1. INTRODUCTION
1. INTRODUCTION
The mode of transport is one of the most important criterions The mode of transport is one of the most important criterions these days. The vehicles safety is thus essential. Accidents are also these days. The vehicles safety is thus essential. Accidents are also increasing at a quick pace. There are several factors which causes these increasing at a quick pace. There are several factors which causes these accidents. The improper inflation of tyres is one among them. Tyres accidents. The improper inflation of tyres is one among them. Tyres lose air through normal driving (especially after hitting pot holes or lose air through normal driving (especially after hitting pot holes or curbs), permeation and seasonal changes in temperature. When tyres curbs), permeation and seasonal changes in temperature. When tyres are under inflated, the tread wears more quickly. Under inflated tyres are under inflated, the tread wears more quickly. Under inflated tyres ge
get t dadamamageged d ququicicklkly y dudue e to to ovovererheheatatining g as as cocompmpareared d to to prpropoperlerlyy inflated tyres. The under inflation also causes a small depreciation in inflated tyres. The under inflation also causes a small depreciation in the mileage as well. Above all the vehicles running with under inflated the mileage as well. Above all the vehicles running with under inflated tyres can cause accidents.
tyres can cause accidents.
Thus to rectify all these defects we are using self inflating Thus to rectify all these defects we are using self inflating systems. The pressure monitoring systems in such systems helps in systems. The pressure monitoring systems in such systems helps in monitoring the tyre pressure constantly. The system which contains monitoring the tyre pressure constantly. The system which contains sensors feed the information to a display panel which the driver can sensors feed the information to a display panel which the driver can operate manually. The electronic unit controls all the information. The operate manually. The electronic unit controls all the information. The source of air is taken from the vehicles air braking system or from the source of air is taken from the vehicles air braking system or from the pneumatic systems. Thus it helps in re-inflation of the tyres to proper pneumatic systems. Thus it helps in re-inflation of the tyres to proper pressure conditions.
2. HOW TYRES WORK
2. HOW TYRES WORK
If you're in the market for new tyres, all of the variables in If you're in the market for new tyres, all of the variables in tyre specifications and the confusing jargon you might hear from tyre tyre specifications and the confusing jargon you might hear from tyre salesmen or "experts" might make your purchase rather stressful. Or salesmen or "experts" might make your purchase rather stressful. Or maybe you just want to fully understand the tyres you already have, the maybe you just want to fully understand the tyres you already have, the concepts at work, the significance of all of those sidewall markings. concepts at work, the significance of all of those sidewall markings. What does all this stuff mean in regular terms?
What does all this stuff mean in regular terms?
In this article, we will explore how tyres are built and see In this article, we will explore how tyres are built and see what's in a tyre. We'll find out what all the numbers and markings on what's in a tyre. We'll find out what all the numbers and markings on the sidewall of a tyre mean, and we'll decipher some of that tyre jargon. the sidewall of a tyre mean, and we'll decipher some of that tyre jargon. By the end of this article, you'll understand how a tyre supports your By the end of this article, you'll understand how a tyre supports your car, and you'll know why heat can build up in your tyres, especially if car, and you'll know why heat can build up in your tyres, especially if the pressure is low. You'll also be able to adjust your tyre pressure the pressure is low. You'll also be able to adjust your tyre pressure correctly and diagnose some common tyre problems!
correctly and diagnose some common tyre problems!
How Tyres are Made How Tyres are Made
As illustrated below, a tyre is made up of several different As illustrated below, a tyre is made up of several different components.
The Bead Bundle The Bead Bundle
The bead
The bead is a is a looloop p of high-sof high-stretrengtngth h stesteel el cabcable le coacoated withted with rubber. It gives the tyre the strength it needs to stay seated on the wheel rubber. It gives the tyre the strength it needs to stay seated on the wheel rim and to handle the forces applied by tyre mounting machines when rim and to handle the forces applied by tyre mounting machines when the tyres are installed on rims.
the tyres are installed on rims.
The Body The Body
The body
The body is is madmade e up up of of sevseveraeral l laylayers of ers of didiffefferent fabrrent fabricsics,, calle
called d pliesplies. The . The most common ply fabric is most common ply fabric is polyepolyester cord. The ster cord. The cordscords in a radial tyre run perpendicular to the tread. Some older tyres used in a radial tyre run perpendicular to the tread. Some older tyres used diagonal bias tyres, tyres in which the fabric ran at an angle to the diagonal bias tyres, tyres in which the fabric ran at an angle to the tread. The plies are coated with rubber to
tread. The plies are coated with rubber to help them bond with the other help them bond with the other compo
components and to seal in thnents and to seal in the air. e air. A tyre's strA tyre's strength is oftength is often describen describeded by the number of plies it has. Most car tyres have two body plies. By by the number of plies it has. Most car tyres have two body plies. By comparison, large commercial jetliners often have tyres with 30 or comparison, large commercial jetliners often have tyres with 30 or more plies.
The Belts The Belts
In steel-belted radial tyres, belts made from steel are used to In steel-belted radial tyres, belts made from steel are used to re
reininfoforcrce e ththe e arearea a ununder der ththe e trtreaead. d. ThThesese e bebeltlts s prprovovidide e pupuncnctuturere resistance and help the tyre stay flat so that it makes the best contact resistance and help the tyre stay flat so that it makes the best contact with the road.
with the road.
Cap Plies Cap Plies
Some tyres have cap plies, an extra layer or two of polyester Some tyres have cap plies, an extra layer or two of polyester fabric to help hold everything in place. These cap plies are not found on fabric to help hold everything in place. These cap plies are not found on all tyres; they are mostly used on tyres with higher speed r
all tyres; they are mostly used on tyres with higher speed ratings to helpatings to help all the components stay in place at high speeds.
all the components stay in place at high speeds.
The Sidewall The Sidewall
The sidewall provides lateral stability for the tyre, protects the The sidewall provides lateral stability for the tyre, protects the b
bodody y plplieies s anand d hehelplps s kekeep ep ththe e aiair r frfrom om esescacapiping. ng. It It mamay y cocontntaiainn additional components to help increase
additional components to help increase the lateral stability.the lateral stability.
The Tread The Tread
The tread is made from a mixture of many different kinds of The tread is made from a mixture of many different kinds of natural and synthetic rubbers. The tread and the sidewalls are extruded natural and synthetic rubbers. The tread and the sidewalls are extruded and cut to length. The tread is just smooth rubber at this point; it does and cut to length. The tread is just smooth rubber at this point; it does not have the tread patterns that give the tyre traction.
not have the tread patterns that give the tyre traction.
Assembly Assembly
All of these components are assembled in the tyre-building All of these components are assembled in the tyre-building
machine. This machine ensures that all of the components are in the machine. This machine ensures that all of the components are in the correct location and then forms the tyre into a shape and size fairly correct location and then forms the tyre into a shape and size fairly close to its finished dimensions.
close to its finished dimensions.
3. HOW TYRES SUPPORT A CAR
3. HOW TYRES SUPPORT A CAR
You may have wondered how a car tyre with 30 pounds per You may have wondered how a car tyre with 30 pounds per square inch ( psi ) of pressure can support a car. This is an interesting square inch ( psi ) of pressure can support a car. This is an interesting question, and it is related to several other issues, such as how much question, and it is related to several other issues, such as how much force it takes to push a
force it takes to push a tyre down the road and why tyres get hot whentyre down the road and why tyres get hot when you drive (and how this can lead to problems).
you drive (and how this can lead to problems).
The next time you get in your car, take a close look at the tyres. You The next time you get in your car, take a close look at the tyres. You will notice that they are not really round. There is a flat spot on the will notice that they are not really round. There is a flat spot on the bottom where the tyre meets the road. This flat spot is called the bottom where the tyre meets the road. This flat spot is called the
contact patch. contact patch.
If you were looking up at a car through a glass road, you If you were looking up at a car through a glass road, you could measure the size of the contact patch. You could also make a could measure the size of the contact patch. You could also make a pretty good estimate of the weight of your car, if you measured the area pretty good estimate of the weight of your car, if you measured the area of the contact patches of each tyre, added them together and then of the contact patches of each tyre, added them together and then multiplied the
few square inches of contact patch to carry the weight of the car. If you few square inches of contact patch to carry the weight of the car. If you add more weight or decrease the pressure, then you need even more add more weight or decrease the pressure, then you need even more square inches of contact patch, so the flat spot gets bigger.
square inches of contact patch, so the flat spot gets bigger.
A properly inflated tyre and an under inflated or A properly inflated tyre and an under inflated or
overloaded tyre overloaded tyre
You can see that the under inflated/overloaded tyre is less You can see that the under inflated/overloaded tyre is less round than the properly inflated, properly loaded tyre. When the tyre is round than the properly inflated, properly loaded tyre. When the tyre is spinning, the contact patch must move around the tyre to
spinning, the contact patch must move around the tyre to stay in contactstay in contact with the road. At the spot where the tyre meets the road, the rubber is with the road. At the spot where the tyre meets the road, the rubber is bent out. It takes force to bend that tyre, and the more it has to bend, the bent out. It takes force to bend that tyre, and the more it has to bend, the
more force it takes. The
more force it takes. The tyre is not tyre is not perfecperfectly elastitly elastic, so c, so when it returnswhen it returns to its original shape, it does not return all of the force that it took to to its original shape, it does not return all of the force that it took to bend it. Some of that force is converted to heat in the tyre by the bend it. Some of that force is converted to heat in the tyre by the friction and work of bending all of the rubber and steel in the tyre. friction and work of bending all of the rubber and steel in the tyre.
Since an under inflated or overloaded tyre needs to bend more, it takes Since an under inflated or overloaded tyre needs to bend more, it takes more force to push it down the road, so it generates more heat.
more force to push it down the road, so it generates more heat.
Tyre manufacturers sometimes publish a coefficient of rolling Tyre manufacturers sometimes publish a coefficient of rolling friction (CRF) for their tyres. You can use
friction (CRF) for their tyres. You can use this number to calculate howthis number to calculate how much force it takes to push a tyre down the road. The CRF has nothing much force it takes to push a tyre down the road. The CRF has nothing to do with how much traction the tyre has; it is used to calculate the to do with how much traction the tyre has; it is used to calculate the amount of drag or rolling resistance caused by the tyres. The CRF is amount of drag or rolling resistance caused by the tyres. The CRF is just like any other coefficient of rolling friction: The force required to just like any other coefficient of rolling friction: The force required to overcome the friction is equal to the CRF multiplied by the weight on overcome the friction is equal to the CRF multiplied by the weight on the tyre. This table lists typical CRF for several different types of the tyre. This table lists typical CRF for several different types of wheels.
wheels.
Tyre Type
Tyre Type Coefficient of RollingCoefficient of Rolling Friction
Friction L
Loow w rroolllliinngg resistance car tyre
resistance car tyre 0.006 - 0.010.006 - 0.01 O
Orrddiinnaarry y ccaar r ttyyrree 00..001155 T
Trruucck k ttyyrree 00..00006 6 - - 00..0011 T
Trraaiin n wwhheeeell 00..000011
Let's figure out how much force a typical car might use to Let's figure out how much force a typical car might use to push its tyres down the road. Let's say our car weighs 4,000 pounds push its tyres down the road. Let's say our car weighs 4,000 pounds (1814.369 kg), and the tyres have a CRF of 0.015. The force is equal to (1814.369 kg), and the tyres have a CRF of 0.015. The force is equal to 4,000 x 0.015, which equals 60 pounds (27.215 kg). Now let's figure 4,000 x 0.015, which equals 60 pounds (27.215 kg). Now let's figure out how much power that is. We know that power is equal to force out how much power that is. We know that power is equal to force times speed. So the amount of power used by the tyres depends on how times speed. So the amount of power used by the tyres depends on how
fast the car is going. At 75 mph (120.7 kph), the tyres are using 12hp, fast the car is going. At 75 mph (120.7 kph), the tyres are using 12hp, and at 55 mph (88.513 kph) they use 8.8 horsepower. All of that power and at 55 mph (88.513 kph) they use 8.8 horsepower. All of that power is turning into heat. Most of it goes into the tyres, but some of it goes is turning into heat. Most of it goes into the tyres, but some of it goes into the road (the road actually bends a little when the car drives over into the road (the road actually bends a little when the car drives over it).
it).
From these calculations you can see that the three things that From these calculations you can see that the three things that affect how much force it takes to push the tyre down the road (and affect how much force it takes to push the tyre down the road (and therefore how much heat builds up in the tyres) are the weight on the therefore how much heat builds up in the tyres) are the weight on the tyres, the speed you drive and the CRF (which increases if pressure is tyres, the speed you drive and the CRF (which increases if pressure is decrea
decreased). sed). If you drive on sofIf you drive on softer surfaceter surfaces, such as sand, more of thes, such as sand, more of the heat goes into the ground, and less goes into the tyres, but the CRF heat goes into the ground, and less goes into the tyres, but the CRF goes way up.
4. TYRE-INFLATION BASICS
4. TYRE-INFLATION BASICS
About 80 percent of the cars on the road are driving with one or more About 80 percent of the cars on the road are driving with one or more tyres underinflated. Tyres lose air through normal driving (especially tyres underinflated. Tyres lose air through normal driving (especially after hitting pot holes or curbs), permeation and seasonal changes in after hitting pot holes or curbs), permeation and seasonal changes in temperature. They can lose one or two psi (pounds per square inch) temperature. They can lose one or two psi (pounds per square inch) each month in the winter and even more in the summer. And, you can't each month in the winter and even more in the summer. And, you can't tell if they're properly inflated just by looking at them. You have to use tell if they're properly inflated just by looking at them. You have to use a tyre-pressure guage. Not only is underinflation bad for your tyres, but a tyre-pressure guage. Not only is underinflation bad for your tyres, but it's also bad for your gas mileage, affects the way your car handles and it's also bad for your gas mileage, affects the way your car handles and is generally unsafe.
is generally unsafe.
PROBLEMS WITH TYRES PROBLEMS WITH TYRES
When tyres are under-inflated, the tread wears more quickly. When tyres are under-inflated, the tread wears more quickly. According to Goodyear, this equates to 15 percent fewer miles you can According to Goodyear, this equates to 15 percent fewer miles you can dr
drivive e on on ththem em fofor r eveverery y 20 20 pepercrcenent t ththat at ththeyey'r're e unundederirinfnflalateted.d. Underinflated tyres also overheat more quickly than properly inflated Underinflated tyres also overheat more quickly than properly inflated tyres, which cause more tyre damage. The faded areas below indicate tyres, which cause more tyre damage. The faded areas below indicate areas of excessive tread wear.
Because tyres are flexible, they flatten at the bottom when Because tyres are flexible, they flatten at the bottom when they roll. This contact patch rebounds to its original shape once it is no they roll. This contact patch rebounds to its original shape once it is no longer in contact with the ground. This rebound creates a wave of longer in contact with the ground. This rebound creates a wave of motion along with some friction. When there is less air in the tyre, that motion along with some friction. When there is less air in the tyre, that wave is larger and the friction created is greater and friction creates wave is larger and the friction created is greater and friction creates heat. If enough heat is generated, the rubber that holds the tyre's cords heat. If enough heat is generated, the rubber that holds the tyre's cords together begin to melt and the tyre fails. Because of the extra resistance together begin to melt and the tyre fails. Because of the extra resistance an underinflated tyre has when it rolls, your car's engine has to work an underinflated tyre has when it rolls, your car's engine has to work harder
harder. A . A statistatistics show that tyres stics show that tyres that are underinflathat are underinflated by as ted by as littlittle asle as 2 psi
2 psi reduce fuel efficreduce fuel efficiency by 10 percent. Over a iency by 10 percent. Over a year of driving, thatyear of driving, that can amount to several hundred dollars in extra gas purchases.
5. HOW TYRE PRESSURE GAUGES WORK
5. HOW TYRE PRESSURE GAUGES WORK
Underinflation can cause tyres to wear more on the outside Underinflation can cause tyres to wear more on the outside than the inside. It also causes reduced fuel efficiency and increased heat than the inside. It also causes reduced fuel efficiency and increased heat buildup in the tyres. It is important to check the tyre pressure with a buildup in the tyres. It is important to check the tyre pressure with a guage at least once a month. so it is essential to have a tyre pressure guage at least once a month. so it is essential to have a tyre pressure monitoring system in our vehicles.
monitoring system in our vehicles.
Inside the Pressure Gauge the parts of a typical pressure gauge look Inside the Pressure Gauge the parts of a typical pressure gauge look like this:
like this:
There are three simple steps involved in measuring a tyre's There are three simple steps involved in measuring a tyre's pressure with a pressure gauge: Get in a steady position to apply the pressure with a pressure gauge: Get in a steady position to apply the pressure gauge to the valve stem.
pressure gauge to the valve stem.
•
• Apply the gauge, forming a good seal between the gauge and theApply the gauge, forming a good seal between the gauge and the
stem and releasing air from the tyre into the gauge. Note how the pin stem and releasing air from the tyre into the gauge. Note how the pin inside the gauge presses against the valve pin inside the valve stem to inside the gauge presses against the valve pin inside the valve stem to release air from the tyre.
•
• Read the pressure from the gauge.Read the pressure from the gauge.
Inside the tube that makes up
Inside the tube that makes up the body of the the body of the pressupressure gauge,re gauge, th
therere e is is a a smsmalall, l, titighght-st-seaealiling ng pipistston on mumuch ch lilike ke ththe e pipistston on ininsiside de aa bicy
bicycle pump. The cle pump. The insidinside e of the of the tube is polished smooth. The piston istube is polished smooth. The piston is made of soft rubber so it seals nicely against the tube, and the inside of made of soft rubber so it seals nicely against the tube, and the inside of the tube is lubricated with a light oil to improve the seal. In the picture the tube is lubricated with a light oil to improve the seal. In the picture below, you can see that the piston is at one end of the tube and the stop below, you can see that the piston is at one end of the tube and the stop is at the other. A spring runs the length of the tube between the piston is at the other. A spring runs the length of the tube between the piston and the stop, and this compressed spring pushes the piston toward the and the stop, and this compressed spring pushes the piston toward the left-hand side of the tube.
The funny spherical thing on the left end of the gauge is The funny spherical thing on the left end of the gauge is hollow. The opening in the sphere is designed to engage a tyre's valve hollow. The opening in the sphere is designed to engage a tyre's valve stem. If you look in the opening, you will be able to see a rubber seal stem. If you look in the opening, you will be able to see a rubber seal and a
and a smasmall fixed pin. The ll fixed pin. The rubbrubber seal er seal prespresses againses against the st the lip of lip of thethe valve stem to prevent air from leaking during the measurement, and the valve stem to prevent air from leaking during the measurement, and the pin depresses the valve pin in the valve stem to let air flow into the pin depresses the valve pin in the valve stem to let air flow into the gauge. The air will flow around the pin, through the hollow passage gauge. The air will flow around the pin, through the hollow passage inside the sphere and into the piston chamber. When the pressure gauge inside the sphere and into the piston chamber. When the pressure gauge is applied to the valve stem of a tyre, the pressurized air from the tyre is applied to the valve stem of a tyre, the pressurized air from the tyre rushes in and pushes the piston toward the right. The distance the rushes in and pushes the piston toward the right. The distance the pist
piston travels is on travels is relatrelative to ive to the pressure in the pressure in the tyre. The pressurized air the tyre. The pressurized air iis s pupushshining g tthe he pipistston on tto o ththe e ririghght, t, anand d ththe e spspriring ng is is pupushshiningg back. The gauge is designed to have some maximum pressure, and for back. The gauge is designed to have some maximum pressure, and for the sake of example let's say it is 60 psi. The spring has been calibrated the sake of example let's say it is 60 psi. The spring has been calibrated so that 60-psi air will move the piston to the far-right of the tube, while so that 60-psi air will move the piston to the far-right of the tube, while 30 psi moves the piston half-way along the tube, and so on. When you 30 psi moves the piston half-way along the tube, and so on. When you release the gauge from the valve stem, the flow of pressurized air stops release the gauge from the valve stem, the flow of pressurized air stops and the spring immediately pushes the piston back to the left. To allow and the spring immediately pushes the piston back to the left. To allow you to read the pressure, there is a calibrated rod inside the tube:
you to read the pressure, there is a calibrated rod inside the tube:
The spring is not shown in this figure, but the calibrated rod The spring is not shown in this figure, but the calibrated rod fits inside the spring. The calibrated rod rides on top of the piston, but fits inside the spring. The calibrated rod rides on top of the piston, but
between the rod and the stop. When the piston moves to the right, it between the rod and the stop. When the piston moves to the right, it pushes the calibrated rod. When the pressure is released, the piston pushes the calibrated rod. When the pressure is released, the piston moves back to the left but the rod stays in its maximum position to moves back to the left but the rod stays in its maximum position to allow you to read the pressure.
allow you to read the pressure.
6. SELF-INFLATING SYSTEMS
6. SELF-INFLATING SYSTEMS
Tyre-inflation systems have three general goals: Tyre-inflation systems have three general goals:
•
• Detect when the air pressure in a pDetect when the air pressure in a particular tyre has dropped -articular tyre has dropped
-This means they have to constantly (or intermittently) monitor the air This means they have to constantly (or intermittently) monitor the air pressure in each tyre.
pressure in each tyre.
•
• Notify the driver of the problem Notify the driver of the problem •
• Inflate that tyre back to the proper level - This means thereInflate that tyre back to the proper level - This means there
has to be an air supply as well as a check valve that opens only when has to be an air supply as well as a check valve that opens only when needed.
needed.
Parts of Any Self-inflating System Parts of Any Self-inflating System
While the available tyre inflation systems vary in design, they While the available tyre inflation systems vary in design, they share some common elements.
•
• They all use some type of valve to isolate individual tyres toThey all use some type of valve to isolate individual tyres to
prevent airflow from all tyres when one is being checked or prevent airflow from all tyres when one is being checked or
inflated. inflated.
•
• They have a method for sensing the tyre pressures. This isThey have a method for sensing the tyre pressures. This is
ad
addrdresessesed d in in momost st cacaseses s wiwith th cecentntraral l sesensnsorors s ththat at rerelalayy in
infoformrmatatioion n to to an an elelecectrotroninic c cocontntrorol l ununit it anand d ththen en to to ththee driver.
driver.
•
• They have an air source, which is usually an existing onboardThey have an air source, which is usually an existing onboard
source such as
source such as braking or pneumatic systebraking or pneumatic systems. When using ms. When using anan existing system, however, they have to ensure that they don't existing system, however, they have to ensure that they don't je
jeopaopardizrdize e its its origoriginainal l funfunctiction. on. For For thithis s reareasonson, , thethere re areare safety checks to ensure that there is enough air pressure for safety checks to ensure that there is enough air pressure for the source's primary use before pulling air for tyre inflation. the source's primary use before pulling air for tyre inflation.
•
• There has to be a way to get the air from the air source to theThere has to be a way to get the air from the air source to the
tyres, which is usually through the axle. Systems either use a tyres, which is usually through the axle. Systems either use a sealed-hub axle with a hose from the hub to the tyre valve or sealed-hub axle with a hose from the hub to the tyre valve or else they run tubes through the axle with the axle acting as a else they run tubes through the axle with the axle acting as a conduit.
conduit.
•
• There has to be a pressure relief vent to vent air from the tyreThere has to be a pressure relief vent to vent air from the tyre
without risking damage to the hub or rear-axle seals. without risking damage to the hub or rear-axle seals.
7. CENTRAL TYRE INFLATION SYSTEM
7. CENTRAL TYRE INFLATION SYSTEM
(CTIS)
(CTIS)
The idea behind the CTIS is to provide control over the air The idea behind the CTIS is to provide control over the air pressure in each tyre as a way to improve performance on different pressure in each tyre as a way to improve performance on different surfaces. For example, lowering the air pressure in a tyre creates a surfaces. For example, lowering the air pressure in a tyre creates a larger area of contact between the tyre and the ground and makes larger area of contact between the tyre and the ground and makes driving on softer ground much easier. It also does less damage to the driving on softer ground much easier. It also does less damage to the surface. This is important on work sites and in agricultural fields. By surface. This is important on work sites and in agricultural fields. By giving the driver direct control over the air pressure in each tyre, giving the driver direct control over the air pressure in each tyre, maneuverability is greatly improved.
maneuverability is greatly improved.
Another function of the CTIS is to maintain pressure in the Another function of the CTIS is to maintain pressure in the tyres if there is a slow leak or puncture. In this case, the system controls tyres if there is a slow leak or puncture. In this case, the system controls inflation automatically based on the selected pressure the driver has set. inflation automatically based on the selected pressure the driver has set.
There are two main manufacturers of the CTIS: U.S.-based There are two main manufacturers of the CTIS: U.S.-based Dan
Dana a CorCorporaporatiotion n and and FraFrancence-bas-based ed SyeSyegon gon (a (a divdivisiision on of of GIAGIAT).T). Da
Dana na CoCorprpororatatioion n hahas s twtwo o veversrsioionsns, , ththe e CTCTIS IS fofor r mimililitatary ry ususee (developed by PSI) and the Tyre Pressure Control System (TPCS) for (developed by PSI) and the Tyre Pressure Control System (TPCS) for
com
commercmercialial, heavy mach, heavy machineinery use. ry use. In the In the nexnext sectiot section, we'll takn, we'll take e aa look at the inner workings of a basic CTIS setup.
look at the inner workings of a basic CTIS setup.
CTIS: Inside CTIS: Inside
Here is a look at the overall system: Here is a look at the overall system:
A wheel valve is
A wheel valve is locatlocated at ed at each wheel end. For dual wheels,each wheel end. For dual wheels, th
the e vavalvlves es arare e tytypipicacalllly y coconnennectcted ed ononly ly to to ththe e ououteter r whwheeeel l so so ththee pressure between the two tyres can be balanced. Part of the wheel pressure between the two tyres can be balanced. Part of the wheel
valve
valve's job 's job is to is to isolaisolate the te the tyre from the system when it's not in tyre from the system when it's not in use inuse in order to let the pressure off of the seal and extend its life. The wheel order to let the pressure off of the seal and extend its life. The wheel valve also enables on-demand inflation and deflation of the tyres.
valve also enables on-demand inflation and deflation of the tyres.
An electronic control unit (ECU) mounted behind the An electronic control unit (ECU) mounted behind the
passenger seat is the brain of the system. It processes driver commands, passenger seat is the brain of the system. It processes driver commands, monitors all signals throughout the system and tells the system to check monitors all signals throughout the system and tells the system to check tyre pressures every 10 minutes to make sure the selected pressure is tyre pressures every 10 minutes to make sure the selected pressure is being maintained.
being maintained.
The ECU sends commands to the pneumatic control unit, which The ECU sends commands to the pneumatic control unit, which di
direcrectltly y cocontntrolrols s ththe e whwheeeel l vavalvlves es anand d aiair r sysyststemem. . ThThe e pnpneumeumataticic control unit also contains a sensor that transmits tyre-pressure readings control unit also contains a sensor that transmits tyre-pressure readings to the ECU.
to the ECU.
An
An opeoperatrator or concontrotrol l panepanel l allallows the ows the dridriver ver to to selselect tyre-ect tyre- pressure modes to match current conditions. This dash-mounted panel pressure modes to match current conditions. This dash-mounted panel
dis
displaplays ys curcurrent rent tyrtyre e prepressussures, res, selselectected ed modmodes es and and syssystem tem stastatustus.. When the driver selects a tyre-pressure setting, signals from the control When the driver selects a tyre-pressure setting, signals from the control panel travel to the
panel travel to the electelectronic control unit to ronic control unit to the pneumatithe pneumatic c controcontrol unitl unit to the whe
to the wheel valel valvesves. . WhWhen vehien vehiclcles are es are momoviving fastng faster (lier (like on ke on aa highway), tyre pressure should be higher to prevent tyre damage. The highway), tyre pressure should be higher to prevent tyre damage. The CTIS includes a speed sensor that sends vehicle speed information to CTIS includes a speed sensor that sends vehicle speed information to the electroni
the electronic c controcontrol l unit. If the unit. If the vehiclvehicle e conticontinues moving at nues moving at a a highehigher r speed for a set period of time, the system automatically inflates the speed for a set period of time, the system automatically inflates the tyres to an appropriate pressure for that speed.
This type of system uses air from the same compressor that This type of system uses air from the same compressor that su
supppplilies es aiair r to to ththe e brabrakekes. s. A A prepressssurure e swswititch ch mamakekes s susure re ththe e brabrakeke system gets priority, preventing the CTIS from taking air from the system gets priority, preventing the CTIS from taking air from the supply tank until the brake system
supply tank until the brake system is fully charged.is fully charged.
8.
8. TYRE
TYRE MAINTENANCE
MAINTENANCE SYSTEM
SYSTEM (TMS)
(TMS)
Da
Dana na CoCorprporaoratitionon's 's TTyre yre MaMainintetenanancnce e SySyststem em is is a a "s"smamartrt"" system for tractor trailers that monitors tyre pressure and inflates system for tractor trailers that monitors tyre pressure and inflates tyres as necessary to keep pressure at the right level. It uses air tyres as necessary to keep pressure at the right level. It uses air from the trailer's brake supply tank
The system has three main components: The system has three main components:
•
• The tyre hose assembly provides the air route to inflate theThe tyre hose assembly provides the air route to inflate the
tyre and has check valves so that the air lines and seals do not have tyre and has check valves so that the air lines and seals do not have to be pressurized when the system is not checking or inflating the to be pressurized when the system is not checking or inflating the tyres. This cuts down on wear and tear on the seals.
tyres. This cuts down on wear and tear on the seals.
•
• The rotary joint is comprised of air and oil seals and bearingsThe rotary joint is comprised of air and oil seals and bearings
and connects the air hose from the non-rotating axle to the rotating and connects the air hose from the non-rotating axle to the rotating hubcap. Its air seals prevent leakage, and the oil seal prevents hubcap. Its air seals prevent leakage, and the oil seal prevents co
contntamamininatatioion. n. ThThe e rorotatary ry huhub b alalso so hahas s a a vevent nt to to rereleleasase e aiair r pressure in the hubcap.
pressure in the hubcap.
•
• The The manmanifoifold ld houhouses ses the the prepressussure re proprotectectiotion n valvalve, ve, whiwhichch
makes sure the system doesn't pull air if the brakes' air supply is makes sure the system doesn't pull air if the brakes' air supply is below 80 psi. It also houses an inlet filter to keep the air clean, a below 80 psi. It also houses an inlet filter to keep the air clean, a p
presressusure re sesensnsor or to to memeasasurure e tytyre re prpresessusures res anand d sosolelenonoidids s ththatat control airflow to the tyres.
control airflow to the tyres.
Like the CTIS, this
Like the CTIS, this systesystem m also has an also has an electelectronic control unitronic control unit that runs the entyre system. It performs checks to make sure the system that runs the entyre system. It performs checks to make sure the system is operational, notifies the driver via a warning light on the trailer is operational, notifies the driver via a warning light on the trailer (visible through the rear-view mirror) if a tyre's pressure drops more (visible through the rear-view mirror) if a tyre's pressure drops more th
than an 10 10 pepercrcenent t bebelolow w itits s nonormrmal al prpresessusure re anand d peperfrfororms ms sysyststemem diagnostics.
The system perform
The system performs an s an initiinitial pressure check and adds al pressure check and adds air toair to any tyre that needs it. The check valves in each tyre hose ensure that any tyre that needs it. The check valves in each tyre hose ensure that the other tyres don't lose pressure while one tyre is being inflated. After the other tyres don't lose pressure while one tyre is being inflated. After an initial pressure check, the system depressurizes to relieve pressure an initial pressure check, the system depressurizes to relieve pressure from the seals. Every 10 minutes, the system pressurizes the lines and from the seals. Every 10 minutes, the system pressurizes the lines and rechecks tyre pressures.
rechecks tyre pressures.
The system measures tyre pressure using a series of air pulses The system measures tyre pressure using a series of air pulses in the air lines. If the target pressure in the line is not reached after a in the air lines. If the target pressure in the line is not reached after a certain amount of time, the system begins inflating the tyres until the certain amount of time, the system begins inflating the tyres until the correct pressure is reached.
9. THE FUTURE OF SELF-INFLATING TYRES
9. THE FUTURE OF SELF-INFLATING TYRES
Michelin is working with several other companies to develop an Michelin is working with several other companies to develop an act
active ive prepressurssure-me-manaanagemgement ent syssystem tem calcalled led TIPTIPM M (T(Tyre yre IntIntellelligeigentnt Pressure Management), due to be available sometime in 2005. This Pressure Management), due to be available sometime in 2005. This system has a compressor that automatically adjusts the pressure in each system has a compressor that automatically adjusts the pressure in each tyre while the vehicle is in operation to compensate for leaks and tyre while the vehicle is in operation to compensate for leaks and slow-leak punctures. The driver will be able to adjust the pressure depending leak punctures. The driver will be able to adjust the pressure depending on
on ththe e dedesisirered d dridriviving ng momodede: : cocomfmfortort, , spsporortyty, , alall-l-teterrarrain in or or ovover er--obstacle.
obstacle.
There are at least two other systems in the early development There are at least two other systems in the early development st
stagages es ththat at are orieare orientnted ed totowaward rd ththe e coconsnsumumer er mamarkerket t ththe e EnEn-t-tyryree system and the Cycloid Air Pump system.
system and the Cycloid Air Pump system.
The entire self inflating system uses a valve that pulls in air The entire self inflating system uses a valve that pulls in air from the atmosphere. It then
from the atmosphere. It then pumps the air pumps the air into the under-inflainto the under-inflated tyreted tyre using a peristaltic-pump action. The goal is to constantly maintain a using a peristaltic-pump action. The goal is to constantly maintain a
The En-tyre system is based on this type of peristaltic pump The En-tyre system is based on this type of peristaltic pump
mechanism. mechanism.
The Auto Pump tyre-inflator system has a small, The Auto Pump tyre-inflator system has a small, wheel-hub-mounted pump that is powered by the turning of the wheels. When the mounted pump that is powered by the turning of the wheels. When the system's monitor detects a drop in pressure of 2 to 3 psi, it pumps air system's monitor detects a drop in pressure of 2 to 3 psi, it pumps air into the underinflated tyre. Auto Pump has a warning system that is into the underinflated tyre. Auto Pump has a warning system that is activated when there is a puncture.
activated when there is a puncture.
Self-inflating Tyres for Bicycles and Motorcycles Self-inflating Tyres for Bicycles and Motorcycles
Now cyclists can also motor with the peace of mind that a flat Now cyclists can also motor with the peace of mind that a flat ty
tyre re isisn'n't t gogoining g to to ruruin in ththeieir r riride. de. BriBridgdgesestotone ne CyCyclcle e of of JaJapapan n hahass developed the Air Hub, which uses a rotating air pump that replenishes developed the Air Hub, which uses a rotating air pump that replenishes air in the tyre as you pedal. Like the En-tyre method, it keeps the air in air in the tyre as you pedal. Like the En-tyre method, it keeps the air in the tyres at a constant pressure level
the tyres at a constant pressure level. The air . The air pump is in the pump is in the hub and ishub and is run by the rotation of the wheel. A small tube runs compressed air to run by the rotation of the wheel. A small tube runs compressed air to
the tyre is where it should be, excess air is exhausted through a device the tyre is where it should be, excess air is exhausted through a device in the middle of the hose.
in the middle of the hose.
Pirelli has also come up with a self-inflating tyre system for Pirelli has also come up with a self-inflating tyre system for mot
motorcorcyclycles es and and scoscooteoters. rs. The The PirPirellelli i SafSafety Wheel ety Wheel SysSystem tem useuses s aa mo
moninitotoriring ng sysyststem em alalonong g wiwith th a a spespecicial al ririm m anand d an an ininteternarnal l tutubebe containing compressed air. It also has a valve to regulate the pressure containing compressed air. It also has a valve to regulate the pressure between the tube and the tyre. When the tyre deflates naturally, the between the tube and the tyre. When the tyre deflates naturally, the valve opens and pumps air into the tyre until it reaches the correct valve opens and pumps air into the tyre until it reaches the correct pressure. If there is a puncture, the system warns the rider as it allows pressure. If there is a puncture, the system warns the rider as it allows
air to move into the tyre. air to move into the tyre.
10. CONCLUSION
10. CONCLUSION
Thus self inflating tyres help us in attaining certain helpful Thus self inflating tyres help us in attaining certain helpful criterions.
criterions. 1.
1. It helps in the monitoring of tyre pressure constantlyIt helps in the monitoring of tyre pressure constantly 2.
2. Thus it provides inflation or deflation of the tyreThus it provides inflation or deflation of the tyre 3.
3. It helps in attaining better It helps in attaining better mileagemileage 4.
11. REFERENCES
11. REFERENCES
1.
1. Crouse.Anglin,” Automotive Mechanics”, Tata McGraw Hills.Crouse.Anglin,” Automotive Mechanics”, Tata McGraw Hills. 2
2.. wwwwww..hhoowwssttuuffffsswwoorkrk..ccoomm 3
3.. wwwwww..ccyyccllooiidd..ccoomm 4.