MBD Simulation on IC Engine Valve Train

Objective

1. Model all the parts of IC Engine Valve Train and assemble them in SolidWorks.
2. Run the simulation using the below parameter

   • S . No	Cam lift (mm)	Speed (rpm)	Material
     1	3.5	1500	Cast carbon steel
     2	6	1500	Cast carbon steel

3. Obtain the plot for valve lift , The contact force between Cam and Push Rod , between Pushrod and Rocker Arm and between Rocker Arm and Valve

IC Engine Valve Train

A valvetrain or valve train is a mechanical system that controls operation of the intake and exhaust valves in an internal combustion engine.The intake valves control the flow of air/fuel mixture (or air alone for direct-injected engines) into the combustion chamber, while the exhaust valves control the flow of spent exhaust gasses out of the combusion chamber once combustion is completed.

Parts : -

• Cam : - The timing and lift profile of the valve opening events are controlled by the cam, through use of a carefully shaped lobe on a rotating shaft.
  • 3.5mm : - cam of 3.5mm lift
  • 6mm:- Cam of 6mm lift

• Pushrod :- Pushrods are long, slender metal rods that are used in overhead valve engines to transfer motion from the camshaft (located in the engine block) to the valves (located in the cylinder head). The bottom end of a pushrod is fitted with a lifter , upon which the camshaft makes contact. The camshaft lobe moves the lifter upwards, which moves the pushrod. The top end of the lifter pushes on the rocker arm, which opens the valve.
  
  • File : - Aman_pushrod

• Rocker arm : - Depending on the design used, the valves are actuated by a rocker arm , finger or bucket tappet. Overhead camshaft engines use fingers or bucket tappets, upon which the cam lobes contact.Overhead valve engines use rocker arms, which are actuated by a pushrod and pivot on a shaft or individual ball studs in order to actuate the valves.
  
  • File : - Aman_rocker_arm

• Valve and valve stem : - Valve is used in most reciprocating engines to open and close the intake and exhaust ports in the cylinder head. The valve is usually a flat disk of metal with a long rod known as the "valve stem" attached to one side, Valves are typically opened by the rocker arm, and closed by a coiled spring called a valve spring whitch is placed in between the rocker arm and valve stem
  
  • File : - Aman_valve
  • File : - Aman_valve_stem

Motion Analysis

1. Add motor of 1500rpm to the axis of cam
2. Add solid body contact between different parts which are in contact with each other
3. Add a spring between rocker arm and valve stem of length 45mm(available distance between parts is 35mm so spring is in pretension by 10mm) with spring constact 10N/mm
4. Change frames per second to 9000 with precise contact selected for better result
5. Select all assembly then go to materials -> edit materials and select cast carbon steel

Plots

case 1 : - 3.5mm lift

• Assembly File : - Aman_Engine_valve_3mm_lift

• Animation
  • https://youtu.be/Rg9W4R0rNI8

• Valve lift
  

• The contact force between Cam and Push Rod

• The contact force between Pushrod and Rocker Arm

• The magnitude of contact force between Rocker Arm and Valve

• The contact force between Rocker Arm and Valve in x-direction

case 2 : - 6mm lift

• Assembly file : - Aman_Engine_valve_6mm_lift

• Animation
  • https://youtu.be/TeQSCha4m1w

• Valve lift

• The contact force between Cam and Push Rod

• The contact force between Pushrod and Rocker Arm

• The magnitude of contact force between Rocker Arm and Valve

• The contact force between Rocker Arm and Valve in x-direction
  

Observation and conclusion

• The valve lift in both the cases is period function of time so that equal amount of air fuel mixture is added in each cycle but it is greater for 6mm lift and more air fuel mixture is entered in IC engine as compared to 3.5mm lift
• The contact force between different parts is high for 6mm lift and the maximum magnitude of contact force in both the cases is different for different cam rotations .
• The magnitude of contact force between Rocker Arm and Valve in both the cases is always positive and at highest value when the valve is fully open (at bottom most position ) but the contact force in x direction is only due to the frictional force between rocker arm and valve which change its direction i.e in positive direction when the valve is pushed downwords by the rocker arm and in negatve direction when the valve is comming upwards with the help of spring force so the contact force in x direction changes its sign.