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Automobile Engineering (4 Stroke Cycle)

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Published in: Mechanical
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Notes on 4 Stroke Cycle for Automobile Engineering.

Trinity A / Chandigarh

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Teaches: Indian National Mathematical Olympiad (INMO), Mental Maths, Olympiad Exam Preparation, Regional Mathematical Olympiad (RMO), Advanced Excel, Basic Computer, MS Office, School Level Computer, Mathematics, Statistics, Science, Social Studies, B.Tech Tuition, Drawing, Mechanical, AutoCAD Training, French, German, Study in Germany

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  1. Automobile Engine 4 Stroke Cycle
  2. 1. 2. 3. 4. 5. 6. 7. Automobile: Main systems Engine — convert energy of fuel to energy of motion Powertrain — transfer power from engine to driven wheels Brakes — slow and stop vehicle Steering — control direction of travel Suspension Absorb bumps Maintain alignment Keep wheels in contact with road Electrical — generate and distribute electricity Body — protect occupants (
  3. Automobile: Main Theme Visually apparent how form follows function. Visually Accessible. How it works is there to see if look in the right place. Components performing specific function in overall system also very apparent. Systems and subsystems of components contributing to overall operation also readily apparent in automobile.
  4. Engine Chemical energy of fuel and air Fuel Air Engine Convert chemical to Kinetic energy (energy of motion) Exhaust Heat Kinetic Energy Engine RPM System Boundary — automobile engine Start at location where air and fuel are burned and work out from there. Put the car together starting with the combustion
  5. Engine: Underlying Principle Internal combustion engine — Energy conversion device — Heat engine — Heat -> Work Converts energy of fuel into energy of motion. 4 —stroke cycle Otto cycle
  6. Engine Construction Basic "generic" Internal Combustion Automobile Engine. Start where air/fuel are burned and work out from there. Strip off components Engine put together in two halves — Upper half = head — Lower half = block — Seal between upper and lower = head gasket Engine Engine head Engine block Engine head gasket
  7. Engine Construction Look at single cylinder Most automobile engines have more than one cylinder Same process in each one 3 IN LINE 4 IN LINE V-6 5 IN LINE Fig. 12-1 Various ways of arranging engine cylinders. (ATW) 6 IN LINE FLAT 6
  8. parts 1. 2. 3. 4. 5. 6. 7. 8. 9. Engine: Main Cylinder — contain burning air/fuel — hole in metal block Piston — convert pressure of burning air/fuel to force — metal plug Crank — convert linear to rotary motion — crank-shaped metal Connecting Rod — Transfer force from piston to crank — metal bar Spark plug — Ignite air/fuel mixture — Insulated gap Intake port — allow air/fuel into cylinder — hole in engine head Intake valve — control flow through intake port — upside down metal T Exhaust port — allow exhaust to exit cylinder — hole in engine head Exhaust valve — control flow through exhaust port — upside down metal T
  9. Valves EXHAUST VALVE INTAKE VALVE Fig. 11-11 Intake and exhaust valves for one cylinder of an engine. As in many engines, the intake valve is larger. VALVE GUIDE CYLINDER HEAD VALVE STEM VALVE-SEAT INSERT VALVE Fig. 11-12 Valve and valve seat in a cylinder head. Some engines have valve-seat inserts for the exhaust valves.
  10. Crankshaft son. CAR ENGINE CmNKSHAFT Powered by the explosion of the fuel, a piston moves inside each cylinder of a car engine. A connecting rod links the piston to a crank 011 the crankshaft. The rod turns the crank, which then continues to 1*0tate and drives the piston back up the cylinder. In this way the crankshaft converts the movement the pistons •into-rotary powerF
  11. 4-Stroke Stg COUNTERWEIGHT (A) INTAKE (B) COMPRESSION Cycle (C) POWER (D) EXHAUST Fig. 11-10 The four piston strokes. (A) Intake stroke. The intake valve (at left) has opened. The piston is moving downward, allowing the air-fuel mixture to enter the cylinder. (B) Compression stroke. The intake valve has closed. The piston is moving upward, compressing the mixture. (C) Power stroke. The ignition system has delivered a spark to the spark plug that ignites the com- pressed mixture. As the mixture burns, it creates a high pressure that pushes the piston down. (D) Exhaust stroke. The exhaust valve has opened. The piston moves upward as the burned gases escape from the cylinder.
  12. ? ? ? ? ? ) ? ? ? ? ? ? ? ? ? ? ? 0 3 ? ? 0 0 ? ? ? ? 3 ? MO 1 ? 1 ? 1 ? ? ? ? ? ? ? ? ? 0A0 ? MO ? ? ? n ? ? ? ? ? ? ? u ? p ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ( 0 ? ? S - ? ~ ) ? Od ? ? - = ? ? ? ? ? 1 ? ? ? ? ? ? ? ? ? ? 0 ? ? ? 0 ? ? ? ? ? ? 1 ? ? ? ? ~ ? ? ? ? ? = ? ? 3 ? ? ? ? ? ? ? ? ? ? ? ? ? = : ? ? ? ? ? ? ? ? 3N0 IS NO ? 1 ? ? 10 ? ? 1 ? ?
  13. 4-Stroke Cycle Details Cams Open and close intake and exhaust valves. Camshaft: several cams connected together. OHC: Over head Cam, cam is above valves, allows higher engine speeds. DOHC: Double Overhead Cam, separate control of intake and exhaust valve to optimize performance. Timinq Belt (also timinq chain, timinq gears) Connects crankshaft to camshaft Coordinates opening and closing of valves with up and down motion of pistons. Insures that valves are opened and closed at proper time. Flywheel Heavy metal disk at the end of the crankshaft. Helps to smooth out surges from the power strokes to keep engine rotating at a uniform rate. Rings Help seal pistons to cylinder walls Firing Order Each cylinder in different part of the cycle Insures always one cylinder pushing the others Smooths out vibrations Distributes heat input to engine block Multi valve engines Small valves move quicker
  14. Illustrations Form following function More than one design possible — Valve trains - Timing
  15. Firing Order Fig. 12-1 Various ways of arranging engine cylinders. (AIW) FLAT 6
  16. Rings CYLINDER WALL PISTON CLEARANCE PISTON LEAKAGE (BLOWBY) Fig. 11-6 The clearance between the cylinder wall and the piston must be filled. Otherwise, compressed air-fuel mixture or high- pressure combustion gas will "blow by" the piston.
  17. PISTON PIN CONNECTING ROD CRANK CRANKSHAFT Rings PISTON PISTON R NGS ROD BOLT ROD CAP OIL-RING ASSEMBLY GROOVES FOR RINGS INDENT— ASSEMBLE TOWARD FRONT OF ENGINE PISTON PIN UPPER COMPR ESSI ON RING LOWER COMPRESSION RING I S TON PISTON PISTON RINGS CONNECTING Fig. 11-7 Piston-and-connecting-rod assembly attached to a con- necting-rod journal on the crankshaft. The piston is partly cut away to show how the piston pin attaches the piston to the con- necting rod. Fig. 11-5 Piston and piston rings. Top, rings separated and above e piston. Bottom, piston rings installed in grooves in the piston. Piston is attached to the connecting rod by the piston pin, Only upper part of the connecting rod is shown. m pr th th lu ch ne c
  18. CAM HEEL TOE LOBE CAMSHAFT Fig. 11-16 Cam on a camshaft. Note locations of the toe and heel. ROD CAM CAM ROD CAM Cams VAP,Y. R ENGINE CAMSHAFT OéEN The egg-cracker uses a cam, a device which in its most basic form is simply a fixed wheel with one or more projections. A rod is pressed against the wheel, and as the wheel rotates, the rod moves out and in as the projection passes. chcylinder of a car engine contains valves that admit the fuel or expel the exhaust gases. Each valve -is operated by a cam attached to a rotating camshaft. The opetus the valve by [orcing it down against a spring. fiespring then closes the valve until the cam comes around again. The cam may operate the valve directly, here, or through levers, as shown on the next page.
  19. CANSHAFT SHIM BUCKET T APPET VALVE CAM LOBE RETAINER VALVE SPRING EXHAUST CAMSHAFT CHAIN CHAIN TENSIONER CHAIN SLIPPER INTAKE CAMSHAFT ADJUSTING SHIMS BUCKET TAPPETS INTAKE VALVES Fig. 14-4 Arrangement of the camshafts and valve train in a DOHC fouræylinder engine. The intake camshaft is chain- driven from the crankshaft. The exhaust camshaft is driven through a gear on the intake camshaft. (Toyota Motor Sales. U.SA.. Inc.) EXHAUST VALVES CHAIN DAMPER VALVE CLOSED VALVE OPEN Fig. 11.17 Operation of a cam on an overhead-camshaft engine as the camshaft rotates. Top. the cam lobe is away from the bucket tappet and the valve is closed. Bottom, the cam lobe is pushing the tappet and valve down, opening the valve.
  20. Valve CAMSHAFT SHIM BUCKET TAPPET VALVE (Al OVERHEAD CAMSHAFT WITH BUCKET TAPPET Fig. 12-17 Types of valve trains. Trains (Cam ROCKER CAM LOBE RETAINER VALVE SPRING Variation) ROCKER ARM STUD VALVE ROCKER VALVE LIFTER CAM CYLINDER VALVE SPRING VALVE O PUSHROD VALVE LIFTER (B) OVERHEAD CAMSHAFT wiTH ROCKER ARM CAMSHAFT IN BLOCK WITH PUSHROD
  21. OHC CAR ENGINE CAMSHAFT ch cylinder of car engine contains valves that admit the fuel or expel the exhaust gases] Each valve is c eperyted by a cam attached toa rotating camshaft. The amopens the valve by forcing it down against a spring. Thespring then closes the valve until the cam comes ground again. The cam may operate the valve directly; here, or through -levers, as shown on the next page: and OHV
  22. OH V and OHC ROCKER ARM BALL PIVOT Valve Trains CAMSHAFT SPROCKET CAMSHAFT BUCKET TAPPET rte, CAM LOBE CAMSHAFT CAM VALVE SPRING VALVE PUSHROD VALVE RELIEFS HYDRAULIC VALVE LIFTER The camshaft BELT TENSIONER 4.1 TOOTHED TIMING BELT CRANKSHAFT SPROCKET VALVE IGNITION DISTRI BUTOR SPARK PLUG PISTON OIL PUMP CYLINDER JACKSHAFT Fig. 14-2 Valve train in an overhead-valve engine. is driven by gears from the crankshaft. Fig. 11-1 An inline four-cylinder spark-ignition engine with overhead camshaft. (Chrysler Corporation)
  23. Gear CAMSHAFT GEAR (o O CRANKSHAFT Timing Chain CAMSHAFT SPROCKET CAMSHAFT SPROCKET ctk) CHAIN GUIDE O o TIMING CHAIN O Belt CAMSHAFT SPROCKET O@O oo TIMING BELT BELT TENSIONER o GEAR (A) TIMING GEARS (TO DRIVE CAMSHAFT IN CYLINDER BLOCK) (B) CRANKSHAFT SPROCKET TIMING CHAIN (TO DRIVE CAMSHAFT IN CYLINDER BLOCK) CRANKSHAFT SPROCKET TIMING CHAIN PLATED LINK o o CRANKSHAFT SPROCKET o o o o o TIMING BELT (TO DRIVE CAMSHAFT ON CYLINDER HEAD) (C) TIMING CHAIN (TO DRIVE CAMSHAFT ON CYLINDER HEAD) Fig. 12-16 Four methods of driving the camshaft. (ATWO Connects crankshaft and camshaft Coordinates valves and pistons
  24. BUCKET TAPPET CAMSHAFT SPROCKET BELT TENSIONER WATER PUMP 4 CRANKSHAFT SPROCKET 9 Timing 4 TOOTHED TIMING BELT Fig. 14-9 Front end of an OHC engine using a toothed belt and sprockets to drive the camshaft. A belt tensioner is used to prevent the belt from jumping time. (Ford Motor Company) Belt CAMSHAFT SPROCKET CAMSHAFT BELT TENSIONER 4.1 TOOTHED TIMING BELT CRANKSHAFT SPROCKET VALVE IGNITION DISTRI BUTOR .9 SPARK PLUG PISTON OIL PUMP CYLINDER JACKSHAFT Fig. 11-1 An inline four-cylinder spark-ignition engine with overhead camshaft. (Chrysler Corporation)
  25. Timing Chain EXHAUST CAMSHAFT INTAKE CAMSHAFT ADJUSTING SHIMS BUCKET TAPPETS INTAKE VALVES Fig. 14-4 Arrangement of the camshafts and valve train in a DOHC four-cylinder engine, The intake camshaft is chain- driven from the crankshaft. The exhaust camshaft is driven through a gear on the intake camshaft. (Toyota Motor Sales. U.SA, Inc.) CHAIN CHAIN TENSIONER CHAIN SLIPPER EXHAUST VALVES CHAIN DAMPER
  26. Gear rte, CAM LOBE CAMSHAFT Timing ROCKER ARM BALL PIVOT VALVE SPRING VALVE PUSHROD VALVE RELIEFS HYDRAULIC VALVE LIFTER CAM Fig. 14-2 Valve train in an overhead-valve engine. The camshaft is driven by gears from the crankshaft.
  27. Flywheel CAMS AND CRANKS IN THE CAR plivsecond timing is essential for smooth and powerful running in a car engine. It is achieved by the engines camshaft and crankshaft working in concert. As the pistons move up and down in the cylinders. they drive the crankshaft which turns the flywheel and. ultimately, thewhcels, But. through a chain linkage, the crankshaft also turns the camshaft As the camshaft rotates. the cams operate the cylinder valves tn an overhead camshaft engine, the cams lie over the valves and move the valves directly, Here, the camshaft is to one side, and it operates the valves through push-rods and rockers- The cams and cranks involved open and close the valves in step with the movements of the pistons to follow the four-stroke cycle (see p. 156-7). The camshaft and crankshaft may also drive other parts of the engine. A gear wheel on the camshalt, for example. drives the oil pump (sce p. 124) and the distributor (see p,289).
  28. Multi TAPPET VALVE SPRING SPARK PLUG Valve Engines Normal Innovation VALVE CONNECTING ROD CAMSHAFT PISTON y; Fig. 14-5 Valve and canshaft arrangement for a four-cylinder DOHC engine with bucket tappets and four valves per cylinder (two intake and two exhaust). (Nissan Motor Corporation)
  29. Rotary Engine COMPRESSION INTAKE EXHAUST IGNITION http://upload.wikimedia.org/wikipedia/commons/f/fc/Wankel_Cycle_anim_en.gi
  30. Combustion chamber Socfron stroke 60 50 40 30 20 -360 Campression stroke Pressure 5 to 30 ms VuWkirg Temperature Electiffi Exhaust stroke 2000 1000 Crank Angle [dega

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