JP2020033148A - Medium feeding device and image reading device - Google Patents

Abstract

To provide a medium feeding device capable of improving a degree of freedom in adjusting separation ability of right and left separation rollers without depending only on adjustment of a torque in a torque limiter.SOLUTION: A medium feeding device including a medium mounting part for mounting media, feeding rollers for feeding the media from the medium mounting part, separation rollers for nipping the media between the feeding rollers to separate the media, and torque limiters for idly rotating the separation rollers in the first rotation direction; the separation rollers are constituted so as to include a first separation roller and a second separation roller provided at an interval in a medium width direction crossing a medium feeding direction; the first separation roller and the second separation roller have independently rotary shafts and the torque limiters and are pressed to the feeding rollers by independent pressing means.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a medium feeding device that feeds a medium and an image reading device including the same.

  Hereinafter, a scanner which is an example of the image reading apparatus will be described as an example. Some scanners are provided with a document feeder that automatically feeds a document as an example of a medium, and are configured to be able to automatically feed and read a plurality of documents. This document feeder is sometimes called an ADF (Auto Document Feeder).

  The document feeder includes a document tray on which a plurality of documents are placed on a loading surface, and a feed roller for sending a document from the document tray by rotating by contacting a document set on the document tray. And a separation roller that comes into contact with the feeding roller to separate the document.

The method of separating documents by the separation roller is an inactive method that separates documents only by the rotation resistance of the torque limiter without driving the power torque of the motor, and the drive torque in the rotating direction to return the document via the torque limiter. There is an active system that transmits the data to the separation roller.
Patent Literature 1 discloses a configuration including such inactive type and active type separation rollers. Note that, in Patent Literature 1, the separation roller is referred to as a brake roller.

JP 2013-184819 A

In the configuration described in Patent Document 1, two separation rollers are provided in a document width direction that is a direction intersecting with the document feeding direction. In addition, a torque limiter is separately provided for one of the two separation rollers and the other roller, and the amount of rotation in the direction opposite to the feeding direction differs for each roller, reducing the skew of the original Let me.
However, in the configuration described in Patent Literature 1, the adjustment of the separation ability of the left and right separation rollers depends exclusively on the torque adjustment of the torque limiter, and the degree of freedom in adjusting the separation ability is limited.

  In order to solve the above problems, a medium feeding device of the present invention includes a medium mounting portion for mounting a medium, a feeding roller for feeding the medium from the medium mounting portion, and the feeding roller. A roller for nipping the medium between the rollers to separate the medium, wherein a driving torque by a driving source is applied in a second rotation direction opposite to a first rotation direction for sending the medium downstream. And a torque limiter that idles the separation roller in the first rotation direction when the rotation torque applied to the separation roller in the first rotation direction exceeds a limit torque that is a predetermined torque upper limit value. Wherein the feed roller includes a first feed roller and a second feed roller provided at intervals in a medium width direction which is a direction intersecting a medium feed direction, and the separation roller is 1 feed b A first separation roller in contact with the first roller and a second separation roller in contact with the first feed roller, wherein the torque limiter is provided for the first torque limiter and the second separation roller provided for the first separation roller. A second torque limiter provided, the first separation roller is rotatable about a first rotation axis, and is pressed toward the feed roller by first pressing means, and the second separation roller is Is rotatable about a second rotation axis different from the first rotation axis, and is pressed toward the feed roller by a second pressing means different from the first pressing means. I do.

FIG. 2 is an external perspective view of the scanner. FIG. 2 is a side sectional view showing a document feeding path in the scanner. FIG. 2 is a block diagram showing a control system of the scanner. The top view of a supply roller and a separation roller. The side view of a supply roller and a separation roller. FIG. 9 is a plan view showing a problem when the separation roller is connected left and right. The side view of a supply roller and a separation roller. The top view of a supply roller and a separation roller. 6 is a flowchart illustrating control of the left and right separation rollers. The figure which shows the state which connected the left and right feed roller with the differential gear. FIG. 9 is a plan view showing a problem when the feed rollers are connected left and right.

Hereinafter, the present invention will be schematically described.
A medium feeding device according to a first aspect of the present invention includes a medium placement unit on which a medium is placed, a feed roller that feeds the medium from the medium placement unit, and a feeding roller. A roller that nips the medium and separates the medium, wherein a separation roller to which a driving torque is applied by a driving source in a second rotation direction opposite to the first rotation direction that sends the medium downstream, A torque limiter that idles the separation roller in the first rotation direction when a rotation torque applied to the separation roller in the first rotation direction exceeds a limit torque that is a predetermined torque upper limit, The feed roller includes a first feed roller and a second feed roller provided at intervals in a medium width direction that is a direction intersecting with the medium feed direction, and the separation roller includes the first feed roller. Feed roller and A first separating roller and a second separating roller that is in contact with the first feeding roller, wherein the torque limiter is provided for the first torque limiter and the second separating roller provided for the first separating roller. A second torque limiter, wherein the first separation roller is rotatable about a first rotation axis, and is pressed toward the feed roller by first pressing means, and the second separation roller is It is rotatable about a second rotation axis different from the first rotation axis, and is pressed toward the feed roller by a second pressing means different from the first pressing means.

According to this aspect, the separation roller facing the feeding roller includes the first separation roller and the second separation roller provided at intervals in the medium width direction that is a direction intersecting with the medium feeding direction. Since the first separation roller and the second separation roller have their own rotating shaft and torque limiter, one roller can rotate without being affected by the other roller, and skew can be properly corrected.
Since the first separation roller and the second separation roller are pressed toward the opposing feed roller by a unique pressing unit, the first separation roller and the second separation roller are separately and independently pressed. When the skew occurs, the skew can be appropriately suppressed by optimizing the pressing load between the first separation roller and the second separation roller. That is, the degree of freedom in adjusting the separation ability is improved.

  According to a second aspect of the present invention, in the first aspect, the first pressing means and the second pressing means are each configured to be capable of adjusting a pressing load under the control of a control means. And

  According to this aspect, the first pressing means and the second pressing means are each configured to be able to adjust the pressing load under the control of the control means, so that a serviceman or a user can adjust the pressing load. And the convenience is improved.

  According to a third aspect of the present invention, in the first aspect, the drive source includes a first drive source that drives the first separation roller, and a second drive source that drives the second separation roller. A first medium detection unit and a second medium detection unit, with the intermediate position between the first separation roller and the second separation roller in the medium width direction as a symmetric center, and the first medium detection unit And the second medium detection unit includes a plurality of sensors along the medium feeding direction, and an arrangement area of the plurality of sensors in the medium feeding direction is a region in which the feeding roller and the separation roller are disposed. A control unit that includes a nip position and controls the first drive source and the second drive source, based on detection information of the first medium detection unit and the second medium detection unit, And the second To those who are prior to the tip of the medium downstream of the releasing roller, it is characterized by increasing the rotational amount per unit time to the second rotational direction.

  According to this aspect, the skew of the medium is detected by the first medium detection unit and the second medium detection unit, and the medium is selected from the first separation roller and the second separation roller according to the state of the skew. The skew of the medium can be more accurately corrected because the tip of which is advanced downstream is rotated more in the second rotation direction.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, between the first feed roller and the second feed roller, the rotation of the first feed roller and the (2) It is characterized by including a differential gear that causes a difference in rotation of the feed roller.

In a configuration in which the first feed roller and the second feed roller are attached to a single rotating shaft and rotate synchronously, the rear end of the skewed medium is connected to the first feed roller and the second feed roller. When the paper feed roller passes through the feed roller, the leading end of the next waiting medium is sent out due to the rotation of the feed roller on the side from which the rear end has come off earlier due to skew, resulting in skew. Such a skew of the succeeding medium due to the skew of the preceding medium is hereinafter referred to as a chain skew.
According to this aspect, a differential gear that causes a difference between the rotation of the first feeding roller and the rotation of the second feeding roller is provided between the first feeding roller and the second feeding roller. Therefore, the feed roller on the side from which the rear end has previously escaped due to skew can be stopped, thereby suppressing chain skew.
In addition, it is possible to suppress an increase in cost as compared with a case where a one-way clutch is provided for each of the first feed roller and the second feed roller to obtain a similar operation and effect.

  A medium feeding device according to a fifth aspect of the present invention includes a medium placement unit that places a medium, a feeding roller that feeds the medium from the medium placement unit, and a medium feeding unit. A roller that nips the medium and separates the medium, wherein a separation roller to which a driving torque is applied by a driving source in a second rotation direction opposite to the first rotation direction that sends the medium downstream, A torque limiter that idles the separation roller in the first rotation direction when a rotation torque applied to the separation roller in the first rotation direction exceeds a limit torque that is a predetermined torque upper limit, The separation roller includes a first separation roller and a second separation roller provided at intervals in a medium width direction that is a direction intersecting with a medium feeding direction. One A first feeding roller facing the first separating roller, and a second feeding roller facing the second separating roller, provided with an interval between the first feeding roller and the first feeding roller. A differential gear for causing a difference between the rotation of the first feeding roller and the rotation of the second feeding roller is provided between the second feeding roller and the second feeding roller.

In a configuration in which the first feed roller and the second feed roller are attached to a single rotating shaft and rotate synchronously, the rear end of the skewed medium is connected to the first feed roller and the second feed roller. When the paper feed roller passes through the feed roller, the leading end of the next waiting medium is sent out due to the rotation of the feed roller on the side from which the rear end has come off earlier due to skew, resulting in skew. Such a skew of the succeeding medium due to the skew of the preceding medium is hereinafter referred to as a chain skew.
According to this aspect, a differential gear that causes a difference between the rotation of the first feeding roller and the rotation of the second feeding roller is provided between the first feeding roller and the second feeding roller. Therefore, the feed roller on the side from which the rear end has previously escaped due to skew can be stopped, thereby suppressing chain skew.
In addition, it is possible to suppress an increase in cost as compared with a case where a one-way clutch is provided for each of the first feed roller and the second feed roller to obtain a similar operation and effect.

An image reading device according to a sixth aspect of the present invention is a reading device for reading a medium, and the medium feeding device according to any of the first to fifth aspects, wherein the medium is fed to the reading device. And characterized in that:
According to this aspect, in the image reading apparatus, the same operation and effect as any of the above-described first to fifth aspects can be obtained.

Hereinafter, the present invention will be described specifically.
Hereinafter, an embodiment of a medium feeding device and an image reading device according to the present embodiment will be described with reference to the drawings. In the present embodiment, as an example of the image reading apparatus, a document scanner (hereinafter, simply referred to as a scanner 1A) capable of reading at least one of the front and back surfaces of a document (hereinafter, referred to as a document P), which is an example of a medium, will be described. I will.

  In the XYZ coordinate system shown in each drawing, the X direction is the apparatus width direction, and the document width direction is a direction that intersects the document feeding direction (conveying direction). The Y direction is the document feeding direction (conveying direction). The Z direction is a direction that intersects the Y direction and generally indicates a direction that is orthogonal to the surface of the conveyed document. The + Y direction is defined as the front side of the apparatus, and the −Y direction is defined as the rear side of the apparatus. When viewed from the front of the apparatus, the left direction is the + X direction, and the right direction is the -X direction. Further, the + Z direction is defined as the upper part of the apparatus (including the upper and upper surfaces), and the −Z direction side is defined as the lower part of the apparatus (including the lower part and the lower surface). The direction in which the document P is fed (+ Y direction) is referred to as “downstream”, and the opposite direction (−Y direction) is referred to as “upstream”.

Hereinafter, a scanner 1A as an image reading apparatus according to the present invention will be described mainly with reference to FIG. FIG. 1 is an external perspective view showing a scanner 1A according to the present invention.
The scanner 1A includes an apparatus main body 2 having a reading unit 20 (FIG. 2) for reading an image of a document P therein.
The apparatus main body 2 includes a lower unit 3 and an upper unit 4. The upper unit 4 is provided so as to be openable and closable with respect to the lower unit 3 with a rotation fulcrum at the downstream side in the document conveying direction. Thus, the jam of the document P can be easily processed.

A document placement unit 11 having a placement surface 11a on which the fed document P is placed is provided in the back side of the apparatus main body 2. The document placement unit 11 is provided detachably with respect to the apparatus main body 2.
In addition, the document placement unit 11 is provided with a pair of edge guides for guiding the side edges of the document P in the document width direction, that is, a first edge guide 12A and a second edge guide 12B. The first edge guide 12A and the second edge guide 12B have guide surfaces U1 and U2 for guiding the side edges of the document P, respectively.

  The document placement unit 11 includes a first paper support 8 and a second paper support 9. The first paper support 8 and the second paper support 9 can be housed inside the document placing portion 11 and can be pulled out from the document placing portion 11 as shown in FIG. The length can be adjusted.

The apparatus main body 2 includes an operation panel 7 on the upper surface of the upper unit 4, on which various reading settings and reading execution operations are performed, and a user interface (UI) indicating the contents of the reading settings is realized. In the present embodiment, the operation panel 7 is a so-called touch panel that can perform both display and input, and also serves as an operation unit for performing various operations and a display unit for displaying various information.
At the upper part of the upper unit 4, there is provided a feed port 6 connected to the inside of the apparatus main body 2, and a document P placed on the document placing section 11 is read from the feed port 6 by a reading provided inside the apparatus main body 2. It is sent to the unit 20.
On the front side of the apparatus of the lower unit 3, there is provided a paper discharge tray 5 for receiving a document P to be discharged.

Next, the document feeder 1B according to the present invention, that is, the document feed path in the scanner 1A will be described mainly with reference to FIG. 2 and other drawings as necessary. FIG. 2 is a side sectional view showing a document feeding path in the scanner 1A according to the present invention.
The scanner 1A includes a document feeder 1B. The document feeder 1B generally includes components related to document feed in the scanner 1A, specifically, a document placement unit 11, an edge guide 12, a feed roller 14, a separation roller 15, and the like. From another viewpoint, the document feeder 1B can be regarded as a device related to document reading from the scanner 1A, specifically, a device in which a reading unit 20 described later is omitted. Alternatively, even if the reading unit 20 is provided, the scanner 1A itself can be regarded as a document feeding device from the viewpoint of document feeding.
In FIG. 2, a solid line indicated by a symbol T indicates a document feeding path, that is, a path of passage of the document P. The document feeding path T is a space sandwiched between the lower unit 3 and the upper unit 4. Note that the document feed path T can be defined as a path from the document placement unit 11 to the transport roller pair 16, and therefore, in FIG. 2, the document transport path downstream from the transport roller pair 16 is indicated by a broken line.

  An original placing section 11 is provided at the most upstream of the original feeding path T, and the original P placed on the placing surface 11 a of the original placing section 11 is provided downstream of the original placing section 11. A feed roller 14 that feeds toward the reading unit 20 and a separation roller 15 that nips and separates the document P between the feed roller 14 and the feed roller 14 are provided.

The feed roller 14 is in contact with the lowest one of the originals P placed on the placing surface 11 a of the original placing portion 11. Therefore, when a plurality of originals P are set on the original placing portion 11 in the scanner 1A, the originals P are sequentially fed downstream from the original P on the placing surface 11a side.
The document placement unit 11 is provided with a placement detection unit 35 as placement detection means for detecting whether or not the document P exists on the document placement unit 11.

A separation roller 15 is provided at a position facing the feeding roller 14, and the separation roller 15 prevents double feeding of the document P.
The feeding roller 14 and the separation roller 15 will be described later in detail.

Downstream of the feed roller 14, a transport roller pair 16, a reading unit 20 for reading an image, and a discharge roller pair 17 are provided. The transport roller pair 16 includes a transport drive roller 16a that is rotationally driven by a transport roller motor 46 (FIG. 3), and a transport driven roller 16b that is driven and rotated.
The document P nipped by the feed roller 14 and the separation roller 15 and fed downstream is nipped by the transport roller pair 16 and transported to the reading unit 20 located downstream of the transport roller pair 16.

  Subsequently, a first document detection unit 31 is provided downstream of the nip position between the feed roller 14 and the separation roller 15. The first document detection unit 31 is configured as an optical sensor as an example, and includes a light emitting unit 31a and a light receiving unit 31b that are arranged to face each other with the document feeding path T interposed therebetween. An electric signal indicating the intensity of the detection light is transmitted to (FIG. 3). When the conveyed document P blocks the detection light emitted from the light-emitting portion 31a, the electric signal indicating the intensity of the detection light changes, whereby the control section 40 (FIG. 3) controls the front end or the rear end of the document P. Can be detected.

  A double feed detection unit 30 that detects double feed of the document P is disposed downstream of the first document detection unit 31. The double feed detecting unit 30 includes an ultrasonic transmitting unit 30a opposed to the original feeding path T and an ultrasonic receiving unit 30b that receives ultrasonic waves. The ultrasonic receiving unit 30b is a control unit. An electric signal indicating the intensity of the detected ultrasonic wave is transmitted to 40 (FIG. 3). When the double feeding of the document P occurs, the electric signal indicating the intensity of the ultrasonic wave changes, whereby the control unit 40 (FIG. 3) can detect the double feeding of the document P.

Further, a second document detection unit 32 is provided downstream of the double feed detection unit 30, more specifically, downstream of the transport roller pair 16. The second document detection unit 32 is configured as a contact-type sensor having a lever, and when the lever rotates with the passage of the leading end or the rear end of the document P, the second document detection unit 32 sends the control unit 40 (FIG. 3). ) Changes, whereby the control unit 40 (FIG. 3) can detect the passage of the leading edge or the trailing edge of the document P.
The control unit 40 (FIG. 3) can grasp the position of the document P on the document feeding path T by using the first document detection unit 31 and the second document detection unit 32 described above.

  Next, the reading unit 20 provided downstream of the second document detection unit 32 includes an upper reading sensor 20a provided on the upper unit 4 side and a lower reading sensor 20b provided on the lower unit 3 side. I have. In the present embodiment, the upper reading sensor 20a and the lower reading sensor 20b are configured as a contact type image sensor module (CISM) as an example.

The document P is read by the reading unit 20, at least one of the front surface and the back surface of the document P, and is nipped by a pair of discharge rollers 17 located downstream of the reading unit 20. It is discharged from a discharge port 18 provided on the side.
The discharge roller pair 17 includes a discharge drive roller 17a that is rotationally driven by a transport roller motor 46 (FIG. 3), and a discharge driven roller 17b that is driven and rotated.

Hereinafter, a control system in the scanner 1A and the document feeder 1B will be described with reference to FIG. FIG. 3 is a block diagram showing a control system of the scanner 1A according to the present invention.
In FIG. 3, a control unit 40 as a control unit performs various controls of the scanner 1A and the document feeding device 1B, including feed, transport, discharge control and reading control of the document P. A signal from the operation panel 7 is input to the control unit 40, and a signal for controlling display on the operation panel 7 is transmitted from the control unit 40 to the operation panel 7.
The control unit 40 controls the feed roller motor 45 and the transport roller motor 46. As described above, the feed roller motor 45 is a drive source of the feed roller 14 shown in FIG. 2, and the transport roller motor 46 is the separation roller 15, the transport roller pair 16, and the discharge roller shown in FIG. 2. Pair 17, these driving sources.
The read data from the reading unit 20 is input to the control unit 40, and a signal for controlling the reading unit 20 is transmitted from the control unit 40 to the reading unit 20.
The control unit 40 also receives signals from the double feed detection unit 30, the first document detection unit 31, the second document detection unit 32, and the placement detection unit 35.

The control unit 40 includes a CPU 41, a ROM 42, and a memory 43. The CPU 41 performs various arithmetic processes according to the program 44 stored in the ROM 42, and controls the operation of the entire scanner 1A. The memory 43, which is an example of the storage unit, is a readable and writable nonvolatile memory, and all parameters and the like necessary for various controls are stored in the memory 43, and the values are updated by the control unit 40 as necessary. Is done.
The scanner 1 </ b> A is configured to be connectable to an external computer 90, and information is input to the control unit 40 from the external computer 90.

Next, the feeding roller 14 and the separation roller 15 will be described in detail with reference to FIG.
In the present embodiment, as shown in FIG. 4, two feeding rollers 14 are arranged at intervals so as to be symmetrical with respect to the center position CL in the document width direction. In FIG. 4, the feed roller on the left side of the center position CL is denoted by reference numeral 14A as a first feed roller, and the feed roller on the right side of the center position CL is denoted by reference numeral 14B as a second feed roller.
Similarly, two separation rollers 15 are arranged at an interval so as to be symmetric with respect to the center position CL. In FIG. 4, the separation roller on the left side with respect to the center position CL is denoted by reference numeral 15A as a first separation roller, and the feed roller on the right side with respect to the center position CL is denoted by reference numeral 15B as a second supply roller.
Hereinafter, when it is not necessary to particularly distinguish the first feed roller 14A and the second feed roller 14B, the first feed roller 14A and the second feed roller 14B are referred to as a feed roller 14, and similarly, it is necessary to particularly distinguish the first separation roller 15A and the second separation roller 15B. If there is no such roller, it is referred to as a separation roller 15.

In FIG. 2, a driving force of a feed roller motor 45 (FIG. 3) is transmitted to the feed roller 14 via a one-way clutch 49. The feed roller 14 receives the rotation torque from the feed roller motor 45 and rotates the counterclockwise direction in FIG. 2 to feed the document P downstream. Hereinafter, the rotation direction of the feed roller 14 when the feed roller 14 feeds the document P downstream is referred to as a forward rotation direction, and the opposite rotation direction is referred to as a reverse rotation direction.
Similarly, as for the rotation direction of the feed roller motor 45, the rotation direction when the document P is sent downstream is referred to as a forward rotation direction, and the opposite rotation direction is referred to as a reverse rotation direction.

Since the one-way clutch 49 is provided in the driving force transmission path between the feed roller 14 and the feed roller motor 45 (FIG. 3), even if the feed roller motor 45 rotates in the reverse direction, The roller 14 does not rotate backward. In addition, when the feed roller motor 45 is stopped, the feed roller 14 can be driven to rotate in the forward rotation direction by the document P being conveyed.
For example, when the leading end of the document P is detected by the second document detection unit 32 disposed downstream of the pair of conveyance rollers 16, the control unit 40 stops driving the motor 45 for the feeding roller and sets the motor Only 46 is driven. As a result, the document P is transported by the transport roller pair 16, and the feeding roller 14 is driven to rotate in the forward rotation direction in contact with the transported document P.

Subsequently, the rotation torque is transmitted to the separation roller 15 from the transport roller motor 46 (FIG. 3) via the torque limiter 55.
In FIG. 4, reference numeral 50 denotes a transmission shaft that is rotated by receiving power from the transport roller motor 46. A gear 51 is provided on the transmission shaft 50, and is transmitted from the gear 51 to a gear 53 via a gear 52.
The driving force is transmitted to the first torque limiter 55A and the second torque limiter 55B via the gear 53.
The first torque limiter 55A transmits a driving force to the first rotation shaft 56A. The second torque limiter 55B transmits a driving force to the second rotation shaft 56B. In the following, the first torque limiter 55A and the second torque limiter 55B will be referred to as the torque limiter 55 unless it is particularly necessary to distinguish them.
A first separation roller 15A is attached to the first rotation shaft 56A, and a second separation roller 15B is attached to the second rotation shaft 56B. The first rotation shaft 56A and the second rotation shaft 56B are different shafts.

Returning to FIG. 2, when the document P does not intervene between the feeding roller 14 and the separation roller 15 or when only one sheet intervenes, the separation roller 15 slips in the torque limiter 55 and is Regardless of the rotational torque received from the motor 46, the motor 46 is driven to rotate in the forward rotation direction.
Hereinafter, a direction in which the separation roller 15 rotates following the rotation of the feed roller 14 or following the fed document P is referred to as a forward rotation direction, and a reverse rotation direction is referred to as a reverse rotation direction.
Similarly, also with respect to the rotation direction of the transport roller motor 46, the rotation direction when rotating the separation roller 15 in the forward rotation direction is referred to as the forward rotation direction, and the opposite rotation direction is referred to as the reverse rotation direction.
During the feeding of the document P, the transport roller motor 46 basically rotates in the reverse direction, that is, generates a driving torque that causes the separation roller 15 to rotate in the reverse direction.

  Next, when the second and subsequent documents P, in addition to the document P to be fed, enter between the feeding roller 14 and the separation roller 15, slippage occurs between the documents, and the separation roller 15 Are rotated in reverse by the driving torque received from the transport roller motor 46. As a result, the second and subsequent documents P to be multi-fed are returned to the upstream, that is, the multi-feed is prevented.

  The outer peripheral surfaces of the feed roller 14 and the separation roller 15 are formed of an elastic material such as an elastomer. Assuming that the friction coefficient between the feeding roller 14 and the document P is μ3 and the friction coefficient between the separation roller 15 and the document P is μ4, the relationship of μ1> μ2 is established. Further, the relationship of μ1> μ3, μ4 holds. Further, the relationship of μ2 <μ3, μ4 holds. In this embodiment, μ4 ≧ μ3 is set. However, as another embodiment, μ4 <μ3 may be satisfied.

In FIG. 4, the first rotation shaft 56A is supported by a first separation roller holder 60A, and the second rotation shaft 56B is supported by a second separation roller holder 60B. In the following, the first separation roller holder 60A and the second separation roller holder 60B will be referred to as separation roller holders 60 when it is not particularly necessary to distinguish them.
The separation roller holder 60 is provided to be swingable about the transmission shaft 50. That is, the separation roller holder 60 is provided so as to be swingable with respect to the upper unit 4, and causes the separation roller 15 to advance and retreat with respect to the feeding roller 14 by swinging.

The separation roller holder 60 is provided with a spring retaining portion 60a as shown in FIG. 5, and a coil spring 61, which is an example of a pressing unit, is mounted on the spring retaining portion 60a and a frame (not shown) of the upper unit 4. A spring force acts between the spring engaging portion 62 provided. The separation roller holder 60, that is, the separation roller 15 is pressed toward the feeding roller 14 by the spring force of the coil spring 61.
As shown in FIG. 4, the coil spring 61 includes a first coil spring 61A as a first pressing unit that presses the first separation roller holder 60A, and a first pressing unit that presses the second separation roller holder 60B. Includes a second coil spring 61B as a different second pressing means. In the present specification, the first coil spring 61A and the second coil spring 61B are referred to as a coil spring 61 when there is no particular need to distinguish between them.

Next, with reference to FIG. 6, a problem in a case where the pair of the first separation roller 15A and the second separation roller 15B are connected and rotated in synchronization with each other, which is different from the present embodiment, will be described.
In FIG. 6, a pair of first separation roller 15A and second separation roller 15B are provided on a common rotating shaft 56C, and have a configuration in which the driving force of the motor is transmitted via a torque limiter 55C.

The symbol N1 is a region where the first feeding roller 14A and the first separation roller 15A are in contact, that is, a nip region, and the symbol N2 is a region where the second feeding roller 14B and the second separation roller 15B are in contact, that is, a nip region. is there.
Since a driving torque that rotates in the reverse rotation direction is transmitted to the separation roller 15, when the document P is interposed between the separation roller 15 and the feeding roller 14, the separation roller 15 can rotate in the reverse direction and move the document P upstream. Can be returned to.

  However, as shown in FIG. 6, due to the skew of the document P, the document P is located in the nip area N1 of the first separation roller 15A and the first feeding roller 14A, and the other second separation roller 15B and the second feeding roller 15A. In a state where the document P is out of the nip area N2 of the roller 14B, neither the first separation roller 15A nor the second separation roller 15B can rotate in the reverse direction. Since the feed roller 14 cannot rotate in the reverse direction due to the function of the one-way clutch 49 (FIG. 2), the second separation roller 15B that is in direct contact with the second feed roller 14B also cannot rotate in the reverse direction and is integrated with the second separation roller 15B. This is because the first separation roller 15A that has been formed cannot be reversed.

Hereinafter, the above principle will be described mechanically. 6 shows the force generated by the first feeding roller 14A and the first separation roller 15A, and the right drawing of FIG. 6 shows the force generated by the second feeding roller 14B and the second separation roller 15B. Is shown.
In the figure, reference symbol TL indicates a limit torque value of the torque limiter 55C. Symbols FL and FR indicate pressing forces for pressing each separation roller toward each feed roller. The symbol R is the radius of the separation roller 15. The return force of the separation roller 15 is TL / R.

When the document P is returned to the upstream, the feed roller 14 is stopped by the function of the one-way clutch 49 (FIG. 2), and the document P is returned to the upstream while sliding on the outer peripheral surface of the feed roller 14. When the document return amount further increases, contact between the feed roller 14 and the separation roller 15 starts.
Considering a configuration in which only the separation roller 15 and the feeding roller 14 are provided in a pair, when the separation roller 15 is pressed against the feeding roller 14 by the pressing force F, the pressing force F is It is decomposed into a pressure F1 and a pressing force F2 in a range where a document exists.
Assuming that the friction coefficient between the feeding roller 14 and the separation roller 15 is μ1 and the friction coefficient between the feeding roller 14 and the document P is μ3, the following equation is satisfied when the document P is at rest.
TL / R = μ1 × F1 + μ3 × F2
Here, the original returning force by the separation roller 15 is only μ3 × F2.

The above expression is for a case where only one pair of the separation roller 15 and the feeding roller 14 is provided, and in a configuration where two pairs are provided, the following expression is obtained. The pressing force FL is divided into a pressing force FL1 in a range without a document and a pressing force FL2 in a range with a document. Similarly, the pressing force FR is divided into a pressing force FR1 in a range without a document and a pressing force FR2 in a range with a document.
TL / R = (μ1 × FL1 + μ3 × FL2) + (μ1 × FR1 + μ3 × FR2)
= (FL1 + FR1) × μ1 + (FL2 + FR2) × μ3
Here, since μ1> μ3, when the separation roller 15 comes into contact with the feeding roller 14, the inter-roller braking force starts to work, and the original returning force is rapidly lost. Therefore, at the document return position, the contribution ratio of the pressing forces FL1 and FR1 increases, and the second separation roller 15B that directly contacts the second feeding roller 14B in a wide range cannot rotate in the reverse direction. The integrated first separation roller 15A cannot be rotated in the reverse direction, and the skew of the document P remains.

  As described above, in the configuration in which the pair of the first separation roller 15A and the second separation roller 15B are connected and rotated synchronously, the skew of the document P in the feeding standby state cannot be properly corrected. There is.

On the other hand, in the present embodiment, as shown in FIG. 4, the first separation roller 15A is provided on the first rotation shaft 56A, and the second separation roller 15B is provided on the second rotation shaft 56B. That is, the first separation roller 15A and the second separation roller 15B have their own rotation axes. Thus, the problem described with reference to FIG. 6, that is, one roller can be prevented from being affected by the other roller, and the skew can be properly corrected.
As described with reference to FIG. 4, the first separation roller 15A is pressed toward the first feed roller 14A by the first coil spring 61A, and the second separation roller 15B is pressed by the second coil spring 61B. It is pressed toward the feed roller 14B. That is, since the first separation roller 15A and the second separation roller 15B are pressed toward the feeding roller 14 by a unique pressing means, when skew occurs, the first separation roller 15A and the second separation roller 15B are separated. Skew can be appropriately suppressed by optimizing the pressing load.
Specifically, different spring forces can be set for the first coil spring 61A and the second coil spring 61B, and the degree of freedom in adjusting the separation capability is improved.
In addition, different limit torque values can be set for the first torque limiter 55A and the second torque limiter 55B, thereby further improving the degree of freedom in adjusting the separation capability.

In addition, the pressing unit that presses the first separation roller 15A is a first pressing unit, and the pressing unit that presses the second separation roller 15B is a second pressing unit. Under the above control, the pressing load can be adjusted respectively.
FIG. 7 shows an example of such a configuration, and a cam 62A is employed instead of the spring retaining portion 62 shown in FIG. The cam 62A is a cam that rotates by receiving a driving force from a cam drive motor 63 controlled by the control unit 40, and has a shape in which the distance from the center of rotation to the outer periphery changes with rotation, for example, an elliptical shape. . Therefore, the pressing force applied to the separation roller holder 60 by the coil spring 61 changes due to the rotation of the cam 62A, whereby the load at which the separation roller 15 contacts the feeding roller 14 changes. In such a configuration, it is preferable to provide a means for detecting the phase of the cam 62A.
With such a configuration, there is no need for the serviceman or the user to adjust the pressing load, and the convenience is improved.

Further, the first separation roller 15A and the second separation roller 15B can be driven by different driving sources. In FIG. 8, reference numeral 65A denotes a motor for driving the first separation roller 15A, and reference numeral 65B denotes a motor for driving the second separation roller 15B.
Also, as shown in FIG. 8, a first medium detection unit 66A is provided beside the first separation roller 15A with the intermediate position CL between the first separation roller 15A and the second separation roller 15B symmetrical in the document width direction. A second medium detection unit 66B is provided beside the second separation roller 15B.

The first medium detecting means 66A and the second medium detecting means 66B include a plurality of optical sensors 67 along the document feeding direction. The arrangement area of the plurality of optical sensors 67 in the document feeding direction includes the nip position between the feeding roller 14 and the separation roller 15.
The control unit 40 that controls the motor 65A that is the drive source of the first separation roller 15A and the motor 65B that is the drive source of the second separation roller 15B outputs the detection information of the first medium detection unit 66A and the second medium detection unit 66B. The skew of the document P can be corrected more accurately by rotating the one of the first separation roller 15A and the second separation roller 15B in which the leading end of the document precedes downstream in the reverse rotation direction.

Hereinafter, further description will be made with reference to FIGS. 9 and 8. In FIG. 9, the control unit 40 obtains the left-right difference of the leading edge of the original P based on the detection information of the first medium detecting unit 66A and the second medium detecting unit 66B when correcting the skew of the original P in the feeding standby state. (Step S101).
If the acquired left / right difference is ahead of the left side (Yes in step S102), the left separation roller is driven to reversely rotate based on the acquired left / right difference (step S105). Here, the left separation roller is the first separation roller 15A shown in FIG.
Conversely, if the acquired left-right difference is ahead of the right (Yes in step S103), the right separation roller is driven to rotate in reverse based on the acquired left-right difference (step S104). The right separation roller here is the second separation roller 15B shown in FIG.
For example, in the example of FIG. 8, the leading end of the document P has the first separation roller 15A side ahead of the second separation roller 15B side, so the first separation roller 15A is separated from the second separation roller 15B. Also rotate a lot in the reverse rotation direction.
Thereby, the skew of the document P can be corrected more accurately.

Subsequently, another embodiment of the feeding roller will be described. As shown in FIG. 10, a differential gear 70 that causes a difference between the rotation of the first feeding roller 14A and the rotation of the second feeding roller 14B is provided between the first feeding roller 14A and the second feeding roller 14B. Can be provided.
10, the driving force of the conveying roller motor 46 (FIG. 3) is transmitted from the shaft 71 to the shaft 72 via the one-way clutch 49, and the driving force is transmitted from the gear 73 attached to the shaft 72 to the reduction gear 74. Is done.

  The differential gear 70 includes a differential large gear 75A provided integrally with the first feed roller 14A, a differential large gear 75B provided integrally with the second feed roller 14B, and differential large gears 75A, 75B. And differential gears 76A and 76B provided between the gears. The differential gear 70 can cause a difference between the rotation of the first feeding roller 14A and the rotation of the second feeding roller 14B.

Hereinafter, a configuration in which the differential gear 70 is not provided between the first feed roller 14A and the second feed roller 14B, that is, a configuration in which the first feed roller 14A and the second feed roller 14B rotate integrally. The problem will be described with reference to FIG.
In the upper part of FIG. 11, the original P1 previously fed is skewed. Here, when the trailing end of the document P1 comes out from between the feed roller 14 and the separation roller 15, basically the driven roller 14 stops rotating in the forward rotation direction.
However, since the document P1 is skewed, in the example of FIG. 11, even if the trailing edge of the document comes out from between the right second feed roller 14B and the second separation roller 15B, the left first feed roller 14A Since the trailing edge of the document does not fall out from between the first separation roller 15A, the first feeding roller 14A continues to rotate in the forward rotation direction.

  Since the first feed roller 14A and the second feed roller 14B are integrated, the rear end of the original P1 fed earlier is formed by the second feed roller 14B and the second separation roller 15B. Even if the document P2 is pulled out from the space, the second feed roller 14B continues to rotate in the forward rotation direction, and as a result, the leading end of the next original P2 waiting is sent out as shown in the lower diagram of FIG. As a result, the skew is linked to the next original P2.

However, as described above, by providing the differential gear 70 between the first feed roller 14A and the second feed roller 14B, in the example of FIG. 11, the first feed roller 14B is stopped and the first feed roller 14B is stopped. Only the feed roller 14A can rotate, thereby suppressing chain skew.
As another means for obtaining the same effect, it is conceivable to provide a one-way clutch for each of the first feed roller 14A and the second feed roller 14B. However, the cost is increased as compared with such a configuration. Can be suppressed.

  Further, by providing the differential gear 70, one of the first feed roller 14A and the second feed roller 14B can rotate in the reverse direction while one of the first feed roller 14A and the second feed roller 14B is stopped. Accordingly, when the embodiment described with reference to FIGS. 8 and 9 is applied, the feed roller 14 that comes into contact with the first separation roller 15A or the second separation roller 15B when the one of the first separation roller 15A and the second separation roller 15B is rotated in the reverse direction. The skew of the document P waiting for feeding can be more reliably corrected.

  The above embodiment has described the case where the medium feeding apparatus according to the present invention is applied to a scanner which is an example of an image reading apparatus.However, a recording apparatus having a recording head for performing recording on a medium, such as a printer, is used. It is also possible to apply.

1A: Scanner (image reading device), 1B: Document feeder, 2: Device body, 3: Lower unit, 4: Upper unit, 5: Discharge tray, 6: Feeding port, 7: Operation panel, 8 ... 1st paper support, 9 ... 2nd paper support, 11 ... original placement part, 12A, 12B ... edge guide, 14 ... feeding roller, 14A ... 1st feeding roller, 14B ... 2nd feeding roller, 15 ... Separation roller, 15A: first separation roller, 15B: second separation roller, 16: conveyance roller pair, 16a: conveyance drive roller, 16b: conveyance driven roller, 17: discharge roller pair, 17a: discharge drive roller, 17b: discharge Driven roller, 18 discharge port, 20 reading section, 20a upper reading sensor, 20b lower reading sensor,
Reference numeral 30: double feed detecting unit, 30a: ultrasonic transmitting unit, 30b: ultrasonic receiving unit, 31: first original detecting unit, 31a: light emitting unit, 31b: light receiving unit, 32: second original detecting unit, 35: mounting Position detector,
40: control unit, 41: CPU, 42: ROM, 43: memory, 44: program, 45: motor for feeding roller, 46: motor for conveying roller, 49: one-way clutch, 50: transmission shaft, 51, 52, 53: gear, 55: torque limiter, 55A: first torque limiter, 55B: second torque limiter, 56: rotating shaft, 56A: first rotating shaft, 56B: second rotating shaft, 60: separating roller holder, 60A ... 1st separation roller holder, 60B ... 2nd separation roller holder, 61 ... coil spring, 61A ... 1st coil spring, 61B ... 2nd coil spring, 62 ... spring latch part, 62A ... cam, 63 ... cam drive motor, 65A, 65B: motor, 66A: first medium detecting means, 66B: second medium detecting means, 67: optical sensor, 70: differential Lugia, 71, 72 ... shaft, 73 ... gear, 74 ... reduction gear wheel, 75A, 75B ... differential large gear, 76A, 76B ... differential gears, 90 ... external computer, P ... document (medium)

Claims (5)

A medium placement unit for placing the medium,
A feed roller for feeding the medium from the medium placement unit,
A roller for nipping the medium between the feeding roller and the medium to separate the medium, wherein a driving torque by a driving source in a second rotation direction opposite to the first rotation direction for sending the medium downstream is reduced. A separating roller to be applied;
A torque limiter that idles the separation roller in the first rotation direction when a rotation torque applied to the separation roller in the first rotation direction exceeds a limit torque that is a predetermined torque upper limit,
The feeding roller includes a first feeding roller and a second feeding roller provided at intervals in a medium width direction that is a direction intersecting with a medium feeding direction,
The separation roller includes a first separation roller in contact with the first feeding roller and a second separation roller in contact with the first feeding roller,
The torque limiter includes a first torque limiter provided for the first separation roller and a second torque limiter provided for the second separation roller,
The first separation roller is rotatable about a first rotation axis, and is pressed toward the feed roller by first pressing means,
The second separation roller is rotatable around a second rotation axis different from the first rotation axis, and is pressed toward the feed roller by a second pressing means different from the first pressing means. ,
A medium feeding device characterized by the above-mentioned. 2. The medium feeding device according to claim 1, wherein the first pressing unit and the second pressing unit are configured to be capable of adjusting a pressing load under control of a control unit.
A medium feeding device characterized by the above-mentioned. 2. The medium feeding device according to claim 1, wherein the drive source includes a first drive source that drives the first separation roller, and a second drive source that drives the second separation roller. ,
A first medium detection unit and a second medium detection unit, with an intermediate position between the first separation roller and the second separation roller in the medium width direction as a symmetric center;
The first medium detection unit and the second medium detection unit include a plurality of sensors along the medium feeding direction,
The arrangement area of the plurality of sensors in the medium feeding direction includes a nip position between the feeding roller and the separation roller,
The control unit that controls the first drive source and the second drive source is configured to control the first separation roller and the second separation roller based on detection information of the first medium detection unit and the second medium detection unit. The amount of rotation per unit time in the second rotation direction is increased with respect to the roller in which the leading end of the medium precedes downstream.
A medium feeding device characterized by the above-mentioned. 4. The medium feeding device according to claim 1, wherein the rotation of the first feeding roller and the rotation of the first feeding roller are between the first feeding roller and the second feeding roller. 5. 2 equipped with a differential gear that causes a difference in rotation of the feed roller,
A medium feeding device characterized by the above-mentioned. Reading means for reading a medium;
The medium feeding device according to any one of claims 1 to 4, which feeds the medium to the reading unit,
An image reading device comprising:

Images