MBD Simulation on IC Engine Valve Train

Aim:

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.

A typical valve-train consists of valves, rocker arms, push-rod, lifters, and cam. Valve-train opening/closing and duration, as well as the geometry of the valve-train, controls the amount of air and fuel entering the combustion chamber at any given point in time. Valve-trains are built in several configurations, each of which varies slightly in layout but still performs the task of opening and closing the valves at the time necessary for proper operation of the engine.

A typical Valve-train which describes each part is shown below.

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

After designing all the parts we have to complete the assembly.

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:

2. Creating a 3D Model

• Cam: A cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion. It is often a part of a rotating wheel or shaft that strikes a lever at one or more points on its circular path.

• Pushrod: This is the part to which the lift is provided, which is transmitted to the rocker arm.

• Rocker Arm: This is part which is connected to push rod in one end and valve on the other end.

• Valve: This allows the air-fuel mixture to enter the cylinder or exhaust the gases out from the cylinder by opening and closing of the inlet/exhaust port.

• Valve Mount: This acts as the stoppage for the valve and limits the movement of the valve.

• Final Assembly: Assembly is made using the assembly mate option by properly aligning them as shown. Physical dynamics is used here for making contact between valve, rocker arm, push rod and cam which locks them in position and motion analysis is performed.

3. 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,

Cam Lift Formula:

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

With the above information, Cam is modelled for the case 1 analysis.

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)

Animation:

IC Engine Valve-Train at Cam lift = 3.5

https://youtu.be/dikIIUPT41c