JP2004020979A - Flat scanning system and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flat scanning system which reads a document image with high precision. <P>SOLUTION: Positioning members 210a and 210b which slide in contact with the underneath of a document table glass 61 are fixed to longitudinal both ends of a CIS 210. The positioning member 210a is fixed to one of the longitudinal ends of the CIS 210 and made of a material (e.g., POM, polyacetal resin) which is excellent in slidability. The positioning member 210b, on the other hand, is fixed to the other longitudinal end of the CIS 210 and made of a material (e.g., ABS, acrylonitrile butadiene styrene) which is slightly less excellent in slidability than the material of the positioning member 210. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a planar scanning device for reading an image (document image) recorded on a document and an image forming apparatus provided with the planar scanning device.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an image forming apparatus that reads an image recorded on a document and forms the read document image on a recording medium such as recording paper has been used. As a device for reading a document image, a planar scanning device is usually used.
[0003]
For example, the flat-surface scanning device places a document on an upper surface (front surface) of a platen glass and scans a contact image sensor (CIS) in a predetermined scanning direction along a lower surface (back surface) of the platen glass. It reads a document image. This planar scanning device will be described with reference to FIG.
[0004]
FIG. 4 is a top view showing a schematic configuration of a conventional planar scanning device.
[0005]
The planar scanning device 10 includes a carriage 12 that carries a CIS 13 and scans in the sub-scanning direction (the direction of arrow B), a guide shaft 14 that guides the carriage 12 in the sub-scanning direction, and a sub-scanning range that the carriage 12 scans. An idler pulley 16 and a driving pulley 18 respectively disposed near both ends in the scanning direction, and an endless belt 20 that is wound around these pulleys 16 and 18 and moves in the sub-scanning direction to scan the carriage 12. It has. The carriage 12 is fixed to the belt 20 and movably fixed to the guide shaft 14.
[0006]
The belt 20 moves in a direction indicated by an arrow B and in a direction opposite thereto by the rotation force (drive force) of the drive motor 22. The torque of the drive motor 22 is transmitted to the drive pulley 18 via a pulley gear 24 and an idler gear 26. Further, a constant tension is applied to the belt 20 in order to transmit the rotational force and the rotational speed of the drive motor 22 accurately. In order to obtain such a tension, when assembling the planar scanning device 10, the idler pulley 16 is fixed to the idler pulley support 28, and the idler pulley support 28 is pulled by a predetermined force in the direction of arrow B. In this state, it is fixed to the guide shaft 14.
[0007]
Positioning members 30, 30 for maintaining a constant distance between the CIS 13 and the lower surface of the platen glass are fixed to both ends of the CIS 13 in the longitudinal direction (the direction orthogonal to the arrow B direction). These positioning members 30, 30 are always in contact with the lower surface of the platen glass while the carriage 12 is scanning and slide. As the sliding resistance of the positioning members 30, 30 with respect to the lower surface of the platen glass increases, the drive motor 22 having a higher driving force is required. In addition, the positioning members 30, 30 may be worn due to repeated scanning of the carriage 12, and in this case, the distance between the CIS 13 and the lower surface of the platen glass may not be kept constant. If the distance is no longer kept constant, the image read out of focus of the CIS 13 is out of focus.
[0008]
Therefore, the positioning members 30, 30 are often made of a material having low sliding resistance, such as POM (polyacetal resin) or polyolefin.
[0009]
[Problems to be solved by the invention]
However, there may be variations in the state of the lower surface of the platen glass (surface roughness and the like), and in this case, the sliding resistance of the positioning members 30 may fluctuate while the carriage 12 is scanning. Due to this variation, the sliding resistance with respect to the lower surface of the original table glass varies at both ends in the longitudinal direction of the carriage 12, so that the carriage 12 behaves in an unstable manner during scanning. As a result, the CIS 13 also behaves in an unstable manner, and the accuracy in reading the document image may be reduced.
[0010]
The present invention has been made in view of the above circumstances, and has as its object to provide a planar scanning device capable of reading a document image with high accuracy and an image forming apparatus including the planar scanning device.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, a flat scanning device according to the present invention scans in a predetermined sub-scanning direction below a platen glass on which an original is placed, and extends in a longitudinal direction orthogonal to the sub-scanning direction. A carriage, reading means mounted on the carriage for reading the image of the document on the platen glass while scanning in the sub-scanning direction, and extending in the longitudinal direction; and A guide shaft, which guides in the scanning direction, a central portion in the longitudinal direction of the carriage is movably mounted, and a lower surface of the platen glass so that a distance from the reading unit to the platen glass is kept constant. A planar scanning device comprising: a positioning member fixed to the reading unit;
(1) The positioning member is
(1-1) a first positioning member fixed to one longitudinal end of the reading means;
(1-2) a second positioning member fixed to the other longitudinal end opposite to the one longitudinal end with the guide shaft interposed therebetween,
(2) The sliding resistance of the first positioning member on the lower surface of the platen glass is different from the sliding resistance of the second positioning member on the lower surface of the platen glass. is there.
[0012]
here,
(3) The first positioning member and the second positioning member have different sliding resistances by different shapes of portions of these members that contact the lower surface of the platen glass. There may be.
[0013]
further,
(4) The first positioning member and the second positioning member may have different sliding resistances by making the materials of these members different from each other.
[0014]
Further, an image forming apparatus of the present invention for achieving the above object,
(5) It is provided with the above-mentioned flat-surface scanning device, and forms a document image read by this flat-surface scanning device on a recording medium.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to FIG.
[0016]
FIG. 1 is a schematic diagram showing the internal structure of an image forming apparatus provided with the flat-surface scanning device of the present invention.
[0017]
A digital copier 50 (an example of an image forming apparatus according to the present invention) forms a first housing 60 in which a plurality of components for reading an image recorded on a document are incorporated, and an image on a recording medium. And a second housing 100 in which a plurality of components are incorporated. The second housing 100 is arranged below the first housing 60 as shown in the figure. Therefore, the first housing 60 is placed on the second housing 100.
[0018]
On the top surface of the copying machine 50, a rectangular parallelepiped document pressure plate 62 that can be opened and closed is arranged. An optical housing 64 in which the planar scanning device 200 (see FIG. 2) is incorporated is arranged below the original cover 62. The planar scanning device 200 includes a light source LED (not shown) and the like. The upper surface (upper wall) of the optical housing 64 is a platen glass 61 on which a document is placed. A first housing 60 is configured by the original cover 62 and the optical housing 64.
[0019]
An image reading area 82 for reading an image of a document is formed at one end of the platen glass 61 opposite to the fixing device 126 across the photosensitive drum 112. Further, a transport guide table 95 that guides the document transported to the image reading area 82 to the discharge tray 86 is formed slightly downstream of the image reading area 82 in the direction of arrow B. The transport guide table 95 is elongated and extends in a direction orthogonal to the directions of the arrows A and B. On the other hand, at the other end of the platen glass 61 opposite to the one end where the transport guide table 95 is formed, a butting plate 67 against which a document placed on the platen glass 61 is abutted is formed. Have been. The abutment plate 67 is elongated and extends in a direction orthogonal to the directions of the arrows A and B.
[0020]
An automatic document feeder 80 for automatically feeding a document is incorporated in the document pressing plate 62. The automatic document feeder 80 will be described later.
[0021]
An operation panel (not shown) for inputting the number of copies and the like is arranged on the front side (front side) of the second housing 100 with respect to the first housing 60. At the lower portion of the second housing 100, a cassette 104 for accommodating a plurality of cut sheets is provided so as to be able to be taken in and out of the second housing 100. On the right side wall of the second housing 100, a rectangular manual tray 106 capable of feeding small-sized recording paper such as a postcard is provided. The manual feed tray 106 rotates in the direction of arrow C about the lower side 106a, and opens to a position where a recording medium can be placed. Further, a space is formed in the left side portion of the second housing 100, and a paper discharge tray 108 on which the discharged recording paper is stacked is formed.
[0022]
In the copying machine 50, when an image recorded on a document is formed on a recording medium, a fixed document scanning mode and a moving image scanning mode can be selected. In the original fixed scanning mode, an original is placed on the original platen glass 61, and the CIS 210 (an example of a reading unit according to the present invention) is moved below the original platen glass 61 in the direction of arrow B (scanning direction). This is a mode for reading an image of a document while scanning. On the other hand, the image reading scanning mode is a mode in which the CIS 210 is kept stationary below the image reading area 82, and while the original is conveyed to the image reading area 82 by the automatic document feeder 80, the image of the original is imaged using the CIS 210. This is a reading mode in the reading area 82.
[0023]
When the original fixed scanning mode is selected, first, the original cover 62 is opened, the original is placed on the upper surface of the platen glass 61, and is positioned by abutting against the abutment plate 67. Press and fix with. Next, when a predetermined operation button or the like is pressed, light guided by a light guide (not shown) from the LED light source irradiates the original, and the CIS 210 incorporated in the optical housing 64 is a two-dot chain line. The scanning is performed in the direction of arrow B from the position indicated by. The image recorded on the document is read by the CIS 210. The read image is converted into a digital signal, and this digital signal is transmitted to the laser scanner 110. The platen glass 61 is fixed to a rectangular platen frame 63 formed in the optical housing 64.
[0024]
The automatic document feeder 80 includes a document tray 84 on which a document is placed, and a document discharge tray 86 on which a document passing through the image reading area 82 is placed. Further, the automatic document feeder 80 has a plurality of rollers (a feed roller 90 and a registration roller 90) for transferring the document placed on the document placing tray 84 to the document discharge tray 86 through the image reading area 82. Pair 92).
[0025]
The document placed on the document placing tray 84 is transported from the paper feed port 90a to the separation roller 91 by the paper feed roller 90, and further transported to the registration roller pair 92 to correct the skew. The skew-corrected document is conveyed to the platen roller 94 by the pair of registration rollers 92 and passes through the image reading area 82.
[0026]
The CIS 210 is stationary below the image reading area 82, and a document passing through the image reading area 82 is illuminated by an LED (not shown) and read by the CIS 210. The read image is converted into a digital signal, and this digital signal is transmitted to the laser scanner 110.
[0027]
The document that has passed through the image reading area 82 is guided to the transport rollers 96 by the transport guide table 95. The transport roller 96 transports the original to the discharge roller 98 while reversing the original. The document conveyed to the discharge roller 98 is discharged to the document discharge tray 86 by the discharge roller 98.
[0028]
As described above, in the copying machine 50, the read image of the original is converted into a digital signal, and the digital signal is transmitted to the laser scanner 110 in both the image scanning mode and the original fixed scanning mode. . The signal transmitted to the laser scanner 110 is converted into a laser beam, and the laser beam is applied to the photosensitive drum 112 via a scanner mirror 110a rotating at a high speed and a return mirror 110b. The photosensitive drum 112 is uniformly charged by the charging roller 111, and an electrostatic latent image is formed on the photosensitive drum 112 irradiated with the laser beam. This electrostatic latent image is developed with the developer supplied from the developing roller 114 to form a developed image.
[0029]
On the other hand, a recording medium such as recording paper is fed from the cassette 104 by a feed roller 116 in the direction of arrow D (feed direction), and is fed to a transfer roller 122 by a feed roller 118 and a registration roller 120. The transfer roller 122 transfers the developed image on the photosensitive drum 112 to the conveyed recording medium. The recording medium on which the developed image has been transferred is transported to the fixing device 126 by the transport device 124. The fixing device 126 includes a heating roller 126a and a pressure roller 126b. The recording medium is conveyed while being sandwiched between these two rollers 126a and 126b, and the developed image is fixed on the recording medium. The recording medium on which the developed image has been fixed in this manner is discharged by the discharge roller 128 and stacked on the discharge tray 108.
[0030]
The recording medium can be fed from the manual feed tray 106, and the procedure for forming an image on the recording medium fed from the manual feed tray 106 is the same as described above. The copier 50 also has a built-in electrical board 129 on which a power supply for driving various components and electric components are mounted.
[0031]
As described above, the copier 50 incorporates various components and members. Among these components, the charging roller 111, the photosensitive drum 112, the developing roller 114, and the like are incorporated in the process cartridge 130. The process cartridge 130 is detachably mounted on the copying machine 50.
[0032]
With reference to FIGS. 2 and 3, a description will be given of the planar scanning device 200 incorporated in the optical housing 64.
[0033]
FIG. 2 is a top view illustrating the planar scanning device. FIG. 3 is a top view showing the planar scanning device of FIG. 2 in an enlarged manner.
[0034]
The plane scanning device 200 includes a carriage 250 on which the above-described CIS 210 is mounted. The carriage 250 moves in the directions of arrows A and B below the platen glass 61. When the carriage 250 moves (scans) in the direction of arrow B (sub-scanning direction), the CIS 210 reads a document image. A signal carrying an image read by the CIS 210 is transmitted to the main body via the flexible cable 211.
[0035]
Further, a guide shaft 206 that guides the carriage 250 in the sub-scanning direction is arranged in the planar scanning device 200. The guide shaft 206 extends in the sub-scanning direction, and a drive pulley 212 and an idler pulley (follower pulley) 214 are respectively provided near both ends in the longitudinal direction (the sub-scanning direction, directions of arrows A and B). Are located. An endless belt 216 to which the carriage 250 is fixed is stretched over these two pulleys 212 and 214. As the belt 216 moves (reciprocates) in the directions of arrows A and B, the CIS 210 moves in the directions of arrows A and B together with the carriage 250.
[0036]
The drive pulley 212 is rotated by the rotational force (drive force) of the drive motor 240, and the belt 216 moves in the directions of arrows A and B with this rotation. The torque of the drive motor 240 is transmitted to the drive pulley 212 via the motor belt 241, the pulley gear 242, and the idler gear 244.
[0037]
The idler pulley 214 is rotatably fixed to one end of a pulley support 218. The pulley support 218 extends in a direction substantially perpendicular to the scanning direction, and extends from the position where the idler pulley 214 is fixed to the opposite side beyond the guide shaft 206. The idler pulley 214 is fixed to one end of the pulley support 218 in the longitudinal direction.
[0038]
A central portion of the pulley support 218 is rotatably fixed to the guide shaft 206 by a step screw 220 from the back side of the paper surface of FIG. One end 222a of a tension coil spring 222 is attached to the other longitudinal end of the pulley support 218. The other end 222 b of the tension coil spring 222 is attached to a fixed plate 224 fixed to the guide shaft 206. Accordingly, the pulling force (biasing force) of the pulling coil spring 222 pulls the other end of the pulley support 218 in the direction of arrow A, whereby the pulley support 218 rotates clockwise in FIG. Accordingly, the idler pulley 214 is urged away from the drive pulley 212. As a result, a tension corresponding to the tension of the tension coil spring 222 acts on the belt 216.
[0039]
The above-described carriage 250 is elongated and extends in a longitudinal direction orthogonal to the sub-scanning direction. The CIS 210 is mounted on the carriage 250, and the CIS 210 extends in the longitudinal direction of the carriage 250. Therefore, the CIS 210 also has an elongated shape. A central portion in the longitudinal direction of the carriage 250 is attached to the guide shaft 206 so as to be movable in the directions of arrows A and B. The position of the longitudinal center of the carriage 250 corresponds to the longitudinal center of the CIS 210. For this reason, the central portion in the longitudinal direction of the CIS 210 is located directly above the guide shaft 206.
[0040]
A pressing spring (not shown) for urging the CIS 210 toward the platen glass 61 is disposed on the carriage 250. Further, positioning members 210a and 210b for maintaining a constant distance from the CIS 210 to the lower surface of the document table glass 61 are fixed to both ends in the longitudinal direction of the CIS 210. The positioning members 210 a and 210 b are in contact with the lower surface of the document table glass 61. Therefore, as the carriage 250 and the CIS 210 scan in the sub-scanning direction, the positioning members 210 a and 210 b slide on the lower surface of the document table glass 61.
[0041]
The positioning member 210a (an example of a first positioning member according to the present invention) is fixed to one longitudinal end of the CIS 210. The positioning member 210b (an example of a second positioning member according to the present invention) is fixed to the other end of the CIS 210 in the longitudinal direction. The positioning member 210a is made of a material having excellent slidability (for example, POM (polyacetal resin)), while the positioning member 210b is made of a material (for example, ABS) slightly less slidable than the material of the positioning member 210a. (Acrylonitrile-butadiene-styrene)).
[0042]
Therefore, when the positioning members 210a and 210b slide on the lower surface of the platen glass 61, the sliding resistance of the positioning member 210a becomes smaller than the sliding resistance of the positioning member 210b. That is, the sliding resistance of the positioning member 210a <the sliding resistance of the positioning member 210b.
[0043]
As described above, since the sliding resistances of the positioning members 210a and 210b are different from each other, when the carriage 250 moves in the direction of arrow B, the carriage 250 is viewed from above the paper surface (from the upper surface side of the document table glass 61) in FIG. A moment in the counterclockwise direction (the direction of arrow E) acts on the carriage 250 about the longitudinal central portion of the carriage 250. Therefore, even when the state (surface roughness and the like) of the lower surface of the platen glass 61 slightly varies, the magnitude of the sliding resistance of both the first positioning member 210a and the second positioning member 210b during the scanning of the carriage 250 is small. Since it does not change, the CIS 210 does not behave in an unstable manner. For this reason, in the planar scanning device 200, the image blur caused by the fluctuation of the sliding resistance is prevented, and the document image can be read with high accuracy. As a result, the copying machine 50 can form a high-quality image on a recording medium. When the carriage 250 moves in the direction of arrow A, a moment opposite to the above acts on the carriage 250.
[0044]
In the example described above, the sliding resistance of the two positioning members 210a and 210b is made different from each other by making the materials of the two positioning members 210a and 210b different from each other. The sliding resistance of the positioning members 210a and 210b may be made different from each other by making the shapes of the portions contacting the lower surface of the base 61 different from each other. Further, by changing the number of positioning members at both ends in the longitudinal direction of the CIS 210, the sliding resistance at both ends in the longitudinal direction of the CIS 210 may be made different from each other.
[0045]
【The invention's effect】
As described above, in the flat scanning device of the present invention, since the sliding resistances of both the first positioning member and the second positioning member with respect to the lower surface of the platen glass are different from each other, when the carriage scans in the sub-scanning direction, Either the first positioning member or the second positioning member generates a greater sliding resistance with respect to the lower surface of the platen glass than the other positioning member. Therefore, even if there is some variation in the state of the lower surface of the document table glass (surface roughness or the like), the magnitude of the sliding resistance of both the first positioning member and the second positioning member does not change. As a result, the reading means does not behave in an unstable manner. For this reason, in the planar scanning device of the present invention, the image blur caused by the fluctuation of the sliding resistance is prevented, and the original image can be read with high accuracy.
[0046]
Here, the first positioning member and the second positioning member have different sliding resistances by different shapes of portions of these members that come into contact with the lower surface of the platen glass. In some cases, the sliding resistance can be made different from each other with a simple configuration.
[0047]
Further, when the first positioning member and the second positioning member have different sliding resistances by making the materials of these members different from each other, if the sliding resistances are different from each other, the sliding resistances can be mutually reduced by a simple configuration. Can be different.
[0048]
Further, according to the image forming apparatus of the present invention, since a document image can be read with high accuracy, a high quality image can be formed on a recording medium.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an internal structure of an image forming apparatus provided with a planar scanning device of the present invention.
FIG. 2 is a top view showing the planar scanning device.
FIG. 3 is an enlarged top view showing the planar scanning device of FIG. 2;
FIG. 4 is a top view showing a schematic configuration of a conventional planar scanning device.
[Explanation of symbols]
50 Copier 61 Platen glass 210 CIS
250 carriage 210a, 210b positioning member

Claims (4)

A carriage extending in a longitudinal direction perpendicular to the sub-scanning direction, which scans in a predetermined sub-scanning direction below the platen glass on which the original is placed, and the platen glass while scanning in the sub-scanning direction Reading means for reading an image of an upper document, mounted on the carriage and extending in the longitudinal direction,
A guide shaft that extends in the sub-scanning direction and guides the carriage in the sub-scanning direction, and a central portion in the longitudinal direction of the carriage that is movably mounted;
A positioning member fixed to the reading means for determining a position of the reading means by contacting a lower surface of the document glass so that a distance from the reading means to the platen glass is kept constant. In a planar scanning device,
The positioning member,
A first positioning member fixed to one longitudinal end of the reading unit;
A second positioning member fixed to the other longitudinal end opposite to the one longitudinal end with the guide shaft interposed therebetween,
A flat scanning device, wherein a sliding resistance of the first positioning member with respect to a lower surface of the platen glass is different from a sliding resistance of the second positioning member with respect to a lower surface of the platen glass. The first positioning member and the second positioning member,
2. The flat scanning apparatus according to claim 1, wherein the sliding resistance of the members is different from each other by changing the shape of a portion that contacts the lower surface of the platen glass. The first positioning member and the second positioning member,
2. The flat scanning apparatus according to claim 1, wherein the sliding resistance is made different by making the materials of these members different from each other. An image forming apparatus, comprising: the planar scanning device according to claim 1, wherein a document image read by the planar scanning device is formed on a recording medium.

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