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WAYNE STATE UNIVERSITY

CENTER FOR AUTOMOTIVE RESEARCH

DYNAMICS AND FRICTION OF VALVE TRAINS

BY DINU TARAZA, NAEIM A. HENEIN MIRCEA TEODORESCU, RADU CEAUSU WALTER BRYZIC

ARC ANNUAL MEETING, MAY 25-26, 1999 UNIVERSITY OF MICHIGAN

DYNAMICS AND FRICTION OF VALVE TRAINS

VALVE TRAINS are influencing: Engine performance by optimizing the gas exchange process Engine noise Engine friction losses

GOALS: Increase flow areas controlled by the valves Reduced vibration of Valve Train elements, and corresponding Valve Train noise Reduce friction losses

Contents

1. 2. 3. 4. 5. 6. 7. 8.

Types of valve trains Kinematics Dynamics of valve trains Friction in valve trains Experimental investigation Model validation Conclusion Future work

Types of Valve Trains

Push-rod systems Used in large Diesel engines Reduce the number of gears necessary to drive the camshaft Increased mass of moveable parts and reduced stiffness of the systems Limit the maximum allowable acceleration Prone to larger vibration

Variants: Roller follower

Overhead camshafts

Reduces mass of movable parts Increased stiffness of the system Increased maximum allowable acceleration Better engine breathing Lower vibration

Asymmetrical cam profile Concavities of the cam profile

Direct acting camshaft

Higher cam profile Larger camshaft bearings Cannot avoid sliding friction

Valve motion

Valve lift

1.E-02 8.E-03 6.E-03 4.E-03 2.E-03 0.E+00 -2.E-03 0 50 100 <deg> 150 200 250

Essential for Better engine breathing Valve train dynamics (vibration) In use: - Polynomial cams - Continuos sinusoidal acceleration - Cubic spline continuous acceleration

Polynomial Cams

hv = hmax + Ca + Cb + Cc + Cd + Ce t t t t t

Valve Lift for Three Different Polynomial Laws

9.E-03 8.E-03 7.E-03 6.E-03 5.E-03 4.E-03 3.E-03 2.E-03 1.E-03 0.E+00 1 201 401 601 <deg> 801 1001 1201

a

b

c

d

e

2-8-14-20-26 2-10-18-26-34 2-12-22-32-42

<m>

Valve Lift Acceleration for Three Different Polynomial Laws

5.E+02 4.E+02 <m/sec^2> 3.E+02 2.E+02 1.E+02 0.E+00 -1.E+02 1 -2.E+02 <deg> 201 401 601 801 1001 1201 2-8-14-20-26 2-10-18-26-34 2-12-22-32-42

Continuos Sinusoidal Acceleration

Cubic Spline Continuos Acceleration

Influence of Ramps

Necessity of ramps: Blending the base cycle into the active cam profile

Types of Ramps

Constant Acceleration

Sinusoidal Acceleration

Forces in Valve Train

a) Without Vibrations

Dynamics of Valve Train Two Mass System One Mass System

n=1330 rpm Intake Valve

9.00E-03 8.00E-03 7.00E-03 Inlet Valve Lift [m] 6.00E-03 5.00E-03 4.00E-03 <N> 3.00E-03 2.00E-03 1.00E-03 0.00E+00 -1.00E-03 0 180 360 540 720 900 Crank Angle [degree] 1.E+02 0.E+00 -1.E+02 0 -2.E+02 -3.E+02 -4.E+02 -5.E+02 -6.E+02 -7.E+02 <deg> 100 200 300 400 500 600 700 800

The Force on the Intake Cam

1.50E+00 Inlet Valve Speed [m/sec] 1.00E+00

The Contribution of the Intake Cam to the Total Torque

6.E+00

5.00E-01

4.E+00

0.00E+00 0 -5.00E-01 -1.00E+00 -1.50E+00 Crank Angle [degree] 180 360 540 720 900

<Nm>

2.E+00 0.E+00 -2.E+00 0 -4.E+00 -6.E+00 <deg> 100 200 300 400 500 600 700 800

1.20E+03 1.00E+03 Inlet Valve Acceleration [m/sec^2] 8.00E+02 6.00E+02 4.00E+02 2.00E+02 0.00E+00 -2.00E+02 0 -4.00E+02 -6.00E+02 Crank Angle [degree] 180 360 540 720 900

<Nm> 6.E+00 4.E+00 2.E+00 0.E+00 -2.E+00 -4.E+00 -6.E+00 0

The Total Torque for the Camshaft

100

200

300

400

500

600

700

800

<deg>

Friction Model

u1 = ( Rb + hc ) c u2 = 0

v2 = c e

a2 =

dv2 & =e c dt

Velocity of contact point along the cam surface

& & & s = u1 + e = ( Rb + hc ) c + e

Radius of curvature

Rc = & s ds dt ds = = & dt d d

Flat follower

Rc = & s c

Rc = Rb + hc +

& e a = Rb + hc + 22 c c

ELASTOHYDRODYNAMIC (EHD) LUBRICATION

Non dimensional Film Thickness (Dowson and Toyoda) EHD Oil film Thickness

H = 2.65U 0.7 G 0.54W - 0.13

h = HRc

U=

Non dimensional Velocity

0

E' G = E

0 (u1 + u2 ) 2 E ' Rc

W Fc / b E ' Rc

Viscosity at bulk lubricant temperature and ambient pressure Composite modulus of elasticity (207 Gpa) Material parameter -8 Pressure-viscosity coefficient of lubricant (2.2*10 m2/N) Non dimensional load Cam Width

b

RMR surface roughness of cam and follower 1,2 Composite surface roughness

= HRc

= 12 + 22

Film Thickness parameter EHD Lubrication Boundary Lubrication Mixed Lubrication

> 1 1 0< < 1

Ff = Fb + F Fb = fFc (1 - ) F = 2b (u1 + u2 ) for < 1 for > 1

Friction force Boundary friction component Viscous Friction Component

M f = Ff ( Rb + hc ) M c = - Fc e + M f

(

)

Frictional Torque Total torque required to drive the camshaft

The Experimental and M o d e l e d C a m Shaf t T o r q ue - 13 3 0 r p m

6.00E+00

4.00E+00

2.00E+00

0.00E+00 1 -2.00E+00 73 145 217 28 36 43 50 577 64 721 M odel Experiment

-4.00E+00

-6.00E+00

-8.00E+00 <deg>

The A mp l i t ud e f o r t he f i r s t 10 0 Harmonics - 13 3 0 r p m

2.5

2

1.5

M o d el Experiment

1

0.5

0

The Experiment a l a nd M o d e l e d C a m S h a f t T o r q u e - 12 54 r p m

6.00E+00 4.00E+00 2.00E+00 0.00E+00 1 -2.00E+00 -4.00E+00 -6.00E+00 -8.00E+00 -1.00E+01 <deg> 73 145 217 28 36 43 50 577 64 721 M odel Experiment

The A mp l i t ud e f o r t he f i r s t 10 0 Harmo nics - 12 54 r p m

2.5

2

1.5

M odel Experiment

1

0.5

0

Conclusion

- Valve train is a very important engine component. It influences engine breathing, noise and friction losses - Cam profile and valve train parameters determine the dynamic response and valve train vibration - Friction losses are strongly influenced by the valve train design

Future work

- Further develop the dynamic model to include bending and torsional flexibility of the camshaft - Study the influence of different cam profiles on the valve train dynamics and friction - Instrument the engine for measuring valve acceleration in order to better validate the dynamic model - Develop a design method for low noise, low friction valve trains

Acknowledgments

The authors acknowledge the technical support and sponsorship of the Automotive Research Center by the U. S. Army National Automotive Center and TARDEC, Warren Michigan.

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TARAZA

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