Measuring and testing – Gas analysis
Reexamination Certificate
2000-08-04
2001-11-13
Williams, Hezron (Department: 2856)
Measuring and testing
Gas analysis
C123S686000, C338S014000
Reexamination Certificate
active
06314789
ABSTRACT:
FIELD OF INVENTION
The present invention relates to a sensor unit, in particular an air quality sensor, having a first support element, on which are arranged a first sensor element and a first heat source, assigned to the latter, and having at least one further second support element, on which are arranged a second sensor element and a second heat source, assigned to the latter.
BACKGROUND INFORMATION
Sensor units of this type constitute so-called air quality dual sensors, which can carry out a carbon monoxide and a nitrogen oxide measurement for quantifying the exhaust gas quality of motor vehicle internal combustion engines. In modern internal combustion engines, a multiplicity of input parameters is processed in the course of electronic engine management. These are, for example, the instantaneous engine revolutions per unit time, the gas pedal position, etc. A further characteristic quantity for engine management is the pollutant concentration of the exhaust gases arising from combustion. These pollutants, as is conventional, are measured using sensors, the data from the sensors being taken into account in the engine management.
International Patent Application WO 93/10441, describes a conventional method which, for determining small quantities of carbon monoxide and nitrogen oxide in oxygen-containing gas mixtures, makes use of a sensor, whose electrical resistance changes in response to an increase in temperature. The magnitude of the change is a function of the carbon monoxide and nitrogen oxide concentration in the gas mixture. Therefore, the change represents a measure for these pollutants. For each pollutant, a separate sensor is used, an electrical heating element being assigned to each of which for traversing the temperature range.
SUMMARY
The sensor unit according to the present invention includes two support elements which are combined, in a U shape, in a support unit. The two support elements each form one leg of the U and the slot in between them constitutes a heat barrier. A common support area joins the support elements and supports electrical printed circuit traces and contacts, which make it possible to connect the sensor unit in an electrical receiving socket.
The heat barrier prevents thermal “cross-talk” between the support elements, so that the first heat source cooperates only with the first sensor element, and the second heat source cooperates only with the second sensor element, i.e., the heat barrier creates a thermal isolation between the two sensor elements and between respective sensor element and the heat source not assigned to that sensor element. As a result of the arrangement according to the present invention, the time is shortened that the sensor unit requires, after the heat source(s) is(are) switched on, to reach a stationary temperature distribution and to deliver precise measuring results.
According to a refinement of the present invention, the two support elements form a one-piece support unit. Therefore, the aforementioned “common” support unit does not, as a matter of course, have to be in one piece, but can be composed of two parts, which, however, are secured to each other using appropriate means. Alternatively, it is also possible, discussed above, to combine the two support elements into a one-piece support unit.
In addition, it is advantageous if the support unit is configured as a substrate furnished with electrical printed circuit traces. Consequently, the support unit is preferably constituted by a printed circuit board.
The heat barrier, situated between the two support elements, is to be understood as penetrating the support unit so that at this location something like a thermal air-insulation point is created. It can include a plurality of cutouts arranged in rows, between which lie only thin material segments of the support unit, these thin material segments contributing to the desired thermal isolation. The aforementioned cutout preferably does not extend over the entire longitudinal extent of the support unit, but rather only over a partial segment of the support unit so that the heating elements and the sensor elements lie to the right and to the left of it, and the electrical leads and contacts lie, in the area not occupied by the cutout, in the common support area, in order to be able to plug the sensor unit in an electrical receiving socket.
According to a refinement of the present invention, the two heat sources are configured as electrical resistance leads. The two resistance leads can be configured on the substrate as resistance circuit traces. This results in a very simple design.
It is also advantageous if the two sensor elements are formed by sensor circuit traces arranged on the substrate.
If a printed circuit board furnished with printed circuit traces is used as the substrate, then the substrate is a plate-shaped one, the resistance circuit traces being located on the one side and the sensor circuit traces being located on the other side of the substrate. Consequently, in each case, one resistance circuit trace and one sensor circuit trace are located on the front and back side of the substrate, the heat barrier being located between the two resistance circuit traces and between the two sensor circuit traces, in particular in the form of a slot.
The printed circuit traces may routed up to the edge area of the substrate and, there, form plug-in contacts and/or soldering or welding contacts.
It is also advantageous if the two resistance circuit traces are connected in series, since then the number of plug-in contacts or soldering or welding contacts is very small.
According to a refinement of the present invention, at least one resistance circuit trace is connected in an electrically conductive manner to at least one sensor circuit trace by a via hole (plated-through hole) through the substrate. The via hole is may be electrically connected with only one plug-in contact and/or soldering or welding contact, so that the via hole supplies a common electrical potential, preferably the zero potential, to the electrical heating elements and the two sensor units.
REFERENCES:
patent: 4151503 (1979-04-01), Cermak et al.
patent: 5211053 (1993-05-01), Nolting et al.
patent: 5217692 (1993-06-01), Rump et al.
patent: 0 527 258 (1993-02-01), None
patent: 93 10441 (1993-05-01), None
Kenyon & Kenyon
Politzer Jay L.
Robert & Bosch GmbH
Williams Hezron
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