JP2006330648A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To clean a corona discharge member without affecting an image forming process. <P>SOLUTION: A cleaning member 52 has a holding frame 60 that holds a pair of sponge bodies 63a and 63b sandwiching a discharge wire 32. A moving member 61 fixed to the holding frame 60 is moved by the rotation of a screw conveying member 51, thereby cleaning the discharge wire 32. A recording control section 40 includes: a judgement control part 46 designed such that a voltage is applied to the discharge wire 32 from a constant current source 70 to cause discharge, a discharge voltage caused by it is detected by a voltage detecting circuit 71, and a judgment is made whether cleaning is necessary or not; and an operation control section 47 that performs a cleaning operation when the judgement is made that cleaning is necessary and again causes the judgment control section 46 to exert judgment control. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

  As an electrophotographic image forming apparatus, for example, a photosensitive drum is used as an image carrier, the surface is charged and exposed to form an electrostatic latent image, and toner is attached to the electrostatic latent image. An image forming apparatus that forms a visible image and transfers the image onto a sheet is known. In such an image forming apparatus, a corotron charging device or a scorotron charging device using corona discharge has been put to practical use as a charging device for charging the photosensitive drum. In these apparatuses, as a corona discharge member, for example, a corona discharge is generated by stretching a thin discharge wire and applying a high voltage, and the surface of the photosensitive drum is charged by ions generated by the discharge. ing. When a positive or negative high voltage is applied to the discharge wire, particles charged in the opposite polarity with fine particles floating in the air, for example, foreign particles such as toner particles and paper dust are attracted to the discharge wire and become attached. Therefore, if a high voltage is continuously applied to the discharge wire, there is a problem that the adhered foreign matter accumulates and the discharge wire becomes dirty and corona discharge cannot be normally performed.

In order to cope with such problems, for example, in Patent Document 1, in an image forming apparatus including a constant current power source for applying a voltage to a corona discharge wire, a means for detecting an applied voltage of the corona discharge wire, and a cleaning control means. A cleaning member composed of two different members, an A cleaning member made of an elastic material and a B cleaning member made of an abrasive material, and the cleaning control means has a fluctuation range of the applied voltage exceeding a reference voltage fluctuation range Describes that the corona discharge wire is determined to be deteriorated, the B cleaning member is used to clean the corona discharge wire, and when the corona discharge wire is periodically cleaned, the A cleaning member is used for cleaning.
Japanese Patent Laid-Open No. 11-24375

  In the above-mentioned patent documents, when the applied voltage is detected during the image forming process and the fluctuation range of the applied voltage is large, the corona discharge wire is cleaned, so the process may be interrupted, and the convenience is reduced accordingly. There is a fear.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of cleaning a corona discharge member without affecting image forming processing.

  The image forming apparatus according to the present invention includes an image carrier, a charging unit that charges the surface of the image carrier with a corona discharge member, and an exposure that forms an electrostatic latent image by exposing the charged surface of the image carrier. Means, developing means for attaching a toner to the electrostatic latent image formed on the surface of the image carrier to visualize it, and transfer means for transferring the toner image formed on the surface of the image carrier to a sheet And a cleaning means for cleaning dirt adhering to the corona discharge member in an image forming apparatus comprising: control means for controlling the rotation of the image carrier and controlling the means so as to form an image on a sheet; A discharge detection means for detecting a discharge voltage or a discharge current applied to the corona discharge member, and the control means applies a discharge voltage to the corona discharge member and detects the discharge detection means during voltage application. Trust And a cleaning determination control means for determining whether or not to perform cleaning by the cleaning means, and cleaning by the cleaning means while the rotation of the image carrier is stopped when the cleaning determination control means determines to perform cleaning. And cleaning operation control means for performing determination by the cleaning determination control means after cleaning. Further, the cleaning determination control means is periodically performed based on a predetermined parameter. Further, the cleaning determination control means is performed while the rotation of the image carrier is stopped.

  With the above configuration, when the cleaning determination control unit determines that cleaning is performed, the cleaning operation control unit performs cleaning by the cleaning unit while the rotation of the image carrier is stopped. In addition, the cleaning operation by the cleaning means is not performed, and the image forming process is not affected. Further, since the cleaning determination control means applies the discharge voltage to the corona discharge member and makes the determination based on the detection signal of the discharge detection means, the determination can be made without performing the rotation operation of the image carrier. Can be set freely. Further, the cleaning operation control means performs the determination again by the cleaning determination control means after the cleaning, and confirms the cleaning effect. Therefore, when the cleaning effect is not recognized, the corona discharge member has reached the end of its life. Therefore, it is possible to prevent a trouble caused by a defective corona discharge member.

  Then, the cleaning determination control means periodically performs the corona based on the predetermined parameters, for example, the number of sheets subjected to the image forming process, the accumulated operation time of the apparatus, the time, etc. without affecting the image forming process. The timing of cleaning the discharge member can be set accurately. Further, if the cleaning determination control means is executed while the rotation of the image carrier is stopped, the processing relating to the cleaning of the corona discharge member can be performed separately from the image forming processing, and the image forming processing may be affected. Disappear.

  Hereinafter, embodiments according to the present invention will be described in detail. The embodiments described below are preferable specific examples for carrying out the present invention, and thus various technical limitations are made. However, the present invention is particularly limited in the following description. Unless otherwise specified, the present invention is not limited to these forms.

  FIG. 1 is a schematic cross-sectional view of the entire image forming apparatus according to the present invention. A paper discharge tray 10 is provided in the upper part of the image forming apparatus 1, and a recording unit 2 and a paper feeding unit 3 are arranged in the lower part thereof.

  In the paper feed unit 3, a paper feed cassette 11 is arranged, and a plurality of sheets of a predetermined size are stacked on the flapper 12. A pickup roller 13 is disposed at the right end of the paper feed cassette 11. The flapper 12 is urged upward by a spring member (not shown) so that the upper surface of the stacked paper comes into pressure contact with the pickup roller 13. When the pickup roller 13 is rotationally driven in this state, the sheets are fed one by one to the sheet conveyance path by the frictional force.

  The fed paper is first conveyed to the recording unit 2 by the feed roller 14 and the press roller 15. The recording unit 2 includes a developing device 16, a cleaning mechanism 17, a corona charger 18, a photosensitive drum 19, a transfer roller 20, an exposure device 21, and a fixing roller 22 for recording on the conveyed paper. The cleaning mechanism 17 cleans the surface of the photoconductive drum 19 by capturing foreign particles such as residual toner and paper dust attached to the surface of the photoconductive drum 19 after the transfer with a cleaning roller. The corona charger 18 uniformly charges the surface of the photosensitive drum 19 by corona discharge from the discharge wire. An electrostatic latent image is formed on the uniformly charged photosensitive drum 19 by exposing the photosensitive drum 19 in accordance with an image recording signal. Then, the toner in the developing device 16 is transferred to the electrostatic latent image formed on the photosensitive drum 19 to visualize the electrostatic latent image. The transfer roller 20 is installed at a position facing the photosensitive drum 19 with the paper interposed therebetween, and a toner image formed on the surface of the photosensitive drum 19 is transferred to the paper when a predetermined voltage is applied. The transferred toner image is sandwiched between the fixing roller 22 and the press roller 23 and heated and pressed to be fixed on the paper. The fixed sheet is sandwiched between the sheet discharge roller 24 and the press roller 25 and is carried out to the sheet discharge tray 10.

  Further, a manual paper feed mechanism and a reverse conveyance mechanism are provided on the side surface of the apparatus main body, and when performing manual paper feed, the side cover 26 is opened and the paper is inserted into the paper feed roller 27. . The inserted paper is conveyed to the feed roller 14 and the press roller 15 by the paper feed roller 27 and recording operation is performed. Also, when performing reverse conveyance, the paper recorded on one side is once sandwiched between the paper discharge roller 24 and the press roller 25 and then conveyed, and then the paper discharge roller 24 is rotated in reverse to be conveyed to the reverse conveyance path. Then, the feed roller 28 and the press roller 29, and the feed roller 30 and the press roller 31 are transported downward by two pairs of transport rollers. Then, the sheet is conveyed again to the feed roller 14 and the press roller 15 and a recording operation is performed on the other side, and recording is performed on both sides of the sheet.

  FIG. 2 is a schematic diagram illustrating a circuit configuration in the recording unit 2. A recording control unit 40 that controls the entire recording operation includes a charging voltage application circuit 41 that applies a charging voltage to the discharge wire 32 of the corona charger 18, a development that applies a development voltage and a supply voltage to the developing roller 33 and the supply roller 34. A control signal is transmitted to a cleaning voltage application circuit 43 that applies a predetermined voltage to the voltage application circuit 42, the cleaning roller 35, the collection roller 36, and the sponge body 37, and voltage control of each member is performed. Note that the recording control unit 40 also performs voltage control of members such as the transfer roller 20 and the fixing roller 22, but is omitted in FIG. Further, the recording control unit 40 performs exposure control of the exposure device 21 based on the image signal, and forms an electrostatic latent image on the surface of the photosensitive drum 19 uniformly charged by the corona charger 18.

  The recording control unit 40 transmits a control signal to the main motor (RX) 44 and the sub motor (DUP) 45 to perform rotational drive control. The main motor 44 is based on a control signal from the recording control unit 40, and includes a pickup roller 13, a feed roller 14, a cleaning roller 35, a collection roller 36, a photosensitive drum 19, a supply roller 34, a developing roller 33, a transfer roller 20, The fixing roller 22 is driven to rotate. Further, the paper discharge roller 24 is rotated in the direction of discharging the paper via the clutch by the rotational driving force from the main motor 44. The sub motor 45 rotates the feed rollers 29 and 31 based on a control signal from the recording control unit 40 and also rotates the paper discharge roller 24 in the direction of reversing and conveying the sheet via the clutch.

  FIG. 3 shows an external perspective view of the wire cleaning mechanism 50 for the discharge wire 32. FIG. 3 is an external perspective view of a drum unit in which the cleaning mechanism 17, the corona charger 18, and the photosensitive drum 19 are unitized. The wire cleaning mechanism 50 is a screw transport provided in parallel with the extending direction of the discharge wire 32. It comprises a member 51, a cleaning member 52 conveyed by the screw conveying member 51, and a drive mechanism 53 that rotationally drives the screw conveying member 51. The drive mechanism 53 includes a motor 54, a transmission gear train 55 that transmits the drive of the motor 54 to the screw conveying member 51, and a bracket 56 that supports the motor 54 and the transmission gear train 55.

  FIG. 4 is a schematic side view of the vicinity of the drive mechanism 53 as viewed from a direction orthogonal to the direction in which the discharge wire 32 is stretched. The discharge wire 32 is stretched around the frame 100 (only one is shown in the figure), and a screw conveying member 51 is rotatably supported on the frame 100 above the discharge wire 32. In the screw conveying member 51, screw blades 58 are fixed spirally around a screw shaft 57 that is pivotally supported by the frame 100. A rotation gear 59 is fixed on the drive mechanism 53 side of the screw shaft 57, and the rotation gear 59 meshes with the transmission gear train 55. The cleaning member 52 has a pair of sponge bodies that sandwich the discharge wire 32 mounted in the holding frame 60, and a moving member 61 that fits the screw blades 58 is fixed to the holding frame 60. A cushion spring 62 is attached to the side surface of the holding frame 60.

  When the screw conveying member 51 is rotated by the driving mechanism 53, the moving member 61 is moved along the extending direction of the discharge wire 32 by the rotation of the screw blade 58. Therefore, the sponge body in the holding frame 60 moves while sliding on the discharge wire 32, and the dirt attached to the surface of the discharge wire 32 is wiped off by the sponge body and cleaned. In order for the cleaning member 52 to reciprocate the discharge wire 32, the motor may be rotated in the opposite direction after rotating the motor by the number of rotations set in advance by the drive mechanism 53. The arrival of the cleaning member 52 may be detected by a detection mechanism provided at the end, and may be rotated in the opposite direction to reciprocate.

  FIG. 5 is a schematic diagram showing a circuit configuration for cleaning the discharge wire 32 by the cleaning member 52. As described above, the cleaning member 52 includes the holding frame 60 that holds the pair of sponge bodies 63 a and 63 b that sandwich the discharge wire 32, and the moving member 61 fixed to the holding frame 60 rotates the screw conveying member 51. To move. A constant current source 60 is connected to the discharge wire 32, and a predetermined voltage is applied to discharge from the discharge wire 32. A grid 64 is installed between the discharge wire 32 and the photosensitive drum 19, and the ion flow generated by the discharge is attracted to the grid 64 and reaches the surface of the photosensitive drum 19 to be charged.

  The discharge voltage applied to the discharge wire 32 is detected by a voltage detection circuit 71 connected to the constant current source 70. Further, a leakage current detection circuit 73 is connected to the grid 64 to detect the discharge current.

  The discharge voltage detected by the voltage detection circuit 71 and the discharge current detected by the leakage current detection circuit 73 are transmitted to the recording control unit 40, and the recording control unit 40 controls driving of the motor driver 72 based on these discharge detection signals. And control to perform the cleaning operation. The recording control unit 40 is determined to apply a voltage from the constant current source 70 to the discharge wire 32 and discharge it, and to determine whether or not to perform cleaning based on a discharge detection signal associated therewith, and to perform cleaning. In this case, an operation control unit 47 that performs a cleaning operation and causes the determination control unit 46 to perform determination control again is provided.

  Since it becomes difficult to discharge when dirt is attached to the discharge wire 32, it is necessary to apply a higher voltage. For this reason, when a predetermined threshold value is set and the voltage value exceeds the threshold value, cleaning is performed. do it. In addition, regarding the leakage current, the current value becomes small when the discharge wire 32 is difficult to discharge. Therefore, cleaning may be performed when the current value is a predetermined value or less. For example, when the diameter of the discharge wire is 30 μm to 100 μm, a leak current value of 200 μA to 300 μA is desirable in order to stably supply the generated ion flow. In this case, the applied voltage is 5.5 kV to 6 kV. The threshold value may be set based on such current value and voltage value.

  FIG. 6 shows a flow for detecting the discharge voltage in the discharge state during the rotation process of the photosensitive drum and performing the cleaning process after the rotation is stopped. When the discharge is started (S100), the discharge voltage is detected by the voltage detection circuit 61 (S101), and the discharge voltage detected after the discharge is finished and the rotation of the photosensitive drum is stopped (S102a, S102b). It is determined whether or not cleaning is performed based on whether the voltage is equal to or higher than a predetermined voltage (S103). If the detected voltage is equal to or higher than the predetermined value, it is determined that cleaning is to be performed, and cleaning operation processing is performed (S104). For example, the cleaning operation is performed by sliding the cleaning member 52 on the discharge wire 32 several times. After the cleaning is completed, a voltage is applied to the discharge wire again, and a series of processes including discharge start → discharge voltage detection → discharge end is performed (S105a to c), and it is determined whether the detected voltage is equal to or higher than a predetermined value for cleaning. It is determined whether or not it is necessary (S106). When it is determined that cleaning is necessary again when the detected voltage is equal to or higher than a predetermined value, an error message is displayed to prompt the user to replace the discharge wire (S107). If the detected voltage is lower than the predetermined value in step S103 or S106, the process proceeds to standby processing as it is (S111).

  As described above, only the discharge voltage is detected during the rotation process of the photosensitive drum, and the cleaning operation is performed after the rotation of the photosensitive drum is stopped. Therefore, the cleaning is performed without affecting the image forming process. Can do.

  FIG. 7 shows a flow in the case where the cleaning process is performed at a set time (eg, midnight) as a predetermined parameter while the rotation of the photosensitive drum is stopped. First, it is checked whether or not the set time has been reached (S200), and if the set time has been reached, it is checked whether or not the photosensitive drum is stopped rotating (S201). If the photosensitive drum is rotating, the process ends. When the rotation of the photosensitive drum is stopped, a voltage is applied to the discharge wire to perform a series of processes such as discharge start → discharge voltage detection → discharge end (S202a to c), and the detected voltage is equal to or higher than a predetermined value. It is determined whether or not cleaning is necessary (S203). When it is determined that the detection voltage is equal to or higher than the predetermined value and cleaning is performed, a cleaning operation process is performed (S204). In the cleaning operation process, for example, the cleaning operation is performed by sliding the cleaning member 52 on the discharge wire 32 several times. It is necessary to apply a voltage to the discharge wire again after the cleaning is completed, perform a series of processes including discharge start → discharge voltage detection → discharge end (S205a to c), and perform cleaning depending on whether the detected voltage is equal to or higher than a predetermined value. It is determined whether or not there is (S206). If it is determined that cleaning is necessary again at a predetermined value or more, an error message is displayed to prompt the user to replace the discharge wire (S207). If the detected voltage is lower than the predetermined value in step S203 or S206, the process proceeds to standby processing as it is (S208).

  As described above, if the cleaning process is performed while the rotation of the photosensitive drum is stopped, the image forming process is not affected. Further, in the above example, it is performed at the set time, but it may be performed when the number of sheets subjected to image forming processing is accumulated by a counter and the counted number reaches the set number. Similarly, the operation time of the apparatus can be counted and performed when the accumulated time becomes equal to or greater than a set value.

1 is a schematic sectional view of an entire image forming apparatus according to an embodiment of the present invention. It is a schematic block diagram of the circuit structure in a recording part. It is an external appearance perspective view regarding the cleaning mechanism of a discharge wire. FIG. 4 is a partially enlarged side view of the cleaning mechanism shown in FIG. 3. It is the schematic which shows the circuit structure for performing a cleaning process. It is a flow in the case of performing a cleaning process. It is another flow in the case of performing a cleaning process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Recording part 3 Paper feeding part
17 Cleaning mechanism
18 Corona charger
19 Photosensitive drum
32 discharge wire
40 Recording controller
50 Wire cleaning mechanism

Claims (3)

  An image carrier, a charging unit for charging the surface of the image carrier by a corona discharge member, an exposure unit for exposing the charged surface of the image carrier to form an electrostatic latent image, and a surface on the surface of the image carrier. Development means for making a visible image by attaching toner to the formed electrostatic latent image, transfer means for transferring the toner image formed on the surface of the image carrier to paper, and rotation control of the image carrier In addition, in the image forming apparatus including a control unit that controls each of the units so as to form an image on a sheet, a cleaning unit that cleans dirt adhering to the corona discharge member, and a discharge applied to the corona discharge member A discharge detection means for detecting a voltage or a discharge current, and the control means applies a discharge voltage to the corona discharge member and controls the cleaning means based on a detection signal of the discharge detection means during voltage application. A cleaning determination control means for determining whether or not to perform cleaning, and when the cleaning determination control means determines to perform cleaning, cleaning is performed by the cleaning means while the rotation of the image carrier is stopped, and the cleaning determination is performed after cleaning. An image forming apparatus comprising: a cleaning operation control unit that performs determination by the control unit.   The image forming apparatus according to claim 1, wherein the cleaning determination control unit is periodically performed based on a predetermined parameter.   The image forming apparatus according to claim 1, wherein the cleaning determination control unit is performed while the rotation of the image carrier is stopped.

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