Assessment of Friction for Cam-Roller Follower Valve Train System Subjected to Mixed Non-Newtonian Regime of Lubrication

Turturro, Antonietta Celeste; Rahmani, Ramin; Rahnejat, Homer; Delprete, Cristiana; Magro, L.

doi:10.1115/ices2012-81050

Cited by 12 publications

(13 citation statements)

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“…However, roller slippage was disregarded in their analysis and no results concerning the working frictional losses at the lubricated interfaces were presented. Turtorro et al 15 also presented a cam-roller lubrication model which allows for roller slippage; however, their solution for the lubricant film thickness is obtained using analytical expressions rather than solving the Reynolds equations.…”

Section: Introductionmentioning

confidence: 99%

Lubrication and frictional analysis of cam–roller follower mechanisms

Alakhramsing

Rooij

Schipper

et al. 2017

Proceedings of the Institution of Mechanical Engineers, Part J:

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In this work, a full numerical solution to the cam-roller follower-lubricated contact is provided. The general framework of this model is based on a model describing the kinematics, a finite length line contact isothermal-EHL model for the cam-roller contact and a semi-analytical lubrication model for the roller-pin bearing. These models are interlinked via an improved roller-pin friction model. For the numerical study, a cam-roller follower pair, as part of the fuel injection system in Diesel engines, was analyzed. The results, including the evolution of power losses, minimum film thickness and maximum pressures, are compared with analytical solutions corresponding to infinite line contact models. The main findings of this work are that for accurate prediction of crucial performance indicators such as minimum film thickness, maximum pressure and power losses a finite length line contact analysis is necessary due to non-typical EHL characteristics of the pressure and film thickness distributions. Furthermore, due to the high contact forces associated with cam-roller pairs as part of fuel injection units, rolling friction is the dominant power loss contributor as roller slippage appears to be negligible. Finally, the influence of the different roller axial surface profiles on minimum film thickness, maximum pressure and power loss is shown to be significant. In fact, due to larger contact area, the maximum pressure can be reduced and the minimum film thickness can be increased significantly, however, at the cost of higher power losses.

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Section: Introductionmentioning

confidence: 99%

Lubrication and frictional analysis of cam–roller follower mechanisms

Alakhramsing

Rooij

Schipper

et al. 2017

Proceedings of the Institution of Mechanical Engineers, Part J:

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“…Previously developed cam-roller follower lubrication models (see, for instance Chiu, 3 Ji and Taylor, 4 and Turturro et al 5 ), which include the possibility of roller slippage, all rely on (semi)-analytical formulations for the film thickness distribution in the cam-roller contact. In those studies the frictional forces working at the roller-pin contact were also estimated using simple analytical formulas or were considered to be constant throughout the whole operating range.…”

Section: Introductionmentioning

confidence: 99%

A full numerical solution to the coupled cam–roller and roller–pin contact in heavily loaded cam–roller follower mechanisms

Alakhramsing

Rooij

Schipper

et al. 2017

Proceedings of the Institution of Mechanical Engineers, Part J:

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In cam-roller follower units two lubricated contacts may be distinguished, namely the cam-roller contact and roller-pin contact. The former is a nonconformal contact while the latter is conformal contact. In an earlier work a detailed transient finite line contact elastohydrodynamic lubrication model for the cam-roller contact was developed. In this work a detailed transient elastohydrodynamic lubrication model for the roller-pin contact is developed and coupled to the earlier developed cam-roller contact elastohydrodynamic lubrication model via a roller friction model. For the transient analysis a heavily loaded cam-roller follower unit is analyzed. It is shown that likewise the cam-roller contact, the rollerpin contact also inhibits typical finite line contact elastohydrodynamic lubrication characteristics at high loads. The importance of including elastic deformation for analyzing lubrication conditions in the roller-pin contact is highlighted here, as it significantly enhances the film thickness and friction coefficient. Other main findings are that for heavily loaded cam-roller follower units, as studied in this work, transient effects and roller slippage are negligible, and the roller-pin contact is associated with the highest power losses. Finally, due to the nontypical elastohydrodynamic lubrication characteristics of both cam-roller and roller-pin contact numerical analysis becomes inevitable for the evaluation of the film thicknesses, power losses, and maximum pressures. IntroductionCam-roller follower mechanisms as part of fuel injection units in heavy-duty diesel engines are subjected to very high fluctuating loads coming from the fuel injector. Apart from the high fluctuating contact forces, varying radius of curvature and lubricant entertainment velocity make the tribological design of these components even more challenging. The lubricant entrainment speed of the cam-roller contact on itself is a function of geometrical configuration, cam rotational velocity, and roller angular speed. Two lubricated contacts may be distinguished when considering a cam-roller follower unit, namely the cam-roller contact and roller-pin contact (see Figure 1). The former is a nonconformal contact while the latter is conformal contact. The roller angular speed is a function of the working frictional forces at the cam-roller and roller-pin contact and inertia torque caused by angular acceleration of the roller itself. Roller slip is defined as the difference between the cam and roller surface velocities at the point of contact.Khurram et al. 1 proved the existence of roller slip experimentally. Lee and Patterson 2 showed that the problem of wear on the interacting surfaces still occurs if slip is present.Previously developed cam-roller follower lubrication models (see, for instance Chiu, 3 Ji and Taylor, 4 and Turturro et al. 5 ), which include the possibility of roller slippage, all rely on (semi)-analytical

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“…The contact of cam-follower pairs in many applications such as vehicular valve train systems also operate in EHL, where for a flat tappet, the contact is of finite line contact geometry [35][36][37][38] and for the cam-roller follower is an elliptical point contact [39][40][41][42].…”

Section: Introductionmentioning

confidence: 99%

Transient Analysis of Isothermal Elastohydrodynamic Point Contacts under Complex Kinematics of Combined Rolling, Spinning and Normal Approach

2020

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This paper presents a brief review of elastohydrodynamic analysis in commemoration of the immense contributions of Duncan Dowson. This paper also presents an elastohydrodynamic analysis of the elliptical point contact problem under steady state as well as transient conditions. The overall methodology is validated against numerical predictions and experimental observations of acknowledged historical sources. The validated methodology is used to make original contributions in the elastohydrodynamics of elliptical point contact subjected to complex combined contact kinematics, including rolling/sliding, mutual convergence and separation (squeeze film motion) of contacting pairs, when subjected to reciprocating and spinning motions. This combined complex contact kinematics under transient conditions has not hitherto been reported in the literature. This paper shows the critical role of squeeze film motion upon lubricant film thickness. The results also show that the influence of spin motion is only significant at fairly high values of angular velocity and in the absence of a rolling/sliding motion.

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Assessment of Friction for Cam-Roller Follower Valve Train System Subjected to Mixed Non-Newtonian Regime of Lubrication

Cited by 12 publications

References 0 publications

Lubrication and frictional analysis of cam–roller follower mechanisms

Lubrication and frictional analysis of cam–roller follower mechanisms

A full numerical solution to the coupled cam–roller and roller–pin contact in heavily loaded cam–roller follower mechanisms

Transient Analysis of Isothermal Elastohydrodynamic Point Contacts under Complex Kinematics of Combined Rolling, Spinning and Normal Approach

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