JPH0315178Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field This invention oscillates ultrasonic waves by applying a high-frequency voltage between a drive electrode and a counter electrode, and uses the vibration energy to atomize the liquid in contact with the counter electrode. This invention relates to a bimorph piezoelectric ultrasonic transducer.

Structure of a conventional example and its problems A conventional bimorph piezoelectric ultrasonic transducer is structured as shown in FIG. The counter electrode 3 is provided up to the periphery of the surface on which the electrode 2 is provided. In order to protect the counter electrode 3 and the piezoelectric element from reflected ultrasonic waves from the liquid surface and chemical substances contained in the liquid, a protective metal plate 4 made of stainless steel or the like is attached to the counter electrode 3 using a heat-resistant conductive adhesive 5. It is attached with. A vibrator lead 6 is connected to the drive electrode 2 and counter electrode 3 with solder.

By the way, in general, when the liquid in contact with the counter electrode of this type of vibrator is depleted, the acoustic impedance is drastically reduced, so an overcurrent flows through the vibrator and it generates self-heating, which not only destroys the vibrator itself, but also damages the vibrator. may cause thermal stress to the object holding it. Therefore, it is effective if the vibrator itself has a structure to cut off thermal runaway. However, in order to protect the vibrator from destruction and thermal runaway caused by driving it even when the liquid is depleted, conventionally the side driving the vibrator detects the presence or absence of liquid and the level of current flowing through the vibrator. Therefore, if an abnormality is detected, a method is implemented in which the drive of the vibrator is stopped. However, if the detection system does not operate properly, the problem of thermal runaway remains. Conventional vibrators do not take any special measures to prevent this thermal runaway.

Purpose of the Invention In view of the above-mentioned circumstances, the present invention provides a bimorph piezoelectric vibrator that can break the thermal runaway state and do not apply thermal stress to the object holding the vibrator.

Structure of the Invention In order to achieve the above object, the present invention has a structure in which a metal plate for drawing out lead wires is bonded to the drive electrode using an epoxy heat-resistant conductive adhesive. When a large amount of heat is generated from the piezoelectric element, the metal plate is separated from the drive electrode by the heat, thereby ensuring safety.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

FIG. 2 is a structural diagram of the bimorph piezoelectric ultrasonic transducer of the present invention. Compared to FIG. 1, the only difference is the structure around the drive electrode 2, so the same parts are given the same numbers and explained. omitted. The characteristic structure of this embodiment is that the metal plate 8 for leading out the leads is partially covered with a heat-resistant conductive adhesive 5 containing a room temperature curable epoxy type epoxy-based conductive adhesive 5 mixed with silver or copper metal powder at a volume ratio of 60%. It has a structure in which it is pasted together using As the material of this lead drawing metal plate 8, steel or the like is effective from the viewpoint of solderability and conductivity.
The vibrator lead 6 is connected to a metal plate 8 for lead extraction with solder 9.

In the above structure, when the liquid is depleted and the piezoelectric element 1 starts to generate heat and the temperature rises,
Since the heat-resistant conductive adhesive 5 coated on the drive electrode 2 is located at the connection between the metal plate 8 for lead extraction and the drive electrode 2, it becomes locally high temperature due to the contact resistance between the two.
In the heat-resistant conductive adhesive 5, the strength of the cured adhesive itself decreases, and the air contained therein thermally expands, weakening the internal bonding force. Furthermore, since the swinging force due to the vertical vibration of the piezoelectric element 1 is added,
The lead drawing metal plate 8 is separated from the drive electrode 2, and the drive of the piezoelectric element 1 is stopped. It is better to provide the metal plate 8 for lead extraction on the drive electrode 2, which has a smaller area and has a smaller heat dissipation effect than on the counter electrode 3.
This form is in line with the purpose of this invention.

Effects of the Invention As is clear from the description of the above embodiment, according to the present invention, the thermal runaway state of the vibrator caused by driving it even though the liquid is depleted can be prevented by thermally applying heat to the object holding the vibrator. It is possible to cut off stress before it causes stress, which has a great practical effect.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional bimorph piezoelectric ultrasonic transducer, and FIG. 2 is a sectional view of a bimorph piezoelectric ultrasonic transducer according to an embodiment of the present invention. 2... Drive electrode, 5... Heat resistant conductive adhesive, 6
... Vibrator lead, 8 ... Metal plate for lead extraction, 9 ... Solder.

Claims (1)

[Scope of utility model registration request] On a part of the drive electrode formed by sintering metal,
A bimorph piezoelectric ultrasonic transducer in which a metal plate for lead extraction is bonded with an epoxy heat-resistant conductive adhesive mixed with metal powder, and a lead wire is soldered to the metal plate.