MBD Simulation on IC Engine Valve Train
MULTIBODY DYNAMICS OF IC ENGINE VALVE TRAIN
1. INTRODUCTION
The valve train refers to the assembly of components designed to open and close the intake and exhaust valves. Most new engines have overhead cam assemblies like the one shown. Other designs locate the camshaft lower in the engine and use push rods to move valve assemblies. The camshaft is rotated by a timing belt, timing chain, or direct gear.
2. OBJECTIVE
- Modelling IC Engine Valve Train Mechanism
- Obtaining Plots
- Valve Lift vs Time
- Contact Force for
- (Cam & Pushrod) vs Time
- (Pushrod & Rocker Arm) vs Time
- (Rocker Arm & Valve) vs Time
SIMULATION CASES:
|
S. NO |
CAM LIFT (mm) |
SPEED (RPM) |
MATERIAL |
|
CASE 1 |
3.5 |
1500 |
Cast Carbon Steel |
|
CASE 2 |
6 |
1500 |
Cast Carbon Steel |
CAM LIFT FORMULA:
CAM Lift can be derived from the sketch
- The diameter of the lower circle (D1)- 35 mm
- The diameter of the upper circle (D2)- 20 mm
- The distance between two centers (L)- 30 mm
CAM LIFT = (L - R1) + R2
3. PROCEDURE
- CAM
Since the cam lift is different in both cases two different cams are modeled. This helps the pushrod to translate up and down.
- PUSH ROD
This is used to translate the pivoted rocker arm.
- ROCKER ARM
Rocker arm moves the valve up and down depending upon the cam rotation.
- VALVE
This helps in opening and closing the engine valves during the combustion process.
- VALVE MOUNT
This helps the valve to move in a fixed direction.
- ASSEMBLY
Two different assemblies are made with two different cams.
4. PLOTS
FOR 3.5MM CAM
Before running the motion analysis the rotation speed is set to 1500rpm and 9000 is set as frames per second.
Linear displacement
The valve movement is between 50.5 and 53. This is accurate due to the increased frames per second. The Valve Lift depends on the cam and Rocker arm thereby giving successive moments of opening and closing of Valve.
Contact force between
- Cam and push rod
This represents the contact force between the pushrod and cam. The peak reaction force shows the reaction force when the push rod slides over the peak of the cam.
- Pushrod and rocker arm
This represents the contact force between the pushrod and rocker arm. The peak reaction force shows the reaction force when the pushrod pushes the rocker arm up, due to the cam movement.
- Rocker arm and valve
This represents the contact force between the rocker arm and valve. The peak reaction force shows the reaction force when the rocker arm pushes the valve down, against the spring.
- Rocker arm and valve in the x component
This represents the contact force between the rocker arm and valve. The peak reaction force shows the reaction force when the rocker arm pushes the valve down, against the spring. The difference between magnitude and x-component is friction is taken into account.
FOR 6 MM CAM
Linear displacement
Before running the motion analysis the rotation speed is set to 1500rpm and 9000 is set as frames per second.
Contact force between
- Cam and push rod
- Pushrod and rocker arm
- Rocker arm and valve
- Rocker arm and valve in the x component
5. CONCLUSION:
While measuring and plotting the Magnitude of Contact Force, the direction is not kept in mind and the Contact Line performs a to and fro motion in the vertical direction which negates the need for measuring the direction. Hence the Contact Force between Rocker Arm and Valve varies while measuring with respect to the magnitude and measuring with respect to X- component as the result in X Direction depicts Negative Values due to Frictional Contact. This is the reason for the output to be Positive while choosing the magnitude.
The Motion Analysis gives an idea about the functioning of the IC Engine Valve Train. This type of study helps us to determine the areas where changes can be made in order to make the plot smoother than that is achieved in this study.
Motion animation
3.5mm cam lift
6mm cam lift
SOLIDWORKS FILES
https://drive.google.com/drive/folders/1fSDgdSDaB9OGogcECv6g_b3wh9fFSEjW?usp=sharing