JPS61155975

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DESCRIPTION JPS61155975
[0001]
FIELD OF THE INVENTION The present invention relates to an ultrasonic sensor comprising an
ultrasonic transmission sensor for transmitting ultrasonic waves and an ultrasonic reception
sensor for receiving reflected waves from an object, and in particular to the beam width of its
directivity pattern. It relates to the technology to spread. Prior Art A conventional ultrasonic
sensor in an ultrasonic moving object detector for detecting the presence or absence of a moving
object using the Doppler effect of ultrasonic waves is an ultrasonic wave transmitting surface of
an ultrasonic wave transmission sensor and an ultrasonic wave receiving sensor. Directionality in
a plane parallel to a perpendicular bisector of a line connecting the center of the ultrasonic wave
transmitting surface and the center of the ultrasonic wave receiving surface, with the ultrasonic
wave receiving surface being disposed away from the ultrasonic wave receiving surface by a
predetermined length The main beam width of the pattern is narrow. For this reason, the angle
desired from the ultrasonic sensor is narrow (it was suitable for home use, but not suitable for
automobile which must be monitored over a wide angle. That is, when an ultrasonic moving
object detector is attached to a car in order to protect equipment such as radios, cassette decks,
radios and the like installed in the car from the car, generally, for example, as shown in FIG. The
ultrasonic sensor 2 is mounted near the rearview mirror in the passenger compartment ceiling,
but since the main beam width is as narrow as α °, only the inside of the car and the rear
window 3 and part of the side window 4 can be monitored with a good S / N ratio. Can not. Of
course, if the ultrasonic sensor is driven with a large transmission power and a sufficient S / N
ratio is obtained, the side beam 4 can be covered by the sub beam, but the power consumption
becomes extremely large and the cause of the battery upset. Become. 18 o to fully cover the side
window. Although some beam widths are required, none of the commercially available ultrasonic
sensors have such directivity. The problem to be solved by the invention The present invention
has been made in view of such circumstances, and its object is to expand the beam width of an
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ultrasonic sensor with a simple configuration. Means for Solving the Problems When the present
invention is applied to an automobile, the distance from the ultrasonic sensor is about 1 to 2 m
for detecting an intruder, so that a sufficiently small reception level is obtained even if the gain is
somewhat small. In view of the above, the beam width can be expanded by dispersing part of the
energy in the conventional main beam to the left and right, so that both movement of a person in
the vehicle compartment and breakage of a side window can be detected. The ultrasonic wave
transmission sensor transmits an ultrasonic wave, the ultrasonic wave reception sensor receives
a reflected wave from an object, and detects the presence or absence of a moving object based on
the beat signal of the reception signal and the transmission signal. In an ultrasonic sensor for a
moving object detector, on the ultrasonic wave transmitting surface of an ultrasonic wave
transmitting sensor and an ultrasonic wave receiving surface of an ultrasonic wave receiving
sensor, a part of ultrasonic waves from the ultrasonic wave transmitting surface is one of Turn to
the side And a first surface for guiding a part forward by diffraction, and a second surface for
reflecting a part of the ultrasonic wave from the ultrasonic wave transmitting surface to the other
side and guiding a part forward by diffraction. A third surface for reflecting a reflected wave
from one side to be incident on the ultrasonic receiving surface and causing a reflected wave
from the front to be incident on the ultrasonic receiving surface by diffraction, and the other
surface from the other side A reflection / diffraction plate is provided having a fourth surface
which reflects the reflected wave and makes it incident on the ultrasonic wave receiving surface
and causes the reflected wave from the front to be incident on the ultrasonic wave receiving
surface by diffraction.
The four surfaces may be flat as shown in the embodiments described later, or may be surfaces
having some unevenness. In the preferred embodiment, the first and third surfaces are
comprised of the same surface, and the second and fourth surfaces are also comprised of the
same surface, but may be separate surfaces. The ultrasonic waves transmitted from the active
ultrasonic wave transmission sensor are partially reflected to both sides of the sensor by the
reflection and diffraction plate and diffracted and transmitted to the front of the sensor from the
both sides of the sensor. The incoming reflected wave is reflected by the reflection and
diffraction plate and is incident on the receiving surface of the ultrasonic wave receiving sensor,
and the reflected wave coming from the front of the sensor is incident on the receiving surface of
the ultrasonic wave receiving sensor by diffraction. The beam width of the directivity pattern of
the plane parallel to the perpendicular bisector of the line connecting the center of the plane and
the center of the reception plane is expanded compared to the prior art. Embodiment A trust
sensor 12 is an ultrasonic wave receiving sensor. The ultrasonic wave transmission sensor 11 is
driven by a pulse from a pulse oscillation circuit (not shown) to transmit ultrasonic waves from
the ultrasonic wave transmission surface 11a, and the ultrasonic wave reception sensor 12 uses
an ultrasonic wave reception surface 12a. When an ultrasonic wave is incident, it is converted
into an electric signal and output, and the two are arranged at a predetermined interval so that
the transmitting surface 11a and the receiving surface 12a are positioned substantially in the
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same plane. On the ultrasonic wave transmitting surface 11a and the ultrasonic wave receiving
surface 12a, a V-shaped reflection / diffraction plate 10 made of a hard material such as plastic
or metal capable of sufficiently reflecting ultrasonic waves is bent at its central portion Are
measured by a measuring system which is extracted by a support machine filter 54 (not shown)
so as to be almost directly above the delivery surface 11a and the receiving surface 12a and
amplified by an amplifier 55. In addition, for comparison, the directivity pattern in a state where
the reflection and diffraction plate was removed was measured by the same measurement
system. The solid line in FIG. 4 shows this. As can be seen from FIG. 4, without the reflective /
diffraction plate 30, the gain is extremely reduced at angles of + 50 ° or more and -50 ° or
less, and the beam width is narrowed. On the other hand, when the reflection and diffraction
plate 30 is provided, sufficient gain is obtained over a wide range of 180 ° or more, and the
beam width is expanded. FIG. 6 shows an embodiment in which the ultrasonic wave sensor of the
present invention is applied to an antitheft device for a car, 40 is an ultrasonic moving object
detector, 41 is a microcomputer, 42 is a car battery, 44 is an AND circuit, 6 Is an alarm. The
ultrasonic moving object detector 40 includes a pulse oscillation circuit 60, an ultrasonic
transmission sensor 32 to which this pulse is applied, a reflection and diffraction plate 30.
The ultrasonic wave sensor 50 comprising the ultrasonic wave reception sensor 33, the mixing
circuit 61 for mixing the output of the ultrasonic wave reception sensor 33 and the output of the
pulse oscillation circuit 60, and the beat component extracted from the output of the mixing
circuit 62 A band pass filter 62, an amplifier 63 for amplifying the output of the band pass filter
62, and a comparison circuit 65 for obtaining a single reference voltage V obtained by dividing
the voltage Vcc by the resistor 64 using the output of the amplifier 63 as ten power. And a level
integrating circuit 66 which performs level integration on the output of the comparison circuit @
65, and a waveform shaping circuit which shapes the output of the level integrating circuit 66
into a rectangular wave. The ultrasonic sensor 50 is mounted, for example, in the vicinity of a
rearview mirror on the ceiling of a passenger compartment of a car. The microcomputer 41 is a
so-called one-chip microcomputer including a ROM, a RAM, etc., and receives an ignition switch
state signal, an open / close state signal of a car door, and an output signal a of the waveform
shaping circuit 67 as input. A start signal and an open / close signal of the AND circuit 45 are
generated. The constant voltage circuit 43 converts the voltage of the car battery 42 to a
constant voltage to generate a voltage cc and supplies it to each part of the ultrasonic moving
object detector. FIG. 7 is a flow chart showing an example of processing performed by the
microcomputer 41. マイクロコンピュータ４１はイグニッションスイッチのオン。 If the ignition
switch status signal determines that it has been turned off, as shown in FIG. 7, the signal is first
made "θ" to close the AND circuit 44 (Sl>, constant voltage The circuit 43 is activated to activate
the ultrasonic moving object detector (S2). As a result, a pulse is applied from the pulse
oscillation circuit 60 to the ultrasonic transmission sensor 32, and transmission of ultrasonic
waves is performed. Because the beam width of the ultrasonic sensor 50 is wide, the ultrasonic
waves are sufficiently input not only to the rear window but also to the side windows, and the
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reflected ultrasonic waves are input to the ultrasonic wave receiving sensor 33. The
microcomputer 41 then reads the door open / close state signal to determine whether all the
doors are closed or not S3). When the doors are all closed, the output a of the waveform shaping
circuit 67 is for a predetermined time, for example, several seconds to several tens seconds It is
determined whether it is "0" (S4). そして、ステップＳ３． When the condition of S4 is satisfied,
the AND circuit 44 is opened with the signal at the position so that the alarm 5 can be activated
by the output a of the ultrasonic moving object detector (S5). Such control is performed so that
the essential operation of the car antitheft device is performed after the person in the car turns
off the ignition switch and closes all the down doors from the car.
When there is no abnormality in the window glass or the like, the beat signal becomes almost
zero, so the output voltage of the amplifier 63 is smaller than that of the reference voltage
section 7 and the output a of the waveform shaping circuit 67 is "0". However, if the window
glass is strongly struck or broken, a beat signal is generated due to vibration of the window glass
or a broken glass piece etc., and the output voltage of the amplifier 63 becomes larger than the
reference voltage 3 and the waveform shaping circuit The output a of 67 becomes "1". As a
result, the alarm 45 operates and an alarm is issued. As the alarm 45, a horn circuit of a car can
be used. The microcomputer 41 monitors the door open / close state signal after the ultrasonic
moving object detector 40 is properly activated as shown in FIG. 7 (S6), and when any door is
opened, the constant voltage is maintained. The operation of the circuit 43 is stopped and the
operation of the ultrasonic moving object detector 40 is stopped (S7). This is to prevent the
driver or the like from issuing a false alarm when the door is opened and the vehicle enters. FIG.
6 shows that the ultrasonic sensor according to the present invention is used as an antitheft
device for a car, but the ultrasonic sensor 50 can be applied to the detection of moving objects in
a bank of a car by attaching the ultrasonic sensor 50 to the rear of the car. It can also be applied
to home use. As described in detail in the invention, the present invention is provided with a
reflection and diffraction plate in front of an ultrasonic wave transmission sensor and an
ultrasonic wave reception sensor, and the beam width of the directional pulse can be expanded
compared to the prior art. effective. Therefore, it is suitable for an ultrasonic mobile object
detector for automobiles that must be monitored over a wide angle. Further, since the
wavelength of the ultrasonic wave is very short and the dimension of the reflection and
diffraction plate is correspondingly small, the mounting property to an automobile or the like is
also good.
[0002]
Brief description of the drawings
[0003]
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1 is a schematic diagram of the embodiment of the present invention, FIG. 2 is a side view
thereof, FIG. 3 is an external perspective view of another embodiment of the present invention,
and FIG. 4 is a directivity pattern of the embodiment of the present invention. (Dotted line) and a
diagram showing the directivity pattern (solid line) of the conventional example, FIG. 5 is a block
diagram showing a measurement system of the directivity pattern, and FIG. 6 is an antitheft
vehicle for automobile using the ultrasonic sensor of the present invention. FIG. 7 is a block
diagram of an embodiment of the apparatus, FIG. 7 is a flowchart showing an example of
processing of the microcomputer 41, and FIG. 8 is an explanatory view of a conventional
problem.
10.30 is a reflection and diffraction plate, 11.32 is an ultrasonic wave transmission sensor, and
12.33 is an ultrasonic wave reception sensor.
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