Bonding of strain gauges to the deformable body of a force-measuring cell

1. Force-measuring cell comprising:

at least one strain gauge which has a strain-sensitive electrical resistor track arranged on a polymer carrier substrate and which is installed on a deformable body by means of an adhesive layer, wherein the adhesive layer includes an inorganic-organic hybrid polymer;

wherein the deformable body is made of aluminum, wherein the deformable body has on its surface an aluminum oxide layer which in comparison to a natural oxide layer has an increased thickness and/or an increased porosity due to a chemical, electrochemical or thermal treatment, whereby a bond to the adhesive layer is strengthened by a mechanical anchoring of the adhesive layer in the aluminum oxide layer.

2. Force-measuring cell according to claim 1 , wherein the adhesive layer consists essentially of the inorganic-organic hybrid polymer.

3. Force-measuring cell according to claim 1 , wherein the at least one strain gauge is provided with a protective coating against moisture penetration, wherein the protective coating is underlaid with a surface-smoothing polymer layer.

4. Force-measuring cell according to claim 3 , wherein the protective coating is a multilayered coating which is composed of an alternating sequence of a barrier layer, and an intermediate layer.

5. Force-measuring cell according to claim 4 , wherein the barrier layer is silicon nitride and the intermediate layer is silicon oxide.

6. Force-measuring cell according to claim 3 , wherein the surface-smoothing layer that lies under the protective coating comprises an inorganic-organic hybrid polymer that matches the adhesive layer.

7. The force-measuring cell of claim 1 , wherein the deformable body comprises a body comprises a plurality of elastic bending zones formed by thin material portions.

8. The force-measuring cell of claim 7 , comprising four elastic bending zones.

9. The force-measuring cell of claim 7 , wherein the at least one strain gauge measures a magnitude of deformation in at least one of the elastic bending zones.

10. Method of fastening a strain gauge on an aluminum deformable body of a force-measuring cell, comprising:

heating the deformable aluminum body under oxygen atmosphere at a temperature between 40° C. and 100° C. to increase an aluminum oxide layer on a surface of the deformable aluminum body prior to applying an adhesive compound for producing an adhesive layer;

applying the adhesive compound having an inorganic-organic hybrid polymer in solution to the deformable body to produce the adhesive layer;

placing the strain gauge on the adhesive compound; and

hardening the applied adhesive layer at a temperature between 80° C. and 130° C.by exposing the deformable body with the strain gauge to the temperature for a duration between half an hour and three hours.

11. Method according to claim 10 , comprising:

subjecting the strain gauge to a contact pressure between 100 kN/m 2 and 1000 kN/m 2 during the hardening.

12. Method according to claim 10 , comprising,

subjecting the deformable body, formed of aluminum, to a chemical or electrochemical treatment to increase an aluminum oxide layer on a surface of the deformable body prior to applying the adhesive compound for producing the adhesive layer.

13. Method according to claim 10 , comprising;

performing application of the adhesive compound for producing the adhesive layer using a tampon-printing method.

14. Method according to claim 10 , wherein the adhesive compound consists of the inorganic-organic hybrid polymer in solution.