MBD Simulation on IC Engine Valve Train

Aim: To study the motion analysis of IC engine valve train assembly with modelling various parts of assembly using solidworks software.

Objective :To create 3D model for IC engine valve train and assemble and performed a motion analysis and also to study contact force between parts such as cam, push rod, rocker arm, valve and valve mount.

Theory: A valve train is a mechanical system that controls operation of the valve in an internal combustion engine, whereby a sequence of components transmits motion throughout the assembly. A conventional reciprocating internal combustion engine uses valves to control the flow of air/fuel mixture into and out of the combustion chamber.

Problem Statement:

• Model the parts and assemble them in SolidWorks.
• Run the simulation using the below parameters

Sl.No CAM Lift (mm) Speed (RPM) Material

1 3.5 1500 Cast Carbon Steel

2 6 1500 Cast Carbon Steel

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

CAM Lift can be derived from the sketch

• The diameter of lower circle (D1)- 35 mm
• The diameter of upper circle (D2)- 20 mm
• The distance between two centres (L)- 30 mm

CAM Lift = (L-R1) +R2

• We have to design all the different parts of the valve train arrangements separately. The parts are as follows:

• Cam
• Push rod
• Rocker arm
• Valve
• Valve mount
• Cam: A cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion.

• Push rod: This is the part to which the lift is provided, which is transmitted to the rocker arm.

• Rocker arm: This is the part which is connected to push rod in one end and valve on the other end.

• Valve: This allows the air-fuel mixture to enter the cylinder or exhaust the gases out from the cylinder by opening and closing of the inlet/exhaust port.

• Valve mount: This act as the stoppage for the valve and limits the movement of the valve.

• Final Assembly: Assembly is made using the assembly mate option by properly aligning them as shown. Physical dynamics is used for making contact between valve, rocker arm, push rod and cam which locks them in position and motion analysis is performed.

Assembly of IC engine valve train can be given in below link,

https://drive.google.com/file/d/1D_feLtOirp_4MzqHR4uolAsWxyL8_iT0/view?usp=sharing

• Result

• Case 1: Motion analysis for cam lift 3.5 mm

To calculate the distance between the two centres (L)

Given: R1 = 12.5 mm; R2 = 5 mm; Cam lift = 3.5 mm

Cam lift = (L – R1) + R2

L= (12.5 +3.5) – 5

L = 11mm

With above length cam is modelled for the case 1 analysis.

• Valve Lift

• Contact forces plots
• Cam and Push rod (Magnitude)

• Push rod and rocker arm (Magnitude)

• Rocker arm and valve (Magnitude)

• Rocker arm and valve (X direction)

• Case 2: Motion analysis for cam lift 6 mm

To calculate the distance between the two centres (L)

Given: R1 = 12.5 mm; R2 = 5 mm; Cam lift = 6 mm

Cam lift = (L – R1) + R2

L= (12.5 +6) – 5

L = 13.5 mm

With above length cam is modelled for the case 2 analysis.

• Valve Lift

• Contact forces plots
• Cam and Push rod (Magnitude)

• Push rod and rocker arm (Magnitude)

• Rocker arm and valve (Magnitude)

• Rocker arm and valve (X direction)

• Animation of engine valve train assembly at cam lift 3.5 mm

• Animation of engine valve train assembly at cam lift 6 mm

• Conclusion

• With increase in cam lift, valve displacement can be increased.
• Valve lift is mainly depends on the Design of CAM and rocker arm.
• Selection of spring plays very important role in valve train mechanism (free length and spring constant).
• The contact force between the rocker arm and valve varies while measuring with respect to the X direction and measuring with respect to magnitude because of the fact that an overall net force acting on the system is calculated in the magnitude whereas only the Force/reaction force/frictional force between rocker arm surface and valve surface during sliding is calculated in X direction.