Attracting Tomorrow Media-resistant pressure sensors for aggressive fuel line environments

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1 Technologies & Products Press Conference 2017 Media-resistant pressure sensors for aggressive fuel line environments Highest accuracy for compliance with stricter emissions regulations Malte Fengler Product Marketing Pressure Sensors Temperature & Pressure Sensors Business Group November 21, 2017

2 Drivers for automotive fuel applications Attracting Tomorrow Legal requirements Reduction of fuel consumption Reduction of hazardous vapors Direct on-board diagnostics (OBD) New and stricter environmental regulations (especially NAFTA, China and Europe) Fuel trends Less sulfur More bio-fuel blends Higher alcohol content More non-standardized fuels and fuel-blends Throttle Evaporative emission control system Vapor canister Vent Fuel tank pressure sensor Fuel level sensor Fuel in tank Sealed fuel cap Vapors Increasing requirements for accurate pressure sensing CC 11/17 2

3 Prerequisites for accurate pressure sensing Basic functional principle of a pressure sensor Pressure applied Diaphragm bends Resistance changes Voltage changes Signal is conditioned Wafer level package Bond pads Key performance factors for accurate pressure sensing over lifetime High selectivity High sensitivity High stability CC 11/17 3

4 Challenges of accurate pressure sensing in aggressive fuel environments Design of conventional pressure sensors Elastomer p absolute Diaphragm Fuel Wire bond Plastic housing Offset error (typ.) [%FS] Time after media contact [h] Time to peak 1 h 8 h Saturation: ±0.3%FS Time to saturation: 5 h 40 h Potential failure mechanisms Result Swelling and shrinking close to stress-sensitive elements Swelling within geometrical constraints Chemical embrittlement Signal drift Fissures drift and leakage Signal drift and leakage CC 11/17 4

5 What happens when elastomers and fuel interact? Aggressive fuels cause elastomers to diffuse, swell, dissolve or become brittle Material Solvent Conditions Swelling range [%] Gummy bears Water C Elastomers Fuel C 4 60 C CiBu24a 4 60 C Plastics Fuel C C 0-8 CiBu24a C 0-25 Good values are <30% for elastomers and <5% for plastics Fuel blends may cause nonlinear behavior: Highest swelling for some elastomers is reported for blends with 20% to 30% ethanol Fuel C 50% Isooctane, 50% Toluene CiBu24a Fuel C with 24% isobutanol (same oxygen content as E15) Reaction of elastomers with fuel mixtures is the main root cause of signal drift and mechanical failures CC 11/17 5

6 Advanced sensor design for fuel lines Attracting Tomorrow All plastics and elastomers that come into contact with fuel are replaced with glass-based CTE-matched materials Silicon pressuresensitive element Elastomer replaced with CTE-matched material CTE = coefficient of thermal expansion Fuel Fuel No swelling of materials and interconnections No diffusion High temperature resistance up to 125 C for flexible integration No impact expected for future fuel mixtures and additives CC 11/17 6

7 Fuel line sensor platform for high accuracy pressure sensing applications Key applications Electrical controlled fuel pump Vapor and tank control, especially for hybrid vehicles Tank venting valve FEATURES Different pressure readings Absolute or gauge 350 mbar to 25 bar (35 kpa to 2500 kpa) Flexible output signals Digital interface (SENT) for OBD and additional temperature sensing Analog output (0.5 V to 4.5 V) Highest accuracy over lifetime For new demanding applications One technology many integration options multiple applications CC 11/17 7

8 Today s sensing accuracy requirements Absolute pressure accuracy at 0 C < T op < 80 C mbar +10 mbar 8 Accuracy [mbar] Accuracy requirements of conventional fuel tank systems mbar -10 mbar Pressure (gauge) [mbar] Relatively high accuracy only possible within a small pressure range Limited possibilities for different fuel applications CC 11/17 8

9 Future sensing accuracy requirements Absolute pressure accuracy at 0 C < T op < 80 C mbar +10 mbar 8 Accuracy [mbar] mbar -5 mbar Accuracy requirements of future fuel vapor leakage controls mbar -10 mbar Pressure (gauge) [mbar] Narrower tolerance over the entire pressure range is necessesary to fullfill stricter evaporative emission requirements CC 11/17 9

10 New pressure sensor for most accurate fuel vapor leakage detection Key technical data Relative sensing accuracy of <0.2% Gauge measurement over range from -100 mbar to 500 mbar (-10 kpa to 50 kpa) Digital interface (SENT) for OBD and additional temperature sensing Wide operating temperature range of -40 C to 125 C Advantages over conventional leakage control systems Simplified integration Miniaturization Improved accuracy Cost reduction for material and power consumption CC 11/17 10

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