JP2007199374A - 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 regardless of environmental variation such as temperature and humidity and change with lapse of time of the image carrier and a charging member or the like. <P>SOLUTION: The charging controller 1 for the image forming apparatus which controls the output voltage of a high voltage generation circuit 4 for applying oscillating voltage obtained by superposing DC voltage and AC voltage to the charging member 3 arranged in contact with or proximately to the image carrier 2, includes: a current detection means 10 for detecting a DC current value Idc between the charging member 3 and the image carrier 2; and a DC voltage control means 11 for controlling the DC voltage so that the DC current value Idc detected by the current detection means 10 may be maintained within a target current range 50. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a charging control for an image forming apparatus that controls an output voltage of 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 arranged in contact with or close to an image carrier. Relates to the device.

  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.

  Therefore, Patent Document 2 discloses that there is no problem such as deterioration 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, the current value when a peak-to-peak voltage less than twice Vth of at least one point is applied to the charging means, and at least twice 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. In a high temperature and high humidity environment where the electrical resistance value of the charging member is low, as shown in FIG. 5, the desired discharge current value D is obtained from the measured alternating current value characteristics. However, in the normal temperature and normal humidity environment and the low temperature and low humidity environment, it was found that it is difficult to obtain the desired discharge current value D based on the measured alternating current value characteristics.

  Such a situation is considered to depend on various fluctuation factors depending on variations in characteristics of the members constituting the charging device, fluctuations in the surrounding environment, and the type of the image carrier, and in various usage environments of the image forming apparatus. In order to set the charging potential of the image carrier capable of performing appropriate image formation, the need for further improvement has been desired.

  In view of the above-described conventional problems, an object of the present invention is to control charging of an image forming apparatus capable of controlling the charging potential of an image carrier regardless of environmental fluctuations such as temperature and humidity and changes over time of the image carrier or charging member. The point is to provide a device.

  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 charging control device for an image forming apparatus for controlling an output voltage of a high voltage generating circuit that applies a vibration voltage in which a DC voltage and an AC voltage are superimposed on a charged charging member, the charging member and the image carrier Current detecting means for detecting a DC current value Idc between the DC voltage control means for controlling the DC voltage so that the DC current value Idc detected by the current detecting means is maintained in a target current range. In the point.

  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 oscillating voltage, and as shown in FIG. It has been confirmed through various experiments that the charging potential Vo is in a proportional relationship, and that this relationship does not change significantly due to environmental fluctuations such as temperature and humidity and aging of the image carrier, the charging member, etc. It was confirmed that the charging potential Vo can be set to a target potential by adjusting the direct current value Idc.

  According to Patent Document 1, it is shown that when the DC voltage Vdc is equal to or higher than the discharge start voltage Vth, the DC voltage Vdc and the charging potential Vo have a linear function relationship, and the DC voltage Vdc is discharged. When it is equal to or higher than the start voltage Vth, as shown in FIG. 3, the DC voltage Vdc and the DC current value Idc have a linear function relationship. It is also shown that the surface potential is stabilized by controlling the peak-to-peak voltage of the AC voltage to a value that is twice or more the discharge start voltage.

  Therefore, according to the above-described configuration, the DC voltage control means controls the DC voltage Vdc so that the DC current value Idc is targeted while the surface potential is stabilized by adjusting the peak-to-peak voltage of the AC voltage. By maintaining the current range, the charging potential Vo can be set within a predetermined range while avoiding the generation of discharge products accompanying application of an excessive level of AC voltage.

  According to a second characteristic configuration of the charging control device of the image forming apparatus according to the present invention, as described in claim 2 of the claims, in addition to the first characteristic configuration described above, the DC voltage is used as a reference voltage. AC voltage for setting the peak-to-peak voltage value Vpp of the AC voltage to the appropriate peak-to-peak voltage value Vpp (O) so that the DC current value Idc becomes the target current value Idc (O) when the value Vdc (R) is set. The DC voltage control means includes a target current in which the DC current value Idc includes the target current value Idc (O) after the appropriate peak-to-peak voltage value Vpp (O) is set by the AC voltage control means. The DC voltage is controlled so as to be maintained in the range.

  While examining the setting of the appropriate peak-to-peak voltage value Vpp (O), the present inventors have conducted various experiments and the charging member and the image generated by the vibration voltage applied to the charging member by the high-voltage generation circuit. When the DC current value Idc between the carriers was measured, as shown in FIG. 4, when the DC voltage Vdc was an arbitrary reference voltage value Vdc (R), the peak-to-peak voltage value Vpp was gradually increased from a low level. When the DC current value Idc is increased, the DC current value Idc increases with a substantially constant slope, and then transitions with a slope lower than the constant slope or with a slope of zero, and the image holding when the peak-to-peak voltage value Vpp is changed. When the surface potential of the body and the direct current value Idc are in a proportional relationship, and the point where such inclination is changed is an inflection point, the position of the inflection point varies depending on environmental conditions. To Although, the peak-to-peak voltage value Vpp is the surface potential at the high pressure side of the inflection point has been confirmed to be stable.

  Accordingly, the AC voltage control means adjusts the appropriate peak-to-peak voltage value Vpp (O) as an inflection point or a value slightly higher than the inflection point while monitoring the DC current value Idc, thereby obtaining a desired surface potential. It can be adjusted stably.

  However, when the DC voltage Vdc and the peak-to-peak voltage value Vpp are adjusted to a predetermined value, environmental changes such as temperature and humidity, and secular changes of the image carrier, the charging member, etc., are shown in FIG. As described above, the DC current value Idc fluctuates, and the charging potential Vo of the image carrier cannot maintain the desired value.

  In such a case, the peak-to-peak voltage value Vpp needs to be adjusted, but the peak-to-peak voltage value Vpp required by the maximum output voltage value of the high-voltage generating circuit, the withstand voltage characteristics of the image carrier, etc. is applied. If this is not possible, the charging potential Vo of the image carrier is lowered, and there is a risk that the toner will be developed in the background region or the inter-image region where the toner is not originally developed in the image carrier.

  According to the above-described configuration, when the target current value Idc (O) with respect to the appropriate peak-to-peak voltage value Vpp (O) varies for some reason, that is, when the charging potential Vo varies, the peak-to-peak voltage value Vpp. Even if the new appropriate peak-to-peak voltage value Vpp (O) cannot be set by changing the DC voltage Vdc, the DC voltage Vdc is controlled by the DC voltage control means, and the DC current value Idc is the target current value Idc (O). In other words, the charged state of the image carrier is not stable, but the charging potential Vo can be set within a predetermined range. In addition to being executable, unnecessary toner consumption can be avoided.

  According to a third characteristic configuration of the charge control device of the image forming apparatus according to the present invention, as described in claim 3 of the claims, in addition to the first characteristic configuration described above, the DC voltage is used as a reference voltage. AC voltage for setting the peak-to-peak voltage value Vpp of the AC voltage to the appropriate peak-to-peak voltage value Vpp (O) so that the DC current value Idc becomes the target current value Idc (O) when the value Vdc (R) is set. Control means, and the DC voltage control means is configured such that when the AC voltage control means cannot set the appropriate peak-to-peak voltage value Vpp (O), the DC current value Idc is the target current value Idc (O). The DC voltage is controlled to be maintained in a target current range including

  The appropriate peak-to-peak voltage within the output adjustment range of the high-voltage generation circuit so that the DC current value Idc becomes the target current value Idc (O) under the predetermined reference voltage value Vdc (R). Although the value Vpp (O) is adjusted, as shown in FIG. 4, even if the DC voltage Vdc and the peak-to-peak voltage Vpp are constant voltage values, environmental fluctuations such as temperature and humidity, the image carrier, The DC current value Idc with respect to the peak-to-peak voltage value Vpp may vary due to aging of the charging member or the like.

  In particular, since the rate of change of the DC current value Idc with respect to the peak-to-peak voltage value Vpp is small at low temperatures, the DC current value Idc is set to the target current value Idc (O) unless a high peak-to-peak voltage Vpp is applied. I can't.

  In such a case, if a high peak-to-peak voltage value Vpp is applied to obtain the target current value Idc (O), the image carrier or the charging member may be deteriorated due to generation of discharge products, etc. In some cases, such a high peak-to-peak voltage value Vpp cannot be output.

  Even in such a case, according to the above configuration, when the appropriate peak-to-peak voltage value Vpp (O) cannot be set by the AC voltage control means, the DC voltage Vdc is set by the DC voltage control means. And the DC current value Idc is maintained in a target current range including the target current value Idc (O). That is, the charged state of the image carrier is not stable, but the charging potential Vo is set within a predetermined range. Therefore, although the image quality is expected to be lowered, it is possible to perform image formation and avoid unnecessary toner consumption.

  According to a fourth characteristic configuration of the charging control device of the image forming apparatus according to the present invention, in addition to any one of the first to third characteristic configurations described above, as described in claim 4 of the claims, The DC voltage control means is configured to control the DC voltage so that the DC current value Idc is maintained in the target current range at least during an image forming process by the image forming apparatus.

  According to the above-described configuration, since image formation is not performed in the non-image forming process period, it is not necessary to maintain the charged potential of the image carrier at an expected value. However, at least in the image forming process period, By controlling the DC voltage so that the DC current value Idc is maintained within the target current range, an adverse effect such as an increase in discharge products caused by applying an excessive peak-to-peak voltage value Vpp can be suppressed. It is possible to appropriately form an image by securing the charging potential of the period.

  As described above, according to the present invention, there is provided a charge control device for an image forming apparatus capable of controlling the charging potential of an image carrier regardless of environmental fluctuations such as temperature and humidity, and secular changes of an image carrier or a charging member. I was able to do it.

  Hereinafter, a charging control device of an image forming apparatus according to the present invention will be described. As shown in FIG. 1, a charging control device 1 is incorporated in an image forming apparatus that employs an electrophotographic system, and is placed in contact with an image carrier 2 to charge a charging member 3 that charges the image carrier 2 with a high voltage generation circuit. DC voltage control means 11 for controlling the DC voltage Vdc of the oscillating voltage applied by 4; AC voltage control means 12 for controlling the peak-to-peak voltage value Vpp of the AC voltage of the oscillating voltage; the charging member 3; A current detection means 10 for detecting a direct current value Idc between the image carriers 2 is provided.

  The image carrier 2 is composed of 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, and is fixed around a center support shaft by a driving device (not shown). It is configured to be driven at high speed.

  The charging member 3 is constituted by a charging roller 3 in which a cored bar 30 is coated with an epichlorohydrin rubber layer 31 that is a conductive elastic material.

  The high voltage generating circuit 4 is controlled by the DC voltage control means 11 and is controlled by the AC control means 12 similarly to a DC voltage power source 40 that outputs an arbitrary voltage by a pulse transformer. An AC voltage power supply 41 that outputs an AC voltage having an arbitrary peak-to-peak voltage value Vpp, which is composed of a sine wave of 3 [kHz].

  The AC voltage control means 12 controls the reference voltage value Vdc stored in the storage means 5 of the image forming apparatus when the DC voltage control means 11 controls the DC voltage power supply 40 during the non-image forming processing period of the image forming apparatus. When outputting (R), the AC voltage power supply 41 is controlled so that the DC current value Idc becomes the target current value Idc (O) stored in the storage means 5, and the appropriate peak-to-peak voltage value Vpp ( Set and output O). When the optimum peak-to-peak voltage value Vpp (O) cannot be set, the settable peak-to-peak voltage value Vpp is output.

  Further, when there is a change in the target current value Idc (O) detected by the current detecting means 10 during the image forming process period of the image forming apparatus, the peak-to-peak voltage value Vpp is controlled to control the target current value Idc. (O) is maintained.

  The DC voltage control means 11 controls the DC voltage power supply 40 and outputs the reference voltage value Vdc (R) during the non-image forming process period. Further, when the target current value Idc (O) cannot be detected by the control of the peak-to-peak voltage value Vpp by the AC voltage control means 12 during the image forming process period, the target current value Idc (O) is included, The DC voltage Vdc is controlled so that the DC current value Idc is maintained in the target current range 50 stored in the storage means 5.

  Here, the target current range 50 is set within the range of the charging potential Vo where excessive toner consumption does not occur, and may be set to an appropriate range based on the results obtained from experiments or the like. .

  The control of the DC voltage Vdc by the DC voltage control means 11 will be described in detail. In the non-image forming processing period, the DC voltage control unit 11 outputs the reference voltage value Vdc (R). Even if the AC voltage control unit 12 controls the peak-to-peak voltage value Vpp, the appropriate peak value is output. When the inter-voltage value Vpp (O) cannot be set, the DC current value Idc includes the target current value Idc (O) according to the peak-to-peak voltage value Vpp set by the AC voltage control means 12. The DC voltage control means 11 controls the DC voltage Vdc to change the voltage value from the reference voltage value Vdc (R) so as to be maintained in the range 50.

  In the image forming process period, when the DC current value Idc detected when the appropriate peak-to-peak voltage value Vpp (O) is set / output varies from the target current value Idc (O), If the AC voltage control means 12 cannot adjust the target current value Idc (O) even if the peak-to-peak voltage value Vpp is controlled, the DC current value Idc includes the target current value Idc (O). The DC voltage control means 11 controls the DC voltage Vdc to change the voltage value from the reference voltage value Vdc (R) so as to be maintained in the range 50.

  When the AC voltage control means 12 controls the peak-to-peak voltage value Vpp and the DC current value Idc recovers to the target current value Idc (O), the DC voltage control means 11 causes the reference voltage value Vdc (R ).

  Another embodiment will be described below. In the above-described configuration, 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 is used as the image carrier 2. 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 this case, depending on the charging characteristics of the photoconductor, You may change suitably the positive / negative polarity of the oscillating voltage applied to the charging member 3. FIG.

  In the above-described configuration, the charging member 3 is configured as a charging roller in which the core metal 31 is coated with the epichlorohydrin rubber layer 32 that is a conductive elastic material. However, the charging member 3 has a shape such as a fur brush, a felt, or a cloth. It may be made of a material.

  In the above-described configuration, the charging member 3 is arranged in contact with the image carrier 2, but may be arranged in close proximity.

  In the above-described configuration, the waveform of the alternating voltage component 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.

  In the configuration described above, the peak-to-peak voltage value Vpp of the AC voltage is set so that the DC current value Idc becomes the target current value Idc (O) when the DC voltage Vdc is set to the reference voltage value Vdc (R). The appropriate peak-to-peak voltage value Vpp (O) is set. However, the target current value Idc (O) depends on the environmental conditions such as temperature and humidity, the driving time of the charging member and the image carrier, the number of printed sheets, and the charging time. The table data of the appropriate peak-to-peak voltage value Vpp (O) corresponding to can be provided, and the appropriate peak-to-peak voltage value Vpp (O) may be set based on the table data.

  In the above-described configuration, the DC current value Idc detected when the appropriate peak-to-peak voltage value Vpp (O) is set / output is an image formation processing period, and fluctuates from the target current value Idc (O). When the AC voltage control means 12 does not recover the target current value Idc (O) even if the AC voltage control means 12 controls the peak-to-peak voltage value Vpp, the DC current value Idc becomes equal to the target current value Idc (O). The DC voltage control means 11 controls the DC voltage Vdc so as to change the voltage value from the reference voltage value Vdc (R) so that the target current range 50 is maintained. Even during the processing period, the DC current value Idc detected when the appropriate peak-to-peak voltage value Vpp (O) is set and output varies from the target current value Idc (O). When the AC voltage control means 12 does not recover the target current value Idc (O) even if the AC voltage control means 12 controls the peak-to-peak voltage value Vpp, the DC current value Idc becomes equal to the target current value Idc (O). The DC voltage control means 11 may be configured to control the DC voltage Vdc and change the voltage value from the reference voltage value Vdc (R) so that the target current range 50 is maintained.

  The above-described embodiments are merely examples of the present invention, and the scope of the present invention is not limited by the description, and the specific configuration of each part is appropriately changed within the scope of the effects of the present invention. It goes without saying that it can be done.

1 is a block diagram of a partial configuration of an image forming apparatus according to an embodiment of the present invention. Graph showing the relationship between charging potential and DC current value Graph showing the relationship between DC current value and DC voltage Graph showing the relationship between DC current value and peak-to-peak voltage value Graph showing the relationship between AC current value and peak-to-peak voltage value

Explanation of symbols

1: Charge control device 2: Image carrier (photosensitive drum)
3: Charging member (charging roller)
4: High voltage generation circuit 5: Storage means 10: Current detection means 11: DC voltage control means 12: AC voltage control means 50: Target current range (data)

Claims (4)

A charge control device for an image forming apparatus for controlling an output voltage of a high voltage generation circuit that applies a vibration 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. ,
Current detection means for detecting a direct current value Idc between the charging member and the image carrier, and the direct current voltage is controlled so that the direct current value Idc detected by the current detection means is maintained in a target current range. A charging control device for an image forming apparatus, comprising a DC voltage control means.   The peak-to-peak voltage value Vpp of the AC voltage is set to an appropriate peak-to-peak voltage value Vpp (O) so that the DC current value Idc becomes the target current value Idc (O) when the DC voltage is a reference voltage value Vdc (R). ), And the DC voltage control means sets the DC current value Idc to the target current value Idc (after the setting of the appropriate peak-to-peak voltage value Vpp (O) by the AC voltage control means. 2. The charging control device for an image forming apparatus according to claim 1, wherein the direct current voltage is controlled so as to be maintained within a target current range including O).   The peak-to-peak voltage value Vpp of the AC voltage is set to an appropriate peak-to-peak voltage value Vpp (O) so that the DC current value Idc becomes the target current value Idc (O) when the DC voltage is a reference voltage value Vdc (R). ), And the DC voltage control means sets the DC current value Idc to the target when the AC voltage control means cannot set the appropriate peak-to-peak voltage value Vpp (O). The charge control device for an image forming apparatus according to claim 1, wherein the DC voltage is controlled so as to be maintained in a target current range including a current value Idc (O).   4. The DC voltage control unit according to claim 1, wherein the DC voltage control unit controls the DC voltage so that the DC current value Idc is maintained in the target current range at least during an image forming process by the image forming apparatus. Charge control device for image forming apparatus.

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