JPH0599605A - Non-contact type thickness detection unit - Google Patents

Abstract

PURPOSE:To provide a non-contact type thickness detection unit of high accuracy which is not affected by fluctuations in the interval between a detection electrode connected to an electrostatic sensor and a subject for detection. CONSTITUTION:A first detection electrode 5 and a second detection electrode 6 are disposed opposite to each other via paper mediums 1 on a carrier passage for the paper mediums 1 serving as subjects for detection. The first detection electrode 5 is connected to a first electrostatic sensor 7 and the second detection electrode 6 is connected to a second electrostatic sensor 8. Each of the electrostatic sensors 7, 8 changes the resonance frequency of a resonance circuit according to changes in electrostatic capacity detected by each detection electrode 5, 6, and performs amplitude modulation of a signal corresponding to the change in the resonance frequency with the oscillation frequency signal of an oscillating circuit 14 used as a carrier wave, and then detects the signal and produces an output. An addition circuit 10 adds the detection signals of the first 7 and second 8 electrostatic sensors together, and applies to an external equipped signal processing circuit these outputs added together.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an ATM (Automated Telecommunications)
llerMachine) device, a bill validator, a ticket gate, a papermaking industry, pulp, platemaking, woodworking, food, and the like, and a non-contact thickness detecting device for measuring the thickness and properties of a paper-like medium.

[0002]

2. Description of the Related Art A thickness measuring device using a potentiometer is used to detect the thickness of a sheet-shaped medium such as a film, a copy sheet, and a bill, and the feeding of two sheets. This device has an arm attached to the rotary shaft of the potentiometer,
A roller is rotatably attached to the tip of this arm, and the roller is pressed onto the sheet-shaped medium to be scanned using spring pressure,
The measurement is performed by converting a change in the thickness of the sheet-shaped medium into a change in the amount of rotation of the rotary shaft of the potentiometer.

However, in the contact type thickness measuring device using this potentiometer, when the scanning speed of the sheet-shaped medium increases, the movement of the roller cannot follow the change in the thickness of the sheet-shaped medium, and the thickness measurement reliability is high. There was a drawback that was damaged.

The applicant of the present invention previously proposed in Japanese Patent Laid-Open No. 1-126234 an electrostatic sensor device capable of detecting a change in minute electrostatic capacitance with a high sensitivity of 1 × 10 ⁻⁵ PF. ing. As shown in FIG. 5, this proposed device has a resonance circuit that includes an oscillation circuit 14 including a ceramic resonator 19 and a ceramic resonator 15 that is independent of the ceramic resonator 19 of the oscillation circuit 14. Circuit 21, detection circuit 16, and amplification circuit 17
And an electrostatic sensor including an AFC (Automatic Frequency Control) circuit 18 and a detection electrode 20.

The oscillation circuit 14 outputs a fixed high frequency oscillation frequency signal of 0.5 GHz to 10 GHz. Detection electrode 20
Is arranged so as to face the object to be detected, detects a change in micro capacitance with the object to be detected, and adds this to the resonance circuit 21. Resonant circuit
Reference numeral 21 changes the resonance frequency according to the change in the minute electrostatic capacitance applied from the detection electrode 20, and uses the oscillation frequency signal of the oscillation circuit 14 as a carrier wave to generate an amplitude modulation signal corresponding to the change in the resonance frequency. Is added to the detection circuit 16. The detection circuit 16 envelope-detects this detection signal and applies it to the amplification circuit 17. The amplifier circuit 17 amplifies the envelope detection signal added from the detection circuit 16 and applies it to a desired signal processing circuit. The AFC circuit 18 corrects the resonance frequency of the resonance circuit 21 that is biased by the influence of environmental changes and stabilizes the resonance frequency.

According to this proposed device, the change of the minute electrostatic capacitance detected by the detection electrode 20 is detected as the change of the resonance frequency of the resonance circuit, so that 1 × 10 ⁻⁵ PF is impossible until then. It has become possible to detect changes in the small electrostatic capacitance with high sensitivity.

The present inventor paid attention to the performance of the proposed device,
Using this proposed device, we are developing a device suitable for measuring the thickness of paper-like media.

[0008]

When the proposed apparatus is applied to the measurement of the thickness of a sheet-shaped medium, as shown in FIG. 6, the detection electrode 20 and the ground electrode 3 are passed through the passage gap 2 of the sheet-shaped medium 1. Are arranged so as to face each other, and the detection electrode 20 detects a change in capacitance when the sheet-shaped medium 1 passes between the detection electrode 20 and the ground electrode 3, and this is detected by the ceramic resonance of the circuit shown in FIG. In addition to the container 15, an apparatus configuration that detects properties such as the thickness of the sheet-shaped medium 1, the moisture absorption state, the unevenness of the surface, and the state of adhering foreign matter can be provided.

However, the paper-like medium 1 is connected to the electrodes 3 and 20.
When the sheet-shaped medium 1 and the detection electrode 20 change in distance when being conveyed between them, the capacitance between the sheet-shaped medium 1 and the detection electrode 20 changes, and the accurate thickness of the sheet-shaped medium 1 is detected. There was a problem that I could not do it.

The present invention has been made to solve the above problems, and an object of the present invention is to accurately detect the thickness of a sheet-shaped medium even if the distance between the conveyed sheet-shaped medium and the detection electrode changes. It is to provide a non-contact type thickness detection device that can perform the above.

[0011]

In order to achieve the above object, the present invention is configured as follows. That is, the present invention includes at least a pair of detection electrodes that are arranged to face each other at a position sandwiching a detection target object, one detection electrode being connected to the first electrostatic sensor, and the other detection electrode being the second detection electrode. The detection signals connected to the electrostatic sensor and output from the first electrostatic sensor and the second electrostatic sensor are added by an adding circuit.

[0012]

In the present invention having the above-mentioned structure, when the detection object passes between the pair of detection electrodes and is displaced toward one of the detection electrodes, the capacitance between the detection electrode on one side and the detection object increases. And the detection signal output of the first electrostatic sensor increases. On the other hand, the capacitance between the detection electrode on the other side and the detection target changes in the decreasing direction, and the detection signal output from the second electrostatic sensor changes in the decreasing direction.

The detection signal of the first electrostatic sensor and the detection signal of the second electrostatic sensor are added by the adder circuit, and as a result, the detection signal increases due to the decrease in the gap between the detection object and the detection electrode on one side. And the decrease in the detection signal due to the increase in the gap between the electrodes on the other side cancel each other out, and the thickness of the detection target can be accurately determined without being affected by the change in the gap between each detection electrode and the detection target. Will be possible.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a schematic configuration of an embodiment of a non-contact type thickness detecting device according to the present invention. In the figure,
A first detection electrode 5 and a second detection electrode 6 are arranged opposite to each other in a position where the sheet-shaped medium 1 is sandwiched via a passage gap 2 in a conveyance path of the sheet-shaped medium 1. Then, the first detection electrode 5
Is connected to the ceramic resonator 15 of the first electrostatic sensor 7 having the circuit shown in FIG. 5, and the second detection electrode 6 is also the second electrostatic electrode having the circuit shown in FIG. It is connected to the ceramic resonator 15 of the sensor 8.

In this embodiment, the first electrostatic sensor 7 and the second electrostatic sensor 7
The oscillating circuit 14 of the electrostatic sensor 8 is made common, and an oscillating frequency signal is applied from one oscillating circuit 14 to the resonance circuit 21 of each electrostatic sensor 7, 8 shown in FIG. And the first
Of the detection signal of the electrostatic sensor 7 and the second electrostatic sensor 8
The output of the detection signal of 1 is added to the addition circuit 10, and the addition output of the detection signals of the first electrostatic sensor 7 and the second electrostatic sensor 8 is extracted from the addition circuit 10.

This embodiment is constructed as described above,
Next, the operation will be described. As shown in FIG. 1, the first detection electrode 5
When the sheet-shaped medium 1 passes between the second detection electrode 6 and the second detection electrode 6, the capacitance corresponding to the thickness of the sheet-shaped medium 1 through which the electric field of the first detection electrode 5 passes and the dielectric constant of the gap δ ₁ is detected. This electrostatic capacitance detection signal is applied to the first electrostatic sensor 7 and corresponds to the electrostatic capacitance detected by the first detection electrode 5 as in the case of the proposed device of FIG. The detected signal is output. Similarly, the second detection electrode 6 detects the electrostatic capacitance corresponding to the dielectric constant between the thickness of the sheet-shaped medium 1 and the gap δ _2, and the detection signal corresponding to this electrostatic capacitance is the second electrostatic sensor. It is output from 8. Then, the detection signal of the first electrostatic sensor 7 and the detection signal of the second electrostatic sensor 8 are added by the adding circuit 10, and the addition output is taken out from the adding circuit 10.

FIG. 2 shows the output A of the detection signal of the first electrostatic sensor 7 when the sheet medium 1 is moved from the first detection electrode 5 side to the second detection electrode 6 side, and 2 shows the relationship between the output B of the detection signal of the second electrostatic sensor 8 and the addition output C of the addition circuit 10. According to this, the sheet-shaped medium 1
Is on the first detection electrode 5 side, since the gap δ ₁ is small, the capacitance detected by the first detection electrode 5 becomes large, and the detection signal of the first electrostatic sensor 7 shows a large value. .. On the other hand, the electrostatic capacitance detected by the second detection electrode 6 has a large δ ₂ , and therefore has a small electrostatic capacitance, and the detection signal output from the second electrostatic sensor 8 also becomes small. As the sheet-shaped medium 1 moves from the first detection electrode 5 side to the second detection electrode 6 side, δ ₁ gradually increases and δ ₂ gradually decreases. The detected electrostatic capacitance gradually decreases, and the electrostatic capacitance detected by the second electrostatic sensor 8 gradually increases. As a result, the output A of the detection signal of the first electrostatic sensor 7 becomes a downward-sloping curve. The output B of the detection signal of the second electrostatic sensor 8 is a curve that rises to the right.
Then, the summed output C of the detection signal of the first electrostatic sensor 7 and the detection signal of the second electrostatic sensor 8 is approximately flat in the central portion between the first detection electrode 5 and the second detection electrode 6. It becomes a curve that is convex downward at the bottom.

As is clear from the result of this addition output,
In the intermediate region of the gap between the first detection electrode 5 and the second detection electrode 6, even if the gaps δ ₁ and δ ₂ between the sheet-shaped medium 1 and the detection electrodes 5 and 6 change, the added output is almost constant. It becomes an output. That is, when the gaps δ ₁ and δ ₂ change in the central area of the gap between the detection electrodes 5 and 6, the decrease rate (or increase rate) and the increase rate of the detection capacitance of the first detection electrode 5 due to the change in the gap The increase rate (or the decrease rate) of the detection capacitance of the second detection electrode 6 becomes substantially equal, so that the addition circuit 10 adds the detection signals of both the electrostatic sensors 7 and 8 to one side. That is, the increase in the electrostatic capacitance of and the decrease in the electrostatic capacitance on the other side are canceled out, and a substantially constant signal output is obtained.

Therefore, according to this embodiment, by arranging the detection electrodes 5 and 6 with the sheet-shaped medium 1 sandwiched substantially at the center, the gaps δ ₁ and δ ₂ are caused by the displacement of the sheet-shaped medium 1.
Even if fluctuates, the thickness of the sheet-shaped medium 1 can be accurately detected without being affected by this fluctuating gap.

The present invention is not limited to the above-mentioned embodiment, and various embodiments can be adopted. For example, in the above embodiment, the pair of detection electrodes 5 and 6 with the sheet-shaped medium 1 sandwiched therebetween.
However, a plurality of these detection electrodes may be arranged to face each other in the width direction of the sheet-shaped medium 1 and each detection electrode may be connected to the corresponding electrostatic sensor. Further, the accuracy is further improved by obtaining the characteristic function and mutually calculating the coefficient.

Also, when a pair of detection electrodes are arranged with the sheet-shaped medium 1 sandwiched therebetween, the detection electrodes 5 and 6 are, as shown in FIG. 3, plate-shaped and have a length substantially equal to the width of the sheet-shaped medium 1. 4 may be used, but as shown in FIG. 4, the detection electrodes 5 and 6 may be divided into a plurality of pieces, and the divided detection electrodes may be connected by an impedance such as an inductance or a capacitor. Thus, by dividing the detection electrodes into a plurality, the effect of reducing the fixed capacitance of the detection electrodes 5 and 6 becomes effective especially when the circuit is driven at a high frequency in the GHz band as in this embodiment. The thickness of the sheet medium 1 can be detected with higher accuracy.

[0022]

According to the present invention, at least a pair of detection electrodes are arranged so as to face each other at a position sandwiching an object to be detected, each detection electrode is connected to a corresponding electrostatic sensor, and an electrostatic capacitance detected by each detection electrode is detected. Since the output of the electrostatic sensor is added by an adder circuit, the detection object passing between the detection electrodes is slightly displaced toward the detection electrode side and the gap between the detection object and each detection electrode fluctuates. However, the thickness of the object to be detected can be accurately detected without being affected by the gap variation, and the reliability of the detection can be dramatically improved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a non-contact type thickness detection device according to the present invention.

FIG. 2 is a graph showing the relationship between the detection output of each electrostatic sensor and the addition output of the addition circuit when a gap change between the detection target and the detection electrode in the apparatus of the embodiment is generated.

FIG. 3 is an explanatory view showing one form example of a detection electrode in the same Example.

FIG. 4 is an explanatory diagram showing another example of the form of the detection electrode in the example.

FIG. 5 is a circuit diagram of an electrostatic sensor previously proposed by the inventor.

FIG. 6 is an explanatory diagram showing an arrangement example of detection electrodes that can be considered when the electrostatic sensor previously proposed by the inventor is applied as a thickness detection device.

[Explanation of symbols]

 1 Paper Medium 5 First Detection Electrode 6 Second Detection Electrode 7 First Electrostatic Sensor 8 Second Electrostatic Sensor 10 Adder Circuit

Claims (1)

[Claims] 1. At least a pair of detection electrodes are arranged opposite to each other at a position sandwiching a detection target, one detection electrode being connected to a first electrostatic sensor, and the other detection electrode being a second detection electrode.
The first electrostatic sensor and the second electrostatic sensor.
The non-contact type thickness detection device in which the detection signal output from the electrostatic sensor is subjected to addition processing by an addition circuit.