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JP2008099103

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JP2008099103
PROBLEM TO BE SOLVED: To realize an on-vehicle ultrasonic sensor which can improve the
crosstalk characteristic of an ultrasonic wave receiving element and can be miniaturized.
SOLUTION: A receiving element having a plurality of vibrating parts is mounted on a receiving
member 31, and the receiving member 31 is divided into areas 31a and 31b corresponding to
the respective vibrating parts. Between the areas 31a and 31b, a shielding part 31i formed in a
groove shape in the direction perpendicular to the receiving parts 31e and 31f is provided, and
the transmission of ultrasonic waves is separated between the areas 31a and 31b. Can be done.
Since it is not necessary to provide a shock absorbing material for absorbing vibration between
the regions 31a and 31b, the ultrasonic sensor 70 can be miniaturized. The position detection
accuracy required for an on-vehicle ultrasonic sensor when the relationship of 0.35 ≦ L / T ≦
0.60 holds between the depth L of each shielding portion and the thickness T of the receiving
member. Can be realized. [Selected figure] Figure 3
Ultrasonic sensor
[0001]
The present invention relates to a vehicle-mounted ultrasonic sensor that receives and detects an
ultrasonic wave transmitted from a transmission element and reflected by a detection target by a
reception element.
[0002]
In recent years, as an ultrasonic sensor of this type, for example, an obstacle sensor mounted on
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a car (vehicle) is known.
The ultrasonic sensor transmits ultrasonic waves from an element capable of transmitting and
receiving ultrasonic waves, and receives ultrasonic waves reflected by the object to be detected,
thereby measuring the position of an object located around the automobile or It performs
distance measurement, measurement of the two-dimensional shape or three-dimensional shape
of the object, and the like. As ultrasonic sensors applicable to the above applications, it is possible
to use a sensor that receives reflected sound from an obstacle by a plurality of receiving elements
and determines the position of the obstacle by the deviation of the timing. In such ultrasonic
sensors, receiving members for receiving ultrasonic waves and transmitting them to the receiving
elements are provided corresponding to the respective receiving elements, but transmission of
ultrasonic waves between the receiving members becomes a noise component It is a cause of
crosstalk between elements. That is, since the ultrasonic waves received by the receiving member
are not separated for each corresponding receiving element, there is a problem that the detection
sensitivity of the ultrasonic waves is lowered. Therefore, for example, Patent Document 1
discloses an ultrasonic sensor provided with a plurality of diaphragms for receiving ultrasonic
waves, in which a buffer material for blocking transmission of the ultrasonic waves is filled in a
gap between the diaphragms. It is done. Unexamined-Japanese-Patent No. 05-347797
[0003]
However, this configuration requires a step of placing a buffer in the gap of each diaphragm to
inhibit the transmission of ultrasonic waves, which is disadvantageous in cost and requires a gap
to put the buffer, so ultrasonic waves The physical size of the sensor becomes large, and there is
a problem that it is not suitable as a vehicle-mounted ultrasonic sensor that requires
designability.
[0004]
Then, this invention aims to implement | achieve the vehicle-mounted ultrasonic sensor which
can improve the crosstalk characteristic of the receiving element of an ultrasonic wave, and can
be reduced in size.
[0005]
In order to achieve the above object according to the present invention, in the invention
according to claim 1, an ultrasonic sensor for mounting on a vehicle is transmitted from a
transmitting means for transmitting an ultrasonic wave, and the ultrasonic wave reflected by the
object to be detected A receiving element having a vibrating part that transmits and vibrates, a
supporting member that supports the vibrating part and transmits an ultrasonic wave, and a
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receiving part that receives the ultrasonic wave reflected by the object to be detected The
ultrasonic detecting element is attached to the surface exposed to the space side where the object
to be detected exists and facing the receiving unit in the transmitting unit, and the ultrasonic
wave received by the receiving unit is transmitted to the transmitting unit A plurality of the
vibration units are attached to the reception member via the support members, and the reception
member is divided into areas corresponding to the respective vibration sections, and In between,
perpendicular to the receiver Shields which are formed in a groove shape in a vertical direction
or in a substantially vertical direction and prevent the transmission of the ultrasonic waves
received by the receiver between the respective regions, and the depth L of each shield and The
technical means is used such that the relationship of 0.35 ≦ L / T ≦ 0.60 holds with the
thickness T of the receiving member.
[0006]
According to the first aspect of the present invention, in the ultrasonic sensor for mounting on a
vehicle, the receiving element having a plurality of vibration parts to which the ultrasonic wave
reflected by the detected body transmits and vibrates is the receiving member. It is mounted, and
the receiving member is divided into regions corresponding to the respective vibrating portions.
A shielding portion is formed in a groove shape in a direction perpendicular to or substantially
perpendicular to a receiving unit that receives ultrasonic waves between the respective regions,
and that blocks transmission of the ultrasonic waves received by the receiving unit between the
respective regions. Are provided respectively.
In the shielding unit, the ultrasound transmission medium becomes air and the attenuation
increases, so that the ultrasound transmission between the regions can be interrupted, and the
ultrasound received in each of the divided regions of the receiving member is It is transmitted
only to the corresponding vibration part and not to the other vibration parts.
Therefore, it becomes possible to separate the transmission of the ultrasonic waves between the
respective regions, and to prevent the ultrasonic waves respectively received by one receiver
from being transmitted to the adjacent regions and becoming noise components. Since this can
be done, the crosstalk characteristics of each vibrating portion can be improved. In addition, it is
sufficient to form the shielding part in the receiving member, and it is not necessary to provide a
shock absorbing material for absorbing vibration between the respective regions, so that the
process of providing the shock absorbing material is unnecessary and Can be Here, when the
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relationship of 0.35 ≦ L / T ≦ 0.60 holds between the depth L of each shielding portion and the
thickness T of the receiving member, the case of using as an on-vehicle ultrasonic sensor It is
possible to realize an ultrasonic sensor that satisfies the detection accuracy of the position of the
detection subject required for the above.
[0007]
According to the invention of claim 2, in the ultrasonic sensor for mounting on a vehicle
according to claim 1, L / T = 0 between the depth L of each shielding portion and the thickness T
of the receiving member. It uses technical means that it is formed so that the following
relationship holds.
[0008]
According to the second aspect of the present invention, the relationship of L / T = 0.45 can be
established between the depth L of each shielding portion and the thickness T of the receiving
member.
At this time, since the noise component is eliminated, the sensitivity of the ultrasonic sensor can
be most improved.
[0009]
According to the invention of claim 3, in the ultrasonic sensor for mounting on a vehicle
according to claim 1, 0.35 ≦ L / between the depth L of each shielding portion and the thickness
T of the receiving member. Use the technical means that the relationship of T <0.45 is
established.
[0010]
According to the third aspect of the present invention, the relationship of 0.35 ≦ L / T <0.45 is
established between the depth L of each shielding portion and the thickness T of the receiving
member. Therefore, since the depth of the shielding part is shallow, the noise component can be
reduced while maintaining the strength of the receiving member high.
[0011]
In the invention according to claim 4, in the ultrasonic sensor for mounting on a vehicle
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according to claim 1, a relationship between the depth L of each of the shielding portions and the
thickness T of the receiving member is 0.45 <L /. Use the technical means that the relationship of
T ≦ 0.60 is established.
[0012]
According to the fourth aspect of the present invention, a relation of 0.45 <L / T ≦ 0.60 is
established between the depth L of each shielding portion and the thickness T of the receiving
member. it can.
At this time, since the signal of the noise component is in anti-phase, the signal component of
anti-phase can be easily processed as the noise component.
[0013]
In the invention according to claim 5, in the ultrasonic sensor for mounting on a vehicle
according to any one of claims 1 to 4, the stress relieving portion for smoothly connecting the
side surface and the bottom surface of the shielding portion is provided. Use technical means to
be provided.
[0014]
According to the fifth aspect of the present invention, since the stress relieving portion that
smoothly connects the side surface and the bottom surface of the shielding portion is provided,
there is no corner portion where stress concentrates, so the strength of the receiving member is
increased. Even when the receiving member is loaded with an external force or when a shear
stress is generated in the shielding portion due to the transmission of an ultrasonic wave, the
possibility of breakage can be reduced.
[0015]
In the invention according to claim 6, in the ultrasonic sensor for mounting on a vehicle
according to any one of claims 1 to 5, the shielding portion is formed in a plurality of parallel
grooves. Use technical means.
[0016]
According to the invention of claim 6, since the shielding part is formed in a plurality of parallel
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groove shapes, the width of the opening of the shielding part becomes narrow, so that foreign
matter that inhibits the shielding of the ultrasonic wave penetrates Can reduce the risk of
[0017]
In the invention according to claim 7, in the ultrasonic sensor for mounting on a vehicle
according to any one of claims 1 to 6, the shielding portion has a Young's modulus lower than
that of the receiving member, and the ultrasonic wave is used. Material is used to inhibit the
transmission of
[0018]
According to the seventh aspect of the present invention, since the shielding portion is filled with
a material having a lower Young's modulus than the receiving member and inhibiting the
transmission of the ultrasonic wave, the shielding effect of the ultrasonic wave by the shielding
portion is maintained. As it is, it is possible to eliminate the possibility of the foreign matter
which obstructs the shielding of the ultrasonic wave from entering the shielding part.
[0019]
In the invention according to claim 8, in the ultrasonic sensor for mounting on a vehicle
according to any one of claims 1 to 6, a lid member for covering the opening of the shielding
portion is provided on the shielding portion. Use the technical means of
[0020]
According to the invention as set forth in claim 8, since the cover portion is provided in the
shield portion to cover the opening portion of the shield portion, the ultrasonic wave is applied to
the shield portion while maintaining the shielding effect of the ultrasonic wave by the shield
portion. It is possible to eliminate the possibility that foreign substances that block the shielding
of
[0021]
In the invention according to claim 9, in the ultrasonic sensor for mounting on a vehicle
according to any one of claims 1 to 8, the vibration unit is constituted using a piezoelectric
material, and distortion caused by vibration is generated. A technical means is used that is a
piezoelectric vibration detection unit that detects vibration according to.
[0022]
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According to the invention as set forth in claim 9, since the vibrating portion is a piezoelectric
vibration detecting portion which is configured using a piezoelectric material and detects the
vibration by the strain caused by the vibration, the displacement of the vibrating portion caused
by the resonance Since the signal intensity that is converted into a signal and output from the
receiving element is strong and the ultrasonic wave reception sensitivity is high, the ultrasonic
wave detection sensitivity can be improved.
[0023]
In the invention according to claim 10, in the ultrasonic sensor for mounting on a vehicle
according to any one of claims 1 to 8, the vibrating portion includes a pair of electrodes, and the
capacitance change between the electrodes A technical means is used that is a capacitive
vibration detection unit that detects vibration by
[0024]
According to the invention as set forth in claim 10, the vibrating portion is a capacitive vibration
detecting portion having a pair of electrodes and detecting the vibration by a change in
capacitance between the electrodes, and the capacitive vibration detecting portion has a broad
resonant frequency. Therefore, high dimensional accuracy is not required for the vibrating part,
and it can be easily manufactured.
[0025]
In the invention according to claim 11, in the ultrasonic sensor for mounting on a vehicle
according to any one of claims 1 to 10, it is technically said that the receiving member is formed
of a polycarbonate resin material. Use means.
[0026]
According to the invention as set forth in claim 11, since the receiving member is made of a
polycarbonate resin material, the acoustic impedance of the receiving member can be made close
to the acoustic impedance of the support member, and ultrasonic waves can be efficiently
transmitted to the receiving element. Can be transmitted.
In addition to being exposed to the outside air, the receiving element can be protected from the
load of external force because it is a robust material with high weather resistance.
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Furthermore, since a polycarbonate resin is used as a constituent material of a bumper and the
presence of the ultrasonic sensor can be made inconspicuous, an ultrasonic sensor excellent in
design can be manufactured.
[0027]
The invention according to claim 12 uses the technical means that the ultrasonic sensor for
mounting on a vehicle according to any one of claims 1 to 11 is provided in a vehicle.
[0028]
In particular, when the ultrasonic sensor is provided in the bumper of a vehicle as in the
invention according to claim 12, it is effective when applying the ultrasonic sensor to the
detection of an obstacle that hinders the progress of the vehicle.
[0029]
An embodiment of an ultrasonic sensor according to the present invention will be described with
reference to the drawings.
Here, the case where an ultrasonic sensor is mounted on a vehicle and used as an obstacle sensor
will be described as an example.
FIG. 1 is an explanatory view of a receiving element of an ultrasonic sensor.
FIG. 1A is a plan view of the receiving element, and FIG. 1B is a cross-sectional view taken along
the line A-A of FIG.
FIG. 2 is an explanatory view of the arrangement of the receiving elements in the ultrasonic
sensor.
FIG. 3 is a cross-sectional view of an ultrasonic sensor mounted on a vehicle.
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FIG. 4 is an explanatory view showing an output signal at adjacent receiving elements by
ultrasonic waves received by different receiving units.
FIG. 5 is an explanatory view showing the relationship between the depth of the shielding portion
and the transmission rate of the noise component of the ultrasonic wave.
FIG. 6 is an explanatory view showing the relationship between the orientation error of the
ultrasonic sensor and the SN ratio.
7 and 8 are explanatory views showing a modification of the shielding portion.
In each of the drawings, a part is enlarged for the purpose of explanation.
[0030]
(Structure of Receiving Element) First, the receiving element used in the ultrasonic sensor of the
present embodiment will be described.
As shown in FIGS. 1A and 1B, the receiving element 10 is formed using a square semiconductor
substrate 11 having an SOI (Silicon On Insulator) structure.
The semiconductor substrate 11 is formed by laminating a first insulating film 11b, a silicon
active layer 11c, and a second insulating film 11d in this order on the upper surface 11m of the
support member 11a made of silicon.
In the central portion of the semiconductor substrate 11, the central portions of the support
member 11a and the first insulating film 11b are removed in a square shape by the MEMS
technology.
As a result, the support member 11a is formed in the form of a flat plate whose center is
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hollowed out in a square, and the remaining silicon active layer 11c and the second insulating
film 11d are formed in the form of a square thin film.
[0031]
A piezoelectric vibration detection unit 12 is formed on the second insulating film 11 d so as to
cover the thin film-formed portion.
The vibration detection unit 12 is formed, for example, by sandwiching a piezoelectric thin film
12 a made of lead zirconate titanate (PZT) with the lower electrode 13 and the upper electrode
14. Thus, the vibrating portion 15 whose end is lifted by the support member 11a is formed. The
vibration unit 15 has a predetermined resonance frequency, receives an ultrasonic wave
reflected by the detection object and transmitted to the receiving element 10, and resonates. The
displacement of the vibration unit 15 generated by this resonance is converted into a voltage
signal by the piezoelectric vibration detection unit 12 to detect an ultrasonic wave. As described
above, the receiving element 10 manufactured by using the MEMS technology is suitable as a
receiving element because the receiving sensitivity of ultrasonic waves is high.
[0032]
(Structure of Ultrasonic Sensor) Next, the structure of the ultrasonic sensor will be described. In
the ultrasonic sensor 70 according to the present embodiment, a plurality of receiving elements
are arranged in an array. In FIG. 2, the arrangement of only the receiving elements in the
ultrasonic sensor 70 is shown. As shown in FIG. 2, in the present embodiment, a total of four
receiving elements 10a, 10b, 10c, and 10d are disposed, two each in the vertical and horizontal
directions. When the receiving elements are arranged as described above, the time difference and
the phase difference of the ultrasonic waves received by each of the receiving elements 10a to
10d are determined, and based on the respective differences, not only the distance to the object
to be detected The position of can be measured in three dimensions.
[0033]
In FIG. 3, the lower part in the figure shows the outside of the vehicle. Here, in FIG. 3, the
structure of the vibrating portion 15 (15a, 15b) is simplified and shown. As shown in FIG. 3, the
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ultrasonic wave is transmitted from the transmitting element 19 for transmitting the ultrasonic
wave, and the ultrasonic wave reflected by the detection object such as the obstacle M existing in
the vicinity of the vehicle is received. The formed receiving member 31 is attached to the bumper
52 of the vehicle in a state where the receiving units 31e and 31f that receive the ultrasonic
waves are exposed to the outside of the vehicle. Here, the bumper 52 is provided with an
attachment portion 52a formed to have a size that allows the reception member 31 to be
inserted therethrough, and the reception member 31 prevents transmission of ultrasonic waves
between the attachment portion 52a and the attachment portion 52a. It is attached to the
attachment portion 52a with a shock absorbing material 41 formed of a material having high
vibration isolation such as rubber interposed.
[0034]
In order to efficiently transmit ultrasonic waves to the receiving elements 10a and 10b, it is
effective to make the acoustic impedance of the receiving member 31 close to the acoustic
impedance of the support member 11a. In addition to being exposed to the external air, the
receiving member 31 must protect the receiving elements 10a and 10b from the load of external
force, and therefore, needs to be formed using a robust material having high weather resistance.
Therefore, in the present embodiment, the receiving member 31 is formed of a polycarbonate
resin. Here, since the polycarbonate resin is a constituent material of the bumper 52, the
presence of the ultrasonic sensor 70 can be made inconspicuous, so that the ultrasonic sensor 70
excellent in design can be manufactured. Can maintain the beauty of In addition, as a material
which comprises the receiving member 31, various metal materials, such as stainless steel and
aluminum alloy, various synthetic resins, glass, ceramics, rubber, etc. can also be used.
[0035]
A groove-shaped shielding portion 31i is formed in the receiving member 31 from the central
portion in the surface direction toward the outside of the vehicle, and the receiving member 31 is
divided into an area 31a and an area 31b by the shielding portion 31i. There is. The shielding
part 31i is opened on the inner wall parts 31g and 31h side, and closed on the receiving part 31e
and 31f side. In the shielding part 31i, the transmission medium of the ultrasonic wave becomes
air, and the attenuation becomes large. Therefore, the ultrasonic wave does not propagate from
the area 31a to the area 31b across the shielding part 31i.
[0036]
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The receiving elements 10a and 10b are attached to the inner wall portions 31g and 31h of the
receiving member 31 on the attachment surface 11n of the support member 11a via the bonding
layer 24 made of an adhesive, glass, etc. It is housed inside. That is, the receiving member 31 is
divided into areas 31a and 31b corresponding to the receiving elements 10a and 10b,
respectively, by the shielding unit 31i.
[0037]
Circuit elements 21 for detecting a voltage signal output from the vibration detection unit 12
(FIG. 2) are electrically connected to the reception elements 10a and 10b. A terminal 22 for
outputting a signal to the ECU is electrically connected to the circuit element 21. The terminal 22
is exposed to the outside of the housing member 23 and electrically connected to the ECU. The
two adjacent receiving elements of the receiving elements 10a to 10d have the same structure as
the sectional structure of the above-described receiving elements 10a and 10b.
[0038]
(Transmission of Ultrasonic Waves) As shown in FIG. 3, the ultrasonic waves transmitted from
the transmission element 19 and reflected by the obstacle M as a detection object are received by
the reception units 31 e and 31 f of the reception member 31, The light is transmitted in the
thickness direction of the receiving member 31 toward the receiving elements 10a and 10b.
Next, the ultrasonic waves propagating through the receiving member 31 are transmitted from
the inner wall portions 31g and 31h of the receiving member 31 through the bonding layer 24
to the supporting member 11a as vibrations in the solid. The ultrasonic wave transmitted to the
support member 11a is transmitted inside the support member 11a to vibrate the vibrating
portions 15a and 15b. Then, when the vibration units 15a and 15b vibrate, a voltage signal is
output from the piezoelectric vibration detection unit 12 (FIG. 1) to the circuit element 21.
[0039]
Then, the circuit element 21 performs arithmetic processing based on the voltage signal output
from the vibration detection unit 12 and, for example, amplification of the signal and removal of
noise, or the ultrasonic wave transmitted from the transmitting element 19 and the receiving
element 10 By comparing the received ultrasonic waves with each other to obtain the time
difference and the phase difference, it is possible to measure the distance to the object to be
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detected.
[0040]
By the way, as shown in FIG. 4, when the ultrasonic wave reflected by the obstacle M is
transmitted to the ultrasonic sensor 70 from the side of the receiving element 10 a in front of the
receiving member 31, that is, the lower left in the figure Only the ultrasonic wave received by the
receiving unit 31e is transmitted to the vibrating unit 15a of the receiving element 10a, and is
detected as an output A corresponding to the ultrasonic wave received from the receiving
element 10a.
On the other hand, the ultrasonic wave received by the receiving unit 31f is transmitted to the
vibrating unit 15b of the receiving element 10b, and is detected as an output B delayed by ΔT
from the output A from the receiving element 10b. The received ultrasonic wave is transmitted to
the vibration unit 15 b via the area 31 b and detected as an output C. Thereby, from the receiving
element 10b, the output C which is a noise component by the ultrasonic wave received by the
receiving unit 31e is output superimposed on the output B by the ultrasonic wave received by
the receiving unit 31f. The crosstalk characteristic of 15a and 15b is degraded, and the
measurement accuracy of the time difference and phase difference of the ultrasonic waves
received by each of the receiving units 31e and 31f is reduced, so that the accuracy of position
measurement of the obstacle is degraded. was there.
[0041]
Therefore, the applicant separately examines the shape of the shielding part 31i in order to
separate and detect the ultrasonic wave received by the receiving part 31e and the ultrasonic
wave received by the receiving part 31f and reduce the output C which is a noise component.
went. As a result, it has been found that the crosstalk characteristics of the respective vibrating
portions 15a and 15b can be improved by setting the depth L of the shielding portion 31i within
a predetermined range with respect to the thickness T of the receiving member 31. FIG. 5 shows
the ratio (depth ratio L / T) of the depth L of the shielding portion 31i to the thickness T of the
receiving member 31 and the ultrasonic wave received by the receiving portion 31e transmitted
to the vibrating portion 15b. It is a graph which shows a relationship with the transmissivity
showing the ratio of an ultrasonic wave. Here, the lower the transmission rate, the better the
crosstalk characteristic. From the state in which the depth ratio L / T is 0, that is, the state in
which the shielding portion 31i is not formed, the transmission rate decreases as the depth L is
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increased. At this time, the signal waveform of the output C is in phase with the output A and the
output B. Then, when L / T becomes 0.45, the transmissivity becomes 0, and the ultrasonic wave
received by the receiving unit 31 e is not transmitted to the receiving element 10 b. That is, the
output C which is a noise component is not detected. Further, when the depth L is increased, the
signal waveform of the output C shifts to the phase opposite to that of the output A and the
output B, and the transmission ratio becomes higher.
[0042]
In the case of parking assistance, passing of narrow alleys, etc., an ultrasonic sensor mounted on
a car for use is required to have a position accuracy with an error within 10%. In order to satisfy
the positional accuracy of 10%, it is necessary to set the azimuth error, which is the error of the
angle obtained from the phase difference of the ultrasonic waves, to 5.7 Deg or less. That is, as
shown in FIG. 6, the SN ratio is required to be 16 dB or more. Here, the fact that the SN ratio is
16 dB or more corresponds to the fact that the transmission ratio is 4% or less. Therefore, as
shown in FIG. 5, the depth L of the shielding part 31i may be formed to satisfy the following
formula, and it is most preferable to set it to 0.45.
[0043]
0.35≦L/T≦0.60 (1)
[0044]
In the present embodiment, the depth L of the shielding portion 31i is formed to 1.8 mm with
respect to the receiving member 31 having a thickness of 4 mm so as to satisfy the optimum
condition that the depth ratio L / T is 0.45. ing.
Thereby, the ultrasonic wave received by the receiving unit 31e is transmitted only to the
vibrating unit 15a of the receiving element 10a, and the ultrasonic wave received by the
receiving unit 31f is transmitted only to the vibrating unit 15b of the receiving element 10b. It is
not transmitted to the vibrator. Therefore, transmission of ultrasonic waves can be performed
separately between the regions 31a and 31b, and the crosstalk characteristics of the vibration
units 15a and 15b can be improved. Therefore, reception is performed by the reception units
31e and 31f. Since the time difference and the phase difference of the ultrasonic waves can be
accurately determined, the accuracy of the position measurement of the obstacle can be
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improved. In addition, since the width of the shielding portion 31i does not affect the output C, it
can have an arbitrary shape.
[0045]
Here, if the shielding portion 31i has a shape satisfying 0.35 ≦ L / T <0.45, the depth L of the
shielding portion 31i is shallow, so that the noise component is maintained with the strength of
the receiving member 31 kept high. Can be reduced. Further, when the shape satisfies 0.45 <L /
T ≦ 0.60, the output C is in reverse phase with the output B, so that signal components in
reverse phase can be easily processed as noise components.
[0046]
(Modification) The shielding portion 31i can be formed in various shapes as long as the condition
of the equation (1) of the depth ratio L / T is satisfied. For example, as shown in FIG. 7A, the end
of the bottom 31m of the shield 31i is rounded, or as shown in FIG. 7B, the bottom of the shield
31i is formed in a semicircular cross section. Can be According to this, the stress relaxation
portion that smoothly connects the side surface and the bottom surface 31m of the shielding
portion 31i is provided, and there is no corner portion where stress concentrates, so the strength
of the receiving member 31 can be increased. Even when a shear stress is generated in the
shielding portion 31i due to the transmission of an external force or the transmission of an
ultrasonic wave, the possibility of breakage can be reduced. Moreover, as shown to FIG. 7 (C) and
(D), it can also form in a taper shape.
[0047]
As shown in FIG. 8A, the shielding portion 31i is filled with a filler 31n made of a material having
a lower Young's modulus than the receiving member 31 and inhibiting the transmission of
ultrasonic waves, such as a gel-like material or rubber. It is also good. Further, as shown in FIG.
8B, a configuration can be used in which the opening of the shielding portion 31i is closed by a
lid material 82 formed in a foil shape or a plate shape made of a resin or a metal material. When
this configuration is used, it is possible to eliminate the possibility that foreign matter that
inhibits the shielding of the ultrasonic wave may intrude into the shielding portion 31i while
maintaining the shielding effect of the ultrasonic wave by the shielding portion 31i. Further, as
shown in FIG. 8C, the shielding portion 31i may be formed in a plurality of narrow grooves.
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When this configuration is used, the width of the opening of the shielding portion 31i is
narrowed, so that the risk of entry of foreign matter that inhibits the shielding of the ultrasonic
wave can be reduced.
[0048]
In the present embodiment, an example in which the rectangular receiving element 10 and the
receiving member 31 are used has been described, but the shape of these members is not limited
to this, and may be, for example, a disc or polygonal shape. . Also, the number of receiving
elements is not limited to four. Also, the arrangement of the receiving element is optional
depending on the application. For example, in the case of performing two-dimensional detection
only in the vertical direction or in the horizontal direction, the number of receiving elements may
be two. Also, the receiving elements can be arranged circumferentially or in a straight line.
[0049]
The ultrasonic sensor 70 can be attached to the end in the moving direction of the vehicle other
than the bumper 52, for example, immediately above or directly below the bumper 52. With this
configuration, the ultrasonic wave reflected by an obstacle or the like is not blocked by a part of
the vehicle, so the ultrasonic sensor 70 can be reliably detected, and the ultrasonic wave sensor
70 is used as an obstacle sensor or the like. It is effective when applying. Furthermore, the
ultrasonic sensor 70 can be attached to another member according to the application of the
ultrasonic sensor 70. For example, when the ultrasonic sensor is used as an obstacle sensor on
the side of the vehicle, it can be attached to a winker cover or the like. In addition, the ultrasonic
sensor 70 can be attached to a head lamp cover, a rear lamp cover, a back lamp cover, a body, or
the like.
[0050]
[Effect of the best embodiment]
[0051]
(1) In the ultrasonic sensor 70 for mounting on a vehicle, the receiving elements 10a to 10d
provided with the plurality of vibrating portions 15a to 15d are attached to the receiving
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member 31, and the receiving member 31 includes the vibrating portions 15a to 15d. Are
divided into areas 31a and 31b corresponding to.
Between the areas 31a and 31b, grooves are formed in a direction perpendicular to or
substantially perpendicular to the receiving units 31e and 31f that receive the ultrasonic waves,
and each of the ultrasonic waves received by the receiving units 31e and 31f Shielding portions
31i are provided to prevent transmission between the regions 31a and 31b. In the shielding part
31i, the transmission medium of the ultrasonic wave becomes air and the attenuation becomes
large, so that the transmission of the ultrasonic wave between the areas 31a and 31b can be
interrupted, and the divided areas 31a and 31b of the receiving member 31 The ultrasonic waves
received at step (c) are transmitted only to the corresponding vibrating units 15a and 15b, and
are not transmitted to the other vibrating units. Therefore, it becomes possible to separate the
transmission of the ultrasonic waves between the areas 31a and 31b, and the ultrasonic waves
received by one receiver can be transmitted to the adjacent areas and become noise components.
Since this can be prevented, the crosstalk characteristics of the respective vibrating portions 15a
to 15d can be improved. Further, it is only necessary to form the shielding portion 31i in the
receiving member 31, and there is no need to provide a shock absorbing material for absorbing
vibration between the regions 31a and 31b, so that the process of providing the shock absorbing
material is unnecessary. The ultrasonic sensor 70 can be miniaturized. Here, when the
relationship of 0.35 ≦ L / T ≦ 0.60 holds between the depth L of each shielding portion and the
thickness T of the receiving member, an on-vehicle ultrasonic sensor, for example, a vehicle The
ultrasonic sensor 70 can be provided which is provided in the bumper and satisfies the detection
accuracy of the position of the detection target M required when used for detection of an
obstacle that hinders the progress of the vehicle.
[0052]
(2) If the shielding portion 31i is formed to have a depth ratio L / T of 0.45, noise components
are eliminated, so that the sensitivity of the ultrasonic sensor can be most improved. If the
relationship of 0.35 ≦ L / T <0.45 is established, the noise component can be reduced while
maintaining high strength of the receiving member 31 because the depth L of the shielding
portion 31i is shallow. it can. Further, when the relationship of 0.45 <L / T ≦ 0.60 is established,
the noise component signal is in anti-phase, so that the anti-phase signal component can be
easily processed as the noise component.
[0053]
(3) The side and the bottom of the shielding portion 31i are connected smoothly by rounding the
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end of the bottom 31m of the shielding portion 31i or forming the bottom 31m of the shielding
portion 31i in a semicircular cross section. By using the configuration in which the stress
relieving portion is provided, there is no corner where the stress is concentrated, so the strength
of the receiving member 31 can be increased, and shielding by external force applied to the
receiving member 31 or transmission of ultrasonic waves. Even when shear stress occurs in the
portion 31i, the possibility of breakage can be reduced.
[0054]
(4) When the shielding portion 31i is formed into a plurality of parallel grooves, the width of the
opening of the shielding portion 31i becomes narrow, so that the risk of the intrusion of foreign
matter that obstructs the shielding of the ultrasonic wave is reduced. Can.
[0055]
(5) When the shield 31i is filled with a filler 31n having a lower Young's modulus than the
receiving member 31 to inhibit the transmission of the ultrasonic wave, the shielding effect of
the ultrasonic wave by the shield 31i is maintained. Thus, the risk of the foreign matter that
inhibits the shielding of the ultrasonic wave from entering the shielding part 31i can be
eliminated.
In addition, the same effect can be obtained by using a configuration in which the cover portion
82 that covers the opening of the shielding portion 31i is provided in the shielding portion 31i.
[0056]
(6) Since the vibration detection unit 12 of a piezoelectric type configured using a piezoelectric
material and detecting vibration by strain caused by vibration is adopted as the vibration unit 15,
the displacement of the vibration unit 15 generated by resonance is a voltage signal Since the
signal intensity output from the receiving element 10 is high and the ultrasonic wave reception
sensitivity is high, the ultrasonic wave detection sensitivity can be improved.
[0057]
(7) Since the receiving member 31 is made of a polycarbonate resin material, the acoustic
impedance of the receiving member 31 can be made close to the acoustic impedance of the
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18
support member, and ultrasonic waves can be efficiently transmitted to the receiving element 10
it can.
In addition to being exposed to the outside air, the receiving element 10 can be protected from
the load of external force because it is a robust material with high weather resistance.
Furthermore, since the polycarbonate-based resin is used as a constituent material of the bumper
52 and the presence of the ultrasonic sensor 70 can be made inconspicuous, the ultrasonic
sensor 70 excellent in design can be manufactured.
[0058]
[Other Embodiments] (1) By forming the shielding part 31i on the inner surface of the bumper
52 and attaching the receiving element 10, an ultrasonic sensor using a part of the bumper 52 as
the receiving member 31 can be formed. . When this configuration is used, the receiving member
31 is not exposed from the bumper 52, so that a vehicle excellent in design can be manufactured.
Furthermore, other members of the vehicle can be used as the receiving member 31 according to
the application of the ultrasonic sensor. For example, in the case of using an ultrasonic sensor as
an obstacle sensor on the side of the vehicle, it is possible to use the cover of a blinker as the
receiving member 31 and attach the receiving element 10. In addition, the receiving element 10
can be attached by using a head lamp cover, a rear lamp cover, a back lamp cover, a body, or the
like as the receiving member 31.
[0059]
(2) As the receiving element 10, a receiving element in which the vibrating portion 15 is
supported in a cantilever manner by the support member 11a may be employed. When this
configuration is used, compared to the case where both ends of the vibrating portion 15 are
supported, there are few parts that restrain the deformation of the vibrating portion 15, and
therefore, when the vibration is transmitted, the ultrasonic sensor 70 is greatly deformed. The
sensitivity can be improved.
[0060]
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19
(3) Although the piezoelectric vibration detection unit 12 is used as the vibration unit 15 of the
receiving element 10, the present invention is not limited to this. For example, the vibration unit
15 includes a pair of electrodes. It is also possible to use a capacitive vibration detection unit or
the like that detects Since the capacitive vibration detection unit has a broad resonance
frequency, the vibration unit is not required to have high dimensional accuracy, and can be easily
manufactured.
[0061]
It is explanatory drawing of the receiving element of an ultrasonic sensor. FIG. 1A is a plan view
of the receiving element, and FIG. 1B is a cross-sectional view taken along the line A-A of FIG. It is
explanatory drawing of arrangement | positioning of the receiving element in an ultrasonic
sensor. It is a section explanatory view of the ultrasonic sensor carried in vehicles. It is
explanatory drawing which shows the output signal in the adjacent receiving element by the
ultrasonic wave received by the different receiving part. It is explanatory drawing which shows
the relationship between the depth of a shielding part, and the transmission factor of the noise
component of an ultrasonic wave. It is explanatory drawing which shows the relationship
between the azimuth | direction error of an ultrasonic sensor, and SN ratio. It is explanatory
drawing which shows the example of a change of a shielding part. It is explanatory drawing
which shows the example of a change of a shielding part.
Explanation of sign
[0062]
10, 10a, 10b, 10c, 10d Receiving element 11a Support member 15, 15a, 15b Vibrating section
19 Transmitting element 31 Receiving element 31e, 31f Receiving section 31a, 31b Area 31i
Shielding section 31n Filling material 41 Buffer material (second shielding Means) 42 Damping
member (third shielding means) 52 Bump 70 Ultrasonic sensor 82 Lid material L Depth of
shielding portion M Obstacle T Thickness of receiving member
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