An exemplary embodiment for embodying the invention will be described in detail hereinbelow with reference to the drawings.
In
The scanner 2000 for reading an original document (hereinbelow, also referred to as an original) has: a scanning optical system light source 201; platen glass 202; and an original pressing plate 203 which is freely opened and closed. The scanner 2000 also has: a lens 204; a photosensing element (photoelectric conversion) 205; an image processing unit 206; a memory unit 208 for storing an image processing signal processed by the image processing unit 206; and the like.
When the original is read, light is irradiated from the scanning optical system light source 201 onto the original (not shown) put on the platen glass 202. The read original image is processed by the image processing unit 206, thereafter, converted into an electric signal 207 which has electrically been encoded, and transmitted to a laser scanner 111a as an image forming unit. Image information which has been processed by the image processing unit 206 and encoded can be also temporarily stored into the memory unit 208 and transmitted to the laser scanner 111a as necessary in response to a signal from a controller 120.
The printer main body 1001 has: a sheet feeding apparatus 1002; a sheet conveying apparatus 1004 for conveying the sheet S fed by the sheet feeding apparatus 1002 to an image forming unit 1003; and the controller 120 as a control unit for controlling the printer 1000.
The sheet feeding apparatus 1002 has: sheet cassettes 100; pickup rollers 101; and separating units each of which is constructed by a feed roller 102 and a retard roller 103. The sheets S in the cassette 100 are separated and fed one by one by the operation of the pickup roller 101 which is elevated up and down and rotated at predetermined timing and the separating unit.
The sheet conveying apparatus 1004 has: a conveying roller pair 105 (105a, 105b); and a registration roller unit 1 having a conveying roller pair 10 (10a, 10b), skew correcting roller pairs (20A, 20B), and a registration roller pair 30 (30a, 30b).
The sheet S fed by the sheet feeding apparatus 1002 is conveyed by the conveying roller pair 105, passes through a sheet conveying path 108 constructed by guide plates 106 and 107, and thereafter, is guided to the registration roller unit 1. After that, in the registration roller unit 1, a skew of the sheet is corrected as will be described hereinafter and, subsequently, the sheet S is conveyed to the image forming unit 1003.
The image forming unit 1003 is of an electrophotographic system and has: a photosensitive drum 112 as an image bearing member; the laser scanner 111a as an image writing unit; a developing unit 114; a transfer charging unit 115; and a separating charging unit 116.
When an image is formed, first, a laser beam emitted from the laser scanner 111a is folded back by a mirror 113 and irradiated to an exposing position 112a on the photosensitive drum which rotates clockwise, so that a latent image is formed on the photosensitive drum. After the latent image was formed on the photosensitive drum in this manner, it is developed as a toner image by the developing unit 114.
Subsequently, the toner image developed on the photosensitive drum as mentioned above is, thereafter, transferred onto the sheet S by the transfer charging unit 115 in the transfer unit 112b. A distance between the laser beam irradiating position 112a on the photosensitive drum 112 and a transfer unit 112b is assumed to be lo.
Further, the sheet S on which the toner image has been transferred as mentioned above is electrostatically separated from the photosensitive drum 112 by the separating charging unit 116. Thereafter, the sheet is conveyed to a fixing device 118 by a conveying belt 117 and the toner image is fixed and, subsequently, the sheet is ejected by a discharge roller 119.
According to the printer 1000, in the sheet conveying path until the sheet is ejected by the discharge roller 119 after the sheet was fed from the sheet feeding apparatus 1002, the sheet is conveyed by what is called a “center reference” in which it is conveyed while setting a center of the conveying path to a reference. The invention is not limited to the printer of the center reference but can be also used in a printer of what is called a one-side reference in which one of the sides in the lateral direction of the sheet is set to a reference.
In
Although the printer main body 1001 and the scanner 2000 have separately been provided in the embodiment, there is also a case where the printer main body 1001 and the scanner 2000 are integratedly provided. Although the printer main body 1001 is provided separately from or integratedly with the scanner 2000, when the processing signal of the scanner 2000 is input to the laser scanner 111a, the printer main body 1001 functions as a copying apparatus and when a transmission signal from a facsimile apparatus is input, the printer main body 1001 functions as a facsimile apparatus. Further, when an output signal of a personal computer is input, the printer main body 1001 also functions as a printer. On the contrary, if the processing signal of the image processing unit 206 of the scanner 2000 is transmitted to another facsimile apparatus, the printer main body 1001 functions as a facsimile apparatus. In the scanner 2000, if an automatic document feeder (hereinafter, abbreviated to an ADF) 250 as shown by a section surrounded by an alternate long and two-short dashes line is attached in place of the original pressing plate 203, the originals can be also automatically read.
In
One roller 10a of the conveying roller pair 10 is a conveying driving roller which is driven by a driving source (not shown) and generates a conveying force to the sheet. The other roller 10b is a conveying driven roller which is come into pressure contact with the conveying driving roller 10a by a pressing unit such as a spring or the like (not shown) and sandwiches the sheet.
The conveying driven roller 10b (an axis 10b1 thereof) is supported by a pressure cancelling arm 314 which is rotated in the direction of an arrow B by a pressure cancelling cam 315 which is rotated by a cancelling motor M3 shown in
A downstream curved conveying guiding portion 303 guides the sheet S conveyed by the conveying roller pair 10 to the skew correcting roller pairs (20A, 20B). The downstream curved conveying guiding portion 303 is constructed by a downstream upper curved guide 303b and a downstream lower curved guide 303a. A curved conveying guiding portion 109 for guiding the sheet S in the curved state is constructed by the downstream curved conveying guiding portion 303 and the upstream curved conveying guiding portion 301. Straight guides 308a and 308b finally guide the sheet S guided by the downstream curved conveying guiding portion 303 to the skew correcting roller pairs (20A, 20B). Surfaces of the downstream upper curved guide 303b, downstream lower curved guide 303a, and straight guides 308a and 308b which are come into slide contact with the sheet construct a sheet guiding surface.
In a center portion of the downstream upper curved guide 303b in the lateral direction, an outside center-guiding portion 304 as a projecting portion for guiding an upper center portion of the sheet S which passes through the downstream curved conveying guiding portion 303 is formed in the sheet conveying direction so as to be projected. As illustrated in
In a center portion of the downstream lower curved guide 303a in the lateral direction, an inside center-guiding portion 306 as a projecting portion for guiding a lower center portion of the sheet S which passes through the downstream curved conveying guiding portion 303 is formed in the sheet conveying direction so as to be projected. As illustrated in
As mentioned above, by denting the both sides of the center portions, the projecting portions are formed in the center portions.
Therefore, in the downstream curved conveying guiding portion 303, an interval in the center portion in the lateral direction, that is, an interval G2 between the outside side-guiding surface 305 and the inside side-guiding surface 307 is larger than an interval G1 between the outside center-guiding portion 304 and the inside center-guiding portion 306. That is, by forming the inside center-guiding portion 306 on the downstream lower curved guide 303a so as to be projected and by forming the outside center-guiding portion 304 on the downstream upper curved guide 303b so as to be projected, the interval G1 in the vertical direction of the center portion of the downstream curved conveying guiding portion 303 is narrowed.
An interval between both side portions of the downstream curved conveying guiding portion 303 in the lateral direction, that is, the interval G2 between the inside side-guiding surface 307 of the downstream lower curved guide 303a and the outside side-guiding surface 305 of the downstream upper curved guide 303b is wider than the interval G1 in the center portion. By constructing as mentioned above, spaces are formed in both edge portions of the downstream curved conveying guiding portion 303 in the lateral direction.
Thus, as will be described hereinafter, when the skew is corrected by the skew correcting roller pairs (20A, 20B), the sheet is conveyed while being guided by the center portion of the downstream curved conveying guiding portion 303. At this time, the sheet is conveyed while permitting a torsional deformation of the sheet which is caused when the skew is corrected by the spaces formed in the both edge portions of the downstream curved conveying guiding portion 303 in the lateral direction.
The skew correcting roller pairs (20A, 20B) is coaxially provided. One roller 20b constructing each of the skew correcting roller pairs (20A, 20B) is a skew correcting driving roller arranged coaxially in the lateral direction. The rollers 20b are connected to pulse motors M1 and M2 serving as driving sources and illustrated in
In the embodiment, a part of the peripheral surface of the skew correcting driving roller 20b is omitted. As illustrated in
Two optical activation sensors 312a and 312b are arranged at a predetermined interval in the lateral direction in an upstream just near the skew correcting roller pairs (20A, 20B). Two optical sheet leading edge detecting sensors 310a and 310b are also arranged at a predetermined interval in a downstream of the skew correcting roller pairs (20A, 20B).
As shown in
Similarly, based on detection signals from the sheet leading edge detecting sensors 310a and 310b, the controller 120 discriminates whether or not the skew has been corrected by the sheet conveying speed control of the first time based on the detection signals from the activation sensors 312a and 312b. If it is determined that the skew is not corrected, the controller 120 detects the skew amount of the sheet leading edge based on the signals from the sheet leading edge detecting sensors 310a and 310b and increases or decreases the rotational speeds of the pulse motors M1 and M2 according to the detected skew amount, thereby correcting the skew of the sheet leading edge.
Subsequently, the sheet skew correcting operation of the registration roller unit 1 constructed as mentioned above will now be described. First, the sheet S fed out of the cassette 100 by the sheet feeding apparatus 1002 as already mentioned above is conveyed by the conveying roller pair 105 and, thereafter, passes through the conveying roller pair 10. After that, a driven roller 105b is nip-cancelled every sheet size as necessary by a roller cancelling motor (not shown).
Subsequently, when the front edge of the sheet S conveyed by the conveying roller pair 10 is detected by the activation sensors 312a and 312b, the pulse motors M1 and M2 are activated based on the detection signals from the activation sensors 312a and 312b. Thus, as illustrated in
At this time, the controller 120 calculates the skew amount of the sheet leading edge from a detection time difference Δt1 between the activation sensors 312a and 312b illustrated in
After the sheet entered the nip of the skew correcting roller 20B, the controller 120 makes the speed control as illustrated in
There is a case where the conveying roller pair 10 sandwiches a rear edge of the sheet S during the skew correcting operation depending on the sheet size. In such a case, the controller 120 drives the cancelling motor M3 so as to rotate the pressure cancelling cam 315 for a period of time until the skew correcting operation is started after the sheet S entered the nip of the skew correcting roller.
Thus, the pressure cancelling arm 314 is rotated in the direction of the arrow B as illustrated in
Subsequently, after such a skew correcting operation was finished, the front edge of the sheet S is similarly detected by the sheet leading edge detecting sensors 310a and 310b (refer to
After that, as illustrated in
During such a skew correcting operation, the sheet S is pulled out of the upstream curved conveying guiding portion 301 and the downstream curved conveying guiding portion 303 illustrated in
If the interval in the center portion of the downstream curved conveying guiding portion 303 in the lateral direction is equal to the interval in each of both edge portions, since the shape of the sheet is restricted by the guiding surfaces, the sheet is difficult to be deformed. Thus, if the force adapted to cause the torsional deformation acts on the sheet S upon correcting the skew, the sheet S receives a reaction from the guiding surfaces of the downstream curved conveying guiding portion 303 and such a reaction appears as a conveying load of the sheet upon correcting the skew. This conveying load becomes a cause of a slip between the skew correcting roller pairs (20A, 20B) and the sheet and becomes a cause of deterioration in skew correcting precision.
In the embodiment, therefore, the interval G2 between the outside side-guiding surface 305 and the inside side-guiding surface 307 of the downstream curved conveying guiding portion 303 with which the sheet S which is curved and conveyed as mentioned above is come into slide contact is larger than the interval G1 between the outside center-guiding portion 304 and the inside center-guiding portion 306. By constructing as mentioned above, spaces adapted to enable the sheet to be deformed are formed in the both edge portions of the downstream curved conveying guiding portion 303 in the lateral direction. Therefore, upon correcting the skew, the sheet enters a state where both side portions of the sheet are easily deformed.
Thus, upon correcting the skew, in the downstream curved conveying guiding portion, the sheet S is guided while being come into slide contact with the outside center-guiding portion 304 and the inside center-guiding portion 306. On the outside side-guiding surface 305 and the inside side-guiding surface 307, the sheet S is conveyed while being torsion-deformed.
Since the sheet S is easily torsion-deformed according to the acting force of the skew correcting rollers upon correcting the skew, the sheet is easily rotated and the skew is corrected. Thus, the sheet is conveyed in a balanced state and the skew correcting precision can be improved.
By narrowing the interval G1 in the center portion of the downstream curved conveying guiding portion 303 in the lateral direction as mentioned above, when the sheet is rotated and the skew is corrected by the skew correcting roller pair (20A, 20B), the load which the sheet to be corrected receives from the downstream curved conveying guiding portion 303 can be reduced.
Therefore, when the sheet is active-registration corrected, the sheet can be easily torsion-deformed and rotated. It is difficult to cause a slip between the sheet and the skew correcting roller pairs (20A, 20B). Consequently, the sheet conveying load upon correcting the skew of the sheet can be reduced by a simple construction. The skew correcting precision of the sheet can be improved without enlarging the apparatus size.
Although the nip of the conveying roller pair 10 has been cancelled during the skew correcting operation so as not to become the load on the rotating of the sheet in the embodiment, in place of cancelling the nip, the conveying roller pair can be also moved in the direction which perpendicularly crosses the conveying direction.
The second embodiment of the invention in which the conveying roller pair is moved in the direction which perpendicularly crosses the conveying direction at the time of such a skew correcting operation of the sheet will now be described.
In
In the embodiment, control is made so as to move the conveying roller pair 11 in the lateral direction synchronously with the operation of the skew correcting roller pairs (20A, 20B). It is assumed that a movement control amount and a control speed of the conveying roller pair 11 almost coincide with a movement amount and a speed of the sheet in the nip portion of the conveying roller pair 11 which is rotated by the skew correcting roller pairs (20A, 20B).
In the embodiment, upon correcting the skew, the conveying roller pair 11 is moved from a position P1 to a position P2 synchronously with the operation of the skew correcting roller pairs (20A, 20B) as illustrated in
Thus, the skew correcting precision is improved. Further, the sheet is easily torsion-deformed by providing the center-guiding portions 304 and 306 and the side-guiding surfaces 305 and 307 for the curved conveying guiding portion. Thus, even if differences occur between the shift movement amount and the shift moving speed of the conveying roller and the movement amount and the speed of the sheet in the nip portion of the conveying roller pair 11, the sheet is deformed and such differences can be absorbed.
Consequently, the conveying load which is caused when the sheet is rotated and moved can be reduced. In association with it, the skew can be precisely corrected and the shift control can be simplified.
The third embodiment of the invention will now be described.
In
Although the example in which the roller 313 is provided for the inside center-guiding portion 306 has been shown in
Although the example in which the sheet is rotated and the skew is corrected by independently controlling the speeds of the two skew correcting roller pairs 20A and 20B as skew correcting units has been shown in the above description, the invention is not limited to such an example. The invention can be also applied to a construction in which, for example, a pair of rollers are provided so that they can be turned, the skew amount of the sheet which is fed in the skew state is detected by the sensor, the pair of rollers are turned in the sheet sandwiched state based on the skew amount, thereby rotating the sheet and correcting the skew.
Although the example in which the center-guiding portions 304 and 306 are provided for the downstream upper curved guide 303b and the downstream lower curved guide 303a constructing the downstream curved conveying guiding portion 303 so as to be projected has been shown above, the invention is not limited to such an example. For example, it is also possible to use a construction in which the center-guiding portion is arranged only for the downstream lower curved guide 303a by which the sheet is mainly guided upon skew correction and the other downstream upper curved guide 303b is set to the same surface shape.
Although the center-guiding portions 304 and 306 are provided in the center portion in the lateral direction, it is not always necessary to arrange them in the center portion so long as they exist in the width of the minimum size among the sheets which can be conveyed. That is, it is sufficient that the center-guiding portions 304 and 306 are provided at positions where the sheet of the minimum size among the sheets which can be conveyed can be come into slide contact. As illustrated in
The case where the sheet conveying unit according to the invention is used for the image forming apparatus has been described above. However, the invention is not limited to such an example. For example, the invention can be also applied to an image reading apparatus such as a scanner 2000 illustrated in
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 such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2006-147174, filed May 26, 2006, which is hereby incorporated by reference herein in its entirety.
Number | Date | Country | Kind |
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2006-147174 | May 2006 | JP | national |