Vpp) = D is determined as a desired discharge current amount, and the peak-to-peak voltage of the AC voltage applied to the charging unit during image formation is determined based on the determined peak-to-peak voltage value. Constant voltage control is performed.
JP-A 63-149668 JP 2001-201921 A

  However, the technique described in Patent Document 2 described above is applied to a charging member made of an epichlorohydrin rubber charging roller brought into contact with an image carrier having a diameter of 30 μm and having a photosensitive layer of 20 μm thick amorphous silicon with a pressing force of 1 kgf, for example. When applied to a charging device equipped with the above, the following problems arise from the properties of epichlorohydrin rubber whose characteristics fluctuate greatly depending on the environment.

  That is, as shown in FIG. 2, in a low-temperature environment (low-temperature environment 1 in the figure) where the electrical resistance value of the charging member is high, the movement of conductive ions in the epichlorohydrin rubber is slow, so that the charged potential of the image carrier is stabilized. In order to adjust to the potential, it is necessary to control the peak-to-peak voltage value of the AC voltage to a peak-to-peak voltage value Vpp2 that is larger than the peak-to-peak voltage value Vpp1 in the normal temperature environment, especially when the temperature becomes extremely low, such as 0 ° C. No matter how large the inter-voltage value is, it cannot be adjusted to a predetermined target potential. In such a low-temperature state (low-temperature environment 2 in the figure), the charged potential of the image carrier does not reach the target potential, and thus there is a problem that fog or density unevenness occurs in an image formed by the image forming apparatus. It was.

  In view of the above-described conventional problems, an object of the present invention is to provide a charge control device for an image forming apparatus capable of controlling the charge potential of an image carrier so that fog and density unevenness do not occur even when used in a low temperature environment. In the point.

  In order to achieve the above-mentioned object, the first characteristic configuration of the charging control device of the image forming apparatus according to the present invention is the contact arrangement or the proximity arrangement on the image carrier as described in claim 1 of the claims. A high voltage generating circuit for applying an oscillating voltage in which a DC voltage and an AC voltage are superimposed on the charged charging member, current detecting means for detecting a DC current value between the image carrier and the charging member, and a detected DC current A charge control device for an image forming apparatus, comprising a voltage control means for controlling the AC voltage so that a value is maintained in a target current range, wherein the AC voltage and the DC voltage are set to a predetermined voltage. An aging control means for holding and rotatingly driving the image carrier is provided.

  While examining the setting of the charging potential Vo of the image carrier, the present inventors measured the DC current value Idc generated by the application of the oscillating voltage, and as shown in FIG. The direct current value Idc and the charging potential Vo are in a proportional relationship, and this relationship does not change greatly due to environmental fluctuations such as temperature and humidity, and secular changes of the image carrier and the charging member. Through experiments, it was confirmed that the charging potential Vo can be set to a target potential by adjusting the direct current value Idc.

  Patent Document 1 shows that when the DC voltage Vdc is equal to or higher than the discharge start voltage Vth, the DC voltage Vdc is proportional to the charging potential Vo.

  From this fact and the proportional relationship between the DC current value Idc and the charging potential Vo described above, when the DC voltage Vdc is equal to or higher than the discharge start voltage Vth, as shown in FIG. The direct current value Idc has a proportional relationship. Further, in Patent Document 1, the charging potential Vo is stabilized by controlling the peak-to-peak voltage Vpp of the AC voltage to a value that is twice or more the discharge start voltage Vth. At this time, the charging potential Vo is applied. It is shown that it depends on the DC voltage Vdc.

  From the above, in order to set the charging potential Vo to the target potential, the peak-to-peak voltage Vpp of the AC voltage is set to a value more than twice the discharge start voltage Vth, and the DC current is determined from FIG. It is necessary to adjust the value Idc, and in order to increase the DC current value Idc for the adjustment, it is necessary to increase the DC voltage Vdc from FIG.

  According to the above-described configuration, by rotating the image carrier, the movement of the conductive ions in the epichlorohydrin rubber in the charging member is promoted, and the resistance of the charging member is reduced. Comparing the case where the motor is rotationally driven and the case where the motor is not rotationally driven, the DC current value Idc is relatively larger in the case of rotational driving even when the DC voltage Vdc of the same level is applied. Become.

  Therefore, as described above, by rotating the image carrier by the aging control means, the charged potential of the image carrier does not reach the target potential when the DC voltage Vdc of a certain voltage level is applied. Even in this case, it is possible to adjust the DC current value Idc so that the charging potential Vo is set to the target potential without changing the DC voltage Vdc to be applied. It is possible to prevent the occurrence of fog and density unevenness in the printed image.

  In the second characteristic configuration, as described in claim 2, in addition to the first characteristic configuration described above, the aging control unit cannot control the DC current value to the target current range by the voltage control unit. Or when the environmental temperature of the image forming apparatus is lower than a predetermined temperature.

  According to the above-described configuration, even when the maximum DC voltage Vdc that can be applied is applied, even if the DC current value Idc does not reach the target current range, the aging control means is operated to operate the DC current value. By increasing Idc, the DC current value Idc can be set within the target current range without increasing the DC voltage Vdc.

  In addition, when the environmental temperature of the charging control device is lower than a predetermined temperature, that is, when the temperature is low, the movement of the conductive ions in the epichlorohydrin rubber in the charging member is slow, so the resistance of the charging member is high when the temperature is high. Bigger than that. For this reason, even when the same DC voltage Vdc is applied, the DC current value Idc becomes relatively small.

  Therefore, in such a case, the DC current value Idc can be set within the target current range by operating the aging control means to increase the DC current value Idc.

  According to the third feature configuration, as described in claim 3, in addition to the first or second feature configuration described above, the aging control unit may be configured to return the image forming apparatus from power-on or from the power saving mode. It is at a point that sometimes works.

  When the image forming apparatus is turned on or returned from the power saving mode, there is a high possibility that the temperature in the apparatus is low. Therefore, it is a suitable time to execute the rotational drive of the image carrier by the aging control means.

  In the fourth feature configuration, as described in claim 4, in addition to any one of the first to third feature configurations described above, the aging control means includes a direct current detected by the current detection means. The aging operation is terminated when the value reaches the target current range or when a predetermined time set in advance elapses.

  According to the above configuration, when the DC current value Idc detected by the current detection unit reaches the target current range and the aging operation by the aging control unit becomes unnecessary, the useless aging operation is continued. Can be prevented. In addition, by setting a limit on the time for which the aging control means continuously executes the aging operation, the DC current value Idc does not reach the target current range even when the aging operation is performed for a long time. It is possible to prevent the aging control means from continuing the aging operation despite the fact that it is determined that this is wasteful.

  The fifth characteristic configuration is that, in addition to the fourth characteristic configuration described above, the predetermined time is set based on an environmental temperature of the image forming apparatus.

  The characteristics of the peak-to-peak voltage Vpp and the DC current value Idc, the characteristics of the DC current value Idc and the charging potential Vo, and the like vary depending on the value of the environmental temperature. By determining the appropriate predetermined time based on the above, the aging control means for a long time useless aging operation, or because the aging operation is a short time, before the DC current value Idc reaches the target current range It is possible to prevent the aging operation from being finished.

  As described above, according to the present invention, it is possible to provide a charge control device for an image forming apparatus capable of controlling the charge potential of an image carrier so that fog and density unevenness do not occur even when used in a low temperature environment. Became.

  An embodiment in which a charging control device according to the present invention is applied to a digital copying machine as an image forming apparatus will be described below.

  As shown in FIGS. 4 and 5, the digital copying machine 1 includes a document placement unit 2 for setting paper as a document, an image reading unit 3 for converting data read from the document into electronic data, An image forming unit 4 that forms and outputs a toner image on a sheet based on the image data converted into electronic data by the image reading unit 3, and the toner image output on the sheet is heated and fixed on the sheet. A fixing unit 5, a conveyance unit 6 that conveys paper, a plurality of paper feed cassettes 7 (7 a to 7 d) each containing different sizes or types of paper, and a manual paper feed port provided on the left side of the machine (see FIG. (Not shown) and an operation unit 8 on which a plurality of menu setting keys for setting various menus are arranged.

  As shown in FIG. 5, the image forming unit 4 is sequentially arranged around the image carrier 41 and the image carrier 41, and is placed in contact with the image carrier 41 to charge the image carrier 41. A toner is electrostatically attached to the charging member 42, the print head 43 that exposes the charged image carrier 41 to form an electrostatic latent image, and the electrostatic latent image formed on the image carrier 41. A developing unit 44 that visualizes the toner image, a toner cartridge 45 that serves as an exchange unit that is filled with toner and supplies the toner to the developing unit 44, and a transfer unit 46 that transfers the developed toner image onto a sheet. And a cleaner portion 47 that removes and collects toner remaining on the image carrier 41 after the transfer, and a static elimination lamp 48 that lowers the residual potential on the surface of the image carrier 41 to make it uniform. .

  Further, the image forming unit 4 includes a charging control device 9 according to the present invention that controls charging by applying a voltage to the charging member 42.

  Further, as shown in FIG. 6, the digital copying machine 1 is provided with a plurality of control means for controlling each functional block described above. Specifically, the image reading control unit 100 that controls the reading operation of the original or data by the image reading unit 3 and the system of the digital copying machine 1 are integrated, and the image forming unit 4, the fixing unit 5, the conveyance The image output control means 200 for controlling the unit 6 and the paper feed cassette 7 and the operation control means 300 for controlling the input / output signals of the operation section 8 are provided.

  Each control means 100, 200, 300 includes a single or a plurality of CPUs on a single or a plurality of control boards, a ROM storing a control program executed by the CPU, a RAM storing control data, An input / output interface circuit that outputs signals to various loads to be controlled and inputs detection values from various sensors is provided. The CPUs are connected to each other via a serial communication line 400 to construct a distributed control system, and cause the digital copying machine 1 to execute image forming processing using a control program executed by each CPU and related hardware. A predetermined function is configured to be realized.

  Hereinafter, the charging control device 9 will be described. As shown in FIG. 1, the charging control device 9 includes a high voltage generation circuit 91 that applies an oscillating voltage in which a DC voltage and an AC voltage are superimposed on a charging member 42 disposed in contact with the image carrier 41, and the image A current detection unit 92 for detecting a DC current value between the carrier 41 and the charging member 42; and a voltage control unit 96 for controlling the AC voltage so that the detected DC current value is maintained in a target current range. It is prepared for.

  The image carrier 41 comprises a photosensitive drum having a photosensitive body in which an amorphous silicon layer, which is a positively chargeable photoconductor, is deposited on the surface of an aluminum cylinder, and is rotated around a central support shaft by a driving device (not shown). It is configured to be driven. The image carrier 41 includes a ROM, and the ROM carries a value of a direct current voltage as a discharge start voltage and a value of a target current range, which will be described later, and the image carrier 41 is mounted on the digital copying machine 1. Stored as a value to be used when

  The charging member 42 is composed of a charging roller in which a cored bar 421 is coated with an epichlorohydrin rubber layer 422 which is a conductive elastic material.

  The high voltage generation circuit 91 is controlled by a DC voltage control means 93 to be described later, and a DC voltage power source 911 that outputs an arbitrary DC voltage by a pulse transformer (not shown), as well as an AC voltage control means 94 to be described later. An AC voltage power supply 912 which is controlled and outputs an AC voltage having an arbitrary peak-to-peak voltage value Vpp made of a sine wave of a predetermined frequency (in this embodiment, a frequency of 1.6 [kHz]) by a pulse transformer (not shown). And is configured.

  The current detection unit 92 is configured to detect a direct current value Idc flowing between the image carrier 41 and the charging member 42 based on the vibration voltage applied to the charging member 42 from the high voltage generation circuit 91. Has been.

  The voltage control unit 96 includes a DC voltage control unit 93 that controls the DC voltage, and an AC voltage control unit 94 that controls the AC voltage so that the DC current value Idc is maintained in the target current range. Configured.

  Here, the target current range is a predetermined current range centered on the target current value Idc (0) of the DC current value Idc set so that the image carrier 41 has a predetermined surface potential.

  The DC voltage control means 93 reads the DC voltage value stored in the ROM of the image carrier 41 and applies the read DC voltage value to the charging member 42 as a discharge start voltage. The voltage power supply 911 is controlled. The direct current value stored in the ROM of the image carrier 41 is, for example, about 400 [V].

  The AC voltage control means 94 reads the DC voltage value stored in the ROM of the image carrier 41 and the target current range, and generates an AC voltage that is twice the DC voltage value read by the peak-to-peak voltage Vpp. Then, the AC voltage source 912 is controlled so as to be applied to the charging member 42 as a discharge start voltage. Note that the peak-to-peak voltage value Vpp of the AC voltage is, for example, about 800 [V].

  As described above, when the voltage control unit 96 controls the high voltage generation circuit 91 to apply an oscillating voltage in which the DC voltage and the AC voltage are superimposed on the charging member 42, the current detection unit 92 A direct current value Idc flowing between the image carrier 41 and the charging member 42 is detected.

  The AC voltage control means 94 performs so-called feedback control that changes the AC voltage applied to the charging member 42 in accordance with the detected DC current value Idc.

  More specifically, the AC voltage control means 94 reads the DC current value Idc detected by the current detection means 92 and determines whether or not the read DC current value Idc is within the target current range. .

  As a result of the determination, when the current value is within the target current range, the peak-to-peak voltage value Vpp of the AC voltage applied to the charging member 42 is maintained at the current value, and when the current value is smaller than the target current range, When the peak-to-peak voltage value Vpp of the AC voltage to be applied is larger than the current value by a predetermined value set in advance, and larger than the target current range, the peak-to-peak voltage value Vpp of the AC voltage to be applied to the charging member 42 is set in advance. The AC voltage power source 912 is controlled so as to be smaller than the current value by a set predetermined value.

  Then, the AC voltage control means 94 repeats the above processing until the read DC current value Idc falls within the target current range.

  The charging control device 9 includes aging control means 95 that rotates and drives the image carrier 41 while holding the AC voltage and the DC voltage at a predetermined voltage set in advance. The function of the aging control means 95 is realized by executing the control program in the image output control means 200.

  The aging control means 95 operates when the digital copying machine 1 is turned on or returned from the power saving mode. The aging control means operates when the DC current value Idc cannot be controlled within the target current range by the voltage control means 96 or when the environmental temperature of the digital copying machine 1 is lower than a predetermined temperature.

  In other words, the aging control means 95 operates during the adjustment of the AC voltage performed by the charging control device 9 when the digital copying machine 1 is turned on or returned from the power saving mode, and then the voltage control means 96 is operated. Therefore, the operation is performed even when the DC current value Idc cannot be controlled within the target current range or when the environmental temperature of the digital copying machine 1 becomes lower than a predetermined temperature.

  Here, when the DC current value Idc cannot be controlled within the target current range by the voltage control means 96, the AC voltage control means 94 controls the AC voltage power supply 912, and the AC voltage power supply 912 This is a case where the DC current value Idc does not fall within the target current range even when an AC voltage having the maximum peak-to-peak voltage Vpp that can be applied to the charging member 42 is applied.

  The environmental temperature is a temperature derived from a detection value of the environmental temperature sensor 10 provided in the vicinity of the image carrier 41 in the digital copying machine 1 and detecting the ambient temperature of the image carrier 41. That is.

  Here, determination of the maximum aging time T that is the maximum time for the aging control means 95 to drive the image carrier 41 to rotate (that is, to execute the aging operation) will be described. The maximum aging time T is set based on the environmental temperature of the digital copying machine 1.

  More specifically, when the digital copying machine 1 is turned on or returned from the power saving mode, the detected value of the environmental temperature sensor 10 is sent to the aging control means 95, and the detected value of the environmental temperature sensor 10 is obtained. The received aging control means 95 refers to the table data about the temperature stored in the ROM provided in the image output control means 200, for example, the temperature table as shown in FIG. To decide.

  At this time, when the environmental temperature is equal to or higher than a predetermined temperature (in this embodiment, the temperature is 15 degrees or higher), the maximum aging time T is zero, so the aging operation by the aging control means 95 is not executed. Is less than 15 degrees, the aging operation is executed for the maximum aging time T determined by the temperature table.

  Hereinafter, the aging operation by the aging control means 95 will be described in detail. When the aging control means 95 satisfies a predetermined condition (that is, when the digital copying machine 1 is turned on or returned from the power saving mode, the voltage control means 96 sets the DC current value Idc to the target current range. When the environmental temperature of the digital copying machine 1 becomes lower than a predetermined temperature), the image carrier 41 and the charging member 42 are started to be driven (not shown). By sending a signal, the image carrier 41 and the charging member 42 are rotationally driven, that is, an aging operation is performed.

  In a state where the image carrier 41 and the charging member 42 are rotationally driven, the aging control unit 95 is connected to the DC voltage control unit 93 and the AC voltage control unit 94 in addition to the DC voltage power supply 911 and the AC voltage. The power supply 912 is controlled to apply the vibration voltage to the charging member 42.

  Here, the time for applying the oscillating voltage to the charging member 42 is from the start of the rotational driving until the maximum aging time T elapses.

  The aging control means 95 ends the aging operation when the DC current value Idc detected by the current detection means 92 reaches the target current range or when a predetermined time has elapsed.

  More specifically, the aging control means 95 is a result of a determination made by the AC voltage control means 94 during a period in which the image carrier 41 and the charging member 42 are rotationally driven (that is, an aging operation) ( Specifically, the DC voltage value Idc read by the current detection unit 92 is detected at regular intervals, and the AC voltage control unit 94 detects the DC current value Idc within the target current range. When the read DC current value Idc reaches the target current range, the aging operation is terminated.

  When the predetermined time set in advance, that is, when the maximum aging time T determined based on the value of the environmental temperature sensor 10 has elapsed, the aging control means 95 is read by the AC voltage control means 94. The aging operation is terminated regardless of whether or not the obtained DC current value Idc has reached the target current range.

  When the aging operation is finished, the aging control means 95 causes the DC voltage control means 93 and the AC voltage control means 94 to output an output stop signal of the oscillating voltage, and receives the output stop signal. 911 and the AC high-voltage power supply 912 stop outputting the DC voltage and the AC voltage, respectively. Thereafter, the digital copying machine 1 shifts to a normal startup operation when the power is turned on or when returning from the power saving mode.

  Hereinafter, the rotation driving process when the digital copying machine 1 is turned on will be described with reference to the flowchart shown in FIG.

  When the power of the digital copying machine 1 is turned on (S1), the aging control means 95 determines the maximum aging time T based on the detected value of the environmental temperature sensor 10 (S2).

  Further, the aging control means 95 has a case where the environmental temperature detected by the environmental temperature sensor 10 is less than 15 degrees (S3) and the DC current value Idc cannot be controlled within the target current range by the voltage control means 96. (S4), the rotational driving of the image carrier 41 and the charging member 42, that is, the aging operation is started (S5).

  On the other hand, when the environmental temperature is 15 ° C. or higher (S3), or when the DC current value Idc can be controlled to the target current range by the voltage control means 96 (S4), the aging operation is not started and the step S6 and thereafter are started. AC voltage adjustment processing as described in FIG. In the case of step S9, the AC voltage adjustment process in this case is not executed because the aging operation is not started, so that the elapse of the maximum aging time in step S9 and the aging operation end process in step S10 are not executed. Instead of determining whether the maximum aging time has elapsed, it determines whether a predetermined time that has been set separately is elapsed.

  When the aging operation is started (S5), the aging control means 95 causes the DC voltage control means 93 and the AC voltage control means 94 to control the DC voltage power supply 911 and the AC voltage power supply 912, thereby generating the vibration voltage. Application is made to the charging member 42 (S6).

  When an oscillating voltage is applied, the current detection unit 92 detects a direct current value Idc flowing between the image carrier 41 and the charging member 42 (S7), and the aging control unit 95 detects the detected direct current. If the current value Idc has reached the target current range (S8), the aging operation is terminated (S10).

  On the other hand, when the DC current value Idc does not reach the target current range (S8), the aging control means 95 determines whether or not the maximum aging time T has elapsed from the start of the rotational drive (S9). .

  If not, the current detection unit 92 detects a DC current value Idc when a new AC voltage is applied by feedback control of the AC voltage control unit 94 (S7), and the aging The control means 95 determines whether or not the newly detected DC current value Idc has reached the target current range (S8).

  On the other hand, if it has elapsed, the aging control means 95 terminates the aging operation (S10).

  Thereafter, the aging control means 95 causes the DC voltage control means 93 and the AC voltage control means 94 to control the DC voltage power supply 911 and the AC voltage power supply 912, so that the vibration voltage is applied to the charging member. The application is stopped (S11), and the digital copying machine 1 shifts to a normal startup operation (S12).

  Hereinafter, another embodiment will be described. In the above-described embodiment, the configuration in which the voltage control unit 96 controls the AC voltage so that the detected DC current value is maintained within the target current range has been described. However, the detected DC current value is within the target current range. The DC voltage may be controlled so as to be maintained.

  Further, the voltage control means 96 may be configured to maintain the DC current value Idc in the target current range by controlling the DC voltage after controlling the peak-to-peak voltage of the AC voltage, and vice versa. In addition, the voltage control means 96 may be configured to maintain the DC current value Idc within the target current range by controlling the peak-to-peak voltage of the AC voltage after controlling the DC voltage.

  In the above-described embodiment, the configuration in which the aging control unit 95 terminates the aging operation when the DC current value Idc detected by the current detection unit 92 reaches the target current range has been described. When the direct current value Idc reaches the target current value Idc (0), the aging control means 95 may be configured to end the aging operation.

  In the above-described embodiment, the configuration in which the predetermined time (maximum aging time T) is set based on the environmental temperature of the image forming apparatus 1 has been described, but the predetermined time (maximum aging time T) is the image forming apparatus 1. The configuration may be set based on the environmental humidity.

  For example, in the image forming apparatus 1, environmental humidity that is the ambient humidity of the image carrier 41 is provided in the vicinity of the image carrier 41 in place of or in addition to the environmental temperature sensor 10. An environmental humidity sensor to be detected is provided, and the aging control means 95 is a humidity table (or temperature / humidity table) which is table data on humidity (or temperature and humidity) stored in a ROM provided in the image output control means 200. ) To determine the maximum aging time T.

  In the above-described embodiment, the image bearing member 41 is a photoreceptor drum having a photoreceptor in which an amorphous silicon layer, which is a positively chargeable photoconductor, is deposited on the surface of an aluminum cylinder. An OPC drum that is a photoconductor or another type of photoconductive semiconductor drum in which the photoconductor is selenium or the like may be employed.

  In the above-described embodiment, the charging member 42 is configured as a charging roller in which the core metal 421 is coated with the chlorohydrin rubber layer 422 that is a conductive elastic material. However, the charging member 42 may be a fur brush, a felt, a cloth, or the like. It may be composed of a shape / material.

  In the above-described embodiment, the configuration in which the charging member 42 is disposed in contact with the image carrier 41 has been described. However, the charging member 42 may be disposed in proximity to the image carrier 41.

  In the above-described embodiment, the configuration in which the current detection unit 92 is provided outside the high voltage generation circuit 91 has been described. However, the current detection unit 92 may be configured in the high voltage generation circuit 91.

  In the above-described embodiment, the configuration in which the voltage control unit 96 is provided in the charging control device 9 has been described. However, the voltage control unit 96 may be configured in the image output control unit 200.

  In the above-described embodiment, the waveform of the alternating voltage of the oscillating voltage has been described as being a sine wave, but may be a rectangular wave, a triangular wave, a pulse wave, or the like.

  The above-described embodiments are merely examples 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. Needless to say, it can be changed.

Block configuration diagram of a charging control device to which the present invention is applied Graph showing the relationship between peak-to-peak voltage value and charging potential (A) shows the relationship between the DC current value and the charging potential, and (b) is a graph showing the relationship between the DC voltage and the DC current value. External view of a digital copying machine to which the present invention is applied Explanatory drawing of a digital copying machine to which the present invention is applied Block diagram of control means of digital copying machine Explanatory diagram of temperature table Flow chart for explaining the aging operation

Explanation of symbols

1: Digital copier 9: Charge control device 10: Environmental temperature sensor 41: Image carrier 42: Charging member 91: High voltage generation circuit 911: DC voltage power supply 912: AC voltage power supply 92: Current detection means 93: DC voltage control means 94: AC voltage control means 95: Aging control means 96: Voltage control means

Claims (5)

A high voltage generating circuit for applying an oscillating voltage in which a DC voltage and an AC voltage are superimposed on a charging member arranged in contact with or close to the image carrier, and a current for detecting a DC current value between the image carrier and the charging member A charge control device for an image forming apparatus, comprising: a detection unit; and a voltage control unit that controls the AC voltage so that a detected DC current value is maintained in a target current range.
A charge control device for an image forming apparatus, comprising: an aging control unit that holds the AC voltage and the DC voltage at a predetermined voltage set in advance and rotationally drives the image carrier.   2. The image forming apparatus according to claim 1, wherein the aging control unit operates when the DC current value cannot be controlled within the target current range by the voltage control unit, or when the environmental temperature of the image forming apparatus is lower than a predetermined temperature. Device charging control device.   The charging control device for an image forming apparatus according to claim 1, wherein the aging control unit operates when the image forming apparatus is turned on or returned from the power saving mode.   The aging control means terminates the aging operation when the direct current value detected by the current detection means reaches the target current range or when a predetermined time has elapsed in advance. A charge control device for an image forming apparatus according to any one of the above.   The charging control device for an image forming apparatus according to claim 4, wherein the predetermined time is set based on an environmental temperature of the image forming apparatus.

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