JPH0518320B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to an ultrasonic transducer using bonded piezoelectric elements, and particularly relates to an ultrasonic transducer with improved fall characteristics during transmission. .

Conventional configurations and their problems Various types of ultrasonic transducers using bonded piezoelectric elements have been put into practical use or proposed, such as the structure shown in Figure 1. is extremely common.

In the ultrasonic transducer shown in FIG. 1, a conical diaphragm 2 is attached to the center of a bonded piezoelectric element 1 via an elastic adhesive 3, and the vibration nodes of the piezoelectric element 1 are It is fixed to the end of the support base 4 with an elastic adhesive 5. In addition, in Figure 1, 6
7 is a terminal, 7 is a case that covers the piezoelectric element 1, etc., 8 is a protective member provided in the upper hole of the case 7, and 9 is a lead wire that electrically connects the piezoelectric element 1 and the terminal 6.

However, it is known that the conventional ultrasonic transducer as described above has extremely poor vibration especially falling characteristics during ultrasonic transmission.

Now, a circuit as shown in FIG. 2 is constructed using the ultrasonic transducer as shown in FIG. 11, transformer 12, ultrasonic transducer 13 shown in FIG. 1, resistor 14,
Protection diodes 15, 16, coupling capacitor 1
7. A circuit consisting of a signal amplifier 18 and an output end 19 is configured, and the output end 19 when a pulse signal of a predetermined frequency is supplied to the input terminal 10 for 300 μsec
When we measured the output signal, we obtained an output waveform as shown in Figure 3. For convenience of drawing, the output waveform shown in FIG. 3 is a so-called envelope waveform that connects only the peaks of the vibration signal waveform originally output to the output terminal 19. The waveforms shown or explained as output waveforms of the signals outputted to the terminal 19 are all the above-mentioned envelope waveforms.

As is clear from Figure 3, by supplying an input signal for 300 μsec, the damped vibration at the time of falling continues for about 11 msec, and as a result, the ultrasonic transducer shown in Figure 1 cannot be used, for example, in a distance measuring device that measures the distance to a desired object by transmitting and receiving ultrasonic waves.

In other words, if the object whose distance you want to measure is relatively close (within 1 meter), even if you receive the reflected wave from the object due to ultrasonic transmission, the received signal will continue for about 11 msec as mentioned above. It is conceivable that it will be buried in the damped vibration waveform and cannot be detected.

For this reason, in recent years, the above-mentioned piezoelectric elements have been used in JP-A-57-97798, JP-A-57-97799, JP-A-57-97800, and JP-A-58-85698. Ultrasonic transducers with improved falling characteristics during transmission have been proposed or partially put into practical use.

To briefly explain the gist of each of the above proposals,
In both cases, the cause of the damped vibration explained in FIG. 3 is the piezoelectric element 1 or the diaphragm 2 in FIG.
In order to restrict the free vibration of the piezoelectric element 1 or the diaphragm 2, that is, to make it difficult to vibrate, the piezoelectric element 1 or the diaphragm 2 are elastically fixed to the case 7 via a cushioning material, or the diaphragm 2 is It is characterized by providing a cushioning material only in the periphery.

FIGS. 4A to 4D illustrate the structure of the embodiment shown in each of the above-mentioned publications, and the above gist becomes clearer from these figures. In addition, in the figure, the first
Components with the same numbers as those shown in the drawings indicate the same functional members, 3' is a coupling shaft, and 20 is a cushioning material.

In the ultrasonic transducer _disclosed in Japanese Patent Application Laid-Open No. 57-97798 shown in FIG. Fixed to the diaphragm 2, the diaphragm 2
is elastically fixed to the case 7 via a cushioning material 20.

The ultrasonic transducer disclosed in Japanese Patent Application Laid-Open No. 57-97799 shown in FIG. , the diaphragm 2 and the piezoelectric element 1 are elastically fixed to the case 7.

In the ultrasonic transducer disclosed in Japanese Unexamined Patent Publication No. 57-97800 shown in FIG.

In the ultrasonic transducer disclosed in Japanese Unexamined Patent Publication No. 58-85698 shown in FIG. 4D, a buffer material 20 is provided around the diaphragm 2.

However, even with the above-mentioned ultrasonic transducer, when it is desired to measure the distance to an object at a very close distance, it is still necessary to consider the influence of the falling characteristic. Due to the falling characteristic, the limit on the short distance side that can be measured is limited to several tens of centimeters, and it has been impossible to accurately measure this distance for objects located at a distance of 20 to 30 centimeters.

By the way, when any one of the ultrasonic transducers shown in FIG. 4A is replaced with the ultrasonic transducer 13 having the circuit configuration shown in FIG. 2, the result is as follows.
At the output end 19, an output signal having a characteristic output waveform partially including a saturated region as shown in FIG. 5 was obtained.

The output waveform shown in Figure 5 starts to attenuate from the saturation region 400 μsec after the end of the 300 μsec pulse signal supply, and has extremely good characteristics compared to the characteristics shown in Figure 3. When used as a distance measurement station, the distance measurement limit on the short distance side can be extended to several tens of centimeters compared to the conventional example shown in FIG.

However, if we look at the characteristics in Figure 5 in more detail, we can see that the damped oscillation completely disappears approximately 1.3 msec after the start of transmission, and the falling characteristic is extremely gradual. Under normal atmospheric conditions, transmission begins. Approximately 1.5msec later, the received signal can be obtained at approximately 25cm.
It is difficult to use it as an ultrasonic transducer for distance measurement of an object at a distance of .

In other words, if all the structures shown in Figure 4A have the characteristics shown in Figure 5, there will be no problem, but if any one of the structures shown in Figure 4B has the characteristics shown in Figure 5, The fact that the vibration is present for more than 1 msec after the start of transmission and has a gradual falling characteristic means that the slope of the damped vibration characteristic fluctuates due to manufacturing variations in the ultrasonic transducer. For example, there is a very high possibility that a product with even more moderate characteristics as shown by the broken line in FIG. 5 will be manufactured, and it will be extremely difficult to put it into practical use considering the cost of sorting work and unusable products. It goes without saying that if the characteristics are even more gradual than those in FIG. 5 and some vibration signal is present for about 1.5 msec or more after the start of transmission, accurate distance measurement will no longer be possible.

On the other hand, if we consider the other ultrasonic transducers shown in Figure 4 B, C, and D, the ones shown in Figure 4 C and D have lower free vibration than those shown in A above. There is no need to discuss in detail that the suppressing force is weak due to its structure, and it is unthinkable that the falling characteristic becomes steeper. In addition, in the case of the one shown in Figure B, the suppressing force is too strong, and it may be difficult to obtain the output signal level in the vertical direction in the characteristic diagram shown in Figure 5 etc. If the target is a target, it may not be possible to detect it as vibration even if the reflected wave from the target is received, or it may not be possible to cause sufficient vibration to occur in a very short time when starting transmission. Both methods are considered to have problems in practical application.

Note that when attempting to measure distances only for objects that are more than a few tens of centimeters away, ignoring objects that are very close, that is, the method shown in Figure 4 A, which is considered to be the most effective of the four embodiments described above, is used. When considering the practical application of an ultrasonic transducer, there is no problem in terms of characteristics, but as is clear from the structure shown, extremely detailed work is required to install the buffer plate 20, and the manufacturing process is It is thought that the process will become extremely complex, leading to unavoidable problems such as reduced efficiency and increased costs.

As mentioned above, conventional ultrasonic transducers using piezoelectric elements have various problems, and there is a strong desire to reduce costs by improving characteristics and simplifying manufacturing operations. This is the current situation.

OBJECTS OF THE INVENTION An object of the present invention was made in consideration of the above-mentioned current situation, and it is an object of the present invention to provide an ultrasonic transducer that has improved fall characteristics and is easy to manufacture.

Another object of the present invention is to elastically fix a diaphragm and a piezoelectric element to each other by a cylindrical buffer member having a notched groove in the axial direction of a hollow portion without using a case, thereby transmitting vibration to the case. An object of the present invention is to provide an ultrasonic transducer that suppresses free vibration of a diaphragm and a piezoelectric element without causing any damage.

Still another object of the present invention is to elastically fix a diaphragm and a piezoelectric element to each other by a cylindrical buffer member having a notched groove in the axial direction of a hollow part without using a case, and to provide electricity to the piezoelectric element. A middle part of the lead wire extending from the terminal that supplies the electrical energy is fixed to a part of the support of the piezoelectric element, and the vibration of the piezoelectric element, diaphragm, and lead wire is suppressed without transmitting the vibration to the case. An object of the present invention is to provide a suppressed ultrasonic transducer.

Structure of the Invention The ultrasonic transducer according to the present invention has a structure in which there is a space between the piezoelectric element and the diaphragm in order to suppress the free vibration of the piezoelectric element and the diaphragm without transmitting the vibration of the piezoelectric element to the case. A cylinder whose one end holds the outer periphery of the diaphragm and whose other end is fixed to the piezoelectric element and an elastic adhesive, and which has an inner diameter slightly smaller than the outer diameter of the diaphragm and a notched groove formed in the axial direction of the hollow part. It is configured by providing a shaped buffer member.

Further, the ultrasonic transducer according to the present invention is configured as described above, and a part of the lead wire that connects the piezoelectric element and the electrical terminal and supplies electrical energy is attached to the support base of the piezoelectric element. It is constructed by being partially fixed.

DESCRIPTION OF EMBODIMENTS FIG. 6 shows an embodiment of an ultrasonic transducer according to the present invention, in which A is a sectional view and B is a top surface of the buffer member designated by number 21 in A. It is a diagram. In the drawings, the same numbers as those in FIG. 1 indicate the same members.

The buffer member 21 is connected to the diaphragm 2 at one end 21a.
The other end 21b holds the outer periphery of the piezoelectric element 1.
It is fixed by an elastic adhesive 22.

The buffer member 21 has a cylindrical shape with a notched groove 21c in the axial direction of its hollow part, and the buffer member 21 is made of a suitable elastic body having a cylindrical shape and having an inner diameter slightly smaller than the outer diameter of the diaphragm 2, for example. It is composed of.

Therefore, in the ultrasonic transducer according to the present invention, the vibrations of the piezoelectric element 1 etc. are not transmitted to the case 7, unlike the conventional example shown in FIGS.

Furthermore, unlike the conventional examples shown in FIGS. 4A, 4C, and 4D, not only the vibration of the diaphragm 2 but also the vibration of the piezoelectric element 1 is suppressed.

Therefore, in the present invention, the falling characteristic during transmission can be improved compared to the conventional example shown in FIG. 4, and will be specifically explained below.

Now, the ultrasonic transducer according to the present invention as shown in FIG. 6A is replaced with the transducer 13 in the circuit configuration as shown in FIG. When the output signal at the output terminal 19 was detected when the signal was supplied to the intermediate input terminal 10 and driven, an output waveform having a partially saturated region as shown in FIG. 7 was obtained.

As is clear from FIG. 7, the output waveform during transmission in the embodiment of the present invention shown in FIG. 6A is approximately
After 300μsec, it starts to decay from the saturation region, and about
It almost disappears after 500μsec.

That is, compared to the characteristics of the conventional example shown in FIG. 4A shown in FIG. 5, the time point at which the attenuation starts is earlier, and the slope from the start to the end of the attenuation is extremely steep.

In other words, the ultrasonic transducer according to the present invention is
After the supply of input signals is stopped, the free vibration is stopped extremely sharply, so even if the above-mentioned fluctuation in the slope due to variations in cutting occurs, it will be
As shown by the broken line in the figure, the vibration that appears 1 msec after the start of transmission becomes extremely small.
Since it is unlikely that variations such as vibrations exist for a long time of 1.5 msec or more will occur, and almost all of the manufactured products can be actually used, the falling characteristics are as shown in Figure 5 above. This means that it can be considered to have improved and stable characteristics compared to .

As a result, the ultrasonic transducer according to the present invention can reliably detect a received signal of a reflected wave from an object at a distance of 20 to 30 cm, when considering application to distance measurement and measurement, for example. Therefore, the distance measurement limit on the short distance side can be further expanded than in the conventional example shown in FIG. 4A.

Next, let's think about manufacturing work.

As is clear from its structure, the manufacturing process of the ultrasonic transducer according to the present invention does not require any elastic fixing work to the case 7, and the process shown in FIGS. This is simpler than the conventional example.

Furthermore, since the buffer member 21 is provided with the notch groove 21c in the axial direction of the hollow portion, the mounting operation can be realized by widening the buffer member 21 and inserting the diaphragm 2 therebetween. As a result, the work of attaching the buffer member 21 becomes an extremely simple work and has the following features.

That is, although the diaphragm 2 is normally formed of a thin aluminum plate and is extremely easily deformed, the above-described mounting operation prevents the diaphragm 2 from being inadvertently deformed. Moreover, the influence on the holding of the diaphragm 2 by the piezoelectric element 1 itself can be made extremely small.

Furthermore, the soldered part 1a between the piezoelectric element 1 and the lead wire 6 can be located in the notch groove 21c of the buffer member 21, so that the shape of the diaphragm 2 is approximately the same as or slightly different from the shape of the piezoelectric element 1. Even if the soldered portion 1a is present in the mounting area of the buffer member 21 due to the above size, the buffer member 21 can be mounted without any problem.

8A and 9B and FIG. 9A and 9B respectively show a top view and a sectional view showing other embodiments of the cylindrical buffer member 21 used in the ultrasonic transducer according to the present invention. .

In the embodiment shown in FIGS. 8A and 8B, on the inner circumferential surface of one end 21a of the buffer member 21 shown in FIGS.
Holding portion 21d to increase contact area with diaphragm 2
was formed.

Therefore, the diaphragm 2 and the buffer member 21 can be fixed with the elastic adhesive via the holding portion 21d, and the diaphragm 2 can be held by the buffer member 21 in an extremely stable manner.

In the embodiment shown in FIGS. 9A and 9B, a bottom portion 21e to be fixed to the piezoelectric element 1 is further formed on the other end 21b.

Therefore, even if the diaphragm 2 becomes somewhat larger, sufficient elastic coupling with the piezoelectric element 1 can be achieved with such a buffer member.

On the other hand, as a result of various studies, the inventor of the present application found that in ultrasonic transducers using piezoelectric elements, the vibration motion of the lead wire that electrically supplies energy to the piezoelectric element also has a negative effect on the falling motion. It was confirmed that

In other words, the vibrational motion of the lead wire cannot be said to have a large influence when the falling characteristic is extremely long as shown in Figure 2, but it can be If the signal waveform attenuates to almost 0 level in a short period of time,
The oscillating motion of the lead wire is the generation of irregular signals that appear after 1.2 msec and after 800 μsec, respectively in the figure, in other words, most of the irregularly fluctuating signals that continue for a while after attenuating to almost 0 level. I confirmed that this was the cause.

Such a signal near the 0 level may have a large output level, and will never have a positive effect on the detection operation of the received signal, so it is desirable that the signal does not exist.

FIGS. 10A and 10B are a cross-sectional view and a plan view of essential parts of another embodiment of the ultrasonic transducer according to the present invention, which can eliminate the adverse effects caused by the vibrating operation of the lead wires as described above.

The lead wire indicated by the drawing number 9 in Figure 6A etc. is used to improve workability during manufacturing, that is, to facilitate connection to the piezoelectric element 1 or terminal 6, and to avoid the risk of disconnection due to voltage application. It is housed in the case 7 with a certain amount of slack, which results in an undesirable vibrating motion.

Therefore, in the embodiment shown in FIG.
As is clear from the drawings, a portion of the lead wire 9 is fixed to a portion of the support base 4 holding the piezoelectric element 1 with an elastic adhesive 23 in order to suppress the above-mentioned vibrational movement.

Here, the output end when an example in which a part of the lead wire 9 is fixed to the support base 4 as described above is driven by replacing the ultrasonic transducer 13 in the circuit configuration shown in FIG. When the output signal No. 19 was detected, an output waveform having characteristics as shown in FIG. 11 was obtained.

As is clear from FIG. 11, the embodiment of the ultrasonic transducer according to the present invention shown in FIG. Therefore, the operation of detecting the received signal of the reflected wave from the object can be performed more accurately than in the embodiment described in FIG. 6 above.

Effects of the Invention As described above, the ultrasonic transducer according to the present invention connects the piezoelectric element and the diaphragm to each other through a cylindrical buffer member having a notched groove in the axial direction of the hollow part, without using a case. Because they are elastically coupled, the falling characteristic during transmission can be such that attenuation begins shortly after the input signal supply stops, and the attenuation is steep. equipment that needs to detect a received signal within a short time after
For example, a distance measuring device can accurately detect a received signal due to a reflected wave from an object located at a very close distance, and has the effect of expanding the distance measurement limit on the short distance side.

Furthermore, since the buffer member is provided with the notched groove, the diaphragm will not be deformed or the adhering state between the diaphragm and the piezoelectric element will not be adversely affected during the mounting operation.

Furthermore, by locating the soldered portion between the piezoelectric element and the lead wire in the notch, there is also an effect that mounting of the buffer member can be performed without being affected by the position of the soldered portion.

Furthermore, by fixing appropriate points of the lead wire that electrically connects the piezoelectric element and the terminal to the support of the piezoelectric element, irregularities caused by the vibration of the lead wire can be eliminated after the vibration has damped to almost zero level. This also has the effect that the received signal can be detected with higher accuracy since it is possible to eliminate signals that fluctuate.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing a conventional example of an ultrasonic transducer using a piezoelectric element, Fig. 2 is an example of a circuit in which the ultrasonic transducer is used, and Fig. 3 is a conventional example of the ultrasonic transducer shown in Fig. 1. An envelope waveform diagram of the output signal obtained at the output terminal 19 when driven by the circuit shown in Figure 2, Figure 4 A, B, C, and D show other conventional examples of ultrasonic transducers. The cross-sectional view shown in Fig. 5 shows the output terminal 1 when the conventional example shown in Fig. 4 A is driven by the circuit shown in Fig. 2.
9 shows envelope waveform diagrams of the output signals obtained, respectively. 6A and 6B show an embodiment of the ultrasonic transducer according to the present invention, in which FIG. 6A is a sectional view, and FIG. FIG. 7 shows the output terminal 19 when the embodiment shown in FIG. 6A is driven by the circuit shown in FIG.
Envelope waveform diagram of the output signal obtained in Figure 8A,
B, FIGS. 9A and 9B are a top view and a sectional view showing another embodiment of the buffer member designated by the number 21 in FIG. 6A, and FIGS. 10A and 10B are ultrasonic transmission and reception according to the present invention A sectional view and a plan view of main parts showing another embodiment of the corrugator, FIG. 11 is a second embodiment of the embodiment shown in FIG. 10.
Each of the diagrams shows an envelope waveform diagram of an output signal obtained at the output terminal 19 when driven by the circuit shown in the figure. DESCRIPTION OF SYMBOLS 1... Piezoelectric element, 2... Vibration plate, 3, 5... Elastic adhesive, 4... Support stand, 6... Terminal, 7... Case, 9... Lead wire, 21... Buffer member, 21
a...One end, 21b...Other end, 21c...Notch groove, 21d...Slanted surface, 21e...Bottom part, 2
2,23...Elastic adhesive.

Claims (1)

[Claims] 1. An ultrasonic transducer comprising a diaphragm, a bonded piezoelectric element, a support base, a terminal, a lead wire, a case, and a buffer member, the diaphragm comprising: The terminal is made into a conical shape, the terminal is supplied with electrical energy to be applied to the piezoelectric element, the buffer member is made of a cylindrical elastic body having a notched groove in the axial direction of the hollow part, and the diaphragm is placed in the center of the piezoelectric element. The support base is fixed to the vibrating node of the piezoelectric element with an elastic adhesive to support the piezoelectric element, the lead wire electrically connects the terminal and the piezoelectric element, and the case is attached to the vibration plate and the piezoelectric element. , a support base, a part of the terminal, and a lead wire are housed, and one end of the buffer member elastically contacts a part of the outer periphery of the diaphragm including the periphery of the end having the maximum diameter,
An ultrasonic transducer in which the other end of the buffer member is fixed to a part of the surface of the piezoelectric element on which the diaphragm is attached using an elastic adhesive. 2. The ultrasonic transducer according to claim 1, wherein the lead wire has a part of the intermediate portion fixed to the support stand. 3. Ultrasonic wave transmission and reception according to claim 1, characterized in that the buffer member has an inclined surface that matches the side surface shape of the diaphragm on the inner circumferential surface of the end that comes into contact with the periphery of the diaphragm. vessel.