MBD Simulation on IC Engine Valve Train
1.AIM : To model the Valve Train components for IC Engine and assemble than to get the simulations in Solidworks According to the Following cases.
2.OBJECTIVE: -
Our objective is to create a 3D model and Simulation on IC Engine Valve Train in solidwork and plot the variation of linear displacement with time for following conditions:
We also have to plot variation of contact force with time at following contacts:
- Cam and Push rod
- Push rod and Rocker arm
- Rocker arm and valve
3.THEORY:
A valve-train or valve train is a mechanical system that controls operation of the valves in an internal combustion engine, whereby a sequence of components transmits motion throughout the assembly. A conventional reciprocating internal combustion engine uses valves to control the flow of the air/fuel admix into and out of the combustion chamber.
A typical valve-train consists of valves, rocker arms, push-rod, lifters, and cam. Valve-train opening/closing and duration, as well as the geometry of the valve-train, controls the amount of air and fuel entering the combustion chamber at any given point in time. Valve-trains are built in several configurations, each of which varies slightly in layout but still performs the task of opening and closing the valves at the time necessary for proper operation of the engine.
4.PART MODELS :
CAM:
A cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion. It is often a part of a rotating wheel or shaft that strikes a lever at one or more points on its circular path.
To sketch this cam, the front plane is selected and the sketch of the cam is drawn with the given dimensions and constraints in order to make the sketch fully defined, and the sketch is extruded by using midplane extrude option. Now to create the cam with respect to the cam-lift given in the challenge the dimensions of either the larger circle or the smaller one are changed and also at times the distance between them is edited to achieve the needed cam-lift parameter.
To create it, Extrude and several other 2D sketch tool(line,circle,trim,etc) commands are used.
PUSHROAD :
This is the part to which the lift is provided, which is transmitted to the rocker arm.
The front plane is selected for sketching the push rod, the sketch is then revolved by revolve boss base option where one of the lines is selected as the revolving axis of the sketch.
To create it, Revolve and several other 2D sketch tool(line,arc) commands are used.
ROCKER ARM :
This is part which is connected to push rod in one end and valve on the other end.
For sketching the rocker arm there are few types of which we choose the arc's to complete the sketch of the rocker arm. Where there are few or more constraints given to each and every point, arc, and also, the line to make the sketch more appropriate looking like a rocker arm and the dimensions and other constraints are given to the sketch to make it a fully defined one after which few fillets are provided at the corner points, then the sketch is extruded by midplane extrude option.
VALVE :
Valve is a device to close and open a passage. ln motor vehicle engines, two engine valves are used for each cylinder-an inlet (or intake) valve and an exhaust valve. Fuel is allowed to the cylinder by the inlet valve. When closed, the valve seals the combustion space tightly.
The valve is an important component of this assembly, the front face is selected to create the sketch of this valve where the dimensions and constraints are given accordingly and there are few values to take into account which is to be given during dimensioning so that the sketch looks as expected, then the sketch is selected and revolved by selecting the line from the same sketch as the revolving axis.
VALVE MOUNT :
Valve Mount use to support the valve to move in correct direction and spring is attached to the valve mount,
This valve mount is the part where the valve body is mounted, to sketch it the front plane is chosen where the required sketch is created by adding few lines provided with its dimensions from the origin and other parts, then in order to revolve this sketch a construction line from the origin is created and during revolve boss base option, the construction line is selected as the axis of revolution.
ASSEMBLY :
Assembly is made using the assembly mate option by properly aligning them as shown. Physical dynamics is used here for making contact between valve, rocker arm, push rod and cam which locks them in position and motion analysis is performed.
To assemble the components each parts are brought one by one into the assembly window and constrained properly using the proper mate and coincident constraint options to achieve the desired motion.
Motion Study Analysis
In the Motion study the following steps are performed.
- In this input motor is fixed to cam and it rotes at the constant speed of 1 500rpm in two cases.
- Linear spring is added between surface of valve and valve mount with spring constant of 10 N/mm and free length of 45mm.
- We are using motion study properties, 7200 frames per second and using contact Fixing the contact type as solid bodies for IC Engine valve Train and assigning material as Cast Carbon Steel, and calculate the motion analysis.
Case 1: Motion Analysis for cam lift of 3.5mm:
To calculate the distance between the two centres(L)
Given: R1 = 12.5; R2 = 5; Cam lift = 3.5mm
Cam lift = (L-R1)+R2
L = (12.5+3.5) - 5
L = 11mm
With the above information, Cam is modelled for the case 1 analysis
Contact Force plots:
Cam and Push rod(Magnitude)
From the above graph, it is inferred that the linear lines are the points where the push rod is in contact with the lower circular profile of the cam, and the smaller linear lines are same as for upper circular part of the cam, and there are few ups and downs in the graph ie the ups are the point of contact where the push rod is getting higher in displacement and downs are the contact period where the pushrod is sliding down the cam, but there's a high peak during the lower part that is because of the spring we have provided which gives the additional reaction force that causes this high peaks.
Push-rod and Rocker Arm(Magnitude)
Observation:From the above graph, it is inferred that the linear lines are the points where the contact of the pushrod is with the lower circular profile of the cam, and the smaller linear lines are same as for upper circular part of the cam, and there are few ups and downs in the graph ie the ups are the point of contact where the push rod is getting higher in displacement with the rocker arm and downs are the contact period where the pushrod is sliding down the cam or the lowering of rocker arm with a pushrod, but there's a high peak during the lower part that is because of the spring we have provided which gives the additional reaction force that causes this high peaks.
Rocker Arm and Valve(Magnitude):
Observation: The above plot is the contact force between the rocker arm and the valve where similar to other contact forces we have the linear lines which clearly says that their period of contact is with the circular profile with a cam which creates a smooth force transfer on these parts, and there are also similar peaks and drops which are again the displacement of the valve and rocker arm but during the drop, there's a high peak point caused due to the reaction force provided by the linear spring added by us.
Rocker Arm and Valve (X-Direction)
Observation:The above plot is made in order to create a comparison between the normal magnitude contact force between the rocker arm and valve and go the x-directional contact force between the rocker arm and the valve. So from the above plot, it is clear that there are linear lines, similar ups, and downs shown by the magnitude plot but the difference here is the appearance of the plot this plot is moving from positive value to negative value which is because of the measure of force in the one-directional component, where here is X direction.
Case 2: Motion Analysis for cam lift of 6mm:
To calculate the distance between the two centres(L)
Given: R1 = 12.5; R2 = 5; Cam lift = 3.5mm
Cam lift = (L-R1)+R2
L = (12.5+6) - 5
L = 13.5mm
With the above information, Cam is modelled for the case 2 analysis.
Contact Force plots:
Cam and Push Rod(Magnitude):
Observation: From the above graph, it is inferred that the linear lines are the points where the push rod is in contact with the lower circular profile of the cam, and the smaller linear lines are same as for upper circular part of the cam, and there are few ups and downs in the graph ie the ups are the point of contact where the push rod is getting higher in displacement and downs are the contact period where the pushrod is sliding down the cam, but there's a high peak during the lower part that is because of the spring we have provided which gives the additional reaction force that causes this high peaks.
Pushrod and Rocker Arm (Magnitude):
Observation:From the above graph, it is inferred that the linear lines are the points where the contact of the pushrod is with the lower circular profile of the cam, and the smaller linear lines are same as for upper circular part of the cam, and there are few ups and downs in the graph ie the ups are the point of contact where the push rod is getting higher in displacement with the rocker arm and downs are the contact period where the pushrod is sliding down the cam or the lowering of rocker arm with a pushrod, but there's a high peak during the lower part that is because of the spring we have provided which gives the additional reaction force that causes this high peaks.
Rocker Arm and Valve (Magnitude):
Observation :The above plot is the contact force between the rocker arm and the valve where similar to other contact forces we have the linear lines which clearly says that their period of contact is with the circular profile with a cam which creates a smooth force transfer on these parts, and there are also similar peaks and drops which are again the displacement of the valve and rocker arm but during the drop, there's a high peak point caused due to the reaction force provided by the linear spring added by us.
Rocker Arm and Valve (X-Direction):
Observation :The above plot is made in order to create a comparison between the normal magnitude contact force between the rocker arm and valve and go the x-directional contact force between the rocker arm and the valve.
So from the above plot, it is clear that there are linear lines, similar ups, and downs shown by the magnitude plot but the difference here is the appearance of the plot this plot is moving from positive value to negative value which is because of the measure of force in the one-directional component, where here is X direction.
ANIMATION OF VALVE TRAIN ASSEMBLY :
CASE 1 : When cam lift is 3.5 mm
https://drive.google.com/file/d/1yrPeOuhzLFe09z-XWawFxjeg-qAK_-mZ/view?usp=sharing
CASE 2 : When cam lift is 6 mm
https://drive.google.com/file/d/1XSM7eX5AYymYoFnKQvxKi3OZb7idGaUK/view?usp=sharing
7. CONCLUSION:
From the above study, the following points are observed-
i) On increasing the cam lift, the valve lift also gets increased.
ii) The valve lift is directly dependent on the cam & rocker arm profile.
iii) The contact forces between the parts also increases on increasing the cam lift.
iv) The contact force between the rocker arm & valve varies in reference to x-direction & magnitude. Since, the magnitude is the resultant of all the forces acting at a particular point, the plot in reference with magnitude is representing the overall forces acting in between the rocker arm & valve. While the plot in reference with x direction represents forces acting only in the x-direction. So, it is very less in comparison with magnitude. Moreover, the force acting in x direction is only the frictional force.