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JP2002209294

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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
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DESCRIPTION JP2002209294
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
ultrasonic sensor, an electronic device provided with the same, and a back sonar for a vehicle.
[0002]
2. Description of the Related Art For example, in the case of an ultrasonic sensor mounted on the
rear of a vehicle and used as a back sonar for a vehicle, ultrasonic waves are transmitted toward
the rear of the vehicle while being reflected from an obstacle behind the vehicle. Data obtained
by electrically processing the relationship between the transmitted wave and the received wave,
for example, distance information obtained based on the time lag between the transmitted wave
and the received wave, to the rear of the vehicle It can be used to control the operation of a
vehicle as data indicating the relative positional relationship of obstacles.
[0003]
The conventional ultrasonic sensor includes a sensor case having a cylindrical shape with a
bottom with a cylindrical portion having an opening and a bottom portion closing the opening of
the cylindrical portion, and a wall portion constituting the bottom portion of the sensor case The
thickness is made thinner than the thickness of the side portion constituting the cylindrical
portion to form a diaphragm, and the piezoelectric vibration element is adhered on the
substantially central mounting surface of the bottom portion in the case.
[0004]
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In addition, conductive lead terminals are insert-molded in the sensor case, and one end of each
lead terminal is conductively connected to both element electrodes in the piezoelectric vibration
element, and both lead terminals are drawn out of the sensor case. Is connected to an external
circuit.
[0005]
In such an ultrasonic sensor, the piezoelectric vibration element is mechanically vibrated by the
application of an electric signal to both lead terminals, and the diaphragm is vibrated accordingly
to transmit ultrasonic waves while reflecting ultrasonic waves. The diaphragm vibrates due to the
ultrasonic waves, and the piezoelectric vibration element mechanically vibrates in response to the
vibration, and the vibration is converted into an electric signal to be input to an external circuit.
[0006]
In such an ultrasonic sensor, for example, when an ultrasonic signal is set to transmit in the
horizontal direction and receive waves, the wider the transmittable / receivable range in the
vertical direction, the lower the position than the installation position. It makes it easier to detect
what is present.
[0007]
In this transmission / reception possible range, the angle range in which the peak value is
reduced by half with respect to the center direction of the transmission / reception of the
ultrasonic signal is its limit, and the half angle range is called a half reduction angle.
[0008]
In the case of a conventional ultrasonic sensor, the diameter of the diaphragm is 16 mm, the
thickness of the side wall of the sensor case is 1.30 mm, and the half-width angle of directivity in
transmission / reception is 30 °. (See the directivity characteristic shown by the broken line in
FIG. 6).
[0009]
In the conventional ultrasonic sensor of the prior art, for example, in the case where the
ultrasonic signal is set to transmit and receive in the horizontal direction, it is possible to
transmit and receive in the vertical direction, That is, since the half-full angle of the directivity
characteristics of the transmitted and received waves is relatively wide, it is easy to detect the
one located below the installation position, and the lower position than the target that should be
detected originally There is a possibility that false detection may be made by receiving the
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reflected signal from the signal present in the first place.
[0010]
As a specific example, in many of the many parking compartments drawn with white paint
against the ground in the store parking lot, a block made of concrete blocks with a height of
about 10 cm above the ground is used. The vehicle back sonar equipped with the abovementioned conventional ultrasonic sensor having the above-mentioned conventional ultrasonic
sensor having a half transmission angle of 30 ° in the vertical direction although it is deployed,
parks the parking compartment area as described above. When this is done, there is a high
possibility that the reflection signal from the vehicle stop is erroneously detected as an obstacle
behind the vehicle, and if the vehicle stop based on the erroneous detection is performed, there is
a possibility that the interval between the vehicle rear and the vehicle stop becomes long.
The positional relationship between the vehicle M (virtual line) on which the vehicle stop is
erroneously detected and stopped and the vehicle stop 15 is illustrated in FIG.
[0011]
Therefore, although it is necessary to further reverse the vehicle to the parking area in order to
park correctly, a sensor for detecting the stop of the vehicle and notifying the driver of the stop
of the vehicle to the vehicle is detected. There is a problem in that the possibility of outputting
the output is high, and it is difficult to make the vehicle to drive by using the vehicle back sonar.
[0012]
Referring to FIG. 13, if the transmission from the ultrasonic sensor C and the reception by the
ultrasonic sensor C are relatively spread in the vertical direction in the back sonar of the vehicle
M, the ultrasonic sensor C Of the transmitted signals, the signal spreading downward is likely to
be reflected by the car stop 15 or the like near the ground, so when parking in the parking lot
while moving the vehicle M backward, the car stops before reaching the desired stop position A
warning or the like of obstacle detection is issued from the sonar by the detection of 15.
Therefore, there is a possibility that the vehicle may be stopped before the desired parking
position.
[0013]
Therefore, in view of such a request, the applicant of the present application has conducted
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various studies, and first, in the case of using an ultrasonic sensor for vehicle back sonar, by
devising the shape of the diaphragm portion at the bottom of the sensor case. However, we
initially considered narrowing the half-width of the directional characteristics simply to avoid
false detection of the vehicle stop, but narrowing the half-width of the directional characteristics
reduced the reverberation that is important in determining the performance of the ultrasonic
sensor. The reverberation characteristic is destabilized, for example, it may occur relatively long
in the sensor case.
[0014]
Therefore, the applicant of the present invention has further conducted studies to maintain the
reverberation characteristics well even if the half-full angle of the directivity characteristics is
narrowed, and the present invention can be completed here.
[0015]
That is, this invention makes it the issue which should be solved to be able to narrow the half-full
angle of the directivity characteristic of an ultrasonic wave, maintaining a reverberation
characteristic stably.
[0016]
Means for Solving the Problems (1) The ultrasonic sensor according to the present invention has
an ultrasonic sensor in which a piezoelectric vibration element is mounted substantially at the
center of the inner surface of the bottom of a bottomed cylindrical sensor case as a diaphragm. A
sound wave sensor, wherein the digging depth at least in the direction orthogonal to the
vibration plane of the diaphragm is equal to the bottom wall thickness with respect to the bottom
outer peripheral edge portion at the side of the sensor case It is characterized in that a deeper
digging is formed.
[0017]
According to the ultrasonic sensor of the present invention, at least the digging depth at least in
the direction orthogonal to the vibration plane of the diaphragm is equal to the bottom wall
thickness with respect to the bottom outer peripheral edge portion at the side of the sensor case
By forming a deeper digging, the reverberation time becomes shorter than in the past, and the
half-full angle of the directivity of the transmitted / received wave becomes narrower than in the
past. In the above angle range, it is possible to transmit and receive relatively narrow directivity
and sharp.
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And since it is not necessary to detect the reflection signal from the ultrasonic reflection source
which should not be detected from the detection direction by nature, false detection can be
eliminated, and also the reverberation time in the ultrasonic sensor The shorter reverberation
characteristic stabilizes the detection accuracy.
[0018]
In the case of the ultrasonic sensor according to the present invention, the digging is performed
relative to the digging depth in the direction orthogonal to the vibrating face of the diaphragm,
and a predetermined value is obtained with respect to the direction along the vibrating face of
the vibrating plate. When the depth is set, the vibration with respect to the digging in the bottom
outer peripheral edge portion of the cylindrical portion of the sensor case is relatively related to
the digging depth in the direction orthogonal to the vibrating surface of the diaphragm, the
vibration By setting the depth to a predetermined depth in the direction along the vibration plane
of the plate, the digging is formed in a dented state, whereby the transmission and reception of
the ultrasonic signal to the desired detection target is performed. The half-full angle of the
directivity characteristic can be made narrow and sharp, and the risk of false detection of a
reflected signal from ones outside the desired detection range can be reduced.
Furthermore, with this configuration, the reverberation time in the ultrasonic sensor can be
shortened, and the function as the sensor can be enhanced.
[0019]
In the case of the ultrasonic sensor according to the present invention, the digging is 0.7 ≦ X ≦
0.91.0 ≦ Y ≦ 3.0 Y ≦ −5X + 6.5, where X = t1 / At1: vibration plane of diaphragm Depth of
indentation t2 in the direction along the surface: Depth of indentation in the direction
perpendicular to the vibration plane of the diaphragm If the shape satisfies all the above
equations, directivity characteristics of transmitted and received waves in the ultrasonic sensor
As the half-full angle of the head becomes narrower and sharper than before, and the
reverberation time can be shortened, the possibility of erroneous detection of the reflected signal
from ones outside the desired detection range can be reduced, and the reverberation
characteristic is also reduced. It becomes stable and one with high sensor function can be
obtained.
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[0020]
(2) An electronic device comprising the ultrasonic sensor according to the present invention
comprises: the ultrasonic sensor according to any one of claims 1 to 3; applying an electrical
signal to the ultrasonic sensor; And an electrical circuit responsive to the electrical signal from
the sensor.
[0021]
According to the electronic device equipped with the ultrasonic sensor of the present invention,
the directivity characteristic in the required direction of the transmitted and received waves in
the ultrasonic sensor becomes sharp. In other words, the half-full angle can be reduced and the
ultrasonic sensor Since the reverberation time can be shortened and the reverberation
characteristics can be made stable, the electronic device using the ultrasonic sensor can
sufficiently cope with the case of performing transmission or reception with high directivity.
[0022]
(3) A vehicle back sonar equipped with the ultrasonic sensor of the present invention is mounted
on a vehicle and transmits ultrasonic waves toward an obstacle located at the rear of the vehicle
and receives reflected ultrasonic waves from the obstacle. An ultrasonic sensor as claimed in any
one of claims 1 to 3, which is a vehicle back sonar for processing the reflected ultrasonic waves
that have been received and received to detect the obstacle. If a control unit for controlling
transmission and / or reception of ultrasonic waves with respect to the ultrasonic sensor is
controlled by controlling the input and / or output of the electric signal, for example, when
stopping a vehicle in a parking lot It is possible not to receive the reflected ultrasonic signal from
the one that has a possibility of false detection such as a car stop or stone on the ground, and it is
possible to only receive the original detection target, that is, only the obstacle behind the vehicle
in the back sonar. Is intended to be detected, there are advantages such as can be satisfactorily
stop the vehicle.
[0023]
DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in
detail based on the embodiments shown in the drawings.
[0024]
(First Embodiment) FIGS. 1 to 6 relate to an embodiment of the present invention, and FIG. 1 is a
longitudinal sectional view of an ultrasonic sensor according to a first embodiment, and FIG. 2 is
a front view of the same sensor. 3 is a side view of the same sensor shown in FIG. 2, FIG. 4 is a
plan view of the same sensor shown in FIG. 2, FIG. 5 is a partially cutaway perspective view of
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the same sensor shown in FIG. It is a pattern figure which shows the transmission-and-reception
directivity characteristic of the ultrasonic beam by the ultrasonic sensor shown to.
[0025]
In these figures, the ultrasonic sensor according to the first embodiment has an aluminum sensor
case 4 having a cylindrical shape with a bottom with a cylindrical portion 2 having an opening
and a bottom portion 3 closing the opening of the cylindrical portion 2. In the sensor case 4, the
wall thickness of the bottom portion 3 is thinner than the thickness of the side wall 6 as the side
portion of the cylindrical portion 2 to constitute the diaphragm 5, and The piezoelectric vibration
element 7 is bonded on a substantially central mounting surface on the inner side of the bottom
portion 3 in the inside 4.
[0026]
The opening of the sensor case 4 is closed by a lid 8, and a pair of external terminals T, T are
supported by the lid 8 so as to pass therethrough.
A control circuit (not shown) is connected to the external terminals T, T.
[0027]
The respective external terminals T, T are connected to respective one end sides of the
conductive lead wires 9, 9, respectively.
The other end side of one lead wire 9 is directly connected to one element electrode of the
piezoelectric vibration element 7, and the other end side of the other lead wire 9 is via the
cylindrical portion 2 and the bottom portion 3 of the sensor case 4 It is connected to the other
element electrode of the piezoelectric vibrating element 7.
[0028]
In such an ultrasonic sensor, the piezoelectric vibration element 7 is mechanically vibrated by the
application of the electric signal from the control circuit, and along with this, the diaphragm 5 is
vibrated to transmit ultrasonic waves, while the object is The vibration plate 5 is vibrated by the
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ultrasonic wave reflected and received, and the piezoelectric vibration element 7 is mechanically
vibrated accordingly, and the vibration is converted into an electric signal to be input to the
control circuit.
[0029]
And in this ultrasonic sensor, the thickness of the side wall 6 which constitutes cylinder part 2 in
sensor case 4 is a horizontal direction in the state where cylinder part 2 was set as the attitude
which met in the horizontal direction, as shown in Drawing 1. The cross-sectional shape of the
cavity K inside the sensor case 4 is short in the horizontal direction and long in the vertical
direction, as shown in FIG. The central portion in the longitudinal direction of the rectangular
shape is cut out in a circular shape in a front view.
[0030]
In such a sensor case 4, the transmission / reception range in the vertical direction is narrowed
with respect to the outer peripheral edge portion of the bottom portion 3, that is, the outer
peripheral edge portion of the bottom side end of the cylindrical portion 2. A digging 10 is
formed which has the function of reducing the reverberation time in the fourth.
As the range of the outer peripheral edge portion of the bottom 3 in which the digging 10 is
formed, a portion where the longitudinal cross-sectional shape is connected to the bottom 3 and
the end of the cylindrical portion 2 becomes a corner and the cylindrical portion 2 It includes the
outer peripheral part near the opening.
[0031]
As shown in FIG. 2, this digging 10 has a step which is recessed over the entire circumference at
a position corresponding to the end on the side of the bottom 3 in the cylindrical portion 2 at the
outer periphery of the bottom 3 in the sensor case 4 It is formed.
[0032]
The digging 10 is, as shown in FIGS. 1 to 5, in a direction perpendicular to the vibration plane of
the diaphragm 5 of the bottom 3 (direction parallel to the outer peripheral surface of the cylinder
2), ie, a plane along the horizontal direction. That is, two surfaces are formed: a circumferential
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surface concentric with the outer peripheral surface of the cylindrical portion 2 and a surface
along a direction parallel to the vibration surface of the diaphragm 5 of the bottom 3, ie, a plane
along the vertical direction in FIGS. It is formed by cutting or grinding so as to have a concave
shape.
In FIG. 2 to FIG. 5, the lead wires 9, 9, the external terminals T, etc. are omitted.
[0033]
This digging 10 has a shape that suppresses the transmission / reception range in the vertical
direction to 24 ° or less and the reverberation time to 1.2 ms or less. Specifically, the diameter
of the diaphragm is 16 mm. When it is set, it has a shape which satisfies all of following each
Formula (1), (2), (3).
[0034]
0.7 ≦ X ≦ 0.9 (1) 1.0 ≦ Y ≦ 3.0 (2) Y ≦ −5X + 6.5 (3) where X = t1 / At1: vertical direction
(diaphragm Digging depth t2 in the direction along the vibration plane: Digging depth in the
horizontal direction (direction orthogonal to the vibration plane of the diaphragm) All the above
formulas (1), (2) and (3) are satisfied In the case of the ultrasonic sensor of Embodiment 1 having
a shape, as shown in FIG. 6, it has a half-full angle (indicated by a solid line) of directivity
characteristics in transmission and reception in the vertical direction. It has a half full angle of
directivity characteristics in transmission and reception in the horizontal direction (the directivity
shown by the broken line is almost the same as that of the ultrasonic sensor before the
conventional research in transmission and reception in the vertical direction).
[0035]
Therefore, in the case of the ultrasonic sensor of the first embodiment, the vertical direction is
more than the half-full angle of the directivity in transmission / reception in the vertical direction
of the conventional ultrasonic sensor before the improvement of the reverberation characteristics
shown in FIG. The directional characteristics of are becoming more acute.
[0036]
Second Embodiment FIGS. 7 to 10 relate to a second embodiment of the present invention, FIG. 7
is a perspective view of an ultrasonic sensor according to a second embodiment, and FIG. 8 is a
front view of the same sensor shown in FIG. FIG. 9 is a side view of the same sensor shown in
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FIG. 7, and FIG. 10 is a plan view of the same sensor shown in FIG.
Description of the same structure as that of the first embodiment described above will be
omitted, and the same reference numerals will be assigned.
[0037]
In the ultrasonic sensor according to the second embodiment shown in these drawings, the
cylindrical portion 2 of this ultrasonic sensor is horizontally aligned, and the rectangular
longitudinal direction of the cavity K having a substantially rectangular cross section inside the
sensor is vertical. In the posture set along, only in the vicinity of the upper and lower ends of the
outer peripheral edge portion of the bottom 3 of the sensor case 4 is dug so as to have a concave
angle in two planes of a plane along the horizontal direction and a plane along the vertical
direction. , 11 are formed.
However, the plane along the horizontal direction is a plane along the horizontal direction, unlike
the first embodiment.
7 to 10, illustration of the lead wires 9, 9, the external terminals T, etc. provided as shown in FIG.
1, for example, is omitted.
[0038]
As with the ultrasonic sensor according to the first embodiment, the ultrasonic sensor according
to the second embodiment has the following formulas (1), (2), and (3) when the diameter of the
diaphragm is 16 mm. Have a shape that satisfies all of the above.
[0039]
0.7 ≦ X ≦ 0.9 (1) 1.0 ≦ Y ≦ 3.0 (2) Y ≦ −5X + 6.5 (3) where X = t1 / At1: vertical direction
(diaphragm Engraving depth t2 in the direction along the vibration surface: Engraving depth in
the horizontal direction (direction orthogonal to the vibrating surface of the diaphragm) A shape
satisfying the above formulas (1), (2) and (3) Also in the case of the ultrasonic sensor according
to the second embodiment provided, the transmission / reception range in the vertical direction
is narrower when in the attitude shown in FIGS. 8 to 10 as compared with the conventional
ultrasonic sensor. While the directivity characteristic in the vertical direction is sharp, the
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reverberation time becomes short, and the reverberation characteristic becomes stable.
[0040]
Third Embodiment Next, an electronic device provided with the ultrasonic sensor according to
the first or second embodiment will be described.
[0041]
FIG. 11 schematically shows a remote control device R as an example of the electronic device.
The remote control device R has an ultrasonic sensor C disposed at one end of the outer case 12
and the ultrasonic sensor C has a vibrating surface of a diaphragm so as to transmit an ultrasonic
signal as a remote control signal. Facing the outside.
Then, an electric circuit 13 for outputting a driving signal for transmitting a wave to the
ultrasonic sensor C is provided, and a switch SW or the like for manually giving a desired remote
control operation command to the electric circuit 12 is provided. It is equipped with a remote
control device.
The ultrasonic sensor C is dedicated to transmission.
[0042]
This remote control device is capable of remote control operation of, for example, a plurality of
types of electric devices, and even when the electric devices D of the operation object are
adjacent in the lateral direction, only the electric device D of the desired operation object is
operated. The ultrasonic sensor according to the above-described Embodiment 1 or 2 is provided
to enhance directivity in the lateral direction more than in the vertical direction so that the
ultrasonic signal for the purpose of reaching the directivity high. For example, only the electric
device in the direction in which the remote control device is directed can be turned on and off.
[0043]
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On the other hand, the ultrasonic sensor C2 for receiving only, provided on the side of the
electric device D to be operated, also has a sharp directional characteristic of receiving in the
lateral direction. A sound wave sensor may be provided.
In this case, since the electric device D to be operated receives only ultrasonic signals from a
narrow predetermined direction in the lateral direction, it does not receive unnecessary
ultrasonic signals coming from other than the predetermined direction. , Which has the
advantage of being able to prevent erroneous operations.
[0044]
The electronic device provided with such an ultrasonic sensor is not limited to the remote control
device, and the present invention can be applied to various electronic devices.
[0045]
Fourth Embodiment Next, a vehicle back sonar S provided with the ultrasonic sensor according to
the first or second embodiment will be described.
[0046]
FIG. 12 shows a state in which a passenger car M as an example of a vehicle is parked while
moving backward to a parking lot.
The rear bumper of the passenger car M is provided with an ultrasonic sensor C which
constitutes a back sonar S for detecting an approaching state of an obstacle behind the vehicle.
Control is performed to output an electric signal for transmission to the piezoelectric vibrating
element of the ultrasonic sensor C, and an electric signal generated by vibrating the piezoelectric
vibrating element by receiving a reflected ultrasonic signal as a detection signal A control circuit
14 as a control unit to be input is provided on the vehicle body to constitute a back sonar S.
In the control circuit 14, in order to detect an obstacle behind the passenger car M, an ultrasonic
signal is transmitted from the ultrasonic sensor C at predetermined time intervals, and from the
transmission when the reflected ultrasonic wave from the obstacle is received. The distance
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between the rear of the vehicle and the obstacle is calculated based on the elapsed time until the
wave is received, and when it is determined that the rear of the vehicle and the obstacle are
closer than a predetermined distance, The warning means is to issue an alarm.
[0047]
And in this ultrasonic sensor C, this ultrasonic sensor C is made so that directivity characteristics
in transmission and / or reception in the vertical direction become sharper than directivity
characteristics in transmission and / or reception in the horizontal direction. The radiation
surface of the transmission / reception wave of the ultrasonic signal on the side having the
narrower half-full angle in the directivity characteristic of the above is arranged in the vertical
direction.
[0048]
Therefore, in this ultrasonic sensor, the directivity characteristics in the vertical direction of the
transmitted and / or received waves are sharp. For example, when parking while moving
backward, as shown in FIG. On the other hand, since it is out of the range which can be detected
by the signal from the ultrasonic sensor C, the false detection of the vehicle stop 15 can be
avoided and the obstacle 16 such as a wall or another vehicle can be detected. ing.
This makes it possible to avoid such a problem that a warning is issued due to a false detection of
the vehicle stop 15 and the vehicle is stopped at a position before the predetermined parking
position, and the vehicle is stopped at the predetermined parking position. Can.
[0049]
In addition, as an ultrasonic sensor with which a back sonar is equipped, it is not limited to what
can transmit / receive a wave with a single sensor, Even if it is the composition which combined
the sensor only for wave transmission and the sensor only for wave reception. good.
[0050]
In addition, the ultrasonic sensor which concerns on this invention is not limited to the abovementioned embodiment, For example, the various application as shown below and a deformation
| transformation are possible.
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[0051]
(1) As shown in FIG. 14, at the outer peripheral edge of the bottom portion 3 of the sensor case
4, the shape of the recess 10 to be recessed corresponding to the direction in which the
directivity characteristics of transmitted / received waves are to be narrowed The back corner
portion where the digging in the direction orthogonal to the vibrating surface of the diaphragm 5
of the bottom portion 3 and the digging in the direction along the vibrating surface of the
vibrating plate 5 intersect may be configured as a curved surface.
[0052]
(2) As shown in FIG. 15, at the outer peripheral edge of the bottom portion 3 of the sensor case
4, the shape of the recess 10 to be recessed corresponding to the direction in which the
directivity characteristics of transmitted / received waves are to be narrowed In the figure, the
back corner where the digging in the direction orthogonal to the vibration plane of the
diaphragm 5 at the bottom 3 intersects with the digging in the direction along the vibrating
plane of the diaphragm 5 is curved so as to be further recessed upward. You may comprise in the
shape made to let.
[0053]
(3) As shown in FIG. 16, at the outer peripheral edge of the bottom 3 of the sensor case 4, the
shape of the recess 10 to be recessed corresponding to the direction in which the directivity
characteristics of transmitted / received waves are to be narrowed The deep corner portion
where the digging in the direction orthogonal to the vibrating surface of the diaphragm 5 of the
bottom 3 and the digging in the direction along the vibrating surface of the vibrating plate 5 may
be configured in a step shape.
[0054]
(4) As shown in FIG. 17, in the bottom 3 outer peripheral edge portion of the sensor case 4, in
the cross-sectional shape of the digging 10 to form a recess corresponding to the direction in
which the directivity characteristics of transmitted and received waves are desired to be
narrowed. The groove 17 along the circumferential direction may be formed on the outer
peripheral surface located on the upper side by the thickness than the end face position 3.
[0055]
(5) As shown in FIG. 18 and FIG. 19, the cylindrical portion forming the side wall portion of the
sensor case 4 and the bottom portion are constituted by separate members, and the vicinity of
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the connection portion between the outer peripheral edge portion of the bottom portion and the
end portion of the cylindrical portion In this case, the digging 10 having the same structure as
that of the first embodiment may be formed.
(6) In the above embodiment, when the diameter of the diaphragm is 16 mm, the one satisfying
the formula of the invention according to claim 3 of the present application is described, but the
diameter of the diaphragm is 16 mm. It is not limited as long as the digging of claim 1 or claim 2
is formed.
[0056]
Next, an embodiment according to the present invention will be described with reference to FIGS.
[0057]
The inventor made the digging depth of the bottom outer periphery of the ultrasonic sensor with
a diameter of 16 mm of the diaphragm 16 as shown in FIG. 1 along the sensor side wall, as
shown in FIG. Multiple types of depth t2 in the direction and depth t1 in the direction orthogonal
to the vibration plane of the sensor diaphragm are set, and vertical direction directivity is
obtained in combination in which various types of depths are formed by digging The half full
angle of the characteristics and the reverberation time in transmission and reception were
measured.
The results are shown as tables and graphs in FIGS.
In the drawing, A represents the thickness of the side wall 6 of the cylindrical portion 2 in the
vertical direction in the sensor case 4, and B represents the thickness in the transmission /
reception direction of the diaphragm 5.
Therefore, t1 / A corresponds to X in claim 3, and t2 / B corresponds to Y in claim 3.
[0058]
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15
From the above, the inventors set the depth in the direction along the vibration surface of the
diaphragm in the range where X is from 0.7 to 0.9 that the half-full angle is the smallest 24
degrees. And, it was confirmed that the depth was set in the direction orthogonal to the vibration
plane of the diaphragm in the range where Y was from 1.0 to 4.0.
Also, when the reverberation time is within 1.24 ms where there is no adverse effect on
transmission and reception, X is in the range of 0.7 to 0.9, and when X is 0.7, Y is 3.0 or less, It
was confirmed that when X was 0.9, Y was set to a range of 2.0 or less.
Therefore, in the ultrasonic sensor having a diaphragm diameter of 16 mm, the inventor has
pointed out that the directional characteristic in the vertical direction is sharp and the formation
of the digging excellent in the reverberation characteristic is the following formulas (1) and (1) 2)
and (3) were all confirmed to have a satisfactory shape.
[0059]
0.7 ≦ X ≦ 0.9 (1) 1.0 ≦ Y ≦ 3.0 (2) Y ≦ −5X + 6.5 (3) where X = t1 / At1: vertical direction
(diaphragm Digging depth t2 in the direction along the vibrating surface: Digging depth in the
horizontal direction (direction perpendicular to the vibrating surface of the diaphragm)
[0060]
As described above, according to the present invention, the digging depth at least in the direction
orthogonal to the vibration plane of the diaphragm is the bottom of the bottom outer peripheral
edge portion of the side portion of the sensor case. By forming a digging having a depth equal to
or deeper than the wall thickness, the reverberation time becomes shorter than in the prior art
and the half-full angle of the directivity of the transmitted and received waves becomes narrower
than in the past. A relatively narrow and directional sharp transmission / reception can be
performed within an angle range in a required direction with respect to the detection target.
And since it becomes unnecessary to detect the reflection signal from the ultrasonic wave
reflection source which should not be detected originally from the detection direction, false
detection can be eliminated, and the reverberation time in the ultrasonic sensor is further
reduced. The reverberation characteristics can be stabilized and the detection accuracy can be
increased.
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