JPS6053868A - Ultrasonic sensor - Google Patents

Abstract

PURPOSE:To make the titled sensor inexpensive by eliminating influence due to dust, by constituting the same from such a mechanism that an absorbing element of ultrasonic vibration is provided to the front surface of an ultrasonic transducer to sense the change in the reflection of ultrasonic vibration when an article to be sensed is inserted between both of them. CONSTITUTION:An ultrasonic transducer 11 is mounted to an upper part 12 and an ultrasonic signal absorbing element 14 is arranged to the surface 13 opposed to said transducer 11. The ultrasonic transducer 11 is constituted by such a method that two piezoelectric electrode discs each comprising Pb(Zn+Ti)O3 type ceramics and having a thickness of 0.25mm. and a diameter of 4mm. are adhered in bimorph state to be mounted onto a base disc 11-1 by a binder comprising silicone rubber while a radial shape cone 11-2 is mounted to said base disc. On the other hand, the ultrasonic signal absorbing element is constituted by providing a cavity 16 to the leg part of a frame 15 comprising a high-molecular resin having the upper part 12 equipped with the ultrasonic transducer 11 while filling said cavity with a sponge 17.

Description

[Detailed description of the invention] The present invention relates to an ultrasonic sensor.

Sensors using ultrasonic transducers have been well known.

For example, as seen in "Ultrasonic Measurement" by Noboru Niwa, published by Shokodo Co., Ltd., Chapter 5, Section 4 to Section 5 of the same chapter, when sensing an object, it is necessary to block the ultrasonic signal or reflect it. As is well known, it depends on the signal.

The gist of the present invention relates to an ultrasonic sensor that can be placed in a small space.

Conventionally, in limited small spaces, optical sensors using infrared rays etc. were used exclusively, or when ultrasonic signals were used, transducers for transmitting and receiving were placed facing each other. It was designed to sense objects that came between the sensors.

However, the former has extremely serious defects such as the surface of the sensor being covered with dust and the like, resulting in a significant deterioration in sensitivity or false sensing.

Furthermore, the latter type, which has transducers for transmitting and receiving transducers facing each other, has another serious defect in that it requires the use of two transducers, which increases the cost. Ta.

Furthermore, when a conventional reflection-type sensor that uses ultrasonic signals is placed in a small, limited space, it is difficult to detect because it receives reflected waves from objects that make up the space, such as the side walls of the space other than the sensing object. It is unable to perform its function as a vessel.

As a result of various studies regarding these points, we have come to provide the present invention, which is an ultrasonic reflection type and is characterized by providing an ultrasonic signal absorber on the front surface (opposing surface) of the transducer. .

The details of the present invention will be described using electrical diagrams.

An ultrasonic signal absorber 14 (for example, a sponge or a triangular type device having a function of attenuating the reflection of ultrasonic signals An anechoic cone, an organic substance such as a hollow fiber, and an inorganic substance such as a porous ceramic) are arranged.

A specific example of this ultrasonic sensor will be described.

r'b (Zr4-Ti
) Two piezo electrode discs made of 03 series ceramic with a thickness of 0.25 mm and a diameter of 4 mm are glued together in a bimorph shape.
Base board 11. --1-1- is mounted with a bond made of silicone rubber, and then the radial type controller 11-
Completed by installing 2.

On the other hand, the ultrasonic signal absorbing shell is constructed by providing a hollow 16 in the leg of a frame 15 made of polymeric resin with an ultrasonic transducer loaded in the upper part 12, and filling the inside with a sponge 17. Ta.

Convenience of the shape of the effective space in which the ultrasonic sensor is placed
Even if the ultrasonic transducer and the absorber do not necessarily face each other, the scope of the present invention includes a case where a waveguide cavity 21 for ultrasonic signals is provided and the open cavity faces the absorber for ultrasonic signals. include.

An example of an electrical circuit configuration is shown in a block diagram in FIG.

An oscillator for exciting the ultrasonic transducer 11, a detection circuit and a low-pass filter circuit for detecting only reflected waves, a comparator for judging the signal, and a switching circuit.

It consists of a reset circuit (omitted in the drawing).

It is also possible to incorporate some or all of these circuits into the middle of the frame 15.

According to the present invention, there is no influence from dust compared to conventional optical sensors, the unit price is lower than conventional ultrasonic sensors, and it can be used in small spaces, and its characteristics are suitable for industrial applications. It can be said that it has value.

[Brief explanation of drawings]

FIG. 1 is a perspective thin sectional view of the ultrasonic sensor of the present invention, with electrical connections omitted. Number 11 is the ultrasonic transducer, 12 is the frame's second S, t3 is the opposing surface of the ultrasonic transducer,
14 is an ultrasonic signal absorbing shell, 15 is a fly 4, 16 is a cavity (indentation), and 17 is a sponge. FIG. 2 is a cross-sectional view showing an example of a modification of the ultrasonic sensor of the present invention. Number 21 is the waveguide cavity. FIG. 3 is a block diagram showing an example of an electric circuit for utilizing the sensor of the present invention. Patent applicant Figure 1 Figure 2

Claims (1)

[Claims] An ultrasonic sensor characterized in that an ultrasonic vibration absorbing device is provided in front of an ultrasonic transducer, and when an object to be sensed is inserted between the devices, a change in reflection of the ultrasonic vibration is sensed.