JP2015194392A - On-vehicle ultrasonic sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an on-vehicle ultrasonic sensor which has a horn structure capable of securing sufficient sensitivity for detecting the presence/absence of an obstacle existing in the periphery of a vehicle while keeping a horn dimension for achieving the sensor size that can be mounted on the vehicle and the loading condition thereof.SOLUTION: There is provided an on-vehicle ultrasonic sensor which includes an ultrasonic transducer for transmitting and receiving an ultrasonic wave with a frequency between 20 KHz and 60 KHz, and a throat part corresponding to a cut-out portion for installing the ultrasonic transducer. A horn structure is constituted as a parabolic horn including the rotary paraboloid surface shape. The open angle of the horn structure is designed so that the throat position becomes a smaller value than a focal distance of the parabolic horn when it is assumed that the position of the vibration surface of the ultrasonic transducer is installed so as to match the throat position corresponding to a distance from the position of the apex of the rotary paraboloid surface shape to the position of the throat part.

Description

  The present invention relates to an on-vehicle ultrasonic sensor that is mounted on an automobile and detects whether or not an obstacle exists around the vehicle when traveling.

  In particular, an automatic brake system that starts a collision when it is determined that a collision with a preceding vehicle is unavoidable unless braking control is performed during low-speed traveling such as traffic congestion. In such a case, the conventional automatic brake system reduces the speed by automatically performing the brake control without the driver's braking operation, avoiding the collision with the preceding vehicle or reducing the damage of the collision. Yes.

  In order to realize such an automatic brake system, it is necessary to detect an obstacle existing in an area exceeding 5 m ahead of the host vehicle, although it depends on a speed difference from the preceding vehicle. As a sensor for this purpose, a camera, a laser radar, a radio wave radar, an ultrasonic sensor, or the like is used. Among them, the ultrasonic sensor is widely applied for vehicle periphery monitoring, particularly for parking assistance system applications. Although this ultrasonic sensor has a detection distance of less than 5 m with a single sensor element, it is promising as a simple sensor that can realize high sensitivity by loading a horn structure.

However, the prior art has the following problems.
In order to increase the sensitivity of the ultrasonic sensor loaded with the horn structure, in principle, it is necessary to increase the opening diameter of the horn structure and the horn length. As a result, the sensitivity increases, but the sensor size increases. Accordingly, if an ultrasonic sensor with improved sensitivity is applied to the above-described vehicle-mounted automatic brake system as described above, the sensor size is increased and the mountability is impaired. .

  The present invention has been made to solve the above-described problem, and detects the presence or absence of an obstacle around the vehicle while keeping the horn size for achieving a vehicle-mounted sensor size. It is an object of the present invention to obtain an on-vehicle ultrasonic sensor having a horn structure capable of ensuring sufficient sensitivity and a loading condition thereof.

  An in-vehicle ultrasonic sensor according to the present invention includes an ultrasonic transducer that transmits and receives ultrasonic waves having a frequency of 20 KHz to 60 KHz, and a throat portion corresponding to an extraction portion for installing the ultrasonic transducer. Is a vehicle-mounted ultrasonic sensor comprising a horn structure for enhancing the directivity of ultrasonic radiation in each detection direction around the vehicle, and the horn structure is a parabolic including a paraboloid shape. It is configured as a horn, and it is assumed that the position of the vibration surface of the ultrasonic transducer is set to coincide with the throat position corresponding to the distance from the position of the top of the paraboloid shape to the position of the throat part. The opening angle of the horn structure is set so that the throat position at the time is smaller than the focal length of the parabolic horn. By designing, opening diameter of 80mm or less, in which the horn length is determined as satisfying the following conditions optimum shape 50 mm.

  According to this invention, the parabolic horn comprised including the rotation paraboloid shape is employ | adopted as a horn structure. By adopting such a configuration, it is possible to obtain a higher ultrasonic radiation efficiency than other horn shapes and systems, and to remove dirt components such as dust and dirt adhering to the inside of the horn due to vehicle running etc. A shape that is easy to do can be obtained. As a result, radiation efficiency can be improved and maintainability after mounting on the vehicle can also be improved.

  Furthermore, a method for determining the optimum shape of the parabolic horn applied to the ultrasonic sensor and a method for determining the optimum positional relationship between the parabolic horn and the ultrasonic transducer are defined. As a result, it has a horn structure capable of securing sufficient sensitivity to detect the presence or absence of an obstacle existing around the vehicle, while having a horn size for achieving a sensor size that can be mounted on a vehicle, and a loading condition thereof. An on-vehicle ultrasonic sensor can be obtained.

It is a schematic diagram of (a) conical horn, (b) exponential horn, and (c) parabolic horn which are horn structures conventionally loaded on an ultrasonic transducer. It is a schematic diagram which shows the operation principle of the parabolic horn in the ultrasonic sensor which concerns on Embodiment 1 of this invention. It is a schematic diagram which shows the application method of the parabolic horn in the ultrasonic sensor which concerns on Embodiment 1 of this invention. It is explanatory drawing of the shape parameter of the parabolic horn in the ultrasonic sensor which concerns on Embodiment 1 of this invention. FIG. 6 is a graph and a schematic diagram showing results of actual measurements performed to determine the opening angle of the horn that gives the maximum sensitivity in the ultrasonic sensor according to Embodiment 1 of the present invention. 4 is a graph showing an actual measurement result of a radiation pattern when an opening angle of a horn is changed in the ultrasonic sensor according to Embodiment 1 of the present invention. In the ultrasonic sensor which concerns on Embodiment 1 of this invention, it is a figure which shows the measurement result of a sensor sensitivity change at the time of changing the relative positional relationship of a horn throat position and a transducer vibration surface position on a horn pipe axis. In the ultrasonic sensor which concerns on Embodiment 1 of this invention, it is a figure for demonstrating typically the partial structure of the resin molding components for integrally forming a parabolic horn and an ultrasonic sensor case component.

  Hereinafter, a preferred embodiment of an on-vehicle ultrasonic sensor according to the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected and demonstrated about the part which is the same or it corresponds in each figure.

Embodiment 1 FIG.
First, the reason for selecting a parabolic shape (a rotationally symmetric paraboloid obtained by rotating a parabola around its axis of symmetry) as the horn structure will be described. Conventionally, the horn structure loaded on the ultrasonic sensor includes a conical horn 2 shown in FIG. 1A, an exponential horn 3 shown in FIG. 1B, and a parabolic horn 4 shown in FIG. 1C. .

  The conical horn 2 shown in FIG. 1A and the exponential horn 3 shown in FIG. 1B both have an acoustic impedance on the transducer side and an acoustic impedance on the space side in the ultrasonic wave transmitted by the ultrasonic transducer 1. It works to suppress the impedance difference that exists between the two. Accordingly, the shapes shown in FIGS. 1A and 1B are shapes that pursue the effect of suppressing reflection and loss due to impedance mismatching.

  On the other hand, in the parabolic horn 4 shown in FIG. 1C, the inner surface of the horn functions as a so-called parabolic reflector. As a result, in addition to the effect of suppressing impedance mismatching, a higher sensitivity improvement effect can be expected than the conical horn 2 and the exponential horn 3 described above. For this reason, in the first embodiment, a horn structure capable of ensuring sufficient sensitivity to realize an in-vehicle system such as an automatic brake while obtaining a horn size for achieving a sensor size that can be mounted in the vehicle is obtained. For this purpose, a parabolic horn 4 shown in FIG.

  Next, a mechanism for improving sensitivity by the parabolic horn 4 will be described. FIG. 2 is an explanatory diagram relating to a sensitivity improvement mechanism using a horn structure having a parabolic shape in the first embodiment of the present invention.

  In FIG. 2, a parabolic horn 4 is a rotationally symmetric paraboloid obtained by rotating a parabola around its axis of symmetry. When an ideal non-directional point wave source is installed at the position of the focal point F on the paraboloid, the propagation path of the ultrasonic wave emitted from the position of the focal point F is as shown in FIG. That is, a spherical wave is radiated radially from the position of the focal point F, and then reflected by the inner surface of the parabolic horn 4 to be radiated along a path parallel to the horn axis of the parabolic horn 4. As a result, a radiation pattern with enhanced directivity with respect to the horn axis direction can be obtained.

  The above-described operation of the parabolic horn 4 is the operation itself of a general parabolic antenna, and is a known technique. By loading the above-described parabolic horn 4 as the horn structure, the beam pattern of the ultrasonic transducer 1 itself, which was originally broad, is narrowed down, and high sensitivity can be realized.

  Next, a method for realizing an ultrasonic sensor with high sensitivity when the parabolic horn 4 is loaded on the ultrasonic transducer 1 will be described. FIG. 3 is an explanatory diagram relating to a configuration when the parabolic horn 4 is applied to the ultrasonic sensor according to Embodiment 1 of the present invention.

  FIG. 3A shows a state without the ultrasonic transducer 1, and FIG. 3B shows a state with the ultrasonic transducer 1. In FIG. 3A, on the apex side of the parabolic surface of the parabolic horn 4, a punching portion for installing the ultrasonic transducer 1 (hereinafter, the pulling portion is referred to as “throat portion”) is provided.

  And as shown in FIG.3 (b), the ultrasonic transducer 1 is installed in the said throat part. Specifically, the ultrasonic transducer 1 is installed so that the vibration surface 5 of the ultrasonic transducer 1 is exactly at the focal point F of the parabolic horn 4. By installing in this way, in principle, it is possible to optimize the sensitivity (maximum sensitivity) of the ultrasonic sensor loaded with the parabolic horn 4.

  Further, the shape (horn opening angle) of the parabolic horn 4 can be selected so that the position of the focal point F of the parabolic horn 4 becomes the end surface of the throat portion of the parabolic horn 4. By selecting such a shape, it is possible to prevent an unnecessary uneven structure from being generated in the internal structure of the parabolic horn 4. As a result, foreign matters such as dirt and dust attached to the inner surface of the horn can be easily removed.

Here, changing the shape of the parabolic horn 4 (opening angle of the horn) is throat diameter 2r ₀ is after determined in accordance with the outer diameter of the ultrasonic transducer 1, it is changed by adjusting the throat position x _0.

  Then, each parameter which determines the shape of the parabolic horn 4 is demonstrated below. FIG. 4 is an explanatory diagram of the shape parameters of the parabolic horn 4 applied to the ultrasonic sensor according to Embodiment 1 of the present invention. However, since the shape of the parabolic horn 4 is a rotationally symmetric shape, only the one-side cross section is shown as the shape of the parabolic horn 4 shown in FIG.

In FIG. 4, the diameter from the rotational symmetry axis of the parabolic horn 4 is r, and the height from the apex of the parabolic horn 4 at the diameter r of the parabolic horn 4 is x. Here, x is expressed by the parabolic equation of the following equation (1) using r and the focal length a.
x = (1 / 4a) r ² (1)

Further, in the throat portion of the parabolic horn 4, when the throat position is x ₀ and the radius of the throat portion is r ₀ , x ₀ is expressed by the parabolic equation of the following equation (2) using r ₀ and the focal length a. Is done.
x ₀ = (1 / 4a) r ₀ ² (2)

Here, the radius r ₀ of the throat portion is determined in accordance with the diameter of the ultrasonic transducer 1. For example, if the diameter of the ultrasonic transducer 1 is Φ = 14 mm, the clearance from the horn is secured by 1 mm on both sides. Thus, the diameter 2r _{0 of the} throat portion is set to 16 mm. Thus, if it is fixed diameter of the throat portion, the focal distance a parabolic horn 4 is indicated by the following a modification of the above formula (2) (3), uniquely determined by the throat position x _0.
a = (1 / 4x ₀ ) r ² (3)

Thus, the shape of the parabolic horn 4 to be applied to the ultrasonic sensor according to the first embodiment, determines the opening angle of the horn by the throat position x _0, horn opening diameter Φ is determined once the further horn length L. Here, the horn length L is a dimension from the throat position x ₀ of the parabolic horn 4 to the horn aperture end, the horn opening diameter Φ means horn aperture diameter at the horn aperture end.

  Next, a case where the sensitivity of the ultrasonic sensor cannot be optimized under the above-described conditions will be described. When the ultrasonic transducer 1 is installed so that the vibration surface 5 of the ultrasonic transducer 1 is just at the focal point F of the parabolic horn 4, the sensitivity of the ultrasonic sensor loaded with the parabolic horn 4 can be optimized. This has been described above with reference to FIG. However, this condition can be applied only when the shape size of the parabolic horn 4 is sufficiently larger than the wavelength order of the ultrasonic wave used.

  On the other hand, the ultrasonic frequency used in the ultrasonic sensor according to the first embodiment is an extremely low frequency (60 KHz or less) that can relatively suppress atmospheric attenuation so as to be advantageous in extending the detection distance. It is necessary to use sound waves. For this reason, the wavelength order of the ultrasonic waves to be used is about 5.77 mm at the shortest (provided that the air temperature is a standard temperature of 25 ° C. in the actual environment).

  On the other hand, the shape size of the horn has the following restrictions from the viewpoint of mounting space in an automobile. That is, the horn size allowed for the horn structure loaded on the ultrasonic sensor needs to be reduced to 80 mm or less as the horn opening diameter Φ and 50 mm or less as the horn length L.

  Therefore, as described above, the on-vehicle ultrasonic sensor is used in a region where the shape size of the parabolic horn 4 is not sufficiently large compared to the wavelength order of the ultrasonic wave to be used. . As a result, it is expected that the vibration surface 5 of the ultrasonic transducer 1 is deviated from the condition where the focal point F of the parabolic horn 4 is exactly positioned as a condition that can achieve high sensitivity of the ultrasonic sensor efficiently.

From the above, the shape of the parabolic horn 4 applied to the ultrasonic sensor in the first embodiment needs to be determined based on the experimental results. That is, the focal distance a parabolic horn 4 for realizing higher sensitivity, to determine the throat position x ₀ is important.

  Then, the actual measurement result implemented in order to determine the shape of the parabolic horn 4 applied to the ultrasonic sensor in this Embodiment 1 is demonstrated below. FIG. 5 shows the experimentally produced and measured conditions and the measurement results.

In FIG. 5, the position of the vibration surface 5 of the ultrasonic transducer 1 is set to be the throat position x ₀ of the parabolic horn 4, and the opening angle of the horn is changed by shaking the throat position x ₀ . (X ₀ = 2, 3, 4, 5 mm). Moreover, the horn length L was changed under the conditions of L = 20, 30, and 40 mm, and trial manufacture and measurement were performed. However, the ultrasonic frequency is 40 KHz (corresponding to ultrasonic wave wavelength = 8.66 mm) and the throat radius r ₀ = 8 mm (ultrasonic transducer diameter is 14 mm).

FIG. 5A shows the result of trial manufacture / measurement under the above conditions, and shows how the sensitivity in the front direction changes in accordance with changes in the throat position x ₀ and the horn length L. The actual measurement conditions are listed below.
-Load the parabolic horn 4 prototyped in each shape on the ultrasonic sensor.
-Send ultrasonic waves toward the target (Φ75mm PVC pipe) installed in front of the sensor.
-Sensor sensitivity is evaluated from the reception level of echo (reflected wave) from the target.

The horizontal axis of the graph in FIG. 5A is the throat position x ₀ (corresponding to a parameter that changes the opening angle of the horn), and the vertical axis indicates the measured value of sensor sensitivity. Here, all the measured values of sensor sensitivity are normalized values assuming that the sensor sensitivity evaluation value at the horn length L = 20 mm and the throat position x ₀ = 3 mm is 0 dB.

Further, FIG. 5 (b), according to a change in the throat position x ₀ in FIG. 5 (a), the relative positional relationship between the focus F of the vibration surface 5 and the horn of the ultrasonic transducer 1, how the changes It is the figure which showed typically what to do.

Figure 5 (b), the throat position _{x 0} is the case the focal distance a is smaller than _(x 0 <a), the opening angle of the horn is open. For this reason, the position of the focal point F of the horn is located in front of the vibration surface 5. Further, in a case where the throat position _{x 0} is coincident with the focal length _{a (x 0 = a = 4mm} ), opening angle of the horn than in the case of _x 0 <a is narrowed. The position of the focal point F of the horn is on the vibration surface 5 of the ultrasonic transducer 1. Therefore, this condition is an ideal optimum condition for the sensitivity of the ultrasonic sensor described above.

Further, the throat position x ₀ is the greater than the focal length a (x _{0> a),} the opening angle of the horn is closed. For this reason, the focal position F of the horn is located behind the vibration surface 5.

However, the focal length a at each throat position x ₀ is obtained by substituting the throat position x ₀ and the throat radius r ₀ = 8 mm (constant value) into the above equation (3).

As shown in FIG. 5A, for any horn length L, the sensitivity is maximum at x ₀ = 3 mm, and there is an optimum value for the horn opening angle (changed using x ₀ ). However, it is shown that the sensitivity decreases if the opening is too much or the closing is too much.

In addition, as described above, the sensitivity is not maximized at the ideal optimum condition x ₀ = a = 4 mm, but the sensitivity is maximized at the throat position deviating from the ideal optimum condition. I understand. As described above, this is because the shape size of the parabolic horn 4 cannot be regarded as sufficiently large as compared with the wavelength order of the ultrasonic wave to be used (ultrasonic wavelength: 8.66 mm). On the other hand, horn opening diameter Φ (maximum): 60 mm, horn length L (maximum): 40 mm).

Next, as shown in FIG. 5, the measurement result of the angular characteristics of the sensitivity of the ultrasonic sensor when the opening angle of the horn is changed (x ₀ = 2, 3, 4, 5 mm) is shown in FIG. . In FIG. 6, the angle range in which the sensor sensitivity is plotted is a range of −10 deg to +10 deg, and shows an actual measurement result under the condition of the horn length L = 20 mm.

  Both FIG. 5 and FIG. 6 are actual measurement results under a condition in which the position of the vibration surface 5 of the ultrasonic transducer 1 is fixed so as to be positioned on the throat surface of the parabolic horn 4. On the other hand, FIG. 7 shows the results of measuring the sensitivity change when the relative positional relationship between the vibration surface 5 of the ultrasonic transducer 1 and the throat surface of the parabolic horn 4 is changed on the horn tube axis.

FIG. 7A shows an actual measurement value of a change in sensor sensitivity when the positional relationship between the parabolic horn 4 and the ultrasonic transducer 1 is changed. However, it is an actual measurement value under the condition of the throat position x ₀ = 3 mm and the horn length L = 20 mm.

The horizontal axis of the graph in FIG. 7 (a), the vibration face 5 of the ultrasonic transducer 1, an amount of protrusion with respect to the throat position x _0. Specifically, the direction in which the ultrasonic transducer 1 protrudes into the horn (the opening side of the parabolic horn 4) is a positive value. The vertical axis indicates the measured value of the sensor sensitivity, and indicates a value normalized by assuming that the sensor sensitivity is 0 dB under the condition that the protruding amount on the horizontal axis is 0 (twitch).

  FIG. 7B is a diagram schematically showing the positional relationship between the parabolic horn 4 and the ultrasonic transducer 1 in actual measurement.

  As shown in FIG. 7A, it can be seen that the sensor sensitivity can be increased in a state where the amount of protrusion is a positive value and protrudes into the horn than when the amount of protrusion is 0 (twitch). This is nothing but the fact that the position of the vibration surface 5 of the ultrasonic transducer 1 approaches the position of the focal point F of the parabolic horn 4 as shown in FIG.

However, the sensor sensitivity is not the maximum value at a−x ₀ = 2.33 mm corresponding to the pop-out amount for the position of the vibration surface 5 to coincide with the focal position F of the parabolic horn 4. As described above, this is because the shape size of the parabolic horn 4 cannot be regarded as sufficiently large compared to the wavelength order of the ultrasonic wave used (for the ultrasonic wavelength: 8.66 mm, Horn opening diameter Φ (maximum): 60 mm, horn length L (maximum): 40 mm).

Thus, from the measured results shown in FIG. 7 (a), the vibration face 5 of the ultrasonic transducer 1, with respect to amount of protrusion with respect to the throat position x _0, the optimum value for maximum sensor sensitivity, the vibration surface 5 It was 1 to 2 mm instead of the pop-out amount (a−x ₀ ) required to match the position of the focal point F. In other words, it is a value of about 40% to 90% of _{a-x 0} is seen from the measured results.

  As shown in FIG. 7, the vibration surface 5 of the ultrasonic transducer 1 is offset and fixed at a position protruding into the horn, thereby obtaining the following two sensitivity improvement effects. That is, in addition to the sensitivity improvement by being brought close to the position of the focal point F, the sensitivity improvement can also be expected by contributing the ultrasonic radiation component from the side surface of the ultrasonic transducer 1 to the full extent.

  As described above, Embodiment 1 employs a parabolic horn configured to include a paraboloidal shape as a horn structure. This makes it possible to obtain a higher ultrasonic radiation efficiency than other horn shapes and methods, and to obtain a shape that can easily remove dirt components such as dust and dirt adhering to the inside of the horn due to vehicle running or the like. it can. As a result, it is possible to improve radiation performance and maintainability after mounting on a vehicle.

  Furthermore, when installing the ultrasonic transducer so that its vibration surface is positioned at the throat position of the parabolic horn, the opening angle of the horn structure is designed so that the throat position of the parabolic horn is smaller than the focal length of the parabolic horn. In order to improve sensitivity. As a result, sensitivity can be improved while the opening angle can be made wider than when the opening angle of the horn structure is designed so that the focal position matches the throat position. Thus, by determining the optimum shape of the parabolic horn, the horn length can be shortened as a result.

  Furthermore, using a parabolic horn with a wide horn angle, the position of the vibration surface of the ultrasonic transducer jumps out of the horn position of the parabolic horn to the inside of the horn (the opening side of the parabolic horn). In order to further improve the sensitivity. Specifically, by raising the position of the vibration surface of the ultrasonic transducer inside the horn by an amount corresponding to 40 to 90% of (focal length−throat position), the sensitivity can be improved even with the same horn size. It was confirmed by actual measurement that it could be realized. In this way, the optimum positional relationship between the parabolic horn and the ultrasonic transducer can be determined, and as a result, the total length of the sensor can be shortened by the amount that the ultrasonic transducer has popped out.

  Up to this point, the method for determining the optimum shape of the parabolic horn 4 applied to the ultrasonic sensor according to the first embodiment and the method for determining the optimum positional relationship between the parabolic horn 4 and the ultrasonic transducer 1 have been described. Next, a specific method for realizing the above-described ultrasonic sensor will be described.

  In the first embodiment, the structure of the parabolic horn 4 is formed by resin molding. The reason for this is that the metal material easily generates high-frequency sound, easily transmits unnecessary ultrasonic waves, and may cause erroneous sensor detection. If the parabolic horn 4 is formed of a resin material, the attenuation amount of the ultrasonic wave is large, and unnecessary ultrasonic transmission can be made difficult to occur.

  Also, by adopting a resin material, the parabolic horn 4 is integrally molded together with case parts necessary for supporting and casing other mechanical parts such as printed circuit boards and connectors necessary for constituting an ultrasonic sensor. It becomes possible to do. As a result, cost reduction can be achieved.

  FIG. 8 is a cross-sectional view for schematically explaining the structure of a resin molded part for integrally forming the parabolic horn 4 and the ultrasonic sensor case part. The structure shown in FIG. 8 is limited to the minimum structural part necessary for the description among the structural parts necessary for the ultrasonic sensor according to the first embodiment. Therefore, the structure portion for fixing and supporting the ultrasonic transducer 1 and the parabolic horn 4 is not shown.

  The parts of the parabolic horn 4 formed by resin molding are provided with a lightening structure 6 as shown in FIG. Thereby, the thickness which forms the parabolic horn 4 can be made uniform, and generation | occurrence | production of the defect at the time of shaping | molding, such as a warp and a sink, can be suppressed.

  Further, although not limited to resin molding, an R shape 7 as shown in FIG. 8 is added to the opening of the parabolic horn 4. Thereby, compared with the case where the said site | part is edge shape, the unnecessary ultrasonic scattering from the said site | part can be prevented. When unnecessary ultrasonic scattering occurs from the edge portion as described above, this leads to ultrasonic radiation and reception in an unintended direction, which causes false detection as an ultrasonic sensor.

1 Ultrasonic transducer, 2 Conical horn, 3 Exponential horn, 4 Parabolic horn, 5 Vibration surface, 6 Thinning structure, 7 Addition to horn edge, x ₀ throat position, r ₀ throat radius, a focal length, L Horn length, Φ opening diameter.

Claims (8)

An ultrasonic transducer that transmits and receives ultrasonic waves having a frequency of 20 KHz to 60 KHz;
A horn structure for improving the ultrasonic radiation directivity with respect to each detection direction around the vehicle of the ultrasonic wave transmitted and received by the ultrasonic transducer, and having a throat portion corresponding to an extraction portion for installing the ultrasonic transducer In-vehicle ultrasonic sensor equipped with
The horn structure is
It is configured as a parabolic horn including a rotating paraboloid shape,
The throat when assuming that the position of the vibration surface of the ultrasonic transducer is set to coincide with the throat position corresponding to the distance from the position of the top of the paraboloid shape to the position of the throat part By designing the opening angle of the horn structure so that the position is smaller than the focal length of the parabolic horn, it is determined as the optimum shape that satisfies the conditions that the opening diameter is 80 mm or less and the horn length is 50 mm or less. An in-vehicle ultrasonic sensor. The in-vehicle ultrasonic sensor according to claim 1,
The ultrasonic transducer is arranged so that the position of the vibration surface of the ultrasonic transducer protrudes to the opening side of the parabolic horn from the throat position of the parabolic horn determined as the optimum shape. Ultrasonic sensor. The in-vehicle ultrasonic sensor according to claim 2,
The ultrasonic transducer is disposed so that the position of the vibration surface of the ultrasonic transducer protrudes to the opening side of the parabolic horn within the range from the throat position to the focal position. . The in-vehicle ultrasonic sensor according to claim 3,
The vibration surface of the ultrasonic transducer is installed so as to protrude by 1.0 mm to 2.0 mm on the opening side with respect to the throat position. The in-vehicle ultrasonic sensor according to claim 4,
The vibration surface of the ultrasonic transducer is installed on the opening side with respect to the throat position so as to protrude by 40 to 90% of the distance from the throat position to the focal position. . The in-vehicle ultrasonic sensor according to any one of claims 1 to 5,
The parabolic horn is an in-vehicle ultrasonic sensor formed by resin molding. The in-vehicle ultrasonic sensor according to claim 6,
The parabolic horn is an on-vehicle ultrasonic sensor in which the thickness of the molded wall is uniform. The in-vehicle ultrasonic sensor according to any one of claims 1 to 7,
The parabolic horn is an in-vehicle ultrasonic sensor in which an R shape is added to the inner periphery of the opening.

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