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JP2002058091

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JP2002058091
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
device for detecting that there is a possibility of touching an obstacle at the time of parking or
turning of a vehicle, and warning the driver in obstacle collision prevention. The present
invention relates to an ultrasonic sensor used for a clearance sonar used for
[0002]
2. Description of the Related Art An ultrasonic clearance sonar is one that warns a driver by
issuing an alarm based on the distance between a vehicle and an obstacle. A drip-proof ultrasonic
sensor is used for this sensor. By the way, regarding the use of the ultrasonic sensor for the
vehicle, it is desirable not to warn the road surface and the parking curb on the road surface as
an obstacle, so the ultrasonic wave transmission / reception range in the horizontal direction is
wide and the ultrasonic wave transmission / reception in the vertical direction The directivity in
the vertical direction is narrowed with respect to the directivity characteristic in which the wave
range becomes narrow, that is, the directivity in the horizontal direction. In order to obtain such
directional characteristics, a horn is conventionally attached to the sensor housing, and such
directional characteristics are achieved by this horn.
[0003]
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However, in the case of an ultrasonic sensor to which such a horn is attached, rain water, earth
and sand, dust, etc. may remain between the sensor housing and the horn and become clogged,
causing malfunction of the ultrasonic sensor. It was the cause of occurrence. Moreover, when it
attaches to a vehicle etc., in order that a horn may protrude from a vehicle outer surface, for
example, a bumper, there existed a problem that an external appearance was impaired.
Furthermore, there has been the inconvenience of securing the mounting accuracy of attaching
the horn to the sensor housing so as not to affect the directivity characteristics.
[0004]
Therefore, a clearance sonar having a structure without a horn has been developed in recent
years to improve the appearance etc., and there is an ultrasonic transducer as disclosed in
Japanese Patent Laid-Open No. 9-284896. . In this ultrasonic transducer, the hollow portion of
the sensor housing has a rectangular shape or an oval shape in a cross-sectional view, and the
side thickness of the housing is made thicker than the bottom surface thickness as described
above. Such directional characteristics are obtained. That is, in order to narrow the directivity in
the vertical direction and widen the directivity in the horizontal direction, a hollow shape in
which a vibration mode having an oval shape long along the long axis direction of the hollow
portion and short along the short axis direction is obtained. I have to. However, simply providing
a rectangular or oval vibration surface as in this ultrasonic transducer does not reach the narrow
directivity desired for application to a vehicle clearance sonar, and the road surface and the
object on the road surface ( For example, there is a problem that a parking curb) is detected.
[0005]
SUMMARY OF THE INVENTION The present invention has been made in view of the above
problems, and an object thereof is to narrow down the directivity of an ultrasonic sensor and to
use it for a vehicle clearance sonar. It is another object of the present invention to provide an
ultrasonic sensor that enables accurate obstacle determination without detecting a road surface
and a parking curb on the road surface.
[0006]
SUMMARY OF THE INVENTION The present inventors focused attention on the shape of the
vibrating surface and the outer shape of the case of the ultrasonic sensor, and to make the shape
of the vibrating surface close to the outer shape of the case with directivity. It was found to
narrow.
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The present invention provides an ultrasonic sensor described in each claim in the claims as a
means for solving the above-mentioned problems.
[0007]
In the ultrasonic sensor according to the first aspect of the present invention, the vibration plane
is formed along the outline of the sensor housing having the ultrasonic sensor vibration plane,
whereby the directivity of the ultrasonic wave can be obtained. It became possible to narrow
down. Further, according to the present invention, the outline of the vibration surface has the
same curve as the curvature of the outline of the sensor housing, so that the distance from the
center of the vibration surface and the thickness of the sensor housing are uniform. The vibration
surface end is easily vibrated.
[0008]
According to the present invention, a parking curb that is preferably not treated as an obstacle
can be obtained by adopting an ultrasonic sensor capable of narrowing the directivity in the
vertical direction as a vehicle clearance sonar. It can be made undetectable. In the fifth and
eighth aspects of the present invention, the thickness formed by the outer shape of the vibration
surface and the outer shape of the sensor housing on the vibration surface side are equalized,
and the outer shape of the sensor housing is not formed in a circular arc. Even in the case, the
thickness is uniform along the outer shape, and the vibrating surface end is easily vibrated as in
the case of the arc. Furthermore, according to the sixth, seventh, and eighth aspects, the thinnest
portion of the vibration surface is formed along the inside of the outline of the vibration surface,
and the vibration surface is more easily vibrated.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION An ultrasonic sensor according to an
embodiment of the present invention will be described below with reference to the drawings. FIG.
1 is an ultrasonic sensor of the present invention, and its structure is shown using a plan view
and a side view. Reference numeral 1 denotes a circular flat piezoelectric vibrator (PZT), which is
fixed at a central position on the inner bottom surface 20 of the sensor housing 2 with an
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adhesive or the like. The sensor housing 2 has a substantially circular cross-sectional shape, a
hollow portion 21 is formed in the inside, and one surface is opened. As for the external shape of
the sensor housing 2, the opening portion side is partially cut off in an arc shape on the left and
right sides thereof to form an outer step portion 22. The hollow portion 21 is formed by cutting
the inside in an oval shape along the outer shape of the sensor housing 2, and an inner step
portion 23 is formed substantially in the middle in the axial direction. Therefore, the outer step
portion 22 and the inner step portion 23 are provided along the oval shaped side surface. Thus,
the sensor housing 2 is formed to have substantially the same thickness except for the portions
forming the left and right inner and outer stepped portions 22 and 23. The sensor housing 2 is
formed of a highly elastic light alloy such as aluminum or a synthetic resin.
[0010]
An air layer 3 is provided in contact with the piezoelectric vibrator 1 in the hollow portion 21 of
the sensor housing 2. The air layer 3 is made of sponge, felt or the like which absorbs the sound
wave radiated to the inside of the sensor in contact with the air layer 3. The absorbent material 4
is placed on the inner step portion 23, and is further in contact with the absorbent material 4 and
filled with a sealing resin 5 such as silicone rubber to seal the sensor housing 2. Further, lead
wires 6 a and 6 b for transmitting power to the ultrasonic sensor are connected to the
piezoelectric vibrator 1 and the inner side surface of the sensor housing 2 respectively.
[0011]
The vibrating surface 9 is provided by a part of the bottom surface 20 of the sensor housing 2 to
which the piezoelectric vibrator 1 is fixed. In the embodiment of FIG. 1, as shown in the plan
view, the outlines 8 of the upper and lower portions of the vibrating surface 9 are formed by the
same curve as the outline 7 of the sensor housing 2. As shown in the side view of FIG. 1, the
major axis direction of the vibrating surface 9 constitutes the vertical direction contributing
vibrating surface 10, and the short axis direction constitutes the horizontal direction contributing
vibrating surface 11. Furthermore, the thinnest portion 24 of the vibrating surface 9 is formed
on the bottom surface 20 along the arc-shaped outline 8 of the vibrating surface 9.
[0012]
In the operation of the ultrasonic sensor configured as described above, when an electric signal
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having a certain frequency (for example, 40 KHz) is sent through the lead wires 6a and 6b, the
piezoelectric vibrator 1 vibrates, and the sensor case is accompanied accordingly. The vibrating
surface 9 which is a part of the bottom surface 20 of the body 2 vibrates and ultrasonic waves
are emitted into the air. This ultrasonic wave transmits very short time (for example, an
ultrasonic wave of 40 KHz for 250 μsec). Thereafter, transmission / reception is switched using
transmission / reception switching means (not shown). The ultrasonic wave radiated into the air
is reflected back to the object (obstacle) and returned to resonate the vibrating surface 9 and
then received as a voltage. The distance from the object can be determined by measuring the
time it takes for the transmitted ultrasonic wave to bounce back from the object and to be
received by the ultrasonic sensor.
[0013]
FIG. 2 shows the structure of an ultrasonic sensor for comparison with the ultrasonic sensor of
the embodiment of the present invention. The ultrasonic sensor of this comparative example has
an outline 8 'of the vibration plane 9 in the major axis direction of the vibration plane 9, except
that the curvature of the outline 7 of the relevant portion of the sensor housing 2 is different. , It
is the same as the structure of the ultrasonic sensor of the Example of FIG.
[0014]
FIG. 3 is a graph showing the results of experiments and comparisons of the two ultrasonic
sensors. The horizontal axis represents the angle, and the vertical axis represents the sound
pressure. 3-1 shows the horizontal directivity of the ultrasonic sensor having the structure of the
comparative example of FIG. 2, and 3-2 shows the horizontal directivity of the ultrasonic sensor
having the structure of the embodiment of the present invention of FIG. Is shown. Further, 3-3
indicates the vertical directivity of the ultrasonic sensor of the comparative example, and 3-4
indicates the vertical directivity of the ultrasonic sensor of the embodiment. As can be seen from
this graph, in the ultrasonic sensor of the example, the directivity is sharper in the vertical
direction than in the comparative example, and the horizontal directionality is almost the same
between the example and the comparative example. Absent.
[0015]
Thus, the outline 8 of the vibration surface 9 of the ultrasonic sensor (the thin part of the case on
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the ultrasonic radiation side) has the same curvature as the outline 7 of the sensor case 2
corresponding to that part. In the case of the structure having the following, it is understood that
the vertical directivity is sharper as compared with the ultrasonic sensor having the structure in
which the outline 8 ′ of the vibration plane has a different curvature with respect to the sensor
case outline 7 as shown in FIG. Ru. Therefore, by adopting the ultrasonic sensor having such a
housing structure as the vehicle clearance sonar, the vertical directivity can be narrowed, and it
is not possible to detect an object or road surface that should not be treated as an obstacle.
[0016]
In the embodiment of FIG. 1, although the case where the ultrasonic sensor housing outer shape
is formed by an arc is described, when the sensor housing outer shape is not formed by an arc,
the sensor housing is The outer surface of the vibrating surface may be formed along the outer
surface of the sensor, that is, the thickness of the sensor housing may be equalized.
[0017]
Brief description of the drawings
[0018]
1 is a plan view of an ultrasonic sensor according to an embodiment of the present invention and
a side view of each.
[0019]
2 is a plan view of the ultrasonic sensor of the comparative example and a side view of each.
[0020]
It is a graph which shows the comparison experimental result of the ultrasonic sensor of FIG. 3
Example and a comparative example.
[0021]
Explanation of sign
[0022]
DESCRIPTION OF SYMBOLS 1 ... Piezoelectric vibrator 2 ... Sensor housing 3 ... Air layer 4 ...
Absorbent material 5 ... Sealing resin 9 ... Vibration surface
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