DESIGN AND STUDY OF IC ENGINE VALVE TRAIN USING SOLIDWORKS

AIM

1. To design and assemble each part of the I.C engine valve train.

2. To study motion analysis for the following three different conditions

S.no. Cam lift (mm) Cam Speed (Rpm) Material 1 3.5 mm 1500 Cast Carbon Steel 2 6 mm 1500 Cast Carbon Steel

3. To plot the curve for different cases of cam lift
   a. The displacement of the Valve Lift
   b. Contact force between Cam and Push Rod, Push rod and Rocker Arm, Rocker Arm and Valve.

GIVEN

All the simulation should be done for 1500rpm of crank and the material used must be Cast Carbon Steel.

FORMULA USED

BODY OF CONTENT

Introduction

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.

Component used in the IC engine valve train are Cam, Push rod, Rocker arm, Valves.

CAM

The timing and lift profile of the valve opening events are controlled by the cams, 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.

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

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 MOUNT

CALCULATION

CASE 1- when lift is 3.5mm

Cam lift = (L – R₁) + R₂

3.5 = L – 12.5 + 5

L = 11 mm

CASE 2- when lift is 6mm

Cam lift = (L – R₁) + R₂

6 = L – 12.5 + 5

L = 13.5 mm

STEPS OF DESIGNING OF I.C ENGINE VALVE TRAIN ASSEMBLY

Before starting any design make sure the Dimension system is in mm.

CAM

1. Firstly, draw the sketch and provide the dimension according to mention in the figure below
   a. For lift of 3.5mm

b. For lift of 6mm

2. Extrude the sketch made with 10mm as shown in the figure

PUSHROD

1. Firstly, draw the sketch and provide the dimension according to mention in the figure below

2. Now go to revolve base feature, before that select the reference axis.

ROCKER ARM

1. Firstly, draw the sketch and provide the dimension according to mention in the figure below

2. Extrude the sketch made with 20mm as shown in the figure

VALVES

1. Firstly, draw the sketch and provide the dimension according to mention in the figure below

2. Now go to revolve base feature, before that select the reference axis.

VALVE MOUNT

1. Firstly, draw the sketch and provide the dimension according to mention in the figure below

2. Now go to revolve base feature, before that select the reference axis.

MATING OF THE COMPONENT

Now to make the assembly first Go to file menu and select new after that one dialog box will appear and choose assembly option for doing assembly.

Go to insert components option and insert the part to be assemble.

Choose mate option in order to complete the assembly, for this design the mating of the assembly is given in the figure below

MOTION ANALYSIS

For doing motion analysis go to motion study make sure that motion add in is enable. And select the motion study in the place of animation.

Start motion analysis and simulate the design after giving the right position of the assembly.

1. Do proper contact between the mating part. Here I am taken steel (dry) as a contact between two components.

2. Provide motor for rotation of the cam. Here I have taken 1500 rpm

3. Provide spring between valve and valve mount as shown in the figure. Here I have taken 10 N/m stiffness of the spring. Here the spring used is considered as a pre tensioned.

4. Set the frame per second according to design and select precise contact. Here I have taken 7200.

5. Now click on calculate option before that set the length of time span. After that wait for some time in order to finish the simulation.

RESULT

Case 1. For lift of 3.5mm

a. Linear displacement of valve

b. Contact force between cam and push rod

c. Contact force between push rod and rocker arm

d. Contact force between rocker arm and valve

e. Contact force between rocker arm and valve in x direction

YOUTUBE LINK

Youtube link for case 1, when lift is 3.5mm

Case 2. For lift of 6mm

a. Linear displacement of valve

b. Contact force between cam and push rod

c. Contact force between push rod and rocker arm

d. Contact force between rocker arm and valve

e. Contact force between rocker arm and valve in x direction

YOUTUBE LINK

Youtube link for case 2, when lift is 6mm

CONCLUSION

1. The magnitude of linear displacement of valve increases when we increase the lift in the cam.
2. The magnitude of the contact forces between Cam and Push Rod, Push rod and Rocker Arm, Rocker Arm and Valve are increases when we increase the lift of the cam.
3. The magnitude of the contact forces between Rocker Arm and Valve in x direction are also increases when we increase the lift of the cam.

Question. “Explain why the contact force between the Rocker arm and valve varies while measuring with respect to the X direction and measuring with respect to magnitude”?

4. The plot of the Rocker Arm and Valve varies in case of all direction as well as in x direction because it is having some component of reaction force acting in y, z direction also.

In fact, the force is negative and opposite direction when we compared with magnitude plot and in x direction plot because of friction force occur between rocker arm and valve which try to slide the rocker arm over the valve surface.

So alone calculating the force in x direction is less as compared to all direction or magnitude.

GOOGLE DRIVE LINK

https://drive.google.com/drive/folders/1q2hu5Uan1xtlknpyzxS-4y0qH5cvZz-Q?usp=sharing

REFRENCES

1. Lecture of skilllync.com
2. wikkipedia for valve train.