MBD SIMULATION ON IC ENGINE VALVE TRAIN
1.AIM :
TO PERFORM MBD SIMULATION ON IC ENGINE VALVE TRAIN
2.OBJECTIVE :
- To model the parts of IC engine valve train and assemble them in SolidWorks.
- To perform Motion Analysis of the IC engine valve train for 2 cases of cam lift.
- To obtain following plots as a function of time - Valve Lift, contact force (between Cam and Push Rod, Pushrod and Rocker Arm, Rocker Arm and Valve measuring with respect to magnitude and Rocker Arm and Valve measuring with respect to the X direction).
3. INTRODUCTION :
A valve train is a mechanical system that controls operation of the valves in an internal combustion engine, the intake valves control the flow of air-fuel mixture into the combustion chamber and the exhaust valves control the flow of exhaust gasses out of the combusion chamber once combustion is completed.
This operation is made possible by a sequence of motion transmission through a number of components.
A typical valve-train consists of valves, valve mount,spring, rocker arms, push-rod and cam. All these components are responsible for transferring of rotational movement of the camshaft into the opening and closing of the intake and exhaust valves.
The valve train controls the amount of air and fuel entering in the combustion chamber and time of opening and closing of valves.
Here all the parts of the valve train are modeled using Solidworks and motion analysis is conducted for 2 cases of cam lift.
4. MODEL AND ASSEMBLY :
Initially all the parts are made using Solidworks and finally using mates the valve train was made.
CAM
PUSH ROD
ROCKER ARM
VALVE
VALVE MOUNT
IC ENGINE VALVE TRAIN ASSEMBLY
5.MOTION ANALYSIS :
Motion analysis for the IC engine valve train can be done using the SOLIDWORKS Motion feature available as an add-on in the solidworks, inside this feature the option motion analysis can be used to perform the operation.
To rotate the cam a constant 1500 RPM motor (clockwise direction) is assigned to that component, further a solid body contact is established between the components using the contact option.
A linear spring between valve and the valve mount with the spring stiffness of 10 N/mm and free length 45 mm.
Material for all the parts are assigned as cast carbon steel
In settings the frames per second is set to 12000 and precise contact is enabled,
The moiton analysis study is conducted for 2 cases as shown below
| SL. NO | CAM Lift (mm) | Speed (RPM) | Material |
| 1 | 3.5 | 1500 | Cast Carbon Steel |
| 2 | 6 | 1500 | Cast Carbon Steel |
The calculation for the distance between centre as per the cam lift for both the cases is shown below:-
CASE 1 (CAM lift of 3.5mm)
Given: R1 = 12.5mm, R2 = 5mm and Cam lift = 3.5mm
`L = 3.5 + 12.5-5`
`L = 11mm`
CASE 2 (CAM lift of 3.5mm)
Given: R1 = 12.5mm, R2 = 5mm and Cam lift = 6mm
`L = 6 + 12.5-5`
`L = 13.5 mm`
6.RESULTS :
The plots for both the study are given below:-
CASE 1 (CAM lift of 3.5 mm)
i)Valve Lift
The linear displacement of the valve is 2.4 mm, the nature of the graph shows the opening and closing behaviour of the valve.
Opening of valve happens due to push of rocker arm and closing happens because of push from compressed spring.
ii)Contact force between Cam and Push Rod
The magnitude and variation of contact force between Cam and Push Rod can be seen from the above plot.
This variation is beacuse of shape of cam, when the bulged portion of cam engages with the push rod the contact force increases.
iii)Contact force between Pushrod and Rocker Arm
The magnitude and variation of contact force between Pushrod and Rocker Arm can be seen from the above plot.
This variation is beacuse when the cam lifts the push rod at frequent intervals and further the push rod lifts the rocker arm the contact force increases between them.
iv)Contact force between Rocker Arm and Valve (measuring with respect to magnitude)
The magnitude and variation of contact force between Rocker Arm and Valve when measured with respect to magnitude can be seen from the above plot.
When measured with respect to magnitude, we get resultant of the force from all the directions.
This variation is beacuse when the rocker arm pushes the valve at frequent intervals.
v)Contact force between Rocker Arm and Valve (measuring with respect to the X direction)
The magnitude and variation of contact force between Rocker Arm and Valve when measured with respect to x-direction can be seen from the above plot.
The contact force measured 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.
The change in direction of the force is because the rocker arm gives a positive friction force when pushing the valve and gives rise to friction in the negative x-direction when valve pushes back the rocker arm because of spring. Therefore its varies from the contact force variation when measured with respect to magnitude.
Animation video:-
CASE 2 (CAM lift of 6 mm)
i)Valve Lift
The linear displacement of the valve is 6 mm, the nature of the graph shows the opening and closing behaviour of the valve.
Opening of valve happens due to push of rocker arm and closing happens because of push from compressed spring.
ii)Contact force between Cam and Push Rod
The magnitude and variation of contact force between Cam and Push Rod can be seen from the above plot.
This variation is beacuse of shape of cam, when the bulged portion of cam engages with the push rod the contact force increases.
iii)Contact force between Pushrod and Rocker Arm
The magnitude and variation of contact force between Pushrod and Rocker Arm can be seen from the above plot.
This variation is beacuse when the cam lifts the push rod at frequent intervals and further the push rod lifts the rocker arm the contact force increases between them.
iv)Contact force between Rocker Arm and Valve (measuring with respect to magnitude)
The magnitude and variation of contact force between Rocker Arm and Valve when measured with respect to magnitude can be seen from the above plot.
When measured with respect to magnitude, we get resultant of the force from all the directions.
This variation is beacuse when the rocker arm pushes the valve at frequent intervals.
v)Contact force between Rocker Arm and Valve (measuring with respect to the X direction)
The magnitude and variation of contact force between Rocker Arm and Valve when measured with respect to x-direction can be seen from the above plot.
The contact force measured 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.
The change in direction of the force is because the rocker arm gives a positive friction force when pushing the valve and gives rise to friction in the negative x-direction when valve pushes back the rocker arm because of spring. Therefore its varies from the contact force variation when measured with respect to magnitude.
Animation video:-
Link to solidworks files and plots:-
https://drive.google.com/drive/folders/11QEiV0Up4adC-1Bb9p6EeOWgavliQRMw?usp=sharing
7.CONCLUSION :
- The motion analysis of the IC engine valve train for both the was completed.
- Motion analysis helps to simulate the real time perfomance and give various results and plots to better understand the working.
- More the CAM lift, more will be the linear displacement of the valve.
- More the CAM lift, more will be the contact force between parts.
- When contact force is measured with respect to magnitude it represents net contact force between the parts, while the contact force measured 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.
- The change in direction of the force is because the rocker arm first slides towards origin (rocker arm pushing valve) giving a positive friction force and then slides away from the origin (valve pushing rocker arm) giving rise to friction in the negative x-direction. Therefore its varies from the contact force variation when measured with respect to magnitude.
7.REFERENCES :