ACTUATOR FOR OPERATING AN ADJUSTING ELEMENT

Abstract

The actuator (2) comprises a piezoelectric actuator element (4), which is 18 connected to an adjusting element (12) for exerting an adjusting movement in the adjusting direction (14). For the transmission of a deflecting movement of the actuator element (4), a housing (6) is formed with a variable-shape displacer (8) enclosed therein. During operation, a deflecting movement of the actuator element (4) is transmitted to the displacer (8), so that the latter is deformed and, as a result of the deformation, performs a yielding movement. The housing (6) in this case forms a guide for the displacer (8), so that the yielding movement of the displacer (8) is oriented in the adjusting direction (14). The adjusting element (12) is also connected to the displacer (8), so that the yielding movement of the displacer (8) is transmitted to the adjusting element (12).

Claims

1. An actuator (2) for operating an adjusting element (12), which when operated performs an adjusting movement, the actuator comprising: at least one electrically activatable piezoelectric actuator element configured to exert a deflecting movement of the actuator element (4), the actuator element (4) being connected to the adjusting element (12) for transmitting the deflecting movement, a housing (6) with a variable-shape displacer (8) enclosed therein configured to transmit the deflecting movement, wherein the actuator element (4) is arranged such that during operation the deflecting movement is transmitted to the displacer (8), so that, as a result of a deformation, the displacer performs a yielding movement, wherein the housing (6) is formed as a guide for the displacer (8) such that the yielding movement of the displacer (8) in the housing (6) is directed in a defined adjusting direction (14), and wherein the adjusting element (12) is in operative connection with the displacer (8) such that the yielding movement of the displacer (8) is transmitted to the adjusting element (12) for exerting the adjusting movement in the adjusting direction (14).

2. An actuator (2) according to claim 1, wherein the displacer (8) is plastic or elastic.

3. An actuator (2) according to claim 2, wherein the displacer (8) that is plastic or elastic is a solid body.

4. An actuator (2) according to claim 1, wherein the displacer (8) consists of silicone or polyurethane.

5. An actuator (2) according to claim 1, wherein the displacer (8) has a Shore A hardness in the range of 30-50.

6. An actuator (2) according to claim 1, wherein the displacer (8) has a greater hardness in a deflected state of the actuator element than in a non-deflected state.

7. An actuator (2) according to claim 1, wherein both the actuator element (4) and the displacer are disposed within the housing (6).

8. An actuator (2) according to claim 7, wherein the actuator element (4) is arranged between a wall of the housing (6) and the displacer (8).

9. An actuator (2) according to claim 1, wherein at least some of the housing (6) is formed from a piezoelectric material.

10. An actuator according to claim 9, wherein the actuator element (4) is oriented in such a way that the direction of its deflecting movement is different from the adjusting direction (14).

11. An actuator according to claim 10, wherein the direction of the deflecting movement of the actuator element is perpendicular to the adjusting direction (14).

12. An actuator (2) according to claim 1, the actuator (2) being in the form of a micro-actuator, wherein the displacer (8) takes up a volume in the range of 10 mm.sup.3 to 250 mm.sup.3.

13. An actuator (2) according to claim 1 wherein the adjusting element has an adjusting displacement (H) of less than or equal to 1 mm.

14. An actuator (2) according to claim 1, wherein the housing (6) is formed as a tubular hollow body that extends in the adjusting direction (14).

15. An actuator (2) according to claim 1, wherein the adjusting element (12) has a guiding element (22), which is guided in or on the housing (6).

16. An actuator (2) according to claim 15, wherein the guiding element (22) is guided in the interior of the housing (6).

17. An actuator (2) according to claim 15, wherein the guiding element (22) is directly in contact with the displacer (8) and seals off the hollow body.

18. An actuator (2) according to claim 1, wherein the housing (6) has an end face closed by a terminating element (10), the terminating element (10) being connected to the actuator element (4) by way of electrical terminal contacts (28).

19. An actuator (2) according to claim 18, wherein the actuator element (4) is fastened to the terminating element (10) by a fixing end.

20. An actuator (2) according to claim 19, wherein the terminating element (10) has a circuit board or is formed from a circuit board, on which circuit board are arranged control electronics (30) for the activation of the actuator element (4).

21. An actuator (2) according to claim 1, wherein the adjusting element (12) is a pin of a Braille display, an adjusting element of a valve, part of an electrical switching element or part of a locking mechanism.

Description

[0039] An exemplary embodiment of the invention is explained in more detail below on the basis of the single figure. This shows a micro-actuator for a Braille display in the manner of an exploded representation.

[0040] The micro-actuator 2 represented in the figure has at least one piezoelectric actuator element 4, in the exemplary embodiment two piezoelectric actuator elements 4, which in the mounted state are arranged together with a displacer 8 in the interior of a housing 6. In the exemplary embodiment, the housing 6 is formed as a tube with a square cross section. The one end face of the housing 6 is closed by a terminating element 10. Arranged at the opposite end of the tubular housing 6 is an adjusting element 12, which in the exemplary embodiment is mounted in the housing 4 displaceably in the longitudinal direction of the same. This longitudinal direction at the same time defines an adjusting direction 14.

[0041] Apart from these components of the actuator 2, a guiding plate 16 with a guiding hole 18 is also represented in the figure.

[0042] In a way corresponding to the use for a Braille display, the adjusting element 12 has a sensing pin 20, which in the assembled state extends through the guiding hole 18. The sensing pin 20 is in this case connected at its foot to a guiding element 22.

[0043] In particular, the adjusting element 12 is formed as a one-piece component, in particular of plastic. With the aid of the guiding element 22, the adjusting element 12 is guided within the housing 6. The guiding element 22 is formed here with a cross-sectional contour that is adapted to the inner cross-sectional contour of the housing 6. In the exemplary embodiment, this is a square cross-sectional contour. The guiding element 22 is formed in the manner of a rectangular plate. Apart from the necessary tolerance play, the cross-sectional area of the guiding element 22 is identical to the free inner cross-sectional area of the housing 6.

[0044] During operation, the adjusting element 12 can be offset in the adjusting direction 14 by an adjusting displacement H. This adjusting displacement H in this case lies in the lower millimetre range, preferably <2 mm and in particular at approximately 1 mm. This adjusting displacement is sufficient for the function of a Braille display. The adjusting displacement H is therefore dimensioned sufficiently to enable a person to feel from the plurality of such sensing pins 20 arranged in a Braille display the respective position (raised or retracted position).

[0045] The overall length of the adjusting element 12 in the adjusting direction 14 is only altogether a few millimetres, for example in the range between 4 mm and 10 mm.

[0046] In the exemplary embodiment, the displacer 8 is a full solid body of a suitable elastic plastics material. A silicone or else a polyurethane is used here in particular as the plastics material. The plastics material used is here has a Shore A hardness in the range between 30 and 50.

[0047] In the mounted state, the two piezoelectric actuator elements 4 are arranged on opposite regions of the wall 24 of the housing 6. The actuator elements 4 are in this case respectively formed as bending transducers, which extend in the adjusting direction 14 as elongated elements in the form of platelets. At their rear end, remote from the adjusting element 12, they respectively have a fixing end 26, by which they are connected to the terminating element 10. In particular, they are also electrically contacted by their fixing end 26 with respect to the terminating element 10. For this purpose, the terminating element 10 has corresponding terminal contacts 28.

[0048] The actuator elements 4 are for example monomorphous bending transducers or else alternatively bimorphous, trimorphous or else multimorphous bending transducers. These typically have a thickness just in the range of a few 100 m. When a suitable control voltage is applied during operation, a bending of the actuator elements 4 takes place, so that they respectively perform a deflecting movement. This is oriented in the direction of the centre of the housing 6, that is to say substantially perpendicularly in relation to the adjusting direction 14.

[0049] The length of the actuator elements 4 corresponds in this case at least approximately to the length of the displacer 8. The actuator elements 4 therefore lie, in particular directly, with their flat side that is facing the displacer 8 against the displacer 8 in full surface-area contact over their entire length.

[0050] In the exemplary embodiment, the displacer 8 has in the adjusting direction 14 a length l in the range for example of 5 mm to 8 mm. It also has a width b in the range of 2 mm. The edge length of the square base area is therefore approximately 2 mm.

[0051] The dimensions of the displacer 8, the actuator elements 4 and also the housing 6 are in this case made to match one another overall in such a way that in the mounted state the actuator elements 4 lie with their one flat side directly against the wall 24 and lie with their other, opposite flat side against the displacer 8. A deflecting movement of the actuator elements 4 is therefore transmitted to the displacer 8 directly, without any backlash.

[0052] The tubular housing is preferably a plastic housing. This has in the adjusting direction 14 a length which is approximately greater than the length of the displacer 8. This overlength lies for example in the range between 2 mm and 4 mm. On the one hand, this overlength serves for receiving and guiding the guiding element 22 of the adjusting element 12 and on the other hand serves for providing a yielding volume for the displacer 8.

[0053] Finally, in a preferred configuration, the terminating element 10 is formed by a circuit board, or a circuit board is also integrated in the terminating element 10. In addition to the terminal contacts already mentioned, control electronics 30 are arranged on this circuit board. The elements of the control electronics 30 are optionally attached on the side facing the inner side of the housing or else alternatively are attached on the outer side of the terminating element 10.

[0054] The terminating element 10 additionally has external terminals, by way of which control signals and/or a supply voltage for the actuator elements 4 can be received.

[0055] During operation, an activation of the actuator elements 4 takes place by way of the terminal contacts 28. When there is an activation of the actuator elements 4, they are deflected in a way corresponding to their construction as bending transducers at their free end, respectively being bent inwardly against the displacer 8 over their entire length from the fixing end 26. As a result, a compression of the displacer 8 takes place in the region of the actuator elements 4. On account of the elastic choice of material, overall the displacer 8 is variable in shape. The displacement of the plastics material by the actuator elements 4 therefore leads as it were to a material displacement and a yielding movement of the displacer 8. As a consequence of the housing 6, only a defined direction, that is to say the adjusting direction 14, is predetermined for this yielding movement of the displacer 8. The displacer therefore changes its length in the adjusting direction 14. This change in length is transmitted directly to the adjusting element 12, which lies directly on the displacer 8. This leads to the desired adjusting movement of the adjusting element 12 in the adjusting direction 14.

[0056] When the actuator elements 4 return, they revert to their starting position, in which they lie flat against the wall 24. On account of the elastic property, the displacer 8 also reverts to the original state, that is to say shortens its length. The adjusting element 12 then automatically moves back again into the retracted position. This takes place for example automatically on account of gravitational force. As an alternative to this, the guiding element 22 is connected to the displacer 8, so that the adjusting element 12 is actively moved back by the displacer 8 into the retracted starting position again. For this purpose, the adjusting element 12 is for example adhesively bonded to the front end face of the displacer 8.

[0057] In the case of a Braille display, a multiplicity of such micro-actuators 2 are arranged next to one another in rows and columns.

[0058] Apart from the application described here in a Braille display, the actuator 2 here can also be used in further technical areas of application. On the one hand, the actuator 2 is for example used in a valve, the adjusting element 12 then being an adjusting element of the valve for opening and closing a flow path for a fluid. In a further application, the actuator 2 is used in the case of an electrical switching element. In this case, the adjusting element 12 is part of a switching element and operates for example a switching contact. Finally, use of the actuator 2 in a locking mechanism is also envisaged. In this case, the adjusting element 12 is formed as a locking element or acts on a locking element.

[0059] The advantages of this actuator can be seen on the one hand in a configuration of a very small size. Furthermore, the lying of the bending transducers in full surface-area contact against the displacer has the effect that the bending transducers are subjected to very uniform loading, whereby a long lifetime is ensured. The construction described here can also be produced comparatively easily in an automated manner, so that only low production costs are incurred.

LIST OF DESIGNATIONS

[0060] 2 Actuator

[0061] 4 Actuator element

[0062] 6 Housing

[0063] 8 Displacer

[0064] 10 Terminating element

[0065] 12 Adjusting element

[0066] 14 Adjusting direction

[0067] 16 Guiding plate

[0068] 18 Guiding hole

[0069] 20 Sensing pin

[0070] 22 Guiding element

[0071] 24 Wall

[0072] 26 Fixing end

[0073] 28 Terminal contacts

[0074] 30 Control electronics

[0075] H Adjusting displacement

[0076] l Length

[0077] b Width