MBD Simulation on IC Engine Valve Train

Aim: To perform an MBD Simulation on IC Engine Valve Train and plot the results for the given conditions.

Theory:

The valve train typically includes the camshaft, valves, valve springs, retainers, rocker arms and shafts. On engines with traditional mounting of the camshaft in the cylinder block, the valve train also includes lifters and pushrods. Overhead cam engines may use more than one camshaft per cylinder head. Engines use different valve configurations, such as two, three, four or five valves per cylinder. These various valve arrangements are used for different engine breathing requirements. Some engines also use variable valve timing, which allows the engine to change breathing characteristics under different operating conditions.

The cylinder head's valves, when synchronized with the crankshaft of the cylinder block, allow the engine to "breathe". In an engine, this means pulling the air and fuel mixture into the cylinder, then pushing the burned exhaust gases out. The better an engine breathes, the more efficient it becomes.

Components:

Cam: The timing and lift profile of the valve opening events are controlled by the camshaft, through the use of a carefully shaped lobe on a rotating shaft. The camshaft is driven by the crankshaft and— in the case of a four-stroke engine rotates at half the speed of the crankshaft.

Pushrod: A push rod is a rod that pushes up on the rocker arm. It will move depending on the movement of the camshaft follower. Another job of the pushrod is to conduct oil up to the cylinder head.

Rocker Arm: A rocker arm is a pivoting lever that pushes on the valve stem. Rocker arms will sometimes be called rocker levers, or just rockers. Depending on the type of valve train, the rotating camshaft lobes will either push directly on the rocker arm, or on the pushrods, which will conduct that motion up to the rocker arm.

Valve: A valve is composed of two major sections, the valve head, and the valve stem. The head of the valve is what allows air into and out of the cylinder. The stem is what gets pressed on by the rest of the valve train.

Valve mount: It is used to limit the movement of the valve until it reaches a point.

Calculations:

Case 1: When Cam Lift = 3.5mm

Cam lift = (L-R1) + R2

3.5 = (L-17.5) + 10

L = 11 mm

Case 2: When Cam Lift = 6mm

Cam lift = (L-R1) + R2

6 = (L-17.5) + 10

L = 13.5 mm

Study Setup:

For Cases 1 & 2:

The above image shows the body contacts given during the assembly and the motor being connected to the cam at an RPM of 1500.

As the image suggests the material assigned to the pushrod is cast carbon we do the same for all the other elements as well.

We select the fps to be 7200 and use precise contact so that the result we get is an accurate one.

Results:

Case 1: When Cam Lift = 3.5mm

The plot for Linear displacement for the valve is mentioned above. This plot explains the reciprocating motion of the valve when the rocker arm and the valve come in contact. The spring helps the valve to get back to its original position after the valve moves downwards which is clear from the animation. We get a plot that stays consistent for most periods of time baring the initial phase.

The plot for the contact force between cam and pushrod is mentioned above. As the graph suggests whenever there is a contact between the two components there is a spike in the graph and these sets of increases in the forces occur constantly throughout the graph and are maintained until the end.

The plot for the contact force between pushrod and rocker arm is mentioned above. As the graph suggests whenever there is a contact between the two components there is a spike in the graph and these sets of increases in the forces occur constantly throughout the graph and are maintained until the end.

The plot for the contact force between the rocker arm and valve is mentioned above. As the graph suggests whenever there is a contact between the two components there is a spike in the graph and these sets of increases in the forces occurred are mostly consistent with a few exceptions throughout the graph and are maintained until the end barring the initial phase.

Here we are dealing with the negative forces because when considering the forces in the x direction the spring comes into the picture which pushes the valve upwards and then the rocker arm inturn so there we observe the negative spike in the graph due to the friction between them. Apart from this the graph tends to stay consistent for most parts of the graph.

Case 2: When Cam Lift = 6mm

The plot for Linear displacement for the valve is mentioned above. This plot explains the reciprocating motion of the valve when the rocker arm and the valve come in contact. The spring helps the valve to get back to its original position after the valve moves downwards which is clear from the animation. We get a plot that stays consistent for most periods of time baring the initial phase.

The plot for the contact force between cam and pushrod is mentioned above. As the graph suggests whenever there is a contact between the two components there is a spike in the graph and these sets of increases in the forces occur constantly throughout the graph and are maintained until the end barring the initial phase.

The plot for the contact force between pushrod and rocker arm is mentioned above. As the graph suggests whenever there is a contact between the two components there is a spike in the graph and these sets of increases in the forces occur constantly throughout the graph and are maintained until the end.

The plot for the contact force between the rocker arm and valve is mentioned above. As the graph suggests whenever there is a contact between the two components there is a spike in the graph and these sets of increases in the forces occurred are mostly consistent with a few exceptions throughout the graph and are maintained until the end barring the initial phase.

Here we are dealing with the negative forces because when considering the forces in the x-direction the spring comes into the picture which pushes the valve upwards and then the rocker arm inturn so there we observe the negative spike in the graph due to the friction between them. Apart from this the graph tends to stay consistent for most parts of the graph.

Conclusion:

The simulation for the IC Engine Valve Train is successfully simulated and the necessary plots are also made.

Animation:

Assembly 3.5mm Cam Lift

https://www.youtube.com/watch?v=zkulOeip7gY

Assembly 6mm Cam Lift

https://www.youtube.com/watch?v=CkErA-vXJpw

CAD Files:

https://drive.google.com/drive/folders/14l_Z7T-uhb2SIofzxOK21b5mbEmXzO0e?usp=sharing

https://drive.google.com/drive/folders/1d-SVpe7J6DHh7Ft5VNcQ69oG_wdu2Z87?usp=sharing

References:

https://www.mastermechanic.ca/inspection/valve-train-components.php#

https://highwayandheavyparts.com/n-12778-valve-train-function-components-and-repair-options.html