ultrasonic hydrophone

Abstract

To provide an ultrasonic sound hydrophone with excellent durability and a receiver sensitivity.SOLUTION: An ultrasonic sound hydrophone 31 of the present invention, includes: a cylinder hydrophone main body 33; a tip end protection member 34 that is mounted onto the tip end; and an oscillator 35 that is provided to a back surface of the tip end protection member 34. The tip end protection member 34 is made of: a first part 41; and a second part 42 that has an almost conical shape integrally formed on the tip end side. The second prat 42 has a sharp top part 43. An inclination angle θ on an outer front surface 44 of the second part 42 as using a reference of a center shaft line C1 of the hydrophone main body 33 is 40° or more and 60° or less. An outer peripheral surface 45 of the first part 41 and an outer front surface 44 of the second part 42 are continued without a step. In an angle change part 47 positioned at a border of them, a radius bevelling processing is executed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an ultrasonic hydrophone. [Background technology]

[0002] Ultrasonic cleaners, for example, have been well known as devices that utilize ultrasonic waves. Generally, ultrasonic cleaners are configured with an ultrasonic vibrator installed at the bottom of a treatment tank for storing cleaning liquid. The ultrasonic vibrator generates ultrasonic waves, which are then irradiated into the cleaning liquid, cleaning the object to be cleaned. It is known that the ultrasonic waves generated by the ultrasonic vibrator are reflected by the water surface, generating standing waves. It is also known that when powerful ultrasonic waves in a specific frequency range are irradiated into the cleaning liquid, reduced pressure and increased pressure alternately occur, causing bubbles to form in the liquid due to the pressure during reduced pressure, a phenomenon known as "cavitation." It is also known that cavitation is more likely to occur in liquids under high-intensity ultrasonic conditions.

[0003] Cavitation occurs more easily with lower-frequency ultrasound and can be generated with relatively low ultrasonic energy. Therefore, low- and medium-frequency ultrasonic cleaners actively utilize the shock waves generated by the expansion, contraction, and collapse of cavitation to efficiently clean relatively large stains and stubborn oil-based stains. Ultrasonic cleaners for cleaning semiconductor substrates and other devices use ultrasonic waves with relatively high frequencies (several hundred kHz to several MHz), and the cleaning process is carried out while controlling the impact force caused by the collapse of cavitation to prevent damage such as pattern collapse. Therefore, in order to maintain cleaning efficiency, such ultrasonic cleaners require technology to control the generation of cavitation.

[0004] In order to control the generation of cavitation in such ultrasonic cleaners, it is necessary to estimate the amount of cavitation using a sound pressure analyzer, and to achieve this, a means for detecting the sound pressure of ultrasonic waves in the liquid is required. Ultrasonic hydrophones are well known as sensors that detect the ultrasonic sound field in the liquid and output a voltage signal in response to the sound pressure of the sound field. Various ultrasonic hydrophones have been proposed, each with a cylindrical hydrophone body, a tip protection member attached to the tip, and a vibrator located on the back side of the tip protection member (see, for example, Patent Document 1 and Non-Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 6-225884 [Non-Patent Document 1] Proceedings of the Acoustical Society of Japan, March 2018, pp. 1007-1008, "Reexamination of the Structure of Robust Hydrophones" [Non-patent document 2] Ultrasonic TECNO, January-February 2021, pp. 83-87, "Study on a robust hydrophone for measuring sound fields accompanied by the occurrence of acoustic cavitation" Summary of the Invention [Problem to be solved by the invention]

[0006] However, because conventional ultrasonic hydrophones have a flat surface at the tip of the tip protection member, when used under high-intensity ultrasonic conditions, cavitation bubble clouds tend to adhere to and remain on the flat surface. This cavitation bubble cloud can then damage the tip protection member. In other words, conventional ultrasonic hydrophones have the drawback of being unable to be used for long periods due to their poor durability, prematurely reducing reception sensitivity, and in some cases developing holes in the flat surface, rendering them unusable. Furthermore, when a cavitation bubble cloud collides with the tip of the ultrasonic hydrophone, a large pulse-like noise is generated in the received waveform, leading to a decrease in the accuracy of sound pressure measurement.

[0007] Furthermore, a conventional technology has been proposed in recent years in which the tip protection member is formed into an approximately trapezoidal cross section to reduce the flat surface (see Non-Patent Document 2), but this still does not completely prevent the retention of cavitation bubble clouds, and further improvements were considered necessary.

[0008] The present invention was made in consideration of the above-mentioned problems, and its object is to provide an ultrasonic hydrophone with excellent durability and reception sensitivity. Another object of the present invention is to provide an ultrasonic cleaner and ultrasonic processor that can easily and reliably set appropriate ultrasonic processing conditions based on an accurate estimation of the amount of cavitation generated. [Means for solving the problem]

[0009] In order to solve the above problem, claim 1 describes an ultrasonic hydrophone that outputs a voltage signal in response to the sound pressure of ultrasound in a liquid, comprising a cylindrical hydrophone body, a tip protection member attached to the tip of the hydrophone body, and a vibrator arranged so as to contact the back surface of the tip protection member, wherein the tip protection member consists of a first part formed with an outer diameter dimension equal to the outer diameter of the hydrophone body and attached to the tip of the hydrophone body, and a second part of an approximately conical shape formed integrally with the tip side of the first part, wherein the second part has a pointed apex, and the inclination angle of the outer surface of the second part with respect to the central axis of the hydrophone body is set to be between 40° and 60°, the outer peripheral surface of the first part and the outer surface of the second part are continuous without any steps, and the angle change part located at the boundary between them is subjected to a radius chamfering process.

[0010] According to the invention described in claim 1, the second portion constituting the tip protection member has a generally conical shape, and the inclination angle of the outer surface is set within a preferred range of 40° to 60°. It also has a pointed apex with no flat surfaces. Furthermore, due to the radiation pressure from the ultrasonic vibrator, cavitation bubble clouds do not adhere to and remain at the apex, but rather tend to move backward along the outer surface of the second portion, which has a preferred inclination angle. This prevents damage to the second portion due to the cavitation bubble clouds remaining. Furthermore, the outer surfaces of the first and second portions are continuous without any steps, and the angle change portion located at their boundary is chamfered. Therefore, cavitation bubble clouds moving backward do not adhere to and remain at the angle change portion, but tend to move further backward. Furthermore, the lack of steps or depressions makes them less likely to become a source of cavitation. This results in an ultrasonic hydrophone with excellent durability and reception sensitivity.

[0011] The invention described in claim 2 is characterized in that, in claim 1, the angle-changing portion is subjected to a radiused chamfering process having a size of 1 / 100 to 1 / 10 of the outer diameter of the hydrophone body.

[0012] According to the invention described in claim 2, the boundary between the outer surface of the first section and the outer surface of the second section is appropriately chamfered, eliminating edges at the angle change section, resulting in a smooth, continuous surface that is less likely to catch cavitation bubble clouds. This makes it less likely that the movement of cavitation bubble clouds will be hindered, and the absence of steps or depressions makes them less likely to become a source of cavitation. As a result, it is possible to reliably prevent cavitation bubble clouds from accumulating.

[0013] The invention described in claim 3 is the same as claim 1 or 2, wherein the dimension of the second portion along the central axis of the hydrophone body is equal to or less than half the outer diameter of the hydrophone body, and the dimension of the outer peripheral portion of the first portion along the central axis of the hydrophone body is equal to or less than half the outer diameter of the second portion, and the vibrator is minutes The first part minutes The gist of the invention is that the hydrophone is positioned closer to the tip than the joint between the outer surface of the hydrophone and the tip of the hydrophone body, and has a diameter that is at least 1 / 3 of the outer diameter of the hydrophone body.

[0014] Therefore, according to the invention described in claim 3, even if the outer diameter of the hydrophone body is small, the transducer can be made relatively large, and the distance from the top of the second section to the transducer can be made relatively short. As a result, it is possible to easily obtain an ultrasonic hydrophone with excellent reception sensitivity.

[0015] The invention described in claim 4 is an ultrasonic cleaner that uses ultrasonic waves to clean a workpiece immersed in a liquid, and is characterized by comprising: a treatment tank for storing the liquid; an ultrasonic vibrator installed in the treatment tank to irradiate the liquid in the treatment tank with ultrasonic waves; a drive device for driving and controlling the ultrasonic vibrator; and a high-sound-pressure sound field sound pressure analyzer that includes an ultrasonic hydrophone described in any one of claims 1 to 3 and estimates the amount of cavitation generated based on a voltage signal in response to the sound pressure of the sound field output from the ultrasonic hydrophone.

[0016] Therefore, according to the invention described in claim 4, the amount of cavitation generated can be accurately estimated based on the output from an ultrasonic hydrophone which has excellent durability and receiving sensitivity, and based on this, it is possible to easily and reliably set ultrasonic processing conditions appropriate for ultrasonic cleaning.

[0017] The invention described in claim 5 is an ultrasonic treatment device that chemically treats a workpiece immersed in a liquid using ultrasonic waves, and is characterized by comprising a treatment tank for storing the liquid, an ultrasonic vibrator installed in the treatment tank to irradiate the liquid in the treatment tank with ultrasonic waves, a drive device for driving and controlling the ultrasonic vibrator, and an ultrasonic hydrophone described in any one of claims 1 to 3, and a high-sound-pressure sound field sound pressure analyzer that estimates the amount of cavitation generated based on a voltage signal in response to the sound pressure of the sound field output from the ultrasonic hydrophone.

[0018] Therefore, according to the invention described in claim 5, the amount of cavitation generated can be accurately estimated based on the output from an ultrasonic hydrophone with excellent durability and receiving sensitivity, and based on this, it is possible to easily and reliably set appropriate ultrasonic processing conditions for ultrasonic processing. [Effects of the Invention]

[0019] As described above in detail, the inventions of claims 1 to 3 can provide an ultrasonic hydrophone with excellent durability and reception sensitivity. Also, the inventions of claims 4 and 5 can provide an ultrasonic cleaner and ultrasonic processor that can easily and reliably set appropriate ultrasonic processing conditions based on an accurate estimation of the amount of cavitation generated. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a schematic configuration diagram showing an ultrasonic cleaner according to an embodiment of the present invention; [Figure 2] FIG. 2 is a schematic diagram illustrating the configuration of an ultrasonic hydrophone used in the ultrasonic cleaner of the present embodiment. [Figure 3] 2 is a schematic diagram for explaining the external shape of the tip of the ultrasonic hydrophone of the present embodiment. FIG. [Figure 4] (a) and (b) are schematic diagrams for explaining the behavior of cavitation bubble clouds in an ultrasonic hydrophone of a comparative example, and (c) is a schematic diagram for explaining the behavior of cavitation bubble clouds in an ultrasonic hydrophone of this embodiment. [Figure 5] (a) to (c) are photographs showing a sequence of the behavior of cavitation bubble clouds in an ultrasonic hydrophone of a comparative example. [Figure 6] 6(a) to 6(d) are photographs showing a sequence of the behavior of cavitation bubble clouds in the ultrasonic hydrophone of this embodiment. [Figure 7] 5(a) to 5(d) are schematic diagrams for explaining the external shape of the tip of an ultrasonic hydrophone according to another embodiment. [Figure 8] FIG. 10 is a schematic diagram showing the configuration of an ultrasonic cleaner according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] An embodiment in which the ultrasonic hydrophone of the present invention is embodied in an ultrasonic cleaner (ultrasonic processing device) will be described in detail below with reference to FIGS.

[0022] 1 shows a schematic diagram of an ultrasonic cleaner 11 according to this embodiment. This ultrasonic cleaner 11 is a device for using ultrasonic waves to clean an object to be treated immersed in a liquid (cleaning liquid) W1. This ultrasonic cleaner 11 includes a treatment tank 12, an ultrasonic vibrator 13, a driving device, and a frequency analyzer 17 for a high sound pressure field.

[0023] The treatment tank 12 is a container with an open top and a closed bottom, and is configured to store the liquid W1 inside. In this embodiment, a cylindrical double tank with an inner diameter of 56 mm is used as the treatment tank 12, and water (air-saturated water) at 25°C as the liquid W1 is stored therein and circulated.

[0024] The ultrasonic vibrator 13 is a means for irradiating the liquid W1 in the treatment tank 12 with ultrasonic waves and is installed at the bottom of the treatment tank 12. In this embodiment, a vibrator with a diaphragm is attached as the ultrasonic vibrator 13 to the outer surface of the bottom of the treatment tank 12. As the ultrasonic vibrator 13, for example, a multi-frequency vibrator (22, 43, 98 kHz; manufactured by Honda Electronics Co., Ltd.) having a diameter of 45 mm is used, but other vibrators such as a 300 kHz vibrator, a 490 kHz vibrator, a 1 MHz vibrator, a 2 MHz vibrator, and a 5 MHz vibrator having a diameter of 50 mm (all manufactured by Honda Electronics Co., Ltd.) are also used. The ultrasonic vibrator 13 may also be installed on the inner surface of the bottom.

[0025] The driving device of this ultrasonic cleaner 11 is composed of an ultrasonic oscillator 21, a power amplifier 22, and a PC (personal computer) 23 as control means. The ultrasonic oscillator 21 is electrically connected to the ultrasonic vibrator 13 via the power amplifier 22. The ultrasonic oscillator 21 outputs a continuous sine wave oscillation signal of a predetermined frequency (300 kHz and 490 kHz in this embodiment). This oscillation signal is amplified by the power amplifier 22 and then supplied to the ultrasonic vibrator 13 to drive the ultrasonic vibrator 13. Although not shown, when driving the ultrasonic vibrator 13 at a frequency other than 300 kHz and 490 kHz, an impedance matching circuit is provided between the power amplifier 22 and the ultrasonic vibrator 13. The ultrasonic vibrator 13 then generates ultrasonic waves at a frequency corresponding to the oscillation frequency of the ultrasonic oscillator 21 (or an impedance-matched frequency). As a result, ultrasonic waves are irradiated upward from the bottom side of the treatment tank 12 to the liquid W1 in the treatment tank 12. The PC 23 is electrically connected to the ultrasonic oscillator 21 and controls the signal level of the oscillation signal of the ultrasonic oscillator 21 in order to adjust the output of the ultrasonic waves generated from the ultrasonic vibrator 13 and drive it.

[0026] The high-sound-pressure sound field sound pressure analyzer 15 in this ultrasonic cleaner 11 is composed of an ultrasonic hydrophone 31, a preamplifier 16, a frequency analyzer 17, an oscilloscope 18, and a PC 23 as a computing device.

[0027] 2, the ultrasonic hydrophone 31 is an ultrasonic sensor that detects an ultrasonic sound field in the liquid W1 and outputs a voltage signal corresponding to the sound pressure of the sound field, and is fixed to a support member (not shown) with its tip immersed in the liquid W1. The detailed configuration of the ultrasonic hydrophone 31 will be described later.

[0028] As shown in FIG. 1, the ultrasonic hydrophone 31 is electrically connected to the frequency analyzer 17 and oscilloscope 18 via the preamplifier 16. The ultrasonic hydrophone 31 outputs a voltage signal in response to the sound pressure of the sound field to the preamplifier 16. The preamplifier 16 converts the impedance of the voltage signal from the ultrasonic hydrophone 31 and outputs it to the outside. The oscilloscope 18 reads the voltage signal output from the preamplifier 16 and displays it on a screen as a voltage waveform. The oscilloscope 18 is electrically connected to the frequency analyzer 17 and PC 23, as well as to a current-voltage probe 25 to detect the output current from the power amplifier 22.

[0029] The frequency analyzer 17 analyzes the frequency components of the sound field based on the voltage signal from the ultrasonic hydrophone 31 input via the preamplifier 16. As such a frequency analyzer 17, for example, a spectrum analyzer or the like is used.

[0030] The PC 23, which is both the control means and the calculation device, is configured to input the output signal from the frequency analysis device 17, analyze the frequency components obtained by the frequency analysis device 17, and perform predetermined calculations based on the analysis results.

[0031] Next, the configuration of the ultrasonic hydrophone 31 of this embodiment will be described in detail with reference to Figure 3. This ultrasonic hydrophone 31 comprises a cylindrical hydrophone body 33, a tip protection member 34 attached to the tip 33a of the hydrophone body 33, and a vibrator 35 provided so as to contact the back surface of the tip protection member 34.

[0032] The hydrophone body 33 of this embodiment has a diameter of 3.5 mm and is formed using a corrosion-resistant metal material, such as titanium, that can withstand cavitation shock waves. The tip protection member 34 is a member that blocks and protects the tip opening of the hydrophone body 33 and is basically composed of a first portion 41 and a second portion 42. The first portion 41 is formed with an outer diameter (here, a cylindrical shape with a diameter of 3.5 mm) equal to the outer diameter D1 of the hydrophone body 33 and is attached to the tip of the hydrophone body 33 by adhesive or the like. The second portion 42 is a substantially conical member formed on the tip side of the first portion 41. Like the hydrophone body 33, the first portion 41 and the second portion 42 of this embodiment are both formed using a corrosion-resistant metal material, such as titanium. The first portion 41 and the second portion 42 are formed integrally, and therefore there is no seam or step at the boundary between them.

[0033] The vibrator 35 is made of a piezoelectric material. In this embodiment, a PZT (lead zirconate titanate) film, which is chemically synthesized and therefore resistant to peeling, is used as the vibrator 35. That is, one electrode side (front side) of the vibrator 35 is in contact with the back side of the second portion 42, providing electrical continuity. While a thin-film vibrator is used in this embodiment, a thin-plate vibrator that is not a thin film can also be used. A cylindrical acoustic backing material 36 is bonded to the other electrode side (rear side) of the vibrator 35 via a conductive adhesive. The acoustic backing material 36 is formed from a conductive metal material, and an insulating material (not shown) is disposed on its outer periphery. In this embodiment, the titanium acoustic backing material 36 is used to improve sensitivity through noise reduction. The insulating material maintains electrical insulation between the hydrophone body 33, the tip protection member 34, and the acoustic backing material 36. The base end of the acoustic backing material 36 is bonded to the conductor 38 of the coaxial cable 39 via a conductive adhesive. The coaxial cable 39 is drawn out from the base end 33b side of the hydrophone body 33 to the outside.

[0034] Next, the external shape of the tip of the ultrasonic hydrophone 31 will be described. As shown in FIG. 4 , the second portion 42 constituting the tip protection member 34 has a pointed apex 43. That is, the apex 43 does not have a flat surface. The outer surface 44 of the second portion 42 of the hydrophone body 33 is tapered. With respect to the central axis C1 of the hydrophone body 33 as the reference, the inclination angle θ of the outer surface 44 of the second portion 42 is set to approximately half a right angle, specifically, between 40° and 60°. If this inclination angle θ is too small, the second portion 42 will be longer overall and have a more acute shape. This will increase the distance from the apex 43 to the transducer 35, potentially hindering improved reception sensitivity. On the other hand, if the inclination angle θ is too large, the distance from the apex 43 to the transducer 35 will be shorter, but the cavitation bubble cloud 51 may not move smoothly along the outer surface 44 of the second portion 42. The inclination angle θ is preferably between 40° and 50°, and is set to 45° in this embodiment. The inclination angle θ may be uniform over the entire outer surface 44 of the second portion 42, but may also vary slightly, with the difference between the maximum and minimum inclination angles being within ±5°, for example. On the other hand, the outer peripheral surface 45 of the first portion 41 is not particularly inclined with respect to the central axis C1 of the hydrophone body 33, and the inclination angle is 0°.

[0035] As shown in FIG. 3 , the outer surface 45 of the first portion 41 and the outer surface 44 of the second portion 42 are continuous without any steps. The angle-changing portion 47 located at the boundary between them is chamfered along its entire circumference. As a result, there are no edges in this portion, creating a smooth connection. The size of the chamfered portion of the angle-changing portion 47 is not particularly limited, but it is preferably, for example, between 1 / 100 and 1 / 10 of the outer diameter D1 of the hydrophone body 33. If the chamfered portion is too small, an edge will remain in this portion, preventing a smooth connection between the outer surface 45 of the first portion 41 and the outer surface 44 of the second portion 42. This may hinder the smooth movement of the cavitation bubble cloud 51 from the outer surface of the second portion 42 to the outer surface 45 of the first portion 41. On the other hand, if the size of the chamfered radius is too large, the outer diameter of the chamfered portion will be small, which may make it difficult to increase the size of the vibrator 35 while shortening the distance from the top 43 of the second portion 42 to the vibrator 35.

[0036] The dimension L2 of the second portion 42 along the central axis C1 of the hydrophone body 33 is set to be less than half the outer diameter D1 of the hydrophone body 33. If this dimension L2 is too large, the second portion 42 will be longer overall and will have a more acutely angled shape. As a result, the distance from the apex 43 to the transducer 35 will be longer, which may make it difficult to improve the reception sensitivity. Furthermore, the dimension L1 of the outer peripheral portion of the first portion 41 along the central axis C1 of the hydrophone body 33 is set to be less than half the outer diameter D2 of the second portion 42 (which is equal to the outer diameter D1 of the hydrophone body 33 in this embodiment).

[0037] The transducer 35 is disposed on the first portion 41 side at a position closer to the tip than the joint surface 37 between the outer peripheral surface 45 of the first portion 41 and the tip 33a of the hydrophone main body 33. This configuration allows the distance from the top 43 of the second portion 42 to the transducer 35 to be shortened. In this embodiment, the transducer 35 is disposed at a position quite close to the angle change section 47. The transducer 35 also has a diameter d1 that is at least one-third the outer diameter D1 of the hydrophone main body 33. The diameter d1 of the transducer 35 is preferably at least one-half the outer diameter, more preferably at least two-thirds the outer diameter, and in this embodiment, is approximately 75% of the outer diameter.

[0038] Next, a cleaning process for an object to be cleaned using the ultrasonic cleaner 11 configured as above will be described.

[0039] First, an operator places an object to be cleaned in liquid W1 stored in treatment tank 12 of ultrasonic cleaner 11, and then turns on a cleaning start switch (not shown). PC 23, which serves as a driving device, drives ultrasonic oscillator 21 based on the switch operation. At this time, ultrasonic oscillator 21 outputs an oscillation signal of, for example, 300 kHz via power amplifier 22, causing ultrasonic vibrator 13 to generate predetermined high-intensity ultrasonic waves. The ultrasonic waves generated by ultrasonic vibrator 13 propagate through liquid W1 in treatment tank 12, forming a high-sound-pressure sound field that acts on the object to be cleaned. As a result, dirt adhering to the surface of the object to be cleaned is removed.

[0040] At this time, the ultrasonic hydrophone 31 detects the ultrasonic sound field generated in the liquid W1 and outputs a voltage signal corresponding to the sound pressure to the frequency analyzer 17 via the preamplifier 16. The frequency analyzer 17 analyzes the frequency components of the sound field based on the input voltage signal and outputs the analysis results to the PC 23, which is a calculation device. The PC 23 performs a predetermined calculation based on the analysis results of the frequency components obtained by the frequency analyzer 17, and estimates the cavitation threshold, metal erosion threshold, and threshold at which chemical action by ultrasound occurs at that frequency.

[0041] For example, in the case of an object to be cleaned under relatively weak sound pressure conditions, the PC 23 sets an applied voltage to create sound pressure conditions that do not exceed the threshold at which chemical action by ultrasonic waves occurs along with the generation of cavitation, and drives and controls the ultrasonic vibrator 13. In the case of an object to be cleaned under relatively strong sound pressure conditions, the PC 23 sets an applied voltage to create sound pressure conditions that are between the threshold at which chemical action by ultrasonic waves occurs and the threshold at which metal erosion occurs due to mechanical action by ultrasonic waves, and drives and controls the ultrasonic vibrator 13.

[0042] In this way, in the ultrasonic cleaner 11 of this embodiment, ultrasonic cleaning is performed by adjusting the ultrasonic output depending on the cavitation generation state, etc. After a predetermined time has elapsed, when the operator operates a cleaning stop button (not shown), the PC 23 stops the ultrasonic oscillator 21 and ends the ultrasonic cleaning process.

[0043] Here, we will explain a comparative test conducted using the following three types of ultrasonic hydrophones. Figure 4(c) shows the outer shape of the tip of the ultrasonic hydrophone 31 of this embodiment. In contrast, Figure 4(a) shows the outer shape of the tip of an ultrasonic hydrophone of a comparative example. This ultrasonic hydrophone has a tip protection member S1 whose entire tip surface is flat. Figure 4(b) shows the outer shape of the tip of another ultrasonic hydrophone of a comparative example. This ultrasonic hydrophone has a conical tip protection member S2 whose tip has a flat surface. For convenience, the one shown in Figure 4(c) will be referred to as the "pointed conical ultrasonic hydrophone 31," the one shown in Figure 4(a) as the "cylindrical ultrasonic hydrophone," and the one shown in Figure 4(b) as the "flat-tipped conical ultrasonic hydrophone."

[0044] In this comparative test, sound pressure conditions were set so that cavitation bubble clouds 51 were generated, and the ultrasonic cleaner 11 was operated for a predetermined time. The behavior of the cavitation bubble clouds 51 was then observed for each ultrasonic hydrophone, and the presence and extent of damage to the tip protection members 34, S1, and S2 were investigated.

[0045] In the case of a cylindrical ultrasonic hydrophone in which the entire tip surface of the tip protection member S1 is flat, the cavitation bubble cloud 51 generated near the tip of the tip protection member S1 tends to remain attached and remain there rather than move away (see Figure 4(a)). Therefore, the tip protection member S1 is easily affected by the cavitation bubble cloud 51, resulting in early damage to the tip protection member S1. This also resulted in an early decrease in reception sensitivity. Incidentally, Figures 5(a) to (c) are photographs showing a sequence of the behavior of the cavitation bubble cloud 51 in a cylindrical ultrasonic hydrophone. It was observed that the cavitation bubbles remained on the flat surface, forming a cavitation bubble cloud 51 corresponding to the size of the flat surface. Furthermore, when this cylindrical ultrasonic hydrophone was observed, it was found that the flat surface was worn away from the center over time.

[0046] In the case of a flat-tip conical ultrasonic hydrophone with a flat surface on part of the tip of the tip protection member S2, the flat surface at the top is small, which reduces the adhesion and retention of cavitation bubble clouds 51 on the flat surface. However, it was found that the flat surface is damaged over long-term use. Furthermore, even if the cavitation bubble cloud 51 moves along the outer surface of the conical tip protection member S2, there are edges along the path of movement where the angle changes suddenly. For this reason, it was found that the cavitation bubble cloud 51 adheres and retains there, causing damage to the edge (see Figure 4(b)).

[0047] In contrast, in the case of the pointed-conical ultrasonic hydrophone 31 of this embodiment, there is no flat surface at the tip (apex 43) of the tip protection member 34. Therefore, the cavitation bubble cloud 51 does not adhere to or remain on the apex 43, but moves backward along the outer surface 44 of the second section 42 (see FIG. 4(c)). It was also found that the cavitation bubble cloud 51 continues to move backward even when it reaches the angle change section 47, without adhering or remaining there. Therefore, the pointed-conical ultrasonic hydrophone 31 is no longer affected by the cavitation bubble cloud 51, and no damage was observed in the tip protection member S1. Incidentally, FIGS. 6(a) to 6(d) are photographs showing the behavior of the cavitation bubble cloud 51 in the ultrasonic hydrophone 31 of this embodiment in sequence. FIG. 6(a) shows the cavitation bubble approaching from below the ultrasonic hydrophone 31, which is positioned facing downward. FIG. 6(b) shows the cavitation bubble approaching even further. 6(c) shows a state in which the cavitation bubbles have reached the vicinity of the apex 43. In addition, FIG. 6(d) shows a state in which the cavitation bubbles flow along the outer surface 44 without remaining at the apex 43. In other words, in the case of the ultrasonic hydrophone 31 of this embodiment, the cavitation bubbles can be prevented from becoming a cavitation bubble cloud 51.

[0048] Therefore, according to this embodiment, the following effects can be obtained.

[0049] (1) In the ultrasonic hydrophone 31 of this embodiment, the second portion 42 constituting the tip protection member 34 has a substantially conical shape, and the inclination angle θ of the outer surface 44 is set within a preferred range of 40° to 60°. In addition, the second portion 42 has a pointed apex 43 without a flat surface, and there is also radiation pressure from the ultrasonic transducer 13. Therefore, the cavitation bubble cloud 51 does not adhere to and remain at the apex 43, but rather tends to move backward along the outer surface 44 of the second portion 42, which has the preferred inclination angle θ. This prevents damage to the second portion 42 due to the cavitation bubble cloud 51 remaining. Furthermore, the outer peripheral surface 45 of the first portion 41 and the outer surface 44 of the second portion 42 are continuous without any steps, and the angle change portion 47 located at the boundary between them is chamfered. Therefore, the cavitation bubble cloud 51 moving backward does not adhere to and remain at the angle change portion 47, but tends to move further backward. Furthermore, the absence of steps or depressions makes it less likely to become a source of cavitation. Therefore, despite its small size, the ultrasonic hydrophone 31 is robust and has a long lifespan due to its excellent durability, and its excellent reception sensitivity allows for high measurement accuracy.

[0050] (2) In this ultrasonic hydrophone 31, the angle-changing section 47 is chamfered to a radius of an appropriate size, between 1 / 100 and 1 / 10 of the outer diameter D1 of the hydrophone body 33. Therefore, the angle-changing section 47 has a smooth, continuous surface without any edges, making it difficult for the cavitation bubble cloud 51 to become caught thereon. This makes it difficult for the movement of the cavitation bubble cloud 51 to be impeded, and the absence of steps or depressions makes it difficult for them to become a source of cavitation. As a result, it is possible to reliably prevent the cavitation bubble cloud 51 from accumulating.

[0051] (3) In this ultrasonic hydrophone 31, the dimension L2 of the second portion 42 along the central axis C1 of the hydrophone body 33 is less than half the outer diameter D1 of the hydrophone body 33. Furthermore, the dimension L1 of the outer peripheral portion of the first portion 41 along the central axis C1 of the hydrophone body 33 is less than half the outer diameter of the second portion 42. The transducer 35 is disposed on the first portion 41 side, closer to the tip than the joint surface between the outer peripheral surface 45 of the first portion 41 and the tip of the hydrophone body 33, and has a diameter equal to or greater than one-third of the outer diameter of the hydrophone body 33. Therefore, even if the outer diameter D1 of the hydrophone body 33 is small, the transducer 35 can be made relatively large, and the distance from the top 43 of the second portion 42 to the transducer 35 can also be made relatively short. As a result, an ultrasonic hydrophone 31 with excellent reception sensitivity can be easily obtained.

[0052] (4) Furthermore, the ultrasonic cleaner 11 equipped with the above-mentioned excellent ultrasonic hydrophone 31 allows accurate estimation of the amount of cavitation generated based on the output from the ultrasonic hydrophone, which has excellent durability and reception sensitivity, and based on this, it becomes possible to easily and reliably set ultrasonic processing conditions appropriate for ultrasonic cleaning.

[0053] Each embodiment of the present invention may be modified as follows.

[0054] In the above embodiment, the inclination angle θ of the outer surface 44 of the second portion 42 relative to the central axis C1 of the hydrophone body 33 is 45°, but this is not limiting. For example, as in another embodiment of an ultrasonic hydrophone 31A shown in FIG. 7(a), the inclination angle θ may be set to a value smaller than 45°. Alternatively, as in another embodiment of an ultrasonic hydrophone 31B shown in FIG. 7(b), the inclination angle θ may be set to a value larger than 45°.

[0055] In the above embodiment, the inclination angle θ is uniform across the entire outer surface 44 of the second portion 42, but this is not limiting. For example, as in ultrasonic hydrophones 31C and 31D of other embodiments shown in Figures 7(c) and 7(d), the inclination angle θ may vary slightly depending on the location. Incidentally, in Figure 7(c), the outer surface 44 has a slightly concave shape in side view, while in Figure 7(d), the outer surface 44 has a slightly convex shape in side view.

[0056] In the above embodiment, the tip protection member 34 is made of titanium, which has excellent corrosion resistance, but according to the present invention, the tip protection member 34 is less susceptible to the effects of the cavitation bubble cloud 51, so other metal materials with corrosion resistance can be used to make the tip protection member 34. Specifically, stainless steel or the like may be used, or materials other than metals (for example, glass materials such as quartz, or ceramics) may also be used. In other words, according to the present invention, there is greater freedom in the selection of materials for forming the tip protection member 34.

[0057] In the above embodiment, the high-sound-pressure sound field sound pressure analysis device and method of the present invention are embodied in an ultrasonic cleaner 11, but this is not limiting. For example, as shown in FIG. 8 , the present invention may be embodied in a commercially available ultrasonic cleaner 11A equipped with an ultrasonic cleaning tank 12 and an ultrasonic cleaner oscillator 22A. The sound pressure analyzer 15 in this ultrasonic cleaner 11A includes a cavitation meter 18A instead of an oscilloscope 18. That is, an ultrasonic hydrophone 31 may be immersed in the cleaning tank 12 of the commercially available ultrasonic cleaner 11A, and measurements may be performed using the sound pressure analyzer 15. The current / voltage probe 25 may also be omitted. The present invention may also be embodied in other devices, such as an ultrasonic disperser, an ultrasonic sterilizer, or an ultrasonic reactor that uses sonochemistry to induce chemical reactions. The high-sound-pressure sound field sound pressure analysis device of the present invention may also include an ultrasonic cavitation meter for detecting whether cavitation is occurring and measuring the amount of cavitation, as shown in FIG. 8. [Explanation of symbols]

[0058] 11, 11A...Ultrasonic cleaner as ultrasonic processing device 12...Cleaning tank or treatment tank 13...Ultrasonic vibrator 15...Sound pressure analyzer 31...Ultrasonic hydrophone 33...Hydrophone body 34...Tip protection member 35...Oscillator 41…Part 1 42…Second part 43...Top 44...Outer surface of second portion 45...Outer surface of first portion 47...Angle change section C1…Central axis line d1...(diameter of the vibrator) D1: Outer diameter of the hydrophone body D2: Outer diameter of the second part L1: Dimension of the outer periphery of the first part L2: Dimension of the second part θ…Inclination angle

Claims

1. A hydrophone that outputs a voltage signal in response to the sound pressure of an ultrasonic wave in a liquid, A cylindrical hydrophone body, a tip protection member attached to the tip of the hydrophone body, and a vibrator provided so as to contact the back surface of the tip protection member, The tip protection member is formed with an outer diameter dimension equal to the outer diameter of the hydrophone body and attached to the tip of the hydrophone body, and consists of a first part and a substantially conical second part integrally formed on the tip side of the first part, the second portion has a pointed top; The inclination angle of the outer surface of the second portion with respect to the central axis of the hydrophone body is set to be equal to or greater than 40° and equal to or less than 60°, The outer peripheral surface of the first portion and the outer surface of the second portion are continuous without any steps, and an angle change portion located at the boundary between them is subjected to a radius chamfering process. An ultrasonic hydrophone characterized by:

2. 2. The ultrasonic hydrophone according to claim 1, wherein the angle-changing portion is subjected to a radius chamfering process with a size of 1 / 100 to 1 / 10 of the outer diameter of the hydrophone body.

3. a dimension of the second portion along a central axis of the hydrophone body that is equal to or less than half the outer diameter of the hydrophone body; a dimension of an outer peripheral portion of the first portion along a central axis of the hydrophone body is equal to or less than half the outer diameter of the second portion; The transducer is disposed on the first portion side at a position closer to the tip than the joint surface between the outer circumferential surface of the first portion and the tip of the hydrophone body, and has a diameter that is 1 / 3 or more of the outer diameter of the hydrophone body.

3. The ultrasonic hydrophone according to claim 1 or 2.

4. An ultrasonic cleaner that uses ultrasonic waves to clean an object to be treated immersed in a liquid, a treatment tank for storing the liquid; an ultrasonic vibrator installed in the treatment tank to irradiate the liquid in the treatment tank with ultrasonic waves; a driving device that drives and controls the ultrasonic vibrator; a sound pressure analyzer for a high sound pressure field, comprising the ultrasonic hydrophone according to any one of claims 1 to 3, and estimating the amount of cavitation generated based on a voltage signal output from the ultrasonic hydrophone in response to the sound pressure of the sound field; An ultrasonic cleaning machine comprising:

5. An ultrasonic processing device that chemically processes an object to be processed immersed in a liquid using ultrasonic waves, a treatment tank for storing the liquid; an ultrasonic vibrator installed in the treatment tank to irradiate the liquid in the treatment tank with ultrasonic waves; a driving device that drives and controls the ultrasonic vibrator; a sound pressure analyzer for a high sound pressure field, comprising the ultrasonic hydrophone according to any one of claims 1 to 3, and estimating the amount of cavitation generated based on a voltage signal output from the ultrasonic hydrophone in response to the sound pressure of the sound field; An ultrasonic processing machine comprising:

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