JP6486220B2 - Distance detection sensor and object detection device - Google Patents

Description

  The present invention relates to a technique for measuring a distance to a measurement object by transmitting and receiving sound waves.

The technology to measure the distance to the measurement object by transmitting and receiving sound waves is based on the difference between the time when the sound wave is transmitted from the transducer toward the measurement object and the time when the transducer receives the reflection of the transmitted sound wave. This is based on the principle of calculating the distance based on.
The frequency of the sound wave used mainly is a sound wave of 20 kHz or more outside the audible band, which is advantageous in terms of distance resolution, directivity, and noise. Therefore, a method using an ultrasonic wave that is a sound wave of 20 kHz or higher is used in practice, and is applied to, for example, a vehicle back sonar.

  When sound waves propagate through the air, they are attenuated in inverse proportion to the square of the distance due to diffusion. In addition to so-called distance attenuation, there is air absorption due to energy loss due to vibration of air molecules. Is known to grow. As a result, the ultrasonic wave has a greater distance attenuation than the audible sound. Therefore, in distance measurement using ultrasonic waves, the limit of the measurable range is limited due to a decrease in the S / N ratio due to attenuation of sound waves.

  In recent years, there is a demand to apply inexpensive ultrasonic sensors to obstacle detection functions in automatic parking assistance systems or safety functions such as emergency braking during driving, and the detection distance in distance measurement using sound waves is increased. There is also a need for higher accuracy. In order to realize these, Patent Document 1 and Patent Document 2 add a horn to artificially enlarge the transmission surface of the transducer, improve the radiation effect of the sound wave, sharpen the directivity of the sound wave, An ultrasonic transducer that improves the signal-to-noise ratio in distance measurement using ultrasonic waves is disclosed.

JP-A-6-269090 JP 58-85699 A

  However, since the ultrasonic transducers described in Patent Document 1 and Patent Document 2 described above are not premised on mounting on a moving body such as a vehicle, entry of rain, dust, insects, pebbles, and the like due to traveling of the vehicle. Clogging and collision are not considered. For this reason, when the ultrasonic transducer is mounted on a vehicle, there is a problem that the ultrasonic wave transmission performance is deteriorated due to clogging and collision of an entering object that has entered the horn as the vehicle travels.

  The present invention has been made to solve the above-described problems, and it is an object of the present invention to improve the efficiency of sound wave radiation and to suppress the deterioration of the sound wave transmission performance due to the entering material that has entered the horn. .

A distance detection sensor according to the present invention includes: a wave transmitting unit that transmits a sound wave; a wave receiving unit that receives a reflected wave obtained by reflecting the sound wave transmitted from the wave transmitting unit by a measurement object; A transducer having a distance measuring unit for measuring a distance to a measurement object based on a transmission time and a reception time of the sensor, and adjusting a directivity by reflecting a sound wave transmitted by the transmission unit, A horn having a curved surface that radiates toward the surface, the horn having a parabolic surface that is obtained by rotating the parabola about the axis of symmetry of the parabola as a rotational axis, and a sonic wave transmission at the opening of the parabolic surface. and mouth, have a hole in the apex portion of the paraboloid, the curved surface of the horn, a paraboloid, a partial curved surface obtained by cutting in a plane parallel to the rotation axis includes a rotation shaft, transducer, Placed at the focal point of the parabola on a plane parallel to the cutting plane It is those that.

  According to this invention, the radiation efficiency of sound waves can be improved, and the deterioration of the sound wave transmission performance due to the entering material that has entered the horn can be suppressed.

1 is a perspective view showing a configuration of a distance detection sensor according to Embodiment 1. FIG. 3 is a top view showing a configuration of a distance detection sensor according to Embodiment 1. FIG. FIG. 3 is a cross-sectional view taken along the line AA in FIG. 2, illustrating reflection of ultrasonic waves and a moving path of air. It is a figure which shows the structure of the object detection apparatus provided with the distance detection sensor which concerns on Embodiment 1. FIG. It is a figure which shows the structure of the object detection apparatus provided with the distance detection sensor which concerns on Embodiment 1. FIG. It is sectional drawing which shows the other structural example of the distance detection sensor which concerns on Embodiment 1. FIG. It is a figure which shows the other structural example of the distance detection sensor which concerns on Embodiment 1. FIG.

Embodiment 1 FIG.
The configuration of the distance detection sensor that detects the distance to the measurement object will be described with reference to FIGS. 1 to 3.
1 is a perspective view showing a configuration of a distance detection sensor according to Embodiment 1. FIG.
FIG. 2 is a top view showing the configuration of the distance detection sensor according to the first embodiment.
FIG. 3 is a cross-sectional view taken along the line AA in FIG. 2, and is a diagram illustrating a reflection mode of ultrasonic waves and a movement path of air.

  The distance detection sensor 10 includes a transducer 1, a horn 2, and a support member 3. The transducer 1 is composed of, for example, an ultrasonic sensor or the like, and includes an ultrasonic wave transmission surface (transmission unit, see FIG. 3) and a wave reception surface (wave reception unit, see FIG. 3). Furthermore, the transducer 1 measures the distance to the measurement object from the time until the ultrasonic wave output from the transmission surface is reflected by the measurement object and received by the wave reception surface and the propagation speed of the ultrasonic wave. A distance measuring unit (not shown) is provided. A plurality of transducers 1 may be used for measuring the distance to the measurement object, and the transducer 1 having only the ultrasonic wave transmission surface and the transducer 1 having only the ultrasonic wave reception surface may be combined. In the following description, the case where the transducer 1 includes a transmission surface and a reception surface will be described as an example.

  The horn 2 has a reflection curved surface 2 a that reflects the ultrasonic wave transmitted from the transducer 1. The reflection curved surface 2a is a partial curved surface obtained by cutting a rotating paraboloid formed by rotating the parabola with the axis of symmetry of the parabola as a rotation axis, by a plane including the rotation axis and parallel to the rotation axis. is there. The transducer 1 is disposed at the focal position 2b of the paraboloid that forms the reflection curved surface 2a of the horn 2. In particular, the transducer 1 is disposed such that the wave transmitting / receiving surface 1a is located at the focal position 2b. Further, the ultrasonic radiation main axis and the incident main axis of the transducer 1 are arranged facing the reflection curved surface 2a. The support member 3 is a member that supports the transducer 1. As shown in FIG. 2, the support member 3 has a shape that covers the cutting opening of the horn 2 obtained by cutting the paraboloid of the horn 2 along a plane that includes the rotation axis and is parallel to the rotation axis. Yes.

Next, the reflection of ultrasonic waves and the movement of air and objects flowing into the distance detection sensor will be described with reference to FIG.
The ultrasonic wave P transmitted from the wave transmitting / receiving surface 1a of the transducer 1 arranged at the focal position 2b of the parabola is reflected by the reflection curved surface 2a of the horn 2, and collected while the path is parallelized in one direction. The collected ultrasonic wave Pa is transmitted from the transmission / reception port 2c toward the measurement object. When the transducer 1 performs only transmission, the transmission / reception port 2c is a transmission port, and when the transducer 1 performs only reception, the transmission / reception port 2c is a reception port. The ultrasonic wave obtained by reflecting the transmitted ultrasonic wave Pa by the measurement object is reflected by the reflection curved surface 2 a of the horn 2 and received by the transmission / reception wave surface 1 a of the transducer 1.

  Air and flying objects Q flow into the distance detection sensor 10 from the transmission / reception port 2c. When the distance detection sensor 10 is mounted on a moving body such as a vehicle, flying objects such as pebbles, dust, insects, and rain collide with the moving body from the front when the vehicle travels. These flying objects flow into the horn 2 of the distance detection sensor 10 from the transmission / reception port 2c. Therefore, the hole 4 is formed at the apex position 2d of the parabola that forms the horn 2. In the example of FIGS. 2 and 3, the hole 4 is formed in the region from the apex position 2 d of the parabola that forms the horn 2 to the position where the transducer 1 is disposed. The formed hole 4 guides the air and the flying object Q that have flowed into the horn 2 from the wave receiving / receiving port 2 c to the outside of the distance detection sensor 10.

FIG. 4 is a configuration diagram illustrating a case where the distance detection sensor 10 is mounted on a vehicle to configure an object detection device.
4A is a view of the vehicle as viewed from the side, and FIG. 4B is a view of the vehicle as viewed from above. In the example of FIG. 4, a distance detection sensor 10 a is arranged at the front center of the vehicle 30 and a distance detection sensor 10 b is arranged at the rear center. A case will be described in which the vehicle 30 travels in the direction of arrow B and an obstacle existing in the forward direction of the vehicle 30 is detected.

The object detection device 20 includes the distance detection sensor 10, the obstacle detection unit 21, and the notification unit 22 described above. Each function of the obstacle detection unit 21 and the notification unit 22 in the object detection device 20 is realized by a processing circuit. The processing circuit is a CPU (Central Processing Unit, central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, processor, DSP) that executes a program stored in a memory.
The obstacle detection unit 21 is connected to the distance detection sensors 10a and 10b. The obstacle detection unit 21 detects the measurement object as an obstacle based on the distance to the measurement object measured by the transducer 1 of the distance detection sensors 10a and 10b.

  In the case of FIG. 4, the ultrasonic wave Pa transmitted from the transducer 1 of the distance detection sensor 10a is reflected by the measurement object 31, and the reflected ultrasonic wave Pb is incident on the transducer 1 again and received. The distance to the measurement object 31 is measured. The obstacle detection unit 21 detects the measurement object 31 as an obstacle when the distance to the measurement object 31 is within a threshold value. When the obstacle detection unit 21 detects an obstacle, the notification unit 22 notifies the driver 32 by a notification sound or a voice announcement.

FIG. 5 is a diagram illustrating another configuration of the object detection device, as viewed from above the vehicle.
In FIG. 5, distance detection sensors 10a, 10b, and 10c are arranged at three locations in front of the vehicle 30, and distance detection sensors 10d, 10e, and 10f are arranged at three locations in the rear of the vehicle. In addition, the vehicle 30 travels in the direction of arrow B, and the measurement object 31 exists diagonally forward in the travel direction of the vehicle 30. The transducers 1 of the distance detection sensors 10a, 10b, 10c, 10d, 10e, and 10f have a transmission surface and a reception surface. The transmission and reception of the ultrasonic wave Pa in front of the vehicle 30 will be described as an example. The transmission of the ultrasonic wave Pa is performed by any one of the distance detection sensors 10a, 10b, and 10c, and the ultrasonic wave Pa is received. Is performed by all the distance detection sensors 10a, 10b, and 10c. Distance detection sensors that transmit ultrasonic waves are sequentially switched by the distance detection sensors 10a, 10b, and 10c to perform distance detection over a wide range.

  When the distance detection sensor 10a transmits the ultrasonic wave Pa, the transmitted ultrasonic wave Pa is reflected by the measurement object 31, and the reflected ultrasonic wave Pb is a wave receiving surface of the transducer 1 of the distance detection sensors 10a, 10b, and 10c. It is received at. The transducer 1 detects the distance to the measurement object 31. The obstacle detection unit 21 detects the measurement object 31 as an obstacle when the distance to the measurement object 31 is within a threshold value.

  In FIG. 5, ultrasonic waves Pb reflected from an oblique direction are incident on the distance detection sensors 10b and 10c. However, when the distance between the distance detection sensors 10b and 10c and the obstacle is large, the incident angle to the distance detection sensors 10b and 10c approximates that when the ultrasonic wave Pb is incident from the front. Therefore, a configuration in which the ultrasonic wave Pb incident from an oblique direction is received and used for distance detection is effective. Further, by using the distance detection results of the plurality of distance detection sensors 10a, 10b, and 10c, it becomes possible to detect the position of the obstacle in a two-dimensional or three-dimensional manner.

  In the configuration shown in FIGS. 4 and 5, when the vehicle 30 moves in the direction opposite to the arrow B direction, that is, behind the vehicle 30, the distance detection sensor 10d disposed behind the vehicle 30 uses the ultrasonic wave Pa. To transmit. When there is an obstacle behind the vehicle 30, the ultrasonic wave Pa is reflected by the obstacle, and the reflected ultrasonic wave Pb is received by the transducer 1 of the distance detection sensors 10d, 10e, and 10f.

  As described above, according to the first embodiment, the rotation paraboloid formed by rotating the parabola with the parabolic axis as the rotation axis is a plane including the rotation axis and parallel to the rotation axis. Is provided with a horn 2 having a partial curved surface obtained by cutting at a reflection curved surface 2a, and the hole 4 is formed in the region from the apex position 2d of the parabola forming the horn 2 to the position where the transducer 1 is disposed. Even when the distance detection sensor is applied to a moving body such as a vehicle, the air and flying objects that have flowed into the distance detection sensor can be guided outside the distance detection sensor.

  Further, according to the first embodiment, the rotational paraboloid formed by rotating the parabola with the axis of symmetry of the parabola as a rotational axis is cut by a plane including the rotational axis and parallel to the rotational axis. Since the horn 2 having the partial curved surface obtained as a reflection curved surface 2a is provided, the ultrasonic wave reflected and reflected by the reflective curved surface is efficiently transmitted in the transmission direction. be able to.

  In addition, according to the first embodiment, the transmission / reception surface 1a of the transducer 1 is arranged at the focal position 2b of the paraboloid of revolution that forms the reflection curved surface 2a of the horn 2. The wave receiving surface can be arranged in a direction different from the moving direction of the moving body, and flying objects can be prevented from colliding with the wave transmitting surface or the wave receiving surface of the transducer to cause damage, failure or performance degradation of the transducer.

  Further, according to the first embodiment, since the ultrasonic radiation main axis and the incident main axis of the transducer 1 are arranged facing the reflection curved surface 2a side, the sound wave on the front central axis where the sound wave is strongest is Can be radiated toward the reflection curved surface, and strong directivity can be obtained. Thereby, the high radiation efficiency of a transducer is realizable.

In addition, in Embodiment 1 mentioned above, although the structure which provides the hole 4 in the space of the upper part of the horn 2 was shown, you may form in the horn 2. FIG. FIG. 6 is a diagram illustrating another configuration example of the distance detection sensor according to the first embodiment. FIG. 6 corresponds to the cross-sectional view taken along the line AA shown in FIG. 2, and is a diagram illustrating an ultrasonic reflection mode and an air movement path when another configuration example is applied.
As shown in FIG. 6, the hole 4 a may be formed in a region within a range set from the apex position 2 d of the parabola that forms the horn 2. The shape of the hole 4a is not particularly limited, and any size and shape of the opening may be used as long as the shape allows the air, air, dust, and dust flowing in from the transmission / reception port 2c to be guided to the outside. There may be.

  In the first embodiment described above, the configuration in which the partial curved surface of the rotating paraboloid formed by rotating the parabola with the axis of symmetry of the parabola as the rotation axis is the reflection curved surface 2a is shown. It is not limited. For example, a partial curved surface of a spheroidal surface formed by rotating the ellipse about the axis of symmetry of the ellipse may be used as the reflection curved surface 2a.

Moreover, in Embodiment 1 mentioned above, although the structure which used the partial curved surface of a paraboloid as the reflective curved surface 2a was shown, the horn 2 was processed by extrusion molding without being limited to the partial curved surface of a rotating surface. You may comprise by a partial curved surface. An example of the extrusion shape processed by extrusion molding is shown in FIG.
FIG. 7 is a diagram illustrating another configuration example of the distance detection sensor according to the first embodiment.
FIG. 7A is a perspective view of the distance detection sensor, and FIG. 7B is a side view of the distance detection sensor. FIG. 7C is a cross-sectional view taken along the line C-C in FIG. 7B, showing the reflection of ultrasonic waves and the air movement path.

  The horn 2 shown in FIG. 7 has a partial curved surface 2e processed by extrusion molding. The partial curved surface 2 e is a reflective curved surface that reflects the ultrasonic wave transmitted from the transducer 1. The wave transmitting / receiving surface 1a of the transducer 1 is disposed at the focal position of the partial curved surface 2e. The ultrasonic wave P transmitted from the transmission / reception surface 1a of the transducer 1 is reflected by the partial curved surface 2e of the horn 2, and the traveling path is parallelized in one direction and collected. The collected ultrasonic wave Pa is transmitted from the transmission / reception port 2c toward the measurement object. A hole 4b is provided at a position facing the transmission / reception port 2c, and air and flying objects flowing into the horn 2 from the transmission / reception port 2c are guided out of the distance detection sensor 10. Thus, the reflection curved surface is not limited to the partial curved surface of the paraboloid of revolution or the partial curved surface of the spheroid surface, and a partial curved surface processed by extrusion molding can be applied.

  In the present invention, any constituent element of the embodiment can be modified or any constituent element of the embodiment can be omitted within the scope of the invention.

  DESCRIPTION OF SYMBOLS 1 Transducer, 1a Transmission / reception surface, 2 Horn, 2a Reflection curved surface, 2b Focus position, 2c Transmission / reception port, 2d Vertex position, 2e Partial curved surface, 3 Support member, 4, 4a, 4b Hole, 10 Distance detection sensor, 20 object Detection device, 21 obstacle detection unit, 22 notification unit, 30 vehicle, 31 obstacle, 32 driver.

Claims (3)

A wave transmitting unit for transmitting a sound wave; a wave receiving unit for receiving a reflected wave obtained by reflecting a sound wave transmitted from the wave transmitting unit by a measurement object; A transducer having a distance measuring unit that measures a distance to the measurement object based on time;
A horn having a curved surface that reflects the sound wave transmitted by the wave transmitting section of the transducer to adjust the directivity and radiates toward the measurement object;
The horn has a parabolic surface obtained by rotating the parabola about the axis of symmetry of the parabola as the rotation axis, the opening of the parabola surface as the sound wave transmission port, and the apex of the parabola surface. Has a hole in the part,
The curved surface of the horn is a partial curved surface obtained by cutting the paraboloid in a plane including the rotation axis and parallel to the rotation axis.
The transducer is a distance detection sensor disposed on a plane parallel to a cut surface in the cutting and at a focal position of the parabola. The transducer, the distance detecting sensor according to claim 1 Symbol mounting, characterized in that placing the central axis of the sound wave to transmit or reception towards the curved surface of the horn. A distance detection sensor claims 1 or claim 2 Symbol mounting mounted on the vehicle,
Based on the distance to the measurement object measured by the distance detection sensor, an obstacle detection unit that detects the measurement object as an obstacle,
An object detection apparatus comprising: a notification unit that notifies that the obstacle detection unit has detected the obstacle.

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