MBD Simulation on IC Engine Valve Train
Objective: To model the essential parts of an IC Engine Valve Train and run an MBD simulation on that. Obtain the
- Valve Lift.
- The contact force between
- Cam and Push Rod
- Pushrod and Rocker Arm
- Rocker Arm and Valve
Explain why the contact force between the Rocker arm and valve varies while measuring with respect to the X direction and measuring with respect to magnitude.
Cam Lift Formula:
The simulation is done for the following two cases.
| Sl.No | CAM Lift (mm) | Speed (RPM) | Material |
| 1 | 3.5 | 1500 | Cast Carbon Steel |
| 2 | 6 | 1500 |
Cast Carbon Steel |
To calculate cam lift the following formula is used.
Case:1-
Modelling:
Cam lift-3.5
Cam lift formula: (L-R1)+R2 = (12.5-15)+6 = (-2.5)+6 = 3.5
Pushrod
Rocker Arm
Valve
Valve Mount
All of the above models are designed in solidworks with suitable dimensions and asembled to obtain the desired movement as shown below.
Simulation:
A motion study is created and motion analysis boundary conditions are given.
A rotary motor is added to cam in clockwise direction with an rpm of 1500.
Solid contacts is established between cam and pushrod, pushrod and rocker arm, rocker arm and value with steel(dry) material applied for all parts.
A linear spring of length 45mm and and spring constant of 10N/mm was set between valve and valve mount as shown below.
The motion analysis is set to 9000 frames per second and precision contact is used.
All parts are assigned with cast carbon steel material. Material properties are shown below.
The motion analysis was then run for 0.2 seconds and motion study is calculated to obtain following results.
Valve Lift(Displacement):
Contact Force between Cam and Push Rod:
Contact Force between Rocker Arm and Push Rod:
Contact Force between Rocker Arm and Valve: X direction
Contact Force between Rocker Arm and Valve: Magnitude
Case:1-
Cam lift-6
Cam lift formula: (L-R1)+R2 = (12.5-12.5)+6 = (0)+6 = 6
Simulation:
Boundary conditions are the same as case-1. The model is updated with cam dimensions changes and motion study is calculated.
Valve Lift(Displacement):
Contact Force between Cam and Push Rod:
Contact Force between Rocker Arm and Push Rod:
Contact Force between Rocker Arm and Valve: X direction
Contact Force between Rocker Arm and Valve: Magnitude
Conclusion:
- Valve dispalacement varies with respect to cam lift i.e valve lift of cam lift 3.5mm is 3mm and valve lift of cam lift 6mm is 5mm.
- The contact force between the Rocker arm and valve varies while measuring with respect to the X direction and measuring with respect to magnitude. In X direction the contact force is frictional force and is positive when the valve is moving downwards and vice versa.
- Where as in magnitude the contact forces are calculated in all directions and hence the value is much higher when compared with the contact force in x direction.