Improved Oxygen Sensor for Automobile Application and its Manufacturing Thereof

• In order to address the pollution, India has leapfrogged from Bharat stage-IV to Stage-VI in 2020 itself. All the Bharat stage –VI vehicles should be installed with oxygen sensor.
• The oxygen sensor chip is the indigenous solution for the Country’s immediate requirement.

CSIR-NAL has developed the sensing elements for narrow band oxygen sensor by high temperature co-fired ceramic (HTCC) process for Bharat stage VI vehicles. The process is suitable for industrial scale fabrication. The sensor is constructed with durable high temperature ceramics. It consist of inbuilt reference air channel and a Pt heater. The sensor is designed with four terminals. Two terminals are for heater and one terminal is for sensing electrode and the other one is for air reference. The sensing element can be utilized for commercial packages as the dimensions are matched to the commercial sensors. The sensor reaches the maximum temperature (>600 °C) within 10 s. The NAL fabricated oxygen sensor shown performance equivalent to BOSCH oxygen sensor and found to be compatible with vehicle engine control unit (ECU).

Application Sector:

• Energy
• Environment
• Automotive

• Controls the cracks due to thermal mismatch between zirconia sensing part and alumina based heater are avoided by using alumina insulation paste for covering heater from all sides and laminating between YSZ tapes instead of using separate set of alumina tape for heater section
• Sensor lead oxidation is avoided by web of seven filled Pt vias, without the presence of air gap.
• Titania and nano MgAl₂O₄ spinel power mixture is used in poison protection layer over sensing tip for effective protection from exhaust emissions contain phosphorus, silicon, lead, zinc, iron, chromium and calcium.
• Structural integrity of sensing tip is realised by using novel air cavity design wherein the front section is made of printed fugitive paste and only the rear end has channel cavity filled with fugitive ink.
• Laser micro-machining of tapes were carried out to impart 0.7 mm radius of curvature for porous fill cavity.
• Compressed powder consisting of steatite, borosilicate glass and hexagonal boron nitride is used to hermetically seal the sensing end from the rear end of the element during packing in metal casing.
• Novel sensor cap design for preventing heavy particles from entering sensing chamber.