JP3323758B2 - Sheet conveying apparatus, image reading apparatus and image forming apparatus including the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet conveying device, and an image reading device and an image forming device provided with the same.
In particular, the present invention relates to a sheet skew correction operation in a sheet conveying device.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus or an image reading apparatus such as a copying machine, a scanner, a printer or the like, a registration (a position and a position adjustment of a sheet) is performed immediately before an image forming section or an image take-out section. (Skew correction) device is used. These registration devices include, for example, a loop registration method in which a sheet tip is made to deflect by abutting the sheet tip against a nip of a pair of stopped rollers, and the sheet tip is attached to the roller nip by the elasticity of the sheet. Alternatively, a shutter member for stopping the leading edge of the sheet is provided in the sheet conveying path so as to be retractable, and after attaching the leading edge of the sheet to the shutter member, the shutter member is retracted from the conveying path to correct the skew. It is used.

In recent years, as these image forming apparatuses and image reading apparatuses have been digitized, the distance between sheets (hereinafter, referred to as “sheet interval”) has been reduced, and many sheets have been reduced in a short time. By processing, the image forming speed has been substantially improved without increasing the image forming process speed.

For example, in a conventional analog copying machine, when performing continuous copying, an optical device for exposing a document has to reciprocate by the number of copies, so that the space between copies of document information is limited. Inevitably decided. However, since the reading of the document and the image formation thereof are digitized, the image information is electrically encoded and stored in the memory after the document is read once.

At the time of image formation, image information in the memory is read out, and an image corresponding to the image information is formed on a photoreceptor of an image forming section by an exposure device such as a laser beam or an LED array. For this reason, a mechanical movement of an optical device or the like is not required even when copying a plurality of sheets. Therefore, the time for the above-described sheet registration (skew correction) is one of the major factors for determining the sheet interval.

Here, as one of the methods proposed to shorten the registration time, there is an active registration method for correcting skew while conveying a sheet.
In this method, two sensors are arranged on a coaxial line orthogonal to the sheet conveyance direction in a sheet conveyance path, and the inclination of the sheet front is detected based on a signal that the front end of the sheet crosses each sensor. The skew feeding of the sheet is controlled by controlling the sheet feeding speed of skew feeding correcting rollers (hereinafter referred to as registration rollers) which are arranged coaxially perpendicular to the sheet feeding direction and driven independently of each other.
According to this method, the skew correction can be performed while the sheet is conveyed without being temporarily stopped, so that the above-mentioned sheet interval can be reduced as compared with other methods.

[0007]

However, in such a conventional sheet conveying apparatus and an image reading apparatus and an image forming apparatus provided with the same, when the size of the conveyed sheet is not constant, particularly when the sheet is long, When a sheet is conveyed, skew correction of the sheet by the registration roller must be performed in a state where the trailing end of the sheet is nipped by the conveyance roller disposed on the upstream side.

That is, in the active registration method, the skew correction is performed by advancing the delayed side of the sheet by the registration roller or delaying the leading side by the registration roller. Since movement is required, it is difficult to rotate the sheet by a required amount while the rear end of the sheet is held between the transport rollers, and it is difficult to perform accurate skew correction. There was a point.

Further, if the conveyed sheet has a large basis weight, that is, a thick sheet, the conveyance resistance of the registration roller increases due to sliding resistance between the conveyance guide and the sheet, and the sheet is rotated by a necessary amount. It is difficult to perform the skew correction with high accuracy.

Further, when the conveying force of the registration roller is reduced due to durability or the like, a small slip occurs at the time of skew correction, and the accuracy of skew correction is further deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to continuously convey sheets of various sizes and thicknesses at a minimum interval and to endure skew correction of those sheets. Another object of the present invention is to provide a sheet conveying device capable of performing a stable and accurate operation, and an image reading apparatus and an image forming apparatus including the same.

[0012]

According to the present invention, a sheet is conveyed by a sheet conveying means, and skew of the conveyed sheet is corrected by a skew correcting means provided in a sheet conveying path. A first sheet skew amount detecting means for detecting a skew amount of the conveyed sheet; and a skew of the conveyed sheet disposed downstream of the first sheet skew amount detecting means. A second sheet skew amount detecting means for detecting an amount, and a correction operation being controlled based on a skew amount signal input from the first sheet skew amount detecting means; Control means for controlling the skew feed correcting means to perform a skew feed correction operation that could not be corrected by the correction operation based on the skew feed signal input from
Wherein the control means performs a skew amount larger than the skew amount detected by the first sheet skew amount detection means during the correction operation based on the skew amount signal from the first sheet skew amount detection means. The skew feeding correcting means is controlled so as to correct a row.

Further, according to the present invention, the first sheet skew amount detecting means is located at a position downstream of the sheet conveying means and at a position where the distance from the sheet conveying means is shorter than the length of a predetermined sheet in the conveying direction. It is characterized by being provided.

The present invention also provides a sheet conveying apparatus for conveying a sheet by a sheet conveying means and correcting skew of the conveyed sheet by a skew correcting means provided in a sheet conveying path. An image reading unit that reads a sheet conveyed by the device, wherein the sheet conveying device is the sheet conveying device according to any one of the above, and the sheet conveying device is an image reading unit of the image reading unit. It is characterized by being provided upstream in the sheet conveying direction.

The present invention also provides a sheet conveying apparatus for conveying a sheet by sheet conveying means and correcting skew of the conveyed sheet by skew correcting means provided in a sheet conveying path. An image forming apparatus comprising: an image forming unit that forms an image on a sheet conveyed by the apparatus; wherein the sheet conveying apparatus is the sheet conveying apparatus according to any of the above, and the sheet conveying apparatus includes: It is characterized by being provided upstream of the forming section in the sheet conveying direction.

[0016]

[0017]

Further, as in the present invention, the first sheet skew amount detecting means is positioned downstream of the sheet conveying means and at a position where the gap with the sheet conveying means is shorter than the length of the predetermined sheet in the conveying direction. One or more other sheet skew amount detecting means are arranged downstream of the first sheet skew amount detecting means. The control means controls the first correction operation based on the skew amount signal input from the first sheet skew amount detection means, and thereafter, the skew amount input from another skew amount detection means. By controlling the skew correction operation that could not be corrected in the first correction operation based on the signal, the skew correction can be performed durably, stably, and accurately.

[0019]

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

FIG. 1 is a cross-sectional view showing a schematic configuration of a sheet conveying apparatus and an image reading apparatus having the same according to an embodiment of the present invention. FIG. 2 is a top view showing a skew feeding correction section of a document of the sheet conveying apparatus. FIG.

In FIG. 1, reference numeral 1 denotes a document table on which a plurality of documents G are set with their image surfaces facing upward. Reference numeral 3 denotes a pickup roller whose outer peripheral surface is covered with rubber or the like having a relatively high coefficient of friction, and feeds out a document G set on the document table 1. Reference numerals 4a and 4b denote separation / feeding roller pairs for separating and feeding the originals G sent out by the pickup roller 3 one by one.
Reference numerals 5a and 5b denote first conveying roller pairs as sheet conveying means, and reference numerals 6a and 6b denote second conveying roller pairs as sheet conveying means.

Reference numeral 8 denotes a registration roller unit which is skew correction means for correcting skew of the document G. The registration roller unit 8 is arranged on a coaxial line orthogonal to the document conveyance direction as shown in FIG. It has two pairs of rollers 8a and 8b which are independently driven to rotate. Here, the registration roller unit 8 is configured to control the pair of rollers 8a and 8b in accordance with the amount of skew
The skew of the document G is corrected by increasing or decreasing one of the rotation speeds. In the present embodiment, the rotation speed of one roller pair (the leading side of the document) is reduced in accordance with the amount of skew of the document G so that skew correction of the document is performed. I have.

Further, in FIG. 1, reference numeral 9 denotes first sheet skew amount detecting means (hereinafter, referred to as first detecting means) for detecting the skew amount (the inclination of the leading edge) of the document G, which is shown in FIG. Sets of light transmitting sensors 9a and 9b arranged on both sides of the conveyance path R and on a coaxial line orthogonal to the document conveyance direction as described above.
have. In FIG. 1, A denotes a first skew correction section. In the first skew correction section A, skew correction of the document G is performed based on the skew amount detected by the first detecting means 9. It has become.

A second sheet skew amount detection means 15 is another sheet skew amount detection means for detecting the skew amount of the document G after the skew correction in the first skew correction section A. (Hereinafter, referred to as a second detecting means), and includes two sets of light transmitting sensors 15a and 15b disposed on both sides of the transport path R and on a coaxial line orthogonal to the document transport direction as shown in FIG. are doing. In FIG. 1, B is a second skew correction section, and skew correction of the document G is performed based on the skew amount detected by the second detection means 15 in the second skew correction section. It has become.

Incidentally, the first detecting means 9 is provided downstream of the second conveying roller pair 6a, 6b and at the second conveying roller pair 6a.
(La + Lb), which is the gap between the second conveying roller pair 6a, 6b and the registration roller unit 8, and the distance Lb between the registration roller unit 8 and the first detecting means 9.
Is provided at a position that is shorter than the predetermined length of the original G in the transport direction.

The first detecting means 9 is located at such a position.
Is provided, the first detecting means 9 detects the skew of the original G when conveying the long-size original G, and corrects the skew based on the skew. At the time of correction, the rear end of the document G is held between the transport rollers 6, so that its movement is restricted, and it becomes impossible to perform appropriate correction. Further, even if the original G has a size of La + Lb or less, the original G having a large basis weight,
In this case, the rotational movement of the rear end of the document G is restricted by the sliding resistance with the conveyance guide 14.

However, the second detecting means 9
The provision of the detection means 15 enables the second detection means 15 to correct the skew of the long document G that could not be corrected in the first correction operation by the first detection means 9. I have.

On the other hand, in FIG. 1, reference numeral 20 denotes a control device which is a control means. As shown in FIG. 3, the control device 20 controls the skew amount information from the first detection means 9 and the skew amount information from the second detection means 15 as shown in FIG. The driving of the drive motors M1 and M2 of the registration roller pairs 8a and 8b is sequentially controlled in accordance with the corrected skew amount information to correct the skew of the document G.

Reference numeral 10 denotes an image reading device,
An illumination lamp 10a for irradiating the image surface of the original G via a transmission glass 11 disposed in the transport path, mirrors 10b, 10c, and 10d for reflecting the irradiation light, and a lens 10e for condensing the reflected light And an image reading element 10f such as a CCD.

Reference numeral 12 denotes a discharge roller pair, which discharges the original G whose image has been read onto a discharge tray 13. A transport guide 14 for guiding the document G is provided between each pair of rollers.

Next, the document conveying operation of the sheet conveying apparatus having the above-described configuration will be described.

When a document G is set on the document table 1 and a start button (not shown) is pressed, the pickup roller 3 first rotates, and the uppermost document G on the document table 1 is rotated.
Is sent out toward the separation feeding roller pair 4a, 4b. Here, the separated feeding roller pair 4a, 4b feeds the original G directly to the first transport roller pair 5a, 5b if the fed original G is one. If two or more originals G are sent at once, the lower roller 4
b rotates in the direction opposite to the transport direction and feeds only the uppermost document G to the first transport roller pair 5a, 5b. Since the separation mechanism does not relate to the essence of the present invention, a detailed description thereof will be omitted.

The fed document is sent to the registration roller section 8 along the transport guide 14 by the first roller pair 5a, 5b and the second transport roller pair 6a, 6b. At this time, the pair of registration rollers 8a and 8b of the registration roller unit 8 are connected to the pair of first and second transport rollers 5a, 5b and 6 respectively.
The document G, which is rotating at the same speed as the speeds a and 6b, is conveyed onto the transmission glass 11 serving as an image reading unit while being held between the registration roller pairs 8a and 8b.

By the way, while being conveyed onto the transmission glass 11 in this way, the original G first passes through the first detecting means 9. Then, the light transmitting sensor 9 of the first detecting means 9
Signals a and 9b each emit a signal at the moment when the document G has passed, and are input to the control device 20. On the other hand, the control device 20
The arithmetic circuit 20a calculates the inclination of the leading edge of the document G based on these signals. Then, based on the calculated inclination, the control device 20 sets the registration roller pair 8a, 8b
, The first skew correction is performed in the first skew correction section A.

During the skew correction, the rear end of the original G tends to rotate greatly. However, when the original G is long, as shown in FIG. The movement is constrained. Even if the original G has a size of La + Lb or less, if the original G is a thick original having a large basis weight, the conveyance guide 1
4, the rotational movement of the rear end of the document G is restricted.

If the movement of the rear end is restricted in this way, a slight slip occurs between the original G and the registration roller section 8 even if the skew correction is attempted, and the skew correction ability is, for example, 95%. It falls to the extent. That is, 10
The skew of mm can be corrected only to 9.5 mm, so that the skew of about 0.5 mm remains. Further, when the surfaces of the pair of registration rollers 8a and 8b rub against each other due to durability, the skew correction ability further decreases, and the skew correction ability drops to, for example, about 90%. That is,
A skew of 10 mm can be corrected only by 9 mm, and a skew of 1 mm remains.

Therefore, the document G is conveyed while leaving the skew, and passes through the second detecting means 15.
Here, the light transmission type sensor 15 of the second detection means 15
The signals a and 15b emit signals at the moment when the document G passes, and the arithmetic circuit 20a of the control device 20 calculates the inclination of the leading edge of the document G based on those signals. Then, based on the calculated inclination, the control device 20 controls the rotation of each drive motor M1, M2 of the registration roller pair 8a, 8b, and performs the second skew correction in the second skew correction section B. .

Here, also in the second skew correction, as described above, the long-size original G and the thick original G
Can be corrected only about 95%. However, 1
Since 95% of the skew has already been corrected by the second skew correction, the correction capability can be improved to 99.75% as a result of the second skew correction operation.
That is, the skew of 10 mm is corrected to 0.5 mm in the first correction, and 0.5 mm × 95% = 0.47 in the second correction.
Since correction is performed by 5 mm, the remaining amount of skew is 0.5 mm-0.
475 mm = 0.025 mm.

Similarly, even if the pair of registration rollers 8a and 8b is deteriorated in durability and the skew correction ability per operation drops to 90%, the correction ability becomes 9 by the second skew correction operation.
It can be improved up to 9%.

The original G whose skew has been corrected in this manner is read by the reading unit 11 and then discharged onto the discharge tray 13 by the discharge roller pair 12.

As described above, the skew correction for the original G is performed by 2
By performing the rotation twice, it is possible to obtain stable and stable skew feeding correction accuracy for originals G of various sizes and thicknesses. In this embodiment, the skew correction frequency is set to 2
However, the present invention is not limited to this, and it goes without saying that the skew correction accuracy is further improved by increasing the number of sheet skew amount detecting means and further increasing the number of skew corrections.

Further, in the present embodiment, the first detecting means 9 is arranged on the downstream side of the registration roller section 8 in the transport direction, but may be located on the upstream side of the registration roller section 8 in the transport direction.

In the above description, the control device 20 calculates the inclination of the leading end based on the signal from the first detecting means 9, and based on the calculated inclination of the leading end, each of the registration roller pairs 8a and 8b. It has been described that the rotation of the drive motors M1 and M2 is controlled.

Here, in order to further improve the skew correction accuracy, the controller 20 controls the motors M1 and M2 to rotate more than the number of rotations for correcting the skew detected by the first detecting means 9. You may make it control.

For example, the rotation control amounts of the motors M1 and M2 are set to 105%, and the sensors 9a and 9b of the first skew detecting means 9 are set.
If the skew amount detected in the first skew correction section A is 10 mm, the skew amount detected in the first skew correction section A is 10.5 m.
m correction. The next second skew feeding correction section B
In the second skew correction is the normal, that is, the motor M
1. Control is performed with the rotation control amount of M2 set to 100%.

Here, as described in the first embodiment, when the skew correction ability per first time by the registration roller is reduced to about 95% depending on the size and type of the original, for example, the skew amount is 10 mm. In the case of, the first correction is performed for 105%, that is, 10.5 mm.
0.5 mm × 95% = 9.975 mm corrected, 0.0
The second correction is performed while leaving a skew of 25 mm.

In the second correction, the correction is performed as detected by the second skew amount detecting means 15. Therefore, in the second correction, 0.025 mm × 95% = 0.02375 mm is corrected. Becomes 0.00125 mm,
The correction accuracy is 99.9 as a result of the first and second control.
875%.

Similarly, even if the correction accuracy per operation drops to 90% due to the durability of the pair of registration rollers 8a and 8b, the correction accuracy can be improved to 99.45% as a result of the second control. it can. In the present embodiment, the first control amount is set to 105%, and the second control amount is set to 10%.
Although 0% was set, it is not limited to this.

As described above, by changing the first skew correction control and the second skew correction control so that the correction amounts are different, the endurance can be maintained even for originals of various sizes and thicknesses. As a result, the skew correction accuracy was significantly improved.

In the above description, an example in which the sheet conveying apparatus is applied to an image reading apparatus has been described. However, the present invention is not limited to this, and it is needless to say that the present invention can be applied to an image forming apparatus. In particular, by disposing the image forming apparatus on the upstream side of the image forming means for forming an image on a document (sheet), an image can be formed at an accurate position on the document (sheet).

[0051]

As described above, according to the present invention, the first
The first correction operation is controlled based on the skew amount signal input from the sheet skew amount detection means, and thereafter, the first correction operation is performed based on the skew amount signal input from another skew amount detection means. By controlling the skew correction operation that could not be corrected by, the sheets of various sizes and thicknesses are continuously conveyed at the minimum interval, and the skew correction of those sheets is durable, stable and accurate. Can do it.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of a sheet conveying apparatus according to a first embodiment of the present invention and an image reading apparatus including the same.

FIG. 2 is a top view illustrating a skew feeding correction unit of the document of the sheet conveying apparatus.

FIG. 3 is a block diagram of a control device that controls skew correction of the sheet conveying device.

[Explanation of symbols]

 6a, 6b Second transport roller pair 8a, 8b Registration roller pair 9 First sheet skew detecting means 11 Transparent glass 15 Second sheet skew detecting means 20 Control device G Original

Claims (4)

(57) [Claims] 1. A sheet conveying apparatus which conveys a sheet by a sheet conveying means and corrects a skew of the conveyed sheet by a skew correcting means provided in a sheet conveying path. that a first sheet skew amount detection means for detecting a skew amount of a sheet, disposed downstream of said first sheet skew amount detection means, said transportable
Second sheet skew amount detecting means for detecting the skew amount of the fed sheet, and skew amount signal input from the first sheet skew amount detecting means.
After the correction operation is controlled based on the
Based on the skew amount signal input from the line amount detection means,
Before performing skew correction operation that could not be corrected by normal operation
Control means for controlling the skew feeding correcting means , wherein the control means outputs a signal from the first sheet skew feeding amount detecting means.
In the correction operation based on the skew amount signal, the first sheet skew
Correct the skew more than the skew detected by the amount detector.
A sheet conveying device for controlling the skew feeding correcting means to perform the skew feeding. 2. The apparatus according to claim 1, wherein the first sheet skew amount detecting means is provided downstream of the sheet conveying means and from the sheet conveying means .
The sheet conveying device according to claim 1, wherein the distance is provided at a position where the distance is shorter than a length of the predetermined sheet in the conveying direction. 3. A sheet conveying device that conveys a sheet by a sheet conveying unit and corrects skew of the conveyed sheet by a skew correcting unit provided in a sheet conveying path. An image reading device comprising: an image reading unit that reads a conveyed sheet; wherein the sheet conveying device is the sheet conveying device according to claim 1 or 2 , and the sheet conveying device is configured to convey the sheet by the image reading unit. image reading apparatus being characterized in that provided in the upstream. 4. A sheet conveying device that conveys a sheet by a sheet conveying unit and corrects skew of the conveyed sheet by a skew correcting unit provided in a sheet conveying path. An image forming apparatus comprising: an image forming unit that forms an image on a conveyed sheet, wherein the sheet conveying device is the sheet conveying device according to claim 1 or 2 , and the sheet conveying device is the image forming unit. an image forming apparatus characterized by providing for the sheet conveying direction upstream.