JPH0736083U - Ultrasonic sensor - Google Patents

Abstract

(57) [Abstract] [Purpose] To suppress reverberation and vibration during ultrasonic pulse transmission in an ultrasonic sensor in a short time. [Structure] In an ultrasonic sensor in which a piezoelectric vibrator 1 is fixed to the inner bottom surface of a bottomed case 2 whose one end is open, and a reverberation is attenuated by a sound absorbing material, a piezoelectric vibration is generated by a sound absorbing material 7 infiltrated with an oily liquid. It is characterized in that the child 1 is contacted or contact-pressurized.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an ultrasonic sensor, and more particularly to an ultrasonic sensor that suppresses reverberation and vibration during ultrasonic pulse transmission in a short time.

[0002]

[Prior art]

 The ultrasonic sensor is used for detecting an object, detecting a distance to an object, etc. by reflecting the generated ultrasonic wave on a detected object and receiving the reflected ultrasonic wave.

Conventionally, as shown in FIG. 3 (A), an ultrasonic sensor has a piezoelectric vibrator 1 attached to the bottom of a case 2 with one end open, and a sponge inside the case 2 on the open side. A sound absorbing material 3 such as a felt and a damper material 4 such as a rubber material were used for sealing.

Alternatively, as shown in FIG. 3 (B), the inside of the case 2 is sealed with a sound absorbing material 3 such as sponge or felt, a damper material 4 such as a rubber material, and a cushion 5 such as an O-ring. Thus, the substrate 6 is fixed and one end thereof is sealed.

Now, as shown in FIG. 4, time t is applied to the voltage oscillator 1 from a terminal (not shown). ₀ During this period, when the drive signal Vd is applied, the piezoelectric vibrator 1 outputs ultrasonic waves in the arrow direction shown in FIG. At this time, the reverberation time t shown in FIG.₁Since reverberation and vibration exist during the period, it is necessary to distinguish the reflected signal Vr received by the ultrasonic wave reflected from the detection object from the reverberation signal. Therefore, the reverberation time t₁Of the above, when a reverberation signal larger than the reflection signal V r exists, the reflection signal and the reverberation signal cannot be separated, and therefore t₁Up to ′ is an unmeasurable time when the reflected signal is hidden by the reverberation signal, and the object cannot be detected.

The distance L (meter) to the normal sensing object is obtained by the following. L = 1/2 (331 + 0.6T) t In this formula, T is the temperature in degrees Celsius, and t is the time (seconds) until the reflected signal is input.

Therefore, in order to detect an object at a short distance, it is necessary to suppress the existence time of the reverberation signal indicated by t ₁ to be small. For this reason, as shown in FIGS. 3 (A) and 3 (B), the sound absorbing material 3 and the damper material 4 are used, or the base plate 6 is arranged on the sound absorbing material 3 and the damper material 4 via the cushion 5.

Further, as methods for suppressing reverberation signals and the like, there are JP-A-61-296899 and JP-A-64-269078.

[0009]

[Problems to be solved by the device]

 By the way, in the structure shown in FIG. 3, since the piezoelectric vibrator 1 is only suppressed by the sound absorbing material 3 and the damper material 4, there is no space between the piezoelectric vibrator 1 and the sound absorbing material 3 or between the case and the sound absorbing material. There was a drawback that the reverberation signal was not sufficiently suppressed due to the presence of the body, the reverberation time and the unmeasurable time became long, and it was not possible to measure or detect an object at a short distance.

The device disclosed in Japanese Patent Laid-Open No. 61-296899 suppresses the piezoelectric vibrator with a laminated body of rubber and sponge or a thick backing layer. However, this was not sufficient for suppressing the reverberation signal because there was a reflecting surface between the piezoelectric vibrator and the rubber layer or between the piezoelectric vibrator and the backing layer. Moreover, when this is covered with a case, a cavity and a reflecting surface exist between the case and these rubber layers and backing layer. Therefore, suppression of reverberation and vibration of the piezoelectric vibrator and the case was insufficient.

The device disclosed in Japanese Patent Laid-Open No. 62-269078 is not sufficient for suppressing reverberation and vibration because the back surface of the piezoelectric vibrator is not suppressed at all.

[0012] Therefore, an object of the present invention is to provide an ultrasonic sensor which has improved the reverberation suppression and vibration suppression inadequate, and which has a non-measurable time and a short reverberation time.

[0013]

[Means for Solving the Problems]

 In order to achieve the above-mentioned object, in the ultrasonic sensor of the present invention, as shown in FIG. 1, a piezoelectric vibrator 1 is fixed to the inner bottom surface of a bottomed case 2 whose one end is open. The sound absorbing material 7 in which the oily liquid has penetrated to the side opposite to the fixed surface is brought into contact with or pressed against the piezoelectric vibrator 1.

[0014]

[Action]

As a result, the sound absorbing material 7 having a large acoustic impedance in which the oil liquid is permeated into the piezoelectric vibrator 1 is configured so that the cavity between the piezoelectric vibrator 1 and the case 2 does not exist. since suppress the occurrence of generation or vibration of reverberation by matching the acoustic impedance between the case 2 and the damper member 4, it is possible to effectively suppress the reverberation generator and the vibration generator, the reverberation time t ₁ Can be shortened.

[0015]

【Example】

 An embodiment of the present invention will be described with reference to FIG. FIG. 1 is a configuration diagram of an embodiment of the present invention. Reference numeral 1 is a piezoelectric vibrator, which is composed of, for example, a piezoelectric ceramic vibrator, which generates ultrasonic waves when a drive signal is applied, and 2 is present. In the bottom case, for example, a cylindrical case, 4 is a damper material, for example, a rubber material, and 7 is a sound absorbing material, into which an oily liquid has permeated.

The sound absorbing material 7 is made of a porous material that does not muffle the sound, and is preferably a felt or a sponge through which an oily liquid can penetrate. However, the sound absorbing material 7 is not limited to these, and cloth or paper can be used.

Silicon oil can be used as the oily liquid with which the sound absorbing material 7 is impregnated, but is not limited thereto. Now, as shown in FIG. 1, after mounting the piezoelectric vibrator 1 on the bottom of the case 2, the sponge sound absorbing material 7 impregnated with silicon oil is brought into contact or contact pressure on the opening side of the case 2. Further, the damper material 4 was further stacked to form an ultrasonic sensor. The terminals for applying a voltage to the piezoelectric vibrator 1 are not shown for the sake of simplicity of the description.

As a result, the sound absorbing material 7 impregnated with the oily liquid and having a large acoustic impedance allows the sound absorbing material 7 and the piezoelectric vibrator 1 and the sound absorbing material 7 and the case 2 to be closely packed without any cavities. The sound absorbing material 7 is suppressed, and the sound absorbing material 7 is impregnated with an oily liquid, so that the sound absorbing material 7 has a large acoustic impedance. Moreover, the sound absorbing material 7 matches the acoustic impedance with the case 2 and the damper material 4, and the suppression effect can be further increased. As a result, the reverberation time t ₁ was about 35% and the undecidable time t ₁ ′ was about 30% shorter than in the conventional case.

A second embodiment of the present invention will be described with reference to FIG. In the embodiment shown in FIG. 2, the piezoelectric vibrator 1 is attached to the bottom of a cylindrical case 2 having a bottom, and a sound absorbing material 7 made of sponge impregnated with silicon oil is laid on the opening side of the piezoelectric vibrator 1 to contact the piezoelectric vibrator 1 or Contact pressure is applied.

As a result, the reverberation time and the undecidable time were significantly shortened and improved. For example, compared with the case where a sponge sound absorbing material is stacked on a piezoelectric vibrator, this is also greatly improved as in the case of FIG.

In each of the above-mentioned embodiments, an example in which the sound absorbing material is impregnated with silicone oil has been described, but the oily liquid that is impregnated in the sound absorbing material is not limited to this, and other liquids may be used. .

As the liquid that can permeate the sound absorbing material, it is also possible to use, for example, a silicone resin or a fluorine resin, which is gel-like after being permeated, that is, a rubber-like substance that naturally hardens and hardens at room temperature.

[0023]

[Effect of device]

 According to the present invention, since the sound absorbing material impregnated with the liquid is contacted or pressed against the piezoelectric vibrator, the sound absorbing material and the piezoelectric vibrator and the sound absorbing material and the case are closely packed without any cavity. In addition to suppressing, it is also possible to suppress with a large acoustic impedance, so it is possible to increase the suppression effect and effectively suppress the reverberation vibration of the piezoelectric vibrator and the case, making it possible to judge the reflected signal. You can reach it quickly.

Further, by matching the acoustic impedance of the sound absorbing material with the case and the damper material, it is possible to further suppress the occurrence of reverberation and vibration. Therefore, it is possible to easily detect an object at a short distance, which was not possible in the past, without error. Further, it is possible to detect a long-distance to short-distance object and a distance without using a special sensor. Moreover, in this case, this can be done only by impregnating the sound absorbing material part of the ultrasonic sensor of the conventional structure with the oily liquid, so that the ultrasonic sensor can detect with almost the same ultrasonic sensor as the conventional one. It can be done inexpensively without using a measuring device.

[Brief description of drawings]

FIG. 1 shows a block diagram of an embodiment of the present invention.

FIG. 2 is a block diagram of a second embodiment of the present invention.

FIG. 3 shows a configuration diagram of a conventional example.

FIG. 4 is an explanatory diagram of operating characteristics of the ultrasonic sensor.

[Explanation of symbols]

 1 Piezoelectric vibrator 2 Case 3 Sound absorbing material 4 Damper material 5 Cushion 6 Substrate 7 Sound absorbing material

Claims (5)

[Scope of utility model registration request] 1. An ultrasonic sensor in which a piezoelectric vibrator (1) is fixed to the inner bottom surface of a bottomed case (2) whose one end is open, and reverberation is attenuated by a sound absorbing material, in which an oily liquid is permeated. An ultrasonic sensor characterized in that the piezoelectric vibrator (1) is brought into contact or contact pressure with a sound absorbing material (7). 2. The ultrasonic sensor according to claim 1, wherein the sound absorbing material (7) is made of felt, sponge, cloth, or paper impregnated with an oily liquid. 3. The ultrasonic sensor according to claim 1, wherein the oily liquid is silicone oil. 4. The ultrasonic sensor according to claim 1 or 2, wherein the oily liquid is one that hardens into a rubber shape after permeating the sound absorbing material (7). 5. The ultrasonic sensor according to claim 1 or 2, wherein a damper material (4) is laminated on the opposite side of the sound absorbing material (7) to the piezoelectric vibrator (1).