Attachment for ultrasonic transducer

Abstract

Provided is an attachment that is for a ultrasonic transducer and that can be modified to use differing directional characteristics in accordance with conditions, even if there is only one ultrasonic transducer. An attachment 30 according to the present invention is to be attached to an ultrasonic transducer 10 and comprises a holding member 31, a buoyant body 41, and a directional characteristics modification member 51. The holding member 31 has a holding recess 34 which holds the ultrasonic transducer 10 in a detachable manner. The buoyant body 41 is provided so as to encircle the holding member 31 from the outer peripheral side thereof, is composed of a material having a specific gravity lower than water, and keeps the ultrasonic transducer 10 horizontal by means of buoyancy acting on the buoyant body 41 itself. The directional characteristics modification member 51 is disposed at the side of the ultrasonic transducer 10 that is toward an acoustic radiation surface 10a thereof and modifies the directional characteristics of an ultrasonic wave emitted from the acoustic radiation surface 10a.

Description

[Technical Field]

[0001] The present invention relates to an attachment that is attached to an ultrasonic transducer. [Background technology]

[0002] Conventionally, there has been known an ultrasonic transmitter / receiver that contains an ultrasonic vibrator and is suspended by a signal transmission cable and immersed in water, and that performs fish detection by transmitting and receiving ultrasonic waves using the ultrasonic vibrator. This ultrasonic transmitter / receiver is used, for example, in ice fishing such as smelt fishing. In ice fishing, the ultrasonic transmitter / receiver is inserted into the water through a hole drilled in the ice.

[0003] There is a demand for adjusting (changing) the directional characteristics of ultrasound waves emitted from an ultrasound transducer. Conventionally, it has been proposed to use an acoustic lens having a convex or concave surface (see, for example, Patent Documents 1 to 5) or an acoustic window having an opening (see, for example, Patent Document 6) as a component for changing the directional characteristics of ultrasound waves. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 59-85972 (Figs. 2, 5, 6, etc.) [Patent Document 2] JP 5-212355 A (Claim 2, paragraphs

[0012] and

[0023] , Figures 1 and 2, etc.) [Patent Document 3] JP-A-10-179582 (paragraph

[0017] , Figure 1, etc.) [Patent Document 4] JP 2001-169393 A (claims 1, 3, 4, paragraphs

[0010] and

[0016] , figures 1 and 4, etc.) [Patent Document 5] JP-A-9-298795 (Claim 3, paragraphs

[0035] and

[0037] , Figures 6 to 8, etc.) [Patent Document 6] Jpn. Jpn. Appln. KOKAI Publication No. 52-44038 (Jpn. Appln. KOKAI Publication No. 48-37659) (Figures 1 to 3, etc.) DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0005] However, in the conventional technologies described in Patent Documents 1 to 6, the acoustic lens or acoustic window is directly attached to the ultrasonic transducer, which causes a problem that the directional characteristics of the ultrasonic waves cannot be changed to different directional characteristics even if the situation changes.

[0006] Furthermore, to improve the detection accuracy of an ultrasonic transmitter / receiver, it is preferable to keep the acoustic emitting surface of the ultrasonic transmitter / receiver horizontal and radiate (transmit) ultrasonic waves vertically downward. Conventionally, the acoustic emitting surface is kept horizontal by the weight of the ultrasonic transmitter / receiver. However, if the ultrasonic transmitter / receiver is tilted, the acoustic emitting surface also tilts, causing the direction of the radiated ultrasonic waves to tilt relative to the vertical. In this case, fish schools cannot be detected accurately, resulting in errors in the display on the fish finder.

[0007] The present invention has been made in view of the above problems, and a first object thereof is to provide an attachment for an ultrasonic transmitter / receiver that can change the directional characteristics depending on the situation even when there is only one ultrasonic transmitter / receiver, and a second object thereof is to provide an attachment for an ultrasonic transmitter / receiver that can transmit ultrasonic waves vertically downward by maintaining the ultrasonic transmitter / receiver horizontally, thereby improving detection accuracy. [Means for solving the problem]

[0008] In order to solve the above problem, the invention described in claim 1 is an attachment to be attached to an ultrasonic transmitter / receiver that is suspended from a cable, houses an ultrasonic vibrator that transmits and receives ultrasonic waves in a molded state, and has a bottom surface that serves as an acoustic radiation surface, and is characterized by comprising: a cup-shaped holding member having a holding recess that detachably holds the ultrasonic transmitter / receiver; a buoyant body that is arranged to surround the holding member from the outer periphery, is made of a material with a specific gravity less than water, and keeps the ultrasonic transmitter / receiver horizontal by the buoyancy acting on it; and a directional characteristic changing member that is arranged on the acoustic radiation surface side of the ultrasonic transmitter / receiver and changes the directional characteristics of the ultrasonic waves irradiated from the acoustic radiation surface.

[0009] According to the invention of claim 1, an ultrasonic transmitter / receiver is detachably held in a holding recess of a holding member, and a directional characteristic changing member is disposed on the acoustic emission surface side of the ultrasonic transmitter / receiver held in the holding recess. Therefore, even with only one ultrasonic transmitter / receiver, it is possible to change the directional characteristics of the ultrasonic waves emitted from the acoustic emission surface to different directional characteristics depending on the situation. Specifically, by holding the ultrasonic transmitter / receiver in the holding recess, the directional characteristics of the ultrasonic waves can be changed using the directional characteristic changing member. On the other hand, by removing the ultrasonic transmitter / receiver from the holding recess, the directional characteristics of the ultrasonic waves can be restored to their original directional characteristics. Furthermore, because the buoyancy acting on the buoyant body keeps the ultrasonic transmitter / receiver horizontal, the acoustic emission surface of the ultrasonic transmitter / receiver is also horizontal. As a result, ultrasonic waves can be transmitted vertically downward, improving the detection accuracy of the ultrasonic transmitter / receiver.

[0010] The invention described in claim 2 is characterized in that in claim 1, the directivity characteristic changing member is an acoustic lens having a flat surface and a convex surface located on the opposite side.

[0011] Therefore, according to the invention described in claim 2, by using the flat surface of the acoustic lens in close contact with the acoustic emitting surface of the ultrasonic transducer via a coupling material such as water, it is possible to make the directional characteristics of the ultrasonic waves wider than the original directional characteristics. Note that the convex surface can be a spherical surface, a conical surface, etc.

[0012] The invention described in claim 3 is characterized in that, in claim 1, the directional characteristic changing member is an acoustic window used with the ultrasonic transmitter / receiver placed thereon, and the acoustic window is made of a soundproof material and has an opening hole with an area smaller than that of the acoustic radiation surface.

[0013] Therefore, according to the invention described in claim 3, when the ultrasonic transmitter / receiver is placed on the acoustic window, ultrasonic waves emitted from the acoustic emitting surface pass only through the opening in the acoustic window, and do not pass through the acoustic window, which is made of soundproof material. This opening has a smaller area than the acoustic emitting surface and is used to narrow the acoustic emitting area of ​​the ultrasonic waves, so as the ultrasonic waves pass through the opening, the directional angle of the ultrasonic waves widens. As a result, the directional characteristics of the ultrasonic waves can be made wider than the original directional characteristics depending on the situation.

[0014] The invention described in claim 4 is characterized in that, in claim 3, a first magnetic material is provided on at least one of the holding member and the acoustic window, a second magnetic material that attracts the first magnetic material is provided in a position facing the first magnetic material on the ultrasonic transmitter / receiver, and at least one of the first magnetic material and the second magnetic material is a permanent magnet.

[0015] Therefore, according to the invention described in claim 4, the attachment (holding member and acoustic window) and the ultrasonic transmitter / receiver are attracted to each other by the magnetic force of the permanent magnet and come into close contact with each other. As a result, the attachment is less likely to fall off the ultrasonic transmitter / receiver when the ultrasonic transmitter / receiver is lifted. In addition, since the upper surface of the acoustic window can be used in close contact with the acoustic emission surface (bottom surface) of the ultrasonic transmitter / receiver, the directional characteristics of the ultrasonic waves can be reliably made wide.

[0016] The invention described in claim 5 is characterized in that in claim 4, a plurality of the first magnetic materials are arranged at intervals around the opening hole of the acoustic window.

[0017] Therefore, according to the invention of claim 5, since a plurality of first magnetic materials are spaced apart around the opening of the acoustic window, the attachment can be made lighter than when the first magnetic material is arranged around the entire circumference of the opening of the acoustic window. Furthermore, the lighter attachment ensures sufficient buoyancy of the attachment (enough to prevent it from sinking).

[0018] The invention described in claim 6 is characterized in that in any one of claims 3 to 5, the retaining member, the buoyancy body, and the acoustic window are made of foamed polyethylene and are integrally formed.

[0019] Therefore, according to the invention described in claim 6, since the holding member, buoyancy body, and acoustic window are made of foamed polyethylene, the buoyancy of the holding member, buoyancy body, and acoustic window can be appropriately adjusted, for example, to the extent that the water surface reaches the top surface of the acoustic window when the ultrasonic transmitter / receiver is not held by the holding member. Furthermore, the holding member, buoyancy body, and acoustic window can be sufficiently strong and water-resistant. Furthermore, since the holding member, buoyancy body, and acoustic window made of foamed polyethylene have soundproofing properties, they can prevent ultrasonic waves radiated from the acoustic emitting surface from passing through locations other than the opening of the acoustic window. Furthermore, since the brittle temperature of foamed polyethylene is, for example, approximately -40°C, the cold resistance of the holding member, buoyancy body, and acoustic window is enhanced. Furthermore, since it is not necessary to separately form the holding member, buoyancy body, and acoustic window, the number of parts of the attachment can be reduced, thereby reducing the manufacturing cost of the attachment.

[0020] The invention described in claim 7 is characterized in that, in any one of claims 1 to 5, the directional characteristic changing member is detachably held on the holding member and is selected from a plurality of types of directional characteristic changing members that differ from each other in at least one of dimensions and shape.

[0021] Therefore, according to the invention described in claim 7, even if there is only one ultrasonic transmitter / receiver, the directional characteristics of the ultrasonic waves can be switched to various directional characteristics by holding a directional characteristic changing member selected from multiple types of directional characteristic changing members in the holding member depending on the situation.

[0022] The invention as set forth in claim 8 is characterized in that in any one of claims 1 to 7, the buoyant body is integrally formed with the holding member.

[0023] Therefore, according to the invention described in claim 8, since it is not necessary to form the buoyant body and the holding member separately, the number of parts of the attachment can be reduced, and the manufacturing costs of the attachment can be kept down.

[0024] The invention described in claim 9 is characterized in that, in any one of claims 1 to 8, the holding recess holds the directional characteristic changing member on the lower side and accommodates and holds the ultrasonic transmitter / receiver on the upper side, and the buoyant body is attached so as to surround the outer wall surface of the holding member.

[0025] Therefore, according to the invention described in claim 9, by holding the directivity changing member on the lower side of the holding recess and accommodating and holding the ultrasonic transmitter / receiver on the upper side of the holding recess, the directivity changing member and the ultrasonic transmitter / receiver can be stably held. Furthermore, because the buoyant body is attached so as to surround the outer wall surface of the holding member, buoyancy acts evenly on the holding member, making it easier to eliminate tilting of the holding member. As a result, the position of the ultrasonic transmitter / receiver held by the holding member in water can be easily stabilized, and the acoustic emission surface of the ultrasonic transmitter / receiver becomes horizontal, making it easy to improve the detection accuracy of the ultrasonic transmitter / receiver. [Effects of the Invention]

[0026] As described above in detail, according to the inventions of claims 1 to 9, even if there is only one ultrasonic transmitter / receiver, it can be used by changing the directional characteristics depending on the situation. Also, by maintaining the ultrasonic transmitter / receiver horizontally, ultrasonic waves can be transmitted vertically downward, improving detection accuracy. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a side view showing an ultrasonic transmitter / receiver according to the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing an attachment for an ultrasonic transmitter / receiver in the first embodiment. [Figure 3] FIG. [Figure 4] 1 is a graph showing the relationship between frequency and full angle at half extinction in Examples A1 and A2 and Comparative Example A. [Figure 5] 10 is a graph showing the relationship between frequency and transmitted wave voltage sensitivity in Examples A1 and A2 and Comparative Example A. [Figure 6] 10(a) and 10(b) are graphs showing the relationship between angle and transmitted wave voltage sensitivity in sample A. [Figure 7] 10(a) and 10(b) are graphs showing the relationship between angle and transmitted wave voltage sensitivity in sample B. [Figure 8] FIG. 10 is a cross-sectional view showing an attachment for an ultrasonic transmitter / receiver in a second embodiment. [Figure 9] FIG. [Figure 10] 10 is a graph showing the relationship between frequency and directivity angle in Examples B1 and B2 and Comparative Example B. [Figure 11] 10 is a graph showing the relationship between frequency and transmission / reception sensitivity in Examples B1 and B2 and Comparative Example B. [Figure 12] FIG. 11 is a plan view showing an attachment for an ultrasonic transmitter / receiver in a third embodiment. [Figure 13] FIG. [Figure 14] FIG. [Figure 15]FIG. [Figure 16] FIG. 10 is a cross-sectional view showing an attachment for an ultrasonic transmitter / receiver according to another embodiment. [Figure 17] FIG. 10 is a cross-sectional view showing an attachment for an ultrasonic transmitter / receiver according to another embodiment. [Figure 18] FIG. 10 is a cross-sectional view showing an attachment for an ultrasonic transmitter / receiver according to another embodiment. BEST MODE FOR CARRYING OUT THE INVENTION

[0028] [First embodiment] A first embodiment of the present invention will now be described in detail with reference to the drawings.

[0029] As shown in Fig. 1, the ultrasonic transmitter / receiver 10 of this embodiment is a device for a fish finder that detects schools of fish in water by irradiating ultrasonic waves into the water. The ultrasonic transmitter / receiver 10 is used while suspended from a cable 11. The ultrasonic transmitter / receiver 10 also includes an ultrasonic transducer 12 that transmits and receives ultrasonic waves, and a case 13 that houses the ultrasonic transducer 12 in a molded state. Note that the ultrasonic transducer 12 of this embodiment is a composite transducer having piezoelectric elements such as a 0-3 composite structure, a 1-3 composite structure, and a 2-2 composite structure, and therefore the phase across the entire radiation surface is relatively uniform.

[0030] The case 13 is bell-shaped and includes a lower case 21 that forms the lower half of the case 13 and an upper case 22 that forms the upper half of the case 13. The lower case 21 is open at its upper end and has a bottom surface 23 and an outer peripheral surface 24 that is perpendicular to the bottom surface 23. The ultrasonic transducer 12 is housed inside the lower case 21. The outer diameter of the ultrasonic transducer 12 is larger than the inner diameter of the opening 52 of the acoustic window 51 shown in FIGS. 2 and 3 and slightly smaller than the outer diameter of the bottom surface 23. The bottom surface 23 of the lower case 21 is flat and functions as an acoustic radiation surface 10a for irradiating (transmitting) ultrasonic waves. Furthermore, a groove 25 is formed in the outer peripheral surface 24 of the lower case 21 for receiving a screw 114 or the like shown in FIG. 18. The groove 25 has a rectangular cross section and extends circumferentially around the cylindrical lower case 21, continuously formed around the entire circumference of the lower case 21.

[0031] 1, upper case 22 is open at the bottom and has an outer diameter that gradually decreases toward the top. A through-hole (not shown) is provided at the top end of upper case 22 for inserting cable 11 therethrough.

[0032] During normal use, the ultrasonic transmitter / receiver 10 of this embodiment is used in a state in which it is suspended from a cable 11 (see FIG. 1). However, it can also be used in a state in which an attachment 30 (see FIGS. 2 and 3) is attached to the ultrasonic transmitter / receiver 10. Specifically, the attachment 30 includes a holding member 31, a buoyant body 41, and an acoustic window 51 (a directional characteristic changing member). The holding member 31 is a substantially cylindrical member made of a resin material such as ABS resin, and is configured in a cup shape by a cylindrical portion 32 and an upper end portion 33. The inner area of ​​the cylindrical portion 32 forms a holding recess 34 that detachably holds the ultrasonic transmitter / receiver 10. The inner diameter of the holding recess 34 (cylindrical portion 32) is slightly larger than the outer diameter of the ultrasonic transmitter / receiver 10.

[0033] The buoyant body 41 is provided so as to surround the holding member 31 from the outer periphery. Specifically, the buoyant body 41 is attached so as to surround the outer wall surface 32a of the cylindrical portion 32 by wrapping a strip-shaped sponge around the entire outer wall surface 32a. The buoyant body 41 is formed using a material with a specific gravity lower than that of water, such as polystyrene foam, polyethylene foam, or polyurethane foam. The buoyant body 41 maintains the holding member 31, acoustic window 51, and ultrasonic transmitter / receiver 10 horizontally by the buoyancy acting on itself. The buoyant body 41 has a buoyancy such that the water surface W1 reaches the upper surface 53 of the acoustic window 51 when the ultrasonic transmitter / receiver 10 is not held in the holding recess 34.

[0034] As shown in FIGS. 2 and 3 , the acoustic window 51 is attached to the lower end surface 32b of the cylindrical portion 32 using double-sided tape (not shown). This allows the acoustic window 51 to be detachably held by the holding member 31. The acoustic window 51 of this embodiment is a disk-shaped member formed using a soundproof material (rubber sponge) with a closed-cell structure, such as neoprene rubber. An opening 52 for adjusting the directional characteristics of ultrasound is provided in the center of the acoustic window 51. The opening 52 is circular and has a smaller area than the acoustic emitting surface 10a of the ultrasonic transmitter / receiver 10. This allows the acoustic window 51 to cover the entire acoustic emitting surface 10a except for the center. The inner diameter of the opening 52 is smaller than the outer diameter of the piezoelectric element constituting the ultrasonic transducer 12. The area of ​​the opening 52 is 15% to 40% of the area of ​​the acoustic emitting surface 10a. Furthermore, the amount of deviation between the central axis O1 of the opening hole 52 and the central axis O2 of the ultrasonic transmitter / receiver 10 is 2% or less (0% in this embodiment) of the external dimensions of the ultrasonic transmitter / receiver 10. If the amount of deviation were to be greater than 2%, the center of gravity would be shifted, causing the holding member 31 and the ultrasonic transmitter / receiver 10 to tilt, which could prevent ultrasonic waves from being directed directly downward.

[0035] The acoustic window 51 is used with the ultrasonic transmitter / receiver 10 placed thereon (see FIG. 2). In other words, the acoustic window 51 is disposed on the acoustic emitting surface 10a side of the ultrasonic transmitter / receiver 10, and has the function of changing the directional characteristics of the ultrasonic waves radiated from the acoustic emitting surface 10a.

[0036] Next, a method of using the attachment 30 for the ultrasonic transmitter / receiver 10 will be described.

[0037] The ultrasonic transmitter / receiver 10 of this embodiment is used in ice fishing such as smelt fishing. In normal ice fishing, the ultrasonic transmitter / receiver 10 is immersed in water while suspended by a cable 11. Then, fish detection is performed by transmitting and receiving ultrasonic waves using the ultrasonic vibrator 12 in the ultrasonic transmitter / receiver 10. Specifically, first, the ultrasonic transmitter / receiver 10 and the LCD monitor (not shown) are turned on. The LCD monitor is used, for example, while being held by the user. The LCD monitor also includes a control device (not shown) that controls the entire device. The control device is configured by a well-known computer including a CPU, ROM, RAM, etc.

[0038] Next, the CPU of the control device controls the ultrasonic transducer 12 in the ultrasonic transmitter / receiver 10 to output an oscillation signal via the cable 11, thereby driving the ultrasonic transducer 12. At this time, the ultrasonic transducer vibrates, and ultrasonic waves are emitted (transmitted) into the water from the ultrasonic transducer 12, and ultimately from the acoustic emission surface 10a of the ultrasonic transmitter / receiver 10. When the ultrasonic waves reach the school of fish, they are reflected by the school of fish as reflected waves, which propagate toward the ultrasonic transmitter / receiver 10 and are input (received) by the ultrasonic transducer 12. The ultrasonic waves (reflected waves) received by the ultrasonic transducer 12 are then converted into received signals and input to the CPU via the cable 11. At this point, the school of fish is detected. When the user then turns off the power, the emission of ultrasonic waves and the reception of reflected waves end.

[0039] However, there is a demand for detecting schools of fish over a wider range than usual. In this case, after the attachment 30 is attached to the ultrasonic transmitter / receiver 10, the attachment 30 is used while immersed in water (see FIG. 2). Specifically, first, the ultrasonic transmitter / receiver 10 is inserted into the holding recess 34 of the holding member 31 with the acoustic emitting surface 10a facing downward, and the ultrasonic transmitter / receiver 10 is placed on the acoustic window 51 attached to the lower end surface 32b of the holding member 31 (cylindrical portion 32). As a result, the attachment 30 is attached to the ultrasonic transmitter / receiver 10. Next, the ultrasonic transmitter / receiver 10 and the attachment 30 are immersed in water. At this time, water enters the holding recess 34 through the opening 52 of the acoustic window 51 and enters between the upper surface 53 of the acoustic window 51 and the acoustic emitting surface 10a of the ultrasonic transmitter / receiver 10. When the ultrasonic transmitter / receiver 10 is placed on the upper surface 53 of the acoustic window 51, the acoustic emission surface 10a of the ultrasonic transmitter / receiver 10 is surely in contact with the liquid (here, in contact with water), so that ultrasonic radiation is not hindered by air pockets. Also, the holding member 31 and the ultrasonic transmitter / receiver 10 float on the water and are maintained horizontally due to the buoyancy acting on the buoyant body 41.

[0040] In this state, the CPU of the control device controls the driving of the ultrasonic vibrator 12 in the ultrasonic transmitter / receiver 10. As a result, the ultrasonic vibrator 12 vibrates, and ultrasonic waves are emitted (transmitted) into the water from the acoustic emission surface 10a of the ultrasonic transmitter / receiver 10. The ultrasonic waves emitted from the acoustic emission surface 10a pass only through the opening 52 of the acoustic window 51. Because this opening 52 has a smaller area than the acoustic emission surface 10a, the acoustic emission area of ​​the ultrasonic waves is narrowed, thereby widening the beam angle of the ultrasonic waves. As a result, the directional characteristics of the ultrasonic waves become wider than the original directional characteristics, making it possible to detect schools of fish over a wider range than usual.

[0041] Next, the attachment evaluation method and the results will be described.

[0042] First, measurement samples were prepared as follows. An attachment with an acoustic window having an opening hole with an inner diameter of 25 mm was prepared, and this was designated Example A1 (see "◆" in Figures 4 and 5). Also, an attachment with an acoustic window having an opening hole with an inner diameter of 31 mm was prepared, and this was designated Example A2 (see "●" in Figures 4 and 5). On the other hand, an attachment without an acoustic window was prepared, and this was designated Comparative Example A (see "■" in Figures 4 and 5).

[0043] Next, the directional characteristics of ultrasonic waves were verified for each measurement sample (Examples A1 and A2 and Comparative Example A). Specifically, ultrasonic waves were irradiated from an ultrasonic vibrator in an ultrasonic transmitter / receiver to which an attachment was attached, and the directional characteristics during irradiation (transmission) were verified. In addition, the frequency was switched in multiple steps between 160 kHz and 300 kHz, and ultrasonic waves were irradiated at each switched frequency. Figure 4 is a graph showing the verification results of the directional characteristics of ultrasonic waves.

[0044] As a result, it was confirmed that in Comparative Example A, which does not have an acoustic window, when ultrasonic waves are radiated from the ultrasonic transducer, the directional characteristics have a relatively narrow full angle at half power (directional angle) at all frequencies. On the other hand, in Examples A1 and A2, when ultrasonic waves are radiated from a single opening hole in the center of the acoustic window, the directional characteristics have a wider full angle at half power than Comparative Example A at all frequencies. In particular, it was confirmed that Example A1, in which the inner diameter of the opening hole is 25 mm, has a directional characteristic with a wider full angle at half power than Example A2, in which the inner diameter of the opening hole is 31 mm, at all frequencies.

[0045] Therefore, it was confirmed that if ultrasonic waves are irradiated from the opening of the acoustic window, the directivity angle of the ultrasonic waves becomes wider, and the detection range of the ultrasonic transducer becomes wider.Furthermore, it was confirmed that if the inner diameter of the opening is reduced, the directivity angle of the ultrasonic waves becomes wider, and the detection range of the ultrasonic transducer becomes wider.

[0046] Next, a voltage was applied to the ultrasonic transducer of each measurement sample (Examples A1 and A2, and Comparative Example A), and the transmission voltage sensitivity was measured at a position on the central axis of the ultrasonic transducer and 1 m away from the ultrasonic transducer. Specifically, ultrasonic waves were first irradiated (transmitted) perpendicularly to the surface of a reflector located 1 m away from the ultrasonic transducer. The frequency was switched between 160 kHz and 300 kHz in multiple steps, and ultrasonic waves were irradiated at each switched frequency. The ultrasonic waves reflected by the surface of the reflector were received by the ultrasonic transducer a predetermined time after transmission, generating voltage signals at both electrodes of the ultrasonic transducer. The voltage amplitudes of the ultrasonic transducer during transmission and reception were measured using an oscilloscope, and the transmission / reception sensitivity was calculated based on the results. The transmission / reception sensitivity is the ratio of the reception voltage amplitude V2 to the transmission voltage amplitude V1, and is calculated using the formula 20 × log(V2 / V1). Next, the transmission voltage sensitivity was calculated based on the calculated transmission / reception sensitivity. The transmitted wave voltage sensitivity is calculated from the formula: (transmitting / receiving sensitivity)-(microphone sensitivity). The results of Examples A1 and A2 and Comparative Example A are shown in FIG.

[0047] As a result, it was confirmed that Examples A1 and A2, which have a wide beam angle because they irradiate ultrasonic waves through the opening of the acoustic window, have lower transmission voltage sensitivity at all frequencies than Comparative Example A, which has a narrow beam angle because it does not have an opening. Furthermore, in Examples A1 and A2, it was confirmed that Example A1 (inner diameter 25 mm), which has a wide beam angle because the inner diameter of the opening is relatively small, has lower transmission voltage sensitivity than Example A2 (inner diameter 31 mm), which has a narrow beam angle because the inner diameter of the opening is relatively large. It was also confirmed that in all of Examples A1 and A2 and Comparative Example A, the transmission voltage sensitivity was maximized at a frequency of 200 kHz. From the above, it was confirmed that reducing the inner diameter of the opening of the acoustic window makes it possible to widen the beam angle of ultrasonic waves, but that the sensitivity decreases.

[0048] To solve this problem, it is possible to adjust the gain of the receiver (not shown) so that the fish shadows are displayed on the fish finder screen in a consistent manner. Specifically, if the received voltage at the center of the ultrasonic transducer is lowered by, for example, 20 dB, the amplification factor is increased by 20 dB. In this way, even if the ultrasonic beam angle is widened by adding an acoustic window, a wider range of fish shadows can be detected.

[0049] Next, the method for evaluating the ultrasonic transducer and the results thereof will be described.

[0050] First, measurement samples were prepared as follows: A circular ultrasonic vibrator was prepared and designated as Sample A. Also, an ultrasonic vibrator having a piezoelectric element with a 2-2 composite structure was prepared and designated as Sample B.

[0051] Next, the directional characteristics of the ultrasonic transducer were verified for each measurement sample (Sample A, B). Specifically, first, the ultrasonic transducer suspended from a crane was placed in a water tank. A microphone was also placed in the water tank 1 m away from the ultrasonic transducer. Then, while emitting 200 kHz ultrasonic waves from the ultrasonic transducer, the angle of the ultrasonic transducer was changed between -90° and 0°. The emitted ultrasonic waves were also received by the microphone. The received voltage of the microphone was measured using an oscilloscope, and the measured received voltage was corrected using the microphone's sound pressure calibration value. The transmission and reception sensitivity was then calculated based on the corrected received voltage, and directional pattern data of the transmission voltage sensitivity in the range of -90° to 0° was calculated (acquired) based on the calculated transmission and reception sensitivity. The acquired directional pattern data was also inverted to obtain directional pattern data of the transmission voltage sensitivity in the range of 0° to 90°. The results for sample A are shown by the dashed line graph in FIG. 6(a), and the results for sample B are shown by the dashed line graph in FIG. 7(a).

[0052] A sponge (acoustic window) with an opening with an inner diameter of 31 mm was then attached to the ultrasonic transducer of each measurement sample. The same process as when the sponge was not attached was then performed, and directional pattern data for the transmitted voltage sensitivity in the range of -90° to 90° was obtained. The results for Sample A are shown in the solid line graph in Figure 6(a), and the results for Sample B are shown in the solid line graph in Figure 7(a). Furthermore, the results for Sample A when the center sensitivity (transmitted voltage sensitivity at 0°) was normalized to 0 dB are shown in Figure 6(b), and the results for Sample B when the center sensitivity was normalized to 0 dB are shown in Figure 7(b).

[0053] As a result, it was confirmed that the acoustic window had the effect of expanding the directivity angle in both ultrasonic transducer samples A and B, meaning that the transmission and reception sensitivity was unlikely to decrease even when the angle (absolute value) was large (see Figures 6(b) and 7(b)). However, it was also confirmed that the installation of the acoustic window reduced the central sensitivity by nearly 8 dB (see Figures 6(a) and 7(a)).

[0054] Therefore, according to this embodiment, the following effects can be obtained.

[0055] (1) In the attachment 30 for the ultrasonic transmitter / receiver 10 of this embodiment, the ultrasonic transmitter / receiver 10 is held in the holding recess 34 of the holding member 31, and an acoustic window 51 is arranged on the side of the acoustic emission surface 10a of the ultrasonic transmitter / receiver 10 held in the holding recess 34. In this case, even if there is only one ultrasonic transmitter / receiver 10, it is possible to change the directional characteristics of the ultrasonic waves radiated from the acoustic emission surface 10a to different directional characteristics depending on the situation. Specifically, by holding the ultrasonic transmitter / receiver 10 in the holding recess 34, the directional characteristics (directional angle) of the ultrasonic waves can be widened using the acoustic window 51. On the other hand, by removing the ultrasonic transmitter / receiver 10 from the holding recess 34, the directional characteristics of the ultrasonic waves can be restored to their original directional characteristics.

[0056] Furthermore, simply by wrapping a strip-shaped sponge around the cylindrical portion 32 of the holding member 31, the buoyant body 41 is provided so as to surround the holding member 31 from the outer periphery, so that the buoyancy acting on the buoyant body 41 can keep the ultrasonic transmitter / receiver 10 horizontal without a complex configuration, and the acoustic emission surface 10a of the ultrasonic transmitter / receiver 10 can be made horizontal. As a result, ultrasonic waves can be transmitted vertically downward, improving the detection accuracy of the ultrasonic transmitter / receiver 10.

[0057] (2) In this embodiment, when the ultrasonic transmitter / receiver 10 is placed on the acoustic window 51, ultrasonic waves emitted from the acoustic emitting surface 10a pass only through the opening 52 of the acoustic window 51 and do not pass through the acoustic window 51, which is made of soundproof material. This opening 52 has a smaller area than the acoustic emitting surface 10a and is intended to narrow the acoustic emitting area of ​​the ultrasonic waves. Therefore, the beam angle of the ultrasonic waves widens as the ultrasonic waves pass through the opening 52. As a result, the directional characteristics of the ultrasonic waves become wider than the original directional characteristics, making it possible to detect schools of fish over a wider range than usual.

[0058] (3) The acoustic window 51 of this embodiment is attached to the lower end surface 32b of the cylindrical portion 32 of the holding member 31 and is detachably held by the holding member 31. Therefore, by replacing the acoustic window 51 with another acoustic window having a different inner diameter of the opening 52, the directional characteristics of the ultrasonic waves can be changed in more ways even if there is only one ultrasonic transmitter / receiver 10.

[0059] (4) In this embodiment, the acoustic window 51 that changes the directional characteristics of the ultrasonic waves is used as the directional characteristic changing member. This acoustic window 51 is formed by simply providing an opening 52 in a disc-shaped rubber sponge, so the manufacturing cost of the attachment 30 can be reduced compared to when, for example, an acoustic lens 81 (see FIG. 8) is used as the directional characteristic changing member.

[0060] (5) In this embodiment, the upper case 22 constituting the upper half of the case 13 has a shape that prevents snagging, and the groove 25 formed in the lower case 21 constituting the lower half of the case 13 has a shape that does not protrude from the lower case 21. This makes it difficult for the fishing line to become tangled in the case 13, especially during normal ice fishing.

[0061] [Second embodiment] A second embodiment of the present invention will be described below with reference to the drawings. The following will focus on differences from the first embodiment. In this embodiment, the structure of the attachment is different from that of the first embodiment.

[0062] More specifically, as shown in Fig. 8, the attachment 60 of this embodiment includes a holding member 61, a buoyant body 71, and an acoustic lens 81 (directivity characteristic changing member). As shown in Figs. 8 and 9, the holding member 61 is a substantially cylindrical member made of a resin material, and is configured in a cup shape by a bottom portion 62, a cylindrical portion 63, and an upper end portion 64. The space formed by the bottom portion 62 and the cylindrical portion 63 forms a holding recess 65 that detachably holds the ultrasonic transmitter / receiver 10.

[0063] Furthermore, one fitting hole 66 is provided in the bottom 62 of the holding member 61. The fitting hole 66 is circular and provided in the center of the bottom 62. The fitting hole 66 is intended to fit the convex surface 83 of the acoustic lens 81 with its flat surface 82 facing up, causing it to protrude downward from the bottom surface 61a of the holding member 61 (see FIG. 8). At this time, the outer periphery of the acoustic lens 81 is supported from below by the bottom 62. The acoustic lens 81 is detachably held to the holding member 61. Furthermore, four water supply and drainage holes 67 are formed by widening a portion of the fitting hole 66. Each water supply and drainage hole 67 has a corner located on the outer periphery of the bottom 62. The water supply and drainage holes 67 are arranged at equal angular intervals (90° intervals) based on the center C1 of the fitting hole 66 (see FIG. 9). Each water supply / drain hole 67 is for supplying water into the holding recess 65 and discharging the water in the holding recess 65 to the outside of the holding member 61 .

[0064] As shown in FIG. 8, the buoyant body 71 has a buoyancy such that the water surface W1 reaches the flat surface 82 of the acoustic lens 81 when the ultrasonic transmitter / receiver 10 is not held in the holding recess 65. The acoustic lens 81 is a substantially conical member made of urethane resin. Meanwhile, the portion of the ultrasonic transmitter / receiver 10 on the acoustic emission surface 10a side is made of a molded material such as rubber or urethane resin. Therefore, the specific acoustic impedance of the acoustic lens 81 is approximately equal to the specific acoustic impedance of the molded material. The sound speed of ultrasonic waves propagating within the acoustic lens 81 is different from the sound speed of ultrasonic waves propagating through water.

[0065] The acoustic lens 81 has a flat surface 82 and a convex surface 83 located on the opposite side. The outer diameter of the flat surface 82 is larger than the outer diameter of the fitting hole 66 and equal to the outer diameter of the acoustic emitting surface 10a. Therefore, the area of ​​the flat surface 82 is equal to the area of ​​the acoustic emitting surface 10a. The outer diameter of the flat surface 82 is slightly larger than the outer diameter of the ultrasonic transducer 12 housed in the lower case 21 of the ultrasonic transmitter / receiver 10. The tip region of the convex surface 83 (the region including the apex P1 of the acoustic lens 81) is spherical, and the region of the convex surface 83 excluding the tip region is inclined. The entire spherical surface constituting the convex surface 83 and a portion of the inclined surface constituting the convex surface 83 protrude downward from the bottom surface 61a of the holding member 61. The portion of the inclined surface is supported by the open end of the fitting hole 66 on the upper surface 61b side. Furthermore, the deviation between the central axis O3 (axis passing through the vertex P1) of the acoustic lens 81 and the central axis O2 of the ultrasonic transmitter / receiver 10 is less than 2% (0% in this embodiment) of the external dimensions of the ultrasonic transmitter / receiver 10.

[0066] 8, the holding recess 65 of the holding member 61 holds an acoustic lens 81 on the lower side and accommodates and holds the ultrasonic transmitter / receiver 10 on the upper side. The acoustic lens 81 is disposed on the acoustic emitting surface 10a side of the ultrasonic transmitter / receiver 10, and has the function of changing the directional characteristics of the ultrasonic waves radiated from the acoustic emitting surface 10a.

[0067] Next, how to use the attachment 60 will be described.

[0068] In normal ice fishing, an ultrasonic transmitter / receiver 10 is immersed in water while suspended by a cable 11. Then, fish detection is performed by transmitting and receiving ultrasonic waves using an ultrasonic vibrator 12 inside the ultrasonic transmitter / receiver 10.

[0069] Incidentally, there is also a demand for detecting schools of fish over a wider range than usual by fixing the ultrasonic transmitter / receiver 10 to the attachment 60 and using the attachment 60 while it is submerged in water (see FIG. 8 ). Specifically, first, the convex surface 83 of the acoustic lens 81, with its flat surface 82 facing up, is fitted into the fitting hole 66 provided in the holding member 61. This holds the acoustic lens 81 below the holding recess 65 of the holding member 61. Next, the ultrasonic transmitter / receiver 10, with its acoustic emitting surface 10a facing down, is inserted into the holding recess 65, and the ultrasonic transmitter / receiver 10 is placed on the flat surface 82 of the acoustic lens 81 fitted into the fitting hole 66. As a result, the ultrasonic transmitter / receiver 10 is housed and held in the holding recess 65, and the attachment 60 is attached to the ultrasonic transmitter / receiver 10.

[0070] Next, the ultrasonic transmitter / receiver 10 and the attachment 60 are immersed in water. At this time, water enters the holding recess 65 through the four water supply / drain holes 67 provided in the holding member 61 and enters between the flat surface 82 of the acoustic lens 81 and the acoustic emitting surface 10a of the ultrasonic transmitter / receiver 10. As a result, the flat surface 82 comes into close contact (acoustically coupled) with the acoustic emitting surface 10a via the coupling material (water in this case).

[0071] In this state, the ultrasonic transducer 12 in the ultrasonic transmitter / receiver 10 is driven to radiate (transmit) ultrasonic waves from the acoustic radiating surface 10a into the water. The ultrasonic waves radiated from the acoustic radiating surface 10a have a wider beam angle when passing through the acoustic lens 81. As a result, the directional characteristics of the ultrasonic waves become wider than the original directional characteristics, making it possible to detect schools of fish over a wider range than usual.

[0072] Next, the attachment evaluation method and the results will be described.

[0073] First, measurement samples were prepared as follows. An attachment equipped with a conical acoustic lens (conical lens) was prepared, and this was designated Example B1 (see "▲" in Figures 10 and 11). An attachment equipped with a hemispherical acoustic lens (hemispherical lens) was prepared, and this was designated Example B2 (see "●" in Figures 10 and 11). On the other hand, an attachment without an acoustic lens was prepared, and this was designated Comparative Example B (see "■" in Figures 10 and 11).

[0074] Next, the directional characteristics of ultrasonic waves were verified for each measurement sample (Examples B1 and B2 and Comparative Example B). Specifically, ultrasonic waves were irradiated from an ultrasonic vibrator in an ultrasonic transmitter / receiver to which an attachment was attached, and the directional characteristics during irradiation (transmission) were verified. In addition, the frequency was switched in multiple steps between 160 kHz and 300 kHz, and ultrasonic waves were irradiated at each switched frequency. Figure 10 is a graph showing the verification results of the directional characteristics of ultrasonic waves.

[0075] As a result, it was confirmed that in Comparative Example B, which did not have an acoustic lens, when ultrasonic waves were irradiated from the ultrasonic transducer, the directional characteristics had a relatively narrow directivity angle at all frequencies. On the other hand, in Examples B1 and B2, when ultrasonic waves were radiated via an acoustic lens, the directional characteristics had a wider directivity angle at all frequencies than Comparative Example B. In particular, it was confirmed that Example B1, which used a conical acoustic lens, had a directional characteristic with a wider directivity angle at all frequencies than Example B2, which used a hemispherical acoustic lens.

[0076] Therefore, it was confirmed that irradiating ultrasound through an acoustic lens widens the beam angle of the ultrasound and widens the detection range of the ultrasound transducer.Furthermore, it was confirmed that using a conical acoustic lens widens the beam angle of the ultrasound and widens the detection range of the ultrasound transducer.

[0077] Next, a voltage was applied to the ultrasonic transducer of each measurement sample (Examples B1 and B2, and Comparative Example B), and the transmission / reception sensitivity was measured at a position on the central radiation axis of the ultrasonic transducer and vertically below the ultrasonic transducer. Specifically, ultrasonic waves were first irradiated (transmitted) perpendicularly to the surface of a reflector positioned away from the ultrasonic transducer. The frequency was switched between multiple stages between 160 kHz and 300 kHz, and ultrasonic waves were irradiated at each switched frequency. The ultrasonic waves reflected by the surface of the reflector were received by the ultrasonic transducer a predetermined time after transmission, generating voltage signals at both electrodes of the ultrasonic transducer. The voltage amplitudes of the ultrasonic transducer during transmission and reception were measured using an oscilloscope, and the transmission / reception sensitivity was calculated based on the results. The results of Examples B1 and B2 and Comparative Example B are shown in FIG. 11.

[0078] As a result, it was confirmed that Examples B1 and B2, which have a wide beam angle because they irradiate ultrasound through an acoustic lens, have lower transmission and reception sensitivity at all frequencies than Comparative Example B, which has a narrow beam angle because it does not have an acoustic lens. Furthermore, in Examples B1 and B2, it was confirmed that Example B1, which has a relatively wide beam angle because it uses a conical acoustic lens, has higher transmission and reception sensitivity than Example B2, which has a relatively narrow beam angle because it uses a hemispherical acoustic lens. It was also confirmed that in all of Examples B1 and B2 and Comparative Example B, the transmission and reception sensitivity was maximized at a frequency of 200 kHz. From the above, it was confirmed that using an acoustic lens makes it possible to widen the beam angle of ultrasound, but that sensitivity decreases. It is believed that if an appropriate material is selected for forming the acoustic lens, sensitivity at a practical level can be obtained.

[0079] Therefore, according to this embodiment, the following effects can be obtained.

[0080] (6) In the attachment 60 for the ultrasonic transmitter / receiver 10 of this embodiment, the ultrasonic transmitter / receiver 10 is held in the holding recess 65 of the holding member 61, and an acoustic lens 81 is disposed on the side of the acoustic emission surface 10a of the ultrasonic transmitter / receiver 10 held in the holding recess 65. In this case, even if there is only one ultrasonic transmitter / receiver 10, it is possible to change the directional characteristics of the ultrasonic waves radiated from the acoustic emission surface 10a to different directional characteristics depending on the situation. Specifically, by holding the ultrasonic transmitter / receiver 10 in the holding recess 65, the directional characteristics (directional angle) of the ultrasonic waves can be widened using the acoustic lens 81. On the other hand, by removing the ultrasonic transmitter / receiver 10 from the holding recess 65, the directional characteristics of the ultrasonic waves can be restored to their original directional characteristics.

[0081] (7) In this embodiment, the bottom 62 of the holding member 61 is provided with a fitting hole 66 and a water supply / drainage hole 67. In this case, when the attachment 60 attached to the ultrasonic transmitter / receiver 10 is immersed in water, water is supplied into the holding member 61 through the water supply / drainage hole 67 and enters between the acoustic emission surface 10a of the ultrasonic transmitter / receiver 10 and the flat surface 82 of the acoustic lens 81. As a result, the ultrasonic transmitter / receiver 10 and the acoustic lens 81 can be used in close contact with each other via water, which acts as a coupling material, thereby enabling the directional characteristics of the ultrasonic waves to be wider than the original directional characteristics. Furthermore, when the attachment 60 is pulled out of the water, the water can be smoothly discharged outside the holding member 61 through the water supply / drainage hole 67.

[0082] (8) In this embodiment, a conical acoustic lens 81 is used as a directivity characteristic changing member that changes the directivity characteristics of the ultrasound, and therefore the directional angle can be wider than when, for example, a hemispherical acoustic lens is used (see FIG. 10 ). Note that if the acoustic lens 81 were simply conical, there would be a problem of reduced sensitivity at a position on the central axis O3 of the acoustic lens 81 and vertically below the acoustic lens 81. In addition, it is difficult to form the tip of the cone with high precision, which also poses a problem of increased product variation. Therefore, in this embodiment, the tip region of the convex surface 83 of the acoustic lens 81 is spherical, thereby solving these problems.

[0083] (9) In this embodiment, an acoustic lens 81 is used as a directivity changing member that changes the directivity of ultrasonic waves. Using this acoustic lens 81 makes it possible to widen the directional angle of ultrasonic waves, but it also comes with the problem of reduced sensitivity. However, by selecting an appropriate material for forming the acoustic lens 81, it is possible to improve sensitivity compared to using, for example, an acoustic window 51 (see FIGS. 2 and 3) as a directivity changing member.

[0084] [Third embodiment] A third embodiment of the present invention will be described below with reference to the drawings. The following focuses on differences from the first embodiment. The third embodiment differs from the first embodiment in the structure for attaching and detaching the ultrasonic transmitter / receiver to the attachment.

[0085] 12 and 13, the attachment 120 of this embodiment includes a holding member 121, a buoyant body 122, and an acoustic window 123 (a directional characteristic changing member). The holding member 121, the buoyant body 122, and the acoustic window 123 are made of a foamed resin, such as foamed polyethylene, whose specific gravity is lower than that of water, and are integrally formed into a cup shape. The space formed by the acoustic window 123 and the holding member 121 (the buoyant body 122) forms a holding recess 124 that detachably holds the ultrasonic transmitter / receiver 130. The attachment 120 has such buoyancy that the water surface W1 (see FIG. 2) reaches the upper surface 123a of the acoustic window 123 when the ultrasonic transmitter / receiver 130 is not held in the holding recess 124.

[0086] A circular opening 125 for adjusting the directional characteristics of ultrasound is provided in the center of the acoustic window 123. The opening 125 has a shape in which the inner diameter gradually increases toward the lower surface 123b of the acoustic window 123. The inner wall surface of the opening 125 is inclined at approximately 45° with respect to the lower surface 123b of the acoustic window 123. Three permanent magnets 141 (first magnetic material) having a circular shape in a plan view are provided around the opening 125 of the acoustic window 123. In this embodiment, neodymium magnets are used as the permanent magnets 141. Each permanent magnet 141 is fixed with an adhesive while embedded in the acoustic window 123, and its surface (top surface) is flush with the upper surface 123a of the acoustic window 123. The permanent magnets 141 are spaced apart from each other on the upper surface 123a of the acoustic window 123. Specifically, the permanent magnets 141 are arranged at equal angular intervals (120° intervals) with the center C2 of the opening hole 125 (see FIG. 12) as the reference.

[0087] 14 and 15, an annular metal plate 142 (second magnetic material) that attracts the permanent magnets 141 is attached to a position of the ultrasonic transmitter / receiver 130 facing each permanent magnet 141, specifically, to the outer periphery of the acoustic emission surface 130a of the ultrasonic transmitter / receiver 130. The metal plate 142 is disposed outside the piezoelectric elements that constitute the ultrasonic vibrator 12. Note that examples of materials that can be used to form the metal plate 142 in this embodiment include ferritic stainless steel, Fe-Ni alloys, Fe-Si alloys, and iron.

[0088] Next, how to use the attachment 120 will be described.

[0089] When detecting a school of fish over a wider range than usual, the attachment 120 is attached to the ultrasonic transmitter / receiver 130, and then the attachment 120 is used while immersed in water. Specifically, first, the ultrasonic transmitter / receiver 130 is inserted into the holding recess 124 of the holding member 121 with the acoustic emission surface 130a facing downward, and the ultrasonic transmitter / receiver 130 is placed on the upper surface 123a of the acoustic window 123. At this time, the permanent magnet 141 on the attachment 120 side and the metal plate 142 on the ultrasonic transmitter / receiver 130 side are attracted to each other by the magnetic force of the permanent magnet 141, so that the attachment 120 and the ultrasonic transmitter / receiver 130 come into close contact with each other. As a result, the attachment 120 is attached to the ultrasonic transmitter / receiver 130. Thereafter, the ultrasonic transmitter / receiver 130 and the attachment 120 are placed in water, and ultrasonic waves are emitted (transmitted) into the water from the acoustic emission surface 130a of the ultrasonic transmitter / receiver 130, thereby making it possible to detect schools of fish.

[0090] Therefore, according to this embodiment, the following effects can be obtained.

[0091] (10) In this embodiment, the attachment 120 and the ultrasonic transmitter / receiver 130 are attracted to each other by the magnetic force of the permanent magnet 141 and come into close contact with each other. As a result, even if the ultrasonic transmitter / receiver 130 is lifted by grasping the cable 11, the attachment 120 is less likely to fall off the ultrasonic transmitter / receiver 130. Furthermore, since the ultrasonic transmitter / receiver 130 can be used with the top surface 123a of the acoustic window 123 in close contact with the acoustic emission surface 130a (bottom surface 23) of the ultrasonic transmitter / receiver 130, the directional characteristics of the ultrasonic waves can be reliably made wide.

[0092] (11) In this embodiment, a permanent magnet 141, which is a first magnetic material, is disposed on the upper surface 123a of the acoustic window 123, and a metal plate 142, which is a second magnetic material, is disposed on the bottom surface 23 of the ultrasonic transmitter / receiver 130. In this case, the force that attracts the attachment 120 and the ultrasonic transmitter / receiver 130 to each other (the magnetic force of the permanent magnet 141) acts mainly in the same direction as the direction that pulls the ultrasonic transmitter / receiver 130 and the attachment 120 out of the water. Therefore, it is possible to reliably prevent the attachment 120 from falling off the ultrasonic transmitter / receiver 130.

[0093] (12) In this embodiment, the inner wall surface of opening 125 provided in acoustic window 123 is inclined with respect to bottom surface 123b of acoustic window 123, and therefore the beam angle of ultrasonic waves is wider when the ultrasonic waves pass through opening 125. If the inner wall surface of opening 125 were positioned perpendicular to bottom surface 123b of acoustic window 123, the beam angle of ultrasonic waves passing through opening 125 would tend to be slightly narrower.

[0094] The above embodiments may be modified as follows.

[0095] The acoustic window 51 of the first embodiment may be selected from a plurality of types of acoustic windows that differ from one another in, for example, the inner diameter or shape of the aperture. Similarly, the acoustic lens 81 of the second embodiment may be selected from a plurality of types of acoustic lenses that differ from one another in, for example, the diameter of the flat surface, the height from the center of the flat surface to the apex, the shape of the convex surface, etc.

[0096] In the attachments 30, 60 of the first and second embodiments, the buoyant body 41, 71 and the holding member 31, 61 are formed separately, but the buoyant body 41, 71 may be formed integrally with the holding member 31, 61. This reduces the number of parts in the attachment, thereby reducing the manufacturing costs of the attachment.

[0097] The openings 52, 125 provided in the acoustic windows 51, 123 in the first and third embodiments are circular, but may be other shapes such as elliptical or polygonal.

[0098] In the second embodiment, the bottom 62 of the holding member 61 is provided with four water supply / drainage holes 67, but the number of water supply / drainage holes 67 may be five or more, three or fewer, or none at all. Furthermore, the water supply / drainage holes 67 are formed by widening a portion of the fitting hole 66, but they may be holes independent of the fitting hole 66.

[0099] In the third embodiment, the first magnetic material provided on the attachment 120 side was the permanent magnet 141, and the second magnetic material provided on the ultrasonic transmitter / receiver 130 side was the metal plate 142. However, the first magnetic material provided on the attachment 120 side may be a metal plate, and the second magnetic material provided on the ultrasonic transmitter / receiver 130 side may be a permanent magnet. Also, both the first magnetic material and the second magnetic material may be permanent magnets. Note that the first magnetic material and the second magnetic material may be omitted.

[0100] In the third embodiment, the permanent magnet 141, which is the first magnetic material, is provided on the upper surface 123a of the acoustic window 123, and the metal plate 142, which is the second magnetic material, is provided on the bottom surface 23 of the ultrasonic transmitter / receiver 130. However, the first magnetic material may be provided on the inner circumferential surface 124a of the holding recess 124 of the holding member 121 (see FIGS. 12 and 13 ), and the second magnetic material may be provided on the outer circumferential surface 24 of the ultrasonic transmitter / receiver 130. The second magnetic material may be provided in a groove 25 formed in the outer circumferential surface 24. Furthermore, the first magnetic material may be provided on both the upper surface 123a of the acoustic window 123 and the inner circumferential surface 124a of the holding recess 124, and the second magnetic material may be provided on both the bottom surface 23 and the outer circumferential surface 24 of the ultrasonic transmitter / receiver 130. The second magnetic material may be provided inside the ultrasonic transmitter / receiver 130.

[0101] Although three permanent magnets 141 were provided in the acoustic window 123 of the third embodiment, the number of permanent magnets 141 may be five or more, or may be one to three. Furthermore, although the permanent magnets 141 were individual permanent magnets having a circular shape in a plan view, they may also be sheet-shaped permanent magnets (magnet sheets).

[0102] Although the permanent magnet 141 was embedded in the acoustic window 123 in the third embodiment, the permanent magnet 141 may be provided so as to protrude from the upper surface 123a of the acoustic window 123. Furthermore, although the permanent magnet 141 was embedded in the acoustic window 123 with its surface (upper surface) exposed to the upper surface 123a, it may be embedded completely in the acoustic window 123. Furthermore, although the permanent magnet 141 was fixed to the acoustic window 123 with an adhesive, it may be fixed to the acoustic window 123 using screws or the like.

[0103] 16, a holding member 91 may be provided with an insertion hole 92 into which the convex surface 83 of the acoustic lens 81, with the flat surface 82 facing up, is inserted so that the convex surface 83 protrudes downward from the bottom surface 91a of the holding member 91, and the insertion hole 92 may be formed so that its inner diameter gradually increases upward. In this way, the acoustic lens 81 is held by the holding member 91 with part of the inclined surface that constitutes the convex surface 83 in surface contact with the inner surface of the insertion hole 92, making it easier to insert the ultrasonic transmitter / receiver 10 into the insertion hole 92.

[0104] Although the acoustic lens 81 in the second embodiment is placed in the holding recess 65 of the holding member 61, it is preferable that it is fixed to the holding member 61 by fitting or gluing. If it is not fixed to the holding member 61, when the ultrasonic transmitter / receiver 10 is lifted, the attached acoustic lens 81 will be lifted up along with the ultrasonic transmitter / receiver 10, and there is a risk that it will then fall into the water.

[0105] 17, one example of a manner in which the acoustic lens 81 can be fixed is to fix an annular mounting fixture 101 to the inner periphery of the holding recess 65 of the holding member 61, and use the mounting fixture 101 to press down on the outer periphery of the flat surface 82 of the acoustic lens 81 fitted into the fitting hole 66. In this way, the acoustic lens 81 is fixed in a sandwiched state between the holding member 61 and the mounting fixture 101, so that the acoustic lens 81 can be reliably fixed and held in place.

[0106] 18, a screw 114 (fastening member) may be inserted through a through hole 113 formed in a cylindrical portion 112 of a holding member 111, and the tip of the screw 114 inserted through the through hole 113 may be fitted into a groove 25 formed in the outer peripheral surface 24 of the ultrasonic transmitter / receiver 10. In this case, fitting the screw 114 into the groove 25 prevents the case 13 (ultrasonic transmitter / receiver 10) and the acoustic lens 81 located below it from coming loose, thereby reliably fixing and holding the ultrasonic transmitter / receiver 10 and the acoustic lens 81. Instead of using the screw 114, a second magnetic material (e.g., a permanent magnet) may be provided in the groove 25, and a first magnetic material (e.g., a metal plate) may be provided in a position on the cylindrical portion 112 facing the second magnetic material. In this case, the permanent magnet and the metal plate are attracted to each other and come into close contact with each other, preventing the case 13 and the acoustic lens 81 from coming loose, thereby reliably fixing and holding the ultrasonic transmitter / receiver 10 and the acoustic lens 81. If the screw 114 is not used, the through hole 113 and the groove 25 do not need to be provided.

[0107] In the above embodiments, the case 13 of the ultrasonic transmitter / receiver 10, 130 is formed by joining the upper case 22 and the lower case 21, but the case may be formed as a single unit.

[0108] The attachments 30, 60, 120 in the above embodiments are used in fish finders, but may also be used in measuring devices such as depth sounders that measure water depth.

[0109] Next, in addition to the technical ideas set forth in the claims, the technical ideas grasped by the above-described embodiments will be listed below.

[0110] (1) In claim 2, an attachment for an ultrasonic transmitter / receiver is provided with an insertion hole in the holding member for inserting the convex side of the acoustic lens with the flat side facing up so that the convex side protrudes downward from the bottom surface of the holding member, and the insertion hole has a shape in which the inner diameter gradually increases as it goes upward.

[0111] (2) In claim 2, an attachment for an ultrasonic transmitter / receiver is provided, characterized in that the holding member has an insertion hole into which the convex side of the acoustic lens, with the flat side facing up, is inserted so that it protrudes downward from the bottom surface of the holding member, and the attachment is provided with a mounting fixture that is fixed to the inner side of the holding member and presses down the flat side of the acoustic lens inserted into the insertion hole.

[0112] (3) In claim 2, an attachment for an ultrasonic transmitter / receiver is provided in which an insertion hole is provided in the bottom of the holding member for inserting the convex side of the acoustic lens with the flat side facing up so that it protrudes downward from the bottom surface of the holding member, and a water supply / drain hole is provided for supplying water into the holding member and discharging the water from the holding member, the water supply / drain hole being formed by widening a part of the insertion hole, and the acoustic emitting surface of the ultrasonic transmitter / receiver and the flat surface of the acoustic lens are in close contact with each other via water.

[0113] (4) An attachment for an ultrasonic transmitter / receiver, as set forth in claim 3, characterized in that the deviation between the central axis of the opening hole and the central axis of the ultrasonic transmitter / receiver is 2% or less of the outer diameter dimension of the ultrasonic transmitter / receiver.

[0114] (5) An attachment for an ultrasonic transmitter / receiver according to any one of claims 1 to 9, wherein the buoyant body has a buoyancy such that the water surface reaches above the directivity changing member when the ultrasonic transmitter / receiver is not held in the holding recess. In this way, when the ultrasonic transmitter / receiver is held in the holding recess, the acoustic emission surface of the ultrasonic transmitter / receiver is surely in contact with the liquid (here, the water), so that ultrasonic wave emission is not hindered by air pockets.

[0115] (6) An attachment for an ultrasonic transmitter / receiver according to any one of claims 1 to 9, characterized in that a groove extending in the circumferential direction of the ultrasonic transmitter / receiver is formed on the outer peripheral surface of the ultrasonic transmitter / receiver, and a fastening member passing through the holding member is fitted into the groove. [Explanation of symbols]

[0116] 10,130...Ultrasonic transmitter / receiver 10a, 130a...acoustic radiation surface 11...Cable 12...Ultrasonic vibrator 23...Bottom of ultrasonic transducer 30, 60, 120...Attachment 31, 61, 91, 111, 121...Retaining members 32a...outer wall surface of holding member 34, 65, 124...Retaining recess 41, 71, 122... Buoyancy body 51,123...Acoustic windows as directional characteristic changing components 52...Acoustic window opening 81... Acoustic lens as a directivity change member 82…Flat surface 83…Convex surface 123a...Top surface of acoustic window 141... Permanent magnet as first magnetic material 142...Metal plate as second magnetic material

Claims

1. An attachment to be attached to an ultrasonic transducer that is suspended from a cable, houses an ultrasonic transducer that transmits and receives ultrasonic waves in a molded state, and has a bottom surface that serves as an acoustic radiation surface, a cup-shaped holding member having a holding recess for detachably holding the ultrasonic transmitter / receiver; a buoyant body that is provided so as to surround the holding member from the outer periphery side, is made of a material having a specific gravity smaller than that of water, and maintains the ultrasonic transmitter / receiver horizontally by buoyancy acting on the buoyant body; a directivity characteristic changing member that is arranged on the acoustic radiation surface side of the ultrasonic transmitter / receiver and changes the directivity characteristic of the ultrasonic waves irradiated from the acoustic radiation surface; An attachment for an ultrasonic transmitter / receiver, comprising:

2. 2. The attachment for an ultrasonic transducer according to claim 1, wherein the directivity characteristic changing member is an acoustic lens having a flat surface and a convex surface located on the opposite side.

3. 2. An attachment for an ultrasonic transmitter / receiver as described in claim 1, characterized in that the directional characteristic changing member is an acoustic window that is used with the ultrasonic transmitter / receiver placed on it, and the acoustic window is made of a soundproof material and has an opening hole with a smaller area than the acoustic radiation surface.

4. a first magnetic material is provided on at least one of the holding member and the acoustic window; a second magnetic material that is attracted to the first magnetic material is provided at a position facing the first magnetic material in the ultrasonic transmitter / receiver; At least one of the first magnetic material and the second magnetic material is a permanent magnet.

4. The attachment for an ultrasonic transducer according to claim 3, wherein the attachment is a flexible member.

5. 5. The attachment for an ultrasonic transducer according to claim 4, wherein a plurality of the first magnetic materials are spaced apart around the opening of the acoustic window.

6. 6. An attachment for an ultrasonic transducer according to claim 3, wherein the holding member, the buoyant body and the acoustic window are made of foamed polyethylene and are integrally formed.

7. An attachment for an ultrasonic transmitter / receiver as described in any one of claims 1 to 5, characterized in that the directional characteristic changing member is detachably held on the holding member and is selected from a plurality of types of directional characteristic changing members that differ from each other in at least one of dimensions and shape.

8. 8. The attachment for an ultrasonic transmitter / receiver according to claim 1, wherein the buoyant body is integrally formed with the holding member.

9. the holding recess holds the directivity characteristic changing member on a lower side and accommodates and holds the ultrasonic transmitter / receiver on an upper side; The buoyant body is attached so as to surround the outer wall surface of the holding member.

9. An attachment for an ultrasonic transducer according to claim 1.

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