MBD Simulation on IC Engine Valve Train
AIM - TO STUDY AND ANALYSE THE MOTION OF AN ENGINE VALVE TRAIN MECHANISM
THEORY - An engine valve train mechanism comprises of a valve, a rocker arm, a cam, a pushrod, a valve mount and stiffness spring. The main component of this mechanism is the cam which is designed in such a way so to transmit motion to the valve at regular intervals. The cam is responsible for opening and closing of the intake and the exhaust valve of the engine.
WORKING PRINCIPLE - When the cam is rotated in clockwise direction the lobe on the top of the cam tends to push the rod in upward direction. The rocker arm which is pivoted about its axis is then pushed pushed upwards causing its other side to move downwards. Thus the rocker arm pushes the valve and the intake air goes into the engine now as soon the dwell period of the cam ends the pushrod rod goes downwards and the valve closes due to the stiffness spring.
SETUP At first we make the cad model of the components to be used in the mechanism
CAM
ROCKER ARM
VALVE
PUSHROD
VALVE MOUNT
CALCULATIONS
CASE 1
CAM LIFT = 3.5 MM
THUS WE GET THE FOLLOWING GEOMETRY WE GET THE FOLLOWING GEOMETRY
CASE 2
CAM LIFT = 6 MM
THUS BY THE GEOMETRY WE GET THE FOLLOWING GEOMETRY
ASSEMBLY
We have to assemble all the components the same way as shown in the assembly diagram.
MOTION STUDY SETUP
After the assembly of the components we have to run the motion analysis, for that we need to undergo foolowing steps:-
STEP 1 - Go to SOLIDWORKS Motion in the ADD Ins.
STEP 2 - Choose Motion Study Properties and enter the value of frames per second as 9000 FPS and choose precise contact.
STEP 3 - Now go to contacts and apply solid contacts b/w all the pairs in contact one by one.
STEP 4 - Go to motors and choose the axis of the cam and enter the value of 1500 rpm .
STEP 5 - Go to sprin and applt the spring with its one end on the upper face of the valve mount and the other end lower end of the cylindrical part on the valve.
STEP 6 - Enter the value of spring stiffness as 10N/mm and choose free length as 45mm.
STEP 7 - RUN THE STUDY.
STEP 8 - In the second case just change the cam profile and edit the cam lift to be 6mm and then run the study without changing anything else.
PLOTS AND OBSERVATIONS
CASE 1 - WHEN CAM LIFT IS 3.5MM
CASE 2 - WHEN CAM LIFT IS 6MM
RESULTS
From the plots of linear displacement of valve and the pushrod we can makeout that the displacement was regular with respect to time in both the cases but there were some irregularities in the plot of contact force. This could be due to the material of the components.
DOWNLOAD THE FILES FROM THE LINK
https://drive.google.com/drive/folders/1Ijlq9Rfr82I5DKwuI-1O4Fa6YhnrDJSb?usp=sharing