Instantaneous Friction Torque Research Articles

Study of Total Instantaneous Friction Torque of a Compression Ignition (CI) engine - A numerical and experimental approach.

To be able to provide an accurate estimate of the effective torque, friction losses must be modeled. The details of a model that predicts the total instantaneous friction torque for compression ignition engines are described. The model is based on a combination between the dynamic model of the crankshaft and the thermodynamic model. The total instantaneous friction torque is determined, via the instantaneous measurements or numerical predictions of the gas pressure in the combustion chamber, the speed of rotation of the crankshaft and load torque. The comparison between the experimental data and the results of the numerical simulation shows a good agreement.

Real-time friction torque estimation on a diesel engine using the crankshaft speed fluctuation

Under the pressure of stricter regulations on pollutant emissions and the desire of users for lower fuel consumption and more comfortable driving, engine control based on torque has been developed. To provide an accurate estimate of effective torque, friction losses must be modeled. The details of a model that predicts the total instantaneous friction torque for compression ignition engines are described. The model is based on a combination of the dynamic model of the crankshaft and the thermodynamic model. The total instantaneous friction torque is determined using the instantaneous measurements or numerical predictions of the gas pressure in the combustion chamber, the rotational speed of the crankshaft and the load torque. The experimental data and the numerical simulation results were compared. The comparison between the different variables shows a good agreement between the simulation and the experimental results.

Modelling of an automotive dual mass flywheel

Accurate knowledge of the instantaneous friction torque of an automotive clutch is a key claim while achieving comfortable, automated gearshifts, improving fuel economy or reducing wear. Nevertheless, torque sensors are not commonly used in automotive drive trains because of their additional size and costs. Thus, to estimate the clutch torque, a detailed dynamic model of each component integrated into a clutch system is needed.In the following, a nonlinear dynamic model of a Dual Mass Flywheel (DMF) as autonomous part of a clutch system is presented and verified by test bench data. A DMF is used to reduce the cyclic irregularity of the torque generated by a combustion engine. It is typically assembled between crankshaft and clutch. The level of detail of the modelled DMF dynamics is chosen in a way that a real-time simulation on a car's control unit is feasible. Using the engine speed and the clutch torque as model inputs, the proposed model has the ability to simulate the DMF deflection and therefore the clutch rotational speed. Resulting torques acting on the DMF's primary and secondary mass are reconstructed, too. If both rotation speeds of the DMF masses (the engine and clutch speed) can be measured, this model can also be used to reconstruct the clutch torque.

Enhancement of the accuracy of the ( P–ω) method through the implementation of a nonlinear robust observer

The ( P–ω) method is a model-based approach developed for determining the instantaneous friction torque in internal combustion engines. This scheme requires measurements of the cylinder gas pressure, the engine load torque, the crankshaft angular displacement and its time derivatives. The effects of the higher order dynamics of the crank-slider mechanism on the measured angular motion of the crankshaft have caused the ( P–ω) method to yield erroneous results, especially, at high engine speeds. To alleviate this problem, a nonlinear sliding mode observer has been developed herein to accurately estimate the rigid and flexible motions of the piston-assembly/connecting-rod/crankshaft mechanism of a single cylinder engine. The observer has been designed to yield a robust performance in the presence of disturbances and modeling imprecision. The digital simulation results, generated under transient conditions representing a decrease in the engine speed, have illustrated the rapid convergence of the estimated state variables to the actual ones in the presence of both structured and unstructured uncertainties. Moreover, this study has proven that the use of the estimated rather than the measured angular displacement of the crankshaft and its time derivatives can significantly improve the accuracy of the ( P–ω) method in determining the instantaneous engine friction torque.

Experimental and Theoretical Study of Instantaneous Engine Valve Train Friction

A new method has been developed to directly measure valve train friction as a function of crank angle using specially designed timing belt pulley torque transducers fitted to the inlet and exhaust camshafts of a single-cylinder gasoline engine. Simultaneous and instantaneous friction torque of both the inlet and exhaust camshafts at any engine speed can be measured, with no apparent detrimental effect of timing belt loading on the output reading. Experiments are reported for valve train friction at a range of motored engine operating conditions with different lubricant formulations, with and without a friction modifier. These are compared with the predictions of an existing valve train friction model based upon elastohydrodynamic lubrication theory. Measured friction decreased with increasing engine speed but increased with increasing oil temperature and the fuel economy benefit of friction modifiers was observed. The model yielded similar magnitudes of friction at medium engine speeds and above but predicted much lower friction with high oil temperatures at low speed. Comparison of theory and experiments also suggests that some oil may leak from hydraulic lash adjusters during the cam event with a consequent reduction in geometric torque.

A New Approach to Determine Lubrication Regimes of Piston-Ring Assemblies

A new approach is developed to determine piston-ring assembly lubrication regimes from the instantaneous frictional torque measured for the whole engine. This is based on the variation of the friction coefficient with the duty parameter in the Stribeck diagram over the mixed and hydrodynamic lubrication regimes. The derived equation determines the lubrication regimes from the slope of the line in the Stribeck diagram. A single cylinder spark ignition engine was instrumented to determine the total instantaneous frictional torque of the engine. Experiments were conducted under different loads at a constant speed. Results show that the regime is mixed lubrication near the top dead center (TDC) and shifts to the hydrodynamic lubrication regime as the piston moves away from TDC. The extent of the mixed lubrication regime depends on engine load and speed.

Error Analysis of Time-Dependent Frictional Torque in Reciprocating Engines: Effect of Cylinder Gas Pressure

Errors in the cylinder gas pressure due to zero drift, and changes in sensitivity caused by thermal stresses were investigated. Five quartz-crystal pressure transducers, of different makes and designs, were used in a single-cylinder diesel engine to measure the cylinder gas pressure and determine the instantaneous frictional torque and frictional mean effective pressure. All pressure data were obtained by using calibration constants determined from a dead-weight tester at atmospheric conditions, according to the manufacturer's specifications. Errors in the pressure caused by steady and transient variations in the transducer temperature were investigated under simulated engine conditions. The calibration of the transducer which gave the best performance was made at elevated temperatures. A new calibration constant was determined. The error in the instantaneous frictional torque due to the calibration at atmospheric conditions was determined. Presented as a Society of Tribologists and Lubrication Engineers ...

Tappet Rotation and Friction Reduction in a Center Pivot Rocker Arm Contact

The instantaneous tappet rotation velocity and instantaneous friction torque were measured simultaneously for the CVH center pivot rocker arm geometry. The measurements were made in a cam/tappet friction apparatus equipped with a laser reflectance tappet rotation monitor capable of following rapid changes in tappet rotation velocity. The data showed that more rapid tappet rotation resulted in lower friction. The effect was greatest in the region of maximum cam lift. Several tappets were modified to produce higher rotation rates than production tappets. The best results were obtained with tappets incorporating an internal squeeze film bearing to reduce resistance to rotation. The data were analyzed to elucidate the cause for the friction reduction effect. The analysis showed that most important effect was the partial rolling motion between the surfaces, rather than enhancement of the oil film thickness. A model based on that conclusion agreed reasonably well with the experimental data.

Measurement and Analysis of an Instantaneous Friction Torque Utilizing an Accurate Revolutional Speed Detector

エンジンのシリンダ内圧力, 正味トルク, クランク角速度からサイクル内摩擦トルク変化を計測することを試みた. これに必要な高精度角速度計, および多気筒のシリンダ内圧力と回転数を同時に時系列に記録できる解析装置, 両者を開発した. これらを用いた実験から, この方法は従来の平均値のみの計測よりも多くの知見が得られることおよび駆動系のねじり振動解析におけるエンジン減衰係数の測定にも利用できることがわかった.