JP2013161036A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of preventing wear of a cleaning member that cleans a charging member of a charger to extend the life of the cleaning member.SOLUTION: An image forming apparatus includes a photoreceptor drum 32, a charging line 51, a cleaning member 52, a motor for moving a cleaning member 55, and a charger shield member 60. After completion of a print job by the image forming apparatus, in response to measurement of a lapse of predetermined time by a time measurement unit 124, the motor for moving a cleaning member 55 moves both the cleaning member 52 and the charger shield member 60 along the charging line 51. Accordingly, the charging line 51 and the photoreceptor drum 32 are shielded by the charger shield member 60.

Description

  The present invention relates to an image forming apparatus applied to a copying machine, a facsimile, a printer, and the like.

  Conventionally, in an image forming apparatus (copying machine) that performs copying by an electrophotographic process, an electrostatic latent image corresponding to an original image is formed on the surface of a photosensitive drum, and a visible image obtained by developing the electrostatic latent image is recorded. Copying is done by transferring to paper. That is, the surface of the photosensitive drum is first charged by a charger, then exposed to form an electrostatic latent image, developed with toner, and transferred to a toner image on paper, and finally applied to the photosensitive drum. The process ends with the charge removal of the remaining electrostatic latent image. Thereafter, the image forming apparatus repeats copying by continuing the rotation of the photosensitive drum while repeating the above steps.

  Thus, as copying is repeated in the image forming apparatus, ozone is generated in the charger due to the corona discharge, and accordingly, charged products (discharge products) such as nitrogen oxides (NOx) accumulate. The discharge product accumulated in the charger moves from the charger to the surface of the photosensitive drum when the rotation of the photosensitive drum is stopped.

  The photosensitive drum is deteriorated by such discharge products. Moisture tends to adhere to the deteriorated portion of the photosensitive drum, and a flow (image flow) occurs in the charged charge. As a result, a defect occurs in the printed matter generated by the image forming apparatus. This tendency is particularly noticeable in high temperature and high humidity environments. During sleep at night when the image forming apparatus is not used, the temperature inside the image forming apparatus becomes low, and the photosensitive drum is not rotated for a long time.

  Conventionally, there is a method of preventing the adhesion of discharge products to the photosensitive drum by removing the moisture adhering to the photosensitive drum by heating the photosensitive drum with a drum heater. However, such a discharge product adhesion preventing method uses a drum heater to heat the photosensitive drum, which increases power consumption.

  Accordingly, a method has been proposed in which a charger shielding member is attached between the photosensitive member and the charger, and the discharge product is blocked by the charger shielding member so as not to adhere to the photosensitive drum (see, for example, Patent Document 1). In addition, a technique for reducing cost is proposed by using a driving source for a cleaning member for cleaning a charging member (wire) of a charger and a driving source for opening and closing a charger shielding member as the same driving source ( For example, see Patent Document 2).

Japanese Patent Application Laid-Open No. 07-104565 JP 2007-72212 A

  The image forming apparatus configured to share the driving source for the cleaning member for cleaning the charging member of the charger and the driving source for opening and closing the charger shielding member in the conventional example has the following problems. In order to prevent discharge products from adhering to the photosensitive drum every time a print job is completed in the image forming apparatus, when the charger shielding member is closed, the driving source is shared, so that the cleaning member is also used together with the charger shielding member. Since it is driven, there is a problem that the durability of the cleaning member is reduced.

  Further, it is known that many discharge products are generated in an environment where the image forming apparatus is installed in a hot and humid environment. When a large amount of printing is performed by the image forming apparatus, a large amount of discharge products are generated. In these cases, the discharge product causes a flow in the charged charge, resulting in an image flow. In order to prevent image flow, it is necessary to prioritize image quality and close the charger shielding member earlier than usual. However, as described above, when the charger shielding member is closed, the cleaning member is driven together with the charger shielding member, so that there is a problem that durability of the cleaning member is reduced.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of preventing wear of a cleaning member for cleaning a charging member of a charger and extending the life of the cleaning member.

  To achieve the above object, the present invention provides an image carrier that carries an image, a charging member that charges the image carrier, a cleaning member that cleans the charging member, and the charging member attached to the cleaning member. A shielding member that shields between a member and the image carrier, a driving unit that moves the cleaning member and the shielding member along the charging member, a time measuring unit that measures time, and the image forming apparatus After the completion of the image forming job by the above, the shielding member is moved by moving the cleaning member and the shielding member along the charging member by the driving unit in response to the passage of a predetermined time by the time measuring unit. Control means for shielding between the charging member and the image carrier by a member.

  According to the present invention, in the configuration in which the driving source of the cleaning member that cleans the charging member and the driving source of the shielding member that shields between the charging member and the image carrier are shared, the charging member and the image carrier are held by the shielding member. The timing of shielding between the body and the body is shifted for a certain time, not immediately after image formation. This eliminates the need for the cleaning member to clean the charging member even when the charging member does not need to be cleaned, thereby preventing wear of the cleaning member and extending the life of the cleaning member.

1 is a configuration diagram showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a schematic diagram illustrating a configuration of a charger of the image forming apparatus. 2 is a block diagram illustrating a configuration of a control system of the image forming apparatus. FIG. 6 is a flowchart illustrating a control flow for closing a charger shielding member of the image forming apparatus. 5 is a flowchart showing a continuation of FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a configuration diagram showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention.

  In FIG. 1, the image forming apparatus includes an image forming apparatus main body 1 having an image reader unit 20 and a printer unit 30, and a document feeding unit 10, and is configured as a copying machine that forms an image in an electrophotographic process. Yes. The image reader unit 20 includes a scanner unit 21, mirrors 22a, 22b, and 22c, a lens 23, and an image sensor 24. The printer unit 30 includes an exposure control unit 31, a photosensitive drum 32 (image carrier), a transfer unit 36, a developing unit 40, a primary charger 50, a charger shielding member 60, a fixing unit 37, and the like. In the description of FIG. 1, the description of parts that are not directly related to the gist of the present invention will be simplified.

  The document feeder 10 feeds the documents set on the document tray one by one, flows on the platen glass 11 through a curved path, transports it through the reading position, and then discharges it to the sheet discharge tray 12. . When the original passes through the flow reading position, the original image is read by irradiating light from a lamp (not shown) of the scanner unit 21 to the original (original flow reading). The reflected light from the document forms an image on the imaging surface of the image sensor 24 via the mirrors 22a, 22b, 22c and the lens 23.

  When transporting and reading a document, the document is transported in the sub-scanning direction (document transport direction) while the image sensor 24 reads the document image line by line in the main scanning direction (direction orthogonal to the document transport direction). Then, the entire original image is read. The image sensor 24 optically reads an image from a document, converts it into image data, and outputs the image data. The image data is subjected to a prescribed process by an image signal control unit (not shown) and then input as a video signal to the exposure control unit 31 of the printer unit 30.

  It is also possible to read the document by transporting the document onto the platen glass 11 by the document feeding unit 10 and stopping it at the specified position, and scanning the scanner unit 21 in this state (document fixed reading). The user can also read the document by lifting the document feeding unit 10 and placing the document on the platen glass 11 and scanning the scanner unit 21 (fixed document reading).

  The exposure control unit 31 of the printer unit 30 modulates and outputs the laser beam based on the input video signal. The laser beam is applied to the surface of the photosensitive drum 32 while being scanned by a polygon mirror. An electrostatic latent image corresponding to the scanned laser beam is formed on the surface of the photosensitive drum 32. Here, the exposure control unit 31 outputs a laser beam so that an image that is not a mirror image is formed at the time of fixed document reading.

  The printer unit 30 is provided with a plurality of paper feed cassettes 33 for storing paper so that the paper can be pulled out from the main body of the image forming apparatus. When paper is fed during image formation, sheets are fed one by one to the transfer position of the photosensitive drum 32 by the separation paper feeding unit 33a corresponding to the corresponding paper feeding cassette 33. Further, the printer unit 30 is provided with a reversing path 34 for reversing the paper and a double-sided transport path 35 for transporting the reversed paper to the transfer position again during double-sided recording in which image formation is performed on both sides of the paper.

  Around the photosensitive drum 32, a transfer unit 36, a developing unit 40, a primary charger (hereinafter referred to as a charger) 50, and a charger shielding member 60 are disposed. For example, amorphous silicon is used as the material of the photosensitive drum 32. When an electrostatic latent image is formed on the photosensitive drum 32, first, a voltage is applied to the charger 50 to uniformly charge the surface of the photosensitive drum 32 with a specified charging potential. Subsequently, exposure is performed by the exposure control unit 31 so that the image portion on the charged photosensitive drum 32 has a prescribed exposure potential. The exposure control unit 31 forms an electrostatic latent image corresponding to the read image of the document by turning on / off based on the image signal.

  The developing unit 40 is configured such that the developing roller 41 is always in contact with the photosensitive drum 32, and at the time of development, the electrostatic latent image on the photosensitive drum 32 is developed with a developer (toner) by switching to a high voltage bias. On the other hand, at the timing synchronized with the start of laser beam irradiation on the photosensitive drum 32, the paper is conveyed from the corresponding paper feed cassette 33 or the double-sided conveyance path 35 to the transfer position between the photosensitive drum 32 and the transfer unit 36. .

  The developer image formed on the photosensitive drum 32 is transferred to a sheet by the transfer unit 36. The sheet on which the developer image is transferred is conveyed to the fixing unit 37. The fixing unit 37 fixes the developer image on the paper by heating and pressing the paper. The sheet that has passed through the fixing unit 37 is discharged from the printer unit 30 to the tray 70 via the discharge roller 38.

  Here, when the sheet is discharged with the image forming surface facing downward, the sheet that has passed through the fixing unit 37 is guided to the reverse path 34 by a switching operation of a flapper (not shown). After the trailing edge of the sheet passes through the flapper, the sheet is switched back and discharged from the printer unit 30 by the discharge roller 38.

  Further, when image formation is performed by feeding hard paper such as OHP paper from the manual paper feed unit 39, the paper is discharged by the discharge roller 38 with the image forming surface facing upward without guiding the paper to the reverse path 34. To do. Further, during double-sided recording in which image formation is performed on both sides of the paper, the paper is guided to the reversing path 34 by a switching operation of a flapper (not shown) and then conveyed again to the transfer position via the double-sided conveyance path 35.

  FIG. 2 is a schematic diagram illustrating a configuration of a charger of the image forming apparatus.

  In FIG. 2, the charger 50 includes a charging line 51 (charging member), a cleaning member 52, a power transmission unit 53, a winding unit 54, a cleaning member moving motor 55 (driving means), and a charger shielding member position detection unit 56. The charger shielding member 60 (shielding member) is provided.

  The charging line 51 is disposed along the longitudinal direction of the charger 50. During the charging operation, the photosensitive drum 32 (see FIG. 1) is charged by applying a high voltage to the charging wire 51 of the charger 50 from a power source (not shown). The cleaning member 52 is provided so as to be movable along the charging wire 51 between both ends in the longitudinal direction of the charging wire 51.

  The charger shielding member 60 is a member that shields between the charging wire 51 and the photosensitive drum 32. Both ends in the longitudinal direction are attached to the cleaning member 52 and the winding unit 54, respectively. It is wound up by the part 54. The cleaning member moving motor 55 is coupled to a power transmission unit 53 disposed in parallel with the charging wire 51. The cleaning member 52 and the charger shielding member 60 are moved in conjunction with a direction (longitudinal direction of the charging line 51) orthogonal to the sheet conveyance direction via the power transmission unit 53 by driving the cleaning member moving motor 55. .

  When the image forming (printing) operation is continuously performed in the image forming apparatus, the electrostatic latent image formed on the photosensitive drum 32 is formed on the charging line 51 of the charger 50 disposed on the outer peripheral side of the photosensitive drum 32. The toner used for the development is attached. Therefore, it is necessary to clean the charging line 51 using the cleaning member 52. During the cleaning operation, the charging member 51 is cleaned by reciprocating the cleaning member 52 between both ends in the longitudinal direction of the charging wire 51, for example, about five times.

  Since the charger shielding member 60 is attached to the cleaning member 52, the charger shielding member 60 opens and closes in conjunction with the operation of the cleaning member 52. In a state in which the charger shielding member 60 is closed (a state in which the space between the charging wire 51 and the photosensitive drum 32 is shielded), the charger shielding member 60 is disposed between the winding portion 54 and the longitudinal ends of the charging wire 51. It is drawn out and expanded. In a state where the charger shielding member 60 is opened (a state where the shielding between the charging wire 51 and the photosensitive drum 32 is released), the charger shielding member 60 is wound around the winding unit 54.

  When the cleaning member 52 is moved to one end side in the longitudinal direction of the charging wire 51 (right end in FIG. 2) by the cleaning member moving motor 55, the charger shielding member 60 is linked to the operation of the cleaning member 52. 54 is paid out. As a result, the charging wire 51 and the photosensitive drum 32 are closed (shielded).

  When the cleaning member 52 is moved to the other end side in the longitudinal direction of the charging wire 51 (left end in FIG. 2) by the cleaning member moving motor 55, the charger shielding member 60 is wound in conjunction with the operation of the cleaning member 52. The portion 54 is wound up. As a result, the charging wire 51 and the photosensitive drum 32 are opened (the shield is released).

  The charger shielding member position detection unit 56 is provided at a location along the movement path of the charger shielding member 60. The charger shielding member position detection unit 56 detects the position of the charger shielding member 60, that is, detects that the charger shielding member 60 is opened in conjunction with the operation of the cleaning member 52.

  FIG. 3 is a block diagram illustrating a configuration of a control system of the image forming apparatus.

  In FIG. 3, the image forming apparatus performs controller 100 for managing print jobs, image formation for forming a toner image obtained by developing the electrostatic latent image formed on the photosensitive drum 32, and paper conveyance control. A printer control unit 110.

  The controller unit 100 includes a CPU 101, a RAM 102, a ROM 103, an external interface (I / F) unit 104, a PDL control unit 105, an internal interface (I / F) unit 106, and an operation unit 107. The printer control unit 110 includes a CPU 111, a RAM 112, a ROM 113, a device control unit 114, and an internal interface (I / F) unit 115.

  In the controller unit 100, the CPU 101 controls each unit of the image forming apparatus. A RAM 102 and a ROM 103 are connected to the CPU 101 via an address bus and a data bus. A control program is written in the ROM 103. The RAM 102 stores data for the CPU 101 to perform various processes.

  The CPU 101 is connected to an external I / F unit 104, a PDL control unit 105, and an internal I / F unit 106. The external I / F unit 104 communicates with the outside of the image forming apparatus. The PDL control unit 105 performs processing, accumulation, and image processing on the received data. The internal I / F unit 106 communicates with the printer control unit 110.

  Further, the CPU 101 is connected with an operation unit 107 having a display unit and various keys. The CPU 101 controls display on the operation unit 107 and key input. The user instructs the CPU 101 to switch the display of the operation unit 107 through key input. The CPU 101 displays the operation state of the image forming apparatus and the operation mode set by key input on the operation unit 107.

  In the printer control unit 110, the CPU 111 performs basic control of the image forming operation. A RAM 112 and a ROM 113 are connected to the CPU 111 via an address bus and a data bus. The ROM 113 stores a control program and stores a control procedure and the like described later. The RAM 112 stores data for performing image forming operation processing.

  Further, a device control unit 114 and an internal I / F unit 115 are connected to the CPU 111. The device control unit 114 is an electric circuit including an input / output port and the like for controlling each component of the printer unit of the image forming apparatus. The internal I / F unit 115 exchanges an image signal and a timing signal with the controller unit 100 through the signal line 108.

  The CPU 111 receives an image signal via the controller unit 100 and the internal I / F unit 115 according to the contents of the control program, and controls the device control unit 114 to execute an image forming operation. The device control unit 114 includes a motor control unit 120, a charger shielding member position detection unit 56, a fixing control unit 122, a temperature / humidity measurement unit 123, and a time measurement unit (timer) 124.

  The motor control unit 120 controls driving of the cleaning member moving motor 55 that moves the cleaning member 52 and the charger shielding member 60 in conjunction with each other. The charger shielding member position detection unit 56 detects the position of the charger shielding member 60 (a state where the charger shielding member 60 is opened). The fixing control unit 122 controls the fixing unit 37. The temperature / humidity measurement unit 123 measures the temperature and humidity inside the image forming apparatus. The time measuring unit 124 measures time.

  Next, the operation of the image forming apparatus of the present embodiment having the above configuration will be described with reference to FIGS.

  4 and 5 are flowcharts showing a control flow for closing the charger shielding member of the image forming apparatus. This processing is executed by the CPU 111 of the printer control unit 110 of the image forming apparatus based on the control program.

  4 and 5, after the end of the print job (image formation job) in the image forming apparatus, the CPU 111 of the printer control unit 110 takes time until the user starts closing the charger shielding member 60 using the operation unit 107 in advance. Is determined (step S1). When the user has set the time from the end of the print job to the start of closing the charger shielding member 60, the CPU 111 sets the time for starting the time measuring unit (timer) 124 in advance by the user. (Step S2).

  When the user has not set the time from the end of the print job to the start of closing the charger shielding member 60 (when the setting value is −1), the CPU 111 causes the temperature / humidity measurement unit 123 to perform the image forming apparatus. The internal temperature is measured (step S3). Further, the CPU 111 measures the humidity inside the image forming apparatus by the temperature / humidity measuring unit 123 (step S4). Next, the CPU 111 calculates the amount of water contained in the image forming apparatus from the measured temperature and humidity (step S5).

  Hereinafter, the time set in the time measurement unit 124 (the time from the end of the print job to the start of closing the charger shielding member 60) is changed according to the calculated water content. The value of is an example and is not limited to a specific value. The time from the end of the print job to the start of closing the charger shielding member 60 can be adjusted.

  Next, the CPU 111 determines whether or not the amount of water contained in the image forming apparatus is 15 [g] or more (step S6). If the amount of water contained in the image forming apparatus is 15 [g] or more, the CPU 111 sets the set time of the time measuring unit 124 for closing the charger shielding member 60 to 10 [min] (step S7). ).

  When the amount of water contained in the image forming apparatus is not 15 [g] or more, the CPU 111 determines whether the amount of water contained in the image forming apparatus is less than 15 [g] and 13 [g] or more. (Step S8). When the amount of water contained in the image forming apparatus is less than 15 [g] and greater than or equal to 13 [g], the CPU 111 sets the set time of the time measuring unit 124 for closing the charger shielding member 60 to 30 [min]. (Step S9).

  If the moisture content contained in the image forming apparatus is not 13 [g] or more, the CPU 111 determines whether or not the moisture content contained in the image forming apparatus is less than 13 [g] and 6 [g] or more. (Step S10). When the amount of water contained in the image forming apparatus is less than 13 [g] and 6 [g] or more, the CPU 111 sets the set time of the time measuring unit 124 for closing the charger shielding member 60 to 60 [min]. (Step S11).

  When the amount of water contained in the image forming apparatus is not 6 [g] or more, that is, when the amount of water is less than 6 [g], the CPU 111 uses the time measuring unit 124 for closing the charger shielding member 60. The set time is set to 90 [min] (step S12).

  After the setting of the set time (setting means) for starting the time measuring unit 124 is completed in any of the above steps S7, S9, S11, and S12, the CPU 111 starts the operation of the time measuring unit 124 (step S13). Next, the CPU 111 determines whether or not the activation time of the time measurement unit 124 is the set time set in the corresponding step (a certain time has elapsed after the end of the image forming job) (step S14). ).

  If the activation time of the time measuring unit 124 is not the set time, the CPU 111 reads the internal I / F unit 115 and determines whether a new print job exists in the controller unit 100 (step S15). . When there is a new print job, it is not necessary to close the charger shielding member 60, so the CPU 111 stops the time measuring unit 124 (step S16) and ends this process. If there is no new print job, the CPU 111 determines again whether or not the activation time of the time measuring unit 124 is the set time (step S14).

  When the activation time of the time measuring unit 124 reaches the set time (YES in step S14), the CPU 111 sets the moving time of the cleaning member 52 and the charger shielding member 60 operating in conjunction with each other for a certain time (for example, 15 seconds). Is set in the time measuring unit 124 (step S17). Further, the CPU 111 moves the cleaning member in a direction in which the charger shielding member 60 operating in conjunction with the cleaning member 52 is closed (a direction in which the charger shielding member 60 shields between the charging wire 51 and the photosensitive drum 32). The motor 55 is driven (step S18).

  Next, the CPU 111 starts the operation of the time measurement unit 124 again (step S19), and waits until the activation time of the time measurement unit 124 reaches the set time set in the corresponding step (step S20). As a result, the charger shield member 60 shields between the charging wire 51 and the photosensitive drum 32.

  As described above, when the amount of water in the image forming apparatus is small and image flow is unlikely to occur, the time from the end of the print job to the start of closing the charger shielding member 60 is set longer. Thereby, the lifetime of the charging wire 51 and the cleaning member 52 can be lengthened. On the other hand, if the amount of moisture in the image forming apparatus is large and image flow is likely to occur, the time from the end of the print job to the start of closing the charger shielding member 60 is set short. Thereby, it is possible to suppress the occurrence of image flow.

  As described above, according to the present embodiment, in the configuration in which the driving source of the cleaning member 52 that cleans the charging wire 51 of the charger 50 and the driving source of the charger shielding member 60 are shared, the charger shielding is performed. The timing for closing (blocking) the member 60 is shifted for a certain time, not immediately after printing. This eliminates the need for the cleaning member to clean the charging line even when it is not necessary to clean the charging line of the charger as in the prior art, so that the cleaning member 52 can be prevented from being worn and the life of the cleaning member 52 can be reduced. Can be prolonged.

[Other Embodiments]
In the above-described embodiment, the time until the charger shielding member 60 set in the time measurement unit 124 starts to close is set according to the amount of water calculated based on the temperature and humidity inside the image forming apparatus, but is not limited thereto. It is not a thing. The time required to start closing the charger shielding member 60 set in the time measuring unit 124 may be set according to the number of printed sheets (the number of sheets on which image formation has been performed) in the image forming apparatus.

  In the above embodiment, the case where the image forming apparatus of the present invention is applied to a copying machine that forms an image by an electrophotographic process is described as an example. However, the present invention is not limited to this. The present invention can also be applied to a facsimile machine that forms an image using an electrophotographic process and a printer that forms an image using an electrophotographic process.

50 Charger 51 Charging Wire 52 Cleaning Member 55 Cleaning Member Moving Motor 60 Charger Shielding Member 111 CPU

Claims (4)

An image carrier for carrying an image;
A charging member for charging the image carrier;
A cleaning member for cleaning the charging member;
A shielding member that is attached to the cleaning member and shields between the charging member and the image carrier;
Drive means for moving both the cleaning member and the shielding member along the charging member;
A time measuring means for measuring time;
After the completion of the image forming job by the image forming apparatus, the cleaning unit and the shielding member are moved along the charging member by the driving unit in response to the passage of a predetermined time by the time measuring unit. Control means for shielding between the charging member and the image carrier by the shielding member,
An image forming apparatus comprising:   Setting means for setting a time period from the end of the image forming job until the shielding member is moved by the driving unit to start closing the shielding member in order to shield the space between the charging member and the image carrier; The image forming apparatus according to claim 1, further comprising:   The time from the end of the image forming job to the start of closing the shielding member is a time set according to the amount of water contained in the image forming apparatus calculated from the temperature and humidity inside the image forming apparatus. 3. The image according to claim 2, wherein the time is one of a time set according to the number of sheets on which an image is formed by the image forming apparatus and a time set by a user. Forming equipment.   The image forming apparatus according to claim 2, wherein a time from the end of the image forming job to the start of closing the shielding member can be adjusted.

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