Apparatus and method of producing pressure sensors and diaphragms for said pressure sensors

1. Field of the Invention

The present invention relates to an improved method for producing pressure sensors comprising diaphragms and to diaphragms for said pressure sensors.

2. Prior Art

The invention relates to a diaphragm for a pressure sensor as generically defined by the preamble to the main claim.

In conventional metal diaphragms, especially for high-pressure sensors, the entire diaphragm, including the support elements, is preferably made in one piece of stainless steel. Because of the stringent demands made in terms of the properties of the diaphragms, production of the one-piece metal part requires complicated work steps such as turning, grinding, lapping and polishing to a high gloss. To further complete the diaphragm with sensor elements, a thin-film coating on the metal diaphragms is necessary in many cases.

The diaphragm according to the invention is advantageous because the diaphragm face can be made separately and economically as a part comprising a special steel band, and the required properties are assured in a simple way. For diaphragm thicknesses of approximately 0.4 to 1 mm (and optionally even greater), thickness tolerances of <5% of the diaphragm thickness should be adhered to. The surface quality on the top side should have a value of Rz<0.1 μm.

To make it simple to positionally fix the metal diaphragm, the diaphragm part stamped out of the special steel band has a fixation lug on its outside.

The diaphragm of the invention can also advantageously be produced in a group blank production process, in which a single sheet-metal part can include a plurality of support bodies and thus a plurality of diaphragms. The requisite production processes for the thin-film coating can advantageously be applied to all the diaphragm faces of the special steel band simultaneously.

Further advantageous embodiments are defined by the dependent claims.

Exemplary embodiments of a diaphragm for a pressure sensor will be described in conjunction with the drawing. Shown are:

FIG. 1, a basic illustration of a pressure sensor with a diaphragm conventionally produced in one piece;

FIG. 2, a basic illustration of a diaphragm according to the invention, with a support body soldered onto it;

FIG. 3, a view of a support body with the fixation lug; and

FIG. 4, a view of diaphragms produced in a group-blank version.

In FIG. 1, a pressure sensor 1 is shown, which in its interior has a diaphragm 2 that can be acted upon, on the side of the diaphragm face 3 , with a liquid or gas pressure and which carries sensor elements on one side of the diaphragm face 3 . The diaphragm 2 of FIG. 1 is a conventional version, which is produced in one piece with a support body 4 .

The diaphragm 2 of FIG. 2 is a version according to the invention, which comprises a pre-fabricated band part 3 as the diaphragm face and a likewise separately produced support body 4 and joined to it via a solder seam 5 . A rolled or stamped part, a special steel band, or a sheet-metal part can for instance be used as the band part 3 . The support body 4 may be embodied as a ring or as a part of rectangular or square cross section. In a simple way, it can be produced economically as a stamped part.

The embodiment of FIG. 3 has a band part 3 , which for positional fixation of the diaphragm 2 and the pressure sensor 1 has a fixation lug 6 .

In the embodiment of FIG. 4, a number of diaphragms 2 are made on a single band part 3 . This group blank is then, after the thin-film coating, divided up into the individual parts. The support bodies 4 are soldered to the band part 3 as described above. The thin-film coating, not visible here, for producing sensor elements can be applied in a manner known per se to the top side of the band part 3 .