WO2002067283A1

WO2002067283A1 - Electromechanical component

Info

Publication number: WO2002067283A1
Application number: PCT/DE2002/000469
Authority: WO
Inventors: Stefan Kautz; Matthias Marondel
Original assignee: Siemens Aktiengesellschaft
Priority date: 2001-02-22
Filing date: 2002-02-08
Publication date: 2002-08-29
Also published as: DE10108634A1; DE10108634C2

Abstract

The invention relates to an electromechanical component comprising at least one actuator consisting of a shape memory alloy that changes its shape when a given temperature is reached and moves in a change conditioned manner, wherein a heating element (4, 10, 18) that is motion coupled to the actuator (2, 9, 13) is provided.

Description

description

Electromechanical component

The invention relates to an electromechanical component with at least one actuator made of a shape memory alloy, which changes its shape when a certain temperature is reached and moves as a result of the change.

Such an electromechanical component is for example in the form of a circuit breaker device, for. B. known as a circuit breaker. This isolating switch device is used to open and close a circuit that is closed via it in the event of a fault in order to prevent interference-related overvoltages or the like from acting on devices integrated in the circuit and from damaging or destroying them. Disconnect switch devices of this type use an actuator made of a shape memory alloy to open the circuit quickly. These actuators are often also SMA

Actuators (shape memory alloy actuators) named. Such actuators are characterized by the fact that they can change shape depending on their temperature. This is achieved by applying a preferred direction to them by means of suitable form annealing, in which the grains preferentially align themselves during the temperature-related phase change. Single-action actuators are known which, when the temperature rises from a certain transition temperature, change from the shape of the cold state to another, which occurs due to the phase change from martensite to austenite and the grain growth in the direction of the impressed preferred direction. After it has cooled again, the actuator remains in the form it was in, ie it does not change its shape back. This is the case with so-called one-way actuators. Two-eg actuators automatically change their shape between "cold * and" warm * states. When used, for example, in a disconnector device, one-way actuators are often used Use which are coupled, for example, to a spring element, for example a spring clip. The circuit is closed via the spring clip. The actuator is arranged in such a way that it is bent by the spring clip, for example, out of the horizontal position. The horizontal position corresponds to the stamped high temperature shape. If the circuit has to be opened due to a malfunction, the actuator is briefly heated to above the transition temperature so that it converts to the horizontal or elongated form and thereby entrains the spring clip.

In another known type of disconnector device, the switch contact is opened by means of a bimetal strip integrated in the current path and connected to a movable contact part of the switch contact. In the event of an overload, the bimetal strip is usually heated directly. With this type of heating, a curvature of the bimetal strip is also connected, which leads to the switching contact opening. After the heating is no longer present, the bimetallic strip returns to its elongated shape with the switching contact closed.

Also in the electromechanical component according to the invention with an actuator made of a shape memory alloy, fast switching of the actuator which initiates the shape change is crucial for reliable switching. However, since the actuators have a very low electrical resistance due to the material - in contrast to the bimetallic type - direct heating of the actuator to initiate the change of shape usually does not make sense.

The invention is therefore based on the problem of specifying an electromechanical component in which it is ensured at all times that the actuator can be heated sufficiently. To solve this problem, it is provided according to the invention in an electromechanical component of the type mentioned at the outset that a heating element which is coupled to the actuator is provided.

According to the invention, indirect heating of the actuator is proposed, the heating element provided for indirect heating - preferably a resistance heating element - being motion-coupled to the actuator. This movement coupling advantageously leads to the heating element also being moved when the actuator moves and consequently being carried along with the actuator. The heating element is therefore always in the immediate vicinity of the actuator, even if the actuator changes from a first shape to a second embossed shape due to the shape change. This is particularly advantageous during the

Shape change process and then ensure that the actuator can be heated continuously and evenly, regardless of the shape or position it takes.

It is expedient if the actuator and the heating element are in the form of strips or strips and run essentially parallel to one another, the parallel arrangement being maintained even during the common movement. The length of the heating element should be at least a quarter of the length of the actuator. It is therefore not absolutely necessary for the actuator and heating element to be of the same length. Rather, it is sufficient if the heating element only extends over a certain actuator length, because the shape memory alloy from which an actuator used is made has a very high thermal conductivity. As a result, locally limited indirect heating achieves that the entire actuator can be heated to a temperature above the transition temperature in an extremely short time.

In order to be able to implement the largest possible switching path, it is expedient if the actuator and the heating element are clamped at one common point with one end and with the free end are movable. This configuration enables the free end of the actuator, which is generally connected to the switch contact via a shift linkage, by several millimeters, so that a reliable tearing open of the switch contact is ensured.

As already stated, the heating element is expediently a resistance heating element. This can expediently be energized via supply lines lying at its ends. If, as described, the heating element is clamped with the actuator at a common point with one end, the first supply line can rest on the clamping point. At the free end of the actuator, the second supply line is e.g. attached in the form of a copper strand or the like, expediently dotted, so that simple energization and (thus) resistance heating is possible. As a result of the quasi-direct coupling of the actuator and the heating element, it is expedient if an insulation layer, in particular a Kapton film, is arranged between the actuator and the heating element, which separates the actuator and the heating element from one another over most of their length, and above all the actuator from the second supply line insulated so that it is avoided that the heating current flows through the actuator having a very low electrical resistance.

According to a particularly expedient embodiment of the invention, it can further be provided that the heating element is resilient. The heating element is therefore not only used for rapid heating, it is also used to exert a force on the actuator depending on the configuration due to its spring-elastic properties and thereby initiate or support movement of the actuator depending on the direction of force exerted. According to a first embodiment of the invention, the resilient heating element can exert a force on the actuator that counteracts the movement caused by the shape change. In addition to the actual heating function, the spring-elastic heating element also has the function of a spring to. If the actuator is heated and it bends, the spring-elastic heating element is tensioned by the bending and a force which counteracts the movement caused by the deformation is built up. If the heating is now ended and the actuator changes from its hard austenite structure to the softer martensite structure, it is pulled back into the starting position by the restoring force. This configuration is particularly advantageous in the case of a one-way actuator which only changes its shape in one direction as a result of heating and does not convert the shape back when cooling, but only uses a structural change. This actuator is automatically returned by the spring-elastic, tensioned heating element. If the actuator is a two-way actuator, the restoring force is motion-supporting, that is to say the back-conversion movement of the two-way actuator to its initial form, which begins when the actuator cools down, is supported.

According to an alternative of the invention, the configuration can also be such that the spring-elastic heating element exerts a force on the actuator that supports the movement caused by the shape change. Here, the heating element is switched so that it supports the actuator in its movement due to the temperature increase. This configuration is used, for example, in a two-way actuator which, due to its conversion back when the temperature drops, is able to return to its original shape and to take the spring-elastic heating element with it and to brace it.

Overall, the use of a resilient heating element according to the invention in conjunction with a parallel guidance of the heating element and the actuator offers the possibility of being able to arrange the structural unit even with very little space available at low cost and optimized system properties, especially since no separate elements generating a restoring force such as e.g. B. a separate spring element must be provided. Nevertheless, a restoring force exerting on the actuator can of course also be provided, by means of which the z. B. trained as a one-way actuator is returned to the starting position. If necessary, this spring element can also be provided in addition to the spring-elastic heating element if this z. B. exerts a force supporting the deformation due to a temperature increase on the actuator. By means of the additional spring element, it is ensured here that the two-way actuator does not have to do the work for returning to the starting position on its own, rather the spring element acts as a support. Of course, this also applies if a one-way actuator is used.

According to a first alternative of the invention, the actuator and the heating element, and optionally also the insulating layer, can be fastened to one another via an adhesive connection. As an alternative to this, the actuator and the heating element, if appropriate also the insulating layer, can be fastened to one another by means of a fastening means arranged in the region of the free end, in particular a clip or the like. Any fastener that firmly binds the elements together is conceivable.

The actuator itself can be a one-strip actuator, either in the form of a one-way actuator or a two-way actuator. As an alternative to this, it is also conceivable to use an actuator that consists of two parallel-coupled, motion-coupled actuator strips that have different shapes

Change temperatures exists. Since with such an actuator the respective actuator strips change their shape at different temperatures, it is possible to bring the actuator into different defined positions, depending on which temperature is impressed via the heating element. This configuration consequently results in a multi-layer configuration. It can further be provided that a stop is provided which limits the movement path caused by the change in shape or the movement path of the actuator caused by the spring force. Finally, the heating element is expediently made of spring steel.

Further advantages, features and details of the invention result from the exemplary embodiments described below and from the drawings. Show:

1 shows a basic illustration of an electromechanical component according to the invention of a first embodiment in a first position,

FIG. 2 shows the component from FIG. 1 in a second position due to shape change,

3 shows a second embodiment of a component according to the invention in a first position,

FIG. 4 shows the component from FIG. 3 in the second position due to the shape change, FIG.

5 shows a third embodiment of a component according to the invention with an actuator consisting of two actuator strips in a first position,

6 shows the component from FIG. 3 in a second position due to shape change, and

FIG. 7 shows the component from FIG. 2 in a third position due to shape change.

1 shows an electromechanical component 1 according to the invention in a first embodiment. In the component, one embodiment of a known isolating switch establishment z. B. in the form of a circuit breaker. Fig. 1 shows the component only schematically in the form of a schematic diagram, since the exact structure of a disconnector device is not important for the actual functional principle. As a result, only the elements central to the invention are shown in FIG. 1 and the following figures.

The electromechanical component 1 shown in FIG. 1 comprises an actuator 2 made of a shape memory alloy, which in the example shown is designed as a bending strip and is arranged at one end on a fastening part 3. The other, free end of the actuator 2 interacts with known isolating switch devices with a spring clip that is rotatable about an axis. A switch that closes or opens an associated circuit is actuated via this spring clip via a shift linkage depending on the position of the actuator and thus the position of the spring clip.

In parallel to the actuator 2 there is also a strip or band-shaped heating element 4 in the form of a resistance heating element. Between the actuator 2 and the heating element 4, an insulation layer 5 z. B. introduced in the form of a Kapton film. Heating element 4 and insulating layer 5 are expediently thermally stably bonded to one another and form a structural unit. The heating element 4 is also attached to the fastening part 3 at the same end as the actuator 2, e.g. B. welded together with the actuator 2 there.

In order to bring about the change in shape of the actuator 2 from the shape shown in FIG. 1 to the shape shown in FIG. 2, the heating element is heated. For this purpose, a supply line 6 z. B. attached in the form of a copper strand, for. B. soldered. The heating element 4 can be supplied with current via a current source I for heating via this supply line 6 and via the component 3. The Ak- gate 2 is isolated via the insulating layer and due to its distance from the supply line 6.

Fig. 1 shows the starting position of the switching unit. This is assumed when a relatively low temperature T is reached, here T = Ti applies.

In the event of an overload of the circuit, for whatever reason, the heating element 4 is suddenly energized and thus heated. Due to the parallel and adjacent arrangement of the heating element 4 to the actuator 2, this is also heated abruptly. As soon as the temperature is above the shape change temperature, a shape change begins, which results from a change in the structure of the actuator 2, which consists of the shape memory alloy. This will be discussed in the following. In the example shown, the temperature is heated to T = T ₂ , where T ₂ > Ti. The actuator bends downward as shown in FIG. 2. In this case, the heating element, which due to the positioning is necessarily coupled to the actuator 2, is taken along. The movement is limited by a stop 7. Due to the movement of the actuator, the spring clip (not shown in detail) is also moved and the switching linkage is actuated with it, by means of which the electrical contact (also not shown in more detail) is torn open and the circuit is suddenly interrupted. This reliably prevents damage to any external devices integrated in the circuit.

The heating element 4 itself expediently consists of spring steel and has spring-elastic properties. During the movement of the configuration shown from the position shown in FIG. 1 to the position shown in FIG. 2, the resilient heating element 4 is braced. A restoring force F is built up which counteracts the actuator movement, as shown in FIG. 2. This restoring force always pushes the actuator 2 back into the starting position shown in FIG. 1. However, this force is less than the generated counterforce. As long as the temperature T ₂ , which is above the transition temperature, the configuration remains in the position shown in FIG. 2. However, if the temperature drops below the transformation temperature and a new structural transformation begins in the actuator material, it becomes softer. The generated restoring force F is then greater than the counterforce, which is why the heating element can relax and return the configuration to the starting position shown in FIG. 1.

3 shows a second embodiment of an electromechanical component 8 according to the invention. An actuator 9, a heating element 10 and a separating insulating layer 11 are also used here, but the configuration is different from that according to FIGS. 1 and 2. Here the heating element 10 is used arranged directly on the fastening part 3, followed by the actuator 9. The actuator 9 is curved in the starting position shown in FIG. 3, in which the assigned switch and with it the assigned circuit is closed. The heating element 10 is pre-bent according to the shape of the actuator 9. If the heating element 10 is now energized in the event of danger, the actuator 9 is also heated above its transition temperature. It then assumes the stamped elongated shape shown in FIG. 4, in which the associated switching element is opened and the circuit is interrupted. Due to the resilient properties of the heating element, a restoring force F is also generated here.

5 shows a third embodiment of an electromechanical component 12 according to the invention. Here, the actuator 13 consists of two separate actuator strips 14, 15, which are separated from the heating element 18 arranged therebetween via respective insulating layers 16, 17. The two actuator strips 14, 15 and the heating element 18 are in turn arranged on a common fastening part 3. Here, too, the heating element 18 can be powered by a current source I and the fastening part 3 and on the heating element 18 at the free end arranged supply line 19 are energized.

The two actuator strips 14, 15 each have different transition temperatures. For example, the actuator 14 converts at a lower temperature than the actuator 15. The conversion-dependent direction of movement of the actuator strips 14, 15 is the same in the exemplary embodiment shown.

If, starting from the configuration shown in FIG. 5, the temperature T is increased from Ti to T ₂ , only the actuator strip 14 changes its shape, since T ₂ is above the conversion temperature of the actuator 14, but below the conversion temperature of the actuator 15 lies. The entire configuration bends around a first section as shown in FIG. 6. Due to the movement coupling of the two actuator strips 14, 15 and the heating element 18, which in the example shown are coupled to one another in the form of a clamp by means of a fastening means 20 which crosses over the free ends of the actuator strips 14, 15 and the heating element 18, the entire configuration is bent. Since the heating element 18 is also resilient here, a restoring force is generated due to bending. If the temperature were to drop below the transition temperature here, the entire actuator mimic would be returned to the position shown in FIG. 5 due to the relaxation of the heating element 18.

If, starting from the position in FIG. 6, the temperature is increased further to a temperature T = T ₃ which is above the transformation temperature of the actuator strip 15, then this too changes its shape. The entire facial expression bends further around the stop 7 into its end position, as shown in FIG. 7. The heating element is also bent further, which is why the restoring force F generated thereby increases. As stated, all of the actuators or actuator strips shown consist at least partially of a known shape memory alloy. Examples of such alloys are Ti-Ni alloys, the Ti component as well as the Ni

Component form the main components and there may be other alloy partners. In addition, Cu-Al alloys with other alloy partners are also known, it being possible for the proportion of the Al component to be larger or smaller than that of the further alloy partner. Ti-Ni alloys are particularly suitable. So go z. B. from "Materials Science and Engineering *, Vol. A 202, 1995, pages 148 to 156 differently composed Ti-Ni and Ti-Ni-Cu alloys. In "Intermetallic *, Vol. 3, 1995, pages 35 to 46 and" Scripta METALLURGICA et MATERIALIA *, Vol. 27, 1992, pages 1097 to 1102, various Ti ₅ oNi ₅ o-χPd _x shape memory alloys are described. Instead of the Ti-Ni alloys, other shape memory alloys are of course also suitable. For example, Cu-Al shape memory alloys come into question. A corresponding Cu-Zn24A13 alloy is from “Z. Metallkde. *, Vol. 79, H. 10, 1988, pages 678 to 683. In “Scripta Materia- lia *, Vol. 34, No. 2, 1996, pages 255 to 260, another Cu-Al-Ni shape memory alloy is described. Of course, other alloy partners, such as, for example, can be added to the aforementioned binary or ternary alloys. B. Hf, Pd, Au, Pt, Cr or optionally Ti may be added in a conventional manner. For example, the proportion of this at least one further component is less than 5 atomic percent. However, it can also deviate more from this. More possible

Alloy partner of various binary memory metals, including a. also for Ni-Mn alloys, are mentioned in “Transactions of the ASME *, Vol. 121, Jan. 1999, pages 98 to 101.

Claims

claims

1. Electromechanical component with at least one actuator made of a shape memory alloy, which changes shape when a certain temperature is reached and moves as a result of the change, characterized in that a heating element (4, 10) coupled to the actuator (2, 9, 13) is in motion , 18) is provided.

2. Electromechanical component according to claim 1, so that the actuator (2, 9, 13) and the heating element (4, 10, 18) are strip-shaped and run essentially parallel to one another.

3. Electromechanical component according to claim 2, so that the length of the heating element (4, 10, 18) is at least a quarter of the length of the actuator (3, 9, 13)

4. Electromechanical component according to one of the preceding claims, characterized in that the actuator (3, 9, 13) and the heating element (4, 10, 18) are clamped at one common point (3) with one end and are movable with the free end ,

5. Electromechanical component according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that the heating element (4, 10, 18) is a resistance heating element.

6. Electromechanical component according to claim 5, characterized in that the heating element (4, 10, 18) can be energized via supply lines (3, 6, 19) resting at its ends.

7. Electromechanical component claim 5 or 6, characterized in that between the actuator (2, 9, 13) and the heating element (4, 10, 18) an insulation layer (5, 11, 16, 17), in particular a Kapton film, is arranged is.

8. Electromechanical component according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that the heating element (4, 10, 18) is spring-elastic.

9. The electromechanical component as claimed in claim 8, so that the resilient heating element (4, 10, 18) exerts a force on the actuator (3,

9. 13) exercises.

10. The electromechanical component according to claim 8, so that the spring-elastic heating element exerts a force on the actuator that supports the change in shape due to a temperature increase.

11. Electromechanical component according to one of the preceding claims, that a spring element exerting a restoring force on the actuator is provided.

12. Electromechanical component according to one of the preceding claims, that the actuator (3, 9) and the heating element (4, 10), optionally also the insulation layer (5, 11), are attached to one another by means of an adhesive connection.

13. Electromechanical component according to one of claims 1 to 11, characterized in that the actuator (13) and the heating element (18), if appropriate the insulating layer (16, 17) are also fastened to one another by means of a fastening means (20) arranged in the region of the free end, in particular a clip or the like.

14. Electromechanical component according to one of the preceding claims, characterized in that the actuator (3, 9) is a single-strip actuator, or from two parallel, mutually motion-coupled actuator strips (14, 15) that change their shape at different temperatures consists.

15. Electromechanical component according to claim 14, so that the heating element (18) is arranged between the actuator strips (14, 15).

16. Electromechanical component according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that a stop (7) is provided which limits the movement path caused by the change in shape or the movement path of the actuator caused by spring force.

17. Electromechanical component according to one of the preceding claims, d a d u r c h g e k e n n - z e i c h n e t that the heating element (4, 10, 18) consists of a spring steel.