JP2006350087A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device having a charging device of a system that overlaps a direct current voltage with an alternating current voltage, which is capable of preventing filming and an occurrence of a defective image from arising by compensating for an alternating current leaking to peripheral parts by a capacitor component of a conducting wire in which the current output from a high voltage power supply runs. <P>SOLUTION: When a charging voltage is applied from a high voltage power source 20 to a charging member 2a, the amperage outputted from the high voltage power source 20 is compensated for according to the length of the conducting wires 21-24 so that an image carrier 1 can keep the charging amperage required for image forming. By this arrangement, the alternating current leaking to peripheral parts by capacitor components of conducting wires 21-24 is compensated for, and filming and occurrences of defective images can be prevented. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a facsimile, and a printer.

  In an electrophotographic image forming apparatus, a photoconductor as an image carrier is uniformly charged by a charging device, and the uniformly charged photoconductor is irradiated with laser light modulated by image data. To form an electrostatic latent image on the photosensitive member, supply a developer to the photosensitive member on which the electrostatic latent image is formed, and develop to form a developer image on the photosensitive member. The agent image is transferred to transfer paper to form an image.

  In order to improve the quality of an image formed by such an image forming apparatus, it is important to uniformly charge the photoreceptor with a charging device. Therefore, in a charging device, a charging voltage obtained by superimposing an AC voltage on a DC voltage is applied to a charging member for charging a photoconductor as an image carrier, and a discharge is generated between the charging member and the photoconductor. Thus, the photoreceptor is uniformly charged (see, for example, Patent Document 1).

JP 2004-138801 A

  However, in an image forming apparatus having a charging device that superimposes an AC voltage on a DC voltage, the AC current output from the high-voltage power supply leaks to peripheral components due to the capacitor component of the conducting wire, and the amount of charging current varies. As a result, there is a problem that a filming phenomenon occurs on the photosensitive member, and the filming portion cannot be charged, and an abnormal image is generated. Here, “filming” means that the surface of the photoconductor as an image carrier is deteriorated due to electric discharge or other factors, and toner, paper powder, or the like adheres to the surface of the photoconductor.

  The present invention has been made in view of the above, and in an image forming apparatus having a charging device that superimposes an AC voltage on a DC voltage, a peripheral component is formed by a capacitor component of a conducting wire through which a current output from a high-voltage power supply passes. The purpose is to compensate for alternating current leaking to parts and prevent filming and image defects.

  In order to solve the above-described problems and achieve the object, an image forming apparatus according to a first aspect of the present invention is a high-voltage power source that supplies a high voltage obtained by superimposing an alternating voltage on a direct-current voltage, and is output from the high-voltage power source. A charging member that is connected through a conducting wire through which a current flows, and charges a peripheral surface of the image carrier to a predetermined potential by applying a charging voltage in which an AC voltage is superimposed on a DC voltage from the high-voltage power source, and the high-voltage When applying a charging voltage from a power source to the charging member, the amount of current output from the high-voltage power source is corrected according to the length of the conductive wire, and the amount of charging current required for the image carrier to form an image. Current amount correcting means for maintaining the current.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the current amount correction unit corrects the amount of current output from the high-voltage power supply as follows:
I _out = I ₁ + I _L
I _out : Amount of current output from the high voltage power supply I ₁ : Amount of current required when the image carrier forms an image I _L : A current leaking from the lead wire to peripheral components.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, in the case where a plurality of the image carriers are provided, the current amount correction unit corresponds to each of the image carriers. Correcting the amount of current output from the high-voltage power source in accordance with the length of each conducting wire to which each charging member is connected, and maintaining the amount of charging current required for image formation by each image carrier. It is characterized by.

  According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the current amount correcting means outputs a current amount output from the high-voltage power source in consideration of a combination of output presence / absence with respect to each image carrier. And the image carrier maintains a charging current amount necessary for image formation.

  According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the current amount correcting means takes into account the amount of current output from the high-voltage power supply in consideration of the frequency of the AC voltage. And the image carrier maintains a charging current amount necessary for image formation.

  According to the first aspect of the present invention, when the charging voltage is applied to the charging member from the high-voltage power supply, the amount of current output from the high-voltage power supply is corrected according to the length of the conductor, and the image carrier is provided. By maintaining the amount of charging current necessary for image formation, it is possible to compensate for an alternating current leaking to peripheral components by the capacitor component of the conducting wire, and to prevent filming and image defects.

According to the invention of claim 2, the current amount correcting means corrects the amount of current output from the high-voltage power supply as shown in the following equation.
I _out = I ₁ + I _L
I _out : Amount of current output from the high-voltage power supply I ₁ : Amount of current required for image formation by the image carrier I _L : A current leaked from the lead wire to peripheral components, thereby calculating a current amount output from the high-voltage power supply to the length of the lead wire The image carrier can maintain the amount of charging current necessary for image formation by correcting according to the above, and the capacitor component of the lead wire compensates for the alternating current leaking to the peripheral parts, thereby preventing filming and image defects. There is an effect that can be done.

  According to the third aspect of the present invention, when there are a plurality of image carriers, the current amount correction means is configured to provide the length of each conductive wire to which each charging member corresponding to each image carrier is connected. Accordingly, the amount of current output from the high-voltage power supply is corrected so that each image carrier maintains a charging current amount necessary for image formation, so that the output of the high-voltage power supply is K, for example. , M, C, and Y, the amount of charging current required for each image carrier to form an image is added to the output current by adding a current correction amount corresponding to the length of each conducting wire through which the output AC current passes. The effect that can be maintained.

  According to the invention of claim 4, the current amount correction means corrects the amount of current output from the high-voltage power source in consideration of the combination of the presence / absence of output to each image carrier, and each image carrier forms an image. For example, in a full-color image forming apparatus, when the output of the high-voltage power supply has four outputs of K, M, C, and Y, the current output according to the combination of the presence or absence of the output By controlling the amount, each image carrier can maintain the amount of charging current necessary for image formation by compensating for the leakage current that changes depending on the combination of the presence or absence of output, and can prevent filming and image defects. There is an effect.

  According to the fifth aspect of the present invention, the current amount correction means corrects the amount of current output from the high voltage power source in consideration of the frequency of the AC voltage, and the charging current required for each image carrier to form an image. By maintaining the amount, the amount of current leaking from the lead wire to the peripheral parts differs because the frequency of the alternating voltage applied varies depending on the rotational speed of the photoconductor during image formation, so that the leakage current that changes due to the difference in frequency is compensated. There is an effect that the image carrier can maintain a charging current amount necessary for image formation.

  Exemplary embodiments of an image forming apparatus according to the present invention will be explained below in detail with reference to the accompanying drawings.

  An embodiment of the present invention will be described with reference to FIGS. This embodiment is an example in which a so-called tandem color image forming apparatus is applied as an image forming apparatus.

  FIG. 1 is a schematic configuration diagram showing an image forming unit 101 of a color image forming apparatus 100 according to an embodiment of the present invention. As shown in FIG. 1, the image forming unit 101 of the color image forming apparatus 100 includes a plurality (four in this case) of photosensitive drums 1 as image carriers. That is, the color image forming apparatus 100 includes K (black), M (magenta), C (cyan), and Y (yellow) along the upper side of the transfer paper transport belt unit 10 that transports transfer paper (not shown). This is a so-called tandem type full-color image forming apparatus in which photosensitive drums 1 corresponding to four colors are arranged. In the present embodiment, the configuration of the image forming unit 102 centering on each photosensitive drum 1 is the same, and therefore, a single image forming unit 102 will be described below as a representative.

  FIG. 2 is a schematic configuration diagram showing the image forming unit 102 centered on the photosensitive drum 1. As shown in FIG. 2, around the photosensitive drum 1 as an image carrier, a charging device 2 for charging the surface of the photosensitive drum 1, and each color toner is supplied to the electrostatic latent image and developed for each color. A developing device 3 for obtaining a toner image, a transfer roller 4 for transferring the toner image to the transfer paper transport belt unit 10, a cleaning unit 5 for removing toner remaining on the surface of the photosensitive drum 1 after transfer, and a photosensitive member after transfer. A static elimination lamp (QL) 6 for removing charges remaining on the surface of the drum 1 is provided. The charging device 2 includes a charging roller 2a as a charging member and a cleaning brush (brush roller) 2b. The cleaning unit 5 is a blade type cleaning means. In the present embodiment, the LED array head 7 which is a solid-state optical writing device that forms an electrostatic latent image by irradiating light onto the uniformly charged surface of the photosensitive drum 1 includes the image forming units 102. It is provided for each.

  Here, FIG. 3 is an explanatory diagram showing application of a bias voltage to the charging roller 2a of the charging device 2. FIG. The high voltage power supply 20 shown in FIG. 3 outputs a current by a charging method in which an AC voltage Vac having a frequency f is superimposed on a DC voltage Vdc. That is, the bias voltage (Vdc + Vac) obtained by superimposing the AC voltage Vac having the frequency f on the DC voltage Vdc is applied from the high voltage power supply 20 to the charging roller 2a of the charging device 2 of each image forming unit 102. As a result, the peripheral surface of each photosensitive drum 1 rotating the image forming unit 102 is charged to a predetermined potential.

  Next, a control system built in the color image forming apparatus 100 will be described. As shown in FIG. 4, the control system includes a CPU (Central Processing Unit) 50 that controls the entire apparatus. The CPU 50 includes a ROM (Read Only Memory) 51, a RAM (Random Access Memory) 52, and various parameters. An NV-RAM (nonvolatile RAM) 53 for storing the control program is connected. The NV-RAM 53 stores product data, and it is possible to take over the product data even when the PCB is replaced by changing the product data. In addition, the NV-RAM 53 performs setting on the software by a method of dividing the inside into a plurality of areas and storing the same data. Further, the CPU 50 includes an operation unit 54 that allows the operator to operate the apparatus, an electrical control unit 55 that performs general I / F of mechanical control control of electrical components of the apparatus, an image memory 56 that stores image data, and image processing. An image processing unit 57 that performs processing is connected. The high-voltage power supply 20 is connected to the CPU 50 and the electrical control unit 55, and applies a predetermined charging discharge voltage to the charging roller 2a of the charging device 2.

  Incidentally, as shown in FIG. 3, in the color image forming apparatus 100 according to the present embodiment, the currents output from the high-voltage power source 20 pass through the conductors 21 to 24 having different lengths (L1 to L4). Charging is performed by each of the charging rollers 2a after partly leaking to the peripheral parts due to the capacitor components 21 to 24. That is, the amount of current that flows through the photosensitive drum 1 is the amount of current that is output from the high-voltage power supply 20 minus the amount of current that leaks to the peripheral components due to the capacitor components of the conductors 21 to 24. For this reason, the amount of charging current varies as it is, and a filming phenomenon occurs in each photosensitive drum 1, and the filming portion cannot be charged and an abnormal image is generated.

  Therefore, in the color image forming apparatus 100 of the present embodiment, the current correction amount determined by the lengths (L1 to L4) of the conductors 21 to 24 so that the photosensitive drum 1 maintains the charging current amount necessary for image formation. Is added to the output current. This point will be described below.

  In the present embodiment, the color image forming apparatus performs a current correction process that causes the high-voltage power supply 20 to perform output by adding a current correction amount determined by the lengths (L1 to L4) of the conductors 21 to 24 to the output current. The CPU 50 is operated and executed by a computer program installed in the NV-RAM 53 of 100 (current amount correcting means).

Here, when current correction processing is not performed,
Current for charging the photosensitive drum 1: I
Current leaking to peripheral parts: I _L
Output current of high-voltage power supply 20: I _out
Then,
I = I _out −I _L
It becomes. That is, in order to flow the current amount I necessary for charging the photosensitive drum 1, the current _Iout output from the high voltage power source 20 may be set to “ _Iout + I _L ”.

  By the way, the current IL leaking to the peripheral parts depends on the lengths of the conductors 21 to 24, the combination of the output of K (black), M (magenta), C (cyan), Y (yellow), and the frequency f of the AC voltage Vac. Change. Specifically, the leakage current varies depending on the combination of the presence or absence of output to each image carrier, and the frequency f of the alternating voltage applied varies depending on the rotational speed of the photosensitive drum 1 during image formation, so that the surroundings from the conductors 21 to 24 This is because the amount of current leaking to the parts is also different.

Therefore, in the present embodiment, when the color image forming apparatus 100 outputs from the high-voltage power supply 20 at the time of image formation, the lengths of the conducting wires 21 to 24 (L1 to L4) at the outputs of K, M, C, and Y, respectively. , K (black), M (magenta), C (cyan), Y (yellow) combination of presence or absence of output, current IL that leaks to peripheral parts is determined by frequency f of AC voltage Vac, and current output from high-voltage power supply 20 in addition to I _out CPU 50 operates to perform the output.

For example,
The amount of current required for the photosensitive drum 1 to form an image: I ₁
Conductor length: L
Current leaking from conductor to peripheral parts: αLI ₁
A value based on the difference in leakage current amount depending on the presence or absence of output of each color, or the difference in leakage current amount depending on the frequency f of the AC voltage Vac: Iβ
Then, the CPU 50 controls the amount of current I _out output from the high-voltage power supply 20 as shown in the following formula (1).
I _out = I ₁ + (αLI ₁ + Iβ) (1)
It should be noted that the value Iβ can be determined by applying the difference in the leakage current amount depending on whether or not each color is output and the difference in the leakage current amount depending on the frequency f of the AC voltage Vac to a table or the like.

  As described above, according to the present embodiment, when a charging voltage is applied from the high-voltage power supply 20 to the charging roller 2a, the amount of current output from the high-voltage power supply 20 is corrected according to the lengths of the conductors 21 to 24. Thus, the photosensitive drum 1 keeps the amount of charging current necessary for image formation. Thereby, the alternating current which leaks to peripheral components with the capacitor component which the conducting wires 21-24 have can be compensated, and a filming phenomenon and an image defect can be prevented.

  In the case where a plurality of photosensitive drums 1 are provided, the current amount correcting means corresponds to the length of each of the conductive wires 21 to 24 to which the respective charging rollers 2a corresponding to the respective photosensitive drums 1 are connected. By correcting the amount of current output from the high-voltage power supply 20 and maintaining each photosensitive drum 1 at a charging current amount necessary for image formation, each photosensitive drum 1 can maintain a charging current amount necessary for image formation. it can.

  Further, the current amount correcting means corrects the amount of current output from the high voltage power source 20 in consideration of the combination of the presence / absence of output to each photoconductor drum 1, and sets the charge current amount necessary for each photoconductor drum 1 to form an image. By maintaining the amount, it is possible to compensate for the leakage current that changes depending on the combination of the presence or absence of output and to maintain the amount of charging current required for each photoconductor drum 1 for image formation.

  Further, the current amount correction means corrects the amount of current output from the high voltage power source 20 in consideration of the frequency f of the AC voltage, and maintains the charging current amount necessary for image formation by each photosensitive drum 1, so that an image is obtained. Since the frequency f of the alternating voltage applied differs depending on the rotation speed of the photosensitive drum 1 at the time of formation, the amount of current leaking from the conductors 21 to 24 to the peripheral parts also differs, so that the leakage current that changes due to the difference in the frequency f is compensated. The photosensitive drum 1 can maintain a charging current amount necessary for image formation.

1 is a schematic configuration diagram illustrating an image forming unit of a color image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram showing an image forming unit centered on a photosensitive drum. It is explanatory drawing which shows application of the bias voltage with respect to the charging roller of a charging device. It is a block diagram which shows the control system incorporated in a color image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image carrier 2a Charging member 20 High voltage power supply 21-24 Conductor 100 Image forming apparatus

Claims (5)

A high voltage power supply for supplying a high voltage obtained by superimposing an AC voltage on a DC voltage;
The peripheral surface of the image carrier is charged to a predetermined potential by applying a charging voltage obtained by superimposing an alternating current voltage on a direct current voltage from the high voltage power supply, which is connected through a conducting wire through which a current output from the high voltage power supply passes. A charging member;
When a charging voltage is applied to the charging member from the high-voltage power supply, the amount of current output from the high-voltage power supply is corrected according to the length of the conducting wire so that the image carrier is charged for image formation. Current amount correction means for maintaining the current amount;
An image forming apparatus comprising: The current amount correction means corrects the amount of current output from the high-voltage power supply as shown in the following equation.
I _out = I ₁ + I _L
The image forming apparatus according to claim 1, wherein I _{out is} an amount of current output from a high-voltage power source. I ₁ is an amount of current required when the image carrier forms an image. I _L is a current that leaks from a conductor to peripheral components. In the case where a plurality of the image carriers are provided, the current amount correction means is configured to use the high-voltage power supply according to the length of each conductor to which the charging members corresponding to the image carriers are connected. Correcting the amount of current output from the image carrier to maintain the charging current amount necessary for image formation,
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The current amount correction means corrects the amount of current output from the high-voltage power supply in consideration of the combination of the presence / absence of output to each image carrier and maintains the charge current amount necessary for image formation by each image carrier. ,
The image forming apparatus according to claim 3. The current amount correction means corrects the amount of current output from the high-voltage power source in consideration of the frequency of the alternating voltage, and maintains the charging current amount required for image formation by the image carriers.
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

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