JP2008216750A - Charging controller for image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charging controller for a color 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 color 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 each of a plurality of image carriers 41 arranged in series; and a voltage control means 96 for controlling the AC voltage so that a DC current value between each image carrier 41 and the charging member 42 may be maintained within a target current range. The controller includes an aging control means 95 for driving and rotating the image carrier 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 in close proximity to each of a plurality of image carriers arranged in series, and each image carrier The present invention relates to a charging control device for a color image forming apparatus, comprising voltage control means for controlling the AC voltage so that the DC current value between the charging member and the charging member 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 the image formed by the image forming process. It was.

  The above-mentioned problem similarly exists even when the contact charging method is adopted in a color image forming apparatus provided with an image carrier for each color corresponding to four colors of YMCK.

  In view of the above-described conventional problems, an object of the present invention is to provide a charge control device for a color 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. There is in point to do.

  In order to achieve the above object, the first characteristic configuration of the charge control device of the color image forming apparatus according to the present invention is that the charging member is arranged in contact with or in close proximity to each of the plurality of image carriers arranged in series. A high voltage generating circuit for applying an oscillating voltage in which a DC voltage and an AC voltage are superimposed; and a voltage control means for controlling the AC voltage so that a DC current value between each image carrier and the charging member is maintained in a target current range. A charge control device for a color image forming apparatus, comprising aging control means for rotating and driving each image carrier while holding the AC voltage and the DC voltage at a predetermined voltage set in advance. It is in.

  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 feature configuration, as described in claim 2, in addition to the first feature configuration described above, the high-voltage generation circuit is a single unit in which a plurality of linear DC regulators are connected in parallel on the secondary side. A DC transformer, a plurality of AC transformers in which the outputs of the respective linear DC regulators are separately connected to the secondary side, and a DC current between the charging member and the image carrier connected to the secondary side of the DC transformer are detected. And a single current detection circuit configured to detect the DC current value separately by adjusting one of the linear DC regulators to a voltage lower than the discharge start voltage except for one of the linear DC regulators. It is in the point which is comprised.

  According to the above-described configuration, when detecting a direct current between a specific charging member and the image carrier, corresponding linear direct current regulators are prevented so that no direct current flows between the other charging member and the image carrier. As a result, the DC voltage is adjusted to be lower than the discharge start voltage, so that the specific DC current value can be detected by the current detection circuit. Therefore, it is not necessary to provide each of the current detection circuits corresponding to the number of the image carriers, so that an increase in cost can be suppressed and mounting efficiency can be increased.

  In the third feature configuration, as described in claim 3, in addition to the second feature configuration described above, the aging control means holds the AC voltage and the DC voltage at a predetermined voltage set in advance. Each image carrier is rotated and driven for a preset reference time, and then each DC current value is adjusted by adjusting the other outputs to be lower than the discharge start voltage except for one of the linear DC regulators. The unit aging operation for detecting sequentially is repeated once or a plurality of times.

  When the DC current value of each image carrier is detected by a single current detection circuit, the total DC current value of each image carrier is detected. Whether or not the total value is within the target current range. When determining whether or not the charging potential of each image carrier is appropriate, if the DC current value of one image carrier is smaller than the appropriate value and the DC current value of another image carrier is larger than the appropriate value, Even if the total value is within the target current range, it cannot be said that the charging potential is set within the proper range for the image carrier whose DC current value is larger (or smaller) than the proper value.

However, in the above-described configuration, one or a plurality of unit aging operations for sequentially detecting each DC current value by adjusting the other outputs to be lower than the discharge start voltage except for one of the linear DC regulators. By repeating the unit aging operation until the DC current values of all the image carriers are within the target current range,
The charging potential can be set within an appropriate range for all image carriers.

  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 may be any DC current by the voltage control means. When the value cannot be controlled within the target current range, or when the environmental temperature of the image forming apparatus is lower than a predetermined temperature, it operates.

  According to the above configuration, in any one of the plurality of image carriers, the DC current value Idc does not reach the target current range even when the maximum applicable DC voltage Vdc is applied. Even in such a case, by operating the aging control means to increase the DC current value 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.

  In the fifth feature configuration, as described in claim 5, in addition to any of the first to fourth feature configurations described above, the aging control means may be configured such that the image forming apparatus is turned on or power-saving. It is in the point that it operates when returning from the mode.

  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 sixth feature configuration, as described in claim 6, in addition to any one of the first to fifth feature configurations described above, the aging control means is configured so that each DC current value is equal to the target current. The point is that the aging operation is ended when the range is reached or when a predetermined time set in advance elapses.

  According to the above configuration, when the aging operation by the aging control means becomes unnecessary because each DC current value Idc between each image carrier and the charging member reaches the target current range, useless aging is performed. It is possible to prevent the operation from continuing. Further, by setting a limit on the time for which the aging control means continuously executes the aging operation, any of the DC current values 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 even when the operation is judged to be a waste of time.

  The seventh feature configuration is that, in addition to the sixth feature 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 a color 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. It became so.

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

  As shown in FIGS. 4 and 5, the color 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 heats and fixes the toner image output on the sheet to the sheet A fixing unit 5 for transporting paper, a transport unit 6 for transporting paper, a plurality of paper feed cassettes 7 (7a to 7d) each containing paper of a different size or type, and a manual paper feed port provided on the left side of the machine ( (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 (a), the image forming unit 4 forms four color toner images by forming toner images of any color of YMCK. It is configured with. As shown in FIG. 5B, each of the image forming units 4a to 4d is sequentially arranged around the image carrier 41 and the image carrier 41, and is arranged in contact with the image carrier 41 so as to contact the image. A charging member 42 for charging the carrier 41, a print head 43 for exposing the charged image carrier 41 to form an electrostatic latent image, and an electrostatic latent image formed on the image carrier 41 A developing unit 44 that visualizes a toner image by electrostatically adhering toner, a toner cartridge 45 that is filled with toner and supplies toner to the developing unit 44, and the developed toner image A transfer unit 46 that transfers to a sheet, a cleaner unit 47 that removes and collects toner remaining on the image carrier 41 after transfer, and a static elimination lamp 48 that lowers the residual potential on the surface of the image carrier 41 to make it uniform. With It is.

  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 of each of the image forming units 4a to 4d.

  Further, as shown in FIG. 6, the color digital copying machine 1 is provided with a plurality of control means for controlling the functional blocks 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 color digital copying machine 1 are integrated, and the image forming unit 4, the fixing unit 5, An image output control unit 200 that controls the transport unit 6 and the paper feed cassette 7 and an operation control unit 300 that controls input / output signals of the operation unit 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 to cause the color digital copying machine 1 to execute image forming processing using a control program executed by each CPU and related hardware. The predetermined function is realized.

  Hereinafter, the charging control device 9 will be described. As shown in FIG. 1, the charging control device 9 applies a DC voltage and an AC voltage to the contact arrangement charging members 42 (42 a to 42 d) on each of the plurality of image carriers 41 (41 a to 41 d) arranged in series. A high voltage generating circuit 91 for applying the superposed vibration voltage, and a voltage control means 96 for controlling the AC voltage so that the DC current value Idc between each image carrier 41 and the charging member 42 is maintained in the target current range. It is prepared for.

  Each of the image carriers 41 is composed of 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. It is comprised so that it may be rotationally driven. Each of the image carriers 41 includes a ROM, and 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, are mounted on the color digital copying machine 1. It is stored as a value to be used when

  Each of the charging members 42 is constituted by a charging roller in which a cored bar 421 is covered with an epichlorohydrin rubber layer 422 which is a conductive elastic material.

  As shown in FIG. 7, the high-voltage generating circuit 91 is connected to the charging member 42 (42a to 42d) composed of a charging roller disposed in contact with the image carrier 41 (41a to 41d). A circuit for generating an oscillating voltage on which the voltage is superimposed, and a single DC transformer 911 in which shunt regulators 912 as linear DC regulators corresponding to the number of the image carriers 41 are connected in parallel on the secondary side; The output of each shunt regulator 912 is connected to the secondary side of the AC transformer 913 corresponding to the number of the image carriers 41, and the secondary side of the DC transformer 911 is connected to the charging member 42 and the image carrier. And a single current detection circuit 914 that detects the DC current Idc between the bodies 41, except for one of the shunt regulators 912. The DC current value Idc is configured to detect each other by adjusting the pressure lower than the starting voltage.

  This will be described in detail below. As shown in FIG. 8, a pulse signal from a pulse signal generation unit 911a that outputs a pulse signal based on a remote drive signal input from the voltage control unit 96 is input to the primary side of the DC transformer 911 and has a predetermined voltage. So that the high-voltage AC voltage boosted to the secondary side is output from the secondary side, and the high-voltage AC voltage is smoothed by the rectifier circuit including the diode D10 and the capacitor C10 so that the high-voltage DC voltage is output from the output terminals t1 and t2. It is configured.

  Similarly to the above, a pulse signal from the pulse signal generation unit 911a that outputs a pulse signal based on the remote drive signal input from the voltage control unit 96 is input to the primary side of the AC transformer 913 and boosted to a predetermined voltage. The high-voltage AC voltage thus output is output from the secondary side. Here, the AC voltage is variably controlled by a pulse signal voltage generated based on a variable analog input voltage inputted from the voltage control means 96 to the pulse signal generation means 911a.

  The shunt regulator 912 is connected in four circuits in parallel to the terminals t1 and t2 of the DC transformer 911 so as to supply a DC voltage separately to the charging members 42 corresponding to the respective image carriers 41 of YMCK. 9, an operational amplifier OP20 as a differential amplifier, a pass transistor Q20 driven by an output current of the operational amplifier OP20, and a Zener diode ZD20 having a breakdown voltage of 250 V connected to the collector of the pass transistor Q20. Etc. are provided.

  A divided voltage obtained by dividing the output voltage of the shunt regulator 912 by the resistors R21 and R20 is input to the non-inverting input terminal of the operational amplifier OP20, and a reference voltage is input to the inverting input terminal. Accordingly, a base current is supplied from the operational amplifier OP20 to the pass transistor Q20 so that the reference voltage and the divided voltage are equal, and as a result, the DC voltage Vdc is adjusted by the current flowing through the resistor R23 and the Zener diode ZD20.

  The reference voltage is variably adjusted by a fixed comparison voltage Vref and a control voltage Vcnt controlled by the voltage control means 96, and each control voltage Vcnt is individually adjusted to be applied to each charging member 42. The DC voltage Vdc is adjusted variably and stably between 250V and 750V.

  As shown in FIG. 7, the output terminal of the shunt regulator 912 is connected to the secondary side terminal of each AC transformer 913 via a bypass capacitor C that bypasses the AC voltage, and the DC voltage from the shunt regulator 912 is And an oscillating voltage on which an AC voltage from the AC transformer 913 is superimposed is applied to each charging member 42.

  As shown in FIG. 10, the current detection circuit 914 includes a current / voltage conversion operational amplifier OP41 and an amplification operational amplifier OP40. The inverting input terminal of the operational amplifier OP41 is connected to the secondary low voltage side terminal t2 of the DC transformer 911, and the non-inverting input terminal is supplied with a voltage obtained by dividing the comparison voltage Vref by resistors R43 and R44 as a reference voltage. The current value flowing through the feedback resistor R42 is converted into a voltage so that the voltage between the reference voltage and the secondary low-voltage side terminal t2 is equal, and further amplified by the operational amplifier OP40 and then input to the voltage control means 96. The

  The detection of the direct current Idc will be described in detail. In the operational amplifier OP41, the direct current Idc between the charging member 42 and the image carrier 41 flowing from each of the image carriers 41 to the ground is supplied to the operational amplifier OP41. The applied control voltage flows from the ground side terminal to the output terminal. The DC current Idc flows to the low voltage side of the DC transformer 911 via the resistor R42, and forms a DC current component loop of the high voltage generation circuit 91.

  In addition, the voltage control means 96 stores the voltage value input from the current detection circuit 914 and the current value corresponding to the voltage value in association with each other in a ROM provided with the voltage / current table data. The voltage value inputted after the voltage value of the current flowing through the feedback resistor R42 (that is, the DC current Idc) is converted and amplified by the operational amplifier OP40 is applied to the voltage / current table data. The value of the direct current Idc is recognized.

  When the DC current Idc between the specific charging member 42 and the image carrier 41 is measured by the current detection circuit 914, the outputs of the other shunt regulators 912 are excluded except for the shunt regulator 912 corresponding to the specific charging member 42. Then, the output of the AC transformer 913 corresponding to the specific charging member 42 is adjusted to be lower than the discharge start voltage.

  Specifically, the voltage control means 96 adjusts the control voltage Vcnt of the other three shunt regulators 912 to be about 250 V lower than the discharge stop level, and the AC transformer 913 is turned off except for one. Later, the value of the current detection circuit 914 is read. In this way, when detecting the direct current Idc between the specific charging member 42 and the image carrier 41, each corresponding shunt is prevented so that no current flows between the other charging member 42 and the image carrier 41. The control voltage Vcnt is adjusted to be lower than the discharge start voltage by the regulator 912 and the AC transformer 913 so that the DC current value Idc from the specific charging member 42 can be detected by the single current detection circuit 914. Become.

  The voltage control means 96 maintains the output of each shunt regulator 912 or the output of each AC transformer 913 at a predetermined target value based on the DC current value Idc from each charging member 42 thus detected. Adjust as follows.

  This will be described in detail below. The voltage control means 96 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. To control. Specifically, the voltage control means 96 inputs the analog input voltage at a level at which the read DC voltage value can be applied to the high voltage generation circuit 91 to the DC transformer 911 of the high voltage generation circuit 91. To do. The DC voltage value stored in the ROM of the image carrier 41 is, for example, about 500 [V].

  The voltage control means 96 reads the DC voltage value stored in the ROM of the image carrier 41 and the target current range, and the AC voltage that is twice the DC voltage value read by the peak-to-peak voltage Vpp. Is applied to the charging member 42 as a discharge start voltage. Specifically, the voltage control means 96 outputs the analog input voltage at a level at which an AC voltage twice as large as the read DC voltage value can be applied to the high voltage generation circuit 91. Input to the transformer 913. Note that the peak-to-peak voltage value Vpp of the AC voltage is, for example, about 1000 [V].

  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 each of the image carriers 41 has a predetermined surface potential. is there.

  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 circuit 914 A direct current value Idc flowing between the image carrier 41 and the charging member 42 is detected.

  The voltage control means 96 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 voltage control means 96 recognizes the value of the DC current Idc by applying the voltage value input from the current detection circuit 914 to the voltage / current table data, and the DC current value Idc is It is determined whether it 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 high voltage generation circuit 91 is controlled so as to make the set predetermined value smaller than the current value. As described above, the high voltage generation circuit 91 is controlled by varying the analog input voltage input to the DC transformer 10 by the voltage control means 96.

  The voltage control unit 96 repeats the above processing until the read DC current value Idc falls within the target current range.

  The charging control device 9 includes an aging control means 95 that rotates and drives each 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 color digital copying machine 1 is turned on or returned from the power saving mode. Further, the aging control means 95 is used when any 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 color digital copying machine 1 is lower than a predetermined temperature. Operate.

  That is, the aging control means 95 operates at the time of adjusting the AC voltage performed by the charging control device 9 when the color digital copying machine 1 is turned on or returned from the power saving mode, and then the voltage control means 95 96 also operates when the DC current value Idc cannot be controlled within the target current range due to 96, or when the environmental temperature of the color digital copying machine 1 becomes less 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 voltage control means 96 controls the high voltage generation circuit 91, and the high voltage generation circuit 91 is charged. 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 member 42 is applied.

  The environmental temperature is provided in or near any one of the image carriers 41 in the color digital copying machine 1, and detects the ambient temperature of any or each of the image carriers 41. It is the temperature derived from the detection value of the temperature sensor 10.

  When the environmental temperature sensor 10 is provided in the vicinity of each of the image carriers 41, the aging control means 95 is in the vicinity of the image carrier 41 that is the measurement target of the DC current Idc. The configuration may be such that the environmental temperature is recognized by the value of the environmental temperature sensor 10 provided.

  Here, determination of the maximum aging time which 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 is set based on the environmental temperature of the color digital copying machine 1.

  More specifically, when the color 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 to detect the detected value of the environmental temperature sensor 10. The aging control means 95 having received the maximum aging time by referring to table data on the temperature stored in the ROM provided in the image output control means 200, for example, a temperature table as shown in FIG. To decide.

  In the present embodiment, the maximum aging time is indicated as the maximum number of repetitions T in the temperature table. In other words, in the present embodiment, the aging operation is executed as a unit aging operation in which one operation sequentially detects the DC current value Idc for each charging member 42 as described later. A time obtained by multiplying a predetermined vibration voltage application time of the operation by the maximum number of repetitions T is the maximum aging time.

  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 number of repetitions T is zero, so the aging operation by the aging control means 95 is not executed. When the temperature is less than 15 degrees, the unit aging operation is executed for the maximum number of repetitions T determined by the temperature table.

  Hereinafter, the aging operation by the aging control means 95 will be described. The aging control means 95 holds the AC voltage and the DC voltage at a preset predetermined voltage and rotationally drives each image carrier 41 for a preset reference time, and then in each shunt regulator 912. The unit aging operation for sequentially detecting each DC current value is repeated once or a plurality of times by adjusting one of the other outputs to a voltage lower than the discharge start voltage.

  More specifically, the aging control means 95 has the DC current value Idc by the voltage control means 96 when a predetermined condition is satisfied (that is, when the color digital copying machine 1 is turned on or returned from the power saving mode). Are not controlled within the target current range, or when the environmental temperature of the color digital copying machine 1 becomes lower than a predetermined temperature), the driving devices (see FIG. By sending a drive start signal to (not shown), the image carrier 41 and the charging member 42 are rotationally driven, that is, an aging operation is performed.

  In a state where each of the image carrier 41 and the charging member 42 is rotationally driven, the aging control unit 95 causes the voltage control unit 96 to control the high voltage generation circuit 91 to charge the vibration voltage. Apply to each of the members 42.

  Specifically, the aging control unit 95 causes the voltage control unit 96 to transmit the analog input voltage to the DC transformer 911 and apply the DC voltage Vdc to the charging member 42 (42a to 42d). Then, the voltage control means 96 transmits the analog input voltage to the AC transformer 913 to apply the AC voltage to the charging member 42 (42a to 42d). In this embodiment, the application of the oscillating voltage to each of the charging members 42 is performed for 30 seconds.

  Thereafter, the aging control means 95 causes the voltage control means 96 to control the high voltage generation circuit 91 to apply the vibration voltage applied to the charging members 42 (42b to 42d) other than a specific charging member (for example, the charging member 42a). Is adjusted to low pressure.

  Specifically, in the voltage control means 96, the control voltage Vcnt of the shunt regulator 912 (912b to 912d) that applies the DC voltage Vdc to the charging members 42b to 42d other than the specific charging member 42a is lower than the discharge stop level. The analog input voltage output to the shunt regulators 912b to 912d is adjusted so as to be about 250V.

  In this state, the current detection circuit 914 detects the DC current value Idc (that is, the DC current value Idc flowing between the charging member 42a and the image carrier 41a) for 1 second. For example, detection is performed by detecting DC current 20 times every 50 milliseconds.

  Thereafter, the DC current values of the charging members 42b to 42d are also detected in the same manner as the detection of the DC current value of the charging member 42a.

  The aging control means 95 ends the aging operation when all the DC current values Idc detected by the current detection circuit 914 reach the target current range, or when a predetermined time has elapsed. .

  More specifically, the aging control means 95 returns to all the charging members 42 again when the DC current value Idc does not reach the target current range for at least one of the charging members 42a to 42d. The voltage application for 30 seconds and the DC current detection operation of each charging member 42 are repeated.

  The aging control unit 95 repeats this operation when the DC current value Idc reaches the target current range in all the charging members 42a to 42d, or the unit aging operation is repeated a predetermined number of times. If this occurs, the process is continued until the aging operation is completed. That is, when the preset number of times (the maximum number of repetitions T determined based on the value of the environmental temperature sensor 10) is reached, the aging control means 95 performs the direct current on all the charging members 42a to 42d. The aging operation is terminated regardless of whether or not the current value Idc has reached the target current range.

  When the aging operation is completed, the aging control means 95 causes the voltage control means 96 to output an output stop signal of the oscillating voltage, and the high voltage generation circuit 91 that has received the output stop signal receives the DC voltage and the AC voltage. Stop output. Thereafter, the color 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 color digital copying machine 1 is turned on will be described with reference to the flowcharts shown in FIGS.

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

  Further, the aging control means 95 has an environmental temperature detected by the environmental temperature sensor 10 of less than 15 degrees (S3), and the voltage control means 96 causes a direct current value Idc for any one of the charging members 42. Is not controlled to the target current range (S4), the rotational drive of all the image carriers 41a to 41d and the charging members 42a to 42d, 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 for all the charging members 42 can be controlled to the target current range by the voltage control means 96 (S4), an aging operation is performed. The AC voltage adjustment process as described in step S6 and subsequent steps is performed without starting the operation. In the AC voltage adjustment process in this case, since the aging operation is not started, it is needless to say that the determination as to whether or not the maximum number of repetitions in step S12 has been reached and the aging operation end process in step S13 are not executed. In the case of step S12, instead of determining whether or not the maximum number of repetitions has been reached, whether or not a predetermined time has been set is determined.

  When the aging operation is started (S5), the aging control means 95 causes the voltage control means 96 to control the high voltage generation circuit 91 to apply a vibration voltage to the charging members 42a to 42d for a certain time (S6).

  Thereafter, the aging control means 95 controls the voltage control means 96 to control the high voltage generation circuit 91 to adjust the vibration voltage applied to the charging members 42b to 42d other than the specific charging member 42a to a low voltage. In this state, the current detection circuit 914 detects the DC current value Idc (that is, the DC current value Idc flowing between the charging member 42a and the image carrier 41a) for 1 second. (S7).

  Similarly to step S7, the vibration voltage applied to the charging member 42 other than the charging member 42b is adjusted to a low pressure (S8), and the vibration voltage applied to the charging member 42 other than the charging member 42c is adjusted to a low pressure. In the state (S9), in the state (S10) in which the oscillating voltage applied to the charging members 42 other than the charging member 42d is adjusted to a low pressure (S10), the current detection circuit 914 has the respective DC current values (the charging members 42b to 42d and the A DC current value Idc) flowing between the image carriers 41b to 41d is detected for 1 second. (S8-S10)

  If all of the detected direct current values Idc for the respective charging members 42 have reached the target current range (S11), the aging control means 95 ends the aging operation (S13).

  On the other hand, when at least one of the DC current values Idc does not reach the target current range (S11), the aging control means 95 has the number of operations from step S6 to step S11 (that is, unit aging operation). It is determined whether the maximum number of repetitions T has been reached (S12).

  When the maximum number of repetitions T has not been reached, the aging control means 95 performs the unit aging operation again. That is, the current detection circuit 914 detects a DC current value Idc for each charging member 42 when a new AC voltage is applied by feedback control of the voltage control means 96 (S7 to S10), and the aging is performed. The control means 95 determines whether all of the newly detected DC current values Idc have reached the target current range (S11).

  On the other hand, if the maximum number of repetitions T has been reached, the aging control means 95 terminates the aging operation (S13).

  Thereafter, the aging control means 95 causes the voltage control means 96 to control the high voltage generation circuit 91 to stop the application of the oscillating voltage to the charging member 42 (S14). (S15).

  Hereinafter, another embodiment will be described. In the above-described embodiment, the voltage control unit 96 has been described with respect to the configuration in which the AC voltage is controlled so that the DC current value between each image carrier 41 and the charging member 42 is maintained in the target current range. The DC voltage may be controlled so that the DC current value between the body 41 and the charging member 42 is maintained in the target current range.

  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 has been described in which the aging control unit 95 terminates the aging operation when the DC current value Idc for all the charging members 42 detected by the current detection circuit 914 reaches the target current range. When the DC current values Idc for all the charging members 42 detected by the current detection circuit 914 reach the target current value Idc (0), the aging control means 95 may end the aging operation.

  In the above-described embodiment, the configuration in which the predetermined time (the maximum number of repetitions T) is set based on the environmental temperature of the image forming apparatus 1 has been described, but the predetermined time (the maximum number of repetitions 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, the ambient humidity of the image carrier 41 in the vicinity of any one or each of the image carriers 41, instead of or in addition to the environmental temperature sensor 10. And an aging control unit 95 is a humidity table which is table data on humidity (or temperature and humidity) stored in a ROM provided in the image output control unit 200. The maximum number of repetitions T is determined by referring to (or the temperature / humidity table).

  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 voltage control unit 96 is provided in the charging control device 9 has been described. However, the voltage control unit 96 may be provided 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 color digital copying machine to which the present invention is applied (A) is a color digital copying machine to which the present invention is applied, and (b) is an explanatory view showing an image forming unit. Block diagram of control means of color digital copying machine Block diagram of high voltage generation circuit DC transformer circuit diagram Shunt regulator circuit diagram Circuit diagram of current detection circuit Explanatory diagram of temperature table Flow chart for explaining the aging operation Flow chart for explaining the aging operation

Explanation of symbols

1: Color digital copying machine 4: Image forming units 4a to 4d: Image forming unit 9: Charge control device 10: Environmental temperature sensor 41 (41a to 41d): Image carrier 42 (42a to 42d): Charging member 91: High pressure Generation circuit 914: current detection circuit 95: aging control means 96: voltage control means

Claims (7)

A high-voltage generating circuit that applies an oscillating voltage in which a DC voltage and an AC voltage are superimposed on a charging member that is in contact with or in close proximity to each of a plurality of image carriers arranged in series, and between each image carrier and the charging member A charge control device for a color image forming apparatus comprising voltage control means for controlling the AC voltage so that a direct current value of the current is maintained in a target current range,
A charge control device for a color image forming apparatus, comprising: an aging control means for rotating and driving each image carrier while holding the AC voltage and the DC voltage at predetermined voltages.   The high-voltage generating circuit includes a single DC transformer in which a plurality of linear DC regulators are connected in parallel on the secondary side, a plurality of AC transformers in which outputs of the respective linear DC regulators are separately connected to the secondary side, A single current detection circuit connected to the secondary side of the DC transformer and detecting a DC current between the charging member and the image carrier, and other outputs except for one of the linear DC regulators 2. The charge control device for a color image forming apparatus according to claim 1, wherein the direct current value is detected separately by adjusting the voltage to a voltage lower than a discharge start voltage. 3.   The aging control means holds the AC voltage and the DC voltage at a preset predetermined voltage and rotationally drives each image carrier for a preset reference time, after which one of the linear DC regulators 3. The charge control device for a color image forming apparatus according to claim 2, wherein the unit aging operation for sequentially detecting each DC current value by adjusting other outputs to be lower than the discharge start voltage is repeated once or a plurality of times.   The aging control unit operates when any 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. A charge control device for a color image forming apparatus according to any one of the above.   5. The charge control device for a color 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.   6. The aging control means ends the aging operation when each of the DC current values reaches the target current range or when a preset predetermined time has elapsed. Charge control device for color image forming apparatus.   The charge control device of a color image forming apparatus according to claim 6, wherein the predetermined time is set based on an environmental temperature of the image forming apparatus.

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