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DESCRIPTION JP2007183185

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DESCRIPTION JP2007183185
An ultrasonic sensor capable of preventing a decrease in transmission (reception) efficiency due
to temperature is provided. A drive signal corresponding to the frequency is generated so as to
vibrate a transmission / reception transducer 20c for converting a drive signal to vibration and
to convert a vibration to a reception signal and the transmission / reception transducer 20c at a
predetermined frequency. The vibration generated by the transmission / reception transducer
20c is provided with the drive signal generation unit 42, and the filter unit 44 that selectively
outputs a predetermined frequency range including the frequency among the signals output from
the transmission / reception transducer 20c. The ultrasonic sensor 100 is configured to output
the ultrasonic wave to the outside through the bottom surface portion 11 of the case 10, and the
transmission / reception transducer 20c receives a reflected wave of the ultrasonic wave through
the bottom surface portion 11, and the bottom surface The drive signal generation unit 42
generates a drive signal according to the output signal of the temperature sensing device 41, and
the filter unit 44 includes a temperature sensing device. Depending on 41 the output signal of
varying the frequency band. [Selected figure] Figure 4
Ultrasonic sensor
[0001]
The present invention relates to an ultrasonic sensor.
[0002]
Conventionally, an ultrasonic sensor in which an ultrasonic transducer is fixed to a bottomed
cylindrical case is known (see Patent Document 1).
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[0003]
In the ultrasonic sensor disclosed in Patent Document 1, the piezoelectric vibrator is fixed to the
inner surface of the thin portion formed on the bottom surface of the metal case in such a
manner that one of the vibrating surfaces is in close contact.
Therefore, at the time of transmission, the piezoelectric vibrator receiving the electric signal
vibrates, transmits the ultrasonic wave to the outside through the thin portion of the metal case
body, and at the time of reception, the ultrasonic wave is transmitted to the piezoelectric vibrator
through the thin portion And converted into electrical signals.
Unexamined-Japanese-Patent No. 8-237796 gazette
[0004]
As shown in Patent Document 1, in the case of transmitting or receiving an ultrasonic wave
through a part of the case, the case (thin portion) is resonated at a predetermined frequency in
order to improve the efficiency in transmitting or receiving. Need to be configured.
[0005]
However, since the Young's modulus of the material constituting the case changes depending on
the ambient temperature of the environment, the temperature characteristic of the Young's
modulus changes the resonance frequency of the case.
Therefore, the resonant frequency of the sensor has a temperature characteristic, and depending
on the operating temperature, the transmission efficiency or the reception efficiency may be
reduced, and the sensor may not be able to exhibit a sufficient function.
[0006]
An object of the present invention is to provide an ultrasonic sensor capable of preventing a
decrease in transmission efficiency or reception efficiency due to temperature.
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[0007]
In order to achieve the above object, the invention according to claim 1 generates a drive signal
corresponding to a frequency so that the transmission vibrator for converting the drive signal
into vibration and the transmission vibrator vibrate at a predetermined frequency. An ultrasonic
sensor configured to output a vibration generated by a transmission vibrator as an ultrasonic
wave to the outside through a vibration transmission member, comprising: a drive signal
generation unit, wherein the temperature sensor detects an ambient temperature of the vibration
transmission member The drive signal generation unit includes an element, and generates a drive
signal according to an output signal of the temperature sensing element.
[0008]
As described above, according to the present invention, even if the Young's modulus of the
vibration transfer member changes according to the temperature and the resonance frequency
changes, a drive signal according to the resonance frequency of the vibration transfer member is
provided to the transmission vibrator. Can.
Therefore, it is possible to prevent a decrease in transmission efficiency due to temperature.
[0009]
The invention according to claim 2 comprises: a receiving transducer for converting vibration
into a received signal; and a filter unit for selectively outputting only a predetermined frequency
range of the received signal output from the receiving transducer. The ultrasonic sensor includes
a temperature sensing element configured to receive an ultrasonic wave through the vibration
transmitting member, and the filter unit includes a temperature sensing element that detects an
ambient temperature of the vibration transmitting member. The frequency range is changed
according to the output signal of
[0010]
As described above, according to the present invention, even if the Young's modulus of the
vibration transfer member changes according to the temperature and the resonance frequency
changes, the filter unit selects a signal in the frequency range according to the resonance
frequency of the vibration transfer member. Output.
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Therefore, it is possible to prevent a drop in reception efficiency due to temperature.
[0011]
The invention according to claim 3 is characterized in that the transmission vibrator for
converting the drive signal into vibration, the reception vibrator for converting the vibration into
reception signal, and the frequency for vibrating the transmission vibrator at a predetermined
frequency. A vibration for transmission comprising: a drive signal generation unit that generates
a corresponding drive signal; and a filter unit that selectively outputs only a predetermined
frequency range including the frequency among reception signals output from the reception
vibrator. An ultrasonic sensor configured to output the vibration generated by the transducer to
the outside as an ultrasonic wave through a vibration transmission member, and the ultrasonic
transducer for reception receives a reflected wave of the ultrasonic wave through the vibration
transmission member. , And the drive signal generation unit generates a drive signal according to
the output signal of the temperature sensitive device, and the filter unit corresponds to the
output signal of the temperature sensitive device. Change the frequency range It is characterized
in.
[0012]
Thus, according to the present invention, it is possible to expect the effects of the invention
according to claim 1 and the invention according to claim 2.
That is, in the ultrasonic sensor for transmission and reception, it is possible to prevent a
decrease in transmission efficiency and reception efficiency due to temperature.
[0013]
In the invention according to claim 3, as described in claim 4, the transmitting transducer and
the receiving transducer can be configured as one ultrasonic transducer.
With such a configuration, the physical size of the ultrasonic sensor can be miniaturized.
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[0014]
According to the fifth aspect of the present invention, the vibration transmitting member may
include the bottom of a bottomed cylindrical case in which the vibrator is fixed to the inner
surface of the bottom, and the vehicle according to the sixth aspect of the present invention It is
good also as composition including a body or a bumper of. Therefore, the vibration transmission
member may be configured by the bottom of the case and either the vehicle body or the bumper.
[0015]
The invention according to any one of claims 1 to 6 is particularly effective when the vibration
transmission member is made of a synthetic resin as described in claim 7. In the case of a
synthetic resin, the amount of change in Young's modulus with temperature is larger than that of
metal. That is, the change width of the resonant frequency of the vibration transfer member is
large. As described above, by applying the invention according to any one of claims 1 to 6 to a
synthetic resin having a large change due to temperature, it is possible to prevent a decrease in
transmission efficiency (reception efficiency) due to temperature. In addition, since a synthetic
resin is employed as the constituent material, the cost can be reduced as compared with the case
of employing a metal.
[0016]
As the temperature sensitive element, any element capable of detecting the ambient temperature
of the vibration transfer member can be adopted. For example, as described in claim 8, if a
temperature sensitive resistor is adopted as the temperature sensitive element, integration with
the above-described drive signal generation unit and filter unit is possible. By constructing one
chip, the size of the sensor can be miniaturized. As the temperature sensitive resistance, for
example, as described in claim 9, a diffusion resistance formed on the substrate can be adopted.
Besides the diffusion resistance, a carbon resistance or the like formed on the substrate can be
adopted as the temperature sensitive resistance. In addition to the temperature sensitive
resistance, for example, a thermistor or the like can be adopted as the temperature sensitive
element.
[0017]
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Hereinafter, embodiments of the present invention will be described based on the drawings. First
Embodiment First, a schematic configuration of a (common) ultrasonic sensor according to each
embodiment of the present invention described below will be described with reference to FIG.
FIG. 1 is a cross-sectional view showing a schematic configuration of an ultrasonic sensor
according to each embodiment of the present invention.
[0018]
As shown in FIG. 1, the ultrasonic sensor 100 has an ultrasonic wave that performs at least one
of a case 10, a transmission function that converts a drive signal into vibration, and a reception
function that converts ultrasonic vibration into a reception signal. It includes the transducer 20
and the circuit board 30 in which the processing circuit is configured in accordance with the
function of the ultrasonic transducer 20.
[0019]
The case 10 is made of, for example, a synthetic resin and formed in a bottomed cylindrical
shape.
The ultrasonic transducer 20 is, for example, bonded and fixed to the inner surface of the bottom
surface portion 11 of the case 10. That is, the bottom surface portion 11 of the case 10
corresponds to the vibration transmission member described in the claims. As the ultrasonic
transducer 20, a piezoelectric transducer made of a piezoelectric ceramic such as PZT or barium
titanate as a sintered body can be employed. The electrodes of the ultrasonic transducer 20 are
electrically connected to the circuit board 30 via the leads 21. In the present embodiment, a thin
film made of a conductive material is formed on the inner surface of the case 10 made of a
synthetic resin, and one lead 21 is connected to the inner surface of the case 10 in contact with
one of the electrodes.
[0020]
The circuit board 30 is formed by mounting an IC chip 40 in which processing circuits are
integrated on a printed circuit board. In the IC chip 40, a transmission circuit for generating a
drive signal (drive voltage) for generating an ultrasonic wave by vibrating the ultrasonic
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transducer 20 in accordance with the function of the ultrasonic transducer 20, ultrasonic
vibration A receiving circuit is configured to process the received signal originating from the
child 20. Details of the processing circuit according to the present embodiment will be described
later.
[0021]
In addition to the ultrasonic transducer 20 and the circuit board 30, the sound absorbing
material 50, the vibration absorber 60, and the like are disposed in the case 10 as sensor
components. Further, reference numeral 70 shown in FIG. 1 denotes a connector, which connects
the processing circuit of the circuit board 30 and a control unit (ECU) which is provided, for
example, in a vehicle compartment and performs notification processing and the like.
[0022]
In the ultrasonic sensor 100 configured as described above, when the ultrasonic transducer 20
performs a transmission function, a drive signal (drive voltage) is generated by the processing
circuit, and the ultrasonic transducer 20 vibrates in response to the drive signal. Then, ultrasonic
waves are output to the outside through the bottom portion 11 of the case 10. In addition, when
the ultrasonic transducer 20 performs a receiving function, an external ultrasonic wave is
transmitted to the ultrasonic transducer 20 as a vibration through the bottom portion 11 of the
case 10, and a reception signal generated by the piezoelectric effect is a processing circuit
Output to That is, in either case, the vibration is transmitted through the bottom portion 11 of
the case 10. Therefore, in order to improve the efficiency at the time of transmission (reception),
it is necessary to configure the bottom portion 11 of the case 10 to resonate at a predetermined
frequency.
[0023]
However, since the Young's modulus of the material constituting the case 10 changes depending
on the surrounding environmental temperature, the resonant frequency of the bottom portion 11
of the case 10 changes due to the temperature characteristic of the Young's modulus. Therefore,
the resonant frequency of the sensor has temperature characteristics. For example, when the
ultrasonic sensor 100 performs a transmission function, even if a predetermined drive signal is
generated to vibrate the ultrasonic transducer 20 at a predetermined frequency, the resonance
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frequency of the bottom portion 11 is excessive depending on the temperature of the use
environment. There is a possibility that the ultrasonic wave output to the outside may be
weakened by shifting from the vibration frequency of the sound wave vibrator. That is, there is a
possibility that the ultrasonic sensor 100 can not exhibit a sufficient function.
[0024]
Therefore, the characteristic part of the ultrasonic sensor 100 according to the first embodiment,
which solves the above problem, will be described with reference to FIG. FIG. 2 is a block diagram
showing a schematic configuration of a processing circuit in the ultrasonic sensor 100 according
to the first embodiment. The ultrasonic sensor 100 according to the present embodiment is
configured as a transmission ultrasonic sensor that transmits ultrasonic waves.
[0025]
As shown in FIG. 2, the IC chip 40 is configured with a processing circuit for transmission, and a
temperature sensitive element 41 for detecting the ambient temperature of the case 10 (bottom
surface portion 11), and a transmission transducer 20a (ultrasonic wave In order to vibrate the
vibrator 20) at a predetermined frequency, the drive signal generation unit 42 that generates a
drive signal corresponding to the frequency is included.
[0026]
The temperature sensitive element 41 is formed by forming a temperature sensitive resistance
on a substrate.
In the present embodiment, a diffusion resistance formed by diffusing an impurity is formed in
the semiconductor substrate to be a temperature sensitive resistance. In addition to the diffusion
resistance, for example, a carbon resistance formed on a substrate can be adopted as the
temperature sensitive resistance. As described above, when the temperature sensitive resistor is
adopted, it can be integrated on the same semiconductor substrate together with the drive signal
generation unit 42 using a general semiconductor process.
[0027]
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The drive signal generation unit 42 includes a frequency determination unit 42a, an oscillation
circuit 42b, and a drive circuit 42c. The frequency determination unit 42 a determines the
vibration frequency of the transmission transducer 20 a based on the signal from the
temperature sensing element 41. That is, the vibration frequency is determined so that the
vibration frequency of the transmission vibrator 20 a substantially matches the resonance
frequency of the bottom surface portion 11 of the case 10. The oscillation circuit 42b transmits a
pulse signal of the frequency instructed from the frequency determination unit 42a to the drive
circuit 42c, and the drive circuit unit 42c is driven by receiving supply of the power supply
voltage input to the ultrasonic sensor 100, and oscillates. The transmission vibrator 20a is driven
by the pulse signal from the circuit 42b.
[0028]
As described above, according to the ultrasonic sensor 100 according to the present
embodiment, the Young's modulus of the bottom portion 11 of the case 10 changes according to
the temperature, and even if the resonance frequency changes, it corresponds to the resonance
frequency of the bottom portion 11 A drive signal (pulse signal) can be applied to the
transmission transducer 20a. That is, the drive signal (pulse signal) suitable for each temperature
can be given to the transmission transducer 20a. Therefore, it is possible to prevent a decrease in
transmission efficiency due to temperature.
[0029]
In the present embodiment, as described above, the bottom portion 11 of the case 10 which is
the vibration transmitting member is made of synthetic resin. In the case of a synthetic resin, the
amount of change in Young's modulus with temperature is larger than that of metal. That is, the
change width of the resonance frequency is large. However, according to the configuration
according to the present embodiment, it is possible to prevent the decrease in the transmission
efficiency due to the temperature while using the synthetic resin having a large change due to
the temperature as the constituent material of the bottom surface portion 11. In addition, since a
synthetic resin is employed as the constituent material, the cost can be reduced as compared
with the case of employing a metal.
[0030]
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Second Embodiment Next, a second embodiment of the present invention will be described based
on FIG. FIG. 3 is a block diagram showing a schematic configuration of a processing circuit in the
ultrasonic sensor 100 according to the second embodiment of the present invention.
[0031]
The ultrasonic sensor 100 according to the second embodiment has many parts in common with
the ultrasonic sensor 100 shown in the first embodiment, and thus detailed description of
common parts will be omitted, and different parts will be mainly described. .
[0032]
The ultrasonic sensor 100 according to the present embodiment is configured as a receiving
ultrasonic sensor that receives ultrasonic waves.
As described above, since the resonance frequency of the bottom portion 11 of the case 10
changes due to the temperature characteristic of Young's modulus, the resonance frequency of
the sensor has temperature characteristics. When the ultrasonic sensor 100 performs the
reception function, depending on the operating temperature, the resonant frequency of the
bottom portion 11 and the frequency range selectively output from the filter portion forming the
processing circuit may be different. The sensor signal to be output may be weak. That is, there is
a possibility that the ultrasonic sensor 100 can not exhibit a sufficient function.
[0033]
On the other hand, as shown in FIG. 3, the IC chip 40 according to the present embodiment
includes, as a processing circuit for reception, a temperature-sensitive element 41 that detects
the ambient temperature of the case 10 (bottom surface portion 11); And a signal processing
circuit 45 configured to selectively output only a predetermined frequency range among the
signals output from the receiving transducer 20 b (the ultrasonic transducer 20) for converting
the vibration into a received signal. It contains.
[0034]
As the temperature sensing element 41, a diffusion resistance which is a temperature sensing
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resistance is employed as in the first embodiment.
Therefore, the amplifier circuit 43, the filter unit 44, and the processing circuit 45 can be
integrated on the same semiconductor substrate.
[0035]
The filter unit 44 includes a filter constant determination unit 44a and a filter circuit 44b. The
filter constant determination unit 44 a determines the filter constant based on the signal from
the temperature sensing element 41. That is, the filter constant is determined such that the
resonance frequency of the bottom surface portion 11 of the case 10 is included in the frequency
range selectively output from the filter circuit 44b. The filter circuit 44b filters the reception
signal from the receiving vibrator 20b input through the amplification circuit 43 based on the
filter constant instructed from the filter constant determination unit 44a, passes through the
signal processing circuit 45, and then the sensor As described above, according to the ultrasonic
sensor 100 according to the present embodiment, the Young's modulus of the bottom portion 11
of the case 10 changes according to the temperature, and even if the resonance frequency
changes. The filter unit 44 can perform filtering with a filter constant corresponding to the
resonance frequency of the bottom unit 11. Therefore, it is possible to prevent a drop in
reception efficiency due to temperature.
[0036]
As in the first embodiment, the bottom portion 11 of the case 10, which is a vibration transfer
member, is made of a synthetic resin, but the structure of the bottom portion 11 is a synthetic
resin having a larger change in Young's modulus due to temperature compared to metal. While
being a material, it is possible to prevent a drop in reception efficiency due to temperature. In
addition, since a synthetic resin is employed as the constituent material, the cost can be reduced
as compared with the case of employing a metal.
[0037]
Third Embodiment Next, a third embodiment of the present invention will be described based on
FIG. FIG. 4 is a block diagram showing a schematic configuration of a processing circuit in an
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ultrasonic sensor 100 according to a third embodiment of the present invention.
[0038]
The ultrasonic sensor 100 according to the third embodiment has many parts in common with
the ultrasonic sensor 100 shown in the first embodiment and the second embodiment, so the
detailed description of the common parts will be omitted hereinafter, and different parts will be
described. Emphasize.
[0039]
The ultrasonic sensor 100 according to the present embodiment is configured by combining the
configurations shown in the first embodiment and the second embodiment.
That is, it is configured as an ultrasonic sensor for transmission and reception. Specifically, the
transmission / reception transducer 20 c is provided, and an ultrasonic wave is transmitted by
one ultrasonic transducer 20, and a reflected wave due to an obstacle is detected.
[0040]
As shown in FIG. 4, a processing circuit for transmission and reception is configured in the IC
chip 40, and a temperature sensitive element 41 that detects the ambient temperature of the
case 10 (bottom surface portion 11); In order to vibrate the vibrator 20) at a predetermined
frequency, a drive signal generation unit 42 for generating a drive signal corresponding to the
frequency, an amplification circuit 43, and a receiving vibrator 20b for converting vibration to a
reception signal (ultrasonic vibrator 20 includes a signal processing circuit 45 and a filter unit 44
which selectively outputs only a predetermined frequency range among the signals output from
20). These are the same as the configurations shown in the first embodiment and the second
embodiment, respectively. Further, the present embodiment also includes a switch 46 that
switches the connection between the transmission processing circuit unit and the reception
processing circuit unit with respect to the transmission vibrator 20c.
[0041]
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Therefore, when receiving a transmission instruction from the control unit (not shown), the
frequency determination unit 42a determines the vibration frequency of the transmission /
reception transducer 20c based on the signal from the temperature sensing element 41, and the
oscillation circuit 42b determines the frequency determination unit. The pulse signal of the
frequency instructed from 42a is transmitted to the drive circuit 42c. Further, the switch 46 is
connected to the drive circuit 42c side. Then, the drive circuit unit 42c receives and supplies the
supply of the power supply voltage input to the ultrasonic sensor 100, and drives the
transmission / reception transducer 20c by the pulse signal from the oscillation circuit 42b.
Thereby, an ultrasonic wave is output from the ultrasonic sensor 100.
[0042]
When receiving a reception instruction from the control unit (not shown), the filter constant
determination unit 44a determines the filter constant based on the signal from the temperature
sensing element 41, and the switch 46 is connected to the amplification circuit 43 side. In this
embodiment, an ultrasonic wave is transmitted by one transmission / reception transducer 20c
and a reflection wave due to an obstacle is detected, so that the vibration frequency for driving
the transmission / reception transducer 20c and A filter constant is determined to selectively
output a frequency range including the same frequency. Then, the filter circuit 44 b filters the
reception signal from the receiving vibrator 20 b input through the amplification circuit 43
based on the filter constant instructed from the filter constant determination unit 44 a, and the
signal processing circuit 45 For example, based on the time from transmission to reception of
ultrasonic waves, the distance to an obstacle or the like is calculated and output as a sensor
signal to the outside (ECU).
[0043]
As described above, according to the ultrasonic sensor 100 according to the present
embodiment, it is possible to expect the effects of the configuration shown in the first
embodiment and the effects of the configuration shown in the second embodiment. That is, in the
ultrasonic sensor 100 for transmission and reception, it is possible to prevent a decrease in
transmission efficiency and reception efficiency due to temperature.
[0044]
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In the present embodiment, the configuration has been shown in which transmission and
reception are performed by one ultrasonic transducer 20 (transmission / reception transducer
20c). With this configuration, the physical size of the ultrasonic sensor 100 can be miniaturized.
However, the transmission transducer 20a and the reception transducer 20b may be separately
provided, and corresponding processing circuits may be connected to the respective transducers
20a and 20b.
[0045]
The preferred embodiments of the present invention have been described above. However, the
present invention is not limited to the above-described embodiments, and various modifications
can be made without departing from the scope of the present invention.
[0046]
In the present embodiment, an example in which the temperature sensitive element 41 is
included in the IC chip 40 has been shown.
However, the temperature sensing element 41 may be configured separately from the IC chip 40.
As the temperature sensitive element 41, for example, a thermistor or the like can be adopted
other than the temperature sensitive resistance. In addition, the processing circuit components
other than the temperature sensitive device 41 may not be integrated. It can also be configured
by mounting an electronic component on the substrate portion of the circuit substrate 30 or the
like.
[0047]
In the present embodiment, an example is shown in which the bottom portion 11 of the case 10
is adopted as the vibration transmission member. However, the vibration transmission member is
not limited to the above example. For example, as shown in FIG. 5, a bumper 80 of a vehicle may
be employed. In FIG. 5, the bumper 80 is made of synthetic resin, and one surface of the
ultrasonic transducer 20 is directly disposed on the bumper 80. Therefore, it is effective to apply
the configuration shown in the above-described embodiment to the bumper 80 of the vehicle.
Further, the outer surface of the bottom surface portion 11 of the case 10 may be brought into
contact with the bumper 80 of the vehicle for fixing, and the bumper 80 of the vehicle may be
used as the vibration transmission member.
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[0048]
In the present embodiment, an example in which the vibration transmission member is made of
synthetic resin has been shown. However, you may be comprised using materials other than a
synthetic resin. For example, it can also be configured using a metal material such as aluminum
or iron. Therefore, in FIG. 5, the body of the vehicle can be employed instead of the bumper 80 of
the vehicle.
[0049]
The schematic configuration of the ultrasonic sensor 100 shown in FIGS. 1 and 5 is merely an
example. Various modifications can be made without departing from the spirit of the present
invention.
[0050]
It is sectional drawing which shows schematic structure of the ultrasonic sensor common to each
embodiment. FIG. 3 is a block diagram showing a schematic configuration of a processing circuit
in the ultrasonic sensor according to the first embodiment. The ultrasonic sensor which concerns
on 2nd Embodiment WHEREIN: It is a block diagram which shows schematic structure of a
processing circuit. The ultrasonic sensor which concerns on 3rd Embodiment WHEREIN: It is a
block diagram which shows schematic structure of a processing circuit. It is sectional drawing
which shows a modification.
Explanation of sign
[0051]
10: Case 11: Bottom portion (vibration transmission member) 20: Ultrasonic transducer 20a:
Transmission transducer 20b: Reception transducer 20c: Transmission / reception transducer 30
· · Circuit board 40 · · · IC chip 41 · · · Temperature-sensitive element 42 · · · Drive signal
generation unit 44 · · · · · · · · · · · · · filter unit 100 · · · ultrasonic sensor
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