JP2005082350A - Double feed detection device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device capable of increasing double feed detection accuracy by reducing the effect of reflected waves by a sound wave reflector near a position where an ultrasonic sensor is installed. <P>SOLUTION: In the double feed detection part U2 of the image forming device, a cylindrical sound absorbing material 38A is disposed on the transmitter 32 of the ultrasonic sensor 17, and a cylindrical sound absorbing material 38B is disposed on a receiver 33. The opening ends of the sound absorbing materials 38A and 38B are connected to a carrying route 24. The opening dimensions of the sound absorbing materials 38A and 38B are smaller than the opening dimensions of the carrying route. In this case, a porous material with a density of 25 to 90 kg/m<SP>3</SP>is used for the sound absorbing materials 38A and 38B. Also, the sound absorbing materials 38A and 38B comprise ozone resistant properties. By this, since ultrasonic radiation to members near the position where the ultrasonic sensor 17 is installed can be eliminated and the reflected wave from transfer paper P can be absorbed, the effect of the reflected wave can be reduced and the double feed detection accuracy can be increased. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double feed detection device suitable for being applied to a copying machine, a multifunction machine, a printer, a facsimile machine, etc. having a function of detecting double feed using an ultrasonic sensor, and an image forming apparatus using the same. .

  Conventionally, an ultrasonic sensor is used to detect double feeding of transfer paper. However, when detecting double feeding using an ultrasonic sensor, the detection signal is unstable due to reflection on the surface of the transfer paper and the influence of reflected waves from an ultrasonic reflector such as a peripheral sheet metal part.

  In order to reduce the influence of reflected waves, a method of arranging ultrasonic sensors obliquely with respect to the conveyance path has been proposed (see, for example, Patent Document 1).

  In this case, when feeding sheets such as cut sheets, plastic sheets, glass plates, etc. one by one to the printing machine, etc., it is detected by a multi-feed detection device that detects whether or not two or more sheets are fed in layers. The target moving surface is tilted with respect to a plane perpendicular to the ultrasonic seeding axis composed of the ultrasonic transmitter and the ultrasonic receiver, so that the surface of the detection target is emitted from the ultrasonic transmitter. Since the ultrasonic wave reflected by the laser beam does not return to the transmitter, the amount of ultrasonic wave detected by the receiver is stable, and the double feed of the detection target can be reliably detected.

  Moreover, an ultrasonic horn provided with a sound absorbing material on the inner surface has been proposed (see, for example, Patent Document 2).

  In this case, an ultrasonic sensor and a horn are provided on the ultrasonic wave transmission side of the ultrasonic sensor, and a sound absorbing material is provided on the inner surface of the horn. Thereby, reflection of the ultrasonic wave in a horn can be eliminated and it can prevent that an ultrasonic wave is transmitted to the area | region beyond a horn angle.

Japanese Utility Model Publication No. 5-56851 (pages 5, 6 and 1) Japanese Patent Laid-Open No. 10-136490 (second page, FIG. 1)

  As described above, in the conventional double feed detection method (Patent Document 1), the ultrasonic sensor is arranged obliquely with respect to the conveyance path, thereby transferring more than the case where the ultrasonic sensor is arranged perpendicular to the conveyance path. Although it is possible to reduce the influence of the reflected wave directly reflected from the paper surface, etc., the detection signal is unstable due to the influence of the reflected wave from the ultrasonic reflector such as a sheet metal around the ultrasonic sensor. There was a problem that the accuracy of. Moreover, the paper dust adhering to the surface of the ultrasonic transmitter or receiver could not be removed.

  In addition, in the case of Patent Document 2, since an ultrasonic horn is provided only on the transmission side, reflection from the horn can be eliminated and ultrasonic waves can be prevented from being transmitted to a region beyond the horn angle. The influence of the reflected wave on the side could not be prevented.

  Therefore, the present invention provides a double feed detection device and an image forming apparatus that can reduce the influence of a reflected wave by a sound wave reflector near the installation position of the ultrasonic sensor and can improve the double feed detection accuracy. The purpose is to do.

  The multifeed detection device according to the present invention transmits ultrasonic waves from a transmitter of an ultrasonic sensor opposed across a transfer paper conveyance path to a receiver, and when the transfer paper passes between the transmitter and the receiver. A device for detecting double feed by comparing an output signal due to attenuation with a threshold for detecting double feed, and comprising a transmitter, a transmitter and a receiver, or a sound absorbing material disposed on a member around the transmitter It is what is done.

  According to the present invention, in the double feed detection device, the sound absorbing material is disposed on the transmitter of the ultrasonic sensor, the transmitter and the receiver, or a member around the transmitter. As a result, the sound wave reflector near the ultrasonic sensor installation position, for example, the ultrasonic wave irradiated directly on the sheet metal around the ultrasonic sensor or indirectly by the reflection from the transfer paper is absorbed, and these sound wave reflectors Is suppressed. Therefore, it becomes possible to reduce the influence of the reflected wave by the sound wave reflector near the installation position of the ultrasonic sensor.

  For example, the sound absorbing material is formed in a cylindrical shape, and is arranged so as to surround the transmitter and the receiver with the cylindrical sound absorbing material. In this case, there is no need to attach a sound absorbing material to the conveyance path, the sensor interval can be minimized, and the maximum receivable signal level can be obtained. In addition, since the opening surface of the sound absorbing material is brought into contact with the conveyance path, it is possible to eliminate the ultrasonic irradiation to the members near the ultrasonic sensor installation position and to absorb the reflected wave from the transfer paper. It becomes.

Further, the sound absorbing material has ozone resistance characteristics, and the sound absorbing material has a density in the range of 25 to 90 kg / m ³ . Thereby, it is hard to corrode with ozone generated by discharge, and a long life can be achieved. Moreover, since the sound absorption rate of the sound absorbing material is high, reflection from a sound wave reflecting object in the vicinity of the installation position of the ultrasonic sensor is effectively prevented.

  In addition, for example, a cleaning means for cleaning paper powder on the surface of the transmitter or receiver of the ultrasonic sensor is further provided, and the sound absorbing material disposed in the transmitter or receiver installed at a lower position with respect to the conveying path is made of paper. A slit is provided to eliminate powder. Thereby, since the paper dust adhering to the surface of the ultrasonic transmitter or the receiver is removed by the cleaning means, it is possible to prevent a decrease in detection accuracy due to the paper dust.

  An image forming apparatus according to the present invention transmits ultrasonic waves from a transmitter of an ultrasonic sensor opposed to a transfer paper conveyance path to a receiver, and attenuation when the transfer paper passes between the transmitter and the receiver. In the image forming apparatus for forming an image on transfer paper based on arbitrary image data, the multi-feed detection unit A sound absorbing material is arranged on a transmitter, a transmitter and a receiver, or members around the transmitter.

  According to the image forming apparatus of the present invention, the multifeed detection device according to the present invention is applied to the multifeed detection unit, and when detecting multifeed, the sonic reflector near the installation position of the ultrasonic sensor is irradiated. The ultrasonic wave that has been absorbed is absorbed by the absorber, and its reflection is suppressed. Thereby, the influence of the reflected wave on the detection signal can be reduced and the possibility of erroneous detection can be eliminated.

  As described above, according to the double feed detection device according to the present invention, in the double feed detection device using the ultrasonic sensor, the transmitter of the ultrasonic sensor, the transmitter and the receiver, or the periphery of the transmitter. A sound absorbing material is disposed on the member.

  With this configuration, the ultrasonic wave applied to the sound wave reflector near the installation position of the ultrasonic sensor is absorbed by the absorber and the reflection is suppressed, so that the reflected wave of the sound wave reflection object near the installation position of the ultrasonic sensor is reduced. The influence can be reduced, and the double feed detection accuracy can be improved. Therefore, it is possible to install the ultrasonic sensor even at a position that is surrounded by an ultrasonic reflector and is more easily affected by the reflected wave.

  According to the image forming apparatus of the present invention, since the multifeed detection apparatus according to the present invention is applied, it is possible to reduce the influence of the reflected wave by the sound wave reflection object near the installation position of the ultrasonic sensor, and to detect the double feed detection accuracy. Can be improved. For this reason, when an image is formed, it is possible to reliably detect double feeding of transfer paper, and it is possible to suppress output of a defective image due to double feeding.

  Hereinafter, a double feed detection device according to a first embodiment of the present invention and an image forming apparatus using the same will be described with reference to the drawings.

  The image forming apparatus according to the first embodiment includes a double feed detection unit (double feed detection device), a transmitter of an ultrasonic sensor as a double feed detection unit, a transmitter and a receiver, or a transmitter. By arranging the sound absorbing material on the surrounding members, the influence of the reflected wave by the sound wave reflection object near the installation position of the ultrasonic sensor can be reduced, and the detection accuracy of double feed can be improved. .

  FIG. 1 is a block diagram showing a configuration of an image forming apparatus 100 according to the first embodiment of the present invention. An image forming apparatus 100 shown in FIG. 1 performs double feed detection before forming an image on a transfer sheet, and executes image formation control based on this double feed detection, and has a copying function using an electrophotographic system. It is suitable for application to copiers, multifunction machines, printers, facsimiles, and the like.

  As shown in FIG. 1, the image forming apparatus 100 includes a control unit 10, an operation unit 11, a display unit 12, a paper feeding unit 13, a paper detection sensor 13 s, a conveying unit 14, an image reading unit 15, an image forming unit 16, An ultrasonic sensor 17, a paper discharge tray 18, and a paper discharge detection sensor 18s as feed detection means are provided.

  The control unit 10 includes a CPU 10a, a ROM 10b, a RAM 10c, and an image memory 10d. The CPU 10a controls the overall operation of the image forming apparatus 100 while using the RAM 10c as a work area according to a control program stored in the ROM 10b. The image memory 10d functions as a storage device that temporarily stores the image data read from the image reading unit 15.

  The control unit 10 controls the conveying unit 14 and the image forming unit 16 based on the double feed detection information obtained by the ultrasonic sensor 17. In this control system, when the double feeding of the transfer paper is detected, the control unit 10 controls the conveying unit 14 so that a predetermined image indicating the occurrence of double feeding is formed on the transfer paper related to the double feeding and is discharged. The

  The control unit 16 performs control so that the transfer paper on which the image is formed is discharged to a predetermined paper discharge tray. For example, when there are multiple output trays, the transfer paper for multi-feed is discharged to an empty output tray other than the specified output tray, and there is one output tray or no empty output tray Controls the image forming operation to be stopped and the display means provided in the display unit 12 to indicate that double feeding has occurred after discharging the double-fed transfer paper to a predetermined paper discharge tray.

  The operation unit 11 is configured by a touch panel with a liquid crystal display function, for example, and functions as an interface for interacting with an operator in settings such as a single-sided mode, a double-sided mode, and a post-processing mode. The operation unit 11 outputs operation information related to image formation to the control unit 10. The operation unit 11 includes an operation unit that restarts the image forming operation of the image forming unit 16, and when the double feed detection unit detects the double feed of the transfer paper, the transfer sheet being conveyed to the upstream portion of the double feed detection unit. After the operation is temporarily stopped, the operator can issue an instruction to resume image formation of the image data on the transfer sheet from the operation unit 11.

  The display unit 12 is a means for displaying the setting contents and the operation state when performing image formation, and includes, for example, an LCD (Liquid Crystal Display). The display unit 12 includes display means for displaying that double feed has occurred. When a double feed of the transfer sheet is detected by the double feed detection means, a warning mark or the like is displayed to indicate the occurrence of double feed. The operator can confirm the occurrence of double feed on the display unit 12.

  The paper feed unit 13 has a manual paper feed tray (not shown) and a paper feed cassette 13a (see FIG. 2). As shown in FIG. 2, a plurality of transfer papers P are accommodated in the paper feed cassette 13a, and among these transfer papers P, the paper feed roller 20 contacts the uppermost one. Yes. When the paper feed roller 20 is driven to rotate counterclockwise in the drawing by a drive system (not shown), the transfer paper P located at the uppermost part is discharged from the paper feed unit 13. ing. The paper feed unit 13 is provided with a paper detection sensor 13s that detects the presence or absence of the transfer paper P.

  The transport unit 14 includes a paper feed roller 20, transport rollers 21, 21A, 21B, a registration roller 22, a pre-transfer roller 23, and a transport path 24 for the transfer paper P (see FIG. 2). The registration rollers 22 are provided to synchronize the conveyance start timing in the second paper feed and the transfer start timing in the image forming unit 16.

  The image reading unit 15 is a device that reads a document image. In addition, the image reading unit 15 allows the operator to read an image indicating the occurrence of a double feed by himself / herself. The image forming unit 16 includes a developing unit 25, a transfer electrode 26, and a separation electrode 27 (see FIG. 2). The image forming unit 16 performs processing such as rotation or enlargement / reduction of the image read by the image reading unit 15, and then forms an image on the transfer paper P conveyed by the conveying unit 14 by an electrophotographic method. Made.

  As shown in FIG. 2, the ultrasonic sensor 17 is provided in a double feed detection unit (double feed detection device) U <b> 1 between the conveyance roller 21 and the registration roller 22. FIG. 3 is a diagram illustrating a configuration example of the ultrasonic sensor.

  As shown in FIG. 3, the ultrasonic sensor 17 includes a transmission circuit 31, a transmitter 32, a receiver 33, and a reception circuit 34. The receiving circuit 31 includes an oscillation circuit that generates a predetermined frequency signal and a power amplifier circuit that amplifies the predetermined frequency signal. The reception circuit 34 includes a resonance circuit that converts vibration energy into an electrical signal, an amplification circuit that amplifies the reception signal, a rectification circuit that detects the amplified signal, and a comparison circuit that compares the reception signal with a reference value. And an output circuit.

  An electric signal of a predetermined frequency output from the transmission circuit 31 is input to the transmitter 32, converted into acoustic energy (ultrasonic waves) by a transducer (piezoelectric element) in the transmitter 32, and the receiver via the transfer paper P Radiated toward 33. A part of the ultrasonic wave emitted from the transmitter 32 is reflected by the transfer paper P in the transfer path. The ultrasonic wave that has passed through the transfer paper P is received by the receiver 33, converted into an electrical signal by a transducer (piezoelectric element) in the receiver 33, and input to the receiving circuit 34. The receiving circuit 34 detects the presence or absence of double feeding of the transfer paper based on the attenuation amount after passing through one transfer paper and the transfer paper at the time of double feeding and the reference value.

  The paper discharge tray 18 is a device for receiving the discharged transfer paper P after image formation. The paper discharge tray 18 includes at least one tray. In this example, a plurality of trays are provided. The paper discharge tray 18 is provided with a paper discharge detection sensor 18s for detecting the presence or absence of the transfer paper P discharged into each tray.

  Further, in the double feed detection unit U1 of the image forming apparatus 100, in order to reduce the influence of the reflected wave by the sound wave reflection object near the installation position of the ultrasonic sensor 17, the sound absorbing material is applied to the sound wave reflection object around the ultrasonic sensor 17. Is made to arrange. FIG. 4 is a diagram illustrating a configuration example of the double feed detection unit according to the first embodiment.

As shown in FIG. 4, in the double feed detection unit U1, the sound absorbing material 37A, on the ultrasonic reflector around the ultrasonic sensor 17, for example, the lower surface of the conveyance path 24 on the ultrasonic transmitter 32 side and the surface of the roller shaft 21S. 37B is pasted. In this case, since the diameter of the transmitter and receiver of the ultrasonic sensor is 20 to 25 mm, the sound absorbing materials 37A and 37B are arranged within a radius of 50 mm. It is desirable that the sound absorbing materials 37A and 37B have irregularities on the surface and have a porous material, for example, a density in the range of 25 to 90 kg / m ³ . Moreover, in order to suppress corrosion by ozone generated by discharge, it is desirable that the sound absorbing material has ozone resistance characteristics. In this example, porous urethane is used.

  Here, the opening size of the sound absorbing materials 37 </ b> A and 37 </ b> B disposed on the upper and lower surfaces of the conveyance path 24 is set smaller than the opening dimension of the conveyance path 24. In this case, a cover 36 is provided on the receiver 33 side in order to prevent disturbance. The sound absorbing material 37C is partially arranged inside the cover 36. The materials of the sound absorbing materials 37A, 37B, and 37C are the same.

  FIG. 5 is a diagram illustrating an installation state of the ultrasonic sensor when measuring the transmission amount and the reflection amount of the sound absorbing material. FIG. 5A shows an installation state when the amount of transmission is measured. In this case, as shown in FIG. 5A, the sound absorbing material 37 is inserted between the transmitter 32 and the receiver 33 of the ultrasonic sensor 17, and the amount of ultrasonic waves transmitted through the sound absorbing material 37 is measured. FIG. 5B shows an installation state when the amount of reflection is measured. In this case, as shown in FIG. 5B, the transmitter 32 and the receiver 33 of the ultrasonic sensor 17 are installed on the same side of the sound absorbing material 37, obliquely with respect to the surface of the sound absorbing material. Measure the amount of ultrasound reflected from.

FIG. 6 is a diagram showing the density dependency of the ultrasonic sound absorption coefficient. As shown in FIG. 6, it was found that the sound absorption coefficient was relatively high when the density was in the range of 25 to 90 kg / m ³ . Moreover, FIG. 7 is a figure which shows the measurement result of the sound absorption rate of a different sound absorption material. From the results shown in FIG. 7, it was found that the sound absorption rate of maltoprene SC, SM-55, RSM, seal material SD, and sound absorbing foam F-1 was high. When such a material having a high sound absorption rate is used as the sound absorbing material, the antireflection effect can be improved.

As described above, in the present embodiment, the sound absorbing materials 37A, 37B, and 37C are arranged on the lower surface of the conveyance path 24 around the ultrasonic sensor 17, the roller shaft 21S, and the inner surface of the cover 36. The sound absorbing materials 37A, 37B, and 37C are porous materials having irregularities on the surface and a density in the range of 25 to 90 kg / m ³ , and the opening size of the sound absorbing material 37A is larger than the opening size of the conveyance path 24. It has been made smaller.

  Accordingly, the ultrasonic wave irradiated directly by the sheet metal around the ultrasonic sensor 17 or by reflection from the transfer paper P is absorbed, and reflection from these sound wave reflecting objects is suppressed. The influence of the reflected wave by the sound wave reflector near the installation position can be reduced, and the double feed detection accuracy can be improved. Therefore, it is possible to install the ultrasonic sensor even at a position that is surrounded by an ultrasonic reflector and is more easily affected by the reflected wave.

In addition, since the sound absorbing material has an ozone resistance characteristic, it is difficult to be corroded by ozone generated by discharge, and a long life can be achieved. Moreover, since the sound absorbing material having a density in the range of 25 to 90 kg / m ³ is used, the sound absorbing effect can be improved.

  Next, a double feed detection device and an image forming apparatus using the same according to a second embodiment of the present invention will be described with reference to the drawings.

  The image forming apparatus according to the second embodiment includes a double feed detection unit (double feed detection device), and a transmitter and a receiver of an ultrasonic sensor as a double feed detection unit are surrounded by a cylindrical sound absorbing material. By arranging in this way, it is possible to reduce the influence of the reflected wave by the sound wave reflection object near the installation position of the ultrasonic sensor, and to improve the detection accuracy of double feed.

  The image forming apparatus according to the second embodiment has the same configuration as that of the image forming apparatus 100 according to the first embodiment described above except for the shape of the sound absorbing material of the double feed detection unit, and detailed description thereof is omitted.

  FIG. 8 is a diagram illustrating a configuration example of a double feed detection unit according to the second embodiment. As shown in FIG. 8, in the double feed detection unit U2, the sound absorbing materials 38A and 38B are formed in a cylindrical shape. A sound absorbing material 38A is disposed in the transmitter 32 of the ultrasonic sensor, and a sound absorbing material 38B is disposed in the receiver 33. The transmitter 32 or the receiver 33 is fixed to one end of the sound absorbing materials 38A and 38B, and the other end has an inclined end surface formed at a predetermined angle α with respect to the central axis of the cylindrical sound absorbing material. Contact with the transport path. The opening size of the sound absorbing materials 38A and 38B is formed smaller than the opening size of the conveyance path. Further, the sound absorbing material 38A and the sound absorbing material 38B are made of the same material, and the shapes of the sound absorbing material 38A and the sound absorbing material 38B are symmetrical. FIG. 9 is a diagram illustrating the shape of the sound absorbing material. As shown in FIG. 9, the inclined end surfaces of the sound absorbing materials 38A and 38B are elliptical.

  By providing such cylindrical sound-absorbing materials 38A and 38B, the ultrasonic wave is not irradiated to the peripheral parts, and the influence of the reflected wave by the sound wave reflection object near the installation position of the ultrasonic sensor 17 can be reduced. Further, since the reflected wave reflected by the transfer paper P is absorbed by the inner surface of the cylindrical sound absorbing material, the influence of the reflected wave can be reduced.

  FIG. 10 is a diagram illustrating an example in which a filter is arranged. As shown in FIG. 10, in the double feed detection unit U <b> 2, a filter 39 is disposed between the sound absorbing material 38 </ b> A disposed in the transmitter 32 disposed below the transport path 24 and the transport path 24. The filter 39 has a thickness of λ / 4 or less. Here, λ is the wavelength of the ultrasonic wave. By providing this filter 39, it is possible to prevent paper dust from entering from the conveyance path 24.

  As described above, in the present embodiment, the cylindrical sound absorbing material 38 </ b> A is disposed in the transmitter 32 of the ultrasonic sensor 17, and the cylindrical sound absorbing material 38 </ b> B is disposed in the receiver 33. As a result, it is possible to eliminate the ultrasonic wave irradiation on the member near the installation position of the ultrasonic sensor 17 and absorb the reflected wave from the transfer paper P, thereby reducing the influence of the reflected wave and detecting the double feed. Accuracy can be improved. Therefore, it is possible to install the ultrasonic sensor 17 at a position that is surrounded by an ultrasonic reflector and is more easily affected by the reflected wave. In this case, it is not necessary to attach a sound absorbing material to the conveyance path, the sensor interval can be minimized, and the maximum receivable signal level can be obtained.

  Further, by placing the filter 39 between the sound absorbing material 38 </ b> A arranged in the transmitter 32 and the conveyance path 24, it is possible to prevent paper dust from entering from the conveyance path 24.

  Next, a double feed detection device according to a third embodiment of the present invention and an image forming apparatus using the same will be described with reference to the drawings.

  The image forming apparatus according to the third embodiment includes a double feed detection unit (double feed detection device), and a cylindrical sound absorbing material is disposed in a transmitter and a receiver of an ultrasonic sensor as a double feed detection unit. At the same time, by providing a cleaning means for cleaning the paper dust on the transmitter surface, it is possible to reduce the influence of the reflected wave by the sound wave reflection object near the installation position of the ultrasonic sensor, and to improve the detection accuracy of the double feed. The paper dust attached to the transmitter surface can be eliminated, and the deterioration of detection accuracy due to the paper dust can be prevented.

  The image forming apparatus according to the third embodiment has the same configuration as that of the image forming apparatus 100 according to the first embodiment described above, except that the sound absorbing material shape of the double feed detection unit and the cleaning unit are included. Detailed description thereof is omitted.

  FIG. 11 is a diagram illustrating a configuration example 1 of the double feed detection unit according to the third embodiment. As shown in FIG. 11, in the double feed detection unit U3, the sound absorbing materials 40A and 40B are formed in a cylindrical shape. A sound absorbing material 40A is disposed in the transmitter 32 of the ultrasonic sensor, and a sound absorbing material 40B is disposed in the receiver 33. The transmitter 32 or the receiver 33 is fixed to one end of the sound absorbing materials 40A and 40B, and the other end has an inclined end surface formed at a predetermined angle with respect to the central axis of the cylindrical sound absorbing material, and this inclined end surface is conveyed. Contact with the road. The opening size of the sound absorbing materials 40A and 40B is formed smaller than the opening size of the conveyance path.

  In addition, the sound absorbing material 40A on the transmitter 32 side is provided with a slit 41 for removing paper dust. The slit 41 is a circular hole or a long hole. A blower 42 is provided as a cleaning means for cleaning the paper dust on the surface of the transmitter 32 of the ultrasonic sensor 17. When cleaning the paper dust on the surface of the transmitter 32, the blower 42 is blown, and the wind passes through the slit 41 on the sound absorbing material 40A so that the paper dust attached to the surface of the transmitter 32 is the other end. Excluded from.

  FIG. 12 is a diagram illustrating a configuration example 2 of the double feed detection unit according to the third embodiment. As shown in FIG. 12, in the double feed detection unit U3, a slit 41 for removing paper dust is provided in the sound absorbing material 40A on the transmitter 32 side. The slit 41 is a circular hole or a long hole. Further, a suction device 43 is provided as a cleaning means for cleaning the paper dust on the surface of the transmitter 32 of the ultrasonic sensor 17. When cleaning the paper dust on the surface of the transmitter 32, by operating this suction device 43 and sucking air from the slit 41 of the sound absorbing material 40A, a suction airflow is formed at the slit 41 on the sound absorbing material 40A, Paper dust on the surface of the transmitter 32 is removed from the slit 41 on the suction device 43 side.

  FIG. 13 is a diagram illustrating a configuration example 3 of the double feed detection unit according to the third embodiment. As shown in FIG. 13, in the double feed detection unit U3, a slit 41 for removing paper dust is provided in the sound absorbing material 40A on the transmitter 32 side. The slit 41 is a circular hole or a long hole. Further, a cleaning brush 44 is provided as a cleaning means for cleaning the paper dust on the surface of the transmitter 32 of the ultrasonic sensor 17. A driving source of the cleaning brush 44 is a solenoid 45. A motor may be used as a drive source.

  When cleaning the paper dust on the surface of the transmitter 32, the paper dust on the surface of the transmitter 32 is removed from the other end by driving the cleaning brush 44 by the solenoid 45.

  Thus, in the present embodiment, the sound absorbing material 40A is disposed in the transmitter 32, and the sound absorbing material 40B is disposed in the receiver 33. Further, a cleaning means for cleaning the paper dust on the surface of the transmitter 32, for example, a blower 42, a suction device 43 or a cleaning brush 44 is provided, and the transmitter 32 is disposed at a lower position with respect to the conveyance path 24. The sound absorbing material 40A is provided with a slit 41 for removing paper dust.

  As a result, it is possible to eliminate the irradiation of ultrasonic waves to the member near the installation position of the ultrasonic sensor 17 and to absorb the reflected wave from the transfer paper, thereby reducing the influence of the reflected wave and detecting the double feed. Can be improved, paper dust adhering to the surface of the ultrasonic sensor (transmitter or receiver) can be eliminated, and deterioration in detection accuracy due to paper dust can be prevented.

  In the second and third embodiments described above, the cylindrical sound absorbing materials 38A, 38B and 40A, 40B are fixed to the transmitter 32 or the receiver 33, but are not limited thereto. It is not a thing. The cylindrical sound absorbing material may be detachable.

  FIG. 14 is a diagram illustrating a configuration example of a removable cylindrical sound absorbing material. FIG. 14A shows a configuration on the sound absorbing material side. As shown in FIG. 14A, a resin portion 47 is provided below the sound absorbing material 46, and a position fixing ball 48 is provided on the resin portion 47. FIG. 14B shows the configuration on the receiving side. As shown in FIG. 14 (b), a recess 50 is provided on the inner wall of the receiving side 48 to fit the position fixing ball 48. FIG. 14C shows the wearing state. When such a configuration is used, it is possible to easily clean the paper powder and replace the sound absorbing material.

  In the second and third embodiments described above, the transmitter 32 and the receiver 33 of the ultrasonic sensor 17 are arranged with the cylindrical sound absorbing materials 38A, 38B and 40A, 40B. It is not limited. For example, only the transmitter 32 may be provided with the cylindrical sound absorbing material 38A or 40A.

  INDUSTRIAL APPLICABILITY The present invention is extremely suitable for application to detection of double transfer paper transfer in an image forming apparatus that forms an image based on image data on transfer paper that is conveyed one by one from a paper feeding unit on which a plurality of transfer papers are stacked. It is.

1 is a block diagram illustrating a configuration example of an image forming apparatus 100 according to a first embodiment. It is a figure which shows the example of an attachment position of an ultrasonic sensor. It is a figure which shows the structural example of an ultrasonic sensor. It is a figure which shows the structural example of the double feed detection part of 1st Embodiment. It is a figure which shows the measurement state of permeation | transmission amount and reflection amount of a sound-absorbing material. It is a figure which shows the density dependence of the sound absorption rate of a sound-absorbing material. It is a figure which shows the sound absorption rate of a different sound absorption material. It is a figure which shows the structural example of the double feed detection part of 2nd Embodiment. It is a figure which shows the shape of a sound-absorbing material. It is a figure which shows the structural example at the time of arrange | positioning a filter. It is a figure which shows the structural example 1 of the double feed detection part of 3rd Embodiment. It is a figure which shows the structural example 2 of the double feed detection part of 3rd Embodiment. It is a figure which shows the structural example 3 of the double feed detection part of 3rd Embodiment. It is a figure which shows the structural example of the cylindrical sound-absorbing material which can be attached or detached.

Explanation of symbols

17 Ultrasonic sensor (multifeed detection means)
24 transport path 31 transmitter circuit 32 transmitter 33 receiver 34 receiver circuit 35 storage means 37A, 37B, 37C, 38A, 38B, 40A, 40B sound absorbing material 39 filter 41 slit 42 blower 43 suction device 44 cleaning brush 45 solenoid 100 image Forming device P Transfer paper U1, U2, U3 Double feed detector (Double feed detector)

Claims (15)

Ultrasonic waves are transmitted from the transmitter of the ultrasonic sensor facing the transfer paper conveyance path to the receiver, and the output signal due to attenuation when the transfer paper passes between the transmitter and the receiver is used for double feed detection. A double feed detection device for detecting double feed in comparison with a threshold of
A double feed detection device, wherein a sound absorbing material is arranged on the transmitter, the transmitter and the receiver, or members around the transmitter. The multi-feed detection apparatus according to claim 1, wherein the sound absorbing material is formed in a cylindrical shape and is disposed so as to surround the transmitter and the receiver. The transmitter or the receiver is fixed to one end of the sound absorbing material, and the other end has an inclined end surface formed at a predetermined angle with respect to the central axis of the cylindrical sound absorbing material, and the inclined end surface is elliptical. Yes,
The multifeed detection device according to claim 2, wherein the inclined end surface is brought into contact with the conveyance path. The double feed detection device according to claim 3, wherein an opening size of the inclined end surface is equal to or smaller than an ultrasonic passage hole size of the conveyance path. The multifeed detection device according to claim 2, wherein the sound absorbing material disposed in the transmitter and the sound absorbing material disposed in the receiver are symmetrical. The multi-feed detection device according to claim 2, wherein the sound absorbing material has a detachable structure. Having a filter for preventing paper dust from entering between the opening surface of the sound absorbing material and the transport path;
The thickness of the said filter is 1/4 or less of the ultrasonic wavelength which the said ultrasonic sensor generate | occur | produces. The double feed detection apparatus of Claim 2 characterized by the above-mentioned. A cleaning means for cleaning paper dust on the surface of the ultrasonic sensor;
The weight according to claim 2, wherein a slit for removing the paper dust is provided in a sound absorbing material disposed in the transmitter or receiver installed at a lower position with respect to the conveyance path. Feed detection device. The multifeed detection device according to claim 8, wherein the cleaning unit is a device that is disposed in the vicinity of the sound absorbing material and that blows or sucks the sound absorbing material. The multifeed detection device according to claim 8, wherein the cleaning unit includes a cleaning mechanism that moves a cleaning member to clean paper dust on the surface of the ultrasonic sensor. The double feed detection device according to claim 10, wherein a driving source of the cleaning unit is a motor or a solenoid. The multi-feed detection device according to claim 1, wherein the sound absorbing material has an ozone resistance characteristic. The double feed detection device according to claim 1, wherein the density of the sound absorbing material is in a range of 25 to 90 kg / m ³ . The multifeed detection apparatus according to claim 1, wherein the transmitter and the receiver, or the sound absorbing material disposed on each member around the transmitter are made of the same material. Ultrasonic waves are transmitted from the transmitter of the ultrasonic sensor facing the transfer paper conveyance path to the receiver, and the output signal due to attenuation when the transfer paper passes between the transmitter and the receiver is used for double feed detection. In an image forming apparatus that has a double feed detection unit that detects double feed in comparison with a threshold value of and forms an image on the transfer paper based on arbitrary image data,
An image forming apparatus comprising: a sound absorbing material disposed in a transmitter of the double feed detection unit, the transmitter and a receiver, or a member around the transmitter or around the receiver.

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