Patent Grant
10101691
This patent application is based on and claims priority pursuant to 35 U.S.C. § 119 to Japanese Patent Application No. 2015-127798 filed on Jun. 25, 2015, and Japanese Patent Application No. 2016-024644 filed on Feb. 12, 2016 in the Japan Patent Office, the entire disclosure of each of which is hereby incorporated by reference herein.
Technical Field
Exemplary aspects of the present invention relate to a fixing device and an image forming apparatus, such as a copier, a printer, a facsimile machine, or a multi-function peripheral including the fixing device, the multi-function peripheral having at least two of the copying, printing, and facsimile functions.
Related Art
Image forming apparatuses such as copiers, printers, facsimile machines, or multi-function peripherals having at least two of copying, printing, and facsimile functions include a fixing device that fixes a developer image on a recording medium. The fixing device includes a fixing rotator and a pressing rotator to form a fixing nip through which the recording medium is passed, so that the developer image on the recording medium is fixed with heat and pressure in the fixing nip. Such a fixing device includes a guide for correctly guiding the recording medium to the fixing nip.
For example, as illustrated in
In at least one embodiment of this disclosure, there is provided an improved fixing device that includes a fixing rotator, a pressing rotator, and a guide. The pressing rotator forms a fixing nip with the fixing rotator. The guide guides a recording medium to the fixing nip. The guide includes a guide surface that contacts a surface of the recording medium against a guide the recording medium. The guide surface is provided parallel to a line tangent to the fixing rotator and the pressing rotator.
The aforementioned and other aspects, features, and advantages of the present disclosure would be better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
The accompanying drawings are intended to depict exemplary embodiments of the present disclosure and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted.
In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this patent specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that have a similar function, operate in a similar manner, and achieve similar results.
Referring now to the drawings, exemplary embodiments of the present disclosure are described below. In the drawings for explaining the following exemplary embodiments, the same reference codes are allocated to elements (members or components) having the same function or shape and redundant descriptions thereof are omitted below.
In
In particular, the process units 9Y, 9M, 9C, and 9K respectively include photoconductor drums 10Y, 10M, 10C, and 10K, charging rollers 11Y, 11M, 11C, and 11K, and developing devices 12Y, 12M, 12C, and 12K. Each of the photoconductor drums 10Y, 10M, 10C, and 10K as drum-shaped rotators includes a surface that can bear toner serving as developer. The charging rollers 11Y, 11M, 11C, and 11K uniformly charge the surfaces of the respective photoconductor drums 10Y, 10M, 10C, and 10K. The developing devices 12Y, 12M, 12C, and 12K respectively include developing rollers 13Y, 13M, 13C, and 13K that supply toner to the surfaces of the respective photoconductor drums 10Y, 10M, 10C, and 10K.
Moreover, in an upper portion of the image forming apparatus 1, toner bottles 26Y, 26M, 26C, and 26K respectively filled with yellow, cyan, magenta, and black toners are detachably arranged. The yellow, cyan, magenta, and black toners stored in the toner bottles 26Y, 26M, 26C, and 26K are respectively supplied to the developing devices 12Y, 12M, 12C, and 12K via supply paths arranged between the toner bottles 26Y, 26M, 26C, and 26K and the respective developing devices 12Y, 12M, 12C, and 12K.
Moreover, the image forming apparatus 1 includes an exposure unit 3 disposed below the process units 9Y, 9M, 9C, and 9K. The exposure unit 3 emits a laser beam based on image data.
The image forming apparatus 1 includes a transfer unit 4 disposed above the image forming unit 2. The transfer unit 4 includes an endless intermediate transfer belt 16, primary transfer rollers 17Y, 17M, 17C, and 17K, a secondary transfer roller 18 as a transfer rotator, a secondary transfer backup roller 14 as an opposite rotator, a cleaning backup roller 15, a tension roller 27, and a belt cleaning device 28. The primary transfer rollers 17Y, 17M, 17C, and 17K are arranged in positions opposite the respective photoconductor drums 10Y, 10M, 10C, and 10K of the process units 9Y, 9M, 9C, and 9K with the intermediate transfer belt 16 therebetween.
The intermediate transfer belt 16 is an endless belt and is entrained around the secondary transfer backup roller 14, the cleaning backup roller 15, and the tension roller 27. Herein, rotation of the secondary transfer backup roller 14 moves (rotates) the intermediate transfer belt 16 in a direction indicated by an arrow A shown in
The four primary transfer rollers 17Y, 17M, 17C, and 17K and the respective photoconductor drums 10Y, 10M, 10C, and 10K nip the intermediate transfer belt 16 to form primary transfer nips. Each of the primary transfer rollers 17Y, 17M, 17C, and 17K is connected to a power source so as to receive a predetermined direct current (DC) voltage and/or a predetermined alternating current (AC) voltage.
The secondary transfer roller 18 and the secondary transfer backup roller 14 nip the intermediate transfer belt 16 to form a secondary transfer nip M as a transfer nip. Similar to the primary transfer rollers 17Y, 17M, 17C, and 17K, the secondary transfer roller 18 is connected to a power source so as to receive a predetermined DC voltage and/or a predetermined AC voltage.
The belt cleaning device 28 includes a cleaning brush and a cleaning blade that are arranged to contact the intermediate transfer belt 16. A waste toner collected by the belt cleaning device 28 is stored in a waster toner bottle via a waster toner transporting hose.
A sheet feeding unit 5 is disposed in a lower portion of the image forming apparatus 1. The sheet feeding unit 5 includes a sheet cassette 19 for storing sheets P as recording media, and a sheet feeding roller 20 for conveying a sheet P from the sheet cassette 19.
A sheet P fed from the sheet feeding unit 5 is conveyed along a conveyance path 6. A plurality of conveyance roller pairs including a registration roller pair 21 is arranged as appropriate along the conveyance path 6 to a sheet ejection unit 8.
A fixing device 7 includes a fixing roller 22 as a fixing rotator, and a pressing roller 23 as a pressing rotator. The fixing roller 22 is heated by a heat source, and the pressing roller 23 can press the fixing roller 22. The pressing roller 23 and the fixing roller 22 form a fixing nip N.
The sheet ejection unit 8 is disposed on the extreme downstream side of the conveyance path 6 in the image forming apparatus 1. The sheet ejection unit 8 includes a pair of ejection rollers 24 for ejecting the sheet P outside, and an ejection tray 25 on which the ejected sheet P is stacked.
The image forming unit 2, the exposure unit 3, and the transfer unit 4 function to form an image on the sheet P.
Hereinafter, a basic operation of the image forming apparatus 1 is described with reference to
When the image forming apparatus 1 starts an image forming operation, electrostatic latent images are formed on surfaces of the photoconductor drums 10Y, 10M, 10C, and 10K of the respective process units 9Y, 9M, 9C, and 9K. Herein, the exposure unit 3 emits beams to the photoconductor drums 10Y, 10M, 10C, and 10K based on image information that is single color image information obtained by dividing a desired full-color image into color information of yellow, cyan, magenta, and black. When the electrostatic latent images are formed on the photoconductor drums 10Y, 10M, 10C, and 10K, the drum-shaped developing rollers 13Y, 13M, 13C, and 13K respectively supply the toners stored in the developing devices 12Y, 12M, 12C, and 12K to the photoconductor drums 10Y, 10M, 10C, and 10K. Thus, the electrostatic latent images become visible as toner images (developer images).
In the transfer unit 4, when the secondary transfer backup roller 14 is rotated, the intermediate transfer belt 16 moves in a direction indicated by the arrow A shown in
Meanwhile, in the lower portion of the image forming apparatus 1, the sheet feeding roller 20 of the sheet feeding unit 5 is rotated to feed a sheet P stored in the sheet cassette 19 to the conveyance path 6 when the image forming apparatus 1 starts the image forming operation. The registration roller pair 21 times conveyance of the sheet P fed to the conveyance path 6, so that the sheet P is conveyed to the secondary transfer nip M between the secondary transfer roller 18 and the secondary transfer backup roller 14. Herein, a transfer voltage having a polarity opposite to the toner charge polarity of the toner image on the intermediate transfer belt 16 is being applied, and a transfer electric field is being formed in the secondary transfer nip M. With the electric field in the secondary transfer nip, the toner images on the intermediate transfer belt 16 are collectively transferred to the sheet P.
The sheet P with the transferred toner image is conveyed to the fixing device 7, so that the toner image is fixed on the sheet P with heat and pressure applied by the fixing roller 22 and the pressing roller 23. Subsequently, the sheet P with the fixed image is separated from the fixing roller 22 and then conveyed by the conveyance roller pair to the sheet ejection unit 8 in which the sheet P is ejected by the ejection roller pair 24 to the ejection tray 25.
The image forming operation has been described using an example case in which a full-color image is formed on a sheet P. However, the image forming operation can be applied to a case in which a single color image is formed using any one of the four process units 9Y, 9M, 9C, and 9K, or a two-color image or a three-color image is formed using two or three out of the four process units 9Y, 9M, 9C, and 9K.
On the conveyance path 6, a guide 30 for guiding the sheet P to the fixing nip N of the fixing device 7 is disposed on an upstream side of the fixing device 7 in a conveyance direction of the sheet P (hereinafter, the conveyance direction of the sheet P is also called a conveyance direction).
In such a configuration, however, an electric charge tends to be accumulated in a position of the edge portion 401. When a surface of the sheet P slides against the edge portion 401, the edge portion 401 is charged. This causes a problem of irregularity in a toner image on the surface of the sheet P.
The guide preferably has an electrical resistance of approximately 108Ω to approximately 1012Ω. In a case in which the guide is made of a conductive material, an electric charge retained by the sheet P or an electric charge applied to the sheet P by a transfer unit flows to the guide when the sheet P contacts the guide. This causes the irregularity in the toner image on the sheep P and a transfer process failure in the transfer unit. Although such failures can be prevented if a coating agent or a paste having moderate electrical resistance is applied to a surface of the guide, the cost of the guide increases as a result.
Moreover, in a case in which a guide is made of a non-conductive material similar to the related-art guide 40 illustrated in
The guide 30 of the present exemplary embodiment is configured to solve such problems. Hereinafter, the guide 30 is described.
According to the present exemplary embodiment, as illustrated in
Next, relative positions of the guide 30 and each components of the fixing device 7 according to the present exemplary embodiment of the present invention is described with reference to
In the present exemplary embodiment, as illustrated in
The first guide surface 301 is provided on the extreme downstream side of the guide 30 in the conveyance direction. Moreover, as illustrated in
As illustrated in
Moreover, the entire area of the first guide surface 301 (in particular, the end portion 303 of the first guide surface 301) is arranged on the side of the fixing roller 22 relative to the line tangent N2.
Such arrangement facilitates conveyance of the sheet P along a surface of the fixing roller 22 when the sheet P is guided from the first guide surface 301 to the fixing nip N. Since the fixing roller 22 has higher rigidity than the pressing roller 23, the conveyance of the sheet P along the surface of the fixing roller 22 enables not only a conveyance position of the sheet P to be stable but also the sheet P to be conveyed to the fixing nip N with higher accuracy.
Although the arrangement of the first guide surface 301 on the side of the fixing roller 22 can provide the above effects, a friction between the first guide surface 301 and the sheet P increases. This increases a charge on the first guide surface 301. That is, since the sheet P is nipped between the first guide surface 301 and the surface of fixing roller 22 of the fixing nip N, the friction between the sheet P and the first guide surface 301 is high in comparison with a case in which the first guide surface 301 is arranged on the line tangent N2 or the side closer to the pressing roller 23.
Even in such a case, the arrangement of the first guide surface 301 parallel to the line tangent N2 in the guide 30 of the present exemplary embodiment can reduce the charge on the first guide surface 301. Accordingly, even if a friction between the sheet P and the first guide surface 301 is increased, the arrangement of the first guide surface 301 on the side of the fixing roller 22 can prevent the charge on the first guide surface 301 from being excessively large. Hence, a toner image on the surface of the sheet P does not tend to be affected.
Since the guide 30 is disposed near an inlet of the fixing nip N, temperature of the guide 30 is liable to increase. Hence, the guide 30 needs to have resistance to heat. Moreover, a user may touch the guide 30 when dealing with a paper jam. Thus, the guide 30 needs to be made of a material that can keep a surface temperature to 80 degrees Celsius or below. Moreover, the guide 30 needs to have surface smoothness so that a friction resistance is not increased when the guide 30 guides the sheet P.
Therefore, the guide 30 of the present exemplary embodiment is made of a heat-resistant resin material such as liquid crystal polymer (LCP) that is capable of forming a smooth surface and has good size stability. The resin material can be mixed with a reinforcing filler to maintain heat resistance and strength.
However, there is a possibility that the mixture may be deposited on the surface of the guide 30. In some cases, such deposition of the mixture can affect the surface smoothness of the guide 30. Consequently, the mixture is not used in the present exemplary embodiment. Moreover, an amount of a material such as carbon to be blended is set to be low from a molding standpoint.
If a surface roughness of the first guide surface 301 is excessively low, a contact area between the first guide surface 301 and the sheet P increases. This may cause an increase in a charge on the guide 30. On the other hand, if a surface roughness of the first guide surface 301 excessively high, the rough surface may interrupt guidance of the sheet P.
Herein, as for the first guide surface 301 of the present exemplary embodiment, a surface roughness can be determined in consideration of charge protection. The surface roughness of the first guide surface 301 is set to approximately 50 μm to approximately 150 μm.
The surface roughness of the first guide surface 301 can be set by a crimping process that is performed on the surface of the first guide surface 301. However, as long as the above surface roughness can be acquired, other processes can be employed.
Hereinafter, a fixing device of another exemplary embodiment of the present exemplary embodiment is described with reference to
First, a description is given mainly of differences between the image forming apparatus 1 illustrated in
The image forming apparatus 1000 of the present exemplary embodiment includes a sheet feeding unit 5, an image forming unit 2, a fixing device 7, and an sheet ejection unit 8.
The image forming unit 2 includes an exposure device, a developing device, a cleaning unit. In the image forming unit 2, a toner stored in the developing device is supplied to a photoconductor drum 10 as an opposite rotator, so that an electrostatic latent image on the photoconductor drum 10 becomes visible as a toner image.
Meanwhile, a registration roller 21 times conveyance of a sheet P fed from the sheet feeding unit 5 to convey the sheet P to a nip portion at a transfer roller 34 as a transfer rotator. In the nip portion, the toner image is transferred to the sheet P.
The sheet P with the transferred image is conveyed to the fixing device 7 via a conveyance path, so that the toner image is fixed on the sheet P with heat and pressure applied by a fixing roller 22 and a pressing roller 23.
The sheet P with the fixed image is separated from the fixing roller 22 by a separation unit 35, and then further conveyed to a downstream side.
Subsequently, in a sheet ejection unit 8, the sheet P is ejected by an ejection roller pair 24 to an ejection tray 25.
On an upstream side of the fixing nip N in the conveyance direction, an opposite guide 33 is disposed opposite the guide 30. The opposite guide 33 is inclined toward the fixing nip N (or the line tangent D) as it approaches the downstream side from the upstream side in the conveyance direction. This enables the conveyance path along which the sheet P is conveyed to be narrowed toward the fixing nip N, thereby guiding the sheet P in a correct conveyance direction.
The guide 30 can be set as a first guide. In such a case, on an upstream side of the first guide 30 in the conveyance direction, a second guide 31 and a third guide 32 for guiding a sheet P are arranged on the side of the pressing roller 23 relative to the line tangent D (the side opposite the first guide surface 301 with the line tangent D therebetween). Moreover, a space B is provided between the line tangent D and the first guide 30, the second guide 31, the third guide 32, and a transfer roller 34. The space B serves as a predetermined area in which the sheet P can pass.
A rotation speed of each of the fixing roller 22 and the pressing roller 23 is set to be lower than that of each of the transfer roller 34 and the photoconductor drum 10. A linear velocity in the fixing nip N is lower than that in the transfer nip MM, so that the sheet P is prevented from being pulled toward the fixing device 7. Herein, a linear velocity difference between the fixing nip N and the transfer nip MM causes slack of the sheet P. However, the sheet P can be slackened off to absorb the slack in the space B.
In a case in which the second guide 31 and the third guide 32 are arranged on the line tangent D or the side closer to the fixing roller 22, the sheet P slides against the second guide 31 or the third guide 32 with a large friction force when being conveyed from the transfer nip MM to the fixing nip N. This charges the second guide 31 and the third guide 32, causing a failure such as the aforementioned image dust particles.
In the present exemplary embodiment, the first guide 30, the second guide 31, and the third guide 32 are arranged on the side of the pressing roller 23 relative to the line tangent D. Such arrangement enables the sheet P to be slackened toward the pressing roller 23 in the space B, thereby preventing a large friction force from being generated due to strong slide of the sheet P against the second guide 31 and the third guide 32. The second guide 31 and the third guide 32 can be provided as one unit, or three or more guides can be arranged.
In the present exemplary embodiment, the first guide surface 301 can be arranged on the side of the fixing roller 22 relative to the line tangent D.
According to the fixing device of the exemplary embodiment of the present invention, therefore, a guide surface for guiding a recording medium is provided parallel to a line tangent to a fixing rotator and a pressing rotator. This construction enables the recording medium to contact the guide surface as a plane without any projection of the guide surface with respect to the recording medium when the recording medium is conveyed from the guide surface to a fixing nip. Accordingly, a charge on the guide surface when the recording medium is guided can be low in comparison with a case in which a recording medium contacts a projection of the guide surface as a point. Hence, adverse effects such as image irregularities that occur when a developer image on the recording medium surface is fixed can be reduced.
Therefore, at least one exemplary embodiment of the present invention can provide a fixing device including a low-cost guide that can guide a recording medium to a fixing nip and reduce a charge amount when a recoding medium is guided.
Embodiments of the present invention have been described above with reference to specific exemplary embodiments. Note that the present disclosure is not limited to the details of the embodiments described above, but various modifications and enhancements are possible without departing from the scope thereof.
In the exemplary embodiment described above with reference to
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-127798 | Jun 2015 | JP | national |
| 2016-024644 | Feb 2016 | JP | national |
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| Number | Date | Country | |
|---|---|---|---|
| 20160378032 A1 | Dec 2016 | US |
