IC Engine ValveTrain MBD Simulation Using Solidworks
IC Engine Valve Motion Analysis Using SolidWorks
Aim:- To perform motion analysis on different components of IC Engine Valve such as cam,push rod,rocker arm,valve,etc. for calculating contact forces between them.
Theory :-
A valvetrain 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 combusion chamber once combustion is completed.
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 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 timming 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. 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,side 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)
Objective:-
To study motion analysis of internal combustion engine valvetrain. In which contact force between each contact, lift force of push rod is calculated and graph are plotted.
Calculation of Camlift:-
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
Different Parts:-
Cam
Push rod
Rocker Arm:-
Valve:-
Mount
Assembly :-
1st
2nd
Plots :-
Case 1
Linear displacement of cam
In this plot as the cam peak part touches push rod there is sudden increase in linear displacement with respect to time
Contact between cam and pushrod
In this plot as pushrod touches peak point of cam their is sudden increase in contact force with respect to time.
Contact force between pushrod and rockerarm
In this plot push rod is in contact with backside of rocker arm which makes a sudden contact when its linear displacement changes.
Rockerarm and valve (magnitude)
In this plot the rockerarm touches only when it is pushed by pushrod from backside and it is resisted by spring action.
Contact force between Rocker arm and Valve (X component)
As difference between the plot of contact forces between rocker arm and valve on X component or Magnitude basis is In magnitude form the plot is stable and always increase whereas in x-component it is not stable and decreasing in between.
Case 2
Linear Displace of Cam
In this plot as the cam peak part touches push rod there is sudden increase in linear displacement with respect to time
Contact force between cam and pushrod
In this plot as pushrod touches peak point of cam their is sudden increase in contact force with respect to time.
Contact force between Pushrod and Rockerarm
In this plot push rod is in contact with backside of rocker arm which makes a sudden contact when its linear displacement changes.
Contact force between Rockerarm and valve (Magnitude)
In this plot the rockerarm touches only when it is pushed by pushrod from backside and it is resisted by spring action.
Contact force between Rockerarm and valve (X Component)
As difference between the plot of contact forces between rocker arm and valve on X component or Magnitude basis is In magnitude form the plot is stable and always increase whereas in x-component it is not stable and decreasing in between.
Conclusion:-
It can be concluded that as we change the cam dimensions using camlift formula the plot of their contact force and pushrod lift varies. And also more energy is required to overcome camlift if the dimension of upper circle is more.