Real-Time Torque Estimation of an Air Conditioner Compressor for the CO2 Emissions Reduction from an Engine Vehicle

Reducing the CO2 emissions from all new cars is essential to prevent a climate emergency. Even in the trend of accelerating the uptake of zero-emission models, the market forecasting of engine vehicles is still high in 2030. The technology to improve the CO2 emissions from conventional engine cars is getting more important. This paper introduces the new technology which is about the optimization of engine control to reduce the CO2 emissions of conventional engine cars. The engine has various accessories and the engine controller considers loads of various engine accessories to control the engine power. While running of air conditioner, the load of the air conditioner compressor has a huge portion of the total engine load. The torque of the A/C compressor is about 10 ~ 30% of the total engine torque at idle conditions. Inaccurate compressor torque estimation causes huge RPM fluctuation or even engine shut-down. And it results in NVH issues, poor drivability, poor fuel economy, and serious car accidents. Variable displacement A/C compressor has become the most popular compressor type for fuel economy. While driving, engine RPM is continuously changed by a driver. A/C compressor RPM is also changed by this dramatic engine RPM changes. These RPM changes cause mass flow changes of refrigerant which are results in the unstable cooling capacity of an evaporator. Thus variable displacement compressor continuously changes the stroke by itself to maintain the stable cooling capacity. The control valve of the compressor senses the changes of suction pressure of the refrigerant and controls the stroke mechanically by controlling the mass flow of pressurized refrigerant in the compressor. By this mechanical stroke control of the control valve, the compressor can react to the dramatic changes of engine RPM. But, due to this dynamic and mechanical stroke changes, the A/C controller can not estimate the accurate changing timing and values of A/C compressor torque. By real-time stroke sensing of A/C compressor and the new torque logic which uses stroke signal, the accurate torque value at transient engine RPM conditions can be estimated. This paper focuses on testing to validate the torque estimation accuracy and the effect of CO2 emissions reduction. This technology has been validated at the compressor test bench, A/C system test bench, and vehicle.