Measuring and testing – Gas analysis
Reexamination Certificate
1998-11-19
2001-03-06
Williams, Hezron (Department: 2856)
Measuring and testing
Gas analysis
C204S425000
Reexamination Certificate
active
06196049
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a sensing element, in particular for an electrochemical sensor, for determining the oxygen content of gases, as well as to a method for manufacturing the sensing element.
BACKGROUND INFORMATION
Sensing elements are known. They are configured, for example, as so-called planar sensing elements, which have a first electrode exposed to a measured gas, on a solid electrolyte configured as a support, and a second electrode exposed to a reference gas. In a number of applications, the sensing element must be heated to a specific temperature. It is known for this purpose to associate with the sensing element a heating device, which usually has heating conductors running below the electrode that is exposed to the reference gas.
In order to deliver a reference gas onto the reference gas electrode, a reference gas conduit which extends in the longitudinal direction of the sensing element is provided inside the layered, planar sensing element.
To manufacture sensing elements of this kind, it is known that the individual functional layers yielding the sensing element are arranged one above another as so-called green films, the individual functional layers having a specific layout corresponding to the structure of the sensing element. The entire sensing element is then sintered. It is disadvantageous in this context that, because the functional layers are present as green films, the sensing element is relatively labile; handling both during application of the functional layers and during sintering can thus be performed only with the greatest of care in order to prevent damage to the sensing element.
SUMMARY OF THE INVENTION
The sensing element according to the present invention offers, in contrast, the advantage that the manufacture and handling thereof are simplified. Because the sensing element is patterned on a presintered support, a porous adhesion layer being arranged between the support and the sensing element, a relatively solid support, which is easy to handle and at the same time protects the applied functional layers of the sensing element from mechanical damage, is available both while the individual functional layers of the sensing element are being printed on, and during subsequent sintering of the functional layers.
In a preferred embodiment of the present invention, provision is made for the support to have on its one side a sensing device and on its other side a heating device. It thereby becomes advantageously possible to decouple the manufacture of the heating device from the manufacture of the sensing device, so that they can be accomplished in separate process sequences. In addition to the resulting optimization of both the application of the heating device and the application of the sensing device onto the opposite sides of the support, an increase in yield can also be attained, since when the heating device and the sensing device are manufactured in succession, any heating devices that may be manufactured defectively no longer need to be equipped with the sensing device. This allows not only material but also time and cost to be saved when manufacturing the sensing elements.
In addition, the method according to the present invention for manufacturing the sensing element offers the advantage that the time for sintering the sensing element can be reduced. Because the support substrate is already pre-sintered, all that is necessary is a post-sintering of the applied functional layers. Since the latter are relatively thin, the sintering time can be kept correspondingly short.
REFERENCES:
patent: 4282080 (1981-08-01), Muller et al.
patent: 4300990 (1981-11-01), Maurer
patent: 4334974 (1982-06-01), Muller et al.
patent: 4505807 (1985-03-01), Yamada
patent: 4610741 (1986-09-01), Mase et al.
Kenyon & Kenyon
Politzer Jay
Robert & Bosch GmbH
Williams Hezron
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