JP7252742B2 - Ultrasonic sensor and vehicle control system - Google Patents

Description

The present invention relates to ultrasonic sensors and vehicle control systems.

Various sensors such as millimeter wave radars, infrared lasers, cameras, infrared cameras, and ultrasonic sensors are installed in automobiles to improve the safety of automobiles and automatic driving, and practical use of systems that detect and recognize obstacles around automobiles. is progressing. In particular, an ultrasonic sensor is used as a sensor for detecting an object at a close range that is applied to a parking assistance system (see Patent Document 1, for example). The ultrasonic sensor transmits highly directional ultrasonic waves, detects reflected waves from objects (obstacles), and detects objects based on the time from when the ultrasonic waves are transmitted until when the reflected waves are received. Detecting.

JP 2009-236776 A

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

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ultrasonic sensor capable of improving the appearance design of the part where the ultrasonic sensor is installed while reducing the manufacturing cost.

In order to solve the above-described 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 at one longitudinal end of the propagation path. An ultrasonic transmitter that transmits and excites the propagation path, and an ultrasonic wave that is provided at the other end in the longitudinal direction of the propagation path and propagates through the propagation path excited by the pulsed ultrasonic wave, An ultrasonic receiver for receiving a direct wave propagating only in the propagation path and a reflected wave radiated to the outside and returned to the propagation path after being reflected by an object; and both ends in the longitudinal direction of the propagation path. A convex portion provided between and projecting from the propagation path in the lateral direction of the propagation path, a time at which the direct wave was received by the ultrasonic receiver, and the reflected wave by the ultrasonic receiver and a detection unit that detects an object existing in the vicinity of the propagation path based on the difference from the time when the is received , and the convex portion detects the direct wave that has flowed into the convex portion. In the ultrasonic sensor, the direct wave is reflected in the shape portion to resonate, and the direct wave whose signal level is amplified by the resonance is radiated to the outside.

According to the present invention, a pulsed ultrasonic wave is transmitted to excite a thin plate, a time at which a direct wave propagating only through the thin plate is received among the excited ultrasonic waves propagating through the thin plate, and 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 at which the reflected wave that is radiated to the outside and returned to the thin plate after being reflected by the object is received. Ultrasonic waves emitted from the thin plate excited by pulsed ultrasonic waves have low directivity and are radiated so as to cover the entire surface of the thin plate. It is not necessary to two-dimensionally arrange a plurality of ultrasonic sensors each including a set of . Therefore, the number of ultrasonic sensors required for object detection can be reduced. As a result, it is possible to provide an ultrasonic sensor capable of suppressing damage to the appearance design of the site where the ultrasonic sensor is installed while reducing the manufacturing cost.

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 of the ultrasonic sensor shown in FIG. 1 along line AA. FIG. 3 is a diagram schematically showing the state of ultrasonic waves (direct waves) flowing into the convex portion of the first embodiment. FIG. 4 is a diagram for explaining the effect of amplifying the signal level 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 arrangement of convex portions according to a modification. FIG. 7 is a diagram showing an example of arrangement of convex portions according to a modification. FIG. 8 is a diagram showing an example of arrangement of convex portions according to a modification. FIG. 9 is a diagram showing an example of arrangement of convex portions according to a modification. FIG. 10 is a diagram showing a schematic configuration of a vehicle control system according to the second embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION 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 of the ultrasonic sensor shown in FIG. 1, taken along line AA. Note that the arrows shown in FIG. 2 schematically represent the propagation direction of the ultrasonic waves, and do not represent the strength of the signal level of the ultrasonic waves.

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. FIG. The ultrasonic receiver 2 also includes a detector 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 vehicle door, but is not limited to this. The thin plate 3 does not necessarily have to be flat, and the scale in the thickness direction (vertical direction in FIG. 2) is different from the scale in the horizontal direction (horizontal direction in FIGS. 1 and 2). Also, in FIG. 2, the upper surface of the thin plate 3 is referred to as "front surface 3a", and the lower surface thereof is referred to as "back surface 3b". Here, the "front surface 3a" refers to the surface of the thin plate 3 that is exposed to the outside, and the "back 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 3 b 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, the propagation path 31 can be formed on the front surface 3a of the thin plate 3 by applying a damping material to the front surface 3a of the thin plate 3. It is good also as a form to form.

The ultrasonic transmitter 1 is provided on one end side in the longitudinal direction of the propagation path 31 (provided without penetrating). Also, 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 through the propagation path 31 due to excitation becomes a Lamb wave (bending wave) whose vibration direction is perpendicular to the thin plate 3 . At this time, the ultrasonic waves (Lamb waves) propagating through the propagation path 31 are also radiated into the air as spatial transmission waves P2. Specifically, the spatial transmission wave P2 has a radiation angle θ determined from the 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, and the propagation path 31 (the surface 3a of the thin plate 3) is radiated into the air. When an object O (obstacle) exists near the surface of the propagation path 31, the spatial transmission wave P2 radiated into the air is reflected by the object O and returns to the thin plate 3 again.

In the following description, of the ultrasonic waves (Lamb waves) that propagate through the thin plate 3 excited by pulsed ultrasonic waves, the ultrasonic wave that propagates only through the thin plate 3 is referred to as a "direct wave P1" and is radiated to the outside. The ultrasonic wave reflected by the object O is called "reflected wave P3". The reflected wave P3 reaching the thin plate 3 excites the thin plate 3, becomes an ultrasonic wave (Lamb wave) that propagates 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". In other words, among the ultrasonic waves that propagate through the thin plate 3 excited by pulsed ultrasonic waves, the “reflected waves” that are radiated to the outside and return to the thin plate 3 after being reflected by the object O are those that are reflected by the object O. It may be the reflected wave P3 that is input to the thin plate 3 by the reflected wave P3, or it may be the reflected wave P4 that propagates through the thin plate 3 excited by the reflected wave P3.

The ultrasonic receiver 2 divides the ultrasonic wave propagating through the thin plate 3 into a direct wave P1 that propagates only through the thin plate 3 and a reflected wave P4 that is radiated to the outside and returned to the thin plate 3 after being reflected by the object O. receive. In the present embodiment, the ultrasonic receiver 2 is configured to receive the reflected wave P4, but the configuration is not limited to this, and a configuration in which the ultrasonic receiver 2 directly receives the reflected wave P3 is also possible.

Based on the difference (time difference) between the time at which the ultrasonic receiver 2 receives the direct wave P1 and the time at which the ultrasonic receiver 2 receives the reflected wave P4, the detection unit 4 detects near the thin plate 3. Detect an existing object O. 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 an object O existing in the vicinity of the thin plate 3". In the present embodiment, the ultrasonic receiver 2 and the detection unit 4 are configured integrally, but the configuration is not limited to this, and 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 spatial transmission wave P2, the more distant the object O can be detected. can. However, since the signal level of the direct wave P1 attenuates 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 amount of attenuation of the signal level of the space transmission wave P2.

Therefore, in the ultrasonic sensor of the present embodiment, in order to suppress the attenuation of the signal level of the ultrasonic waves transmitted from the ultrasonic transmitter 1, between both ends in the longitudinal direction of the propagation path 31, that is, the ultrasonic transmitter 1 and the ultrasonic receiver 2, a convex portion 32 projecting 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 waves that have flowed into the convex portion 32 . Specifically, the convex portion 32 is formed with two opposing sides 32a and 32b 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 shape of the convex portion 32 is substantially rectangular. In addition, FIG. 1 shows an example in which a pair of upper and lower convex portions 32 are provided so as to be symmetrical with respect to the longitudinal direction of the propagation path 31 . Like the propagation path 31, the convex portion 32 is formed by a non-applied area of the thin plate 3 where the damping material is not applied.

Here, the width of the convex portion 32, that is, the length between the sides 32a and 32b is an integer multiple (eg, 10 times) of the half wavelength of the ultrasonic wave transmitted by the ultrasonic transmitter 1. FIG. Also, 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. Actions and effects of the convex portion 32 will be described below.

As described above, the ultrasonic waves transmitted from the ultrasonic transmitter 1 propagate through the propagation path 31 as the direct waves P1 and are radiated into the air as the spatial transmission waves P2. At this time, part of the direct wave P1 propagating on 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 the state of the ultrasonic wave (direct wave P1) flowing into the convex portion 32. As shown in FIG.

As shown in FIG. 3 , the direct wave P1 that has entered the convex portion 32 is reflected within the convex portion 32 . Specifically, the direct wave P1 that has flowed into the convex portion 32 is repeatedly reflected (fixed end reflection) between the two opposing sides 32a and 32b of the convex portion 32. As shown in FIG. That is, between the sides 32a and 32b, the direct wave P1 reflected on one side is reflected again on the other side. The signal level of the direct wave P1 is amplified by resonating the direct wave P1 in the process of this repeated reflection. In addition, since the width of the convex portion 32 is the integral multiple of the half wavelength of the ultrasonic wave transmitted by the ultrasonic transmitter 1, the direct wave P1 whose signal level is amplified by the resonance is the original direct wave P1. are in phase without disturbing the waveform of

As a result, an 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, the ultrasonic waves radiated from the position of the convex portion 32 are radiated into the air at the position of the ultrasonic transmitter 1 because they are reflected in the convex portion 32 and have directivity in multiple directions. It is radiated in all directions in the air in the same way as 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 receiver 2, and is transmitted into the air at the radiation angle θ as the spatial transmission wave P2. be radiated.

Thus, the convex portion 32 amplifies the signal level of the space transmission wave P2 by functioning as a planar resonator. Therefore, by providing the convex portion 32 on the propagation path 31, the same effect as adding a new ultrasonic transmitter 1 to the installation position of the convex portion 32 can be obtained.

Also, the signal level of the reflected wave P4 that has been reflected by the object O and returned to the propagation path 31 is amplified in the same manner as the above-described direct wave P1 because the reflected wave P4 flows 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 reception sensitivity of the reflected wave P4 can be improved.

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

Graph G1 represented by a solid line shows the measurement result of the signal level in the ultrasonic sensor of the present embodiment, and graph G2 represented by a broken line shows the configuration in which the convex portion 32 is removed from the propagation path 31 ( Below, the measurement results of the signal level in Comparative Example) are shown. The conditions for driving the ultrasonic transmitter 1 are the same between the graphs G1 and 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) radiated from the propagation path 31 increases with the distance from the installation position of the ultrasonic transmitter 1. decreases as it goes on.

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 varies depending on the installation of the ultrasonic transmitter 1 as in the comparative example. Although the signal level decreases with distance from the position, the signal level rises 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 rises at the convex portion 32 decreases as the distance from the convex portion 32 increases while maintaining a signal level higher than that of the graph G2.

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

In addition, in the ultrasonic sensor of the present embodiment, reverberation may occur due to repeated reflection of ultrasonic waves within the convex portion 32 . The reverberation generated by repeated reflections interferes with the detection of the object O, and may reduce the detection accuracy. Therefore, in the ultrasonic sensor of the present embodiment, the detection unit 4 performs an operation (control) for excluding reverberation generated by the convex portion 32 from objects to be detected. 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. 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 (received wave).

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 P<b>1 that directly propagates through the propagation path 31 propagates toward the ultrasonic receiver 2 . Also, part of the ultrasonic waves transmitted from the ultrasonic transmitter 1 is radiated into the air as spatial transmission waves P2 while propagating through the propagation path 31 .

A portion of the direct wave P1 propagating through the propagation path 31 flows into the convex portion 32 provided on 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, so that the spatially transmitted wave P2 whose signal level is amplified is radiated into the air (see A1 in the figure). ) is done. Reverberation PR generated by resonance also propagates through the propagation path 31 .

Of the direct waves P1 propagating through the propagation path 31, the ultrasonic receiver 2 receives the direct waves P1 that have arrived without flowing into the convex portion 32 at timing T2. 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, a reflected wave P4 from the object O due to the spatial transmission wave P2 radiated into the air reaches the ultrasonic receiver 2 after the direct wave P1 and reverberation. More specifically, the speed (sound speed) of ultrasonic waves propagating in the air is slower than the speed (sound speed) of ultrasonic waves propagating through the metal propagation path 31, and the reflected wave P4 reflected by the object O The distance related to 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 by the convex portion 32 .

For example, assuming that the distance between the ultrasonic transmitter 1 and the ultrasonic receiver 2 is 800 mm and the sound velocity of the harmonic wave in the propagation path 31 is 1300 m/s, the ultrasonic wave transmitted from the ultrasonic transmitter 1 The time until the sound wave (direct wave P1) reaches the ultrasonic receiver 2, that is, the time from timing T1 to timing T2 is 800/1300=0.6 ms. Assuming that the ultrasonic transmission pulses transmitted by the ultrasonic transmitter 1 are eight pulses of 58 kHz, the time for the ultrasonic receiver 2 to receive the direct wave P1, that is, the time from timing T2 to timing T3 is , 1/(58×8)=0.14 ms. Assuming that the signal length of the reverberation PR generated in the convex portion 32, that is, the time from timing T3 to timing T4 is 0.86 ms, after the time from timing T1 to timing T4 of 1.6 ms has passed, , the reflected wave P4 from the object O will be received.

When the distance between the thin plate 3 (propagation path 31) and the object O is very small, the reflected wave P4 is generated between the timing T3 when the ultrasonic receiver 2 receives the reverberation PR and the timing T4. It may reach the ultrasonic receiver 2 . For example, when the ultrasonic transmitter 1, the object O, and the ultrasonic receiver 2 are arranged 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 is the shortest, there is a possibility that the reverberation PR and the reflected wave P4 will be received in duplicate. In such a case, since it becomes difficult to distinguish between the reverberation PR and the reflected wave P4, an erroneous detection or the like may occur.

Therefore, of the period from timing T1 to timing T4, the detection unit 4 sets at least the period from timing T3 to timing T4 related to reception of reverberation PR as an invalid period in which the reflected wave P4 is not detected. . Further, the detection unit 4 sets the period from the timing T4 to the timing T1 at which the ultrasonic wave is next transmitted from the ultrasonic transmitter 1 as an effective period for detecting the reflected wave P4. More specifically, the detection unit 4 synchronizes with the transmission timing of the ultrasonic transmitter 1 and the timing at which the ultrasonic receiver 2 receives the first direct wave P1, thereby switching between the invalid period and the valid period. A reflected wave P4 is detected. Note that the length of the invalid period for receiving the reverberation PR may be derived, for example, by actual measurement, and may be the conditions for driving the ultrasonic transmitter 1, the material and dimensions of the propagation path 31, and the convex portion 32. may be derived by a simulation taking into consideration the characteristics of the shape of the .

When the ultrasonic wave receiver 2 receives an ultrasonic wave (reverberation PR) during the invalid period, the detection unit 4 invalidates the ultrasonic wave (reverberation PR) by discarding the received timing without using it for object detection. On the other hand, during the effective period, when the ultrasonic wave receiver 2 receives the ultrasonic wave (reflected wave P4), the detection unit 4 determines the timing T2 at which the direct wave P1 was received and the timing at which this reflected wave P4 was received. An object O existing near the thin plate 3 is detected based on the difference (time difference). Here, the time difference corresponds to the time it takes for the spatial transmission wave P2 radiated into the air near the surface of the thin plate 3 to be reflected by the object O and return. Since the speed of sound of ultrasonic waves in the air is 340 m/s, by multiplying these, the round trip distance from the thin plate 3 to the object O can be calculated, and the distance from the thin plate 3 to the object O can be detected. . In other words, it means that the distance between the propagation path 31 and the object O is shorter for the reflected wave with a shorter elapsed time from the timing T2. It should be noted that the detection unit 4 detects the object O based on the reception timing of the reflected wave P4 that is received first during the effective period.

For example, when object O receives reflected wave P4 at timing T5 and object O receives reflected wave P4 at timing T7, object O receives reflected wave P4 at timing T5. located nearby. Here, the time difference between the direct wave P1 and the reflected wave P4 is the time it takes for the ultrasonic wave to travel the distance from the thin plate 3 to the object O. As shown in FIG.

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

A reflected wave P4 reflected from the object O is composed of a reflected wave P4a corresponding to the spatial transmission wave P2 radiated from the ultrasonic transmitter 1 into the air between the convex portions 32, and a reflected wave P4a corresponding to A reflected wave P4b corresponding to the spatially transmitted wave P2 radiated inside and a reflected wave P4c corresponding to the spatially transmitted wave P2 radiated into the air after passing through the convex portion 32 are roughly divided. These reflected waves P4a to P4c return to the propagation path 31 and are received by the ultrasonic receiver 2. 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 The ultrasonic receiver 2 may receive a reflected wave (synthesized reflected wave P4') obtained by synthesizing any or all of the above. More specifically, since the ultrasonic waves (spatial transmission waves P2) radiated into the air from the propagation path 31 are radiated into the air at a constant radiation angle θ, they are radiated from different positions on the propagation path 31. When the spatially transmitted wave P2 hits the object O almost simultaneously, any or all of the reflected waves P4a to P4c are combined.

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

As described above, in the present embodiment, pulsed ultrasonic waves are transmitted to excite the propagation path 31, and of the excited ultrasonic waves propagating along the propagation path 31, only the propagation path 31 is propagated. The difference between the time at which the direct wave P1 is received and the time at which the reflected wave P4, which is radiated to the outside and returned to the propagation path 31 after being reflected by the object O among the ultrasonic waves propagating in the propagation path 31, is received. , an object O existing in the vicinity of the propagation path 31 is detected.

As a result, since the ultrasonic waves can be emitted so as to cover the entire surface of the propagation path 31, a plurality of ultrasonic waves each including a set of the ultrasonic transmitter 1 and the ultrasonic receiver 2 can be provided over the entire surface of the propagation path 31. There is no need to arrange the ultrasonic sensors two-dimensionally. Therefore, the number of ultrasonic sensors required for object detection can be reduced. In addition, it is possible to improve the appearance design of the part where the ultrasonic sensor is installed while reducing the manufacturing cost. In particular, when the purpose of the ultrasonic sensor is to detect an object near a 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. Otherwise, the exterior 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 near a vehicle door (when the thin plate 3 is a vehicle door).

Further, in this embodiment, the convex portion 32 provided between the ultrasonic transmitter 1 and the ultrasonic receiver 2 allows the spatially transmitted wave P2 emitted to the outside and the reflected wave P4 reflected by the object O to be emitted to the outside. amplifies the signal level of As a result, the ultrasonic sensor of this embodiment can increase the signal levels of the spatially transmitted wave P2 and the reflected wave P4, so that the object O can be detected in a range that cannot be detected with the configuration of the comparative example. Therefore, in the ultrasonic sensor of this embodiment, it is possible to improve the ability to detect an object.

Further, the detection unit 4 detects an object O existing near the propagation path 31 by excluding reverberation components generated by resonance in the convex portion 32 from the ultrasonic waves received by the ultrasonic receiver 2. . As a result, the detection unit 4 can detect the object O based on the signal from which unnecessary noise has been removed, so that the detection accuracy of the object O can be improved.

(Modification 1)
In the above embodiment, a set of convex portions 32 are installed between the ultrasonic transmitter 1 and the ultrasonic receiver 2. However, for example, as shown in FIG. You may With the configuration of FIG. 6, the signal level of the ultrasonic wave can be amplified for each convex portion 32, so that the same effects as in the above embodiment can be obtained.

(Modification 2)
In the above-described embodiment, the convex portions 32 are provided at positions that are symmetrical with respect to the center line in the long side direction of the propagation path 31. For example, as shown in FIG. A shaped portion 32 may be provided. Even with the configuration of FIG. 7, the signal level of the ultrasonic waves propagating through the propagation path 31 can be amplified by the convex portion 32, so that the same effects as those of the above-described embodiment can be obtained.

(Modification 3)
In the above-described embodiment, the convex portion 32 has a substantially rectangular shape, but the shape is not limited to this as long as the shape can resonate ultrasonic waves within the convex portion 32 . For example, as shown in FIGS. 8 and 9, the convex portion 32 may be formed including polygons and curves. 8 and 9, the signal level of the ultrasonic wave propagating through the propagation path 31 can be amplified by the convex portion 32, so that the same effects as those of the above embodiment can be obtained.

(Modification 4)
In the above-described 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, but it is not limited to this, and may be a non-integral multiple. When the length of the width of the convex portion 32 is set to a non-integer multiple of the half wavelength, and when the length of the width of the convex portion 32 is set to an integer multiple of the half wavelength, the super-wavelength reflected within the convex portion 32 is 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 radiated into the air at an angle different from the radiation angle θ when the ultrasonic wave is an integral multiple of the half wavelength. As a result, for example, an object O existing at a position that is difficult to detect at one radiation angle can be detected by ultrasonic waves emitted at another radiation angle. Therefore, by adopting the configuration of this modified example, it is possible to expand the detection range.

(Modification 5)
In the above embodiment, the wavelength of the ultrasonic waves transmitted from the ultrasonic transmitter 1 is fixed, but it may be changed. In this case, the ultrasonic transmitter 1 periodically changes the wavelength of the ultrasonic waves to be transmitted at a predetermined constant period, so that the state of interference between the ultrasonic waves reflected within the convex portion 32 is constant. Vary in cycles. Therefore, by adopting the configuration of this modified example, the same effects as those of the fourth modified example can be obtained.

(Modification 6)
In the above embodiment, the invalid period during which the reflected wave P4 is not detected is the period from the timing T3 to the timing T4, but it is assumed to be 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 In this case as well, the object O can be detected based on the signal from which unnecessary noise (reverberation) has been removed, so the same effects as in the above embodiment can be achieved.

(Second embodiment)
Next, a second embodiment will be described. This embodiment is an embodiment of a vehicle control system that uses the ultrasonic sensor described in each of the above embodiments. A 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 this 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 CAN (Controller Area Network). However, it is not limited to this, and may be connected via a wire, for example. The ultrasonic sensor 100 can apply the ultrasonic sensor of the above-described embodiment. The ultrasonic sensor 100 includes the ultrasonic transmitter 1 described above, the ultrasonic receiver 2 described above, and the detection section 4 described above.

The vehicle control unit 110 is, for example, an ECU (Engine Control Unit), and controls the vehicle using detection results from the ultrasonic sensor 100 . In this example, the vehicle control unit 110 determines whether 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 an obstacle exists at a distance of 10 cm from the door, the vehicle control unit 110 performs control to stop the door opening operation (control to prevent the door from being opened further), and the door is opened. Avoid colliding with obstacles.

Note that the control by the vehicle control unit 110 is not limited to the above example. For example, in a configuration in which the ultrasonic sensors 100 are installed as the thin plates 3 on the exterior surfaces of the front left and right corners or the rear left and right corners of the vehicle, the vehicle control unit 110 detects the corners (thin plates 3) from the detection results of the ultrasonic sensors 100. It may be determined whether or not an obstacle (object O) exists at a distance of 10 cm from the point. Then, when it is determined that an obstacle exists at a distance of 10 cm from the corner, the vehicle control unit 110 may control traveling of the vehicle so as to avoid collision of the vehicle with the obstacle. In short, the vehicle control unit 110 may be in any form as long as it controls the vehicle using the detection result of the ultrasonic sensor 100, and the form of control can be arbitrarily changed.

Although the embodiments according to the present invention have been described above, the present invention is not limited to the above-described embodiments as they are. Also, various inventions can be formed by appropriate combinations of the plurality of constituent elements disclosed in the above-described embodiments. For example, some components may be omitted from all components shown in the embodiments.

Also, the above embodiments and modifications can be combined arbitrarily.

1 Ultrasonic transmitter 2 Ultrasonic receiver 3 Thin plate 31 Propagation path 32 Convex part 4 Detecting part 100 Ultrasonic sensor 110 Vehicle control part 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 at one end in the longitudinal direction of the propagation path and transmits pulsed ultrasonic waves to excite the propagation path;
Of the ultrasonic waves that are provided on the other end side in the longitudinal direction of the propagation path and propagate through the propagation path excited by the pulsed ultrasonic waves, a direct wave that propagates only in the propagation path and a direct wave that is radiated to the outside an ultrasonic receiver for receiving a reflected wave returning to the propagation path after being reflected by an object;
a convex portion provided between both ends in the longitudinal direction of the propagation path and protruding from the propagation path in the lateral direction of the propagation path;
Detection for detecting an object existing near 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 and
with
The convex portion reflects the direct wave that has flowed into the convex portion, causes the direct wave to resonate, and radiates the direct wave whose signal level is amplified by the resonance to the outside. sensor. 2. The ultrasonic sensor according to claim 1, wherein said convex portion has two opposite sides perpendicular to the longitudinal direction of said propagation path. 3. The ultrasonic sensor according to claim 2, wherein the length between the two sides is an integer multiple or a non-integer multiple of the half wavelength of the ultrasonic waves transmitted by the ultrasonic transmitter. 4. The ultrasonic sensor according to any one of claims 1 to 3, wherein the convex portion is provided axisymmetrically or axisymmetrically with respect to the longitudinal direction of the propagation path. 5. The detector according to any one of claims 1 to 4, wherein the detection unit invalidates the reception result of the ultrasonic receiver for a predetermined period after the direct wave is received by the ultrasonic receiver. ultrasonic sensor. 6. The ultrasonic sensor according to claim 5, wherein the detection unit invalidates the reception result of the ultrasonic receiver during the predetermined period of time during which the reverberation generated by resonance in the convex portion is received. 7. The ultrasonic sensor according to any one of claims 1 to 6, wherein the ultrasonic transmitter changes the wavelength of the ultrasonic waves in a predetermined cycle. the lamella 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 a vehicle using the detection result of the ultrasonic sensor,
vehicle control system.

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