Ventilation – Vehicle – Having automatic control means
Patent
1997-10-17
1999-12-21
Joyce, Harold
Ventilation
Vehicle
Having automatic control means
73 2331, B60H 124
Patent
active
06004201&
DESCRIPTION:
BRIEF SUMMARY
It has been suggested to control the ventilation of motor vehicles such that, whenever the vehicle goes through a zone of elevated pollution level, the system switches from admitting outside air to recirculating interior air.
BRIEF DESCRIPTION OF THE DRAWING
In the drawing:
FIG. 1 is a simplified schematic diagram illustrating the invention;
FIGS. 2 and 3 are schematics of circuits embodying the invention;
FIGS. 4 and 5 are diagrams illustrating the response of sensors according to the invention; and
FIGS. 6 and 7 are schematic diagrams of further systems according to the invention.
BACKGROUND OF THE INVENTION
The appropriate sensor system thus determines the pollutant content of the outside atmosphere and operates the ventilation control flap as described above.
See also: DE 3,304,324
Since standard systems only use a single sensor element, e.g. tin-dioxide sensors, only oxidizing gases (carbon monoxide, hydrocarbons) in the exhaust, can be detected while the system is relatively insensitive to diesel exhaust gases (nitrogen oxide, sulfur dioxide, aromatics).
For this reason systems with two sensors have been proposed. One of the sensors (e.g. tungsten trioxide) is provided for diesel exhaust and another sensor (e.g. tin dioxide) for gasoline exhaust. Each sensor is provided on its own signal pad. Each sensor has its own analog/digital convertor which transmits the respective output signals to a central controller (e.g. a microprocessor).
Although the functioning of such two-sensor systems does meet requirements, the two-channel signal evaluation entails relatively high costs.
OBJECT OF THE INVENTION
It is an object of this invention to reduce costs and expense by using single-channel processing.
To this end the invention is basehd on the following observations:
FIG. 4 shows the typical signal curve of a tin-dioxide sensor that is exposed first to gasoline exhaust at 4.1 and then to diesel exhaust at 4.2. The exposure to gasoline exhaust substantially reduces the resistance of the sensor. The exposure to diesel exhaust slightly increases the resistance of the sensor.
FIG. 5 shows the typical signal curve of a tungsten trioxide sensor that is exposed at 5.1 to gasoline exhaust and later at 5.2 to diesel exhaust. The exposure to gasoline exhaust reduces the sensor resistance slightly. The exposure to diesel exhaust increases the sensor resistance substantially.
Practice shows that both gas groups are almost never found at the same time in homogenous stoichiometric mixtures in street traffic. Instead short gas pulses of different type reach the sensor one after another.
The invention thus proposes a main setup corresponding to FIG. 1. A tin-dioxide sensor 1 is connected as a voltage divider with a tungsten-trioxide sensor 2. The voltage-divider output 5 is fed to a signal processor 3. Its output signal 4 controls the ventilation flap. Since the diesel- and gasoline-containing gas pulses encounter the sensors one after the other, either the sensor 1 is at low ohmage (gasoline exhaust) or the sensor 2 is at high ohmage due to the presence of diesel exhaust. In either case a positive voltage pulse is seen on the voltage divider. If the sensors are switched, of course a negative voltage pulse is seen.
Preferably the voltage-divider output is processed as a single channel which substantially reduces costs.
In order to accommodate the different characteristics to physiological requirements, each sensor is as shown in FIG. 6 connected with a series and a parallel resistor. In this manner diesel exhaust at the same initial concentration produces a voltage pulse some 20 to 40 times greater.
FIG. 2 shows a variant whereby the sensors each form a voltage divider with an ohmic resistance. The voltage-divider outputs are added in an operational amplifier 2.5 so that its output produces a gas-dependent voltage pulse that always goes in the correct direction independent of the nature of the detected gas.
FIG. 3 shows a further variant whereby the sensors are in the respective upper and lower legs of a voltage divi
REFERENCES:
patent: 4992965 (1991-02-01), Holter et al.
patent: 5062065 (1991-10-01), Lampe
patent: 5217692 (1993-06-01), Rump et al.
patent: 5320577 (1994-06-01), Tooru et al.
JP2126146, May 15, 1990, Patent Abstracts of Japan.
Dubno Herbert
I.T.V.I. International Techno Venture Invest Aktiengesellschaft
Joyce Harold
Wilford Andrew
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