JP2006343524A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus demonstrating sufficient cleaning effect even for toner which is welded or fusion bonded to a corona discharging member. <P>SOLUTION: A cleaning member 52 is provided with a retaining frame 60 retaining a pair of sponge bodies 63a and 63b holding a discharge wire 32 and cleaning of the discharge wire 32 is carried out by having a moving member 61 which is fixed to the retaining frame 60 moved by rotation of a screw transporting member 51. Heat resistant resin material is used in the sponge body and the retaining frame is composed of a planar heater. Then, the retaining frame 60 is energized to generate heat while having the cleaning member 52 slid on the discharge wire 32 and the discharge wire 32 is heated through the sponge body. <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

  As described above, toner, paper powder, and external additives (silica or the like) contained in the toner adhere to the discharge wire. Paper dust, silica, etc. can be removed to some extent by wiping the discharge wire, but when the toner is welded or fused, the toner welded or fused to the discharge wire is firmly attached, Cannot be removed by wiping with a sponge. Even in the above-mentioned patent documents, a sufficient cleaning effect cannot be exerted on such welded or fused toner. Therefore, when the welded or fused toner gradually adheres and adheres, It will affect the discharge.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of exhibiting a sufficient cleaning effect even with toner fused or fused to a corona discharge member.

  An 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 image forming process that forms a toner image on the surface of the image carrier and transfers the toner image to a sheet. The image forming apparatus includes: a cleaning unit that cleans dirt attached to the corona discharge member by a cleaning member; and a heating unit that heats the cleaning member. The heating means is further provided with a heating control means for controlling the corona discharge member to be heated through the cleaning member. Furthermore, the heating control means controls the heating means so that the corona discharge member is at or above the glass transition temperature of the toner. Furthermore, based on the detection signal of the discharge detection means for detecting the discharge voltage or discharge current applied to the corona discharge member, and the detection signal of the discharge detection means during the voltage application while applying the discharge voltage to the corona discharge member A cleaning determination control means for determining whether or not to perform cleaning by the cleaning means, and cleaning by the cleaning means when the cleaning determination control means determines to perform cleaning and re-determination by the cleaning determination control means after cleaning. A normal cleaning operation control means to perform and cleaning by the cleaning means while heating the corona discharge member by the heating control means when it is determined to perform cleaning by redetermination by the cleaning determination control means and after the cleaning A heating cleaning operation control means for performing re-determination by the cleaning determination control means is provided.

  By having the above configuration, a heating means for heating the cleaning member that cleans the corona discharge member is provided. Therefore, when the cleaning member is heated during the cleaning operation, the corona discharge member is also heated. Therefore, the toner fused or fused to the corona discharge member is softened by heating and can be easily removed by the cleaning member. Since the toner softens when the glass transition temperature (70 ° C. to 80 ° C.) or higher is reached, by controlling the heating of the cleaning member by the heating means so that the corona discharge member is equal to or higher than the glass transition temperature of the toner, A sufficient cleaning effect can be exhibited. In this case, a heat-resistant material that can withstand such heating is preferably used for the cleaning member. An example of the heat resistant material is polyimide resin.

  When the corona discharge member is cleaned by the cleaning means, a discharge detection means for detecting a discharge voltage or a discharge current applied to the corona discharge member is provided, and the discharge voltage is applied to the corona discharge member and between the voltage application. A cleaning determination control unit that determines whether or not to perform cleaning by the cleaning unit based on a detection signal of the discharge detection unit, and a cleaning determination that is performed by the cleaning unit when the cleaning determination control unit determines to perform cleaning and a cleaning determination after cleaning By providing a normal cleaning operation control means for performing re-determination by the control means, it is accurately determined by the cleaning determination control means whether or not cleaning is necessary, and first the cleaning by the cleaning member is performed by the normal cleaning operation control means. I do. By such a cleaning operation, dirt that can be easily removed such as paper dust is cleaned, and the cleaning effect is determined. If there is a cleaning effect at this stage, it is not necessary to perform heating control by the heating means, and power consumption required for heating can be avoided. At this stage, if it is determined that cleaning is to be performed by re-determination by the cleaning determination control unit, there is a high possibility that there remains a toner that has not been easily removed. Then, while the corona discharge member is heated by the heating control means, cleaning by the cleaning means is performed, and after the cleaning, the determination again by the cleaning determination control means is performed. The fused or fused toner is softened and easily removed by the heat cleaning operation control means, so that a sufficient cleaning effect can be exhibited. If cleaning is performed by the heating cleaning operation control means, and it is determined that cleaning is required by repeated determination by the cleaning determination control means, it is determined that the life is due to a discharge failure due to another factor other than the fused or fused toner. Error display or the like.

  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. The sponge body of the cleaning member 52 is made of a material having high heat resistance, and for example, a polyimide resin material is used. Further, the holding frame 60 for holding the sponge body is composed of a planar heater and also functions as a heating means. As the planar heater used for the holding frame 60, a known heater can be used. For example, a sheet heater made by applying and impregnating carbon paint to a fabric woven with conductive wires and heat-sealing with a heat-resistant synthetic resin sheet from both sides, and a metal foil sandwiched from both sides with a heat-resistant resin sheet For example, a molded planar heater may be used. Both of them generate heat uniformly over the entire surface and are flexible, and are suitable for being held in close contact with the sponge body. Further, the sheet heater can be heated to about 200 ° C. If a material having high heat resistance is used as the sponge body, the discharge wire 32 is heated to the glass transition temperature (70 ° C. to 80 ° C.) of the toner through the sponge body. can do.

  When cleaning the discharge wire 32 by the cleaning member 52, the screw conveying member 51 is rotated by the drive mechanism 53, and 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. Then, as will be described later, the holding frame 60 is energized and heated as necessary, and the discharge wire 32 is heated through the sponge body, so that the toner welded or fused to the discharge wire 32 is softened by the sponge body. Remove.

  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. Further, when the holding frame 60 is in a heated state, the moving speed of the cleaning member 52 is adjusted so as to keep the discharge wire 32 at or above the glass transition temperature of the toner.

  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 70 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 moving member 61 fixed to the holding frame 60 is made of metal and is electrically connected to the planar heater of the holding frame 60, and the screw conveying member 51 is also made of metal and comes into electrical conduction by contacting the moving member 61. Become. Therefore, when the screw conveying member 51 is energized by the heating control circuit 74, the energization is also performed from the moving member 61 to the planar heater of the holding frame 60, and the heating control is performed. The heating control circuit 74 adjusts the amount of current to be applied based on the control signal from the recording control unit 40 so that the amount of heat generated by the planar heater appropriately heats the discharge wire 32 through the sponge body. The holding frame 60 may be energized by installing a rail-like conductive member along the moving path of the cleaning member 52 so that the holding frame 60 is always in contact with the conductive member.

  When a discharge voltage is applied to the discharge wire 32 from the constant current source 70, the discharge voltage is detected by the voltage detection circuit 71 connected to the constant current source 70. Further, a leakage current detection circuit 63 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. When it is determined that cleaning is necessary as a result of redetermination by the determination control unit 46, the operation control unit 47 controls the heating control circuit 74 to start heating and heat cleaning by the heated cleaning member 51. And the determination control unit 46 performs control so that the determination is performed again.

  When it is determined whether or not cleaning is performed based on the detection signal of the voltage detection circuit 71, it becomes difficult to discharge when dirt is attached to the discharge wire 32, so that a higher voltage is applied, and therefore a predetermined threshold value is set. Cleaning may be performed when the voltage value is set to a threshold value or more. 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 performing the cleaning process of the discharge wire. When the discharge is started (S100), the discharge voltage is detected by the voltage detection circuit 71 (S101), and the discharge voltage detected after the discharge is completed 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). In this case, the discharge voltage is detected when the discharge wire is discharged before the rotation of the photosensitive drum is stopped.

  If the detected voltage is equal to or higher than the predetermined value, it is determined that cleaning is to be performed, and normal 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. It is necessary to apply a voltage to the discharge wire again after the cleaning is completed, and perform a series of processes such as discharge start → discharge voltage detection → discharge end (S105a to c), and cleaning is performed based on whether the detected voltage is equal to or higher than a predetermined value It is determined again whether or not there is (S106). When it is determined that cleaning is necessary again when the detection voltage is equal to or higher than a predetermined value, a heat cleaning operation process is performed (S107). In the heat cleaning operation process, the heating control circuit 74 is operated to heat the holding frame 60 that is a planar heater, and the cleaning member 52 is slid on the discharge wire 32 several times to perform the heat cleaning operation.

  When the cleaning member 52 is heated, the discharge wire 32 is heated through the sponge bodies 63a and 63b, and the fused or fused toner is softened by the discharge wire 32 being in a temperature state higher than the glass transition temperature of the toner. Thus, the sponge bodies 63a and 63b can be easily removed.

  After the heat cleaning operation process, a voltage is applied to the discharge wire again, and a series of processes including discharge start → discharge voltage detection → discharge end is performed (S108a to c), and cleaning is performed depending on whether the detected voltage is equal to or higher than a predetermined value. It is determined again whether or not it is necessary (S109). 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 (S110). If the detected voltage is lower than the predetermined voltage in step S103, S106, or S109, the process proceeds to standby processing.

  In the example described above, the heating cleaning operation process is performed after the normal cleaning operation process is performed, but the heating cleaning operation process may be performed from the beginning. For example, when the heat cleaning operation process is performed once, it is considered that dirt is easily attached to the discharge wire. Therefore, the next cleaning process may be performed from the heat cleaning operation process.

  In the above example, the discharge voltage is detected using the discharge before stopping the rotation of the drum, and the cleaning operation is performed after the rotation stops. However, the cleaning process is performed by discharging at an unused time such as midnight. May be performed. Also, when the number of sheets on which image formation processing has been performed is accumulated with a counter and is performed when the counted number reaches the set number, or when the cumulative operation time exceeds the set value by counting the operating time of the device It can also be done.

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.

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 (4)

  An image forming apparatus comprising: an image bearing member; a charging unit that charges the surface of the image bearing member with a corona discharge member; and an image forming processing unit that forms a toner image on the surface of the image bearing member and transfers the toner image onto a sheet. An image forming apparatus comprising: a cleaning unit that cleans dirt adhered to the corona discharge member by a cleaning member; and a heating unit that heats the cleaning member.   The image forming apparatus according to claim 1, further comprising a heating control unit that controls the heating unit to heat the corona discharge member through the cleaning member.   The image forming apparatus according to claim 2, wherein the heating control unit controls the heating unit such that the corona discharge member is equal to or higher than a glass transition temperature of toner.   A discharge detection means for detecting a discharge voltage or a discharge current applied to the corona discharge member; and the cleaning means based on a detection signal of the discharge detection means for applying a discharge voltage to the corona discharge member and applying the voltage. 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, and re-determination is performed by the cleaning determination control means after cleaning. When it is determined that cleaning is performed by redetermination by the cleaning operation control unit and the cleaning determination control unit, the heating control unit performs cleaning by the cleaning unit while heating the corona discharge member, and the cleaning determination is performed after cleaning. 4. An image form according to claim 2, further comprising a heating cleaning operation control means for performing re-determination by the control means. Apparatus.

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