MBD Simulation on IC Engine Valve Train

Aim : To model and assemble the parts of IC engine Valve Train to perform motion analysis on various conditions

Objective :

1) To perform motion analysis for the following conditions,

• Condition 1: When cam lift is 3.5mm
• Condition 2: When cam lift is 6mm

2) Plotting the linear displacement of the valve lift, contact force between Cam and Push Rod, contact force between Pushrod and Rocker Arm and contact force between Rocker Arm and Valve.

Introduction :

Motion analysis helps the user to get the actual simulation of the product under observation. It is usually performed on the systems which are complicated. Motion analysis provides various information of the moving components such as velocity, acceleration, reactive forces acting on it, etc. It also plays a significant role in determining the movement and checking the constraints acting on the moving components. The data obtained from the study could be further used for development of the product.

The present report shows the motion analysis performed on a IC engine Valve Train assembly. The control of the inlet and exhaust valves is done with the help of Valve train mechanism. The intake air/fuel mixture is controlled by intake valves while the exhaust takes care of the exhaust gases released after combustion. Hence it becomes necessary to operate these at the right time in order to attain complete combustion.

Procedure :

• The cad models of the assembly are created as per the prescribed dimensions These are shown below :

1. Rocker Arm:

2. Push Rod :

3. Valve :

4.Valve mount :

5. Cam (cam lift 3.5mm) :

For 3.5mm lift following equation should be used,

Therefore,

3.5 = (L-17.5)+(10)

L = 11 mm

6.Cam (cam lift 6mm) :

For 6 mm lift following equation should be used,

Therefore,

6 = (L-17.5)+(10)

L = 13.5 mm

• The models are then assembled by giving required constraints and mates as per the given conditions. This completes the assembly as shown below.

a)Condition 1: When cam lift is 3.5mm

b) Condition 2: When cam lift is 6mm

• Next, motion analysis is to be performed. For this, we need to develop Contacts between the parts, provide gravity, adjust the frames, and give a speed of 1500 RPM to the Cam.
• Once the required parameters are given as input, Run the motion analysis.
• After this, we can plot the required graphs.

Results: The following plots are obtained :

• Condition 1: When cam lift is 3.5mm

1). Valve lift and time:

2) The contact force between Cam and Push Rod :

3) The contact force between Pushrod and Rocker Arm :

4) The contact force between Rocker Arm and Valve :

5) The contact force between Rocker Arm and Valve (x-direction) :

• Condition 2 : When cam lift is 6mm

1). Valve lift and time :

2) The contact force between Cam and Push Rod :

3) The contact force between Pushrod and Rocker Arm :

4) The contact force between Rocker Arm and Valve :

5) The contact force between Rocker Arm and Valve (x-direction) :

Inference :

• From the graph, it can be seen that the linear displacement of the valve for condition 2 is higher than that of condition 1. Condition 1 shows 51.2 mm while condition 2 shows 53.1 mm. It can be concluded that with an increase in the cam lift, linear displacement of the valve increases.
• The selection of the spring also plays a vital role in the linear displacement as well as vibrations of the valve.
• While measuring the contact force between the Rocker arm and Valve in the x-direction, the only frictional force between the rocker arm surface and valve surface is calculated. But in case of magnitude selection, overall net forces acting at the point of contact are calculated.

Video Animation :