JP2020085789A - Ultrasonic wave sensor and vehicle control system - Google Patents

Abstract

To provide an ultrasonic wave sensor that can suppress spoiling of an exterior appearance design of a portion where the ultrasonic wave sensor is installed, as reducing manufacturing costs.SOLUTION: An ultrasonic wave sensor comprises: a substantially rectangular propagation path that is formed of a thin sheet; an ultrasonic wave transmitter that is provided on one end side in a longer direction of the propagation path, and transmits a pulse-like ultrasonic wave to cause the propagation path excitation; an ultrasonic wave receiver that is provided on the other end side in the longer direction of the propagation path, and, of the ultrasonic wave propagating through the propagation path excited by the pulse-like ultrasonic wave, receives a direct wave propagating through only the propagation path and a reflection wave returning to the propagation path after the ultrasonic wave radiated externally is reflected upon an object; a convex-shape part that is provided between both ends in the longer direction of the propagation path, and protrudes in a shorter direction of the propagation path from the propagation path; and a detection part that detects the object existing in the vicinity of the propagation path on the basis of a difference between a time when the direct wave is received by the ultrasonic wave receiver and a time when the reflection wave is received by the ultrasonic wave receiver.SELECTED DRAWING: Figure 1

Description

The present invention relates to an ultrasonic sensor and a vehicle control system.

Various sensors such as millimeter-wave radar, infrared laser, camera, infrared camera, and ultrasonic sensor are mounted on a vehicle to improve the safety of the vehicle and autonomous driving, and a system for detecting and recognizing obstacles around the vehicle is put to practical use. Is becoming more popular. In particular, an ultrasonic sensor is used as a sensor for detecting an object at a close range applied to a parking assistance system or the like (see, for example, Patent Document 1). With such an ultrasonic sensor, an ultrasonic wave with high directivity is transmitted, a reflected wave from an object (obstacle) is detected, and the object is detected based on the time from transmitting the ultrasonic wave to receiving the reflected wave. It is detecting.

JP, 2009-236776, A

However, the conventional ultrasonic sensor has a problem that the range in which an object can be detected is narrowed due to the use of ultrasonic waves having high directivity. For example, when detecting an object near a door of a vehicle, it is necessary to arrange a plurality of ultrasonic sensors two-dimensionally over the entire surface of the door. Therefore, the manufacturing cost is high, and the appearance design of the portion where the ultrasonic sensor is installed may be impaired.

An object of the present invention is to provide an ultrasonic sensor capable of improving the appearance design of a portion where the ultrasonic sensor is installed while reducing the manufacturing cost.

In order to solve the above-mentioned problems and achieve the object, the present invention provides a substantially rectangular propagation path formed of a thin plate and a pulsed ultrasonic wave provided on one end side in the longitudinal direction of the propagation path. An ultrasonic transmitter that transmits and excites the propagation path, and an ultrasonic wave that is provided on the other end side in the longitudinal direction of the propagation path and propagates through the propagation path excited by the pulsed ultrasonic wave, An ultrasonic receiver that receives a direct wave propagating only in the propagation path and a reflected wave that is radiated to the outside and reflected by an object and then returns to the propagation path, and both ends in the longitudinal direction of the propagation path. The convex portion provided between the propagation path and protruding in the lateral direction of the propagation path, the time when the direct wave is received by the ultrasonic receiver, and the reflected wave by the ultrasonic receiver. An ultrasonic sensor including: a detection unit configured to detect an object existing in the vicinity of the propagation path based on a difference from the time when was received.

According to the present invention, a pulsed ultrasonic wave is transmitted to excite a thin plate, and among the ultrasonic waves propagating in the excited thin plate, the time when the direct wave propagating only the thin plate is received, and the excited Among the ultrasonic waves propagating through the thin plate, an object existing in the vicinity of the thin plate is detected based on the difference from the time when the reflected wave that is emitted to the outside and reflected by the object and then returned to the thin plate is received. The ultrasonic waves emitted from the thin plate excited by the pulsed ultrasonic waves to the outside have low directivity and are radiated so as to cover the entire surface of the thin plate. It is not necessary to two-dimensionally array a plurality of ultrasonic sensors each including a set of. Therefore, the number of ultrasonic sensors required for object detection can be reduced. Accordingly, it is possible to provide an ultrasonic sensor that can reduce the manufacturing cost and can prevent the appearance design of the portion where the ultrasonic sensor is installed from being impaired.

FIG. 1 is a plan view showing a schematic configuration of the ultrasonic sensor of the first embodiment. FIG. 2 is a diagram schematically showing a cross section taken along line AA of the ultrasonic sensor shown in FIG. FIG. 3 is a diagram schematically showing a state of ultrasonic waves (direct waves) flowing into the convex portion of the first embodiment. FIG. 4 is a diagram for explaining a signal level amplification effect by the convex portion of the first embodiment. FIG. 5 is a diagram showing an example of transmission/reception timing of ultrasonic waves according to the first embodiment. FIG. 6 is a diagram showing an example of the arrangement of convex portions according to the modification. FIG. 7: is a figure which shows an example of arrangement|positioning of the convex-shaped part which concerns on a modification. FIG. 8: is a figure which shows an example of arrangement|positioning of the convex-shaped part which concerns on a modification. FIG. 9: is a figure which shows an example of arrangement|positioning of the convex-shaped part which concerns on a modification. FIG. 10 is a diagram showing a schematic configuration of the vehicle control system of the second embodiment.

Hereinafter, embodiments of an ultrasonic sensor and a vehicle control system according to the present invention will be described in detail with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is a plan view showing a schematic configuration of the ultrasonic sensor of the first embodiment. 2 is a diagram schematically showing a cross section taken along the line AA of the ultrasonic sensor shown in FIG. Note that the arrows shown in FIG. 2 schematically represent the propagation direction of ultrasonic waves, and do not represent the intensity of ultrasonic signal levels.

As shown in FIGS. 1 and 2, the ultrasonic sensor of this embodiment includes an ultrasonic transmitter 1, an ultrasonic receiver 2, and a thin plate 3. The ultrasonic receiver 2 also includes a detection unit 4.

The ultrasonic transmitter 1 transmits pulsed ultrasonic waves to excite the thin plate 3. The thin plate 3 is a metal plate having a two-dimensional spread. The thin plate 3 is, for example, an exterior surface of a vehicle such as an automobile, and is typically assumed to be a door of the vehicle, but is not limited to this. The thin plate 3 does not necessarily have to be a plane, and the scale in the thickness direction (vertical direction in FIG. 2) is different from the scale in the lateral direction (horizontal direction in FIGS. 1 and 2). Further, in FIG. 2, the upper surface of the thin plate 3 is referred to as a "front surface 3a", and the lower surface thereof is referred to as a "rear surface 3b". Here, the "front surface 3a" refers to the surface of the thin plate 3 that is exposed to the outside, and the "rear surface 3b" refers to the surface that is not exposed to the outside.

A substantially rectangular propagation path 31 is formed in the thin plate 3. The propagation path 31 is formed, for example, by applying a damping material such as resin to a region other than the propagation path 31 on the back surface 3b of the thin plate 3. Although FIG. 1 shows an example in which the propagation path 31 is formed on the back surface 3b of the thin plate 3, by applying a damping material to the front surface 3a of the thin plate 3, the propagation path 31 is formed on the front surface 3a of the thin plate 3. It may be formed.

The ultrasonic transmitter 1 is provided on one end side in the longitudinal direction of the propagation path 31 (is provided without penetrating). The ultrasonic receiver 2 is provided on the other end side in the longitudinal direction of the propagation path 31 (provided without penetrating). The ultrasonic transmitter 1 excites the propagation path 31 by transmitting pulsed ultrasonic waves toward the thin plate 3.

If the thin plate 3 is sufficiently thin, the ultrasonic wave propagating in the propagation path 31 by excitation becomes a Lamb wave (bending wave) whose vibration direction is perpendicular to the thin plate 3. At this time, the ultrasonic wave (Lamb wave) propagating through the propagation path 31 is also radiated into the air as the spatial transmission wave P2. Specifically, the spatial transmission wave P2 has a radiation angle θ determined by a relational expression (cos θ=Va/Vp) between the phase velocity Vp in the thin plate 3 (propagation path 31) and the sound velocity Va in the air. It is radiated into the air so as to cover the entire surface of 31 (the surface 3a of the thin plate 3). When an object O (obstacle) is present near the surface of the propagation path 31, the spatial transmission wave P2 radiated in the air is reflected by the object O and returns to the thin plate 3 again.

In the following description, among the ultrasonic waves (Lamb waves) propagating in the thin plate 3 excited by the pulsed ultrasonic waves, the ultrasonic wave propagating only in the thin plate 3 is referred to as “direct wave P1” and is radiated to the outside. The ultrasonic wave reflected by the object O is referred to as “reflected wave P3”. The reflected wave P3 reaching the thin plate 3 excites the thin plate 3 and becomes ultrasonic waves (Lamb waves) propagating through the thin plate 3 and spreads over the entire thin plate 3. In the following description, this ultrasonic wave (Lamb wave) is referred to as "reflected wave P4". That is, among the ultrasonic waves propagating in the thin plate 3 excited by the pulsed ultrasonic waves, the “reflected wave” that is emitted to the outside and reflected by the object O and then returns to the thin plate 3 is reflected by the object O. The reflected wave P3 input to the thin plate 3 may be the reflected wave P4 or the reflected wave P4 propagating in the thin plate 3 excited by the reflected wave P3.

Among the ultrasonic waves propagating through the thin plate 3, the ultrasonic wave receiver 2 includes a direct wave P1 propagating only in the thin plate 3 and a reflected wave P4 that is radiated to the outside and reflected by the object O and then returns to the thin plate 3. To receive. In the present embodiment, the ultrasonic receiver 2 is configured to receive the reflected wave P4, but the present invention is not limited to this, and the ultrasonic receiver 2 may directly receive the reflected wave P3.

The detection unit 4 determines the proximity of the thin plate 3 based on the difference (time difference) between the time when the direct wave P1 is received by the ultrasonic receiver 2 and the time when the reflected wave P4 is received by the ultrasonic receiver 2. The existing object O is detected. More specifically, the detection unit 4 detects the distance between the thin plate 3 and the object O existing near the thin plate 3 based on the time difference. This is included in the concept of "detecting the object O existing near the thin plate 3." In addition, in the present embodiment, the ultrasonic receiver 2 and the detection unit 4 are integrally configured, but not limited to this, the detection unit 4 may be provided independently (individually). ..

By the way, in the configuration of the ultrasonic sensor described above, the higher the signal level of the spatially transmitted wave P2, the more distant the object O can be detected, so that the range in which the object O can be detected can be expanded. it can. However, since the signal level of the direct wave P1 is attenuated as it propagates through the propagation path 31, the signal level of the spatial transmission wave P2 radiated from the propagation path 31 decreases as the distance from the ultrasonic transmitter 1 increases. Become. Therefore, in order to expand the detection range, it is required to suppress the attenuation amount of the signal level of the spatial transmission wave P2.

Therefore, in the ultrasonic sensor of the present embodiment, in order to suppress the amount of attenuation of the signal level of the ultrasonic wave transmitted from the ultrasonic transmitter 1, between the both ends in the longitudinal direction of the propagation path 31, that is, the ultrasonic transmitter 1 Between the ultrasonic wave receiver 2 and the ultrasonic receiver 2, a convex portion 32 protruding from the propagation path 31 in the lateral direction of the propagation path 31 is provided.

The convex portion 32 has a shape capable of resonating the ultrasonic wave that has flowed into the convex portion 32. Specifically, the convex portion 32 is formed with two opposing sides 32a and 32b which are perpendicular to the longitudinal direction of the propagation path 31 which is the propagation direction of the direct wave P1. FIG. 1 shows an example in which the convex portion 32 has a substantially rectangular shape. Further, FIG. 1 shows an example in which a pair of upper and lower convex portions 32 are provided so as to be line-symmetric with respect to the longitudinal direction of the propagation path 31. It should be noted that the convex portion 32 is formed by the non-application region of the thin plate 3 to which the damping material is not applied, like the propagation path 31.

Here, the width of the convex portion 32, that is, the length between the sides 32a and 32b is an integral multiple (for example, 10 times) of a half wavelength of the ultrasonic wave transmitted by the ultrasonic transmitter 1. The height of the convex portion 32, that is, the height of the sides 32a and 32b is not particularly limited, but it is preferable to set an appropriate length according to the usage environment of the ultrasonic sensor. Hereinafter, the operation and effect of the convex portion 32 will be described.

As described above, the ultrasonic wave transmitted from the ultrasonic transmitter 1 propagates in the propagation path 31 as the direct wave P1 and is radiated into the air as the spatial transmission wave P2. At this time, a part of the direct wave P1 propagating in the propagation path 31 flows into the convex portion 32 provided on the propagation path 31, as shown in FIG. Here, FIG. 3 is a diagram schematically showing a state of an ultrasonic wave (direct wave P1) flowing into the convex portion 32.

As shown in FIG. 3, the direct wave P1 that has flowed into the convex portion 32 is reflected inside the convex portion 32. Specifically, the direct wave P1 that has flowed into the convex portion 32 repeats reflection (fixed-end reflection) between the two opposite sides 32a and 32b of the convex portion 32. That is, between the sides 32a and 32b, the direct wave P1 reflected on one side is reflected again on the other side. The direct wave P1 resonates in the process of this repeated reflection, so that the signal level of the direct wave P1 is amplified. Since the width of the convex portion 32 is an integral multiple of a half wavelength of the ultrasonic wave transmitted by the ultrasonic transmitter 1, the direct wave P1 whose signal level is amplified by resonance is the original direct wave P1. It does not disturb the waveform of and has the same phase.

As a result, the ultrasonic wave whose signal level is amplified is radiated into the air from the convex portion 32 on the propagation path 31 (see FIG. 2 ). More specifically, since the ultrasonic waves emitted from the position of the convex portion 32 have directivity in multiple directions due to reflection inside the convex portion 32, they are radiated into the air at the position of the ultrasonic transmitter 1. It is emitted in all directions in the air like ultrasonic waves. In addition, the ultrasonic wave whose signal level is amplified in the convex portion 32 returns to the propagation path 31 and propagates in the direction of the ultrasonic wave receiver 2, so that the spatially transmitted wave P2 is emitted into the air at the radiation angle θ. Is emitted.

In this way, the convex portion 32 functions as a planar resonator to amplify the signal level of the spatial transmission wave P2. Therefore, by providing the convex portion 32 on the propagation path 31, the same effect as adding a new ultrasonic transmitter 1 at the installation position of the convex portion 32 can be achieved.

Further, the reflected wave P4 reflected by the object O and returned to the propagation path 31 is also amplified in signal level as in the case of the direct wave P1 by the reflected wave P4 flowing into the convex portion 32. That is, the convex portion 32 also functions as an amplifier that amplifies the signal level of the reflected wave P4. As a result, the ultrasonic receiver 2 can receive the reflected wave P4 whose signal level is amplified, so that the receiving sensitivity of the reflected wave P4 can be improved.

FIG. 4 is a diagram for explaining the signal level amplification effect by the convex portion 32. In FIG. 4, the vertical axis represents the ultrasonic signal level (mV), and the horizontal axis represents the distance (mm) from the ultrasonic transmitter 1. Here, the signal level is measured from one end side where the ultrasonic transmitter 1 is provided to the other end side where the ultrasonic receiver 2 is provided while maintaining a constant distance from the surface 3a of the thin plate 3. It is a measurement result when the device is moved.

Further, the graph G1 represented by the solid line shows the measurement result of the signal level in the ultrasonic sensor of the present embodiment, and the graph G2 represented by the broken line is the configuration in which the convex portion 32 is removed from the propagation path 31 ( The measurement results of the signal level in Comparative Example) are shown below. The conditions relating to the driving of the ultrasonic transmitter 1 are the same in the graph G1 and the graph G2.

As shown in the graph G2, in the case of the comparative example in which the convex portion 32 is not provided, the signal level of the ultrasonic wave (spatial transmission wave P2) emitted from the propagation path 31 is separated from the installation position of the ultrasonic transmitter 1. It will decrease as you do.

On the other hand, as shown in the graph G1, in the ultrasonic sensor of the present embodiment, the signal level of the ultrasonic wave (spatial transmission wave P2) radiated from the propagation path 31 is the same as in the comparative example. Although it decreases as the distance from the position increases, the signal level increases near the installation position of the convex portion 32 due to the amplification effect of the convex portion 32. Then, the signal level of the graph G1 that has risen at the convex portion 32 decreases with increasing distance from the convex portion 32 while maintaining the signal level higher than that of the graph G2.

As described above, in the ultrasonic sensor of the present embodiment, the amount of attenuation of the signal level of the spatial transmission wave P2 can be suppressed as compared with the configuration of the comparative example in which the convex portion 32 is not provided. Therefore, the ultrasonic sensor of the present embodiment can detect an object O farther away than the configuration of the comparative example, and thus the detection range and detection sensitivity of the object O can be improved.

In the ultrasonic sensor of this embodiment, reverberation may occur due to repeated reflection of ultrasonic waves within the convex portion 32. The reverberation generated by the repeated reflections interferes with the detection of the object O, which may reduce the detection accuracy. Therefore, in the ultrasonic sensor of this embodiment, the detection unit 4 performs an operation (control) for excluding the reverberation generated in the convex portion 32 from the detection target. The operation of the detection unit 4 will be described below.

FIG. 5 is a diagram showing an example of transmission/reception timing of ultrasonic waves. In FIG. 5, the ultrasonic wave (transmission pulse) transmitted by the ultrasonic transmitter 1, the ultrasonic wave (spatial transmission wave P2) radiated into the air from the propagation path 31, and the ultrasonic wave received by the ultrasonic receiver 2. The timing with (received wave) is shown.

First, the ultrasonic transmitter 1 transmits ultrasonic waves at timing T1. For example, the ultrasonic transmitter 1 transmits ultrasonic waves of 58 Khz and 8 pulses at regular intervals (transmission pulse interval B1). Of the ultrasonic waves transmitted from the ultrasonic transmitter 1, the direct wave P1 that directly propagates through the propagation path 31 propagates toward the ultrasonic receiver 2. Further, a part of the ultrasonic waves transmitted from the ultrasonic transmitter 1 is radiated into the air as a spatial transmission wave P2 while propagating through the propagation path 31.

Part of the direct wave P1 propagating in the propagation path 31 flows into the convex portion 32 provided in the propagation path 31. Then, the ultrasonic wave whose signal level is amplified by the resonance in the convex portion 32 returns to the propagation path 31 as the direct wave P1, and the spatial transmission wave P2 whose signal level is amplified is radiated into the air (see A1 in the figure). ) Will be done. The reverberation PR generated by the resonance also propagates through the propagation path 31.

The ultrasonic receiver 2 receives, at the timing T2, the direct wave P1 that has reached the convex portion 32 without flowing into the direct wave P1 propagating through the propagation path 31. Next, the ultrasonic receiver 2 receives the reverberation PR generated by the resonance of the convex portion 32 (timing T3 to timing T4).

On the other hand, the reflected wave P4 from the object O due to the spatially transmitted wave P2 radiated in the air reaches the ultrasonic receiver 2 after the direct wave P1 and the reverberation. More specifically, the velocity (sonic velocity) of the ultrasonic wave propagating in the air is slower than the velocity (sonic velocity) of the ultrasonic wave propagating in the metal propagation path 31, and the reflected wave P4 reflected by the object O is The distance related to the propagation (propagation distance) is longer than the propagation distance of the direct wave P1 that directly propagates through the propagation path 31. Therefore, the ultrasonic receiver 2 receives the reflected wave P4 from the object O after receiving the direct wave P1 and the reverberation PR generated in the convex portion 32.

For example, if the distance between the ultrasonic transmitter 1 and the ultrasonic receiver 2 is 800 mm, and the sound velocity of the harmonic in the propagation path 31 is 1300 m/s, the ultrasonic wave transmitted from the ultrasonic transmitter 1 is The time required for the sound wave (direct wave P1) to reach the ultrasonic receiver 2, that is, the time from timing T1 to timing T2 is 800/1300=0.6 ms. Further, assuming that the transmission pulse of the ultrasonic wave transmitted by the ultrasonic transmitter 1 is 8 pulses of 58 KHz, the time when the ultrasonic receiver 2 receives the direct wave P1, that is, the time from the timing T2 to the timing T3 is , 1/(58×8)=0.14 ms. Then, assuming that the signal length of the reverberation PR generated in the convex portion 32, that is, the time from the timing T3 to the timing T4 is 0.86 ms, after the time 1.6 ms from the timing T1 to the timing T4 elapses. , The reflected wave P4 from the object O is received.

When the distance between the thin plate 3 (propagation path 31) and the object O is small, the reflected wave P4 is generated between the timing T3 when the ultrasonic receiver 2 receives the reverberation PR and the timing T4. There is a possibility of reaching the ultrasonic receiver 2. For example, when the ultrasonic transmitter 1, the object O, and the ultrasonic receiver 2 are lined up on the same plane, that is, when the object O is in contact with the propagation path 31, the direct wave P1 and the reflected wave P4. Since the time difference between and is the shortest, the reverberation PR and the reflected wave P4 may be received in an overlapping manner. In such a case, it is difficult to distinguish between the reverberation PR and the reflected wave P4, which may cause erroneous detection or the like.

Therefore, the detection unit 4 sets at least the period from the timing T3 to the timing T4 related to the reception of the reverberation PR to the invalid period in which the reflected wave P4 is not detected, among the periods from the timing T1 to the timing T4 described above. .. Further, the detection unit 4 sets the period from the timing T4 to the timing T1 at which the ultrasonic wave is transmitted from the ultrasonic wave transmitter 1 next to the effective period for detecting the reflected wave P4. More specifically, the detection unit 4 synchronizes with the transmission timing of the ultrasonic transmitter 1 or the timing when the ultrasonic receiver 2 receives the first direct wave P1 to switch between the invalid period and the effective period. The reflected wave P4 is detected. Note that the length of the invalid period for receiving the reverberation PR may be derived by, for example, actual measurement, or the conditions relating to the driving of the ultrasonic transmitter 1, the material and size of the propagation path 31, and the convex portion 32. You may derive|lead-out by the simulation which considered the characteristic etc. which concern on the shape of.

When the ultrasonic receiver 2 receives an ultrasonic wave (reverberation PR) during the invalid period, the detection unit 4 invalidates the reception timing by discarding the reception timing without using it for object detection. On the other hand, in the valid period, when the ultrasonic receiver 2 receives the ultrasonic wave (reflected wave P4), the detection unit 4 sets the timing T2 when the direct wave P1 is received and the timing when the reflected wave P4 is received. The object O existing near the thin plate 3 is detected based on the difference (time difference). Here, the time difference corresponds to the time until the spatial transmission wave P2 radiated in the air near the surface of the thin plate 3 is reflected by the object O and returns. Since the speed of sound of ultrasonic waves in the air is 340 m/s, the reciprocating distance from the thin plate 3 to the object O can be calculated by multiplying these, and the distance from the thin plate 3 to the object O can be detected. .. In other words, it means that the shorter the elapsed time from the timing T2, the closer the distance between the propagation path 31 and the object O is. The detection unit 4 is assumed to detect the object O based on the reception timing of the reflected wave P4 received first in the effective period.

For example, regarding the object O when the reflected wave P4 is received at the timing T5 and the object O when the reflected wave P4 is received at the timing T7, the object O that receives the reflected wave P4 at the timing T5 is on the propagation path 31. Located near. Here, the time difference between the direct wave P1 and the reflected wave P4 is the time required for the ultrasonic wave to reciprocate the distance from the thin plate 3 to the object O.

In the configuration of the present embodiment, since the reception result is invalidated during the invalid period (substantially immediately after the timing T1 to the timing T4), the object O is detected according to the length of the invalid period. The minimum possible distance (minimum detection distance) is determined. Specifically, when the time from the timing T1 to the timing T2 when the direct wave P1 reaches the ultrasonic receiver 2 is t1, and the time from the timing T1 to the timing T4 is t2, the minimum detection distance X(m) is It can be derived from the following equation (1).
t1+(X/340)×2>t2 (1)
For example, if t1=0.6 ms and t2=1.6 ms, the minimum detection distance X can be set to about 20 cm.

The reflected wave P4 reflected from the object O is a reflected wave P4a corresponding to the spatial transmission wave P2 radiated into the air between the ultrasonic transmitter 1 and the convex portion 32, and the reflected wave P4 from the convex portion 32 to the air. It is roughly classified into a reflected wave P4b corresponding to the space transmission wave P2 radiated therein and a reflection wave P4c corresponding to the space transmission wave P2 radiated in the air after passing through the convex portion 32. These reflected waves P4a to P4c are received by the ultrasonic receiver 2 by returning to the propagation path 31, but depending on the distance between the propagation path 31 and the object O and the position of the object O, the reflected waves P4a to P4c. There may be a case where the ultrasonic wave is received by the ultrasonic wave receiver 2 as a reflected wave (synthesized reflected wave P4′) obtained by combining any or all of the above. More specifically, since the ultrasonic wave (spatial transmission wave P2) radiated into the air from the propagation path 31 is radiated into the air at a constant radiation angle θ, it is radiated from a different position on the propagation path 31. When the spatial transmission wave P2 hits the object O almost at the same time, any or all of the reflected waves P4a to P4c are combined.

In the example of FIG. 5, the reflected wave received at the timing T6 shows a combined reflected wave P4' obtained by combining the above three reflected waves P4a to P4c. Even when the synthetic reflected wave P4′ is received, the same processing as when the normal reflected wave P4 is received is performed, so that the timing T2 when the direct wave P1 is received and the synthetic reflected wave P4′ are received. The object O can be detected from the difference (time difference) from the timing T6 when P4′ is received.

As described above, in the present embodiment, pulsed ultrasonic waves are transmitted to excite the propagation path 31, and among the ultrasonic waves propagating in the excited propagation path 31, only the propagation path 31 is propagated. The difference between the time when the direct wave P1 is received and the time when the reflected wave P4 of the ultrasonic waves propagating in the propagation path 31 that is emitted to the outside and reflected by the object O and then returning to the propagation path 31 is received. Based on, the object O existing near the propagation path 31 is detected.

Thereby, since it is possible to radiate ultrasonic waves so as to cover the entire surface of the propagation path 31, a plurality of sets including the ultrasonic transmitter 1 and the ultrasonic receiver 2 are provided over the entire surface of the propagation path 31. It is not necessary to arrange the ultrasonic sensors two-dimensionally. Therefore, the number of ultrasonic sensors required for object detection can be reduced. Further, it is possible to improve the appearance design of the portion where the ultrasonic sensor is installed while reducing the manufacturing cost. Particularly, when the ultrasonic sensor is intended to detect an object near the vehicle door (in short, when the thin plate 3 is the vehicle door), the ultrasonic sensor is exposed from the surface of the vehicle door. If so, the external design of the vehicle will be greatly impaired. Therefore, the ultrasonic sensor of the present embodiment described above is particularly effective when used for the purpose of detecting an object in the vicinity of a vehicle door (when the thin plate 3 is a vehicle door).

In addition, in the present embodiment, the convex portion 32 provided between the ultrasonic transmitter 1 and the ultrasonic receiver 2 causes the spatial transmitted wave P2 radiated to the outside or the reflected wave P4 reflected by the object O. Amplifies the signal level of. As a result, the ultrasonic sensor of the present embodiment can raise the signal levels of the spatially transmitted wave P2 and the reflected wave P4, and thus can detect the object O existing in a range that cannot be detected by the configuration of the comparative example. Therefore, the ultrasonic sensor of the present embodiment can improve the ability to detect an object.

Further, the detection unit 4 excludes the reverberation component generated by the resonance in the convex portion 32 from the ultrasonic waves received by the ultrasonic receiver 2, and detects the object O existing near the propagation path 31. .. Accordingly, the detection unit 4 can detect the object O based on the signal from which unnecessary noise is removed, and thus the detection accuracy of the object O can be improved.

(Modification 1)
In the above-described embodiment, a set of convex portions 32 is installed between the ultrasonic transmitter 1 and the ultrasonic receiver 2, but, for example, as shown in FIG. 6, a plurality of sets of convex portions 32 are installed. You may. In the case of the configuration of FIG. 6, since the signal level of the ultrasonic wave can be amplified for each convex portion 32, the same effect as that of the above-described embodiment can be obtained.

(Modification 2)
In the above-described embodiment, the convex portion 32 is provided at a position that is line-symmetric with respect to the center line of the propagation path 31 in the long side direction. However, for example, as shown in FIG. The profile 32 may be installed. Even with the configuration of FIG. 7, since the signal level of the ultrasonic wave propagating through the propagation path 31 can be amplified by the convex portion 32, the same effect as that of the above-described embodiment can be obtained.

(Modification 3)
In the above embodiment, the convex portion 32 has a substantially rectangular shape, but the shape is not limited to this as long as the ultrasonic wave can resonate in the convex portion 32. For example, as shown in FIGS. 8 and 9, the convex portion 32 may be formed to include a polygon or a curve. Even with the configurations of FIGS. 8 and 9, since the signal level of the ultrasonic wave propagating through the propagation path 31 can be amplified by the convex portion 32, the same effect as that of the above-described embodiment can be obtained.

(Modification 4)
In the above-mentioned embodiment, the length of the width of the convex portion 32 is an integral multiple of the half wavelength of the ultrasonic wave transmitted by the ultrasonic transmitter 1. When the width of the convex portion 32 is set to a non-integer multiple of half wavelength, and when the width of the convex portion 32 is set to an integral multiple of half wavelength, it means that the reflection within the convex portion 32 is excessive. The state of interference between sound waves is different. Therefore, the ultrasonic wave whose signal level is amplified by the convex portion 32 can be emitted into the air at an angle different from the emission angle θ when the integral multiple of the half wavelength is used. Thereby, for example, the object O existing at a position that is difficult to detect at one emission angle can be detected by the ultrasonic waves emitted at another emission angle. Therefore, the detection range can be expanded by adopting the configuration of this modification.

(Modification 5)
In the above embodiment, the wavelength of the ultrasonic wave transmitted from the ultrasonic transmitter 1 is set to a fixed value, but it may be changed. In this case, the ultrasonic transmitter 1 periodically changes the wavelength of the ultrasonic waves to be transmitted in a predetermined constant cycle, thereby keeping the interference state between the ultrasonic waves reflected in the convex portion 32 constant. Change in a cycle. Therefore, by adopting the configuration of this modification, it is possible to obtain the same effects as those of modification 4.

(Modification 6)
In the above embodiment, the invalid period in which the reflected wave P4 is not detected is the period from the timing T3 to the timing T4, but is the period from the timing T2 to the timing T4 or the period immediately after the timing T1 to the timing T4. It may be in the form. Even in this case, since the object O can be detected based on the signal from which unnecessary noise (reverberation) is removed, the same effect as that of the above embodiment can be obtained.

(Second embodiment)
Next, a second embodiment will be described. The present embodiment is an embodiment of a vehicle control system using the ultrasonic sensor described in each of the above embodiments. The vehicle control system is a control system mounted on a vehicle. FIG. 10 is a diagram showing an example of a schematic configuration of the vehicle control system of the present embodiment. As shown in FIG. 10, the vehicle control system includes an ultrasonic sensor 100 and a vehicle control unit 110, which are connected via an in-vehicle network such as a CAN (Controller Area Network). However, the present invention is not limited to this, and may be, for example, a form of connection via a wire. The ultrasonic sensor 100 may be the ultrasonic sensor of the above-described embodiment. The ultrasonic sensor 100 includes the above ultrasonic transmitter 1, the above ultrasonic receiver 2, and the above detection unit 4.

The vehicle control unit 110 is, for example, an ECU (Engine Control Unit), and controls the vehicle using the detection result of the ultrasonic sensor 100. In this example, the vehicle control unit 110 determines whether or not an obstacle (object O) exists at a distance of 10 cm from the door based on the detection result of the ultrasonic sensor 100. When it is determined that there is an obstacle at a distance of 10 cm from the door, the vehicle control unit 110 performs control to stop the opening operation of the door (control to prevent the door from being released any more), and the door is released. Avoid hitting obstacles.

The control by the vehicle control unit 110 is not limited to the above example. For example, in a mode in which the ultrasonic sensors 100 are installed using the exterior surfaces of the front left and right corners or the rear left and right corners as the thin plates 3, the vehicle control unit 110 determines the corners (thin plates 3) based on the detection results of the ultrasonic sensors 100. Alternatively, it may be possible to determine whether or not an obstacle (object O) exists at a distance of 10 cm from. Then, when it is determined that the obstacle exists at a distance of 10 cm from the corner, the vehicle control unit 110 may control the traveling of the vehicle so as to prevent the vehicle from colliding with the obstacle. In short, the vehicle control unit 110 has only to be in the form of controlling the vehicle using the detection result of the ultrasonic sensor 100, and the form of the control can be arbitrarily changed.

Although the embodiment according to the present invention has been described above, the present invention is not limited to the above-described embodiment as it is, and constituent elements can be modified and embodied at the stage of implementation without departing from the scope of the invention. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above-described embodiments. For example, some components may be deleted from all the components shown in the embodiment.

Further, the above-described respective embodiments and modified examples can be arbitrarily combined.

1 Ultrasonic Transmitter 2 Ultrasonic Receiver 3 Thin Plate 31 Propagation Path 32 Convex Section 4 Detecting Section 100 Ultrasonic Sensor 110 Vehicle Control Section P1 Direct Wave P2 Spatial Transmission Wave P3 Reflected Wave P4 Reflected Wave

Claims (9)

A substantially rectangular propagation path formed of a thin plate,
An ultrasonic transmitter that is provided on one end side in the longitudinal direction of the propagation path and transmits pulsed ultrasonic waves to excite the propagation path,
Provided on the other end side in the longitudinal direction of the propagation path, among the ultrasonic waves propagating in the propagation path excited by the pulsed ultrasonic waves, a direct wave propagating only in the propagation path and radiated to the outside. An ultrasonic receiver that receives a reflected wave that returns to the propagation path after being reflected by an object,
Provided between both ends in the longitudinal direction of the propagation path, a convex portion protruding from the propagation path in the lateral direction of the propagation path,
Detection for detecting an object existing in the vicinity of the propagation path based on the difference between the time when the direct wave is received by the ultrasonic receiver and the time when the reflected wave is received by the ultrasonic receiver Department,
An ultrasonic sensor including. The ultrasonic sensor according to claim 1, wherein the convex portion has two opposite sides that are perpendicular to a longitudinal direction of the propagation path. The ultrasonic sensor according to claim 2, wherein the length between the two sides is an integer multiple or a non-integer multiple of a half wavelength of an ultrasonic wave transmitted by the ultrasonic transmitter. The ultrasonic sensor according to any one of claims 1 to 3, wherein the convex portion is provided in line symmetry or non-line symmetry with respect to a longitudinal direction of the propagation path. The said detection part invalidates the reception result of the said ultrasonic receiver for a predetermined period, after the said direct wave is received by the said ultrasonic receiver, The any one of the Claims 1 thru|or 4 characterized by the above-mentioned. Ultrasonic sensor. The ultrasonic sensor according to claim 5, wherein the detection unit invalidates the reception result of the ultrasonic receiver during the predetermined period in which the reverberation generated by the resonance in the convex portion is received. The ultrasonic sensor according to claim 1, wherein the ultrasonic transmitter changes the wavelength of the ultrasonic wave in a predetermined cycle. The thin plate is a vehicle door,
The ultrasonic sensor according to any one of claims 1 to 7. The ultrasonic sensor according to any one of claims 1 to 8,
A vehicle control unit that controls the vehicle by using the detection result of the ultrasonic sensor;
Vehicle control system.

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