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In internal combustion engines, mainly the Brazilian flex fuel versions, the compression ratio is an important factor to ensure its correct operation, and especially to ensure that the end customer gets a vehicle with net power within the calculated and specified limits by Product Engineering. An inadequate compression ratio can greatly affect the engine performance and, in the same proportion, affect the end customer satisfaction, reliability and loyalty to the brand. The methodology to be presented in this work is based on the 3D virtual simulation software developed by Dimensional Control Systems Inc., the 3DCS® v.7, where through random combinations of dimensional variations of each component involved in the system it is possible to calculate the nominal compression ratio and the variation limits, simulate statistical values that actually happen in real life, and obtain a ranking of the contribution percentage of each variable to the total variation in compression ratio.

The continuous research for better performance and reduction of fuel consumption demanded the development of analytical techniques to better understand the rattle mechanism, with complex non-linear models being widely used for simulation. In regards to the fuel, the “flexible” engines, which can work with any mixture of gasoline/ethanol, are already a reality in the Brazilian market. These flex-fueled vehicles present higher values of irregularity, creating a specific scenario for this market. Several models with static approach of the clutch damper can be found in the available literature with limited measured data, which makes life difficult to validate or correlate these models. For this reason, the analytical formulation of dynamic clutch dampers developed high importance for solving and/or reducing clearance-induced vibro-impact problems which leads to rattle noise.

The clutch system works basically as an interface between the engine and the vehicle. The engine provides power and torque in a given revolution while the vehicle launches. The slip time is a critical moment for the clutch during vehicle launch. So, lots of studies have been done to predict the total slip time and related amount of energy during clutch engagement. Considerations about this energy are highly important in clutch capacity analysis, and the studies available evaluate several aspects that take place during the slipping phase, where simple or complex models represent all dynamics involved in the related systems.

The internal combustion engine, clutch, transmission, propeller shaft, differential, half shafts and driven wheels compose the powerline of a vehicle which, due to several reasons of refinement and weight, offers low noise “counter resistance” to engine irregularity. If the torsional vibration created by the combustion engine is transmitted to the vehicle driveline, it may cause there transmission rattle noise and body boom. The torsional damper integrated into either the clutch disc or the flywheel is applied to provide the driveline with lower torsional vibration optimizing transmission and body noises. In order to achieve torsional damper development time gains, this report presents a collection of elements to analyze the torsional vibrations created by an engine during calibration phase, and preview the vibration response tendency for a specific driveline by computer simulation.

1 During the development of a new clutch disc damping system and after three months of hard work the engineering team got stuck with unsatisfactory system performance (rattle noise), despite the help of a computer simulation software. The only alternative seemed to be using a more expensive damping concept but, besides the fact that there wasn't much development time left, that option would increase part cost by unacceptable US$ 200, plus development cost. The team then decided to try Taguchi's Robust Engineering optimization approach for the first time. In just two weeks the authors got a 4.6 dB gain on the signal-to-noise ratio. That allowed us to keep the initially proposed system, thus avoiding the cost increase. Besides, the authors were able to keep the development schedule on track.

This paper was prepared in order to supply a complete guide which aims to show the key points of clutch disc, plate and flywheel development, and its release system design for medium and heavy duty vehicles. It will be demonstrated also which is the impact of the potential failures during the whole life of all components involved.