Patent Application
20110299896
This application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2010-131209 filed in Japan on Jun. 8, 2010, the entire contents of which are herein incorporated by reference.
The present invention relates to an oil application roller that contacts the surface of a fixing rotary member of a fixing apparatus to apply oil to the surface, a fixing apparatus using such an oil application roller, and an image forming apparatus provided with such a fixing apparatus.
Conventionally, a fixing apparatus has been applied to image forming apparatuses employing a xerography method, electrostatic recording method, magnetophotographic method or the like. With this type of fixing apparatus, recording paper (e.g., plain paper, electrostatic recording paper, and photo paper) to which a toner image has been transferred is held between a pair of fixing rotary members (e.g., belt and roller), and heated and pressed, thereby fixing the toner image on the recording paper.
With such a fixing apparatus, in order to prevent toner on the recording paper from adhering to the surface of the fixing rotary member, an oil application roller is caused to contact the surface of the fixing rotary member to apply oil thereto.
For example, an oil application roller 101 shown in
JP 2000-284627A (“Patent Document 1”) discloses a configuration in which a gap between the wrapping start edge and the wrapping end edge of a sheet is set to be smaller than the contact width between the oil application roller and the fixing rotary member, thereby suppressing fluctuation in the oil application amount.
Also, JP 2009-300700A (“Patent Document 2”) discloses a configuration employing an oil application roller in which a sheet is wrapped around at least once, and the wrapping end edge of the sheet is wrapped over and bonded to the peripheral surface of the sheet lying under the wrapping end edge.
In the example of either Patent Document 1 or 2, the wrapping start edge of the sheet of the oil application roller is cut parallel to the shaft of the oil application roller. In such a case, as shown in
This step 105 may be caught by the surface of the fixing roller 104, and generates a large resistance for the rotative driving of the oil application roller 101. Therefore, the fixing roller 104 may slide on the surface of the oil application roller 101 and cannot climb over the step 105, or the rotative driving of the oil application roller 101 may be stopped. Also, the surface of the oil application roller 101 and the surface of the fixing roller 104 may be wet with oil, or paper dust may be adhered to the surface of the oil application roller 101. For this reason, frictional resistance generated between the oil application roller 101 and the fixing roller 104 is small, and thus if there is even a small obstacle such as a step 105 in the oil application roller 101, the resistance caused by the step 105 becomes larger than the frictional resistance, which may become a cause for stopping the rotative driving of the oil application roller 101.
If the fixing roller 104 slides on the surface of the oil application roller 101 and fails to clime over the step 105, so that the oil application roller 101 stops being rotatively driven, toner adhered to the surface of the fixing roller 104 accumulates in the step 105 of the oil application roller 101. Then, when the fixing apparatus stops operation, toner accumulated in the step 105 of the oil application roller 101 is cooled and becomes a lump. When the fixing apparatus is re-activated and rotation of the fixing roller 104 is started again, the toner lump accumulated in the step 105 of the oil application roller 101 may damage the surface of the fixing roller 104.
On the other hand, if, for example, the contact pressure applied by the oil application roller 101 against the fixing roller 104 is increased, then the frictional resistance between the oil application roller 101 and the fixing roller 104 increases, so that the oil application roller 101 is kept to be rotatively driven.
However, when the contact pressure applied by the oil application roller 101 is increased, the amount of oil pushed out of the cylindrical member 102 of the oil application roller 101 increases. Then, the service life of the oil application roller 101 is shortened, the rotation load to the fixing roller 104 increases, and the fixing roller 104 will be damaged.
The present invention has been made in view of the conventional issues as described above, and it is an object thereof to provide an oil application roller capable of reliably preventing the oil application roller from stopping being rotatively driven without increasing contact pressure applied by the oil application roller, a fixing apparatus using such an oil application roller, and an image forming apparatus provided with such a fixing apparatus.
In order to solve the above-described issues, an oil application roller comprising a cylindrical member impregnated with oil, and a porous sheet wrapped around a peripheral surface of the cylindrical member, and being configured to be in contact with a surface of a fixing rotary member of a fixing apparatus to apply the oil to the surface of the fixing rotary member, wherein an edge on a wrapping start side of the porous sheet has a shape formed by being cut in a straight line or a curved line that is inclined relative to a rotation shaft of the oil application roller.
With the oil application roller of the present invention, since the edge on the wrapping start side of the porous sheet is inclined relative to the rotation shaft of the oil application roller, the step formed by the edge on the wrapping start side of the porous sheet on the peripheral surface of the oil application roller is also inclined relative to the rotation shaft. Therefore, the oil application roller contacts the fixing rotary member and is rotatively driven, and when the step due to the edge on the wrapping start side of the porous sheet passes between the oil application roller and the fixing rotary member, the contact width of the step to the fixing rotary member is narrow at first, and is gradually widened. At every rotation of the oil application roller, the step repeats passing between the oil application roller and the pressure roller as described above.
Since the contact width of the step is narrow at first, and resistance caused by the step having a narrow width is small, fixing rotary member can easily climb over the narrow-width step of the oil application roller, and the oil application roller 21 is kept to be rotatively driven. Also, once the fixing rotary member climbs over the step, the oil application roller is kept to be rotatively driven even though the contact width of the step of the oil application roller to the fixing rotary member is widened. Therefore, the oil application roller continues to be rotatively driven.
Also, with the oil application roller of the present invention, it is preferable that there are a plurality of said straight or curved lines, intersecting each other.
In such a case, the edge on the wrapping start side of the porous sheet on the peripheral surface of the oil application roller is formed to have a chevron shape or a sawtooth shape. The contact width of the step of the oil application roller to the fixing rotary member at first is also narrow, and thus the fixing rotary member easily climbs over the narrow-width step, and the oil application roller continues to be rotatively driven.
An oil application roller of the present invention is an oil application roller comprising a cylindrical member impregnated with oil, and a porous sheet wrapped around a peripheral surface of the cylindrical member, and being configured to be in contact with a surface of a fixing rotary member of a fixing apparatus to apply the oil to the surface of the fixing rotary member, and it is preferable that the width of the porous sheet is gradually narrowed toward an end portion on a wrapping start side of the porous sheet.
With such an oil application roller of the present invention as well, the contact width of the step of the oil application roller to the fixing rotary member is narrow at first, and is gradually widened with the rotation of the oil application roller. Therefore, the fixing rotary member easily climbs over the narrow-width step, and the oil application roller is kept to be rotatively driven.
Also, with the oil application roller of the present invention, it is preferable that the width of the porous sheet is gradually narrowed such that the end portion on the wrapping start side of the porous sheet is formed in a triangle or a trapezoid shape.
Furthermore, with the oil application roller of the present invention, it is preferable that the porous sheet is wrapped around the peripheral surface of the cylindrical member a number of times corresponding to an integer of two or more, and the shape of an edge on the wrapping start side of the porous sheet is such that on the peripheral surface of the cylindrical member, the edge on the wrapping start side and an edge on a wrapping end side of the porous sheet are adjacent to and parallel to each other, without mutually overlapping.
In the case where the edge on the wrapping start side and the edge on the wrapping end side of the porous sheet are adjacent to and parallel to each other, without mutually overlapping, as described above, on the peripheral surface of the oil application roller, a step projecting out at the edge on the wrapping start side is formed, and an edge on the wrapping end side is fitted into the projecting step, thereby eliminating the projection caused by the step.
Also, in a fixing apparatus of the present invention, the oil application roller of the invention contacts a surface of a fixing rotary member. Also with such a fixing apparatus, an effect similar to the oil application roller of the present invention can be achieved.
Also, an image forming apparatus of the present invention includes the fixing apparatus of the present invention. Also with such an image forming apparatus, an effect similar to the oil application roller of the present invention can be achieved.
Hereinafter, embodiments of the present invention will be described based on the accompanying drawings. Note that the below embodiments are only examples of the present invention, and are not of a nature limiting the technical scope of the present invention.
The transfer belt 3 is circumferentially driven in the direction of arrow B at the same speed as the surface speed of the photosensitive drum 2, and is pressed against the photosensitive drum 2, thereby forming a nip region between the transfer belt 3 and the photosensitive drum 2. Recording paper P that has been transported from below the nip region is introduced to the nip region, and while the recording paper P is transported in the nip region, the toner image on the surface of the photosensitive drum 2 is transferred to the recording paper P. In order to transfer the toner images, a high-voltage transfer bias (a high voltage of the opposite polarity (+) to the charge polarity (−) of the toner) is applied to the transfer belt 3.
The recording paper P is transported upward and guided to the fixing apparatus 4, where heat and pressure are applied to the recording paper P so as to fix the toner image on the recording paper P. The recording paper P is further transported upward via a transport path 5, and is discharged to a discharge tray (not shown in the drawings) or the like.
The pressure roller 11 has a three-layer structure, which is formed by providing an elastic layer on the outer surface of a hollow shaft, and forming a separation layer on the outer surface of the elastic layer. A heater lamp (halogen lamp) that serves as a heater source for heating the roller 11 is provided inside the pressure roller 11 (inside the hollow shaft).
The fixing roller 12 is formed by providing an elastic layer on the outer surface of a hollow shaft, the elastic layer having a sufficient thickness.
The fixing belt 14 is an endless belt made from a material having good heat conduction, and includes a separation layer on its outer peripheral surface.
The heating assistant roller 13 is formed by providing a surface layer on the outer surface of a hollow shaft, and a heater lamp (halogen lamp) that serves as a heater source for heating the roller 13 is provided inside the heating assistant roller 13 (inside the hollow shaft).
Here, since the elastic layer of the fixing roller 12 has a sufficient thickness, when the pressure roller 11 and the fixing roller 12 press against each other with the fixing belt 14 interposed therebetween, the elastic layer of the fixing roller 12 is largely dented so that a wide nip region N is formed between the fixing belt 14 and the pressure roller 11. As a result of the rollers 11, 12 and 13 being rotated in the directions of the corresponding arrows, the fixing belt 14 circumferentially moves via the nip region N while it is heated by the heating assistant roller 13. If a recording paper is transported via the nip region N in this state, the recording paper is heated and pressed by the fixing belt 14 and the pressure roller 11, and the toner image on the recording paper is fixed.
On the other side, the fixing apparatus 4 includes an oil application roller 21 pressed against the pressure roller 11, and a backup roller 25 pressed against the oil application roller 21.
The porous cylindrical member 22 is made of sponge-like synthetic resin, and impregnated with silicone oil or the like. The porous sheet 23 is a porous PTFE (polytetrafluoroethylene) sheet. The sheet 23 is wrapped one to three times around the peripheral surface of the cylindrical member 22, and a wrapping end portion of the sheet 23 is laser-welded to a portion in the peripheral surface of the sheet 23 that lies under the wrapping end portion. Note that thermal compression bonding or adhesive agent may be used instead of laser welding.
The oil application roller 21 is pressed against the surface of the pressure roller 11, and rotatively driven by the pressure roller 11. At this time, oil is supplied in small amounts to the surface of the pressure roller 11 from the porous cylindrical member 22 via the porous sheet 23, such that oil is applied to the surface of the pressure roller 11. Accordingly, it becomes difficult for toner to adhere to the surface of the pressure roller 11 to which oil has been applied.
Also, the backup roller 25 is pressed against the oil application roller 21. The backup roller 25 is provided for removing toner that has been transferred from the surface of the pressure roller 11 to the surface of the oil application roller 21.
Here, even with a thin sheet 23, a step 26 appears in the peripheral surface of the cylindrical member 22 at a position above an edge 23a on the wrapping start side of the sheet 23, and a step 27 appears at a position corresponding to an edge 23b on the wrapping end side.
Also, as apparent from
As a result of the oil application roller 21 being rotatively driven in the direction opposite to the wrapping direction of the sheet 23 as shown in
For this reason, when the oil application roller 21 is rotatively driven, although the step 26 due to the edge 23a on the wrapping start side acts as a resistance, the step 27 due to the edge 23b on the wrapping end side does not act as a resistance.
Also when the step 26 due to the edge 23a on the wrapping start side reaches the location between the oil application roller 21 and the backup roller 25, the backup roller 25 climbs over the step 26, and thus the step 26 due to the edge 23a on the wrapping start side acts as a resistance.
In view of these issues, the present embodiment reduces resistance caused by the step 26 due to the edge 23a on the wrapping start side when the oil application roller 21 is rotatively driven.
Therefore, when the step 26 due to the edge 23a on the wrapping start side passes between the oil application roller 21 and the pressure roller 11 as the oil application roller 21 is rotatively driven, the contact width of the step 26 to the pressure roller 11 is narrow at first, and then gradually widened. At every rotation of the oil application roller 21, the step 26 repeats passing between the oil application roller 21 and the pressure roller 11 as described above.
Also when the step 26 due to the edge 23a on the wrapping start side passes between the oil application roller 21 and the backup roller 25 as shown in
As described above, since the contact width of the step 26 is narrow at first, and the resistance caused by the narrow-width step 26 is small, the pressure roller 11 and the backup roller 25 can easily climb over the narrow-width step 26. Also, once the oil application roller 21 climbs over the step 26, the oil application roller 21 is kept to be rotatively driven even though the contact width of the step 26 of the oil application roller 21 to the pressure roller 11 and the backup roller 25 is widened. Therefore, the oil application roller 21 continues to be rotatively driven.
That is, as a result of the edge 23a on the wrapping start side of the sheet 23 being inclined relative to the longitudinal direction C of the shaft 24, or as a result of the end portion 23c on the wrapping start side of the sheet 23 being formed to have a triangle shape, the contact width of the step 26 to the pressure roller 11 and the backup roller 25 is made narrow at first, and thus the pressure roller 11 and the backup roller 25 can easily climb over the narrow-width step 26, so that the oil application roller 21 continues to be rotatively driven.
In the conventional oil application roller 101, the wrapping start edge 103a of the sheet 103 is cut parallel to the shaft of the oil application roller 101, and due to the wrapping start edge 103a, the step 105 is formed parallel to the shaft of the oil application roller 101.
In the test, the diameters of the oil application rollers 21 and 101 were set to 16 mm, and the diameter of the backup roller 25 was set to 8 mm, the shaft-to-shaft distance between the oil application roller 21 and the backup roller 25 and that between the oil application roller 101 and the backup roller 25 were set to 11.5 mm (pressing amount by the backup roller 25 against the oil application rollers 21 and 101 is assumed to be 0.5. mm), and the contact pressure between the oil application roller 21 and the pressure roller 11 and that between the oil application roller 101 and the pressure roller 11 were set to 1 kgf.
Then, fixing processing by the fixing apparatus 4 was continuously performed by feeding multiple sheets of recording paper “SW-A4”, which produces a large amount of paper dust, and recording paper “M3-A4”, which produces a small amount of paper dust, and the rotation condition of the oil application rollers 21 and 101 was checked after finishing fixing processing for 5,000 (5 k) sheets and 20,000 (20 k) sheets. The test was performed for two types of recording paper which produce different amounts of paper dust because, as the amount of produced paper dust increases, the amount of paper dust that adheres to the peripheral surface of the oil application rollers 21 and 101 increases, and the oil application rollers 21 and 101 are readily caused to stop (SW-A4 and M3-A4 are recording paper recommended by Sharp Corporation).
As clearly understood from the table in
In contrast, the oil application roller 21 of the present embodiment did not stop operation after processing 20,000 (20 k) sheets of recording paper, for both of recording paper SW-A4, which produces a large amount of paper dust, and recording paper M3-A4, which produces a small amount of paper dust.
Accordingly, it is possible to state that stoppage of operation is less likely in the oil application roller 21 of the present embodiment than in the conventional oil application roller 101. This is because the resistance generated when the pressure roller 11 and the backup roller 25 climb over the narrow-width step in the oil application roller 21 of the present embodiment is smaller than the resistance generated when the pressure roller 11 and the backup roller 25 climb over the conventional step parallel to the shaft of the oil application roller 101.
Also in the case where this sheet 31 is wrapped around the peripheral surface of the cylindrical member 22, when the step due to the edge 31a on the wrapping start side passes between the oil application roller 21 and the pressure roller 11 (or the backup roller 25) as the oil application roller 21 is rotatively driven, the contact width of the step to the pressure roller 11 (or the backup roller 25) is narrow at first, and then gradually widened. Therefore, the pressure roller 11 (or the backup roller 25) can easily climb over the narrow-width step, and the oil application roller 21 is kept to be rotatively driven.
Also in the case where the sheets 32 to 35 of the second to sixth modified examples are wrapped around the peripheral surface of the cylindrical member 22, as the oil application roller 21 is rotatively driven, the contact width of the step to the pressure roller 11 (or the backup roller 25) is narrow at first, and then gradually widened. Therefore, the pressure roller 11 (or the backup roller 25) can easily climb over the narrow-width step, and the oil application roller 21 is kept to be rotatively driven.
Similar to the sheet 31 in
If x is the length from the edge 37a on the wrapping start side to the edge 37b on the wrapping end side, along the direction orthogonal to the longitudinal direction C of the shaft 24, the length x is constant regardless of the position in the longitudinal direction C of the shaft 24, and can be set to a length that is an integer multiple (of at least 2 times) of the length of the peripheral surface of the cylindrical member 22. Therefore, it is possible to wrap the sheet 37 around the peripheral surface of the cylindrical member 22 at least twice.
Also, when the sheet 37 is wrapped around the peripheral surface of the cylindrical member 22 as shown in
The present invention may be embodied in various other forms without departing from the spirit or essential characteristics thereof. The embodiments disclosed in this application are to be considered in all respects as illustrative and not limiting. The scope of the invention is indicated by the appended claims rather than by the foregoing description, and all modifications or changes that come within the meaning and range of equivalency of the claims are intended to be embraced therein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-131209 | Jun 2010 | JP | national |
