Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Patent
1999-04-22
2000-08-15
Ramirez, Nestor
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
310328, B06B 106
Patent
active
061041211
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an ultrasonic transducer having a disk-shaped piezoceramic element and having a disk-shaped quarter-wave transformer element.
BACKGROUND INFORMATION
In ultrasonic converters have ultrasonic sensors and proximity switches conventional a relatively narrow acoustic lobe characteristics, and at the same time have comparatively low secondary lobe amplitudes. The quarter-wave transformer element serves to emit and receive ultrasonic waves in a gaseous propagation medium, preferably for use in ultrasonic proximity switches.
German Patent No. 39 11 047 C2 has already disclosed an ultrasonic transducer having a piezoceramic element and a transformer element, in which the surface of the transformer element facing away from the piezoceramic element has a surface area which is slightly different as compared with the base area of the piezoceramic element and with the area of the transformer element which faces the latter. In this context, the lateral line of the transformer element is divergent or convergent, with a straight, concave, or convex profile. The acoustic lobe characteristic achievable therewith, having considerable secondary lobe amplitudes of approximately -19 dB with respect to the principal lobe amplitude, is insufficient for use of the ultrasonic transducer, for example, in confined environmental conditions and in the presence of lateral interfering objects.
European Patent No. 0 655 156 describes an ultrasonic transducer having a transformer element with a cylindrical enveloping surface, which has an indentation on the enveloping surface and/or on the surface facing the piezoceramic element. This indentation allows highly directional acoustic lobes with low secondary lobe amplitudes of less than -30 dB.
SUMMARY OF THE INVENTION
An object of the present invention is to improve an ultrasonic transducer of the kind recited above in such a way that it simultaneously has narrow principal lobe opening angles and low secondary lobe amplitudes.
The object is achieved by configuring the lateral peripheral surface of the quarter-wave transformer element as a stepped profile.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows an ultrasonic transducer with a right-angled stepped profile.
FIG. 2 shows an ultrasonic transducer with a non-right-angled stepped profile.
FIG. 3 shows an ultrasonic transducer having a stepped profile including a right-angled step and a non-right-angled step.
DETAILED DESCRIPTION
FIG. 1 shows a sectioned illustration of an embodiment according to the present invention of an ultrasonic transducer 1 having a cylindrical, disk-shaped piezoceramic element 2 and, for example adhesively bonded thereto, a disk-shaped transformer element 3. The lateral peripheral surface of transformer element 3 is configured here as a simple right-angled stepped profile 4. In the simplified depiction shown in FIG. 1 the upper and lower metallization surfaces of piezoceramic element 2, as well as the metallization surface facing transformer element 3--to which contact is made, for example, via a thin contacting foil made of metal or a metal-plastic composite material and inserted into the adhesive layer--are not shown. The advantageous configuration of the lateral stepped contour results in favorable oscillation forms of the outward-facing, acoustically radiating surface of transformer element 3, resulting in highly directional acoustic lobes with very low secondary lobe amplitudes. In one exemplary embodiment, the diameter of the disk-shaped piezoceramic element 2 and the diameter of the base surface facing piezoceramic element 2 of transformer element 3 is 23 mm. The diameter of the outward-facing surface of transformer element 3 is 28 mm, the overall height of transformer element 3 is 6.5 mm, and the height of the projecting portion of the transformer element with the 28-mm diameter is 2.4 mm. Transformer element 3 consists of a robust syntactic foam made of a mixture of epoxy and hollow glass spheres. The term syntatic foam implies, for example,
REFERENCES:
patent: 4641054 (1987-02-01), Takahata et al.
patent: 4823042 (1989-04-01), Coffey et al.
Ramirez Nestor
Siemens AG
Stefaniw Eliza
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