Measuring and testing – Vehicle chassis – Steering
Reexamination Certificate
2002-06-10
2004-07-06
Lefkowitz, Edward (Department: 2855)
Measuring and testing
Vehicle chassis
Steering
C073S118040, C073S715000, C250S231100, C250S231190
Reexamination Certificate
active
06758086
ABSTRACT:
BACKGROUND OF THE INVENTION
The field of the invention pertains to internal combustion engines and, in particular, to fiber optic sensors for instantaneous cylinder pressure in operating engines.
An automatic cylinder pressure sensor mounted under the hood of a vehicle is exposed to widely fluctuating temperatures both in the transducer tip area as well as in the sensor signal conditioner location. Current signal conditioner specifications require operation at −40° C. to up to 120-150° C., depending on conditioner mounting location, while the transducer tip temperature is specified in the range of −40° C. to 300-350° C. During normal continuous engine operation the transducer temperature is typically in the 150-250° C. range. During a cold engine start the transducer temperature change from −40° C. to its operating temperature occurs in a matter of several seconds.
During a vehicle lifetime, under hood temperatures over 125° C. occur relatively rarely and in special situations such as prolonged driving at maximum load (e.g., up hill towing) or in a hot climate (e.g., Arizona). In addition, the maximum temperature varies significantly depending on under hood location. Mounting near engine exhaust ports may expose a sensor signal conditioner to radiant heat in addition to ambient temperatures, whereas, in contrast locating a sensor signal conditioner near an air intake may reduce peak temperatures by as much as 20-30° C.
Unless protected and compensated, temperatures over 125° C. may result in the failure of an LED light source in the sensor signal conditioner for the fiber optic sensor. While a maximum LED storage temperature is typically 150° C., the maximum operating temperature must be lower so that the LED p-n junction temperature does not exceed 150° C. Typically, the LED current heats the junction leading to a differential between ambient and junction temperature of 10-20° C. When an LED junction reaches 150° C. rapidly growing defects result in output power reduction and potential LED failure. While in some applications an LED can be thermoelectrically cooled, in high volume automotive use the cost constraints prohibit use of any such cooling devices.
SUMMARY OF THE INVENTION
This invention comprises several associated techniques intended to protect a diaphragm type fiber optic cylinder pressure sensor from the effects of maximum under hood temperatures and to minimize errors associated with rapidly changing under hood and engine temperatures. In particular, the invention:(i) reduces maximum LED temperature by attaching the sensor signal conditioner to a fuel line; (ii) limits LED junction temperature to less than 150° C. through “intelligent” management of LED current based on under hood temperature; (iii) minimizes errors associated with sensor temperature changes occurring during the transition between cold engine cranking and engine firing; (iv) reduces temperature-related errors due to fluctuations in the coupling efficiency between optical fibers and the LED (or photodiode); and (v) minimizes the thermal shock error associated with rapidly varying cylinder gas temperatures.
The techniques include electronic compensation in response to temperature change, fuel system cooling of the optoelectronic interface, construction of the interface and construction of the sensor tip.
REFERENCES:
patent: 5446279 (1995-08-01), Hsu
patent: 5693936 (1997-12-01), Komachiya et al.
patent: 6094990 (2000-08-01), Lykowski et al.
patent: 6122971 (2000-09-01), Wlodarczyk
Deimen James M.
Jenkins Jermaine
Lefkowitz Edward
LandOfFree
Automotive cylinder pressure sensors does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Automotive cylinder pressure sensors, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Automotive cylinder pressure sensors will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3234688