Ultrasonic horn

Abstract

To provide an ultrasonic horn enlarged without being limited by constraints on groove processing.SOLUTION: An ultrasonic horn 1 is such that, with respect to three mutually orthogonal axes X, Y and Z, when the direction of ultrasonic application is set to the X or Z direction, each of the X-direction dimension and Z-direction dimension in the XZ cross-section of the ultrasonic horn is an integer multiple of the minimum resonant unit square based on the elastic modulus, Poisson ratio and density of the horn material.SELECTED DRAWING: Figure 12

Description

[Technical field]

[0001] The present invention relates to increasing the size of an ultrasonic horn. [Background technology]

[0002] It has been a common practice to connect an ultrasonic horn to an ultrasonic transducer controlled by an ultrasonic oscillator and use ultrasonic vibration. One example of the use is so-called ultrasonic transport, in which an object is levitated or supported in a non-contact state due to ultrasonic vibration and moved to a desired position. For such ultrasonic transport, a larger ultrasonic horn is required. In addition, larger ultrasonic horns are expected to be used in various fields and applications in the future.

[0003] Here, when trying to make the ultrasonic horn larger, in order to obtain a uniform vibration distribution over a wide area of ​​the enlarged ultrasonic horn, processing may be performed to provide grooves in the ultrasonic horn. For example, Patent Document 1 discloses a technology for providing grooves in an ultrasonic horn.

[0004] However, in practice, the above-mentioned groove machining has a resistance to the drill used to form the groove, and there is a limit to how far the groove can be machined over a wide area, i.e., there is a limit to how large the ultrasonic horn can be made. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent No. 3,113,225 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in view of the above, and has an object to provide a large ultrasonic horn without being restricted by the limitations of groove machining. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the ultrasonic horn of the present invention has three mutually perpendicular axes X, Y, and Z, and when the ultrasonic wave is applied in the X direction or the Z direction, each of the X direction dimension and Z direction dimension of the ultrasonic horn in the XZ cross section is an integer multiple of the smallest unit square that resonates based on the elastic modulus, Poisson's ratio, and density of the horn material. Effect of the Invention

[0008] According to the present invention, it is possible to provide a large ultrasonic horn without being restricted by the limitations of groove machining. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating how a metal material deforms during resonance in relation to Poisson's ratio. [Diagram 2] FIG. 1 is a diagram illustrating compression of a cube under static pressure. [Diagram 3] FIG. 13 is a diagram illustrating a stress distribution under static pressure. [Figure 4] FIG. 13 is a diagram illustrating a stress distribution during resonance. [Diagram 5] 1A and 1B are diagrams showing schematic diagrams of deformation due to resonant vibration in a thin rod or a thin plate. [Figure 6] FIG. 13 is a diagram illustrating stress distribution in a square cross section. [Figure 7] FIG. 13 is a diagram for explaining lamination of the same shape. [Figure 8] FIG. 1 is a diagram illustrating three types of sound speed. [Figure 9] FIG. 1 is a diagram illustrating features of the present invention. [Figure 10] FIG. 10 is a diagram showing another embodiment of FIG. [Figure 11] FIG. 10 is a diagram showing another embodiment of FIG. [Figure 12] FIG. 1 is a diagram showing the technical and conceptual expansion of the features of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an ultrasonic horn according to an embodiment of the present invention will be described with reference to the accompanying drawings. In the drawings, the same reference numerals indicate the same or corresponding parts.

[0011] Moreover, the three mutually orthogonal axes XYZ indicate directions corresponding to each other in FIG. 1 to FIG.

[0012] With respect to the three mutually perpendicular axes X, Y, and Z, when the ultrasonic wave is applied in the X or Z direction, the X and Z dimensions of the ultrasonic horn in its XZ cross section are each an integer multiple of the smallest unit square that resonates, based on the elastic modulus, Poisson's ratio, and density of the horn material.

[0013] First, we will explain the premise for explaining ultrasonic horns. Generally, waves are roughly divided into longitudinal waves and transverse waves, and when the medium is gas or liquid, only longitudinal waves are transmitted. Therefore, in gas or liquid, the resonance of sound and vibration also takes a simple form. On the other hand, solids transmit longitudinal and transverse waves, so that, except for thin rods where transverse vibration can be ignored, the resonance of transverse waves interferes during resonance, resulting in a complex vibration form. Ultrasonic horns are designed and adjusted so that they vibrate at a resonance frequency equivalent to the resonance frequency of the ultrasonic transducer. Therefore, there are many shape and size constraints. For example, for a thin round rod, the wavelength λ can be calculated from the longitudinal sound speed v and resonance frequency f of the metal material in the length direction (Z direction), and λ = v / f, and 1 / 2 the wavelength is the minimum length of the ultrasonic horn. In this case, if the width and thickness (X, Y directions) of a thin rod or thin plate are not easily affected by transverse waves and Poisson's ratio, resonance will occur when the length is an integer multiple of λ / 2.

[0014] On the other hand, as the width and thickness increase, they are affected by shear waves and Poisson's ratio, and when the dimensions exceed λ / 4, complex processing such as groove processing along the longitudinal vibration direction becomes necessary. Due to restrictions on the processing machine and drill bit length, the maximum practical size of an ultrasonic horn is X-direction dimension × Y-direction dimension: Therefore, up until now, ultrasonic horns have not been able to meet the demands of resonating large plates.

[0015] In this invention, the Poisson's ratio of the horn material is taken into consideration as one of the parameters to obtain the smallest unit square that resonates, and this Poisson's ratio will be explained below. Based on Fig. 1, the Poisson's ratio will be explained to explain how metal materials deform during resonance. The Poisson's ratio is the ratio of the strain in the load direction to the strain in the perpendicular direction when a force is applied to a material. If there is no change in volume during compression and expansion, the Poisson's ratio is 0.5. The Poisson's ratio can also be considered as one of the elastic moduli. In Fig. 1, the longitudinal strain α=(ΔL) / (L), the transverse strain β=(Δd) / (d), and the Poisson's ratio σ=β / α.

[0016] Next, the compression of a cube under static pressure will be explained with reference to Fig. 2. As shown in Fig. 2(a), when a cube with a Poisson's ratio of 0.5, which does not change in volume when pressure is applied, is placed on a stand and its bottom surface is fixed to the stand. When pressure is applied from the top surface, the four sides expand equally. In this case, if the amount by which the top surface sinks due to pressure is d as shown in Fig. 2(b), the amount of expansion of each of the four sides is d / 4 as shown in Fig. 2(c). If one side of the cube is L, the strain in the vertical direction (Z direction) = d / L, and the strain in the horizontal direction is (d / 4+d / 4) / L, so Poisson's ratio = horizontal strain / vertical strain = (d / 4+d / 4) / d = 0.5. The maximum Poisson's ratio is 0.5.

[0017] Next, the stress distribution under static pressure will be explained based on Fig. 3. The distribution of stress σ when a rectangular metal material is compressed or stretched is uniform in the compression (stretch) direction. Therefore, the deformation of the material is also uniform in the X direction.

[0018] Next, the stress distribution during resonance will be explained with reference to Figure 4. When a rectangular metal material resonates with half a wavelength, the stress does not occur evenly, but as shown by the stress distribution in the Z direction and the stress distribution in the X direction, the maximum stress appears where the displacement is minimal, and the strain also becomes large at this point. Since the displacement appears as an accumulation of strain, the compression and extension in the longitudinal direction (Z direction) is large, and the compression and extension in the lateral direction (X direction) is small. For example, the resonant vibration of one wavelength in a thin rod or thin plate is as shown in Figure 5.

[0019] Further, the stress distribution in a square cross section will be explained based on FIG. 6. Only when the XZ cross section is a square, the X-direction stress distribution on the center X-axis and the Z-direction stress distribution on the center Z-axis are equal. Since the stress distribution in each axis direction is equivalent, the deformation amount is also equivalent, and the area of ​​the bulging area (diagonal lines) to the left and right and the area of ​​the contracting area (diagonal lines) to the top and bottom are equal. Therefore, the volume change in the thickness direction (Y-axis direction) is zero because the effect of the volume change is not exerted in the Y-axis direction and is completed within the plane. Therefore, the volume change due to compression and expansion of the top and bottom surfaces and the left and right side surfaces is equal. Also, at this time, the volume change in the thickness direction (Y direction) is zero. As shown in FIG. 7, if the deformation of each rectangular parallelepiped does not affect the Y direction, it can be stacked infinitely in the Y direction.

[0020] Next, we will explain the speed of sound. Here, we will look at three types of sound speeds: longitudinal waves (in an infinite medium) C1, longitudinal waves (thin rod) C3, and transverse waves C2, as shown in Figure 8. An infinite medium is a state filled with homogeneous objects that transmit waves left and right and up and down, such as deep seawater, and in this case, the metal itself is the medium. The three types of sound speeds: longitudinal waves (in an infinite medium) C1, longitudinal waves (thin rod) C3, and transverse waves C2, can each be expressed by the formulas shown in Figure 8, with the relationship C1>C3>C2.

[0021] Furthermore, the difference in the speed of sound (m / s) in each medium is as follows: [Table 1] In the case of aluminum, the half wavelength at 40 kHz is 77.5 mm for the longitudinal sound velocity (infinite medium), 63.4 mm for the longitudinal sound velocity (thin rod), and 38.75 mm for the transverse sound velocity.

[0022] Next, we will explain the apparent speed of sound. The apparent speed of sound in a metal material is affected by the applied frequency and the shape of the material, and is not constant. As the width and thickness increase in the direction of longitudinal wave propagation, the apparent speed of sound of the longitudinal wave slows down due to the influence of the transverse waves. When in a resonant state with a square cross section, the apparent longitudinal wave and transverse wave are in perfect agreement. The speed of sound in a square cross section is If the longitudinal wave speed (in an infinite medium) is C1, the longitudinal wave speed (in a rod) is C2, and the shear wave speed is C3, then It can be considered as [{(C1+C3) / 2}+C2] / 2. Using the abovementioned C1 = 6200, C2 = 5070, and C3 = 3100 as the sound speeds (m / s) in aluminum material, the apparent sound speed within a square cross section is calculated to be approximately 4367 m / s, and the half wavelength of 20 kHz is approximately 109 mm. Similarly, if the sound speeds (m / s) in steel are C1 = 5800, C2 = 5060, and C3 = 3150 m / s as mentioned above, the apparent sound speed is calculated to be 4290 m / s, and the half wavelength of 40 kHz is approximately 54 mm.

[0023] When matching the resonant frequency of the transducer with that of the ultrasonic horn, the resonance point can be adjusted by adjusting the length while keeping XL = ZL. This task usually requires an impedance analyzer or a device that combines a signal generator and a high-frequency power supply. The frequency is measured with the ultrasonic transducer and ultrasonic horn screwed together. Start with a low frequency and adjust the resonant frequency by repeatedly screwing and unscrewing and machining until you find the desired frequency. The X-direction dimension = Z-direction dimension determined in this way is called L. At this time, L is equivalent to 0.5 wavelengths for this material and shape.

[0024] As a specific example, the elastic modulus of ordinary aluminum is 70 GPa (10 9Pascal), Poisson's ratio 0.33, density 2.7g / cm 2 Using the finite element method, it can be confirmed that the two sides (XL and ZL) of the square cross section are 110.4 mm and resonate at 20 kHz and 0.5 wavelengths in both the vertical and horizontal directions. Similarly, for iron, the elastic modulus is 200 GPa, the Poisson's ratio is 0.3, and the density is 7.8 g / cm. 2 Using the finite element method, it can be confirmed that the two sides (XL and ZL) will resonate at 40 kHz and 0.5 wavelengths in both the vertical and horizontal directions with a square cross section of 55.5 mm.

[0025] It was also confirmed that the minimum unit square that resonates, whose dimensions in the X direction and Z direction were determined as described above and whose dimensions are based on the elastic modulus, Poisson's ratio, and density of the horn material, does not change the vibration mode (shape). In other words, as shown in Figure 9 (1 wavelength in the X direction x 1 wavelength in the Z direction), even if the dimensions of the ultrasonic horn in the X direction and Z direction are expanded to an integer multiple of the minimum unit square with one side L that resonates, only the phase changes by 180 degrees between adjacent squares, and it was confirmed that the vibration mode (shape) of each square itself does not change.

[0026] As another example of a different shape, as shown in Figure 10 (2 wavelengths in the X direction × 0.5 wavelengths in the Z direction), even if the dimension of the ultrasonic horn only in the X direction is expanded to an integer multiple of a square with one side L, which is the minimum unit of resonance, it was confirmed that only the phase changes by 180 degrees between adjacent squares, and there is no change in the vibration mode (shape) of each square itself.

[0027] As a further example of a different shape, as shown in Figure 11 (2 wavelengths in the X direction × 1 wavelength in the Z direction), even if the dimensions of the ultrasonic horn in the X direction and Z direction are expanded to an integer multiple (another integer multiple different from that in Figure 9) of a square with one side L, which is the minimum unit for resonance, it was confirmed that only the phase changes by 180 degrees between adjacent squares, and there is no change in the vibration mode (shape) of each square itself.

[0028] As can be seen from this, as shown in FIG. 12, the dimensions of the ultrasonic horn 1 in the X and Z directions can be expanded to dimensions that are an integer multiple of the square of the smallest unit that resonates (an integer multiple of 0.5 wavelengths), and it was found that there are no restrictions on the numerical values ​​of the dimensions of the ultrasonic horn in the X and Z directions as long as the condition of an integer multiple of the square of the smallest unit that resonates is satisfied. The present invention is based on this, and by using an ultrasonic horn whose dimensions in the X and Z directions are each an integer multiple of the square of the smallest unit that resonates based on the elastic modulus, Poisson's ratio, and density of the horn material, it is possible to provide an ultrasonic horn that is enlarged without being bound by the limitations of groove processing. Therefore, for example, an ultrasonic transport device requires an enlarged ultrasonic horn that is grooved to obtain a uniform vibration distribution over a wide area, but the ultrasonic horn of the present invention makes it possible to realize an ultrasonic transport device using an ultrasonic horn that obtains a uniform vibration distribution over a wide area without being forced to groove. To give a specific example, an ultrasonic transport device with an XY plane as the transport surface can be configured by using an ultrasonic horn that is enlarged in accordance with the above characteristics.

[0029] The contents of the present invention have been specifically described above with reference to preferred embodiments. However, it is obvious that a person skilled in the art can adopt various modifications based on the basic technical concept and teachings of the present invention. [Explanation of symbols]

[0030] 1 Ultrasonic horn

Claims

[Claim 1] An ultrasonic horn in which, when the direction of ultrasonic application is the X direction or the Z direction with respect to three mutually perpendicular axes X, Y, and Z, each of the X-direction dimension and the Z-direction dimension in the XZ cross section of the ultrasonic horn is an integer multiple of the smallest unit square that resonates based on the elastic modulus, Poisson's ratio, and density of the horn material.

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