JP2006081096A - Image reader and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a document carried type image reader in which a reading image is not deviated and reading quality is improved. <P>SOLUTION: The image reader comprises a plurality of reading means 7, 7' which are provided while being divided, a first feeding roller 1 provided on the upstream side of a feeding direction, a second feeding roller 2 provided on the downstream side of the feeding direction, and at least one of pressing rollers 12 (12') provided in a counter area near the reading means 7, 7' while approximately facing the reading means and driven to be rotated in the feeding direction. The pressing roller 12 (12') is driven in a document feeding direction at a circumferential speed higher than the circumferential speeds of the first and second feeding rollers. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention includes a plurality of reading units that are arranged separately in the conveyance direction and read a document, a first conveyance roller on the upstream side, and a second conveyance roller on the downstream side, and reads the document with the first conveyance roller. The present invention relates to an image reading apparatus such as a scanner which is sent to a means and read by a second conveying roller, and an image forming apparatus as a copying machine, a facsimile, a printer, or a complex machine including the image reading apparatus.

  A conventional image reading apparatus includes a document table, a contact glass portion is provided on the document table, a reading unit is disposed below the contact glass unit, and a pair of first conveying rollers for feeding the document to the reading unit; In some cases, a pair of second transport rollers for feeding out the document from the reading unit is provided (for example, see Patent Document 1).

  FIG. 9A is a schematic cross-sectional view showing a configuration example of a document conveyance type scanner which is this type of image reading apparatus. In the figure, reference numeral 201 is a base, 202 and 202 'are contact type image sensors (reading means) in which a plurality of read pixels made of photoelectric conversion elements are linearly arranged, 203 is a contact glass portion, 204 is a guide portion, Reference numerals 205 and 205 ′ denote conveying rollers (original conveying portions), 206 denotes an original pressing portion, and 207 denotes an original.

  The original 207 is fed onto the contact glass portion 203 by the first conveying roller 205, and after the image information of the original 207 is read by the light receiving element (line sensor) 223 via the lens array 222 constituting the reading sensor, the second It is sent out from the reading means 202, 202 'by the conveying roller 205'. On the other hand, image information read by the light receiving element 223 is A / D converted and temporarily stored in the memory.

  The base 201 is formed to have a U-shaped cross-sectional view extending in the main operation direction. As shown in FIG. 9B, the base 201 has a position in the sub-operation direction divided into a plurality of parts in the width direction (three parts in the figure) in order to divide and read the document 211 in the direction orthogonal to the conveyance direction. A plurality of contact image sensors (reading sensors) 202, 202 'arranged in a staggered manner are arranged in two rows in a staggered manner in the main scanning direction. A contact glass portion 203 made of a transparent glass member is provided on the upper portion of the base 201. The base 201, the contact sensor 202, and the contact glass unit 320 constitute an image reading unit.

  At the front and rear portions of the image reading unit in the sub-scanning direction, a driving roller 251 to which rotational driving force is transmitted by a rotational driving mechanism (not shown), and a pinch that is a driven roller that presses against the driving roller 251 and sandwiches the document 207. Document conveying sections 205 and 205 ′ configured by rollers 252 are provided.

  An image reading of a document image by this image reading apparatus will be specifically described. FIG. 10A is a block diagram showing a main configuration of a circuit for image reading processing. First, the original 207 is inserted between a driven roller 251 and a pinch roller 252 provided on the upstream side in the sub-scanning direction, and is sandwiched between them. Transport to F. In synchronization with the conveyance of the document 207, as shown in FIG. 10B, the reading sensors 202 and 202 provided on the upstream side in the document conveyance direction read the portions A and A of the document 11 in the width direction, and then The unread portion B is sequentially read by the reading sensor 202 ′ arranged at a predetermined distance away from the downstream side.

  At this time, the image data A read by the upstream reading sensors 202 and 202 is A / D converted, and then temporarily stored in a predetermined memory as a delay circuit, and the downstream reading sensor 202 ′ is set for a predetermined distance. The image data A and the image data B are synthesized by the image synthesis unit in accordance with the A / D conversion of the image data B read at a timing delayed by a certain amount, and this is not shown as data for each line in the main scanning direction. It is configured to transmit to the image processing circuit of the control unit.

  Although there are several types of image reading units, the image reading units 202, 202, and 202 'are arranged in the conveyance direction in this way, and the images read by the respective reading sensors are controlled by the control unit. A technique for synthesizing is also disclosed in Patent Document 2, for example. Since the component cost of the reading sensor is proportional to the length in the width direction, the component cost can be kept low by arranging the plurality of reading sensors 202, 202, 202 ′ having such a short width.

  In the contact image sensors 202 and 202 ′ used in the image reading apparatus, the light beam emitted from the light source 221 is reflected from the contact glass unit 203 and enters the lens array 222 to form an image on the line sensor 223. Therefore, in order to perform good image reading, it is indispensable that the document 207 is conveyed in close contact with the contact glass unit 203. In view of this, in this type of document conveyance type image reading apparatus, a document pressing unit 206 that presses the document 207 conveyed on the image reading unit against the contact glass unit 203 is provided. It is comprised so that it may be urged | biased in the direction and it may contact | adhere.

For example, in FIG. 9A, similarly to the image reading apparatus disclosed in Patent Document 1, a document pressing member that acts on a document being read and presses the document in the direction of the image sensor, and the document pressing member serves as a document transport direction. And a base member fixed to the main body of the image reading apparatus that is slidably supported in a direction opposite to the image sensors 202 and 202 ', and is placed on the base member and selected as a document pressing member A document pressing portion 206 is provided which includes a pressing block that is engaged and released.
JP 2003-125159 A JP 59-105762 A

  As in the above [Patent Document 1], in the document pressing mechanism 6 of the conventional image reading apparatus, the urging force for pressing the document against the contact glass is constant. In the case of reading, the following problems have occurred. That is, when reading a drawing output by a large automatic drafting machine, as the medium, a polyester film that does not stretch due to a temperature change or a tracing paper with good fixability such as ink is used. When the document is read by the document conveyance type image reading apparatus, since the medium of the document is thin, if the urging force by the document pressing mechanism is large, this becomes an excessive load and a problem such as a jam phenomenon is likely to occur.

  Therefore, an image reading apparatus that reads such an original is configured such that the weight of the pressing member of the original pressing mechanism is the pressing force. However, the image reading apparatus having such an arrangement is used. For example, when reading a printed material made of high-quality paper such as a large creased map, or a printed material that has been wound and stored in a roll, the weight of the pressing member only In this case, the crease part or the part with the curl of the original cannot be brought into close contact with the contact glass and floats, and there is a problem that the image cannot be read satisfactorily in this part.

  In order to solve this problem, a method of switching the pressing force in multiple steps in the document pressing mechanism in accordance with the type of document can be considered. In this case, the operator can select the document type, whether there is a fold, etc. In this state, the pressing force must be switched, which complicates the operation of the operator and makes it difficult to use.

  Further, in a state where the document is pressed against the contact glass, the friction resistance with the pressing member is maintained until the document whose end of the document has been read is held in the second transport roller that guides and transports the document in the direction opposite to the insertion port. As a result, the conveyance speed of the document is not constant and uneven conveyance occurs, and the data read by the first reading means and the second reading means are misaligned and cannot be matched.

  The present invention has been made to solve the problems in the image reading apparatus as described above, and can read various originals satisfactorily without switching the pressing force depending on the original paper type. It is an object of the present invention to provide an image reading apparatus and an image forming apparatus having good read image quality by including such an image reading apparatus.

  In order to achieve the above object, according to the present invention, an image reading apparatus is divided into a plurality of reading units provided in the document conveyance direction, and a document is provided on the upstream side of the plurality of reading units in the conveyance direction. A first conveying roller that conveys the document, a second conveying roller that is provided on the downstream side in the conveying direction of the plurality of reading units, and is disposed substantially opposite to the vicinity of the plurality of reading units and rotates in the conveying direction. It is set as the structure provided with at least 1 pressure roller driven by.

  With this configuration, the conveyance force to the document is increased, and the gap between the pressure roller and the contact glass can be set narrower than before, so that it is possible to prevent document jamming and density unevenness due to document floating. Since the conveyance speed is constant, it is possible to obtain a good read image with no deviation even if the data read by dividing by the first and second reading means are combined.

  When the pressing roller is driven in the document transport direction at a peripheral speed faster than the peripheral speed of the first transport roller and the second transport roller, even if the leading edge of the document hits the press roller, the transport speed is always constant. It is preferable because a better image can be obtained. In addition, if the pressing roller is configured such that the driving is stopped immediately after the leading edge of the document is added to the second conveying roller, the conveying speed of the document even after the trailing edge of the document passes through the first conveying roller. Is preferable, and a better image can be obtained. For this purpose, the pressing roller may be driven via a clutch mechanism, and the clutch mechanism may be released immediately after the leading edge of the document is added to the second conveying roller.

  In addition, it is preferable that at least the outer peripheral surface of the pressing roller in each of the above configurations is substantially white, so that the shadow of the pressing roller hardly occurs even in a thin document. In addition, a guide plate disposed to face the plurality of reading units may be provided. The image forming apparatus according to the present invention includes any one of the image reading apparatuses configured as described above.

  According to the present invention, various types of originals can be satisfactorily read without switching the pressing force depending on the paper type of the originals. The output image does not shift, and an image reading apparatus with good read image quality and an image forming apparatus with good image quality can be obtained.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is an enlarged cross-sectional view schematically showing a main part of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic plan view showing a state where the cover b is removed. In the following, description of the same configuration and operation as those described in the prior art will be simplified or omitted, and new characteristic points that are different from the conventional one will be mainly described.

  In the figure, a lower roller 1a of the first transport roller 1 is a drive roller for transporting a document 11 inserted from a document insertion port to a reading unit, and an arrow R is driven by a drive means whose main part is shown in a perspective view in FIG. It is rotationally driven in the direction. The upper roller 1b of the first conveying roller 1 is driven to rotate. The upper roller 1b can be displaced in the vertical direction according to the thickness of the document 11, is rotatably supported, and is not shown. This is biased downward by a biasing means such as a spring, and is configured to transport the document 11 at a predetermined speed in cooperation with the driving roller 1 a of the first transport roller 1. On the other hand, the 2nd conveyance roller 2 is similarly comprised by the lower roller 2a and the upper roller 2b.

  Reference numeral 7 denotes a first reading means (light receiving element) that reads a part of the image of the document conveyed by the first conveying roller 1 as in the prior art. Reference numeral 7 ′ denotes a part other than that read by the first reading means 7. In order to read the image area, a second reading means arranged downstream thereof.

  Then, pressing rollers 12 and 12 ′ are provided on the contact glass 4 above the first reading means 7 and the second reading means 7 ′ so as to press the contact glass 4 by the support member 500. FIG. 4 is an exploded perspective view for explaining the assembly of the pressure roller 12 and a guide plate for supporting or assisting the function. Note that the supporting member 500 of the pressing rollers 12 and 12 ′ is positioned outside the passage region 701 of the document 11 (see the longitudinal sectional view of the main part of the mechanism portion in FIG. 5), and the left and right side plates 501 of the pressing roller unit 505. , 502 are provided, and the end portions of the left and right side plates 501 and 502 are in contact with the contact glass 4 so that a constant gap G is maintained between the contact glass 4 and the pressing roller 12. The distance G is preferably 0.1 to 0.3 mm depending on the light receiving element characteristics of the first reading means 7 and the second reading means 7 '.

  The pressure roller unit 505 including the pressure roller 12 is attached to the cover b so as to be rotatable about the axis a of the left and right side plates 501 and 502. When a thick original (t = 1 mm) is inserted by the spring 506, the pressure roller unit 505 can escape upward with the shaft a as a fulcrum.

  The guide plates 13 to 18 are attached to the support member 500 at positions on the contact glass 4 of the first reading means 7 and the second reading means 7 ′ where the pressing roller 12 is not provided. A gap H between the guide plates 13 to 18 and the contact glass 4 is set to 1 to 2 mm so as not to interfere with document conveyance.

  In FIG. 3, the rotation of each transport roller is performed by rotating a first timing belt 143 that is looped around a first pulley 142 attached to a shaft of a drive motor 141 such as a stepping motor, The first transport roller 1 rotates through the pulley 144 and the second transport roller 2 rotates in synchronization with the first transport roller 1 through the third pulley 145 to transport the document.

  The rotation of the pressure rollers 12 and 12 'is synchronized with the document conveyance as described above, and the fourth pulley 146 attached to the second conveyance roller 2 rotates to circulate the annular second timing belt 147, The fifth pulley 148, the second gear 150 meshing with the first gear 149 coaxial with the fifth pulley 148, and the sixth pulley 151 coaxial with the second gear rotate to circulate the annular third timing belt 152. When the third timing belt 152 circulates, the seventh pulley 251 rotates and the second pressing roller 12 'rotates, the eighth pulley 252 rotates and the fourth timing belt 253 circulates, and the ninth pulley 254 rotates. The first pressing roller 12 rotates by rotating.

  As clearly shown in FIG. 1, on the upstream side of the first conveyance roller 1 in the document 11 conveyance direction F, first document detection means (first document detection sensor 113) that detects the presence of a document and outputs a document detection signal. On the downstream side in the transport direction F, second document detection means (second document detection sensor 114) for detecting the presence / absence of a document is provided in order to take a reading start timing or the like.

  FIG. 6A is a block diagram showing a main part related to document conveyance control in the image reading apparatus 100 of the present embodiment. In FIG. 6A, a control unit 190 including a CPU (Centoral Processing Unit) is based on the document detection signals output from the first document detection sensor 113 and the second document detection sensor 114, respectively. By driving and stopping the first conveyance roller 1 and the second conveyance roller 2 by 141, the conveyance of the document is controlled.

  FIG. 6B is a block diagram showing the main part related to the reading process control in the image reading apparatus 100. In FIG. 6B, the (reading) image processing unit 70 is an A / D conversion circuit 71 to which an output signal of the first reading means 7 is input and an A / D conversion to which an output signal of the second reading means 7 'is input. A circuit 72 and a memory 73 connected to the A / D conversion circuit 71, an image synthesis output unit 74 for synthesizing outputs from the memory 73 and the A / D conversion circuit 72 are provided. The control unit 190 controls the image processing unit 70. An operation control unit (not shown) is also connected to the control unit 190 and inputs instructions and designations from the user.

  In this embodiment, as shown in FIG. 1, the image data of the document 11 transported between the contact glass 4 and the pressure plate 13 by the first transport roller 1 is divided and provided in the document transport direction. Are read by the first reading sensor 7 and the second reading sensor 7 ′, and then are discharged by the second conveying roller 2. Image data divided and read by the three first reading sensors 7 and the two second reading sensors 7 'are converted into digital signals (for example, 256 gradations) by the A / D conversion circuits 71 and 72. The A / D-converted data from the first reading sensor 7 is stored in the memory 73 after the conversion, and after a predetermined time delay, the A / D-converted data signal from the second reading sensor 7 ′ and the image composite output at that time point. The signal is synthesized by the unit 74 and output as the original data signal for one line. In this way, image data (main scanning) for each line in the document transport direction is sequentially output to the outside (sub scanning).

  Next, document conveyance control processing performed by the CPU of the control unit 190 in the image reading apparatus 100 of the present embodiment configured as described above will be described with reference to the flowchart of FIG. As shown in FIG. 7, in this image reading apparatus, first, when the leading edge of the document is inserted into the insertion slot, the document 11 placed on the document table is detected by the first document detection means 113 (step: S1). ). That is, it waits until the first document detection sensor 113 is turned on (step: S1; NO), and when it recognizes that the document 11 is inserted (step: S1; YES), the CPU starts driving the stepping motor 141. Then, the first transport roller 1 and the second transport roller 2 are rotated in the transport direction (S2). Thereby, the driving of the first pressing roller 12 and the second pressing roller 12 'is also started. If the second document detection sensor 114 is not turned on within a specified time (step: S3; NO), a jam display is performed by a display unit (not shown) (S4).

  When the second detection sensor 114 is turned on within a specified time (step: S3; YES), the original 11 fed by the rotation of the first conveying roller 1 is used as the first reading means 7 and the second reading means 7. The signals obtained by reading continuously with ′ are processed sequentially. Then, it waits for the second detection sensor 114 to be turned off (S5), and when the second detection sensor 114 is turned off and the trailing edge of the document 11 is detected by the second document detection means 10 (S5: Yes), S After a second has elapsed (corresponding to the predetermined moving distance Ls of the document) (S6; YES), the driving of the first conveying roller 1 and the second conveying roller 2 by the drive motor 141 is stopped (S7).

  As described above, in this embodiment, the control unit manages a section from when the leading edge of the document 11 is detected by the second document detection unit 114 to when the document 11 is discharged from the second conveyance roller 2. Yes.

  During this time, the signals obtained by the first reading means 7 and the second reading means 7 'are sequentially processed in synchronization with the conveyance of the original. That is, the image data output from the first reading unit 7 and the image data output from the second reading unit 7 ′ are converted from analog to digital signals by an A / D converter, and then the image processing micro data. It is synthesized by a processor (synthesizing means) and output to the outside.

  As described above, in this embodiment, the pressing roller 12 facing the first reading unit 7 and the second reading unit 7 'is provided, and the rotation force increases the conveying force to the document 11, and the pressing roller. Since the gap between the contact glass 12 and the contact glass can be 0.1 to 0.3 mm, document jamming and density unevenness due to document floating can be prevented, and the document transport speed is constant and the first and second scanned data are combined. At that time, a good read image without deviation can be obtained.

[Second Embodiment]
In the first embodiment, the peripheral speed of the pressure roller 12 is increased by the first conveying roller 1 and the second conveying roller 2 by appropriately setting the gear between the fourth pulley and the seventh pulley or the number of teeth of the pulley. You may make it set quickly. In this way, the pressing roller is used to press the document against the contact glass and rotates faster than the peripheral speed of the first conveying roller, so even if the leading edge of the document hits the pressing roller, load resistance does not occur and the conveying speed is constant. As a result, a good read image can be obtained.

  Incidentally, in many of the conventional image reading apparatuses, the first conveying roller and the second conveying roller are arranged on the outside of the second conveying roller so that wrinkles are not generated when the document is conveyed in the reading unit and the reading is not defective. By making the diameter (diameter) slightly larger than the outer diameter of the first conveyance roller, the linear velocity of the second conveyance roller is made larger than the linear velocity of the first conveyance roller, and the pulling effect of the second conveyance roller causes Although transport is performed while applying tension, such a design is not necessary in this embodiment.

[Third Embodiment]
Next, a third embodiment will be described. Although not shown, this embodiment has the same configuration as that of the image reading apparatus of the previous embodiment shown in FIGS. 2 to 4, and seems to be surrounded by an alternate long and short dash line circle in FIG. 3. In addition, the electromagnetic clutch 255 is further used, and the fourth pulley 146 at the shaft end of the second conveying roller 2 is attached via the electromagnetic clutch 255 so that the drive can be cut off at this portion. By stopping energization of the electromagnetic crack 255, the pressing roller 12 stops driving and does not rotate autonomously. FIG. 6C shows a block diagram of the main part of the reading process control in this case.

  In the third embodiment, the pressing roller is controlled to stop driving immediately after the leading edge of the document is added to the second roller, so that the document can be removed even after the trailing edge of the document passes through the first conveying roller. The conveyance speed is constant and a good image is obtained. FIG. 8 shows a flowchart of the document conveyance control process. The drive stop timing may be other than this as long as the trailing edge of the document is just before the first conveyance roller passes.

  When the electromagnetic clutch 225 is released, the rotation of the shaft of the second conveyance roller 2 and the rotation of the fourth pulley 146 are free, and the pressing rollers 12 and 12 ′ are rotated along with the second conveyance roller 2 through the document 11. To do. As a result, the tension of the document 11 is reduced only to the inertial resistance of the pressure rollers 12 and 12 ′, so that the variation in the conveyance speed due to the tension of the document when the document 11 is conveyed and the trailing edge is pulled out of the first conveyance roller 1. The image can be read with good image quality without any deviation even on the rear end side of the original 11.

  Although the present invention has been described with reference to the embodiment, the present invention is not limited to the above-described embodiment. For example, in the third embodiment, an electromagnetic clutch is used as the clutch mechanism, but the same effect can be obtained by using a relatively inexpensive one-way clutch instead. Further, in each embodiment, a total of two pressing rollers are arranged at positions facing each of the reading means arranged in two rows, but in a region facing each reading means (for example, in the middle of each reading means) ) Can be provided with only one pressing roller, and substantially the same effect can be obtained.

  The image reading apparatus of the present invention described above is also suitable for use in an image forming apparatus as a copying machine, a facsimile machine, a printer, or a complex machine thereof. Therefore, according to the present invention, an image forming apparatus including a general image forming unit (image forming unit), a paper feeding unit, and the like, which are not described here, and any of the image reading apparatuses of the present invention as described above. Configure. The image that is read and output by the image forming apparatus can be of high quality, and an image forming apparatus with good image quality can be obtained.

1 is a schematic sectional view of a document reading apparatus according to the present invention. FIG. 2 is a top view of a main part of a mechanism part of the image reading apparatus of FIG. It is a disassembled perspective view of the principal part of the image reading apparatus mechanism part of FIG. It is a disassembled perspective view explaining assembly of a pressure roller and a guide plate. FIG. 2 is a longitudinal sectional view of a main part of a mechanism part of the image reading apparatus in FIG. 1. (a), (c) is a block diagram of the principal part regarding the document conveyance control of an image reading apparatus, (b) is a block diagram of the principal part regarding a reading process control. 3 is a flowchart of document conveyance control processing in the image reading apparatus of FIG. 1. 10 is a flowchart of document conveyance control processing in another embodiment. (A) is a principal part schematic diagram of the conventional image reading apparatus, (b) is an explanatory view showing the arrangement of the reading sensor. (A) is a block diagram showing a main configuration of a circuit for image reading processing, and (b) is a diagram for explaining a shift of image data obtained by each reading means.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st conveyance roller 2 2nd conveyance roller 4 Contact glass 7, 7 'Reading means (light receiving element)
DESCRIPTION OF SYMBOLS 11 Document 12, 12 'Press roller 13-18 Guide board 70 (Reading) Image processing part 71, 72 A / D conversion circuit 73 Memory 74 Image synthetic | combination output part 100 Image reader 113 1st document detection sensor 114 2nd document detection Sensor 141 Drive motor (drive means; stepping motor)
142 to 146 Pulley 143, 147, 152, 253 Timing belt 148, 151, 251, 252, 254 Pulley 149, 150 Gear 190 Controller (CPU)
255 Electromagnetic clutch (clutch means)
F Document transport direction

Claims (7)

A plurality of reading means provided separately in the document transport direction;
A first conveying roller provided upstream of the plurality of reading units in the conveying direction and configured to convey a document to the reading unit;
A second transport roller that is provided downstream of the plurality of reading units in the transport direction and transports a document;
An image reading apparatus comprising at least one pressing roller disposed substantially opposite to the vicinity of the plurality of reading means and driven to rotate in the conveying direction.   2. The image reading apparatus according to claim 1, wherein the pressing roller is driven in the document conveyance direction at a peripheral speed faster than peripheral speeds of the first conveyance roller and the second conveyance roller.   2. The image reading apparatus according to claim 1, wherein driving of the pressing roller is stopped immediately after the leading edge of the document is added to the second conveying roller.   2. The drive mechanism of claim 1, wherein the pressing roller is driven via a clutch mechanism, and the clutch mechanism is released immediately after the leading edge of the document is held by the second conveying roller, and the driving of the pressing roller is stopped. Image reading apparatus.   The image reading apparatus according to claim 1, wherein at least the outer peripheral surface of the pressing roller is substantially white.   The image reading apparatus according to claim 1, further comprising a guide plate disposed to face the plurality of reading units. An image forming apparatus comprising the image reading apparatus according to claim 1.

Images