MBD Simulation on IC Engine Valve Train

MBD Simulation on IC Engine Valve Train

Created by Shahbaaz khan deoda

On 11 June 2020

Aim: - To simulate the multibody dynamics of ic engine valve train using solidworks.

Need of engine valve: - we know the working of ic engine, so there are four stroke and two stroke engine kind of ic engine. In that engines there are particular time for opening and closing the valve of inlet and outlet. So, control this valve motion for opening and closing, the valve train mechanism is used.

objective: -This project aims to analyze the motion analysis of the IC engine valve train and the parameters set to achieve the plots of contact force(between cam and push rod, pushrod and rocker arm, and rocker arm and valve) are given below:

Valve-train: - A valvetrain or valve train is a mechanical system that controls operation of the intake and exhaust valves in an internal combustion engine. The intake valves control the flow of air/fuel mixture (or air alone for direct-injected engines) into the combustion chamber, while the exhaust valves control the flow of spent exhaust gasses out of the combustion chamber once combustion is completed.

Parts of engine valve: -

1.Camshaft: -The timing and lift profile of the valve opening events are controlled by the camshaft, through 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.Motion is transferred from the crankshaft to the camshaft most commonly by a rubber timing belt, a metallic timing chain or a set of gears.

2.Pushrod: - Pushrods are long, slender metal rods that are used in overhead valve engines to transfer motion from the camshaft (located in the engine block) to the valves (located in the cylinder head). 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.

3.Rocker arm: -Depending on the design used, the valves are actuated by a rocker arm, finger or bucket tappet. Overhead camshaft engines use fingers or bucket tappets, upon which the cam lobes contact. Overhead valve engines use rocker arms, which are actuated by a pushrod and pivot on a shaft or individual ball studs in order to actuate the valves.

4.Valves: -Most modern engines use poppet valves type, although sleeve valves, slide valves and rotary valves have also been used at times. Poppet valves are typically opened by the camshaft lobe or rocker arm, and closed by a coiled spring called a valve spring.Valve float occurs when the valve spring is unable to control the inertia of the valvetrain at high engine speeds (RPM).

5.Valve mount: -It is a type of hollow cylinder which provides the constrains to the engine valve. By using it the valve only can slide into the cylinder. It has a cap which is used to fixed the spring to follow back the motion valve.

motion Analysis: -

1. To run the motion analysis first go to motion study and establish contact between Cam and push rod, push rod and rocker arm, rocker arm and valve.
2. Next, give the rotation to the cam with 1500 RPM.
3. Set up a linear spring between a valve and the valve mount with the spring stiffness of 10 N/mm and free length 45 mm.
4. Change the frames to 9000 frames per sec and use precise contact.
5. select the entire assembly and assign the material as follows, go to Material-Edit material and select Cast Carbon Steel and click apply.
6. There will be an indication of the material assigned with a change in color of the entire assembly.
7. Now click the calculation button.
8. Run the analysis for the 0.2.

In this project we will simulate the valve train for 2 condition.

CAM Lift Formula

CAM Lift can be derived from the sketch
● The diameter of lower circle (D1)- 35 mm
● The diameter of upper circle (D2)- 20 mm
● The distance between two centres (L)- 30 mm
CAM Lift = (L-R1)+R2

case 1: cam lift = 3.5mm and rotaing at 1500 rpm.

Cam lift = (L-R1)+R2

By the above fig,

• R1 = 11 mm
• R2 = 3.5 mm
• L = 11 mm

So, Cam lift = (11 - 11) + 3.5= 3.5 mm

plot 1 displacement of pushrod

plot 2 displacement of engine valve

plot 3 contact force between cam and pushrod

plot 4 contact force between pushrod and rocker arm

plot 5 contact force between rocker arm and valve

plot 6 contact force between rocker arm and valve in x direction

case 2:

cam lift = 6mm and rotaing at 1500 rpm.

Cam lift = (L-R1)+R2

By the above fig,

• R1 = 12.5 mm
• R2 = 6 mm
• L = 12.5 mm

So, Cam lift = (12.5 - 12.5) + 6 = 6 mm

plot 1 displacement of pushrod

plot 2 displacement of engine valve

plot 3 contact force between cam and pushrod

plot 4 contact force between pushrod and rocker arm

plot 5 contact force between rocker arm and valve

plot 6 contact force between rocker arm and valve in x direction

conclusion: -we have done the simulation for the valve train succesfully. The magnitude of contact force between rocker arm and valve is shown in plot 5 for both cases and contact force between rocker arm and valve in x direction is shown in plot 6 for both the cases.

The reason for differece in the contact force in magnitude and in x direction is that, rocker arm is rotate. So, on the touching surface with valve two types of movement occure so net contact force in magnitude is differ from net contact force in x direction on the contact orf rocker arm and vakve assembly.