MBD Simulation on IC Engine Valve Train
AIM: -
To create a 3D model and Simulation on IC Engine Valve Train in solidwork.
OBJECTIVE: -
Our objective is to create a 3D model and Simulation on IC Engine Valve Train in solidwork and plot the variation of linear displacement with time for following conditions:
We also have to plot variation of contact force with time at following contacts:
- Cam and Push rod
- Push rod and Rocker arm
- Rocker arm and valve
Components:-
- Cam
- Push Rod
- Rocker Arm
- Valve
- Valve Mount
BODY: -
A valve-train or valve train is a mechanical system that controls operation of the valves in an internal combustion engine, whereby a sequence of components transmits motion throughout the assembly. A conventional reciprocating internal combustion engine uses valves to control the flow of the air/fuel admix into and out of the combustion chamber. A typical valve-train consists of valves, rocker arms, push-rod, lifters, and cam, Valve-train opening/closing and duration, as well as the geometry of the valve- train, controls the amount of air and fuel entering the combustion chamber at any given point in time. Valve-trains are built in several configurations, each of which varies slightly in layout but still performs the task of opening and closing the valves at the time necessary for proper operation of the engine.
A typical Valve-train which describes each part is shown below:-
Cam: A camshaft is a device to convert rotational motion into reciprocating motion which actuate the intake and exhaust valves of the cylinder s. The cams and the camshaft are usually formed as a unit, with the cams set at angles so as to open and close the valves in a prescribed sequence as the cams rotate. A separate camshaft for each row of cylinders is driven by gears or chains from the crankshaft. One of the most widely used applications of camshafts is the Opening and closing of fuel valves in virtually all piston-driven internal combustion engines.
Push rod: Push rod is a rod that pushes up rocker arm by actuated by a cam to open or close a valve of an internal combustion engine.
Rocker Arm: Rocker arm is an oscillating lever that conveys radial movement from the cam lobe into linear movement at the poppet valve to open it. One end is raised and lowered by a rotating lobe of the camshaft while the other end acts on the valve. When the camshaft lobe raises the outside of the arm, the inside presses clown on the valve stem, opening the valve. When the outside of the arm is permitted to return due to the camshafts rotation, the inside rises, allowing the valve spring to close the valve. Some overhead cam engines employ short rocker arms in which the cam lobe pushes down on the rocker arm to open the valve. On this type of rocker arm, the fulcrum is at the end rather than the middle, while the cam acts on the middle of the arm. The opposite end opens the valve.
Valve: Valve is a device to close and open a passage. ln motor vehicle engines, two engine valves are used for each cylinder-an inlet (or intake) valve and an exhaust valve. Fuel is allowed to the cylinder by the inlet valve. When closed, the valve seals the combustion space tightly.
Valve Mount: Valve Mount use to support the valve to move in correct direction and spring is attached to the valve mount,
Motion Study Analysis
In the Motion study the following steps are performed.
- In this input motor is fixed to cam and it rotes at the constant speed of 1 500rpm in two cases.
- Linear spring is added between surface of valve and valve mount with spring constant of 10 N/mm and free length of 45mm.
- We are using motion study properties, 7200 frames per second and using contact Fixing the contact type as solid bodies for IC Engine valve Train and assigning material as Cast Carbon Steel, and calculate the motion analysis.
Calculation is performed for the motion analysis for about 0.8 sec. Linear displacement of the piston head w.r.t time is obtained for following conditions.
We also have to plot variation of contact force with time at following contacts:
- Cam and Push rod
- Push rod and Rocker arm
- Rocker arm and valve
RESULTS:
For Cam lift of 3.5mm
- Linear displacement
- Contact force at Cam and Push rod
- Contact force at Push rod and Rocker arm
- Contact force at Rocker arm and valve(Magnitude)
- Contact force at Rocker arm and valve(For X direction)
For Cam lift of 6 mm
- Linear displacement
- Contact force at Cam and Push rod
- Contact force at Push rod and Rocker arm
- Contact force at Rocker arm and valve(Magnitude)
- Contact force at Rocker arm and valve(For X direction)
CONCLUSION: -
With increasing the CAM lift, linear displacement of valve also increased. Valve lift mainly depend on the design of CAM.
Contact force between the rocker arm and valve with respect to the X direction gives the contact force only in X direction which has both negative and positive value when the valve is moving upwards and downwards respectively. Contact force between the rocker arm and valve with respect to magnitude is much higher than that calculated in X direction as the “magnitude” gives net contact force.
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