MBD Simulation on IC Engine Valve Train

IC Engine Valve Train

• A valvetrain or valve train is a mechanical system that controls operation of the valves in an internal combustion engine, whereby a sequence of components transmits motion throughout the assembly.
• Conventional reciprocating internal combustion engine uses valves to control the flow of the air/fuel admix into and out of the combustion chamber.
• A typical valvetrain consists of valves, rocker arms, pushrods, lifters, and camshaft(s).
• Valvetrain opening/closing and duration, as well as the geometry of the valvetrain, controls the amount of air and fuel entering the combustion chamber at any given point in time.
• Timing for open/close/duration is controlled by the camshaft that is synchronized to the crankshaft by a chain, belt, or gear.
• The camshaft is located within the engine block, and operates directly on the valves, or indirectly via pushrods and rocker arms. Because they often require pushrods they are often called pushrod engines.

Pushrod

Rocker arm

Valve

Valve stem

Cam

Final assembly

Animation of the motion study is shown below.

There are 2 cases

Calculations :-

The distance between the centers are calculated and the cam is modified to get the required cam lift.

For case 1,Cam lift = 3.5mm

• R1= 17.5mm
• R2= 10mm
• L=3.5+R1-R2
• L=3.5+17.5-10 =11mm

For case 2 Cam lift = 6mm

• R1= 17.5mm
• R2= 10mm
• L=6+R1-R2
• L=6+17.5-10 =13.5mm

Motion analysis:

1. Establish contact between Cam and push rod, push rod and rocker arm, rocker arm and valve.
2. Give rotary motion to the cam with 1500 RPM.
3. Set up a linear spring between valve and the valve stem(as seen in the assembly) with the spring stiffness of 10 [N/mm] and free lenght 45[mm].
4. Change frames to 7200 frames per sec and use precise contact.
5. Select the entire assembly and assign the material Carbon Steel.
6. Select the required plots for results and analysis.
7. Run the simulation for required time.

Results for the simulation are :-

Contact force between Cam and Push Rod(Magnitude)

Contact force between Pushrod and Rocker(Magnitude)

Contact force between Rocker Arm and Valve(Magnitude)

Contact force between Rocker Arm and Valve(X direction)

Contact force between Cam and Push Rod(Magnitude)

Contact force between Pushrod and Rocker(Magnitude)

Contact force between Rocker Arm and Valve(Magnitude)

Contact force between Rocker Arm and Valve(X direction)

The Magnitude represents net contact force between the parts, while the contact force along X direction is the frictional force between the bodies that arises due to the rocker arm sliding over the surface of valve head.