Tribodynamics of a new declutch mechanism aimed for engine downsizing in off-road heavy-duty vehicles

Abstract

Clutches are commonly utilised in passenger type and off-road heavy-duty vehicles to disconnect the engine from the driveline and other parasitic loads. In off-road heavy-duty vehicles, along with fuel efficiency start-up functionality at extended ambient conditions, such as low temperature and intake absolute pressure are crucial. Off-road vehicle manufacturers can overcome the parasitic loads in these conditions by oversizing the engine. Caterpillar Inc. as the pioneer in off-road technology has developed a novel clutch design to allow for engine downsizing while vehicle’s performance is not affected. The tribological behaviour of the clutch will be crucial to start engagement promptly and reach the maximum clutch capacity in the shortest possible time and smoothest way in terms of dynamics. A multi-body dynamics model of the clutch system is developed in MSC ADAMS. The flywheel is introducing the same speed and torque as the engine (represents the engine input to the clutch). The hydraulic pressure is applied behind the piston to initiate the engagement. The angular motion of the plates is supported by friction torque between the plates and friction linings. The conjunctions between paper-based linings and steel plates are designed to be dry. Friction (the most significant tribological feature of the linings in torque transmission) is measured in a pin-on-disc tribometer and mapped into the dynamics model in MSC ADAMS. The pin-on-disc tribometer is able to capture the variation of friction coefficient with contact pressure and sliding velocity. The surface topography is obtained experimentally to examine the consistency of surface properties. The normal pressure and tribology of the contacting components determines the engagement time, clutch capacity and dynamic behaviour of the clutch.