JPH1191982A - Image reading device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform conveyance of a document reduce the occurrence of jitter through reduction of the occurrence of a torque fluctuation. SOLUTION: An image reading device comprises an R1 conveyance roller 10 to convey a document, fed by a feed roller 8 and a separation roller 9, to a image reading position; an R1 pressurizing roller 11 brought into pressure contact with the R1 conveyance roller 10; a contact glass 12 arranged in an image reading position; a white reference plate 13 arranged in an image reading position and above the contact glass 12; an R2 conveyance roller 14 to discharge a document, passing through the image reading position, to an external part; and an R2 pressurizing roller 15 brought into pressure contact with the R2 conveyance roller 14. By setting The diameter of either the rollers to 16 ±3 mm and setting the diameter of the R1 pressurizing roller 11 to a range of 6-8 mm, the fluctuation of torque is suppressed, and conveying ability for the document is maintained in an excellent state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image reading apparatus applied to a facsimile machine, a plain paper copier, a scanner, and the like.

[0002]

2. Description of the Related Art Conventionally, as this kind of technology, there is a document feeder described in Japanese Patent Application No. 8-41656 by the same applicant. The apparatus sets the rubber hardness of the first conveying roller and the first pressure roller to 5 ° to 40 °,
A nip width between the first transport roller and the first pressure roller can be secured, and as a result, the amount of torque fluctuation at the moment when the trailing edge of the document passes between the first transport roller and the first pressure roller is reduced. This makes it possible to prevent the occurrence of sawtooth-like bleeding (jitter) on an image due to a change in the speed of the first transport roller.

[0003]

Usually, an image is read by moving a document with respect to a fixed reading unit.
2. Description of the Related Art In a sheet-through type image reading apparatus, a configuration in which conveying rollers are arranged before and after a reading unit is generally performed.

If the transport roller immediately before the reading section is an R1 transport roller and the transport roller immediately after the reading section is an R2 transport roller, the transport force of the R1 transport roller takes into account slippage due to back tension in the separation section in front of the R1 transport roller. Therefore, it is set to a large value that is six times or more the back tension. Further, the linear speed of the R1 transport roller is set to be lower than the linear speed of the R2 transport roller, and the original in the reading unit is set to be easily pulled. Further, the transport force of the R2 transport roller is set to １ ／ to の of the transport force of the R1 transport roller.

In the above configuration, large torque fluctuations and jitters generally occur when the leading edge of the document enters the R2 transport roller and when the trailing edge of the document passes through the R1 transport roller. The details of the mechanism of the occurrence of the torque fluctuation and the jitter will not be described here, but these points have already been clarified theoretically and experimentally in the technical field, and the speed fluctuation and the torque fluctuation of the transport roller are determined by the transport roller. It is known that the pressure largely depends on the pressing force and the thickness of the document, and further depends on the rubber hardness and the roller diameter.

If the torque fluctuation is large, the output torque of the motor must of course be set in consideration of this value.
There is also a problem that a larger motor and a larger current are required to obtain stable rotation.

Further, the jitter tends to increase in proportion to the torque fluctuation. However, the transport roller pressing force cannot be reduced by the R1 transport roller because the transport force is set to a large value, and the thickness of the original is restricted by the product standard. It is difficult to reduce the torque fluctuation depending on the pressure and the document thickness.

The present invention is directed to solving such a problem, and it is possible to reduce the diameter of a roller,
It is an object of the present invention to provide an image reading apparatus that realizes the conveyance of a document with less jitter by reducing torque fluctuation.

[0009]

In order to solve and attain the above object, a transport roller for transporting a document having image information, a pressure roller abutting and driven by the transport roller,
In an image reading apparatus having an image reading unit that reads an image of a document conveyed by a conveyance roller at a predetermined reading position, one of the conveyance roller and the pressure roller has a diameter of 16 ± 3 mm. And the other roller diameter is set in the range of 6 to 8 mm. According to another aspect of the present invention, there is provided a transport roller that transports a document having image information, a pressure roller that contacts and follows the transport roller, and an image reading device that reads an image of the document transported by the transport roller at a predetermined reading position. In the image reading apparatus having the means, the diameters of the transport roller and the pressure roller are substantially the same, and these diameters are set to be in a range of 6 to 10 mm. With such a configuration, it is possible to suppress the torque fluctuation and maintain the document transportability in a favorable state.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic diagram showing a configuration of a facsimile apparatus provided with an image reading apparatus according to the present invention. FIG. 2 is a configuration diagram showing an internal configuration of a reading section. Reference numeral 3 denotes a document discharge tray, 4 denotes a recording unit, and 5 denotes a paper supply unit provided with a recording paper cassette. The facsimile apparatus shown in FIG. 1 mainly includes three units, a reading unit 1, a recording unit 4, and a paper feeding unit 5, and the original read by the reading unit 1 is sent to a transmission destination via a line. The image information received from the other party via the line or the image information of the original read by the reading unit 1 is recorded on a sheet by the recording unit 4.

Reference numeral 6 denotes a pickup roller for moving a document set on the document set table 2 toward the image reading position, 7 a pressure plate for pressing the pickup roller 6, 8 a feed roller, 9 abuts on the feed roller 8, A separation roller 10 for separating and transporting the document sent by the pickup roller 6 one by one; an R1 transport roller 10 for transporting the document sent by the separation roller 9 to the image reading position;
Is an R1 pressure roller pressed against the R1 transport roller 10, 12 is a contact glass provided at the image reading position, 13 is a white reference plate provided at the image reading position and above the contact glass 12, and 14 is an image reading position The reference numeral 15 denotes an R2 pressure roller which presses against the R2 conveyance roller 14 for discharging the document having passed through to the outside.

FIG. 3 shows a case where the diameter of the R1 transport roller is 16 mm and the R1
6 is a graph illustrating a relationship between a roller diameter and a fluctuation torque when the diameter of a pressure roller is changed. Note that each numerical value (mm) of the symbol t in the drawing indicates the thickness of the document. As described in the section of the problem to be solved by the invention, it has been found that the jitter generally tends to increase in proportion to the torque fluctuation, and that the torque fluctuation also depends on the roller diameter. For example, as shown in FIG. 3, as the diameter of the R1 pressure roller 11 increases, the torque fluctuation increases, and the thickness t of the document increases.
Increases, the torque fluctuation increases. In order to reduce the torque fluctuation, it is conceivable to reduce the diameter of the R1 pressure roller 11. However, if the diameter is too small, it is difficult for the paper to enter the nip with the R1 transport roller 10 so that the document can be transported easily. Is not only damaged, but also the roller shaft of the R1 pressure roller 11 may be bent.

Therefore, in the first embodiment of the present invention, the roller diameter is used as a control factor, and the diameter of the R1 transport roller 10 is adjusted.
The diameter of the R1 pressure roller 11 is set in a range of 6 to 8 mm within a range of 16 ± 3 mm. In other words, considering that the thickness of a commonly used original document is 0.08 to 0.14 mm, the torque fluctuation can be suppressed to 250 gfcm or less by setting the diameter of the R1 pressure roller 11 to 8 mm or less. Can be. If the torque fluctuation is about 250 gfcm or less, the jitter does not become large enough to affect the read image. Further, the diameter of the R1 pressure roller 11 is set to 5
When the distance is set to be equal to or less than mm, paper hardly enters the nip with the R1 transport roller 10. Therefore, by setting the diameter of the R1 pressure roller 11 in the range of 6 to 8 mm, it is possible to suppress the torque fluctuation and to maintain a good document transportability.

With the configuration of the first embodiment, when the diameter of the R1 transport roller 10 is restricted by the linear speed, the reduction ratio, the number of rotations of the motor, etc., the diameter of the R1 pressure roller 11 is reduced. By doing so, the torque fluctuation can be reduced, and the document transportability can be maintained in a good state.

Next, a second embodiment of the present invention will be described. In the second embodiment, the diameters of the R1 transport roller 10 and the R1 pressure roller 11 are substantially equal, and both diameters are set in a range of 6 to 10 mm.

FIG. 4 is a graph showing the relationship between the roller diameter and the fluctuation torque when the diameter of the R1 transport roller and the diameter of the R1 pressure roller are changed. From the results shown in FIG. 4, it can be seen that the torque fluctuation increases as the diameter of the R1 pressure roller increases, and the torque fluctuation increases as the thickness t of the document increases. here,
Similarly, taking into account the diameter of the R1 transport roller 10, the deflection of the roller shaft of the R1 pressure roller 11, the transportability of the document in the nip, and the thickness of the document, the diameter of the R1 transport roller 10 and the R1 pressure roller 11 By setting the diameter in the range of 6 to 10 mm, torque fluctuation can be reduced,
The document transportability can be maintained in a good state.

[0018]

As described above, according to the present invention,
A drive system with small torque fluctuation can be realized, and the frequency of occurrence of jitter can be extremely reduced.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a facsimile apparatus provided with an image reading device of the present invention.

FIG. 2 is a configuration diagram illustrating an internal configuration of a reading unit.

FIG. 3 is a graph showing the relationship between the roller diameter and the fluctuation torque when the diameter of the R1 pressure roller is changed while the diameter of the R1 conveyance roller is 16 mm.

FIG. 4 is a graph showing the relationship between the roller diameter and the fluctuation torque when the diameter of the R1 transport roller and the diameter of the R1 pressure roller are changed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... reading part, 2 ... original set table, 3 ... original discharge tray, 4 ... recording part, 5 ... paper feeding part, 6 ... pickup roller, 7 ... pressure plate, 8 ... feed roller
9: separation roller, 10: R1 transport roller, 11: R1 pressure roller, 12: contact glass, 13: white reference plate,
14 ... R2 transport roller, 15 ... R2 pressure roller.

Claims (2)

[Claims] A transport roller that transports a document having image information; a pressure roller that is driven in contact with the transport roller; and an image reading device that reads an image of the document transported by the transport roller at a predetermined reading position. In an image reading apparatus having means, one of the roller diameters of the transport roller and the pressure roller is set to be within a range of 16 ± 3 mm,
An image reading apparatus, wherein the diameter of the other roller is set to be in a range of 6 to 8 mm. 2. A transport roller for transporting a document having image information, a pressure roller which is driven in contact with the transport roller, and an image reader which reads an image of the document transported by the transport roller at a predetermined reading position. An image reading apparatus according to claim 1, wherein said conveying roller and said pressure roller have substantially the same diameter, and these diameters are set within a range of 6 to 10 mm.