EP0796669A2 - Ultrasonic transducer - Google Patents

Abstract

The ultrasonic transducer contains a piezoelectric body (2) which is provided on a first flat side (4) with first electrodes (8) which are electrically separated from one another. According to the invention, these first electrodes (8) on the second flat side (6) facing away from the first flat side (4) are assigned to one another and second electrodes (10) which are electrically separated from the first electrodes (8) in such a way that the first electrodes ( 8) and cover the second electrodes (10) in a plan view of one of the flat sides, in each case in at least one partial area. An ultrasonic transducer with these features can be used in a variety of ways and is easy to manufacture. <IMAGE>

Description

The invention relates to an ultrasonic transducer for the non-destructive ultrasonic test.

With non-destructive ultrasound testing it is in the Usually required to rework larger areas of a workpiece to analyze different types of errors. This is it necessary, the ultrasound in different test positions and coupling test directions to the workpiece surface. The number of materials required for a material test Ultrasonic probes and those required with them To reduce position changes, it is known to probe heads use the several ultrasonic transducer elements arranged side by side contain. Such ultrasound transducer arrangements, referred to as arrays allow by delayed Control of the individual transducer elements ultrasonic signals in different directions into the workpiece couple and receive from different directions.

So is with a linear ultrasound transducer array Panning in one plane in the workpiece is possible, which is parallel extends to the longitudinal direction of the ultrasonic transducer array and depending on the geometric shape of a lead body between the ultrasonic transducer array and the workpiece surface, for example a leading wedge, in a predetermined angular range runs to the surface of the workpiece.

While a swivel with linear ultrasonic transducer arrays can be made only in one plane, allow matrix-shaped Ultrasonic transducer arrays, such as, for example are known from EP 0 196 839 A2 or US-A-4,801,835, a pan in two mutually orthogonal planes, so that   with matrix-shaped ultrasound transducer arrays without changing the test head and a large area without changing the location of the test head of the workpiece examined for different errors can be. Such matrix-shaped ultrasound transducer arrays however, require a lot of effort in the production, since the bonding of the internal transducer elements and routing the electrical leads to the electrodes of these Transducer elements is difficult. Also require such a matrix-shaped ultrasound transducer array a control unit, one corresponding to the number of transducer elements Can control the number of channels independently. In practice have a large number of matrix-shaped ultrasound transducer arrays, usually at least 64 transducer elements. This size Number of transducer elements is necessary to get one Pan in one plane a sufficient directional characteristic to be able to generate.

The invention is based on the object of an ultrasonic transducer for the non-destructive ultrasound test, the simply manufactured and with little technical Effort can be controlled and in terms of its technical Properties and its possible uses a matrix Ultrasound transducer array comes as close as possible. The invention is also based on the object of a method specify to operate such an ultrasonic transducer.

The first-mentioned task is solved with the characteristics of Claim 1.

The second task is solved with the features of Claim 7.

In an ultrasonic transducer according to the invention is a piezoelectric one Body on a first flat side with each other provided electrically separated first electrodes, which   on the second flat side facing away from the first flat side from each other and from the first electrodes electrically separate second electrodes are assigned such that the first electrodes and the second electrodes in one Top view of one of the flat sides seen in at least one cover a partial area. This measure will reproduced a matrix-shaped ultrasound transducer array, the individual converter elements through the overlapping Sub-areas are defined.

Preferably, the piezoelectric body is between the Electrodes are provided with grooves that separate them spatially separate. This will in addition to being electrical Separation an acoustic separation of the individual transducer elements enables.

In particular, the depth of the grooves is greater than half Thickness of the piezoelectric body.

In a particularly preferred embodiment, extend the first electrodes extend in a first longitudinal direction and are arranged parallel to each other in this first longitudinal direction. The second electrodes extend in this embodiment in a different way from this first longitudinal direction second longitudinal direction and are in this second Arranged parallel to one another in the longitudinal direction.

The first and the second longitudinal direction are preferred oriented perpendicular to each other.

The piezoelectric body consists in particular of a Piezoceramic.

According to the method for operating the ultrasonic transducer the invention is by driving a predetermined Selection of opposing electrodes a sub-area   of the piezoelectric body for sending or receiving activated by ultrasonic waves. In particular, they are delayed in phase predetermined sub-areas activated. To this Ways can be electronic panning in a variety of ways Single-layer levels can be carried out.

FIG 1 ein Ultraschallwandler gemäß der Erfindung in einer räumlichen Darstellung schematisch veranschaulicht ist. In

FIG 2 ist anhand einer Draufsicht die Funktionsweise des Ultraschallwandlers erläutert.

FIG 3 und 4 zeigen anhand schematischer Darstellungen beispielhaft weitere Ansteuerungsmöglichkeiten eines Ultraschallwandlers gemäß der Erfindung.

To further explain the invention, reference is made to the exemplary embodiments of the drawing, in which

1 shows an ultrasound transducer according to the invention is schematically illustrated in a spatial representation. In

FIG. 2 explains the operation of the ultrasound transducer on the basis of a plan view.

3 and 4 show examples of further control options of an ultrasonic transducer according to the invention using schematic representations.

According to Figure 1 is an ultrasonic transducer from a flat piezoelectric body 2 constructed, each at its opposite flat sides 4 and 6 with strip-shaped Electrodes 8 and 10 are provided.

The electrodes 8 extend parallel to a first one Longitudinal direction 12 and the electrodes 10 extend parallel to a second longitudinal direction 14 perpendicular thereto, so that they are in a top view of the piezoelectric Body 2 seen at the intersection points in a partial area cover their area. Each strip-shaped electrode 8, 10 is thus from each opposite electrode 10 and 8th seen in a plan view covered in a partial area. The electrodes 8 and 10 are on the flat sides 4 and 6, respectively spaced from each other and electrically against each other insulated and are each on the edge of the piezoelectric   Body 2 contacted with electrical lines 16 and 18, respectively.

The electrodes 8, 10, which are orthogonal to one another, disassemble the piezoelectric body 2 into a multiplicity of individual, electrically separate rectangular transducer elements 2 _ij , each of which is formed by the overlapping partial areas of these electrodes 8, 10, and of which in the figure are hatched Transducer element 2 _{11 is} highlighted.

In the exemplary embodiment, one is made of a piezoceramic Piezoelectric body 2 provided on its two flat sides 4 and 6 each provided with grooves 20 and 22, respectively which is parallel to the strip-shaped electrodes 8 or 10 extend. The grooves 20, 22 are each between mutually adjacent electrodes 8 and 10 respectively. With these grooves 20, 22 are at the same time on a flat side 4 and 6 arranged electrodes 8 and 10 from each other electrically isolated.

The grooves 20 and 22 shown in the exemplary embodiment according to the figure have a U-shaped or rectangular cross section and can be produced, for example, by sawing. However, v-shaped grooves produced by oblique saw cuts can also be provided. The depth T of the longitudinal grooves 20, 22 is preferably greater than half the thickness d of the piezoelectric body 2. In a typical embodiment (2 MHz), the piezoelectric body 2 has an edge length a ₁ = a ₂ = 25 mm and a thickness d = 0 , 95 mm and is provided on its flat sides 4, 6 with eight electrodes 8 and 10, respectively, which are separated from one another by grooves 20 and 22 with a width b = 0.1 mm and a depth t = 0.6 mm. The columnar transducer elements 2 _ij formed in this way are each only connected to the adjacent transducer elements 2 _ij by very thin bridges 30. The transducer elements 2 _ij formed in the overlap region of the electrodes 8, 10 are thus additionally acoustically decoupled by the grooves 20, 22.

In the exemplary embodiment, the piezoelectric body 2 is square ( a 1 = a 2nd ). In another embodiment, a rectangular piezoelectric body with an edge length different from one another (a ₁ = | a ₂ ) can also be provided.

The orthogonal arrangement of the electrodes 8 and 10 lying opposite one another thus makes two electrodes one on top of the other reproduced toothed "linear ultrasound transducer arrays, which are oriented perpendicularly to one another with respect to their longitudinal direction and accordingly enable pivoting in mutually perpendicular planes, illustrated in the figure by double arrows 24 and 26 respectively.

In the schematic plan view according to FIG. 2 it can be seen that the five strip-shaped electrodes 8 ₁ to 8 ₅ and the strip-shaped electrodes 10 ₁ to 10 ₅ arranged on the opposite flat side of the ultrasonic transducer result in a matrix-shaped arrangement of transducer elements 2 _ij , of which in the figure the element 2 _{24 is provided} with a reference symbol as an example. They are electrically activated as a single transducer element 2 _ij if, by means of a control device (not shown in the figure), an electrode strip 8 _i on a flat side of the piezoelectric body 2 via a single control line 16 _{i and} an electrode strip 10 _j on the opposite side via a single control line 18 _j Flat side can be controlled. This is illustrated in the figure by hatching, which overlaps to form a cross hatch in the area of the activated converter element 2 _ij , in the figure the converter element 2 ₂₄ .

In this way, a structure made up of m elements can be used linear ultrasound transducer array and another on top of it or arranged below, linear consisting of n elements Ultrasonic transducer array, a structure made up of m x n elements At least matrix-shaped ultrasound transducer array are approximately replicated, the one required for control Number of independent channels of the control unit is reduced from m x n to m + n. The ultrasonic transducer is also easier to manufacture than one Matrix-shaped ultrasound transducer array because of a contact the ultrasonic transducer like a simple linear one Ultrasonic transducer array can be done on the edge surfaces.

FIG. 3 shows a control in which all electrodes 10 ₁ to 10 ₅ on one flat side and only one electrode, in the example electrode 8 ₄ on the opposite flat side, are activated, so that the elements of an entire line are activated. A phase-delayed actuation of the electrodes 8 ₁ to 8 ₅ enables a swivel perpendicular to the plane of the drawing and parallel to the second longitudinal direction 14.

By actuating different rows and columns, different configurations can be activated in a manner similar to a matrix-shaped ultrasound transducer array, as is illustrated, for example, in FIG. 4, in which the elements 2 ₂₄ , 2 ₂₃ , 2 ₃₄ and 2 _{33 are} active. In this way, pivoting in the diagonal direction can also be carried out.

Claims (8)

Ultrasonic transducers for non-destructive ultrasonic testing, in which a piezoelectric body (2) on one first flat side (4) with electrically separated from each other first electrodes (8) is provided, which on the from the first Flat side (4) facing away from the second flat side (6) and electrically separated from the first electrodes (8) second electrodes (10) are assigned such that the first electrodes (8) and the second electrodes (10) seen in a plan view of one of the flat sides in each case cover in at least one area. Ultrasonic transducer according to claim 1, wherein the piezoelectric Body (2) between the electrodes (8, 10) with grooves (20, 22) is provided, each of the electrodes (8, 10) Separate the flat side (4 or 6) from each other. Ultrasonic transducer according to claim 2, wherein the depth (t) the grooves (20, 22) is greater than half the thickness (d) of the piezoelectric body (2). Ultrasonic transducer according to one of the preceding claims, in which the first electrodes (8) into a first Extend in the longitudinal direction (12) and in this first longitudinal direction (12) are arranged parallel to each other, and in which the second electrodes (10) are in one of these first Longitudinal direction (12) different second longitudinal direction (14) extend and parallel in this second longitudinal direction (14) are arranged to each other. Ultrasonic transducer according to claim 4, wherein the first and the second longitudinal direction (12 or 14) perpendicular to each other are oriented.   Ultrasonic transducer according to one of the preceding claims, in which the piezoelectric body (2) made of a piezoceramic consists. Method for operating an ultrasonic transducer according to a of the preceding claims, in which by control a predetermined selection of opposing ones Electrodes (8, 10) a portion of the piezoelectric body (2) enabled to send or receive ultrasonic waves becomes. The method of claim 7, wherein the phase-delayed predetermined Subareas can be activated.