BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be further described below, with reference to the enclosed drawings, wherein
FIG. 1 shows an oblique view of a sensor device according to the invention in a first variant,
FIG. 2 shows the sensor device in a longitudinal section along line II-II of FIG. 1,
FIG. 3 shows an oblique view of a partially cut guiding and protecting element with holder and sensor element,
FIG. 4 shows a holder of the sensor device in an oblique view,
FIG. 5 shows the holder in a side view,
FIG. 6 shows a guiding and protecting element in an oblique view,
FIG. 7 shows the guiding and protecting element in a longitudinal section,
FIG. 8 shows an oblique view of a second variant of the sensor device according to the invention attached to a pipe system,
FIG. 9 shows a first sensor housing part of the sensor device of FIG. 8 in an oblique view,
FIG. 10 shows a second sensor housing part of the sensor device of FIG. 8 in an oblique view,
FIG. 11 shows a third sensor housing part of the sensor device of FIG. 8 in an oblique view,
FIG. 12 shows the ring of the sensor device of FIG. 8 in an oblique view,
FIG. 13 shows a piezoelectric sensor element in a side view as indicated by arrow XIII in FIG. 14,
FIG. 14 shows the sensor element in a view as indicated by arrow XIV of FIG. 13, and
FIG. 15 shows the sensor element in a view as indicated by arrow XV of FIG. 13.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 and FIG. 2 show a piezoelectric sensor device 1 with a sensor housing 2, comprising a first sensor housing part 2a and a second sensor housing part 2b, where the cap nut has been omitted in FIG. 2. The metal sensor housing parts 2a, 2b position in a gas-tight manner a cylindrical guiding and protecting element 3 in a gas stream to be measured. The guiding and protecting element 3 receives a holder 4 (see FIG. 3 to FIG. 5) for a sensor element 30 configured as a strip-shaped resonator element (strip resonator), which is shown in detail in FIG. 13 and FIG. 14. The resonator element 30 is exposed to the gas stream to be measured via an opening 5 in the lower sensor housing part 2b and a slit 6 in the cylindrical guiding and protecting element 3 (FIG. 6).
FIGS. 3 to 5 show the holder 4 in detail. The high-temperature-resistant holder 4 is furnished with a clamping element 7, which comprises an elastic arm 7a and a non-elastic arm 7b. Between the elastic first arm 7a and the non-elastic second arm 7b there is provided a slot 8, which will receive the sensor element 30. The two arms 7a and 7b are placed on an essentially circular base plate 9. The material of the holder assembly is machinable glass ceramics, which has no porosity. The holder assembly stabilizes and provides lateral contacting for the sensor element 30, which is formed by a GaPO4 strip resonator. Due to the spring action of the first arm 7a of the clamping element 7 this function is also upheld in the instance of temperature changes. The holder 4 is provided with an electrically conductive coating, for instance a platinum coating, with the coated regions of the two arms 7a and 7b being electrically separated and connected to electrical leads 17a, 17b.
The holder 4 is inserted into the interior of the cylindrical guiding and protecting element 3. The holder 4 together with the resonator element 30 is thus guided and protected from external influences. FIGS. 6 and 7 show details of the guiding and protecting element 3.
The sensor housing 2 of the sensor device 1 is attached to a pipe system 11 via a gas-tight welded cutting-ring fitting.
FIGS. 8 to 12 show a second variant of a sensor device 1. The sensor housing 2 of the sensor device 1 comprises a first 2a, a second 2b and a third 2c sensor housing part. As in the first variant shown in FIGS. 1 to 7, a holder 4 with a clamping element 7 (not visible here) and a cylindrical guiding and protecting element 3 are employed for guiding and lateral contacting of the resonator element 30. The holder 4 and the cylindrical guiding and protecting element 3 are glued into a bore 12 of a ceramic ring 13. The main surfaces of the ring 13 act as sealing faces.
The sensor housing 2 comprises three sensor housing parts. The second 2b and the third 2c sensor housing part are fixedly joined, for instance by welding. The ring 13, together with the cylindrical guiding and protecting element 3 and the holder 4 with the sensor element 30, is inserted into the second part 2b. The third sensor housing part 2c is a welding nipple and is welded to the pipe system 11. The first sensor housing part 2a is a covering cap, which is screwed onto the second housing part 2b by means of a thread 14. Copper sealing rings 15, 16 are used as additional sealing elements.
FIGS. 13 to 15 show a resonator element 30 with coating, constituted by a GaPO4 strip resonator. Reference number 31a indicates the contact region clamped in the holder 4. The measuring region 31b is subjected to the gas stream to be measured. The shaded area indicates electrodes 32a, 32b, for instance platinum electrodes, extending from the measuring region 31b to the contact region 31a and to the edges 33a, 33b. Electrical contacting is effected at the edges 33a, 33b by the first and the second arm 7a and 7b. In the measuring region 31b a catalytic nickel layer is provided.
Patent Application
20080083284
