The Best Guide On| Camshaft

ntroduction:- In this post of The Best Guide On Camshafts -For Diesel Engines we will discuss what is camshaft in the engine, How does a camshaft works, the difference between camshaft and crankshaft, the function of camshaft, camshaft material, and the camshaft manufacturing process.

What is camshaft in engine?

CAM: A bump on a revolving part in the engine, created to cause sliding contact with the adjacent part to convey reciprocating motion to it. Rotary motion is converted into reciprocating motion by cam.

The Camshaft is a revolving part in an Internal Combustion Engine, which converts rotary motion in to the reciprocating motion. The working of the camshaft is opposite to the working Crankshaft. Crankshaft converts reciprocating motion developed by combustion of fuel in to rotary motion. The function of Crankshaft and camshaft is different. Crankshaft transmits the drive to the machine for generating electricity, propeller to run the Ship and for other various applications it has the different functions.

Primary function of the Camshaft is to operate inlet and exhaust Valves; fuel Injection Pumps and operation of Injectors. Secondary function of the camshaft is to transmit the drive to engine driven Lube oil pump, Cooling water pump and Air distributors. The function of the camshaft is similar in all the engines.

The camshaft speed is half of the crankshaft speed in four-stroke engines, and the speed of the camshaft in a two-stroke engine is similar to the crankshaft speed.

Complete Description of Camshaft

The above image is of a split type for individual cylinders, and each piece is joined to each other by screws. Each piece has a fuel injection cam, intake, and exhaust cam.

Joint screws inspection

Check the joint screws at every available opportunity. Then, carry out the screw for tightness.

Take out the loose stud and carry out the careful inspection. Replace the nut and studs in case of damaged or transformation.

Apply the Loctite 243 and tighten both the nuts and studs’ prescribed torque. Inspection of cams and bearings

Inspect each section’s operating surfaces, cams, and bearings at regular intervals by turning the flywheel. Carefully inspect around the bearings for any abnormal color or dropping of bearing material particles.

In case of suspicion, remove the thrust and inspect the bearing surfaces by sliding the camshaft on one side.

In case of any damage or abnormal condition, inform the engine manufacturer.

Camshafts and drives

The Design of the Engine decides the position of the camshaft in an engine. For example, the location of the camshaft could be in the engine block near to crankshaft. This arrangement is called a push rod or overhead valve system.

No. of camshaft will be the engine type. There will be one camshaft in inline engines, whereas, in “V” shapes engines, two camshafts mount for each bank. In both the designs, the job of the camshaft is the same driving the Valve mechanism, Engine mounted pumps, and distributor.

Material of camshaft is generally hardened alloy of iron or steel, cast, and precisely machined. Grounding of cam lobes is done for the proper shape and position to one other as per the Engine’s firing order. Machining accuracy is vital. The Engine’s fast wear and noisy operation will be caused if the cams are not appropriately shaped or excessively worn out.

The bearing journals are smoothly grounded. Gear for driving the distributor is machined on the camshaft. Induction hardening treatment is given to the cam lobes.

There is a cam for each valve and fuel pump operation. Gears are fitted on the camshaft for driving the pumps and distributor.

Cam lobes perform the following three jobs.

1. Opening of Valve in proper time.
2. Providing the proper lift
3. Keeping the valve open for sufficient time and letting it close the valve at the exact time.

Proper valve timing is vital. Therefore, valve timing will be different for the different engines as per the specified manufacturer’s specifications of the valve timing diagram.

Cam profile is a term used for the cam shape. The valve lift starts from the base circle shown as a valve is fully closed, and there is the clearance between the rocker arm and the valve stem. To open the valve fully open, the nose of cam B is rotated by the cam.

Valve is gradually closed by the closing of flank C. For the engines, without a valve adjuster, a ramp is machined in the cam profile. The ramp is provided for easy operation during the valve opening. The shape of the lobe determines the valve opening period.

Camshaft timing should be perfect for synchronized running with the crankshaft. The timing is carried out with the gears or chains.

Timing belt used in the Engine with the camshaft located at a distance.

This arrangement is a typical chain drive system. It uses a hydraulic pensioner. The chain drive system is fed by oil under pressure from the lubrication system. Noise and vibrations are reduced with the help of guides used by the chain.

Fibber glass or wire reinforced is used for the manufacturing of a toothed timing belt. Teeth of the belt match with the teeth on the crankshaft and camshaft pulley.

Timing belts usually require regular manual tensioning though the timing belts are quieter than the chains. Therefore, the life of timing belts is shorter. Due to this fact, frequent replacement is needed. In addition, any breakage of the belt during the engine operation may cause heavy damage.

Cam Lobe terminology (The Best Guide On Camshafts For Diesel Engines)

• Base Circle
• Angular Period
• Flank
• Lift
• Nose

Base Circle;-The Base circle is the part of the Cam aligned with the bearings and has zero lift.

Ramp;- Shortly adjoining to the base circle, the portion of the Cam with low momentum for preventing the extensive bump as the sluggishness is eliminated from the valve trains at the beginning of the lift action. Alike, a closing ramp is used for the gently seating of valve without any bounce off the seat.

Angular Period;- The time taken to travel the distance between the end of starting ramp and the start of the closing ramp is known as an angular period.

Flanks;- The flank is the part of the Cam responsible for the quickest movement of Valves with significant velocity and acceleration.

Lift; — Vertical distance between the base circle and the nose is known as cam lift.

Nose; — Nose is the part of the Cam with the greatest lift, opposite to the heel with the smallest radius.

Camshaft lobe separation angle and effect on the engine (The Best Guide On Camshaft For Diesel Engines)

The lobe separation angle is the radial distance between the centreline of the inlet and exhaust lobe. The camshaft lobe separation angle will determine peak torque within the engine power range with the effect on idle quality and engine vacuum.

Wide lobe separation lets torque form above a broader speed range and produces enhanced power in the higher speed range. Conversely, the narrow lobe separation produces the peak torque to develop initially in the speed range and cultivates excellent speedup.

Overlap

The period during valve timing in which both inlet and exhaust valves are open is termed as overlap. In this phenomenon, the inlet valve opens just before the end of exhaust stroke before releasing all the exhaust gases, providing more time for the intake air to enter and efficient completion of the scavenging process.

The valve lift and its effect on the Engine operation

Valve lift is the distance by which the valve is raised from its seating position to a fully open position. Consolidation of Rocker arm ration and lobe lift of camshaft will determine the valve lift. The valve lift and the valve speed is the main factor in deciding the intensity of engine torque.

Camshaft Intake and Exhaust centerline

Camshaft intake and exhaust lobe centreline is the theoretical maximum lift point of lobe in relationship to top dead center degree of crankshaft revolution. The centreline can be altered by advancing or retarding position. Advancing and retarding part of the cam will change the power output of an engine. The speed range will go down by advancing, and the speed range will increase by retarding the intake center line.

Camshaft materials (The Best Guide On Camshaft For Diesel Engines)

1. Iron (Harden able)

This grade of iron consists of CI (Cast iron) grade 17 with 1% chrome to create 5 to 7 % carbide.

On completion of the casting process, the material is subjected to induction hardening to give a Rockwell hardness of 52 to 56 on the scale C. This type of material is unsuitable for engines with overhead cams.

• Chilled Chrome Cast iron; — This type of materialcomprises grade 17 cast iron with 1% chrome. During the casting of the camshaft in the foundry, cam lobes are incorporated into the mould. While pouring the iron, pored hardens off rapidly (Process is known as chilling), precipitating the material of the cam lobe to form a pattern of carbide on the cam lobe. This material is exorbitantly resistant to scuffing. Cams manufactured with this process are suitable for engines with OHC (Overhead cam) performance cams.
• Steel camshafts;-
• Carbon Steel.’- carbon steel consists of EN8/EN 99. This material is used for the induction hardened camshaft in concurrence with roller cam followers for the thorough hardening qualities of the material.
• Steels alloyed;- This material is composed of EN351 and EN 34. This material is best while using against a follower manufactured by chilled process.
• Steel nitride;- This material is composed of EN 40B. Steel nitride is the best material for use in camshafts. After the process of nitride and finish, the quality is at par with the chilled iron — this material is used for the many current FI engines.

Camshaft Manufacturing Process (The Best Guide On Camshaft For Diesel Engines)

• Casting; — In this only chilled iron chilled cast iron is primarily used to manufacture camshaft. This process is prone to defects like shrinkage, porosity, cracks, and insufficient pouring. Nonetheless, cast camshafts with induction hardened cam lobes for higher loads in roller contact can be used.
• Forging;- For many high-loaded diesel engines, a steel bar camshaft manufactured with the forging process is used. These camshafts are manufactured on a computer-aided forging system with unified heat treatment or machined from a steel bar.
• Machining;- The machining process gives final dimensions to the cams.

The manufacturing process in detail

1. Drilling and turning;- In this process, a raw forging is loaded in the machine, and turning and drilling is performed here.
2. Journal Grinding;- in this process, the grinding of journals with the Carborundum wheels is performed in the machine.
3. Face grinding;- Face grinding is carried out with the aid of an angular grinding wheel. At this stage, Inspection is also carried out using the measuring gauges.
4. Dowel hole drilling;- With reference to dowel holes, grinding of the cams is performed here in this operation.
5. Lapping of the finished surfaces;- With the aid of lapping/emery papers, super-finish in microns is achieved on cams and oil seal area.
6. Final cleaning with water and air;- Components are cleaned for dust, oil, and chips, etc., with the aid of a washing machine.
7. Final Inspection; — Run out, and the measuring machine checks diameters of journals. The machine ultimately declares the component as OK, NG, or Bad.

Dismantling of Camshaft

To replace the camshaft section or bearing shell of the camshaft:

1. Dismantle the area of the camshaft.
2. Dismantle the cam section one by one through each cam side door.
3. Loosen all the fuel injection pumps.
4. Loosen all the rocker arms
5. Dismantle all the pushrods and rocker arms.
6. Remove the join nuts of the cams shaft
7. Mark the assembly position location.
8. Dismantle the thrust bearing of the camshaft.
9. Dismantle the camshaft timing gear for the free axial movement of the camshaft during dismantling.
10. Remove out the camshaft through the cam side door.

Remounting of Camshaft (The Best Guide On Camshaft For Diesel Engines)

Remounting procedure is the reverse of the dismantling procedure.

Check the following points.

• Carry out the mounting of the camshaft as per cylinder no. it is marked on the camshaft.
• Check the position marking on camshaft flanges and match the marking with the mating camshaft. Remount as per the TDC keeping on both camshafts. Fig
• Apply the coating of Loctite 243 on the threads.
• Tighten all the nuts at the prescribed torque.

What is the camshaft position sensor, how it works?

In the latest design of Internal Combustion engines, the Electronic control unit (ECU) regulates the fuel injectors opening, creation of spark, Phase timing concerning the piston position in cylinders. ECU recognizes the position of each piston as per the signal of camshaft position.

The crankshaft and Camshaft position will be the base of determining the position of the piston in the cylinders. This information helps in performing the engine piston position recognition.

The Sensor transmits the signal to ECU to locate the exact position of the Camshaft.

The Sensor transmits the data to start the fuel injection sequence and precise control of the cylinders.

Where is the camshaft sensor located?

Camshaft position sensor mounts on the cylinder head cover. In fluctuating timing engines, the positioning of the gearwheel is on the camshaft position change system.

Conclusion(The Best Guide On Camshaft For Diesel Engines)

I hope that the post on The Best Guide On Camshafts For Diesel Engines will prove a useful guide to students and marine engineers.