MBD Simulation on IC Engine Valve Train
Aim: 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 Graph:
- 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.
Abstract
A 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.
Introduction:
The valve train consists of all the components responsible for transferring the rotational movement of the camshaft into the opening and closing of the intake and exhaust valves. Typical components are listed below in order from the crankshaft to the valves.
1) Camshaft
The timing and lift profile of the valve opening events are controlled by the camshaft, through use of a carefully shaped lobe on a rotating shaft. The camshaft is driven by the crankshaft and— in the case of a four-stroke engine— rotates at half the speed of the crankshaft. Motion is transferred from the crankshaft to the camshaft most commonly by a rubber timing belt, a metallic timing chain or a set of gears.
2) 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.
3) Rocker arm / bucket tappet
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.
4) Valves
Most modern engines use poppet valves type, although sleeve valves, slide valves and rotary valves have also been used at times. Poppet valves are typically opened by the camshaft lobe or rocker arm, and closed by a coiled spring called a valve spring. Valve float occurs when the valve spring is unable to control the inertia of the valve train at high engine speeds (RPM).
We have to design all the different parts of the valve train arrangement separately. The parts are as follows :
1. Cam
2. Push-rod
3. Rocker Arm
4. Valve
5. Valve Mount
After designing all the parts we have to complete the assembly.
3D Modelling:
1) Valve Stem
2) valve
3) Rocker Arm
4) Pushrod
5) Cam with 3.5 mm Camlift
Case 1:
To calculate the distance between the two centres(L) 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 analysis.
6) Cam with 6 mm Camlift
Case 2:
To calculate the distance between the two centres(L) for cam lift of 6mm:
Given: R1 = 12.5; R2 = 5; Cam lift = 6mm
Cam lift = (L-R1) +R2
L = (12.5+6) -5
L = 13.5 mm
With the above information, Cam is modelled for the analysis.
7) Assembly Of 3D Parts:
Result:
For case-1, the distance between the two centres(L) for cam lift of 3.5mm:
- Contact For Between cam & Pushrod
- Contact For Between Rocker arm & Pushrod
- Contact For Between Rocker arm & Valve
- Contact For Between Rocker arm & Valve along X- axis
- Valve linear Displacement
For case-2, the distance between the two centres(L) for cam lift of 6 mm:
- Contact For Between cam & Pushrod
- Contact For Between Rocker arm & Pushrod
- Contact For Between Rocker arm & Valve
- Contact For Between Rocker arm & Valve along X- axis
- Valve linear Displacement
### Comaprison Of Results under given cases:
- Comaprison Of Contact For Between cam & Pushrod
- Comaprison Of Contact For Between Rocker arm & Pushrod
- Comaprison Of Contact For Between Rocker arm & Valve
- Comaprison Of Contact For Between Rocker arm & Valve along X- axis
- Comaprison Of Valve linear Displacement
Observation:
- Explanation: The Magnitude represents net contact force between the parts, while the contact force along the X direction is the frictional force betweenthe 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 thenslides 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.
Notes: For the files related to this Assignment Please visit the google drive link given Below.
https://drive.google.com/drive/folders/1Yw2WMsB2eCDb3UtHpDbTXx9oBFIpssbB?usp=sharing