Patent Grant
9864305
This application is based upon and claims the benefit of priority from the corresponding Japanese Patent Application No. 2015-147046 filed on Jul. 24, 2015, the entire contents of which are incorporated herein by reference.
The present disclosure relates to an image forming apparatus, and in particular, to an image forming apparatus including a belt cleaning device that removes residual toner adhered to an intermediate transfer belt.
Conventionally, image forming apparatuses, such as copiers and printers, include a belt cleaning device that removes residual toner adhered to an intermediate transfer belt onto which a toner image formed on a photosensitive drum (an image carrier) is transferred.
For example, there have been know image forming apparatuses that include a plurality of photosensitive drums (image carriers), an intermediate transfer belt, a plurality of stretching rollers that rotatably stretch the intermediate transfer belt, and a belt cleaning unit (a belt cleaning device) that removes residual toner adhered to the intermediate transfer belt. In such image forming apparatuses, the plurality of stretching rollers include a driving roller that is disposed at one end in an arrangement direction of the plurality of photosensitive drums and that drives the intermediate transfer belt to rotate, and a tension roller (a driven roller) that is disposed at the other end in the arrangement direction of the plurality of photosensitive drums. The belt cleaning unit is disposed at a position exterior to the tension roller so as to face the tension roller with the intermediate transfer belt interposed between the belt cleaning unit and the tension roller.
According to an aspect of the present disclosure, an image forming apparatus includes a plurality of image carriers, an intermediate transfer belt formed in an endless shape, a plurality of stretching rollers, a belt cleaning device, and a counter roller. Onto the intermediate transfer belt, toner images formed on the image carriers are transferred. The stretching rollers rotatably stretch the intermediate transfer belt. The belt cleaning device has a cleaning blade of which a leading end portion is oriented toward an upstream side in a rotation direction of the intermediate transfer belt and abuts on an outer circumferential surface of the intermediate transfer belt to thereby remove residual toner adhered to the intermediate transfer belt. The counter roller is disposed facing the cleaning blade with the intermediate transfer belt interposed therebetween in such a manner that the counter roller is in contact with an inner circumferential surface of the intermediate transfer belt. The plurality of stretching rollers include a driving roller that is disposed at one end in an arrangement direction of the plurality of image carriers and that drives the intermediate transfer belt to rotate, and a driven roller that is disposed at another end in the arrangement direction. The belt cleaning device is disposed at a position that is downstream of the driving roller in the rotation direction of the intermediate transfer belt but is upstream of the driven roller in the rotation direction of the intermediate transfer belt. A top of the counter roller is disposed to be level with a top of the driving roller and a top of the driven roller, or above the top of the driving roller and the top of the driven roller. A leading end edge portion of the cleaning blade that abuts on the intermediate transfer belt is disposed upstream of the top of the counter roller in the rotation direction of the intermediate transfer belt.
Other features and specific advantages of the present disclosure will become apparent from the following descriptions of preferred embodiments.
Hereinafter, an embodiment of the present disclosure will be described with reference to the accompanying drawings.
With reference to
The image forming apparatus 100 (herein, a color printer) of the present embodiment is a quadruple tandem type color printer that performs image formation with four photosensitive drums 1a, 1b, 1c, and 1d corresponding to four different colors (yellow, cyan, magenta, and black) and arranged parallel to each other.
In an apparatus main body of the image forming apparatus 100, four image forming portions Pa, Pb, Pc, and Pd are arranged in order from a left side in
These image forming portions Pa to Pd are provided with photosensitive drums 1a to 1d that carry visible images (toner images) of corresponding colors, and further, an intermediate transfer belt 8 that rotates in a counterclockwise direction in
The sheet P, onto which the toner images are to be transferred, is accommodated in a sheet cassette 16 disposed in a lower part of the apparatus, and is conveyed via a sheet feeding roller 12a and a registration roller pair 12b to the secondary transfer roller 9. As the intermediate transfer belt 8, a dielectric resin sheet is used, typically in a form of a (seamless) belt having no seam. The intermediate transfer belt 8 and the secondary transfer roller 9 are driven to rotate by a belt driving motor (not shown) at a same linear speed as the photosensitive drums 1a to 1d. For the purpose of removing residual toner remaining on a surface of the intermediate transfer belt 8, a belt cleaning device 30 is disposed at the image forming portion Pd.
Next, the image forming portions Pa to Pd will be described. Around and below the rotatably arranged photosensitive drums 1a to 1d, the following are provided: charging devices 2a, 2b, 2c, and 2d that charge the photosensitive drums 1a to 1d, an exposure unit 5 that performs exposure on each of the photosensitive drums 1a to 1d based on image data, developing units 3a, 3b, 3c, and 3d that develop, with toner, electrostatic latent images formed on the photosensitive drums 1a to 1d, and cleaning devices 7a, 7b, 7c, and 7d that collect and remove developer (toner) remaining on the photosensitive drums 1a to 1d after the toner images on the photosensitive drums 1a to 1d are transferred.
On receipt of image data from a host device such as a personal computer, first, the charging devices 2a to 2d uniformly charge surfaces of the photosensitive drums 1a to 1d. Next, based on the image data, the exposure unit 5 irradiates the photosensitive drums 1a to 1d with light to thereby form electrostatic latent images on the photosensitive drums 1a to 1d according to the image data. The developing units 3a to 3d are provided with developing rollers disposed facing the photosensitive drums 1a to 1d, and the developing units 3a to 3d are filled with a predetermined amount of two-component developer containing toner of yellow, magenta, cyan, and black.
When a proportion of toner in the two-component developer in each of the developing units 3a to 3d falls short of a reference value, toner is supplied from toner containers 4a to 4d to the developing units 3a to 3d. The toner is fed onto the photosensitive drums 1a to 1d by the developing units 3a to 3d, and electrostatically adheres thereto. Thereby, toner images are formed according to electrostatic latent images formed by the exposure that has been performed by the exposure unit 5.
Then, an electric field with a predetermined transfer voltage is applied between primary transfer rollers 6a to 6d and the photosensitive drums 1a to 1d by the primary transfer rollers 6a to 6d, and yellow, cyan, magenta, and black toner images formed on the photosensitive drums 1a to 1d are primarily transferred onto the intermediate transfer belt 8. The toner images of the four colors are formed with a predetermined positional relationship between them that is previously determined for forming a predetermined full-color image. Thereafter, in preparation for formation of new electrostatic latent images to be subsequently performed, toner remaining on the surfaces of the photosensitive drums 1a to 1d is removed by the cleaning devices 7a to 7d.
The intermediate transfer belt 8 is wound around and between the driven roller 10 and the driving roller 11. When the intermediate transfer belt 8 starts to rotate in the counterclockwise direction along with rotation of the driving roller 11 caused by the above-mentioned belt driving motor, the sheet P is conveyed, at a predetermined timing, from the registration roller pair 12b to a nip portion (a secondary transfer nip portion) formed between the intermediate transfer belt 8 and the secondary transfer roller 9 that is provided adjacent to the intermediate transfer belt 8, and at the nip portion, a full-color image is secondarily transferred onto the sheet P. The sheet P onto which the full-color toner image has been transferred is conveyed to the fixing device 13.
The sheet P conveyed to the fixing device 13 has the toner image fixed on the surface thereof by receiving heat and pressure while passing through a fixing nip portion of a fixing roller pair 13a composed of a heating roller and a pressure roller, whereby the predetermined full-color image is formed. The sheet P on which the full-color image has been formed passes through a conveyance roller pair 15 to reach a branching position of a sheet conveyance path 18. The sheet P is directed by a branching member 21 disposed at the branching portion to one of a plurality of conveyance directions, to be then discharged as it is (or after it is sent to a double-sided copying conveyance path 22 and subjected to double-sided copying) onto a discharge tray 20 via a discharge roller pair 19.
The sheet conveyance path 18 is specifically divided into two paths which extend leftward and rightward at a position downstream of the conveyance roller pair 15, and one of the paths (the path extending leftward as seen in
Thereafter, by reversely rotating the discharge roller pair 19 and swinging the branching member 21 substantially horizontally, the sheet P is guided along an upper surface of the branching member 21 to the double-sided copying conveyance path 22, and is then conveyed back to the secondary transfer roller 9 with its image side reversed. Then, a next image formed on the secondary transfer belt 8 is transferred by the secondary transfer roller 9 onto the no-image side of the sheet P, then the sheet P is conveyed to the fixing device 13 where the toner image is fixed thereon, and then the sheet P is discharged onto the discharge tray 20.
Next, a structure of and around the belt cleaning device 30 will be described.
As shown in
The belt cleaning device 30 is disposed at a position that is downstream of the driving roller 11 in the rotation direction of the intermediate transfer belt 8 but is upstream of the driven roller 10 in the rotation direction of the intermediate transfer belt 8. As shown in
The housing 31 has an opening portion 31a that faces the intermediate transfer belt 8, and a waste toner accommodating portion 31b that accommodates waste toner scraped off from the surface of the intermediate transfer belt 8.
The cleaning blade 32 is fixed to a position downstream (on a left side in
At a position opposite to the cleaning blade 32 with respect to the intermediate transfer belt 8, there is disposed a counter roller 40, which is provided so as to be in contact with an inner circumferential surface of the intermediate transfer belt 8 and receives the contact pressure of the cleaning blade 32. The counter roller 40 is caused to rotate in the counterclockwise direction in
Residual toner removed from the surface of the intermediate transfer belt 8 by the cleaning blade 32 is discharged to outside the belt cleaning device 30 along with rotation of the collecting screw 33, and is then conveyed into a toner collection container (not shown) to be stored therein.
The seal member 35 is fixed to the housing 31, at a position upstream (on a right side in
Here, in the present embodiment, as shown in
As shown in
The leading end edge portion 32a is disposed downstream (on a left side in
As shown in
In the present embodiment, as has been described above, the belt cleaning device 30 is disposed at a position that is downstream of the driving roller 11 in the rotation direction of the intermediate transfer belt 8 but is upstream of the driven roller 10 in the rotation direction of the intermediate transfer belt 8. This arrangement allows the belt cleaning device 30 to be disposed between the driving roller 11 and the driven roller 10 in the arrangement direction of the photosensitive drums 1a to 1d (the left-right direction in
Furthermore, the counter roller 40 is provided, which is disposed so as to face the cleaning blade 32 with the intermediate transfer belt 8 interposed therebetween in such a manner that the counter roller 40 is in contact with the inner circumferential surface of the intermediate transfer belt 8. This arrangement allows the contact pressure of the cleaning blade 32 to be received by the counter roller 40, and thus makes it possible to reduce the possibility of degradation of the cleaning performance caused by the intermediate transfer belt 8 escaping (warping away from the cleaning blade 32).
Furthermore, the leading end edge portion 32a of the cleaning blade 32 that abuts on the intermediate transfer belt 8 is disposed upstream (on a right side in
As described above, the leading end edge portion 32a is disposed 0.5 mm or more upstream of the top P40a of the counter roller 40 in the rotation direction of the intermediate transfer belt 8. This arrangement makes it possible to securely prevent the leading end edge portion 32a from being disposed downstream of the top P40a of the counter roller 40 in the rotation direction of the intermediate transfer belt 8 even when there is a member dimension error or a member fitting error.
As described above, the amount by which the cleaning blade 32 digs into the intermediate transfer belt 8 is 1.0 mm or more. This arrangement allows the cleaning blade 32 to securely abut on the intermediate transfer belt 8.
As described above, when the tilt angle of the part of the intermediate transfer belt 8 that extends from the driving roller 11 toward the counter roller 40 with respect to the horizontal plane is represented by θ1, and the tilt angle of the cleaning blade 32 with respect to the part of the intermediate transfer belt 8 that extends from the driving roller 11 toward the counter roller 40 is represented by θ2, θ1<θ2 holds. This arrangement helps secure a satisfactory cleaning performance.
Further, as described above, the tilt angle θ1 fulfills 0°≦θ1≦15°, and the tilt angle θ2 fulfills 10°≦θ2≦40°. This arrangement helps easily secure a satisfactory cleaning performance.
Further, as described above, the tilt angles θ1 and θ2 fulfill θ2−θ1≦30°. This arrangement helps reduce the possibility of the leading end of the cleaning blade 32 warping (blade curling-up occurring) toward the downstream side in the rotation direction of the intermediate transfer belt 8.
Further, as described above, the leading end edge portion 32a is disposed downstream (on a left side in
Next, a description will be given of confirmation experiments conducted to confirm the above advantages.
In these confirmation experiments, the above-described image forming apparatus 100 was used, and the diameter of the counter roller 40 was 10 mm. And, with the tilt angle θ1 set to angles from 0° to 15° at intervals of 5°, and the tilt angle θ2 set to angles from 10° to 40° at intervals of 5°, the cleaning performance of the cleaning blade 32 in cleaning the intermediate transfer belt 8 and the presence/absence of the occurrence of blade curling-up (that is, warping of the leading end of the cleaning blade toward the downstream side in the rotation direction of the intermediate transfer belt) were checked. Results of the confirmation experiments are shown in Table 1 and Table 2. As for the cleaning performance, a case where residual toner was completely removed is indicated by “good”, while a case where incomplete removal of residual toner was observed is indicated by “poor”. As for blade curling-up, a case where no blade curling-up was observed is indicated by “good”, while a case where blade curling-up was observed is indicated by “poor”.
From Table 1, it is clear that, with the arrangement where θ1<θ2, it is possible to achieve a satisfactory cleaning performance of the cleaning blade 32 in cleaning the intermediate transfer belt 8.
From Table 2, it is clear that, with the arrangement where θ2−θ1≦30°, it is possible to reduce occurrence of blade curling-up.
It should be understood that the embodiments disclosed herein are merely illustrative in all respects, and should not be interpreted restrictively. The range of the present disclosure is shown not by the above descriptions of the embodiments but by the scope of claims for patent, and it is intended that all modifications within the meaning and range equivalent to the scope of claims for patent are included.
For example, the above descriptions have dealt with a case where the present disclosure is applied to a color printer, but the present disclosure is not limited to this. Needless to say, the present disclosure is applicable to various image forming apparatuses, such as color copiers and facsimile machines, provided with an intermediate transfer belt, a belt cleaning device, and a counter roller.
The above description of embodiment have dealt with an example where the tilt angle θ1 fulfills 0°≦θ1≦15°, and the tilt angle θ2 fulfills 10°≦θ2≦40°, but the present disclosure is not limited to this. One or both of 0°≦θ1≦15° and 10°≦θ2≦40° may be unfulfilled.
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