KR102052187B1 - Ultrasonic radiator and manufacturing method of radiating plate for the ultrasonic radiator - Google Patents

Abstract

The ultrasonic radiator includes a transducer, a mechanical amplifier, and a radiating plate. The transducer is coupled with the piezoelectric element and converts the input electrical signal into a mechanical vibration signal of the piezoelectric element. The mechanical amplifier amplifies the vibration of the piezoelectric element. The radiating plate includes a metal plate and a plurality of convex parts positioned on the radiating surface of the metal plate, and radiates ultrasonic waves into the air by receiving the amplified vibration signal from the mechanical amplifying unit. The plurality of convex portions include a polymer material, have a thickness greater than that of the metal plate, and satisfy a Young's modulus and density condition such that an error rate between the natural frequency of the metal plate and the natural frequency of the radiating plate is 5% or less.

Description

Ultrasonic Radiator and Manufacturing Method of Radiating Plate for Ultrasonic Radiator {ULTRASONIC RADIATOR AND MANUFACTURING METHOD OF RADIATING PLATE FOR THE ULTRASONIC RADIATOR}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic radiator, and more particularly, to an ultrasonic radiator having a radiating plate having an uneven structure, and a manufacturing method of a radiating plate for an ultrasonic radiator.

Ultrasonic emitters can be applied to the production of loudspeakers that require high power and high directional sound waves. 1 is a view showing the radiation characteristics by the strain vibration in the general radiation plate. In general, the wider the radiation plate and the higher the frequency of the sound wave, the higher the directional sound wave. However, in reality, as shown in FIG. 1, since all the micro-planes of the radiating plate do not vibrate in the same phase, it is difficult to expect high directivity and high power.

One other way of generating directional sound waves is to use a parametric array phenomenon. The parametric array phenomenon is characterized by the fact that when harmonics with two different frequencies f1 and f2 propagate through a medium, various harmonics with frequencies of 2f1, 2f2, f1 + f2, f1-f2, etc. harmonics).

Among these harmonics, sound waves with relatively high frequencies 2f1, 2f2, and f1 + f2 disappear within a relatively short distance by the damping effect. On the other hand, sound waves having a relatively low difference frequency fd (f1-f2, fd << f1, fd << f2) are distributed in the form of lines in the medium, wherein the formed acoustic beam has a relatively low frequency. Although it has a high degree of directivity of the ultrasonic level.

Therefore, by using the parametric array phenomenon, it is possible to generate a high-oriented audible sound wave by setting the difference frequency fd to enter the audible frequency band by appropriately using the ultrasonic waves f1 and f2.

In order to solve the problem that the micro-planes of the radiating plate do not all oscillate in the same phase, a method of making a radiator by arranging a plurality of membrane transducers of small size has also been proposed, but the manufacturing is complicated and the cost increases. Korean Patent No. 10-0774516 discloses an ultrasonic speaker system in which a yaw portion and an iron portion are formed on a sound wave emitting surface of a radiation plate.

In the case of the radiating plate without the unevenness, in order to increase the output and directivity, the area of the radiating plate may be larger than the area of the piezoelectric element as the driving unit. However, as shown in FIG. And lowers the directivity. 2 is a view showing a principle for correcting the phase difference in the radiating plate of the uneven structure.

Referring to FIG. 2, the oscillation mode of the radiation plate causes sound waves generated at the radiation surface to generate sound waves of opposite phases to have low power. However, when the convex portion 20 having a thickness corresponding to the half wavelength (λ / 2) of the sound wave to be propagated into the air is disposed on the radiation surface, the wavelength of the sound wave generated in the convex portion 20 is in a dotted line state in a solid line state. Is corrected. Therefore, the sound waves generated in the concave portion 25 and the convex portion 20 have the same phase, and can compensate for the phase difference due to the vibration mode.

However, in order to apply the concave-convex structure to the radiating plate, there should be no significant change in the natural frequency of the radiating plate before and after the convex portion 20 is provided, and the vibration mode of the radiating plate at the natural frequency maintains the sink function shape as shown in FIG. 3. Should be. FIG. 3 is a diagram illustrating vibration modes before (a) and after (b) of convex portions in a spinning plate in which convex portions 20 of the same material as the metal plate 10 are positioned on the thick metal plate 10.

However, the convex portion 20 added for the phase compensation causes a change in the natural frequency and the vibration mode of the metal plate 10, and the extent of the metal plate 10 is significantly greater than that of the convex portion 20 as shown in FIG. 4. If it is small, it gets worse. FIG. 4 is a diagram illustrating vibration modes before (a) and after (b) of convex portions in the spinneret in which convex portions 20 of the same material as the metal plate 10 are positioned on the thin metal plate 10.

The thickness of the convex portion 20 is determined by the frequencies f1 and f2 for generating a parametric array phenomenon, the thickness of the metal plate 10 is determined as thin as possible in consideration of the radiation efficiency. In this process, since the natural frequency and the vibration mode of the radiating plate are different from those before the convex portion 20 is provided, it is difficult to achieve the intended phase compensation, and the width and position of the convex portion 20 are determined each time for the desired phase compensation. To do is a very complicated process.

The present invention provides an ultrasonic radiator capable of effectively implementing a parametric array phenomenon without large changes in vibration mode and natural frequency of the radiating plate before and after providing the convex portion on the radiating surface of the radiating plate, and a method of manufacturing the radiating plate for the ultrasonic radiator. I would like to.

An ultrasonic radiator according to an embodiment of the present invention includes a transducer, a mechanical amplifier, and a radiating plate. The transducer is coupled with the piezoelectric element and converts the input electrical signal into a mechanical vibration signal of the piezoelectric element. The mechanical amplifier amplifies the vibration of the piezoelectric element. The radiating plate includes a metal plate and a plurality of convex parts positioned on the radiating surface of the metal plate, and radiates ultrasonic waves into the air by receiving the amplified vibration signal from the mechanical amplifying unit. The plurality of convex portions include a polymer material, have a thickness greater than that of the metal plate, and satisfy a Young's modulus and density condition such that an error rate between the natural frequency of the metal plate and the natural frequency of the radiating plate is 5% or less.

The metal plate may comprise aluminum, a plurality of convex portions may have a density of 0kg / m ³ greater than less than 1,000kg / m ^3. The plurality of convex portions may have a Young's modulus that falls within a range between a minimum value derived from Equation (1) and a maximum value derived from Equation (2).

^{x = (1.31 × 10 - 4} ) y 4 - 0.0302y 3 + 542y 2 + (1.34 × 10 6) y + 7.85 × 10 6 --- (1)

^{x = (7.69 × 10 - 6} ) y 5 - 0.0172y 4 + 13.7y 3 - 4970y 2 + (4.47 × 10 6) y + 9.10 × 10 8 --- (2)

Here, y represents a specific density value belonging to more than 0 kg / m ^{3 and} less than 1,000 kg / m ³ , and x represents a Young's modulus value Pa for a specific density value y.

On the other hand, the metal plate may comprise titanium, and the plurality of convex portions may have a density of more than 0 kg / m ^{3 and} less than 1600 kg / m ³ . The plurality of convex portions may have a Young's modulus that falls within a range between a minimum value derived from Equation (3) and a maximum value derived from Equation (4).

x = 0.0503y ³ + 292y ² + (1.34 × 10 ⁶ ) y + 1.74 × 10 ⁷ --- (3)

^{x = (1.23 × 10 - 6} ) y 5 - (4.28 × 10 - 3) y 4 + 5.38y 3 - (3.15 × 10 3) y 2 + (4.26 × 10 6) y + 1.33 × 10 9 --- (4)

Here, y represents the specific density value that belongs to 0kg / m is less than ³ more than 1,600kg / m ^3, x represents a Young's modulus value (Pa) for a given density value (y).

The plurality of convex portions may include a plurality of circular rings arranged concentrically. The plurality of convex portions may further include a circular protrusion located at the center of the metal plate. The plurality of convex portions may comprise a mixture of epoxy and acrylic.

According to an embodiment of the present invention, a method of manufacturing a radiating plate for an ultrasonic radiator includes selecting a shape and a size and a material of a metal plate, a shape and a size of a convex part, changing a Young's modulus and density of the convex part, and changing a natural frequency change of the radiating plate. Selecting the Young's modulus and density range of the steel part whose natural frequency error rate of the radiation plate is 5% or less from the simulation result, and selecting a polymer material satisfying the selected Young's modulus and density range as the material of the iron part. And fabricating the metal plate and the convex part according to the selected shape, size and material.

The method of manufacturing a spinneret for an ultrasonic radiator may further include selecting a Young's modulus and a density range of the convex part, and then simulating a change in the vibration mode of the radiator plate before and after the convex part to select the density range of the convex part without changing the vibration mode. can do.

The metal plate may comprise aluminum, the density of the convex portions may be selected for 0kg / m is less than ³ more than 1,000kg / m ^3. The Young's modulus of the convex portion may be selected to be larger than the value derived from Equation (1) and smaller than the value derived from Equation (2).

^{x = (1.31 × 10 - 4} ) y 4 - 0.0302y 3 + 542y 2 + (1.34 × 10 6) y + 7.85 × 10 6 --- (1)

^{x = (7.69 × 10 - 6} ) y 5 - 0.0172y 4 + 13.7y 3 - 4970y 2 + (4.47 × 10 6) y + 9.10 × 10 8 --- (2)

Here, y represents a specific density value belonging to more than 0 kg / m ^{3 and} less than 1,000 kg / m ³ , and x represents a Young's modulus value Pa for a specific density value y.

On the other hand, the metal plate may comprise titanium, and the density of the iron portion may be selected to be greater than 0 kg / m ^{3 and} less than 1600 kg / m ³ . The Young's modulus of the convex portion may be selected to be larger than the value derived from Equation (3) and smaller than the value derived from Equation (4).

x = 0.0503y ³ + 292y ² + (1.34 × 10 ⁶ ) y + 1.74 × 10 ⁷ --- (3)

^{x = (1.23 × 10 - 6} ) y 5 - (4.28 × 10 - 3) y 4 + 5.38y 3 - (3.15 × 10 3) y 2 + (4.26 × 10 6) y + 1.33 × 10 9 --- (4)

Here, y represents the specific density value that belongs to 0kg / m is less than ³ more than 1,600kg / m ^3, x represents a Young's modulus value (Pa) for a given density value (y).

The convex portion may include a plurality of circular rings arranged concentrically. The convex portion may further include a circular protrusion located at the center of the metal plate.

According to the embodiment, it is possible to fabricate an ultrasonic radiator having the same vibration mode of the radiation plate before and after the convex portion and having a natural frequency change rate (error rate) of 5% or less. Ultrasonic radiator of the present embodiment can implement a high efficiency parametric array phenomenon without additional equipment, it is possible to manufacture a high-directional speaker capable of individual listening at a long distance.

1 is a view showing the radiation characteristics by the strain vibration in the general radiation plate.
2 is a view showing a principle for correcting the phase difference in the radiating plate of the uneven structure.
3 is a view showing a vibration mode before and after the arrangement of the iron portion in the spinning plate where the iron portion of the same material as the metal plate on the thick metal plate.
4 is a view showing the vibration mode before and after the placement of the iron portion in the spin plate in which the iron portion of the same material as the metal plate on the thin metal plate.
5 is a configuration diagram of a sound wave generation system.
6 is a perspective view of an ultrasonic radiator according to an embodiment of the present invention.
FIG. 7 is a cross-sectional view of the ultrasonic radiator shown in FIG. 6.
8 is a perspective view showing a modification of the ultrasonic radiator shown in FIG.
9 is a cross-sectional view of the ultrasonic radiator shown in FIG. 8.
FIG. 10 is a simulation diagram illustrating the natural frequency error rate of the spin plate according to the Young's modulus and density change of the convex part when the metal plate includes aluminum.
FIG. 11 is a diagram illustrating a vibration mode before and after arranging convex portions in the radiating plate of Example 1 having a plurality of convex portions having a Young's modulus and a density at point A shown in FIG. 10.
FIG. 12 is a diagram illustrating a vibration mode of the radiation plate of Comparative Example 1 having a plurality of convex portions having a Young's modulus and a density at point B shown in FIG. 10.
FIG. 13 is a diagram illustrating a vibration mode of the radiation plate of Comparative Example 2 having a plurality of convex portions having a Young's modulus and a density at point C shown in FIG. 10.
FIG. 14 is a diagram illustrating a vibration mode of the radiation plate of Comparative Example 3 having a plurality of convex portions having a Young's modulus and a density at point D shown in FIG. 10.
FIG. 15 is a simulation diagram illustrating a natural frequency error rate of a spin plate according to a change in Young's modulus and density of a convex part when a metal plate includes titanium.
FIG. 16 is a view showing a vibration mode before and after arranging convex portions in the spinning plate of Example 2 having a plurality of convex portions having a Young's modulus and a density at point E shown in FIG. 15.
FIG. 17 is a diagram illustrating a vibration mode of the radiation plate of Comparative Example 4 having a plurality of convex portions having a Young's modulus and a density at point F shown in FIG. 15.
FIG. 18 is a view showing a vibration mode of the radiation plate of Comparative Example 5 having a plurality of convex portions having a Young's modulus and a density at point G shown in FIG. 15.
FIG. 19 is a diagram showing a vibration mode of the radiation plate of Comparative Example 6 having a plurality of convex portions having a Young's modulus and a density at point H shown in FIG. 15.
20 is a process flowchart showing a method of manufacturing a spin plate according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

5 is a configuration diagram of a sound wave generation system. Referring to FIG. 5, the sound wave generation system 100 includes a signal generator 110, a signal amplifier 120, and an ultrasonic radiator 130.

The signal generator 110 modulates the signal, and the modulated signal is amplified by the signal amplifier 120 and then transmitted to the ultrasonic radiator 130. The ultrasonic emitter 130 emits ultrasonic waves into the air to generate a parametric array phenomenon.

6 is a perspective view of the ultrasonic radiator according to an embodiment of the present invention, Figure 7 is a cross-sectional view of the ultrasonic radiator shown in FIG. FIG. 8 is a perspective view illustrating a modification of the ultrasonic radiator illustrated in FIG. 6, and FIG. 9 is a cross-sectional view of the ultrasonic radiator illustrated in FIG. 8.

6 to 9, the ultrasonic radiator 130 includes a transducer 40, a piezoelectric element 50, a mechanical amplifier 60, and a radiating plate 30 having an uneven structure.

The transducer 40 converts an electrical signal into a mechanical vibration signal of the piezoelectric element 50. The piezoelectric element 50 may be made of piezoelectric ceramics, and the transducer 40 may be of a Langvin type fastened to the piezoelectric element 50 by a bolt.

The mechanical amplification unit 60 may be configured as a horn having various structures such as a stepped horn, a linear horn, and an exponential horn. The mechanical amplifier 60 receives and amplifies the mechanical vibration signal of the piezoelectric element 50 and transmits it to the radiation plate 30.

The radiation plate 30 emits ultrasonic waves from the amplified vibration signal. The radiation plate 30 includes a metal plate 10 having a predetermined thickness and a plurality of iron portions 20 positioned on the radiation surface of the metal plate 10 and made of a polymer material. The plurality of convex portions 20 may have the same thickness or two or more different thicknesses, and the thickness of the metal plate 10 is smaller than the minimum thickness of the convex portion 20.

That is, the radiation plate 30 of the present embodiment has a structure in which the iron portion 20 of the polymer material thicker than the metal plate 10 is added on the thin metal plate 10.

6 and 7, the plurality of convex portions 20 may include a plurality of circular rings arranged in concentric circles. The plurality of circular rings may have the same width and may be arranged at equal intervals from each other. Concave portions between the plurality of convex portions 20 function as concave portions of the concave-convex structure, and the center of the metal plate 10 corresponds to the concave portion.

On the other hand, as shown in FIGS. 8 and 9, the plurality of convex portions 20 are circular protrusions 21 positioned in the center of the metal plate 10, and a plurality of circularly arranged concentric circles about the circular protrusions 21. It may include a ring 22. The plurality of circular rings 22 may have the same width and may be arranged at equal intervals from each other. The recessed part between the circular protrusion 21 and the some circular ring 22 functions as a recessed part of an uneven structure.

In general, the performance of the spin plate can be determined using the Rayleigh integral. Rayleigh integration is to integrate the entire area of the radiating plate by assuming a small area of the radiating plate as a simple source, so that the pattern of the acoustic beam according to the vibration mode of the radiating plate can be grasped.

In an ideal spin plate, the Rayleigh integration results in either positive or negative numbers on the spin plate, thus contributing to the output in the same phase. However, in the case of the actual radiating plate, the negative part and the positive part appear at the same time and cancel each other according to the vibration mode of the radiating plate, thereby showing low power and low directivity.

Accordingly, when the convex portion 20 having a thickness corresponding to the half wavelength (λ / 2) of the sound wave to be generated is located at any one of two portions having phases opposite to each other, as shown in FIG. The phase is corrected with a dashed line in the solid line. In conclusion, the phases of the recesses 25 and the phases of the convex portions 20 become the same, which means that all the minute areas are close to the ideal spin plate performance having the same phase.

At this time, when the plurality of convex portions 20 have the same thickness, the radiation plate 30 exhibits a strong compensation effect for a specific frequency. When the plurality of convex portions 20 have two or more different thicknesses, the radiating plate 30 exerts a compensating effect for two or more different frequencies.

On the other hand, correcting the phase of the sound wave by using the convex portion 20 is a method that the vibration mode of the radiation plate 30 before and after the convex portion 20 is the same sink function (sinc function) form. As shown in FIG. 3, when the metal plate 10 is thicker than the convex portion 20, the radiating plate is implemented in the same sink function form as before and after the convex portion 20 is positioned.

However, as shown in FIG. 4, when the metal plate 10 is thinner than the convex portion 20, the radiation plate before the convex portion 20 is positioned shows a vibration mode in the form of a sink function, but is completely different after the convex portion 20 is positioned. It shows the vibration mode of the form. This means that the phase correction using the convex portion 20 is not effective.

6 to 9 again, in the ultrasonic radiator 130 of the present embodiment, the radiation plate 30 has a structure in which the convex portion 20 of the polymer material is disposed on the thin metal plate 10. The metal plate 10 may include any one of aluminum, titanium, and iron. The plurality of convex portions 20 includes a polymer material, and the weight per unit volume of the convex portion 20 is smaller than the weight per unit volume of the metal plate 10.

The plurality of convex portions 20 includes a polymer material, and the natural frequency of the radiating plate before the convex portion 20 is disposed without changing the vibration mode of the radiating plate 10 before and after the convex portion 20 is disposed (intrinsic to the metal plate itself). And the Young's modulus and density condition that the error of the natural frequency of the radiating plate 30 after the arrangement of the iron part is 5% or less.

The natural frequency error rate of the radiation plate 30 is equal to the design error of the radiation plate 30. In order to secure the design error of the radiating plate 30 to within 5%, the natural frequency error rate of the radiating plate 30 is selected to be within the range of 5% or less.

Once the shape, size, and material of the metal plate 10 are determined, the vibration mode and the natural frequency of the metal plate 10 can be known. In addition, when the shape and size of the convex portion 20 are determined, the vibration mode of the radiating plate 30 according to the Young's modulus and the density of the convex portion 20, and the natural frequency change of the radiating plate 30 are changed using a computer. Can simulate

FIG. 10 is a simulation diagram illustrating the natural frequency error rate of the radiation plate according to the Young's modulus and density change of the convex part when the metal plate includes aluminum. In the figure, the horizontal axis x represents the Young's modulus of the convex portion, and the vertical axis y represents the density of the convex portion.

The natural frequency error rate of the spin plate represents the ratio of the difference between the natural frequency of the metal plate and the other of the natural frequency of the spin plate. In other words, if the natural frequency of the metal plate and the natural frequency of the radiating plate are the same, the error rate is 0%. The Young's modulus of the metal plate applied in the simulation is 72 GPa, and the density is 2,780 kg / m ³ . In FIG. 10, the natural frequency error rate of the radiating plate is divided by 5% and illustrated in different patterns.

Referring to FIG. 10, when the metal plate includes aluminum, a region in which the natural frequency error rate of the radiating plate is 5% or less is defined in the center portion of the drawing, and the natural frequency error rate of the radiating plate is greater than 5% on each of the left and right sides of the region. Regions of 10% or less and regions of more than 10% and 15% are located in this order.

When the metal plate is aluminum, the density of the convex portions 0kg / m ³ greater than 1,000kg / m ³ may be less than, the Young's modulus of the convex portion is radial with respect to the specific density value that belongs to less than 0kg / m ³ greater than 1,000kg / m ³ plates Has a specific range where the natural frequency error rate of satisfies 5% or less.

Specifically, when the density of the iron portion is 300kg / m ³ , the Young's modulus of the iron portion may be in the range of approximately 0.5GPa to 2.1GPa. If the density of the convex part is 500 kg / m ³ , the Young's modulus of the convex part may be in the range of approximately 0.9 GPa to 2.7 GPa. When the density of the convex part is 700 kg / m ³ , the Young's modulus of the convex part may be in the range of about 1.3 GPa to 3.5 GPa.

The left boundary of the region where the natural frequency error rate of the radiating plate is 5% or less means the minimum value of the Young's modulus for a specific density value, and the right boundary means the maximum value of the Young's modulus for a specific density value.

By using a known polynomial regression method from the simulation diagram of FIG. 10, the left boundary line and the right boundary line of a region having a natural frequency error rate of 5% or less can be represented by a second or more polynomial function. Polynomial regression is a well-known numerical method for obtaining a polynomial that best represents n data consisting of (x1, y1), (x2, y2), (x3, y3) ... (xn, yn).

When the density (y) of the convex portion is greater than 0 kg / m ^{3 and} less than 1,000 kg / m ³ , the Young's modulus (x) of the convex portion is larger than the value derived from Equation (1) below and is higher than the value derived from Equation (2) below. It has a small value. That is the Young's modulus of the convex portion (Pa units) is in the range between the maximum value and the minimum value is derived from the equation (2) derived from equation (1) with respect to a particular density value belonging to 0kg / m is less than ³ more than 1,000kg / m ³ Can belong to.

^{x = (1.31 × 10 - 4} ) y 4 - 0.0302y 3 + 542y 2 + (1.34 × 10 6) y + 7.85 × 10 6 --- (1)

^{x = (7.69 × 10 - 6} ) y 5 - 0.0172y 4 + 13.7y 3 - 4970y 2 + (4.47 × 10 6) y + 9.10 × 10 8 --- (2)

FIG. 11 is a (b) before and after arranging convex portions in the spinning plate of Example 1 having a plurality of convex portions having a Young's modulus (1.5 GPa) and a density (500 kg / m ³ ) of the point A shown in FIG. 10; The vibration mode of FIG. In Example 1, the vibration mode of the radiation plate is the same as that of the metal plate, and the natural frequency error rate of the radiation plate is approximately 0.4%.

FIG. 12 is a diagram illustrating a vibration mode of the radiation plate of Comparative Example 1 having a plurality of convex portions having a Young's modulus (0.5GPa) and a density (900 kg / m ³ ) of point B shown in FIG. 10. The vibration mode before convex part placement is the same as that shown in FIG. The vibration mode of the radiation plate according to Comparative Example 1 did not show a clear sink function shape (different from the vibration mode of the metal plate), and the natural frequency error rate of the radiation plate was approximately 35%.

FIG. 13 is a diagram illustrating a vibration mode of the radiation plate of Comparative Example 2 having a plurality of convex portions having a Young's modulus (2.5GPa) and a density (1,000 kg / m ³ ) at point C shown in FIG. 10. The vibration mode before convex part placement is the same as that shown in FIG. The radiation plate according to Comparative Example 2 has a natural frequency error rate of approximately 4.7% and satisfies 5% or less, but the vibration mode of the radiation plate is different from that of the metal plate, and implements an unintended vibration mode.

In view of the vibration mode, when the metal plate is aluminum, the density of the convex portion may be less than 0kg / m ³ greater than 1,000kg / m ^3. If the density of the convex part is 1,000 kg / m ³ or more, the vibration mode of the radiating plate is different from the vibration mode of the metal plate (vibration mode before arranging the convex part), as shown in FIG. 13.

FIG. 14 is a diagram illustrating a vibration mode of the radiation plate of Comparative Example 3 having a plurality of convex portions having a Young's modulus (4.5 GPa) and a density (100 kg / m ³ ) at the point D shown in FIG. 10. The vibration mode before convex part placement is the same as that shown in FIG. The vibration mode of the radiation plate according to Comparative Example 3 is the same as that of the metal plate, but the natural frequency error rate of the radiation plate is approximately 17%.

FIG. 15 is a simulation diagram illustrating the natural frequency error rate of the radiation plate according to the Young's modulus and density change of the convex part when the metal plate includes titanium. The Young's modulus of the metal plate applied in the simulation is 116 GPa, and the density is 4,500 kg / m ³ . In FIG. 15, the natural frequency error rate of the radiating plate is divided into 5% units and illustrated in different patterns.

As shown in FIG. 15, when the metal plate includes titanium, a region in which the natural frequency error rate of the radiating plate is 5% or less is defined in the center portion of the figure, and the natural frequency error rate of the radiating plate is greater than 5% on each of the left and right sides of the region. The area | region which is% or less, and the area | region which is more than 10% and 15% or less are located in order.

When the metal plate is titanium, the density of the convex portions 0kg / m ³ greater than 1,600kg / m ³ may be less than, the Young's modulus of the convex portion is radial with respect to the specific density value that belongs to less than 0kg / m ³ greater than 1,600kg / m ³ plates Has a specific range where the natural frequency error rate of satisfies 5% or less.

Specifically, when the density of the iron portion is 400kg / m ³ , the Young's modulus of the iron portion may be in the range of approximately 0.5GPa to 3GPa. When the density of the convex portion is 800 kg / m ³ , the Young's modulus of the convex portion may be in the range of about 1.2 GPa to 4.2 GPa. When the density of the convex portion is 1,200 kg / m ³ , the Young's modulus of the convex portion may be in the range of approximately 2 Gpa to 6 GPa.

By using a known polynomial regression method from the simulation diagram of FIG. 15, the left boundary line and the right boundary line of a region having a natural frequency error rate of 5% or less can be represented by a second or more polynomial function.

When the density of the convex portion (y) is 0kg / m ³ greater than 1,600kg / m ³ below, to the Young's modulus (x) of the convex portion is greater than the value derived from the following equation (3) than the value derived from the formula (4) It has a small value. That is the Young's modulus of the convex portion (Pa units) is in the range between the maximum value and the minimum value is derived from the equation (4) derived from the equation (3) with respect to a particular density value belonging to 0kg / m is less than ³ more than 1,600kg / m ³ Can belong to.

x = 0.0503y ³ + 292y ² + (1.34 × 10 ⁶ ) y + 1.74 × 10 ⁷ --- (3)

^{x = (1.23 × 10 - 6} ) y 5 - (4.28 × 10 - 3) y 4 + 5.38y 3 - (3.15 × 10 3) y 2 + (4.26 × 10 6) y + 1.33 × 10 9 --- (4)

FIG. 16 shows (a) and (b) before and after arranging the convex portions in the spinning plate of Example 2 having a plurality of convex portions having a Young's modulus (2GPa) and a density (600 kg / m ³ ) of the point E shown in FIG. 15. It is a figure which shows the vibration mode. In Example 2, the vibration mode of the radiation plate is the same as that of the metal plate, and the natural frequency error rate of the radiation plate is approximately 0.6%.

FIG. 17 is a diagram showing a vibration mode of the radiation plate of Comparative Example 4 having a plurality of convex portions having a Young's modulus (0.8GPa) and a density (1,400 kg / m ³ ) of the point F shown in FIG. 15. The vibration mode before convex part placement is the same as that shown in FIG. The vibration mode of the radiation plate according to Comparative Example 4 is different from the vibration mode of the metal plate, and the natural frequency error rate of the radiation plate is approximately 35%.

FIG. 18 is a view showing a vibration mode of the radiation plate of Comparative Example 5 having a plurality of convex portions having a Young's modulus (7GPa) and a density (1,600 kg / m ³ ) of the point G shown in FIG. 15. The vibration mode before convex part placement is the same as that shown in FIG. The radiation plate according to Comparative Example 5 has a natural frequency error rate of approximately 4.7% and satisfies 5% or less, but the vibration mode of the radiation plate is different from the vibration mode of the metal plate, and implements an unintended vibration mode.

In view of the vibration mode, when the metal plate includes titanium, the density of the convex portion may be greater than 0 kg / m ^{3 and} less than 1600 kg / m ³ . If the density of the convex portion is 1,600 kg / m ³ or more, it is not preferable because the vibration mode of the radiating plate is different from the vibration mode of the metal plate (vibration mode before arranging the iron part) as shown in FIG. 18.

FIG. 19 is a diagram illustrating a vibration mode of the radiation plate of Comparative Example 6 having a plurality of convex portions having a Young's modulus (7.5 GPa) and a density (200 kg / m ³ ) of the H point shown in FIG. 15. The vibration mode before convex part placement is the same as that shown in FIG. The vibration mode of the radiation plate according to Comparative Example 6 is the same as that of the metal plate, but the natural frequency error rate of the radiation plate is approximately 17%.

When the Young's modulus and density of the iron portion are determined from the simulation results of FIGS. 10 and 15, a polymer material satisfying the determined Young's modulus and density is selected as the material of the iron portion. For example, the plurality of convex portions may include a mixture of epoxy and acrylic, but is not limited to this example. It is possible to produce a polymer material satisfying the desired Young's modulus and density conditions according to the mixing ratio of the polymer material, the type of the additive and the content of the additive.

In general, when the additional structure is attached to the base structure, the modified structure will have a natural frequency and vibration mode different from the base structure. In the deformed structure, even if the additional structure occupies a large volume, if the Young's modulus and density of the additional structure are properly determined due to the characteristics of the natural frequency determined by the Young's modulus and density of the material, then the deformed structure will not have the same natural frequency as the base structure. It may have a vibration mode.

In the radiating plate, the plurality of convex portions occupy a larger volume than the metal plate, but are formed of a polymer material having a weight less than the metal plate per unit volume, and the simulation shows a Young's modulus and density condition in which the natural frequency error rate of the radiating plate is 5% or less. Satisfies. Therefore, the radiation plate of this embodiment can maintain the natural frequency error rate before and after the convex portion at 5% or less while maintaining the same vibration mode before and after the convex portion arrangement.

Next, the manufacturing method of the radiation plate for an ultrasonic radiator is demonstrated. 20 is a process flowchart showing a method of manufacturing a spin plate according to an embodiment of the present invention.

Referring to FIG. 20, the manufacturing method of the spinning plate includes a first step (S10) of selecting a shape and a size and a material of a metal plate, a shape and a size of a steel plate, and changing the Young's modulus and density of the steel plate and changing a natural frequency of the spinning plate. And a third step (S30) of selecting a Young's modulus and a density range of the convex portion having a natural frequency error rate of 5% or less of the radiating plate.

In addition, the manufacturing method of the spinning plate is a fourth step (S40) of selecting a polymer material satisfying the Young's modulus and density conditions selected in the third step (S30) as the material of the iron portion, and the metal plate and the plurality of iron portions A fifth step (S50) to produce. The first to fourth steps S10, S20, S30, and S40 correspond to a design process.

6 to 9 and 20, in the first step S10, the shape and size and material of the metal plate 10 and the shape and size of the convex portion 20 are selected. The metal plate 10 is a disc of a certain thickness and may include any one of aluminum, titanium, and iron. The thickness of the metal plate 10 is smaller than the minimum thickness of the convex portion 20. The convex portion 20 may include a plurality of circular rings, or may include a circular protrusion 21 and a plurality of circular rings 22.

When the shape, size, and material of the metal plate 10 are determined, the vibration mode and the natural frequency of the metal plate 10 may be known. The vibration mode and the natural frequency of the metal plate 10 correspond to the vibration mode and the natural frequency of the radiation plate before the convex portion 20 is disposed.

In the second step (S20), the vibration mode of the radiation plate 30 according to the Young's modulus and density change of the convex portion 20 and the natural frequency change of the radiation plate 30 are simulated using a computer. The change in natural frequency of the radiation plate 30 may be calculated as a change rate (error rate) with respect to the natural frequency of the metal plate 10. 10 and 15 show the natural frequency error rate of the radiation plate 30 according to the Young's modulus and density change of the convex portion 20 when the metal plate includes aluminum and titanium, respectively.

In the third step (S30), the Young's modulus and density range of the convex portion 20 having a natural frequency error rate of 5% or less of the radiating plate 30 is selected from the simulation result of the second step (S20). At this time, even if the natural frequency error rate of the radiating plate 30 satisfies 5% or less, since the vibration mode before and after the convex part 20 may be changed, the convex part 20 without further changing the vibration mode by further simulating the vibration mode change. Further select the density range of.

The metal plate 10 in this case comprises aluminum, the density of the convex portion 20 has a Young's modulus (Pa) of the 0kg / m ³ greater than and be less than 1,000kg / m ^3, the convex portion 20 is 0kg / m ³ greater than 1,000kg For a particular density value that falls below / m ³ , it may fall within the range between the minimum value derived from Equation (1) below and the maximum value derived from Equation (2) below.

^{x = (1.31 × 10 - 4} ) y 4 - 0.0302y 3 + 542y 2 + (1.34 × 10 6) y + 7.85 × 10 6 --- (1)

^{x = (7.69 × 10 - 6} ) y 5 - 0.0172y 4 + 13.7y 3 - 4970y 2 + (4.47 × 10 6) y + 9.10 × 10 8 --- (2)

Specifically, when the density of the iron portion is 300kg / m ³ , the Young's modulus of the iron portion may be in the range of approximately 0.5GPa to 2.1GPa. If the density of the convex part is 500 kg / m ³ , the Young's modulus of the convex part may be in the range of approximately 0.9 GPa to 2.7 GPa. When the density of the convex part is 700 kg / m ³ , the Young's modulus of the convex part may be in the range of about 1.3 GPa to 3.5 GPa.

The metal plate 10, in this case containing titanium, and the density of the convex portion 20 has a Young's modulus (Pa) of the 0kg / m ³ greater than and be less than 1,600kg / m ^3, the convex portion 20 is 0kg / m ³ greater than 1,600kg For a particular density value that falls below / m ³ , it may fall within the range between the minimum value derived from Equation (3) below and the maximum value derived from Equation (4) below.

x = 0.0503y ³ + 292y ² + (1.34 × 10 ⁶ ) y + 1.74 × 10 ⁷ --- (3)

^{x = (1.23 × 10 - 6} ) y 5 - (4.28 × 10 - 3) y 4 + 5.38y 3 - (3.15 × 10 3) y 2 + (4.26 × 10 6) y + 1.33 × 10 9 --- (4)

Specifically, when the density of the iron portion is 400kg / m ³ , the Young's modulus of the iron portion may be in the range of approximately 0.5GPa to 3GPa. When the density of the convex portion is 800 kg / m ³ , the Young's modulus of the convex portion may be in the range of about 1.2 GPa to 4.2 GPa. When the density of the convex portion is 1,200 kg / m ³ , the Young's modulus of the convex portion may be in the range of approximately 2 GPa to 6 GPa.

When the above-described conditions are satisfied, the radiating plate 30 may maintain the natural frequency error rate before and after the convex portion 20 at 5% or less while maintaining the vibration mode before and after the convex portion 20 arrangement.

In the fourth step S40, a polymer material satisfying the Young's modulus and the density condition selected in the third step S30 is selected and selected as the material of the iron part 20. For example, the iron portion 20 may include a mixture of epoxy and acrylic, but is not limited thereto, and any one of various polymer materials satisfying selected Young's modulus and density conditions may be selected.

The fifth step S50 is a process of manufacturing the actual metal plate 10 using the material of the metal plate 10 selected in the first step S10, and the metal plate using the polymer material selected in the fourth step S40. The process of arranging the actual plurality of convex portions 20 on the radial surface of the (10).

For example, a mold having a plurality of concave portions corresponding to the plurality of convex portions 20 is prepared, a liquid polymer material is filled in the concave portion of the mold, and the mold is brought into close contact with the radiating surface of the metal plate 10. The plurality of convex portions 20 may be fixed to the metal plate 10 through a process of transferring the transferred to the metal plate 10 and curing the transferred polymer material.

On the other hand, a plurality of pre-fabricated iron portion 20 is attached to the radial surface of the metal plate 10 using an adhesive, or by applying a liquid polymer material on the metal plate 10 and hardened by a method such as machining The material may be patterned and processed into a plurality of convex portions 20.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the range of.

10: metal plate 20: convex
25: main part 30: radiation plate
40: transducer 50: piezoelectric element
60: mechanical amplification unit 100: sound wave generation system
110: signal generator 120: signal amplifier
130: ultrasonic radiator

Claims (16)

A transducer coupled to the piezoelectric element and converting the input electrical signal into a mechanical vibration signal of the piezoelectric element;
A mechanical amplifier for amplifying the vibration of the piezoelectric element; And
It includes a metal plate, and a plurality of convex parts located on the radiation surface of the metal plate, and comprises a radiation plate for receiving ultrasonic waves amplified from the mechanical amplification unit to emit ultrasonic waves into the air,
The plurality of convex portions include a polymer material and have a thickness greater than the thickness of the metal plate, and the ultrasonic radiator satisfies the Young's modulus and density conditions such that an error rate of the natural frequency of the metal plate and the natural frequency of the radiating plate is 5% or less. . The method of claim 1,
The metal plate includes aluminum,
The plurality of convex portions having a density of more than 0 kg / m ^{3 and} less than 1,000 kg / m ³ . The method of claim 2,
And the plurality of convex portions have a Young's modulus falling within a range between a minimum value derived from Equation (1) and a maximum value derived from Equation (2).
^{x = (1.31 × 10 - 4} ) y 4 - 0.0302y 3 + 542y 2 + (1.34 × 10 6) y + 7.85 × 10 6 --- (1)
^{x = (7.69 × 10 - 6} ) y 5 - 0.0172y 4 + 13.7y 3 - 4970y 2 + (4.47 × 10 6) y + 9.10 × 10 8 --- (2)
Here, y represents a specific density value belonging to more than 0 kg / m ^{3 and} less than 1,000 kg / m ³ , and x represents a Young's modulus value Pa for a specific density value y. The method of claim 1,
The metal plate comprises titanium,
And said plurality of convex portions have a density of greater than 0 kg / m ^{3 and} less than 1600 kg / m ³ . The method of claim 4, wherein
And the plurality of convex portions have a Young's modulus falling within a range between a minimum value derived from Equation (3) and a maximum value derived from Equation (4).
x = 0.0503y ³ + 292y ² + (1.34 × 10 ⁶ ) y + 1.74 × 10 ⁷ --- (3)
^{x = (1.23 × 10 - 6} ) y 5 - (4.28 × 10 - 3) y 4 + 5.38y 3 - (3.15 × 10 3) y 2 + (4.26 × 10 6) y + 1.33 × 10 9 --- (4)
Here, y represents the specific density value that belongs to 0kg / m is less than ³ more than 1,600kg / m ^3, x represents a Young's modulus value (Pa) for a given density value (y). The method according to any one of claims 1 to 5,
And the plurality of convex portions comprises a plurality of circular rings arranged concentrically. The method of claim 6,
The plurality of convex portion further comprises a circular protrusion located in the center of the metal plate. The method of claim 6,
And said plurality of convex portions comprises a mixture of epoxy and acrylic. A method of manufacturing a spin plate for an ultrasonic radiator comprising a metal plate and an iron part disposed on a radial surface of the metal plate and made of a polymer material,
Selecting a shape and a size and a material of the metal plate, a shape and a size of the convex portion, changing a Young's modulus and density of the convex portion, and simulating a natural frequency change of the radiating plate;
Selecting a Young's modulus and a density range of the convex portion whose natural frequency error rate of the radiating plate is 5% or less from the simulation result;
Selecting a polymer material satisfying the selected Young's modulus and density range as a material of the iron portion; And
And manufacturing the metal plate and the iron part according to the selected shape, size, and material. The method of claim 9,
Selecting the Young's modulus and density range of the convex portion, and then simulating the vibration mode change of the radiating plate before and after the convex portion to select the density range of the convex portion without a change in the vibration mode further comprising: Method of preparation. The method of claim 10,
The metal plate includes aluminum,
Density of the convex portions 0kg / m ³ greater than 1,000kg / m ultrasonic emitter process for producing a radiation plate for being selected as less than ^3. The method of claim 11,
The Young's modulus of the convex part is larger than the value derived from Equation (1), and the method of manufacturing a radiation plate for an ultrasonic radiator is selected to a value smaller than the value derived from Equation (2).
^{x = (1.31 × 10 - 4} ) y 4 - 0.0302y 3 + 542y 2 + (1.34 × 10 6) y + 7.85 × 10 6 --- (1)
^{x = (7.69 × 10 - 6} ) y 5 - 0.0172y 4 + 13.7y 3 - 4970y 2 + (4.47 × 10 6) y + 9.10 × 10 8 --- (2)
Here, y represents a specific density value belonging to more than 0 kg / m ^{3 and} less than 1,000 kg / m ³ , and x represents a Young's modulus value Pa for a specific density value y. The method of claim 10,
The metal plate comprises titanium,
Density of the convex portions 0kg / m ³ greater than 1,600kg / m ultrasonic emitter process for producing a radiation plate for being selected as less than ^3. The method of claim 13,
The Young's modulus of the convex portion is larger than the value derived from Equation (3), and the method of manufacturing a radiation plate for an ultrasonic radiator is selected to a value smaller than the value derived from Equation (4).
x = 0.0503y ³ + 292y ² + (1.34 × 10 ⁶ ) y + 1.74 × 10 ⁷ --- (3)
^{x = (1.23 × 10 - 6} ) y 5 - (4.28 × 10 - 3) y 4 + 5.38y 3 - (3.15 × 10 3) y 2 + (4.26 × 10 6) y + 1.33 × 10 9 --- (4)
Here, y represents the specific density value that belongs to 0kg / m is less than ³ more than 1,600kg / m ^3, x represents a Young's modulus value (Pa) for a given density value (y). The method according to any one of claims 9 to 14,
The convex portion manufacturing method of the radiation plate for an ultrasonic radiator including a plurality of circular rings arranged in a concentric circle. The method of claim 15,
The convex part further comprises a circular protrusion located at the center of the metal plate.

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