JP2010105791A - Double feeding detecting device, paper feeding device, and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a double feeding detecting device suppressing a rise in costs, preventing an increase in mounting dimensions, and eliminating the trouble of mounting work, and also to provide a paper feeding device including such a double feeding detecting device. <P>SOLUTION: In this double feeding detecting device in which a supersonic wave generator and a supersonic wave receiver are disposed sandwiching a sheet conveyance path, for detecting double feeding of paper sheets passing through the sheet conveyance path based on output of supersonic waves from the supersonic wave generator reaching the supersonic wave receiver, the arrival time of the supersonic waves from the supersonic wave generator reaching the supersonic wave receiver is measured, and an output value of the supersonic waves from the supersonic wave generator reaching the supersonic wave receiver is corrected based on the change in the arrival time. <P>COPYRIGHT: (C)2010,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. Conventionally, an optical method for detecting the amount of light transmitted through the paper and detecting the degree of overlap of the paper is the mainstream as a method for detecting such a multi-feed state. However, in recent years, an ultrasonic wave measuring the amount of ultrasonic waves passing through the paper is used. 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 the ultrasonic wave is transmitted from the ultrasonic transmitter to the ultrasonic receiver. Detects double feed of paper passing through the paper transport path.
However, it is known that an ultrasonic sensor consisting 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, especially temperature changes. This affects the detection accuracy of double feed.
For this reason, Patent Document 1 discloses a paper feeding device that uses a temperature detection element such as a thermistor to measure the ambient temperature, and changes the transmission method or the reference level of the received voltage according to the measured temperature to correct it.
Specifically, as shown in FIG. 2, the paper feeder includes an ultrasonic transmitter 24a and an ultrasonic receiver across a paper conveyance path 22 through which the paper P fed from the double feed prevention roller pair 20 is conveyed. 24b is provided, and a double feed detection device Y1 for detecting double feed of the paper P passing through the paper transport path 22 based on the output of the ultrasonic wave that reaches the ultrasonic receiver 24b from the ultrasonic transmitter 24a is provided. ing.
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 are overlapped, that is, in a double feed state. .., In other words, the fact that the ultrasonic wave detected by the ultrasonic wave receiver 24b varies depending on the thickness of the paper that is interrupted. That is, after the output signal from the ultrasonic receiver 24b is amplified by the amplifier circuit 26, the data processor 28 compares it with a predetermined threshold value to detect the presence or absence of double feeding.
However, since the ultrasonic sensor 24 comprising the ultrasonic transmitter 24a and the ultrasonic receiver 24b as described above has the characteristic that the output fluctuates depending on the change of temperature and humidity, particularly temperature, as described above, An error occurs in the detection result.
Therefore, in the conventional double feed detection device Y1, the ambient temperature of the ultrasonic sensor is measured using a temperature detection element such as the thermistor T, and the measured value is input 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

However, in the configuration of Patent Document 1, a temperature sensing element such as an expensive thermistor must be used as described above, and a temperature sensing element such as a thermistor must be installed near the ultrasonic sensor. There are problems such as high costs, increased mounting dimensions, and complicated mounting work.
Accordingly, the present invention has been made in view of the above circumstances, and the object of the present invention is to suppress an increase in cost, without causing an increase in mounting dimensions, and to eliminate the complexity of the mounting work. It is an object of the present invention to provide a multifeed detection device capable of performing the above, a paper feed device including such a multifeed detection device, or an image forming apparatus including such a paper feed device.

In order to achieve the above object, the present invention provides:
An ultrasonic transmitter and an ultrasonic receiver are arranged across the paper conveyance path, and based on the output of the ultrasonic waves that reach the ultrasonic receiver from the ultrasonic transmitter, double feeding of the paper passing through the paper conveyance path In the double feed detection device that detects
The arrival time of the ultrasonic wave reaching the ultrasonic receiver from the ultrasonic wave transmitter is measured, and the output value of the ultrasonic wave reaching the ultrasonic wave receiver from the ultrasonic wave transmitter is corrected based on the change in the arrival time. It is configured as a double feed detection device.
In this double feed detection device, based on the output of the ultrasonic wave reaching the ultrasonic receiver from the ultrasonic transmitter, the double feed of the paper passing through the paper conveyance path is detected, and the ultrasonic transmitter transmits the ultrasonic wave. The ultrasonic wave reaching the ultrasonic wave receiver is measured by measuring the arrival time of the ultrasonic wave that reaches the ultrasonic wave receiver (or the pulse count if pulsed ultrasonic waves), and the ultrasonic wave reaching the ultrasonic wave receiver from the ultrasonic wave transmitter based on the change in the arrival time Therefore, a temperature detection element such as a thermistor for detecting the environmental temperature, which has been conventionally required, is unnecessary. Therefore, the cost regarding the said temperature detection element can be reduced, and size reduction of a machine can be advanced by omitting a useless space by providing a temperature detection element. Of course, since a temperature detection element is unnecessary, it can contribute to simplification of assembly work.
When pulsed ultrasonic waves having a fixed period are used as the ultrasonic waves, the arrival time is determined by the pulse of the pulsed ultrasonic waves generated before the ultrasonic waves reach the ultrasonic receiver from the ultrasonic transmitter. It can be calculated as a number.
In addition, when the ultrasonic wave is a pulsed ultrasonic wave having a constant period, the output value of the ultrasonic wave that reaches the ultrasonic receiver from the ultrasonic wave transmitter is transmitted to the ultrasonic wave receiver from the ultrasonic wave transmitter. Correction can be made on the basis of the environmental temperature calculated based on the number of pulses of the pulsed ultrasonic wave emitted before reaching.
The double feed detection device according to the present invention can be used for a paper feeding device as an example.
Furthermore, the double feed detection device according to the present invention can be used for a paper feeding device used in an image forming apparatus as an example.

  According to the present invention, a temperature detecting element such as a thermistor for detecting an environmental temperature, which has been conventionally required, is unnecessary. Therefore, the cost regarding the said temperature detection element can be reduced, and size reduction of a machine can be advanced by omitting a useless space by providing a temperature detection element. Of course, since the temperature detection element is unnecessary, it can contribute to simplification of the assembly work.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
An embodiment in which the present invention is applied to a document reading apparatus of an image forming apparatus will be described below with reference to the accompanying drawings. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
FIG. 1 is a block diagram showing the entire control system of the image forming apparatus according to an embodiment of the present invention, and FIG. 2 is a schematic configuration diagram of a double feed detecting device used in a conventional paper feeding device. FIG. 3 is a signal path diagram of the double feed detection device according to the embodiment of the present invention.

An image forming apparatus X in which a double feed 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 main control unit 1, an operation / display unit 2, a data storage unit 3, an image processing calculation unit 4, a NIC 5, a scanner unit 6, a printing unit 7, a facsimile unit 8, and the like. They are connected in such a way that information can be exchanged through the bus 11.

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 when processing image data obtained by reading from a document or printing processing of image data. .

  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. A process for converting to bitmap image data to be used, a process for generating image data to be transmitted to an external device (for example, image data 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) with an external device such as an information processing terminal or an e-mail server through a network including a LAN and the Internet conforming to 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) to a color (R, G, B). ) Is a color scanner that distinguishes and reads.

The print 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 to 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 for feeding sheets taken out from the paper feed cassette one by one to prevent double feed. In the double feed prevention roller pair 20, even if a plurality of stacked sheets are supplied as shown in FIG. 2, they must be fed to a single sheet P each time. A double feed detection device Y for detecting whether the number of sheets P is one, or two or more 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 main control unit 1 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 main control unit 1 causes the printing unit 7 to execute a printing process (image forming process) based on a print job received through the NIC 5. Further, the main control unit 1 causes the facsimile unit 8 to execute a facsimile transmission process for calling a designated transmission destination telephone number and transmitting image data to be transmitted. Further, the main control unit 1 causes the scanner unit 6 to execute a scanning process for reading an image formed on the original from the original.
Next, with reference to FIG. 3, 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 with a paper conveyance path 22 for the paper P supplied from the double feed prevention roller pair 20 interposed therebetween. 2 is the same as the conventionally known double feed detection device shown in FIG. 2, but the double feed detection device Y does not include temperature detection means such as the thermistor T. Different from the device.
On the other hand, in this double feed detection device Y, the temperature of the medium is detected from the change in the speed of sound 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 the double feed detection device Y, the main control unit 1 or another control unit under its control (hereinafter referred to as the control unit 1a), as described below, the propagation speed of the sound wave in the vicinity of the ultrasonic sensor, That is, the speed of sound is measured.
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, it may be executed 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. As a result, 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, the speed of sound V is V = 331.5 + 0.5 × atmosphere temperature Tc.
It is well known that
Therefore, the ambient temperature Tc is
Tc = (V−331.5) /0.5
Calculated by
On the other hand, the time t required for the ultrasonic wave to reach the ultrasonic receiver 24b from the ultrasonic transmitter 24a is set to H (constant / known) as the ultrasonic pulse period.
t = H × N
Therefore, if the distance between the ultrasonic transmitter 24a and the ultrasonic receiver 24b is L (constant / known), the sound speed V is
V = L / (H × N).
From the above,
Atmospheric temperature Tc = (L / (H × N) −331.5) /0.5
In this equation, L and H are known, and it can be seen that the ambient temperature Tc is obtained from the count number N.
Therefore, if the relationship between the ambient temperature and the output of the ultrasonic sensor is measured and stored in advance, the ambient temperature is detected from the above equation by detecting the count number N, and the ultrasonic sensor is detected based on the detected ambient temperature. The detection accuracy of the double feed detection device can be improved by correcting the output or the threshold value to be compared with it.
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.
At this time t, when the distance L between the sensors is 0.01 m,
t = 0.01 / 343.5 = 0.0291 (S)
When the pulse period H is 100 (nS), the count number N (reference pulse number) is N = 0.00291 / 100 = 291.1 (pulse)
It becomes.
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.
As described above, in the double feed detection device Y according to this embodiment, the double feed of the paper passing through the paper conveyance path is detected based on the output of the ultrasonic wave that reaches the ultrasonic receiver 24b from the ultrasonic transmitter 24a. At the same time, the arrival time of the ultrasonic wave that reaches the ultrasonic receiver 24b from the ultrasonic transmitter 24a (or the pulse count if pulsed ultrasonic waves) is measured, and based on the change in the arrival time, The output value of the ultrasonic wave that reaches the ultrasonic receiver 24b from the ultrasonic transmitter 24a can be corrected.

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

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a ... 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)

An ultrasonic transmitter and an ultrasonic receiver are arranged across the paper conveyance path, and based on the output of the ultrasonic waves that reach the ultrasonic receiver from the ultrasonic transmitter, double feeding of the paper passing through the paper conveyance path In the double feed detection device that detects
The arrival time of the ultrasonic wave reaching the ultrasonic receiver from the ultrasonic wave transmitter is measured, and the output value of the ultrasonic wave reaching the ultrasonic wave receiver from the ultrasonic wave transmitter is corrected based on the change in the arrival time. A double feed detector.   The ultrasonic wave is a pulsed ultrasonic wave having a fixed period, and the arrival time is the number of pulses of the pulsed ultrasonic wave emitted until the ultrasonic wave reaches the ultrasonic receiver from the ultrasonic wave transmitter. The double feed detection device according to claim 1, which is synonymous.   The ultrasonic wave is a pulsed ultrasonic wave having a fixed period, and the output value of the ultrasonic wave that reaches from the ultrasonic wave transmitter to the ultrasonic wave receiver is the ultrasonic wave value that reaches the ultrasonic wave receiver from the ultrasonic wave transmitter. The double feed detection device according to claim 1, wherein the double feed detection device is corrected based on an environmental temperature calculated based on the number of pulses of the pulsed ultrasonic wave emitted so far.   A sheet feeding device comprising the double feed detection device according to claim 1.   An image forming apparatus comprising the paper feeding device according to claim 4.

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