JP2002209294A - Ultrasonic sensor, electronic unit provided with the same and vehicle rear sonar - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic sensor which narrows the half attenuation angle in the directivity characteristic of ultrasonic wave while keeping a reverbation characteristic stable. SOLUTION: The boom part of a cylindrical sensor case 4 is adopted as a diaphragm 5 and a piezoelectric vibrating element 7 is mounted at the nearly center of the inner surface of the diaphragm 5 in the ultrasonic sensor. In the sensor, a carved part whose depth in the direction at right angles to the vibrating surface of the diaphragm 5 is at least equal to or larger than the bottom thickness is formed in the outer peripheral edge of the bottom at the side part of the sensor case 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an ultrasonic sensor, an electronic device including the same, and a back sonar for a vehicle.

[0002]

2. Description of the Related Art For example, in the case of an ultrasonic sensor mounted on the rear part of a vehicle and used as a back sonar for a vehicle, the ultrasonic wave is transmitted toward the rear of the vehicle, while being reflected from an obstacle behind the vehicle and returned. While receiving the ultrasonic waves
Data obtained by electrically processing the relationship between the transmitted wave and the received wave, for example, distance information obtained based on the time lag between the transmitted wave and the received wave is used to determine the relative positional relationship of the obstacle to the rear of the vehicle. The data shown can be used for vehicle operation control.

[0003] A conventional ultrasonic sensor has a sensor case in the form of a cylinder with a bottom having a tubular portion having an opening and a bottom closing the opening of the tubular portion, and this sensor case constitutes a bottom portion. The thickness of the wall is made thinner than the thickness of the side part constituting the cylindrical part to form a diaphragm,
The piezoelectric vibrating element is bonded to a mounting surface at the substantially center of the bottom in the case.

Also, conductive lead terminals are insert-molded in each of the sensor cases, one end of each of the lead terminals is conductively connected to each of the two device electrodes of the piezoelectric vibrating element, and both of the lead terminals are connected to the sensor case. It is drawn out and connected to an external circuit.

In such an ultrasonic sensor, the piezoelectric vibrating element is mechanically vibrated by the application of an electric signal to both lead terminals, whereby the vibrating plate vibrates and the ultrasonic wave is transmitted while being reflected. The vibration plate is vibrated by the received ultrasonic waves, and the piezoelectric vibrating element is mechanically vibrated with the vibration. The vibration is converted into an electric signal and input to an external circuit.

In such an ultrasonic sensor, for example, in a case where an ultrasonic signal is set to be transmitted and received in the horizontal direction, the wider the transmittable / receivable range in the vertical direction, the larger the position where the ultrasonic signal is installed. It is easier to detect the object located at the lower position.

Note that the transmittable / receivable range is limited to an angle range in which the peak value is reduced by half with respect to the center direction of the transmission and reception of the ultrasonic signal.

In the case of a conventional ultrasonic sensor, as a specific example, the diaphragm has a diameter of 16 mm, the thickness of the side wall portion of the sensor case is 1.30 mm, and the directional characteristic in transmission and reception waves is reduced by half-width. Was 30 ° (see the directional characteristic indicated by the broken line in FIG. 6).

[0009]

In such a conventional ultrasonic sensor, for example, when an ultrasonic signal is set to be transmitted and received in a horizontal direction, a transmittable / receivable range in a vertical direction, In other words, since the half-width full-width of the directional characteristics of the transmitted and received waves is relatively wide, it is easy to detect an object existing below the installation position, and the position below the target that should be detected is lower. There is a possibility that erroneous detection may be caused by receiving a reflected signal from a signal existing in the first.

[0010] As a specific example, in a store parking lot, many of the lots of parking compartments drawn with white paint on the ground are made of concrete blocks having a height of about 10 cm above the ground. Although the car stop is provided, the transmitting / receiving range in the vertical direction has a half angle of 30 °. When parking is performed, there is a high possibility that a reflected signal from the vehicle stop is erroneously detected as a rear obstacle, and if the vehicle is stopped based on the erroneous detection, the distance between the rear portion of the vehicle and the vehicle stop may be increased. FIG. 13 illustrates the positional relationship between the vehicle M (virtual line) that has been stopped due to erroneous detection of the vehicle stop and the vehicle stop 15.

Therefore, the vehicle back sonar detects the stop and informs the driver of the stop of the vehicle, even though the vehicle must be further moved backward into the parking area for proper parking. Therefore, there is a problem that the possibility of outputting a sensor output for the vehicle increases, and it is difficult to guide the vehicle using the vehicle back sonar.

Referring to FIG. 13, if the wave transmitted from the ultrasonic sensor C and the wave received by the ultrasonic sensor C in the back sonar of the vehicle M are relatively wide in the vertical direction, the ultrasonic wave Since the signal that spreads downward among the transmission signals from the sensor C is easily reflected by the parking stop 15 or the like near the ground, when the vehicle M is parked in the parking lot while moving backward, the vehicle reaches the desired stop position. An alarm or the like for detecting an obstacle from the sonar based on the detection of the vehicle stop 15 is issued beforehand, so that the vehicle may be stopped short of the desired parking position.

In view of such demands, the applicant of the present invention has conducted various studies, and firstly, by devising the shape of the bottom diaphragm portion of the sensor case, for example, an ultrasonic sensor is used for a back sonar for a vehicle. Even when used, we first thought of simply reducing the halving angle of the directional characteristics so as not to erroneously detect a car stop, but narrowing the halving angle of the directional characteristics is important in determining the performance of an ultrasonic sensor. Reverberation characteristics become unstable, for example, a long reverberation occurs relatively long in the sensor case.

[0014] Therefore, the applicant of the present application has further studied to maintain good reverberation characteristics even when the halving angle of the directional characteristics is narrowed, and the present invention has been completed.

That is, an object of the present invention is to solve the problem of making it possible to narrow the halving angle of the directional characteristics of ultrasonic waves while maintaining the reverberation characteristics stably.

[0016]

(1) An ultrasonic sensor according to the present invention is a supersonic sensor in which a piezoelectric vibrating element is mounted substantially at the center of the inner surface of a sensor case having a bottomed cylindrical shape as a diaphragm. An acoustic wave sensor, wherein at least a digging depth in a direction orthogonal to a vibration surface of the diaphragm is equal to or smaller than a bottom wall thickness with respect to the bottom outer peripheral edge portion on a side portion of the sensor case. It is characterized in that a deeper digging is formed.

According to the ultrasonic sensor of the present invention, the depth of the digging at least in the direction perpendicular to the vibration surface of the diaphragm is equal to the bottom wall thickness at the side of the sensor case with respect to the outer peripheral edge of the bottom. By forming a deeper or deeper dig, the reverberation time becomes shorter than before and the halving angle of the directional characteristics of the transmitted and received waves becomes narrower than before, so that the desired detection target This makes it possible to transmit and receive sharply directional and relatively narrow waves in the angle range in the required direction. This eliminates the need to detect a reflected signal from an ultrasonic reflection source that should not be detected, which deviates from the detection direction, so that erroneous detection can be eliminated, and the reverberation time in the ultrasonic sensor also increases. By being able to shorten it, reverberation characteristics are stabilized and detection accuracy can be increased.

In the case of the ultrasonic sensor according to the present invention, the digging is performed relative to the digging depth in a direction orthogonal to the vibration surface of the diaphragm, and is formed in a direction along the vibration surface of the diaphragm. And set it to a predetermined depth,
The digging into the outer peripheral edge portion on the bottom side of the cylindrical portion of the sensor case is predetermined with respect to the direction along the vibrating surface of the diaphragm in relation to the digging depth in a direction orthogonal to the vibrating surface of the diaphragm. By setting the depth, the dug-up is formed in a recessed state, whereby the half-reduction angle of the directivity characteristic of the transmission and reception of the ultrasonic signal with respect to the desired detection target becomes narrow and sharp. It is possible to reduce the risk of erroneously detecting a reflected signal from a signal outside the desired detection range. Further, with this configuration, the reverberation time of the ultrasonic sensor can be shortened, and the function as the sensor can be enhanced.

In the case of the ultrasonic sensor of the present invention, the digging is performed as follows: 0.7 ≦ X ≦ 0.9 1.0 ≦ Y ≦ 3.0 Y ≦ −5X + 6.5, where X = t ₁ / A Y = t ₂ / B a: cylindrical portion thickness B: bottom wall thickness t _1: vibration digging depth in a direction along the plane of vibration of plate t _2: digging depth in the direction perpendicular to the vibration surface of the diaphragm When the ultrasonic sensor has a shape that satisfies all of the above expressions, the half angle of the directional characteristic of the transmitted / received wave in the ultrasonic sensor becomes narrower and sharper than in the past, and the reverberation time can be shortened. Therefore, it is possible to reduce the risk of erroneously detecting a reflected signal from a signal that is out of the desired detection range, and to stabilize reverberation characteristics, thereby obtaining a sensor having a high sensor function.

(2) An electronic device provided with an ultrasonic sensor according to the present invention includes an ultrasonic sensor according to any one of claims 1 to 3, and an electric signal applied to the ultrasonic sensor. An electric circuit responsive to an electric signal from the ultrasonic sensor.

According to the electronic apparatus equipped with the ultrasonic sensor of the present invention, the directivity of the ultrasonic sensor in the required direction of the transmitted and received waves becomes sharp, in other words, the half angle can be reduced and the ultrasonic wave can be reduced. Since the reverberation characteristics of the ultrasonic sensor can be stabilized by shortening the reverberation time at the sensor, the electronic device using the ultrasonic sensor can sufficiently cope with transmitting or receiving with high directivity. .

(3) A back sonar for a vehicle equipped with an ultrasonic sensor according to the present invention is mounted on a vehicle to transmit ultrasonic waves toward an obstacle behind the vehicle and to reflect ultrasonic waves from the obstacle. A back sonar for a vehicle that receives a sound wave and processes the received reflected ultrasonic wave to detect the obstacle,
The ultrasonic sensor according to claim 1, and transmitting and / or receiving ultrasonic waves related to the ultrasonic sensor by controlling input and / or output of an electric signal to the piezoelectric vibrating element. When a vehicle is stopped in a parking lot, for example, when a vehicle stops at a parking lot, a reflected ultrasonic signal from an object that may be erroneously detected, such as a bollard or a stone on the ground, receives a signal. In addition to this, there is an advantage that only the original detection target, that is, only the obstacle behind the vehicle can be detected in the back sonar, and the vehicle can be stopped satisfactorily.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below based on embodiments shown in the drawings.

(Embodiment 1) FIGS. 1 to 6 relate to an embodiment of the present invention. FIG. 1 is a longitudinal sectional view of an ultrasonic sensor according to Embodiment 1, and FIG. FIG. 3
2 is a side view of the same sensor shown in FIG. 2, FIG. 4 is a plan view of the same sensor shown in FIG. 2, FIG. 5 is a partially cutaway perspective view of the same sensor shown in FIG. 2, and FIG. It is a pattern diagram which shows the transmission / reception directional characteristic of the ultrasonic beam by the ultrasonic sensor shown.

In these figures, the ultrasonic sensor according to the first embodiment has a sensor case 4 made of aluminum having a cylindrical shape with a bottom having a tubular portion 2 having an opening and a bottom 3 closing the opening of the tubular portion 2. In the sensor case 4, the thickness of the wall constituting the bottom 3 is made thinner than the thickness of the side wall 6 as a side constituting the cylindrical portion 2, thereby forming the diaphragm 5. The piezoelectric vibrating element 7 is bonded to a substantially central mounting surface inside the bottom 3 in the sensor case 4.

The opening of the sensor case 4 is closed by a lid 8, and a pair of external terminals T, T are supported through the lid 8. A control circuit (not shown) is connected to the external terminals T and T.

Each one end of the conductive lead wires 9 is connected to each of the external terminals T. The other end of one lead 9 is directly connected to one element electrode of the piezoelectric vibrating element 7, and the other end of the other lead 9 is connected via the cylindrical portion 2 and the bottom 3 of the sensor case 4. It is connected to the other element electrode of the piezoelectric vibration element 7.

In such an ultrasonic sensor, the piezoelectric vibrating element 7 is mechanically vibrated by the application of an electric signal from the control circuit, and the vibrating plate 5 vibrates accordingly, so that ultrasonic waves are transmitted. Then, the vibration plate 5 vibrates due to the ultrasonic wave reflected and received by the object, and the piezoelectric vibration element 7 mechanically vibrates accordingly, and this vibration is converted into an electric signal and input to the control circuit. ing.

In this ultrasonic sensor, the wall thickness of the side wall 6 forming the cylindrical portion 2 in the sensor case 4 is set in a state where the cylindrical portion 2 is set in a posture along the horizontal direction as shown in FIG. By being thicker on both sides of the horizontal transmission / reception range and thinner on both sides of the vertical transmission / reception range, the cross-sectional shape of the cavity K inside the sensor case 4 is short in the horizontal direction and vertical, as shown in FIG. It has a substantially rectangular shape elongated in the direction, and a central portion in the longitudinal direction of the rectangular shape is cut out in a circular shape in a front view.

In such a sensor case 4, the transmission / reception range in the vertical direction is narrowed with respect to the outer peripheral edge of the bottom 3, that is, the outer peripheral edge of the bottom end of the cylindrical portion 2, and at the same time, the received ultrasonic waves are reduced. Digging 10 having the effect of shortening the reverberation time in the sensor case 4 due to the above. In addition, the range of the outer peripheral edge portion of the bottom 3 where the digging 10 is formed is a portion where the vertical cross-sectional shape connecting the bottom 3 and the end of the tube 2 is a corner, and a portion of the tube 3 from the portion. Including the outer peripheral portion near the opening.

As shown in FIG. 2, this dug 10
In the outer peripheral portion of the bottom portion 3 of the sensor case 4, the cylindrical portion 2 has a stepped portion which is recessed over the entire circumference at a position corresponding to the end on the bottom portion 3 side.

As shown in FIGS. 1 to 5, the digging 10 is in a direction perpendicular to the vibration surface of the diaphragm 5 of the bottom 3 (a direction parallel to the outer peripheral surface of the cylindrical portion 2), that is, in the horizontal direction. , That is, a circumferential surface concentric with the outer peripheral surface of the cylindrical portion 2, and a surface along a direction parallel to the vibration surface of the diaphragm 5 of the bottom portion 3, that is, a plane along the vertical direction in FIGS. Are formed by a cutting process, a grinding process, or the like so as to have a reentrant shape in which a circle is formed. 2 to 5,
Illustration of the lead wires 9, 9 and the external terminals T is omitted.

The digging 10 has a shape that suppresses the vertical transmission / reception range to 24 ° or less and the reverberation time to 1.2 ms or less.
When the diameter of the diaphragm is 16 mm, the following equations (1),
It has a shape that satisfies all of (2) and (3).

0.7 ≦ X ≦ 0.9 (1) 1.0 ≦ Y ≦ 3.0 (2) Y ≦ −5X + 6.5 (3) where X = t ₁ / A Y = t ₂ / B a: cylindrical portion thickness B: bottom wall thickness t _1: vertical digging depth t (in the direction along the plane of vibration of the vibrating plate) _2: the horizontal direction (direction perpendicular to the plane of vibration of the vibrating plate) In the case of the ultrasonic sensor according to the first embodiment having a shape that satisfies all of the above expressions (1), (2), and (3), as shown in FIG. It has a half-angle of the directional characteristic in transmission and reception (shown by a solid line) and has a half-angle of the directional characteristic in the transmission and reception in the horizontal direction shown by a broken line (the directional characteristic shown by the broken line is This is almost the same as the directivity characteristics of the ultrasonic sensor before the conventional research in the transmission and reception of waves at the same time).

Therefore, in the case of the ultrasonic sensor according to the first embodiment, the directional characteristic of the conventional ultrasonic sensor before and after the reverberation characteristic improvement shown in FIG. The directional characteristics in the vertical direction are sharper.

(Embodiment 2) FIGS. 7 to 10 relate to Embodiment 2 of the present invention. FIG. 7 is a perspective view of an ultrasonic sensor according to Embodiment 2, and FIG. 9 is a side view of the sensor shown in FIG. 7, and FIG. 10 is a plan view of the sensor shown in FIG. The description of the same structure as in the first embodiment is omitted, and
Assign the same reference numerals.

In the ultrasonic sensor according to the second embodiment shown in these figures, the cylindrical portion 2 of the ultrasonic sensor is arranged along the horizontal direction, and the rectangular longitudinal direction of the hollow K having a substantially rectangular cross section inside the sensor is changed. In a posture set so as to be along the vertical direction, only the upper and lower ends of the outer peripheral edge portion of the bottom portion 3 of the sensor case 4 have a concave angle on two surfaces, a plane along the horizontal direction and a plane along the vertical direction. Recesses 11, 11 are formed. However, for surfaces along the horizontal direction,
Unlike the first embodiment, it is a horizontal plane. 7 to 10, for example, FIG.
The illustration of the lead wires 9, 9 and the external terminals T provided as shown in FIG.

Similarly to the ultrasonic sensor according to the first embodiment, when the diameter of the diaphragm is 16 mm, the ultrasonic sensor according to the second embodiment has the following formulas (1), (2),
It has a shape that satisfies all of (3).

0.7 ≦ X ≦ 0.9 (1) 1.0 ≦ Y ≦ 3.0 (2) Y ≦ −5X + 6.5 (3) where X = t ₁ / A Y = t ₂ / B a: cylindrical portion thickness B: bottom wall thickness t _1: vertical digging depth t (in the direction along the plane of vibration of the vibrating plate) _2: the horizontal direction (direction perpendicular to the plane of vibration of the vibrating plate) In the case of the ultrasonic sensor according to the second embodiment having a shape satisfying the above equations (1), (2), and (3), the digging depth of FIG. Or when the posture of FIG. 10 is set, the transmission / reception range in the vertical direction is narrow,
The directional characteristics in the vertical direction are sharp, and the reverberation time is short, so that the reverberation characteristics are stable.

(Embodiment 3) Next, the first embodiment will be described.
Alternatively, an electronic device including the two ultrasonic sensors will be described.

FIG. 11 schematically shows a remote controller R as an example of an electronic apparatus. This remote control device R
An ultrasonic sensor C is provided at one end of the outer case 12, and the ultrasonic sensor C faces the vibration surface of the diaphragm outward so as to transmit an ultrasonic signal as a remote control signal. ing. An electric circuit 13 for outputting a drive signal for transmitting waves to the ultrasonic sensor C is provided, and a switch SW and the like for giving a desired remote control operation command to the electric circuit 12 by an artificial operation are provided. It is provided in the remote control device. Note that the ultrasonic sensor C is dedicated to transmitting waves.

This remote control device is capable of remote-controlling, for example, a plurality of types of electrical equipment. Even when the electrical equipment D to be operated is horizontally adjacent to the electrical equipment D to be operated, The ultrasonic sensor according to the first or second embodiment is provided so as to increase the directivity in the horizontal direction rather than the vertical direction, so that the ultrasonic signal for operation reaches only with high directivity. The operator can, for example, turn on and off only the electric device in the direction of the remote control device.

On the other hand, the ultrasonic sensor C2 for exclusive use of reception provided on the side of the electric appliance D to be operated also has the configuration according to the first or second embodiment so that the directivity of reception in the horizontal direction is sharp. Two ultrasonic sensors may be provided. In this case, since the electric device D to be operated receives only ultrasonic signals from a predetermined narrow direction in the horizontal direction, it should not receive unnecessary ultrasonic signals coming from directions other than the predetermined direction. Thus, there is an advantage that erroneous operation can be prevented.

The electronic device provided with such an ultrasonic sensor is not limited to a remote control device, and the present invention can be applied to various electronic devices.

(Embodiment 4) Next, the above-mentioned Embodiment 1
Or vehicle back sonar S equipped with two ultrasonic sensors
Will be described.

FIG. 12 shows a state in which a passenger car M as an example of a vehicle is parked while moving backward in a parking lot. An ultrasonic sensor C constituting a back sonar S for detecting an approach state of an obstacle behind the vehicle is provided on a rear bumper of the passenger car M. Controlling to output an electric signal for transmission to the piezoelectric vibrating element of the ultrasonic sensor C is performed, and an electric signal generated by receiving the reflected ultrasonic signal and vibrating the piezoelectric vibrating element is used as a detection signal. A back sonar S is configured by providing a control circuit 14 as a control unit for inputting the vehicle body. The control circuit 14 transmits an ultrasonic signal from the ultrasonic sensor C every predetermined time in order to detect an obstacle behind the passenger car M, and transmits the ultrasonic signal when the reflected ultrasonic wave from the obstacle is received. The distance between the rear of the vehicle body and the obstacle is calculated based on the elapsed time until the wave reception, and if it is determined that the rear of the vehicle body and the obstacle are approaching by a predetermined amount or more based on the calculation result, the driver is notified. The warning means is used to issue a warning.

In the ultrasonic sensor C, the directional characteristics in transmitting and / or receiving waves in the vertical direction are sharper than the directional characteristics in transmitting and / or receiving waves in the horizontal direction. The ultrasonic wave sensor C is arranged so that the radiation surface of the transmitted / received wave of the ultrasonic signal on the side where the half-height angle in the directivity characteristic is narrow is vertical.

Therefore, in this ultrasonic sensor, the directivity of the transmitted wave and / or the received wave in the vertical direction is sharp.
For example, in the case of parking while moving backward, as shown in FIG. 12, the hull 15 in the parking space is out of the range that can be detected by the signal from the ultrasonic sensor C, so that the erroneous detection of the hull 15 may be detected. By avoiding the obstacle, for example, an obstacle 16 such as a wall or another vehicle can be detected. As a result, it is possible to avoid a problem that an alarm is issued due to erroneous detection of the vehicle stop 15 and the vehicle is stopped at a position before the predetermined parking position, and the vehicle is stopped at the predetermined parking position. Can be.

The ultrasonic sensor provided in the back sonar is not limited to a single sensor capable of transmitting and receiving waves, but may be a combination of a sensor dedicated to transmitting waves and a sensor dedicated to receiving waves. You may do it.

It should be noted that the ultrasonic sensor according to the present invention is not limited to the above-described embodiment, and various applications and modifications as described below are possible, for example.

(1) As shown in FIG. 14, an indentation 10 is formed at the outer peripheral edge of the bottom 3 of the sensor case 4 so as to correspond to the direction in which the directional characteristics of transmitted and received waves are to be narrowed.
In the cross-sectional shape, the depth of the cross section where the digging in the direction perpendicular to the vibration surface of the diaphragm 5 of the bottom 3 and the digging in the direction along the vibration surface of the vibration plate 5 intersect is a curved surface. You may comprise in a shape.

(2) As shown in FIG. 15, at the outer peripheral edge of the bottom portion 3 of the sensor case 4, a digging 10 is formed corresponding to the direction in which the directional characteristics of the transmitted and received waves are to be narrowed.
In the figure, a cross-section where the digging of the bottom 3 in the direction orthogonal to the vibration surface of the diaphragm 5 and the digging in the direction along the vibration surface of the diaphragm 5 intersect with each other is shown in the figure. , May be configured to be curved so as to be further dented upward.

(3) As shown in FIG. 16, in the outer peripheral edge portion of the bottom portion 3 of the sensor case 4, a digging 10 is formed corresponding to the direction in which the directional characteristics of the transmitted and received waves are to be narrowed.
In the cross-sectional shape, the depth angle where the digging of the bottom 3 in the direction perpendicular to the vibration surface of the diaphragm 5 and the digging in the direction along the vibration surface of the diaphragm 5 intersect is defined by a step. You may comprise in a shape.

(4) As shown in FIG. 17, at the outer peripheral edge of the bottom portion 3 of the sensor case 4, a recess 10 is formed corresponding to the direction in which the directional characteristics of the transmitted and received waves are to be narrowed.
In the cross-sectional shape, a groove 17 extending in the circumferential direction on the outer peripheral surface located above the end face position of the bottom 3 by the thickness thereof.
May be formed.

(5) As shown in FIGS. 18 and 19, the cylindrical portion forming the side wall portion of the sensor case 4 and the bottom portion are formed by different members, and the outer peripheral edge portion of the bottom portion and the end portion of the cylindrical portion are formed. In the vicinity of the connection portion, a dug 10 having the same structure as that of the first embodiment may be formed. (6) In the above embodiment, when the diameter of the diaphragm is 16 mm, the one that satisfies the expression of the invention according to claim 3 of the present application has been described. However, the diameter of the diaphragm is 16 mm. The present invention is not limited to this, and it is sufficient that the digging of claim 1 or 2 is formed.

[0056]

Next, an embodiment according to the present invention will be described with reference to FIGS.

The inventor of the present invention has made an ultrasonic sensor having a diaphragm having a diameter of 16 mm, in which a digging 10 at the bottom outer peripheral edge is provided on the entire circumference as shown in FIG. A plurality of types of depth t ₂ in the direction along the side wall and depth t ₁ in the direction orthogonal to the vibration plane of the sensor diaphragm are set, and dug portions are formed by combining the various depths. The half angle of the directional characteristic in the vertical direction and the reverberation time in the transmitted and received waves were measured. The results are shown as tables and graphs in FIGS. In the drawing, A is the thickness of the side wall 6 of the cylinder portion 2 in the vertical direction in the sensor case 4, and B is the thickness of the diaphragm 5 in the wave transmission / reception direction. Therefore, t ₁ / A corresponds to X in claim 3, and t ₂ / B corresponds to Y in claim 3.

From the above, the inventor of the present invention has found that the smallest half-width of 24 degrees is 24 degrees, when X is 0.7 to 0.5.
The depth in the direction along the vibration surface of the diaphragm is set in a range up to 9, and the depth in the direction orthogonal to the vibration surface of the diaphragm in a range in which Y is from 1.0 to 4.0. I confirmed that it was a digging that set the depth. Also, when the reverberation time is within 1.24 ms that does not adversely affect the transmission and reception, X is equal to 0.1.
In the range of 7 to 0.9, when X is 0.7, Y is 3.0 or less, and when X is 0.9, Y is 3.0.
Was dug in the range of 2.0 or less. Therefore, the present inventor believes that the diameter of the diaphragm is 16 mm
In the ultrasonic sensor described above, the digging in which the directivity in the vertical direction is sharp and the reverberation characteristics are excellent has a shape that satisfies all of the following equations (1), (2), and (3). I confirmed that it was.

0.7 ≦ X ≦ 0.9 (1) 1.0 ≦ Y ≦ 3.0 (2) Y ≦ −5X + 6.5 (3) where X = t ₁ / A Y = t ₂ / B a: cylindrical portion thickness B: bottom wall thickness t _1: vertical digging depth t (in the direction along the plane of vibration of the vibrating plate) _2: the horizontal direction (direction perpendicular to the plane of vibration of the vibrating plate) Digging depth

[0060]

As described above, according to the present invention,
At the side of the sensor case, at the bottom outer peripheral edge portion, at least a digging depth in the direction orthogonal to the vibration surface of the diaphragm is equal to or greater than the bottom thickness. As a result, the reverberation time becomes shorter than before, and the half angle of the directional characteristics of the transmitted and received waves becomes narrower than in the past, so that the directivity is relatively narrow in the angle range in the required direction with respect to the desired detection target. Can be transmitted and received sharply. This eliminates the need to detect the reflected signal from the ultrasonic reflection source that should not be detected, which deviates from the detection direction, so that erroneous detection can be eliminated and the reverberation time in the ultrasonic sensor can be further reduced. Can be shortened, and the reverberation characteristics are stable,
Detection accuracy can be increased.

[Brief description of the drawings]

FIG. 1 is a longitudinal side view of an ultrasonic sensor according to Embodiment 1 of the present invention.

FIG. 2 is a front view of the ultrasonic sensor.

FIG. 3 is a side view of the ultrasonic sensor.

FIG. 4 is a plan view of the ultrasonic sensor.

FIG. 5 is a partially broken perspective view of the ultrasonic sensor.

FIG. 6 is a characteristic diagram showing a directional characteristic of the ultrasonic sensor.

FIG. 7 is a perspective view of an ultrasonic sensor according to Embodiment 2 of the present invention.

FIG. 8 is a front view of the ultrasonic sensor.

FIG. 9 is a side view of the ultrasonic sensor.

FIG. 10 is a plan view of the ultrasonic sensor.

FIG. 11 is a schematic side view showing a remote control device or the like as an example of an electronic apparatus including the ultrasonic sensor according to the invention.

FIG. 12 is a side view showing a vehicle including a back sonar according to the present invention;

FIG. 13 is a side view showing a conventional vehicle equipped with a back sonar.

FIG. 14 is a sectional view showing a main part of an ultrasonic sensor according to another embodiment.

FIG. 15 is a sectional view showing a main part of an ultrasonic sensor according to another embodiment.

FIG. 16 is a sectional view showing a main part of an ultrasonic sensor according to another embodiment.

FIG. 17 is a sectional view showing a main part of an ultrasonic sensor according to another embodiment.

FIG. 18 is a sectional view showing a main part of an ultrasonic sensor according to another embodiment.

FIG. 19 is a sectional view showing a main part of an ultrasonic sensor according to another embodiment.

FIG. 20 is a table showing the results of reverberation time for various digging dimensions.

FIG. 21 is a graph corresponding to the result of FIG.

FIG. 22 is a table showing results of half-width full-width results of directional characteristics for various digging dimensions.

FIG. 23 is a graph corresponding to the result of FIG. 22.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ultrasonic sensor 2 Tube part 3 Bottom part 4 Sensor case 5 Vibration plate 6 Side wall (side part) 7 Piezoelectric vibration element

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04R 1/02 330 G01S 7/52 A

Claims (5)

[Claims] 1. An ultrasonic sensor in which a bottom of a cylindrical sensor case having a bottom is used as a diaphragm and a piezoelectric vibrating element is mounted substantially at the center of an inner surface of the sensor case. In the outer peripheral edge portion, at least a digging depth in a direction orthogonal to the vibration surface of the diaphragm is equal to or greater than the bottom thickness, and a digging is formed. Ultrasonic sensor. 2. The ultrasonic sensor according to claim 1, wherein the digging is performed in a direction along the vibration surface of the diaphragm relative to a digging depth in a direction orthogonal to the vibration surface of the diaphragm. An ultrasonic sensor, wherein the ultrasonic sensor is set at a predetermined depth. 3. The ultrasonic sensor according to claim 1, wherein said digging has a shape satisfying all of the following expressions. 0.7 ≦ X ≦ 0.9 1.0 ≦ Y ≦ 3.0 Y ≦ −5X + 6.5 where X = t ₁ / A Y = t ₂ / B A: Thickness of cylindrical portion B: Thickness of bottom portion t _1: vibration digging depth in a direction along the plane of vibration of plate t _2: digging depth in the direction perpendicular to the vibration surface of the diaphragm 4. An ultrasonic sensor according to claim 1, further comprising: an electric circuit that applies an electric signal to the ultrasonic sensor and responds to the electric signal from the ultrasonic sensor. An electronic device comprising: 5. An apparatus mounted on a vehicle for transmitting ultrasonic waves toward an obstacle behind the vehicle, receiving reflected ultrasonic waves from the obstacle, and processing the received reflected ultrasonic waves. A back sonar for a vehicle that detects the obstacle by controlling the ultrasonic sensor according to any one of claims 1 to 3, and the input and / or output of an electric signal to the piezoelectric vibration element. Ultrasonic wave transmission and / or ultrasonic sensor
Or a control unit for controlling wave reception, comprising: a back sonar for a vehicle.