JP2005057341A - Image reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading apparatus capable of particularly enhancing read image quality by a second read means in the image reading apparatus being a double-side image reading apparatus of a sheet-through type provided with first and second read means. <P>SOLUTION: In the image reading apparatus for sequentially reading a carried double-side original by providing the first and second read means along an original carrying path 7 of an automatic draft feeder 1, the first read means includes a mobile optical system unit 13 capable of reading a standstill original and configured to be at a standstill at a prescribed position on the original carrying path 7 in the case of reading the original fed from the automatic draft feeder, while the second read means comprises a fixed optical system unit 16 and a platen roller 17 in slide-rolling contact with a read face of the unit 16, and the fixed optical system unit 16 and the platen roller 17 are fitted to a side frame 21 of the automatic draft feeder. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a so-called sheet-through type double-sided image reading apparatus that reads a double-sided image of a document conveyed by an automatic document feeder by one sheet passing.
[0002]
[Prior art]
In general, an electrophotographic copying machine or a facsimile apparatus includes an automatic document feeder (ADF device) that separates documents set on a document tray one by one and continuously supplies them to a reading unit. As a reading method of document image information, a reading unit is arranged in the middle of the document conveyance path of the ADF apparatus to read the document while conveying the document, and a lower surface of the document on which the reading optical system is placed on the platen glass. A combination with a flatbed scanner (FBS) method that scans while moving the image has been widely adopted. In this method, when reading an automatically fed document, the reading optical system moves to a reading point in the middle of the document conveyance path and stops, and sequentially reads image information of the conveyed document. The sheet-through type double-sided image reading apparatus is configured such that a fixed reading optical system is arranged at a position on a document conveyance path different from the reading point, and image information on the opposite surface is read while conveying the document. Is done.
[0003]
As an example of an image reading apparatus that employs a sheet-through type double-sided reading system as described above, the one disclosed in Patent Document 1 can be cited. The document reading device disclosed in Patent Document 1 reads the image information while moving the lower surface of the document placed on the platen glass, and reads the image information of the automatically fed document under the slit glass. A first reading means (moving optical system) that reads the document that is moved and stationary and that is conveyed, and a second reading that is attached to the ADF apparatus and reads image information on the surface opposite to the reading surface by the first reading means. Means (fixed optical system) (see, for example, Patent Document 1).
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 01-194658
[Problems to be solved by the invention]
In the document reading apparatus disclosed in Patent Document 1, since compactness is required due to the installation space by conveying the document in a U-turn shape, the contact type image sensor is used as the second reading unit. In many cases, a reading optical system that is made into a small unit using a CCD (charge coupled device) is used. By the way, such a compact reading means such as a contact image sensor has a shallow depth of focus (subject depth) due to its structural characteristics. Therefore, depending on the mounting position, the vibration of the opening / closing mechanism of the document guide body In addition, the relative variation in the distance between the object images may be increased due to the influence of the load fluctuation during the separation / conveyance of the original document, which causes a reduction in the read image quality. On the other hand, since the first reading unit can secure a large distance between the object images due to the space, the relative variation is small, and as a result, the image quality of both reading units is unbalanced. Therefore, this may cause a reduction in the commercial value of this type of double-sided image reading apparatus, and an improvement has been desired.
[0006]
SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to improve the image quality read by the second reading unit, particularly in the sheet-through type double-sided image reading apparatus including the first and second reading units. It is what.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problems, an image reading apparatus according to a first aspect of the present invention includes a first reading unit and a second reading unit arranged along a document transport path of an automatic document feeder, and An image reading apparatus in which double-sided image information is sequentially read by the first and second reading means, wherein the first reading means comprises a moving optical system unit capable of reading a stationary document. The unit is configured to be stationary at a predetermined position in the document conveyance path when reading an automatically fed document, while the second reading unit includes a fixed optical system unit and a platen roller that is slidably rotated on a reading surface thereof. The fixed optical system unit and the platen roller are attached to a side frame constituting the machine body of the automatic document feeder.
[0008]
According to the above configuration, since the fixed optical system unit and the platen roller constituting the second reading means are attached to the side frame constituting the machine body of the automatic document feeder, the second reading means is the document guide. The vibration of the body opening / closing mechanism or the like is not directly received, and the load fluctuation at the time of separation / conveyance of the document with respect to the second reading unit is hardly transmitted. Furthermore, since the fixed optical system unit and the platen roller are attached to the same side frame, there is no difference in how the vibrations are transmitted to both. Accordingly, the variation in the relative distance between the object images is small, and the read image quality is not deteriorated.
[0009]
According to a second aspect of the present invention, the fixed optical system unit has a horizontally long shape having a reading line extending over the width of the document conveying path, and is fixed to the side frame via a shaft parallel to the reading line. The shaft is provided with a guide member for guiding the document. According to this configuration, since the fixed optical system unit is attached and fixed to the side frame via a shaft parallel to the reading line, the reading line can be accurately positioned with reference to the shaft. Since the document guide member is attached to the shaft parallel to the reading line, the guide member is also attached to the transported document with a good left-right balance.
[0010]
The invention according to claim 3 is characterized in that the guide member is attached to the shaft so as to be able to swing up and down with its axis as a fulcrum. Therefore, when a jam or the like of a document occurs in the vicinity of the guide member, it is possible to easily grasp the jam state and take out the jammed paper by lifting the guide member with fingers.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view of a main part of an ADF 1 in a facsimile machine, a copying machine, or a so-called multifunction machine having both functions of a facsimile and copying. The ADF 1 shown in the figure is configured as a document feeding device for reading images on both sides of a sheet of document D conveyed one by one and outputting them as digital signals.
[0012]
A document tray 2b is detachably attached to the document supply port 2a of the ADF 1 so that the document tray 2b is inclined downward toward the document supply port 2a, and a document placement unit is formed by the document supply port 2a and the document tray 2b. 2 is configured. A pickup roller 3 is provided on the document supply port portion 2a to feed the document D deposited on the document placement portion 2 from the upper layer portion. The pickup roller 3 is followed to separate the fed documents one by one. The document separation device 4 for feeding is provided. The document separating device 4 includes a separating roller 5 and a retard roller 6 that is urged to elastically contact with a peripheral body of the separating roller 5 and rotates opposite to the separating roller 5 via a torque limiter. . The document fed out by the pickup roller 3 is introduced between the separation roller 5 and the retard roller 6, and is separated one by one due to the action of the opposing rotation of both and the difference in the coefficient of friction with respect to the paper, and to the downstream side. Be fed. Since the mechanism of the retard roller 6 is substantially the same as that disclosed in Japanese Patent Application Laid-Open No. 2001-233491 relating to the present applicant, the detailed description thereof is omitted here. A compression spring is mounted for elastic contact with the separation roller 5, and 6 b is an adjustment screw for adjusting the spring force of the compression spring 6 a. The retard roller 6 is supported via a first arm 6c and a second arm 6d that are swingably attached to a drive shaft 8b of the first transport roller 8 described later, and two idler gears (not shown). Via the drive shaft 8b.
[0013]
The originals separated one by one by the original separating device 4 are resist-conveyed by a first conveying roller 8 and a second conveying roller 9 which are sequentially arranged along an original conveying path 7 formed in a U-turn shape. The first reading point P 1 is reached, and the paper is further fed to the second reading point P 2, and discharged to the discharge tray 11 by the discharge roller 10. A platen (slit glass) 12 is disposed at the first reading point P1, and when the document passes over the platen 12, a reading scanning device (first scanning optical device) serving as a moving optical system unit waiting under the platen 12 is provided. Reading means) 13 sequentially reads the image information on the surface of the document and outputs it as a digital signal as described above.
[0014]
The reading scanning device 13 includes a light source 13a formed of a fluorescent lamp or a cold cathode tube, a plurality of mirrors 13b..., A condensing lens 13c, and a CCD (charge coupled device) 13d. It is mounted on 13e. Irradiation light from the light source 13a is reflected by the original passing through the reading point P1 on the platen 12, and then repeatedly reflected by the four mirrors 13b, is condensed by the condenser lens 13c, and enters the CCD 13d ( (Refer to the light path of the one-dot chain line). In the CCD 13d, image information drawn on the surface of the document is converted into an electric signal and output as a digital signal.
[0015]
The reading scanning device 13 in the figure is configured to be used also as a flat bed scanner (FBS). That is, although a part of the illustration is omitted, the FBS part 14 is coupled to the right side of the broken part in FIG. Although the carriage 13e is stationary at the reading position of the ADF document in the illustrated example, when the FBS document is read, the carriage 13e moves into the FBS unit 14 and reciprocates in the FBS unit 14 along the lower surface of the platen glass 15. The image information of the document placed on the platen glass 15 is read by the reading scanning device 13 in the same manner as described above. The ADF 1, the document tray 2b, and the discharge tray 11 are integrated to form a platen cover, and can be opened and closed up and down with the back side of the paper surface as a hinge portion (not shown). Accordingly, when the FBS unit 14 reads a document, the platen cover is opened and the document is placed on the exposed platen glass 15. In FIG. 1, the front side of the drawing is the front of the apparatus.
[0016]
As described above, the original on which the front (single side) image is read at the first reading point P1 further reaches the second reading point P2, and this second reading point P2 is the back side of the transported original ( This is a contact point between the contact image sensor (fixed optical system unit) 16 disposed on the other surface side and the platen roller 17 disposed in contact therewith. That is, the contact type image sensor 16 and the platen roller 17 constitute a second reading unit, and a document introduced between the contact type image sensor 16 and the platen roller 17 is rotated by the platen roller 17. 16 is fed while sliding on the reading surface. During this time, the back image of the original is read by the contact image sensor 16, converted into an electrical signal, and output as a digital signal.
[0017]
The separation roller 5, the retard roller 6, the first and second transport rollers 8 and 9, the platen roller 17, and the discharge roller 10 use a single motor (not shown) as a drive source and appropriately transmit gears or belts. Drive transmission is made through (same as above), and ON / OFF control is performed individually by an electromagnetic clutch (same as appropriate). Although not shown in the drawings, these drive transmission systems are mainly installed in a body frame on the back side of the page.
[0018]
The pickup roller 3 is configured to be transmitted from the drive shaft 5 a of the separation roller 5. Briefly, a frame 3a is attached to the drive shaft 5a via a torque limiter (not shown) so as to be able to swing up and down, and a support shaft 3b is supported on the front side of the frame 3a so as to be rotatable. ing. A belt 3d is stretched between a pulley 5b attached to the drive shaft 5a and a pulley 3c attached to the support shaft 3b, and the rotation of the drive shaft 5a passes through the pulley 5b, the belt 3d and the pulley 3c. The rotation of the support shaft 3b is transmitted to the pickup roller 3 via a one-way clutch (not shown). Needless to say, such a drive transmission system is not limited to a pulley and a belt, but can be a gear.
[0019]
The pickup roller 3 configured as described above is positioned above the frame 3a in the standby state, and when the drive shaft 5a rotates in the forward direction (A direction), the frame 3a has the drive shaft 5a as a fulcrum by the action of the torque limiter. Swings downward. This swinging is stopped when the pickup roller 3 is pressed against the uppermost layer portion of the document D deposited on the document placing portion 2, but the transmission system (pulley 5b, belt) is rotated by the continued rotation of the drive shaft 5a. The pickup roller 3 rotates via 3d and the pulley 3c). In this manner, while the drive shaft 5a is rotating forward, the pickup roller 3 rotates while being pressed against the uppermost layer portion of the stacked originals D, so that the original document D is sequentially fed out from the uppermost layer portion. When the drive shaft 5a is temporarily stopped and reversely rotated (counter A direction), the frame 3a swings upward by the action of the torque limiter, and is held stationary in a standby state by the subsequent stop of the drive shaft 5a.
[0020]
The separation roller 5 is driven and transmitted from the drive shaft 5a via a not-shown one-way clutch. Accordingly, the document D is fed out from the pickup roller 3 as described above by the forward rotation of the drive shaft 5a, and the fed document is introduced between the separation roller 5 and the separation pad 4b, one by one as described above. Separated and fed downstream. The document D fed from the separation roller 5 is registered by the first transport roller 8 and transported further downstream. The peripheral speeds of the rollers 9, 17, 10 after the first transport roller 8 are as follows: The peripheral speed of the separation roller 5 and the pickup roller 3 is set to be larger than the peripheral speed of the separation roller 5 and the first conveying roller 8 so as to ensure the page interval of the document. Accordingly, when the leading edge of the document D fed from the separation roller 5 reaches the first transport roller 8, a transport load (tensile force) is applied to the document due to the difference in peripheral speed, but the separation roller 5 and the pickup roller 3 are applied. As described above, a one-way clutch (not shown) is incorporated, whereby both rollers 5 and 3 are idly rotated, and the conveying load is alleviated.
[0021]
Pressure rollers 8a, 9a and 10a are respectively provided on the first conveyance roller 8, the second conveyance roller 9 and the discharge roller 10, and the document is nipped and conveyed by these rollers. The separation roller 5 and the pickup roller 3 and pressure roller 8a associated with the separation roller 5 are attached to the inside of a jam access cover 18 pivotally attached to the hinge pin 18a so as to be opened and closed vertically. Therefore, when a document jam occurs in the document conveyance path 7 leading to the second conveyance roller 9, the gap between the retard roller 6 and the first conveyance roller 8 is opened by opening the jam access cover 18. Therefore, it is possible to easily take out the jam original.
[0022]
The supporting mechanism including the pressure roller 10a, the retard roller 6 and the compression spring 6a is an intermediate frame pivotally attached to the drive shaft 8b of the first conveying roller 8 so that it can be opened and closed up and down with its axis as a fulcrum. 19 is attached. Reference numeral 19a denotes an operation knob for opening and closing the intermediate frame 19. Accordingly, when a document jam occurs in the vicinity of the discharge roller 10, the operation knob 19a is lifted with a finger and the intermediate frame 19 is opened to release the jam. Further, the spring force of the compression spring 6a can be adjusted by the adjusting screw 6b with the intermediate frame 19 opened.
[0023]
The first conveying roller 8, the second conveying roller 9, the discharge roller 10 and the platen roller 17 are provided on a machine frame 20 which forms a machine frame of the platen cover, with respective drive shafts 8b, 9b, 10b and 17a. The pair of front and rear parallel side frames 21 are rotatably supported. In addition, a curved inner guide portion 22 constituting a part of the sheet conveyance path 7 is integrally constructed between the side frames 21 between the first conveyance roller 8 and the second conveyance roller 9. 2 A guide frame 23 urged downward (not shown) on the downstream side of the drive shaft 9a of the transport roller 9 is attached to be able to swing up and down. A small protrusion 23 a is formed on the lower surface of the swing end side of the guide frame 23, and the transported original is read between the guide frame 23 and the platen 12 by the small protrusion 23 a coming into contact with the surface of the platen 12. A gap that can pass through the point P1 without flapping is secured.
[0024]
Then, the jam access cover 18 and the intermediate frame 19 are opened, and the guide frame 23 is lifted against the elastic force of the urging spring, thereby removing the jammed original under the guide frame 23 and the surface of the platen 12. Cleaning is possible. Reference numeral 24 denotes a flexible sheet that elastically contacts the guide surface of the guide frame 23, and guides the document that has passed through the second conveying roller 9 along the guide surface of the guide frame 23. The flexible sheet 24 and the guide frame 23 allow the document to pass very smoothly without flapping over the reading point P1, and image information on one side thereof is sequentially read with high accuracy by the reading scanning device 13.
[0025]
Further, a horizontally long contact image sensor 16 is attached and fixed to the side frame 21 via a shaft 16a. This will be described in detail with reference to FIG. FIG. 2 is a schematic plan view of the main part. The shaft 16a is fixed to both end faces in the longitudinal direction of the contact image sensor 16, and the contact image sensor 16 is connected to both side frames 21 by using both shafts 16a. It is fixed in a state maintained at a predetermined angle in between. A contact glass 16b is fixed to the reading surface side of the contact image sensor 16, and the platen roller 17 is in close contact with the surface of the contact glass 16b so as to be slidably rotated.
[0026]
A line segment continuous in the longitudinal direction of the second reading point P2 existing on the surface of the contact glass 16b is a reading line L, and the reading line L and the axis of the shaft 16a are parallel to each other. Accordingly, by accurately positioning and fixing the shaft 16a to the side frame 21, the reading line L can be accurately positioned. In the illustrated example, the platen roller 17 is disposed so as to be in close contact with the contact glass 16b along the reading line L, that is, the surface area where the reading line L connects the axis of the shaft 16a and the axis of the platen roller 17. The layout is set to exist above. With such a setting, the original is smoothly introduced between the platen roller 17 and the contact glass 16b, and the image information on the other side is accurately read at the second reading point P2, but the platen roller 17 and the contact glass 16b are read. The same reading accuracy can be obtained even if the contact point is provided slightly upstream from the reading line L.
[0027]
A document guide member 16c is attached to the shaft 16a so as to be able to swing up and down and located upstream of the contact image sensor 16. The document guide member 16c is for smoothly guiding the document that has passed through the first reading point P1 to the second reading point P2, so that the image information on the other surface is transferred to the second reading point P2. Is read accurately. Further, since the document guide member 16c can be swung up and down, it is easy to check the state of the document at this portion and take out the jammed document. Furthermore, in combination with the function of the guide frame 23, cleaning of the surface of the platen 12 is facilitated. Similar to the guide frame 23, the document guide member 16c can be configured to always spring-bias downward. In FIG. 2, the intermediate frame 19 is indicated by a virtual line (one-dot chain line), and the illustration of the retard roller 6, its mechanism, and pressure roller 10 a mounted on the intermediate frame 19 is omitted.
[0028]
As described above, the document D fed out and separated one by one by the pickup roller 3 and the document separation device 4 is registered by the first transport roller 8 and transported along the inner guide 22 along the document transport path 7 to be second. The feed roller 9 feeds the first reading point P1. At the first reading point P1, the image information on one side of the document D is sequentially read well by the reading scanning device 13 disposed below the first reading point P1. The document D is continuously fed and introduced into the nip position between the contact image sensor 16 and the platen roller 17, that is, the second reading point P <b> 2, and slidably contacts the surface of the contact glass 6 b by the rotational action of the platen roller 17. Image information on the other side is sequentially read by the contact image sensor 16. Thereafter, the discharge roller 10 discharges and accumulates on the discharge tray 11. The image information on both sides of the original D read in this way is taken out as a digital signal and appropriately printed or transmitted.
[0029]
The contact image sensor 16 and the platen roller 17 constituting the second reading unit are attached to a side frame 21 different from the opening / closing mechanism that easily generates vibration, such as the jam access cover 18 and the intermediate frame 19. The side frame 21 is less susceptible to these vibrations, and the side frame 21 is not directly involved in supporting the pickup roller 3 and the document separation device 4 that are likely to generate vibrations. Therefore, the influence of vibration on the contact image sensor 16 and the platen roller 17 is also affected. In addition, since both are supported by the common side frame 21, there is no difference in the way the vibration is transmitted. Therefore, the variation in the distance between the object images in the optical system is small, and highly accurate image reading is possible. Guaranteed. In particular, when the depth of field is shallow, such as a contact-type image sensor having a compact optical system, the variation in relative distance between object images increases even with small vibrations. In this case, the absolute value of the variation in the distance between the object images becomes small, and a difference from the image quality read by the reading scanning device 13 does not occur. Incidentally, since the reading and scanning device 13 constituted by the optical system as described above can set the distance between the object images large, the influence of the vibration due to the load fluctuation or the like as described above is small and is inherently low. The reading quality is high.
[0030]
FIG. 3 shows another embodiment, in which a guide member 16 c is integrally formed on a housing 16 d of the contact image sensor 16. Shafts 16a are attached and fixed to both end faces of the housing 16d, and the contact image sensor 16 is fixed to the side frame 21 using the shaft 16a as described above. As described above, if the guide member 16c is integrated with the contact image sensor 16, there is no merit due to the swing as in the first embodiment, but in this embodiment, it is not necessary to provide a separate guide member. Since the mounting means is also unnecessary, the number of parts and mounting man-hours are reduced, contributing to cost saving. Since other configurations are the same as those in the example shown in FIGS. 1 and 2, common portions are denoted by the same reference numerals and description thereof is omitted.
[0031]
In the above embodiment, the contact image sensor 16 is used as the fixed optical system unit constituting the second reading unit. However, the reading unit has a compact optical system using a CCD, or a sheet-through type image reading unit. It goes without saying that other reading means applicable to the apparatus can be adopted as appropriate. Further, in the illustrated example, the second reading unit is disposed on the downstream side of the first reading unit, but this can be reversed, and can be appropriately changed as a design matter according to the installation space or the like. Needless to say.
[0032]
【The invention's effect】
In the image reading apparatus of the present invention, the fixed optical system unit and the platen roller constituting the second reading means are attached to the side frame constituting the machine body of the automatic document feeder, so the second reading means is In addition, vibrations of the document guide body opening / closing mechanism or the like are not directly received, and load fluctuations during separation and conveyance of the document with respect to the second reading unit are not easily transmitted. Furthermore, since the fixed optical system unit and the platen roller are attached to the same side frame, the way in which the vibrations and the like are transmitted to both of them is not different. Accordingly, the variation in the relative distance between the object images is small, the read image quality is not deteriorated, and particularly, there is no imbalance with the read image quality of the first reading unit, and the structure is simple. A double-sided image reading apparatus with extremely high commercial value can be provided.
[0033]
In the invention of claim 2, since the fixed optical system unit is attached and fixed to the side frame via a shaft parallel to the reading line, the reading line can be accurately positioned with reference to the shaft. Further, since the document guide member is attached to the shaft parallel to the reading line, the guide member is also attached to the transported document with a good left-right balance. Further, in the invention of claim 3, when a jam or the like of a document occurs in the vicinity of the guide member, it is possible to easily grasp the jam state and take out the jammed paper by lifting the guide member with fingers. In addition, it is easy to carry out cleaning maintenance of the document conveyance path.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing main parts of an ADF and a scanning device.
FIG. 2 is a schematic plan view of a peripheral main part of a second reading unit.
FIG. 3 is a schematic longitudinal sectional view of a main part of another embodiment.
[Explanation of symbols]
1 ADF (paper transport device)
13 Reading scanning device (moving optical system unit, first reading means)
16 Contact type image sensor (fixed optical system unit, second reading means)
16a Shaft 16c Guide member 17 Platen roller (fixed optical system unit, second reading means)
21 Side frame L Reading line

Claims (3)

Image reading in which a first reading unit and a second reading unit are arranged along the document conveyance path of the automatic document feeder, and the double-sided image information of the conveyed document is sequentially read by the first and second reading units. A device,
The first reading unit includes a moving optical system unit that can also read a stationary document. The moving optical system unit is configured to be stationary at a predetermined position in the document conveyance path when reading an automatically fed document. The second reading means includes a fixed optical system unit and a platen roller that rotates in sliding contact with the reading surface of the fixed optical system unit, and the fixed optical system unit and the platen roller are arranged on a side frame that constitutes the body of the automatic document feeder. An image reading apparatus which is attached. The fixed optical system unit has a horizontally long shape having a reading line extending over the width of the document conveying path, and is fixed to the side frame via a shaft parallel to the reading line, and a document is placed on the shaft. The image reading apparatus according to claim 1, wherein a guide member for guiding is attached. The image reading apparatus according to claim 2, wherein the guide member is attached to the shaft so as to be able to swing up and down around the shaft center.

Images