Tribodynamics of a New De-Clutch 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.

Oil film separation and drag torque in disengaged wet brakes

“…Commonly, lubricant is supplied to wet brake packs through their partial immersion into a sump (4) and via centrifugal splashing (see figure 1). This is preferred rather than the pressurised oil feed method, which is more commonly used for wet clutch applications.…”

“…Subsequently, these measured losses are subtracted from the measurements taken with the sump (4) filled to the shaft centre line (representative of wet brake operating conditions). The sump (4) temperature is altered by a heating element (6), which is used in conjunction with a control unit and thermocouple to regulate the sump temperature.…”

“…In a similar manner to wet clutches, disengaged wet brake packs can experience significant losses due to viscous drag. [8][9][10][11] Leighton et al 11 presented a combined experimental-numerical study of partially submerged, centrifugally fed wet brake losses at different sump temperatures. It was shown that the combination of cold start-up and high-speed road driving conditions would lead to a 20 kW power loss.…”

Automotive dry clutch fully coupled transient tribodynamics

“…where l kin is the kinetic friction coefficient and the effective radius ðR ef Þ is calculated as [36,37]:…”

Tribodynamics of hydraulic actuated clutch system for engine-downsizing in heavy duty off-highway vehicles

“…Dynamic models using multi-body approach with application of clamped load have been used for clutch engagement and study of take-up judder. [4][5][6][7][8] The complexity of clutch models can increase with the level of required accuracy from the predictive analysis. For example, a detailed dynamic model is essential for the traction control of a dual clutch transmission [9][10][11][12] and the study of clutch in driveline vibrations.…”