PSI - Issue 14

Varatharaj Neelakandan et al. / Procedia Structural Integrity 14 (2019) 345–353 Varatharaj Neelakandan / Structural Integrity Procedia 00 (2018) 000–000

347

3

2. Process of Design optimization for housing bracket The starter motor housing bracket is mounted on the engine block through bolts with the adequate designed tightening torque. It is initially mounted with pre-stress load and the additional load of the torque transferring to the housing bracket which is more sever to the fatigue life. The requirement of the starter motor weight reduction is more demanding from the vehicle manufacturers for the various reasons like emission reduction and higher efficiency requirements along with vehicle package constrains. The housing bracket is identified as a more potential component to reduce the weight from the teardown study. The housing bracket operation and its functions are understood and prepared the optimization process considering the material feasibility and fatigue life targets. The following Figure 3: Housing bracket optimization procedure. Housing bracket optimization procedure is followed in this study.

Collect the Starter motor pinion torque

Calculate Housing bracket bearing reaction force

Prepare the 3D Model – Housing Bracket

Start

Apply loads and constrains and FE meshing

Apply material property and S-N curve

Stress analysis and results review

Fatigue analysis and results review

Set the Weight / Ftaigue target for optimisation

Stress and fatigue anlysis / Calculate FOS

Design modifications

Check the results and End

Figure 3: Housing bracket optimization procedure

2.1. Housing bracket bearing load calculation Housing bracket hold the internal parts like motor armature, shafts, solenoid and bearings. The torque load coming from the pinion is a reaction applied to the housing through bearing mounted into the housing bracket. The pinion is connected to the flywheel ring gear with the orientation with respect to the engine mounting configuration. The housing bracket bearing load is calculated after the detailed free body diagrams study references by Rishikesh patil (2017) as shown in Figure 4: Bearing reaction load free body diagrams. The pinion force is considered while the pinion engage condition with ring gear and the pinion parameter is considered for the bearing reaction load calculation. From the free body diagrams, the pinion rotates at anticlockwise direction while seeing from the pinion side and the bearing locations are measured for the reaction load calculation. The pinion torque is taken from the starter motor performance curve as shown Figure 1: Starter motor and ring gear engagement . and that is the lock torque of 34Nm which is the higher torque expected during normal operation. Pinion pitch circle diameter and pressure angle 20 degree are considered for the force calculation.