JP4818071B2 - Image reading device - Google Patents

Description

  The present invention relates to an image reading apparatus having a double feed detection device that detects double feed of paper using ultrasonic waves.

  2. Description of the Related Art Conventional image reading apparatuses such as copiers and multifunction peripherals are mainly optical double feed detection devices as double feed detection means for detecting double feed of paper. 2. Description of the Related Art In recent years, ultrasonic double feed detection devices that use ultrasonic waves as new double feed detection means have been employed in facsimiles, scanners, and the like. An example of such an ultrasonic double feed detector is shown in FIG.

  In FIG. 8, the ultrasonic double-feed detection device includes an ultrasonic transmitter 53 and an ultrasonic receiver 54 arranged so as to sandwich a conveyance path through which paper 51 and 52 are conveyed, and an output of the ultrasonic receiver 54. And a waveform analysis unit 55 to which a signal is input.

  The ultrasonic wave transmitted from the ultrasonic transmitter 53 passes through the paper conveyed in the conveyance direction (arrow C in the figure) and is received by the ultrasonic receiver 54. Then, the ultrasonic receiver 54 generates an ultrasonic reception signal based on the received ultrasonic wave and outputs it to the waveform analysis unit 55.

  The double feed detection method in the ultrasonic double feed detection device is roughly classified into, for example, a level method disclosed in Patent Document 1 and a phase method disclosed in Patent Document 2.

  In the level method, the waveform analysis unit 55 analyzes the amplitude of the ultrasonic reception signal or a signal corresponding to the reception intensity of the ultrasonic wave generated by a method such as detecting the ultrasonic reception signal.

  In the level method, the ultrasonic wave is transmitted through two or more sheets (when passing through part B in FIG. 8) compared to when passing through one sheet (when passing through part A in FIG. 8). Becomes more attenuated, the ultrasonic reception intensity becomes weaker. Therefore, in the level method, the waveform analysis unit 55 compares a signal corresponding to the amplitude of the ultrasonic reception signal or the ultrasonic reception intensity with a predetermined threshold value to determine whether or not the double feeding is performed.

  On the other hand, in the phase method, ultrasonic waves having a predetermined phase are transmitted from the ultrasonic transmitter 53. The ultrasonic receiver 54 receives the ultrasonic wave transmitted through the paper and outputs an ultrasonic reception signal to the waveform analysis unit 55.

  In the phase method, the case where two or more sheets are transmitted (when the portion B in FIG. 8 is transmitted) is greater than the case where one sheet is transmitted (when the portion A in FIG. 8 is transmitted). The sound wave reception signal is more delayed. Therefore, in the phase method, the phase difference between the phase of the transmitted ultrasonic wave and the phase of the ultrasonic reception signal is compared with a predetermined reference value, and the presence or absence of double feeding is detected from the comparison result.

  However, regardless of which method is used, since the ultrasonic sensor that is the ultrasonic receiver 54 has temperature characteristics, the ultrasonic reception signal fluctuates due to changes in external factors such as ambient temperature, and double feed detection There is a problem that the accuracy of the is reduced. In order to solve this problem, there is one that improves the detection accuracy by including temperature detection means for detecting temperature and control means for controlling the frequency of ultrasonic waves transmitted from the ultrasonic transmitter (for example, patents). Reference 3). When the decrease in the amplitude of the ultrasonic reception signal occurs due to the temperature decrease, the amplitude of the ultrasonic reception signal is increased and corrected by changing the frequency of the ultrasonic wave to a frequency closer to the resonance frequency of the resonance circuit.

Further, in general, the circuit constituting the ultrasonic double feed detection device includes a signal amplifying unit because the ultrasonic reception signal output from the ultrasonic sensor becomes weak when the ultrasonic wave transmitted through the paper and attenuated is received. It is used.
Japanese Patent No. 1725105 Japanese Patent Laid-Open No. 52-40379 JP 2005-350253 A

  However, when the conventional ultrasonic double feed detection device is used in an environment where the temperature is low, it is erroneously detected because the S / N ratio of the signal obtained through the signal amplification means is reduced. There is a risk. In addition, the method of controlling the frequency of the ultrasonic wave according to the change of the sensor sensitivity due to the temperature drop using the temperature detecting means or the like is expensive.

  Accordingly, the present invention has been made in view of the above problems, and provides an image reading apparatus capable of performing double feed detection with stable detection accuracy even when used in an environment where the temperature is low. For the purpose.

  Another object of the present invention is to provide an image reading apparatus provided with an inexpensive ultrasonic double feed detection device without providing a temperature detection means.

  In order to achieve the above object, the image reading apparatus according to claim 1, wherein an ultrasonic wave transmitted to a sheet on a conveyance path is received by an ultrasonic wave receiving unit to detect double feeding of the sheet. And a display means including a light source and a base, wherein the display means is disposed in the vicinity of the ultrasonic wave receiving means, and the ultrasonic wave is generated by heat emitted from the light source. It is characterized by being arranged to warm the receiving means.

  According to the present invention, even when used in an environment where the temperature is low, it is possible to prevent a decrease in reception sensitivity of the ultrasonic receiving means due to a decrease in temperature, and it is possible to perform double feed detection with stable detection accuracy. It becomes. In addition, an ultrasonic multifeed detection device can be provided at low cost without providing a temperature detection means.

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

  FIG. 1 is a cross-sectional view showing a schematic structure of an image reading apparatus according to an embodiment of the present invention.

  In FIG. 1, the image reading apparatus 100 is stacked on a sheet stacking unit 160 that stacks and stores a plurality of sheets S, a discharge stacking unit 170 that stacks and stores sheets S after image reading, and a sheet stacking unit 160. A separation feeding unit 110 that feeds a plurality of sheets S one by one and feeds them into the apparatus, conveyance rollers 121, 122, and 124 that convey the sheets S at a predetermined speed, and a driven roller 131 that is pressed against each conveyance roller. , 132, 134, image reading units 140, 150 that respectively read the images of the front and back surfaces of the sheet S that have been sent, and a first conveyance that guides the sheet S from the sheet stacking unit 160 to the image reading units 140, 150. A path 300 and a second transport path 301 for guiding the sheet S from the image reading units 140 and 150 to the paper discharge stacking unit 170 are provided.

  The image reading unit 140 is supported so as to be movable substantially vertically while maintaining a posture parallel to the sheet surface. On the other hand, the image reading unit 150 is fixedly supported with respect to the conveyance path. The image reading units 140 and 150 include a CCD, a lens (not shown), a lamp, and a reflection mirror, respectively, and perform image reading by forming an image of reflected light from the sheet S. Note that the image reading units 140 and 150 may use a contact type reading sensor (CIS).

  In addition, the image reading apparatus 100 displays an image read by the ultrasonic sensor 20 and the ultrasonic transmission element 21 for detecting double feeding with ultrasonic waves and the image reading units 140 and 150, and indicates operation instructions and apparatus states. And a liquid crystal display unit 200 for displaying. The upper constituent unit 101 including the ultrasonic sensor 20, the image reading unit 140, the liquid crystal display unit 200, and the like is configured to be openable and closable with respect to the apparatus main body, and can easily remove the sheet S when a paper jam or double feed occurs. It has become.

  The ultrasonic sensor 20 and the ultrasonic transmission element 21 are arranged in the vertical direction of the apparatus across the first conveyance path 300 through which the sheet S is conveyed, similarly to the ultrasonic transmitter 53 and the ultrasonic receiver 54 described above. Opposed to each other. Then, the ultrasonic wave transmitted from the ultrasonic transmission element 21 passes through the sheet S conveyed in the first conveyance path 300 and is received by the ultrasonic sensor 20. In the present embodiment, the ultrasonic sensor 20 and the ultrasonic transmission element 21 are arranged on the first conveyance path 300 side, but may be arranged on the second conveyance path 301 side.

  Next, an image reading operation in the image reading apparatus 100 of FIG. 1 will be described.

  When the image reading operation is started, the plurality of sheets S placed on the sheet stacking unit 160 are fed one by one by the separation feeding unit 110 and sent into the image reading apparatus 100. The sheet S that has been rolled up is conveyed by the conveying roller 121 and the driven roller 131 and passes in a state of being in close contact with the image reading units 140 and 150. The image formed on the front or back surface of the sheet S is line-scanned while the sheet S passes between the image reading unit 140 and the image reading unit 150, and is output from each image reading unit as an electrical signal. The After the image reading is performed in this manner, the sheet S is discharged to the discharge stacking unit 170.

  FIG. 2 is a perspective view showing a schematic configuration of the liquid crystal display unit 200 in FIG.

  In FIG. 2, the liquid crystal display unit 200 includes a lamp-shaped reflector 4, a light guide plate 6, a prism sheet, a condensing sheet, a diffusion sheet, and other optical system sheets 8, and an array The liquid crystal display panel members of the cell 10 are sequentially stacked. The lamp 12 which is a light source for illuminating the liquid crystal from the back is made of a fluorescent lamp or the like, and is attached at a predetermined position.

  FIG. 3 is a block diagram of a circuit constituting the ultrasonic double-feed detection device of the image reading device of FIG.

  In FIG. 3, the ultrasonic transmission element 62 and the ultrasonic sensor 63 correspond to the ultrasonic transmission element 21 and the ultrasonic sensor 20. The sheet-like member 61 corresponds to the sheet S.

  When an ultrasonic transmission pulse is input to the ultrasonic transmission element 62 from a drive unit 65 mounted on a control board (not shown), an ultrasonic wave is transmitted from the ultrasonic transmission element 62. And when the sheet-like member 61 exists in a conveyance path, the ultrasonic wave which permeate | transmitted the said sheet-like member 61 is received by the ultrasonic sensor 63. FIG. When there is no sheet-like member in the conveyance path, ultrasonic waves are directly received by the ultrasonic sensor 63.

  The control unit 64 mounted on the control board supplies a 200 KHz pulse signal to the drive unit 65. Then, the drive unit 65 amplifies the pulse signal and inputs it as an ultrasonic transmission pulse to the ultrasonic transmission element 62 to transmit a 200 KHz ultrasonic wave. Ultrasonic waves are transmitted over a plurality of periods at a frequency of 200 KHz. This is generally called a burst wave, and such an ultrasonic burst wave is transmitted once every several ms.

  When a sheet-like member is inserted between the ultrasonic transmission element 62 and the ultrasonic sensor 63, the ultrasonic wave transmitted from the ultrasonic transmission element 62 is attenuated before reaching the ultrasonic sensor 63 and becomes very weak. turn into. Therefore, the ultrasonic reception signal output from the ultrasonic sensor 63 is amplified through the signal amplifying unit (amplifier) 66 and pulled up to a signal amplitude that allows determination of double feed detection.

  The ultrasonic reception signal amplified by the amplifier 66 is input to the AD conversion unit 67 on the control board. The A-D conversion unit 67 converts the amplified ultrasonic reception signal, which is an analog signal, into a digital signal, and outputs the digital signal to the signal analysis unit 68 as a signal representing the signal strength of the ultrasonic reception signal.

  The storage unit 69 stores the number of ultrasonic transmission pulses, the ultrasonic amplitude, the ultrasonic frequency, the ultrasonic acquisition time, and the like that affect the signal strength of the ultrasonic reception signal, the multifeed detection level, and the like. Is used to perform the double feed detection operation.

  Here, the characteristics of the waveform analyzer used in the present embodiment will be described. The waveform analysis unit corresponds to the amplifier 66, the A / D conversion unit 67, and the signal analysis unit 68 described above.

  FIG. 9 is a diagram showing noise characteristics measured in the waveform analysis unit constituting the ultrasonic double feed detection device.

  In FIG. 9, the vertical axis represents the signal intensity of the amplified ultrasonic reception signal obtained through the amplifier 66 on the vertical axis, noise generated in the ultrasonic sensor 20, noise generated in the amplifier 66, and the like. The S / N ratio representing the ratio with the total noise intensity, and the horizontal axis represents the temperature of the ultrasonic sensor 20. The ultrasonic reception signal at this time is a signal output from the ultrasonic sensor 20 that has received the ultrasonic wave transmitted through one sheet S.

  If the S / N ratio is small, it is difficult to determine whether there is one sheet or two or more sheets that block the ultrasonic wave, and it becomes difficult to detect double feed. For this reason, in the present embodiment, the threshold value of the S / N ratio that can determine whether or not double feeding is set to 2. As can be seen from the graph shown in the figure, it can be seen that the S / N ratio is below the threshold value 2 in the temperature region where the temperature is lower than around 10 ° C. This is because when the temperature is lowered, the detection sensitivity of an ultrasonic detection element such as a piezoelectric element inside the ultrasonic sensor 20 is lowered, and the intensity of the ultrasonic output signal is weakened. This is because the strength of the components becomes relatively strong.

  Further, the environment around 10 ° C. is included in the usage environment in which various devices to which the double feed detection device is mounted are specified to be operable. It is also in the vicinity of the minimum temperature of the environment where it is defined that the general office machine and the image reading apparatus equipped with the double feed detection device can be used. Therefore, if some measures are not taken, there is a possibility of erroneous detection when used in such an environment where the temperature is low.

  Moreover, it can be seen from the graph shown in FIG. 9 that there are few temperature regions in which the S / N ratio falls below the threshold value. That is, it is possible to make the S / N ratio exceed the threshold value by slightly raising the temperature of the ultrasonic sensor 20. Increasing the temperature to such a level can be sufficiently achieved, for example, by the heat released by the lamp 12 of the liquid crystal display unit 200 being lit by heating the ultrasonic sensor 20 in about several tens of seconds. it can. Further, even when the ultrasonic sensor 20 is always warmed by the heat released from the lamp 12 of the liquid crystal display unit 200, the temperature of the ultrasonic sensor 20 only rises to around 70 ° C. There is enough room. In this state, as can be seen from the graph, since the S / N ratio sufficiently exceeds the threshold value, stable detection can be performed.

  FIG. 4 is a cross-sectional view showing the characteristic part of the image reading apparatus according to the first embodiment of the present invention.

  In FIG. 4, the ultrasonic sensor 20 is disposed close to a part of the bottom surface of the frame 201 constituting the liquid crystal display unit 200, and the lamp 12 is disposed near the ultrasonic sensor 20 on the frame 201. Yes. The frame 201 is formed of a material having high thermal conductivity such as iron or aluminum, and plays a role of a heat conductor that transfers heat emitted from the lamp 12 to the ultrasonic sensor 20.

  The lamp 12 is disposed at the corner of the frame 201. As a result, the surface of the frame 201 facing the lamp 12 is increased, heat is more efficiently transmitted to the frame 201, and the ultrasonic sensor 20 can be quickly warmed. In addition, when the lamp 12 and the ultrasonic sensor 20 are close to each other in such a configuration, it is also effective to make the material of the frame 201 a material having high thermal conductivity only in a portion close to the lamp 12 and the ultrasonic sensor 20. is there.

  FIG. 5 is a cross-sectional view showing a characteristic part of an image reading apparatus according to the second embodiment of the present invention.

  In FIG. 5, the upper component unit 101 a includes a liquid crystal display unit 200 a, an ultrasonic sensor 20, driven rollers 131, 132, and 134, and a surface image reading unit 140.

  In the second embodiment, the lamp 12 constituting the liquid crystal display unit 200 a is disposed at a position away from the ultrasonic sensor 20. Since the frame 201 can transmit the heat emitted from the lamp 12 to the ultrasonic sensor 20, the lamp 12 and the ultrasonic sensor 20 may be arranged at a distance from each other. In other words, the lamp 12 may be disposed anywhere as long as the position of the lamp 12 is easy to transfer heat to the frame 201.

  FIG. 6 is a cross-sectional view showing a characteristic part of an image reading apparatus according to the third embodiment of the present invention.

  In FIG. 6, the upper constituent unit 101 b includes a liquid crystal display unit 200 b, an ultrasonic sensor 20, driven rollers 131, 132, and 134, and a surface image reading unit 140.

  In the third embodiment, as shown in FIG. 6, the frame 202 constituting the liquid crystal display unit 200 b is provided with an opening 202 a at a position between the lamp 12 and the ultrasonic sensor 20. Thereby, the heat released from the lamp 12 is directly transmitted to the ultrasonic sensor 20 in the form of radiant heat or the like without passing through the frame 202. The shape of the opening 202a is not limited to a circle but may be any shape such as a polygon. Further, the number of openings 202a is not limited to one, and a plurality of openings 202a may be provided.

  FIG. 7 is a cross-sectional view showing a characteristic part of an image reading apparatus according to the fourth embodiment of the present invention.

  In FIG. 7, the upper configuration unit 101 c includes a liquid crystal display unit 200 c, an ultrasonic sensor 20, driven rollers 131, 132, and 134, and a surface image reading unit 140.

  In the fourth embodiment, the frame 203 constituting the liquid crystal display unit 200c is provided with an opening 203a and a plurality of protrusions 203b provided around the opening 203a. As shown in FIG. 7, the protrusion 203 b has a shape surrounding the ultrasonic sensor 20. As a result, the heat emitted from the lamp 12 warms the ultrasonic sensor 20 from the surroundings by the projection 203b surrounding the ultrasonic sensor 20, so that the heat can be more efficiently heated. In the present embodiment, the protruding portion 203b is provided so as to sandwich the ultrasonic sensor 20, but it may be cylindrical so as to surround the sensor 20. Moreover, although the opening part 203a is provided, only the projection part 203b may be sufficient.

  As in the third and fourth embodiments shown in FIGS. 6 and 7, when the opening is provided to directly transfer the heat of the lamp 12 to the ultrasonic sensor 20, the frames 202 and 203 have low thermal conductivity. It may be a material. For example, when a resin frame is used, it is conceivable that the heat of the lamp is trapped between the frame and the liquid crystal display member and concentrated from the opening of the frame. Therefore, it is desirable to select a material for the frame that can efficiently warm the ultrasonic sensor.

  As described above, according to each of the above embodiments, the liquid crystal display unit 200 having the lamp 12 and the frame 201 is disposed in the vicinity of the ultrasonic sensor 20, and the frame 201 is superheated by the heat emitted from the lamp 12. Since the ultrasonic sensor 20 is arranged so as to be heated, the ultrasonic sensor can be heated using the light source of the liquid crystal display unit as a heat source, and even when used in an environment where the temperature is low, the reception sensitivity of the ultrasonic sensor due to the temperature drop. It is possible to prevent the decrease in the feed rate, and it is possible to detect double feed with stable detection accuracy.

  In addition, it is possible to provide an ultrasonic double feed detection device at low cost without providing a temperature detection means or a control means for controlling the frequency of ultrasonic waves according to the temperature.

  In each of the above embodiments, the present invention has been described with respect to an embodiment in which the present invention is applied to an image reading apparatus equipped with a liquid crystal display unit and a multifeed detection device. However, the present invention is not limited to this, and the present invention is not limited to this. You may apply.

  In each of the above embodiments, the amplifier 66 that is a signal amplifying unit is mounted on the control board. However, the amplifier 66 may be built in the ultrasonic sensor side or in both. The amplifier 66 may have a detection function.

  In the above embodiments, the lamp 12 as the light source is a fluorescent lamp or the like, but any light source that generates a large amount of heat may be used.

1 is a cross-sectional view illustrating a schematic structure of an image reading apparatus according to an embodiment of the present invention. It is a perspective view which shows schematic structure of the liquid crystal display part in FIG. It is a block diagram of the circuit which comprises the ultrasonic double feed detection apparatus of the image reading apparatus of FIG. 1 is a cross-sectional view illustrating a characteristic part of an image reading apparatus according to a first embodiment of the present invention. It is a cross-sectional view showing the characterizing portion of the image reading apparatus according to the second embodiment of the present invention. It is a cross-sectional view showing the characterizing portion of the image reading apparatus according to the third embodiment of the present invention. It is a cross-sectional view showing the characterizing portion of the image reading apparatus according to the fourth embodiment of the present invention. It is a block diagram which shows the outline of the circuit which comprises an ultrasonic multifeed detection apparatus. It is a figure which shows the noise characteristic measured in the waveform analysis part which comprises an ultrasonic double feed detection apparatus.

Explanation of symbols

12 Lamp 20 Ultrasonic sensor 21 Ultrasonic transmitting element 100 Image reading device 140, 150 Image reading unit 200, 200a, 200b, 200c Liquid crystal display unit 201, 202, 203 Frame

Claims (5)

In an image reading apparatus, comprising: a multifeed detecting unit that receives ultrasonic waves transmitted to a sheet on a conveyance path by an ultrasonic receiving unit to detect multifeed of the sheet; and a display unit including a light source and a base. ,
The image reading apparatus, wherein the display unit is arranged in the vicinity of the ultrasonic wave receiving unit, and the base is arranged to warm the ultrasonic wave receiving unit by heat emitted from the light source.   The image reading apparatus according to claim 1, wherein the base is made of a material having high thermal conductivity, and the ultrasonic wave receiving means is disposed in the vicinity of the base.   The image reading apparatus according to claim 1, wherein the base is provided with an opening between the ultrasonic wave receiving means and the light source.   The image reading apparatus according to claim 3, wherein the opening has a protrusion around the opening so as to surround the ultrasonic wave receiving unit.   The image reading apparatus according to claim 1, wherein the display unit includes a liquid crystal panel.

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