MBD Simulation on IC Engine Valve Train
MBD Simulation on IC Engine Valve Train
Aim : Model the parts and assemble and simulation on IC Engine Valve Train and 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 |
and obtain the The contact force between
Cam and Push Rod
Pushrod and Rocker Arm
Rocker Arm and Valve
Introduction :
A valve-train 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. A 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 valve-train consists of valves, rocker arms, push-rod, lifters, and cam. Valve-train opening/closing and duration, as well as the geometry of the valve-train, controls the amount of air and fuel entering the combustion chamber at any given point in time. Valve-trains are built in several configurations, each of which varies slightly in layout but still performs the task of opening and closing the valves at the time necessary for proper operation of the engine.
A typical Valve-train which describes each part is shown below.
there are different parts in IC engine valve train, the parts are as follows :
- Cam
- Push-rod
- Rocker Arm
- Valve
- Valve Mount
Parts : creating 3D parts:
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 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 acts 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 here for making contact between valve, rocker arm, push rod and cam which locks them in position and motion analysis is performed.
Motion Analysis :
- first go to motion study and establish contact between Cam and push rod, push rod and rocker arm, rocker arm and valve.
- Next attached servo motor in the cam axis and give the rotation to the cam with 1500 RPM.
- Set up a linear spring between a valve and the valve mount with the spring stiffness of 10 N/mm and free length 45 mm.
- Change the frames to 7200 frames per sec and use precise contact.
- select the entire assembly and assign the material as follows, go to Material-Edit material and select Cast Carbon Steel and click apply.
- Now click the calculation button.
There are two cases to follow to get the desired motion analysis and the plots. They are as follows,
| Sl.No | CAM Lift (mm) | Speed (RPM) | Material |
| 1 | 3.5 | 1500 | Cast Carbon Steel |
| 2 | 6 | 1500 |
Cast Carbon Steel |
use cam lift formula to calculate the distance between the two centres (L)
Case 1: Motion Analysis for cam lift of 3.5mm:
Given: R1 = 12.5; R2 = 5; Cam lift = 3.5mm
Cam lift = (L-R1)+R2
L = (12.5+3.5) - 5
L = 11mm
With the above information, Cam is modelled for the case 1 analysis.
The contact force graph between Cam and Push Rod (Magnitude)
The contact force graph between Pushrod and Rocker Arm (Magnitude)
The contact force Graph between Rocker Arm and Valve (Magnitude)
The contact force between Rocker Arm and Valve (X-Direction)
Case 2: Motion Analysis for cam lift of 6mm:
To calculate the distance between the two centres(L)
Given: R1 = 12.5; R2 = 5; Cam lift = 3.5mm
Cam lift = (L-R1)+R2
L = (12.5+6) - 5
L = 13.5mm
With the above information, Cam is modelled for the case 2 analysis.
The contact force graph between Cam and Push Rod (Magnitude)
The contact force graph between Pushrod and Rocker Arm (Magnitude)
The contact force Graph between Rocker Arm and Valve (Magnitude)
The contact force between Rocker Arm and Valve (X-Direction)
4. Observation and Results
Explanation:
- The Magnitude represents net contact force between the parts, while the contact force along the X direction is the frictional force between the bodies that arise due to the rocker arm sliding over the surface of the valve head.
- The change in direction of the force is because the rocker arm first slides towards origin giving a positive friction force (opposing the motion) and then slides away from the origin giving rise to friction in the negative x-direction. Therefore the plots are opposite to each other.
- The explanation is same for the cam lift of 6 mm, only it differs in magnitude of contact forces. The movement in this case is quite smoother compared to the cam lift of 3.5 mm as observed. As the cam lift increases more air-fuel mixture can enter into the cylinder of IC engine.
Animation of IC Engine Valve-Train at Cam lift = 3.5:
Animation of IC Engine Valve-Train at Cam lift = 6mm :
thanks.