Design and MBD Simulation on IC Engine Valve Train

Aim: Design and Motion analysis of IC Engine Valve Train using Solidworks Multi-Body Dynamics.

Theory: A valve train or valve train is a mechanical system that controls the 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.

It consists of five components :

• Cam
• Push Rod
• Rocker Arm
• Valve
• Valve Mount

The valvetrain consists of all the components responsible for transferring the rotational movement of the camshaft into the opening and closing of the intake and exhaust valves. Typical components are listed below in order from the crankshaft to the valves.

Camshaft:

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.

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.

Pushrod:

Pushrods are long, slender metal rods that are used in overhead valve engines to transfer motion from the camshaft to the valves. 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.

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.

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).

Valve mount: Acts a spring for the valve.

Assembly of IC Engine valve train:

Drawing of CAM for Case 01 and Case 02:

Case 01:

Case 02:

Procedure for Motion Analysis:

1. At first, we will make part modeling of all the 5 parts in Solidworks and the unit should be MMGS.
2. Then we will open Solidworks assembly to start assembling the five components in Solidworks assembly.
3. In this, the material we will be using will be Cast Carbon Steel.
4. Now Since we have completed the assembly and defining the material we will go for motion analysis and for that we will go in add-in and click on Solidworks motion.
5. Now we will define the motor at Cam axis as 1500 rpm in a clockwise direction.
6. For this case 1 we will keep the distance from origin to the smaller circle axis as 11mm and for case 2 as 13.5mm.
7. Now we will define contact between Cam and Push Rod then Push Rod and Rocker Arm and then between Rocker Arm and Valve.
8. Now we will apply Spring between Valve and Valve Mount with the stiffness of 10N/mm and distance as 35mm.
9. Now Since our defining of Parts is done we can change the motion analysis to 9000 frames per second.
10. Now we can hit on calculate and then can go for results and plots after the calculation is done.

Results:

Case 01:-

Cam and Push Rod:

Linear Displacement of Valve:

Pushrod and Rocker arm:

Rocker arm and Valve in X-Direction:

Rocker arm and Valve (Magnitude):

Case 02:

Cam and Pushrod:

The linear displacement of Valve:

Push Rod and Rocker Arm:

Rocker arm and Valve in X-Direction:

Rocker Arm and Valve ( Magnitude);

The formula for calculation of the distance is:

L = R1 - R2 + (cl)

where cl is the cam lift

All units are in mm

Observation:

With an Increase in Cam lift, linear displacement of the valve also increased. Thus, Valve lift is dependent on the design of Cam.

the Contactforce between the Rocker Arm and valve with respect to the X-direction force gives the contact force only in the X-direction. But in X direction force has both negative and positive when the Valve is moving upwards and downwards.

CAD Parts link: https://drive.google.com/drive/folders/1c3jF7BtGO-C9E-90d3_89bp0WDDl17To?usp=sharing

Animation Link:https://www.youtube.com/playlist?list=PLgFSZcr_6YgzsnVN7DwYnxWJ3Y82uPCz4

Reference: https://www.wikipedia.org/