MBD Simulation on IC Engine Valve Train
AIM: Model, Assemble & Motion Analysis Of IC Engine Valve Train
Objectives:
- Model & assemble parts in SolidWorks
- Obtain valve lift for given CAM lift of 3.5 mm & 6 mm at same speed (1500 RPM)
- Obtain Plots between contact force of, cam & Push rod, Push rod & rocker arm, Rocker arm & valve
BODY OF CONTENT:
IC engine valve train is a mechanism used in every four stroke & two stroke engine. It is used to open & close the inlet & exhaust valve at regular interval of time. Cam is mounted on the cam shaft. Periphery of the cam is in contact with the push rod. Push rod is oscillated along its axis & transfer motion to the rocker arm. Other end of rocker arm is in contact with the valve. Hence, motion is transfered from cam to the valve.
CAM Lift:
As shown in figure overall height of the cam is the total of cam lift & base circle.
Hence, cam lift = overall height - base circle.
cam lift depends upon the overall height. More overall height results in more cam lift.
If cam lift is more than valve lift will be more which results in more amount of air-fuel comusion in the engine & vice-versa.
Design of parts:
Software used - SolidWorks
CAM:
As discussed for cam lift,
Here we have two case,
A) Cam lift = 3.5 mm
B) Cam lift = 6 mm
for each case we have to find center distance L.
For case A) Cam lift = 3.5 mm,
3.5 = (L - R1) + R2
here R1 = 12.5 mm & R2 = 5 mm.
Hence, L = 11 mm.
For case B) Cam lift = 6 mm,
6 = (L - R1) + R2
here R1 = 12.5 mm & R2 = 5 mm.
Hence, L = 13.5 mm.
now extruded to 10 mm.
PUSH ROD:
ROCKER ARM:
VALVE:
VALVE MOUNT:
Now assemble all the parts such that mid plane of all the parts are in the same plane.
Now go to motion analysis. Apply rotary motor to the axis of the crank and give 1500 RPM as an input speed.
Assign body contacts. Assign spring between valve stem & valve having stiffness 10 N/mm.
Now, for Case A) Cam lift = 3.5 mm
Run the motion analysis.
Study following plots.
Valve lift vs time
As we can see that the value of valve lift fluctuates in between 50 to 53.
Contact force between Cam & Push rod Vs time
Max. value= 2285 N
CF between Push rod & Rocker arm Vs time
Max. value= 2338 N
CF between Rocker arm & valve(X axis) vs time
Max. value= 123 N
CF between Rocker arm & valve(Magnitude) vs time
Max. value= 510 N
Now for Case B) Cam lift = 6 mm
Run the motion analysis.
Study following plots.
Valve lift vs time
As we can see that the value of valve lift fluctuates in between 50 to 56.
Contact force between Cam & Push rod Vs time
Max. value= 12340 N
CF between Push rod & Rocker arm Vs time
Max. value= 12560 N
CF between Rocker arm & valve(X axis) vs time
Max. value= 585 N
CF between Rocker arm & valve(Magnitude) vs time
Max. value= 2405 N
RESULT & CONCLUSION:
By comparing the Case A) & Case B) we can see that for the Case B) for which cam lift is high valve lift is also high. Due to the high cam lift value of all the contact forces are also high in case B).
One can see for the plot of contact force of rocker arm & valve vs time has two consideration one with X axis & another one is magnitude. In which we can see that in case of X axis the value of contact force is in negative direction. This is due to the fact that the friction is more in that case.
Hence, higher the cam lift higher the valve lift & contact forces.