JP2005343668A - Image reading device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading device capable of preventing line image by preventing or reducing remaining of foreign matter at a reading position in an image reading part of sheet through system by a configuration capable of being comparatively easily loaded in a current and standard configuration of a reading part being effective for a minute object by taking dimensional effect into account. <P>SOLUTION: In this image reading device having an automatic document feeding device of sheet through system for fixing the reading part E and reading image while conveying document, a charged member 52 is arranged on the upstream side of the reading part E. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image reading apparatus applied to a facsimile, a scanner, a copying machine, a multi-function machine, and the like having an automatic document feeder (ADF).

As a conventional image reading device, there is a type called a sheet-through method in which a document is read by a reading unit placed at a fixed position in a process of transferring a document in the sub-scanning direction (see, for example, Patent Documents 1 to 3).
Patent Document 1 discloses an electrostatic force that charges a document by friction between a guide plate and mylar on the upstream side of the reading in order to prevent generation of a streak image due to dust remaining at an image reading position of an automatic document feeder (ADF). In this method, the original is charged and dust on the reading unit is adsorbed to the original and carried away.
In the conventional example of Patent Document 2, the Coulomb force is generated on the document table located upstream in the document transport direction from the exposure position so that the dust adhering to the document image surface is adsorbed so that the dust does not stay on the contact glass. However, it cannot cope with dust (such as dust in the atmosphere) other than that carried by the manuscript, and there is a backup roller, which is a shading correction roller.
The conventional example of Patent Document 3 uses a substance that easily generates static electricity as a material of a mirror shielding plate of an image reading device, and adsorbs dust in the air to the shielding plate, thereby generating a streak image due to dust adhering to the mirror. Is preventing. Although it is a technique using electrostatic force related to dust removal in the image reading unit, it is related to mirror dust and not related to the dust on the document conveying side.
Japanese Patent Laid-Open No. 11-305495 JP 11-139609 A JP-A-10-210201

Some image reading apparatuses such as a copying machine, a facsimile machine, and a scanner have a sheet-through type image reading unit that stops an image reading unit and moves an original to read an image. In such a sheet-through image reading unit, image defects due to sticking and staying of foreign matters at the reading position become a serious problem.
This means that sticky substances such as post-it or cut-and-paste original glue, undried ink and correction fluid, eraser or rubber dust on the transport roller or transport belt have just adhered to the reading position, or on paper When floating objects such as dust, toner residue, and other dust do not adhere, but are present at the scanning position, foreign objects are always read at the same time as the original is read. It appears as a streak.
Here, in many cases, the sheet-through type image reading unit includes a reading glass for protecting the reading unit or for matching the original with the focal position of the reading unit.
Further, the reading glass is often subjected to a surface treatment such as a surfactant treatment or a conductive treatment so that the sticky matter adheres or the suspended matter does not stay easily. It is not possible to completely prevent stagnation.
The idea for preventing sticking foreign substances from adhering to the reading position and preventing (removing) the suspended matter is mutually exclusive (a trade-off) and is difficult to achieve at the same time. That is, in such a configuration, when the original is conveyed so that the original comes into contact with the reading glass, the adhesive substance may adhere to the reading glass, but the suspended matter is removed from the reading position by the original. Can be expected. On the other hand, when the original is conveyed so that the original does not come into contact with the reading glass, the adhesive substance does not adhere to the reading glass, but it cannot be expected that the floating substance is removed from the reading position by the original.
Although the frequency of deposits adhering to the reading unit is relatively low, if they are deposited, the streak image becomes very conspicuous. Also, it is relatively difficult to remove even after cleaning. On the other hand, when suspended matter stays in the reading unit, streaks may not be so noticeable and can be removed relatively easily by cleaning, but the frequency of occurrence is relatively high.
In any case, if you notice a streak image after reading the image, it is necessary to read the image again after cleaning and removing the stagnant that causes the streak. Is troublesome for the operator.

Conventionally, with respect to the above, with regard to the adhesive and floating matter, cleaning by the operator, cleaning member such as brush and scraper in the image reading device, or some cleaning means such as an air flow, the reading glass is automatically cleaned, Furthermore, for suspended matter, methods have been implemented or studied, such as providing a slope on the reading glass and dropping the suspended matter to the bottom of the slope.
However, when the size of an object becomes small, the force acting on the object becomes more dominant in adhesive force and electrostatic force than inertial force. It is a small minute object.
For this reason, there are cases where methods such as applying a physical force by a cleaning member or an air flow and blowing off by an inertial force, or providing an inclined portion on the reading glass and sliding off from the reading position by gravity may not always be effective. In addition, the apparatus for that purpose becomes large-scale, or the current reading section configuration must be changed significantly.
In addition, a method of adsorbing dust by Coulomb force is disclosed in Patent Document 2, but according to this method, dust attached to a document can be removed before reading, but other dust (for example, atmospheric air) It is not possible to remove dust or the like floating in the reading section.
Therefore, an object of the present invention is to compare the retention of foreign matter at the reading position of a sheet-through type image reading unit with respect to a minute object considering the size effect and the current standard reading unit configuration. It is an object of the present invention to provide an image reading apparatus that prevents or reduces streak images due to the above cause by a configuration that can be easily mounted.

In order to solve the above-described problem, the invention described in claim 1 is directed to an image reading apparatus having a sheet-through type automatic document feeder that reads an image while feeding a document while fixing a reading unit. An image reading apparatus in which a charging member is arranged upstream of the unit is characterized.
According to a second aspect of the present invention, the image reading device according to the first aspect is characterized in that the charging member is disposed on a contract glass.
According to a third aspect of the present invention, there is provided the image reading apparatus according to the first or second aspect, wherein the charging member is formed in a roller shape.
According to a fourth aspect of the present invention, there is provided the image reading device according to the third aspect, wherein the roller-shaped charging member is configured to rotate.
According to a fifth aspect of the present invention, there is provided the image reading apparatus according to the fourth aspect, wherein a removing member for removing foreign matter adhering to the roller-shaped charging member is formed on a part of the roller surface.
According to a sixth aspect of the present invention, there is provided the image reading apparatus according to any one of the first to fifth aspects, wherein the charging member is charged by static electricity due to friction.
The invention according to claim 7 is the image reading apparatus according to any one of claims 3 to 6, wherein each of the roller-shaped charging member and the charging addition member is formed from a material separated from the charging column. And

  According to the present invention, by arranging the charging member on the upstream side of the reading position, the foreign matter is adsorbed in front of the reading portion, so that the foreign matter can be prevented from being sent to the reading portion.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present embodiment relates to an automatic document feeder (ADF) for an original to be read, which is used in an apparatus that reads an original to be read to a fixed reading device unit and reads an image while being conveyed at a predetermined speed.
FIG. 1 is a block diagram showing the periphery of a reading unit (ADF) of a copying machine. FIG. 2 is a block diagram showing a controller of the copying machine of FIG. FIG. 3 is a control block diagram showing the configuration of the second reading unit in FIG.
In FIG. 1, the configuration around the reading unit includes an original setting unit A for setting a read original bundle, and a separation feeding unit B for separating and feeding originals one by one from the set original bundle. Yes.
The configuration around the reading unit also includes a resist unit C that performs primary abutting and alignment of a fed document and a function that pulls out and transports the aligned document. A turn portion D that conveys toward the reading side (downward) and a first reading conveyance portion E that reads the surface image of the document from below the contact glass 21 are included.
Furthermore, the configuration around the reading unit includes a second reading conveyance unit F that reads the back side image of the original after reading, a paper discharge unit G that discharges the original whose front and back sides have been read out, and the original after reading. A stack portion H for stacking and holding, drive units (motors) 36 to 40 for driving these transport operations, and a controller 35 for controlling a series of operations are included.
The original bundle 1 to be read is set on the original table 2 including the movable original table 3 with the original surface facing upward. Further, the width direction of the document bundle 1 is positioned in a direction perpendicular to the conveyance direction by a side guide (not shown).

The document set is detected by the set filler 4 and the set sensor 5 and transmitted to the main body control unit 44 by the I / F 42. Further, a document length detection sensor 30 or 31 (a reflection type sensor or an actuator type sensor that can detect even one document) is provided on the surface of the document table 2 to determine the length of the document in the conveyance direction. The outline is determined (at least a sensor arrangement that can determine whether the document size is vertical or horizontal is necessary).
The movable document table 3 can be moved up and down in the a and b directions shown in the figure by a bottom plate raising motor 40. When the set filler 4 and the document set sensor 5 detect that a document has been set, the bottom plate raising motor 40 is moved. 40 is rotated forward to raise the movable document table 3 so that the uppermost surface of the document bundle 1 comes into contact with the pickup roller 7.
The pickup roller 7 is moved by the pickup motor 36 in the c and d directions shown in the figure by the cam mechanism, and the movable document table 3 is raised, and is pushed by the upper surface of the document on the movable document table 3 to be raised in the c direction. The upper limit can be detected by the rise detection sensor 8.
When a print key (not shown) is pressed from the main body operation unit 43 and a document feed signal is transmitted from the main body control unit 44 to the ADF control unit (controller) 35 via the I / F 42, the pickup roller 7 is fed. The roller is rotationally driven by the normal rotation of the paper motor 37 to pick up several (ideally one) originals on the original table 2.
The rotation direction is a direction in which the uppermost document is conveyed to the sheet feeding port. The paper feeding belt 9 is driven in the paper feeding direction by the normal rotation of the paper feeding motor 37, and the reverse roller 10 is driven to rotate in the reverse direction to the paper feeding by the normal rotation of the paper feeding motor 37, and the uppermost original document and the original document therebelow. Are separated, and only the uppermost document can be fed.

More specifically, the reverse roller 10 is in contact with the paper feed belt 9 at a predetermined pressure, and when the paper is in direct contact with the paper feed belt 9 or through a single document, the reverse roller 10 rotates. Turned counterclockwise.
In the unlikely event that two or more originals enter between the sheet feeding belt 9 and the reverse roller 10, the revolving force is set to be lower than the torque of the torque limiter. Rotate clockwise to push back excess originals and prevent double feeding.
The original separated by the action of the paper feeding belt 9 and the reverse roller 10 is further fed by the paper feeding belt 9, and is detected by the abutting sensor 11 and further advanced to the pull-out roller 12 which stops. bump into.
Thereafter, the sheet feeding motor 37 is stopped in a state where a predetermined distance is determined from the detection of the abutting sensor 11 and as a result is pressed against the pull-out roller 12 with a predetermined amount of bending. As a result, the driving of the paper feed belt 9 is stopped.
At this time, the pickup motor 36 is rotated so that the pickup roller 7 is retracted from the upper surface of the document and the document is fed only by the conveying force of the paper feed belt 9, whereby the leading edge of the document enters the nip of the upper and lower roller pairs of the pull-out roller 12. Then, tip alignment (skew correction) is performed.
The pull-out roller 12 has a skew correction function and is a roller for conveying the skew-corrected document after separation to the intermediate roller 14 and is driven by the reverse rotation of the paper feed motor 37.
At this time (at the time of reverse rotation of the paper feed motor 37), the pull-out roller 12 and the intermediate roller 14 are driven, but the pickup roller 7 and the paper feed belt 9 are not driven. A plurality of document width sensors 13 are arranged in the depth direction and detect the size in the width direction perpendicular to the conveyance direction of the document conveyed by the pull-out roller 12.
The length of the document in the conveyance direction is detected from the motor pulse by reading the passage of the leading edge and the trailing edge of the document with the butting sensor 11. When the original is transported from the resist section C to the turn section D by driving the pull-out roller 12 and the intermediate roller 14, the transport speed at the resist section C is set higher than the transport speed at the read transport section E. The processing time for sending the document to the reading unit is shortened.
When the leading edge of the document is detected by the reading entrance sensor 15, deceleration is started in order to make the document conveyance speed the same as the reading conveyance speed before the document leading edge enters the nip between the upper and lower roller pairs of the reading inlet roller 16.
At the same time, the reading motor 38 is driven forward to drive the intermediate roller 14, the reading inlet roller 16, the charging roller 19 (described later), the reading outlet roller 23, and the CIS outlet roller 27.

The intermediate roller 14 is connected to both the paper feed motor 37 and the reading motor 38, and the pulley that transmits the drive to the intermediate roller 14 includes a one-way clutch in the same idling direction. When driving, the rotational speed follows the higher rotational speed.
For this reason, when the original is fed from the registration portion C to the turn portion D, it is driven by a paper feed motor 37 that is driven at high speed, and when the paper feed motor 37 is stopped, it is driven by a reading motor 38.
When the registration sensor 17 detects the leading edge of the document, the registration sensor 17 decelerates over a predetermined conveyance distance, temporarily stops before the reading position 20, and transmits a registration stop signal to the main body control unit 44 via the I / F 42.
Subsequently, when a reading start signal is received from the main body control unit 44, the document whose registration has been stopped is transported at an increased speed so as to rise to a predetermined transport speed until the leading end of the document reaches the reading position.
A gate signal indicating an effective image area in the sub-scanning direction on the first surface to the main body control unit 44 at the timing when the leading edge of the document detected by the pulse count of the reading motor 38 reaches the first reading unit (reading conveyance unit) E. Is transmitted through the first reading unit E until the trailing edge of the original comes off.
Due to the reverse rotation of the paper feed motor 37, the document is fed a predetermined distance after the trailing edge is detected by the abutting sensor 11, and when the document trailing edge passes through the pull-out roller 12, the rotation of the paper feed motor 37 is normal. The drive to the pull-out roller 12 and the intermediate roller 14 is stopped.
At this time, the intermediate roller 14 is driven by the driving of the reading motor 38. In the case of single-sided document reading, the document that has passed through the reading conveyance unit E is conveyed to the paper discharge unit G through the second reading unit F. At this time, when the leading edge of the original is detected by the paper discharge sensor 24, the paper discharge motor 39 is driven forward to rotate the paper discharge roller 28 counterclockwise.
In addition, the discharge motor pulse count from the detection of the leading edge of the document by the discharge sensor 24 reduces the discharge motor drive speed immediately before the trailing edge of the document comes out of the nip of the pair of upper and lower rollers of the discharge roller 28 to discharge the document. Control is performed so that the document discharged onto the tray 29 does not jump out.

In the case of double-sided original reading, the discharge motor 24 detects the leading edge of the original and then counts the pulse count of the reading motor 38. As a result, at the timing when the leading edge of the document reaches the second reading device 25 of the second reading unit F, the gate signal indicating the effective image area in the sub-scanning direction is sent from the DF control unit 35 to the second reading device 25. The document is transmitted until the trailing edge of the original comes off the reading unit F.
The second reading roller 26 serves as a reference white portion for acquiring shading data in the second reading device 25 as well as suppressing the floating of the original in the second reading portion F.
In FIG. 3, the second image reading device 25 includes a light source unit 45, a sensor chip 46, an amplifier 47, an A / D converter 48, an image processing unit 47, a frame memory 50, an output control circuit 51, and an I / F circuit 42. Has been.
In FIG. 1, a bottom plate home position sensor 6, a table raising sensor 8, a reading motor document width sensor 13, a reading entrance sensor 15, and a paper discharge sensor 24 are further arranged.
By performing a coating process on the contact glass 21, adhesion of adhesive foreign matter (glue or correction liquid) can be prevented. However, when the flat contact glass 21 is attached, the contact glass 21 and the document are always conveyed in contact with each other.

Next, characteristic portions of the present invention will be described with reference to FIGS. FIG. 4 is a schematic view showing the charging member disposed near the downstream of the reading entrance roller together with the transport path in the vicinity of the reading portion of the ADF. FIG. 5 is a schematic view showing the charging member disposed immediately before the reading unit, along with the conveyance path in the vicinity of the reading unit of the ADF.
In FIG. 4, the charging member 52 is disposed near the downstream of the reading entrance roller 16, and in FIG. 5, the charging member 52 is disposed immediately before the reading unit. The charging member 52 is a conductive material, and is charged by means such as a current flowing from a power supply unit (not shown), so that foreign matters such as paper dust carried by the original can be adsorbed.
When there is no restriction such as space, the effect of FIG. 5 is higher because foreign matter can be adsorbed immediately before. It is important to adsorb just before the floating dust can be generated from any timing and situation.
FIG. 6 is a schematic view showing a roller-shaped charging member disposed on the contact glass immediately before the reading unit, along with a conveyance path in the vicinity of the ADF reading unit. In FIG. 6, a roller-shaped charging member (hereinafter referred to as charging roller) 19 is disposed on a contact glass 21 immediately before the reading unit. The charging roller 19 is configured to be arranged at a position keeping a minute distance from the contact glass 21, and is rotated by a motor (not shown).
Similarly to the charging member 52, the charging roller 19 may be charged by means such as a current flowing from the power supply unit. However, the charging addition member 53 is brought into contact with the roller, and the friction is caused by the friction between them. If foreign matter is attracted by the generated static electricity, the configuration becomes simpler.
By making the charging member 52 a rotating roller, the area of the portion to which the foreign matter adheres increases, and the position changes as needed, so that the effect is higher than that of a fixed roller.
In Patent Document 2, a backup roller is provided at a position opposite to the upper part of the reading unit. However, this is a roller that manages the reflection density for shading correction and cannot be easily charged. Even if it can be charged, if dust adheres to this roller, the original shading function will be defective.
FIG. 7 is a schematic view showing a foreign matter removing member arranged on a part of the roller surface together with a conveyance path in the vicinity of the reading portion of the ADF. In FIG. 7, the foreign matter removing member 54 scrapes off the foreign matter adsorbed by the charging roller 19 and prevents the foreign matter from being sent again to the reading unit. The foreign matter removing member 54 is, for example, a thin sheet piece that comes into contact with the peripheral surface of the charging roller 19 and scrapes off the foreign matter.
If the double-sided tape 55 is arranged in connection with the foreign matter removing member 54 in order to collect the foreign matter scraped off by the foreign matter removing member 54, the effect is enhanced with a simple configuration. Note that it is advantageous that the charging roller 19 and the charging addition member 53 are made of a material that is separated from the charging column (for example, the charging roller 19 is made of polyethylene and the charging addition member 53 is made of nylon or the like) because static electricity is easily generated.

According to the present invention, the charging member 52 is arranged on the upstream side of the reading position 20, so that foreign matter is sucked in front of the reading unit E and is not sent to the reading unit E, and the charging member 52 is placed on the contact glass 21. By setting the position immediately before the reading unit, it is possible to enhance the foreign matter adsorption effect.
According to the present invention, the roller 19 is used as the charging member, so that foreign matter adsorbed at a specific position of the charging member can be prevented, and the size of the apparatus can be increased by rotating the charging roller. As it is, only the area of the charging portion can be increased.
According to the present invention, since there is a foreign matter removing member for scraping off the foreign matter adhering to the charging roller 19 so as not to be sent again to the reading unit, the attached foreign matter can be scraped off so as not to be sent again to the reading unit. .
According to the present invention, by charging the charging member with static electricity due to friction, foreign matters can be adsorbed with a simple configuration that does not require a power supply unit, and the roller and the charging material can be separated from the charging train. Therefore, the effect of generating static electricity can be enhanced.

FIG. 2 is a configuration diagram showing the periphery of a reading unit of a copying machine. FIG. 2 is a block diagram showing a controller of the copying machine of FIG. 1. The control block diagram which shows the structure of the 2nd reading part of FIG. Schematic which shows the charging member arrange | positioned near the downstream of a reading entrance roller with the conveyance path | route of the reading part vicinity of ADF. Schematic which shows the charging member arrange | positioned just before a reading part with the conveyance path | route near the reading part of ADF. Schematic which shows the roller-shaped charging member arrange | positioned on the contact glass immediately before a reading part with the conveyance path | route of the reading part vicinity of ADF. Schematic which shows the foreign material removal member arrange | positioned at a part of roller surface with the conveyance path | route of the reading part vicinity of ADF.

Explanation of symbols

1 Original (original bundle)
19 Charging roller 20 Reading position 21 Contact glass 25 Second reading device 35 Controller 43 Operation unit 44 Main body control unit 52 Charging member 53 Charging addition member 54 Foreign matter removing member E Reading unit (first reading unit)
F Second reading unit

Claims (7)

  An image reading apparatus having a sheet-through type automatic document feeder that reads an image while conveying a document while fixing a reading unit, wherein a charging member is disposed upstream of the reading unit.   The image reading apparatus according to claim 1, wherein the charging member is disposed on a contract glass.   The image reading apparatus according to claim 1, wherein the charging member has a roller shape.   4. The image reading apparatus according to claim 3, wherein the roller-shaped charging member is configured to rotate.   5. The image reading apparatus according to claim 4, wherein a removing member for removing foreign matter adhering to the roller-shaped charging member is formed on a part of the roller surface.   6. The image reading apparatus according to claim 1, wherein the charging member is charged by static electricity due to friction. 7. The image reading apparatus according to claim 3, wherein each of the roller-shaped charging member and the charging addition member is formed of a material separated from a charging column.

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