close

Вход

Забыли?

вход по аккаунту

?

DESCRIPTION JP2012156622

код для вставкиСкачать
Patent Translate
Powered by EPO and Google
Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
financial decisions, should not be based on machine-translation output.
DESCRIPTION JP2012156622
An object of the present invention is to provide a piezoelectric sensor capable of reducing the
spurious of a vibrator. SOLUTION: A piezoelectric body (10), a diaphragm (20) forming a vibrator
(2) capable of transmitting or receiving an ultrasonic wave in combination with the piezoelectric
body, and mechanical vibration generated in the vibrator And a pedestal (42) for supporting the
vibrator in the vicinity of the node, and the pedestal is in point contact, line contact, or partial
surface contact with the vibrator in the vicinity of the node of vibration. It comprises a rib (46)
for supporting the element, and a withdrawal part (50) which is juxtaposed to the rib near the
node of vibration and which is separated from the vibrator and does not support the vibrator.
[Selected figure] Figure 4
Piezoelectric sensor
[0001]
The present invention relates to a piezoelectric sensor capable of transmitting and receiving
ultrasonic waves using mechanical vibration of a piezoelectric body.
[0002]
This type of piezoelectric sensor can be used, for example, as a sensor for an automatic door, and
is a noncontact detection sensor using ultrasonic waves as a detection medium.
Specifically, the piezoelectric sensor includes a piezoelectric body, and this piezoelectric body has
14-04-2019
1
a function of converting mechanical energy and electrical energy mutually (piezoelectric effect,
inverse piezoelectric effect). For example, when a voltage is applied to the piezoelectric body,
piezoelectric The body stretches.
[0003]
Then, a structure of a vibrator in which a piezoelectric body and a diaphragm are combined is
disclosed (for example, see Patent Document 1). Specifically, a vibrator including a piezoelectric
body and a diaphragm is disposed on a pedestal, and a terminal is held by the pedestal. Further,
the vibrator and the terminal are electrically connected by a conductive wire, and when a voltage
is applied to the piezoelectric body through the terminal and the conductive wire, the vibrator is
bent and mechanically vibrated as the piezoelectric body expands and contracts. Because of the
resonance phenomenon, the piezoelectric sensor can transmit ultrasonic waves.
[0004]
When the transmitted ultrasonic wave is reflected by the object and the piezoelectric sensor
receives the reflected ultrasonic wave, a voltage is obtained by the bending motion of the
transducer. Thus, the presence or absence of an object approaching the door and the distance to
the object can be detected, and the control unit of the automatic door can output a drive signal to
the motor for opening and closing the door.
[0005]
Japanese Utility Model Publication No. 55-51568
[0006]
By the way, in the structure as in the above-mentioned prior art, the vibrator is supported on the
pedestal at its mechanical vibration node, and all of the vibration nodes are in contact with the
pedestal.
More specifically, a cylindrical rib is provided on the base so as to protrude toward the vibrator,
and a tip end face of the annularly closed rib supports the vibrator. Further, on the inner
14-04-2019
2
circumferential side of this rib, a cylindrical adhesive portion is formed as well, and a vibrator is
similarly fixed by an adhesive at a node of vibration.
[0007]
However, this has a problem that unnecessary vibration (spurious) occurs in the vibrator. That is,
even if the pedestal is brought into contact with the vibrator at a position where the amplitude is
zero, if the contact area between the pedestal and the vibrator becomes large, the pedestal
inhibits the vibration of the vibrator, resulting in spurious and vibrator. The vibration
performance of the
[0008]
As described above, in the configuration in which the vibrator is simply supported by the
cylindrical rib and the bonding portion, no special consideration is given to the occurrence of the
spurious, and it is necessary to take measures to reduce the spurious. In addition, there is also a
method of fixing with an adhesive in a state in which the pedestal and the vibrator are not in
contact with each other, but a jig for floating the vibrator is required, which is complicated in
manufacturing. Then, the objective of this invention is providing the piezoelectric sensor which
can eliminate the said subject and can reduce the spurious of a vibrator | oscillator.
[0009]
According to a first aspect of the present invention for achieving the above object, there is
provided a piezoelectric body, a vibration plate forming a vibrator capable of transmitting or
receiving an ultrasonic wave in combination with the piezoelectric body, and mechanical
vibration generated in the vibrator. And a pedestal for supporting the vibrator, the pedestal
supporting the vibrator in point contact, line contact, or partial surface contact with the vibrator
near the node of vibration. Equipped with a rib.
[0010]
According to the first aspect of the invention, the piezoelectric sensor has a vibrator formed of a
piezoelectric body and a diaphragm, and the vibrator can transmit or receive an ultrasonic wave.
14-04-2019
3
Here, the vibrator is supported on a pedestal in the vicinity of a node of mechanical vibration,
and the pedestal is in point contact, line contact, or partial surface contact with the vibrator to
cause the vibrator to It has a rib that supports the As described above, if the contact area
between the pedestal and the vibrator is made smaller than in the prior art, the pedestal does not
inhibit the vibration of the vibrator, and the spurious can be reduced. As a result, the vibration
performance of the vibrator is improved, which contributes to the improvement of the reliability
of the piezoelectric sensor.
[0011]
According to a second aspect of the invention, in the configuration of the first aspect, the
pedestal is the rib described above, and a retracting portion which is juxtaposed to the rib near
the node of vibration and does not support the vibrator apart from the vibrator. And the like.
According to the second invention, in addition to the function of the first invention, the base
further includes a rib and a retracting portion, and the rib is in point contact, line contact, or
partial surface contact with the vibrator. Support the vibrator. On the other hand, although the
retracting portion is provided in the vicinity of the node of vibration of the vibrator as with the
rib, it does not contact the vibrator and does not support the vibrator. As a result, the contact
area between the pedestal and the vibrator is surely reduced, and the spurious can be further
reduced.
[0012]
According to a third aspect of the invention, in the configuration of the first and second aspects,
the pedestal is formed in a substantially cylindrical shape, and the ribs are disposed at three
locations at substantially equal intervals when viewed in the circumferential direction of the
pedestal It is characterized by According to the third invention, in addition to the function of the
first and second inventions, the ribs are arranged at three equal intervals with substantially equal
intervals when viewed in the circumferential direction of the pedestal formed in a substantially
cylindrical shape. Therefore, even if the contact area with the vibrator is reduced, the vibrator
can be stably supported. Also, if the intervals between the ribs are the same, it is easier to
provide the ribs on the base as compared to the case where the ribs are simply provided at three
locations.
[0013]
14-04-2019
4
A fourth invention is characterized in that, in the configurations of the first to third inventions,
the rib is formed in a flat shape and has a tip surface in surface contact with the vibrator.
According to the fourth invention, in addition to the functions of the first to third inventions, in
the case of a rib partially in surface contact with the vibrator, if the tip end surface is formed flat,
the pedestal is This point also contributes to the improvement of the vibration performance of
the vibrator, since the vibration of the vibrator is not further inhibited.
[0014]
According to a fifth invention, in the configurations of the first to fourth inventions, a conductive
wire, which is drawn from the vibrator and electrically connects the vibrator to a terminal
connected to the circuit board, and a surface for holding the terminal The apparatus further
comprises a case having a pedestal on the opposite surface, and a spacer for securing a space
between the surface and the circuit board is provided on the surface holding the terminal.
According to the fifth invention, in addition to the functions of the first to fourth inventions,
transmission of vibration on the case side to the circuit board side can be avoided, and damage to
the circuit board and the case by solder is also possible. Can be suppressed.
[0015]
According to the present invention, it is possible to provide a piezoelectric sensor in which the
contact area between the pedestal and the vibrator is reduced and the pedestal does not inhibit
the vibration of the vibrator and the spurious of the vibrator can be reduced.
[0016]
It is an external appearance perspective view of the piezoelectric sensor of a present Example.
It is a disassembled perspective view of the piezoelectric sensor of FIG. 1, and is a figure which
shows the state before the assembly. It is a longitudinal cross-sectional view of the piezoelectric
sensor of FIG. It is a top view of the case of FIG. It is a side view of the case of FIG. It is
explanatory drawing of an experimental result.
14-04-2019
5
[0017]
Hereinafter, embodiments of the present invention will be described with reference to the
drawings. FIG. 1 is an external perspective view of the piezoelectric sensor 1 according to this
embodiment as viewed from above, and FIG. 2 is an exploded perspective view of the
piezoelectric sensor 1 before assembly as viewed from below. The piezoelectric sensor 1 is a
noncontact detection sensor that is used, for example, as a sensor for an automatic door and uses
an ultrasonic wave as a detection medium.
[0018]
As shown in FIGS. 1 and 2, the piezoelectric sensor 1 mainly includes a vibrator 2 and a case 40,
and the vibrator 2 is accommodated in the case 40. 1 and 2 correspond to the bottom side of the
case 40, and the piezoelectric sensor 1 faces the bottom side of the case 40 to the mounting
surface of the circuit board (not shown) of the sensor. Will be implemented in
[0019]
The vibrator 2 of this embodiment is formed in a unimorph structure in which a piezoelectric
ceramic (piezoelectric body) 10 is superimposed on a metal diaphragm 20. Specifically, the
piezoelectric ceramic 10 is made of, for example, lead zirconate titanate ceramic (PZT) or the like,
and has a predetermined thickness in the height direction of the case 40 (vertical direction in
FIG. 1 and FIG. 2) Figure 3). The shape of the piezoelectric ceramic 10 is not particularly limited,
but a substantially square flat plate can be mentioned as an example here.
[0020]
As shown in FIG. 2 and FIG. 3, one lead wire 16 is fixed by solder 18 at an appropriate position
on the other surface 14 of the piezoelectric ceramic 10. Although the lead wire (conductive wire)
16 of this embodiment is a copper wire, a coated wire or a gold thread wire may be used.
Further, the diaphragm 20 is superimposed on the upper side of the piezoelectric ceramic 10.
Specifically, this diaphragm 20 is also a circular flat plate having a predetermined thickness in
the height direction of the case 40 (FIG. 3), and is formed in such a size that the four corners of
the piezoelectric ceramic 10 can be inscribed. .
14-04-2019
6
[0021]
Then, in order to give vibration of the piezoelectric ceramic 10 to the diaphragm 20 to obtain
large vibration, the piezoelectric ceramic 10 and the diaphragm 20 are superposed, and the back
surface 24 of the diaphragm 20 and one surface 12 of the piezoelectric ceramic 10 are bonded
with an adhesive. I'm glued. In FIG. 3, the thickness of the piezoelectric ceramic 10 and the
diaphragm 20 is exaggerated in order to help the understanding of the structure.
[0022]
One lead wire (conductive wire) 26 is also fixed by solder 28 at an appropriate position on the
back surface 24 of the diaphragm 20 (Figs. 2 and 3). It is a line. On the other hand, a metal horn
30 is placed on the surface 22 of the diaphragm 20 (FIG. 3). The horn 30 is formed in a
substantially bowl shape, and is expanded in the direction away from the diaphragm 20. The
diameter-reduced lower end portion of the horn 30 is bonded to a substantially central position
of the surface 22 of the diaphragm 20. A predetermined coating is applied to the expanded
surface of the horn 30 which can be seen in FIG.
[0023]
Here, the case 40 of the present embodiment is formed in a cup shape made of a plastic resin,
and a pedestal 42 forming a bottom portion of the cup shape and a peripheral wall 70 having an
opening portion are integrally formed. . Specifically, as shown in FIG. 4 which is a plan view of
the case 40 of FIG. 3 and FIG. 2, first, the pedestal 42 is formed in a substantially cylindrical
shape and has an upper surface 44 for supporting the vibrator 2. .
[0024]
A total of three columns (ribs) 46 project toward the vibrator 2 on the upper surface 44 of the
present embodiment. More specifically, as shown in FIG. 4, the columns 46 are disposed at three
positions at substantially equal intervals of a central angle of 120 degrees as viewed in the
circumferential direction of the pedestal 42. These columns 46 have a small area and flat tip
14-04-2019
7
surface 47, and the tip surface 47 is in surface contact with the other surface 14 of the
piezoelectric ceramic 10. In addition, although the support | pillar 46 of a present Example is
integrally formed by the upper surface 44 (FIG. 3), you may form separately from this upper
surface 44. As shown in FIG.
[0025]
Further, on the upper surface 44, on the concentric circle on which the support 46 is formed, a
cutaway portion (evacuation portion) 50 having a height smaller than that of the support 46 is
provided. Specifically, the notches 50 of this embodiment are disposed one by one between the
three columns 46, and a large space is formed between the columns 46. That is, the notch 50 is
separated from the other surface 14 of the piezoelectric ceramic 10 and does not contact the
other surface 14.
[0026]
On the other hand, an adhesive portion 52 is formed in the notch portion 50 (FIG. 4), and the
other surface 14 of the piezoelectric ceramic 10 is fixed and supported by an adhesive. The
bonding portion 52 of the present embodiment is formed in a part of the notch 50, and is
provided adjacent to the support 46 at a position substantially symmetrical with respect to the
center line of the pedestal 42 in the present embodiment (for example, 2 places). Further, these
bonding portions 52 are formed not only on the inner peripheral side of the support 46 but also
at positions concentric with the support 46 as viewed in the radial direction of the pedestal 42.
Face contact with
[0027]
More specifically, the bonding portion 52 is formed at a node (position where the amplitude
becomes zero) of the mechanical vibration generated in the vibrator 2. In the case of the circular
vibrator 2 as in this embodiment, the bonding portion 52 is formed on the circumference of the
diameter φ of the vibrator 2 because it is bent by the expansion and contraction in the width
direction and the length direction of the substantially square piezoelectric ceramic 10. Partially
supports the position near the center by φ / 4.
14-04-2019
8
[0028]
This is because the vibrator 2 of this embodiment is driven by the voltage of its natural
resonance frequency, and the node of vibration at that time is a position near the center by φ / 4
from the circumference of the diameter φ, In other words, it is located on the circumference of
about diameter φ / 2 with respect to the center of the vibrator 2. Although smaller than the
expansion and contraction that occurs in the width direction and the length direction of the
piezoelectric ceramic 10, the expansion and contraction also occurs in the thickness direction of
the piezoelectric ceramic 10.
[0029]
On the other hand, the pedestal 42 is provided with the lower surface 54 facing the mounting
surface of the circuit board described above. As shown in FIG. 3, terminal holding portions 56, 56
are formed at appropriate positions on the lower surface 54, and hold the terminals 80, 82
having a circular cross section to project toward the mounting surface. In addition, the shape of
the terminals 80 and 82 does not differ at all even if it is a rectangular shape in cross section.
[0030]
Further, spacers 58 and 60 are provided in the vicinity of the peripheral edge of the lower
surface 54 (FIGS. 2 and 5). These spacers 58 and 60 are formed in a substantially rectangular
parallelepiped, and the longitudinal direction extends along the lower surface 54, are disposed at
symmetrical positions with respect to the center of the lower surface 54, and can be in contact
with the mounting surface. Thus, a space between the lower surface 54 and the mounting surface
is secured to protect the case 40 and the circuit board. Therefore, since the lower surface 54
does not contact the circuit board, it is possible to avoid transmitting the vibration on the case 40
side to the circuit board side. When the lead wires 16 and 26 are fixed to the terminals 80 and
82 with the solders 86 and 88 as in this embodiment, the solders 86 and 88 can be released to
the circuit board, and furthermore, the terminals When 80 and 82 are fixed to the circuit board
by solder, the solder portion for fixing the terminal can be separated from the lower surface 54,
so that the resin case 40 can be prevented from melting or the like.
[0031]
14-04-2019
9
5 (a) is a side view of the case 40 when FIG. 4 is viewed from below. 5 (b) is a side view of the
case 40 when FIG. 5 (a) is viewed from the left side, and the column 46 located on the left side
when viewed in FIG. The adhesive portion 52 located at the lower side (located on the right side
of the support 46 in FIG. 5B) or the adhesive portion 52 located at the right side in FIG. 4 (FIG.
5B) the left back side of the support 46 Can be seen respectively).
[0032]
Further, on one of the spacers 58 and 60, a pin 62 for identifying the polarity of the terminals 80
and 82 is protruded. Although the pins 62 in the present embodiment are provided on the spacer
60, they may be provided on the lower surface 54. The pedestal 42 of the present embodiment is
provided with protective portions 64, 64 in the vicinity of the peripheral edge (FIG. 4).
[0033]
Specifically, the protection portions 64 are holes of a substantially rectangular shape in a plan
view, which are drilled through the upper surface 44 and the lower surface 54 in the height
direction of the case 40. The longitudinal direction of the protective portions 64, 64 does not
extend toward the center of the upper surface 44 or the lower surface 54, but extends obliquely
toward, for example, the other spacer 58 of the spacers 58, 60 described above (see FIG. 2, FIG.
4), lead wires 16 and 26 can be hooked and held.
[0034]
Next, the peripheral wall 70 extends upward from the peripheral edge of the pedestal 42 and is
erected. Specifically, as shown in FIGS. 3 to 5, the peripheral wall 70 of the present embodiment
has its lower end 74 located substantially at the same height as the lower surface 54 of the
pedestal 42 and extends upward from the lower end 74. . And it extends further and covers the
upper surface 44 of the pedestal 42 and the sides of the vibrator 2 and the horn 30, and has a
circular upper opening 72 at its upper end.
[0035]
14-04-2019
10
The circumferential wall 70 has a portion in which the inner circumferential side and the outer
circumferential side are completely in communication in the height direction of the case 40.
Specifically, the peripheral wall 70 of the present embodiment has conductive wire receiving
openings 76, 76 (FIG. 2). The conductive wire receiving openings 76, 76 are provided
corresponding to the positions of the protective portions 64, 64 described above (FIGS. 3 to 5),
and the upper openings are wide enough to receive at least the respective lead wires 16, 26. The
inner circumferential side and the outer circumferential side of the peripheral wall 70 are formed
so as to extend from 72 to the lower end 74 respectively.
[0036]
The conductive wire receiving opening 76 is continuous with the corner portion of the protective
portion 64 closest to the periphery of the lower surface 54 at the position facing the pedestal 42
(FIGS. 3 and 4). It communicates with the outer peripheral side of the peripheral wall 70 through
the conductive wire receiving opening 76. On the other hand, the conductive wire receiving
openings 76, 76 of the present embodiment have horn window portions 78, 78 at positions
facing the vibrator 2 and the horn 30, respectively.
[0037]
The horn window portions 78 and 78 are opened with a width much larger than the width that
can receive the respective lead wires 16 and 26, and a range across the narrow portion of the
conductive wire receiving opening 76 in the circumferential direction of the peripheral wall 70
(FIG. 4, FIG. 5 (b)). Returning to FIG. 2 again, first, in the assembly of the piezoelectric sensor 1,
the case 40 holding the terminals 80 and 82 is prepared, and the vibrator 2 including the lead
wires 16 and 26 is lowered toward the pedestal 42.
[0038]
At that time, the lead wires 16, 26 are respectively received by the wide portions of the
conductive wire receiving openings 76, 76 located at the upper opening 72, that is, the horn
windows 78, 78. It is pulled out respectively to the outer peripheral side. Subsequently, the
vibrator 2 is lowered toward the upper surface 44, and the other surface 14 of the vibrator 2 is
brought into contact with each of the columns 46 only, and the vibrator 2 is bonded and fixed by
14-04-2019
11
two bonding portions 52.
[0039]
Next, the lead wire 16 drawn to the outer peripheral side of the peripheral wall 70 through the
horn window portion 78 is gripped by the operator and routed around the narrow portion of the
conductive wire receiving opening 76 in the vicinity into the protective portion 64. Ru. Thereby,
as shown in FIG. 3, the side portion of the lead wire 16 is held on the inner wall of the protective
portion 64, and the tip end portion of the lead wire 16 is drawn below the lower surface 54.
[0040]
The lead wire 26 drawn to the outer peripheral side of the peripheral wall 70 through the horn
window portion 78 is drawn around the narrow portion of the conductive wire receiving opening
76 in the vicinity thereof into the protective portion 64. Thus, the side surface portion of the lead
wire 26 is held by the inner wall of the protective portion 64, and the tip end portion of the lead
wire 26 is drawn below the lower surface 54 (FIG. 3). Then, the lead wire 16 is wound around the
peripheral surface 81 of the terminal 80 in the vicinity of the lower surface 54 and fixed by the
solder 86, and the lead wire 26 is also wound around the peripheral surface 83 of the terminal
82 in the vicinity of the lower surface 54. When fixed, the vibrator 2 and the terminals 80 and
82 are conducted.
[0041]
Thereafter, by bonding the horn 30 to the surface 22 of the diaphragm 20, the piezoelectric
sensor 1 is completed. The piezoelectric sensor 1 configured as described above can transmit and
receive ultrasonic waves, the spacers 58 and 60 are mounted on the mounting surface of the
circuit board of the sensor, and the terminals 80 and 82 are electrically connected to the circuit
portion. Connected
[0042]
When a voltage is applied to the piezoelectric ceramic 10 through the terminals 80 and 82 and
14-04-2019
12
the lead wires 16 and 26, the thickness direction of the piezoelectric ceramic 10 and the width
direction and length direction of the piezoelectric ceramic 10 orthogonal to the thickness
direction expand and contract ( Reverse piezoelectric effect). The expansion and contraction in
the width direction and the length direction of the piezoelectric ceramic 10 is a force that causes
the entire vibrator 2 to bend, and an ultrasonic wave is generated by mechanical vibration due to
the bending motion of the vibrator 2. The generated ultrasonic waves are amplified by the horn
30. As described above, the piezoelectric sensor 1 can convert an electric signal into an
ultrasonic wave, and transmit the ultrasonic wave from the upper opening 72 side toward an
object.
[0043]
On the other hand, the transmitted ultrasonic wave propagates in the air, and when it collides
with an object, it is reflected toward the piezoelectric sensor 1. The piezoelectric sensor 1 can
convert received ultrasonic waves into electrical signals. Specifically, when the piezoelectric
sensor 1 receives the reflected ultrasonic wave via the horn 30, the piezoelectric ceramic 10
expands and contracts with the bending movement of the vibrator 2 to obtain a voltage
(piezoelectric effect). .
[0044]
Thus, the piezoelectric sensor 1 can transmit and receive ultrasonic waves by using the
piezoelectric effect and the inverse piezoelectric effect. The control unit of the automatic door
using the piezoelectric sensor 1 can detect the presence or absence of an object approaching the
door and the distance to the object, and can output a drive signal to the motor for opening and
closing the door.
[0045]
As described above, according to the present embodiment, the piezoelectric sensor 1 includes the
unimorph vibrator 2 formed of the piezoelectric ceramic 10 and the diaphragm 20, and the
vibrator 2 can transmit and receive ultrasonic waves. Here, the vibrator 2 is supported by the
pedestal 42 in the vicinity of the node of the mechanical vibration, and the pedestal 42 partially
contacts the vibrator 2 in surface contact to support the vibrator 2. A support 46 is provided. As
described above, if the contact area between the pedestal 42 and the vibrator 2 is made smaller
14-04-2019
13
than in the prior art, the pedestal 42 does not inhibit the vibration of the vibrator 2 and the
spurious can be reduced. As a result, the vibration performance of the vibrator 2 is improved,
which contributes to the improvement of the reliability of the piezoelectric sensor 1.
[0046]
If this point is explained in full detail, FIG. 6 has shown the experimental result of the vibration
characteristic which used three types of piezoelectric sensors. First, in Comparative Examples 1
and 2 (shown by the alternate long and short dash lines and the alternate long and short dash
lines in FIG. 6), all the pedestals having cylindrical ribs and adhesive portions support the
transducers with perfect surface contact. An upward peak appears on the lower side of the
resonance frequency (leftward with respect to the resonance frequency in FIG. 6), and it can be
seen that the resonance resistance Z (Ω) is high.
[0047]
It can be inferred that this is a result of the occurrence of spuriousness due to the fact that the
pedestal is difficult to vibrate because the pedestal supports the transducer with perfect surface
contact. Moreover, in these comparative examples 1 and 2, the upward peak does not appear at
the resonance frequency, and the upward peak appears slightly higher than the resonance
frequency (rightward with respect to the resonance frequency in FIG. 6). This is considered to be
due to the fact that the peak that should originally occur with respect to the resonance frequency
is shifted by the influence of the peak that has appeared on the above-mentioned lower band
side.
[0048]
Furthermore, in Comparative Example 1 indicated by the alternate long and short dash line, it is
understood that the upward peak appearing on the slightly higher frequency side is smaller than
the peak at the same position in Comparative Example 2 indicated by the alternate long and two
short dashes line. This is considered to be the effect that the upward peak of the comparative
example 1 becomes larger than the peak at the same position of the comparative example 2 on
the lower band side described above.
14-04-2019
14
[0049]
On the other hand, in the piezoelectric sensor 1 of the present embodiment, the pedestal 42 is
provided with the support 46 and the notch 50, and the support 46 partially contacts the
vibrator 2 to support the vibrator 2 . On the other hand, although the notch portion 50 is
provided in the vicinity of the node of vibration of the vibrator 2 similarly to the support 46, it
does not contact the vibrator 2 and does not support the vibrator 2.
[0050]
That is, since the place other than leaving as the support | pillar 46 was removed among the said
cylindrical ribs, as shown by the continuous line in FIG. 6, the upward peak like Comparative
Example 1 and 2 appears in the low-pass side mentioned above. Absent. Moreover, according to
the present embodiment, an upward peak appears at the resonance frequency. That is, it can be
seen that the pedestal 42 does not inhibit the vibration of the vibrator 2 and the spurious is
reduced.
[0051]
Further, according to the present embodiment in which the contact area between the pedestal 42
and the vibrator 2 is surely reduced, the range from the downward peak appearing at this
resonance frequency to the upward peak corresponds to the above Comparative Examples 1 and
2. It appears widely compared to the range from the downward peak to the upward peak. That is,
it can be seen that good vibration is obtained, the range of the resonance resistance Z is
broadened, and the piezoelectric sensor 1 is efficient.
[0052]
Furthermore, when viewed in the circumferential direction of the pedestal 42 formed in a
substantially cylindrical shape, the columns 46 are arranged at three equal intervals. Although
the points provided at equal intervals do not contribute to the reduction of the above-mentioned
spurious, if provided at equal intervals, even if the contact area with the vibrator 2 is reduced, the
vibrator 2 can be supported stably. . Further, if the distance between the columns 46 is the same,
the columns 46 can be easily provided on the pedestal 42 as compared with the case where the
14-04-2019
15
columns 46 are simply provided at three places, which contributes to the reduction of the
manufacturing cost of the piezoelectric sensor 1.
[0053]
Furthermore, when supporting the vibrator 2 in the vicinity of a node of vibration, an adhesive
can be applied to the notch 50 as well, so the bonding portion can be seen only in the radial
direction of the pedestal 42 and on the inner circumferential side than the support 46 The
surface area of the bonding portion 52 is larger than that in the case where it is provided.
Therefore, even if the contact area between the pedestal 42 and the vibrator 2 is reduced, the
vibrator 2 can be reliably bonded to the pedestal 42 in the vicinity of the node of vibration.
[0054]
Further, in the case of the column 46 in partial surface contact with the vibrator 2 described
above, if the tip end surface 47 is formed in a flat shape, the pedestal 42 does not further inhibit
the vibration of the vibrator 2, this point This also contributes to the improvement of the
vibration performance of the vibrator 2. Furthermore, in the present embodiment, lead wires 16
and 26 which are drawn from the vibrator 2 and electrically connect the vibrator 2 to the
terminals 80 and 82 connected to the circuit board, and a lower surface 54 for holding the
terminals 80 and 82. And a case 40 having a pedestal 42 on the opposite upper surface 44, and
the lower surface 54 is provided with spacers 58 and 60 for securing a space between the lower
surface 54 and the circuit board There is. Therefore, transmission of vibration on the case 40
side to the circuit board side can be avoided, and damage to the circuit board and the case 40
due to solder can be suppressed.
[0055]
The present invention is not limited to the above embodiment, and various modifications can be
made without departing from the scope of the claims. For example, although the piezoelectric
sensor of the above embodiment is configured to be able to transmit and receive ultrasonic
waves, the piezoelectric sensor of the present invention may have either transmission or
reception functions. In addition to the above-described sensor for an automatic door, it can be
mounted on various modules that operate using detection results of the presence or absence of
an object and the distance to the object.
14-04-2019
16
[0056]
More specifically, as a module that uses the detection result of the distance to the object, for
example, there is a liquid level meter, a back sonar of a car, distance measurement, automatic
switching of traffic signals, and the like. Moreover, as a module using the presence or absence of
an object, there are an intruder alarm device, an automatic lighting switch, and the like. This is
because the distance to the object and the presence or absence of the object can be detected by
measuring the reflection time of the ultrasonic wave or observing the frequency (Doppler effect).
[0057]
Furthermore, the above embodiment is an explanation of an optimum example in which the
production of the piezoelectric sensor 1 is also taken into consideration. More specifically, in the
above embodiment, an example in which the pedestal 42 and the vibrator 2 are in partial surface
contact with each other is described. However, the present invention mainly aims to reduce the
contact area with the vibrator 2 instead of the large contact area due to the cylindrical rib and
the adhesive portion as in the prior art.
[0058]
In other words, the pedestal 42 and the vibrator 2 are point-contacted at a plurality of places, or
line-contacted at a plurality of places, or the contact area with the vibrator 2, These may be
combined to support the vibrator 2 as long as
[0059]
Furthermore, although three ribs 46 are provided in the above embodiment, the present
invention is not necessarily limited to the configuration of this embodiment, and the balance of
the vibrator can be maintained if two or more locations are provided. .
And, in any of these cases, similar to the above, it is possible to reduce the spurious of the
vibrator.
14-04-2019
17
[0060]
DESCRIPTION OF SYMBOLS 1 piezoelectric sensor 2 unimorph vibrator (vibrator) 10
piezoelectric ceramics (piezoelectric body) 16, 26 lead wire (conductive wire) 20 diaphragm 40
case 42 pedestal 44 upper surface 46 support 46 (rib) 47 front end surface 50 notch (retraction)
Part) 52 Bonded part 54 Bottom surface 58, 60 Spacer
14-04-2019
18
Документ
Категория
Без категории
Просмотров
0
Размер файла
31 Кб
Теги
description, jp2012156622
1/--страниц
Пожаловаться на содержимое документа