JP2007105908A - Paper size detecting means - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means which surely discriminates a sheet size in a sheet conveyance apparatus. <P>SOLUTION: A reflection type photo-sensor is loaded on a means which reciprocates in a sheet width direction. When the sheet size is discriminated by detecting sheet both ends by the sensor, the paper is held by two pairs of roller pairs from upstream and downstream both sides of the sensor, and conveyed while a tension is applied to the paper. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sheet conveying apparatus for conveying a sheet associated with an image forming apparatus such as a printer, a FAX, or a copying machine.

  Among image forming apparatuses such as printers, FAX machines, and copiers, line printers typified by inkjet printers have image forming means that reciprocates in the sheet width direction. The image forming apparatus includes a reflection type photosensor associated with the image forming unit, and the sheet size is specified by detecting the length in the sheet width direction by the reflection type photosensor. Has the following technique (for example, refer to Patent Document 1).

Hereinafter, the conventional technique will be described in detail with reference to FIG. 5 by taking B5 size sheet detection as an example. As shown in the drawing, the B5 size sheet P stored in the sheet storage unit 2 is fed by the sheet feeding roller 5 and passes through the sheet conveyance path section A to send the sheet to the image forming section B. It is conveyed to the image forming roller pair 9 and 10. Further, when the carriage 11 is reciprocated in the sheet width direction by the pair of image forming rollers, the sheet is conveyed to the downstream side of the platen 18 by the reflection type photosensors 23 provided in the carriage. Part. The sheet size can be specified by calculating the sheet width from the carriage position when the sheet edge is detected. That is, for example, when the sheet width length is calculated to be 210 mm by the sheet width detection unit, the A4 size is determined, and when the sheet width length is calculated to be 182 mm, the B5 size is determined. However, there are actually variations in sheet width and sensor detection errors, so the calculated sheet width length is not a constant value even for sheets of the same size. A certain measurement margin. That is, for example, for a B5 size, an arbitrary value αmm is used as a margin, and the B5 size is determined to be 182 mm ± αmm. (Hereinafter, the above “standard sheet length” ± “measurement margin” will be referred to as “sheet size discrimination range”.) The arbitrary value α varies depending on the sensor detection accuracy and the like.
JP-A-4-122661

  In the above-described prior art, the EXTECTIVE size sheet size determination range is 184.2 mm ± β mm. Further, as described above, the discrimination range of the B5 size is 182 mm ± α mm. Therefore, since it is necessary to prevent the discrimination ranges of the B5 size and the EXTECTIVE size from overlapping, it is necessary to satisfy αmm + βmm <2.2 mm (= 184.2 mm-182.0 mm). Therefore, both α and β cannot take large values, and the sheet size discrimination range must be set to a narrow range.

  Therefore, as shown in FIG. 6B, when the sheet wavy in the width direction, the apparent length becomes shorter than the original sheet width in FIG. For example, there is a possibility that the calculated width of the EXECUTE size is included in the 182 mm ± α mm that is the discrimination range of the B5 size. Then, there is a possibility that the EXTECTIVE size is erroneously detected as the B5 size.

  The wave in the sheet width direction may be naturally generated by the temperature or humidity of the outside air, or may be positively generated by cockling control performed in the image forming unit in the ink jet printer. “Cockling” means that the ink adheres to and is absorbed by the recording sheet material, and that portion of the paper swells and floats. “Cockling control” means that the paper is intentionally printed in the image forming unit. Say to control the cockling. Therefore, as shown in FIG. 5 in particular, in the conventional technique in which detection is performed by the reflective photosensor 23 on the platen 18 that performs cockling control, the above-described erroneous detection can occur.

  Sheet storage means for storing the sheet, a pair of transport rollers for transporting the sheet, a reflective photosensor positioned upstream of the pair of transport rollers and reciprocating in the sheet width direction, and upstream of the sensor Another pair of conveyance rollers (load roller pair) that is positioned and applies a light load to the sheet conveyance by the conveyance roller pair, and in a state where the conveyed sheet maintains tension, The sheet size is specified by detecting the length in the sheet width direction.

  Further, for example, the reflection type photosensor that reciprocates in the sheet width direction of the sheet conveying apparatus is attached to an image forming unit that reciprocates in the sheet width direction.

  Further, for example, the load roller pair of the sheet conveying apparatus applies a light load by conveying at a slower speed than the conveying speed of the conveying roller pair.

  In addition, for example, the load roller pair of the sheet conveying device may be rotated by contact friction with the sheet with respect to the sheet conveyance, thereby applying a light load.

  Further, for example, the pair of conveying rollers of the sheet conveying apparatus is an image forming roller for feeding a sheet to the image forming unit.

  In a sheet conveying apparatus that determines a sheet size by detecting an end in the width direction of the sheet, a means for reliably determining the sheet size by reducing erroneous detection of the size due to a wave of the sheet or the like is provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  1, 2, and 3 are a cross-sectional view, a perspective view, and a perspective view of a sheet storage unit of an ink jet printer that is an example of an image forming apparatus including a sheet conveying device according to an embodiment of the present invention.

  Reference numeral 1 denotes an ink jet printer main body, 11 denotes a recording head, and 12 denotes a carrier on which the recording head 11 is placed.

  The recording head 11 has a plurality of nozzle rows (not shown) in the sub-scanning direction of the surface facing the printing surface, and discharges ink of different colors for each nozzle row. The recording head 11 is supplied with ink of each color from an ink tank 14 via a supply tube 13 for each color nozzle. Further, both ends of the carrier 12 are fixed to the frame 15 of the apparatus main body 1 and supported so as to be slidable along the guide shaft 16 and the guide rail 17 that are arranged in parallel to each other.

  Reference numeral 25 denotes a recording head recovery means, and the recording head recovery means is provided at a position that can be opposed to a home position provided in the vicinity of one end of the movable range of the recording head 11. Then, the head recovery means 25 is operated during standby, before and after the recording operation or between recordings for each row, and by causing the recording head 11 to perform operations such as capping, suction, wiping, etc. The performance of the recording head 11 is maintained by preventing clogging and the like.

  The paper feed cassette 2 is detachably attached to the apparatus main body 1 and stores a sheet bundle P. The sheet feed cassette 2 includes a sheet support plate 3 for rotatably supporting the sheet bundle P and a sheet side for regulating the position in the width direction of the sheets stacked on the sheet support plate. It is composed of an end regulating plate 4. The sheet side end regulating plate 4 is provided on the bottom surface of the sheet feeding cassette 2 and is movable in the sheet width direction so that the sheet side end can be regulated according to different size sheets. The sheet support plate 3 is rotatably attached to the paper feed cassette 2 and is rotated in the direction of the arrow shown in FIG. 1 by receiving a load of a sheet regulating plate urging spring (not shown) from below in the extension direction. To do. Accordingly, the sheet bundle P stacked on the sheet support plate 3 is pressed against the paper feed roller 5 provided in the apparatus main body 1. The sheet feeding roller 5 is driven by a sheet feeding motor (not shown) and rotates counterclockwise in the drawing, thereby feeding the uppermost sheet P1 of the sheet bundle P pressed by the sheet support plate 3. At that time, the lower sheet P2 may follow the frictional force generated between the uppermost sheet P1 and the lower sheet P2, but the lower sheet P2 is conveyed by the frictional resistance of the separation roller 6. Is prevented. However, the separation roller 6 does not block the conveyance of the uppermost sheet P1. That is, if the frictional force generated between the sheet feeding roller 5 and the sheet P is F1, the frictional force generated between the sheets is FP, and the frictional force generated between the sheet P and the separation pad 6 is F3. The relationship is set so that F1> F3> FP. Accordingly, only the uppermost sheet P1 is sent out from the sheet feeding cassette 2 to the sheet conveyance path A.

  The sheet P1 eventually reaches the nip portion of the pair of transport rollers C7, 8 in the transport path, and is transported by obtaining a transport force from the pair of rollers, and eventually the nip portion of the image forming roller pair 9, 10. To reach. Then, the sheet P1 is conveyed onto the platen 18 provided at the image forming position facing the recording head 11 by the image forming roller pair 9, 10.

  An image is recorded on the sheet by ejecting ink from the recording head 11 while reciprocating the carrier 12 toward the sheet P that has been conveyed to just below the recording head 11. The carrier 12 is reciprocated by a drive motor (not shown) and a belt drive device.

  Here, in the present embodiment, when printing for one scan by the recording head 11 is completed, the printing operation is temporarily interrupted, and the sheet P1 positioned on the platen 18 is conveyed by a predetermined amount by the image forming roller 9. Then, while the recording head 11 is moved again along the guide shaft 16, image formation for the next one scan is performed. Then, after printing is sequentially performed by the recording head 11 on the platen 18, the sheet P is conveyed by the discharge roller 19 and the discharge spur 20 and discharged onto the discharge tray 24.

  In the present embodiment, the pair of image forming rollers 9 and 10 are positioned upstream of the image forming unit B surrounded by the dotted line, and the reflective photosensor 23 associated with the image forming unit 11 is positioned further upstream, and further A pair of conveying rollers C7 and 8 are located upstream. In this embodiment, the sheet conveying speed by the conveying roller pair C7, 8 is set to be slower than the sheet conveying speed by the image forming roller pair 9, 10, so that the conveying roller pair C7, 8 A light load is applied to the sheet conveyance, and the sheet is conveyed while maintaining tension in a section sandwiched between the two pairs of rollers. Therefore, in the conveyance path immediately below the reflective photosensor 23, the sheet continues to maintain tension, and the wave of the sheet is suppressed. Therefore, it is possible to prevent the problem of erroneous detection due to the wave of the sheet in the prior art as described above, and to provide a reliable sheet size detecting means.

  FIG. 4 is a schematic view showing the configuration of an ink jet printer which is another embodiment of the present invention. In this embodiment, the reflection type photosensor 23 associated with the image forming unit 11 is positioned upstream of the transport roller pair D21, 22, and another transport roller pair C7, 8 is positioned further upstream. Since the sheet conveying speed by the conveying roller pair C7, 8 is set to be slower than the sheet conveying speed by the conveying roller pair D21, 22, the conveying roller pair C7, 8 is lighter than the sheet conveying. In a section where a load is applied and is sandwiched between the two pairs of rollers, the sheet is conveyed while maintaining tension. Therefore, in the conveyance path immediately below the reflection type photosensor 23, the sheet is kept in tension to suppress the wave of the sheet, and the above-described problem of erroneous detection due to the wave of the sheet in the prior art is prevented. Yes. Further, the sheet forming speed of the image forming roller pair 9 and 10 is set slower than that of the conveying roller pair D21 and 22, and therefore, the image forming roller pair 9 and 10 and the conveying roller pair D21 and 22 are sandwiched. In such a section, since the sheet is bent and conveyed, consideration is given so as not to be a load on the conveyance of the image forming roller pairs 9 and 10 that require accuracy.

Sectional drawing which shows schematic structure of the inkjet printer which is an example of the image forming apparatus provided with the sheet conveying apparatus which concerns on embodiment of this invention The perspective view which shows schematic structure of the said printer The perspective view of the sheet storage means of the printer Sectional drawing which shows schematic structure of the inkjet printer which is an example different from the said embodiment Sectional drawing which shows schematic structure of the inkjet printer which is an example of the conventional printer Sheet cross-sectional view in the sheet width direction, (a) Original sheet width, (b) Apparent sheet width (when wavy)

Explanation of symbols

A Sheet transport path B Image forming unit P Sheet (sheet bundle)
P1 Sheet topmost sheet 1 Inkjet apparatus body 2 Sheet storage means (paper feed cassette)
3 Sheet support plate 4 Sheet side edge regulating plate 5 Paper feed roller 6 Separation roller 7, 8 Conveying roller pair C
9, 10 Image forming roller pair 11 Recording head 12 Carrier 13 Supply tube 14 Ink tank 15 Main body frame 16 Guide shaft 17 Guide rail 18 Platen 19 Paper discharge roller 20 Paper discharge spur 21, 22 Carrying roller pair D
23 reflection type photo sensor 24 paper discharge tray 25 head recovery means

Claims (5)

  Sheet storage means for storing the sheet, a pair of transport rollers for transporting the sheet, a reflective photosensor positioned upstream of the pair of transport rollers and reciprocating in the sheet width direction, and upstream of the sensor Another pair of conveyance rollers (load roller pair) that is positioned and applies a light load to the sheet conveyance by the conveyance roller pair, and in a state where the conveyed sheet maintains tension, A sheet conveying apparatus that identifies a sheet size by detecting a length in a sheet width direction.   2. The sheet conveying apparatus according to claim 1, wherein the reflection type photosensor that reciprocates in the sheet width direction of the sheet conveying apparatus is attached to an image forming unit that reciprocates in the sheet width direction.   3. The sheet conveying device according to claim 1, wherein the load roller pair of the sheet conveying device applies a light load by conveying at a slower speed than a conveying speed of the conveying roller pair.   The sheet conveying device according to claim 1 or 2, wherein the load roller pair of the sheet conveying device is rotated by contact friction with the sheet with respect to the sheet conveyance, thereby applying a light load.   5. The sheet conveying apparatus according to claim 1, wherein the pair of conveying rollers of the sheet conveying apparatus is an image forming roller for feeding a sheet to an image forming unit.

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