Patent Application
20110211887
1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine or printer of an electrophotographic system, and, more particularly, to a sheet conveying apparatus and an image forming apparatus having this sheet conveying apparatus of a suctioning-conveying system using endless conveying belts.
2. Description of the Related Art
Recently, image forming apparatuses such as copying machines, printers and facsimile machines using an electrophotographic system are spreading. Further, these image forming apparatuses are required to output all sheets such as thin paper, thick paper and coated paper while maintaining high productivity (a number of sheets to form images per unit time), and, moreover, provide durability for maintaining quality in a long term of use.
Incidentally, in a sheet conveying portion, paper dust (sheet dust) is produced from sheets when rollers or guides which convey the sheets contact sheets. Further, with the electrophotographic system image forming apparatuses, part of toner used to form images remains in a photoreceptor (this is referred to as “transfer remaining toner”), and this transfer remaining toner flies before it is cleaned. Furthermore, there are cases where such paper dust and transfer remaining toner accumulate in sheet conveying portions which convey sheets to which toner is transferred, and the paper dust and transfer remaining toner additionally accumulated adhere to sheets to be conveyed and are heated and pressured by a fixing apparatus, thereby causing a problem that quality of images becomes poor. In addition, if paper dust and transfer remaining toner which adhere to sheets are little, image quality does not become poor even when the sheets are heated and pressured by the fixing apparatus. However, image quality becomes poor when a great amount of accumulated paper dust and transfer remaining toner collectively adhere to sheets at one time.
To solve this problem, a sheet conveying apparatus is proposed which is configured to make a cleaning member, which cleans sheet conveying surfaces of endless belts, slidably contact belt surfaces of the conveying belts. This technique is disclosed in Japanese Patent Laid-open No. 2006-131375.
With a conventional sheet conveying apparatus which cleans conveying belts using a cleaning member, the cleaning member slidably contacts the belt surfaces of the conveying belts at all times. Therefore, the belt surfaces of the conveying belts gradually become rough due to friction with the cleaning member in a long period of use and significant unevenness is formed. A great amount of paper dust and transfer remaining toner accumulate in the uneven portions, and therefore the cleaning member cannot sufficiently clean the sheet conveying surfaces. Particularly, with a configuration of a suctioning-conveying system of attracting a sheet to sheet conveying surfaces by applying negative pressure of air to conveying belts and conveying the sheet, a plurality of inlet holes for suctioning air is formed in the conveying belts, and therefore corner portions of the inlet holes are scraped and a great amount of paper dust and transfer remaining toner accumulate in these scraped portions. Further, contact pressure between the conveying belts and a sheet increases because the sheet is suctioned by means of negative pressure, and a great amount of paper dust and transfer remaining toner is likely to adhere to sheets collectively. Hence, the above problem that image quality becomes poor cannot be solved reliably even if a cleaning member is used.
The present invention provides a sheet conveying apparatus and an image forming apparatus having this sheet conveying apparatus which can prevent image quality from becoming poor by reducing a great amount of paper dust and transfer remaining toner adhered to sheets without decreasing cleaning performance of a cleaning member which cleans conveying belts of a suctioning-conveying system.
According to the present invention, in the sheet conveying apparatus which has, an attracting and conveying portion which attracts and conveys a sheet, the attracting and conveying portion comprising, an conveying belt portion which attracts the sheet to a sheet conveying surface by negative pressure of air and conveys the sheet, and a cleaning member which contacts and cleans a belt surface of the conveying belt portion, wherein an attracting area which attracts the sheet to the sheet conveying surface is set on an inner side of a range in a width direction orthogonal to a conveying direction in a minimum size sheet which can be conveyed by the attracting and conveying portion, and the cleaning member is arranged to contact the belt surface outside the attracting area.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
An embodiment according to the present invention will be described below referring to
As illustrated in
The photosensitive drum 1 is formed with a metallic cylinder on the surface of which a photosensitive layer of a negative charge polarity is formed, and rotates in the direction of an arrow R1. A black toner image formed on the photosensitive drum 1 is primarily transferred by a primary transfer portion T1 to an intermediate transfer belt 4 which rotates and moves in the direction of an arrow R2, and conveyed to a secondary transfer portion T2 by the intermediate transfer belt 4 and secondarily transferred to a sheet S.
In a sheet deck 9 arranged in the lower portion of the image forming apparatus main body, a plurality of sheets S is stored and stacked. The sheets S are sent one by one from the sheet deck 9, wait at a registration roller 16 positioned below the intermediate transfer belt 4 and are sent to the secondary transfer portion T2 according to the timing of the toner image on the intermediate transfer belt 4. Then, the sheet S to which the toner image is secondarily transferred in the secondary transfer portion T2 is delivered from the secondary transfer portion T2 to a fixing apparatus 17 by a sheet conveying apparatus 18 which is a pre-fixing conveying portion using belts having a shape without ends (endless belts). The sheet S delivered to the fixing apparatus 17 is heated and pressured in a fixing nip portion F1 formed with a pressure roller 19 and fixing roller 20 inside the fixing apparatus 17. The toner image is fixed the toner image on the sheet surface, and then the sheet S is discharged to the exterior of the image forming apparatus main body.
In addition, an image forming portion which forms images includes the above photosensitive drum 1, exposure apparatus 15, developing apparatus 3, primary transfer roller 6 and intermediate transfer belt 4. The above secondary transfer portion T2 forms a transfer portion which transfers to a sheet a toner image formed as an image by the image forming portion.
The sheet conveying apparatus 18 has an attracting and conveying portion which conveys a sheet on which a toner image is transferred by the secondary transfer portion T2 of a transfer portion. As illustrated in
Inside the convey frame 108 and on the inner side of the suctioning endless belts 182 and 183 (lower portion of the interior) on the projection plane from the sheet conveying upper direction, the suctioning fan 115 is disposed. The sheet conveying apparatus 18 produces negative pressure in the convey frame 108 by means of rotation of the suctioning fan 115, and generates attracting force in attracting areas described later by generating the difference in pressure between the sheet conveying surfaces and their back surfaces via a plurality of inlet holes 180. By this means, the sheet conveying apparatus 18 suctions the sheets S in the direction of an arrow B in
With the non-suctioning endless belts 181 and 184 and suctioning endless belts 182 and 183, the driving force from a driving motor (not illustrated) disposed on the front side plate 131 of the image forming apparatus main body is transmitted sequentially from a transmission belt 124 to the drive roller 18a. By this means, accompanying rotation of the drive roller 18a, the endless belts 181 and 184 rotate in the direction of an arrow A in
The suctioning endless belts 182 and 183 are arranged as a pair of belts which are parallel in the width direction orthogonal to the sheet S conveying direction. The non-suctioning endless belts 181 and 184 are arranged as a pair of belts which are parallel on the outer side of each of the suctioning endless belts 182 and 183 in the width direction orthogonal to the sheet S conveying direction.
The non-suctioning endless belts 181 and 184 arranged on the outer side of each of the suctioning endless belts 182 and 183 in the width direction orthogonal to the sheet conveying direction do not convey the sheets S by attracting the sheets S, and functions subsidiarily without the inlet holes 180. The positions of the non-suctioning endless belts 181 and 184 in the width direction orthogonal to the sheet conveying direction are arranged such that their ends in the width direction orthogonal to the sheet conveying direction of all sheets which can be conveyed are positioned so as not to contact the front side plate 131 and rear side plate 132 of the convey frame 108. By this means, it is possible to prevent sheets from contacting and scraping the mold convey frame 108, and prevent sheets from hitting the scraped portion of the convey frame 108 and causing failure to convey the sheets.
The convey frame 108 is configured to be longer than the entire width dimension ranging from the non-suctioning endless belt 181 to the non-suctioning endless belt 184, in the width direction orthogonal to the sheet conveying direction. The convey frame 108 supports each end of the drive roller 18a, driven rollers 18b and 18d and rocking roller 18c by the front side plate 131 and rear side plate 132 provided in both ends of the convey frame 108. The convey frame 108 has duct portions 108c and 108d each accommodating the suctioning fan 115 and having suctioning ports 108a and 108b for suctioning air. With the convey frame 108, these suctioning ports 108a and 108b are provided by being positioned on the inner side of each of the suctioning endless belts 182 and 183. That is, the sheet conveying apparatus 18 has the suctioning ports 108a and 108b to set the attracting areas for attracting sheets to the sheet conveying surfaces, on the inner side of the range of the width direction orthogonal to the conveying direction in which the sheets S of the minimum size which can be conveyed on the sheet conveying surfaces are conveyed. This is because, when the suctioning ports 108a and 108b protrude beyond the minimum size to the outer side in the width direction, air is suctioned from this portion and sufficient negative pressure cannot be acquired, thereby causing failure of attraction. Particularly, small size sheets include many types of high rigidity such as postcards and envelopes, and, if sheets are not sufficiently attracted while being delivered to a fixing entrance guide 102 described later, the sheets float, thereby causing failure to convey the sheets.
An air suctioning portion which generates attracting force in attracting areas provided on the sheet conveying surfaces on which the sheets S can be attracted (areas in which a plurality of inlet holes 180 is formed in the range of the size H1 in the width direction) includes the suctioning fan 115 accommodated in the duct portions 108c and 108d. That is, with the suctioning endless belts 182 and 183, the above attracting areas are provided (set) to oppose the suctioning ports 108a and 108b of the above air suctioning portion in the width direction orthogonal to the sheet S conveying direction.
Further, the non-suctioning endless belts 181 and 184 are configured to rotate and move in the direction of the arrow A in
Next, a cleaning configuration of cleaning the sheet conveying surfaces of the non-suctioning endless belts 181 and 184 will be described referring to
As illustrated in
As illustrated in
A cleaning support member 203a is attached to the convey frame 108 in the position where the cleaning support member 203a does not contact non-suctioning endless belts 181 and 184 respectively, and a cleaning frame 203 is fixed to the convey frame 108 via this cleaning support member 203a. The cleaning frame 203 is attached to the lower portion of the cleaning support member 203a, and a brush pressure stay 201 is supported by this cleaning frame 203 via a brush pressure stay rotating shaft 201a. A pressure spring 202 is installed in a compressed state between the brush pressure stay 201 and cleaning frame 203. The cleaning brush 200a is attached to the brush pressure stay 201 via the stay 200b.
Therefore, force is applied by the pressure spring 202 to the brush pressure stay 201 to rotate around the brush pressure stay rotating shaft 201a toward the non-suctioning endless belts 181 and 184, thereby making the cleaning brush 200a abut on the sheet conveying surfaces of the non-suctioning endless belts 181 and 184. Then, when the drive roller 18a rotates, the front end of the cleaning brush 200a falls down toward the direction of an arrow C in
As described above, the cleaning brush 200a of the cleaning member is arranged to slidably contact the belt surfaces of the non-suctioning endless belts 181 and 184 which are belt portions of the conveying belts according to the present invention corresponding to the sheet conveying surfaces outside the attracting areas. In the non-suctioning endless belts 181 and 184 which are the belt surfaces (belt portions) of the convey belt corresponding to the sheet conveying surfaces outside the attracting areas which the cleaning brush 200a slidably contacts, the inlet holes 180 are not formed as described above.
Further, as illustrated in
Further, in the downstream of the conveying direction of the sheet conveying apparatus 18, the fixing apparatus 17 is disposed with respect to the image forming apparatus main body. With this fixing apparatus 17, the fixing roller 20 and pressure roller 19 form a fixing nip portion F1. When receiving the driving force from the fixing motor (not illustrated) and rotating in the direction of an arrow E in
Here, the relationship in position between the suctioning ports 108a and 108b will be described referring to
Here, the cause that paper dust and transfer remaining toner adhere to the suctioning endless belts 182 and 183 and non-suctioning endless belts 181 and 184 will be described.
That is, with recent sheet conveying apparatuses, the conveying velocity of the sheets S is increased to improve productivity, or, when the sheets S are conveyed continuously, the distance between the rear end of a preceding sheet and the front end of a subsequent sheet is shortened as much as possible. However, shortening the distance between the rear end of the preceding sheet and the front end of the subsequent sheet causes a problem in an image forming process, and is difficult to perform.
Also, with the present embodiment, there is a distance between the rear end of the preceding sheet and the front end of the subsequent sheet. Between sheets, paper dust and transfer remaining toner which are flying around and which cannot be suctioned by the suctioning fan 115 and remain adhere to the suctioning endless belts 182 and 183 and non-suctioning endless belts 181 and 184 near the suctioning ports 108a and 108b.
Then, there is a concern that paper dust and transfer remaining toner adhered to the endless belts 181, 182, 183 and 184 gradually accumulate if sheets are repeatedly conveyed, and adhere to the sheets to be conveyed, thereby deteriorating image quality. In this case, if paper dust and transfer remaining toner adhered to the convey belts are gradually adhere to sheets and are brought out, paper dust and transfer remaining toner do not deteriorate image quality of sheets. However, if a great amount of paper dust and transfer remaining toner gradually adhered to and accumulated in the endless belts 181 to 184 adhere to sheets at one time, paper dust and transfer remaining toner significantly deteriorate image quality of sheets.
Here, the phenomenon that paper dust and transfer remaining toner adhere to sheets will be described. Generally, when sheets are conveyed while contacting the endless belts 181 to 184, although gradually, paper dust and transfer remaining toner on surfaces of these endless belts 181 to 184 adhere to the sheets and are conveyed, so that paper dust and transfer remaining toner on the surfaces of the endless belts 181 to 184 are reduced. In this case, paper dust and transfer remaining toner adhere to sheets little by little and are brought out, and therefore influence images of the sheets little.
However, as described above, there has been a proposal conventionally to make a cleaning member abut on the belt surfaces to clean and remove paper dust and transfer remaining toner from sheet conveying surfaces of conveying belts. According to this proposal, for example, unevenness is formed on endless conveying belt surfaces due to a long term of use, and therefore the surface nature is destroyed.
Particularly, when the cleaning member is made slidably contact suctioning endless belts, the vicinity of inlet holes of the suctioning endless belts is scraped due to great friction with the cleaning member, and paper dust and transfer remaining toner are more likely to accumulate. Further, when the degree of unevenness is greater, the amount of accumulated paper dust and transfer remaining toner increases and the contact area between endless belts and sheets decreases, and therefore the amount of paper dust and transfer remaining toner to adhere to the sheets and be gradually brought out decreases. Further, in the attracting areas where inlet holes are provided, the contact pressure between sheets and belt conveying surfaces is high, and therefore paper dust and transfer remaining toner of sheets are more likely to adhere to the sheets collectively. Therefore, when the cleaning member is made slidably contact these suctioning endless belts 182 and 183, a great amount of paper dust and transfer remaining toner on the surfaces accumulate and cause deterioration in image quality of sheets.
The present embodiment is proposed to analyze and solve this problem.
As illustrated in
With this sheet conveying apparatus 18, the amount of paper dust and transfer remaining toner which accumulate in the suctioning endless belts 182 and 183 and non-suctioning endless belts 181 and 184 is great, and therefore coating is applied to these surfaces. By this means, the amount of paper dust and transfer remaining toner which adhere to sheets and are brought out is increased. However, when the conveying belts have natural surfaces, if the amount of paper dust and transfer remaining toner which accumulate in the conveying belts is less than the amount of paper dust and transfer remaining toner which adhere to sheets and can be conveyed, the effect can be expected even by increasing the pressure (suctioning force).
If no cleaning mechanism is provided in an area where there is a concern that image quality is deteriorated because the surface nature of the conveying belts is deteriorated and accumulated paper dust and transfer remaining toner adhere to sheets to be conveyed by slidably contact of the cleaning member, it is possible to improve quality of images to be conveyed.
That is, with the present embodiment, the cleaning brush 200a is not made slidably contact the suctioning endless belts 182 and 183 which pass the suctioning ports 108a and 108b, and the cleaning brush 200a is made slidably contact the non-suctioning endless belts 181 and 184 which do not pass the suctioning ports 108a and 108b. With this configuration, in the attracting areas where the inlet holes 180 are formed in the range of the size H1 in the width direction in
Therefore, in the attracting areas of the suctioning endless belts 182 and 183, roughness of the surface nature due to friction with the cleaning brush 200a is not produced, so that it is possible to prevent accumulation of a great amount of paper dust and transfer remaining toner. By contrast with this, although roughness of surface nature is produced in the non-suctioning endless belts 181 and 184 which are belt surfaces (belt portions) of the conveying belts corresponding to the sheet conveying surfaces outside the attracting areas, paper dust and transfer remaining toner can be cleaned by making the cleaning brush 200a slidably contact the non-suctioning endless belts 181 and 184. The contact pressure between sheets and belt conveying surfaces due to suctioning does not become high outside the attracting areas, and therefore a great amount of paper dust and transfer remaining toner do not adhere to the sheets. By this means, it is possible to smoothly convey sheets while stably maintaining image quality of sheets.
In addition, it is difficult to bring out all of paper dust and transfer remaining toner which adhere to the suctioning endless belts 182 and 183, and the remaining amount may increase in the long period of use. Therefore, when maintenance of the cleaning brush 200a is performed, the suctioning endless belts 182 and 183 may be cleaned.
With the present embodiment, although endless conveying belts which convey sheets on sheet conveying surfaces are configured separately as four of suctioning endless belts 182 and 183 and non-suctioning endless belts 181 and 184, an endless conveying belt may be configured as one endless belt. In this case, in one endless belt, the cleaning brush 200a only needs to be configured not to slidably contact the attracting area opposing the suctioning ports 108a and 108b in the width direction, and slidably contact only the area except this attracting area. When one endless belt is used, a configuration is possible where the inlet holes 180 are formed on the entire surface of the endless belt, in addition to the configuration where the inlet holes 180 are formed only in the attracting area opposing the suctioning ports 108a and 108b in the width direction.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all modifications, equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2010-042838, filed Feb. 26, 2010, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-042838 | Feb 2010 | JP | national |
