The Over-Head Cam (OHC) Valve Train Computer Model

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Irena Matějková
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1 The Over-Head Cam (OHC) Valve Train Computer Model Radek Tichanek, David Fremut Robert Cihak

Josef Bozek Research Center of Engine and Content Introduction Work Objectives Model Description Cam Design Results Conclusion Work Objectives ¾ The development of a partly flexible multi-body

2 Josef Bozek Research Center of Engine and Content Introduction Work Objectives Model Description Cam Design Results Conclusion Work Objectives ¾ The development of a partly flexible multi-body model of an OHC valve train. ¾ The determination of its dynamic behavior. ¾ The development of a spring model. ¾ Model usage for the optimization of cam profiles. ¾ The measurement of valve lift.

3 Model Description OHC Valve Train Flexible parts: Springs Rocker arm Camshaft Part Spring Rocker arm Camshaft Rigid parts: Cam lobe Roller follower Roller s shaft Spring retainers Valve lash adjusters Valves Number of elements

4 Model Description Valve Spring Valve Spring CAD Model Coordinates of Valve Spring Markers Valve Spring Model in Simpack

5 Cam Design Cam Design Method: Based on valve lift design. Used multiple-polynomial polynomial scheme with 16 zones. The polynomial profile in each of the zones. The solution of a system of linear equations. The computation of cam profile coordinates. Cam Design Objectives: Smooth acceleration rise. Small theoretical peak acceleration. Small dynamic spring load. Kinematical Cam Follower Mechanism Cam Profiles Schemes Theoretical valve acceleration Technická 4, Praha 6 tichanek@fsid fsid.cvut..cvut.czcz

6 Results The comparison of computed valve acceleration for Cam A and Cam B at 5000 camshaft rpm. The valve train model with a valve lash. Both non-uniformity in angular velocity and gas force acting on the valves were not taken in to account.

7 Results The theoretical and computed order spectra of valve acceleration for Cam B at 5000 camshaft rpm. The valve displacement order spectra shows that the amplitudes of higher orders are too small and do not excite the valve train mechanism. Displacement Order Spectra Acceleration Order Spectra

8 Results The comparison of the computed order spectra of valve acceleration for Cam A to the case when Cam B was used at 5000 camshaft rpm. Figure shows that the valve has the lower amplitudes of acceleration when Cam B is used as could be expected from the theoretical acceleration curve as well. Acceleration Order Spectra

Test setup for measurement of valve lift Both contact and contactless measurement of valve displacement. The measurement of camshaft angular position.

9 Test setup for measurement of valve lift Both contact and contactless measurement of valve displacement. The measurement of camshaft angular position. Optical Sensors TCST1000 Dynamometer MS (max. power 25 kw at 6000 rpm) Data Acquisition Cards: ČVUT - FEL KEITHLEY iiista-300 Lešikar Contactless Position Sensor Incremental Position Sensor LARM MSL 30

10 Conclusion The flexible valve train model was developed. There were two various cam shapes used in the model and the analysis of computation results was done. This analysis was focused on valve movement in the first step. The model is prepared for a cam and a spring design, it is possible to insert various springs as substructures into the model. The building of a valve train test stand has been started which allows to motor a valve train. Next Tasks The completion of the valve train test stand. The comparison results of computation with measured data. Model parameters setup. Acknowledgement The work was supported by the Josef Bozek Research Center II, No. 1M This help is gratefully appreciated.

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