MBD Simulation on IC Engine Valve Train

AIM:

To analyze the motion of IC engine valve train using Motion Analysis feature in SolidWorks.

INTRODUCTION AND THEORY:

A valve train is a mechanical system that controls the operation of inlet and exhaust valves in the internal combustion engines. It usually consists of a cam, follower, rocker, valve stem and a valve. As the technology has evolved in recent years, the mechanical actuation usually found in the valve train has been replaced by electronic actuation. In addition, mechanical springs are being replaced by air springs. But here, the mechanical system is considered for the motion analysis.

The cam is connected to a camshaft which in turn is driven by crankshaft using a timing chain. Valve train design determines how efficient the engine can operate because the valve opening and closing instant of time determines how much fuel can enter into the engine cylinder during suction stroke. Valve timing is being studied and the inferences made out of the studies are implemented to maximize the efficiency of IC engine.

INPUT DATA:

DESIGNED CAD MODELS:

CAM:

Case 1 (3.5mm Cam Lift):

From the Cam Lift Formula,

R1 = 25/2 = 12.5 mm

R2 = 10/2 = 5 mm

Cam Lift = 3.5 mm (Given)

Therefore, L = 3.5 + 12.5 -5 = 11 mm

Case 2 (6.5mm Cam Lift:

From the Cam Lift Formula,

R1 = 25/2 = 12.5 mm

R2 = 10/2 = 5 mm

Cam Lift = 6 mm (Given)

Therefore, L = 6 + 12.5 -5 = 13.5 mm

FOLLOWER OR PUSHROD:

ROCKER:

VALVE:

VALVE STEM:

VALVE TRAIN ASSEMBLY:

PROCEDURE:

1. The components of the valve train are modelled using SolidWorks as per the dimensions given in the drawing sheet.

2. Cam for two cases are separately modelled.

3. Cast Carbon Steel material is applied to every component in the assembly.

4. Motion Analysis parameters are set as per the requirement:

Frames Per Second = 9000

Spring parameters: 45 mm free length and 10 N/mm stiffness.

Motor speed at cam = 1500 rpm.

5. The necessary contacts between the components are enabled.

6. Once everything is done, the analysis is carried out and results are obtained.

RESULTS:

CASE 1:

CASE 2:

OBSERVATIONS:

VALVE LIFT:

In case 1, the minimum and maximum value obtained are 72.2 and 75.4 mm. So, valve lift is 75.4 - 72.2 = 3.2 mm.

In case 2, the minimum and maximum value obtained are 71 and 75 mm. So, valve lift is 75 - 71 = 4 mm.

CAM AND FOLLOWER CONTACT:

In case 1, the maximum contact force obtained is 5427 N.

In case 2, the maximum contact force obtained is 13701 N.

FOLLOWER AND ROCKER CONTACT:

In case 1, the maximum contact force obtained is 5692 N.

In case 2, the maximum contact force obtained is 14301 N.

ROCKER AND VALVE (MAGNITUDE):

In case 1, the maximum contact force obtained is 1089 N.

In case 2, the maximum contact force obtained is 2639 N.

ROCKER AND VALVE (X DIRECTION):

In case 1, the contact force obtained is -264 N.

In case 2, the contact force obtained is -640 N.

INFERENCE:

As you can see from the observations, the contact forces in case 2 have higher magnitude when compared to that in case 1. This is mainly due to increase in cam lift value which compresses the spring to a larger extent that it exerts more resistive force against the rocker which in turn affects the other components in sequence that it has contact with. Hence the contact forces are a bit higher in case 2 when compared to that in case 1.

The 'rocker and valve contact force in x-direction' is different from 'rocker and valve contact force in magnitude'. This is simply because the x-direction force is due to friction between the contact surfaces. But the contact force magnitude includes the frictional component and the axial component of force. So, the contact force is a bit higher in case 2 when compared to that in case 1. The positive and negative values indicate the direction of contact force (frictional part) along positive and negative x-direction.

CONCLUSION:

Hence the motion analysis of valve train assembly is successfully carried out and the results are verified.