WO2002049059A1

WO2002049059A1 - Electromechanical component

Info

Publication number: WO2002049059A1
Application number: PCT/DE2001/004472
Authority: WO
Inventors: Stefan Kautz; Hannes KÜHL
Original assignee: Siemens Aktiengesellschaft
Priority date: 2000-12-15
Filing date: 2001-11-29
Publication date: 2002-06-20
Also published as: DE10062704A1

Abstract

The invention relates to an electromechanical component comprising at least one actuator consisting of a shape-memory alloy, which changes its shape upon reaching a certain temperature and is displaced as a result of said change. Said component is provided with at least two actuators (2, 3, 8, 9, 15, 16, 21, 22, 28, 29), which are or can be coupled by means of their displacement and which change their shape at different temperatures.

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 implemented, for example, in the form of an isolating switch device. This isolating switch device is used to open a circuit closed via it very quickly in the event of a fault and thus to be able to interrupt it in order to prevent interference-related overvoltages or the like from reaching the

Applied circuit equipment affect and this can be damaged or destroyed. To quickly open the circuit, such isolating switch devices use an actuator made of a shape memory alloy. These actuators are often also called SMA actuators (shape memory alloy actuators). 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. One-way 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 preferred direction. After cooling 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-way actuators automatically change their shape between "cold" and "warm" states. When used, for example, in a disconnector device, one-way actuators are frequently used, which are coupled, for example, with 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 from 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 warmed up above the transition temperature so that it converts to the horizontal or elongated form and thereby entrains the spring clip.

However, it is disadvantageous that the one actuator can only move between two end positions, namely the position that it holds in the cold state and the position that it has in the warm state. However, this only applies to a two-way actuator; a one-way actuator can only be brought into the starting position using a reset element. It is therefore only possible to assume two positions, each of which is assigned a specific temperature or a specific temperature range. For some applications, however, it would be expedient if the electromechanical component were sensitive at more than two temperatures in order to be able to react to different temperature-related situations. Such a component would then make it possible, for example, to switch at different operating temperatures, which could be used to close different circuits, etc.

The invention is based on the problem of specifying an electro-mechanical component which is improved in terms of its sensitivity to temperatures at the actuator end.

To solve this problem, it is provided according to the invention in an electromechanical component of the type mentioned at the outset that at least two motion-coupled or movably tion-couplable actuators are provided that change their shape at different temperatures.

The component according to the invention is characterized by the coupling of two actuators, which carry out the shape change at different temperatures. While both actuators are in a first or initial switch position at low temperatures, one of the actuators changes its shape when a first higher temperature is reached, ie it assumes a second position, which enables a first switch actuation or the like. In a still further increase in temperature now also the second actuator changes its shape due to the inventively provided coupling movement is hereby also moves the other actuator and is guided out of its first ^'switch position, a second switching position is achieved. The actuator system according to the invention is therefore sensitive to different temperatures, so that consequently different temperatures are also detected and the switching state of the component changes as a function thereof. With this component it is therefore possible, for example, to react to changing ambient temperatures and to be able to switch accordingly, for example to open a valve or to switch appropriate displays. In addition, it is of course also possible to actively vary corresponding switch positions, namely when one or all actuators are energized for temperature variation.

According to the invention, the actuators can be designed as one-way actuators or as two-way actuators, that is to say the type of actuator is the same for all the actuators provided. Alternatively, there is also the possibility that one actuator is a one-way actuator and the other is a two-way actuator. The actuator types used in each case are expediently selected on the basis of the type of movement coupling selected.

The actuators can be arranged such that they move in the same direction when there is a change in shape. In this embodiment, the first shape-changing actuator takes the second one along; when the temperature rises further, the shape of the second actuator changes, which moves in the same direction as the first actuator. The facial expressions are guided from the first switching position into a second switching position that has a larger actuating or switching path.

Alternatively, the actuators can also be arranged such that they move in the opposite direction. If the shape of the first actuator changes here, the second actuator is also moved. If the temperature rises further, the shape of the second actuator changes, which, for example, returns the entire facial expression to a position corresponding to or close to the starting position.

Depending on the field of application of the electromechanical component according to the invention, it is conceivable that the actuators react exclusively to the prevailing ambient temperature. Such a configuration of the component is expedient where it is used in an environment with an increased, changing temperature. As an alternative to this, there is of course also the possibility of actively achieving the temperature change required for the shape change, for which purpose one or both actuators can be supplied with current via supply lines. The same current can be applied to both actuators, alternatively there is the possibility that each actuator can be energized separately.

Furthermore, it is expedient if the actuators generate or exert forces of different magnitude on each other during their shape conversion, the actuator that changes its shape at a higher temperature should be the stronger, since it is the shape that has already been converted, which in comparison to the low temperature - The temperature of the "harder" phase structure of the actuator must also be moved when the shape changes. The actuators can consist of different materials in order to achieve differently large forces; additionally or alternatively, the actuators can also have different geometries, in particular cross-sections of different sizes.

According to a first alternative of the invention, the actuators can be designed as strips which are expediently positioned next to one another and parallel to one another, are fixed at one end and are freely movable at the other end. The strips can optionally be insulated from one another by an intermediate layer.

The movement coupling can take place either by the actuators contacting one another during the shape change, that is to say touching one another and taking one with the other. This configuration is particularly useful when the two actuators work against each other. In addition, there is the possibility that the actuators in the region of their free ends are connected to one another via a connecting part, in particular a clamp, so that the actuator, which does not change or is already deformed, is carried along in the same direction even when the actuator moves Reinforce actuators is possible. Furthermore, at least one stop can be provided, against which one of the actuators strikes before the conversion-related end position is reached.

In a further development of the concept of the invention it can be provided that a restoring force generating means, in particular a restoring spring, is provided which is tensioned during the movement-related movement of one or both actuators. This reset means, e.g. B. in the form of a spiral spring, is particularly useful when the actuators are designed as a one-way actuator and both move in the same direction. If the temperature drops below the transition temperature of the actuator, which changes at the lower temperature, both actuators are back in the "Soft" state has passed. By means of the tensioned return spring, they can be pulled back into the starting position. In addition, the return spring can also support an actuator combination consisting of a one-way and a two-way actuator, which "reset" the Actuator system supported by the two-way actuator which returns to the initial state at a sufficiently low temperature.

An alternative to the strip actuators according to the invention provides that the actuators are designed as spiral springs, which are expediently arranged to press against one another, with their opposite ends being clamped in a fixed manner. These actuators work against each other, depending on the prevailing temperature or the temperature at the respective actuator, one spring expands, the other is compressed.

In addition, there is finally the possibility that the actuators are designed as wires that change their length during the shape change. In this embodiment too, it is expedient if a restoring force generating means, in particular a restoring spring, is provided, which is tensioned during the movement-dependent movement of one or both actuators.

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

1 is a schematic diagram of a first component according to the invention with two actuators in different temperature-related positions,

2 shows a basic illustration of a second embodiment of a component with two actuators in different temperature-related positions, 3 shows a schematic diagram of a third embodiment of a component according to the invention with separately energized actuators,

Fig. 4 shows a fourth embodiment of a component according to the invention with over a common circuit bestro ble actuators, and

5 shows a basic illustration of a fifth embodiment of a component according to the invention with two actuators in different temperature-related positions.

1 shows, in the form of a schematic diagram, a first embodiment of an electromechanical component 1 according to the invention comprising two actuators 2, 3, which are accommodated at one end in a holder 4, preferably made of a non-conductive plastic. Its free upper ends are movable.

Practically all shape memory alloys can be used for an actuator. 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 Ti5o i ₅₀ -χPd _x shape memory alloys are described. Instead of the Ti-Ni

Alloys are of course also suitable for other shape memory alloys. For example, Cu-Al shape memory alloys come into question. A corresponding Cu-Zn24A13 alloy is from “Z. Metallkde. ^Λ , Vol. 79, H. 10, 1988, pages 678 to 683. A further Cu-Al-Ni shape memory alloy is described in "Scripta Materialia", Vol. 34, No. 2, 1996, pages 255 to 260. understandable can further alloy partners to the aforementioned binary or ternary alloys such. B. Hf be alloyed in a manner known per se.

The two actuators can be, for example, two one-way actuators. The two actuators change their shape at different temperatures. The actuator 2 changes its shape at a temperature Ti, the actuator 3 changes its shape at a higher temperature T ₂ .

1A shows the initial state at a low temperature o. In this idealized initial state, both actuators 2, 3 designed as strips show their elongated, non-bent "basic shape".

If the temperature is now increased from T ₀ to Ti, the actuator 2 changes its shape, it bends to the left. During its shape-related movement, it strikes the actuator 3, which is still having a "soft" martensite structure, it picks it up and thereby also bends it. At the end of the actuation path's change-dependent travel, an electrical contact 5 is actuated, for example.

If the temperature is increased further, the actuator 3 changes its shape when a temperature T _{2 is reached} . The actuator 3 is designed to be stronger than the actuator 2, so that when the phase of the actuator 2 changes to the “hard” austenite phase, the actuator 2 already present in the “hard” austenite phase is carried along. When the shape of the actuator 3 changes, it moves in the opposite direction, that is to say the actuator system is moved away from its contact attack, and the contact 5 is no longer touched or closed.

Since both actuators 2, 3 are one-way actuators, they remain essentially in the position shown in FIG. IC, even if the temperature is reduced again to a temperature below Ti. If the temperature is When the temperature rises to Ti, the actuator 2 moves again to the left and takes the still "soft" actuator 3 with it. If the temperature rises again, the actuator 3 is converted again with the sequence described above. 5

It should be noted that the actuator 3 can also be designed such that it bends significantly further to the right than shown in FIG. IC, and with it the actuator 2. It is then possible to add another one, not shown here

10 and to the right of the actuator system arranged contact to contact or close. In this case, however, it is expedient if at least the actuator 2 is designed as a two-way actuator, which “returns” to its basic position shown in FIG. 1A at a temperature <Tχ and thus the actuator

15 tormimik leads from their contact with the second, not shown contact point.

Finally, with reference to FIG. 1B, reference is made to the stop 6, which is shown here only by way of example, and which detects the movement of the

20 two actuators 2, 3 limited. This limitation of the travel is advantageous in suppressing long-term aging effects and in such a way that the desired travel is covered even after the actuator has been actuated very frequently. In this context, the still unpublished

25 German patent application 100 392 03.2, in which such an electromechanical component is described in more detail.

FIG. 2 shows a second electromechanical component 7 according to the invention, which likewise holds two actuators 8, 9 u, which change their shape at different temperatures. The free ends of the two actuators 8, 9 are firmly coupled to one another in motion by a connecting part 10, advantageously in the form of a clamp. On the actuator 8 further 35. A reset element 11, z. B. in the form of a return spring which is clamped at the other end. Starting from the starting temperature To, at which the actuator mimic shows the starting position shown in FIG. 2A, the temperature now becomes a temperature. T _x increases, the actuator 8 also changes here and bends to the left. Due to the coupling of motion, the actuator 9 is also taken along. As FIG. 2B shows, the shape change of the actuator 8 leads to the fact that a first contact point 12 is contacted. Due to the movement of the actuator mimic, the resetting means 11 is simultaneously tensioned.

If the temperature is now increased further to the temperature T ₂ , the second actuator 9 also changes. It can be seen that it bends in the same direction as the actuator 8, which is taken along due to the movement coupling via the connecting part 10, the entire one Facial expressions bend even further to the left and contact the second contact point 13. Thus, two different contact points can be approached at the different temperatures. When cooling below the temperature T ₂ , the phase of the actuator 9 changes back into the “soft” martensite phase. Due to the restoring force of the restoring means 11, the actuator mimicry is withdrawn into the position shown in FIG. 2B, where the first Contact point 12 is contacted again, and upon further cooling below the temperature Ti, the entire facial expression is pulled back into the starting position shown in FIG.

1 and 2 show electromechanical components 1, 7 in which the actuators react to the prevailing ambient temperature, FIG. 3 shows an electromechanical component 14 according to the invention in which the two actuators 15, 16 are connected via separate circuits 17 , 18 can be energized separately. An insulation layer 19 is provided between the actuators 15, 16. With this configuration, the temperature of each actuator 15, 16 can thus be set individually via the respective circuit 17, 18 and the switching or movement behavior of the actuator mimics can be controlled in a defined manner. An alternative embodiment of an electromechanical component 20 according to the invention is shown in FIG. 4. Here, the two actuators 21, 22, which are electrically coupled at their end facing the holder 23 via a conductive connecting part 24, are energized together via a common circuit 25. For this purpose, the free ends are connected to the current source shown via a common line connection 26. In this embodiment, the temperature of the two actuators 21, 22 is thus increased simultaneously and uniformly via the current impressed together. The respective actuator changes depending on the given temperature. The "working temperature" of the complete actuator system can thus be controlled via a circuit.

Finally, FIG. 5 shows an electromechanical component 27 according to the invention in a fifth embodiment. This u comprises two actuators 28, 29 designed as spiral springs, which are clamped at their respective ends at corresponding brackets 30, 31. With their free ends, the actuators 28, 29 are coupled in motion via a contact element 32.

If, starting from the initial state shown in FIG. 5A, the temperature is raised to i at a temperature T ₀ , the actuator 28 first changes its shape, the spiral spring expands. The spiral spring 29, which is still in the “soft” martensite structure, is compressed. By extending the actuator 28, the contact element 32 is simultaneously moved to the right and contacts a first contact point 33.

If the temperature is now increased to T ₂ , the actuator 29 changes its shape and expands. Since it is dimensioned or selected in its material such that it can exert a greater force than the actuator 28 opposite it in the "hard" austenite structure, the actuator 28 is compressed. The contact element 32 is pushed to the left and contacts the second contact point 34 at the end of the travel range.

In this embodiment, both actuators 28, 29 are expediently designed as two-way actuators, which return to the initial state shown in FIG. 5A after a temperature drop below Ti.

As an alternative to the embodiment shown in FIGS. 5A-C, it is also conceivable to connect two springs in series, one spring being firmly clamped in place and, for example, the movable switching contact being fastened to the free end of the other spring. At the temperature Ti, for example, the clamped spring first lengthens, which also displaces the other spring together with the switch contact. At T ₂ , this spring also expands in the same direction as the first, so that a considerable distance or switching distance can be covered.

Finally, it should be noted that the different

The actuating force of the two actuators can either be caused by the fact that the two actuators are made of different materials, or that the two actuators are of different dimensions, that is to say they have different shapes, in particular with regard to the cross-sectional area. A thicker actuator is stronger than a thinner actuator. Overall, a free choice of the materials used and the free design of the shapes. B. with known bimetallic components very large travel and a remarkably large actuating force.

The invention is not restricted to the examples shown. The design of the actuator mimics with regard to the arrangement of the actuators, the directions of movement of the actuators, the type of actuator (one or two-way) and the actuator shape (strip, spring or wire) can be chosen as desired and adapted to the respective application.

Claims

claims

1. Electromechanical component with at least one actuator made of a shape memory alloy, which changes its shape when it reaches a certain temperature and moves as a result of the change, since you are characterized by the fact that at least two actuators (2, 3, 8, 9, 15, 16, 21, 22, 28, 29) are provided, which change their shape at different temperatures.

2. Electromechanical component according to claim 1, since you rchgek characterized that the actuators (2, 3, 8, 9, 15, 16, 21, 22, 28, 29) one-way actuators or two-way actuators or that one actuator is a one-way actuator and the other is a two-way actuator.

3. Electromechanical component according to claim 1 or 2, d a du r c h g e k e n z e i c h n e t that the

Actuators (2, 3, 8, 9, 15, 16, 21, 22, 28, 29) are arranged in such a way that they move in the same or the opposite direction when there is a change in shape.

4. Electromechanical component according to one of the preceding claims, that a one or both actuators (16, 16, 21, 22) can be energized via supply lines.

5. Electromechanical component according to claim 4, so that the two actuators (21, 22) can be acted upon with the same current, or that each actuator (15, 16) can be energized separately.

6. Electromechanical component according to one of the preceding claims, dadurchgeke nn - is characterized in that the actuators (2, 3, 8, 9, 15, 16, 21, 22, 28, 29) generate or exert forces of different magnitude on each other during their shape transformation.

7. Electromechanical component according to claim 6, characterized in that the actuators (2, 3, 8, 9, 15, 16, 21, 22, 28, 29) consist of different materials and / or have different geometries, in particular cross sections of different sizes. sen.

8. Electromechanical component according to one of the preceding claims, dadurchgekennzeic hn et that the actuators (2, 3, 8, 9, 15, 16, 21, 22) ^{'are formed} as strips.

9. Electromechanical component according to claim 8, so that the strips are insulated from one another by an intermediate layer (19).

10. Electromechanical component according to claim 8 or 9, since you rchgek characterized that the side by side and parallel to each other positioned actuators (2, 3, 8, 9, 15, 16, 21, 22, 28, 29) with one end fixed and with the other end are freely movable.

11. The electromechanical component as claimed in claim 10, so that the actuators (8, 9) are connected to one another in the region of their free end via a connecting part (10), in particular a clamp.

12. Electromechanical component according to one of claims 8 to 11, since you rchgek characterized that at least one stop (6) is provided against the one of the actuators (2, 3) strikes before reaching the change-related end position.

13. Electromechanical component according to one of claims 8 to 12, so that a restoring force generating restoring means (11), in particular a restoring spring, is provided, which during the change-related movement of one or both actuators

(8, 9) is tensioned.

14. Electromechanical component according to one of claims 1 to 7, d a d u r c h g e k e nn z e i c h n e t that the actuators (28, 29) are designed as spiral springs.

15. Electromechanical component according to claim 14, so that the spiral springs press against one another and their opposite ends are arranged in a fixed manner.

16. Electromechanical component according to one of claims 1 to 7, that the actuators are such that the actuators are wires.

17. The electromechanical component as claimed in claim 16, so that a restoring force generating means, in particular a restoring spring is provided, which is tensioned during the change-related movement of one or both actuators.