Planar polarographic sensor for determining the lambda value of

Details Planar polarographic sensor for determining the lambda value of Planar polarographic sensor for determining the lambda value of

1994-05-23

1996-06-25

Bell, Bruce F.

Chemistry: electrical and wave energy

Apparatus

Electrolytic

204426, 204427, 204429, G01N 2726

Patent

active

055296777

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to a planar polarographic sensor.
2. Background Information
Known polarographic sensors serve to determine the lambda value of gas mixtures which defines the ratio of the total oxygen to the oxygen contained in the fuel-air mixture that is combusted in a cylinder, with the sensors determining the oxygen content of the exhaust gas via a change in the boundary flow. Due to cost-effective production methods, the manufacture of planar polarographic sensors that may be produced in ceramic-sheet and screen-print technology has become popular in practice in recent years. These planar polarographic sensors may be produced in a simple and economic manner based on the sheet-like oxygen conducting solid electrolyte bodies made of, for example, zirconium oxide and each coated on both sides with an inner and outer pumping electrode including associated conductors. The inner pumping electrode in this case is disposed in an advantageous manner in the border region of a diffusion channel through which the measuring gas is fed and which serves as gas diffusion resistance.
To improve the reproducibility of the diffusion resistance, DE-OS 38 11 713 proposes to form the diffusion resistance by means of a porous sintering form body without an air gap which is inserted into the unsintered sensor. To accomplish this, a recess is punched out of a solid electrolye sheet and the porous form body is then inserted into the same. In order to supply the measuring gas, a diffusion channel is either guided transversely through the sensor layers to the porous form body or the porous form body is exposed at the end face of the sensor.
EP-A-01 94 082 discloses a planar polarographic sensor whose diffusion resistance is formed by a gap extending parallel to the solid electrolyte body and by a porous insulating layer disposed opposite the gas and covering the electrode. The measuring gas is supplied to the electrode via the gas and the porous insulating layer. The measured gas is supplied to the electrode via the gap and the porous insulating layer.
The production of known planar polarographic sensors is expensive. For example, in order to set the diffusion hole, a punching process is required whose positioning precision is of special significance for the sensor to function. Configuring the diffusion zone with an air gap, on the other hand, requires additional screen printing steps. Each additional screen printing step means an additional drying step and thus increases the chance of altering the length of the substrate. This, in turn, has a negative effect on the positioning precision of the subsequent screen printing steps, which has an adverse effect on reproducibility, especially if a sensor is widened with Nernst cells.


SUMMARY OF THE INVENTION

The polarographic sensor according to the present invention has the advantage of being of an easy-to-produce configuration which allows the screen printing steps of the sensor to be reduced. It is especially advantageous that the diffusion layer is printed on the entire surface of the multiple panels. This allows the individual sensor to be produced very inexpensively. Another advantage is that the diffusion resistance may be set by way of the respective exposed region of the diffusion layer at the end faces of the sensor.


BRIEF DESCRIPTION OF THE DRAWINGS

Three embodiments of the invention are shown in the drawings and are further described, following description.
FIG. 1 shows the layout of a first embodiment of a sensor according to the invention.
FIG. 2 shows the layout of a second embodiment of a sensor according to the invention.
FIG. 3 shows a longitudinal section through the diffusion zone of the sensors according to FIGS. 1 and 2.
FIG. 4 shows the layout of a third embodiment of a sensor according to the invention which, in addition to being provided with a pumping cell and heating cell is provided with a Nernst cell and thus represents a broad-band sensor.
FIG. 5 shows a longitudinal section through the diff

REFERENCES:
patent: 4579643 (1986-04-01), Mase et al.
patent: 4657659 (1987-04-01), Mase et al.
patent: 4755274 (1988-07-01), Mase et al.
patent: 5137615 (1992-08-01), Friese et al.
patent: 5169512 (1992-12-01), Wiedenmann et al.

Affiliated with

Also associated with

Rating

Planar polarographic sensor for determining the lambda value of does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Planar polarographic sensor for determining the lambda value of , we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Planar polarographic sensor for determining the lambda value of will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2186522