Method of reducing cold start emissions in hybrid electric vehicles

An electronic control unit for use in a hybrid electric vehicle, comprising one or more electronic memory units and processing units that are configured for carrying out the method steps comprising:

• detecting a cold start condition,
• injecting fuel into a combustion engine such that combustion at a lambda value, λ, is achieved for which λ>1,
• running the combustion engine at a speed of 1000 rpm or higher,
• determining if the efficiency of a catalyst reaches a predetermined first level,
• setting λ to about 1 after the predetermined efficiency level of the catalyst has been reached, and
• reducing the engine speed to working conditions when the catalyst efficiency reaches a predetermined second level.

A hybrid electric vehicle having an internal combustion engine with an exhaust duct having a catalyst and an oxygen sensor downstream of the catalyst, an output of the combustion engine being connected to an electric generator that is connected to an electric motor which is coupled to a drive shaft of two or more wheels and a motor control unit connected to the combustion engine and to the electric motor for controlling the injection of fuel into the cylinders of the combustion engine and for the operation of the electric motor, the control unit being configured for carrying out the method steps comprising:

• detecting a cold start condition,
• injecting fuel into the combustion engine such that combustion at a lambda value, λ, is achieved for which λ>1,
• running the combustion engine at a speed of 1000 rpm or higher,
• determining if the efficiency of the catalyst reaches a predetermined first level,
• setting λ to about 1 after the predetermined efficiency level of the catalyst has been reached, and
• reducing the engine speed to working conditions when the catalyst efficiency reaches a predetermined second level.