Patent Grant
9014607
1. Field of the Invention
The present invention relates to electrophotographic image forming apparatuses such as copiers, printers, facsimile machines, and multifunction peripherals having functions of the aforementioned devices.
2. Description of the Related Art
In fixing devices that use heat and pressure, a pressure member is pressed against a fixing member having a heat source provided inside. A transfer sheet with an unfixed toner image is passed through the part between the fixing member and the pressure member, to fix the toner onto the transfer sheet (a recording medium).
The surface of the fixing member is covered by, for example, fluorine coating, to prevent toner from adhering to the fixing member. However, depending on various conditions relevant to the environment or the recording medium, a slight amount of toner on the recording medium may adhere to the fixing member, which is referred to as offset. The offset toner remains on the fixing member and the pressure member that contacts the fixing member. This toner may transfer to the recording medium and soil the image on the recording medium. To prevent such a situation, the fixing member is provided with a cleaning member such as a cleaning web or a cleaning roller.
The cleaning member is pressed against the fixing member and the pressure member to collect the offset toner. To collect the offset toner, particularly, in a reliable manner, a cleaning web involving a roll-up operation is used for appropriately collecting the toner, with which high cleaning performance can be constantly achieved.
A cleaning web is typically impregnated with a small amount of silicone oil (for example, 5 g/m2 through 10 g/m2) for the purpose of achieving high cleaning performance. However, when the oil is unevenly applied, the resultant image may have uneven gloss.
Furthermore, when the cleaning web is brought in contact with the pressure roller, the oil that is unevenly applied on the pressure roller may be transferred to the fixing belt or the fixing roller. In this case, because the cleaning web is disposed at the pressure roller, the fixing belt or fixing roller does not contact the cleaning web. Therefore, the unevenness on the fixing belt or fixing roller cannot be evened out by contacting the cleaning web immediately after performing a fixing operation of one sheet. Accordingly, the resultant image may have a significant level of uneven gloss. A supplying roller stores the cleaning web in a rolled-up state. The amount of impregnated silicone oil increases toward the center of the diameter of the rolled-up cleaning web. That is to say, the amount of impregnated silicone oil increases toward the end of the operating life of the cleaning web.
To address this problem, patent documents 1 and 2 disclose mechanisms for separating the web contact roller from the contact object while the machine is in a standby state, so that excessive oil is prevented from exuding during the standby state. However, a link mechanism or an actuator mechanism is required for the separating motion, which requires high cost. Furthermore, when there is excessive silicone oil while the machine is operating, effects of this mechanism cannot be expected to be achieved. Patent document 3 discloses a method of providing a cleaning web including silicone oil and a cleaning web that does not include silicone oil. The cleaning webs are brought into contact or separated from the object according to fixing conditions, so that unevenness in gloss caused by silicone oil is eliminated. However, this method requires complex control operations, and requires high cost, as apparent from the configuration. Furthermore, in cases where the cleaning web including silicone oil needs to be used for achieving high cleaning performance, effects of this method cannot be expected to be achieved.
Among the above-described fixing devices, some devices have a function of moving the pressure member with respect to the fixing member for applying pressure, reducing pressure, and not applying pressure (by separating the pressure member from the fixing member). This function is used for the purpose of preventing the degradation of the fixing member and the pressure member. Specifically, the members are separated when the device is not used so that load is not applied to the members. Furthermore, the members may be separated for the purpose of cooling only the pressure member. Furthermore, some devices have a function of implementing plural positional relationships between the pressure member and the fixing member when the pressure member is pressed against the fixing member, such as strong press-contact and weak press-contact. This function is used for the purpose of achieving the optimum press-contact state according to the environment and conditions of the recording medium.
In a configuration where the cleaning member (contact roller) is brought into contact with a movable pressure member as described above, when the length between the contact roller and the pressure member increases and the cleaning web is not sufficiently pressed against the pressure member, the cleaning function cannot be sufficiently implemented and consequently the image is soiled. Furthermore, when the length between the contact roller and the pressure member decreases and the cleaning web is excessively pressed against the pressure member, the materials forming the contact roller and the pressure member are degraded, and the torque required for rolling up the cleaning web increases, and the cleaning web may not be properly retrieved.
That is to say, when the positional change of the pressure member is sufficiently small at the location where the cleaning member contacts the pressure member, the cleaning member can be completely fixed with respect to the fixing device. However, when the pressure member is configured to separate from such a location, the positional change of the pressure member is large. Thus, the toner cleaned off from the pressure member may fly out, transfer to the recording medium, and cause failures.
Furthermore, there may be cases where a large amount of toner enters the cleaning nip part where the cleaning web is pressed against a member that is the object of cleaning (cleaning object), due to factors such as a fixing failure occurring while the fixing device is operating or a paper jam occurring at the fixing nip. In such a case, a large amount of melted or half-melted toner is expected to accumulate at the cleaning nip. When a large amount of melted or half-melted toner is accumulated at the cleaning nip, and the fixing device stops operating and is left to cool down until the toner is fixed on the cleaning web and the cleaning object, the following problem may arise. That is, when the fixing device starts operating once again, the cleaning web may be unexpectedly discharged from the roll-up roller (that rolls up the used web to retrieve the used web) and the supplying roller (that supplies a new web).
When the web is unexpectedly discharged, the web may sag and tangle with surrounding components, thus causing various operational failures. For example, when the cleaning object is a pressure roller, the web may be wound around the pressure roller. In another example, the web may tangle with a separation mechanism for separating the recording medium with fixed toner from the fixing member. As a result, the separation mechanism may not be able to separate the recording medium from the fixing member. Furthermore, when the web is rolled out from the roll-up roller and the web sags, a web that is soiled from being used for a cleaning operation may be used once again for cleaning. Accordingly, a cleaning failure is caused, which leads to abnormal images.
To prevent the web from being discharged as described above, there are means for preventing reversal, such as providing the roll-up roller with a one-way clutch mechanism, or using a worm gear as the roll-up roller driving system. However, as the roll-up roller retrieves the used web, the diameter of the rolled-up cleaning web increases. Therefore, the torque required for retrieving the web continuously increases assuming that the web is pulled with a constant force at the cleaning nip part. Under such circumstances, when a large amount of unfixed toner enters the cleaning nip as described above, and conditions by which toner is fixed are fulfilled, excessive load is disadvantageously applied on the means for preventing reversal. Furthermore, even if the means for preventing reversal can withstand the torque, if the used web is loosely rolled-up by the roll-up roller, the web that is loosely rolled-up may be discharged in the direction opposite to the web roll-up direction under the conditions in which toner is fixed. Consequently, the used web may enter the cleaning nip part once again.
A method of adding some means for preventing reverse rotation to the shaft of the roll-up roller (see, for example, patent document 4) is typically known as a means for preventing reversal. This method is for adding a reversal torque to the roll-up roller shaft, and therefore as the diameter of the roll-up roller increases, the required torque increases.
Patent Document 1: Japanese Laid-Open Patent Publication No. 2001-215838
Patent Document 2: Japanese Laid-Open Patent Publication No. H08-152801
Patent Document 3: Japanese Laid-Open Patent Publication No. 2009-025519
Patent Document 4: Japanese Laid-Open Patent Publication No. 2008-01544
The present invention provides a heating device, a fixing device, and an image forming apparatus in which one or more of the above-described disadvantages are eliminated.
A preferred embodiment of the present invention provides a heating device, a fixing device, and an image forming apparatus, in which excessive silicone oil impregnated in a cleaning web is collected before guiding the cleaning web to the cleaning nip.
According to an aspect of the present invention, there is provided a heating device including a fixing member; a pressure member that comes in pressure contact with a surface of the fixing member; and a cleaning web unit including a contact roller that contacts the pressure member via a web that is impregnated with a lubricant agent, a supplying roller that supplies a new web, a roll-up roller that rolls up and retrieves the web that has been used for wiping off adhering matter from the pressure member, and a lubricant agent absorption member that absorbs the lubricant agent by contacting the web at a web path extending from the supplying roller to the contact roller.
According to an aspect of the present invention, there is provided a heating device including a fixing belt that is an endless belt wound around plural rollers or sliding members, the fixing belt being caused to move around the plural rollers or sliding members; a pressure member that comes in pressure contact with a surface of the fixing belt, so that a toner layer resting on a recording medium is fixed to the recording medium by heat and pressure when the recording medium passes through a nip part between the fixing belt and the pressure member, the fixing belt having a higher toner releasability than a pressure member; a mechanism that changes a position where the pressure member contacts the fixing belt so that the nip part becomes present or absent and a width of the nip part is adjusted; and a web cleaning unit including a contact roller that contacts the pressure member via a web that is impregnated with a lubricant agent, a supplying roller that supplies a new web, a roll-up roller that rolls up and retrieves the web that has been used for wiping off adhering matter from the pressure member, and a lubricant agent absorption member that absorbs the lubricant agent by contacting the web at a web path extending from the supplying roller to the contact roller.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings, in which:
In an embodiment of the present invention, excessive silicone oil that is impregnated in a cleaning web is collected before the cleaning web is guided to a cleaning nip. According to an aspect of the present invention, there is provided a heating device including an endless fixing belt as a fixing member wound around plural rollers or sliding members, the fixing belt being caused to move around the plural rollers or sliding members, the fixing belt having a higher toner releasability than a pressure member; the pressure member that comes in pressure contact with a surface of the fixing belt, so that a toner layer resting on a recording medium is fixed to the recording medium by heat and pressure when the recording medium passes through a nip part between the fixing belt and the pressure member; a mechanism that changes a position where the pressure member contacts the fixing belt, by which the nip part becomes present or absent and by which a width of the nip part is adjusted; and a web cleaning unit including at least a contact roller that contacts the pressure member via a web that is impregnated with a lubricant agent, a supplying roller that supplies a new web, a roll-up roller that rolls up and retrieves the web that has been used for wiping off adhering matter from the pressure member, and a lubricant agent absorption member that absorbs the lubricant agent by contacting the web at a web path extending from the supplying roller to the contact roller. That is to say, the silicone oil collecting member is brought in direct contact with the web before the web is guided into the cleaning nip, to collect excessive silicone oil that is impregnated in the web. Accordingly, excessive silicone oil is prevented from being applied onto the surface of the fixing member during the cleaning operation, and uneven gloss and gloss streaks are prevented from being formed on the fixed image. The fixing member is not limited to a belt; the fixing member may be, for example a roller. Furthermore, it is also possible to use any lubricant agent other than silicone oil, which can be used in these types of heating devices and fixing devices.
Furthermore, in an embodiment of the present invention, in order to maintain an oil impregnation amount that does not degrade the cleaning performance and to collect excessive silicone oil during the operating life of the cleaning web unit, the silicone oil absorption member does not contact the web when the web is initially supplied from the supplying roller, but the silicone oil absorption member contacts the web at the web path when a consumption amount of the web reaches a predetermined amount, and continues to contact the web thereafter.
Furthermore, in an embodiment of the present invention, in order to collect excessive silicone oil impregnated in the web and to prevent the silicone oil absorption member from degrading even if it is used near the heating member, the silicone oil absorption member has heat resistance for resisting heat of a temperature greater than or equal to the maximum temperature of the pressure roller with which the web is brought into contact, and the silicone oil absorption member includes a microscopic pore structure provided inside the silicone oil absorption member.
Furthermore, in an embodiment of the present invention, a mechanism for collecting excessive silicone oil can be provided even if the cleaning web unit operates in accordance with the pressure application operation and pressure reduction operation, and in order to maintain good cleaning properties, the position of the cleaning web unit is changed in accordance with the pressure application operation and the pressure reduction operation.
A description is given, with reference to the accompanying drawings, of embodiments of the present invention.
The printer engine 300 includes four image forming units for yellow (Y), cyan (C), magenta (M), and black (K) configuring a sheet transfer unit 5, which are disposed in parallel above an intermediate transfer belt 30 that is an endless belt. The image forming units include electrophotographic processing members or units such as a charging unit, an optical writing unit, a developing unit, and a cleaning unit, which are arranged along the outer periphery of drum-type photoconductors 1Y, 1C, 1M, and 1K provided for the respective colors.
Although not illustrated in detail, the charging unit performs a charging process on the surface of the photoconductor 1Y, 1C, 1M, 1K, and the optical writing unit writes image information onto the surface of the photoconductor 1Y, 1C, 1M, 1K by radiating laser beams. An electrostatic latent image is formed on the surface of the photoconductor 1Y, 1C, 1M, 1K by an exposure process. The developing unit develops the electrostatic latent image that has been formed on the photoconductor 1Y, 1C, 1M, 1K into a visible toner image. A cleaning unit is used to remove/collect toner remaining on the surface of the photoconductor 1Y, 1C, 1M, 1K, after the toner image is transferred from the photoconductor 1Y, 1C, 1M, 1K to the intermediate transfer belt 30. Color images of the respective colors Y, C, M, and K, are sequentially formed on the intermediate transfer belt 30, so that four color images are superposed on one another to form a single four-color image. Specifically, first, a Y image forming unit develops a Y toner image, and transfers the Y toner image onto the intermediate transfer belt 30. Next, a C image forming unit develops a C toner image, and transfers the C toner image onto the intermediate transfer belt 30. Next, an M image forming unit develops an M toner image, and transfers the M toner image onto the intermediate transfer belt 30. Lastly, a K image forming unit develops a K toner image, and transfers the K toner image onto the intermediate transfer belt 30. Then, the four-color image is transferred, by a sheet transfer unit 5, onto a transfer sheet that is fed from the sheet feeding unit 200. The image is fixed onto the transfer sheet by a fixing device 7. The sheet is ejected to the sheet eject tray 8 by a sheet eject roller. Meanwhile, after the full-color toner image has been transferred from the intermediate transfer belt 30 to the transfer sheet, the toner remaining on the surface of the intermediate transfer belt 30 is removed and collected by a belt cleaning unit.
The sheet feeding unit 200 includes the four stages of sheet feeding cassettes 221A through 221D described above, in which transfer sheets set by a user are stacked and held. The sheet sizes and sheet types set in the respective sheet feeding cassettes 221A through 221D may be determined by the user. Furthermore, there may be a means for determining the sheet size, the sheet type, or the sheet thickness according to a device for measuring the positions of the side guides aligning the transfer sheets and for measuring the resistance of stacked sheets in the sheet feeding cassettes 221A through 221D, and automatically setting the determined results as the conditions of the sheet feeding cassettes 221A through 221D. The sheet feeding cassettes 221A through 221D, the bypass tray 6, and resist rollers 11 are connected by a conveying path 12. A transfer sheet fed from any sheet feeding location is transferred to the resist rollers 11 via the conveying path 12. The transfer sheet is temporarily stopped at the resist rollers 11. The sheet is then sent into the sheet transfer part at a timing to attain a predetermined positional relationship between the toner image on the intermediate transfer belt 30 and the leading edge of the transfer sheet. The resist rollers 11 function in the same manner with respect to a transfer sheet conveyed from the bypass tray 6.
Although not illustrated in detail, the scanner 400 includes plural moving bodies provided with a light source for radiating light to original documents, and mirrors. The moving bodies move back and forth to scan an original document placed on a contact glass 401. Image information obtained by the scanning process of the moving bodies is focused by lenses onto an imaging surface of a CCD provided at the back. The image information is read as image signals by the CCD. The image signals are then converted into digital signals and are subjected to image processing. Then, based on the signals that have been subjected to image processing, optical writing is performed on the surface of the photoconductor with light emitted from a laser diode LD in an optical writing unit, to form an electrostatic latent image. The light signals from the LD reach the photoconductor via a polygon mirror and lenses. On top of the scanner 400, there is provided an automatic document feeder 500 for automatically conveying an original document onto the contact glass 401.
The pressure roller 22 is rotated by a motor (not shown) in a direction indicated by an arrow A in
As described above, the fixing device according to the present embodiment includes an endless belt that circulates and that is wound around plural rollers. In the example shown in
In the above embodiment and modifications, nips are formed by rollers. However, some or all of the rollers may be replaced by sliding members to form nips.
After the cleaning web 54 is used for wiping off the toner, the cleaning web 54 is rolled up by the cleaning web roll-up roller 52 that is rotated by a driving unit (not shown) in a direction indicated by an arrow E in
In the present embodiment, in the cleaning web unit, in an initial state before the cleaning web 54 is consumed (
The silicone oil collecting members 71 and 72 may be made of a heat-resistant nonwoven cloth or a heat-resistant sponge that is resistant to heat of a higher temperature than the maximum temperature of the pressure roller 22 against which the cleaning web 54 is pressed by the cleaning web contact roller 51. Furthermore, by using felt having microscopic pores as the silicone oil collecting members 71 and 72, the silicone oil can be collected. Furthermore, by using a heat-resistant material as the silicone oil collecting members 71 and 72, the silicone oil collecting members 71 and 72 are prevented from degrading even when they are located near the heated fixing member, so that silicone oil can be stably collected.
In the first embodiment described with reference to
By providing an image forming apparatus with a fixing device having a heating device including the above described cleaning unit, an image forming apparatus having good fixing properties can be achieved.
According to one embodiment of the present invention, a heating device, a fixing device, and an image forming apparatus are provided, in which excessive silicone oil is prevented from being applied to a fixing member surface during a cleaning operation, so that uneven gloss and gloss streaks are prevented from being formed on the fixed image.
The present invention is not limited to the specific embodiments described herein, and variations and modifications may be made without departing from the scope of the present invention.
The present application is based on Japanese Priority Patent Application No. 2010-056810, filed on Mar. 12, 2010, the entire contents of which are hereby incorporated herein by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-056810 | Mar 2010 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 6792236 | Yoda et al. | Sep 2004 | B2 |
| 7113717 | Bott et al. | Sep 2006 | B2 |
| 7483663 | Ide et al. | Jan 2009 | B2 |
| 7630675 | Tateishi et al. | Dec 2009 | B2 |
| 20100232846 | Watanabe | Sep 2010 | A1 |
| 20100316421 | Komuro | Dec 2010 | A1 |
| Number | Date | Country |
|---|---|---|
| 61-23183 | Jan 1986 | JP |
| 8-152801 | Jun 1996 | JP |
| 9-292791 | Nov 1997 | JP |
| 10-288908 | Oct 1998 | JP |
| 2000-98790 | Apr 2000 | JP |
| 2001-42683 | Feb 2001 | JP |
| 2001-215838 | Aug 2001 | JP |
| 2001-272875 | Oct 2001 | JP |
| 2002-189374 | Jul 2002 | JP |
| 2003-295667 | Oct 2003 | JP |
| 2007-328161 | Dec 2007 | JP |
| 2008-1544 | Jan 2008 | JP |
| 2008-225183 | Sep 2008 | JP |
| 2009-25519 | Feb 2009 | JP |
| Entry |
|---|
| Office Action issued on Oct. 10, 2013, in Japanese patent Application No. 2010-056810. |
| Number | Date | Country | |
|---|---|---|---|
| 20110222923 A1 | Sep 2011 | US |
