MBD Simulation on IC Engine Valve Train

AIM: MBD SIMULATION ON IC ENGINE VALVE TRAIN

Design considerations:

OBJECTIVE:

1.1 Model the parts and assemble them in SolidWorks.

2.1 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

2.2 To Obtain the:

1. Valve Lift.

2.3 The contact force between:

1. Cam and Push Rod

iii. Pushrod and Rocker Arm

1. Rocker Arm and Valve

The contact force between the Rocker arm and valve varies while measuring with respect to the X-direction and measuring with respect to magnitude.

Theory of IC engine valve train mechanism

A valvetrain or valve train is a mechanical system that controls the operation of the intake and exhaust valves in an internal combustion engine.^[1] 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.

Components :

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/cam

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 (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.

Rocker arm/bucket tappet

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.^[3] 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)

• 3D Models of the IC ENGINE VALVE TRAI parts and Assemble

1.Cam:

2.Pushrod:

3. 3. Rocker arm:

   4.Valve:

   1. Valve Mount:

      6.IC ENGINE VALVE TRAI Assemble

      2.1 Simulate by using the following parameters

      Sl .No	CAM Lift (mm)	Speed (RPM)	Material
      1	3.5	1500	Cast Carbon Steel
      2	6	1500	Cast Carbon Steel

      CASE 1:

      Sl .No	CAM Lift (mm)	Speed (RPM)	Material
      1	3.5	1500	Cast Carbon Steel

      1. Valve Lift:

      Theory:

      This is the distance of the cam lobe rises away from the base circle of the camshaft. It is the distance of the lifter will move. It is also called "lobe lift." A more cam lift means the valve will open further.

      Here we need to calculate the center distance between the two circles of the cam. We have diameters of two circles of cam and cam lift for two different cases. So, by using the following formula for cam lift we can calculate the center distance between the two circles.

      Formula For Cam Lift:

      1. Calculation:

      for Case-1:

      We have, Cam lift = 3.5 mm ; Major Circle Radius (R1) = 12.5 mm ; Minor Circle Radius(R2) = 5 mm

      Therefore, using a formula,

      Cam lift = (L − R1) + R2

      3.5 = (L − 12.5) + 5

      L = 11

      Modification in Cam:

      MOTION ANALYSIS & RESULTS

      1.moter speed -1500rpm

      2.Contact b/w the parts

      3.adding spring

      4.Adding the number of frames

      5.Assigning the material

      RESULTS:

      1.Magnitude of linear displacement of the valve:

      1. Contact force Between Cam and Push Rod:
      1. Contact force Between Pushrod and Rocker Arm:
      1. Contact force Between Rocker Arm and Valve with respect to magnitude:
      1. Contact force Between Rocker Arm and Valve with respect to X direction:

      Animation video:

      CASE 2:

      Sl .No	CAM Lift (mm)	Speed (RPM)	Material
      2	6	1500	Cast Carbon Steel

      1. Valve Lift:
      2. Theory:

      This is the distance of the cam lobe rises away from the base circle of the camshaft. It is the distance of the lifter will move. It is also called "lobe lift." A more cam lift means the valve will open further.

      Here we need to calculate the center distance between the two circles of the cam. We have diameters of two circles of cam and cam lift for two different cases. So, by using the following formula for cam lift we can calculate the center distance between the two circles.

      Formula For Cam Lift:

      Calculation:

      for Case-2:

      We have, Cam lift = 6 mm ; Major Circle Radius (R1) = 12.5 mm ; Minor Circle Radius(R2) = 5 mm

      Therefore, using a formula,

      Cam lift = (L − R1) + R2

      6 = (L − 12.5) + 5

      L = 13.5

      Modification in Cam:

      MOTION ANALYSIS & RESULTS

      1.moter speed -1500rpm

      2.Contact b/w the parts

      3.adding spring

      4.Adding the number of frames

      5.Assigning the material

      RESULTS:

      1.Magnitude of linear displacement of the valve:

      The displacement of the valve will be uniform

      but initially which is low due to the low cam lift.

      1. Contact force Between Cam and Push Rod:
      2. Contact force Between Pushrod and Rocker Arm:
      3. Contact force Between Rocker Arm and Valve with respect to magnitude:

      4. The contact will more (2400 N) in the time of 0.24s and 0.275s

         1. Contact force Between Rocker Arm and Valve with respect to X direction:

            The valve will travel below its initial potion

            Animation video:

            https://youtu.be/5me0MM4yNkE

            conclusion:

            The linear displacement of valve is depending on the cam lift/'lobe lift'