JP2000296926A - Sheet conveyance device and image reading device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet conveyance device and an image reading device stabilizing sheets during conveyance. SOLUTION: A CPU keeps track of the position of a document 2 from a detected information of a pre-separation sensor 7 positioned directly in front of a comb-teethed roller A, calculates, using the obtainment of the detected information as a trigger, a timing T1 seconds for the document 2 to reach the comb-teethed roller A from a distance from the pre-separation sensor 7 to the comb-teethed roller A and a document conveyance speed, judges whether or not the timing T1 seconds has passed, and if it has passed, increases torque by a torque switching means.

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 for conveying a sheet such as a document,
In particular, the present invention is suitably used for a sheet conveying apparatus for separating and conveying a bundle of sheets, and is applied to, for example, an image reading apparatus which reads a document image and records it in an external storage device.

[0002]

2. Description of the Related Art Documents loaded on a platen are taken in,
In a document feeder that separates and transports a document one by one with a comb-shaped roller, the comb-shaped roller transports the document by driving an upper roller in a normal rotation direction with respect to the transport direction. The lower roller is driven in the reverse direction to separate originals one by one.

The upper and lower rollers can contact and separate from each other. When the original is not transported, the upper and lower rollers are in contact with each other, and when the original is transported, a gap corresponding to the thickness of the original is generated.

A method of generating a gap is to raise the comb-shaped upper roller by triggering the detection information of a sensor located immediately before the comb-shaped roller to turn on, and to position the gap immediately after the comb-shaped roller. This is performed by stopping the ascent, triggered by the detection information of the sensor being turned ON.

[0005] As described above, a document is conveyed with a gap corresponding to the thickness of the document.

[0006]

However, in the case of the above-described prior art, the following problems have occurred.

When a document is conveyed, while the document passes between the comb-shaped rollers, the load on each roller increases due to friction of the document.

[0008] Therefore, the torque of the motor driving each roller may be insufficient.

[0009] If the torque is insufficient, the conveying force is reduced, so that the conveying speed of the document passing through the comb-shaped roller may be reduced or stopped.

Since the gap continues to be opened until the rear sensor detects the original, if the conveying speed of the original passing between the comb-shaped rollers is reduced, the opening amount increases,
In some cases, the opening amount does not correspond to the thickness of the document.

As described above, the insufficient torque may cause a jam due to the inability to convey the original, a double feed due to a gap corresponding to the thickness of the original being not generated, and a stable paper feed. It is the cause of failure.

On the other hand, it is conceivable to increase the torque in advance. However, a motor having a strong torque generates a loud noise when driven under a condition close to no load, and consumes extra power. There is.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a sheet conveying apparatus and an image reading apparatus which stabilize a sheet to be conveyed. is there.

[0014]

According to the present invention, there is provided a sheet conveying apparatus having a pair of separation and conveyance rollers for separating and conveying a sheet, the position for detecting the position of the sheet to be conveyed. It is provided with a detecting means, and a torque switching means for switching a torque of a motor for driving the separation / conveyance roller based on a detection result of the position detecting means.

Therefore, by providing the torque switching means, it is possible to apply a required torque according to the position of the conveyed sheet.

It is preferable that a feed roller for feeding stacked sheets is provided upstream of the separation / conveyance roller, and the torque switching means also switches the torque of a motor for driving the feed roller.

The position detecting means includes an upstream side detecting means for detecting the presence or absence of a sheet passing upstream of the sheet separating / conveying section by the separating / conveying roller, and a downstream side of the sheet separating / conveying section by the separating / conveying roller. Downstream detection means for detecting the presence or absence of the passage of the sheet on the side, and the position of the sheet may be detected based on the detection result by the upstream detection means and the downstream detection means.

While the position detecting means detects that a sheet is being conveyed by the separation / conveyance roller by the separation / conveyance roller, the torque switching means conveys the sheet by the separation / conveyance part. It is better to increase the torque as compared with the case where the fact is not detected.

The separation / conveyance roller comprises a feed roller which rotates in the sheet conveyance direction and a separation roller which rotates in the direction opposite to the conveyance direction, and relatively moves the feed roller and the separation roller in the contact / separation direction. It is preferable to provide a movably provided positioning means for positioning the feed roller and the separation roller in the contact / separation direction according to the thickness of the conveyed sheet.

In the image reading apparatus of the present invention,
An image reading means for reading an image on a sheet conveyed by the sheet conveying device is provided.

[0021]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the dimensions of the components described in this embodiment,
The materials, shapes, relative arrangements, and the like are not intended to limit the scope of the present invention only to them unless otherwise specified.

With reference to FIGS. 1 to 5, a sheet conveying apparatus and an image reading apparatus according to an embodiment of the present invention will be described.

FIG. 1 is a schematic sectional view of a sheet conveying device (image reading device) having a function of reading a document image.

First, each configuration of the sheet conveying device will be described.

The document table 1 is provided so as to be movable up and down so that a large number of documents can be loaded.

The lower limit sensor 3 and the upper limit sensor 4 detect the document table lower limit position and the upper limit position, respectively.

The document feed sensor 5 detects the presence or absence of a document 2, which is a sheet on the document table 1.

Pickup roller 6 as feed roller
Rotates in the conveying direction, takes in the original 2 on the original table 1, and conveys it to the comb-shaped roller A as a separating and conveying roller.

Pre-separation sensor 7 as upstream detecting means
Detects that the original 2 to be captured has reached just before the comb-shaped roller A.

The comb-shaped roller A is configured such that the original can be separated and conveyed by the feed roller 8 rotating in the conveying direction and the separating roller 9 rotating in the reverse direction.

Further, the feed roller 8 is provided so as to be able to move up and down freely, and the feed roller 8 and the separation roller 9 are configured to be able to come and go.

Separation sensor 10 as downstream detection means
Detects that the document 2 to be taken is passing through the comb-shaped roller A (the position detection means is constituted by the pre-separation sensor 7 and the separation sensor 10).

The pre-registration roller sensor 11 detects that the document 2 has reached just before the registration roller 12.

The registration roller 12 conveys the document 2 while rotating at a predetermined interval.

The post-registration sensor 13 detects that the document 2 is passing through the registration roller 12.

Image input sensor 1 as image reading means
Reference numerals 4 and 15 respectively obtain front and back image data of the document to be conveyed.

A pair of rollers 16, 17,
Reference numerals 18 and 19 rotate and drive in synchronization with a main transport motor (not shown) to transport the document 2 while pinching it.

The transport path 20 is a transport path through which the document 2 passes.

The paper discharge tray 21 places the original 2 conveyed through the conveyance path 20.

Next, the operation of the sheet conveying apparatus according to the present embodiment will be described with reference to the flowchart shown in FIG.

First, when an operator of the document feeder presses a feed start button (not shown) of the document feeder to start feeding, the CPU (not shown) of the document feeder includes a feed roller 8 of the comb-shaped roller A and a separation roller. 9 is positioned so as to be in contact with the comb teeth (gap home setting) (S10).
1).

Then, the CPU determines whether or not the document 2 is on the document table 1 based on the detection information of the document feed sensor 5 (S102).

If not, it is determined from the detection information of the upper limit sensor 3 whether or not the document table 1 has reached the upper limit position (S10).
3).

If the upper limit sensor 4 is also negative, the document table is raised (S104), and the process waits until one of the sensors is turned on.

When the upper limit sensor 4 is turned on, the CPU determines that the document 2 is no longer on the platen 1 and lowers the platen 1 until the lower limit sensor 3 is turned on to terminate the sheet feeding operation. Waits for the user to press the transport start button (S105
To S109).

When the document feed sensor 5 is turned on,
The document table 1 is stopped (S110).

The CPU determines from the detection information of the pre-separation sensor 7
It is determined whether there is a document before separation (S111).

Here, the case where the first sheet is fed will be described first.

When the first sheet is fed, there is naturally no document on the pre-separation sensor 7.

If there is no original, the CPU sets the torque of each of the pickup roller 6, the feed roller 8, and the separation roller 9 to a small (weak) torque (S112), and operates each roller (S113). .

As a result, first, the original 2 is taken in by the pickup roller 6 and is conveyed to the comb-shaped roller A (FIG. 2A).

The CPU grasps the position of the document 2 from the detection information of the pre-separation sensor 7 located immediately before the comb-shaped roller A,
Triggered by the detection information being turned on (S114,
In FIG. 2B, the timing T1 [s] at which the document reaches the comb-shaped roller A is calculated from the distance from the pre-separation sensor 7 to the comb-shaped roller A and the document conveyance speed (S115).

Specifically, as shown in FIG. 3, T1 is a value obtained by dividing the distance from the pre-separation sensor 7 to the comb-shaped roller A by the document conveying speed (feeding speed).

The CPU determines whether or not the timing T1 [s] has elapsed (S116), and when it has elapsed, increases the torque (increases the torque) by the torque switching means (S116).
121).

The torque switching means changes the value of the current flowing through the windings of the pulse motor, which is the roller driving means, by the CPU switching the current limiting circuit in the configuration shown in FIG.

The reason for switching the torque in this manner is as follows.

That is, while the document passes through the comb-shaped roller A, kinetic friction occurs due to the document.

Therefore, by waiting for the timing T1 [s], the friction increases, and especially at the timing when the load on the feed roller 8 increases, the torque of the motor is increased, so that the increased load can be reliably prevented. , The step-out of the motor can be prevented, the transport stability (the stability of the transport speed) can be increased, and jamming and double feed can be prevented.

In parallel with this, the feed roller 8 is raised (S122).

As the feed roller 8 moves up, the comb-shaped roller A gradually separates, and finally has a gap that allows the document to pass.

When the gap is generated, the document starts to pass between the comb-shaped rollers A (FIG. 2C).

The CPU grasps the position of the document 2 from the detection information of the post-separation sensor 10 located immediately after the comb-shaped roller A,
The feed roller 8 is triggered by the detection information being turned ON.
Is stopped (S124, FIG. 2D).

Thus, the feed roller 8 and the separation roller 9
Is maintained according to the thickness of the conveyed sheet (positioning means), so that the sheet can be conveyed properly.

Thereafter, the CPU operates the sensor 10 after the document is separated.
(S128), after which the pickup roller 6 and the feed roller 8 are stopped (S12).
9), a gap home is set (S130, FIG. 2)
(E)).

After the gap home is set, the CPU starts an operation for feeding the next original.

Next, the operation of feeding the second and subsequent sheets will be described.

As for the position of the second and subsequent originals, the standby position differs depending on the ratio of bringing in and separating according to the feeding operation of the original fed immediately before.

The different document positions are determined by the CPU.
Are divided into three cases: a case where the pre-separation sensor 7 is turned off, a case where only the pre-separation sensor 7 is turned on, and a case where both the pre-separation sensor 7 and the post-separation sensor 10 are turned on.

The operation for feeding the original at the position where the pre-separation sensor 7 is turned off is the same as the operation for feeding the first sheet.

If a document at a position where only the pre-separation sensor 7 is turned on is fed (S111, S112 '), the process goes to S1.
Then, the process proceeds to S17, where the torque is set to low (small), and then each roller is operated (S118).

The CPU starts the operation of the roller as a trigger, and the timing at which the document reaches the comb-shaped roller A is T2.
[S] is calculated.

However, in this case, since it is not known where the document is from the pre-separation sensor 7 to the comb-shaped roller A, the calculation is performed on the assumption that the document is at the intermediate position.

Therefore, it is assumed that T2 = T1 / 2.

The CPU waits for a predetermined amount of time T2 to elapse (S119, S120), and joins S121.

As described above, in this case, the torque is increased at the timing when the load on the feed roller 8 becomes large by waiting for the average time T2 [s] for the document to reach the comb-shaped roller A.

The sensor 7 before separation and the sensor 10 after separation
When feeding a document that is in the position where both are turned on,
The process proceeds to S125 (S111, S112 ', S125).

The CPU increases the torque by the torque switching means, raises the feed roller 8 by a predetermined amount (S127), and drives the pickup roller 6 and the feed roller 8 (S126).

Thereafter, the flow merges with S128.

In this case, since the document is fed between the comb-shaped rollers while the document is stationary, static friction is generated.

Therefore, by starting the roller operation after setting the torque to a high value, it is possible to feed the paper properly without losing the static friction.

[0081]

As described above, according to the present invention, the provision of the torque switching means makes it possible to apply a necessary torque in accordance with the position of the conveyed sheet, thereby stabilizing the conveyed sheet. Can be planned.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a sheet conveying apparatus having a function of reading a document image.

FIG. 2 is a schematic diagram illustrating a state of sheet feeding of the sheet conveying device according to the embodiment of the present invention.

FIG. 3 is an explanatory diagram for detecting a position of a conveying sheet of the sheet conveying apparatus according to the embodiment of the present invention.

FIG. 4 is a circuit diagram for changing the torque of the sheet conveying device according to the embodiment of the present invention.

FIG. 5 is a flowchart for explaining the operation of the sheet conveying apparatus according to the embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 document table 2 document 3 lower limit sensor 4 upper limit sensor 5 document feed sensor 6 pickup roller 7 pre-separation sensor 8 feed roller 9 separation roller 10 separation sensor 11 pre-registration roller sensor 12 registration roller 13 post-registration sensor 14, 15 image input sensor 16, 17, 18, 19, a pair of rollers 20, a conveyance path 21, a paper discharge tray

Claims (6)

[Claims] 1. A sheet conveying apparatus having a pair of separating and conveying rollers for separating and conveying a sheet, a position detecting means for detecting a position of the conveyed sheet, and the separating and conveying based on a detection result of the position detecting means. A sheet conveying device comprising: a torque switching unit that switches torque of a motor that drives a roller. 2. A feed roller for feeding sheets to be stacked is provided upstream of the separation / conveyance roller, and the torque switching means also switches a torque of a motor for driving the feed roller. The sheet conveying device according to claim 1, wherein: 3. An apparatus according to claim 2, wherein said position detecting means comprises: an upstream side detecting means for detecting the presence or absence of a sheet at a position upstream of said sheet separating / conveying section by said separating / conveying roller; And a downstream detection means for detecting the presence or absence of a sheet passing on the downstream side, wherein the position of the sheet is detected based on a detection result by the upstream detection means and the downstream detection means. Item 3. The sheet conveying device according to item 1 or 2. 4. While the position detecting means detects that a sheet is being conveyed by the separation / conveyance roller by the separation / conveyance roller, the torque switching means conveys the sheet by the separation / conveyance part. 4. The sheet conveying apparatus according to claim 1, wherein the torque is increased as compared with a case where the detection is not performed. 5. The separation / conveyance roller includes a feed roller that rotates in a sheet conveyance direction and a separation roller that rotates in a direction opposite to the conveyance direction. And a positioning means for positioning the feed roller and the separation roller in the contact / separation direction according to the thickness of the conveyed sheet. A sheet conveying device according to one of the above. 6. An image reading apparatus comprising an image reading means for reading an image on a sheet conveyed by the sheet conveying apparatus according to any one of claims 1 to 5.