Measuring and testing – Gas analysis – By thermal property
Reexamination Certificate
1999-07-12
2001-08-21
Larkin, Daniel S. (Department: 2856)
Measuring and testing
Gas analysis
By thermal property
C073S023310, C073S025050, C073S031010, C073S031020, C073S031050, C073S031060, C422S094000, C454S075000
Reexamination Certificate
active
06276192
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improved digital gas detecting device for detecting a pollution level of the air in the vicinity of a vehicle and controlling a ventilation system of the vehicle, and more particularly, to a gas detecting sensor having a novel structure for detecting concentrations of a gasoline gas and a diesel gas and a gas detecting device for estimating a pollution level of the air around a vehicle using the gas detecting sensor and controlling a ventilation system.
2. Description of Related Art
A typical gas detecting sensor is a semiconductor sensor using tin dioxide as an active layer. This typical gas detecting sensor has a defect that it cannot sense two kinds of exhaust gases generated by a gasoline vehicle and a diesel vehicle all together. To sense both exhaust gases together, two sensors should be used. A tin dioxide (SnO
2
) sensor is used to detect the gasoline exhaust gas and a tungsten trioxide (WO
3
) sensor is used to detect the diesel exhaust gas. However, if two sensors are used, a sensor installation structure and a sensing circuit should be constituted in dual, thereby increasing the size and cost of the gas detecting device.
There have been provided with gas detecting sensors doped with sensing material comprising a compound of various metallic oxides, for detecting gases based upon increase/decrease of resistance caused by the effects of typical gases. However, when only one sensor is used, it is difficult to separate a sensor signal generated due to gasoline exhaust gas from a sensor signal generated due to diesel gas exhaust gas. Besides, complicated sensor signal conversion and signal processing is required. Moreover, when using the sensor having a metallic oxide compound, it may happen that the sensor wrongly senses polluted air and performs a wrong operation with respect to the ventilation system if very harmful material has influenced the sensor device at constant concentration for a long time, for example, if the vehicle has been parked in a very polluted underground parking lot for a long time.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a gas detecting sensor and a gas detecting device for controlling ventilation systems that substantially obviates one or more of the limitations and disadvantages of the related art.
An objective of the present invention is to provide a gas detecting sensor having a novel structure and a gas detecting device for simply separating a gasoline exhaust gas sensing signal from a diesel exhaust gas sensing signal using a single gas detecting sensor and controlling a ventilation system.
Another objective of the present invention is to provide a gas detecting device for detecting variation of an absolute value of the amount of a gas based upon a sensor signal received from a gas detecting sensor in a pulse width modulation (PWM) mode and performing digital signal processing, thereby realizing gas detection only with a low-priced signal processing device.
Additional features and advantages of the invention will be set forth in the following description, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure as illustrated in the written description and claims hereof, as well as the appended drawings. To achieve these and other advantages, and in accordance with the purpose of the present invention as embodied and broadly described, a gas detecting sensor comprises: first and second sensing layers that respectively react to a gasoline exhaust gas and a diesel exhaust gas and are separately doped around an outer circumference of a sensor body; and first and second heaters for periodically heating the first and second sensing layers to different optimal reaction temperatures.
A gas detecting device of the present invention comprises: a gas detecting sensor; a sensor signal detecting unit for connecting internal resistance of a first sensing layer to internal resistance of a second sensing layer in the gas detecting sensor in parallel and connecting the internal resistance to an external fixed resistor in parallel to detect a sensor signal; a heater drive unit for periodically driving first and second heaters by turns; a PWM signal converting unit for detecting the sensor signal of the sensor signal detecting unit in a PWM mode at a predetermined time in synchronization with drive of the first or second heater; and a control unit implemented by a one chip microprocessor for controlling the first and second heaters periodically, controlling the PWM signal converting unit to receive the sensor signal, converting the sensor signal into a digital signal, and generating a control signal for controlling a ventilation system based upon a result of comparison of the digital signal and a predetermined reference value.
As illustrated, the present invention includes separately formed sensing layers for sensing gases and heaters for heating the sensor to different temperatures at which the respective sensing layers have optimal sensing characteristics. The two sensing layers are connected in parallel and a parallel resistance value is detected as a sensor signal. The sensor signal is converted into a PWM signal for gas detection. Accordingly, the present invention realizes a compact sensor and simplification of the gas detecting device. The present invention senses two different kinds of gases using a single sensor and discriminates the sensor signal by the kinds of gases through simple signal processing. The present invention detects the concentration of a sensed gas in aspect of an absolute value on the basis of a gas sensing data in the clean air and estimates a pollution level.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
REFERENCES:
patent: 5217692 (1993-06-01), Rump et al.
patent: 5320577 (1994-06-01), Tooru et al.
patent: 5725425 (1998-03-01), Rump et al.
patent: 6004201 (1999-12-01), Rump
Lim Cheol
Sim Hae Kyung
Auto Electronic Corporation
Dykema Gossett PLLC
Larkin Daniel S.
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