Lambda probe

Oxygen sensor or lambda sensor, the sensor is usually placed in the exhaust pipe. With modern cars it can be found both before and after the catalytic converter, so they are usually two. Lambda probe evaluates the amount of oxygen in the exhaust gases. This information provides a control unit which, based on data obtained regulates fuel mix ratio.

The most effective way to reduce harmful emissions in the exhaust gases from the engines is the lambda control in conjunction with a catalyst . For proper functioning of the three-way (directed) catalyst, the engine burned stoichiometric mixture with the value λ = 0.99 - 1 This very small range is acceptable for the modern internal combustion engines with direct fuel injection difficult to maintain in all modes of engine operation. For this reason, using lambda control. Lambda probe is the main part of a regulatory circuit that keeps the air fuel mixture composition in the optimal region, the so-called lambda window.

dependence of excess air λ and the production of harmful gases

Principle:

Processing of the three components of the exhaust gases is possible only in a very narrow range, the so-called lambda window. This can be achieved only lambda control. Is used to control oxygen sensor (lambda probe), which is located before the catalytic converter in the exhaust stream. When λ = 1 jumps almost step change in voltage from one voltage level to another. Lamda probe is the engine control unit provides information on whether the mixture is combusted rich (λ <1) or poor (λ> 1).

lambda probe cut

A cold engine needs to run an even richer mix (λ <1), lamba regulation can therefore be started only after exceeding a certain threshold temperature of the engine. Therefore, today the most used heated lambda probe with zirconium oxide ceramics. The lambda sensor contains a ceramic plate coated with layers that serve as electrodes. One electrode is connected with ambient air and the other with the exhaust gases. Due to differences in oxygen concentration occurs between the electrodes voltage U. The resulting voltage is fed to the engine control unit, which calculates the value of λ.

Ceramic IUD is placed in a metal tube with multiple holes to protect against thermal shock and mechanical damage. The ceramic material becomes conductive when the temperature of 350 ° C, which is why today all lamba probe heated. This is achieved faster readiness to probe measurements, which may also be located away from the engine, which is less stressed. To prevent damage to the catalytic active external platinum electrodes, the motor must be powered by unleaded fuel!

History

Lambda probe was developed in the late sixties by Bosch. First use of passenger cars came in 1976 with the Volvo 240 car / 260th The development went on, however, and in 1982, Bosch introduced the first heated lambda probe, which began to operate within a minute of starting a cold engine, furthermore, the probe was twice extended life. In 1994, Bosch became the first manufacturer of Lambda sensors with planar ceramic technology. This model is fully functional for 10 seconds after the engine is started. With a broadband lambda sensor can measure rapid changes in the composition of exhaust gases of individual cylinders and regulate the amount of fuel injected in each cylinder engine separately.

What you did not know

Lambda sensor for diesel engines
The company started to use Robert Bosch lambda probe in the control systems of diesel engines. With their help can be even more efficient diesel engines and achieve lower emissions. With lambda probes can be closer synchronization control injection system and custom engine to reduce fuel consumption and emissions.