JP2001016694A - Ultrasonic wave sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a ultrasonic wave sensor where the directivity, that is, a radiation spread angle can be made narrow in spite of a simple configuration. SOLUTION: The ultrasonic wave sensor is provided with a cylinder section (support cylinder section) 22 of a cylindrical case 2 whose bottom 21 is formed in a diaphragm and on which an ultrasonic wave vibrator 1 is fixed and with an interposition member 4 that is placed between an outer frame 3 and the case 2 to absorb vibration energy. The interposition member 4 has a groove 42 that is close to a circumferential edge of the diaphragm 21 and not closely adhered to the support cylinder 2 of the cylindrical case 2. The groove 42 of this interposition member 4 may be provided over the entire circumference or provided over a prescribed angular range in the circumferential direction. In the case of providing the groove 42 of the interposition member 4 over the entire circumference of the diaphragm 21, the directivity of an ultrasonic wave energy emitted from the sensor, that is, a radiation spread angle can be made narrow, and in the case of providing the groove 42 of the interposition member 4 over a prescribed angular range in the circumferential direction of the diaphragm 21, the directivity of the ultrasonic wave energy emitted from the sensor, that is, the radiation spread angle can be made narrow at a side at which the groove 42 is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic sensor, and more particularly, to an ultrasonic sensor applicable to an obstacle detecting sensor for a vehicle.

[0002]

2. Description of the Related Art In a conventional vehicle obstacle detecting device, ultrasonic waves are transmitted from a vehicle rear or a corner by an ultrasonic sensor provided on a vehicle bumper, and ultrasonic waves reflected by an obstacle are received to prevent the obstacle. They try to detect things.

FIG. 1 shows an example of an ultrasonic sensor used as a conventional vehicle obstacle detecting device.

[0004] 1 is an ultrasonic vibrator in which electrodes are provided on both main surfaces of a porcelain piezoelectric plate made of PZT or the like, 2 is a cylindrical case to which the ultrasonic vibrator 1 is fixed, 3 is a flanged cylinder An outer frame 40 having a shape is an interposed member provided between the outer frame 3 and the cylindrical case 2, and the outer frame 3 is fitted into a hole of a bumper (not shown).

[0005] The cylindrical case 2 is formed of a metal can having a bottomed cylindrical shape, and the bottom portion 21 of the cylindrical case 2 emits ultrasonic waves as a diaphragm to detect reflected waves. The ultrasonic vibrator 1 is fixed to the bottom portion of the cylindrical case 2, that is, the center on the back side of the vibration plate 21, and an AC voltage is applied between both electrodes of the ultrasonic vibrator 1 to vibrate the vibration plate 21.

The tubular portion of the tubular case 2 (also called a support tubular portion)
Reference numeral 22 is supported by the outer frame 3 via an interposed member 40 made of a rubber body for vibration suppression having a cylindrical shape with both ends open. That is, the diaphragm 21 vibrates with the periphery of the diaphragm 21 adjacent to the tubular portion (supporting tubular portion) 22 as a node and the center of the diaphragm 21 in the radial direction as an antinode.
Vibration of the diaphragm 21 is prevented from being transmitted to the external bumper through the outer frame 3.

[0007]

In the above ultrasonic sensor, if the directional characteristic in the vertical direction, that is, the radiation spread angle is wide, there is a problem that the reflected wave due to the unevenness of the road surface erroneously detects the reflected wave from the obstacle. In particular, it was necessary to narrow the directional characteristics toward the lower side, that is, the radiation spread angle.
The directional characteristics, that is, the radiation spread angle, can be narrowed by increasing the frequency, but the frequency selection is not free in view of other conditions, and the directional characteristics, that is, the radiation spread angle, can be narrowed without changing the frequency. There was a request to do so.

The present invention has been made in view of the above problems, and has as its object to provide an ultrasonic sensor capable of narrowing the directional characteristics, that is, the radiation spread angle, with a simple configuration.

Further, in the above-described ultrasonic sensor used as the conventional vehicle obstacle detecting device, the axial direction (vibration direction)
On the other hand, it is important to set the directional characteristics in the left, right, up and down directions, that is, the radiation spread angle. In particular, in order to reduce the reflected wave due to the unevenness of the road surface, it has been desired to reduce the downward directivity characteristics, that is, the radiation spread angle.

In order to solve this problem, the axial direction (vibration direction) may be turned upward by a necessary angle from the horizontal direction. However, in this case, the ultrasonic sensor forms an ultrasonic radiation surface. There is a problem that the diaphragm 21 protrudes outward from the outer surface of the bumper 1 or is depressed to the rear side, thereby deteriorating the aesthetic appearance.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has a simple configuration and a directional characteristic, that is, a radiation spread angle in an axial direction (vibration direction) orthogonal to a main surface of a diaphragm, which is predetermined in a circumferential direction of the diaphragm. It is an object of the present invention to provide an ultrasonic sensor that can be selectively narrowed only at a site.

[0012]

According to the first aspect of the present invention, there is provided an ultrasonic sensor, wherein a bottom portion of the cylindrical case has a diaphragm and an ultrasonic vibrator is fixed. The outer peripheral surface of ()) is supported on the inner peripheral surface of the supporting outer frame through an intervening member having a vibration energy absorbing function. In this configuration, particularly, the interposed member has a groove that is close to the peripheral edge of the diaphragm and does not adhere to the supporting cylinder of the tubular case.
The groove of the interposed member may be provided over the entire circumference of the diaphragm, or may be provided only in a predetermined angular range in the circumferential direction.

According to experiments, it has been found that when the groove of the interposed member is provided over the entire circumference of the diaphragm, the directivity characteristic of the ultrasonic energy radiated from the sensor, that is, the radiation spread angle can be reduced.

According to a second aspect of the present invention, in the ultrasonic sensor according to the first aspect, the groove portion is provided only at a portion close to a portion of the peripheral edge of the diaphragm within a predetermined angle range.
According to an experiment, it was found that this configuration can reduce the directional characteristic toward the side having the groove, that is, the radiation spread angle.

According to a third aspect of the present invention, in the ultrasonic sensor according to the second aspect, the ultrasonic sensor is used as an obstacle sensor for a vehicle, and the groove of the interposition member is
It is arranged adjacent to the lower part of the support cylinder part adjacent to the lower edge of the diaphragm.

According to a fourth aspect of the present invention, there is provided an ultrasonic sensor, wherein the bottom portion forms a diaphragm and the ultrasonic vibrator is fixed thereto. The portion of the interposed member interposed between the frame and the portion that is in close contact with the peripheral edge of the diaphragm and that is in close contact with the support cylindrical portion is a low restraint region that restrains the support cylindrical portion more weakly than other portions. It is characterized by. The low constraint region may be provided over the entire circumference of the diaphragm, or may be provided over a predetermined angle.

According to experiments, when the low restraint region of the interposed member is provided over the entire circumference of the diaphragm, the directivity characteristic of the ultrasonic energy radiated from the sensor, that is, the radiation spread angle can be reduced. When the low restraint area of the interposed member is provided only within a predetermined angular range in the circumferential direction of the diaphragm, the directional characteristic of the ultrasonic energy radiated from the sensor, that is, the radiation spread angle may be reduced on the side where the low restraint area is provided. I knew I could do it.

According to a fifth aspect of the present invention, in the ultrasonic sensor according to the fourth aspect, the ultrasonic sensor is further used as an obstacle sensor for a vehicle, and the low restraining region of the interposition member is provided with a diaphragm of the diaphragm. It is arrange | positioned adjacent to the lower part of the support cylinder part adjacent to a lower edge part.

[0019]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention.

One embodiment of the ultrasonic sensor of the present invention used as a sensor unit of a vehicle obstacle detection device will be described below with reference to a schematic longitudinal sectional view shown in FIG.

Reference numeral 1 denotes an ultrasonic vibrator in which electrodes are provided on both main surfaces of a porcelain piezoelectric plate made of PZT or the like, 2 denotes a cylindrical case to which the ultrasonic vibrator 1 is fixed, and 3 denotes a flanged cylinder. The outer frame 4 having the shape is an interposed member provided between the outer frame 3 and the cylindrical case 2, and the cylindrical portion 30 of the outer frame 3 is fitted into a hole of a bumper (not shown).

The cylindrical case 2 is formed of a bottomed cylindrical metal can, and the bottom portion 21 of the cylindrical case 2 emits ultrasonic waves as a diaphragm and detects reflected waves. The ultrasonic vibrator 1 is fixed to the bottom portion of the cylindrical case 2, that is, the center on the back side of the vibration plate 21, and an AC voltage is applied between both electrodes of the ultrasonic vibrator 1 to vibrate the vibration plate 21.

The cylindrical portion of the cylindrical case 2 (also referred to as a support cylindrical portion)
Reference numeral 22 is supported by the outer frame 3 via an intervening member 4 made of a rubber body for vibration suppression having a cylindrical shape with both ends open.
In other words, the diaphragm 21 has its tubular portion (supporting tubular portion) 2
The vibrating plate 21 vibrates around the radial center of the vibrating plate 21 as a node, and the vibration of the vibrating plate 21 derives the vibration of the supporting cylindrical portion 22 of the cylindrical case 2. The vibration of the portion 22 is caused by the interposition member 4 and the cylindrical portion 3 of the outer frame 3.
0 to an external bumper (not shown).

The interposed member 4 which is a feature of this embodiment is
Supporting cylindrical portion 22 of cylindrical case 2 and cylindrical portion 3 of outer frame 3
0 is formed in a cylindrical shape having a constant thickness in accordance with a cylindrical gap between the support member 4 and the inner peripheral surface of the support tubular portion 22. Is in close contact with the inner peripheral surface of the outer frame 3. As a result, even if the vibration plate 21 of the cylindrical case 2 vibrates due to the bending vibration of the ultrasonic vibrator 1, thereby causing the supporting cylindrical portion 22 of the cylindrical case 2 to vibrate accordingly, the vibration of the supporting cylindrical portion 22 will not occur. Energy is attenuated by the interposition member 4 and vibration of the cylindrical portion of the outer frame 3 is suppressed. It is conventional that the ultrasonic transducer 1 is formed in a rectangular shape so that the directional characteristics of the diaphragm 21 in the vibration direction are wide in the horizontal direction and narrow in the vertical direction. The bottom surface of the cylindrical case 2, that is, the main surface 211 outside the diaphragm 21, the end surface 41 outside the interposition member 4
The upper half and the outer surface 31 of the outer frame 3 form a flat surface extending in a substantially vertical direction to enhance the appearance of the bumper.

In this embodiment, in particular, the lower half of the outer end face 41 of the interposition member 4 (approximately 140 degrees).
Are recessed by a predetermined depth from the outer main surface 211 of the diaphragm 21 and the outer surface 31 of the outer frame 3, thereby forming a groove 42.

(Modification 1) A modification is shown in FIG.

In this modification, the groove 42 is provided over the entire circumference. By doing so, the directional characteristic, that is, the radiation spread angle is reduced over the entire circumference as compared with the case where the groove 42 is not provided over the entire circumference of the diaphragm 21.

(Modification 1) A modification is shown in FIG.

In this modification, the groove 42 is moved upward by 90 degrees.
Two angles were provided in the angle range of 90 degrees.
In this way, the directional characteristics of the upper and lower sides, that is, the radiation spread angles are narrower than when there is no groove.

(Modification 3) A modification is shown in FIG.

In this modification, in the first embodiment, the groove portion 42a is adjacent to a thin end wall portion (low constraint region in the present invention) 43 and a thin thin tube portion (low constraint region in the present invention) 44, This makes the groove 42a invisible from the outside.

In this way, the directivity characteristics, that is, the effect of narrowing the radiation spread angle is reduced, but the aesthetic appearance is improved because the groove 42a is invisible.

(Modification 4) FIG. 4 shows a modification.

In this modification, in the modification 3,
Instead of the thin thin-walled tube portion (low-constrained area referred to in the present invention) 44 which is in close contact with the outer peripheral surface of the support cylindrical portion 22, a thin thin-walled tube portion (low-constrained region referred to in the present invention) in close contact with the inner peripheral surface of the outer frame 3 45 is provided.

In FIG. 1, if the restraining force of the support cylinder 22 is weak, the groove 42 may be filled with something like a soft putty.

(Modification 5) A modification is shown in FIG.

In this modified embodiment, in the first embodiment, the shielding flange portion (low restraint region in the present invention) 21a is extended so as to hide the groove portion 42 from the lower portion of the peripheral edge of the diaphragm 21. However, a gap g is ensured such that the lower end of the shielding flange 21a does not contact the inner peripheral surface of the outer frame 3 due to vibration.

By doing so, the groove 42 can be formed with a simple structure.
Can be made invisible, and the appearance is improved.

(Experimental Results) The experimental results will be described below.
The experimental conditions are as follows.

The sample model A shown in FIGS. 6 and 7 has the shape shown in FIG. 2 and has a structure in which the groove 42 is provided on the entire circumference of the diaphragm 21. The sample model B shown in FIG. 8 and FIG. The sample model C shown in FIGS. 10 and 11 is a sample model B in which the groove 42 is provided only on the lower side. 12 and 13, the radial width of the groove 42 in the sample model B is reduced to about half,
Is provided adjacent to the diaphragm 21 side. FIG.
In the sample model E shown in FIG. 15, the outer main surface 211 of the diaphragm 21 is recessed in the axial direction by a distance J from the outer surface 31 of the outer frame 3.

The cylindrical case 2 having a bottomed cylindrical shape is formed of aluminum, has a substantially rectangular parallelepiped concave portion inside, and the outer peripheral surface has a radius of 8 mm, and the cylindrical case 2 facing this concave portion. , Ie, the thickness of the diaphragm 21 is about 0.7 mm, and the length of the support cylinder 22 is 9 mm.

The ultrasonic vibrator 1 is fixed to the bottom of the cylindrical case 2, that is, to the back side of the center of the diaphragm 21, and its oscillation frequency is 40 kHz. Tube part 3 of outer frame 3
0 has an inner diameter of 19 mm, and thus the thickness of the interposed member 4 is 1.5 mm. Silicon rubber was used as the interposition member 4. FIGS. 16 to 29 show directivity characteristics when various dimensions are changed in each of these sample models. 16 to FIG.
9, among the wide and narrow directional characteristics, the wider directional characteristic indicates the directional characteristic in the left-right direction, and the narrower directional characteristic indicates the directional characteristic in the vertical direction. The difference between these directional characteristics is caused by the rectangular shape of the diaphragm 21 that is long in the vertical direction. For the directional characteristics, a pole is vertically set at a position 30 cm away from the diaphragm 21, and the diaphragm 21, that is, the sensor is first rotated left and right to check the directional characteristics in the horizontal direction. The directional characteristics of the directions were examined. Of course, the oscillation time of the vibrator 1 is set to end before the reflected wave from the pole enters the vibrator 1.

FIG. 16 shows the directivity characteristics when the depth A of the groove 42 shown in FIG. 7 (sample model A) is 0 mm.

FIG. 17 shows that the depth of the groove 42 shown in FIG.
The directional characteristic when mm is set is shown.

FIG. 18 shows that the depth of the groove 42 shown in FIG.
The directional characteristic when mm is set is shown.

From the comparison between FIG. 16 and FIG. 17, it can be seen that in the sample model A, the provision of the groove 42 improves the directional characteristics. 17 and 18, it can be seen that although slightly, the directional characteristics deteriorate if the groove 42 is too deep.

FIG. 19 shows directivity characteristics when the width B of the groove 42 shown in FIG. 9 (sample model B) is 8 mm and the depth C is 1.5 mm.

FIG. 20 shows the width B of the groove 42 shown in FIG.
Is 10 mm and the depth C is 1 mm.

FIG. 21 shows the width B of the groove 42 shown in FIG.
Is 10 mm and the depth C is 1.5 mm.

FIG. 22 shows the width B of the groove 42 shown in FIG.
Is 10 mm and the depth C is 2.0 mm.

According to FIG. 17 to FIG.
It can be seen that the directivity is sharper than that of the grooveless type shown in FIG.

FIG. 23 shows directional characteristics when the width D of the groove 42 shown in FIG. 11 (sample model C) is 10 mm and the depth E is 1 mm.

FIG. 24 shows directivity characteristics when the width D of the groove 42 shown in FIG. 11 is 10 mm and the depth E is 3 mm.

According to FIG. 23, it can be seen that only the directional characteristics on the upper side are wider than those in FIG. 20 in which the grooves 42 are provided on the upper and lower sides. From the comparison between FIG. 23 and FIG.
It can be seen that when the depth is deeper, the lower directivity is slightly wider and the upper directivity is narrower.

FIG. 25 shows the directivity characteristics when the lateral width F of the groove 42 shown in FIG. 13 (sample model D) is 10 mm and the depth G is 1.5 mm. From FIG. 25, it can be seen that the directional characteristics in the vertical direction are particularly narrowed by reducing the radial width of the groove 42.

FIG. 26 shows a lateral width H of the groove 42 shown in FIG. 15 (sample model E) of 10 mm, a depression distance I of the diaphragm 21 of 1.5 mm, and an axial depth J of the groove 42 of 0.5 mm.
This shows the directional characteristics when.

FIG. 27 shows the directivity characteristics when the width H of the groove 42 shown in FIG. 15 is 10 mm, the distance I of the depression of the diaphragm 21 is 2 mm, and the depth J of the groove 42 in the axial direction is 0.5 mm. .

FIG. 28 shows that the width H of the groove 42 shown in FIG. 15 is 10 mm, the distance I of the depression of the diaphragm 21 is 2.5 mm,
The directional characteristics when the axial depth J of the groove 42 is 0.5 mm are shown.

FIG. 29 shows that the width H of the groove 42 shown in FIG. 15 is 10 mm, the recess distance I of the diaphragm 21 is 3.0 mm,
The directional characteristics when the axial depth J of the groove 42 is 0.5 mm are shown.

From the comparison between FIG. 26 and FIG.
It can be seen that the directional characteristics can be made sharper by providing than when the diaphragm 21 is not depressed. Also, FIG.
By comparing FIG. 27 with FIG. 27 to FIG.
It can be seen that, if the value is too large, the directional characteristics are rather widened.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of an ultrasonic sensor according to the present invention.

FIG. 2 is a longitudinal sectional view showing a modified embodiment of the ultrasonic sensor of the present invention.

FIG. 3 is a longitudinal sectional view showing a modified embodiment of the ultrasonic sensor of the present invention.

FIG. 4 is a longitudinal sectional view showing a modified embodiment of the ultrasonic sensor of the present invention.

FIG. 5 is a longitudinal sectional view showing a modified embodiment of the ultrasonic sensor of the present invention.

FIG. 6 is a schematic front view of a sample model A.

FIG. 7 is a schematic axial sectional view of a sample model A.

FIG. 8 is a schematic front view of a sample model B.

FIG. 9 is a schematic axial sectional view of a sample model B.

FIG. 10 is a schematic front view of a sample model C.

11 is a schematic axial sectional view of a sample model C. FIG.

FIG. 12 is a schematic front view of a sample model D.

FIG. 13 is a schematic axial sectional view of a sample model D.

FIG. 14 is a schematic front view of a sample model E.

FIG. 15 is a schematic axial sectional view of a sample model E.

FIG. 16 is a diagram showing the directional characteristics of a sample model A.

FIG. 17 is a diagram showing the directivity characteristics of a sample model A.

FIG. 18 is a diagram showing the directional characteristics of a sample model A.

FIG. 19 is a diagram showing the directional characteristics of a sample model B.

FIG. 20 is a diagram showing the directional characteristics of a sample model B.

FIG. 21 is a diagram showing the directional characteristics of a sample model B.

FIG. 22 is a diagram showing the directional characteristics of a sample model B.

FIG. 23 is a diagram showing the directional characteristics of a sample model C;

FIG. 24 is a diagram showing the directivity characteristics of a sample model C;

FIG. 25 is a diagram showing the directivity characteristics of a sample model D.

FIG. 26 is a diagram showing the directional characteristics of a sample model E.

FIG. 27 is a diagram showing the directional characteristics of a sample model E.

FIG. 28 is a diagram showing the directional characteristics of a sample model E.

FIG. 29 is a diagram showing the directional characteristics of a sample model E.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Ultrasonic vibrator 2 ... Cylindrical case 3 is an outer frame 4 is an interposition member 21 is a diaphragm 42 is a groove part 44 ... Thin-walled cylinder part (low restraint area referred to in the present invention) 45 ... Thin-walled cylinder part (in the present invention) Low restraint area)

Claims (6)

[Claims] A cylindrical case having a bottom portion forming a diaphragm, and a cylindrical support tube protruding from a peripheral edge of the bottom portion toward one side; a main part of the one side of the diaphragm; A thin plate-shaped ultrasonic vibrator fixed to a surface and vibrating the vibrating plate in a thickness direction thereof; an outer frame provided at a predetermined distance from the supporting cylindrical portion of the cylindrical case; Interposed between the frame and the outer peripheral surface of the support cylinder of the ultrasonic sensor, supports the support cylinder while being supported by the frame, and attenuates the vibration energy of the support cylinder. An ultrasonic sensor, comprising: a member, wherein the interposed member has a groove that is close to a peripheral edge of the diaphragm and does not adhere to the support cylinder. 2. The ultrasonic sensor according to claim 1, wherein the interposed member has a groove that does not adhere to a predetermined part in a circumferential direction of the support cylinder adjacent to a periphery of the diaphragm. An ultrasonic sensor having no groove on the side opposite to the groove in the circumferential direction. 3. An ultrasonic sensor according to claim 2, wherein said ultrasonic sensor is fixed to a side surface of a vehicle and radiates ultrasonic waves from said vehicle at a predetermined spread angle in a vertical direction with respect to a horizontal direction, thereby reflecting off an obstacle. It is used for a vehicle obstacle sensor for detecting a wave, and the groove of the interposed member is disposed adjacent to a lower portion of the support cylinder adjacent to a lower edge of the diaphragm. Ultrasonic sensor. 4. A cylindrical case having a bottom surface forming a diaphragm, and a cylindrical support tube protruding from a peripheral edge of the bottom surface toward one side. A thin plate-shaped ultrasonic vibrator fixed to a surface and vibrating the vibrating plate in a thickness direction thereof; an outer frame provided at a predetermined distance from the supporting cylindrical portion of the cylindrical case; Interposed between the frame and the outer peripheral surface of the support cylinder of the ultrasonic sensor, supports the support cylinder while being supported by the frame, and attenuates the vibration energy of the support cylinder. An ultrasonic sensor, comprising: a member, wherein the interposed member is close to the peripheral edge of the diaphragm and is in close contact with the support cylinder portion, and restrains the support cylinder portion weaker than other portions. . 5. The ultrasonic sensor according to claim 4, wherein the interposed member is in a vicinity of a predetermined part of a peripheral edge of the diaphragm, and a low restraint region for weakly restraining the support tubular portion; An ultrasonic sensor, comprising: a high-constrained region for strongly constraining the support cylinder in proximity to a remaining portion of a peripheral edge of the plate. 6. An ultrasonic sensor according to claim 5, wherein said ultrasonic sensor is fixed to a side surface of a vehicle and radiates ultrasonic waves from said vehicle at a predetermined vertical spread angle with respect to a horizontal direction, thereby reflecting off an obstacle. It is used for a vehicle obstacle sensor that detects a wave, and the low restraint region of the interposed member is disposed adjacent to a lower portion of the support cylinder adjacent to a lower edge of the diaphragm. Ultrasonic sensor.