Design and Motion Analysis of IC Engine Valve train Assembly
INTRODUCTION: A Valvetrain or 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 combustion chamber once combustion is completed.
OBJECTIVE:
- Performing Motion Analysis of IC Engine Valve Train Mechanism
- Obtaining Plots
- Valve Lift vs Time
- Contact Force (Cam & Pushrod) vs Time
- Contact Force (Pushrod & Rocker Arm) vs Time
- Contact Force (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 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
PROCEDURE:
- Initially, a Cam is designed according to the mentioned Cam Lift.
- The 3D model of Pushrod is designed keeping in mind the Cam and the Rocker Arm.
- The Rocker Arm is modelled with appropriate dimensions in order to have harmony between the parts with contact.
- The Valve Stem is designed with shaft hole size equal to the valve width.
- The final part is the valve which is loaded with the spring. This component is the most calibrated due to its precise performance.
- The parts modelled above are assembled in an assembly file with adequate number of mates and constraints.
ANIMATIONS:
- CASE 1:
- CASE 2:
RESULTS:
- CASE 1:
Valve Lift vs Time
The Valve Lift depends on the Rocker Arm Ratio thereby giving successive moments of opening and closing of Valve.
Contact Force (Cam & Pushrod) vs Time
The Contact Force projected shows the time of engagement between the Cam and Pushrod with the extent of force transmitted from the Cam to the Pushrod.
Contact Force (Pushrod & Rocker Arm) vs Time
The above graph shows tremendous similarity to the previous graph, thereby resembling the uniform transfer of motion.
Contact Force (Rocker Arm & Valve) vs Time - MAGNITUDE
The graph intends to represent the downward force that the Rocker Arm exerts on the Valve.
Contact Force (Rocker Arm & Valve) vs Time - X DIRECTION
The plot works as a comparison between the Contact Force measured as Magnitude or in the X Direction.
- CASE 2:
Valve Lift vs Time
Contact Force (Cam & Pushrod) vs Time
Contact Force (Pushrod & Rocker Arm) vs Time
Contact Force (Rocker Arm & Valve) vs Time - MAGNITUDE
Contact Force (Rocker Arm & Valve) vs Time - X DIRECTION
LINK FOR SOLIDWORKS PARTS AND ASSEMBLY FILES:
"https://drive.google.com/drive/folders/1sak1BYoR7UD13zAks7lNYzH3C2VvkjhW?usp=sharing"
CONCLUSION:
The Contact Force between Rocker Arm and Valve varies while measuring with respect to the X Direction and measuring with respect to Magnitude as the result in case of X Direction depicts Negative Values due to Frictional Contact. But 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 vertical direction which negates the need for measuring the direction. Hence, output comes out to be Positive.
The Motion Analysis gives a satisfactory idea about the functioning of the IC Engine Valve Train wherein further scope of improvements exist to make it more smooth and efficient.