WO2013065359A1 - 超音波センサ - Google Patents
超音波センサ Download PDFInfo
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- WO2013065359A1 WO2013065359A1 PCT/JP2012/067538 JP2012067538W WO2013065359A1 WO 2013065359 A1 WO2013065359 A1 WO 2013065359A1 JP 2012067538 W JP2012067538 W JP 2012067538W WO 2013065359 A1 WO2013065359 A1 WO 2013065359A1
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- WIPO (PCT)
- Prior art keywords
- temperature
- case
- elastic modulus
- loss elastic
- ultrasonic sensor
- Prior art date
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- 239000000463 material Substances 0.000 claims abstract description 104
- 238000013016 damping Methods 0.000 claims abstract description 34
- 229920002803 thermoplastic polyurethane Polymers 0.000 claims abstract description 32
- 230000009477 glass transition Effects 0.000 claims abstract description 24
- 239000008393 encapsulating agent Substances 0.000 abstract 1
- 230000000052 comparative effect Effects 0.000 description 21
- 239000003566 sealing material Substances 0.000 description 18
- 229920002050 silicone resin Polymers 0.000 description 10
- 239000011358 absorbing material Substances 0.000 description 8
- 239000000758 substrate Substances 0.000 description 8
- 230000003247 decreasing effect Effects 0.000 description 6
- CNQCVBJFEGMYDW-UHFFFAOYSA-N lawrencium atom Chemical compound [Lr] CNQCVBJFEGMYDW-UHFFFAOYSA-N 0.000 description 6
- 229920005862 polyol Polymers 0.000 description 5
- 150000003077 polyols Chemical class 0.000 description 5
- 239000012779 reinforcing material Substances 0.000 description 5
- 230000007423 decrease Effects 0.000 description 4
- 239000011256 inorganic filler Substances 0.000 description 4
- 229910003475 inorganic filler Inorganic materials 0.000 description 4
- JOYRKODLDBILNP-UHFFFAOYSA-N Ethyl urethane Chemical compound CCOC(N)=O JOYRKODLDBILNP-UHFFFAOYSA-N 0.000 description 3
- 239000000853 adhesive Substances 0.000 description 3
- 230000001070 adhesive effect Effects 0.000 description 3
- 229910052782 aluminium Inorganic materials 0.000 description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- WABPQHHGFIMREM-UHFFFAOYSA-N lead(0) Chemical compound [Pb] WABPQHHGFIMREM-UHFFFAOYSA-N 0.000 description 3
- 238000013459 approach Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 230000000704 physical effect Effects 0.000 description 2
- 229920001296 polysiloxane Polymers 0.000 description 2
- 230000003014 reinforcing effect Effects 0.000 description 2
- 229920005989 resin Polymers 0.000 description 2
- 239000011347 resin Substances 0.000 description 2
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
- 230000003139 buffering effect Effects 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
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- 229920000728 polyester Polymers 0.000 description 1
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- 229910052725 zinc Inorganic materials 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
Images
Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
- G01S7/521—Constructional features
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
- B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
- B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
- B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
- B06B1/06—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction
- B06B1/0644—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element
- B06B1/0662—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element with an electrode on the sensitive surface
- B06B1/0681—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element with an electrode on the sensitive surface and a damping structure
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H11/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by detecting changes in electric or magnetic properties
- G01H11/06—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by detecting changes in electric or magnetic properties by electric means
- G01H11/08—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by detecting changes in electric or magnetic properties by electric means using piezoelectric devices
-
- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K9/00—Devices in which sound is produced by vibrating a diaphragm or analogous element, e.g. fog horns, vehicle hooters or buzzers
- G10K9/18—Details, e.g. bulbs, pumps, pistons, switches or casings
- G10K9/22—Mountings; Casings
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
- G01S15/88—Sonar systems specially adapted for specific applications
- G01S15/93—Sonar systems specially adapted for specific applications for anti-collision purposes
- G01S15/931—Sonar systems specially adapted for specific applications for anti-collision purposes of land vehicles
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
- G01S15/88—Sonar systems specially adapted for specific applications
- G01S15/93—Sonar systems specially adapted for specific applications for anti-collision purposes
- G01S15/931—Sonar systems specially adapted for specific applications for anti-collision purposes of land vehicles
- G01S2015/937—Sonar systems specially adapted for specific applications for anti-collision purposes of land vehicles sensor installation details
- G01S2015/938—Sonar systems specially adapted for specific applications for anti-collision purposes of land vehicles sensor installation details in the bumper area
Definitions
- the present invention relates to an ultrasonic sensor having a structure in which a piezoelectric element is joined to a case, for example, an ultrasonic sensor used for a corner sonar, a back sonar, etc. of an automobile.
- the ultrasonic sensor detects an obstacle or a target by intermittently transmitting an ultrasonic pulse signal and receiving a reflected wave (see, for example, Patent Document 1).
- Ultrasonic sensors are used for back sonars, corner sonars of automobiles, and parking spot sensors for detecting the presence or absence of obstacles such as side walls in parallel parking.
- FIG. 5A is a cross-sectional view showing a configuration example of a conventional ultrasonic sensor.
- the ultrasonic sensor 101 includes a case 102, a piezoelectric element 103, a sound absorbing material 106, a damping material 104, pin terminals 107A and 107B, and lead wires 108A and 108B.
- the case 102 has a bottomed cylindrical shape and is made of a material such as a conductive metal.
- the piezoelectric element 103 is bonded to the bottom surface of the opening of the case 102 with a conductive adhesive or the like.
- FIG. 5B is a perspective view illustrating a configuration example of the piezoelectric element 103.
- the piezoelectric element 103 has drive electrodes 103A and 103B formed on both main surfaces.
- the tips of the pin terminals 107A and 107B are inserted into the opening of the case 102.
- the damping material 104 seals the tips of the pin terminals 107 ⁇ / b> A and 107 ⁇ / b> B within the opening of the case 102.
- the lead wire 108B is connected between the tip of the pin terminal 107B and the case 102, and is electrically connected to the drive electrode 103A provided on the lower surface of the piezoelectric element 103 via the case 102.
- the lead wire 108 ⁇ / b> A connects between the tip of the pin terminal 107 ⁇ / b> A and the drive electrode 103 ⁇ / b> B formed on the upper surface of the piezoelectric element 103.
- the damping material 104 is provided for the purpose of suppressing reverberation of the case 102 and preventing unnecessary vibration from being transmitted to the pin terminals 107A and 107B.
- a viscoelastic body such as a silicone resin or a urethane resin is usually employed.
- ultrasonic sensors such as automobile back sonar, corner sonar, and parking spot sensor are required to satisfy the required performance in a temperature range of about ⁇ 40 to 85 ° C.
- One of the performance requirements for an ultrasonic sensor is reverberation characteristics, and it is generally required to suppress the maximum value of reverberation time. It is known that the reverberation characteristic (maximum value of reverberation time) of the ultrasonic sensor is affected by the material and physical properties of the damping material, particularly the loss elastic modulus.
- the loss elastic modulus of the viscoelastic body constituting the damping material is temperature-dependent, and the loss elastic modulus increases and becomes harder as the temperature approaches (decreases) the glass transition point at an extremely low temperature. Therefore, even if the loss elastic modulus becomes appropriate at a certain temperature and a good reverberation characteristic is obtained, a good reverberation characteristic can be obtained in the entire actual use temperature range (for example, ⁇ 40 to 85 ° C.). Not necessarily.
- the urethane resin has a glass transition point in the vicinity of ⁇ 40 ° C.
- the loss elastic modulus gradually increases as the temperature decreases from room temperature, and the loss elastic modulus increases rapidly as the temperature approaches ⁇ 40 ° C.
- the silicone resin has a glass transition point on the lower temperature side than ⁇ 40 ° C., and the loss elastic modulus is substantially constant over the entire actual use temperature range.
- the loss modulus at which good reverberation characteristics can be obtained is constant over the entire actual use temperature range, good reverberation characteristics can be obtained over the entire actual use temperature range by using silicone resin. It becomes possible.
- the loss elastic modulus itself that actually provides good reverberation characteristics also has temperature dependence. Therefore, even if silicone can be used to improve the reverberation characteristics at room temperature, the loss elastic modulus is too low in the entire operating temperature range (especially in the cryogenic temperature range), and good reverberation characteristics can be obtained. It is difficult.
- Urethane resin can adjust the level of loss elastic modulus according to the content and composition of the mixed filler, curing conditions, and the like. Therefore, they can be controlled so that good reverberation characteristics can be obtained at extremely low temperatures, but in that case, good reverberation characteristics cannot be obtained at room temperature.
- the urethane resin is less permeable to moisture than the silicone resin and is low in cost. In this respect, it is preferable to use the urethane resin for the vibration damping material rather than the silicone resin.
- an object of the present invention is to realize an ultrasonic sensor capable of obtaining good reverberation characteristics over substantially the entire actual temperature range while using a vibration damping material mainly composed of urethane resin.
- the ultrasonic sensor of the present invention includes a case, a piezoelectric element, a terminal portion, and a damping material.
- the case has a bottomed cylindrical shape and has a vibration region on the bottom surface.
- the piezoelectric element is attached to the vibration region within the opening of the case.
- the terminal portion has a tip disposed in the opening of the case and is drawn out from the opening of the case.
- the damping material is mainly made of urethane resin, and is filled in the opening of the case. With such a configuration, the vibration damping material is made of a material whose glass transition point is lower than the lower limit temperature of the actual use temperature range, and its loss elastic modulus-temperature characteristic is centered on the glass transition point.
- the actual operating temperature range is characterized by a peak deviating from the actual operating temperature range.
- the peak centered at the glass transition point is out of the actual operating temperature range.
- the inflection point located on the high temperature side of the peak centered at the glass transition point is the actual operating temperature. It is located on the low temperature side of the range.
- the actual operating temperature range may vary depending on the application of the ultrasonic sensor, but is, for example, ⁇ 40 to 85 ° C. for an automobile.
- the damping material has a temperature range in which the peak 3 dB width centering on the glass transition point is lower than the lower limit temperature of the actual use temperature range in the loss elastic modulus-temperature characteristics. More preferably, it is preferable that the temperature range having a 5 dB width of the peak centered on the glass transition point or a temperature range wider than that be on the lower temperature side than the lower limit temperature of the actual use temperature range.
- the damping material has a loss elastic modulus of more than 1.5 Mpa at the lower limit temperature (about ⁇ 40 ° C.) of the actual use temperature range, a loss elastic modulus of 0 at room temperature (about 25 ° C.). It is preferable to exceed 2 Mpa. In addition, it is preferable that the damping material has a loss elastic modulus of less than 53.5 Mpa over the entire actual use temperature range.
- FIG. 1A is a cross-sectional view showing a cross-sectional configuration of the ultrasonic sensor 1 according to the first embodiment of the present invention at a position indicated by AA ′ in FIG.
- FIG. 1B is a rear view of the ultrasonic sensor 1.
- the ultrasonic sensor 1 includes a case 2, a piezoelectric element 3, a sound absorbing material 4, a reinforcing material 5, a supporting material 6, a buffering material 7, a sealing material 8, a flexible substrate 9, and a terminal holding material 10. And pin terminals 11A and 11B.
- the case 2 has a bottomed cylindrical shape in which the lower end surface (front surface) in FIG. 1 (A) is closed and the upper end surface (rear surface) in FIG. 1 (A) is opened. And a plate-like bottom plate 2B.
- the case 2 is configured, for example, as a highly elastic and lightweight forged aluminum body.
- the material of the case 2 is not limited to a conductive material such as aluminum, and may be an insulating material.
- the side wall 2A is thin on the opening side to increase the inner diameter, and thick on the bottom plate side to reduce the inner diameter.
- the bottom plate 2B includes a recess 2B1 and a step 2B2.
- the recess 2B1 is formed such that a predetermined direction (lateral direction in FIG.
- the recess 2B1 has both ends in the longitudinal direction reaching the side wall 2A.
- the step 2B2 is provided on both sides in the short direction of the recess 2B1 and is formed so as to rise from the recess 2B1.
- the bottom surface of the recess 2B1 becomes the main vibration region of the case 2, and the ultrasonic sensor 1 has a narrow directivity in the longitudinal direction of the recess 2B1 and a wide directivity in the lateral direction.
- the piezoelectric element 3 has a flat plate shape and vibrates in an in-plane direction when a driving voltage is applied between the upper and lower surfaces.
- the piezoelectric element 3 is disposed inside the recess 2B1 of the case 2 and is attached to the bottom plate 2B.
- the piezoelectric element 3 and the bottom plate 2B are joined together to form a unimorph vibrator, and the bottom plate 2B (recessed portion 2B1) bends and vibrates in the vertical direction in FIG. become.
- the sound absorbing material 4 is a flat plate made of polyester felt, for example, and is provided to absorb unnecessary sound waves that try to escape from the piezoelectric element 3 to the opening side of the case 2.
- the sound absorbing material 4 is disposed in the recess 2 ⁇ / b> B ⁇ b> 1 of the case 2 and is laminated and bonded to the piezoelectric element 3.
- the reinforcing material 5 is a ring-shaped molded body having an opening in the center, and is configured to have high acoustic impedance. That is, it is made of a material having higher density and rigidity than the case 2 such as SUS and zinc so as to be a so-called weight. In addition, you may comprise with the same material (aluminum) as Case 2 by adjusting sizes, such as thickness.
- the reinforcing member 5 is disposed on the bottom plate 2B of the case 2 in contact with the inner peripheral surface of the thick portion of the side wall 2A. By providing the reinforcing material 5 in this way, the rigidity around the recess 2B1 of the case 2 is increased, and the vibration in the bottom plate 2B of the case 2 can be prevented from being transmitted to the side wall 2A of the case 2.
- the support member 6 has a ring shape with an opening at the center made of a urethane resin that is a viscoelastic body, and is filled with a resin in the case and cured with a mold member that is a shaped mold inside the case. And the mold member is drawn out.
- the support material 6 functions as a part of the vibration damping material in the present embodiment.
- the support material 6 is provided to support a buffer material 7 described later without contacting the case 2. By providing the support member 6, it is possible to suppress vibration from being transmitted to the buffer material 7 through the side wall 2 ⁇ / b> A.
- the buffer material 7 is a cup-shaped molded body made of a urethane resin that is a viscoelastic body, and functions as a part of the vibration damping material in the present embodiment.
- a convex portion that engages with the opening of the reinforcing member 5 is formed at the lower portion of the cushioning material 7, and an opening that engages with a terminal holding member 10 to be described later is formed at the upper portion thereof.
- the terminal holding member 10 is an L-shaped molded body made of a resin such as PBT, and holds pin terminals 11A and 11B, which will be described later, in a posture along an axis passing through the center of the opening of the case 2.
- the lower part of the terminal holding member 10 is bent so as to be engaged with the buffer member 7 described above, and a convex portion is formed on the bottom surface. Further, a window for exposing the pin terminals 11A and 11B is formed at the center of the terminal holding member 10.
- the pin terminals 11 ⁇ / b> A and 11 ⁇ / b> B are metal linear pins to which a driving voltage is applied, and are held by the terminal holding material 10.
- the lower ends of the pin terminals 11 ⁇ / b> A and 11 ⁇ / b> B are disposed in the opening of the case 2 so as to be exposed from the window of the terminal holding material 10.
- the upper ends of the pin terminals 11 ⁇ / b> A and 11 ⁇ / b> B protrude from the upper end of the terminal holding member 10 and are arranged outside the case 2.
- the flexible substrate 9 is a wide strip-shaped wiring part, and it is wired between the pin terminals 11A and 11B and the piezoelectric element 3.
- the flexible substrate 9 is wired to the pin terminals 11A and 11B with the first end facing the same direction as the lower ends of the pin terminals 11A and 11B.
- the flexible substrate 9 is bent at the second end from the first end and pulled out in the radial direction of the case 2, and is wired on the upper surface of the piezoelectric element 3 via a conductive adhesive.
- the weight of the wiring connection portion can be reduced as compared with the case where the lead wire is soldered. Thereby, the vibration of the piezoelectric element 3 can be brought closer to an ideal one.
- the sealing material 8 is made of a urethane resin that is a viscoelastic body, and functions as a part of the vibration damping material in the present embodiment.
- the sealing material 8 fills the inside of the case 2 and seals the lower ends of the pin terminals 11 ⁇ / b> A and 11 ⁇ / b> B and the flexible substrate 9 disposed in the opening of the case 2.
- the sealing material 8 since the space on the bottom plate side of the case 2 is covered by the support material 6 and the buffer material 7, the sealing material 8 is filled only in the space on the opening side of the case 2.
- the sealing material 8 has a function of suppressing vibration of the side wall 2 ⁇ / b> A of the case 2 and also functions as a retaining member for the support material 6 and the buffer material 7 from the case 2.
- the vibration of the case 2 is attenuated by the sound absorbing material 4, the support material 6, the buffer material 7, and the sealing material 8, so that the terminal holding material 10 and the pin terminals 11 ⁇ / b> A and 11 ⁇ / b> B are hardly affected. There is no propagation. Further, since the sealing material 8, the support material 6, and the cushioning material 7 suppress vibration (damping) of the side wall 2 ⁇ / b> A of the case 2, unnecessary reverberation of the case 2 can be suppressed. Therefore, vibration leakage that occurs when the pin terminals 11A and 11B are mounted on the external substrate is greatly reduced.
- all of the sealing material 8, the support material 6 and the buffer material 7 are made of urethane resin satisfying a desired loss elastic modulus-temperature characteristic to suppress (suppress) the vibration of the case 2.
- the material may be a material, but at least one of them may be made of a silicone resin (silicone rubber) as long as one of them is a vibration damping material.
- the support material 6 may be a vibration damping material
- the sealing material 8 and the buffer material 7 may be configured to suppress the propagation of vibration to the pin terminals 11A and 11B.
- the sealing material 8 and the buffer material 7 have a lower elastic modulus than the support material 6.
- the elastic modulus includes a storage elastic modulus and a loss elastic modulus. It is preferable that the sealing material 8 and the buffer material 7 have a small storage elastic modulus and the support material 6 has a large loss elastic modulus.
- FIG. 2 is a diagram for explaining the relationship between the loss elastic modulus and the reverberation time in the vibration damping material (support material 6).
- 2A shows the reverberation time at room temperature (25 ° C.)
- FIG. 2B shows the reverberation time at extremely low temperature ( ⁇ 40 ° C.).
- the reverberation time at various loss moduli is measured by using different damping materials
- the reverberation time increases as the loss moduli increase so that the loss moduli and reverberation times are inversely proportional at room temperature (25 ° C). Showed a gradual change.
- the reverberation time showed a quadratic change indicating an extreme value according to the loss modulus. Specifically, at room temperature, as the loss elastic modulus changes from a small state to a large state, the reverberation time sharply decreases until the loss elastic modulus is about 0.2 Mpa, and the loss elastic modulus is about 0.00.
- the loss elastic modulus is less than 0.2 Mpa at room temperature, the rate of change of reverberation time is large and the reverberation time is greatly deteriorated. Therefore, at room temperature, a material having at least a loss elastic modulus exceeding 0.2 Mpa is used. It can be seen that it should be used for damping materials.
- FIG. 3A is a diagram for explaining the relationship between the loss elastic modulus and temperature for each material.
- the data shown in the drawing are obtained by measuring the loss elastic modulus while producing test pieces of various materials and changing the temperature for each test piece.
- the shape of each test piece was 10 ⁇ 12 ⁇ 3 mm (however, the length of 12 mm is the distance between chucks in the test apparatus).
- the test piece was periodically deformed and its frequency was 10 Hz.
- the measurement temperature was ⁇ 100 ° C. to 130 ° C. The measurement starts from ⁇ 100 ° C., and the loss elastic modulus is measured while increasing the temperature at a rate of temperature increase of 4 ° C./min.
- Comparative Example 1 is a urethane resin that does not satisfy the conditions of the present invention, and is obtained by mixing a polyol-based urethane with an inorganic filler and curing it under standard curing conditions.
- the glass transition point is about ⁇ 40 ° C., which is the lower limit temperature of the actual use temperature range, and shows a peak in loss elastic modulus-temperature characteristics. It was.
- the loss elastic modulus at that time was about 125.37 Mpa. Further, when the temperature was further raised from there, the loss elastic modulus gradually decreased, and the loss elastic modulus was about 1.45 Mpa at room temperature (25 ° C.).
- the urethane resin of Comparative Example 1 is so high that the loss elastic modulus at cryogenic temperature exceeds 53.5 Mpa, even if the loss elastic modulus at room temperature is more than 0.2 Mpa. However, it was too hard to suppress reverberation.
- Comparative Example 2 is a urethane resin that does not satisfy the conditions of the present invention, and is obtained by mixing an inorganic filler with a polyol-based urethane as a main material and curing under standard curing conditions. is there.
- the glass transition point is moved to a lower temperature side than the examples described later by changing the polyol configuration from the production conditions of Comparative Example 1. I am letting.
- the urethane resin of Comparative Example 2 when the temperature was raised from ⁇ 100 ° C., about ⁇ 85 ° C. became the glass transition point, and showed a peak in loss elastic modulus-temperature characteristics.
- the loss elastic modulus when the temperature was further raised, the loss elastic modulus gradually decreased, and the loss elastic modulus was about 2.06 Mpa at about ⁇ 40 ° C. which is the lower limit temperature of the actual use temperature range. From this point, when the temperature was further increased, the loss elastic modulus was about 0.16 Mpa at room temperature (25 ° C.).
- the urethane resin of Comparative Example 2 has a loss elastic modulus at a cryogenic temperature of more than 1.5 Mpa and less than 53.5 Mpa, but has a loss elastic modulus at room temperature of less than 0.2 Mpa and at room temperature. It was too soft to suppress reverberation.
- Comparative Example 3 is a silicone resin that does not satisfy the conditions of the present invention, and is obtained by mixing inorganic fillers with silicone as the main material and curing under standard curing conditions.
- the temperature of the silicone resin of Comparative Example 3 was raised from ⁇ 100 ° C., about ⁇ 80 ° C. became the glass transition point, and showed a peak in loss elastic modulus-temperature characteristics.
- the loss elastic modulus decreased rapidly and stabilized, and the loss elastic modulus was about 0.17 Mpa at the lower limit temperature of ⁇ 40 ° C. in the actual use temperature range.
- the loss elastic modulus was about 0.09 Mpa at room temperature (25 ° C.).
- the silicone resin of Comparative Example 3 has a loss elastic modulus at room temperature of less than 0.2 Mpa, a loss elastic modulus at a cryogenic temperature of less than 1.5 Mpa, is too soft, and suppresses reverberation. It was not suitable for.
- the examples are urethane resins that satisfy the conditions of the present invention.
- the glass transition point is shifted from the lower limit temperature of the actual use temperature range to a lower temperature side to some extent, and the glass transition point in the loss elastic modulus-temperature characteristics is the center.
- the temperature up to the inflection point (the point at which the second derivative polarity of the curve changes) located on the high temperature side of the peak is removed from the actual use temperature range.
- the temperature range of 3 dB width based on the glass transition point is sufficiently separated from the actual use temperature range.
- This urethane resin is obtained by mixing a polyol-based urethane as a main material, mixing an inorganic filler, and curing it under standard curing conditions.
- the glass transition point is shifted to a low temperature side to some extent by changing the configuration of the polyol.
- the temperature of the urethane resin of this example was increased from ⁇ 100 ° C.
- the glass transition point was between about ⁇ 60 ° C. and ⁇ 70 ° C., and showed a peak in loss elastic modulus-temperature characteristics.
- the loss modulus decreased, and the loss modulus was about 21.40 Mpa at the lower limit temperature of ⁇ 40 ° C. in the actual use temperature range. From this point, as the temperature was further raised, the loss elastic modulus gradually decreased, and the loss elastic modulus was about 0.88 Mpa at room temperature (25 ° C.).
- the urethane resin of the example is appropriate when the loss elastic modulus at room temperature exceeds 0.2 Mpa, and the loss elastic modulus at cryogenic temperature exceeds 1.5 Mpa and is appropriate when less than 53.5 Mpa. It had moderate softness necessary for suppressing reverberation.
- the loss elastic modulus in the urethane resin by controlling the loss elastic modulus in the urethane resin, the physical properties satisfying both the room temperature side condition and the cryogenic temperature side condition in the loss elastic modulus-temperature characteristic can be obtained. It becomes possible.
- FIG. 3B is a diagram showing reverberation time at room temperature and reverberation time at a very low temperature in each of the example and the comparative example.
- the reverberation time at room temperature was about 0.75 ms, and the reverberation time at extremely low temperature was about 1.43 ms.
- the reverberation time at room temperature (about 25 ° C.) is about 0.65 ms
- the reverberation time at extremely low temperature is about 1.times. It was 80 ms.
- the reverberation time at room temperature was about 1.01 ms
- the reverberation time at extremely low temperature was about 1.40 ms.
- the reverberation time at room temperature was about 1.05 ms
- the reverberation time at extremely low temperature was about 2.20 ms.
- Comparative Example 1 deteriorated the reverberation characteristics at cryogenic temperature
- Comparative Example 2 deteriorated the reverberation characteristics at normal temperature
- Comparative Example 3 deteriorated the reverberation characteristics at normal temperature and cryogenic temperature.
- the ultrasonic sensor using the urethane resin of the example was able to realize a good and short reverberation time at both extremely low temperature and normal temperature.
- the ultrasonic sensor according to the present embodiment by using a urethane resin having a controlled loss elastic modulus as a vibration damping material, a desired characteristic can be realized in the loss elastic modulus-temperature characteristic.
- the reverberation time can be suppressed over the entire actual temperature range.
- FIG. 4 is a cross-sectional view of the ultrasonic sensor 21 according to the present embodiment.
- the ultrasonic sensor 21 is different from that of the first embodiment in the shapes of the support material 16, the buffer material 17, and the sealing material 18.
- the support material 16 does not change in that it is ring-shaped or in which urethane resin is cured and molded, but its length reaches the opening surface of the case 2.
- the buffer material 17 is fixed by being pressed into the opening of the support material 16.
- the sealing material 18 is filled in the opening of the support material 16.
- the present invention can be applied similarly to the first embodiment. That is, by configuring at least one of the support material 16, the buffer material 17, and the sealing material 18 with a urethane resin whose glass transition point is controlled so as to have a desired loss elastic modulus-temperature characteristic, The reverberation time can be suppressed over the entire actual temperature range.
- the present invention can be implemented, but the specific configuration of the ultrasonic sensor that can be implemented by the present invention is not limited to the above-described one.
- any specific shape or material such as a buffer material, a support material, a reinforcing material, a sound absorbing material, or a sealing material may be used.
- at least one member to be a vibration damping material may be provided, and other various members, cushioning materials, support materials, reinforcing materials, sound absorbing materials, sealing materials, and the like are not necessarily provided.
- the structure of the case is not limited to that described above, and the material and shape thereof may be changed in any way.
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- Acoustics & Sound (AREA)
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Abstract
Description
なお、実使用温度範囲は、超音波センサの用途などによって異なることもあるが、例えば、自動車用である場合には、-40~85℃である。
図1(A)は、本発明の第1の実施形態に係る超音波センサ1の、図1(B)にA-A’で示す位置での断面構成を示す断面図である。また、図1(B)は、超音波センサ1の背面図である。
側壁2Aは、開口側を薄肉にして内径を大きく、底板側を厚肉にして内径を小さくしている。底板2Bは、凹部2B1と段部2B2とを備えている。凹部2B1は、所定方向(図1(B)における横方向)が短手方向となり、短手方向に直交する方向が長手方向となるように形成している。より具体的には、凹部2B1は、長手方向の両端を側壁2Aまで到達させている。また、段部2B2は、凹部2B1の短手方向の両脇に設けていて、凹部2B1から立ち上がるように形成している。この凹部2B1の底面が、ケース2の主たる振動領域となり、超音波センサ1は、凹部2B1の長手方向に狭く、短手方向に広い指向性を持つことになる。
具体的には、室温においては、損失弾性率が小さい状態から大きい状態に変化していくに従い、損失弾性率が約0.2Mpaまでは急峻に残響時間が低減し、損失弾性率が約0.2Mpaを超えると緩やかに低減して略一定の残響時間を示すようになった。
また、極低温においては、損失弾性率が小さい状態から大きい状態に変化していくに従い、損失弾性率が約1.5Mpaまでは急峻に残響時間が低減し、損失弾性率が約1.5Mpaを超えると変化が緩やかになり、損失弾性率が約6Mpaで残響時間が下限極値である1.268msを示した。そして、損失弾性率が約53.5Mpaを超えると再び残響時間が急峻な増加を示すようになった。
このウレタン樹脂は、ポリオール系ウレタンを主材として、無機系フィラーを混成し、標準的な硬化条件のもとで硬化させたものである。ここでは、ポリオールの構成を変更することにより、ガラス転移点をある程度低温側にシフトさせている。この実施例のウレタン樹脂は、-100℃から昇温させていくと、約-60℃~-70℃の間がガラス転移点となり、損失弾性率-温度特性上のピークを示した。また、そこから、さらに昇温させていくと、損失弾性率が低下していき、実使用温度範囲の下限温度-40℃において、損失弾性率は約21.40Mpaを示した。そこから、さらに昇温させていくと、損失弾性率が次第に低下していき、室温(25℃)において、損失弾性率は約0.88Mpaを示した。
次に、本発明の第2の実施形態に係る超音波センサについて説明する。図4は、本実施形態に係る超音波センサ21の断面図である。超音波センサ21は、支持材16、緩衝材17、および封止材18の形状が、第1の実施形態のものと相違する。具体的には、支持材16は、リング状である点、ウレタン樹脂を硬化し成形した点では変わらないが、その長さが、ケース2の開口面にまで到達するものである。そして、緩衝材17は、支持材16の開口内に圧入して固定されたものである。また、封止材18は支持材16の開口内に充填されるものである。
2…ケース
2A…側壁
2B…底板
2B1…凹部
2B2…段部
3…圧電素子
4…吸音材
5…補強材
6…支持材
7…緩衝材
8…封止材
9…フレキシブル基板
10…端子保持材
11A,11B…ピン端子
16…支持材
17…緩衝材
18…封止材
Claims (5)
- 底面に振動領域を有する有底筒状のケースと、
前記ケースの開口内で前記振動領域に貼り付けられている圧電素子と、
前記ケースの開口内に先端が配置され、前記ケースの開口内から外部に引き出されている端子部と、
ウレタン樹脂を主材としていて、前記ケースの開口内に充填されている制振材と、
を備え、
前記制振材は、ガラス転移点が実使用温度範囲の下限温度よりも低温側である材料からなり、その損失弾性率-温度特性において、ガラス転移点を中心とするピークの高温側に位置する変曲点が実使用温度範囲から外れることを特徴としている、超音波センサ。 - 前記制振材は、損失弾性率‐温度特性において、ガラス転移点を中心とするピークの3dB幅となる温度範囲が、実使用温度範囲の下限温度よりも低温側である、請求項1に記載の超音波センサ。
- 前記制振材は、室温で、損失弾性率が0.2Mpaを超える、請求項1又は2に記載の超音波センサ。
- 前記制振材は、実使用温度範囲の全域に亘って、損失弾性率が53.5Mpa未満である、請求項1~3のいずれかに記載の超音波センサ。
- 前記制振材は、実使用温度範囲の下限温度で、損失弾性率が1.5Mpaを超える、請求項1~4のいずれかに記載の超音波センサ。
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WO2016158762A1 (ja) * | 2015-03-31 | 2016-10-06 | 株式会社村田製作所 | 圧電素子およびこれを備える超音波センサ |
CN114273192A (zh) * | 2020-10-01 | 2022-04-05 | Tdk株式会社 | 超声波换能器 |
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