MBD Simulation on IC Engine Valve Train
MBD Simulation on IC Engine Valve Train
AIM:
- Model the parts and assemble them in SolidWorks.
-
Obtain the valve Lift.
- The contact force between
- Cam and Push Rod
- Pushrod and Rocker Arm
- Rocker Arm and Valve
4. Explain why the contact force between the Rocker arm and valve varies while measuring w.r.t the X-direction and measuring with respect to magnitude.
5. Run the simulation using the below parameters
| Sl.No | CAM Lift (mm) | Speed (RPM) | Material |
| 1 | 3.5 | 1500 | Cast Carbon Steel |
| 2 | 6 | 1500 |
Cast Carbon Steel |
INTRODUCTION:
A valve train mechanism of an internal combustion engine including a cylinder head formed with an intake port and an exhaust port, and a camshaft including a valve for opening or closing the intake port and the exhaust port formed in the cylinder head of the engine, a cam mounted to the camshaft so as to be rotated together, and a rocker arm supported on a rocker shaft to be swingable, in which the valve is opened or closed by swinging the rocker arm by rotation of the cam. The rocker shaft is formed with an oil passage, inside the rocker shaft, extending in an axial direction and with an oil outlet communicating with the oil passage and extending in the radial direction of the rocker shaft.
THEORY:
The valve train consists of the valves and a mechanism that opens and closes them.
Working of the valve train
The bottom end of a pushrod is fitted with a lifter, upon which the camshaft makes contact. The camshaft lobe moves the lifter upwards, which moves the pushrod. The top end of the lifter pushes on the rocker arm, which opens the valve.
Types of valve trains
Hydraulic valve lifter, mechanical lifter, and roller lifter. Some pushrods are hollow, providing a means to feed oil from the lifters to the rocker arms. This reduces wear on the pushrod tip and rocker arm.
Parts of the valve train
The valve train typically includes the camshaft, valves, valve springs, retainers, rocker arms, and shafts. On engines with the 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.
THE 3D MODEL OF THE PARTS OF THE VALVE TRAIN IS SHOWN BELOW:
Cam: A part that provides the lift for the push rod which actuates the valve at regular time intervals.
Pushrod: This is the part to which the lift is provided, which is transmitted through rocker arm.
Rocker arm: This is the part that is connected to push rod in one end and valve on the other end.
Valve: This allows the air-fuel mixture to enter the cylinder or exhaust the gas out from the cylinder by opening and closing of the inlet/exhaust port.
Valve mount: This acts as the stoppage of the valve and limits the movement of the valve.
Final Assembly: Assembly is made using the assembly mate option by properly aligning them as shown. Physical dynamics are used here for making the contact between valve, rocker arm, pushrod, and cam which locks them in position, and motion analysis are performed.
Motion Analysis:
To run the motion analysis first go to the motion study and establish The contact force between
- Cam and Push Rod
- Pushrod and Rocker Arm
- Rocker Arm and Valve
The motor is given to the cam with 1500 RPM.
Set up the linear spring between the valve and the valve mount with the spring stiffness of 10 N/mm and free length of 45mm.
Change the frames per second to 7200 and use precise contact.
Select the entire assembly and assign the material as follows,
Material -> edit material -> cast carbon steel -> apply.
There will be an indication of a change in the color of the entire assembly.
Now click the calculation button and run the analysis for the required time.
| Sl.No | CAM Lift (mm) | Speed (RPM) | Material |
| 1 | 3.5 | 1500 | Cast Carbon Steel |
| 2 | 6 | 1500 |
Cast Carbon Steel |
Case 1:
Can lift = 3.5mm
R1 = 12.5mm
R2 = 10mm
CAM lift formula = L - R1 + R2
Thus, L = 6mm
Case 2:
Can lift = 6mm
R1 = 12.5mm
R2 = 10mm
CAM lift formula = L - R1 + R2
Thus, L = 8.5mm
CONTACT FORCE GRAPH FOR CASE 1:
Cam and Push Rod
Pushrod and Rocker Arm
Rocker Arm and Valve (Magnitude)
Rocker Arm and Valve (X-direction)
CONTACT FORCE GRAPH FOR CASE 1:
Cam and Push Rod
Pushrod and Rocker Arm
Rocker Arm and Valve (Magnitude)
Rocker Arm and Valve (X-direction)
Simulation of motion analysis: