Displacement Calculation And Optimization Of Powertrain Mounting In Full Vehicle Acceleration

Powertrain is one of the key vibration sources of passenger cars.As connections between vehicles with powertrain mount system serves for vibration isolation.In this paper vehicle mount system is investigated,linear segment of the stiffness curve is optimized in order to solve the problem of excessive vibration inside vehicle.Several different types of mount systems install with a powertrain system,while sustaining and hanging are most widely used.The decoupling rate of hanging type is about30%higher than the sustaining type,and for the vibration isolation of the second order in Z direction,the hanging type is 10dB higher than the sustaining type.For better NVH performance,the hanging type is more advantageous than the sustaining type.Under the condition of rapid acceleration,there is a large vibration inside vehicle when the engine speed reaches 2600rpm,and subjective evaluation is unacceptable.Compared with the benchmark vehicle,powertrain system,sub-frame,mounting system and steering wheel are respectively investigated and analyzed,for locating the reason for the large vibration under this condition.When the engine speed reaches 2600rpm,the powertrain outputs large peak torque,while maximum displacement of the left mount in X direction is 8.02mm,which exceeds the static stiffness of the linear length of 6.5mm,leading the suspension rubber no longer function properly,so that vibrations transmit to the vehicle directly.The feasible solution to this problem is to optimize the left mount static stiffness curve,so that the length of the linear length could be greater than the maximum displacement.After comparison calculation of the displacement with test result,there is a gap of 1mm between,which does not affect the result optimization.The displacement of the static section is increased from the original design of 6.5mm to 11mm,the maximum displacement is8.75mm under the 3rd gear under the whole throttle condition,the length of the linear segment is larger than the displacement,and the feasibility of the scheme is higher.The length of the linear segment increases from 53N/mm to 140N/mm,and the length of the linear segment increases by 5.5mm compared with the original design.When we test the protype mount on the vehicle,the 2600rpm vibration peak of the steering wheel decreased from 3.2 m/s~2 to 1.1 m/s~2,the improvement amount was 65%,the seat decreased from 0.14m/s~2 to 0.08 m/s~2,the improvement amount was 43%,the subjective evaluation improved obviously,and reached the level of the benchmark vehicle.The design of the linear section of the left static stiffness curve satisfies the displacement demand of the acceleration condition,and the mount decoupling rate,idle vibration,idle noise and acceleration noise also have some improvement,which proves that the scheme is successful.According to the mount optimization process,the general process of NVH performance development and adjustment of the mount system is summarized.