ENGINE COOLING SYSTEM: COMPONENTS, TYPES AND WORKING PRINCIPLES
A vehicleβs engine-cooling system serves not just to keep the engine cool, but to also keep its temperature warm enough to ensure efficient, clean operation. System components include a radiator to dissipate heat, a fan or fans to ensure adequate airflow for radiator cooling, a thermostat valve that opens when the desired operating temperature is reached and a water pump (or coolant pump) to circulate coolant through the engine, hoses and other components. Most vehicles now employ an expansion tank that allows the coolant to expand, and exit, the cooling circuit when hot, and to return when the car is turned off and the engine cools.
The cooling system also incorporates elements of the cabinβs ventilation system, because engine heat is used to warm the carβs interior.
While running, an engine continuously produces heat and converts it into power.
This heat is derived by burning fuel in the engine.
But as we all know, there is no engine in the world which is 100% efficient.
There is always some amount of heat energy which gets wasted. If we do not transmit this heat energy into the atmosphere, this heat will overheat the engine.
This overheating will result in engine seizing. In engine seizing, due to excess heat piston gets melted inside the cylinder.
It avoids this trouble of overheating a car is provided with the engine cooling system.
An engine cooling system is a system integrated with the engines. It carries away excess heat from the engine with the help of a flowing fluid.
This fluid can be air or water.
A vehicleβs engine-cooling system serves not just to keep the engine cool, but to also keep its temperature warm enough to ensure efficient, clean operation. System components include a radiator to dissipate heat, a fan or fans to ensure adequate airflow for radiator cooling, a thermostat valve that opens when the desired operating temperature is reached and a water pump (or coolant pump) to circulate coolant through the engine, hoses and other components. Most vehicles now employ an expansion tank that allows the coolant to expand, and exit, the cooling circuit when hot, and to return when the car is turned off and the engine cools.
The cooling system also incorporates elements of the cabinβs ventilation system, because engine heat is used to warm the carβs interior.
While running, an engine continuously produces heat and converts it into power.
This heat is derived by burning fuel in the engine.
But as we all know, there is no engine in the world which is 100% efficient.
There is always some amount of heat energy which gets wasted. If we do not transmit this heat energy into the atmosphere, this heat will overheat the engine.
This overheating will result in engine seizing. In engine seizing, due to excess heat piston gets melted inside the cylinder.
It avoids this trouble of overheating a car is provided with the engine cooling system.
An engine cooling system is a system integrated with the engines. It carries away excess heat from the engine with the help of a flowing fluid.
This fluid can be air or water.
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TYPES OF COOLING
Or we can say there are two types of cooling systems
1. Liquid or indirect cooling system
2. Air or direct cooling system
LIQUID OR INDIRECT COOLING SYSTEM
In a liquid cooling system, an engine is surrounded with water jackets. With the help of a pump, this water gets circulated in this water jacket.
Water flowing in these jackets takes out heat from the engine. This hot water then flows through a radiator, where it gets cooled from the cold heat blown through a fan.
In this system, the water takes heat from the engine and that water gets cooled by the air and then again gets circulated to the engine.
This is an indirect cooling process, where an actual cooling thing that is air is not directly cooling the system. The air is cooling the water and water is cooling the engine.
Liquid or indirect cooling system is mainly used in big engines, like that of cars and trucks.
Advantages
1. The compact design of engines
2. It provides even cooling to the engine
3. The engine can be installed at any location of the vehicle. It is not necessary to install an engine at the front.
4. It can be used in both small and big engines
Limitations
1. Here water jacket becomes one extra part of the engine.
2. Water circulation consumes power, thus reduces engine efficiency.
3. In case of failure of the cooling system, serious damage could happen to the engine.
4. Cost of the system is considerably high.
5. It requires routine maintenance, and thus puts extra maintenance cost burden.
AIR OR DIRECT COOLING SYSTEM
In a direct cooling system, an engine is cooled directly with the help of air flowing through it. It is the same cooling system which is used to cool our bike engines.
As we can see here, the air is in direct contact with the engine hence it is also known as a direct cooling system.
Air cooling system is used for small engines, like that of bikes and grass cutter, etc.
Advantages
1. Design of the engine becomes simpler.
2. Repair is easy in case of damages.
3. Absence of bulky cooling system makes system maintenance easily.
4. No danger of coolant leakage.
5. The engine is not subjected to freezing troubles.
6. Weight of the system is less.
7. It is a self-contained unit, as it does not requires a radiator, header, tanks, etc.
8. Installation of the air-cooled system is easy.
Limitations
1. It is applicable to only small and medium-sized engines.
2. It can only be used at the places where ambient temperatures are lower.
3. Cooling is not uniform.
4. Higher working temperature as compared to water-cooled engines.
5. It produces more aerodynamic noise.
6. Specific fuel consumption is slightly higher.
7. Lower maximum allowable compression ratios.
8. The fan, if used consumes almost 5% power generated by the engines.
Characteristics of an efficient engine cooling system
Following are two main characteristics of an efficient engine cooling system.
1. It should be capable of removing about 30% of the heat generated in the engine while maintaining the optimum working temperature in the engine.
2. It should remove heat at a faster rate when the engine is hot and remove the engine at a slow rate when the engine is cold.
Or we can say there are two types of cooling systems
1. Liquid or indirect cooling system
2. Air or direct cooling system
LIQUID OR INDIRECT COOLING SYSTEM
In a liquid cooling system, an engine is surrounded with water jackets. With the help of a pump, this water gets circulated in this water jacket.
Water flowing in these jackets takes out heat from the engine. This hot water then flows through a radiator, where it gets cooled from the cold heat blown through a fan.
In this system, the water takes heat from the engine and that water gets cooled by the air and then again gets circulated to the engine.
This is an indirect cooling process, where an actual cooling thing that is air is not directly cooling the system. The air is cooling the water and water is cooling the engine.
Liquid or indirect cooling system is mainly used in big engines, like that of cars and trucks.
Advantages
1. The compact design of engines
2. It provides even cooling to the engine
3. The engine can be installed at any location of the vehicle. It is not necessary to install an engine at the front.
4. It can be used in both small and big engines
Limitations
1. Here water jacket becomes one extra part of the engine.
2. Water circulation consumes power, thus reduces engine efficiency.
3. In case of failure of the cooling system, serious damage could happen to the engine.
4. Cost of the system is considerably high.
5. It requires routine maintenance, and thus puts extra maintenance cost burden.
AIR OR DIRECT COOLING SYSTEM
In a direct cooling system, an engine is cooled directly with the help of air flowing through it. It is the same cooling system which is used to cool our bike engines.
As we can see here, the air is in direct contact with the engine hence it is also known as a direct cooling system.
Air cooling system is used for small engines, like that of bikes and grass cutter, etc.
Advantages
1. Design of the engine becomes simpler.
2. Repair is easy in case of damages.
3. Absence of bulky cooling system makes system maintenance easily.
4. No danger of coolant leakage.
5. The engine is not subjected to freezing troubles.
6. Weight of the system is less.
7. It is a self-contained unit, as it does not requires a radiator, header, tanks, etc.
8. Installation of the air-cooled system is easy.
Limitations
1. It is applicable to only small and medium-sized engines.
2. It can only be used at the places where ambient temperatures are lower.
3. Cooling is not uniform.
4. Higher working temperature as compared to water-cooled engines.
5. It produces more aerodynamic noise.
6. Specific fuel consumption is slightly higher.
7. Lower maximum allowable compression ratios.
8. The fan, if used consumes almost 5% power generated by the engines.
Characteristics of an efficient engine cooling system
Following are two main characteristics of an efficient engine cooling system.
1. It should be capable of removing about 30% of the heat generated in the engine while maintaining the optimum working temperature in the engine.
2. It should remove heat at a faster rate when the engine is hot and remove the engine at a slow rate when the engine is cold.
COMPONENTS OF COOLING SYSTEM
1. RADIATOR:
Cools off the anti-freeze/coolant mixture by allowing air passing through the tube/fin area to dissipate the heat generated by the engine.
2. WATER PUMP:
Draws the cooled anti-freeze from the radiator and pumps it through the engine block, cylinder head(s), heater core and back to the radiator.
3. FREEZE PLUGS:
Is actually a steel plug designed to seal holes in the engine block and cylinder head(s) created from the casting process. In freezing weather they may push out if there is not enough anti-freeze protection.
4. HEAD GASKET /TIMING COVER GASKET:
Seals the major parts of the engine. Prevents oil, anti-freeze and cylinder pressure from mixing together.
5. HEATER CORE:
Provides heat to the interior of the car by using heat removed from the antifreeze and blown in by the blower motor. May cause steam, odor or actual dripping inside the car when it leaks.
6. THERMOSTAT :
Controls the minimum operating temperature of the engine. The thermostat is closed when the engine is cold in order to speed warm-up and opens when the normal operating temperature is reached to allow the anti-freeze / coolant to pass through the radiator.
7. HOSES (Radiator, Heater, By-pass):
Connect the other main components of the cooling system. Hose manufacturers recommend replacing every 4 years regardless of appearance because there may be deterioration of the inside of the hose which cannot be seen.
8. FAN CLUTCH:
Senses the temperature of the air coming through the radiator and either slips or binds up to pull the required amount of air through the radiator.
9. ELECTRIC COOLING FAN:
Most front-wheel-drive cars use this because of the transversely mounted engine. It is turned on by a system of sensors and relays when the engine reaches about 230 F and stays on until R is cooled to about 200 F.
1. RADIATOR:
Cools off the anti-freeze/coolant mixture by allowing air passing through the tube/fin area to dissipate the heat generated by the engine.
2. WATER PUMP:
Draws the cooled anti-freeze from the radiator and pumps it through the engine block, cylinder head(s), heater core and back to the radiator.
3. FREEZE PLUGS:
Is actually a steel plug designed to seal holes in the engine block and cylinder head(s) created from the casting process. In freezing weather they may push out if there is not enough anti-freeze protection.
4. HEAD GASKET /TIMING COVER GASKET:
Seals the major parts of the engine. Prevents oil, anti-freeze and cylinder pressure from mixing together.
5. HEATER CORE:
Provides heat to the interior of the car by using heat removed from the antifreeze and blown in by the blower motor. May cause steam, odor or actual dripping inside the car when it leaks.
6. THERMOSTAT :
Controls the minimum operating temperature of the engine. The thermostat is closed when the engine is cold in order to speed warm-up and opens when the normal operating temperature is reached to allow the anti-freeze / coolant to pass through the radiator.
7. HOSES (Radiator, Heater, By-pass):
Connect the other main components of the cooling system. Hose manufacturers recommend replacing every 4 years regardless of appearance because there may be deterioration of the inside of the hose which cannot be seen.
8. FAN CLUTCH:
Senses the temperature of the air coming through the radiator and either slips or binds up to pull the required amount of air through the radiator.
9. ELECTRIC COOLING FAN:
Most front-wheel-drive cars use this because of the transversely mounted engine. It is turned on by a system of sensors and relays when the engine reaches about 230 F and stays on until R is cooled to about 200 F.
STARTING SYSTEM: COMPONENTS AND WORKING PRINCIPLES
The engine canβt βstartβ rotational movement on its own. It needs an electric motor to get it up to a minimal RPM to run, then the engine can run under its own power. The starter is the biggest load on the vehicles electrical system. We cannot simply run all that current through the ignition switch, in most systems a relay is used to activate the starter solenoid, and the starter solenoid itself acts as another relay to engage the starter motor (explained later). Before electric starters, automobile owners needed to crank the engine over themselves! This was not ideal for any kind of quick getaway.
The starter motor is an electric motor that rotates your engine in order to allow the spark and fuel injection systems to begin the engine's operation under its own power. Typically, the starter is a large electric motor and stator coil mounted to the bottom (generally to one side) of the vehicle's transmission bell housing where it connects to the engine itself. The starter has gears which mesh with a large flywheel gear on the backside of the engine, which turns the central crankshaft. Because this is a lot of physical weight and friction to overcome, starter motors are generally powerful, high-speed motors and use an ignition coil to ramp up their power before engaging.
The engine canβt βstartβ rotational movement on its own. It needs an electric motor to get it up to a minimal RPM to run, then the engine can run under its own power. The starter is the biggest load on the vehicles electrical system. We cannot simply run all that current through the ignition switch, in most systems a relay is used to activate the starter solenoid, and the starter solenoid itself acts as another relay to engage the starter motor (explained later). Before electric starters, automobile owners needed to crank the engine over themselves! This was not ideal for any kind of quick getaway.
The starter motor is an electric motor that rotates your engine in order to allow the spark and fuel injection systems to begin the engine's operation under its own power. Typically, the starter is a large electric motor and stator coil mounted to the bottom (generally to one side) of the vehicle's transmission bell housing where it connects to the engine itself. The starter has gears which mesh with a large flywheel gear on the backside of the engine, which turns the central crankshaft. Because this is a lot of physical weight and friction to overcome, starter motors are generally powerful, high-speed motors and use an ignition coil to ramp up their power before engaging.
COMPONENTS OF STARTING SYSTEM
1. Battery
The automotive battery, also known as a lead-acid storage battery, is an electrochemical device that produces voltage and delivers current. In an automotive battery, we can reverse the electrochemical action, thereby recharging the battery, which will then give us many years of service. The purpose of the battery is to supply current to the starter motor, provide current to the ignition system while cranking, to supply additional current when the demand is higher than the alternator can supply and to act as an electrical reservoir.
2. Ignition Switch
The ignition switch allows the driver to distribute electrical current to where it is needed. There are generally 5 key switch positions that are used:
1. Lock- All circuits are open ( no current supplied) and the steering wheel is in the lock position. In some cars, the transmission lever cannot be moved in this position. If the steering wheel is applying pressure to the locking mechanism, the key might be hard to turn. If you do experience this type of condition, try moving the steering wheel to remove the pressure as you turn the key.
2. Off- All circuits are open, but the steering wheel can be turned and the key cannot be extracted.
3. Run- All circuits, except the starter circuit, are closed (current is allowed to pass through). Current is supplied to all but the starter circuit.
4. Start- Power is supplied to the ignition circuit and the starter motor only. That is why the radio stops playing in the start position. This position of the ignition switch is spring-loaded so that the starter is not engaged while the engine is running. This position is used momentarily, just to activate the starter.
5. Accessory- Power is supplied to all but the ignition and starter circuit. This allows you to play the radio, work the power windows, etc. while the engine is not running.
Most ignition switches are mounted on the steering column. Some switches are actually two separate parts;
* The lock into which you insert the key. This component also contains the mechanism to lock the steering wheel and shifter.
* The switch which contains the actual electrical circuits. It is usually mounted on top of the steering column just behind the dash and is connected to the lock by a linkage or rod.
3. Neutral Safety Switch
This switch opens (denies current to) the starter circuit when the transmission is in any gear but Neutral or Park on automatic transmissions. This switch is normally connected to the transmission linkage or directly on the transmission. Most cars utilize this same switch to apply current to the backup lights when the transmission is put in reverse. Standard transmission cars will connect this switch to the clutch pedal so that the starter will not engage unless the clutch pedal is depressed. If you find that you have to move the shifter away from park or neutral to get the car to start, it usually means that this switch needs adjustment. If your car has an automatic parking brake release, the neutral safety switch will control that function also.
4. Starter Relay
A relay is a device that allows a small amount of electrical current to control a large amount of current. An automobile starter uses a large amount of current (250+ amps) to start an engine. If we were to allow that much current to go through the ignition switch, we would not only need a very large switch, but all the wires would have to be the size of battery cables (not very practical). A starter relay is installed in series between the battery and the starter. Some cars use a starter solenoid to accomplish the same purpose of allowing a small amount of current from the ignition switch to control a high current flow from the battery to the starter. The starter solenoid in some cases also mechanically engages the starter gear with the engine.
5. Battery Cables
1. Battery
The automotive battery, also known as a lead-acid storage battery, is an electrochemical device that produces voltage and delivers current. In an automotive battery, we can reverse the electrochemical action, thereby recharging the battery, which will then give us many years of service. The purpose of the battery is to supply current to the starter motor, provide current to the ignition system while cranking, to supply additional current when the demand is higher than the alternator can supply and to act as an electrical reservoir.
2. Ignition Switch
The ignition switch allows the driver to distribute electrical current to where it is needed. There are generally 5 key switch positions that are used:
1. Lock- All circuits are open ( no current supplied) and the steering wheel is in the lock position. In some cars, the transmission lever cannot be moved in this position. If the steering wheel is applying pressure to the locking mechanism, the key might be hard to turn. If you do experience this type of condition, try moving the steering wheel to remove the pressure as you turn the key.
2. Off- All circuits are open, but the steering wheel can be turned and the key cannot be extracted.
3. Run- All circuits, except the starter circuit, are closed (current is allowed to pass through). Current is supplied to all but the starter circuit.
4. Start- Power is supplied to the ignition circuit and the starter motor only. That is why the radio stops playing in the start position. This position of the ignition switch is spring-loaded so that the starter is not engaged while the engine is running. This position is used momentarily, just to activate the starter.
5. Accessory- Power is supplied to all but the ignition and starter circuit. This allows you to play the radio, work the power windows, etc. while the engine is not running.
Most ignition switches are mounted on the steering column. Some switches are actually two separate parts;
* The lock into which you insert the key. This component also contains the mechanism to lock the steering wheel and shifter.
* The switch which contains the actual electrical circuits. It is usually mounted on top of the steering column just behind the dash and is connected to the lock by a linkage or rod.
3. Neutral Safety Switch
This switch opens (denies current to) the starter circuit when the transmission is in any gear but Neutral or Park on automatic transmissions. This switch is normally connected to the transmission linkage or directly on the transmission. Most cars utilize this same switch to apply current to the backup lights when the transmission is put in reverse. Standard transmission cars will connect this switch to the clutch pedal so that the starter will not engage unless the clutch pedal is depressed. If you find that you have to move the shifter away from park or neutral to get the car to start, it usually means that this switch needs adjustment. If your car has an automatic parking brake release, the neutral safety switch will control that function also.
4. Starter Relay
A relay is a device that allows a small amount of electrical current to control a large amount of current. An automobile starter uses a large amount of current (250+ amps) to start an engine. If we were to allow that much current to go through the ignition switch, we would not only need a very large switch, but all the wires would have to be the size of battery cables (not very practical). A starter relay is installed in series between the battery and the starter. Some cars use a starter solenoid to accomplish the same purpose of allowing a small amount of current from the ignition switch to control a high current flow from the battery to the starter. The starter solenoid in some cases also mechanically engages the starter gear with the engine.
5. Battery Cables
Battery cables are large diameter, the multi-stranded wire which carries the high current (250+ amps) necessary to operate the starter motor. Some have a smaller wire soldered to the terminal which is used to either operate a smaller device or to provide an additional ground. When the smaller cable burns, this indicates a high resistance in the heavy cable. Care must be taken to keep the battery cable ends (terminals) clean and tight. Battery cables can be replaced with ones that are slightly larger but never smaller.
6. Starter Motor
The starter motor is a powerful electric motor, with a small gear (pinion) attached to the end. When activated, the gear has meshed with a larger gear (ring), which is attached to the engine. The starter motor then spins the engine over so that the piston can draw in a fuel/ air mixture, which is then ignited to start the engine. When the engine starts to spin faster than the starter, a device called an overrunning clutch (Bendix drive) automatically disengages the starter gear from the engine gear.
6. Starter Motor
The starter motor is a powerful electric motor, with a small gear (pinion) attached to the end. When activated, the gear has meshed with a larger gear (ring), which is attached to the engine. The starter motor then spins the engine over so that the piston can draw in a fuel/ air mixture, which is then ignited to start the engine. When the engine starts to spin faster than the starter, a device called an overrunning clutch (Bendix drive) automatically disengages the starter gear from the engine gear.
STARTER MOTOR PARTS
1. Starter Solenoid
The starter solenoid sits on top of the starter motor and performs two main functions, it acts as a heavy-duty relay for the starter and it engages the starter pinion gear to the ring gear on the flywheel/flex-plate/torque converter. The solenoid has 3 terminals; a B+ terminal, an S terminal, and an M terminal. The B+ terminal is connected directly to the battery positive at all times. This wire is infused meaning that if there is a short to ground on this wire, there will be sparks until the battery is drained. The wire from the battery to the B+ terminal will be very thick because it needs to carry call the current necessary to turn the starter motor and overcome engine compression. The S terminal receives power from the ignition switch either directly or indirectly with a relay. The S terminal connects to two winding, the pull-in winding and the hold in the winding. These winding are simply coils of wire wrapped around a plunger, which when energized produce and electromagnet. The pull-in winding is made up of thicker winding and creates a strong electromagnet. It is grounded through the M terminal and starter motor. The hold-in winding is smaller and creates a weaker electromagnet. It is grounded directly to the starter case. The plunger sits in the middle of the winding and is held in place by a spring. The plunger gets pulled/held in by the winding when they are energized. At one end it is connected to a lever which forces the starter pinion gear to mesh with the ring gear. At the other end, when the plunger reaches the end of its travel, it pushes a contact disk which connects the B+ terminal to the M terminal which is connected to the starter motor. This energizes the starter motor and also causes the pull-in winding to stop flowing power. This is because once the contact disk connects B+ to M there is 12v on both sides of the pull-in winding and no ground. The hold-in winding continues to flow electricity and holds the plunger in place until the key is returns to the run position. The solenoid needs both windings to pull the plunger in but only the hold-in winding to keep it there. It takes much more effort to move the plunger to engage the starter than it does to hold it there. Since the pull-in winding is no longer necessary, it would only waste electrical power to continue to power it.
2. Starter Motor
1. Starter Solenoid
The starter solenoid sits on top of the starter motor and performs two main functions, it acts as a heavy-duty relay for the starter and it engages the starter pinion gear to the ring gear on the flywheel/flex-plate/torque converter. The solenoid has 3 terminals; a B+ terminal, an S terminal, and an M terminal. The B+ terminal is connected directly to the battery positive at all times. This wire is infused meaning that if there is a short to ground on this wire, there will be sparks until the battery is drained. The wire from the battery to the B+ terminal will be very thick because it needs to carry call the current necessary to turn the starter motor and overcome engine compression. The S terminal receives power from the ignition switch either directly or indirectly with a relay. The S terminal connects to two winding, the pull-in winding and the hold in the winding. These winding are simply coils of wire wrapped around a plunger, which when energized produce and electromagnet. The pull-in winding is made up of thicker winding and creates a strong electromagnet. It is grounded through the M terminal and starter motor. The hold-in winding is smaller and creates a weaker electromagnet. It is grounded directly to the starter case. The plunger sits in the middle of the winding and is held in place by a spring. The plunger gets pulled/held in by the winding when they are energized. At one end it is connected to a lever which forces the starter pinion gear to mesh with the ring gear. At the other end, when the plunger reaches the end of its travel, it pushes a contact disk which connects the B+ terminal to the M terminal which is connected to the starter motor. This energizes the starter motor and also causes the pull-in winding to stop flowing power. This is because once the contact disk connects B+ to M there is 12v on both sides of the pull-in winding and no ground. The hold-in winding continues to flow electricity and holds the plunger in place until the key is returns to the run position. The solenoid needs both windings to pull the plunger in but only the hold-in winding to keep it there. It takes much more effort to move the plunger to engage the starter than it does to hold it there. Since the pull-in winding is no longer necessary, it would only waste electrical power to continue to power it.
2. Starter Motor
The starter motor converts electric energy into rotational motion, using electromagnetism or electromagnetic repulsion. Most starters used in automotive today are permanent magnet starters. These starters have several permanent magnets placed inside the case around an armature. An armature is used to make an electromagnetic field of the same polarity as the permanent magnets, causing the armature to repel the magnets. Power from the M terminal and ground from the case is supplied to the commutator strip through the brushes. The commutator strips Are connected to each other through the armature windings, this causes an electromagnetic field to form around the armature strips that are flowing power. If power is fed to commutator strip 1, the ground is on commutator strip 5, power will have to travel through armature strips 2,3, and 4 to get to commutator strip 5. This will create a magnetic field around armature strips 2,3 and 4. To get the armature to rotate, a permanent magnet is placed near, but not right on top of where the electromagnetic field is formed. When the two like polarities repel, the armature begins to rotate. As the armature rotates, the brushes will contact the next commutator strips, keeping the electromagnetic field in one place (just next to the permanent magnet) but allowing the armature to spin. This is what creates the rotational movement necessary to start the engine. Starters may also have a planetary gear-set to reduce RPM and increase torque to the ring gear. Heavy-duty starters use field coils instead of permanent magnets. Basically, they make both magnetic fields using electromagnetism instead of relying on permanent magnets. These starters are much more powerful than a permanent magnet starter but they take up more space, are much heavier and cost more to produce.
3. Starter Drive Pinion
The starter drive pinion is held out mesh with the ring gear by a spring until the starter solenoid engages and moves the lever, pushing the starter pinion into mesh with the ring gear. When the engine starts, the operator allows the key to return to the run position. This cuts power to the starter solenoid, which allows the spring to push the plunger back to its normal position. The plungers lever will pull the starter drive pinion back, out of mesh with the ring gear. It is important that the starter drives the flywheel and not the other way around. This is why starter drives have a one-way clutch. The one-way clutch allows the starter to turn the flywheel, but if the flywheel starts to cause the starter pinion to turn faster than the armature, the one-way clutch will slip. This protects the starter from spinning too fast.
3. Starter Drive Pinion
The starter drive pinion is held out mesh with the ring gear by a spring until the starter solenoid engages and moves the lever, pushing the starter pinion into mesh with the ring gear. When the engine starts, the operator allows the key to return to the run position. This cuts power to the starter solenoid, which allows the spring to push the plunger back to its normal position. The plungers lever will pull the starter drive pinion back, out of mesh with the ring gear. It is important that the starter drives the flywheel and not the other way around. This is why starter drives have a one-way clutch. The one-way clutch allows the starter to turn the flywheel, but if the flywheel starts to cause the starter pinion to turn faster than the armature, the one-way clutch will slip. This protects the starter from spinning too fast.
WORKING PRINCIPLES
πTo make an engine start it must be turned at some speed, so that it sucks fuel and air into the cylinders, and compresses it.
πThe powerful electric starter motor does the turning. Its shaft carries a small pinion (gear wheel) which engages with a large gear ring around the rim of the engine flywheel.
πIn a front-engine layout, the starter is mounted low down near the back of the engine.
πThe starter needs a heavy electric current, which it draws through thick wires from the battery. No ordinary hand-operated switch could switch it on: it needs a large switch to handle the high current.
πThe switch has to be turned on and off very quickly to avoid dangerous, damaging sparking. So a solenoid is used - an arrangement where a small switch turns on an electromagnet to complete the circuit.
πThe starter switch is usually worked by the ignition key. Turn the key beyond the 'ignition on' position to feed current to the solenoid.
πThe ignition switch has a return spring so that as soon as you release the key it springs back and turns the starter switch off.
πWhen the switch feeds current to the solenoid, the electromagnet attracts an iron rod.
πThe movement of the rod closes two heavy contacts, completing the circuit from the battery to the starter.
πThe rod also has a return spring -when the ignition switch stops feeding current to the solenoid, the contacts open and the starter motor stops.
πThe return springs are needed because the starter motor must not turn more than it has to in order to start the engine. The reason is partly that the starter uses a lot of electricity, which quickly runs down the battery.
πAlso, if the engine starts and the starter motor stays engaged, the engine will spin the starter so fast that it may be badly damaged.
πThe starter motor itself has a device, called a Bendix gear, which engages its pinion with the gear ring on the flywheel only while the starter is turning the engine. It disengages as soon as the engine picks up speed, and there are two ways by which it does so - the inertia system and the pre-engaged system.
πThe inertia starter relies on the inertia of the pinion - that is, its reluctance to begin to turn.
πThe pinion is not fixed rigidly to the motor shaft - it is threaded on to it, like a freely turning nut on a very coarse-thread bolt.
πImagine that you suddenly spin the bolt: the inertia of the nut keeps it from turning at once, so it shifts along the thread of the bolt.
πWhen an inertia starter spins, the pinion moves along the thread of the motor shaft and engages with the flywheel gear ring.
πIt then reaches a stop at the end of the thread, begins to turn with the shaft and so turns the engine.
πOnce the engine starts, it spins the pinion faster than its own starter-motor shaft. The spinning action screws the pinion back down its thread and out of engagement.
πThe pinion returns so violently that there has to be a strong spring on the shaft to cushion its impact.
πThe violent engagement and disengagement of an inertia starter can cause heavy wear on the gear teeth. To overcome that problem the pre-engaged starter was introduced, which has a solenoid mounted on the motor.
πThere's more to a car starter system: As well as switching on the motor, the solenoid also slides the pinion along the shaft to engage it.
πThe shaft has straight splines rather than a Bendix thread so that the pinion always turns with it.
πThe pinion is brought into contact with the toothed ring on the flywheel by a sliding fork. The fork is moved by a solenoid, which has two sets of contacts that close one after the other.
πThe first contact supplies a low current to the motor so that it turns slowly - just far enough to let the pinion teeth engage. Then the second contacts close, feeding the motor a high current to turn the engine.
πThe starter motor is saved from over-speeding when the engine starts by means of a freewheel clutch, like the freewheel of a bicycle. The return spring of the solenoid withdraws the pinion from engagement.
πTo make an engine start it must be turned at some speed, so that it sucks fuel and air into the cylinders, and compresses it.
πThe powerful electric starter motor does the turning. Its shaft carries a small pinion (gear wheel) which engages with a large gear ring around the rim of the engine flywheel.
πIn a front-engine layout, the starter is mounted low down near the back of the engine.
πThe starter needs a heavy electric current, which it draws through thick wires from the battery. No ordinary hand-operated switch could switch it on: it needs a large switch to handle the high current.
πThe switch has to be turned on and off very quickly to avoid dangerous, damaging sparking. So a solenoid is used - an arrangement where a small switch turns on an electromagnet to complete the circuit.
πThe starter switch is usually worked by the ignition key. Turn the key beyond the 'ignition on' position to feed current to the solenoid.
πThe ignition switch has a return spring so that as soon as you release the key it springs back and turns the starter switch off.
πWhen the switch feeds current to the solenoid, the electromagnet attracts an iron rod.
πThe movement of the rod closes two heavy contacts, completing the circuit from the battery to the starter.
πThe rod also has a return spring -when the ignition switch stops feeding current to the solenoid, the contacts open and the starter motor stops.
πThe return springs are needed because the starter motor must not turn more than it has to in order to start the engine. The reason is partly that the starter uses a lot of electricity, which quickly runs down the battery.
πAlso, if the engine starts and the starter motor stays engaged, the engine will spin the starter so fast that it may be badly damaged.
πThe starter motor itself has a device, called a Bendix gear, which engages its pinion with the gear ring on the flywheel only while the starter is turning the engine. It disengages as soon as the engine picks up speed, and there are two ways by which it does so - the inertia system and the pre-engaged system.
πThe inertia starter relies on the inertia of the pinion - that is, its reluctance to begin to turn.
πThe pinion is not fixed rigidly to the motor shaft - it is threaded on to it, like a freely turning nut on a very coarse-thread bolt.
πImagine that you suddenly spin the bolt: the inertia of the nut keeps it from turning at once, so it shifts along the thread of the bolt.
πWhen an inertia starter spins, the pinion moves along the thread of the motor shaft and engages with the flywheel gear ring.
πIt then reaches a stop at the end of the thread, begins to turn with the shaft and so turns the engine.
πOnce the engine starts, it spins the pinion faster than its own starter-motor shaft. The spinning action screws the pinion back down its thread and out of engagement.
πThe pinion returns so violently that there has to be a strong spring on the shaft to cushion its impact.
πThe violent engagement and disengagement of an inertia starter can cause heavy wear on the gear teeth. To overcome that problem the pre-engaged starter was introduced, which has a solenoid mounted on the motor.
πThere's more to a car starter system: As well as switching on the motor, the solenoid also slides the pinion along the shaft to engage it.
πThe shaft has straight splines rather than a Bendix thread so that the pinion always turns with it.
πThe pinion is brought into contact with the toothed ring on the flywheel by a sliding fork. The fork is moved by a solenoid, which has two sets of contacts that close one after the other.
πThe first contact supplies a low current to the motor so that it turns slowly - just far enough to let the pinion teeth engage. Then the second contacts close, feeding the motor a high current to turn the engine.
πThe starter motor is saved from over-speeding when the engine starts by means of a freewheel clutch, like the freewheel of a bicycle. The return spring of the solenoid withdraws the pinion from engagement.
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SHOCK ABSORBERS/ DAMPERS: WORKING PRINCIPLE, CLASSIFICATION, AND FUNCTIONS
Shock absorbers are basically oil pumps. A piston is attached to the end of the piston rod and works against hydraulic fluid in the pressure tube. As the suspension travels up and down, the hydraulic fluid is forced through tiny holes, called orifices, inside the piston. However, these orifices let only a small amount of fluid through the piston. This slows down the piston, which in turn slows down spring and suspension movement.
All modern shock absorbers are velocity-sensitive hydraulic damping devices β meaning the faster the suspension moves, the more resistance the shock absorber provides.
Because of this feature, shock absorbers adjust to road conditions. As a result, shock absorbers reduce the rate of:
β’ Bounce
β’ Roll or sway
β’ Brake dive and Acceleration squat
Shock absorbers work on the principle of fluid displacement on both the compression and extension cycle. A typical car or light truck will have more resistance during its extension cycle then its compression cycle. The compression cycle controls the motion of a vehicle's unsprung weight, while extension controls the heavier sprung weight.
FUNCTIONS OF DAMPER
The main function of the shock absorber is to absorb the shocks and damp them as soon as possible so that a smooth ride can be obtained.
Some other important functions of the shock absorber are
ο§ It limits vehicle body movement
ο§ It stabilizes our ride as discussed above
ο§ It stabilizes vehicle tires which are disturbed due to sudden shock, hence it is very important for safety purpose also
ο§ It also minimizes tire and bodywear of the automobile and hence reduces overall maintenance cost
It may sound a simple job but this is the main thing on which the comfort level of your ride depends.
WORKING PRINCIPLE
To understand the shock absorber, it is very important to understand its working.
First of all, we should know that there are generally two types of shock absorbers one is hydraulic and another one is pneumatic. However, working of both the types of shock absorbers is same.
A shock absorber is generally coupled with a spring, which converts sudden shock waves into oscillatory motion. This oscillatory motion gives us instant relief from the shock but, nobody can have his or her whole ride with these oscillations.
Here is the need for shock absorber arises, it is used to damp those oscillations which are made by the springs.
A general shock absorber contains a perforated piston in a hydraulic chamber. The chamber is totally sealed and hence if piston has to make some movement the only way is to let the hydraulic liquid pass through it.
When a shock comes, the piston has to move due to shock. When the piston moves than the hydraulic liquid in the shock absorber has to pass through it.
When the liquid is passed through the very tiny perforated holes in the piston the piston has to do some work against it. That work is done on that expense of the energy generated due to the shock and hence soon the shock absorber loses all the shock energy, which results in no oscillation and smooth ride.
SHOCK ABSORBER DESIGN TYPES
There are several shock absorber designs in use today:
1. Twin Tube Designs
β’ Gas Charged
β’ PSD (position sensitive damping)
β’ ASD (Acceleration Sensitive Damping)
2. Mono-Tube
A. Twin-Tube β Gas Charged Design
The prime function of gas charging is to minimize aeration of the hydraulic fluid. The pressure of the nitrogen gas compresses air bubbles in the hydraulic fluid. This prevents the oil and air from mixing and creating foam. Foam affects performance because it can be compressed β fluid can not. With aeration reduced, the shock is able to react faster and more predictably, allowing for quicker response time and helping keep the tire firmly planted on the road surface.
Shock absorbers are basically oil pumps. A piston is attached to the end of the piston rod and works against hydraulic fluid in the pressure tube. As the suspension travels up and down, the hydraulic fluid is forced through tiny holes, called orifices, inside the piston. However, these orifices let only a small amount of fluid through the piston. This slows down the piston, which in turn slows down spring and suspension movement.
All modern shock absorbers are velocity-sensitive hydraulic damping devices β meaning the faster the suspension moves, the more resistance the shock absorber provides.
Because of this feature, shock absorbers adjust to road conditions. As a result, shock absorbers reduce the rate of:
β’ Bounce
β’ Roll or sway
β’ Brake dive and Acceleration squat
Shock absorbers work on the principle of fluid displacement on both the compression and extension cycle. A typical car or light truck will have more resistance during its extension cycle then its compression cycle. The compression cycle controls the motion of a vehicle's unsprung weight, while extension controls the heavier sprung weight.
FUNCTIONS OF DAMPER
The main function of the shock absorber is to absorb the shocks and damp them as soon as possible so that a smooth ride can be obtained.
Some other important functions of the shock absorber are
ο§ It limits vehicle body movement
ο§ It stabilizes our ride as discussed above
ο§ It stabilizes vehicle tires which are disturbed due to sudden shock, hence it is very important for safety purpose also
ο§ It also minimizes tire and bodywear of the automobile and hence reduces overall maintenance cost
It may sound a simple job but this is the main thing on which the comfort level of your ride depends.
WORKING PRINCIPLE
To understand the shock absorber, it is very important to understand its working.
First of all, we should know that there are generally two types of shock absorbers one is hydraulic and another one is pneumatic. However, working of both the types of shock absorbers is same.
A shock absorber is generally coupled with a spring, which converts sudden shock waves into oscillatory motion. This oscillatory motion gives us instant relief from the shock but, nobody can have his or her whole ride with these oscillations.
Here is the need for shock absorber arises, it is used to damp those oscillations which are made by the springs.
A general shock absorber contains a perforated piston in a hydraulic chamber. The chamber is totally sealed and hence if piston has to make some movement the only way is to let the hydraulic liquid pass through it.
When a shock comes, the piston has to move due to shock. When the piston moves than the hydraulic liquid in the shock absorber has to pass through it.
When the liquid is passed through the very tiny perforated holes in the piston the piston has to do some work against it. That work is done on that expense of the energy generated due to the shock and hence soon the shock absorber loses all the shock energy, which results in no oscillation and smooth ride.
SHOCK ABSORBER DESIGN TYPES
There are several shock absorber designs in use today:
1. Twin Tube Designs
β’ Gas Charged
β’ PSD (position sensitive damping)
β’ ASD (Acceleration Sensitive Damping)
2. Mono-Tube
A. Twin-Tube β Gas Charged Design
The prime function of gas charging is to minimize aeration of the hydraulic fluid. The pressure of the nitrogen gas compresses air bubbles in the hydraulic fluid. This prevents the oil and air from mixing and creating foam. Foam affects performance because it can be compressed β fluid can not. With aeration reduced, the shock is able to react faster and more predictably, allowing for quicker response time and helping keep the tire firmly planted on the road surface.
Advantages:
β’ Improves handling by reducing roll, sway, and dive
β’ Reduces aeration offering a greater range of control over a wider variety of road conditions as compared to non-gas units
β’ Reduced fade β shocks can lose damping capability as they heat up during use. Gas-charged shocks could cut this loss of performance, called fade
B. Twin Tube β PSD Design
Ride engineers had to compromise between soft valving and firm valving. With soft valving, the fluid flows more easily. The result is a smoother ride, but with poor handling and a lot of roll/sway. When valving is firm, fluid flows less easily. Handling is improved, but the ride can become harsh.
With the advent of gas charging, ride engineers were able to open up the orifice controls of these valves and improve the balance between comfort and control capabilities available in traditional velocity sensitive dampers.
A leap beyond fluid velocity control is an advanced technology that takes into account the position of the valve within the pressure tube. This is called Position Sensitive Damping (PSD).
The key to this innovation is precision tapered grooves in the pressure tube. Every application is individually tuned, tailoring the length, depth, and taper of these grooves to ensure optimal ride comfort and added control. This in essence creates two zones within the pressure tube.
The first zone, the comfort zone, is where normal driving takes place.
The second zone, the control zone, is utilized during demanding driving situations.
Advantages:
β’ Allows ride engineers to move beyond simple velocity sensitive valving and use the position of the piston to fine-tune the ride characteristic.
β’ Adjusts more rapidly to changing road and weight conditions than standard shock absorbers
β’ Two shocks into one β comfort and control
C. Twin Tube -ASD Design (Reflex )
A new twist on the comfort/ control compromise is an innovative technology which provides greater control for handling while improving ride comfort called Acceleration Sensitive Damping (ASD).
This technology moves beyond traditional velocity-sensitive damping to focus and address impact. This focus on impact is achieved by utilizing a new compression valve design. This compression valve is a mechanical closed-loop system, which opens a bypass to fluid flow around the compression valve.
Advantages:
β’ Control is enhanced without sacrificing driver comfort
β’ Valve automatically adjusts to changes in the road condition
β’ Reduces ride harshness
2. Mono-tube design (Standard Types)
These are high-pressure gas shocks with only one tube, the pressure tube. Inside the pressure tube, there are two pistons: a dividing piston and a working piston. The working piston and rod are very similar to the twin-tube shock design. The difference in actual application is that a mono-tube shock absorber can be mounted upside down or right side up and will work either way. In addition to its mounting flexibility, mono-tube shocks are a significant component, along with the spring, in supporting vehicle weight. Another difference you may notice is that the mono-tube shock absorber does not have a base valve. Instead, all of the control during compression and extension takes place at the piston.
During operation, the dividing piston moves up and down as the piston rod moves in and out of the shock absorber, keeping the pressure tube full all times.
Advantages:
β’ Can be mounted upside down, reducing the unsprung weight
β’ May run cooler since the working tube is exposed to the air
β’ Original equipment many import and performance domestic passenger cars, SUV and light truck applications
β’ Improves handling by reducing roll, sway, and dive
β’ Reduces aeration offering a greater range of control over a wider variety of road conditions as compared to non-gas units
β’ Reduced fade β shocks can lose damping capability as they heat up during use. Gas-charged shocks could cut this loss of performance, called fade
B. Twin Tube β PSD Design
Ride engineers had to compromise between soft valving and firm valving. With soft valving, the fluid flows more easily. The result is a smoother ride, but with poor handling and a lot of roll/sway. When valving is firm, fluid flows less easily. Handling is improved, but the ride can become harsh.
With the advent of gas charging, ride engineers were able to open up the orifice controls of these valves and improve the balance between comfort and control capabilities available in traditional velocity sensitive dampers.
A leap beyond fluid velocity control is an advanced technology that takes into account the position of the valve within the pressure tube. This is called Position Sensitive Damping (PSD).
The key to this innovation is precision tapered grooves in the pressure tube. Every application is individually tuned, tailoring the length, depth, and taper of these grooves to ensure optimal ride comfort and added control. This in essence creates two zones within the pressure tube.
The first zone, the comfort zone, is where normal driving takes place.
The second zone, the control zone, is utilized during demanding driving situations.
Advantages:
β’ Allows ride engineers to move beyond simple velocity sensitive valving and use the position of the piston to fine-tune the ride characteristic.
β’ Adjusts more rapidly to changing road and weight conditions than standard shock absorbers
β’ Two shocks into one β comfort and control
C. Twin Tube -ASD Design (Reflex )
A new twist on the comfort/ control compromise is an innovative technology which provides greater control for handling while improving ride comfort called Acceleration Sensitive Damping (ASD).
This technology moves beyond traditional velocity-sensitive damping to focus and address impact. This focus on impact is achieved by utilizing a new compression valve design. This compression valve is a mechanical closed-loop system, which opens a bypass to fluid flow around the compression valve.
Advantages:
β’ Control is enhanced without sacrificing driver comfort
β’ Valve automatically adjusts to changes in the road condition
β’ Reduces ride harshness
2. Mono-tube design (Standard Types)
These are high-pressure gas shocks with only one tube, the pressure tube. Inside the pressure tube, there are two pistons: a dividing piston and a working piston. The working piston and rod are very similar to the twin-tube shock design. The difference in actual application is that a mono-tube shock absorber can be mounted upside down or right side up and will work either way. In addition to its mounting flexibility, mono-tube shocks are a significant component, along with the spring, in supporting vehicle weight. Another difference you may notice is that the mono-tube shock absorber does not have a base valve. Instead, all of the control during compression and extension takes place at the piston.
During operation, the dividing piston moves up and down as the piston rod moves in and out of the shock absorber, keeping the pressure tube full all times.
Advantages:
β’ Can be mounted upside down, reducing the unsprung weight
β’ May run cooler since the working tube is exposed to the air
β’ Original equipment many import and performance domestic passenger cars, SUV and light truck applications