Resolution of Automotive Air Compressor Noise in Low Powered ICE vehicle

Passenger compartment's interior noise and thermal performance are one of the essential criteria for the driving comfort of vehicles. This paper explains that how the AC compressor noise is optimized in specific to low powered 1 L - ICE engine and 120 cc IVDC compressor combination. This combination is quite challenging due to high operational load & higher operating pressure. For better in-cabin cooling efficiency, compressor operating efficiency to be improved which in turn leads to higher displacement of the compressor. Higher displacement will lead to higher internal forces which leads to more structure borne induced noise in-side the cabin. For this specific combination, the compressor operating pressure reached to 25 bar at most of the driving condition. During dynamic driving condition, compressor metallic tonal noise was reported in one of the A segment vehicle developments. It was reported as very annoying to inside passenger. Transfer Path Analysis, Compressor fixation point stiffness, Dynamic noise signature analysis have been done as a part of Root Cause Analysis. It has been identified that compressor metallic noise signature is a mixture of moaning & whining noise. The root cause is identified as compressor internal excitation forces are creating dominant excitation at higher compressor operating pressure which causes the metallic tonal noise. Several countermeasures like compressor pulley ratio change to decouple the engine firing frequency excitation, AC pipe bend to reduce the excitation force, acoustic mass & compressor mounting stiffness optimization has been tried. Collaboration work has been done with compressor supplier to deep dive on MFCV settings, compressor shaft tolerance adjustment. Compressor pulley ratio change & Compressor planetary plate angle modification gives almost 6 dB(A) improvement in compressor order & avoided the customer perceived annoyance. As a capitalization, key NVH rules have been deployed.