Practical Approach to Enhance Gear Shift Quality in Automatic Transmissions 2021-01-0688

Passenger utility vehicles like car, SUVs, MPVs are used in wide application all over the world. Luxuries are becoming essential features of product mix along with comfort and ergonomics. Customer desires best shift quality with emerging technologies like AT, DCT, CVT, etc. and every OEM is working hard to achieve it. It is very difficult to satisfy the customer desire because of diversities in demographics and geographic. Gear shift quality (GSQ) is very crucial touch point in overall drive feel of vehicle. It consist of various parameters like mode selection feel, precision, comfort, select Noise, etc. It demands tradeoff practices among various parameters as stated.

In this paper, external mode selection system of automatic transmission is explained. Various contributing parameters are explained with practical design approach for detent profile, mode selection mechanism, cable & dampers, etc. Among various GSQ parameters, in-cabin noise occurred during mode selection is also one of the crucial parameters. This paper thoroughly explains inter-relation between different parameters of GSQ and its effect on mode selection noise and feel; this is explained with help of various DOEs and relation matrix. In this study various practical approaches are explained to reduce in-cabin noise and to improve shift feel without making any changes inside gearbox parameters. The intensity and causes of different parameters are explained with help problem solving tool and fish bone diagrams in the later part of paper. The conclusion is derived by referring the interrelationship matrix to decide the priority of critical contributing factors with optimized cost for reducing cabin noise & thereby improve gear shift feel.