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40 KSME Journal, VolA, No.1, pp. 40-47,1990.ANALYTICAL AND EXPERIMENTAL MOTION ANALYSISOF FINGER FOLLOWER TYPE CAM-VALVE SYSTEMWITH A HYDRAULIC TAPPETWon-Jin Kim-, Hyuck-Soo Jeon- and Youn-Sik Park-(Received September 11, 1989)In this paper, the motion of a fingerfollower type cam valve system with a hydraulic tappet was analytically and experimentallystudied. First, the exact contact point between cam and follower for each corresponding cam angle was searched by kinematicanalysis. Then a 6 degree of freedom lumpe-0)Mf0.05981K:5.92 x 10; 1.128 0, Fo/ Ksewhere Fois the precompressed force of valve spring (in thisstudy, Fo=275N)The contact forces Ff Ffc, and FOfcan be determined asEq.(9).(10)34.0014.2222.53unit:mm36.4031.6713.00Table 3 Kinematic dimensionsBetween tappet and follower:Yf- Y,-Lf ,sin8f -12-8 -4 0 4 8x-coord. (mml(a)2.50. 2.0.,L.EL.1.5flIIL.1.00.51001100cam-angle(deg.1(b)Fig. 5 Contact point locus and fluctuating rocker arm ratioANALYTICAL AND EXPERIMENTAL MOTION ANALYSIS OF FINGER FOLLOWER TYPE CAM-VALVE SYSTEM WITH 45.Im.expo100l:70,i1:140-u.!i-100-2030 70110ca.-angIe (deg. )(a)150190. -,.1.expo100l:70ie 400.!2-100-2030Fig. 7120i:OIl.,OIl90I0-0SOClI:0Cl8,30CI.k:l0900 1400 2000 260Q 3200ell_shllft speed (rpm)Fig.8 Maximum tappet leakage down versus camshaft speed70 110 150 190call1-ang) e(l:Ie9)(b)(a) Camshaft speed 900 rpm(b) Camshaft speed 1600 rpmTappet leakage down9, 10,11, we can conclude that the 6 degree of freedom lumpedmass model used in this work is quite reliable to predict valvemotion even in high operating speed.Figure 12 shows a sample of contact forces at all contactpoints when the operation speed is 2450 rpm. It can beobserved that the contact forces at the first peak position arereduced and at the second peak position are accentuated ascompared with the value of constant rocker-arm ratio camsystem due to fluctuationg rocker-arm ratio. As examiningthe contact force record, we can easily predict the mostpossible area and corresponding cam angle where unwantedvalve train separation can be occurred.The experimentally verified model can be expanded notonly to predict the maximum operation speed but also toFig.6 Experimental apparatus5. RUSULT AND DISCUSSION4. EXPERIMENTFigure 7 compares the measured and simulated tappetleakage down at camshaft speed 900 and 1600 rpm. Figure 8shows the measured maximum tappet leakage down. It isknown that hydraulic tappet is stiffened as the speed ofcamshaft is increased. The maximum compression of thehydraulic tappet was about 100 /lm at 800 rpm and approa ched a limit of about 60/lm as the camshaft speed goes beyond3000 rpm, as shown in Fig. 8. As explained before, themeasured tappet motion was used to determine the weightingparamenters a and 3, which determine the plunger dragforce, by least square curve fit between the measurement andthe analysis record. It was found that the weighting parame ter varies with operation speed. For example, a and 3 where0.0071 and 0.28 when camshaft is driven by 900 rpm, but thevalues were changed to 0.0094 and 0.30 when the runningspeed was raised to 1600rpm.Figures 9, 10, 11 show the measured and simulated valvedisplacements and velocities. The valve velocity wasobtained by differentiating the measured valve displacementrecord.Figure 9 compares the measured and analyzed valvemotion when the camshaft was driven at 600rpm. It can besaid that the model can simulate not only the peak valvedisplacement but also the cam event angle quite precisely.Figure 10, 11 show the analysis and measurement when thecamshaft speeds are 1600 rpm 2450rpm. As glancing at Figs.In order to prove the effectiveness of the model simulation,experimental work was done and compared each other.Figure 6. shows the experimental apparatus. While theOHC type cam-valve train was driven by a 100kW DCmotor, valve displacement and hydraulic tappet motion weremeasured simultaneously. The valve displacement was mea sured with an opt-follow(noncontact type optical dis placement measurement device), and the tappet motion wasmeasured with a gap sensor. An encoder was placed at theone end of camshaft in order to average the measured signal.Special care was taken to eliminate problems caused bycirculating engine oil. All the measurement were done asvarying the camshaft running speed from 600 to 2450rpm.Won-jin Kim, Hyuck-Soo jeon and Youn-Sik Park180180- 81 ._- expo- 81 -expo45 90 135cam-ang 1e (deg. )10.(; ,.-,E7.5.,CQJE5.0QJUlQ.2.5tlU0.00600u300QJen-EB0-.,u0-300QJ-6000 45 90 135cam-ang I e(deg. )Fig. 11 Valve displacement and velocity (camshaft speed 2450rpm)180180-si.-expo45 90 135call1-angleldeg. )45 90 135cam-angleldeg.)4610.0E7.5.,CQJE5.0QJUlQ.2.5tlU0.00200U100QJtl-EU-0.,u0-100aJ-2000Fig. 9 Valve displacement and velocity(camshaft speed 600 rpm)400 .-.,45 90 135 180cam-ang 1eIdeg. )(h)45 90 135 180cam-angleldeg. )(a)16001200B 800400oo16001200800 f400o _.L-J:O:C:=.:;.;-.L-.-o18045 90 135cam-ang e (deg.)o0.010.0-i- 2.5U! 7.5.,c5.0l-400 L.-_.L._-l ._-180. I16001200800.,u0-200QJ45 90 135call1-angle(deg. )Fig. 10 Valve displacement and velocity (camshft speed 1600rpm)ANALYTICAL AND EXPERIMENTAL MOTION ANALYSIS OF FINGER FOLLOWER TYPE CAMVALVE SYSTEM WITH 47optimize the valve train and cam shape.6. CONCLUSIONSIn this work, a 6 degree of freedom lumped mass-spring damper model was constructed and its effectiveness wasexperimentally verified. The varying rocker-arm ratio couldbe effectively included in dynamic model by kinematic analy sis and its effect could be observed from simulation results ofcontact force. The hydrauic tappet model used for the pivotend of oscillating follower was constructed with the aids ofexperimental data. Consequently, it was found that the con structed numerical model is quite effective to predict finger follower type OHC valve motion.ACKNOWLEDGMENTThis research was supported by Daewoo Motor Co.through a KAIST-Industry Consortium Project.REFERENCESChan, C. and Pisano, A., 1987, Dynamic Model of Fluctuat-ing Rocker-Arm Ratio Cam System, ASME J, Mech. Trans.Automation in Design. Vol. 109. pp.356-365.Jeon, H.S., Park, K.J, and Park, Y.S., 1989, An OptimalCam Profile Design Considemg Dynamic Characteristics ofCam-Valve System, Experimental Mechanics, pp. 357 - 363.Kreuter, P. and Maas, G., 1987, Influence of HydraulicValve Lash Adjusters on the Dynamic Behavior of ValveTrains, SAE Technical paper No. 8?0086.Pisano, A.P. and