JP2011035884A - Ultrasonic sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic sensor which improves sensitivity, sound pressure, and directivity, prevents performance degradation due to water dripping, and easily obtains desired characteristics, by using a conventional drip-proof ultrasonic sensor. <P>SOLUTION: The ultrasonic sensor is provided with a drip-proof ultrasonic element in which a piezoelectric element is tightly sealed within a cylindrical case, and arranged in the center of a horn-shaped reflecting plate, and a front reflecting plate arranged in front of the ultrasonic element. The front reflecting plate is composed of chevron planes which are tilted rearward from the central ridgeline toward the left and right ends thereof, while the ridgeline is arranged facing the front surface of the ultrasonic element. A microgap is formed between the ridgeline and the front surface of the ultrasonic element, to obtain vibrational impedance matching between the ultrasonic element and the atmosphere. Thereby, central-part sensitivity (S/N ratio), directivity characteristics, and reverberation characteristics, which are all satisfactory and are equivalent to those of open-type ultrasonic sensors, can be obtained. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a drip-proof ultrasonic sensor, and particularly to a drip-proof ultrasonic sensor with improved sensitivity and directivity.

  The ultrasonic sensor emits ultrasonic waves toward the object at the resonance frequency of the ultrasonic transducer, receives the ultrasonic waves reflected from the object at the same frequency, and takes the time from transmission to reception. It measures the distance of an object or detects an object. These ultrasonic sensors are attached to the rear and four corners of a vehicle to detect obstacles and people when turning backwards and turn, and to detect people in the working range attached to the front, back, left and right of heavy construction equipment. It is used in a wide range of applications such as sensors. In addition, an ultrasonic sensor attached to a vehicle or heavy construction equipment uses a drip-proof ultrasonic element in order to protect the ultrasonic sensor from water droplets such as rain. A general prior art of such a drip-proof ultrasonic sensor will be described below.

  For example, an “ultrasonic transducer” disclosed in Japanese Patent Application Laid-Open No. 63-255679 (Patent Document 1) has a piezoelectric element on the inner surface of a diaphragm having a sealed structure, as shown in FIG. The ultrasonic sensor having a sealed structure (drip-proof type) is joined.

  A technique similar to that of Patent Document 1 is also disclosed for the “drip-proof ultrasonic microphone” disclosed in Japanese Patent Laid-Open No. 4-56597 (Patent Document 2). The sound wave sensor is configured to obtain a drip-proof performance by having such a sealed structure.

  Furthermore, as a method for improving the directivity of such a drip-proof ultrasonic sensor, it is a common technique to provide a horn on the ultrasonic sensor, and Japanese Utility Model Publication No. 2-27665 (Patent Document 3). 1 discloses that a drip-proof ultrasonic transducer is provided with a horn as a conventional example in FIG. 1 of the publication.

  JP-A-63-255679   Japanese Patent Laid-Open No. 4-56597   No. 2-27665

  By the way, the conventional drip-proof ultrasonic sensor has a sealed structure so that water droplets do not enter, so it is difficult to match the vibration impedance between the element and the air, and it has good performance as an ultrasonic sensor. Can't get. When compared with a normal open-type ultrasonic sensor, the sensitivity, sound pressure, and directivity are significantly reduced. As general data, the open-type sound pressure is 115 dB and the drip-proof type is 106 dB. The sensitivity of the open type is reduced to -78 dB with respect to the sensitivity of -67 dB, the directivity of the open type is reduced to 80 ° with respect to the open half-angle of 55 °, and the performance deterioration is remarkable. It is.

  Moreover, in the thing which improved directivity using the horn shown by patent document 3, water drops, such as a raindrop and a water splash, penetrate | invade from the opening part of a horn, and desired ultrasonic sensor is used. It becomes impossible to obtain performance. For this reason, a drain hole is provided inside, but the drain hole may be clogged with dirt or the like, and as a result, it is difficult to obtain desired performance as an ultrasonic sensor.

  Therefore, the present invention utilizes conventional drip-proof ultrasonic sensors to improve sensitivity, sound pressure, directivity, prevent performance degradation due to water droplets, and easily obtain desired desired characteristics. An object of the present invention is to provide an ultrasonic sensor capable of performing the above.

In a drip-proof ultrasonic element comprising a piezoelectric element inside a cylindrical case and hermetically sealed, and a drip-proof ultrasonic sensor comprising the ultrasonic element in the center of a horn-type reflector, A front reflector is provided in front of the ultrasonic element,
The front reflector is formed of a mountain-shaped surface that is inclined backward from the central ridge line portion toward the left and right ends, and the ridge line portion is provided facing the front surface of the ultrasonic element, and the ridge line portion This is solved by providing a fine gap between the ultrasonic device and the front surface of the ultrasonic element.

  Moreover, the ridgeline part of the said front reflector is solved by having formed in the circular arc shape so that it may bulge in the front direction of this ultrasonic element.

  In addition, the front reflector has a conical side surface that is circularly inclined backward from the central apex, and the apex is provided to face the front of the ultrasonic element, and the apex and super This is solved by providing a fine gap between the front surface of the acoustic wave element.

  This can be solved by providing the front opening of the horn-shaped reflector with a lattice plate assembled in a cross beam.

  This is solved by analyzing the sensing signal from the ultrasonic sensor and the image signal from the imaging device provided separately to identify only the human body and issue an alarm.

  According to the first aspect of the present invention, a drip-proof ultrasonic element having a cylindrical case and a hermetically sealed piezoelectric element, and a drip-proof type having the ultrasonic element at the center of a horn-shaped reflector are provided. In the ultrasonic sensor, a front reflector is provided on the front surface of the ultrasonic element, and the front reflector is formed of a mountain-shaped surface that is inclined backward from the central ridge line portion toward the left and right ends, and the ridge line portion. Is provided to face the front surface of the ultrasonic element, and a fine gap is provided between the ridge line portion and the front surface of the ultrasonic element. As a result, the ultrasonic wave generated by the vibration of the ultrasonic element is compressed in the space formed between the horn-type reflector and the front reflector, and the vibration impedance matching between the ultrasonic element and the air is obtained. This makes it possible to obtain good center sensitivity (S / N ratio), directivity characteristics, and reverberation characteristics equivalent to those of an open-type ultrasonic sensor. In addition, raindrops and other water droplets adhere to the front surface of the ultrasonic element, which degrades the performance of the ultrasonic sensor. However, the provision of a front reflector on the front surface of the ultrasonic element allows water droplets to adhere to the ultrasonic element. To prevent performance degradation. Furthermore, even when a water droplet enters the gap between the ultrasonic element and the front reflector, the water droplet naturally flows down due to the fine gap between the ridge line portion of the front reflector and the ultrasonic element, It is possible to reliably prevent the deterioration of the performance of the ultrasonic sensor in the rainy weather or at the work site where there is a puddle.

  According to a second aspect of the present invention, the ridge line portion of the front reflector is formed in an arc shape so as to bulge toward the front surface of the ultrasonic element. Thereby, in addition to the effect of claim 1, since the fine gap between the arc-shaped ridge line portion and the ultrasonic element is closer to a point, it is possible to improve the water droplet adhesion preventing performance, The performance degradation of the acoustic wave sensor can be reliably prevented.

  In claim 3, the front reflector is formed of a conical side surface that is inclined backward and circularly from the central apex portion, the apex portion is provided to face the front surface of the ultrasonic element, and the apex portion A fine gap was provided between the ultrasonic element and the front surface. Thereby, in addition to the effect of claim 1, since the fine gap between the apex and the ultrasonic element is closer to a point, it is possible to improve the performance of preventing the adhesion of water droplets. It was possible to reliably prevent performance degradation.

  According to a fourth aspect of the present invention, the front opening of the horn-type reflector is provided with a lattice plate assembled in a cross beam. This prevents large drops of rain and water from directly adhering to the horn-type reflector, front reflector, and ultrasonic element without changing the performance of the ultrasonic sensor, and prevents performance degradation due to water drops. It is possible to reliably prevent the deterioration of the performance of the ultrasonic sensor in heavy rain and at work sites with deep water pools.

  According to a fifth aspect of the present invention, an alarm is generated by identifying only a human body by analyzing a sensing signal from an ultrasonic sensor and an image signal from an imaging device provided separately. As a result, when used as a human body detection system in a vehicle or heavy construction equipment, it detects the obstacles on the ground other than the human body such as steps, rubble, vegetation, etc. and reliably detects only the human body without issuing a false alarm. It was possible to emit.

It is a figure which shows the 1st Example of this invention. It is principal part expanded BB sectional drawing of FIG. It is a figure which shows the other shape of a front reflector. It is a figure which shows the 2nd Example of this invention. It is detailed explanatory drawing of the 2nd Example of this invention. It is a figure which shows a directivity characteristic. It is a figure which shows the 3rd Example of this invention. It is a figure which shows a directivity characteristic. It is a figure which shows the 4th Example of this invention. It is a block diagram which shows the 5th Example of this invention.

  A first embodiment of an ultrasonic sensor according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a view showing a first embodiment of the present invention, and FIG. 2 is an enlarged view of a main part in a cross-sectional view taken along line BB in the front view of FIG. As shown in FIG. 1, the ultrasonic sensor body (1) includes a drip-proof ultrasonic element (2) formed by sealing a cylindrical case with a piezoelectric element, and the ultrasonic element (2). ) At the center of the horn-type reflector (3), and the front reflector (4) is provided on the front surface of the ultrasonic element (2). As shown in FIG. 2, the front reflector (4) has a mountain-shaped surface that is inclined backward from the central ridge line part (4a) toward the left and right ends, and the ridge line part (4a) is The ultrasonic element (2) is provided so as to face the front surface, and a fine gap (5) is provided between the ridge line portion (4a) and the front surface of the ultrasonic element (2). The fine gap (5) is a state in which the front reflector (4) and the ultrasonic element (2) are in contact with each other, and generally means 1 mm or less.

  As shown in FIG. 2, the ultrasonic sensor main body (1) configured as described above is generated by applying a predetermined voltage to the ultrasonic element (2) and vibrating the ultrasonic element (2). The ultrasonic wave is compressed in the space (5) and the space formed between the horn-type reflector (3) and the front reflector (4), and the ultrasonic compression space (6) is formed. Thereby, it becomes possible to obtain a matching of vibration impedance between the ultrasonic element (2) and the air, and an open type ultrasonic wave that cannot be obtained with a conventional drip-proof ultrasonic sensor without a front reflector. Good center sensitivity (S / N ratio), directivity characteristics, and reverberation characteristics equivalent to those of the sensor can be obtained.

  Further, the conventional drip-proof ultrasonic sensor has a significantly lower performance than the open ultrasonic element because the ultrasonic element has a sealed structure to prevent water droplets from entering. In addition, there has been a problem that performance drops significantly due to water drops such as rain adhering to the front surface of the ultrasonic element. In the present invention, a front reflector (2) is placed on the front surface of the ultrasonic element (2). By providing 4), it was also possible to eliminate water droplet adhesion to the ultrasonic element (2) and prevent performance degradation. In addition, even when a water droplet enters between the ultrasonic element (2) and the front reflector (4), the gap between the ridge (4a) of the front reflector (4) and the ultrasonic element (2) The fine gap (5) allows water droplets to flow down naturally and reliably prevent deterioration of the performance of the ultrasonic sensor when it is raining or at a work site where there is a water pool.

  FIG. 3 shows another shape of the ridge portion of the front reflector (4), and the front reflector (4) shown in FIG. 2 is replaced with this. (A) is an R-shaped ridgeline portion (4b) with an R added to the ridgeline portion, and (B) is a planar ridgeline portion (4c) obtained by flattening the ridgeline portion, both of which are included in the technical scope of claim 1. It has the same effect.

  The front reflector (4) is a mountain-shaped surface that is inclined backward from the central ridge line portion (4a) toward the left and right ends, and is represented by a solid shape in the figure. However, it may be formed using a plate-like metal or resin so as to have a mountain-shaped surface.

  FIG. 6 is a diagram showing the directivity characteristics of the ultrasonic sensor (1) in the present embodiment. The horizontal plane directivity characteristics are such that the front reflector (4) is directed from the central ridge line portion (4a) toward the left and right end portions. Since the ridge line portion (4a) is provided opposite to the front surface of the ultrasonic element (2), it has interference in the horizontal plane and has side lobes. Thus, a wide characteristic in the horizontal plane direction can be obtained. On the other hand, the vertical plane direction has narrow characteristics, which makes it possible to provide an ultrasonic sensor that is less affected by obstacles (stones, steps, etc.) on the ground and that improves the detection accuracy of necessary objects such as the human body. did.

As shown in FIG. 1, the horn-type reflector (3) of the ultrasonic sensor (1) of this embodiment is formed into a perfect circle from a front view and a bowl shape from a cross-sectional view taken along the line AA. As shown in FIG. 2, 4) is formed as a mountain-shaped surface that is inclined backward from the central ridge line portion (4a) toward the left and right ends, but the horn-shaped reflector (3) is viewed from the front. When the shape is changed from a perfect circle to a horizontally long ellipse, it is possible to obtain a wider directivity characteristic in the horizontal direction. Further, by further increasing the depth of the bowl shape, it is possible to detect a distant object at a spot and to obtain unidirectionality.
Furthermore, by adjusting the angle of the chevron surface of the front reflector (4), desired directivity characteristics in the horizontal direction can be obtained, and by designing the shape, depth, angle, etc. of the two appropriately combined It was possible to obtain an excellent drip-proof ultrasonic sensor capable of easily obtaining desired directivity characteristics according to the intended use.

  FIG. 4 is a view showing a second embodiment of the present invention, in which the ridge line portion (4a) of the front reflector (4) in the cross-sectional view taken along the line AA of FIG. In the present embodiment, the ridge line portions (4a), (4b), (4c) of the front reflector (4) are formed in an arc shape so as to bulge toward the front surface of the ultrasonic element (2). The ridge line portion (4d) was configured. Thereby, in addition to the various effects in the first embodiment, the arcuate ridge line portion (4d) and the ultrasonic element (2) are configured close to each other in a state closer to a point via the fine gap (5). Therefore, it is possible to obtain a central sensitivity (S / N ratio), directivity characteristics, and reverberation characteristics that are excellent as an ultrasonic sensor.

  In addition, as shown in FIG. 5, even when a water droplet enters between the arcuate ridge line portion (4d), the ultrasonic element (2), and the front reflector (4), the water droplet moves downward along the arc. In addition to the above, it has been possible to reliably prevent deterioration of the performance of the ultrasonic sensor in a work site where it flows down naturally and is raining or where there is a puddle. Note that the directivity characteristics are the same as those in the first embodiment, and thus the description thereof is omitted.

  FIG. 7 is a diagram showing a third embodiment of the present invention. This embodiment is characterized in that the front reflector is configured as a front reflector (41) having a conical side surface that is inclined backward and circularly from the central apex (41a). In this case, the basic configuration and the effect thereof are the same as those of the first embodiment except that the shape of the front reflector is different. Therefore, the same description is omitted and only different points will be described.

  The front reflector (41) is configured to be closer to the ultrasonic element (2) in a state closer to a point through the minute gap (5) by the apex portion (41a). As a result, even if water droplets enter between the ultrasonic element (2) and the front reflector (4), the drainage performance and the effect of preventing the water droplets from being retained can be improved, and in the rain or in the water pool This makes it possible to reliably prevent the deterioration of the performance of ultrasonic sensors at certain work sites.

  Also in this embodiment, as described in paragraph 0024, even if the vertex (41a) of the front reflector (41) is rounded or flattened, it is included in the technical scope of claim 3. It has a similar effect. It should be noted that the already described FIG. (However, the sign shall not apply.)

  FIG. 8 is a diagram showing the directivity characteristics of the ultrasonic sensor (1) in the present embodiment. Since the front reflector (41) has a conical side surface, the horizontal plane and vertical plane directivity characteristics are extremely spots. Unidirectionality is less affected by obstacles (stones, steps, etc.) on the ground, and the detection accuracy of necessary objects such as the human body can be improved, and the detection of distant objects is also possible.

  As shown in FIG. 7, the horn type reflector (3) of the ultrasonic sensor (1) of the present embodiment is formed into a perfect circle from the front view and a bowl shape from the AA line sectional view, and the front reflector ( 41) has a conical side surface that is circularly inclined backward from the central apex (41a), but it is more spotted by further increasing the bowl-shaped depth of the horn-shaped reflector (3). Can also detect distant objects, and can obtain unidirectionality. Moreover, a desired spot directivity characteristic can be obtained by adjusting the angle of the conical surface of the front reflector (41), and the depth, angle, etc. of the both are appropriately combined and designed according to the intended use. It is possible to obtain an excellent drip-proof ultrasonic sensor that can easily obtain desired directivity characteristics.

  The front reflector (41) has a conical side surface that is circularly inclined backward from the central apex (41a), and is represented by a solid shape in the figure. In other words, a plate-like metal or resin may be used so as to have a conical side surface.

  FIG. 9 is a diagram showing a fourth embodiment of the present invention. A lattice plate (7) assembled in a cross beam is provided at the front opening of the horn-shaped reflector (3). Since the lattice plate (7) is configured in a lattice shape by arranging plates having widths in the front-rear direction, large raindrops and water droplets can be obtained without changing the performance and characteristics of the ultrasonic sensor (1). It cuts off and prevents direct attachment to the horn-type reflector (3), the front reflectors (4) and (41), and the ultrasonic element (2). Water droplets that have flowed to the horn-type reflector (3) side of the lattice plate (7) are discharged from a drain hole (7a) provided in the lower part. Accordingly, it is possible to prevent the performance from being deteriorated due to large raindrops adhering to the ultrasonic element (2), and in addition to the effect of the front reflector (4) according to claim 2 of Examples 1 to 4. By applying it, it was possible to maintain the performance of ultrasonic sensors against raindrops and waterdrops.

  FIG. 10 is a block diagram showing a fifth embodiment of the present invention. By analyzing the sensing signal (10a) from the ultrasonic sensor (1) and the image signal (10b) from the imaging device (10) provided separately by the analysis unit (11b) via the CPU (11a). The human body detection system is characterized in that only a human body is identified and an alarm is issued. In general, an ultrasonic sensor detects an object in a detection area corresponding to directivity. Objects are human bodies, steps, rubble, vegetation, etc. Especially when operating heavy construction equipment at construction or civil engineering work sites, it is necessary to check whether there are workers around. In construction heavy machinery with many blind spots, visual confirmation is difficult, and it is essential to install an ultrasonic sensor to ensure safety. However, as described above, it is extremely difficult to determine whether or not a detected object is a human body in a building or civil engineering work site. In the present embodiment, the information obtained from the image signal (10b) by the analysis unit (11b) is converted into the sensing signal (10a) from the ultrasonic sensor (1) and the imaging device (10) by the human body silhouette analysis algorithm. Whether or not the detected object is a human body is identified by the image signal (10b) from. Then, an alarm is given to the vehicle driver or heavy equipment operator by means of sound, light, vibration, monitor display, etc., each alone or in combination with the identified result in the alarm unit (11c). It goes without saying that the alarm may be set so as to be emitted only when it is a human body, or may be set so as to emit a different sound or light depending on the human body or an obstacle. As a result, when used as a human body detection system such as a large construction heavy machine with a lot of blind spots, it is possible to reliably detect only a human body and issue an alarm without detecting a false alarm by detecting a step or an obstacle on the ground. It has made it possible to achieve significant safety improvements.

DESCRIPTION OF SYMBOLS 1 Ultrasonic sensor main body 2 Ultrasonic element 3 Horn type reflector 4 Front reflector 4a Ridge part 4b R-shaped ridge line part 4c Planar ridge line part 4d Arc-shaped ridge line part 41 Front reflector 41a Vertex part 5 Fine gap 6 Ultrasonic wave Compression space 7 Lattice plate 7a Drain hole 10 Imaging device 10a Sensing signal 10b Video signal 11 Human body detection system 11a CPU
11b Analysis unit 11c Alarm unit

Claims (5)

  In a drip-proof ultrasonic element comprising a piezoelectric element inside a cylindrical case and hermetically sealed, and a drip-proof ultrasonic sensor comprising the ultrasonic element in the center of a horn-type reflector, A front reflector is provided on the front surface of the ultrasonic element, and the front reflector is formed of a mountain-shaped surface that is inclined backward from the central ridge line portion toward the left and right ends, and the ridge line portion of the ultrasonic element. An ultrasonic sensor characterized by being provided so as to face the front surface and having a fine gap between the ridge line portion and the front surface of the ultrasonic element.   2. The ultrasonic sensor according to claim 1, wherein the ridge line portion of the front reflector is formed in an arc shape so as to bulge toward the front surface of the ultrasonic element.   The front reflector has a conical side surface that is circularly inclined backward from a central vertex, and the vertex is provided to face the front surface of the ultrasonic element, and the vertex and the ultrasonic wave are provided. The ultrasonic sensor according to claim 1, wherein the ultrasonic sensor is provided with a fine gap between the front surface of the element.   The ultrasonic sensor according to any one of claims 1 to 3, wherein the front opening of the horn-shaped reflector is provided with a lattice plate assembled in a cross beam.   2. The apparatus according to claim 1, wherein the sensor is configured to identify only a human body and issue an alarm by analyzing a sensing signal from the ultrasonic sensor and an image signal from an imaging device provided separately. The ultrasonic sensor according to claim 4.

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