MBD Simulation on IC Engine Valve Train
Objective: To model & simulate the working of the Valve train of an Internal combustion engine using SOLIDWORKS
The parameters for the simulation are:
Angular velocity of cam: 1500 RPM
Material of all components: Cast Carbon Steel
The simulation is to be carried out for two different cases of Cam lift:
Case 1: Cam lift = 3.5 mm
Case 2: Cam lift = 6 mm
The valve train of an IC engine contains the following components:
- Cam
- Push rod
- Rocker
- Valve
- Valve mount
- Spring
The functions of each of the components are as follows:
- Cam: The cam is connected directly to the crank shaft of the engine, which results in equal angular velocities. The profile of the cam is chosen to adjust the follower speed or the lift of the follower
- Push Rod: It acts as a follower to the cam. The Lift of the push rod is influenced by the profile of the cam. The push rod transfers motion from the cam to the rocker
- Rocker: The Rocker is the main motion transferring element in the valve train. The Rocker performs an oscillatory motion and is constrained by push rod on one side and the valve on the other
- Valve: The rocker's oscillatory motion and the spring below the valve together enable the valve to turn on and off
- Valve mount: It is connected to the valve to support the valve and the spring
Procedure:
- The individual components are modeled in SOLIDWORKS using the correct dimensions
- The assembly is created by applying proper mates between the components
- The Simulation tool is enabled
- Rotation is applied to the cam with a speed of 1500 RPM
- The contacts are enabled between the contacting bodies
- A spring is created concentric to the valve and connecting rocker's surface and valve mounting.
- The number of frames per second is chosen to be 9000 since the angular velocity is high
- Precise contact is activated and the materials are assigned
- The results and plots are obtained
Modeling in SOLIDWORKS:
Cam:
Push Rod:
Rocker:
Valve:
Valve-mount:
Assembly:
Results:
Case 1: Cam lift = 3.5 mm
Push rod Displacement:
Contact Force between Cam and Push rod:
Contact Force between Rocker and Push rod:
Contact Force between Rocker and Valve (Magnitude):
Contact Force between Rocker and Valve (only in x-direction):
Case 2: Cam lift = 6 mm
Push rod Displacement:
Contact Force between Cam and Push rod:
Contact Force between Rocker and Push rod:
Contact Force between Rocker and Valve (Magnitude):
Contact Force between Rocker and Valve (only in x-direction):
Question: Why the contact force between the Rocker arm and valve varies while measuring with respect to the X direction and measuring with respect to magnitude.
Answer: The total contact force between the rocker's end surface and the valve consists of both the components i.e. the x direction component and the y direction component. While measuring on the magnitude of that force, the resultant of both the components is calculated . And while measuring only the x-direction of the contact force only the x-component is displayed. Hence, the magnitude contact force varies from the x-direction force