JP3879264B2 - Ultrasonic sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic sensor. In particular, the present invention relates to an ultrasonic sensor used for automobile back sonar and corner sonar.
[0002]
[Prior art]
The ultrasonic sensor performs sensing using ultrasonic waves, intermittently transmits ultrasonic pulse signals from the piezoelectric vibration element, and receives reflected waves from obstacles existing in the vicinity by the piezoelectric vibration element. Thus, an object is detected. However, in such an ultrasonic sensor, the capacitance of the piezoelectric vibration element greatly fluctuates with respect to the temperature change, and the resonance characteristics change greatly. The temperature drift of an ultrasonic sensor will become large. Therefore, it is attempted to reduce temperature drift by incorporating a temperature compensation capacitor in the ultrasonic sensor.
[0003]
A structure of a known ultrasonic sensor incorporating a single-plate capacitor for temperature compensation is shown in a sectional view of FIG. 7 (Japanese Patent Laid-Open No. 8-237796). In this ultrasonic sensor 51, a thin portion 52a is positioned on the front surface of a bottomed cylindrical metal case 52, and the piezoelectric vibration element 53 is fixed in close contact with the inner surface of the thin portion 52a. One electrode formed on the vibration surface of the element 53 is electrically connected to the thin portion 52a. The ends of the two signal input / output signal lines 54 and 54 are connected to the external electrodes of the single plate capacitor 55 for temperature compensation, and both the external electrodes of the single plate capacitor 55 and the piezoelectric vibration element 53 are connected. The other electrode and the metal case are also connected by signal lines 56 and 56, respectively. With the piezoelectric vibration element 53 and the single plate capacitor 55 connected to the signal lines 54 and 56 thus housed in the metal case 52, the sound absorbing material 57 such as felt, silicon rubber, urethane rubber, etc. The inside of the metal case 52 is sealed by being filled with an insulating resin 58 having the above elasticity. Accordingly, the piezoelectric vibration element 53 is disposed in a space surrounded by the metal case 52 (thin wall portion 52a) and the sound absorbing material 57, and the single plate capacitor 55 is sealed in the insulating resin 58, so that the ultrasonic sensor 51 having an integral structure is provided. Is assembled.
[0004]
A temperature compensation capacitor is built in to reduce temperature drift by itself, and a drip-proof structure is formed by sealing with an insulating member.
[0005]
[Problems to be solved by the invention]
However, the ultrasonic sensor having the above structure has the following problems.
(1) In order to increase the sensitivity output without hindering the vibration of the piezoelectric vibration element, the signal line connected to the piezoelectric vibration element and the single plate capacitor and drawn to the outside of the ultrasonic sensor is particularly thin and soft. It is desirable in terms of sensitivity characteristics to adopt one. However, it is very difficult to electrically connect this thin and soft signal line to a piezoelectric vibration element or a single plate capacitor in a narrow space of a metal case by soldering or the like, and the manufacturing efficiency of the ultrasonic sensor is poor. As a result, it is necessary to check the connection between the signal line and the piezoelectric vibration element or the single plate capacitor, which causes a problem that the process becomes complicated.
[0006]
(2) In addition, the single plate capacitor is in a floating state in the metal case until it is filled with the insulating resin. After connecting the signal line, the insulating resin is injected into the metal case. At this time, the injection pressure may cause the single plate capacitor to be disconnected from the signal line and impair conduction.
[0007]
(3) Even if the single plate capacitor does not come off the signal line during the injection of the insulating resin, the following problems occur in the manufacturing process.
The ultrasonic sensor intermittently creates and amplifies an ultrasonic pulse signal, transmits the ultrasonic pulse signal, receives the reflected wave from the obstacle, and amplifies it. Then, the presence of an obstacle is detected from the received pulse, or the distance to the obstacle is calculated from the elapsed time from transmission of the ultrasonic pulse signal to reception. Therefore, in order to enable detection at a short distance, it is necessary to quickly converge the reverberant wave generated in the ultrasonic sensor after receiving the ultrasonic pulse signal before receiving the received wave. However, if the signal lines connected to the piezoelectric vibration element cross each other or if the signal line sealed with insulating resin has residual tension, the leakage of vibration to the output side increases, and the ultrasonic sensor The reverberation characteristics of are degraded.
[0008]
In addition, when tension is applied to the signal line from the outside, the tension is transmitted to the inside of the ultrasonic sensor so that the signal line is not detached from the single plate capacitor or the piezoelectric vibration element and the ultrasonic sensor is not destroyed. The tension applied to the signal line must be internally dispersed by the insulating resin, and for this purpose, the signal line must be pulled out from the center of the insulating resin.
[0009]
For this purpose, in the manufacturing process of the ultrasonic sensor, even after injecting the insulating resin into the case body, the signal lines do not cross or the tension does not remain on the signal lines. It is necessary to cure the insulating resin while keeping the wire in a fixed position (in particular, so that the signal wire is drawn from the center of the case body).
[0010]
However, before the insulating resin is cured, there is only a signal line as a means for supporting the single plate capacitor. Therefore, the insulating resin is cured by holding the single plate capacitor suspended by the signal line. There is no choice but to wait for the signal line to be tensioned, and the position of the single-plate capacitor and the signal line is easy to move and unstable. As a result, it is difficult to assemble the ultrasonic sensor, and there are problems in terms of quality characteristics and reliability.
[0011]
(4) Moreover, in the ultrasonic sensor of this structure, the single plate capacitor has a function as a relay terminal for obtaining electrical continuity between the signal line and the signal line. It is necessary to use a single-plate capacitor with an external electrode of the area, and it is not possible to sufficiently cope with the miniaturization of the entire ultrasonic sensor, making it difficult to completely store the single-plate capacitor in a metal case, It was difficult to completely cover the electrode with an insulating resin.
[0012]
The present invention has been made in view of the drawbacks of the conventional examples described above, and an object of the present invention is to facilitate the manufacture of an ultrasonic sensor and improve its characteristics and reliability.
[0013]
DISCLOSURE OF THE INVENTION
Ultrasonic sensor according to the present invention, a metal plate provided on the front opening of the case body having a substantially cylindrical shape made of an insulating material, is bonded to the piezoelectric vibrating element on the inner surface of the metal plate, integrally formed on the case body each is electrically connected to the electrodes of the piezoelectric vibrating element a pair of conductive member that, a portion of each of the conductive members at the rear end of the case body is exposed on the rear end surface of the case body, wherein each of the conductive members A signal line is taken out from the exposed portion, and a capacitor is mounted so as to straddle between the ends of the conductive members exposed from the case body .
[0014]
In the ultrasonic sensor of the present invention, a part of each conductive member is exposed on the rear end surface of the case main body at the rear end of the case main body, and the end of each conductive member exposed from the case main body. Since the capacitors are mounted so as to straddle the space, it is possible to easily mount the temperature compensation capacitor automatically. The signal line can also be easily connected by connecting to the exposed portion of the conductive member. Accordingly, the ultrasonic sensor can be easily manufactured and the manufacturing efficiency can be improved.
[0015]
In addition, since the capacitor and signal line are connected to a conductive member formed integrally with the case body, it can be securely attached, and a resin is injected into the case body to seal part of the capacitor and signal line. Even in this case, there is almost no possibility that the capacitor and the signal line are detached from the conductive member. Therefore, the defective product rate of an ultrasonic sensor can be reduced and reliability can be improved.
[0016]
In addition, even when resin is injected into the case body, the resin can be cured in a state where no tension is applied to the signal line and the capacitor and the signal line are held at a fixed position, so that the signal line is generated. Residual stress can be suppressed and reverberation characteristics can be stabilized. Furthermore, even when tension is applied to the signal line from the outside, it is possible to effectively disperse the tension and prevent the ultrasonic sensor from being destroyed. Therefore, variation in reverberation characteristics can be reduced, connection reliability can be improved, and characteristics and reliability of the ultrasonic sensor can be improved.
[0017]
Furthermore, since the signal line is not connected to the capacitor but is connected to a conductive member formed integrally with the case body, a small capacitor can be used, which contributes to miniaturization of the ultrasonic sensor.
[0018]
The exposed portion, in certain embodiments of the present invention, the extended along the rear end surface of the case body, wherein the capacitor is mounted so as to bridge between the ends of the exposed portion on the rear end surface of the case ing.
Further, in another embodiment of the present invention, in the case body is filled with insulating resin, a portion of the signal line is embedded in the insulating resin. According to this embodiment, even if a tensile force is applied to the signal line, the signal line is unlikely to be detached from the conductive member. Therefore, when the user performs the installation work of the ultrasonic sensor, the ultrasonic sensor becomes difficult to break due to the tensile force applied to the signal line, and the workability is improved.
Further, in yet another embodiment of the present invention, the forming a concave portion on the rear end face of the case body, the electrodes of the capacitor pay a capacitor within this recess from the case body in the recess exposed by conducting the end of each conductive member, and sealing the capacitor with an insulating resin. According to such an embodiment, by sealing the inside of the concave portion with an insulating resin, the solder connection portion of the capacitor can be easily covered, and the reliability of the connection portion can be further increased.
Further, in still another embodiment of the present invention, an annular recess is formed on the rear end surface of the case main body, and the capacitor is accommodated in the recess. The capacitor is encapsulated with an insulating resin by conducting to the end of each conductive member. According to such an embodiment, by sealing the inside of the annular recess with the insulating resin, the solder connection portion of the capacitor can be easily covered, and the reliability of the connection portion can be further increased.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
1A and 1B are a plan view and a cross-sectional view showing the structure of an ultrasonic sensor 1 according to an embodiment of the present invention, and FIG. 2 is an exploded cross-sectional view of the sensor case 2 described above. The structure of the ultrasonic sensor 1 will be described with reference to the assembly procedure. The sensor case 2 for housing the piezoelectric vibration element 5 has a bottomed cylindrical shape, and the sensor case 2 is a substantially cylindrical case made of an insulating resin, for example, engineering plastic such as polyphenylene sulfide (PPS) or liquid crystal polymer. A main body 3 and a disk-shaped metal plate (vibrating plate) 4 such as aluminum are formed. As shown in FIG. 2, an annular recess 6 is provided in the inner periphery of the front end opening of the case body 3, and the metal plate 4 that generates vibration and receives reflected waves in the recess 6. Are fitted to form a bottomed cylindrical sensor case 2. In the case main body 3, conductive members 7, 8 made of a metal material such as white or 42 nickel are partially inserted (that is, the tip-side halves 7 a, 8 a). Is exposed in the recess 6, and the tip of the other conductive member 7 protrudes from the inner peripheral surface of the case body 3 toward the end surface opening. By using a metal material such as white or 42 nickel as the conductive members 7 and 8, the strength of the conductive member is improved, and the risk of disconnection as in the case of using a soft signal line is reduced. In addition, electrode pads 9 and 9 for connecting signal lines are provided at the center of both conductive members 7 and 8, and the two electrode pads 9 and 9 are on the opposite side on the rear end face of the case body 3. It arrange | positions so that it may mutually oppose. Furthermore, from the two electrode pads 9 and 9 exposed at the rear end surface of the case body 3, the base end side halves 7 b and 8 b of the conductive members 7 and 8 have an arc shape along the rear end surface of the case body 3. It extends, and the front-end | tips of both base end side half parts 7b and 8b oppose each other with a small space | interval.
[0020]
The piezoelectric vibration element 5 has electrodes 10a and 10b formed on both main surfaces, and one electrode 10a of the piezoelectric vibration element 5 is joined to the central portion of the inner surface of the metal plate 4 by a conductive adhesive. After the case body 3 is integrally formed with the conductive members 7 and 8 and the piezoelectric vibration element 5 is integrated with the metal plate 4 in this way, the outer peripheral portion of the metal plate 4 to which the piezoelectric vibration element 5 is bonded is connected to the case body 3. The sensor case 2 is assembled and the piezoelectric vibration element 5 is accommodated in the sensor case 2. Next, the tip of one conductive member 7 is soldered to the electrode 10 b of the piezoelectric vibration element 5. Since the tip of the other conductive member 8 is in pressure contact with the metal plate 4 and is conducted to the metal plate 4 (the tip of the conductive member 8 and the metal plate 4 may be joined with a conductive adhesive or the like) The conductive members 7 and 8 are electrically connected to both surfaces of the piezoelectric vibration element 5.
[0021]
The chip capacitor 11 is placed between the base ends of the conductive members 7 and 8, and the electrodes 12 and 12 of the chip capacitor 11 are soldered to the base ends of the respective conductive members 7 and 8 to attach the chip capacitor 11 to the case body. 3 is mounted on the rear end face. Next, the ends of the signal lines 13 and 13 are soldered to the electrode pads 9 and 9. Thus, the piezoelectric vibration element 5 is applied with a voltage and takes out a received signal through the signal lines 13 and 13 and the conductive members 7 and 8. Further, the temperature compensating chip capacitor 11 is connected in parallel with the piezoelectric vibration element 5.
[0022]
When mounting and connection of each component is completed in this manner, a sound absorbing material 14 such as felt is put in the case body 3 to cover the vicinity of the piezoelectric vibration element 5 with the sound absorbing material 14, and silicon is placed in the case body 3 after the sound absorbing material 14. An insulating resin 15 having elasticity such as rubber or urethane rubber is filled and cured. As this insulating resin 15, a synthetic resin foam may be used. The chip capacitor 11 may be covered with an insulating resin 15 and sealed.
[0023]
Further, when the insulating resin 15 is filled in the case body 3, if part of the signal lines 13, 13 is embedded in the insulating resin 15, the signal lines 13, 13 can be signaled even if a tensile force is applied. The lines 13 and 13 can be hardly detached from the electrode pads 9 and 9. Thereby, when a user attaches the ultrasonic sensor 1, the ultrasonic sensor 1 becomes difficult to break due to the tensile force applied to the signal lines 13, 13, and the workability is improved. Furthermore, since the vibration transmitted through the conductive members 7 and 8 is alleviated by the insulating resin 15, the reverberation characteristics are improved.
[0024]
In the ultrasonic sensor 1, an alternating voltage is applied to the piezoelectric vibration element 5 via the conductive members 7 and 8 and the metal plate 4 to vibrate the metal plate 4 to generate sound waves. On the contrary, the distortion generated by the deformation of the metal plate 4 by the received reflected sound wave is converted into an electric signal by the piezoelectric vibration element 5, and the signal is taken out through the conductive member 7 and the like to detect an obstacle or the like.
[0025]
In the ultrasonic sensor 1 having such a structure, the conductive members 7 and 8 are disposed on the end surface of the case body 3, and the chip capacitor 11 is mounted between the conductive members 7 and 8 on the end surface of the case body 3. As a result, the chip capacitor 11 can be stably mounted. Further, since the conductive members 7 and 8 are positioned by being embedded or implanted in the case body 3, the wiring path is fixed, and the mounting accuracy of the chip capacitor 11 is also improved. Therefore, the chip capacitor 11 can be automatically mounted by an existing chip component mounting machine, and the manufacture becomes easy. Further, the ultrasonic sensor 1 can be downsized by using the chip capacitor 11 as the temperature compensating capacitor.
[0026]
Further, since the conductive members 7 and 8 are embedded or implanted in the case body 3, the signal transmission path is fixed, and the signal transmission paths (conductive members 7 and 8) intersect or have residual tension. The reverberation characteristics of the ultrasonic sensor are stabilized.
[0027]
(Second Embodiment)
3A and 3B are a plan view and a cross-sectional view showing an ultrasonic sensor 21 according to still another embodiment of the present invention, and FIG. 4 is a partially broken cross-sectional view of the case main body 3 (an outer peripheral surface of the case main body 3). FIG. In this embodiment, the inner peripheral surface of the base end portion of the case main body 3 is partially cut away, and a recess 22 having a size capable of accommodating the chip capacitor 11 is provided. Further, the base end side (base end side half portions 7b and 8b) of the conductive members 7 and 8 from the electrode pads 9 and 9 are also inserted into the case body 3, and the base end side half portions of the conductive members 7 and 8 are inserted. The tips of 7b and 8b are exposed in the recess 22, and the tips are opposed to each other with a gap.
[0028]
Thus, after attaching the metal plate 4 to which the piezoelectric vibration element 5 is bonded to the case body 3 and placing the piezoelectric vibration element 5 in the sensor case 2, the chip capacitor 11 is placed in the recess 22 and the conductive members 7 and 8. The electrodes 12 and 12 of the chip capacitor 11 are soldered to the tips of the conductive members 7 and 8. Further, after soldering the ends of the signal lines 13 and 13 to the electrode pads 9 and 9 and putting the sound absorbing material 14 in the case body 3, the insulating resin 15 is filled to the rear end surface of the case body 3. The inside of the chip capacitor 11 is filled with the insulating resin 15 and the whole chip capacitor 11 is sealed in the insulating resin 15, so that the moisture resistance of the connection portion of the chip capacitor 11 is improved.
[0029]
Sealing the soldered connection portion of the chip capacitor 11 with the insulating resin 15 is effective in improving the moisture resistance. In this embodiment, since the chip capacitor 11 is mounted in the recess 22 provided in the case body 3, the insulating resin 15 is leaked out of the sensor case 2 by filling the recess 22 with the insulating resin 15. Therefore, the chip capacitor 11 can be easily sealed with the insulating resin 15. Therefore, simultaneously with the filling of the insulating resin 15 into the case main body 3, it becomes possible to cover the electrodes of the chip capacitor 11 for temperature compensation, and the reliability such as moisture resistance can be easily improved.
[0030]
(Third embodiment)
5A and 5B are a plan view and a cross-sectional view showing an ultrasonic sensor 31 according to still another embodiment of the present invention, and FIG. 6 shows a case main body in which the sound absorbing material 14 and the insulating resin 15 in the ultrasonic sensor 31 are attached. 3 is a plan view showing a state before entering 3. In this embodiment, the annular recess 23 is formed by cutting out the inner peripheral surface of the base end portion of the case body 3 over the entire circumference. The electrode pads 9 and 9 of the conductive members 7 and 8 inserted in the case body 3 are exposed to the bottom surface of the recess 23, and the base-end-side halves 7b and 8b of the conductive pads are It extends along the bottom surface of the recess 23, and the tips of the base-end-side halves 7 b and 8 b are opposed to each other on the bottom surface of the recess 23. Also in this embodiment, the chip capacitor 11 mounted between the conductive members 7 and 8 is housed in the recess 23 and is entirely sealed in the insulating resin 15. Further, this conductive member is also sealed in the insulating resin 15 and is not exposed.
[0031]
Thus, even if the recess 23 is provided on the entire circumference of the case body 3, as in the second embodiment,
Simultaneously with the filling of the insulating resin 15 into the case body 3, the electrode of the temperature compensating chip capacitor 11 can be covered, and the reliability such as the moisture resistance can be easily improved. Moreover, in this embodiment, since the connection part of the electrically-conductive members 7 and 8 and the signal lines 13 and 13 is also embedded in the insulating resin 15, the connection reliability of the signal lines 13 and 13 is also improved.
[Brief description of the drawings]
1A and 1B are a plan view and a cross-sectional view showing the structure of an ultrasonic sensor according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a case main body and a metal plate of the above ultrasonic sensor.
FIGS. 3A and 3B are a plan view and a cross-sectional view showing the structure of an ultrasonic sensor according to another embodiment of the present invention. FIGS.
FIG. 4 is a partially cutaway cross-sectional view of the case main body of the above ultrasonic sensor.
5A and 5B are a plan view and a cross-sectional view showing the structure of an ultrasonic sensor according to still another embodiment of the present invention.
FIG. 6 is a plan view showing a state before the sound absorbing material and the insulating resin of the ultrasonic sensor are placed.
FIG. 7 is a cross-sectional view showing the structure of a conventional ultrasonic sensor.
[Explanation of symbols]
3 Case body 4 Metal plate 5 Piezoelectric vibration elements 7 and 8 Conductive member 11 Chip capacitor 13 Signal lines 22 and 23 Recess

Claims (5)

Wherein the metal plate is provided on the front opening of the case body having a substantially cylindrical shape made of an insulating material, it is bonded to the piezoelectric vibrating element on the inner surface of the metal plate, a pair of conductive member which is integrally formed on the case body, respectively Conducting to each electrode of the piezoelectric vibration element, exposing a part of each conductive member on the rear end surface of the case body at the rear end portion of the case body, and taking out a signal line from the exposed portion of each conductive member, An ultrasonic sensor , wherein a capacitor is mounted so as to straddle between end portions of the respective conductive members exposed from the case body . The exposed portion extends along a rear end surface of the case body, and the capacitor is mounted on the rear end surface of the case so as to straddle between the end portions of the exposed portion. Item 6. The ultrasonic sensor according to Item 1. Wherein the case body is filled with an insulating resin, wherein a portion of the signal line is embedded in the insulating resin, the ultrasonic sensor according to claim 1 or 2. A recess is formed in a part of the rear end surface of the case body, the capacitor is placed in the recess, and each electrode of the capacitor is conducted to the end of each conductive member exposed from the case body in the recess , characterized in that seals the capacitor with an insulating resin, ultrasonic sensor according to claim 1 or 3. An annular recess is formed on the rear end surface of the case body, and the capacitor is placed in the recess so that each electrode of the capacitor is electrically connected to the end of each conductive member. The ultrasonic sensor according to claim 1, wherein the capacitor is sealed by the step.

Images