阅读说明：本技术 介质输送装置及其介质探测方法、图像读取装置 (Medium conveying device, medium detection method thereof, and image reading device ) 是由 深泽勇介 増田英俊 福光康则 于 2020-08-27 设计创作，主要内容包括：本发明提供一种即使不在输送路径中设置光学传感器,也能够探测介质的介质输送装置及其介质探测方法、图像读取装置。介质输送装置(20)具备：供送辊(21),所述供送辊(21)旋转以沿着输送路径(100)输送介质(M)；电极(41),配置在输送路径(100)中供送辊(21)的下游,并且具有导电性；以及电荷检测电路(42),当沿着输送路径(100)输送的介质(M)与电极(41)接触而使电荷从介质(M)移动到电极(41)时,输出与电荷从介质(M)移动到电极(41)的移动量相应大小的信号。(The invention provides a medium conveying device capable of detecting a medium without providing an optical sensor in a conveying path, a medium detecting method thereof, and an image reading device. A medium conveyance device (20) is provided with: a feeding roller (21), the feeding roller (21) rotating to convey a medium (M) along a conveying path (100); an electrode (41) that is disposed downstream of the feed roller (21) in the conveyance path (100) and that has conductivity; and a charge detection circuit (42) that outputs a signal having a magnitude corresponding to the amount of movement of the charge from the medium (M) to the electrode (41) when the medium (M) conveyed along the conveyance path (100) comes into contact with the electrode (41) and the charge is moved from the medium (M) to the electrode (41).)

1. A medium transport device that transports a medium along a transport path, the medium transport device comprising:

a feeding roller that rotates to convey the medium;

an electrode disposed downstream of the feeding roller in the conveying path and having conductivity; and

and a charge detection circuit that outputs a signal having a magnitude corresponding to a movement amount of the electric charge from the medium to the electrode when the medium conveyed along the conveyance path comes into contact with the electrode and the electric charge is moved from the medium to the electrode.

2. The media transport apparatus of claim 1,

the medium transport device includes a nip portion that nips the medium together with the feed roller,

the electrode is disposed downstream of the nip in the conveyance path.

3. The medium transport apparatus according to claim 1 or 2,

the medium transport device includes a control unit that determines that the medium is in contact with the electrode when a signal output from the charge detection circuit is equal to or greater than a detection determination value when the medium is transported from upstream to downstream in a transport direction along the transport path.

4. The media transport apparatus of claim 3,

the electrodes are disposed at positions different from each other in a width direction of the medium conveyed along the conveyance path,

as the charge detection circuit, a plurality of the charge detection circuits corresponding to the plurality of the electrodes are provided,

the control unit calculates an estimated value of the inclination of the medium as follows:

the estimated value of the inclination is larger as a difference between a time point at which a signal magnitude output from the charge detection circuit corresponding to a first electrode of the plurality of electrodes becomes equal to or larger than the detection determination value and a time point at which a signal magnitude output from the charge detection circuit corresponding to a second electrode of the plurality of electrodes becomes equal to or larger than the detection determination value is larger.

5. The media transport apparatus of claim 4,

the electrode is provided with a third electrode arranged between the first electrode and the second electrode in the width direction,

as the charge detection circuit, the charge detection circuit corresponding to the third electrode is provided,

in this case, a time point at which the magnitude of the signal output from the charge detection circuit corresponding to the first electrode becomes equal to or greater than the detection determination value is set as a first time point, a time point at which the magnitude of the signal output from the charge detection circuit corresponding to the second electrode becomes equal to or greater than the detection determination value is set as a second time point, and a time point at which the magnitude of the signal output from the charge detection circuit corresponding to the third electrode becomes equal to or greater than the detection determination value is set as a third time point,

when the difference between the first time point and the second time point is equal to or less than a difference determination value, the control unit calculates the estimated value of the inclination as follows: the estimated value of the inclination is larger as a difference between the first time point and the third time point is larger.

6. The media transport apparatus of claim 2,

the medium transport device includes a control unit that determines that the medium is in contact with the electrode when a signal output from the charge detection circuit is equal to or greater than a detection determination value when the medium is transported from upstream to downstream in a transport direction along the transport path,

the electrodes are disposed at positions different from each other in a width direction of the medium conveyed along the conveyance path,

as the charge detection circuit, a plurality of the charge detection circuits corresponding to the plurality of the electrodes are provided,

in the plurality of electrodes, the detection determination value corresponding to the electrode that is distant from the nip portion in the width direction is smaller than the detection determination value corresponding to the electrode that is near the nip portion in the width direction.

7. The medium transporting device according to any one of claims 4 to 6,

in the case where the medium is conveyed from upstream toward downstream in the conveying direction along the conveying path,

when the magnitude of the signal output from the charge detection circuit corresponding to one of the two electrodes adjacent in the width direction is equal to or larger than the detection determination value and the magnitude of the signal output from the charge detection circuit corresponding to the other electrode is smaller than the detection determination value,

the control unit determines that a side end of the medium is located between the one electrode and the other electrode in the width direction.

8. An image reading apparatus is characterized by comprising:

the media delivery device of any one of claims 1 to 7; and

and a reading unit configured to read an image of the medium conveyed along the conveyance path.

9. The image reading apparatus according to claim 8,

the reading section is disposed downstream of the electrode in the conveying path.

10. An image reading apparatus is characterized by comprising:

the media delivery device of claim 4; and

a reading section that reads an image of the medium conveyed along the conveyance path,

the control unit stops the conveyance of the medium when the estimated value of the inclination is equal to or greater than an inclination determination value.

11. The image reading apparatus according to claim 10,

the control portion increases the inclination determination value as a dimension of the medium conveyed along the conveyance path in the width direction becomes smaller.

12. A medium detection method for a medium transport device is applied to a medium transport device including:

a feed roller that rotates to convey a medium along a conveyance path;

an electrode disposed downstream of the feeding roller in the conveying path and having conductivity; and

a charge detection circuit that outputs a signal having a magnitude corresponding to an amount of movement of the electric charge from the medium to the electrode when the medium conveyed along the conveyance path comes into contact with the electrode and the electric charge is moved from the medium to the electrode,

when the medium is conveyed from upstream to downstream in the conveyance direction along the conveyance path, the control unit of the medium conveyance device is caused to execute a step of determining that the medium is in contact with the electrode when the magnitude of the signal output from the charge detection circuit is equal to or greater than a detection determination value.

Technical Field

The present invention relates to a medium transport device that transports a medium along a transport path, an image reading apparatus including the medium transport device, and a medium detection method of the medium transport device.

Background

Patent document 1 describes an example of an image reading apparatus that conveys a medium along a conveyance path, reads an image of the medium by a reading unit, and generates image data based on the image. In such an image reading apparatus, an optical sensor that detects a medium is provided upstream of the reading section in the conveyance path.

Patent document 1: japanese patent laid-open publication No. 2017-188542

Disclosure of Invention

In general, an optical sensor includes a light emitting portion and a light receiving portion that receives light output from the light emitting portion. When the transported medium reaches the arrangement position of the optical sensor, the light from the light emitting section is blocked by the medium. As a result, the amount of light received by the light receiving unit decreases. The medium is detected by the change in the amount of light received by the light receiving section. Therefore, if the optical sensor including the light emitting portion and the light receiving portion is provided in the transport path, the device configuration becomes complicated.

In addition, the above-described problem may occur in other apparatuses than the image reading apparatus as long as the apparatus conveys the medium along the conveyance path.

A medium transport device that achieves the above object is a medium transport device that transports a medium along a transport path. The medium conveying device includes: a feeding roller that rotates to convey the medium; an electrode disposed downstream of the feeding roller in the conveying path and having conductivity; and a charge detection circuit that outputs a signal having a magnitude corresponding to a movement amount of the electric charge from the medium to the electrode when the medium conveyed along the conveyance path comes into contact with the electrode and the electric charge is moved from the medium to the electrode.

An aspect of an image reading apparatus that achieves the above object includes: the above-described medium conveyance device; and a reading section that reads an image of the medium conveyed along the conveyance path.

An aspect of an image reading apparatus that achieves the above object includes: the above-described medium conveyance device; and a reading section that reads an image of the medium conveyed along the conveyance path; the control unit stops the conveyance of the medium when the estimated value of the inclination is equal to or greater than an inclination determination value.

The medium detection method of the medium transport apparatus for achieving the above object is applied to a medium transport apparatus including: a feed roller that rotates to convey a medium along a conveyance path; an electrode disposed downstream of the feeding roller in the conveying path and having conductivity; and a charge detection circuit that outputs a signal having a magnitude corresponding to a movement amount of the electric charge from the medium to the electrode when the medium conveyed along the conveyance path comes into contact with the electrode and the electric charge is moved from the medium to the electrode. According to this medium detecting method, when the medium is conveyed from the upstream to the downstream in the conveying direction along the conveying path, the control unit of the medium conveying device is caused to execute the step of determining that the medium is in contact with the electrode when the magnitude of the signal output from the charge detection circuit is equal to or larger than a detection determination value.

Drawings

Fig. 1 is a side view schematically showing an image reading apparatus of a first embodiment.

Fig. 2 is a plan view schematically showing a part of the image reading apparatus.

Fig. 3 is a schematic diagram showing an example of an electrostatic detection sensor of the image reading apparatus.

Fig. 4 is a schematic diagram showing an example of an electrostatic detection sensor of the image reading apparatus.

Fig. 5 is a block diagram showing a charge detection circuit of the electrostatic detection sensor.

Fig. 6 is a flowchart showing a flow of processing executed by the control section of the image reading apparatus.

Fig. 7 is a timing chart showing a transition of a signal value, which is the magnitude of an amplified signal output from the charge detection circuit.

Fig. 8 is a plan view schematically showing a part of the image reading apparatus of the second embodiment.

Fig. 9 is a flowchart showing a flow of processing executed by the control section of the image reading apparatus.

Fig. 10 is a timing chart showing transitions of signal values.

Fig. 11 is a plan view schematically showing a part of an image reading apparatus of a third embodiment.

Fig. 12 is a flowchart showing a flow of processing executed by the control section of the image reading apparatus.

Fig. 13 is a plan view schematically showing a part of an image reading apparatus of a fourth embodiment.

Fig. 14 is a schematic view of the case of the medium transport device of the comparative example.

Fig. 15 is a schematic view of a medium conveyance device of an image reading apparatus according to a fourth embodiment.

Fig. 16 is a timing chart showing transitions of respective signal values.

Fig. 17 is a plan view schematically showing a part of an image reading apparatus of a fifth embodiment.

Fig. 18 is a timing chart showing transitions of respective signal values.

Fig. 19 is a plan view schematically showing a part of an image reading apparatus according to a modification.

Description of the reference numerals

θ … speculative value; dx … conveyance direction distance; dy … width direction distance; m … medium; ma … front end; ms1 … first side end; ms2 … second side end; 10 … image reading device; 10a … frame body; 11 … medium holding part; 12 … a first reading section; 13 … a second reading section; 20 … a media transport device; 21 … supply roll; 22 … a clamping portion; 25 … drive the motor; 30 … detecting a sensor; 31 … detecting a sensor; 32 … electrostatic detection sensor; 32a … electrostatic detection sensor; 32a1 … electrostatic detection sensor; 32B … electrostatic detection sensor; 32B1 … electrostatic detection sensor; 32C … electrostatic detection sensor; 32C1 … electrostatic detection sensor; 32D1 … electrostatic detection sensor; 32E1 … electrostatic detection sensor; 32F1 … electrostatic detection sensor; 41 … electrodes; 42 … charge detection circuit; 42B … base; a 42C … collector electrode; 42E … emitter; 45 … fibers; 45a … conductive plates; 46 … base; 47 … wiring; 48 … wiring; 60 … control section; 100 … conveying path; 231 … conveying the roller; 232 … conveying the roller; 241 … discharge roller; 242 … exit roller; 421 … bipolar transistor; 422 … resistance.

Detailed Description

First embodiment

Next, a medium transport apparatus, a medium detection method thereof, and a first embodiment of an image reading apparatus will be described with reference to fig. 1 to 7.

As shown in fig. 1, an image reading apparatus 10 according to the present embodiment includes: a frame body 10A; a medium holding unit 11 for holding the media M in a stacked state; and a medium conveyance device 20 that conveys the medium M held by the medium holding unit 11 along the conveyance path 100. The medium conveyance device 20 is provided in the housing 10A. The medium M is an insulating medium such as paper.

The image reading apparatus 10 includes a reading unit configured to read an image of the medium M conveyed along the conveyance path 100. In the example shown in fig. 1, the image reading apparatus 10 includes, as reading units, a first reading unit 12 for reading a front image of the medium M and a second reading unit 13 for reading a back image of the medium M.

The medium conveyance device 20 includes: a feeding roller 21 that feeds the medium M held by the medium holding portion 11 to the reading portions 12 and 13; and a nip portion 22 that nips the medium M together with the feed roller 21. Examples of the nip 22 include a separation roller and a separation plate. When the separation roller is used as the nip portion 22, the rotation of the separation roller may be restricted, or the separation roller may be rotated in a direction opposite to a rotation direction for conveying the medium M toward the downstream X in the conveying direction.

In the medium transport device 20 of the present embodiment, the medium M is nipped between the feed roller 21 and the nip portion 22, and the medium M is fed to the downstream X in the transport direction by the rotation of the feed roller 21. At this time, the medium M rubs against both the feed roller 21 and the nip portion 22. Accordingly, static electricity is generated between the medium M and the feeding roller 21, and static electricity is generated between the medium M and the nip portion 22. As a result, the electric charges are charged on both the front and back surfaces of the medium M.

The medium conveyance device 20 includes: conveying rollers 231, 232 arranged between the feeding roller 21 and the reading portions 12, 13 in the conveying direction of the medium M; and discharge rollers 241, 242 arranged downstream of the reading units 12, 13 in the conveying direction X.

The medium conveyance device 20 includes a drive motor 25 as a power source for the feed roller 21, the conveyance roller 231, and the discharge roller 241. When the output of the drive motor 25 is transmitted to the feeding roller 21, the conveying roller 231, and the discharge roller 241, the feeding roller 21, the conveying rollers 231, 232, and the discharge rollers 241, 242 rotate, and the medium M is conveyed from the upstream to the downstream in the conveying direction along the conveying path 100.

The medium transport device 20 of the present embodiment includes a plurality of detection sensors 31 and 32 for detecting the medium M transported from the upstream to the downstream in the transport direction along the transport path 100. The detection sensor 31 is disposed upstream in the conveying direction from the conveying rollers 231 and 232. The detection sensor 31 detects the leading end Ma of the medium M. When the leading end Ma of the medium M is detected by the detection sensor 31, the reading units 12 and 13 start reading the image of the medium M.

As shown in fig. 1 and 2, the electrostatic detection sensor 32 includes: an electrode 41 disposed between the nip portion 22 and the detection sensor 31 in the conveyance direction; and a charge detection circuit 42 connected to the electrode 41. When the width direction of the medium M conveyed along the conveyance path 100 is defined as the width direction Y, the electrode 41 is disposed, for example, at the center of the conveyance path 100 in the width direction Y. The two-dot chain line in fig. 2 corresponds to the center of the conveyance path 100 in the width direction Y.

Examples of the electrode 41 include a brush electrode shown in fig. 3. In this case, the electrode 41 has a plurality of fibers 45 and a base 46 that fixes the base end of each fiber 45. The fibers 45 are made of a material having electrical conductivity. That is, the electrode 41 has conductivity. Therefore, when each fiber 45 comes into contact with the medium M, the electric charge attached to the medium M moves to the electrode 41. Further, the electric charges moved to the electrode 41 are moved toward the electric charge detection circuit 42 via the wiring 47.

The electrode 41 may be, for example, a plate-like conductive plate 45A shown in fig. 4. In this case, the electrode 41 also has conductivity. Therefore, when the medium M comes into contact with the conductive plate 45A, the charge attached to the medium M moves to the conductive plate 45A. Further, the electric charges moved to the conductive plate 45A move toward the electric charge detection circuit 42 via the wiring 47.

As the charge detection circuit 42, for example, an emitter ground circuit shown in fig. 5 can be cited. In fig. 5, an arrow from the medium M toward the electrode 41 indicates movement of electric charges from the medium M toward the electrode 41.

The charge detection circuit 42 shown in fig. 5 has a bipolar transistor 421. Electrode 41 is connected to base 42B of bipolar transistor 421. The emitter 42E of the bipolar transistor 421 is grounded. The resistor 422 is connected to the collector 42C of the bipolar transistor 421 via the wiring 48. Further, control unit 60 is connected to wiring 48 between collector electrode 42C and resistor 422. That is, a signal having a magnitude corresponding to the amount of charge moving from the medium M to the electrode 41 is input to the base 42B of the bipolar transistor 421. In this way, the amplified signal SGa, which is a signal obtained by amplifying the signal inputted to the base 42B, is outputted from the collector 42C of the bipolar transistor 421 to the control unit 60. The control unit 60 includes a CPU and a memory.

Next, a flow of processing in the control unit 60 when the medium M is conveyed will be described with reference to fig. 6. This series of processes corresponds to the medium detection method of the medium transporting apparatus 20. The respective processes shown in fig. 6 are executed by the control unit 60.

As shown in fig. 6, in the first step S11, conveyance of the medium M is started. That is, the driving of the drive motor 25 is started. Thus, the rotation of the feeding roller 21, the conveying rollers 231 and 232, and the discharge rollers 241 and 242 is started. Thereby, the medium M is conveyed along the conveyance path 100 from the upstream to the downstream in the conveyance direction at a constant conveyance speed.

In the next step S12, a signal value SV, which is the magnitude of the amplified signal SGa input from the charge detection circuit 42 to the control unit 60, is derived. The larger the amount of charge moved from the medium M to the electrode 41, the larger the signal value SV.

Then, in step S13, it is determined whether or not the derived signal value SV is equal to or greater than the determination signal value SVTh. As the determination signal value SVTh, a value for determining whether or not the medium M is in contact with the electrode 41 based on the magnitude of the signal value SV is set. That is, when the signal value SV is smaller than the determination signal value SVTh, the medium M is not in contact with the electrode 41. On the other hand, when the signal value SV is equal to or greater than the determination signal value SVTh, the medium M contacts the electrode 41. If the signal value SV is smaller than the determination signal value SVTh (S13: no), the process proceeds to the next step S14. In step S14, it is determined that the medium M is not detected by the electrode 41. Then, the process proceeds to step S16 described later.

On the other hand, when the signal value SV is equal to or greater than the determination signal value SVTh in step S13 (yes), the process proceeds to the next step S15. In step S15, it is determined that the medium M can be detected by the electrode 41. Therefore, in the present embodiment, steps S13 and S14 constitute the following steps: when the medium M is conveyed from the upstream to the downstream in the conveying direction along the conveying path 100, if the signal value SV, which is the magnitude of the amplified signal SGa output from the charge detection circuit 42, is equal to or greater than the detection determination value SVTh, it is determined that the medium M is in contact with the electrode 41. Then, the process proceeds to the next step S16.

In step S16, it is determined whether the conveyance of the medium M has been completed. For example, when the image reading of the medium M by the reading portions 12, 13 is completed and the medium M is discharged from the conveyance path 100, it is determined that the conveyance of the medium M has been completed. If the conveyance of the medium M is not completed (S16: NO), the process proceeds to step S12 described above. On the other hand, when the conveyance of the medium M is completed (S16: YES), the series of processing shown in FIG. 6 is ended.

The operation of the present embodiment will be described with reference to fig. 7.

When the feed roller 21, the transport rollers 231 and 232, and the discharge rollers 241 and 242 start rotating, one medium M is transported from the upstream to the downstream in the transport direction along the transport path 100 from the medium holding portion 11. At this time, when the leading end Ma of the medium M passes through the electrode 41, the electrode 41 is in contact with the medium M.

Here, when the medium M is conveyed, static electricity is generated between the medium M and the feeding roller 21 and between the medium M and the nip portion 22, respectively. This causes the electric charge to be accumulated on both the front and back surfaces of the medium M.

Therefore, when the electrode 41 is in contact with the medium M, electric charges move from the medium M to the electrode 41. The electric charge moved to the electrode 41 moves toward the charge detection circuit 42. As a result, the charge detection circuit 42 generates an amplified signal SGa having a magnitude corresponding to the amount of charge input to the charge detection circuit 42, and the amplified signal SGa is input from the charge detection circuit 42 to the control unit 60.

In the example shown in fig. 7, the medium M is in contact with the electrode 41 at timing t11, and the medium M is separated from the electrode 41 at the subsequent timing t 12. Therefore, the signal value SV, which is the magnitude of the amplified signal SGa, is equal to or greater than the determination signal value SVTh from the timing t11 to the timing t 12. That is, during this period, it is determined that the medium M is detected by the electrode 41.

According to the above embodiment, the following effects can be obtained.

(1) When the medium M is conveyed along the conveyance path 100 by the rotation of the feeding roller 21, the medium M rubs against the feeding roller 21, and thus electric charges are attached to the medium M. Therefore, when the electrode 41 is in contact with the medium M, electric charges move from the medium M to the electrode 41, and an amplified signal SGa of a magnitude corresponding to the amount of movement of the electric charges from the medium M to the electrode 41 is output from the electric charge detection circuit 42. Therefore, the medium M can be detected without providing an optical sensor in the conveyance path 100.

(2) In the present embodiment, the medium M conveyed along the conveyance path 100 is nipped between the feed roller 21 and the nip portion 22. Therefore, a larger static electricity can be generated between the feeding roller 21 and the nip portion 22 and the medium M. As a result, the amount of charge attached to the medium M can be increased.

(3) In the present embodiment, the medium M conveyed along the conveyance path 100 can be detected by comparing the signal value SV, which is the magnitude of the amplified signal SGa, with the determination signal value SVTh.

(4) The electrode 41 is disposed upstream of the reading units 12 and 13 in the conveying direction. Therefore, by using the electrode 41, the medium M can be detected before the medium M reaches the arrangement position of the reading units 12 and 13. In addition, the end of the medium M from which the image is read by the reading units 12 and 13 can be detected by using the electrode 41.

Second embodiment

Next, a second embodiment of the medium conveyance device and the image reading device will be described with reference to fig. 8 to 10. In the present embodiment, the number of the electrostatic detection sensors and the processing contents of the control unit 60 are different from those of the first embodiment. In the following description, the portions different from the first embodiment will be mainly described, and the same reference numerals are given to the same or corresponding component structures as those of the first embodiment, and redundant description will be omitted.

As shown in fig. 8, the medium transport apparatus 20 includes two electrostatic detection sensors 32A and 32B. Each of the electrostatic detection sensors 32A and 32B includes an electrode 41 disposed on the downstream side X in the transport direction from the nip portion 22, and a charge detection circuit 42 connected to the electrode 41. In the example shown in fig. 8, the two electrodes 41 are arranged at the same position in the conveyance direction of the medium M. The two electrodes 41 are disposed at different positions in the width direction Y. The shortest distance from the electrode 41 of the electrostatic detection sensor 32A to the central axis Z of the conveyance path 100 is equal to the shortest distance from the electrode 41 of the electrostatic detection sensor 32B to the central axis Z of the conveyance path 100.

Next, a flow of processing in the control unit 60 when the medium M is conveyed will be described with reference to fig. 9. Each of the processes shown in fig. 9 is executed by the control unit 60. Further, each process shown in fig. 9 is for calculating an estimated value θ of the inclination of the medium M conveyed along the conveyance path 100. In fig. 8, when the central axis Z of the conveyance path 100 is parallel to the central axis of the medium M, the estimated value θ of the inclination is "0".

As shown in fig. 9, in the first step S21, it is determined whether or not the conveyance mode of the medium M is the receipt mode. When the medium M to be conveyed is a receipt, the size of the medium M in the width direction Y is small. When such a medium M having a small size in the width direction Y is conveyed, the presumption value θ of the inclination of the medium M may not be calculated. Therefore, when the conveyance mode is the receipt mode (S21: YES), the series of processing shown in FIG. 9 is ended. On the other hand, if the conveyance mode is not the receipt mode (S21: NO), the process proceeds to the next step S22.

In step S22, conveyance of the medium M is started. That is, the driving of the drive motor 25 is started. Thus, the rotation of the feeding roller 21, the conveying rollers 231 and 232, and the discharge rollers 241 and 242 is started. Thereby, the medium M is conveyed at a fixed conveyance speed.

In the next step S23, it is determined whether or not the first signal value SV1, which is the magnitude of the amplified signal SGa input from the charge detection circuit 42 of the electrostatic detection sensor 32A to the controller 60, is equal to or greater than the determination signal value SVTh. If the first signal value SV1 is equal to or greater than the determination signal value SVTh (S23: yes), the electrostatic detection sensor 32A can detect the medium M, and the process proceeds to the next step S24. In step S24, measurement of the elapsed time T from the time point at which the first signal value SV1 becomes equal to or greater than the determination signal value SVTh is started.

Next, in step S25, it is determined whether or not the second signal value SV2, which is the magnitude of the amplified signal SGa input from the charge detection circuit 42 of the electrostatic detection sensor 32B to the controller 60, is equal to or greater than the determination signal value SVTh. If the second signal value SV2 is smaller than the determination signal value SVTh (S25: no), the determination of step S25 is repeated until the second signal value SV2 becomes equal to or greater than the determination signal value SVTh. On the other hand, if the second signal value SV2 is equal to or greater than the determination signal value SVTh (S25: yes), the electrostatic detection sensor 32B can detect the medium M, and the process proceeds to the next step S29.

In step S23, if the first signal value SV1 is smaller than the determination signal value SVTh (no), the process proceeds to the next step S26. In step S26, it is determined whether or not the second signal value SV2 is equal to or greater than the determination signal value SVTh. If the second signal value SV2 is smaller than the determination signal value SVTh (S26: no), the process proceeds to step S23 described above. On the other hand, if the second signal value SV2 is equal to or greater than the determination signal value SVTh (S26: yes), the electrostatic detection sensor 32B can detect the medium M, and the process proceeds to the next step S27. In step S27, measurement of the elapsed time T from the time point when the second signal value SV2 becomes equal to or greater than the determination signal value SVTh is started.

Next, in step S28, it is determined whether or not the first signal value SV1 is equal to or greater than the determination signal value SVTh. If the first signal value SV1 is smaller than the determination signal value SVTh (S28: no), the determination of step S28 is repeated until the first signal value SV1 becomes equal to or greater than the determination signal value SVTh. On the other hand, when the first signal value SV1 is equal to or greater than the determination signal value SVTh (S28: yes), the electrostatic detection sensor 32A can detect the medium M, and the process proceeds to the next step S29.

In step S29, the measurement of the elapsed time T ends. Then, in the next step S30, the estimated value θ of the inclination of the medium M is calculated based on the measured elapsed time T. For example, the estimated value θ of the inclination can be calculated by using the following relational expression (expression 1). In the relational expression (expression 1), "S" is the transport speed of the medium M, and "Dy" is the distance between the two electrodes 41 in the width direction Y. The larger the difference between the time point at which the magnitude of the amplified signal SGa output from the charge detection circuit 42 corresponding to the first electrode of the two electrodes 41 becomes equal to or greater than the detection determination value VTh and the time point at which the magnitude of the amplified signal SGa output from the charge detection circuit 42 corresponding to the second electrode becomes equal to or greater than the detection determination value SVth, the larger "T · S" in the relational expression (expression 1) becomes. Therefore, the larger the difference is, the larger the inclination presumption value θ is.

[ mathematical formula 1 ]

When the estimated value θ of the inclination is calculated, the process proceeds to the next step S31. In step S31, it is determined whether or not the estimated inclination value θ is equal to or greater than the inclination determination value θ Th. The inclination determination value θ Th is used as a criterion for determining whether or not to stop the conveyance of the medium M and protect the medium M.

Here, when the control portion 60 can acquire the size of the medium M in the width direction Y before conveyance of the medium M, the control portion 60 may change the inclination determination value θ Th according to the size of the conveyed medium M in the width direction Y. Specifically, the smaller the size of the medium M in the width direction Y, the larger the inclination determination value θ Th is set.

If the medium M being conveyed deviates outward in the width direction Y of the conveyance path 100, the medium M may be damaged. The greater the inclination of the conveyed medium M, the higher the possibility that the medium M is deviated outward in the width direction Y of the conveyance path 100. Further, the medium M having a small size in the width direction Y is less likely to be deviated to the outside of the conveyance path 100 even if the medium M is inclined with respect to the conveyance path 100, as compared with the medium M having a large size in the width direction Y. Therefore, the inclination determination value θ Th is set to be larger as the size of the medium M in the width direction Y is smaller.

In step S31, if the estimated value θ of the inclination is smaller than the inclination determination value θ Th (no), the series of processing shown in fig. 9 is ended. That is, the medium M is conveyed.

On the other hand, when the estimated value θ of the inclination is equal to or greater than the inclination determination value θ Th (yes in S31), the process proceeds to the next step S32. In step S32, error processing is performed. For example, as the error processing, the conveyance of the medium M is suspended. In addition, as the error process, the content about the inclination of the medium M being conveyed with respect to the conveyance path 100 is notified. Then, when the error process is executed, the series of processes shown in fig. 9 is ended.

The operation of the present embodiment will be described with reference to fig. 8 and 10.

As shown in fig. 8, the medium M conveyed along the conveyance path 100 is inclined. Thus, in the example shown in fig. 8, the medium M contacts the electrode 41 of the electrostatic detection sensor 32A before the electrode 41 of the electrostatic detection sensor 32B. Therefore, as shown in fig. 10, at the timing t21, the first signal value SV1 becomes equal to or greater than the determination signal value SVTh. That is, the medium M is detected by the electrostatic detection sensor 32A and is not detected by the electrostatic detection sensor 32B. At the subsequent timing t22, the medium M is in contact with the electrode 41 of the electrostatic detection sensor 32B, and therefore the second signal value SV2 becomes equal to or greater than the determination value SVTh.

That is, in the example shown in fig. 10, the time from the timing T21 to the timing T22 corresponds to the elapsed time T. Thus, by using the relational expression (expression 1), the estimated value θ of the inclination of the medium M is calculated. When the estimated value θ of the inclination is smaller than the inclination determination value θ Th, the conveyance of the medium M is continued, and the image of the medium M is read by the reading units 12 and 13. On the other hand, if the estimated value θ of the inclination is equal to or greater than the inclination determination value θ Th, the medium M may be damaged if the conveyance of the medium M is continued. Thus, the conveyance of the medium M is suspended.

According to the present embodiment, the following effects can be obtained in addition to the effects similar to the above (1) to (4).

(5) By arranging the plurality of electrodes 41 along the width direction Y, the estimated value θ of the inclination of the medium M conveyed along the conveyance path 100 can be calculated.

(6) When the calculated estimated value θ of the inclination is equal to or greater than the inclination determination value θ Th, the conveyance of the medium M is stopped. Therefore, breakage of the medium M can be suppressed.

(7) In the present embodiment, the inclination determination value θ Th is set by the size of the medium M to be conveyed in the width direction Y. Therefore, when the medium M having a small size in the width direction Y is conveyed, the inclination determination value θ Th is set to a large value, and therefore, even if the medium M is slightly inclined, the conveyance of the medium M is continued. That is, the image of the medium M can be read.

(8) In the present embodiment, the plurality of electrodes 41 are disposed upstream of the reading units 12 and 13 in the transport direction. Therefore, it is possible to determine whether or not to stop the conveyance of the medium M before the reading of the image of the medium M is started by the reading units 12 and 13. Therefore, the effect of suppressing damage to the medium M can be improved.

(9) In the image reading apparatus 10, the inclination of the medium M can be detected based on the reading results of the reading units 12 and 13. By comparing the detected value of the inclination of the medium M with the estimated value θ of the inclination, it is possible to determine whether the estimated value θ of the inclination is correct.

Third embodiment

Next, a third embodiment of the medium conveyance device and the image reading device will be described with reference to fig. 11 and 12. In the present embodiment, the arrangement position of the electrodes of the electrostatic detection sensor, the processing contents of the control unit 60, and the like are different from those of the second embodiment. In the following description, portions different from the above-described embodiments will be mainly described, and the same reference numerals are given to the same or corresponding component structures as those of the above-described embodiments, and redundant description will be omitted.

As shown in fig. 11, the electrode 41 of the electrostatic detection sensor 32A is disposed on the downstream side X in the transport direction from the electrode 41 of the electrostatic detection sensor 32B. Among the plurality of electrostatic detection sensors 32A and 32B, the electrostatic detection sensor 32A in which the electrode 41 is disposed on the downstream side X in the transport direction also serves as a sensor for detecting the leading end Ma of the medium M. The distance between the electrode 41 of the electrostatic detection sensor 32A and the electrode 41 of the electrostatic detection sensor 32B in the conveyance direction is defined as a conveyance direction distance Dx, and the distance between the electrodes 41 in the width direction Y is defined as a width direction distance Dy.

Next, a flow of processing in the control unit 60 when the medium M is conveyed will be described with reference to fig. 12. Each of the processes shown in fig. 12 is executed by the control unit 60. Further, each process shown in fig. 12 is for calculating an estimated value θ of the inclination of the medium M conveyed along the conveyance path 100.

As shown in fig. 12, in the first step S41, it is determined whether or not the conveyance mode of the medium M is the receipt mode. When the conveyance mode is the receipt mode (S41: YES), the series of processing shown in FIG. 12 is ended. On the other hand, if the conveyance mode is not the receipt mode (S41: NO), the process proceeds to the next step S42. In step S42, conveyance of the medium M is started. That is, the driving of the drive motor 25 is started. Thus, the rotation of the feeding roller 21, the conveying rollers 231 and 232, and the discharge rollers 241 and 242 is started. Thereby, the medium M is conveyed at a fixed conveyance speed.

In the next step S43, it is determined whether or not the signal value SVPe, which is the magnitude of the amplified signal SGa input from the charge detection circuit 42 of the electrostatic detection sensor 32A to the control unit 60, is equal to or greater than the determination signal value SVTh. When the magnitude of the amplified signal SGa input from the charge detection circuit 42 of the electrostatic detection sensor 32B to the control unit 60 is set as the signal value SVS, the electrode 41 of the electrostatic detection sensor 32A is disposed on the downstream side X in the transport direction from the electrode 41 of the electrostatic detection sensor 32B, and therefore the signal value SVPe does not become equal to or greater than the determination signal value SVTh prior to the signal value SVS. In other words, if the signal value SVPe becomes equal to or greater than the determination signal value SVTh before the signal value SVS, some abnormality may occur. Therefore, in step S43, regardless of whether or not the signal value SVS is smaller than the determination signal value SVTh, if the signal value SVPe is equal to or greater than the determination signal value SVTh (yes), the series of processing shown in fig. 12 is ended.

In step S43, when the signal value SVPe is equal to or greater than the determination signal value SVTh (yes), the process may be shifted to step S50, which will be described later. That is, the conveyance of the medium M can be stopped.

On the other hand, if the signal value SVPe is smaller than the determination signal value SVTh (S43: NO), the process proceeds to the next step S44. In step S44, it is determined whether or not the signal value SVS is equal to or greater than the determination signal value SVTh. If the signal value SVS is smaller than the determination signal value SVTh (S44: no), the process proceeds to step S43 described above. On the other hand, when the signal value SVS is equal to or greater than the determination signal value SVTh (yes in S44), the electrostatic detection sensor 32B can detect the medium M, and the process proceeds to the next step S45. In step S45, measurement of the elapsed time T from the time point at which the signal value SVS becomes equal to or greater than the determination signal value SVTh is started.

In step S46, it is determined whether or not the signal value SVPe is equal to or greater than the determination signal value SVTh. If the signal value SVPe is smaller than the determination signal value SVTh (S46: NO), the determination of step S46 is repeated until the signal value SVPe becomes equal to or larger than the determination signal value SVTh. On the other hand, when the signal value SVPe is equal to or greater than the determination signal value SVTh (S46: yes), the electrostatic detection sensor 32A can detect the leading end Ma of the medium M, and the process proceeds to step S47. In step S47, the measurement of the elapsed time T is ended.

As described above, the electrostatic detection sensor 32A also functions as a sensor that detects the leading end Ma of the medium M. Thus, when the electrostatic detection sensor 32A detects the medium M, the position of the leading end Ma of the medium M in the conveyance direction can be estimated. As a result, the timing at which the reading units 12 and 13 read the image of the medium M can be adjusted.

Next, in step S48, the estimated value θ of the inclination of the medium M is calculated. For example, the estimated value θ of the inclination can be calculated by using the following relational expression (expression 2). In the relational expression (expression 2), "S" is the conveyance speed of the medium M. In the relational expression (expression 2), "T · S-Dx" corresponds to the amount of movement of the medium M from the time point when the medium M is in contact with the first electrode of the two electrodes 41 to the time point when the medium M is in contact with the second electrode. Then, according to the relational expression (expression 2), the more the amount of movement, the larger the estimated value θ of the inclination.

[ mathematical formula 2 ]

When the estimated value θ of the inclination is calculated, the process proceeds to the next step S49. In step S49, it is determined whether or not the estimated inclination value θ is equal to or greater than the inclination determination value θ Th. If the estimated value θ of the inclination is smaller than the inclination determination value θ Th (S49: no), the series of processing shown in fig. 12 is ended. That is, the medium M is conveyed.

On the other hand, when the estimated value θ of the inclination is equal to or greater than the inclination determination value θ Th (yes in S49), the process proceeds to the next step S50. In step S50, error processing is performed. For example, as the error processing, the conveyance of the medium M is suspended. In addition, as the error process, the content about the inclination of the medium M being conveyed is notified. Then, when the error process is executed, the series of processes shown in fig. 12 is ended.

According to the present embodiment, the following effects can be obtained in addition to the effects similar to the above (1) to (9).

(10) Even if the two electrodes 41 are arranged at different positions in the transport direction, the estimated value θ of the inclination of the medium M can be calculated because the positions of the two electrodes 41 in the width direction Y are different from each other.

(11) The electrostatic detection sensor 32A also serves as a sensor that detects the leading end Ma of the medium M. Therefore, the detection sensor 31 shown in fig. 1 may be omitted.

Fourth embodiment

Next, a fourth embodiment of the medium conveyance device and the image reading device will be described with reference to fig. 13 to 16. In the present embodiment, the number of the electrostatic detection sensors and the processing contents of the control unit 60 are different from those of the second embodiment. In the following description, portions different from the above-described embodiments will be mainly described, and the same reference numerals are given to the same or corresponding component structures as those of the above-described embodiments, and redundant description will be omitted.

As shown in fig. 13, the medium transport apparatus 20 includes three electrostatic detection sensors 32A, 32B, and 32C. Each of the electrostatic detection sensors 32A to 32C includes an electrode 41 disposed on the downstream side X in the transport direction from the nip portion 22, and a charge detection circuit 42 connected to the electrode 41. In the example shown in fig. 13, the three electrodes 41 are arranged at the same position in the conveyance direction of the medium M. The electrode 41 of the electrostatic detection sensor 32C is disposed between the electrode 41 of the electrostatic detection sensor 32A and the electrode 41 of the electrostatic detection sensor 32B. For example, the electrode 41 of the electrostatic detection sensor 32C is disposed at an intermediate position between the electrode 41 of the electrostatic detection sensor 32A and the electrode 41 of the electrostatic detection sensor 32B.

Here, a comparative example including two electrostatic detection sensors 32A and 32B will be described with reference to fig. 14. In the comparative example, when the medium M is inclined with respect to the conveyance path 100, as shown in fig. 14, the two electrostatic detection sensors 32A, 32B may detect the medium M at the same time.

In the present embodiment, three electrodes 41 are arranged along the width direction Y. Therefore, when the medium M is inclined with respect to the conveyance path 100, the three electrostatic detection sensors 32A to 32C do not simultaneously detect the medium M. For example, as shown in fig. 15, even if the two electrostatic detection sensors 32A, 32B simultaneously detect the medium M, the timing at which the electrostatic detection sensor 32C detects the medium M is different from the timing at which the two electrostatic detection sensors 32A, 32B detect the medium M.

In this case, the electrostatic detection sensor 32C first detects the medium M. After that, the electrostatic detection sensors 32A, 32B detect the medium M. Therefore, as shown in fig. 16, at the timing t41, the third signal value SV3 among the first signal value SV1, the second signal value SV2, and the third signal value SV3 becomes equal to or greater than the determination signal value SVTh. The third signal value SV3 is the magnitude of the amplified signal SGa input from the charge detection circuit 42 of the electrostatic detection sensor 32C to the control unit 60. The first signal value SV1 is the magnitude of the amplified signal SGa input from the charge detection circuit 42 of the electrostatic detection sensor 32A to the control unit 60. The second signal value SV2 is the magnitude of the amplified signal SGa input from the charge detection circuit 42 of the electrostatic detection sensor 32B to the control unit 60.

Next, at the subsequent timing t42, the first signal value SV1 and the second signal value SV2 become equal to or greater than the determination signal value SVTh, respectively. In this case, the difference between the timing at which the electrostatic detection sensor 32A detects the medium M and the timing at which the electrostatic detection sensor 32B detects the medium M is smaller than the difference determination value Δ TTh. Therefore, in this case, the elapsed time T corresponds to the time from the timing T41 to the timing T42. Then, by substituting the elapsed time T, the transport speed S of the medium M, and the distance Dy in the width direction Y between the electrode 41 of the electrostatic detection sensor 32C and the electrode 41 of the electrostatic detection sensor 32A into the relational expression (expression 1), the estimated value θ of the inclination of the medium M can be calculated.

That is, in the present embodiment, when the medium M is inclined with respect to the conveyance path 100, it can be suppressed that the medium M is erroneously determined not to be inclined with respect to the conveyance path 100.

Further, if the difference between the timing at which the electrostatic detection sensor 32A detects the medium M and the timing at which the electrostatic detection sensor 32B detects the medium M is equal to or greater than the difference determination value Δ TTh, it can be determined that the timing at which the electrostatic detection sensor 32A detects the medium M is different from the timing at which the electrostatic detection sensor 32B detects the medium M. Therefore, in this case, the difference between the timing at which the electrostatic detection sensor 32A detects the medium M and the timing at which the electrostatic detection sensor 32B detects the medium M corresponds to the elapsed time T. Then, by substituting the elapsed time T, the transport speed S of the medium M, and the distance Dy in the width direction Y between the electrode 41 of the electrostatic detection sensor 32A and the electrode 41 of the electrostatic detection sensor 32B into the relational expression (expression 1), the estimated value θ of the inclination of the medium M can be calculated.

Fifth embodiment

Next, a fifth embodiment of the medium conveyance device and the image reading device will be described with reference to fig. 17 and 18. In the present embodiment, the number of the electrostatic detection sensors and the processing contents of the control unit 60 are different from those of the second embodiment. In the following description, portions different from the above-described embodiments will be mainly described, and the same reference numerals are given to the same or corresponding component structures as those of the above-described embodiments, and redundant description will be omitted.

As shown in fig. 17, the medium conveyance device 20 of the present embodiment includes four or more electrostatic detection sensors. In the example shown in fig. 17, the medium transport apparatus 20 includes six electrostatic detection sensors 32a1, 32B1, 32C1, 32D1, 32E1, and 32F 1. Each of the electrostatic detection sensors 32A 1-32F 1 has an electrode 41 and a charge detection circuit 42. Each electrode 41 is disposed on the downstream side X in the transport direction from the nip portion 22. Further, the electrodes 41 are arranged along the width direction Y. For example, the electrodes 41 are arranged at equal intervals in the width direction Y.

By arranging the plurality of electrodes 41 along the width direction Y in this manner, the dimension of the medium M in the width direction Y and the positions of the side ends Ms1, Ms2 of the medium M can be detected. The side ends Ms1, Ms2 of the medium M here are the ends of the medium M in the width direction Y.

The magnitude of the amplified signal SGa input from the charge detection circuit 42 of the electrostatic detection sensor 32a1 to the control unit 60 is referred to as a first signal value SV 11. The magnitude of the amplified signal SGa input from the charge detection circuit 42 of the electrostatic detection sensor 32B1 to the control unit 60 is referred to as a second signal value SV 12. The magnitude of the amplified signal SGa input to the controller 60 from the charge detection circuit 42 of the electrostatic detection sensor 32C1 is referred to as a third signal value SV 13. The magnitude of the amplified signal SGa input from the charge detection circuit 42 of the electrostatic detection sensor 32D1 to the control unit 60 is referred to as a fourth signal value SV 14. The magnitude of the amplified signal SGa input from the charge detection circuit 42 of the electrostatic detection sensor 32E1 to the control section 60 is referred to as a fifth signal value SV 15. The magnitude of the amplified signal SGa input to the control unit 60 from the charge detection circuit 42 of the electrostatic detection sensor 32F1 is referred to as a sixth signal value SV 16.

In the example shown in fig. 17, of the both side ends Ms1, Ms2 of the medium M, the first side end Ms1 is located between the electrode 41 of the electrostatic detection sensor 32a1 and the electrode 41 of the electrostatic detection sensor 32B 1. The second side end Ms2 is located between the electrode 41 of the electrostatic detection sensor 32E1 and the electrode 41 of the electrostatic detection sensor 32F 1. Therefore, the electrode 41 of the electrostatic detection sensor 32a1 and the electrode 41 of the electrostatic detection sensor 32F1 do not contact the medium M. On the other hand, the electrodes 41 of the other electrostatic detection sensors 32B 1-32E 1 are in contact with the medium M.

As a result, as shown in fig. 18, the second signal value SV12 becomes equal to or greater than the second determination signal value SVTh2, and the third signal value SV13 becomes equal to or greater than the third determination signal value SVTh 3. The fourth signal value SV14 is equal to or greater than the fourth determination signal value SVTh4, and the fifth signal value SV15 is equal to or greater than the fifth determination signal value SVTh 5. On the other hand, the first signal value SV11 is smaller than the first determination signal value SVTh1, and the sixth signal value SV16 is smaller than the sixth determination signal value SVTh 6. Thus, the controller 60 can determine that the first side end Ms1 of the medium M is located between the electrode 41 of the electrostatic detection sensor 32a1 and the electrode 41 of the electrostatic detection sensor 32B 1. Further, the controller 60 can determine that the second side end Ms2 of the medium M is positioned between the electrode 41 of the electrostatic detection sensor 32E1 and the electrode 41 of the electrostatic detection sensor 32F 1. Further, based on the determination result, the control unit 60 can derive the size of the medium M in the width direction Y.

The dimension of the medium M in the width direction Y derived by using the electrostatic detection sensors 32a1 to 32F1 is referred to as an estimated value of the dimension of the medium M in the width direction Y. In the image reading apparatus 10, the size of the medium M in the width direction Y can be detected based on the reading results of the reading units 12 and 13. By comparing the detected value of the dimension of the medium M in the width direction Y with the estimated value of the dimension of the medium M in the width direction Y, it is possible to determine whether the detected value of the dimension of the medium M in the width direction Y is correct.

Incidentally, the amount of adhesion of the electric charges is large at the portion of the medium M close to the nip 22 and the feeding roller 21 in the width direction Y. On the other hand, the amount of charge adhering to the portion of the medium M distant from the nip 22 and the feed roller 21 in the width direction Y is small. Therefore, even if the electrode 41 comes into contact with a portion of the medium M that is distant from the nip portion 22 and the feeding roller 21 in the width direction Y, the signal value is unlikely to increase. Thus, the first determination signal value SVTh1 and the sixth determination signal value SVTh6 corresponding to the electrostatic detection sensors 32a1 and 32F1 are small. The second determination signal value SVTh2 and the fifth determination signal value SVTh5 corresponding to the electrostatic detection sensors 32B1 and 32E1 are greater than the first determination signal value SVTh1 and the sixth determination signal value SVTh 6. The third determination signal value SVTh3 and the fourth determination signal value SVTh4 corresponding to the electrostatic detection sensors 32C1 and 32D1 are larger than the second determination signal value SVTh2 and the fifth determination signal value SVTh 5.

By changing the magnitude of the corresponding determination signal value for each of the electrostatic detection sensors 32a 1-32F 1 in this manner, the positions of the side ends Ms1, Ms2 of the medium M can be detected well.

Modification example

The above embodiments may be modified and implemented as follows. The above embodiments and the following modifications can be combined and implemented within a range not technically contradictory to each other.

The electrode 41 of the electrostatic detection sensor may be disposed on the downstream side X in the transport direction from the reading units 12 and 13.

In the fifth embodiment, the number of the electrodes 41 arranged along the width direction Y may be any number other than six. For example, the number of the electrodes 41 arranged along the width direction Y may be five, or seven or more.

The inclination determination value θ Th may be fixed to a preset value regardless of the size of the medium M in the width direction Y.

In the second embodiment, when the transport amount of the medium M can be detected, the transport amount of the medium M from the time point when one electrostatic detection sensor detects the medium M to the time point when the other electrostatic detection sensor detects the medium M may be derived, and the estimated value θ of the inclination of the medium M may be derived based on the derived transport amount.

In the fourth embodiment, as shown in fig. 19, the electrode 41 of the electrostatic detection sensor 32C may be disposed on the downstream side X in the transport direction from the electrodes 41 of the other electrostatic detection sensors 32A and 32B. The electrode 41 of the electrostatic detection sensor 32C may be disposed upstream of the electrodes 41 of the other electrostatic detection sensors 32A and 32B in the conveyance direction.

The medium transport device 20 may not include the nip 22 as long as the medium M can be transported toward the downstream X in the transport direction by the rotation of the feed roller 21.

The charge detection circuit 42 may have a configuration different from that shown in fig. 5 as long as it can output a larger signal as the amount of charge moving from the medium M to the electrode 41 increases.

The control unit 60 may be configured as a circuit including: one or more dedicated hardware circuits such as one or more processors operating in accordance with a computer program, dedicated hardware for executing at least a part of various processes, or a combination thereof. As the dedicated hardware, for example, ASIC as an application specific integrated circuit can be cited. The processor includes a CPU and memories such as a RAM and a ROM, and the memories store program codes or instructions configured to cause the CPU to execute processing. Memory, i.e., storage media, includes all available media that can be accessed by a general purpose or special purpose computer.

The medium transport device 20 may be applied to devices other than the image reading device 10. For example, the medium transport apparatus 20 may be applied to a recording apparatus such as a printer.

Next, the technical ideas and the operational effects thereof obtained by the above embodiments and modifications will be described.

(A) The medium transport device is a medium transport device that transports a medium along a transport path. The medium conveying device includes: a feeding roller that rotates to convey the medium; an electrode disposed downstream of the feeding roller in the conveying path and having conductivity; and a charge detection circuit that outputs a signal having a magnitude corresponding to a movement amount of the electric charge from the medium to the electrode when the medium conveyed along the conveyance path comes into contact with the electrode and the electric charge is moved from the medium to the electrode.

When the medium is conveyed along the conveyance path by the rotation of the feeding roller, static electricity is generated between the medium and the feeding roller because the medium rubs against the feeding roller. That is, charge is attached to the media. According to the above configuration, when the medium to which the electric charge is attached is transported, the electrode is in contact with the medium. Thus, the electric charge moves from the medium to the electrode, and a signal of a magnitude corresponding to the amount of movement of the electric charge from the medium to the electrode is output from the electric charge detection circuit. Therefore, according to the above configuration, the medium can be detected without providing an optical sensor in the conveyance path.

(B) One aspect of the medium transport device includes a nip portion that nips the medium together with the feed roller. In this case, the electrode is disposed downstream of the nip portion in the conveying path.

According to the above configuration, the medium conveyed along the conveyance path is nipped between the feed roller and the nip portion. Therefore, a larger static electricity can be generated between the feeding roller and the nip portion and the medium. As a result, the amount of charge attached to the medium can be increased.

(C) One aspect of the medium conveyance device includes a control unit that determines that the medium is in contact with the electrode when a magnitude of a signal output from the charge detection circuit is equal to or greater than a detection determination value when the medium is conveyed from an upstream side to a downstream side in a conveyance direction along the conveyance path.

According to the above configuration, the medium conveyed along the conveyance path can be detected by the signal output from the charge detection circuit.

(D) In one aspect of the medium transport apparatus, a plurality of electrodes arranged at different positions in a width direction of the medium transported along the transport path are provided as the electrodes, and a plurality of the charge detection circuits corresponding to the plurality of electrodes are provided as the charge detection circuits. In this case, the control unit calculates the estimated value of the inclination of the medium as follows: the estimated value of the inclination is larger as a difference between a time point at which a signal magnitude output from the charge detection circuit corresponding to a first electrode of the plurality of electrodes becomes equal to or larger than the detection determination value and a time point at which a signal magnitude output from the charge detection circuit corresponding to a second electrode of the plurality of electrodes becomes equal to or larger than the detection determination value is larger.

In the middle of conveyance, the direction of the medium may be inclined with respect to the conveyance direction of the medium along the conveyance path. According to the above configuration, a plurality of electrodes are arranged along the width direction. Therefore, the presumption value of the inclination of the medium can be calculated by the timing at which the first electrode of the plurality of electrodes detects the medium and the timing at which the second electrode detects the medium.

(E) In one aspect of the above-described medium transporting apparatus, a third electrode disposed between the first electrode and the second electrode in the width direction is provided as the electrode, and the charge detection circuit is provided corresponding to the third electrode. A time point at which the magnitude of the signal output from the charge detection circuit corresponding to the first electrode becomes equal to or greater than the detection determination value is set as a first time point, a time point at which the magnitude of the signal output from the charge detection circuit corresponding to the second electrode becomes equal to or greater than the detection determination value is set as a second time point, and a time point at which the magnitude of the signal output from the charge detection circuit corresponding to the third electrode becomes equal to or greater than the detection determination value is set as a third time point. In this case, when the difference between the first time point and the second time point is equal to or less than a difference determination value, the control unit calculates the estimated value of inclination as follows: the estimated value of the inclination is larger as a difference between the first time point and the third time point is larger.

According to the above configuration, the accuracy of calculating the estimated value of the inclination of the medium can be improved by using the three electrodes arranged along the width direction.

(F) One aspect of the medium conveyance device includes a control unit that determines that the medium is in contact with the electrode when a magnitude of a signal output from the charge detection circuit is equal to or greater than a detection determination value when the medium is conveyed from an upstream side to a downstream side in a conveyance direction along the conveyance path. In this case, a plurality of electrodes arranged at different positions in the width direction of the medium conveyed along the conveyance path are provided as the electrodes, and a plurality of the charge detection circuits corresponding to the plurality of electrodes are provided as the charge detection circuits. In the plurality of electrodes, the detection determination value corresponding to the electrode distant from the nip portion in the width direction is smaller than the detection determination value corresponding to the electrode located near the nip portion in the width direction.

In the width direction, the amount of charge adhesion of a portion of the medium distant from the nip portion is smaller than that of a portion close to the nip portion. According to the above configuration, values corresponding to the positional relationship between the nip portion and the electrode in the width direction are set as the detection determination values corresponding to the respective electrodes. Therefore, even if the electrode is at a position distant from the nip portion in the width direction, the medium can be detected when the medium comes into contact with the electrode.

(G) In the above-described aspect of the medium transport apparatus, when the medium is transported from the upstream to the downstream in the transport direction along the transport path, the control unit may determine that the side end of the medium is located between two electrodes adjacent in the width direction when a magnitude of a signal output from the charge detection circuit corresponding to one of the two electrodes is equal to or larger than the detection determination value and a magnitude of a signal output from the charge detection circuit corresponding to the other electrode is smaller than the detection determination value.

According to the above configuration, by arranging the plurality of electrodes along the width direction, the side edge of the medium, that is, the dimension of the medium in the width direction can be estimated.

(H) An embodiment of an image reading apparatus includes: the above-described medium conveyance device; and a reading section that reads an image of the medium conveyed along the conveyance path.

According to this configuration, the medium conveyed along the conveyance path can be detected.

(I) In one aspect of the image reading apparatus, the reading unit is disposed downstream of the electrode in the conveyance path.

According to the above configuration, the medium conveyed along the conveyance path can be detected before the reading unit starts reading the image of the medium.

(J) One aspect of the image reading apparatus includes: the above-described medium conveyance device; and a reading section that reads an image of the medium conveyed along the conveyance path. In this case, the control unit may stop the conveyance of the medium when the estimated value of the inclination is equal to or greater than an inclination determination value. According to this structure, the medium can be protected.

(K) In one aspect of the image reading apparatus, the control unit may increase the inclination determination value as a size of the medium conveyed along the conveyance path in a width direction decreases.

When the medium having a large width dimension is inclined, the amount of deviation of the medium from the conveyance path is easily increased even if the inclination is small. On the other hand, when the medium having a small width dimension is inclined, even if the inclination is large, the amount of deviation of the medium from the conveyance path is not easily increased. According to the above configuration, the smaller the dimension of the medium in the width direction, the larger the inclination determination value. Therefore, when a document having a small width direction is conveyed, conveyance of the medium is not easily stopped.

(L) the medium detecting method of the medium transporting device is applied to a medium transporting device including: a feed roller that rotates to convey a medium along a conveyance path; an electrode disposed downstream of the feeding roller in the conveying path and having conductivity; and a charge detection circuit that outputs a signal having a magnitude corresponding to a movement amount of the electric charge from the medium to the electrode when the medium conveyed along the conveyance path comes into contact with the electrode and the electric charge is moved from the medium to the electrode. Further, according to the medium detecting method, when the medium is conveyed from the upstream to the downstream in the conveying direction along the conveying path, the control unit of the medium conveying apparatus is caused to execute the step of determining that the medium is in contact with the electrode when the magnitude of the signal output from the charge detecting circuit is equal to or larger than a detection determination value. With this configuration, the same operational effects as those of the medium transport device can be obtained.