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:  

1. Performing Motion Analysis of IC Engine Valve Train Mechanism
2. Obtaining Plots
   1. Valve Lift vs Time
   2. Contact Force (Cam & Pushrod) vs Time

• Contact Force (Pushrod & Rocker Arm) vs Time

1. Contact Force (Rocker Arm & Valve) vs Time

SIMULATION CASES:

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:

https://youtu.be/rodDAylBBjM

• CASE 2:

https://youtu.be/c96D2Hc630I

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.