JP2010235290A - Double-feeding detection device, paper feeder, image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a double-feeding detection device accurately detecting double feeding, a paper feeder provided with such a double-feeding detection device, and an image forming device provided with the paper feeder described above. <P>SOLUTION: The double-feeding detection device Y detects the double feeding of a paper P passing through a paper carriage path by arranging an ultrasonic wave transmitter 24a and an ultrasonic wave receiver 24b on the opposite sides of the paper carriage path, and by comparing the output of the ultrasonic wave, coming from the ultrasonic wave transmitter 24a and reaching to the ultrasonic wave receiver 24b, with the predetermined double-feeding detection threshold value. This device includes: a data storage section 3 storing the history of the receiving signal levels of the ultrasonic wave receiver 24b in the time when the paper is passing; and a threshold value changing section of a control section 1a changing the threshold value for the double-feeding detection in accordance with the history of the receiving signal levels stored in the data storage section 3. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a double feed detection device that detects double feed of paper using ultrasonic waves, a paper feed device including the double feed detection device, and an image forming apparatus including the paper feed device.

  Conventionally, in a paper feeding device in an image forming apparatus such as a copying machine or a multi-function machine, it is a rule to feed paper one by one. However, when paper is not sufficiently rolled by a paper feeding roller, two sheets are used. Multiple feeds in which the above sheets are sent simultaneously may occur. As a method for detecting such a multi-feed state, an optical method that detects the amount of light transmitted through the paper and looks at the degree of overlap of the paper has been the mainstream, but in recent years, an ultrasonic wave that measures the amount of ultrasonic waves that pass through the paper. The method is adopted.

  In the ultrasonic multifeed detection device, an ultrasonic transmitter and an ultrasonic receiver are arranged across the paper conveyance path, and based on the output of the ultrasonic wave reaching the ultrasonic receiver from the ultrasonic transmitter, Detects double feed of paper passing through the paper transport path.

  However, it is known that an ultrasonic sensor composed of an ultrasonic transmitter and an ultrasonic receiver generates an error in the output level even in the same double feed state due to temperature and humidity, particularly a change in temperature. This affects the detection accuracy of double feed.

  For this reason, Patent Document 1 discloses a paper feeding device that measures the ambient temperature using a temperature detection element such as a thermistor, and corrects the transmission method or the reference level of the received voltage according to the measured temperature.

  Specifically, as shown in FIG. 3, the entire sheet feeding device is controlled by a control unit 1 including a CPU and the like, and sandwiches a sheet conveyance path through which a sheet P fed from a pair of feed prevention rollers is conveyed. An ultrasonic transmitter 24a and an ultrasonic receiver 24b are arranged, and by comparing the output of the ultrasonic wave reaching the ultrasonic receiver 24b from the ultrasonic transmitter 24a with a predetermined double feed detection threshold, the paper transport path Is provided with a double feed detection device Y1 for detecting double feed of the paper P passing through.

  In this double feed detection device, the amount of ultrasonic waves that reach the ultrasonic receiver 24b varies depending on whether one sheet passes or two or more sheets overlap, that is, in a double feed state. Detecting this, in other words, utilizing the fact that the ultrasonic wave detected by the ultrasonic wave receiver 24b fluctuates depending on the thickness of the paper that interrupts the middle. In other words, after the output signal from the ultrasonic receiver 24b is amplified by the amplifier circuit 26, the data processor 28 detects the presence or absence of double feed by comparing it with the double feed detection threshold value.

  However, since the ultrasonic sensor 24 including the ultrasonic transmitter 24a and the ultrasonic receiver 24b as described above has a characteristic that the output fluctuates depending on the temperature and humidity, in particular, the temperature change, the double feed state An error occurs in the detection result.

Therefore, in the conventional double feed detection device Y1, the temperature is measured by measuring the ambient temperature of the ultrasonic sensor using a temperature detecting element such as the thermistor T and inputting the measured value to the data processing unit 28. The detection result is corrected by changing the reception voltage from the ultrasonic receiver 24b and the reference level of the reception voltage depending on the temperature.
JP 2005-350253 A

  In general, when the type and thickness of the paper are different, the ultrasonic wave propagation property is also different, so that the threshold value for detecting double feeding is also different. However, the configuration of Patent Document 1 does not take such points into consideration, and thus there is a problem in that it may not be possible to accurately detect double feeding.

  Accordingly, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a double feed detection device capable of accurately detecting double feed and a feed provided with such a double feed detection device. An object of the present invention is to provide an image forming apparatus provided with a paper device or a paper feeding device as described above.

  In order to achieve the above object, a multifeed detection device according to the present invention includes an ultrasonic transmitter and an ultrasonic receiver arranged across a paper conveyance path, and an ultrasonic wave that reaches the ultrasonic receiver from the ultrasonic transmitter. In the double feed detection device that detects the double feed of the paper passing through the paper transport path by comparing the sound wave output with a predetermined double feed detection threshold, the reception level history of the ultrasonic receiver when the paper passes And a threshold value changing unit for changing the double feed detection threshold value according to the history of the reception level stored in the storage unit.

  Since the double feed detection device according to the present invention changes the double feed detection threshold according to the reception level, even when the paper type and thickness are different and the ultrasonic wave propagation property is different, the double feed detection is accurately performed. Can be done.

  Embodiments of the present invention will be described below with reference to the accompanying drawings for understanding of the present invention. In addition, the following embodiment is an example which actualized this invention, Comprising: The thing of the character which limits the technical scope of this invention is not.

  FIG. 1 is a block diagram showing the entire control system of the image forming apparatus according to the embodiment of the present invention, and FIG. 2 is a signal path diagram of the double feed detection apparatus according to the embodiment of the present invention.

  An image forming apparatus X in which a multifeed detection device according to an embodiment of the present invention is incorporated is a so-called multi-function machine having a scanner function, a print function, a copy function, and a facsimile function, and includes a scanner unit 6 as a document reading device. ing.

  The image forming apparatus that is the subject of the present invention may be a scanner itself for the purpose of reading a document, in addition to a copying machine or a facsimile as a multifunction machine as described above.

  First, the configuration of the main part of the image forming apparatus X including the double feed detection device according to the embodiment of the present invention will be described with reference to the block diagram shown in FIG.

  As shown in FIG. 1, the image forming apparatus X includes a control unit 1a including a CPU and other control circuits, an operation / display unit 2, a data storage unit 3, an image processing calculation unit 4, a NIC 5, a scanner unit 6, and a printing unit. 7 and the facsimile unit 8 and the like, and these are connected through the bus 11 so that information can be transferred.

  The operation / display unit 2 includes an operation unit 2a for inputting information and a display unit 2b for displaying information (including images). The operation unit 2a is, for example, a touch panel or a sheet key provided on the surface of the liquid crystal display device. The display unit 2b is, for example, a liquid crystal display device. The operation / display unit 2 constitutes a man-machine interface for the user.

  The data storage unit 3 is a readable / writable large-capacity non-volatile memory that stores processing data as necessary during processing of image data obtained by reading from a document or printing processing of image data. . The data storage unit 3 receives the above-described double feed detection threshold, a program for operating the control unit 1a as various functional units (threshold changing unit and transmission level changing unit, which will be described later), and ultrasonic reception when the paper passes. The history of the reception level of the ultrasonic waves received by the device 24b is stored.

  The image processing arithmetic unit 4 is constituted by a dedicated signal processing circuit or a DSP (Digital Signal Processor) or the like, performs various image processing on the image data, and forms a print job described in a predetermined print job description language into an image. Processing for converting into bitmap image data to be used, processing for generating image data to be transmitted to an external device (for example, image data that has been subjected to predetermined encoding such as JPEG format), and the like are performed.

  The NIC 5 receives data (including data of an image read by the scanner unit 6) from / to an external device such as an information processing terminal or an e-mail server through a network including a LAN and the Internet compliant with the standard IEEE 802.3, for example. It is a communication interface which transmits / receives.

  The scanner unit 6 converts an image formed on a document from a document placed on a glass document table (not shown) or a document conveyed by an ADF (not shown) into a color (R, G, B). ) Is a color scanner that distinguishes and reads.

  The printing unit 7 is a so-called print engine controlled by the main control unit 1 and sequentially feeds recording sheets stored in a sheet feeding cassette (not shown) one by one, and passes through a predetermined image forming position and is a sheet discharge tray. Recording paper (recording paper) based on the image data of the original read from the original by the scanner unit 6 and the image data for printing generated by the image processing calculation unit 4 at the image forming position. It is a set of components such as a device that forms (outputs) an image on an example) and an MPU that controls the device.

  The printing unit 7 is provided with a double feed prevention roller pair 20 (FIG. 2) for feeding sheets taken out from the paper feed cassette one by one to prevent double feed. In the multi-feed prevention roller pair 20, even if a plurality of stacked sheets as shown in FIG. 3 are supplied, they must be spread on a single sheet P one by one. A double feed detection device Y for detecting whether the number of sheets P is one sheet or two or more sheets is attached. Details of the sheet feeding device provided with the double feed detection device Y will be described later.

  The facsimile unit 8 includes communication means such as an NCU (Network Control Unit) and a modem, and performs dial-up and negotiation processing for determining a communication method with a communication partner (partner station). It transmits and receives facsimile data (image data read by the scanner unit 6) with the facsimile apparatus.

  The control unit 1a controls each of the scanner unit 6, the print unit 7, the facsimile unit 8, the operation / display unit 2, the data storage unit 3, and the image processing calculation unit 4.

  For example, the control unit 1a causes the printing unit 7 to execute a printing process (image forming process) based on a print job received through the NIC 5. In addition, the control unit 1a causes the facsimile unit 8 to execute a facsimile transmission process of calling the designated transmission destination telephone number and transmitting the image data to be transmitted. Further, the control unit 1a causes the scanner unit 6 to execute a scanning process for reading an image formed on the document from the document.

  Next, with reference to FIG. 2, the details of the sheet feeding device provided with the double feed detection device Y will be described.

  The double feed detection device Y includes an ultrasonic sensor 24 including an ultrasonic transmitter 24a and an ultrasonic receiver 24b provided across a paper conveyance path of the paper P supplied from the double feed prevention roller pair 20. 3 is the same as the conventionally known double feed detection device shown in FIG. 3, but the double feed detection device Y does not include temperature detection means such as the thermistor T. Is different.

  On the other hand, in this double feed detection device Y, the temperature of the medium is detected from the change in the sound speed by utilizing the fact that the speed of sound depends on the temperature of air that is a medium through which sound waves propagate.

  That is, in this double feed detection device Y, the control unit 1a measures the propagation speed of sound waves in the vicinity of the ultrasonic sensor 24, that is, the sound speed, as described below.

  The method is as follows.

  This measurement is performed each time immediately before the image forming process is performed. When the measured temperature is stable, the measurement may be performed with a sufficient time interval.

  First, the control unit 1a starts pulse output to the ultrasonic transmitter 24a at an appropriate time immediately before the image forming process is performed. Accordingly, an ultrasonic pulse is transmitted from the ultrasonic transmitter 24a toward the ultrasonic receiver 24b. In addition, a timer is started from the start of pulse output, and the elapsed time is counted.

  Eventually, when the ultrasonic receiver 24b receives the ultrasonic wave, this signal is received by the control unit 1a. At this time, the controller 1a stops counting by the timer, and holds and stores the count number N.

  This count number indicates the time for the ultrasonic wave to reach the ultrasonic receiver 24b from the ultrasonic transmitter 24a.

  Here, it is well known that the speed of sound V is calculated by V = 331.5 + 0.5 × atmosphere temperature Tc.

  Accordingly, the ambient temperature Tc is calculated as Tc = (V−331.5) /0.5.

  On the other hand, the time t until the ultrasonic wave reaches the ultrasonic receiver 24b from the ultrasonic transmitter 24a is calculated as t = H × N, where H is a constant (known) pulse period. The sound velocity V is V = L / (H × N), where L (constant / known) is the distance between the ultrasonic transmitter 24a and the ultrasonic receiver 24b.

  From the above, the atmospheric temperature Tc = (L / (H × N) −331.5) /0.5. Since L and H are known in this equation, the atmospheric temperature Tc is obtained from the count number N. You can see that

  Therefore, if the relationship between the ambient temperature and the output of the ultrasonic sensor is measured and stored in advance, the ambient temperature can be detected from the above equation by detecting the count number N.

Alternatively, if the ambient temperature is 24 ° C. as a default, the sound velocity at that time V ₂₄ = 331.5 + 0.5 × 24 = 343.5 m / sec.

  The time t at this time is t = 0.01 / 343.5 = 0.0291 (S) when the distance L between the sensors is 0.01 m, and the count number when the pulse period H is 100 (nS). N (reference pulse number) is N = 0.00291 / 100 = 291.1 (pulses).

  Accordingly, by measuring and storing in advance the change in the output of the ultrasonic sensor when the reference pulse number and the pulse number N change, the ultrasonic wave is directly calculated from the actually measured count number (pulse number) N. The detection accuracy of the double feed detection device can be increased by correcting the output of the sensor or the threshold value to be compared with it. That is, as shown in FIG. 2, the control unit 1 changes the double feed detection threshold according to the reception level of the ultrasonic wave received by the ultrasonic receiver 24b. Specifically, the ultrasonic reception level received by the ultrasonic receiver 24 b is amplified by the amplifier circuit 26, and the history is stored in the data storage unit 3. The control unit 1 refers to the reception level history stored in the data storage unit 3 (for example, calculates an average value of the reception levels). For example, when the reception level is relatively weak (the sheet is relatively thick). The multifeed detection threshold is changed to be small.

As described above, in the double feed detection device Y according to this embodiment, the output of the ultrasonic wave reaching the ultrasonic receiver 24b from the ultrasonic transmitter 24a is compared with a predetermined double feed detection threshold value, thereby making the paper transport path. The double feed detection threshold is changed according to the history of the reception level of the ultrasonic receiver 24b. Therefore, even when the type and thickness of the paper are different and the ultrasonic wave propagation is different, it is possible to accurately detect the double feed.
In the above description, the case where the control unit 1 performs control to reduce the double feed detection threshold when the reception level is relatively weak (that is, the case where it functions as a threshold changing unit) has been described. Instead of the control for reducing the detection threshold, control for increasing the transmission level of the ultrasonic transmitter 24a (function as a transmission level changing unit) may be performed, or the amplification factor (gain) of the amplifier circuit 26 may be performed. ) May be controlled.

1 is a block diagram showing a schematic configuration of a copier according to an embodiment of the present invention. The figure which shows the signal path | route of the double feed detection apparatus which concerns on embodiment of this invention. The schematic diagram which shows schematic structure of the conventional multifeed detection apparatus.

DESCRIPTION OF SYMBOLS 1 ... Control part 20 ... Double feed prevention roller pair 24 ... Ultrasonic sensor 24a ... Ultrasonic transmitter 24b ... Ultrasonic receiver 26 ... Amplification circuit Y ... Double feed detection apparatus

Claims (5)

By placing an ultrasonic transmitter and an ultrasonic receiver across the paper conveyance path, and comparing the ultrasonic output reaching the ultrasonic receiver from the ultrasonic transmitter with a predetermined double feed detection threshold, In the double feed detection device that detects double feed of paper passing through the paper transport path,
A storage unit for storing a history of reception levels of the ultrasonic receiver when the paper passes;
A double feed detection device comprising: a threshold change unit that changes the double feed detection threshold according to the reception level history stored in the storage unit. The double feed detection device according to claim 1,
The multi-feed detection device, wherein the threshold value changing unit changes the multi-feed detection threshold according to an average value of reception levels in the reception level history. By placing an ultrasonic transmitter and an ultrasonic receiver across the paper conveyance path, and comparing the ultrasonic output reaching the ultrasonic receiver from the ultrasonic transmitter with a predetermined double feed detection threshold, In the double feed detection device that detects double feed of paper passing through the paper transport path,
A storage unit for storing a history of reception levels of the ultrasonic receiver when the paper passes;
A multi-feed detection apparatus comprising: a transmission level changing unit that changes a transmission level of the ultrasonic transmitter according to a history of the reception level stored in the storage unit. The double feed detection device according to any one of claims 1 to 3,
A paper feeding device comprising a paper feeding unit for feeding the paper. A sheet feeding device according to claim 4,
An image forming apparatus comprising: an image forming unit that forms an image on the paper.