EP2186147A1

EP2186147A1 - Information processor and method for the production thereof

Info

Publication number: EP2186147A1
Application number: EP08803247A
Authority: EP
Inventors: Heinrich-Jochen Blume; Bernhard Gottlieb; Andreas Kappel; Robert Wolfgang Kissel; Karl-Heinz Mittenbühler; Tim Schwebel; Carsten Wallenhauer
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2007-09-11
Filing date: 2008-08-27
Publication date: 2010-05-19
Also published as: US20100289378A1; US8222797B2; DE102007043263A1; JP2010539693A; WO2009033949A1

Abstract

The invention relates to an information processor, comprising at least two material layers having polygonal base surfaces, which are connected to each other in a shear-rigid way, and wherein at least in one material layer a change of length can be induced. The polygonal base surface has at least two different interior angles. The invention further relates to a method for the production thereof.

Description

description

Information converter and method for its production

The invention relates to an information converter, which consists of at least two layers of material with a polygonal base, which are shear-stiffly connected to each other and wherein at least in a material layer, a change in length is inducible. Such information converters are used in automation technology either as a sensor or as an actuator.

It is known from the prior art to connect at least two material layers with different expansion behavior to one another in a shear-resistant manner to form a composite material. The expansion behavior can be influenced piezoelectrically, magnetostrictively, electrostrictively, by shape memory alloys or thermally. The differential expansion of the two material layers then causes a bending of the composite material, which can be induced electrically or thermally. The outer shape of such a composite material according to the prior art is always cuboid, wherein the interface between the two layers of material is always parallel to the plane of greatest extent. The cutting line of both materials thus runs within the narrow side. The base in the plane of the largest dimension of the cuboid is always rectangular or square.

In order to make the relative bending of the composite material usable as an information converter, usually a narrow side is clamped in a holder. This then defines the zero point of the movement. In the case of an actuator, the movement of the strip on the narrow side opposite the holder can then be tapped off. In the case of a sensor, an electrical signal can be generated from the movement of the narrow side opposite the holder or a thermal stress is converted into a mechanical movement.

In order to increase the mechanical performance or the working capacity of an actuator, it is known from the prior art to connect a plurality of layers of material each shear stiff with each other. Care must be taken to ensure that the respective deformations of the strips do not cancel each other out, but add up. This multiplies the available power.

Based on this prior art, the present invention has the object to improve the working capacity and / or the durability of a known information converter.

The object is achieved by an information converter, comprising at least two layers of material with a polygonal base surface, which are connected to each other in a shear-stiff manner and wherein a change in length is inducible at least in one layer of material, the polygonal base having at least two different internal angles.

The information converter according to the invention has at least two layers of material which are connected to each other in a shear-resistant manner. This compound can be achieved for example by gluing, sintering or welding. Of the at least two material layers, at least one change in length must be able to be induced from the outside by an applied signal. This signal may be, for example, an electric field, a magnetic field or a temperature change.

If only one material layer has an inducible change in length, it is applied shear stable on a carrier material which has a smaller or no change in length. Of course, it is also possible to merge material layers with an inducible change in length so that the mechanical stresses in the material add up and the bending is thereby increased. In this way, for example, two layers of material with an inducible change in length can be applied on both sides of a passive carrier material. Alternatively, 2, 4 or 6 material layers with an inducible change in length can also be brought directly onto one another without a passive carrier.

In order to make the relative bending of the at least two material layers usable for an absolute change in position, a holder is also provided in the information converter according to the present invention, in which one side of the information converter is clamped. The information converter thus consists of a cantilevered cantilever.

According to the invention, it has now been recognized that the mechanical stress can be reduced at the location of the greatest mechanical load occurring, namely directly at the clamping, when the information converter does not have a cuboid shape with a rectangular base, but rather a prismatic shape. As a base in the context of the present invention, the surface of the free bending beam is considered. The area within the clamping is largely released to the person skilled in the art.

The base of the prism is characterized in that it has at least two different internal angles. The interior angle of the base area is the angle enclosed by two sides, which lies within the base area. An interior angle is always at one corner of the base. At the base of the cuboid, all internal angles are always 90 °. Thus, there is only a different interior angle. In contrast, the base area of the prism mold according to the invention has at least two different internal angles. In one embodiment of the information converter according to the invention, the base area is selected in the form of an equilateral triangle. For a symmetrically constructed bimorph bender, ie a composite of two identical material layers whose deformation adds up, it could be shown that with the same deflection of the tip, the mechanical stress at the location of the clamping is one third lower than with a cuboid bimorph , This is particularly advantageous if one or both layers of material are made of ceramic, since ceramic materials can absorb only small stresses. At the same time, some ceramics show a strong piezoelectric effect and are therefore particularly suitable for piezoelectric information converters.

In another embodiment of the invention, the information converter on a symmetrical, square base, in which the width of the holder is greater than the width of the holder opposite side. The base thus forms a tapered trapezoid. By this form, the load capacity of the free-swinging end of acting as a bending beam composite material is increased.

If the polygonal base area of the information converters according to the invention comprises at least an internal angle of approximately 90 °, in one embodiment of the invention the material consumption occurring as a waste in the production of the information converter can be minimized. This is due in particular to the fact that an information converter can be combined again with another point-symmetrical information converter to form the outer shape of a rectangle.

If the internal angles are not right angles, these are selected from the range of about 35 ° to about 85 °, in particular from about 55 ° to about 80 °. These angular ranges correspond to an aspect ratio of length to width of about 2: 3 to about 20: 3. The length is measured from the holder to the outermost, free-swinging edge. The width corresponds to the Cutting line of the material layers with the mechanical restraint. The material layers preferably have a constant thickness. However, since the width changes with length in the information converters according to the invention, the cross section of the at least two layers of material along the length becomes smaller.

If an actuator according to the invention contains at least one material layer which exhibits a piezoelectric effect, it could be demonstrated that the blocking force is greater by one third compared to the prior art due to the basic form according to the invention with the same volume of the actuator. As a blocking force while that force is called, which is necessary for bending back a fully deflected information converter in the zero position.

The idling deflection of an unloaded actuator according to the prior art and according to the present invention is identical. Thus, the quality of the actuator, so the product of blocking force and deflection, also by a third larger. In the case of a piezoelectric bending actuator, this leads to an increased working capacity with the same consumption of piezoelectric material or to a lower material consumption with the same working capacity. In the case of a piezoelectric sensor, for example an acceleration sensor, the electrical measuring signal increases with the same deflection. This results in an improved signal / noise ratio and thus a higher accuracy of measurement.

In order to produce a piezoelectric effect in at least one material layer, a device is provided in order to generate an electric field in the material parallel or antiparallel to the polarization. This can be done for example by electrodes which are applied to the outside of the piezoelectric material layer by sputtering or thermal evaporation. In some cases, it is also possible to use an electrically conductive carrier material on which The piezoelectric material layer is applied shear stable.

Examples of suitable piezoelectric materials are lead zirconate titanates or lead magnesium niobates or mixtures of one or more of these materials. The mentioned ceramic materials show a particularly large piezoelectric effect, ie a particularly large change in shape as a function of the electric field. By applying the electric field see antiparallel to the polarity of the piezoelectric material, this undergoes a longitudinal compression and a transverse strain. When an electric field is applied parallel to the direction of polarization, the material undergoes longitudinal expansion and transverse buckling. If two layers of material are connected shear-stiffly in the opposite direction of the polarization, the composite strip thus formed experiences an increase in its deformation when an electric field is applied. Of course, this amplification can also be achieved by choosing the directions of polarization in the same direction and counteracting the electric field in each material layer.

The invention will be explained in more detail below with reference to figures and examples without limiting the general concept of the invention.

Figure 1 shows a bending actuator according to the prior art in a perspective view.

FIG. 2 shows variants of flexural transducer designs, which can be used both in the prior art and in accordance with the present invention.

FIG. 3 shows various base areas for information converters according to the present invention. FIG. 4 shows possible sectional guides for producing the information converters according to FIGS. 1 and 3.

Figure 1 shows an information converter 1, which is designed as a piezoelectric bending transducer. The actual

The transducer consists of a carrier material 2 and a piezoelectric material 3. Both layers of material are connected to each other in a shear-resistant manner, for example by gluing. One end is fixed in an electrically insulating holder 4. The piezoelectric material layer 3 has a conductive coating on its upper side. Likewise, the carrier 2 is electrically conductive. The polarization direction of the piezoelectric material 3 runs opposite to the arrow E. Outside the holder 4, the free length of the carrier material and piezoelectric material is the same size and shows a substantially rectangular base area. Both layers of material thus form a cuboid of small thickness.

For use as an actuator, an electrical voltage is applied to the holder 2 and the conductive coating of the piezoelectric material layer 3. As a result, an electric field E sets in within the material layer 3. This leads to the length contraction of the material layer 3. The carrier material 2 is not influenced by the electric field and furthermore has a constant length. This leads to a mechanical stress in the information converter and subsequently to its bending along the arrow 6.

Alternatively, the information converter of Figure 1 can also be used as a sensor. If the sensor strip 1 is deformed along the arrow 6, for example by an acceleration force or by the start-up of a further component, not shown, this leads to a compression of the upper material layer 3 and an expansion of the underlying material layer 2. The compression of the piezoelectric Material layer 3 leads to a spatial charge separation in the crystal lattice, resulting in a material layer electric field E trains. Thus, an electrical voltage can be measured between the electrical contacts 5 at the top and bottom of the composite strip.

FIG. 2a shows the information converter from FIG

Cut. Shown again are the electrically conductive carrier 2 and the piezoelectric material layer 3. Both layers of material are shear-stiffly connected to each other and clamped in the holder 4. The voltage source 5 generates an electric field E, which acts in parallel to the polarization of the piezoelectric material 3. Such a construction is called a monomorph.

FIG. 2b shows a trimorphic structure. In contrast to FIG. 2a, a piezoceramic material layer 3a and 3b is applied to the carrier layer 2 on both sides. This too

3-layer layer structure is located with one end in a holder 4. When applying a voltage to the both sides conductive outer surfaces of the material layers 3a, 3b is induced in a material layer, for example 3a, a longitudinal strain. Material layer 3b is then switched so that a longitudinal compression is induced there. Thus, the tip of the bending actuator will move to the left in the direction of the material layer 3.

According to the same principle, the multimorph is constructed according to FIG. 2b. This consists of an even number of piezoceramic material layers, in the example of drawing 4. These are designated 3a to 3d. A substrate 2 is not provided in this embodiment. The material layers 3a to 3d are connected such that upon application of a supply voltage 5, the respective deformation of the material layers 3a to 3d on both sides of the symmetry axis of the stack is different. As a result, the force applied by the bending actuator is increased.

Figure 3 shows 4 embodiments of an information converter according to the present invention. Shown is because the base of the bending transducer in the supervision. In cross-section, each of the embodiments 3a-3d can have a construction according to each of FIGS. 2a to 2c.

Figure 3a shows a bending transducer with a base in the form of an equilateral triangle. For aspect ratios of length to width from 2: 3 to 20: 3, the base has an interior angle of 53 ° to 84 °. By means of the Bernoullie bending theory, a bimorphous layer structure in triangular design according to the invention is compared with a surface and volume-identical rectangular structure according to the prior art. For this purpose, the bending transducer according to the invention is clamped at or near the base edge of the equilateral triangle. The movement is tapped off at the opposite triangle tip. The height of the triangle corresponds to the length of the rectangular information converter.

It has been shown that the maximum possible deflection of the bimorph transducer is independent of the geometry. This deflection is calculated too

⁰ 4 h

Here xo denotes the deflection, E _el the electric field which prevails within the piezoelectric material layer 3, h their thickness and 1 the length of the rectangular information converter or the height of the triangular information converter.

For the blocking force of the rectangular converter applies

F _B = -. EE _d .b - Herein, the blocking force F _B, E the modulus of elasticity and b is the width of the clamp.

Surprisingly, it could be shown that the blocking force of the triangular transducer corresponds to the following formula: F _a = - - E - E ", - b -

Thus, the blocking force of the triangular transducer is one-third larger than that of the prior art volume converter.

The quality of a bending transducer is the product of blocking force and idling deflection. The quality therefore has the unity of an energy and thus gives the theoretically possible working capacity of a bending reactor or in one

Sensor generates signal voltage. Since the blocking force of the information converter according to the invention is one third above the known converter, but the idling deflection is identical in both cases, a value which is one third above the prior art also results for the quality criterion.

The mechanical normal stress on the clamping, which is induced in the composite strip by bending back into the opposite extreme position, is positively influenced by the inventive form of the information converter. Thus, the mechanical stress of an information converter according to the prior art to σ (z) _ 9 z S ₁ E ^{~ ~} Äh In contrast, a transducer according to the present invention, a mechanical stress of σ (z) _ 3 z S ₁ E ^~ 2 h

The mechanical normal stress in the material of the information converter is thus reduced by 1/3 in the case of the mold according to the invention. This results in a higher operational stability and a longer operating time until the failure of the information converter.

The results presented here on the basis of a piezoceramic bender actuator apply mutatis mutandis to bi-metal actuators, magnetostrictive actuators and shape memory actuators. Likewise, the results can be transferred to the corresponding sensors.

The information converter according to FIG. 3b has the shape of a right-angled triangle. This makes it possible to put two bending actuators point-symmetrical to a rectangle. This shape enables the production of a rectangular semi-finished product without cutting. This information converter is clamped to the shorter catheter in a holder 4. The movement is then tapped at the intersection of the longer catheter with the hypotenuse. For aspect ratios of length to width from 2: 3 to 20: 3, the base has an interior angle of 34 ° to 80 °.

In order to increase the mechanical load capacity on the tap, the trapezoidal information converter according to FIG. 3c provides a larger area at the end opposite the clamping. This shape results from the fact that the triangular transducer according to FIG. 3a is effectively shortened at its tip. The actual width at the tap and thus the opening angle α near the clamping will be selected by the skilled person according to the desired application. In this case, the maximum possible load capacity at the tap against the increase of the quality criterion and the reduction of the mechanical stress at the clamping should be weighed.

The embodiment according to FIG. 3d has two right angles, so that two transducers can be assembled to a total of one rectangular outer shape by point mirroring of a transducer. This again results in a minimization of the crop as in the embodiment according to FIG. 3b. This form is theoretically due to the fact that the triangular transducer of Figure 3b is effectively shortened at its tip. This in turn increases the load capacity at the tap. To produce an information converter according to the invention, preferably at least two layers of material are first of all connected to each other in a shear-resistant manner to form a semifinished product, wherein a change in length can be induced at least in one material layer. The semi-finished product has a size which corresponds to several information converters ready for use. These are then separated in a further process step from the semifinished product. In some cases, however, the person skilled in the art will also provide for initially separating individual parts of an information converter from individual material layers, and then joining these together to form the finished transducer in a shear-resistant manner.

The separation takes place by cutting or not cutting. For example, predetermined breaking points can be introduced into the material, along which the information converters are then separated by breaking. For a bending transducer according to Figure 1, the cutting takes place as shown in Fig. 4a.

An inventive bending transducer according to Fig. 3a can be manufactured as shown in Fig. 4b). First, first predetermined breaking edges are introduced substantially at right angles to the outer edges of the semifinished product. The distance between these predetermined breaking edges corresponds to the height 1 of the finished transducer, plus the clamping length with which it is inserted in the holder 4. Next, predetermined breaking edges are made to extend obliquely over the substrate. The angle is chosen so that it corresponds to the base angle α of the transducer. According to the desired aspect ratio, the angle between the first and second predetermined breaking edges is selected from the range of about 53 ° to about 85 °. As the last method step, third predetermined breaking edges are introduced, which likewise run transversely over the entire substrate. These have an angle relative to the first sole fracture edges, which corresponds to the negative of the angle between the first and second predetermined fracture edges. When cutting, it is important to ensure that the intersections the second and third predetermined breaking edges come to lie substantially on the first predetermined breaking edges. In this way, there is a good utilization of the semifinished product, wherein only on the edge of a waste remains.

FIG. 4c describes the production of an information converter according to FIG. 3b. First, first and second predetermined breaking edges are attached, as described by the method according to FIG. 4b. In this case, the second solitary rupture edges with the first predetermined rupture edges enclose an angle β which corresponds to the angle between the short catheter and the hypotenuse of the finished transducer. For an aspect ratio of 2: 3 to 20: 3, the angle β is selected from the range of 34 ° to 80 °.

The third predetermined breaking edge is again introduced at right angles to the first predetermined breaking edge into the material, this always running through the intersections of the first and second predetermined breaking edges. As a result, a rectangular semi-finished product can be completely separated into information converters along the predetermined breaking edges thus introduced, without leaving any unused waste.

Claims

claims

1. Information converter, consisting of at least 2 layers of material with a polygonal base, which are shear-stiff connected to each other and wherein at least in a material layer, a change in length is inducible, characterized in that the polygonal base has at least two different internal angles.

2. Information converter according to claim 1, characterized in that the polygonal base area comprises at least one NEN approximately right interior angle

3. Information converter according to one of claims 1 or 2, characterized in that the polygonal base area comprises at least an internal angle of about 35 ° to about 85 °.

4. Information converter according to claim 3, characterized in that the polygonal base area comprises at least one inner angle of about 55 ° to about 80 °

5. Information converter according to one of claims 1 to 4, characterized in that the polygonal base has 3 or 4 vertices.

6. Information converter according to claim 5, characterized in that the polygonal base has 3 vertices.

7. Information converter according to one of claims 1 to 6, characterized in that the cross section of the at least two layers of material decreases along the largest extent of the polygonal base.

8. Information converter according to one of claims 1 to 7, characterized in that a mechanical support is provided in the region of the largest cross section of the at least 2 material layers.

9. Information converter according to one of claims 1 to 8, characterized in that at least one material layer contains a material which exhibits a piezoelectric effect.

10. Information converter according to claim 9, characterized in that a device is provided, with which within the piezoelectric material, an electric field parallel or anti-parallel to the direction of polarization can be generated.

11. Information converter according to one of claims 9 or 10, characterized in that the direction of polarization of the piezoelectric material is substantially perpendicular to the interface of the at least two layers of material.

12. Information converter according to one of claims 9 to 11, characterized in that the piezoelectric material contains at least one lead zirconate titanate and / or a lead magnesium niobate.

13. Information converter according to one of claims 1 to 12, characterized in that it comprises a bending actuator.

14. Information converter according to one of claims 1 to 12, characterized in that it comprises a sensor.

15. Information converter according to claim 14, characterized in that it is a temperature sensor.

16. Information converter according to claim 14, characterized in that it is an acceleration sensor.

17. A method for producing an information converter in which at least two layers of material are joined together to form a semifinished product, wherein a change in length can be induced at least in one material layer, and subsequent singulation of information converters from the semifinished product along predetermined breaking edges, characterized in that the first Sollbruchkanten be introduced substantially at right angles to the outer edges of the semifinished product and second predetermined breaking edges have an angle of about 35 ° to about 85 ° to the first predetermined breaking edges.

18. A method for producing an information converter according to claim 17, characterized in that third predetermined breaking edges are provided substantially at right angles to the first predetermined breaking edges and the second

Sollbruchkanten run through the intersections of the first and third predetermined breaking edges.

19. A method for producing an information converter according to claim 17, characterized in that third predetermined breaking edges are provided which have an angle of about -35 ° to about -85 ° to the first predetermined breaking edges and the intersections of the second and third predetermined breaking edges substantially on the first predetermined breaking edges come to rest.

20. A method for producing an information converter according to claim 19, characterized in that the angle between the third and first predetermined breaking edges corresponds to the negative of the angle between the second and first predetermined breaking edges.

21. A method for producing an information converter according to one of claims 17 to 20, characterized in that the second predetermined breaking edges have an angle of about 55 ° to about 80 ° to the first predetermined breaking edges.

22. A method for producing an information converter according to one of claims 17 to 21, characterized in that the at least two layers of material are shear-stiffly connected to each other by gluing.

23. A method for producing a bending actuator according to any one of claims 17 to 21, characterized in that the at least two layers of material are sintered shear stiff together.

24. Pointer instrument with a bending actuator according to one of the claims 1 to 16