JP2017178467A - Medium conveyance device and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent reduction in detection accuracy of multi-feeding of media.SOLUTION: A medium conveyance device includes: a conveyance unit which conveys a medium P in a first direction; a transmission unit 30a which transmits an ultrasonic wave for detecting multi-feeding of conveyed media P from a transmission surface; a reception unit 30b which receives the ultrasonic wave transmitted from the transmission surface with a reception surface; a first guide unit which is arranged between the transmission unit 30a and the reception unit 30b and guides the conveyed media P; and a second guide unit which is arranged between the transmission unit 30a and the reception unit 30b and is arranged so as to be apart by a prescribed distance from the first guide unit. The first guide unit includes: a first opening facing the transmission surface; and a first protrusion part which is arranged on the side opposite to the center of the medium P in the first opening with respect to the second direction orthogonal to the first direction. The second guide unit has a second opening facing the reception surface.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a medium conveying apparatus and an image forming apparatus.

  2. Description of the Related Art Conventionally, an image forming apparatus that includes a medium conveying apparatus that conveys a medium such as a document and scans the medium fed and conveyed to the medium conveying apparatus to form an image is used (for example, Patent Document 1). reference.).

  In such a medium transport apparatus, there is a technique that uses ultrasonic waves to detect that a plurality of media are transported in an overlapped state, that is, a medium overrun.

JP2015-217998A

  However, in the conventional medium transport apparatus, when the ultrasonic wave transmitted from the ultrasonic wave transmitting unit wraps around from the end of the medium and is received by the ultrasonic wave receiving unit, the detection accuracy of the medium overrun is high. May decrease.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a medium transport apparatus and an image forming apparatus that can solve the conventional problems and prevent a decrease in detection accuracy of medium overrun.

  Therefore, in the medium conveying apparatus of the present invention, the conveying unit that conveys the medium in the first direction, the transmitting unit that transmits ultrasonic waves from the transmitting surface for detecting double feeding of the medium to be conveyed, A receiving unit that receives ultrasonic waves transmitted from the transmitting surface at the receiving surface, a first guide unit that is disposed between the transmitting unit and the receiving unit and guides a medium to be conveyed, and the transmitting unit and the receiving unit And a second guide part arranged at a predetermined distance from the first guide part, the first guide part facing the transmission surface. And a first protrusion disposed on a side opposite to the center of the medium in the first opening with respect to a second direction orthogonal to the first direction, and the second guide The part has a second opening facing the receiving surface.

  The image forming apparatus of the present invention includes the medium transport device.

  According to the present invention, in the medium transport device, it is possible to prevent a decrease in detection accuracy of medium heavy running.

1 is an external view showing a medium transport device according to a first embodiment of the present invention. It is principal part explanatory drawing of the medium conveying apparatus in the 1st Embodiment of this invention. It is the 1st cross-sectional view which expanded the principal part of the conveyance path of the medium in the 1st Embodiment of this invention. It is the top view to which the principal part of the upper side guide surface and lower side guide surface in the 1st Embodiment of this invention was expanded. It is the 2nd cross-sectional view which expanded the principal part of the conveyance path of the medium in the 1st Embodiment of this invention. It is the 3rd transverse cross section which expanded the principal part of the conveyance path of the medium in the 1st embodiment of the present invention. It is the cross-sectional view which expanded the principal part of the conveyance path of the medium in a 1st comparative example. It is a figure explaining the control system for heavy run detection of the medium conveying apparatus in the 1st Embodiment of this invention. It is the 1st cross-sectional view which expanded the principal part of the conveyance path of the medium in the 2nd Embodiment of this invention. It is the top view to which the principal part of the upper side guide surface and the lower side guide surface in the 2nd Embodiment of this invention was expanded. It is the 2nd cross-sectional view which expanded the principal part of the conveyance path of the medium in the 2nd Embodiment of this invention. It is the cross-sectional view which expanded the principal part of the conveyance path of the medium in a 2nd comparative example. It is a figure explaining the control system for heavy run detection of the medium conveying apparatus in the 2nd Embodiment of this invention. It is the top view to which the principal part of the upper side guide surface and the lower side guide surface in the 3rd Embodiment of this invention was expanded. It is the top view to which the principal part of the upper side guide surface and lower side guide surface in the 4th Embodiment of this invention was expanded.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an external view showing a medium conveying apparatus according to the first embodiment of the present invention, and FIG. 2 is an explanatory view of a main part of the medium conveying apparatus according to the first embodiment of the present invention. 2A is an external view of the medium transport device, and FIG. 2B is a cross-sectional view of a C portion in FIG.

  In the figure, reference numeral 10 denotes a medium carrying device according to the present embodiment, which is relative to the lower portion 11 as indicated by an arrow B via a lower connecting portion 11 and a movable connecting portion 11a including a hinge. And an upper portion 12 pivotably connected to the upper portion. The medium transport apparatus 10 is loaded into the image forming apparatus such that the lower portion 11 is placed on the upper end of the image forming apparatus (not shown). The image forming apparatus is, for example, a multi function peripheral (MFP) having the functions of a scanner, a printer, a facsimile machine, and a copier. The image forming apparatus includes the medium transport device 10 and includes an inkjet method, an electrophotographic method, A printer, a facsimile machine, or a copying machine may be used as long as it can form an image on a paper such as a printing paper using various methods such as a thermal transfer method. There may be any kind of thing. Here, for convenience of explanation, only the case where the image forming apparatus is a multifunction peripheral and the medium transport apparatus 10 is an automatic document feeder (ADF) loaded in the multifunction peripheral will be described.

  As shown in FIG. 1, the medium conveying apparatus 10 conveys only one medium P in a first direction indicated by an arrow A, and sends it to an image reading unit (not shown) provided in the image forming apparatus. The image reading unit includes, for example, a scanner device such as a flatbed scanner, and scans the medium P that is a document fed by the medium transporting device 10 to read an image on the medium P. . When the medium P is transported, the upper portion 12 is in a closed state so as to cover the lower portion 11. That is, the lower portion 11 includes a lower guide surface 13 as a second guide portion facing upward, and the upper portion 12 includes an upper guide surface 14 as a first guide portion facing downward and is closed. In the state, the lower guide surface 13 and the upper guide surface 14 face each other with a predetermined distance therebetween, and the medium P passes through the gap between the lower guide surface 13 and the upper guide surface 14 and the first guide It is conveyed in the direction of 1. That is, a gap between the lower guide surface 13 and the upper guide surface 14 facing each other functions as a conveyance path for the medium P. In the example shown in FIGS. 1 and 2 (a), the upper portion 12 is rotated so as to be separated from the lower portion 11 and opened for the sake of explanation.

  Further, the medium P is a narrow medium such as a check, bill, receipt, slip size paper, etc., but any type and any size of a single sheet, that is, a single sheet medium. It may be a medium.

  On the upper guide surface 14 of the upper portion 12, a pickup roller 15 and a paper feed roller 16 as a transport unit for transporting the medium P are rotatably disposed. The pickup roller 15 and the paper feed roller 16 receive a driving force from a driving source such as a motor (not shown) and rotate to convey the medium P in the first direction. In addition, the upper conveyance auxiliary roller 18a may be rotatably disposed on the upper guide surface 14 on the downstream side in the first direction from the paper feed roller 16 as necessary. Further, on one side (the right side in FIG. 1) of the paper feed roller 16 on the upper guide surface 14, a transmission unit 30 a that transmits ultrasonic waves for detecting the heavy running of the medium P is disposed. The transmission unit 30a needs to be disposed at a position on the upstream side of the conveyance path of the medium P and avoiding the rollers. Therefore, in the example shown in the figure, the transmitter 30a is separated from the paper feed roller 16 in the second direction (the direction perpendicular to the first direction, that is, the width direction of the upper guide surface 14) by a predetermined distance W1. It is offset and arranged at the position. Since the paper feed roller 16 is disposed at a position substantially corresponding to the center in the width direction of the medium P to be transported, the transmitting unit 30a has a predetermined distance W1 from the center of the medium P in the second direction. It can be said that it is offset.

  A separation roller 17 for separating the media P one by one is rotatably disposed on the lower guide surface 13 of the lower portion 11. If necessary, a lower conveyance assisting roller 18b can be rotatably disposed on the lower guide surface 13 downstream of the separation roller 17 in the first direction. In addition, on one side (right side in FIG. 1) of the separation roller 17 on the lower guide surface 13, a receiving unit 30b that receives ultrasonic waves for detecting the heavy running of the medium P is disposed. Similar to the transmitter 30a, the receiver 30b needs to be arranged at a position on the upstream side of the conveyance path of the medium P and avoiding rollers. Therefore, in the example shown in the figure, the receiving unit 30b is offset and disposed at a position away from the separation roller 17 in the second direction by a predetermined distance W2. Since the separation roller 17 is disposed at a position substantially corresponding to the center in the width direction of the medium P to be conveyed, the receiving unit 30b is offset by a predetermined distance W2 from the center of the medium P with respect to the second direction. It can be said that it is. The transmitter 30a and the receiver 30b cooperate to function as an ultrasonic sensor.

  In the state where the upper portion 12 and the lower portion 11 are closed, the upper guide surface 14 and the lower guide surface 13 face each other as described above, and further, as shown in FIG. The unit 30a and the receiving unit 30b are opposed to each other, and the paper feed roller 16 and the separation roller 17 are opposed to each other. The paper feed roller 16 and the separation roller 17 function as a central roller. In the example shown in the figure, the transmitter 30a and the receiver 30b are arranged on the right side of the paper feed roller 16 and the separation roller 17, but are arranged on the left side of the paper feed roller 16 and the separation roller 17. May be.

  FIG. 2B is a cross section of a narrow conveyance path of the medium P formed between the upper guide surface 14 and the lower guide surface 13 with the upper portion 12 and the lower portion 11 being closed, A cross section extending in the second direction at the positions of the paper feed roller 16 and the separation roller 17 as well as the transmitting portion 30a and the receiving portion 30b is shown. As shown in FIG. 2B, the transmitter 30a includes a transmitter 31a and a transmitter-side horn 33a that is a cylindrical or truncated cone-shaped cylindrical member surrounding the transmitter 31a. The transmission-side horn 33a enhances the directivity of ultrasonic waves for detecting the heavy run of the medium P, and the first opening 34a, which is an ultrasonic wave exit end, is a transmission surface of the transmitter 31a. It faces 32a and is open to the upper guide surface 14. In addition, an ultrasonic wave is transmitted from the transmission surface 32a of the transmitter 31a. The transmitting surface 32a is a substantially circular surface extending in a direction orthogonal to the central axis of the transmitting horn 33a, and the ultrasonic wave transmitted from the transmitting surface 32a passes through the transmitting horn 33a and the center thereof. The light travels in the axial direction, and is emitted toward the lower guide surface 13 from the first opening 34a.

  The receiving unit 30b includes a receiver 31b and a receiving-side horn 33b that is a cylindrical member or a truncated cone-shaped cylindrical member surrounding the receiver 31b. The reception-side horn 33b enhances the directivity of the ultrasonic wave for detecting the heavy run of the medium P, and the second opening 34b which is the ultrasonic wave inlet end is the reception surface of the receiver 31b. It faces 32b and opens on the lower guide surface 13. The ultrasonic wave transmitted from the transmission surface 32a of the transmitter 31a is received by the reception surface 32b of the receiver 31b. The reception surface 32b is a substantially circular surface extending in a direction perpendicular to the central axis of the reception-side horn 33b, and the ultrasonic wave that has entered from the second opening 34b passes through the reception-side horn 33b. It travels in the direction of the central axis and is received by the receiving surface 32b.

  As shown in FIG. 2B, the distance W2 is a distance between the center of the second opening 34b and the center of the separation roller 17 in the second direction, and the distance W1 is in the second direction. This is the distance between the center of the first opening 34 a and the center of the paper feed roller 16. In the present embodiment, W1> W2. This is because the imaginary straight line L1 passing through the center of the transmitting surface 32a of the transmitter 31a and the center of the receiving surface 32b of the receiver 31b extends in the second direction in the upper guide surface 14 and the lower guide. It is shown that it is inclined by a predetermined angle with respect to the direction orthogonal to the surface 13. In the present embodiment, the first opening 34a and the second opening 34b oppose each other in the extending direction of the virtual straight line L1.

  As described above, the transmitting unit 30a and the receiving unit 30b are inclined with respect to the conveyance surface of the medium P, that is, the surface of the medium P to be conveyed, in order to improve the detection accuracy of the heavy running of the medium P. ing. In the example shown in the figure, the transmitting unit 30a and the receiving unit 30b have a transverse cross section in which the traveling direction of the ultrasonic wave traveling along the central axis of the transmitting side horn 33a and the receiving side horn 33b extends in the second direction. In FIG. 3, the medium P is disposed so as to be inclined at a predetermined angle of 90 degrees or less with respect to the conveyance surface (or conveyance path) of the medium P.

  Next, details of the configuration of the transmitting unit 30a and the receiving unit 30b will be described.

  FIG. 3 is an enlarged first cross-sectional view of the main part of the medium conveyance path in the first embodiment of the present invention, and FIG. 4 is an upper guide surface and a lower guide in the first embodiment of the present invention. FIG. 5 is a second cross-sectional view enlarging the main part of the medium transport path in the first embodiment of the present invention, and FIG. 6 is the first embodiment of the present invention. FIG. 7 is an enlarged cross-sectional view of the main part of the medium transport path in the first comparative example, and FIG. 7 is an enlarged cross-sectional view of the main part of the medium transport path in the first comparative example. 4A is a plan view of the upper guide surface, and FIG. 4B is a plan view of the lower guide surface.

  As shown in FIG. 7, the ultrasonic wave transmitted from the transmission surface 32a of the transmitter 31a mainly travels in the direction of the central axis of the transmission-side horn 33a and passes through the medium P as indicated by the arrow D. The signal is attenuated and received by the receiving surface 32b of the receiver 31b. However, a part of the ultrasonic wave is reflected on the surface of the medium P as indicated by the arrow D1, and then diffracted at the end in the width direction of the medium P without being attenuated as indicated by the arrow D2. , It may reach into the receiving horn 33b. In particular, when the medium P is narrow, the possibility increases. As described above, when a part of the ultrasonic waves diffracts the end portion in the width direction of the medium P and reaches the reception-side horn 33b, the detection accuracy of the heavy running of the medium P is lowered.

  Therefore, in the present embodiment, the first rib 21 as the first protrusion is disposed on the upper guide surface 14 as the first guide portion, and the lower guide surface 13 as the second guide portion. A second rib 22 is provided as a second protrusion. Note that both the first rib 21 and the second rib 22 do not necessarily have to be provided, and only one of them may be provided, but here both are provided. An example will be described.

  As shown in FIG. 3, the first rib 21 is a protrusion that protrudes downward (toward the lower guide surface 13) from the upper guide surface 14, as shown in FIG. 4 (a). Furthermore, it is an elongated protrusion extending in the first direction in plan view. Further, as shown in FIG. 3, the second rib 22 is a protrusion protruding upward from the lower guide surface 13 (toward the upper guide surface 14), as shown in FIG. 4B. As shown, the projection is an elongated protrusion extending in the first direction in plan view.

  In addition, the dimension of the width direction (second direction) of the first rib 21 is smaller than that of the second rib 22. This is to reduce the transport load of the medium P. In the present embodiment, since the medium P is transported while abutting against the upper guide surface 14, the width of the first rib 21 disposed on the upper guide surface 14 is narrow, that is, the dimension in the width direction is small. Is desirable. If necessary, the width in the width direction of the first rib 21 can be made larger than that of the second rib 22.

  Further, the first rib 21 and the second rib 22 face each other in a direction orthogonal to the upper guide surface 14 and the lower guide surface 13. Further, the first rib 21 and the second rib 22 may be formed integrally with the upper guide surface 14 and the lower guide surface 13, or may be separately formed and the upper guide surface 14 may be formed separately. It may be attached to the surface 14 and the lower guide surface 13.

  Further, the first rib 21 and the second rib 22 are arranged on the opposite side to the center of the medium P in the first opening 34a, that is, near the end of the medium P in the width direction with respect to the second direction. It is installed. In the example shown in the figure, the first rib 21 and the second rib 22 are arranged outside the first opening 34a and the second opening 34b in the width direction of the medium P in the second direction. Has been. Desirably, the first rib 21 and the second rib 22 are located between the end of the medium P in the width direction and the first opening 34a and the second opening 34b. More preferably, the first rib 21 and the second rib 22 are disposed in proximity to the first opening 34a and the second opening 34b.

  As shown in FIG. 3, at least a substantial part of the gap between the upper guide surface 14 and the medium P is blocked by the first rib 21 at a portion outside the first opening 34a in the width direction of the medium P. Is done. As a result, the ultrasonic wave reflected from the surface of the medium P is prevented from traveling to the end in the width direction of the medium P. In addition, the second rib 22 blocks at least a substantial portion of the gap between the lower guide surface 13 and the medium P at a portion outside the second opening 34b in the width direction of the medium P. Thereby, the ultrasonic wave diffracted at the end in the width direction of the medium P is prevented from traveling to the second opening 34b. Therefore, the ultrasonic wave reflected from the surface of the medium P is effectively prevented from diffracting the end portion in the width direction of the medium P and reaching the reception-side horn 33b, and the detection accuracy of the heavy run of the medium P is reduced. Can be effectively prevented.

  As shown in FIG. 5, for example, the width dimension of the first rib 21 is about 1.5 [mm], and the width dimension of the second rib 22 is about 4.5 [mm]. be able to. Since the medium P is conveyed while abutting against the upper guide surface 14 and does not abut against the lower guide surface 13, the width of the second rib 22 disposed on the lower guide surface 13 is increased, that is, in the width direction. Even if the size of the medium is increased, the transport load of the medium P does not increase. In addition, the width direction dimension of the first rib 21 and the second rib 22 is within the range of 0.1 to 5.0 [mm], the upper guide surface 14 and the lower guide surface 13 and the medium P. The ultrasonic waves passing through the gap can be effectively blocked.

  Further, it is desirable that the range in which the first rib 21 and the second rib 22 face each other in the width direction of the medium P, that is, the second direction, is 0.1 [mm] or more. In the medium conveying apparatus 10 according to the present embodiment, the assembly error between the upper portion 12 and the lower portion 11 is considered to be ± 1.0 [mm] with respect to the second direction. For this reason, if the dimension in the width direction of the second rib 22 is set to about 4.5 [mm] in consideration of a certain margin, the first rib 21 and the first rib 21 are surely secured even if the assembly error occurs. The two ribs 22 can be made to face each other, so that the ultrasonic waves reflected from the surface of the medium P are effectively diffracted at the end in the width direction of the medium P and reach the receiving side horn 33b. Can be prevented. Thus, if the first rib 21 and the second rib 22 face each other with a width of 0.1 [mm] or more, the ultrasonic waves can be effectively blocked, and the weight of the medium P can be reduced. It is possible to effectively prevent a decrease in running detection accuracy.

  If the first rib 21 and the second rib 22 do not face each other, the medium P is deformed toward the lower guide surface 13 at the position of the first rib 21 and escapes. At the position of the second rib 22, it is deformed and escapes toward the upper guide surface 14, that is, escapes in a direction where there is no opposing rib. Therefore, the gap between the first rib 21 or the second rib 22 and the medium P becomes large, and the ultrasonic wave passes through without being blocked.

  Further, in the vertical direction, that is, in the thickness direction of the medium P, as shown in FIG. 6, the thickness dimension of the medium P is E1, and the gap between the first rib 21 and the second rib 22 is E2. In this case, it is preferable that the gap E2 between the first rib 21 and the second rib 22 is three times or more the thickness E1 of the medium P so that the relationship 3E1 ≦ E2 is established.

  Next, the operation of the medium transport apparatus 10 having the above configuration will be described. Here, only the operation for detecting the heavy running of the medium P will be described.

  FIG. 8 is a diagram for explaining the control system for heavy run detection of the medium transport device according to the first embodiment of the present invention.

  As shown in the figure, the medium transport apparatus 10 includes a control unit 40. The control unit 40 is a kind of computer including a microprocessor, ROM, RAM, input / output ports, and the like, and controls the operations of the transmitting unit 30a and the receiving unit 30b to detect the heavy running of the medium P. The controller 40 controls the operations of the pickup roller 15, the paper feed roller 16, the separation roller 17, etc., and controls all operations of the medium transport apparatus 10 including the operation of transporting the medium P. Also good. Further, the control unit 40 may cooperate with a control unit (not shown) included in the image forming apparatus, or may be a part of the control unit.

  In the example shown in the figure, the control unit 40 includes a pulse generation circuit 42, an amplification circuit 43, a filter circuit 44, and an amplification circuit 45. The transmission pulse generated by the pulse generation circuit 42 is amplified by the amplification circuit 43 and then transmitted to the transmitter 31a of the transmission unit 30a. The transmitter 31a transmits an ultrasonic wave according to the received transmission pulse. The ultrasonic wave transmitted from the transmission surface 32a of the transmitter 31a mainly travels in the direction of the central axis of the transmission-side horn 33a as shown by the arrow D, passes through the medium P, attenuates, and is received by the receiver 31b. Is received by the receiving surface 32b. The output signal output from the receiver 31b according to the ultrasonic wave received by the receiving surface 32b is amplified by the amplifier circuit 45 after noise is removed by the filter circuit 44. Based on the amplified output signal of the receiver 31b, the control unit 40 determines whether or not the medium P is conveyed in a state where a plurality of sheets are overlapped, that is, determines whether or not the multifeed is performed.

  In addition, a part of the ultrasonic wave transmitted from the transmission surface 32a of the transmitter 31a is reflected by the surface of the medium P as indicated by the arrow D1, and outwards in the width direction of the medium P from the first opening 34a. Proceed toward. However, since a substantial part of the gap between the upper guide surface 14 and the medium P is blocked by the first ribs 21 at the outer side in the width direction of the medium P than the first opening 34a, the surface of the medium P The ultrasonic waves reflected by the interference with the first rib 21 are greatly attenuated. Further, as indicated by the arrow D2, the ultrasonic wave diffracted at the end in the width direction of the medium P is located at the outer side in the width direction of the medium P from the second opening 34b and the lower guide surface 13 and the medium P. Since a substantial part of the gap between the two ribs 22 is blocked by the second rib 22, it interferes with the second rib 22 and further attenuates.

  Thereby, the ultrasonic waves that are reflected by the surface of the medium P, diffracted at the end in the width direction of the medium P, and reach the reception-side horn 33b are reduced. Therefore, substantially only the ultrasonic wave that has passed through the medium P is received by the receiving surface 32b of the receiver 31b, so that the control unit 40 can accurately determine the double feed, and the medium P with high accuracy. Can detect heavy running.

  As described above, in the present embodiment, the first rib 21 and the second rib 22 are disposed on the outer side in the width direction of the medium P than the first opening 34a and the second opening 34b. Accordingly, it is possible to remove the ultrasonic wave that is reflected by the surface of the medium P, diffracts the end portion in the width direction of the medium P, and reaches the reception-side horn 33b, and receives only the ultrasonic wave that has passed through the medium P. It can be received by the receiving surface 32b of the device 31b. Therefore, the heavy run of the medium P can be detected with high accuracy.

  In other words, in this embodiment, by providing a protrusion structure in the vicinity of the horn of the double feed detection sensor, when a narrow medium is used, the ultrasonic wave reflected on the medium is applied to the guide surface on the medium conveyance path transmission side. It can block | interrupt with the provided projection part, and can reach | attain an ultrasonic wave at the edge part of a medium. In addition, some ultrasonic waves that reach the end of the medium and diffract the end of the medium are also blocked by the protrusion provided on the receiving side of the medium conveyance path, so that entry to the receiving-side horn can be prevented. Therefore, only the ultrasonic wave that has passed through the medium can be detected, and it is possible to normally determine double feeding.

  Next, a second embodiment of the present invention will be described. In addition, about what has the same structure as 1st Embodiment, the description is abbreviate | omitted by providing the same code | symbol. The description of the same operation and the same effect as those of the first embodiment is also omitted.

  FIG. 9 is an enlarged first cross-sectional view of the main part of the medium conveyance path in the second embodiment of the present invention, and FIG. 10 is an upper guide surface and a lower guide in the second embodiment of the present invention. FIG. 11 is a second cross-sectional view in which the main part of the medium transport path in the second embodiment of the present invention is enlarged, and FIG. 12 is a medium in the second comparative example. It is the cross-sectional view which expanded the principal part of this conveyance path. 10A is a plan view of the upper guide surface, and FIG. 10B is a plan view of the lower guide surface.

  As shown in FIG. 12, the ultrasonic wave transmitted from the transmission surface 32a of the transmitter 31a mainly travels in the direction of the central axis of the transmission-side horn 33a and passes through the medium P as indicated by the arrow D. The signal is attenuated and received by the receiving surface 32b of the receiver 31b. However, when the medium P has a relatively narrow width, with respect to the second direction, the end in the width direction of the medium P is in the first opening 34a and the second opening 34b, that is, the first opening 34a. And the second opening 34b is positioned on the inner side of the end portion on the outer side in the width direction, so that a part of the ultrasonic wave is connected to the end portion in the width direction of the medium P and the first end as shown by the arrow D3. There may be a case where it passes through the widthwise outer ends of the opening 34a and the second opening 34b and reaches the receiving side horn 33b directly without passing through the medium P. As described above, when a part of the ultrasonic waves directly reaches the reception-side horn 33b without passing through the medium P, the detection accuracy of the heavy running of the medium P is lowered.

  Therefore, in the present embodiment, the first shielding portion 23 is disposed on the upper guide surface 14 serving as the first guide portion, and the second shielding portion is disposed on the lower guide surface 13 serving as the second guide portion. 24 is arranged. Note that both the first shielding part 23 and the second shielding part 24 do not necessarily need to be disposed, and only one of them may be disposed, but here both are disposed. An example will be described.

  As shown in FIG. 9, the first shielding portion 23 is disposed on the opposite side of the center of the medium P in the second direction, and on the upper guide surface 14, the outer end in the width direction of the first opening 34 a. Is a member that extends inward in the width direction and faces the transmission surface 32a of the transmitter 31a. Further, as shown in FIG. 9, the second shielding part 24 is disposed on the opposite side to the center of the medium P in the second direction, and the width of the second opening 34 b is formed on the lower guide surface 13. It is a member extending from the outer side end toward the inner side in the width direction and facing the receiving surface 32b of the receiver 31b.

  The first shielding part 23 and the second shielding part 24 are not necessarily parallel to the transmission surface 32a and the reception surface 32b. As shown in FIG. 9, the transmission surface 32a and the reception surface. It may be inclined with respect to 32 b and may extend on the same plane as the upper guide surface 14 and the lower guide surface 13. Further, the first shielding part 23 and the second shielding part 24 do not need to be close to the transmission surface 32a and the reception surface 32b, but from the transmission surface 32a and the reception surface 32b as shown in FIG. A part of the first opening 34a and the second opening 34b may be shielded apart. In short, the first shielding portion 23 and the second shielding portion 24 are provided in the transmission side horn 33a and the reception side horn 33b, which are ultrasonic paths that are transmitted from the transmission surface 32a and received by the reception surface 32b. Any member may be used as long as it is a member that shields the portion.

  As shown in FIG. 10, when the shielding rate of the first shielding part 23 is F1, and the shielding rate of the second shielding part 24 is F2, F1 and F2 are about 28% and about 28%, for example, respectively. 36 [%]. Note that the shielding rates of the first shielding unit 23 and the second shielding unit 24 do not necessarily have such numerical values, and may be within a range that does not affect the performance of the transmitting unit 30a and the receiving unit 30b. For example, it can be arbitrarily set within a range of about 15 to 45 [%]. As a result, it is possible to effectively shield the ultrasonic wave that directly reaches the reception-side horn 33b without passing through the medium P, and it is possible to effectively prevent a decrease in detection accuracy of heavy running of the medium P. .

  In the example shown in FIG. 10, the shielding rates of the first shielding part 23 and the second shielding part 24 are the same as those of the first opening 34 a and the first guiding part 14 on the same plane as the upper guide surface 14 and the lower guide surface 13. The ratio of the first shielding part 23 and the second shielding part 24 to the area of the two openings 34b is shown as the ratio of the transmission surface 32a and the reception surface on the surfaces of the transmission surface 32a and the reception surface 32b. It can be understood that the ratio of the area shielded by the first shielding part 23 and the second shielding part 24 to the area of 32b is the same.

  As shown in FIG. 11, in the present embodiment, the first shielding part 23 and the second shielding part 24 shield the transmission surface 32a and the reception surface 32b in the direction in which the virtual straight line L1 extends. . Further, the end of the first shielding portion 23 closer to the inner side in the width direction of the first opening 34a in the second direction, that is, the first end 23a is defined as 23a, and the second opening 34b in the second direction If the end closer to the inner side in the width direction, that is, the second end of the second shielding part 24 is 24a, a virtual straight line L2 connecting the first end 23a and the second end 24a is transmitted. It is desirable to be substantially parallel to a virtual straight line L1 connecting the center of the surface 32a and the center of the receiving surface 32b. Here, “substantially parallel” means that the virtual straight line L1 and the virtual straight line L2 are strictly parallel, or even if they are not strictly parallel, the inclination angle with respect to one of the other is 10 degrees or less. It means that the angle between the virtual straight line L1 and the virtual straight line L2 is 0 to 10 degrees. Accordingly, the transmitting unit 30a and the receiving unit that can effectively shield the ultrasonic wave that directly reaches the reception-side horn 33b without passing through the medium P, and transmit and receive ultrasonic waves with high directivity. It does not affect the performance of 30b.

  Further, it is desirable that the first end portion 23a and the second end portion 24a extend linearly in the first direction as shown in FIG. Furthermore, the first shielding part 23 and the second shielding part 24 are arranged in such a manner that the first end part 23a and the second shielding part 24 extend from the outer ends in the width direction of the first opening 34a and the second opening 34b in the second direction. It is desirable that the region up to the end portion 24a is tightly shielded without a gap. As a result, it is possible to effectively shield the ultrasonic wave that directly reaches the reception-side horn 33b without passing through the medium P, and it is possible to effectively prevent a decrease in detection accuracy of heavy running of the medium P. .

  Since the configuration of other points is the same as that of the first embodiment, description thereof is omitted.

  Next, the operation of the medium transport apparatus 10 in the present embodiment will be described. Similar to the first embodiment, only the operation for detecting the heavy running of the medium P will be described.

  FIG. 13 is a diagram for explaining a heavy run detection control system for a medium carrying device according to a second embodiment of the present invention.

  Also in the present embodiment, the medium transport apparatus 10 includes the same control unit 40 as in the first embodiment. The transmission pulse generated by the pulse generation circuit 42 is amplified by the amplification circuit 43 and then transmitted to the transmitter 31a of the transmission unit 30a. The transmitter 31a transmits an ultrasonic wave according to the received transmission pulse. The ultrasonic wave transmitted from the transmission surface 32a of the transmitter 31a mainly travels in the direction of the central axis of the transmission-side horn 33a as shown by the arrow D, passes through the medium P, attenuates, and is received by the receiver 31b. Is received by the receiving surface 32b. The output signal output from the receiver 31b according to the ultrasonic wave received by the receiving surface 32b is amplified by the amplifier circuit 45 after noise is removed by the filter circuit 44. Based on the amplified output signal of the receiver 31b, the control unit 40 determines whether or not the medium P is conveyed in a state where a plurality of sheets are overlapped, that is, determines whether or not the multifeed is performed.

  By the way, when the medium P has a relatively narrow width, with respect to the second direction, the end in the width direction of the medium P is in the first opening 34a and the second opening 34b, that is, the first opening 34a. And it will be located inside the edge part of the width direction outer side of the 2nd opening 34b. However, in the present embodiment, the first shielding portion 23 and the second shielding portion 24 are first to the first end from the width direction outer side of the first opening 34a and the second opening 34b in the second direction. The range to the end part 23a and the second end part 24a is shielded. Therefore, it passes through between the width direction end of the medium P and the width direction outer ends of the first opening 34a and the second opening 34b, and is indicated by an arrow D3 that reaches the receiving side horn 33b directly. Such ultrasound cannot be present. As a result, since substantially only the ultrasonic wave that has passed through the medium P is received by the receiving surface 32b of the receiver 31b, the control unit 40 can accurately determine the double feed, and the medium with high accuracy. P heavy run can be detected.

  Thus, in the present embodiment, the first shielding portion 23 facing the transmission surface 32a of the transmitter 31a is disposed on the upper guide surface 14, and the reception surface 32b of the receiver 31b is disposed on the lower guide surface 13. A second shielding part 24 facing is provided. As a result, even if the width of the medium P is narrow, it passes through the widthwise ends of the medium P and the widthwise outer ends of the first opening 34a and the second opening 34b and reaches the receiving horn 33b. Thus, only the ultrasonic wave that has passed through the medium P can be received by the reception surface 32b of the receiver 31b. Therefore, the heavy run of the medium P can be detected with high accuracy.

  In other words, in the present embodiment, a state in which a gap is generated between the horn of the double feed detection sensor and the medium due to the narrow media width by adding a shielding part to the horn of the double feed detection sensor. This can prevent the transmission of the transmitted ultrasonic wave directly. Therefore, the ultrasonic sensor on the receiving side can receive only the ultrasonic wave that has passed through the paper, and can normally determine double feeding.

  Next, a third embodiment of the present invention will be described. In addition, about the thing which has the same structure as 1st and 2nd embodiment, the description is abbreviate | omitted by providing the same code | symbol. The description of the same operations and effects as those of the first and second embodiments is also omitted.

  FIG. 14 is an enlarged plan view of the main part of the upper guide surface and the lower guide surface in the third embodiment of the present invention. In the figure, (a) is a plan view of the upper guide surface, and (b) is a plan view of the lower guide surface.

  In the present embodiment, the first shielding portion 23 is provided with the first rib 21 as the first protrusion, and the second shielding portion 24 has the second rib 22 as the second protrusion. Is provided. That is, the first shielding part 23 and the first rib 21 are integrally formed, and the second shielding part 24 and the second rib 22 are integrally formed. Therefore, when the upper guide surface 14 is viewed from below, as shown in FIG. 14A, the first opening 34 a is shielded by the first rib 21 in the vicinity of the outer end in the width direction. When the lower guide surface 13 is viewed from above, as shown in FIG. 14B, the vicinity of the outer end in the width direction of the second opening 34 b is shielded by the second rib 22. Yes.

  Thus, in the present embodiment, the first shielding part 23 is provided with the first rib 21 as the first protrusion, and the second shielding part 24 is the second protrusion as the second protrusion. Since the rib 22 is provided, the number of parts of the medium conveying apparatus 10 can be reduced, and the manufacturing cost can be reduced.

  Other configurations, operations, and effects are the same as those in the first and second embodiments, and a description thereof will be omitted.

  Next, a fourth embodiment of the present invention will be described. In addition, about the thing which has the same structure as 1st-3rd embodiment, the description is abbreviate | omitted by providing the same code | symbol. The description of the same operations and effects as those of the first to third embodiments is also omitted.

  FIG. 15 is an enlarged plan view of the main parts of the upper guide surface and the lower guide surface in the fourth embodiment of the present invention.

  In the present embodiment, the third shielding portion 25 is disposed on the upper guide surface 14 as the first guide portion and the lower guide surface 13 as the second guide portion. The third shielding portion 25 is a member facing the transmission surface 32a of the transmitter 31a and the reception surface 32b of the receiver 31b. As shown in the drawing, the third shielding portion 25 is formed on the upper guide surface 14 and the lower guide surface 13. The central part is shielded. That is, the central part of the ultrasonic sensor including the transmitting unit 30 a and the receiving unit 30 b is shielded by the third shielding unit 25.

  In general, an ultrasonic sensor has a large variation in sensitivity, and it is very difficult to use the ultrasonic sensor by such control that the entire range of the variation in sensitivity can be used. For this reason, conventionally, ultrasonic sensors ranked by sensitivity have to be used.

  On the other hand, in the present embodiment, the central portion of the first opening 34a that is the exit end of the ultrasonic wave in the transmission side horn 33a and the second end that is the entrance end of the ultrasonic wave in the reception side horn 33b. Since the central part of the opening 34b is shielded by the third shielding part 25, the ultrasonic wave passing through the central part of the transmitting side horn 33a and the receiving side horn 33b with the maximum sensor sensitivity is blocked.

  When the ultrasonic wave is cut off in this way, the reception level of the ultrasonic wave at the receiving surface 32b of the receiver 31b decreases at a predetermined rate, but this rate does not depend on the sensitivity of each ultrasonic sensor, It is constant. Therefore, while the ultrasonic sensor having a high sensitivity has a large decrease in the reception level of the ultrasonic wave on the reception surface 32b, the ultrasonic sensor having a low sensitivity has a decrease in the reception level of the ultrasonic wave on the reception surface 32b. small. As a result, the difference in the reception level of the ultrasonic wave at the reception surface 32b in each ultrasonic sensor is smaller than that in the conventional art.

  That is, in the present embodiment, it is possible to level the sensitivity variation in the ultrasonic sensor.

  Other configurations, operations, and effects are the same as those in the first and second embodiments, and a description thereof will be omitted.

  In the first to fourth embodiments, the case where the medium conveying apparatus 10 is an automatic document feeder (ADF) has been described. However, the present invention is not limited to this, and the medium P The present invention can be applied to all medium conveyance devices having a function of detecting the heavy running of.

  Furthermore, the present invention is not limited to the above-described embodiment, and various modifications can be made based on the spirit of the present invention, and they are not excluded from the scope of the present invention.

  The present invention can be used for a medium conveying apparatus and an image forming apparatus.

DESCRIPTION OF SYMBOLS 10 Medium conveying apparatus 13 Lower guide surface 14 Upper guide surface 15 Pickup roller 16 Paper feed roller 21 1st rib 22 2nd rib 23 1st shielding part 23a 1st edge part 24 2nd shielding part 24a 2nd Two end portions 30a Transmitting portion 30b Receiving portion 32a Transmitting surface 32b Receiving surface 34a First opening 34b Second opening

Claims (11)

A transport unit for transporting the medium in the first direction;
A transmitter for transmitting ultrasonic waves from a transmission surface for detecting double feeding of a medium to be conveyed;
A receiving unit for receiving the ultrasonic wave transmitted from the transmitting surface at the receiving surface;
A first guide unit that is disposed between the transmitting unit and the receiving unit and guides a medium to be conveyed;
A second guide unit disposed between the transmission unit and the reception unit and disposed at a predetermined distance from the first guide unit;
The first guide part is
A first opening facing the transmitting surface;
With respect to a second direction orthogonal to the first direction, the first protrusion disposed on the opposite side of the center of the medium in the first opening,
The second guide part is
A medium conveying apparatus having a second opening facing the receiving surface. The second guide portion has a second protrusion facing the first protrusion,
The medium conveying apparatus according to claim 1, wherein a dimension of the second protrusion in the second direction is larger than that of the first protrusion. The second guide portion has a second protrusion facing the first protrusion,
The medium conveying apparatus according to claim 1, wherein a dimension of the first protrusion in the second direction is larger than that of the second protrusion.   The medium conveyance device according to claim 1, wherein the first guide portion includes a first shielding portion facing the transmission surface. The second guide part is
The medium conveying apparatus according to claim 1, further comprising a second shielding portion facing the receiving surface.   The medium conveying apparatus according to claim 5, wherein the first shielding part and the second shielding part are arranged on a side opposite to the center of the medium in the second direction.   The medium transport apparatus according to claim 4, wherein the first protrusion is provided on the first shielding part.   The medium conveying apparatus according to claim 5, wherein the second protrusion is provided on the second shielding part. A first imaginary straight line connecting the center of the transmission surface and the center of the reception surface;
The second imaginary straight line connecting the end portion in the second direction in the first shielding portion and the end portion in the second direction in the second shielding portion is:
The medium carrying device according to claim 5 which is substantially parallel.   The medium conveying device according to claim 1, wherein the transmitting unit and the receiving unit are arranged with a predetermined distance from the center of the medium to be conveyed with respect to the second direction. . An image forming apparatus comprising the medium conveying device according to claim 1.

Images