MBD Simulation on IC Engine Valve Train

Aim

The motto of this project is to design, assemble and study the detail analysis of an IC Engine Valve by varying the cam lift.

Introduction

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 into the combustion chamber, while the exhaust valves control the flow of exhaust gasses out of the combustion chamber once combustion is completed.

What is a cam?

A cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion.

What is pushrod?

Pushrods are long, slender metal rods that are used in overhead valve engines to transfer motion from the camshaft to rocker arm which then transfers it to valves.

What is a rocker arm?

A rocker arm (in the context of an internal combustion engine of automotive, marine, motorcycle and reciprocating aviation types) is an oscillating lever that conveys radial movement from the cam lobe into linear movement at the poppet valve to open it. One end is raised and lowered by a rotating lobe of the camshaft (either directly or via a tappet (lifter) and pushrod) while the other end acts on the valve stem. When the camshaft lobe raises the outside of the arm, the inside presses down on the valve stem, opening the valve. When the outside of the arm is permitted to return due to the camshafts rotation, the inside rises, allowing the valve spring to close the valve.

What is a Valve?

A valve typically used to control the timing and flow of vapours in and out of the cylinder.

Application

These are majorly used in the mechanical automobile engines.

Design and parts

Rhere are 5 Major components in this assembly. They are:-

1.Cams

Cams here are designed considering the camlift

The Formula of "Camlift = (L-R1)+R2"

                     Where  L1 is the length between two centres

                               R1 is the radius of the Lower circle

                              R2 is the radius of Upper circle

So here we have considered 2 different camlifts

1)3.5 mm where L1 is 11mm R1 is 12.5mm and R2 is 5mm

2) 6mm where L2 is 13.5mm R1 is 12.5mm and R2 is 5mm

1.1.Cam lift of 3.5mm

1.2.Cam lift of 6 mm

2.Push rod

3.Rocker arm

4.Valve

5.Valve mount

Assembly and Materials

Materials

Working process

As the cam rotates with a speed, the lobe pushes the pushrod in linear way. This linear movement is then transmitted to the Rocker arm,the rocker arm them pushes the valve stem down. Valve mount is present between the valve ends.

As cam rotates the pushrob pushes the rocker arm. When the rocker arm pushes the valve stem down, the valve opens and seals making the gases move inside and out.

Methodology of analysis

The motion analysis is performed considering, the following:-

1. Cam lift of 3.5mm and 6mm

2. The material of the components is cast carbon steel.

3. Obtaining the plots of Valve Lift,The contact force between 

1. Cam and Push Rod
2. Pushrod and Rocker Arm
3. Rocker Arm and Valve

Motion Analysis

1.Mates

Motor, Solid Contacts, Gravity, FPS

1.Motor

2.Solid Contacts

Gravity

FPS

Simualtion and Plots

Simulation

Plots obtained while considering the camlift of 3.5 mm

1.Linear Displacement of Valve lift

Linear Displacement of Valve lift is 2mm

2. Contact force of Cam and Push Rod

Contact force of Cam and Push Rod is 49N

3. Contact force of Pushrod and Rocker Arm

Contact force of Pushrod and Rocker Arm is 47N

4. Contact force of Rocker Arm and Valve w.r.t X direction

Contact force of Rocker Arm and Valve w.r.t X direction is 5N

5. Contact force of Rocker Arm and Valve w.r.t Magnitude

Contact force of Rocker Arm and Valve w.r.t Magnitude is 18N

Plots obtained while considering the camlift of 6 mm

Simulation

1.Linear Displacement of Valve lift

Linear Displacement of Valve lift is 4mm

2. Contact force of Cam and Push Rod

Contact force of Cam and Push Rod 78N

3. Contact force of Pushrod and Rocker Arm

Contact force of Pushrod and Rocker Arm is 63N

4. Contact force of Rocker Arm and Valve w.r.t X direction

Contact force of Rocker Arm and Valve w.r.t X direction is 7N

5. Contact force of Rocker Arm and Valve w.r.t Magnitude

Contact force of Rocker Arm and Valve w.r.t Magnitude is 24N

 

Results and analysis

3.5mm

1. Linear Displacement of Valve lift is 2mm
2. Contact force of Cam and Push Rod is 49N
3. Contact force of Pushrod and Rocker Arm is 47N
4. Contact force of Rocker Arm and Valve w.r.t X direction is 5N
5. Contact force of Rocker Arm and Valve w.r.t Magnitude is 18N

6mm

1.  Linear Displacement of Valve lift is 4mm
2. Contact force of Cam and Push Rod 78N
3. Contact force of Pushrod and Rocker Arm is 63N
4. Contact force of Rocker Arm and Valve w.r.t X direction is 7N 
5. Contact force of Rocker Arm and Valve w.r.t Magnitude is 24N

The contact force between the Rocker arm and valve varies while measuring with respect to the X direction as it calculates only the force exerted in X direction whereas magnitude is the resultant of all forces.

Analysis

As cam lift is increased the linear displacement and contact forces increases.

Conclusion

 The analysis and the study for the IC Valve train mechanism is done considering various camlifts.