JP2015011184A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus for lengthening the life of a cleaning member for removing a foreign matter such as tonner adhered to a fixing member without increasing the size of the cleaning member.SOLUTION: An image forming apparatus includes: an image forming part for forming a tonner image on a recording medium; a cleaning member which can be brought into contact with either a heating member or a pressurizing member configuring a fixing member; and a contacting/separating mechanism for bringing the cleaning member into contact with or separating it from the heating member or the pressurizing member. The image forming apparatus also includes a fixing device for performing fixing processing by inserting a recording medium on which the tonner image is formed into a fixing nip part. The image forming apparatus executes a cleaning mode for separating the cleaning member from the heating member or the pressurizing member at a point of time when the fixing member starts rotational driving, and for bringing the cleaning member into contact with the heating member or the pressurizing member in at least a time which the heating member or the pressurizing member takes to rotate the cleaning member one time after the lapse of a predetermined time, and for separating the cleaning member before the recording medium reaches the fixing nip part.

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer having a fixing device that fixes a toner image transferred onto a recording medium, and in particular, removes foreign matters by bringing a cleaning member into contact with a fixing roller or a pressure roller. It is about how to do.

  In a conventional image forming apparatus, a predetermined electrostatic latent image in which charging is partially attenuated by irradiating a laser beam from an exposure unit onto an image carrier such as a photosensitive drum uniformly charged by a charging unit. After an image is formed and toner is attached to the electrostatic latent image by a developing unit to form a toner image, the toner image is transferred onto a sheet (recording medium) using a transfer unit, and unfixed toner is heated by a fixing device. Then, an image forming process is performed by pressing to form a permanent image.

  In the fixing device as described above, the toner on the recording medium is transferred (offset) and adheres to the heating roller (fixing roller) or the pressure roller constituting the fixing roller pair (fixing member), and is re-applied to the subsequent recording medium. There has been a problem that image defects occur due to adhesion. Accordingly, a method is employed in which the cleaning roller is brought into contact with the fixing roller or the pressure roller to remove the toner transferred from the recording medium to the fixing roller or the pressure roller, thereby preventing reattachment to the recording medium.

  By the way, the amount of toner adhering to the fixing roller and the pressure roller is a minute amount, which is a level that cannot be visually recognized even if it is retransferred to the recording medium. However, the adhered toner is scraped off by the separation claw for peeling the recording medium from the fixing roller and the pressure roller, and if the scraped toner is excessively accumulated, the agglomerated toner is separated from the separation claw and fixed. Reattach to the roller or pressure roller. When such toner is retransferred to the recording medium, it is visually recognized as an image defect.

  When the cleaning roller is used, in addition to the level of toner that is visually recognized as an image defect, the level of toner that is not visually recognized as an image defect is also removed. Here, the amount of toner that can be removed by the cleaning roller is only the outer peripheral area of the cleaning roller. For this reason, in order to extend the service life of the cleaning roller, it is necessary to use a cleaning roller having a large diameter, which leads to an increase in the size of the fixing device.

  Accordingly, a method for extending the life of the cleaning roller has been proposed. For example, Patent Document 1 provides a cleaning roller that contacts the fixing roller and a cleaning blade that contacts the cleaning roller, and the toner adhered to the cleaning roller. A fixing device that physically scrapes off the toner is disclosed. Further, in Patent Document 2, the toner that has moved to the cleaning roller is re-transferred to the fixing roller pair by contacting the cleaning roller only when the sheet passes through the nip portion (fixing nip portion) of the fixing roller pair. There has been proposed a fixing device which prevents the above.

JP 61-221773 A JP 2009-69398 A

  However, in the method of Patent Document 1, it is necessary to contact the ridge line of the cleaning blade and the outer peripheral surface of the cleaning roller without any gap. However, if there is even a slight gap, streaky toner may remain on the outer peripheral surface of the cleaning roller. There was a risk of re-adhering to the fixing roller or pressure roller. Further, the toner staying in the gap between the cleaning blade and the cleaning roller may be fixed and the cleaning roller may not rotate.

  On the other hand, in the method of Patent Document 2, minute toner at a level that is not visually recognized as an image defect is also removed by the cleaning roller, so that the outer peripheral surface of the cleaning roller is saturated with the removed toner in a short period of time. Therefore, it has been difficult to extend the life of the cleaning roller. In addition, since the cleaning roller is not brought into contact until the paper passes through the fixing nip portion, relatively large toner accumulated between the separation claw and the fixing roller is not removed and re-transferred to the recording medium and visually recognized as an image defect. There was a risk of being.

  In view of the above problems, the present invention provides an image forming apparatus capable of extending the life of a cleaning member without increasing the outer diameter of the cleaning member that removes foreign matters such as toner adhering to the fixing member. For the purpose.

  In order to achieve the above object, a first configuration of the present invention is an image forming apparatus including an image forming unit and a fixing device. The image forming unit forms a toner image on the recording medium. The fixing device includes a fixing member that includes a heating member that can rotate at substantially the same speed as the conveyance speed of the recording medium, and a pressure member that is pressed against the heating member with a predetermined pressure to form a fixing nip portion, A recording member having a toner image formed at a fixing nip portion, and a cleaning member that can contact either the member or the pressure member, and a separation / contact mechanism that contacts or separates the cleaning member from the heating member or the pressure member The toner image is fixed by inserting the medium. The image forming apparatus separates the cleaning member from the heating member or the pressure member when image formation in the image forming unit is started and the fixing member starts to rotate, and after the predetermined time has passed, the cleaning member is moved to the heating member or A cleaning mode in which the cleaning member is separated from the heating member or the pressure member before the recording medium reaches the fixing nip portion after the pressure member has been brought into contact for one rotation or more can be executed.

  According to the first configuration of the present invention, the cleaning member is separated from the heating member or the pressure member when rotation of the fixing member is started, and is fixed by bringing the cleaning member into contact with the heating member or the pressure member after starting printing. It is possible to reliably remove a foreign substance at a level that can be visually recognized as an image defect before the processing is executed. In addition, after removing the foreign matter, before the fixing process is started, the cleaning member is again separated from the heating member or the pressure member so that the foreign matter at a level that cannot be visually recognized as an image is not attached to the cleaning member. The amount of foreign matter adhering to the cleaning member is reduced as compared with the configuration in which the member is always in contact with the heating member or the pressure member. Therefore, the useful life of the cleaning member can be extended without using a large diameter cleaning member.

1 is a side sectional view showing an internal structure of an image forming apparatus 100 according to an embodiment of the present invention. FIG. 3 is a side cross-sectional view illustrating an example of the fixing device 15 mounted on the image forming apparatus 100 of the present invention, and illustrates a state in which the cleaning roller 40 is in contact with the pressure roller 20b. FIG. 3 is a side sectional view showing an example of the fixing device 15 mounted on the image forming apparatus 100 of the present invention, and shows a state where the cleaning roller 40 is separated from the pressure roller 20b. Flow chart showing sequence of pressure roller cleaning mode

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a side sectional view showing the internal structure of an image forming apparatus 100 according to an embodiment of the present invention. In an image forming apparatus (for example, a monochrome printer) 100, when performing an image forming operation, the photosensitive drum 5 rotating in the clockwise direction in the drawing is uniformly charged by the charging unit 4, and an exposure unit (laser) based on document image data. An electrostatic latent image is formed on the photosensitive drum 5 by a laser beam from the scanning unit 7), and a developer (hereinafter referred to as toner) is attached to the electrostatic latent image by the developing unit 8 to form a toner image. The

  The toner is supplied to the developing unit 8 from the toner container 9. The image data is transmitted from a personal computer (not shown) or the like. Further, a static elimination device (not shown) for removing residual charges on the surface of the photosensitive drum 5 is provided on the downstream side of the cleaning device 19.

  A sheet is conveyed from the sheet feeding cassette 10 or the manual sheet tray 11 via the sheet conveyance path 12 and the registration roller pair 13 toward the photosensitive drum 5 on which the toner image is formed as described above, and the transfer roller 14 ( The toner image formed on the surface of the photosensitive drum 5 is transferred onto the sheet by the image transfer unit). The charging unit 4, the photosensitive drum 5, the exposure unit 7, the developing unit 8, the transfer roller 14, and the cleaning device 19 constitute an image forming unit that forms a toner image on a sheet. The sheet on which the toner image has been transferred is separated from the photosensitive drum 5 and conveyed to the fixing device 15 to fix the toner image. The sheet that has passed through the fixing device 15 is conveyed to the upper part of the main body of the image forming apparatus 100 through the sheet conveying path 16 and is discharged from the discharge roller pair 17 to the discharge tray 18.

  2 and 3 are side cross-sectional views of the fixing device 15 mounted on the image forming apparatus 100. FIG. 2 shows a state in which the cleaning roller 40 is brought into contact with the pressure roller 20b, and FIG. 3 shows a state in which the cleaning roller 40 is separated from the pressure roller 20b. In FIGS. 2 and 3, the housing of the fixing device 15 is not shown.

  The fixing device 15 includes a heating roller 20a that rotates in a clockwise direction in FIGS. 2 and 3 by a drive motor (not shown), and a pressure roller 20b that rotates in a counterclockwise direction following the heating roller 20a. ing. A heater 21 is built in the heating roller 20a, and the pressure roller 20b is pressed against the heating roller 20a with a predetermined pressure by an urging means (not shown). The heating roller 20a and the pressure roller 20b constitute a fixing roller pair 20 that fixes the unfixed toner on the paper passing through the fixing nip portion N.

  As a configuration of the heating roller 20a used in the present embodiment, for example, a coating layer (release layer) of PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) is laminated on the outer peripheral surface of an aluminum cored bar. Is mentioned. Moreover, as a structure of the pressure roller 20b, what laminated | stacked the silicone rubber layer (elastic layer) on the metal core metal, and coat | covered with the PFA tube (release layer) is mentioned.

  The heater 21 may be a halogen heater or an IH heater including an induction heating unit having an exciting coil and a core. Here, a halogen heater is used as the heater 21.

  On the downstream side of the fixing nip N with respect to the rotation direction (clockwise direction) of the heating roller 20a, a heating-side separation claw 25a that separates the sheet from the heating roller 20a is disposed. The heating-side separation claws 25a are arranged at a plurality of locations in the axial direction of the heating roller 20a (direction perpendicular to the paper surface of FIGS. 2 and 3) so that the tip portion contacts the outer peripheral surface of the heating roller 20a.

  Similarly, on the downstream side of the fixing nip N with respect to the rotation direction (counterclockwise direction) of the pressure roller 20b, a pressure-side separation claw 25b that separates the sheet from the pressure roller 20b is disposed. The pressure-side separation claws 25b are arranged at a plurality of locations in the axial direction of the pressure roller 20b (direction perpendicular to the paper surface in FIGS. 2 and 3) so that the tip portion contacts the outer peripheral surface of the pressure roller 20b. .

  A thermistor 30 that detects the surface temperature of the heating roller 20a in a non-contact manner is disposed upstream of the fixing nip portion N with respect to the rotation direction of the heating roller 20a. The thermistor 30 detects the surface temperature of the heating roller 20a and controls the fixing temperature by turning on / off the current flowing through the heater 21.

  A fixing approach guide 22 for guiding the sheet to the fixing nip N is provided on the upstream side of the fixing nip N with respect to the sheet conveying direction (from right to left in FIGS. 2 and 3). In addition, a paper detection mechanism 23 that detects the passage of the front end portion and the rear end portion of the paper is disposed immediately upstream of the fixing approach guide 22. The sheet detection mechanism 23 includes, for example, a fixing actuator that protrudes on the sheet conveyance path and swings when the sheet passes, and a PI (photo interrupter) sensor that is turned ON or OFF by the swing of the fixing actuator.

  The sheet on which the toner image has been transferred by the transfer roller 14 (see FIG. 1) proceeds to the left in FIG. 2, is carried into the fixing device 15 from the opening on the upstream side of the housing, and a pair of fixing rollers along the fixing entry guide 22. Guided to 20 fixing nips N. When the paper passes through the fixing nip N, it is heated and pressurized with a predetermined temperature and pressure, and the toner image on the paper is made a permanent image. Thereafter, the sheet is conveyed to the outside of the fixing device 15 through the opening on the downstream side of the housing, and is discharged to the outside of the image forming apparatus 100 from the discharge roller pair 17 (see FIG. 1).

  On the upstream side of the fixing nip N with respect to the rotation direction of the pressure roller 20b, a cleaning roller 40 for removing dirt such as toner adhering to the outer peripheral surface of the pressure roller 20b is disposed. The cleaning roller 40 has a configuration in which a heat-resistant felt 40b is wound around an aluminum cored bar 40a, and one end of a coil spring 51 is fixed to a bearing 41 that rotatably supports the cored bar 40a. The other end of the coil spring 51 is fixed to the operation plate 43, and an eccentric cam 53 is in contact with the operation plate 43 from the side opposite to the coil spring 51. The eccentric cam 53 is fixed to the output shaft of a cleaning roller moving motor (not shown).

  In the state of FIG. 2, the large-diameter portion 53a of the eccentric cam 53 is in contact with the operating plate 43, and the coil spring 51 is compressed. The eccentric cam 53 is rotated by a predetermined amount (180 °) from the state shown in FIG. 2 by a cleaning roller moving motor (not shown), and the small-diameter portion 53b of the eccentric cam 53 is attached to the operating plate 43 as shown in FIG. As a result of the contact, the operating plate 43 moves in the direction of the arrow A ′, the compressed coil spring 51 extends, and the cleaning roller 40 is separated from the pressure roller 20b. As described above, the cleaning roller 40 performs the contact / separation operation with respect to the pressure roller 20b.

  FIG. 4 is a flowchart showing a sequence of the pressure roller cleaning mode for removing foreign matters such as toner and paper dust attached to the pressure roller 20b. The execution procedure of the pressure roller cleaning mode will be described along the steps of FIG. 4 with reference to FIGS. Before starting printing, the cleaning roller 40 is separated from the pressure roller 20b as shown in FIG.

  When a print start command is input from a host device such as a personal computer (step S1), the fixing roller pair 20 including the heating roller 20a and the pressure roller 20b starts to rotate (step S2). At the same time, energization of the heater 21 is started, and detection of the surface temperature of the heating roller 20a by the thermistor 30 is also started.

  After a predetermined time has elapsed since the fixing roller pair 20 started to rotate, a control signal is transmitted from a control unit (not shown) to the cleaning roller moving motor, and the eccentric cam 53 is rotated by a predetermined amount to rotate the large diameter portion 53a. Is brought into contact with the operation plate 43. Thereby, the action | operation board 43 moves to the arrow A direction, and as shown in FIG. 2, the cleaning roller 40 contacts the pressurization roller 20b (step S3). The cleaning roller 40 is driven and rotated by the pressure roller 20b, so that a visible level of toner adhering to the surface of the pressure roller 20b, in particular, a lump that has come out from between the pressure roller 20b and the pressure side separation claw 25b. Remove toner.

  In addition, although a lump of toner comes out between the heating roller 20a and the heating side separation claw 25a, the toner usually has a property that it tends to shift from a higher temperature side to a lower side. Therefore, the toner adhering to the heating roller 20a gradually moves to the pressure roller 20b side where the temperature is low in the fixing nip portion N, and is removed by the cleaning roller 40. That is, the toner adhering to the heating roller 20a can also be removed by bringing the cleaning roller 40 into contact with the pressure roller 20b.

  When the surface temperature of the heating roller 20a reaches a predetermined temperature, the paper is sent out from the paper feed cassette 10 or the manual paper tray 11. Then, it is determined whether or not the leading edge of the sheet has passed by the sheet detecting mechanism 23 (step S4). When the passage of the leading edge of the sheet is detected (YES in step S4), the eccentric cam 53 is rotated by a predetermined amount. The small diameter portion 53b is brought into contact with the operation plate 43. As a result, the operation plate 43 moves in the direction of the arrow A ′, and the cleaning roller 40 is separated from the pressure roller 20b again as shown in FIG. 3 (step S5).

  Thereafter, the toner image formed on the surface of the photosensitive drum 5 is transferred onto the paper by the transfer roller 14. The sheet on which the toner image has been transferred is conveyed to the fixing device 15 and passes through the fixing nip portion N of the fixing roller pair 20 to execute a fixing process (step S6).

  Thereafter, it is determined whether or not printing has been completed (step S7). If printing has continued (NO in step S7), the process returns to step S4 and the fixing process is repeated. On the other hand, if the printing is finished (YES in step S7), the process is finished.

  By executing the pressure roller cleaning mode according to the above-described procedure, the cleaning roller 40 causes toner of a level that can be visually recognized as an image defect coming out between the pressure roller 20b and the pressure-side separation claw 25b before the fixing process. Can be reliably removed.

  The cleaning roller 40 is separated from the pressure roller 20b at the start of printing. After the rotation of the fixing roller pair 20 starts to rotate, the cleaning roller 40 comes into contact with the pressure roller 20b to remove the toner and before the fixing process is started. Since it is separated from the pressure roller 20b again, the amount of toner adhering to the cleaning roller 40 is reduced as compared with the configuration in which the cleaning roller 40 is always in contact with the pressure roller 20b. Therefore, the service life of the cleaning roller 40 can be extended without using the large-diameter cleaning roller 40, and the image forming apparatus 100 can be reduced in size and maintenance costs can be reduced.

  When the sheet on which the toner image has been transferred passes through the fixing nip N, toner of a level that cannot be visually recognized as an image defect adheres to the heating roller 20a and is transferred from the heating roller 20a to the pressure roller 20b. This invisible toner adheres to and is removed from the front or back surface of the paper that passes through the fixing nip portion N, and does not adversely affect the image. Therefore, the cleaning roller 40 is a pressure roller when the paper is passing. There is no problem even if it does not contact 20b.

  Further, the time during which the cleaning roller 40 is in contact with the pressure roller 20b is not particularly limited as long as the sheet is not moved into the fixing nip N after the fixing roller pair 20 starts to rotate and is driven. In order to reliably remove the foreign matter adhering to the entire outer peripheral surface of the pressure roller 20b, it is necessary to keep the cleaning roller 40 in contact with the pressure roller 20b for one rotation or more.

  Further, here, a mechanism for moving the cleaning roller 40 to and from the pressure roller 20b using the operation plate 43, the coil spring 51, and the eccentric cam 53 is shown. For example, instead of the eccentric cam 53, a gear mechanism, a solenoid, or the like may be used.

  In addition, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the configuration of the cleaning roller 40 used in the above embodiment, the contact time of the cleaning roller 40 in the pressure roller cleaning mode, and the like can be appropriately set according to the configurations of the fixing device 15 and the pressure roller 20b.

  Further, instead of the heating roller 20a, an endless fixing belt is provided, and a sheet carrying an unfixed toner image is inserted into a fixing nip portion formed by the fixing belt and a pressure member pressed against the fixing belt. The present invention can also be applied to a belt-fixing type fixing device that fixes toner.

  Further, in the above embodiment, the cleaning roller 40 is brought into contact with the pressure roller 20b in order to remove the toner and the like attached to the pressure roller 20b. However, the heating roller is brought into contact with the heating roller 20a. A configuration in which toner or the like attached to 20a is removed is also possible.

  Further, the present invention is not limited to the monochrome printer as shown in FIG. 1, but can be applied to other image forming apparatuses equipped with a fixing device such as a color printer, monochrome and color copying machine, digital multifunction peripheral, or facsimile. Of course.

  The present invention is applicable to an image forming apparatus provided with a cleaning member for cleaning a fixing member of a fixing device. The present invention provides an image forming apparatus capable of extending the life of a cleaning member without removing the outer diameter of the cleaning member by removing only foreign matter at a level that can be visually recognized as an image defect by using the cleaning member. Can do.

DESCRIPTION OF SYMBOLS 4 Charging unit 5 Photoconductor drum 7 Exposure unit 8 Developing unit 14 Transfer roller 19 Cleaning device 15 Fixing device 20 Fixing roller pair (fixing member)
20a Heating roller (heating member)
20b Pressure roller (pressure member)
21 Heater (heating means)
22 fixing approach guide 23 paper detection mechanism (recording medium detection mechanism)
25a Heating side separation claw 25b Pressure side separation claw 30 Thermistor 40 Cleaning roller (cleaning member)
40a Core 41 Bearing part 43 Actuating plate (contact / separation mechanism)
51 Coil spring (contact / separation mechanism)
53 Eccentric cam (contact / separation mechanism)
100 Image forming apparatus

Claims (3)

An image forming unit for forming a toner image on a recording medium;
A fixing member comprising: a heating member capable of rotating at a substantially equal speed to a conveyance speed of the recording medium; and a pressing member that is pressed against the heating member at a predetermined pressure to form a fixing nip portion; and the heating member or the A cleaning member capable of contacting any of the pressure members, and a separation / contact mechanism for bringing the cleaning member into contact with or separating from the heating member or the pressure member, and a toner image is formed at the fixing nip portion. A fixing device for inserting a recording medium and fixing the toner image;
In an image forming apparatus comprising:
When the image formation in the image forming unit is started and the fixing member starts to rotate, the cleaning member is separated from the heating member or the pressure member, and the cleaning member is heated after a predetermined time has elapsed. A cleaning mode in which the cleaning member is separated from the heating member or the pressure member before the recording medium reaches the fixing nip portion after the member or the pressure member has been brought into contact for at least one rotation time can be executed. An image forming apparatus.   When continuous printing is performed on a plurality of recording media in the image forming unit, the cleaning member is separated from the heating member or the pressure member before the first recording medium reaches the fixing nip, and The image forming apparatus according to claim 1, wherein the separated state of the cleaning member is maintained until continuous printing is completed.   A recording medium detection mechanism for detecting the passage of the recording medium is provided upstream of the fixing nip portion with respect to the conveyance direction of the recording medium, and the passage of the leading edge of the recording medium is detected by the recording medium detection mechanism. The image forming apparatus according to claim 1, wherein the cleaning member is separated from the heating member or the pressure member.