MBD Simulation on IC Engine Valve Train
Aim:
The aim of the study is to establish the forces between the parts during the various lift scenarios and to know about the Displacement of the Valve for the cam lifts.
Introduction:
The valve train is the mechanical system that controls the operation of intake and outlet of the Internal combustion engine. These values are used to control the intake during the combustion chamber and outlet during the exhaust stroke of the engine.
The Valvetrain comprises of mechanical parts which transfer linear motion into rotation motion and rotation motion into linear motion.
The parts in the Valvetrain are:
- Cam
- Rocker Arm
- Pushrod
- Valve
The Valvetrain can be of many configurations here we are considering a traditional or simple valve train.
For our study, the above parts are sketched in 2D with dimensions and 3d modeled with Solidworks. The assembly is done with Solidworks and motion analysis is done with 1500 rpm motor and 10000 frames per second.
Creating 3D Models:
Rocker Arm:
Valve:
Valve Mount:
Push Rod:
Conditions:
The Frames per second is assumed as 10000 to get precise points to form a smooth curve.
Cam Lift Formula:
Since the Cam Lift is given, so we can calculate the Cam profile
We refer to the below-given formula for the cam profile.
Using the Cam lift formula,
CASE 1: For the cam lift of 3.5 mm
Cam lift = (L-R1)+R2
D1 = 35 mm
D2 = 20 mm
L = 11 mm
CASE 2: For the cam lift of 6 mm
Cam lift = (L-R1)+R2
D1 = 35 mm
D2 = 20 mm
L = 13.5 mm
Plots:
CASE 1: For the cam lift of 3.5 mm
Linear Displacement:
Cam and Pushrod:
Push Rod and Rocker Arm:
Rocker Arm and Valve (Magnitude):
Rocker Arm and Valve (X Direction):
Youtube Animation for the 3.5 mm cam lift case:
Motion Analysis with 3.5mm cam lift
CASE 2: For the cam lift of 6 mm
Linear Displacement:
Cam and Push Rod:
Push Rod and Rocker Arm:
Rocker Arm and Valve (Magnitude):
Rocker Arm and Valve (X Direction):
Youtube Animation for the 3.5 mm cam lift case:
Motion Analysis with 6mm cam lift
Observation:
The Magnitude along X direction refers to the frictional force between the rocker arm and the valve. The Magnitude of the contact force along the x-direction is more stable in Cam lift 6 mm case while comparing to the Cam lift 3 mm case. Also, we have to keep a note of the air-fuel mixture, because if the valve lift increases the air-fuel mixture input is increased.
The Magnitude graph has both positive and negative values, it is because the rocker arm and valve are rubbing and thus the frictional force is created along the X-direction. While the dwell period of the cam the valve pushes the rocker arm to the original position thus creating the frictional force in the negative X direction.