WO2013068726A2

WO2013068726A2 - Bending transducer and micropump comprising a bending transducer

Info

Publication number: WO2013068726A2
Application number: PCT/GB2012/052735
Authority: WO
Inventors: Jürgen GÜNTHER; Stefan Klump; Michael Riedel
Original assignee: Johnson Matthey Catalysts (Germany) Gmbh; Nunn, Andrew Dominic
Priority date: 2011-11-09
Filing date: 2012-11-02
Publication date: 2013-05-16
Also published as: WO2013068726A3; TW201345135A; DE102011086042A1

Abstract

Bending transducer (2) for deflecting a pumping diaphragm in a diaphragm pump, which transducer has a layered structure (4) comprises a carrier (6), which carrier extends in the longitudinal direction up to a deflecting end (12) and on which there is an applied piezoelectric layer (8a, b), which piezoelectric layer is contacted via electrical contact elements (28a, b), wherein a link holder (14) is fastened to the deflecting end (12) and wherein an actuator (16) is held in the link holder (14), wherein, in the final mounted state in the diaphragm pump, the actuator (16) is connectable to the diaphragm.

Description

BENDING TRANSDUCER AND MICROPUMP COMPRISING A BENDING

TRANSDUCER

The invention relates to a bending transducer, in particular for a micropump, for deflecting a pumping diaphragm, and to a micropump comprising the bending transducer.

Bending transducers are used in a wide variety of technical areas, which use the piezoelectric effect (the internal generation of electrical charge resulting from an applied mechanical force) to generate energy. Further application areas may be exploited by reversing the piezoelectric effect (the internal generation of a mechanical strain resulting from an applied electrical field) so that the bending transducer can act as an actuator for exerting adjusting movements. The present invention relates to an application of the reverse piezoelectric effect.

Bending transducers are particularly distinguished by their compact type of construction, which allows use in confined spaces in small devices and in particular for miniaturization.

Bending transducers are also used in the medical area, for example for atomizers and also for micropumps, by means of which medicaments are dispensed. In particular in the case of patients for whom a medicament has to be administered continuously, for example insulin, the use of micropumps that are constantly carried by the patient is known. In order to achieve the greatest possible comfort for the patient, it is desirable to provide a micropump that is as small as possible. It is also desirable to provide an energy consumption that is as low as possible, in order to ensure that medicaments are dispensed continuously over a period of time that is as long as possible. It is also important here for dosing to be very precise, i.e. a predetermined dosing rate must be maintained continuously with high precision. Against this background, the invention is based on the object of providing a bending transducer for small units, in particular for a diaphragm micropump, that makes high-precision, continuous dosing possible with low energy consumption.

The object is achieved according to the invention by a bending transducer with the features of Claim 1 . The bending transducer extends in the longitudinal direction up to a deflecting end, mounted on which deflecting end is an actuator, which actuator is connectable to, and in the mounted state is preferably connected to, a diaphragm of a diaphragm micropump and deflects the diaphragm periodically. The bending transducer has in this case a layered structure, which comprises a carrier with at least one piezoelectric layer that may be formed from a piezoceram- ic. Preferably, a piezoceramic, in particular precisely one piezoceramic, is arranged on each of both sides of the carrier as the piezoelectric layer. Furthermore, contact elements are provided for the electrical contacting of the piezoelectric layers. Such contact elements may be mechanically fastened to the layered structure, preferably by means of a solder.

In order to ensure high-precision positioning of the actuator in relation to the later installation location, and consequently in relation to the diaphragm, the actuator is fastened to a link holder, which is arranged at the deflecting end of the carrier. The link holder is a separate, independent component, which is connected to the carrier at the deflecting end thereof and which link holder holds the actuator. The link holder is, in particular, a prefabricated structural unit with an integrated actuator, which unit is fastened to the carrier or to the layered structure, in particular by adhesive bonding.

The actuator is reliably kept fixed in place at a defined position by the link holder. It is in this case oriented in particular at an angle of 90° to the plane defined by the layered structure. The actuator itself is preferably flexurally elastic and, in particular, formed from metal, preferably as a simple straight strip. At the end, it expediently has holes or other clearances allowing a positive connection to an adhesive, by which it is connectable to the diaphragm in the final mounting position. The indirect fastening of the actuator to the deflecting end of the bending transducer by way of the link holder makes improved precision possible in the alignment of the actuator, in particular in the setting of its vertical position in terms of height.

The link holder is expediently formed from a different material than the actuator and is in particular formed as a plastic injection-moulded part. The actuator is preferably embedded therein. The plastic therefore surrounds the actuator in a fastening region. The actuator is in this case preferably positioned highly precisely within the link holder. This is implemented by suitable measures during the injection-moulding process, in that, with the aid of aligning elements, the actuator is positioned highly precisely within a mould for the link holder with respect to the bonding surfaces of the link holder. In order to ensure high-precision positioning and to keep the actuator in a defined position during the injection-moulding process, it is expediently provided that the actuator penetrates the link holder, so that it can be held on both sides, for example by the mould itself. The actuator therefore projects from the link holder on opposite sides. An end projecting beyond the link holder on one side can subsequently be removed.

The link holder is fastened, together with the actuator embedded therein, to the deflecting end. In order to ensure high-precision positioning, it is provided that the link holder has a stop edge, with which it bears against the extreme end of the layered structure at the deflecting end. This stop edge is preferably formed by a groove base of a groove that is formed on the link holder. As an alternative to the groove, in principle there is also the possibility of a stair-like step. The deflecting end is accommodated in this groove.

The carrier expediently projects at the deflecting end beyond (in a preferred arrangement) both piezoelectric layers in the longitudinal direction and only the carrier is accommodated by the groove. In this way, an overall link holder height that is as small as possible is achieved, since the groove only engages around the carrier. For positioning the link holder in a way that is as simple and reliable as possible, it expediently extends over the entire width of the layered structure, and therefore particularly finishes flush with the latter on both sides.

The connection of the actuator to the diaphragm of the diaphragm pump takes place during the mounting of the diaphragm pump in a pump housing. High- precision alignment of the entire bending transducer in relation to the diaphragm is required here for a defined pumping result. In particular, the actuator ends at a defined first vertical position in terms of height with a fastening end, in order to ensure the defined deflection of the diaphragm. In a preferred configuration, at least one positioning aid that extends in the direction of the actuator and has a supporting surface is provided on the link holder to achieve this high positioning requirement. With this aid, the entire bending transducer is supported during mounting on an assigned mounting surface, which is formed for example by an auxiliary mounting plate. As a result, the first vertical position in terms of height of the fastening end of the actuator is positioned highly precisely in relation to this supporting surface. The positioning aid is in this case formed in particular in the manner of a spacer cylinder, which has a flat surface at the end as a supporting surface. In order for example to hinder tilting, at least two positioning aids are preferably arranged here, in particular respectively formed on the opposite ends of the link holder. Following precise positioning of the actuator, e.g. following fastening of the actuator to the pumping diaphragm, the assigned mounting surface may be removed to enable free movement of the bending transducer in response to an applied electrical field.

For the electrical activation of the piezoceramic layer, suitable electrical contacting is always required. With the structure that is preferably provided here, in the manner of a bimorphous bending transducer with a carrier and just one piezoelectric layer respectively arranged on each side, in a preferred configuration the carrier is electrically conducting, and consequently forms a common centre electrode for the two piezoelectric layers, e.g. two piezoceramics. For this purpose, the carrier is preferably formed as a CRP (carbon-fibre-reinforced plastic) carrier. The carrier is contacted with the aid of a first contact element, a contact region being formed for this purpose at an end of the carrier that is opposite from the deflecting end. In this contact region, the carrier projects beyond the piezoelectric layer and the contact region is defined between the end of the carrier opposite from the deflecting end and the piezoelectric layer. At the same time, a metal layer, in particular a copper foil, is preferably applied on said contact region, in order to achieve contacting of the carrier over a large area. On this metal layer, the first contact element is fastened in an electrically contacting manner. The contact region is preferably formed just on one side of the carrier, and on the opposite side the piezoelectric layer is taken through completely to the end of the carrier (i.e. the end of the carrier opposite from the deflecting end), in order to make the most optimum possible use of the length available.

For the electrical contacting of the piezoelectric layers, the respective piezoceram- ic is preferably metallized on each of both sides to form a contact layer. In particular, the contact layer is applied by sputtering. The layer thickness is in this case preferably only approximately 150 to 250 nanometres and is in particular approximately 180 nanometres. The contact layer is in this case preferably distinguished by a chromium-nickel-gold layered structure, the individual layer thicknesses preferably being substantially identical and, for example, 60 nanometres. The chromium layer is in this case the layer facing the piezoceramic, the nickel layer is the middle layer and the gold layer is the outer layer.

This contact layer is contacted with the aid of the second contact element, which in a preferred configuration is formed in an L-shaped manner and in particular as a metal bending strip. One of the L legs is in this case led along the side, in particular a longitudinal side, of the layered structure, the L leg maintaining an insulating spacing with respect to the side of the layered structure. This spacing expediently lies in the range from 0.1 to 0.3 mm. This reliably avoids electrical shorting of the layers of the layered structure. At the same time, it makes it possible for all the electrical terminal contacts to be led to one side. With a view to reliable insulation, an adhesive material of an insulating material is preferably introduced into the insulating spacing. The first contact element is expediently formed and arranged in the same way. The two contact elements are intended to be positioned highly precisely at a defined vertical position in terms of height within the later pump housing. In order to make this possible, the contact element is mechanically fastened, and electrically contacted, by its one L leg, the fastening leg, to a fastening point, the fastening point being kept at a distance from a side edge of the layered structure. This makes it possible that, during mounting, the L-shaped contact element is slightly bent away upwards, therefore with the overall effect of elastic yielding. The contact elements are in this case preferably formed in the manner of an elastic metal bending strip. The positioning precision with respect to the vertical position in terms of height is in this case for example in the range from 0.02 to 0.05 mm, in each case with reference to an upper plane of the layered structure of the bending transducer. The "free" ends of the two contact elements preferably lie at an identical height.

In a preferred configuration, the electrical contact elements are soldered onto the piezoelectric layer, in particular with the aid of a thermode soldering process. On account of the extremely thin sputtered-on contact layer, a conventional soldering process is not suitable for this. This would lead to destruction of the layer. At the same time, however, this soldering process offers simple and reliable process control during the production of the bending transducer. Thermode soldering is a temperature-controlled soldering in which a soldering head is placed onto the joint to be soldered and then its temperature is controlled. In particular, the soldering head is placed on cold and subsequently goes through a defined soldering profile. Only after solidification of the solder is the soldering head removed again in the cold state.

Particularly for this process, it is expediently provided in this case that, prior to the soldering operation, the contact elements are provided with a pretinning as the solder and no more additional solder is applied during the actual soldering process. This makes particularly efficient and reliable soldering possible, at the same time ensuring very gentle treatment of the thin contact layer. The object is also achieved according to the invention by a micropump with such a bending transducer.

The dependent claims contain inventive aspects that are in part self-evident. The right to submit divisional applications with respect to these independently inventive aspects, irrespective of the configuration of the link holder, is reserved. This applies in particular to the configurations of the preferably L-shaped contact elements according to the features of Claims 10 to 13, the soldering of contact elements on a sputtered contact layer, in particular with the aid of the thermode soldering process according to Claim 14, and the use of pretinned contact elements, in particular in combination with the thermode soldering according to Claim 15.

An exemplary embodiment of the invention is described in more detail on the basis of the Figures. These show in simplified representations:

Fig. 1 a perspective view of the upper side of the bending transducer,

Fig. 2 a perspective view of the underside of the bending transducer according to Fig. 1 ,

Fig. 3 a side view of the bending transducer according to Fig. 1 and 2,

Fig. 4 a perspective exploded representation of the bending transducer,

Fig. 5 a perspective view of a link holder,

Fig. 6a, 6b cross sections through the link holder according to Fig. 5 in different positions,

Fig. 7 an end view of the link holder according to Fig. 5,

Fig. 8 a simplified exploded representation of a micro diaphragm pump with a bending transducer and

Fig. 9 a sectional representation of the micro diaphragm pump according to

Fig. 8.

In the Figures, parts that act in the same way are provided with the same numerical designations. The bending transducer 2 that is represented in the Figures is fornned in its preferred configurational variant as a bimorphous bending transducer 2, which has a layered structure consisting of a central carrier 6 and piezoelectric layers 8a, b provided on both sides of the carrier. The piezoelectric layers 8a, b are fornned as piezoceramic plates. The thickness of the entire layered structure 4 is typically below 1 mm, for example in the range of 0.8 mm. In the exemplary embodiment, the three layers, that is to say the carrier 6 and the two piezoelectric layers 8 each have the same thickness. The carrier is preferably a fibre composite material, in particular a CRP carrier, which has an electrical conductivity. The bending transducer 2 extends in the longitudinal direction 10 from a contacting end to a deflecting end 12. At the deflecting end 12, a separate component, referred to as the link holder 14, is fastened to the layered structure 4, in particular by adhesive bonding. The link holder bears an actuator 16. In the exemplary embodiment, the link holder 14 is formed as a one-piece plastic injection-moulded part, in which the actuator 16 is embedded. The link holder 14 has a groove 18, which extends over the entire link holder 14. The link holder 14 in turn extends over the entire width of the layered structure 4. Formed at the opposite end sides of the link holder 14 are positioning aids 20 in the form of supporting cylinders, the free end face of which forms a supporting surface 22.

Arranged exactly midway between the two positioning aids 20 is the actuator 16. In this case, it lies exactly on a centre line that joins the centre points of the positioning aids 20 to each other. The actuator 16 is formed as a flexurally elastic strip, in particular a metal bending sheet. In the exemplary embodiment, the actuator 16 has two holes 24 at the end, on a fastening end 23. The actuator 16 passes completely through the link holder 14, from the underside thereof to the upper side. The actuator 16 is embedded highly precisely within the link holder 14. This means that its distance from the side surfaces, both in the longitudinal direction 10 and in the transverse direction thereto, is aligned exactly. Of particular importance here is the exact alignment of the positional height of the actuator 16, a first vertical position in terms of height H1 being defined in relation to the supporting surface 22. During mounting, the bending transducer is placed with the supporting surfaces 22 onto a defined mounting plate and subsequently fastened in the posi- tion in terms of height defined thereby, so that the actuator 16 is aligned with its fastening end 23 at an exact position in terms of height. The actuator 16 is oriented at an angle of 90° to the layered structure 4, and consequently with respect to the longitudinal direction 10. Overall, the actuator projects beyond the supporting surfaces 22 in the transverse direction perpendicularly to the longitudinal direction 10 by the first vertical position in terms of height H1 . The projection is in this case for example approximately 0.5 mm, the length of the positioning aids 20 being slightly over 1 mm.

The entire bending transducer 2, including the link holder 14, has a length of for example 10 to 20 mm, in particular a length of 15 mm. It is formed approximately rectangularly overall, with a width that corresponds to approximately 2/3 of the length. With a length of 15 mm, the width in this case corresponds for example to approximately 10 mm.

For the electrical activation of the bending transducer 2, it has two contact elements 28a, b, which are fastened to the contacting end of the bending transducer 2 that is opposite from the link holder 14. The first, inner contact element 28a serves for the electrical contacting of the inner side of the piezoelectric layers 8a, b that is facing the carrier 6. The first contact element 28a is in this case electrically contacted with the carrier 6 while a metal, e.g. copper, foil 30 formed like a strip is interposed between the carrier and the first contact element 28a. The metal foil 30 thereby defines a two-dimensional contact region. The metal foil 30 adjoins at the end in the longitudinal direction 10 the upper piezoelectric layer 8a, which therefore ends at a distance from the end of the carrier 6. The carrier 6 itself is electrically conducting, so that both inner sides of the piezoelectric layers 8a, 8b can be activated by way of this first, inner contact element 28a. A second, outer contact element 28b has been applied on the exterior outer side of the upper, shorter piezoelectric layer 8a. During mounting in a pump housing, the outer side of the lower piezoelectric layer 8b is electrically contacted with a contact element provided there, in particular with the aid of a conductive adhesive. In the exemplary embodiment, both contact elements are formed in an L-shaped manner, and preferably from a bending metal strip. The one L leg, longer in the exemplary embodiment, serves for the electrical contact connection and has an optional elongated opening. The second (shorter) L leg is angled away approximately by 90° and runs parallel to the side edge 31 of the layered structure 4.

In order to reliably avoid unwanted electrical shorting of a number of layers, this second L leg is kept at a distance from the layered structure 4 by an insulating spacing A. The spacing lies for example in the range of 0.2 mm. The clearance is in this case preferably filled with a non-conductive adhesive 32 (cf. Fig. 4).

The electrical contacting of the contact elements 28a, b, which at the same time defines their mechanical fastening, takes place at a distance from the side edge 31 of the bending transducer 2, to be precise in particular in the region of an elongated hole in the surfaces of the contact elements 28a, b. As a result, there is the possibility that, during mounting, the shorter L arm can yield in a flexurally elastic manner and assume an exactly desired position in terms of height. Independently of this, the second L legs of both contact elements 28a, b are oriented in a defined, common second vertical position in terms of height H2 in relation to the fastening end 26 of the actuator 16. Furthermore, both the positions of the two contact elements 28a, b in the longitudinal direction 10 and the position thereof in the transverse direction thereto are exactly defined. The tolerances here are below 0.1 mm.

Overall, the bending transducer 2 is distinguished by a highly precise form, the exact relative position of the actuator 16 in relation to the supporting surface 22 (first height position H1 ) and additionally with respect to the contact elements 28a, b (second position in terms of height H2) being defined in particular.

The bending transducer 2 is also distinguished by its very small overall height. In order to achieve this, in the exemplary embodiment it is also provided in particular that the carrier 6 projects at the deflecting end 12 beyond the two piezoelectric layers 8a, 8b in the longitudinal direction 10 by an insertion portion. With this in- sertion portion, the carrier 6 engages in the groove 18. It is fastened therein by means of adhesive 32 (cf. Fig. 4). The insertion end has in this case a length of approximately 1 mm in the longitudinal direction 10.

For the electrical contacting of at least the outer, second contact element 28b, a soldering operation is envisaged, in particular that known as thermode soldering. In the case of this soldering process, a soldering head is generally placed in the cold state onto the element to be soldered and a defined temperature profile is subsequently passed through. The soldering head is only removed again after cooling. This soldering process allows particularly gentle soldering. In a preferred configuration, it is therefore also provided that the second contact element 28b is soldered directly onto a metallization layer 34. This metallization layer 34 is a sputtered-on layer, in particular a sputtered-on layered structure.

The entire metallization layer 34 has a thickness typically below 250 nm and in particular below approximately 200 nm. The layered structure preferably consists of a chromium-nickel-gold layer sequence, the chromium layer having been applied to the piezoceramic and the gold layer forming the outer layer, which is contacted. The three layers typically have in this case the same layer thickness.

The soldering on of the contact elements 28a, b is performed in this case with the aid of a soldering paste 35, which is applied to the contact element or the bending transducer 2 prior to the soldering operation.

As an alternative to this, prior to the soldering operation, the contact elements 28a, b are preferably pretinned, at least in the region of their contacting area, so that they have a thin layer of tin, with which they come to lie on the metallization layer 34 or on the metal foil 30. The subsequent soldering operation is then performed without additional solder. The electrical contacting, and consequently also the mechanical fastening, are in this case preferably performed exclusively by way of the layer of tin. By this contacting variant, the loading of the metallization layer 34 is further reduced in an advantageous way. The entire structure of the bending transducer 2 can be well appreciated once again from the exploded representation according to Fig. 4. As this reveals, each of the piezoelectric layers 8a, b is provided on each of both sides with a sputtered- on metallization layer 34.

Details of the link holder 14 emerge from Fig. 5 to 7. As can be seen in particular from Fig. 5, the link holder 14 has on its upper side, opposite from the positioning aids 20, two clearances 36, which in the exemplary embodiment are approximately U-shaped and reach from the side edge to approximately the middle of the link holder 14. An adhesive for the further adhesive bonding of the link holder can preferably be introduced into these clearances.

It can be seen from the representation of Fig. 6a, 6b that the groove 18 is provided with lead-in chamfers 38, in order to make it possible for the carrier 6 to be easily led in. The fact that only the carrier 6, and not the entire layered structure 4, is accommodated in the groove 18 means that the link holder 14 preferably does not project beyond the layered structure 4, or only scarcely. The material thickness of the link holder 14 on both sides of the groove therefore corresponds substantially to the thickness of the piezoelectric layers 8a, b with the applied metallization layers 34. As can be seen in particular from the side representation of Fig. 3, the link holder 14 is in this case exactly dimensioned in such a way that its upper side finishes flush with the upper side of the second contact element 28b. The underside of the link holder 14 on the other hand finishes directly with the lower piezoelectric layer 8b. In order to achieve this, the link holder 14 has a slightly greater material thickness above the groove 18 than below it - as can be seen from Fig. 6a, 6b.

The bending transducer 2 described with respect to Fig. 1 to 4 is used in a micro- pump 40 represented in Fig. 8 and 9. This pump serves in particular for dosing a medicament, for example insulin, over quite a long period of time, in particular over a sustained period.

The micropump has a housing consisting of a lower shell 42A and an upper shell 42B. The lower shell 42A is fastened on a fastening plate 44, which during use is arranged near the patient's body. The main components of the micropump 40 are the actual pumping unit 46 with the bending transducer 2 provided on it, a medicament container 48, a printed circuit board loaded with electronic components as the electronic unit 50 and a battery 52 for supplying energy.

The bending transducer 2 is in this case fastened on a carrier plate 54 of the pumping unit 46, in particular by adhesive bonding. The actuator 16 of the bending transducer 2 is led through a clearance in this carrier plate 54 to the opposite side and is connected there to a pumping diaphragm 56. This diaphragm acts on a line 58, which is connected on the suction side to the medicament container 48 and on the pumping side is led to the outside, to a dosing opening 60. Suitable valves are arranged in the line 58, so that, when there is a movement of the diaphragm, pumping takes place in the direction of the dosing opening 60.

The medicament container 48 holds a volume that is sufficient for several days of dispensing the medicament. The medicament container 48 is subsequently replaced by a new one. The pumping unit 46 with the integrated bending transducer 2 is likewise exchanged with the medicament container 48 in the manner of a disposable article.

The bending transducer described here is distinguished by several aspects, which interact in an advantageous way with regard to the preferred intended application of use in a micro diaphragm pump. These aspects are:

a) the configuration of the link holder with the actuator 16 embedded therein and the moulded-on positioning aids 20,

b) the configuration and arrangement of the contact elements, specifically their bent configuration, in particular the L-shaped configuration, the one L arm serving for the fastening and contacting and the other arm being guided along the side edge 31 of the layered structure 4 while being kept at a distance provided by the insulating spacing A, c) the contacting of the contact elements by means of thermode soldering, in particular on a sputtered layer, d) the contacting and fastening of the contact elements at a fastening point kept at a distance from the side edge,

e) the pretinning of the contact elements, in particular in combination with the thermode soldering.

The individual aspects are regarded in themselves as independently inventive, irrespective of the specific configuration of the bending transducer with the link holder that is claimed in Claim 1 . The right to file divisional applications for each individual one of these aspects or combinations thereof is reserved.

List of designations

2 bending transducer

4 layered structure

6 carrier

8a upper piezoelectric layer

8b lower piezoelectric layer

10 longitudinal direction

12 deflecting end

14 link holder

16 actuator

18 groove

20 positioning aids

22 supporting surface

23 fastening end

24 holes

28a first contact element

28b second contact element

30 metal foil

31 side edge

32 adhesive

34 metallization layer

35 soldering paste

36 clearance

38 lead-in chamfer

H1 first vertical position in terms of height

H2 second vertical position in terms of height

A insulating spacing

Claims

CLAIMS:

1 . Bending transducer (2) for deflecting a pumping diaphragm in a diaphragm pump, which transducer has a layered structure (4) comprising a carrier (6), which carrier extends in the longitudinal direction up to a deflecting end (12) and on which there is an applied piezoelectric layer (8a, b), which piezoelectric layer is contacted via electrical contact elements (28a, b), wherein a link holder (14) is fastened to the deflecting end (12) and wherein an actuator (16) is held in the link holder (14), wherein, in the final mounted state in the diaphragm pump, the actuator (16) is connectable to the diaphragm.

2. Bending transducer (2) according to Claim 1 , wherein the link holder (14) is formed as a plastic injection-moulded part and the actuator is embedded therein.

3. Bending transducer (2) according to Claim 1 or 2, wherein the link holder (14) has a groove (18), in which the deflecting end (12) is accommodated.

4. Bending transducer (2) according to Claim 3, wherein, at the deflecting end (12), the carrier (6) projects beyond the piezoelectric layer (28a, b) in the longitudinal direction (10) and only the carrier (6) is accommodated by the groove (18).

5. Bending transducer (2) according to any preceding claim, wherein the link holder (16) extends over the entire width of the carrier (6).

6. Bending transducer (2) according to any preceding claim, wherein at least one positioning aid (20), which extends in the direction of the actuator (16) and has a supporting surface (22), which at least one positioning aid during the mounting of the bending transducer (2) is supported on an assigned mounting surface and is arranged on the link holder (14), wherein a first vertical position in terms of height (H1 ) of a fastening end (23) of the actuator (16) is positioned highly precisely in relation to the supporting surface (22).

7. Bending transducer (2) according to Claim 6, wherein a positioning aid (20) formed as a spacer cylinder is arranged on each of both sides of the actuator (16), preferably in each case at the end of the link holder (14).

8. Bending transducer (2) according to any preceding claim, wherein, at the end opposite from the deflecting end (12), the carrier (6) projects beyond the piezoelectric layer (28a) and defines there a contact region, preferably by a metal layer (30) which has been applied in the projecting region and on which a first contact element (28a) is contacted.

9. Bending transducer (2) according to Claim 8, wherein the carrier (6) is electrically conducting and wherein a piezoelectric layer (8a, b) is arranged on both sides of the carrier (6), wherein the contact region is only formed on one side of the carrier (6) and wherein, on the other side of the carrier (6), the piezoelectric layer (8b) extends up to the end of the carrier (6).

10. Bending transducer (2) according to any preceding claim, wherein the piezoelectric layer (8a, b) is metallized on its outer side facing away from the carrier (6) to form a contact layer (34), wherein a second contact element (28b) is contacted with the contact layer.

1 1 . Bending transducer (2) according to Claim 8, 9 or 10, wherein at least one of the contact elements (28a, b) is L-shaped, wherein one arm of the at least one L-shaped contact element is fastened at a fastening point on a contact region or a contact layer and the other arm is guided along a side edge (31 ) of the layered structure (4), wherein an insulating spacing (A) lies between the side edge (31 ) and the other arm and is preferably in the range of from 0.1 to 0.3 mm.

12. Bending transducer (2) according to Claim 1 1 , wherein a non-conductive adhesive (32) isinserted in the insulating spacing (A).

13. Bending transducer (2) according to any of Claims 8 to 12, wherein at least one of the contact elements (28a, b) is fastened at a fastening point on the contact layer that is kept at a distance from a side edge (31 ) of the layered structure (4) in such a way that a second vertical position in terms of height (H2) of an end of the contact element (28a, b) can be set in relation to the actuator (16) by elastic yielding of an arm of the contact element (28a, b).

14. Bending transducer (2) according to any of Claims 8 to 13, wherein the contact elements (28a, b) are soldered on, in particular with the aid of a ther- mode soldering process.

15. Bending transducer (2) according to any of Claims 8 to 14, wherein, prior to contacting, the contact elements (28a, b) are provided with a pretinning as the solder, and the contact element (28a, b) is soldered on without any further solder.

16. Micropump with a bending transducer (2) according to any preceding claim, which is arranged in a pump housing.