Motion Analysis of IC Engine Valve Train using Multi-Body Dynamics in SolidWorks
OBJECTIVE:
To model & assemble IC Engine Valve Train and perform motion analysis for two cases (i.e. for different cam lift values).
ABSTRACT:
The purpose of this project was to create the model and perform motion analysis on IC Engine Valve Train. All the components were made according to the given dimensions. The motion analysis was performed for total two cases. The different cases were achieved by providing different length value between the centres of circle of the cam profile, calculated from the cam lift formula. In the first case, the cam lift required was 3.5 mm; so, 11 mm of centre distance was provided. In the second case, the cam lift required was 6 mm; so, 13.5 mm of centre distance was provided. Later, motion analysis was performed for both the cases and graphs were plotted such as Linear Displacement Plot of valve & contact force plot between various bodies was plotted.
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CONTENTS:
1. Introduction
- Cam
- Pushrod
- Rocker Arm
- Valve
- Motion Analysis
- Linear Displacement
- Angular Velocity
- Contact Force
2. Geometry Modelling
- Cam
- Pushrod
- Rocker Arm
- Valve
- Valve Mount
- Assembly
3. Simulation Setup
- Procedure
- Rotary Motor
- Contact
- Spring
- Motion Study Properties
4. Motion Analysis
- Case 1: Cam Lift is 3.5 mm
- Motion Simulation
- Linear Displacement Plot of Valve Lift
- Contact Force Plot between Cam and Push Rod
- Contact Force Plot between Pushrod and Rocker Arm
- Contact Force Plot between Rocker Arm and Valve w.r.t. x-direction
- Contact Force Plot between Rocker Arm and Valve w.r.t. magnitude
- Case 2: Cam Lift is 6 mm
- Motion Simulation
- Linear Displacement Plot of Valve Lift
- Contact Force Plot between Cam and Push Rod
- Contact Force Plot between Pushrod and Rocker Arm
- Contact Force Plot between Rocker Arm and Valve w.r.t. x-direction
- Contact Force Plot between Rocker Arm and Valve w.r.t. magnitude
5. Overall Result
6. Evaluation
7. Conclusion
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1. INTRODUCTION:
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 (e.g. an eccentric wheel) or shaft (e.g. a cylinder with an irregular shape) that strikes a lever at one or more points on its circular path.
Cam Lift Formula
Pushrod
A metal rod actuated by a cam to open or close a valve of an internal combustion engine having the camshaft in the crankcase.
Rocker Arm
A rocker arm (in the context of an internal combustion engine of automotive, marine, motorcycle and reciprocating aviation types) is an oscillating lever that conveys radial movement from the cam lobe into linear movement at the poppet valve to open it. One end is raised and lowered by a rotating lobe of the camshaft (either directly or via a tappet (lifter) and pushrod) while the other end acts on the valve stem. When the camshaft lobe raises the outside of the arm, the inside presses down on the valve stem, opening the valve. When the outside of the arm is permitted to return due to the camshafts rotation, the inside rises, allowing the valve spring to close the valve.
Valve
A valve is a device that regulates, directs or controls the flow of a fluid (or gas) by opening, closing, or partially obstructing various passageways.
Valves form an integral component of an internal combustion engine and every cylinder in an engine atleast has two of them, i.e. an intake (intake of fuel-air mixture) and an exhaust valve (exhaust gases). A multi-valve engine can have three, four and sometimes five valves. Multi-valve engines generally promise increased efficiencies for fuel combustion. These days with BSIV emission norms in place most engine designs have a four-valve system in place, two for intake of fuel and air and two for exhaust gases.
The opening and closing of valves are precisely timed to allow the engine to run efficiently in all conditions.
Valve Mount
Valve Mount is used to guide the valve movement and provides a base to the pre-tensioned spring.
Motion Analysis
SOLIDWORKS Motion studies are graphical simulations of motion for assembly models. Motion simulation assumes all parts to be rigid during the simulation, meaning that during contacts, no deformations will take place.
It can be used for accurately simulating and analysing the effects of motion elements (including forces, springs, dampers, and friction) on an assembly. Motion Analysis uses computationally strong kinematic solvers, and accounts for material properties as well as mass and inertia in the computations. You can also use Motion Analysis to plot simulation results for further analysis.
Angular Velocity
In physics, angular velocity refers to how fast an object rotates or revolves relative to another point, i.e. how fast the angular position or orientation of an object changes with time. In general, angular velocity is measured in angle per unit time, e.g. radians per second. The SI unit of angular velocity is expressed as radians/sec with the radian having a dimensionless value of unity, thus the SI units of angular velocity are listed as 1/sec. Angular velocity is usually represented by the symbol omega (ω).
Linear Displacement
Linear displacement is movement in one direction along a single axis. A linear displacement typically has units of millimetres (mm) or inches (in.) and a negative or positive direction associated with it.
Contact Force
Contact force is a force that is applied by objects in contact with each other. Contact force acts on a point of direct contact between the two objects. This force can either be continuous as a continuous force or can be momentary in the form of an impulse. Contact force is governed by Newton’s Laws. Contact force is responsible for most of the interactions we experience in the daily life. Pushing a car up the hill, writing your name with a pen or picking up a textbook from the table are all examples of contact force and they are also examples of continuous force. On the other hand, hammering a nail, kicking a ball etc are examples of impulse or momentary force.
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2. GEOMETRY MODELLING:
All the parts are assigned Cast Carbon Steel as a material.
Cam
Fig: a) Cam of Case 1 Fig: b) Cam of Case 2
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Pushrod
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Rocker Arm
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Valve
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Valve Mount
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Assembly
Fig: a) Case 1 Assembly Fig: b) Case 2 Assembly
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3. SIMULATION SETUP
Procedure
- Select the SolidWorks Motion from SolidWorks Add-Ins in the ribbon.
- Select motion analysis from the drop-down menu available in the motion analysis toolbar.
- All the tools mentioned below can be availed from the motion analysis toolbar.
- Provide the motor condition i.e. rotary with 1200 rpm.
- Provide all the solid body contacts separately and also assign material to the solid bodies.
- Provide a spring in between the valve head & valve mount. Provide free length of 45 mm to pre-tension it. Provide the spring stiffness of 10 N/mm.
- Select Motion Study Properties and increase the frames to 7,200 to capture the displacement for single degree rotation and checkmark the precise contact option. Number of frames required was calculated as (1200*360)/60 = 7200.
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Motor
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Contact
Fig: a) Total Contacts
Fig: b) Contact 1 Fig: c) Contact 2 Fig: d) Contact 3
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Spring
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Motion Study Properties
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4. MOTION ANALYSIS
Angular Velocity Plot of Cam
The cam is rotating at constant rpm of 1200 and with a constant angular velocity of 7200 deg/sec.
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- Case 1: Cam Lift is 3.5 mm
Motion Simulation
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Result:
Linear Displacement Plot of Valve Lift
The maximum valve lift obtained is 8 mm.
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Contact Force Plot between Cam & Pushrod
The maximum contact force between cam & pushrod is 5500 N.
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Contact Force Plot between Pushrod & Rocker Arm
The maximum contact force between pushrod & rocker arm is 5500 N.
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Contact Force Plot between Rocker Arm & Valve w.r.t. x-direction
The frictional froce acting in between the contact is 80 N.
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Contact Force Plot between Rocker Arm & Valve w.r.t. magnitude
The maximum contact force between rocker arm & valve is 1200 N.
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- Case 2: Cam Lift is 6 mm
Motion Simulation
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Result:
Linear Displacement Plot of Valve Lift
The maximum valve lift obtained is 11 mm.
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Contact Force Plot between Cam & Pushrod
The maximum contact force between cam & pushrod is 17000 N.
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Contact Force Plot between Pushrod & Rocker Arm
The maximum contact force between pushrod & rocker arm is 17000 N.
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Contact Force Plot between Rocker Arm & Valve w.r.t. x-direction
The maximum frictional force acting in between the contact is 100 N.
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Contact Force Plot between Rocker Arm & Valve w.r.t. magnitude
The maximum contact force between rocker arm & valve is 3400 N.
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5. OVERALL RESULT
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6. EVALUATION:
The IC Engine Valve Train was modelled and its motion was analysed for different cases. Further, the linear displacement plot of valve lift was plotted for both the cases to observe the valve lift at different cam lift. The Contact Force Plot between cam & pushrod, pushrod & rocker arm and rocker arm & valve were plotted to observe the forces generated at the mating region. The motion analysis is conducted to determine the forces, displacement, velocities generated inside the assembly and provides a good picture of the complete assembly. This also helps to validate a design. This analysis helps to get much more efficient & reliable design. Additionally, this project led to a great learning including the know-how & capabilities of motion analysis.
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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.
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