Patent Grant
8794626
The present application claims priority under 35 U.S.C §119 to Japanese Patent Application No. 2012-023688 filed Feb. 7, 2012, the entire contents of which are hereby incorporated herein by reference.
1. Field of the Invention
The present invention generally relates to a sheet thickness detecting device detecting the thickness of a sheet passing through a conveying path, a feeding device including the sheet thickness detecting device, and an image forming apparatus such as a copier, a printer, a facsimile machine, a multi-functional peripheral including thereof and the sheet thickness detecting device.
2. Description of the Related Art
To detect a thickness of a sheet passing through a conveying path in an image forming apparatus including a copier, a printer and the like, there has been known a technique using a detecting unit that detects the thickness (sheet thickness) of a sheet (e.g., a sheet material, a recording medium) fed on the conveying path, so as to vary an image forming condition and a feeding condition based on the detection result (see for example in Patent Documents 1 and 2).
Patent Document 1: Japanese Laid-open Patent Publication No. 2004-252233
Patent Document 2: Japanese Patent No. 4152136
Specifically, to detect the sheet thickness, a feeding roller pair including a fixed roller and a movable roller is provided in a conveying path to an image forming part and on the upstream side of the image forming part, so as to detect the displacement amount of the moving roller moving in accordance with the thickness of a sheet by using a detecting unit (sheet thickness detecting unit) while the sheet is sandwiched and fed by the feeding roller pair.
By using an image forming apparatus including such a detecting mechanism, it is no longer necessary for an operator to input data indicating the sheet thickness whenever the operator sets a sheet in the apparatus main body. Therefore, such an image forming apparatus may be an easy-to-use apparatus.
On the other hand, in Patent Document 2 and the like, a technique is disclosed that is aimed to accurately measure the sheet thickness by contacting one end of a lever rotating around a shaft with respect to a moving roller and by detecting the displacement amount of the other end of the lever using a sensor so as to indirectly detect the sheet thickness.
According to an aspect of the present invention, a sheet thickness detecting device for detecting a thickness of a sheet passing through a conveying path includes a fixed roller rotatably supported by a shaft so that the fixed roller faces one side of the sheet passing through the conveying path; a movable roller rotatably provided so that the movable roller and the fixed roller sandwich and feed the sheet, and being displaced in accordance with the thickness of the sandwiched sheet; a swing member rotatably supporting the movable roller and including a shaft so that the swing member is swung around the shaft, wherein the swing member further includes a detection target part formed in a manner that a distance between the detection target part and the shaft is greater than a distance between a position where the movable roller is supported by the swing member and the shaft; and a detecting unit detecting the displacement amount of the detection target part of the swing member.
Other objects, features, and advantages of the present invention will become more apparent from the following description when read in conjunction with the accompanying drawings, in which:
In related art, it may not be possible to accurately detect the thickness of a sheet passing through the conveying path by using a detecting unit. Accordingly, it may not be possible to accurately adjust an image forming condition or a feeding condition to be varied depending on the detection result of the detecting unit.
Especially, in the technique of Patent Document 2, the level contacting the movable (displaceable) roller is unlikely to accurately move in accordance with the displacement of the moving roller. As result, there is a high possibility of inaccurately detecting the sheet thickness.
The present invention is made in light of the above problem, and may provide a sheet thickness detecting device, a feeding device, and an image forming apparatus capable of accurately detecting the thickness of a sheet passing in the conveying path.
In the description, as definition, a term “sheet” refers to any type of recording media. Namely, the “sheet” may include not only a general transfer sheet but also a special sheet such an Over Head Projector (OHP) sheet and a coated sheet.
According to an embodiment, a fixed roller and a movable roller are provided to sandwich and feed a sheet in a conveying path. The movable roller is displaced in accordance with the thickness of the sandwiched sheet. The swing member is swung around a shaft in accordance with the displacement of the movable roller.
The swing member includes a detection target part in a manner that the distance between the detection target part and the shaft is greater than the distance between the movable roller and the shaft. A detection unit detects the distance from the detection target part. By doing this, it may become possible to more accurately detect the thickness of the sheet in the conveying path.
In the following, embodiments of the present invention are described in detail with reference to the drawings. In the figures, the same reference numerals are used to describe the same or equivalent elements, and the repeated descriptions thereof may be omitted.
First, with reference to
As shown in
Under the bottle container 101, there is provided an intermediate transfer unit 85. Also, there are arranged side by side image forming units 4Y, 4M, 4C, and 4K corresponding to yellow, magenta, cyan, and black colors so as to face an intermediate transfer belt 78 of the intermediate transfer unit 85.
In the bottom part of the main body of the image forming apparatus 1, there is provided a sheet supply unit 12 (sheet supply cassette) accommodating a plurality of stacked sheets P (recording media, sheet materials).
The image forming units 4Y, 4M, 4C, and 4K includes respective photoconductive drums 5Y, 5M, 5C, and 5K. Near the photoconductive drums 5Y, 5M, 5C, and 5K, there are disposed respective charging units 75, development units 76, cleaning units 77, discharging units (not shown), and the like. Further, an image forming process (including a charging process, an exposing process, a development process, a transfer process, and a cleaning process) is performed on the photoconductive drums 5Y, 5M, 5C, and 5K, so as to form images thereon in the respective colors.
The photoconductive drums 5Y, 5M, 5C, and 5K (i.e., image carriers) are driven to rotate in the clockwise direction in
After that, the surfaces of the photoconductive drums 5Y, 5M, 5C, and 5K are moved to the positions where the respective laser lights L from an exposure unit 3 are exposed. At the positions, by performing exposure scanning, the electrostatic latent images in the respective colors are formed (exposing process).
After that, the surfaces of the photoconductive drums 5Y, 5M, 5C, and 5K are moved to the positions facing the respective development units 76. At the positions, the electrostatic latent images are developed, so that toner images in the respective colors are formed (development process).
After that, the surfaces of the photoconductive drums 5Y, 5M, 5C, and 5K are moved to the positions facing the intermediate transfer belt 78 and respective primary transfer bias rollers 79Y, 79M, 79C, and 79K. At the positions, the toner images on the photoconductive drums 5Y, 5M, 5C, and 5K are transferred on the intermediate transfer belt (primary transfer process). After that, a slight amount of non-transferred toner remains on the photoconductive drums 5Y, 5M, 5C, and 5K.
After that, the surfaces of the photoconductive drums 5Y, 5M, 5C, and 5K are moved to the positions facing the respective cleaning units 77. At these positions, the non-transferred toner remaining on the photoconductive drums 5Y, 5M, 5C, and 5K are mechanically collected by a cleaning blade of the cleaning units 77 (cleaning process).
Finally, the surfaces of the photoconductive drums 5Y, 5M, 5C, and 5K are moved to the positions facing the respective discharging units. At these positions, residual potential on the photoconductive drums 5Y, 5M, 5C, and 5K is removed.
By doing this, a series of image forming processes performed on the photoconductive drums 5Y, 5M, 5C, and 5K is completed.
After that, the toner images formed on the photoconductive drums in the respective colors are transferred on the intermediate transfer belt 78 serving as an image carrier. By doing this, a color image is formed on the intermediate transfer belt 78.
Here, the intermediate transfer unit 85 includes the intermediate transfer belt 78, the four primary transfer bias rollers 79Y, 79M, 79C, and 79K, a secondary transfer backup roller 82, a cleaning backup roller 83, a tension roller 84, an intermediate transfer cleaning unit 80 and the like.
The intermediate transfer belt 78 is stretched and supported by three rollers 82, 83, and 84, and is driven so as to endlessly move in the arrow direction of
The four primary transfer bias rollers 79Y, 79M, 79C, and 79K and the respective photoconductive drums 5Y, 5M, 5C, and 5K sandwich the intermediate transfer belt 78, so as to form primary transfer nip sections. Further, a transfer bias voltage having a polarity opposite to that of the toner is applied to the primary transfer bias rollers 79Y, 79M, 79C, and 79K.
Further, the intermediate transfer belt 78 is moved in the arrow direction, and sequentially passes through the primary nip sections formed by the primary transfer bias rollers 79Y, 79M, 79C, and 79K. By ding this, the toner images on the photoconductive drums 5Y, 5M, 5C, and 5K and in the respective colors are primarily transferred on the intermediate transfer belt 78.
After that, the intermediate transfer belt 78 on which the toner images in colors are sequentially transferred is fed to a position facing a secondary transfer roller 89. At that position, a secondary nip section is formed by sandwiching the intermediate transfer belt 78 with the secondary transfer backup roller 82 and a secondary transfer roller 89.
Further, the toner image formed on the intermediate transfer belt 78 using the four colors is transferred on a sheet P fed to the secondary nip section. In this case, non-transferred toner which has not been transferred on the sheet P remains on the intermediate transfer belt 78.
After that, the intermediate transfer belt 78 is fed to a position of the intermediate transfer cleaning unit 80. At the position, the non-transferred toner on the intermediate transfer belt 78 is collected.
By doing this, a series of transfer process performed on the intermediate transfer belt 78 is completed.
Here, the sheet P fed to the position of the secondary nip section has been fed from the sheet supply unit 12 formed on the bottom part of the main body of the image forming apparatus 1 via a conveying path K.
More specifically, there are a plurality of stacked sheets P such as transfer sheets accommodated in the sheet supply unit 12. Further, when a sheet feeding roller 51 is driven to rotate in the counterclockwise direction of
The movement of the sheet P fed to the resist roller pair 37 and 38 (timing roller pair) is temporarily stopped at the position of a roller nip (nip section) of the resist roller pair 37 and 38 whose driven rotations are stopped.
Further, in synchronization with the timing of the color image on the intermediate transfer belt 78, the resist roller pair 37 and 38 is driven to rotate to feed the sheet P to the secondary transfer nip (image forming unit). By doing this, a desired color image may be transferred on the sheet P.
After that, the sheet P on which the color image is transferred at the position of the secondary transfer nip is further fed to the position of a fixing unit 20. At the position, due to heat and pressure by a fixed roller 21 and a pressing roller 22, the color image transferred on the surface is fixed to the surface of the sheet P.
After that, the sheet P is discharged outside the device between rollers of a sheet discharging roller pair 99. The sheet P discharged by the discharging roller pair 99 is sequentially stacked on a stack unit 100.
By doing this, a series of image forming processes in the image forming apparatus is completed.
Next, details of the sheet thickness detecting device 30 according to an embodiment are described with reference to
As shown in
Also, as shown in
The fixed roller 31 is rotatably supported by a shaft so that the outer surface of the fixed roller 31 faces one side of the sheet P passing through the conveying path K. Further, the fixed roller 31 is a roller member including a shaft part and a roller part formed on (outside) the shaft part. The shaft part is made of a metal material or the like, and the roller part is made of, for example, a resin material (or a hard rubber member).
The fixed roller 31 is rotatably supported by a shaft which extends in the width direction (i.e., the direction orthogonal to the sheet surface of
Further, the fixed roller 31 is driven to rotate by a drive motor (not shown) via a series of gears including a gear mounted on the shaft, the gear being provided on one side in the width direction. Then, when the fixed roller 31 is driven to rotate by inputting the driven force of the drive motor. In the case of
Similar to the fixed roller 31, the movable roller 32 is also rotatably supported, so that the movable roller 32 and the fixed roller 31 sandwich and feed the sheet P via the feeding belt 34. Namely, as schematically shown in
Further, it should be noted that the movable roller 32 is displaced (moved) in the arrow direction (“D” in
As shown in
The plural rollers 32 are arranged in the width direction (i.e., the direction orthogonal to the sheet of
The shaft roller 33 includes a shaft part 33a which is disposed on the upstream side of the facing position (nip section) between the fixed roller 31 and the movable roller 32 in the feeding direction of the sheet P. The shaft part 33a of the shaft roller 33 is rotatably supported by a shaft bearing mounted on the swing member 35.
As shown in
The feeding belt 34 serving as the belt member is an endless belt made of a rubber material, and is stretched between and supported by the movable roller 32 (roller part 32b) and the shaft roller 33 (roller part 33b. Due to a contact pressure from the movable roller 32, the nip section for the sheet P is formed between the feeding belt 34 and the fixed roller 31.
Further, the feeding belt 34 feeds in the feeding direction to feed the sheet P due to frictional resistance between the feeding belt 34 and the fixed roller 31. In this case, as shown the arrow “B” in
Also, due to the frictional resistance with the feeding belt 34, the fixed roller 31 and the movable roller 32 are driven to rotate in the clockwise direction.
The swing member 35 is a housing, made of a plate (or resin), supporting the movable roller 32 and the shaft roller 33 so that the movable roller 32 and the shaft roller 33 rotates. The swing member 35 is designed to swing (displace) around the shaft part 33a in accordance with the displacement of the movable roller 32 based on the thickness of the sheet P fed into the nip section between the fixed roller 31 and the movable roller 32.
Further, as shown in
Namely the detection target part 35a is disposed on the downstream side of the shaft part 32a (where the movable roller 32 is rotatably supported) in the sheet feeding direction of the sheer P, and the distance between the detection target part 35a and the shaft part 33a is greater than that between the shaft part 32a to the shaft part 33a. The detection target part 35a is not shown in
Specifically, the belt unit including the swing member 35, the movable roller 32, the shaft roller 33, and the feeding belt 34 is rotatably supported by the side plates of the main body of the image forming apparatus 1 via the shaft part 33a.
Further, a compressed spring (not shown) is provided on the shaft part 32a of the movable roller 32 to bias the movable roller 32 (belt unit) to the fixed roller 31.
Further, the detection target part 35a (a protrusion part formed by extending a part of the swing member 35) which is to be detected by the detection sensor 41 (displacement amount detecting sensor) is disposed at the position opposite to the shaft part 33a with respect to the shaft part 32a, so that the distance between the position and the shaft part 33a, which is the center around which the swing member 35 rotates, is sufficiently long.
Further, the displacement amount of the detection target part 35a of the swing member 35 is detected by the detection sensor 41 serving as the detecting unit.
In this state, the detection sensor 41 detects the distance “X1” as the distance between the detection sensor 41 and the detection target part 35a of the swing member 35 (hereinafter may be referred to as the distance “X”)
On the other hand, a part (B) of
As a result of the displacement of the movable roller 32, the swing member 35 is rotated accordingly around the shaft part 33a as the center in the clockwise direction. Then, the detection sensor 41 detects the distance “X2” as the distance between the detection sensor 41 and the detection target part 35a of the swing member 35 when the sheet P is sandwiched in the nip section.
Then, the detection results detected by the detection sensor 41 are transmitted to a control unit (calculation unit) 60. In the control unit 60, the displacement amount (X2-X1) of the detection target part 35a is calculated.
Further, the displacement amount (X2-X1) is multiplied by an arm ratio which is defined as (distance between shaft part 33a and shaft part 32a)/(distance between shaft part 33a and detection target part 35a) to calculate the value “T” which corresponds to the thickness of the sheet P.
Further, based on the calculated value “T” corresponding to the thickness of the sheet P, an image forming condition and a feeding condition may be properly adjusted. For example, when it is determined that the sheet is relatively thick, the transfer efficiency at the secondary transfer nip section is likely to be reduced.
Therefore, in this case, it is possible to adjust to increase the secondary transfer bias voltage to be applied to the secondary transfer roller 89, or to adjust so as to increase the image density of the toner images to be formed on the photoconductive drums 5Y, 5M, 5C, and 5K.
Further, in the case where it is determined that the sheet is relatively thick, the performance of fixing in the fixing process executed in the fixing unit 20 is likely to be reduced because the heat to be applied to the toner image may become insufficient. Therefore, for example, it is possible to adjust to reduce the feeding speed of the recording medium (sheet) P.
As described above, according to an embodiment, in the sheet thickness detecting device 30 according to an embodiment, the displacement of the movable roller 32, which is displaced in accordance with the thickness of the sheet P, is not directly detected by the detection sensor 41. In the sheet thickness detecting device 30 according to an embodiment, it is the displacement amount of the detection target part 35a of the swing member 35 that is detected by the detection sensor 41.
In this case, it is the displacement amount of the detection target part 35a, which is sufficiently separated in distance from the shaft part 32a of the movable roller 32, that is calculated by multiplying the displacement amount of the movable roller 32 by the arm ratio defined as described above.
Therefore, according to an embodiment, it may become possible to more accurately detect the thickness of the sheet P by the detection sensor 41.
For example, even when a sheet P which is extremely thin is fed in the nip section between the between the fixed roller 31 and the movable roller 32 (feeding belt 34), it may become possible to more accurately and reliably detect the thickness of the sheet P. This is because the displacement amount of the movable roller 32 is amplified, so that the amplified displacement amount may be detected by the detection sensor 41.
Further, according to an embodiment, even when an inexpensive sensor having a relatively low detection accuracy is used as the detection sensor 41, the displacement amount of the movable roller 32 in accordance with the thickness of the sheet P is amplified using the arm ratio.
Therefore, it may become possible to accurately detect the thickness of the sheet P as if the displacement amount of the movable roller 32 is detected by using an expensive sensor having relatively high accuracy.
In other words, according to an embodiment, it may become possible to more accurately detect the thickness of the sheet P without using an expensive sensor having relatively high accuracy.
Further, the detection sensor 41 (detecting unit) detecting the displacement amount of the detection target part 35a may be a non-contacting type sensor or a contacting type sensor.
Specifically, for example, as the detection sensor 41 (detecting unit), an optical distance measurement sensor which optically detects the displacement amount of (distance to) the detection target part 35a may be used.
Further, a lever-type encoder sensor which detects the displacement amount of the lever to be displaced in accordance with the displacement of the detection target part 35a may alternatively be used.
Further, a magnetic linear sensor which magnetically detects the displacement of the detection target part 35a (made of a metal material) may alternatively used.
Further, direct-acting-type micro displacement sensors disposed on both sides of the detection target part 35a in the displacement direction thereof may alternatively used.
The sheet thickness detecting device 30 as described above may be functioned as a feeding device that sandwiches and feeds the sheet P by using the fixed roller 31 and the belt unit. Especially, the feeding belt 34 has a function to promote smooth feeding of the sheet P to the nip section between the fixed roller 31 and the movable roller 32 (feeding belt 34).
Further, according to an embodiment, on the upstream side of the sheet thickness detecting device 30, there is formed a curved conveying path K1 by a curved guide plate (curve guide plate) to curve and feed the sheet P which is fed from the sheet supply unit 12.
Further, at the position between the sheet thickness detecting device 30 and the resist roller pair 37 and 38, there is formed a straight conveying path K2 by a straight guide plate (plane guide plate) to linearly feed the sheet P.
By providing the feeding device (sheet thickness detecting device 30) having the belt unit 32 through 35 disposed on the downstream side of the curved conveying path K1, even when the sheet P is much bent in the curved conveying path K1, the sheet P may be smoothly guided and fed to the nip section between the fixed roller 31 and the movable roller 32 (feeding belt 34) by the feeding belt 34.
Further, according to this embodiment, a case is described where the belt unit including the feeding belt 34, the shaft roller 33 and the like is formed, so that the displacement amount of the detection target part 35a of the swing member 35 is detected by the detection sensor 41, the detection target part 35a being moved in accordance with the displacement of the movable roller 32.
Specifically, in this configuration, the movable roller 32 is rotatably provided so as to directly sandwich and feed the sheet P with the fixed roller 31 without the feeding belt 34.
Further, the swing member 35 rotatably supports the movable roller 32 and swings (rotates) around a shaft 36 in accordance with the displacement of the movable roller 32.
Further, the detection target part 35a is formed at the position in a manner that the distance between the detection target part 35a and the shaft 36 is greater than that between the detection target part 35a and the shaft part 32a of the movable roller 32.
Then, the displacement amount of the detection target part 35a of the swing member 35 is detected by the detection sensor 41 disposed at the position facing the detection target part 35a.
Even in the case described above, similar to the embodiment described first, the displacement amount of the detection target part 35a is detected by the detection sensor 41 disposed at the position sufficiently separated from the shaft part 32a of the movable roller 32 by amplifying the displacement of the movable roller 32 by the arm ratio of the swing member 35. Therefore, similar to the embodiment described first, it may become possible to more accurately detect the thickness of the sheet by using the detection sensor 41.
As describe above, according to an embodiment, a fixed roller and a movable roller are provided to sandwich and feed a sheet in a conveying path. The movable roller is displaced in accordance with the thickness of the sandwiched sheet. The swing member is swung around a shaft in accordance with the displacement of the movable roller.
The swing member includes a detection target part in a manner that the distance between the detection target part and the shaft is greater than the distance between the movable roller and the shaft. A detection unit detects the distance from the detection target part. By doing this, it may become possible to more accurately detect the thickness of the sheet in the conveying path.
Further, in the embodiment, a case is described where the present invention is applied to the sheet thickness detecting device 30 included in a color image forming apparatus. However, obviously, the present invention may also be applied to a sheet thickness detecting device included in a monochrome image forming apparatus.
Further, according to an embodiment, a case is described where the sheet thickness detecting device 30 is included in the image forming apparatus 1 employing the electophotographic method. However, the present invention is not limited to this configuration.
Namely, the present invention may also be applied to any of the sheet thickness detecting devices included in an image forming apparatus employing another method (e.g., an image forming apparatus employing the inkjet method, a printer employing any method, and the like). In any of the above cases, it may become possible to obtain the same effect as described in the above embodiments of the present invention.
Although the invention has been described with respect to a specific embodiment for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.
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