WO2012013180A2

WO2012013180A2 - Actuator having a shape-memory alloy

Info

Publication number: WO2012013180A2
Application number: PCT/DE2011/001488
Authority: WO
Inventors: Bernhard Kordowski; Volker Westerwick; Andreas Ziganki; Michael Scholz
Original assignee: Kiekert Aktiengesellschaft
Priority date: 2010-07-30
Filing date: 2011-07-20
Publication date: 2012-02-02
Also published as: WO2012013180A3; DE102010038700A1; DE102010038700B4

Abstract

The invention relates to an actuator, by means of which thermal energy is converted into mechanical work. The aim of the invention is to create a functional actuator on the basis of a shape-memory alloy. In order to achieve said aim, an actuator comprises an actuating element, which can be moved from an initial position to a final position with the aid of a drive device, which comprises a shape-memory alloy. Due to the movement to the final position, contact is established between the shape-memory alloy and a heat sink. Alternatively or additionally, due to the movement to the final position, the current flow by means of which the shape-memory alloy is heated is stopped or at least reduced using a switching element.

Description

Actuator with shape memory alloy

The invention relates to an actuator, with the heat energy in

mechanical work with the help of a shape memory alloy

is converted, in particular for locks or

Closing devices is used. The actuator includes a

Stellelement, which from a starting position with the help of

Shape memory alloy can be moved to an end position. A shape memory alloy is a material that is found in

Exceeding a material-dependent activation temperature is suddenly deformed. It is therefore the temperature of the

Shape memory alloy changed so that it changes the shape by leaps and bounds. The sudden change in shape thus caused causes the movement of the control element from the initial position into the

End position. If the actuator to be moved back to the starting position, the output temperature of the

Shape memory element restored. From the document DE 3820877 AI is an actuator for

Remote operation of locks and locking devices, in which, for example, a trigger lever is moved by a memory alloy called there memory alloy. From this

Document is known inter alia, a plurality of a

Memory alloy existing wires so through each other

Link to connect that the effective wire length is increased.

From the document DE 29914843 Ul, an actuator is disclosed comprising a shape memory alloy, which is a heat actuable switch. For cooling, a cooling plate is used.

It is an object of the present invention, a functional, preferably in locks of (motor) vehicles and buildings usable actuator based on a shape memory alloy (Shape Memory Alloy) to create.

To achieve the object, an actuator comprises an actuating element, which from an initial position to an end position by means of a

Drive device can be moved, the one

Shape memory alloy includes. Through the movement in the

End position, a contact between the shape memory alloy and a heat sink is made, Alternatively or additionally, the current flow is stopped or at least reduced by the movement in the end position by means of a switching element, with the

Shape memory alloy is heated. By making contact with a heat sink in the end position, the shape memory alloy can be rapidly cooled after reaching the end position. By cooling, a rapid movement of the actuating element can be brought into its initial position or at least made possible. By interrupted in the end position of the heating current for the shape memory alloy, in particular by short circuit or at least reduced, the

Shape memory alloy from overheating and thus the actuator protected from damage. With such an actuator, an actuator can be quickly moved from a starting position to an end position and without much time delay then back, so as to actuate, for example, another component mechanically. Such a constructed actuator can be built very compact.

In the initial position, there may already be a first contact between the shape memory alloy and the heat sink. Of the

Contact area increases in this case, when the actuator is moved to the end position, the actuator has reached the end position, so has the contact surface between the Shape memory alloy and the heat sink then increased by a multiple.

In a particularly simple embodiment of the invention, the drive device comprises a wire, which consists of the

If the wire is heated, it contracts in one embodiment of the invention and thereby pulls the actuator from its initial position towards the end position. In the end position, the wire attaches to the heat sink, Preferably, the wire contacted then more than 50% of the

Heatsink, more preferably more than 70%, and based on the total length of the wire, so as to be able to cool particularly well. In particular, with the help of a spring, the cooled wire is stretched back to its initial length and brought into the starting position.

The drive device may not necessarily comprise a wire. The drive device may for example also be a rod or comprise a rod. However, a wire can be more flexibly adapted to existing geometries or incorporated into technically advantageous geometries due to its flexibility compared to a rod.

It is not mandatory that the wire or a

Comparable means contracts by heating or shortened to move an actuator from a starting position to an end position, Thus, a biased in the starting position spring may be present, which presses the actuating element in the direction of the end position. The still cool and thus not stretched wire holds the actuator initially in its end position, If the wire is heated, it expands. The actuator then moves by spring force into the end position,

However, it is advantageous that the actuating element by the

The aforesaid shortening of a wire or similar means pulled into the end position, because with the help of

Shape memory alloy can be generated a large force. It must then be provided so no major spring force acting permanently on the Sfellelement and this would then permanently burden with high force.

In one embodiment, the wire terminates with an adjacent surface of the heat sink in the initial position

Angle. If the actuator is moved to its end position, so this angle is reduced until finally the wire on the

Surface of the heat sink is applied and no angle greater than 0 ° longer exists.

In one embodiment of the invention, the two wire ends are laterally adjacent to a particular rod-shaped or

rod-like actuator mounted so that the wire with the

Adjusting element or the rod in the initial position includes an acute angle greater than 45 °. This angle is special

preferably between 60 ° and 80 °. The wire is also connected to the arranged between the two fixed ends actuator and leads for this purpose in a convenient

Embodiment through a bore or lateral recess of the actuating element. With this embodiment, a particularly large stroke movement of the actuating element can be achieved without the actuator threatening to tilt, since then the wire can be hooked particularly quickly and easily into the recess.

In one embodiment of the invention, each end of the wire is secured to a heat sink made of an electrically conductive material, particularly a metal such as brass. To heat the wire, a voltage is applied to the two heat sinks. In the starting position, a current now flows through the wire. The wire is heated and deforms Exceeding the material-dependent activation temperature. As a result of the deformation, the actuating element is moved in the direction of the end position or at least makes such a movement possible. An electrical connecting element made of electrically conductive material is provided on the actuating element

Material attached, which is moved against the two heat sink, when the actuator is moved in the direction of the end position, in the

Finally, the electrical connection element contacted the two heat sinks, so that then a current can flow through the electrical connection element to the other heat sink, the previously flowing through the wire current is reduced accordingly or even negligible. The electrical connection element therefore causes a short circuit when the current flowing through the wire becomes at least negligibly small. In this embodiment of the invention, the two heat sinks are therefore also part of the

Switching element, which allows a technically particularly simple, compact design.

In one embodiment, the actuator comprises a spring which

is biased at least in the final position. This spring moves the actuator back to its original position when the

Shape memory alloy returns to its original shape by cooling,

With the actuator is in an embodiment of the invention a

Moved component, and in particular a component of a locking device preferably for a motor vehicle or for a

Building, such as the known from the document DE 102008012439 AI sliding connection element of a

Locking device of a motor vehicle body. In a

Embodiment, the actuator is part of a device for unlocking a lock, so for example in the manner known from the document DE 102004 040566 AI. In one embodiment of the invention, the actuator is incorporated in an electrical component carrier, such as in the known from the document DE 10320441 B3 Component carrier, Such a component carrier is in particular part of a door closure, in particular for a motor vehicle or for a building. The shape memory alloy is preferably selected such that the activation temperature is between 100 ° C and 150 ° C, in particular when the actuator is in a motor vehicle

is used. It is expedient to provide an activation temperature of less than 150 ° C, since such a temperature is regularly low enough to be used materials such as

Do not damage plastics.

The actuator is preferably constructed so that the length of a wire consisting of the shape memory alloy through

On the one hand, such a change in length is sufficient to be able to produce a stroke of the actuating element which is relevant to practice. On the other hand, such an excessive

Changing the shape of the wire avoided, which could result in excessive, destructive loads.

A diameter of the wire of 0.1 to 1 mm, preferably from 0.2 to 0.4 mm has proved to be useful. The actuator is used in particular in a lock or a

Closing device used, the lock or the locking device may be part of a motor vehicle or building.

Show it

Flg. 1: Actuator in the starting position

Fig.2: Actuator in the end position

3: wire guide by actuator 4: improved embodiment

Fig.5: further embodiment

Fig .: 6: Switching principle

Figure 1 outlines an actuator 1 with a rod-shaped

Control element 2, which is mounted longitudinally displaceable through bores in the housing 3. The actuator 1 comprises as a drive means a wire 4, which consists of a shape memory alloy. The two ends 5 and 6 of the wire 4 are attached to two heat sinks 7 and 8. The ends 5 and 6 of the wire 4 can be clamped by means of screws 9 and 10, for example. The wire 4 is in

Area of the actuating element 2 by a guide member 11 arcuately held and guided so as to avoid kinks in the wire 4, which could damage the wire 4. The guide member 11 is preferably made of a relatively soft material such as plastic and is attached to the actuator 2. The wire 4 passes through a lateral recess in the control element 2 and can therefore be inserted particularly easily and quickly into the recess. The wire is in the recess, the wire is held by this recess.

Adjacent to the guide element adjoins a serving as an electrical connecting element metallic rod or pin 12, which in a groove of the

Can extend into the guide element to stabilize the position of the electrical connection element 12. A leading around the actuator 2 spring 13 is supported in the prestressed state

on the one hand against the housing 3 and on the other hand against the electrical connection element 12, due to the bias of the spring 13 presses the actuator 2 in its initial position. The wire 4 is thereby mechanically tensioned and held in its intended position, From the housing 3 lead electrical contacts 14 and 15 of the heat sink 7 and 8 out and in opposite directions. When a voltage is applied to the electrical contacts, an electric current flows through the wire 4. The wire 4 in itself constitutes an electrical resistance and heats up due to the electrical current flowing through it. By the

Heating, the wire 4 contracts, whereby the adjusting element 2 is moved in the direction of the arrow 16 and thus in the direction of the end position.

In the initial position of the wire 4 closes with the control element 2 at an angle which is in particular between 60 and 80 °, In the illustrated embodiment, the angle = 70 °, By such an angle is achieved that the associated with a shortening of the wire stroke of the actuating element 2 is significantly greater than the shortening,

The end position is shown in FIG. The electric

Connecting element 12 is now pressed against the two contact tips 17 and 18 of the heat sink 7 and 8. In addition, the wire 4 is predominantly on the two heat sinks 7 and 8 and contacted in this sense, the two heatsink.

A current, which is generated by voltage applied to the two contacts 14 and 15, now flows due to the much larger

Cross-sections practically completely through the two heat sink 7 and 8 and through the electrical connection element 12 and not through the wire 4. The wire is then no longer heated by the introduced short circuit and therefore can not overheat.

Heat can rather be accelerated out of the wire due to the corresponding contact in the heatsink. If the current flow is interrupted, the wire cools quickly and assumes its original shape. The spring 13 then presses the actuator 2 in his starting position back. The actuator is therefore mainly used when a short mechanical pulse is to be generated.

The housing 3 is 59 mm wide and 19 mm high in the illustrated embodiment. The case depth is 8.1 mm. The weight of the actuator shown was without the metal

Actuator only 10 g. The weight of the actuator was 6g. With the help of the invention, therefore, an actuator with a weight of less than 20g can be easily manufactured. The actuator can therefore be built very compact. The contacts 14 and 15 do not need to be led laterally out of the housing 3 as shown. Instead, for example, they may extend up out of the housing 3. With the actuator shown in Figures 1 and 2 succeeds with the specified housing dimension by shortening the wire 4 by 4.8%, a stroke of the actuator of 4 mm. Since the actuator 2 leads out of two sides of the housing, the actuator can be designed for stroke or train. The diameter of the wire 4 can be adapted to the desired situation. With a thicker wire, a higher lifting or pulling force can be generated. A thinner wire cools faster and therefore allows greater dynamics.

It has been found that with a voltage of 12 V and a current of 3A, the end position of the control element can be maintained for several seconds without it "fluttering." In order to effect an adjustment of the control element, a voltage of at least 5V at a current of at least 1A. After switching off the current, a cooling time of one was sufficient

Second to make the actuator jump back to its original position. Within one second, the actuator could be moved by switching the current from the starting position to the end position. In the figure 3, a guide of the wire 4 by a lateral

Recess 19 in the control element 2 illustrates.

FIG. 4 shows an improved embodiment comprising a spring 20. The spring 20 is between the electrical

Connecting element 12 and the guide member 11 is arranged.

For example, the electrical connection element 12 is slidably mounted and can therefore be moved along the control element 2. Shortened the wire due to the passing of the

Activation temperature, the electrical connection element 12 is resiliently pressed against contact tips 17 and 18. An abrupt loading of the wire 4 on reaching the end position is so

avoided, which extends the life of the wire 4. However, the electrical connection element 12 is preferably fixedly connected to the control element 2 when the guide element 11 is slidably disposed along the control element 2. In this way it is avoided that a shortening of the wire 4 can be stopped abruptly due to heating by a hard stop , The spring force of the spring 20, which is arranged between the electrical connection element 12 and the guide element 11, is preferably greater than the spring force of the spring 13, with the cold wire 4 is pressed into its initial position, the spring 13 presses against the fixedly arranged electrical connection element 12 and moves after a sufficient cooling of the wire 4 the

If the spring force of the spring 20 exceeds the spring force of the spring 13, it is ensured that the spring 20 in the

Starting position is not compressed so strong that this can not unfold the wire 4 gentle effect. If the guide element 11 is arranged to be displaceable relative to the actuating element 2, then the position of the guide element 11 in the

Starting position adjusted by a suitable choice of the spring forces so that the wire 4 is not in the direction of movement (direction end position) on the actuator 2 rests. Even in the end position of the wire is then preferably not in the aforementioned manner. The wire 4 then sets if necessary. Compliant to at least one heat sink in the

End position on. Damage to the wire is thus avoided.

Features of the embodiments, which are not yet mentioned in the claims, need not necessarily be combined with each other, so these can be combined individually with the claimed actuator.

In the figure 5, an embodiment is shown in the existing of a shape memory alloy wire through first

Shape change the arm 21 moves. The displacement of the arm 21 causes a displacement of the actuating element. If the actuator by heating the wire in the direction of the housing side

mounted electrical conductor 22, so contacted this in the end position of the electrical conductor 23 which is attached to the control element 2. Due to the thus induced electrical

Short circuit then flows the current, for example, from the electrical outer contact 14 to the electrical outer contact 15 no longer through the shape memory alloy consisting of the existing wire 4, but via the electrically conductive arm 21 in the electrically conductive actuator 2 in and from here on the short

closed electrical conductors 22 and 23 to the outer contact 15. Further heating of the wire 4 is interrupted,

In the figure 6, the switching principle is illustrated, the wire 4 has a resistor 24. If the switch 26 is closed and the resistance 25 of this parallel electrical line is much smaller than the resistance 24 of the wire 4, the current flow through the wire 4 is almost completely interrupted, but a current flows only under the condition that the switch 27 has previously been closed, which represents the activation of an actuator, LIST OF REFERENCE NUMBERS

1: actuator

2: actuator

3: housing

4: wire

5: wire end

6: wire end

7: heat sink

8: heat sink

9: screw

10: screw

11: guide element

12: metalic rod

13: spring

14: Contact

15: contact

16: arrow

17: contact point

18: contact point

19: recess

20: spring

21: poor

22: electrical conductor

23: electrical conductor

24: electrical resistance

25: electrical resistance

26: electrical switch

27: electrical switch

Claims

claims

1. actuator (1) with an actuating element (2) and one of a

Shape memory alloy formed drive means (4) for moving the control element (2) from a starting position to an end position, characterized by a heat sink (7, 8) contacted by the shape memory alloy by moving the control element (2) in the end position and / or a switching element (12, 17, 18), which by moving the adjusting element (2) in the

End position is operated so that one for heating the

Shape memory alloy flowing electric power is reduced or turned off.

2. Actuator according to claim 1, wherein the drive means a

Wire (4) is or includes, in particular shortened by heating.

3. Actuator according to one of the preceding claims, wherein the drive means (4) with an adjacent surface of a heat sink (7, 8) in the initial position includes an acute angle which is at least reduced in the Endsteüung and in the end position is preferably 0 ° ,

4. Actuator according to one of the preceding claims, wherein the two ends (5, 6) serving as a drive device wire (4) are fixed so that the wire (4) with the Steüelement in the initial position an acute angle greater than 45 ° , preferably greater than 60 °.

5. Actuator according to one of the preceding claims, in which the two ends (5, 6) of a wire serving as a drive device (4) are each attached to a heat sink (7, 8) made of electrically conductive material, wherein the two heat sink / 7, 8) in the

End position via an electrical connection element (12) electrically connected to each other.

Actuator according to one of the preceding claims with a spring (13) by spring force the adjusting element (2) in his

Starting position can press.

Actuator according to one of the preceding claims, comprising a spring (20) arranged between a switching element (12) mounted on the adjusting element (2) and a guide element (11) attached to the adjusting element (2).

Actuator according to the preceding claim, wherein the switching element (12) fixed to the Steüelement and the

Guide element (11) displaceable on the actuating element

is arranged.

Actuator according to one of the two preceding claims, in which the spring force of the spring 20 is greater than the spring force of a spring (13) which is arranged between the actuator housing (3) and the switching element (12) attached to the adjusting element (2).

Actuator according to one of the three preceding claims, wherein between the adjusting element (2) and the wire (4) in the direction of the end position, a distance is present.

Use of an actuator (1) according to one of the preceding claims in a motor vehicle and / or in a vehicle

Closing device,