JPH01207613A - Device for detecting thickness of conveyed sheet paper or the like - Google Patents

Abstract

PURPOSE:To eliminate the influence of drift due to temperature variation, etc., and to improve measurement accuracy by processing the output signal of a detecting mechanism part which detects the thickness of the sheet paper, etc., at plural positions by using band-pass filter circuits. CONSTITUTION:Detecting mechanism parts 2L and 2R are provided so as to detect the thickness of the conveyed paper, etc., at the plural positions and convert it into electric signals, thus obtaining thickness detection signals. The detecting mechanism part 2L and 2R are provided with detecting circuits 100 and 101 which have amplifying circuits for amplifying the thickness detection signals and band-pass filter circuits for receiving the output signals of the amplifying circuits and passing them with time constant much larger than the variation quantities of the thickness detection signals. The output signals of the detecting circuits 100 and 101 are sent to a processing circuit 102 to select the signal showing the largest value between those signals. Further, a decision circuit 103 receives the output of the processing circuit 102 to recognize and decide the maximum thickness of the paper, etc. Consequently, level variation in zero thickness due to the temperature drift, etc., is absorbed and only the detection signal corresponding to the thickness of the paper, etc., is extracted.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a conveyed paper sheet thickness detection device that is incorporated into equipment that performs paper sheet conveyance processing, such as automatic bill depositing and dispensing devices, optical character reading devices, and the like.

(Prior Art) In automatic banknote deposit and withdrawal devices, in order to count paper sheets such as banknotes and perform their appraisal, it is necessary to feed the paper sheets one by one into a paper sheet conveyance path.

However, in rare cases, paper sheets may be conveyed overlapping each other, and in this case, identification is impossible.

Therefore, normally, the thickness of the paper sheets being transported is detected by a paper sheet thickness detection device, and the presence or absence of overlap is detected by detecting the thickness of the paper sheets.

Now, as a conventional detection device of this type, there is a reference roller with a small length provided at the paper transport position, and a sensor with a similarly small length that is displaceably pressed against this reference roller. When the detection roller is displaced due to the thickness of the paper sheet when a part of the paper sheet is held between these rollers and conveyed, the amount of displacement is converted into an electrical signal, which causes the paper sheet to be conveyed. There are known devices that can detect the thickness of leaves.

In addition, a detection roller with a small length dimension is arranged at a distance of the thickness of one sheet of paper from the reference roller, and when two or more sheets of paper are conveyed, the detection roller is displaced and the same A conveyed sheet leaf thickness detection device configured to detect the thickness of a leaf is also known.

Furthermore, a detection roller having a certain length dimension is placed at a distance of the thickness of one sheet of paper from a reference roller of the same size, and the detection roller is displaced when two or more sheets of paper are conveyed. There is also known a conveyed sheet thickness detecting device configured to similarly detect the thickness of a sheet.

By the way, banknotes are sometimes repaired by pasting tape or the like on the broken position, or they are spliced together with tape or the like to be counterfeited. Therefore, it is preferable to use the above-mentioned detection device to detect the tape portion where the thickness has increased to prevent the payment of repaired banknotes to the customer and to prevent counterfeit banknotes from being taken into an automatic banknote deposit/dispensing device or the like.

(Problem to be Solved by the Invention) However, in the conveyed paper sheet thickness detection device in which the above-mentioned detection roller having a small length dimension is pressed into contact with the reference roller or separated from the reference roller, only a part of the banknote is held and conveyed by these rollers. Therefore, the detection roller may not be able to detect thick tape parts, etc.
There is a risk of paying customers with repaired banknotes or receiving counterfeit banknotes.

In addition, if the detection roller is placed at a distance from the reference roller, it will take a lot of effort and time to adjust the separation distance, and if the detection roller is not driven independently, it will not be possible to convey the paper sheets smoothly. Not only is it impossible to do so, so-called jams occur, but also there is a risk that if foreign matter is attached to the paper sheets, so-called skew, in which the paper sheets are conveyed diagonally, may occur. When sensing rollers with large lengths are placed apart from each other, if the separation distance (gap) from the reference roller at both ends is different, a uniform pressing force will not be applied to the paper sheet, resulting in skew. This has the disadvantage that it is particularly likely to occur.

Therefore, the inventors of the present invention uniformly pressed a cylindrical detection roller having a similar length onto a cylindrical reference roller having a length larger than the size of a paper sheet over the entire length using a pressing means. We have developed a method that uses pressure to press elastically and independently detects the amount of displacement at both ends of the detection roller using a pair of detection mechanisms.

The problem here is how to effectively process the output signal of the detection mechanism to obtain a detection signal with high sensitivity and excellent stability. In particular, in this type of highly accurate detection mechanism, the drift of the detection signal due to changes in environmental temperature or changes over time greatly affects the determination results.

Moreover, if two or more detection mechanisms are to be operated simultaneously, the variations must be minimized.

Furthermore, it is also necessary to appropriately process a plurality of detection signals when the thickness of the paper sheet differs depending on the location.

The present invention has been made with attention to the above points, and an object of the present invention is to provide a conveyed paper sheet thickness detection device that can perform multiple thickness detection processes with high precision, stability, and accuracy. It is something to do.

(Means for Solving the Problems) The conveyed paper sheet thickness detection device of the present invention includes a plurality of detection mechanism sections that detect the thickness of a conveyed filter paper sheet at a plurality of locations and convert it into an electric signal to obtain a thickness detection signal. , an amplifier circuit that is provided for each of the detection mechanism sections and that amplifies the thickness detection signal; and a band that receives the output signal of the amplifier circuit and passes it with a time constant that is sufficiently large with respect to the amount of change in the thickness detection signal. a detection circuit having a filter circuit; a processing circuit that receives the output signals of each of the detection circuits and selects and outputs an output signal indicating the maximum value among them; The present invention is characterized by comprising a determination circuit that recognizes and makes a determination.

Alternatively, it may include a processing circuit that receives the output signals of each of the detection circuits and outputs the summed value thereof, and a determination circuit that recognizes the average thickness of the sheet from the output of the processing circuit and makes a determination thereof. It is characterized by:

(For now) The above-described device receives the thickness detection signal via the bandpass filter circuit and makes a determination thereof. As a result, level fluctuations at zero thickness caused by temperature drift or the like are absorbed, and only the detection signal corresponding to the thickness of the sheet is extracted.

Furthermore, if only the maximum thickness among the plurality of detection signals is detected and determined, an increase in the thickness of only a portion of the paper sheet can be detected with high sensitivity.

On the other hand, if a plurality of detection signals are added and the average value is taken for determination, the signals are averaged and the influence of variations in the detection signals is reduced, allowing stable detection.

(Example) Hereinafter, the present invention will be explained in detail with reference to Examples.

First, before explaining the processing circuit which is the main part of the present invention, the details of the roller mechanism and the detection mechanism section for detecting the thickness of the paper sheet will be explained.

Structure of Mechanism Part> Figure 2 is a perspective view of the mechanism part of the conveyed paper sheet thickness detection device;
The figure is an exploded perspective view of the device.

In these figures, ■ is a casing, and this casing 1 has a back wall IA and both side walls IB, IB, and is open on the front side. Inside each side wall IB is a detection mechanism section 2 for detecting the amount of displacement at both ends of the detection roller 19, which will be described later.
(L) and (R) are provided, respectively. These detection mechanism parts 2 have an element bracket 3, and the element bracket 3 includes an extension part 3a extending downward. As shown in FIG. 3, this extension portion 3a is provided with a through hole 3b, and is fitted into the large diameter base portion 4a of the support shaft 4 protruding from the side wall IB through the through hole 3b. And this extension part 3
a is elastically pressed against the side wall IB by the pressing piece 7a of the leaf spring 7 in the fitted state. The leaf spring 7 is attached to the side wall I
It is attached to the side wall IB by holding the edge of the window 1b provided at B between other suppressing pieces 7b, 7b.

In addition, the element bracket 3 has a storage hole 3 passing through it in the vertical direction.
C, and the magnetoresistive element 5 is housed in this housing hole 3C. The magnetoresistive element 5 is a detection element whose resistance value changes in response to changes in the magnetic field, and a terminal protruding from its upper surface is inserted into the printed circuit board 6 and soldered. A lead wire or the like is connected to the printed circuit board 6 in order to send a detection signal obtained from the magnetoresistive element 5 to a signal processing circuit to be described later. The printed circuit board 6 is attached to the element bracket 3 by a mounting bracket 8. This mounting bracket 8 has a pair of protrusions 8a, 8a extending downward, and by fitting the protrusions 3d provided on the outer wall of the element bracket 3 into the square holes provided in these protrusions 8a, the printed circuit board 6 is fixedly attached to the element bracket 3 with one touch. The spring piece 8b of the mounting bracket 8 reliably presses the printed circuit board 6 against the upper surface of the element bracket 3, prevents the printed circuit board 6 from coming off due to external force such as vibration, and positions the magnetic resistance element 5 at a predetermined position. The tip of the spring piece 8b is bent upward to prevent the printed circuit board 6 from being damaged.

Furthermore, the element bracket 3 has an extension portion 3e that extends in the lateral direction.
This extension part 3e has a side wall IB as shown in FIG.
It protrudes more outward. This extension part 3e is provided with a mounting hole 3f for fixing one end of the coil spring 9, and the other end of the coil spring 9 is fixed to a bent piece 10 formed by bending a part of the side wall IB outward. There is. Therefore, the coil spring 9 applies a tensile force to the extension portion 3e in the direction of bringing it closer to the other bent piece 11 of the side wall IB.

An adjustment screw lla is screwed through the other bent piece 11 in the thickness direction. On the other hand, a bottle hole 3g is provided in the extension part 3e, and a bottle 12 made of hard metal that does not deform is inserted into the bottle hole 3g. being touched. Therefore, by adjusting the amount of protrusion of the adjustment screw lla, the extension part 3e is pressed against the elastic force of the coil spring 9, and the element bracket 3 is pressed against the elastic force of the coil spring 9.
By rotating the magnetoresistive element 5 by a predetermined amount around the support 1id+4, the magnetoresistive element 5 housed in the element bracket 3 can be positioned at a predetermined position.

A leaf spring 13 is fitted into the other bent piece 11, and the tip end of the adjusting screw lla is screwed into the leaf spring 13, thereby preventing the screw lla from loosening.

A detection lever 14 constituting the detection mechanism section 2 is arranged near the element bracket 3. This detection lever 14
is fitted into the small diameter portion 4b of the support shaft 4 coaxially with the element bracket 3, and a projecting piece 14a for fixing one end of the coil spring 15 is provided above. The other end of the coil spring 15 is attached to an attachment hole 16 provided in the back wall IA. Therefore, the detection lever 14 is given a rotational force to rotate around the support shaft 4 due to the elastic force of the coil spring 15. In addition, the detection lever 14
A storage groove 14b is provided on the upper surface of the storage groove 14b.
A detection rod 17 is positioned and dropped into. The detection rod 17 is made of magnetic material and is positioned below the detection surface (lower surface) of the magnetoresistive element 5 described above. Note that an annular groove is provided at the tip of the support shaft 4, and a snap ring 18 is fitted into this groove to prevent the detection lever 14 from coming off the support shaft 4.

By the way, the element bracket 3 and the detection lever 14 are made of a material having non-conductive and non-magnetic properties, such as plastic resin, in order to electrically and magnetically insulate the magnetoresistive element 5 and the detection rod 17. There is. In this case, it is preferable that the element bracket 3 and the detection lever 14 be made of the same material or at least the same material with the same coefficient of thermal expansion, thereby suppressing variations in the gap between the magnetoresistive element 5 and the detection rod 17 due to thermal expansion. Can be done.

A support protrusion 14c protrudes from one end of the detection lever 14,
This support protrusion 14c is provided with a through hole 14d. A small diameter portion 19a at the end of the detection roller 19 is rotatably fitted into the through hole 14d, and a snap ring 21 is fitted into the shaft portion 19b protruding from the small diameter portion 19a while being supported by a ball bearing 20. has been done. As shown in FIG. 2, the detection roller 19 is formed of a metal material into a cylindrical shape with a length larger than the size of the paper sheet 28, and has a plurality of annular grooves 19A provided on the circumferential surface. These annular grooves 1
9A is set to have a small groove width so that even if a commercially available tape having a width of 1/2 inch (1.27 cm) or more is attached to a sheet of paper, the thickness of the tape portion can be reliably detected.

In this way, the detection roller 19 supported at both ends by the detection lever 14 is rotated about the support shaft 4 by the elastic force of the coil spring 15, so that It is elastically pressed against the lower reference roller 22 via these coil springs 15, 15 with a uniform pressing force over the entire length. The reference roller 22 is similarly formed of a metal material into a cylindrical shape with a length larger than the size of the paper sheet 28, and the detection roller 19
An annular groove 22A having the same groove width is provided at the same position. As shown in FIG. 3, the shaft portions 2 at both ends of the reference roller 22
2a is inserted into a through hole IC of the side wall IB and supported by a ball bearing 23, and the ball bearing 23 is held by a bearing holder 24. Bearing presser foot 24
is provided to absorb rattling of the ball bearing 23, and is fixed to the side wall IB by a screw member 25. The reference roller 22 supported at a fixed position in this manner is arranged at a reference transport position for detecting the thickness of the sheet. As shown in FIG. 2, a helical gear 26 selected to reduce vibration and noise during driving is attached to one shaft portion 22a of the reference roller 22 in order to rotationally drive the reference roller. It is being This reference roller 22 is manufactured with high precision so that errors such as eccentricity can be ignored so that the thickness of the paper sheet can be detected accurately, and is formed to have a large diameter so as to maintain mechanical strength.

On the front side of the detection roller 19 and the reference roller 22, there is a second roller.
As shown in the figure, a pair of guide plates 27°27 are arranged facing each other. These guide plates 27.27 are provided to guide the paper sheet 28 between the detection roller 19 and the reference roller 22 by passing the paper sheet 28 between them, and a plurality of protruding pieces 27a are arranged in the annular grooves 19A, 22A. It enters the area and extends backwards. These protruding pieces 27a are provided to prevent the paper sheet 28 from wrapping around the detection roller 19 and the reference roller 22.

Incidentally, as shown in FIG. 3, the support protrusion 1 of the detection lever 14
4c is provided with a protruding stopper 14e, which stops when the detection lever 14 rotates unnecessarily.
It comes into contact with the opening edge 1a of A to prevent its rotation.

Further, the coil spring 15 that applies rotational force to the detection lever 14 has a function of pulling the detection lever 14 so that the detection lever 14 does not shake and rotate on the support shaft 4 when the paper sheet 28 passes. are doing. The elastic force of this coil spring 15 causes the detection roller 19 to
The time required for the tape (approximately 1/2 inch wide) to hit the edge of the tape attached to the frame sheet, momentarily separate from the reference roller 22 and the paper sheet, and return to the bracket sheet 28 The value is set to be sufficiently smaller than the time required for the

On the other hand, a deposit remover 30.30 is attached to the back wall IA. These deposit removers 3° are made of stainless steel leaf spring material and are used to scrape off deposits such as paper dust on the rollers, and are integrally attached to the connecting portion 30A. A plurality of contact pieces 30 formed
It consists of B. The tip edges of these contact pieces 30B are formed linearly so as to reliably contact the roller circumferential surface in a straight line.
has been done. Each deposit remover 3 having such a configuration
0, the contact pieces 30B are arranged along the tangential direction of the detection roller 19 and the reference roller 22, respectively, and the tip edges of the contact pieces are in contact with the circumferential surfaces of the rollers 19 and 22. Through hole 30a of connecting portion 30A and through hole 3 of retaining plate 31
1a, and is fixed to the back wall IA by inserting the screw member 32 into the back wall IA.

Operation of the device> Next, the operation of the above mechanical parts will be explained.

FIG. 4 is a diagram for explaining the principle of detecting the thickness of a conveyed paper sheet. As the paper sheet 28 is fed between the guide plates 27 and 27, the reference roller is driven by the helical gear 26 shown in FIG. When the detection roller 22 is rotationally driven, the detection roller 19 is driven to rotate, so that the paper sheet 28 is held between both rollers 19 and 22. When the paper sheet 28 is conveyed, the detection roller 19 moves away from the J♂ semi-roller 22 by the thickness thereof against the elastic force of the coil spring 15, and rotates and is displaced about the support shaft 4 together with the detection lever 14.

By the way, the amount of displacement of the detection roller 19 is a, and the amount of displacement of the detection roller 19 is
If the distance between the center of the support shaft 4 and the center of the support shaft 4 is β, and the distance between the center of the support shaft 4 and the center of the detection rod 17 is β, then the detection rod 17
The displacement ff1T becomes T = a 12 /L.

Therefore, when the detection rod 17 is displaced by T with respect to the detection surface of the magnetoresistive element 5, the magnetoresistive element 5
Since the resistance value of the element 5 changes, a detection signal is output from the element 5.

In addition, when conveying the paper sheet 28, the reference roller 22 and the detection roller 1
9 is sealed with deposits such as paper powder, but in this embodiment, the abutting piece 30B of the deposit remover 30 is brought into contact with the circumferential surfaces of both rollers 22 and 19. This contact piece 30B can automatically scrape off deposits on the peripheral surface of the roller.

In this way, the cylindrical reference roller 22 with a large length dimension
When both ends of a cylindrical detection roller 19 having the same length are elastically pressed through a coil spring 15.15, even if foreign matter is attached, a uniform pressing force is applied to the entire sheet 28. Since the paper can be conveyed while being added, it is possible to prevent the occurrence of skew, and since the detection roller 19 is always rotated as a result of pressure contact, it is also possible to prevent the occurrence of jams.

In addition, since the entire paper sheet 28 is pressed uniformly by the detection roller 19, even if the paper sheet 28 has been repaired with tape or the like, the detection roller 19 can reliably come into contact with the tape or the like and the roller 19 can be moved. It can be displaced. When the tape portion or the like passes one end of the detection roller 19, only one end of the detection roller 19 is displaced, but in the present invention, since the detection mechanism section 2 is provided at both ends of the detection roller 19, either The displacement of the detection roller 19 can be detected with high sensitivity by the detection mechanism section 2.

Therefore, even repaired banknotes or counterfeit banknotes can be reliably detected, and payment to the customer can be stopped or the banknotes can be prevented from being taken into the main unit.

Furthermore, since a long cylindrical roller is used as the detection roller 19, the moment of inertia of the detection roller 19 is large. There is also the advantage that the rotational speed hardly changes, so that the paper sheets 28 can be conveyed at a stable speed. Further, there is an advantage that vibrations caused by bouncing of the detection roller 19, etc. are sufficiently suppressed, and a detection signal with less noise can be obtained.

Furthermore, when the long detection roller 19 is pressed against the reference roller 22 as described above, the half-folded part of the paper sheet 28 can be folded to ensure that it overlaps, so that jams can be prevented on the later stage side. This can be prevented from occurring in advance.

<Configuration of Signal Processing Circuit> By the way, the signal detected by the magnetoresistive element 5, which is the detection element of the above-mentioned mechanism part, is introduced into the signal processing circuit shown in FIG.

This circuit consists of a detection circuit (L) +00 connected to the detection mechanism section 2 (L) arranged on the left side in Fig. 2, and a detection circuit connected to the detection mechanism section 2 (R) arranged on the right side in Fig. 2. (
R) 1 old, an LR output OR processing circuit 102 that accepts and processes the outputs of both, a determination circuit 103, and a reference value setting section 104.

First, the common parts of the detection circuit (L) 100 and the detection circuit (R) 100 are given the same reference numerals, and the explanation thereof will be continued.

In the figure, the displacement of the detection rod 17 is detected by the magnetoresistive element 5, the output terminal of which is connected to the non-inverting input terminal of the operational amplifier 41. The output terminal of the operational amplifier 41 is fed back to its inverting input terminal, forming a so-called voltage follower circuit. This converts the output impedance of the magnetoresistive element 5, and its output is connected to the inverting input terminal of the operational amplifier 42 via the resistor 43. A tap of a variable resistor 44 that outputs a voltage approximately equal to the input voltage of the operational amplifier 42 when the thickness of the detected filter paper sheet is zero is connected to the non-inverting input terminal of the operational amplifier 42 via a resistor 45. A power supply voltage Vcc is applied to both ends of the variable resistor 44 .

Further, the output terminal of the operational amplifier 42 is fed back to the inverting input terminal via the resistor 40, and the capacitor 47.
8 to the non-inverting input terminal of the operational amplifier 46. One end of a discharge limiting resistor 49 is connected to the connection point between the capacitor 47 and the capacitor 48 , and the other end of this resistor 49 is connected to the inverting input terminal of the operational amplifier 46 . One end of a discharge limiting resistor 50 is connected to the connection point between the capacitor 48 and the non-inverting input terminal of the operational amplifier 46, and the other end of this resistor 50 is grounded.

On the other hand, the non-inverting input terminal of the operational amplifier 51 is grounded, and the output terminal thereof is connected to the anode of the diode 52.

The cathode of the diode 52 is fed back to the inverting input terminal of the operational amplifier 51 and is connected to the non-inverting input terminal of the operational amplifier 46.

The output terminal of the operational amplifier 46 is fed back to its inverting input terminal, and the detection circuit (L) 100 of the operational amplifier 53 of the LR output OR processing circuit 102 is
R) January is connected to the inverting input terminal of the operational amplifier 61 of the LR output OR processing circuit 102, respectively.

The LR output OR processing circuit 102 also includes a detection circuit (L).
100 and the output of the detection circuit (R) January. That is, the output terminals of the operational amplifiers 53 and 61 are connected to the anodes of the diodes 54 and 62, respectively, and the cathodes of the diodes 54 and 62 are connected to the operational amplifier 5.
It is fed back to both inverting input terminals of 3.61 and connected via a resistor 57 to the non-inverting input terminal of the comparator 56 of the determination circuit 103.

The determination circuit 103 is a circuit that receives the output of the LR output OR processing circuit 102 and determines the thickness of the paper sheet. A resistor 58 is connected to the inverting input terminal of the comparator 56, and the output terminal of the reference value setting circuit 7o is connected to the other end of the resistor 58. The control section 65 is connected to an input terminal of a reference value setting circuit 70 provided in the reference value setting section 104 and to an output terminal of the comparator 56 .

In the figure, the voltages at the output terminals of the operational amplifier 42 are VA (L) and VA (It), respectively, and the voltages at the output terminals of the operational amplifier 46 are V B (L) and Va (R), respectively.
, the voltage at the output terminal of the operational amplifier 53 and 61 is indicated as 6, and the voltage at the output terminal of the comparator 56 is indicated as VD.

<Operation of the signal processing circuit> In the above configuration, the voltages v A (L) and V A (R) corresponding to the displacement of the detection rod 17 are transmitted to the operational amplifier via the magnetoresistive element 5 and the voltage follower operational amplifier 41. Appears at the output end of 42, capacitor 47.48
to charge. While the capacitors 47 and 48 are being charged, current flows through the resistors 49 and 50, and a change in VA appears at the output terminal of the operational amplifier 46 as VB. Moreover, when the charging of the capacitors 47 and 48 is completed, the other end of the resistor 50 (
The terminal (which is not grounded) becomes the ground potential, and the output VB of the operational amplifier 46 becomes OV.

Now, assuming that the circuit consisting of the operational amplifier 51 and the diode 52 is omitted, the relationship between the output (2) of the operational amplifier 42 and the output VB of the operational amplifier 46 can be expressed as follows using the Laplace transform equation.

L= [VB/VAI ・G+ (81・S/(S2+
(1/R5゜) (1/C47÷1/C,a)S+ (
1/C47C411R49R50)) Here, C,,
, C4, are the capacitances of capacitors 47 and 48, respectively, and R4
9R5O is the resistance value of the resistor 49.50, and from the above equation, the discharge time constant T1 of the capacitor 47.48 is expressed by the following equation.

T + = 2 π(C47C4aR4sRso)”
2 Therefore, ■8 is the discharge time constant T of the capacitor 47.48
If the output of the operational amplifier 46 changes at a cycle longer than T1 or remains constant, the output of the operational amplifier 46 does not change; conversely, when the output changes at a cycle shorter than T1, the operational amplifier 46 outputs the amount of change. At this time, if the discharge time constant T1 of the capacitors 47 and 48 is made large, the reference voltage at zero thickness is always OV, and the operational amplifier 46 always outputs a voltage corresponding to the thickness of the paper sheet. As a result, even if the output voltage of the operational amplifier 42 fluctuates (drifts) when the thickness is zero due to various factors, the output of the detection circuit is not affected by this drift.

However, if this is done, the capacitors 47 and 48 will pass through the resistors 49 and 50 while the paper sheets are passing, and the charge corresponding to the thickness of the paper sheets will also be discharged. Now, VA is 0 at time t=O.
Assuming that the unit step function becomes 1 from , the output V8 of the operational amplifier 46 is expressed by the following equation.

Va Ttl = (exp (-at) )
(cos β ta-a sin β 7 / β
)α=(1/2R5゜) (1/C4t"l/C4a)
β-=((1/C47C48R49R5o)-(1/2
Rso) 2(1/C,,+1/C4g) 2) ""
At this time, if the time for the paper leaf to pass is tl, then Vn(0
) Va(tl) = I Va(tl) (7)
A voltage appears as a negative potential at the output terminal of the operational amplifier 46 immediately after the sheet passes, and this voltage becomes the output voltage when the thickness is zero. That is, if the next sheet of paper arrives at the thickness detection device before the output terminal potential of the operational amplifier 46 reaches Ov (before the charging of the capacitors 47 and 48 is completed), the thickness will be greater than the thickness obtained by subtracting the above-mentioned negative potential. However, a low voltage will be output from the operational amplifier 46. Of course, the capacitors 47 and 48 are discharged during the passage of this sheet.

Therefore, as paper sheets pass one after another, the output voltage in the case of zero thickness gradually shifts to the negative side, and the capacitor 47.4
8 becomes stable when the amount of charge discharged while the paper sheet is passing becomes equal to the amount of charge charged while there is no paper sheet.

In this case, the thickness of the paper sheet cannot be accurately detected based on the absolute output voltage of the operational amplifier 46. Therefore,
A correction circuit consisting of an operational amplifier 51 and a diode 52 is connected to this circuit. First, operational amplifier 46
When the non-inverting input terminal of is at a positive potential, that is, while the sheet is passing, the diode 52 is turned off and the capacitor 47.48
Although it is not involved in the charging and discharging of
completes charging instantly, and the output voltage of the operational amplifier 46 becomes O.
It becomes v. Therefore, even if paper sheets come in succession, the output terminal of the operational amplifier 46 accurately outputs a voltage corresponding to the thickness of the paper sheets.

In this way, the thickness voltage VB (L
), VB(R)c, detection circuit (L) 100. (R)
101 to the non-inverting input terminal of an operational amplifier 53.61. The operational amplifier 53 outputs a positive or negative power supply voltage to its output terminal so that the voltage at its inverting input terminal is equal to the voltage V a (t,) at its non-inverting input terminal. The operational amplifier 61 outputs a positive or negative power supply voltage to its output terminal so that the voltage at its inverting input terminal becomes equal to the voltage v, (R) at its non-inverting input terminal.

Now, if V , (L) > V B (R), then V
While c is lower than VB(R), both operational amplifiers 53 and 61 output positive voltages, and diodes 54 and 62 become forward biased. Therefore, in this case, Vc increases, but Vc
, (R), the operational amplifier 61 outputs a negative voltage to lower the voltage at the inverting input terminal. However, at this time, the diode 62 becomes reverse biased, and the operational amplifier 6
The output voltage of 1 is ■. It doesn't reach. Therefore, Vc is further increased by the operational amplifier 53 and becomes equal to V[1(L).

Conversely, when V a (L) < V a (R), the diode 54 is reverse biased and the diode 62 is forward biased, so that V c becomes equal to V a (R).

Therefore, Vc is always v, (R), V a (t,)
It is equal to whichever of the voltage is higher.

Thickness voltage ■ extracted in this way. is resistance 57
to the non-inverting input terminal of comparator 56.

FIG. 5 is a graph showing the relationship between the amount of movement of the detection rod 17 and the output voltage of the magnetoresistive element 5.

As shown in the figure, both are thick (dependent) on each other, and in the figure, they are almost linearly proportional within the range.Therefore, the thickness voltage output from the LR output OR processing circuit in Figure 1 ■. is approximately proportional to the thickness of the paper sheet.

On the other hand, the reference value setting circuit 7o in FIG.

Generally, the thickness of paper sheets is not constant, even for sheets of the same type, but has a certain width. However, as shown in Figure 6, paper sheet 1
There is an appropriate interval between the thickness of one sheet of tape, the thickness of one paper sheet, and the thickness of two sheets of paper, and by setting the reference voltage VSL (slice level) within that range, it is possible to It is possible to identify whether a paper sheet has passed, one piece of paper sheet has passed, or two or more sheets have passed. Note that the reference voltage VSL is a voltage corresponding to the thickness TSL shown in FIG.

For example, if the level of the reference voltage is changed from ■8L to Vst,', it is possible to detect whether there are three or more sheets or two or less sheets.

Furthermore, if the type of paper sheet changes, this reference voltage VSL also needs to be changed accordingly. The control unit 65 controls selection of such reference voltages.

On the other hand, the control unit 65 controls the comparator 5 corresponding to this reference voltage.
The number of sheets to be conveyed is detected by the output of 6. That is, the thickness voltage ■. If is higher than the reference voltage v, L, the output of the comparator will be at the "H++" level, and conversely, if the thickness voltage (■) is lower than the reference voltage (■8L), the comparator will be at the "L" level. In the case of "H" level, it is determined that the number of sheets to be transported is one, and in the case of "H" level, it is determined that the number of sheets to be transported is more than one.The determination result is sent to a processing device (not shown). output towards.

<Detection Signals of Each Part of the Circuit> Next, the detection signals of each part of the circuit shown in FIG. 1 and their operations will be explained using FIG. 7.

At the top of the figure (a), there is a case where there is only one sheet of paper and a case where there are 28 sheets of paper.
If the tape 28' is attached to a part of the sheet, or if the paper sheet is
Three cases in which the sheets overlap are shown in a plan view and a side view, respectively. In the plan view, the upper side (R)
is detected by the detection circuit (R) +00 in FIG. 4, and the lower side (L) is detected by the detection circuit (L).

As shown in the figure, when there is only one sheet of paper, the operational amplifier 4 in Figure 1
The outputs VA (L) and VA (R) of 2 are uniform on the left and right [Figures (b) and (c)], and the output V of the operational amplifier 46 is
, (t,).

All Ve(R) have the same zero level [see the same figure (
d), (e)]. Since both outputs are equal, LR output is O
The output Vc of the R processing circuit 102 is equal to either one,
It is compared with the slice level VSL in the comparator 56 [(f) in the same figure].

As a result, a pulse-like voltage is output to the control section 65 [FIG. 6(g)]. This voltage is caused by mechanical vibrations or electrical transients that occur when the paper sheet enters the device, and is characterized by a very narrow pulse width. Therefore, if this pulse width is narrow, the control unit 65 ignores the signal.

Therefore, here it is determined that one sheet of paper has passed.

On the other hand, when a part of the paper sheet 28 (the part on the right side of the paper sheet) with the tape attached passes through the device, the detection circuit 1 on the right side
01 (Figure 1) output VA (L).

The result is noticeable in VA(R) [Figure 7(b)
.

(c), (d), (e)].

Since the output of the LR output OR processing circuit 102 has a higher level, as shown by the solid line in FIG.
The output of 1 is compared with the slice level SL [FIG. 1(f) 1] As a result, the control unit 65 is manually supplied with a pulse having a width corresponding to the amount exceeding the slice level VSL [FIG. (g)].

This pulse is wide enough to indicate tape adhesion.

In the above embodiment, the thickness is determined using the larger output of the left and right detection circuits, so even if the tape is attached to one side of the sheet, it can be accurately detected. Can be done.

Finally, in cases where two sheets of paper overlap, the overall level of voltage V A (L) is higher than in the case of one sheet.
, V A (R), V B (L), and V B (R) are output [(b), (c), (d), (
e)], when comparing the slice levels v, L and ■o [Figure (f) 1, a pulse corresponding to the full width of the sheet is output to the control unit 51 [Figure (g) 1〜〈detection Modified example of circuit> By the way, in the embodiment shown in FIG. 1, the detection circuit (L) and the detection circuit (R) (7) outputs V a (L), V a
(R) (7) The higher voltage was output to the judgment circuit as vc, but v B (L), V B (
There is also a method of taking the added value of R). An example of this circuit is shown in FIG.

In FIG. 8, each detection circuit (L), (R), reference value setting section 104, and determination circuit 103 have the same configuration as that in FIG. 1. Further, this circuit is provided with an adder circuit 105 in place of the LR output OR processing circuit 102 in FIG.

The output terminal of the operational amplifier 46 of the detection circuit 100 and 101 is fed back to its inverting input terminal, and is also fed back to the operational amplifier 82 of the adder circuit 105 through a resistor 80 on the L side and through a resistor 81 on the R side. Connected to the non-inverting input terminal. The output terminal of operational amplifier 82 is fed back to its inverting input terminal via resistor 84 and is connected via resistor 57 to the non-inverting input terminal of comparator 56 . Furthermore,
The inverting input terminal of the operational amplifier 82 is grounded via a resistor 83.

In the above configuration, the thickness voltages V n (L) and V B (R) with drift and positional deviation removed are as follows:
Appears at the output end of each detection circuit (L), (R). As a result, the non-inverting input terminal voltage VB' of the operational amplifier 82 is
(Ra +Vn (L) ”RaoVB(R) )/
(Lo+Ra +).

Also, the output voltage V of the operational amplifier 82 is (R83÷Ra
4) Ve'/R83. Here, R80+R8
1+ R1131R84 are each resistance 80.81.8
The resistance value is 3.84. Here, Rao=Rag,
R83=R84 and hhaVa' = (Va(L)+
Va(R)) /2°Vc = 2 Va' = (
Vs(L)+Va(R)). That is, the voltage output to the determination circuit is the same as that of each detection circuit (R).

This is the sum of the outputs of (L). Thereafter, the number of sheets to be transported can be determined by performing the same processing as explained in FIG. 1 in the determination circuit 103 and the reference value setting unit 104.

In this embodiment, the detection outputs on the left and right sides of the paper sheet are added to determine the thickness. For example, in the case of the paper sheet 28 shown in FIG. ) is the voltage ■c shown in the dashed line at the slice level v
The determination will be made using stt'.

This allows the thickness to be determined by essentially capturing the average thickness of the paper sheet, and has the advantage that detection can be made at approximately the same level no matter where the tape, etc. is attached. There is. That is, depending on where the tape is attached, the reference roller and the detection roller may not be held parallel to each other, and the detection mechanisms at both ends of the detection roller may detect a thickness that is too small at one end and too large at the other end. In this case, by averaging the detection output signals, an output signal closer to the true thickness can be obtained.

The conveyed sheet thickness detecting device of the present invention is not limited to the above embodiments.

For example, in the previous embodiment, only one pair of long reference rollers and detection rollers were provided parallel to the length direction of the paper sheet, but multiple reference rollers and detection rollers were provided, and each of them was provided with a detection mechanism section. There is no problem even if the signals are processed using the following methods.

(Effects of the Invention) The conveyed paper sheet thickness detection device of the present invention configured as described above detects the thickness of multiple locations on the paper sheet, so even if some portions of the paper sheet have different thicknesses, it is possible to detect the thickness of the sheet. can be detected immediately. Furthermore, since the signal is processed using a bandpass filter circuit, it is not affected by drift due to temperature changes, etc. Furthermore, detection sensitivity can be improved by performing a determination that captures the maximum value of a plurality of detection output signals. Further, by adding a plurality of detection output signals to make a determination, it is possible to suppress variations in detection and achieve stability.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a signal processing circuit of a conveyed sheet thickness detecting device according to the present invention, FIGS. 2 and 3 are a perspective view and an exploded perspective view of the mechanical part of the device of the present invention, and FIG. 4 is the same. Figure 5 is a graph showing the relationship between the thickness detection output voltage and the amount of movement of the detection rod; Figure 6 is a probability distribution diagram showing variations in sheet thickness; FIG. 7 is a time chart showing signal waveforms of each part of the signal processing circuit, and FIG. 8 is a block diagram of the signal processing circuit showing another embodiment of the apparatus of the present invention. 2... Detection mechanism section, 5... Magnetoresistive element of the detection mechanism section, 17... Detection rod, 4'l, 42. 46. 51. 53. 61
... operational amplifier, 56 ... comparator, 65 ... control section, 70 ... reference value setting circuit, 100 ... detection circuit (L), 101 ...
・Detection circuit (R), 102... LR output OR processing circuit, 103... Judgment circuit, 104... Reference value setting section, 1
05...Addition circuit. Patent applicant Oki Electric Industry Co., Ltd.

Claims (1)

[Scope of Claims] 1. A plurality of detection mechanism sections each detecting the thickness of a plurality of places of a sheet being conveyed and converting it into an electric signal to obtain a thickness detection signal; a detection circuit having an amplifier circuit that amplifies the thickness detection signal; and a bandpass filter circuit that receives the output signal of the amplifier circuit and passes it with a time constant that is sufficiently large with respect to the amount of change in the thickness detection signal; a processing circuit that receives the output signals of the detection circuit and selects and outputs an output signal indicating the maximum value among them; and a determination circuit that recognizes and determines the maximum thickness of the sheet from the output of the processing circuit. A device for detecting the thickness of conveyed paper sheets. 2. A plurality of detection mechanism sections each detecting the thickness of a plurality of places of the conveyed paper sheet and converting it into an electric signal to obtain a thickness detection signal; and a plurality of detection mechanism sections provided for each of the detection mechanism sections and amplifying the thickness detection signal. a detection circuit having an amplifier circuit and a bandpass filter circuit that receives an output signal of the amplifier circuit and passes it with a time constant sufficiently large for the amount of change in the thickness detection signal; and an output signal of each of the detection circuits. Detecting the thickness of conveyed paper sheets, comprising: a processing circuit that accepts the received paper sheets and outputs their summed value; and a determination circuit that recognizes the average thickness of the paper sheets from the output of the processing circuit and makes a determination thereof. Device.