JPWO2013051524A1 - Ultrasonic sensor and manufacturing method thereof - Google Patents

Abstract

The ultrasonic sensor (101) includes a bottomed cylindrical case (31) having a bottom (31b) and a side wall (31a), a piezoelectric element (32) provided on the inner bottom surface of the case (31), A terminal (43) that is electrically connected to the piezoelectric element (32) through a conducting member in the case (31) and protrudes to the outside of the case (31), and a terminal holding member (41 that holds the terminal (43)) ), A buffer member (33) for holding the terminal holding member (41) in the case (31), and a damping member (39) provided along the inner peripheral surface of the side wall (31a) of the case (31) And a filling member (36) filled in the upper part of the damping member (39) and the buffer member (33) in the case (31), and between the damping member (39) and the buffer member (33) Is provided with a gap (40). This structure prevents vibration leakage to the terminal and improves reverberation characteristics due to vibration leakage.

Description

  The present invention relates to an ultrasonic sensor and a method of manufacturing the same, and more particularly to an ultrasonic sensor having a piezoelectric element and an input / output terminal electrically connected to the piezoelectric element, and used for, for example, an automobile corner sonar and back sonar, and It relates to the manufacturing method.

  The ultrasonic sensor detects an object by intermittently transmitting an ultrasonic pulse signal and receiving a reflected signal reflected after the transmitted ultrasonic pulse signal reaches the object. Ultrasonic sensors are used for back sonars, corner sonars of automobiles, and parking spot sensors that detect distances from obstacles such as side walls when parallel parking. This type of ultrasonic sensor is disclosed in Patent Documents 1 to 3.

  FIG. 9 is a partially broken front view of the ultrasonic sensor of Patent Document 1. FIG. This ultrasonic sensor includes an ultrasonic transducer 1, a buffer member 2, a shield wire 5, a sound absorbing material 6, and a housing 3. The buffer member 2 has an opening for ultrasonic transmission / reception, and surrounds the ultrasonic transducer 1. The housing 3 is a molded product and houses the ultrasonic transducer 1 and the buffer member 2. One end of the shield wire 5 is connected to the ultrasonic transducer 1 inside the housing 3, and the other end is drawn out from the housing 3. An air layer 4 is formed so as to surround the ultrasonic transducer 1 in a portion corresponding to the side surface of the ultrasonic transducer 1 inside the buffer member 2.

  In Patent Literature 2, an ultrasonic transducer, an inner casing having an ultrasonic radiation wall bonded to form a bottom surface portion and a cylindrical side wall, and a cylindrical side wall of the inner casing are coaxial. And an outer housing having a cylindrical side wall disposed on the outer housing, the outer housing supports the inner housing at a plurality of support locations on the ultrasonic radiation wall side, other than the plurality of support locations. 1 shows a structure in which a gap is formed between the outer wall of the cylindrical side wall of the inner casing and the outer wall of the cylindrical side wall of the outer casing.

  Patent Document 3 discloses an ultrasonic vibrator, a holding member that has an opening for transmitting and receiving ultrasonic waves and surrounds the ultrasonic vibrator, and is a molded product that houses the ultrasonic vibrator and the holding member. In the ultrasonic sensor including the housing, a structure in which a gap is generated in a place other than the convex portion by providing the convex portion inside the holding member is shown.

JP-A-4-238497 JP 2003-315443 A JP-A-5-207594

  In the conventional ultrasonic sensors disclosed in Patent Documents 1 to 3, the vibration of the ultrasonic vibrator is hardly transmitted to the case (housing or housing) due to the action of the air layer and the gap. Therefore, there is an effect of shortening the reverberation time.

  However, if the member that inputs and outputs electrical signals is not a lead wire (or shield wire) but a pin terminal, the vibration of the case propagates to the pin terminal, and the vibration is external to the ultrasonic sensor mounted. A problem of vibrating the circuit board (hereinafter referred to as “vibration leakage”) occurs. This vibration leakage increases the reverberation time (the reverberation characteristics deteriorate). And if the reverberation time is prolonged, when detecting an object located at a short distance, the reflected signal is received within the time when the reverberation by the transmitted ultrasonic pulse signal is continued. It is impossible to detect a positioned object.

  An object of the present invention is to provide an ultrasonic sensor that prevents vibration leakage to a terminal and improves reverberation characteristics due to vibration leakage.

(1) The ultrasonic sensor of the present invention
A bottomed cylindrical case having a bottom and a side wall; and
A piezoelectric element provided on the inner bottom surface of the case;
A terminal that is electrically connected to the piezoelectric element via a conducting member in the case and protrudes to the outside of the case;
A terminal holding member for holding the terminal;
A buffer member for holding the terminal holding member in the case;
A damping member provided along the inner peripheral surface of the side wall of the case;
A filling member filled in the upper part of the damping member and the buffer member in the case,
A gap (air layer) is provided between the damping member and the buffer member.

  With this structure, vibration transmitted from the case is attenuated (blocked) by the damping member, the buffer member, and the gap (air layer), and hardly propagates to the terminal through the terminal holding member. Therefore, when the terminal is mounted on an external circuit board The vibration leakage that occurs in can be greatly reduced.

(2) It is preferable that the said filling member has a smaller elastic modulus than the said damping member. With this structure, vibration leakage directly transmitted from the filling member having a smaller elastic modulus than that of the damping member to the terminal can be reduced. In addition, the damping member does not directly contact the terminal, and the elastic modulus of the damping member is less likely to affect the vibration leakage characteristics, so that options for the damping member are expanded.

(3) It is preferable to provide a closing member (a cover resin) that closes a boundary portion (opening portion of the air layer) between the gap and the filling member. With this structure, the structure of the buffer member can be simplified.

(4) The side wall portion of the case includes a thin portion on the opening side and a thick portion on the bottom side,
It is preferable that a reinforcing material having an acoustic impedance higher than that of the case is provided on the thick portion. With this structure, rigidity around the bottom surface of the case is increased, and vibrations on the bottom surface of the case are suppressed from being transmitted to the side wall portion of the case, and sensitivity as a sensor is improved.

(5) It is preferable that a sound absorbing member is provided between the piezoelectric element and the buffer member. With this structure, unnecessary sound waves are absorbed by the sound absorbing material, and unnecessary sound waves transmitted from the piezoelectric element to the inside of the case can be attenuated more efficiently.

(6) An ultrasonic sensor manufacturing method of the present invention is the ultrasonic sensor manufacturing method according to any one of (1) to (5),
Inserting an annular molded piece having a larger outer diameter than the buffer member into the case;
Filling the periphery of the molding piece in the case with the elastic resin for forming the damping member;
Removing the molding piece from the case, and mounting the buffer member in the case.

  According to the present invention, vibration transmitted from the case is attenuated (blocked) by the damping member, the buffer member, and the gap (air layer), and is hardly propagated to the terminal through the terminal holding member, so that vibration leakage can be greatly reduced. Therefore, deterioration of the reverberation characteristic due to vibration leakage can be prevented, and an object located at a closer distance can be detected.

FIG. 1 is a cross-sectional view of an ultrasonic sensor 101 according to the first embodiment. FIG. 2 is an exploded perspective view excluding a part of the ultrasonic sensor 101. FIG. 3A is a diagram illustrating the reverberation characteristics of the ultrasonic sensor 101 according to the first embodiment, and FIG. 3B is a diagram illustrating the reverberation characteristics of an ultrasonic sensor as a comparative example. FIG. 4 is a diagram showing the relationship between the gap 40 between the damping member 39 and the buffer member 33 and the vibration leakage time. FIG. 5 is a diagram illustrating a process of forming the damping member 39 and the gap 40. FIG. 6 is a cross-sectional view of the ultrasonic sensor 102 according to the second embodiment. FIG. 7 is a cross-sectional view of the ultrasonic sensor 103 according to the third embodiment. FIG. 8 is a cross-sectional view of the ultrasonic sensor 104 according to the fourth embodiment. FIG. 9 is a partially broken front view of the ultrasonic sensor of Patent Document 1. FIG.

<< First Embodiment >>
FIG. 1 is a cross-sectional view of an ultrasonic sensor 101 according to the first embodiment. FIG. 2 is an exploded perspective view excluding a part of the ultrasonic sensor 101.

  The ultrasonic sensor 101 includes a bottomed cylindrical case 31 made of aluminum having a disk-like bottom portion 31b and a cylindrical side wall portion 31a, a piezoelectric element 32 attached to the inner bottom surface of the case 31, a reinforcing material ( A weight) 37, a terminal 43, a terminal holding member 41 for holding the terminal 43, and the like. The terminal 43 and the piezoelectric element 32 are electrically connected by a wiring material (conductive member) not shown in FIG. The wiring material (conductive member) is, for example, a lead wire or a flexible substrate. The piezoelectric element 32 has a flat plate shape and spreads and vibrates in the in-plane direction when a driving voltage is applied. The piezoelectric element 32 is joined to the bottom 31 b of the case 31. The piezoelectric element 32 is made of, for example, piezoelectric ceramics, and includes a disk-shaped piezoelectric substrate and electrodes provided on main surfaces of the piezoelectric substrate facing each other.

  As shown in FIG. 2, the case 31 has a bottomed cylindrical shape that is closed on the bottom 31 b side and opened on the opposite side to the bottom 31 b side, and the opening of the case 31 is circular in plan view. The side wall 31a of the case 31 includes a thin portion 31t on the opening side and a thick portion 31h on the bottom side. A step portion 31ST is formed on the side wall portion 31a of the case 31.

  The reinforcing member (weight) 37 is a ring-shaped member having an opening 37h at the center, and is disposed on the thick portion 31h of the case 31 and at a position not in contact with the inner peripheral surface of the thin portion 31t of the side wall portion 31a. ing. The reinforcing member 37 may be a member having high acoustic impedance and functioning as a weight. For this reason, the reinforcing member 37 may be made of the same material as the case 31 by adjusting the size such as thickness, that is, made of aluminum. However, the reinforcing member 37 is made of a material constituting the case 31 such as stainless steel or zinc. It is preferable that the material is made of a material having high density and high rigidity.

  As shown in FIG. 2, the region surrounded by the step portion 31ST in the bottom 31b is the main vibration region. The main vibration region of the case 31 is rectangular in plan view, and since the y-axis direction is long, the y-axis direction is the long axis and the x-axis direction is short, so the x-axis direction is the short axis. Thus, since the main vibration region has an anisotropic shape, anisotropy occurs in the directivity of ultrasonic waves. That is, the directivity angle in the major axis direction (y-axis direction) is narrow, and the directivity angle in the minor axis direction (x-axis direction) is wide.

  A flat sound absorbing material 38 is provided on the piezoelectric element 32. The sound absorbing material 38 is disposed in a space surrounded by the step portion 31ST inside the case 31. The sound absorbing material 38 is made of, for example, polyester felt or porous silicone, and absorbs unnecessary ultrasonic waves emitted from the piezoelectric element 32 to the opening side of the case 31. A buffer member 33 made of an elastic material such as silicone rubber or urethane rubber is provided between the reinforcing material 37 and the sound absorbing material 38 and the terminal holding member 41. The buffer member 33 holds the terminal holding member 41 in the case 31. A damping member 39, which is a cylindrical member made of an elastic body such as urethane rubber or silicone rubber and having an opening at the center, is provided along the inner peripheral surface of the side wall portion 31a of the case 31. A gap (air layer) 40 is formed between the damping member 39 and the buffer member 33. Specifically, the buffer member 33 has a flange-shaped (collar-shaped) portion that comes into contact with the damping member 39, and the flange-shaped (collar-shaped) portion is provided between the damping member 39 and the buffer member 33. A gap (air layer) 40 is formed.

  Inside the case 31, the space above the damping member 39 and the buffer member 33 is filled with a filling member 36 made of an elastic material such as silicone rubber or urethane rubber. The same material can be used for the filling member 36 and the damping member 39.

  The case 31 is formed by forging, for example. The buffer material 33 is a cup-shaped member, and has a bottom portion having an engaging portion 33e that engages with the opening 37h of the reinforcing material 37, and a cylindrical side wall portion. By providing the buffer material 33, it is possible to suppress the vibration at the bottom 31 b of the case 31 from being transmitted to the terminal holding material 41.

  The terminal holding member 41 is made of a resin such as polybutylene terephthalate (PBT) and holds two pin-shaped terminals 43. The terminal holding member 41 has a flange-like engaging portion (hereinafter referred to as “flange portion”) 41 f that engages with the inner surface of the cylindrical side wall portion of the buffer member 33. The upper surface 41 s of the flange portion 41 f of the terminal holding member 41 is covered with the filling member 36.

  Thus, since the damping member 39 in contact with the inner peripheral surface of the side wall portion 31 a of the case 31 is provided, the vibration of the side wall portion 31 a of the case 31 is attenuated by the damping member 39. Since the gap (air layer) 40 is formed between the damping member 39 and the buffer member 33, the vibration of the side wall portion 31 a of the case 31 is difficult to propagate to the buffer member 33 through the damping member 39. That is, vibration hardly propagates along the path of the buffer member 33 → the terminal holding member 41 → the terminal 43, and vibration leakage is effectively suppressed. In addition, vibration propagating from the case 31 via a portion other than the gap (air layer) 40 is attenuated in the filling member 36 and hardly propagates to the terminal 43 via the terminal holding member 41.

  With the above action, vibration leakage that occurs when the ultrasonic sensor 101 is mounted on an external circuit board can be greatly reduced.

  Further, since the upper surface 41 s of the flange portion 41 f of the terminal holding member 41 is covered with the filling member 36, it is possible to prevent the terminal holding member 41 from being detached from the case 31.

  The buffer member 33 is difficult to propagate vibration, and the damping member 39 and the filling member 36 suppress (dampen) vibration of the side wall 31a of the case 31. That is, the damping member 39 and the filling member 36 preferably have a higher elastic modulus than the buffer member 33. More specifically, the elastic modulus includes a storage elastic modulus and a loss elastic modulus. It is preferable that the damping member 39 and the filling member 36 have a large loss elastic modulus, and that the buffer member 33 has a low storage elastic modulus.

  FIG. 3A is a diagram illustrating the reverberation characteristics of the ultrasonic sensor 101 according to the first embodiment, and FIG. 3B is a diagram illustrating the reverberation characteristics of an ultrasonic sensor as a comparative example. The ultrasonic sensor of this comparative example does not have the gap 40 shown in FIG. 1, and the buffer member 33 is expanded in that portion, and the ultrasonic sensor according to the first embodiment except that the gap 40 is not provided. The configuration is the same as that of the ultrasonic sensor 101. In both FIG. 3A and FIG. 3B, the horizontal axis is 500 μs / div, and the vertical axis is 1 V / div. In both cases, the terminal 43 is fixed to an external circuit board by soldering, 8 burst waves are transmitted at a transmission time of 0.13 ms, and the voltage waveform appearing on the piezoelectric element is amplified and observed. Actually, the attenuation of the amplitude starts immediately after the end of transmission, but since the dynamic range of the amplifier circuit is exceeded for a while, the waveform is saturated during that time.

  As is clear from the comparison between FIG. 3A and FIG. 3B, in the ultrasonic sensor 101 according to the first embodiment, the amplitude converges quickly, vibration leakage is suppressed, and the reverberation time is reduced. Is short.

  FIG. 4 is a diagram showing the relationship between the gap 40 between the damping member 39 and the buffer member 33 and the vibration leakage time. Here, the “vibration leakage time” is a state in which the normal reverberation time in a state where the terminal 43 is fixed to the external circuit board by soldering and the vibration leaking to the terminal 43 is sandwiched between silicone rubbers to suppress the vibration leakage. The reverberation time is defined as the amount of fluctuation of the reverberation. When the gap 40 is not provided, that is, in the case of the comparative example, the fluctuation of the vibration leakage time is large. By providing the gap 40, the vibration leakage time becomes very small and the fluctuation is also reduced. From this result, it can be seen that by providing a gap exceeding 0 mm, the vibration leakage time can be suppressed to a usable level of less than 0.1 ms.

  In addition, according to 1st Embodiment, since the opening part of case 31 is sealed with the terminal holding member 41 and the filling member 36, water penetrate | invades inside the case 31 and a sensitivity falls. There is no problem that corrosion occurs between different metals.

  A manufacturing method for providing the gap 40 in the ultrasonic sensor 101 described above will be described with reference to FIG.

  FIG. 5 is a diagram illustrating a process of forming the damping member 39 and the gap 40. First, as shown in FIG. 5A, the piezoelectric element 32 is joined in the case 31, the reinforcing member 37 is attached, the sound absorbing member 38 is disposed on the piezoelectric element 32, and the molding piece 51 is mounted. The molding piece 51 is disposed so as to have a gap having the same shape as the damping member 39 between the case 31 and the side wall portion 31a of the case 31. Next, as shown in FIG. 5 (B), the weather resin 39P is applied to a part of the gap between the molding piece 51 and the side wall 31a of the case 31 and cured. The weather resin 39P is made of the same material as that of the damping member 39 and later becomes a part of the damping member 39. Next, as shown in FIG. 5C, the resin for the damping member 39 is applied (filled) into the gap between the molding piece 51 and the side wall 31a of the case 31 and cured. Thereafter, the molding piece 51 is removed as shown in FIG. 5D, and the buffer member 33 is mounted as shown in FIG.

  Through the above steps, the gap 40 is provided between the damping member 39 and the buffer member 33.

<< Second Embodiment >>
FIG. 6 is a cross-sectional view of the ultrasonic sensor 102 according to the second embodiment. The structure of the ultrasonic sensor 102 is the same as that of the ultrasonic sensor 101 shown in the first embodiment. However, the filling member 36 is made of a material different from that of the damping member 39. In the ultrasonic sensor 102 of the second embodiment, the elastic modulus of the filling member 36 is smaller than the elastic modulus of the damping member 39.

  For example, the damping member 39 is made of urethane rubber, and the filling member 36 is made of silicone rubber. Further, if the elastic modulus of the filling member 36 is different from that of the damping member 39, both may be urethane rubber. The damping member 39 is an elastic material having a high damping property with respect to the side wall portion 31 a of the case 31, and the filling member 36 may be an elastic material that hardly propagates the vibration of the side wall portion 31 a to the terminal holding member 41.

<< Third Embodiment >>
FIG. 7 is a cross-sectional view of the ultrasonic sensor 103 according to the third embodiment. The ultrasonic sensor 103 includes a closing member 34 that closes a boundary portion between the gap 40 and the filling member 36. Other configurations are the same as those of the ultrasonic sensor 101 shown in the first embodiment.

  The closing member 34 can be provided by applying a resin having a high thixotropic property so as not to enter the gap 40 with a dispenser.

  In this way, the closing member 34 closes (stices) the boundary portion (opening portion of the air layer) between the gap 40 and the filling member 36, thereby preventing the filling resin from flowing into the gap 40 during filling of the filling member 36. The

  Further, by using the closing member 34 in this way, it is not necessary to form a flange-shaped (collar-shaped) portion that contacts the damping member 39 on the buffer member 33, so that the shape of the buffer member 33 can be simplified.

<< Fourth Embodiment >>
FIG. 8 is a cross-sectional view of the ultrasonic sensor 104 according to the fourth embodiment. In the ultrasonic sensor 104, the opening of the gap 40 between the damping member 39 and the buffer member 33 is closed with the filling member 36. Other configurations are the same as those of the ultrasonic sensor 101 shown in the first embodiment.

  For the filling member 36, a resin material having a high thixotropic property is used so that the resin does not flow into the gap 40 during filling.

31 ... Case 31a ... Side wall part 31b ... Bottom part 31h ... Thick part 31ST ... Step part 31t ... Thin part 32 ... Piezoelectric element 33 ... Buffer member 33e ... Engagement part 34 ... Closure member 36 ... Filling member 37 ... Reinforcing member 37h ... Opening 38 ... Sound absorbing member 39 ... Damping member 40 ... Gap 41 ... Terminal holding member 41f ... Flange portion 41s ... Upper surface 43 ... Terminal 51 ... Molding pieces 101-104 ... Ultrasonic sensor

(1) The ultrasonic sensor of the present invention
A bottomed cylindrical case having a bottom and a side wall; and
A piezoelectric element provided on the inner bottom surface of the case;
A terminal that is electrically connected to the piezoelectric element via a conducting member in the case and protrudes to the outside of the case;
A terminal holding member for holding the terminal;
A buffer member for holding the terminal holding member in the case;
A damping member provided along the inner peripheral surface of the side wall of the case;
A filling member filled in the upper part of the damping member and the buffer member in the case,
A gap (air layer) is provided between the damping member and the buffer member ,
The elastic modulus of the damping member is higher than the elastic modulus of the buffer member .

Claims (6)

A bottomed cylindrical case having a bottom and a side wall; and
A piezoelectric element provided on the inner bottom surface of the case;
A terminal that is electrically connected to the piezoelectric element via a conducting member in the case and protrudes to the outside of the case;
A terminal holding member for holding the terminal;
A buffer member for holding the terminal holding member in the case;
A damping member provided along the inner peripheral surface of the side wall of the case;
A filling member filled in the upper part of the damping member and the buffer member in the case,
An ultrasonic sensor, wherein a gap is provided between the damping member and the buffer member.   The ultrasonic sensor according to claim 1, wherein the filling member has a smaller elastic modulus than the damping member.   The ultrasonic sensor according to claim 1, further comprising a closing member that closes a boundary portion between the gap and the filling member. The side wall portion of the case includes a thin portion on the opening side and a thick portion on the bottom side,
The ultrasonic sensor according to claim 1, wherein a reinforcing material having an acoustic impedance higher than that of the case is provided on the thick portion.   The ultrasonic sensor according to claim 1, wherein a sound absorbing member is provided between the piezoelectric element and the buffer member. It is a manufacturing method of the ultrasonic sensor in any one of Claims 1-5,
Inserting an annular molded piece having a larger outer diameter than the buffer member into the case;
Filling the periphery of the molding piece in the case with the elastic resin for forming the damping member;
Removing the molding piece from the case, and mounting the buffer member in the case.

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