Dual Mass Flywheel Research Articles

Compensation of sub-harmonic vibrations during engine idle by variable fuel injection control

Today, in many passenger cars and light trucks, the conventional driveline is extended by a dual mass flywheel (DMF). The DMF reduces driveline oscillations by mechanically decoupling the transmission from the periodic combustion events that excite the engine crankshaft. Existing engine control systems are designed for conventional single mass flywheel (SMF) systems. In the future, to facilitate the optimal control of engines equipped with advanced DMF systems, such conventional control systems may require adaptation, modification or even replacement. The basic task of idle speed control systems is to maintain a defined setpoint of rotational engine speed independent from engine operating conditions (e.g. load disturbances). Due to the torque reactions of the DMF, control systems designed for engines with SMF can be disturbed, leading to unstable engine idle (e.g. sub-harmonic vibrations, oscillations following load rejection, etc.) In this approach, an optimised solution for idle speed control regarding conventional combustion engines equipped with DMF is introduced. The enhanced control system is based on conventional PID-control strategies with improved fuel injection scheduling. Using incremental (i.e. tooth-to-tooth) engine speed, critical dead times, which can lead to limit cycles in non-linear closed-loop control circuits, are minimised. Limit cycles, which are distinguishable as sub-harmonic vibrations at the same frequency, are effectively reduced by improving load rejection at idle. The implementation of these solutions in current engine management systems requires no additional sensors or other hardware.

The DMF as a virtual sensor

In a co-operative project between the University Karlsruhe (TH) and the company LuK a new method has been developed, which permits an accurate estimation of both the instantaneous engine and driveline torques, based upon the systematic modelling of the dual mass flywheel. Real time knowledge of the instantaneous engine torque allows the realisation of efficient and cost-effective algorithms for control and diagnosis (e.g. cylinder balancing and OBD-misfire detection) within future engine management systems.

Gear teeth impacts in hydrodynamic conjunctions promoting idle gear rattle

The rattle phenomenon in vehicular transmissions and its impact on the automotive industry have been widely reported in the literature. A variety of palliative measures have been suggested for attenuation of rattle such as use of backlash eliminators, clutch dampers or dual-mass flywheels. These palliative measures incur further costs and can have untoward implications in powertrain noise and vibration problems. A fundamental investigation of the dynamics of impacting gears is undoubtedly the way forward for a root cause solution. This paper introduces a new approach for understanding the interactions between the transmission gears during engine idle conditions by taking into account the effect of lubrication. Gear impacting surfaces are treated as lubricated conjunctions rather than the usually reported dry impacting solids. Depending on load and speed of entraining motion of the lubricant into the contact domains, the regime of lubrication alters. In this paper, the influence of lubricant in torsional vibration of lightly loaded idling gears is examined which promotes iso-viscous hydrodynamic conditions. It is shown that the lubricant film under these conditions behaves as a time-varying nonlinear spring–damper element. Spectral analysis of the system response is compared to the findings of the linearised system.

ESTIMATION OF THE INSTANTANEOUS ENGINE TORQUE FOR VEHICLES WITH DUAL MASS FLYWHEEL (DMF)

Today, in many passenger cars and light trucks, the conventional driveline is extended by a dual mass flywheel (DMF). The DMF reduces driveline oscillations by mechanically decoupling the crankshaft and the transmission. Existing engine control systems are designed for conventional single mass flywheel (SMF) systems. In the future, to facilitate the optimal control of engines equipped with advanced DMF systems, such conventional control systems may require adaptation, modification or even replacement. In this approach, a method for estimating the instantaneous engine torque of vehicles with conventional combustion engines and dual mass flywheel is introduced. The reconstructed engine torque can be used advantageously for advanced controller designs (e.g. cylinder balancing, misfire detection, anti-jerk control, etc.) as well as for analysing the current state of the combustion engine regarding injection time and quantity, combustion quality, incylinder pressure, etc.

Analysis of Dual Mass Flywheel Using Discrete Arcspring Model

This paper presents a discrete analysis approach to investigate performance of the DMF. An arcspring installed between the flywheels is modeled as n - discrete elements. Each element consists of mass, spring and nonlinear friction element. The nonlinear friction model is proposed to describe Stribeck effect and viscous friction depending on the relative sliding velocity. The DMF performance such as hysterisis characteristics are investigated by comparing the experimental result. In addition, the torque characteristics transmitted to the driveshaft are evaluated by comparing the test result from manual transmission bench tester. It is found that discrete DMF model described the automotive driveline behavior closely. It is also found that the friction characteristics of the arcspring depends on the relative sliding velocity between the friction surfaces, which varies depending on the relative position of the DMF arcspring.

Effect of a Dual-Mass Flywheel on the Impact-Induced Noise in Vehicular Powertrain Systems

The appearance and persistence of impact-induced clonk noise in rear wheel drive light truck drivelines has led to an urgent need for remedial action. The pressure for delivering results within tight schedules and financial constraints has resulted in palliative actions rather than fundamental investigations. It has been speculated that the use of a dual-mass flywheel (DMF) can lead to attenuation of clonk metallic noise, even though its main purpose has been to counter transmission rattle by reducing the input torsional impulse. The present work investigates the effect of DMF on impact-induced clonk noise and its severity through experimentation. Sound measurements in the driveline only reveal a slight reduction in the overall levels of impact-induced noise, but a significant change in its quality - the sharpness associated with the typical metallic content of clonk is absent. The effect is also highlighted by the main frequency content of the response when DMF is employed. The duration of the clonk phenomenon is altered from the case where a traditional single solid-mass flywheel is employed.

Experimental investigation of the dynamic behaviour of torsionally flexible drive elements

This article describes the possibilities that arise from a test rig for drive elements under torsional vibrations at the Institute for machine elements, gears, and transmissions at the University of Kaiserslautern. Considering three examples, it is shown, how dynamic parameters can be collected during use. Examined is a dual-mass flywheel at different revolution speeds, a chain drive system as it is used in a timing assembly as well as a rubber vibration absorber of an auxiliary aggregate.

Launching Performance Analysis of a Continuously Variable Transmission Vehicle With Different Torsional Couplings

This article describes the launching behaviors of passenger cars equipped with continuously variable transmission (CVT), which have different torsional couplings: a torsion damper and a dual mass flywheel. To reduce the driveline vibration and noise, a torsional coupling is installed in the CVT vehicle, in which the wet type multiplate clutch is used as a start device. In addition, a torsional coupling makes considerable effects on the launching performance of a vehicle. The launching performances, considered here, are the acceleration performance with various throttle positions and the transient characteristics of vehicle creep and throttle tip-in. By using the mathematical models of each driveline component, we developed a simulation program to investigate the launching performance in various launching conditions. In order to verify our simulation program, we performed the road test of a prototype vehicle that has torsion damper as a torsional coupling. Finally, we analyzed and compared the launching performances in two cases of a torsion damper and a dual mass flywheel using the developed simulation program.