JP2005039689A - Ultrasonic sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic sensor which is equipped with a vibrator made by bonding a piezoelectric element to the interior surface of a bottom of a cylindrical case with bottom and by which directional characteristics of transmission and reception are asymmetric with respect to the axis passing through the cylindrical case with bottom perpendicularly to the center of the bottom. <P>SOLUTION: The inside of the bottom 4 of the cylindrical case with bottom to which the piezoelectric element 2 is to be bonded is provided with multiple steps or diagonal slits in order that the thickness of the bottom 4 may vary. The piezoelectric element 2 is bonded to the surface where the thickness is the maximum. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ultrasonic sensor having a drip-proof structure that transmits and receives an ultrasonic frequency band.

A conventional drip-proof ultrasonic sensor will be described with reference to FIG.
In the figure, a piezoelectric element 2 is bonded with an adhesive 3 inside a bottom surface 5 of a bottomed cylindrical case to constitute a vibrating body. In this case, the bottom surface 5 of the bottomed cylindrical case to which the piezoelectric element 2 is bonded is provided with only one step.
JP 2000-152387 A

  In conventional ultrasonic sensors with a drip-proof structure, the frequency at which the transmission output and reception sensitivity are maximized is determined by the area and thickness of the bottom surface of the bottomed cylindrical case, and the piezoelectric element attached to that portion. The directivity for transmission and reception was determined by the frequency and the area of the bottom surface of the bottomed cylindrical case. This directivity characteristic has a conical characteristic centered on an axis that passes through the center of the bottom surface and is perpendicular to the bottom surface from the center of the bottom surface. In general, when the frequency is the same, when the area of the bottom surface constituting the vibrating body is increased, narrow directivity is exhibited, and when the area of the bottom surface constituting the vibrating body is the same, the directivity is increased when the frequency of the vibrating body is increased. Indicates. Therefore, in a drip-proof ultrasonic sensor in the 20 to 50 kHz band with good air propagation, it is difficult to manufacture a drip-proof ultrasonic sensor having a small size and narrow directivity. As a countermeasure for this, only one step is provided on the bottom surface of the bottomed cylindrical case as shown in FIG. 2, but it is inclined only about 4 degrees with respect to an axis perpendicular to the center of the bottom surface as shown in FIG. When the drip-proof ultrasonic sensor is used for detecting an object such as a back sensor of an automobile, there is a problem in that reflection on the road surface is widened and accurate control cannot be performed.

At the bottom of the bottomed cylindrical case, two or more steps or diagonal slits are provided on the bottom surface where the piezoelectric element is to be bonded, and the piezoelectric element is bonded to the surface with the maximum thickness, so that the directivity characteristics for transmission and reception can be set in any direction. Tilt to.

In the ultrasonic sensor according to the embodiment of the present invention, two or more steps or oblique slits are provided on the bottom surface of the bottomed cylindrical case, and the directional characteristics to be transmitted and received are centered on the bottom case by bonding the piezoelectric elements. Can be tilted with respect to an axis that passes vertically. Therefore, when used as a back sensor for an automobile, as shown in FIG. 5, accurate object detection control can be performed without receiving reflection from the ground.

When used for detecting an object such as a back sensor of an automobile, the object of accurate control without spreading the reflection of the road surface was realized without changing the external shape of the sensor.

As shown in FIG. 1, a piezoelectric element 2 is bonded with an adhesive 3 to the bottom surface of the bottomed cylindrical case having the maximum wall thickness.
The thickness difference d1 of the bottom surface 4 of the bottomed cylindrical case is set in a range of 0.1 to 0.5 mm, and a piezoelectric element is bonded to the surface having the maximum case thickness to constitute a vibrating body.
As shown in FIG. 4, the conventional product is inclined by 4 degrees with respect to the axis perpendicular to the center of the bottom surface, but in the present invention, it is inclined by θ with respect to the axis perpendicular to the center of the bottom surface as shown in FIG. θ can be 8 degrees or more.

As in Example 1, as shown in FIG.
The thickness d2 of the oblique slit of the bottomed cylindrical case is set in a range of 0.1 to 0.5 mm, and a piezoelectric element is bonded to the surface having the maximum case thickness to constitute a vibrating body.
As shown in FIG. 4, the conventional product is inclined by 4 degrees with respect to the axis perpendicular to the center of the bottom surface, but in the present invention, it is inclined by θ with respect to the axis perpendicular to the center of the bottom surface as shown in FIG. θ can be 8 degrees or more.

When used for detecting an object such as a back sensor of an automobile, it is possible to accurately control without reflecting the road surface.

1 is a schematic structural diagram of a main part of an ultrasonic sensor according to an embodiment of the present invention (claim 1). The schematic structure figure of the principal part of the ultrasonic sensor concerning the conventional form. Explanatory drawing which shows the directional characteristic of the ultrasonic sensor which concerns on embodiment of this invention. Explanatory drawing which shows the directional characteristic of the ultrasonic sensor which concerns on the conventional form. Explanatory drawing which shows the detection area when the ultrasonic sensor which concerns on embodiment of this invention is mounted in the motor vehicle. Explanatory drawing which shows the detection area when the ultrasonic sensor which concerns on the conventional form is mounted in the motor vehicle. The schematic structure figure of the principal part of the ultrasonic sensor concerning the embodiment of the present invention (Claim 2).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bottomed cylindrical case 2 Piezoelectric element 3 Adhesive 4 Bottom surface which has a step of bottomed cylindrical case 5 Side wall part of bottomed cylindrical case 6 Bottom surface of conventional bottomed cylindrical case 7 Diagonal of bottomed cylindrical case Bottom with slit

Claims (2)

In the ultrasonic sensor that transmits and receives the ultrasonic wave on the outer surface of the case, the piezoelectric body is bonded to the inside of the bottom surface of the bottomed cylindrical case. An ultrasonic sensor in which two or more steps are provided on the bottom surface to which the element is bonded, and the directional characteristics for transmission and reception are asymmetric with respect to the axis passing through the center of the bottom surface. In the ultrasonic sensor that transmits and receives the ultrasonic wave on the outer surface of the case, the piezoelectric body is bonded to the inside of the bottom surface of the bottomed cylindrical case. An ultrasonic sensor in which an oblique slit is provided on the bottom surface to which the element is bonded, and the directivity characteristics for transmission and reception are asymmetric with respect to an axis passing through the center of the bottom surface.

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