JPH0684957B2 - Plate wave sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention utilizes a plate wave excited in a plate by an elastic wave obliquely incident from a liquid, and a fluid, powder, or solid The present invention relates to a plate wave sensor that detects the amount, physical properties, and mechanical properties of these foreign matters based on changes in the plate wave coupling state due to adhesion, deposition, or contact.

[Conventional technology]

Taking powder deposition detection as an example, there is a sensor as shown in FIG. Explaining the principle, the movement of the tuning fork 2 excited by the electrostrictive oscillator 1 causes the deposit 3 such as powder to move.
From the electrical circuit 4
It is detected by.

[Problems to be solved by the invention]

By the way, the conventional sensor as described above cannot be used when the powder falls from above, and the tuning fork 2 disturbs the state in the vicinity thereof, so that correct detection cannot be expected.

Therefore, in order to detect the deposit 3 in a non-contact manner, the only method in the past is to see through the window of the side wall with light or ultrasonic waves. However, this method is used especially when the amount of deposition is small. There is a problem that it is extremely difficult to detect accurately.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a plate wave sensor capable of detecting adhesion, deposition, and contact with high sensitivity without affecting an object.

[Means for solving problems]

The plate wave sensor according to the present invention has a case in which at least one side surface is parallel to the front and back sides, and a plate on which the sample is in contact is provided on the front surface side, and a liquid is enclosed in the case. A means for exciting a plate wave on the incident plate and a means for detecting a reflected wave from the plate, and a change for detecting a change in the excited state of the plate wave generated in the plate by the means for detecting the reflected wave The detection means is provided.

[Action]

In the present invention, the incident angle of the elastic wave obliquely incident on the plate, the frequency of the elastic wave and the thickness of the plate are set,
A plate wave propagating on the plate is excited, and the excited state of the plate wave is detected by a change detecting means in a non-contact state of the deposit on the plate or the state of the plate.

〔Example〕

FIG. 1 (a) is a side view showing an embodiment of the present invention.
Is a plate whose front and back are parallel to each other, and the one shown in the figure has a powder deposit 3 deposited on the surface side as a kind of sample. 6 is the plate 5
Is provided on the upper surface, 7 is a liquid enclosed in a casing 6 sealed with the plate 5, 8 is provided in the casing 6 enclosing the liquid 7, and the liquid 5 is interposed between the plate 5 and A wave transmitting element which is a means for transmitting the elastic wave W _e at a required incident angle, and 9 is the casing 6
A wave receiving element which is a means for receiving the reflected wave W _r from the plate 5 provided therein, 10 is an oscillator for giving an alternating current signal to the wave transmitting element 8, and 11 is for amplifying the signal from the wave receiving element 9. An amplifier 12 is an indicator as a plate wave change detecting means for detecting a change in the excited state of the plate wave generated by the wave receiving element 9 for detecting the reflected wave W _r .

FIG. 1 (b) shows an example in which the housing 6 of FIG. 1 (a) is inserted, and in this way, it is possible to detect without affecting the plate 5 or the deposit 3. . Elastic wave W _e
In order to avoid the interference due to the multiple reflection of (1), a pulse voltmeter may be applied as the indicator 12 by making the transmitted signal a pulse.

Next, the principle of the plate wave sensor of the present invention and the experimental results will be described.

In FIG. 1A, one side surface of the housing 6 is formed by a plate 5 whose front and back surfaces are parallel to each other, and the wave transmitting element 8 and the wave receiving element 9 are elastic waves W _e emitted from the wave transmitting element 8. Is reflected by the plate 5 and reaches the wave receiving element 9. Elastic wave W _e for plate 5
It is possible to excite the plate wave propagating through the plate 5 by adjusting the relationship between the incident angle of, the frequency of the elastic wave W _e , and the thickness of the plate 5.
The propagation velocity of the plate wave is determined according to the material and thickness of the plate 5 and the frequency of the elastic wave W _e , and as shown in FIG.
C _p , the velocity of the elastic wave W _e in the liquid 7 is C _l , and the incident angle of the elastic wave W _e is θ, when the condition of C _l = C _p · sin θ is satisfied, Waves are excited. The incident angle of the elastic wave W _e that excites the plate wave is θ, the frequency f of the elastic wave W _e , and the thickness t of the plate 5
FIG. 3 shows a part of the above relationship.

In FIG. 3, hatched lines in the figure are calculated values, ◯ marks are actually measured values, and all numbers indicate the incident angle θ.

When the plate wave is excited, the energy of the elastic wave W _e is transmitted through the plate 5 via the plate wave, so that the amplitude of the reflected wave W _r becomes smaller.

In Fig. 4, the liquid 7 is water and the frequency f of the elastic wave W _e is constant (2.73
MHz) and the reflected wave W for the incident angle θ of the elastic wave W _e
It shows the relationship of the amplitude A of _{r, and} the amplitude A of the reflected wave W _r becomes minimum at the incident angle θ at which the plate wave is excited. Further, the incident angle θ at which the amplitude A becomes minimum differs depending on the thickness t of the plate 5. The plate 5 is made of stainless steel, and the curve 13 has a thickness t of 0.5 mm, the curve 14 has 0.2 mm, and the curve 15 has 0.1 mm.
In this way, the incident angle θ at which the amplitude A of the reflected wave W _r is minimized
The result of the measurement of ∘ is in good agreement with the calculated value indicated by the diagonal lines as shown by the actual measurement value of the circle in FIG.

Since it is not easy to change the incident angle θ of the elastic wave W _e , an example in which the elastic wave W _e is fixed and the frequency f is changed is shown in FIG.

In FIG. 5, the liquid 7 is water, the plate 5 is stainless steel with a thickness t of 0.5 mm, the incident angle θ of the elastic wave W _e is 45 °, and the curve
Reference numerals 16 and 17 show the amplitude A of the reflected wave W _r when the back surface of the plate 5 is air and water, respectively. A curve 18 shows the characteristic of the elastic wave W _e directly propagating from the wave transmitting element 8 to the wave receiving element 9, and the curves 16 and 17 show local minima due to the excitation of the plate wave.

Since the coupled state of the plate wave excitation is subtly related to the elastic property of the plate wave 5, adhesion, deposition, contact of foreign matter on the plate 5 and their properties or corrosion of the plate 5 itself are caused by the change of the coupled state. Can be detected.

Curve 17 in FIG. 6 is the same as that shown in FIG.
Shows an example in which about 150 g / mm ² of silicon powder was deposited on the back surface of the plate 5. In this figure, FIG. 7 shows the relationship between the minimum value of the amplitude A of the reflected wave W _r at the frequency f at which the plate wave is excited and the deposition amount of silicon powder.

In FIG. 7, the vertical axis represents the value of the amplitude A normalized by the amplitude without deposition, and the horizontal axis represents the deposition amount Q of silicon powder.
Indicates. The curve of amplitude A-accumulation amount Q has a peculiar shape according to the property of the deposit 3.

〔The invention's effect〕

INDUSTRIAL APPLICABILITY As described above, according to the present invention, at least one side surface is parallel to the front surface, and a plate on which the sample is in contact is provided on the front surface side. A means for exciting a plate wave on the incident plate and a means for detecting a reflected wave from the plate, and a change for detecting a change in the excited state of the plate wave generated in the plate by the means for detecting the reflected wave Since the detection means is provided, in addition to the non-contact detection of powder deposition and deposition, which is difficult with the conventional sensor, it is possible to detect the adhesion and contact of liquids and solids.
The nature of the deposit can be identified. In addition, all the parts that will be the sensor are stored in the housing, so it is easy to handle, and the means for exciting the plate wave on the plate and the means for detecting the reflected wave from the plate are also installed in the liquid. Therefore, it has the advantages that it is easy and that quantitative measurement is possible.

[Brief description of drawings]

FIG. 1 (a) is a block diagram showing a first embodiment of the present invention.
1B is a side view showing an example in which the plate wave sensor of FIG. 1A is mounted, FIG. 2 is a view showing a principle of plate wave excitation by oblique incidence of elastic waves, and FIG. FIG. 4 is a diagram showing the relationship between the thickness of the plate, the frequency of the elastic wave, and the incident angle of the elastic wave when excited, and FIG. 4 shows the incident angle of the elastic wave at which the plate wave is excited when the frequency of the elastic wave is constant. Fig. 5 shows that the amplitude of the reflected wave becomes minimum. Fig. 5 shows the reflected wave at the frequency at which the plate wave is excited when the frequency of the elastic wave is changed with the incident angle of the elastic wave and the plate thickness kept constant. Fig. 6 shows that the amplitude becomes the minimum, Fig. 6 shows that the deposition of powder on the plate changes the coupling state of the plate wave excitation, and Fig. 7 shows the minimum amplitude of the reflected elastic wave due to the excitation of the plate wave. FIG. 8 shows a state in which the value changes depending on the amount of powder deposited, and FIG. 8 shows an example of a conventional sensor for detecting the deposition of powder. It is a formed view. In the figure, 3 is a deposit, 5 is a plate, 6 is a housing, 7 is a liquid, 8 is a wave transmitting element, 9 is a wave receiving element, 10 is an oscillator, 11 is an amplifier, 12
Is an indicator, W _e is an elastic wave, and W _r is a reflected wave.

Claims (1)

[Claims] 1. A housing in which at least one side surface is parallel to the front and back, and a plate on the front surface is in contact with the sample, and a liquid is sealed inside.
Means for exciting elastic waves into the plate by injecting elastic waves obliquely to the plate through the liquid, means for detecting reflected waves from the plate, and means for detecting the reflected waves A plate wave sensor, comprising: a change detection unit that detects a change in an excited state of a plate wave generated in a plate.