MBD Simulation on IC Engine Valve Train

Objective:-

In this project, the main objective is to model an IC engine valve train which consists of essential parts such as a cam, push rod, rocker arm, valve mount, and valve, then assemble them in SolidWorks. Then run the motion analysis to find the contact force encountered between the parts(between cam and push rod, push-rod and rocker arm, and rocker arm and valve) and explain the results.

1. Introduction

A valve-train or valve train is a mechanical system that controls operation of the valves in an internal combustion engine, whereby a sequence of components transmits motion throughout the assembly. A conventional reciprocating internal combustion engine uses valves to control the flow of the air/fuel admix into and out of the combustion chamber.

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

This project aims to analyze the motion analysis of the IC engine valve train and the parameters set to achieve the plots of contact force(between cam and push rod, pushrod and rocker arm, and rocker arm and valve) are given below:

3D Models:-

CAM:

PUSHROD:

ROCKER ARM:

VALVE:

VAVLE MOUNT:

FINAL ASSEMBLY:

Motion Analysis:-

1. To run the motion analysis first go to motion study and establish contact between Cam and push rod, push rod and rocker arm, rocker arm and valve.
2. Next, give the rotation to the cam with 1500 RPM.
3. Set up a linear spring between a valve and the valve mount with the spring stiffness of 10 N/mm and free length 45 mm.
4. Change the frames to 7200 frames per sec and use precise contact.
5. select the entire assembly and assign the material as follows, go to Material-Edit material and select Cast Carbon Steel and click apply.
6. There will be an indication of the material assigned with a change in color of the entire assembly.
7. Now click the calculation button.
8. Run the analysis for the required time.

There are two cases to follow to get the desired motion analysis and the plots. They are as follows,

Case 1: Motion Analysis for cam lift of 3.5mm:

To calculate the distance between the two centres(L)

Given: R1 = 12.5; R2 = 5; Cam lift = 3.5mm

Cam lift = (L-R1)+R2

L = (12.5+3.5) - 5

L = 11mm

Contact Force plots:

• Cam and Push rod(Magnitude)

• Push-rod and Rocker Arm(Magnitude)

• Rocker Arm and Valve(Magnitude)

• Rocker Arm and Valve (X-Direction)

Case 2: Motion Analysis for cam lift of 6mm:

To calculate the distance between the two centres(L)

Given: R1 = 12.5; R2 = 5; Cam lift = 3.5mm

Cam lift = (L-R1)+R2

L = (12.5+6) - 5

L = 13.5mm

With the above information, Cam is modelled for the case 2 analysis.

Contact Force plots:

• Cam and Push Rod(Magnitude)

• Pushrod and Rocker Arm (Magnitude)

• Rocker Arm and Valve (Magnitude)

• Rocker Arm and Valve (X-Direction)

4. Observation and Results

1. The Magnitude represents net contact force between the parts, while the contact force along the X direction is the frictional force between the bodies that arise due to the rocker arm sliding over the surface of the valve head.
2. 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 then slides away from the origin giving rise to friction in the negative x-direction. Therefore the plots are opposite to each other.
3. 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.