Self Inflating System

SELF INFLATING TYRE SYSTEM.

AUTHORS KORE VARUN. Email : [email protected] PRRMEC (PARENT COLLEGE)

Sree Viveswarayya Institute Of Technology And Science.(JKC)

SELF INFLATING TYRES ABSTRACT Have you ever been frustrated when any of your important tasks has been obstructed by a FLAT TYRE? Have you ever imagined your tyres swell up as if by magic? If your answer yes, then we have a solution for your woes. According to AAA, about 80 percent of the cars on the road are driving with one or more tyres under inflated. Tires lose air through normal driving (especially after hitting pot holes or curbs), permeation and seasonal changes in 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 tell if they're properly inflated just by looking at them. You have to use a tire-pressure gauge. Not only is under inflation bad for your tires, but it's also bad for your gas mileage, affects the way your car handles and is generally unsafe.

Currently, lots of consumer vehicles are equipped with pressure-monitoring systems, but there's no way for the driver to do anything about it without an external air source. But that is where the ENTIRE TYRE SYSTEM comes in as a revolutionary new concept for inflating tyres without the use of external air source. It uses a pump system known as peristaltic pump to achieve this which has been built into the tyre using some higly advanced tyre building techniques. In this paper, we're going to deal about some of the tyre-inflation systems out there and how the entire tyre system is set to change everything and take the world by strom.

KORE VARUN, (Sree Viveswarayya Institute Of Technology)(JKC) (PRRMEC) [email protected]

BASIC TERMINOLOGY OF TYRES

The Bead Bundle The bead is a loop of high-strength steel cable coated with rubber. It gives the tire the strength it needs to stay seated on the wheel rim and to handle the forces applied by tire mounting machines when the tires are installed on rims. The Body The body is made up of several layers of different fabrics, called plies. The most common ply fabric is polyester cord. The cords in a radial tire run perpendicular to the tread. Some older tires used diagonal bias tires, tires in which the fabric ran at an angle to the tread. The plies are coated with rubber to help them bond with the other components and to seal in the air.

A tire's strength is often described by the number of plies it has. Most car tires have two body plies. By comparison, large commercial jetliners often have tires with 30 or more plies. The Belts In steel-belted radial tires, belts made from steel are used to reinforce the area under the tread. These belts provide puncture resistance and help the tire stay flat so that it makes the best contact with the road. Cap Plies Some tires have cap plies, an extra layer or two of polyester fabric to help hold everything in place. These cap plies are not found on all tires; they are mostly used on tires with higher speed ratings to help all the components stay in place at high speeds. The Sidewall The sidewall provides lateral stability for the tire, protects the body plies and helps keep the air from escaping. It may contain additional components to help increase the lateral stability. The Tread The tread is made from a mixture of many different kinds of 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 not have the tread patterns that give the tire traction. Assembly All of these components are assembled in the tire-building machine. This machine ensures that all of the components are in the correct location and then forms the tire into a shape and size fairly close to its finished dimensions. At this point the tire has all of its pieces, but it's not held together very tightly, and it doesn't have any markings or tread patterns. This is called a green tire. The next step is to run the tire into a curing machine, which functions something like a waffle iron, molding in all of the markings and traction patterns. The heat also bonds all of the tire's components together. This is called vulcanizing. After a few finishing and inspection procedures, the tire is finished.

Pneumatic tires Air-filled tires are known as pneumatic tires, and these are the type in almost universal use today. Pneumatic tires are made of a flexible elastomer material such as rubber with reinforcing threads/wires inside the elastomer material. The air compresses as the wheel goes over a bump and acts as a shock absorber. Tires are inflated through a Schrader valve Attempts have been made to make various types of solid tire

but none has so far met with much success. The "steering feel" of such tires is different from that of pneumatic tires,

as

their solidity does not allow the amount of torsion that

exists in the carcass of a pneumatic tire under steering forces, and the resultant sensory feedback through the steering apparatus. The common motor vehicle tire is mounted around a steel rim at service stations or repair shops for vehicles using a special tire mounting apparatus while the wheel is off the vehicle. After mounting, the tire is inflated (pressurized) with air through the valve stem to manufacturer's specified pressure, which is more than atmospheric pressure. The rim with the tire mounted onto it comprises the removable wheel, which is then attached to the vehicle through a number of holes in the rim using lug nuts. Because tires are often not made with perfectly even mass all around the tire, a special tire-balancing apparatus at a repair shop spins the wheel with the tire to determine where small weights should be attached to the outer edge of the rim to balance out the wheel. Such tire balancing with these kind of weights avoids vibration when the vehicle is driven at higher speeds. With the introduction of radial tires, however, it was found that some vibrations could not be cured by adding balance weights. This was because the structure and manufacture of a radial tire lends itself to the problems of variation in stiffnes around the tyre. These variations are measured as Radial Force Variation and Lateral Force Variation, which are measured on a Force Variation Machine at the end of the manufaturing process. Tires outside the specified limits for RFV and LFV are rejected. This is known in general throughout the industry as Tyre Uniformity.

How Tires Support a Car You may have wondered how a car tire with 30 pounds per 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 force it takes to push a tire down the road and why tires get hot when you drive (and how this can lead to problems). The next time you get in your car, take a close look at the tires. You will notice that they are not really round. There is a flat spot on the bottom where the tire meets the road. This flat spot is called the contact patch 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 pretty good estimate of the weight of your car, if you measured the area of the contact patches of each tire, added them together and then multiplied the sum by the tire pressure. Since there is a certain amount of pressure per square inch in the tire, say 30 psi, then you need quite a 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 square inches of contact patch, so the flat spot gets bigger.

A properly inflated tire and an underinflated or overloaded tire

You can see that the under inflated/overloaded tire is less round than the properly inflated, properly loaded tire. When the tire is spinning, the contact patch must move

around the tire to stay in contact with the road. At the spot where the tire meets the road, the rubber is bent out. It takes force to bend that tire, and the more it has to bend, the more force it takes. The tire is not perfectly elastic, so when it returns 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 tire by the friction and work of bending all of the rubber and steel in the tire. Since an under inflated or overloaded tire needs to bend more, it takes more force to push it down the road, so it generates more heat. Tire manufacturers sometimes publish a coefficient of rolling friction (CRF) for their tires. You can use this number to calculate how much force it takes to push a tire down the road. The CRF has nothing to do with how much traction the tire has; it is used to calculate the amount of drag or rolling resistance caused by the tires. The CRF is just like any other coefficient of friction: The force required to overcome the friction is equal to the CRF multiplied by the weight on the tire. This table lists typical CRFs for several different types of wheels.

Tire Type Low rolling resistance car tire

Coefficient of Rolling Friction 0.006 - 0.01

Ordinary car tire

0.015

Truck tire

0.006 - 0.01

Train wheel

0.001

Let's figure out how much force a typical car might use to push its tires down the road. Let's say our car weighs 4,000 pounds (1814.369 kg), and the tires have a CRF of 0.015. The force is equal to 4,000 x 0.015, which equals 60 pounds (27.215 kg). So the amount of power used by the tires depends on how fast the car is going. At 75 mph (120.7 kph), the tires are using 12 horsepower, 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 tires, but some of it goes into the road (the road actually bends a little when the car drives over it).

Problems with Tires

Over inflation causes tires to wear more in the center of the tread. The tire pressure should never exceed the maximum that is listed on the side of the tire. Car manufacturers often suggest a lower pressure than the maximum because the tires will give a softer ride. But running the tires at a higher pressure will improve mileage.

Under inflation can cause tires to wear more on the outside than the inside. It also causes reduced fuel efficiency and increased heat buildup in the tires. It is important to check the tire pressure with a gauge at least once a month. When tires are under inflated, the tread wears more quickly. According to Goodyear, this equates to 15 percent fewer miles you can drive on them for every 20 percent that they're under inflated. Under inflated tires also overheat more quickly than properly inflated tires, which cause more tire damage. The faded areas below indicate areas of excessive tread wear.

Because of the extra resistance an under inflated tire has when it rolls car's engine has to work harder. AAA statistics show that tires that are under inflated by as little as 2 psi reduce fuel efficiency by 10 percent. Over a year of driving, that can amount to several hundred dollars in extra gas purchases

Self-inflating Systems SystemsTyre-inflation systems have three general goals: •

Detect when the air pressure in a particular tire has dropped - This means they have to constantly (or intermittently) monitor the air pressure in each tire.

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Notify the driver of the problem

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Inflate that tire back to the proper level - This means there has to be an air supply as well as a check valve that opens only when needed.

Parts of Any Self-inflating System While the available tire inflation systems vary in design, they share some common elements. •

They all use some type of valve to isolate individual tires to prevent airflow from all tires when one is being checked or inflated.

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They have a method for sensing the tire pressures. This is addressed in most cases with central sensors that relay information to an electronic control unit and then to the driver.

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They have an air source, which is usually an existing onboard source such as braking or pneumatic systems. When using an existing system, however, they have to ensure that they don't jeopardize its original function. For this reason, there are safety checks to ensure that there is enough air pressure for the source's primary use before pulling air for tire inflation.

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There has to be a way to get the air from the air source to the tires, which is usually through the axle. Systems either use a sealed-hub axle with a hose from

the hub to the tire valve or else they run tubes through the axle with the axle acting as a conduit. •

There has to be a pressure relief vent to vent air from the tire without risking damage to the hub or rear-axle seals.

There have been many developments in this field .Among them are as follows

Central Tire Inflation System (CTIS)

A wheel valve is located at each wheel end. For dual wheels, the valves are typically connected only to the outer wheel so the pressure between the two tires can be balanced. Part of the wheel valve's job is to isolate the tire from the system when it's not in use in 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 tires. An electronic control unit (ECU) mounted behind the passenger seat is the brain of the system. It processes driver commands, monitors all signals throughout the system and tells the system to check tire pressures every 10 minutes to make sure the selected pressure is being maintained. The ECU sends commands to the pneumatic control unit, which directly controls the wheel valves and air system. The pneumatic control unit also contains a sensor that transmits tire-pressure readings to the ECU. An operator control panel allows the driver to select tire-pressure modes to match current conditions. This dash-mounted panel displays current tire pressures, selected modes and system status. When the driver selects a tire-pressure setting, signals from the

control panel travel to the electronic control unit to the pneumatic control unit to the wheel valves. When vehicles are moving faster (like on a highway), tire pressure should be higher to prevent tire damage. The CTIS includes a speed sensor that sends vehicle speed information to the electronic control unit. If the vehicle continues moving at a higher speed for a set period of time, the system automatically inflates the tires to an appropriate pressure for that speed. This type of system uses air from the same compressor that supplies air to the brakes. A pressure switch makes sure the brake system gets priority, preventing the CTIS from taking air from the supply tank until the brake system is fully charged.

A Closer Look Here is what happens on the road: The electronic control unit tells the pneumatic control unit to check current pressure and either inflate or deflate the tire to the pressure selected by the driver. If the system determines that inflation is needed, it first checks to make sure that brake pressure reserves are where they should be; if they are, it applies a slight pressure to the wheel valve to allow inflation. If the tires are overinflated, the system applies a slight vacuum to the wheel valve. When the pneumatic control unit reads that the appropriate pressure is reached, the valve closes.

Tire Maintenance System (TMS) Dana Corporation's Tire Maintenance System is a "smart" system for tractor trailers that monitors tire pressure and inflates tires as necessary to keep pressure at the right level. It uses air from the trailer's brake supply tank to inflate the tires.

The system has three main components: •

The tire hose assembly provides the air route to inflate the tire 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 tires. This cuts down on wear and tear on the seals.

•

The rotary joint is comprised of air and oil seals and bearings and connects the air hose from the non-rotating axle to the rotating hubcap. Its air seals prevent leakage, and the oil seal prevents contamination. The rotary hub also has a vent to release air pressure in the hubcap.

The manifold houses the pressure protection valve, which 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 pressure sensor to measure tire pressures and solenoids that control airflow to the tires.

Like the CTIS, this system also has an electronic control unit that runs the entire system. It performs checks to make sure the system is operational, notifies the driver via a warning light on the trailer (visible through the rear-view mirror) if a tire's pressure drops more than 10 percent below its normal pressure and performs system diagnostics. The system performs an initial pressure check and adds air to any tire that needs it. The check valves in each tire hose ensure that the other tires don't lose pressure while one tire is being inflated. After an initial pressure check, the system depressurizes to relieve pressure from the seals. Every 10 minutes, the system pressurizes the lines and rechecks tire pressures. The system measures tire pressure using a series of air pulses 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 tire(s) until the correct pressure is reached.

The Future of Self-inflating Tires EnTIRE SYSTEM EnTire system is based on the peristaltic pump principle i.e. the peristaltic principle was patented in 1925 and has been used in many products since then. The peristaltic pump operates by compressing a plastic tube between an element attached to a rotor and the internal wall of the pump case or housing. Fluid in the tube is forced from the inlet side of the pump toward the discharge by the squeezing or compressing motion of the element on the rotor of the pump as it rotates. This peristaltic action is in some ways similar in nature to that of the human digestive tract. Peristaltic pumps are simple, cheap, reliable and precise and can be very small. Those are the reasons why they are preferred in medical applications and chemistry industry. •

EnTire system consists of a thin tube that has a peristaltic part and a reservoir part, which has constant volume. The ratio of the total tube volume (peristaltic

part volume + reservoir part volume) to the volume of the reservoir part defines the output pressure of EnTire. •

EnTire tube is "sucking in" atmospheric air through a simple valve similar to today’s tire valve, which lets air in and does not let it out.

•

Summarized, integrating a simple thin tubing into a tire and mounting a simple valve on one end of the tubing will secure inflation of the tire with small amounts of air at constant pressure at every revolution of the tire until the tire pressure reaches EnTire's predefined output pressure. Then inflation stops. Changes are not necessary to any other car part than the tire. Depending on the EnTire configuration, wheel valve may need to change too. . EnTire system may be made even in separated rubber strip enclosed between the tire and rim. One option is in form of cavity in tire wall. Such cavity is then covered and sealed by rim when tire and rim are assembled together. The final look of EnTire system will result from R&D results and from market expectations for EnTire functionality. Some "candidates" for placement of EnTire within the tire are animated down on this page. 1. A valve is connected to a tube the red part of which is the reservoir part, which has constant minimal volume (it means that inner volume never falls bellow some known limit), and green part is the peristaltic part of tube. 2. When deformation of the tire (yellow block) encloses air inside the tube (blue color) between deformation and valve, pressure of enclosed air is equal to the tire pressure. Volume of this enclosed air is determined by volume of the reservoir part of tube.

3. A yellow block shows movement of the deformation and actual position of the deformation. Deformation moves in the direction of the yellow arrow and expands air into the whole tube. When the tire pressure falls below the external pressure the tube sucks air through the valve from outside the tire. Air inserting the tire is shown by blue arrow pointing to the valve. Setting EnTire system output pressure: Output pressure is determined by the ratio between the reservoir volume of tube and the total volume of the tube. When the reservoir volume = 1/30 cubic inch and total tube volume (sum of reservoir and peristaltic part of tube) = 1/10 cubic inch then output pressure will be 1/10 ci divided by 1/30 ci = 3. Then we multiply it by the pressure outside the tire 14 psi = 42 psi. When the peristaltic part of tube is deformed, it distributes all the air enclosed originally in reservoir volume = 1/30 ci into the whole chamber volume = 1/10 ci and pressure inside the tube decreases 3 times. If the tire pressure was equal or higher then 42 psi ii and the pressure inside tube decreased 3 times then the pressure inside tube will not be lower then atmospheric pressure 14 psi and the tube will not allow air to enter through valve. If the tire pressure is lower than 42 psi and the pressure inside the tube decreases 3 times, the pressure inside the tube become to be lower then atmospheric pressure 14 psi and the chamber will allow air through the valve from outside the tire. i.

Volume of 1/10 cubic inch is a very small volume similar to 4 pieces of common

matches sticks. Total volume of air inside a properly inflated tire is approximately 2 000 ci and pressure 28 psi (42 psi ii). Outside the tire (at atmospheric pressure 0 psi (14 psi ii)) the same air would occupy a volume of approximately 6 000 ci. A typical car tire spins approximately 800 times during a 1-mile ride. If we would pump every revolution 1/30 ci into the tire, it would increase the tire pressure by 10% during a 8 to 24 mile ride, depending on the level of under inflation of the tire. Please note that we used 1/30 ci only as an example. The EnTire tube volume may be larger than this example.

ii.

If tires are inflated to a pressure of 3 times greater then atmospheric pressure, your tire

gauge will show only pressure of 28 psi and not 42 psi because tire gauges measure only pressure above atmospheric pressure.

Self inflating bicycle tyres The newly developed Air Hub works by converting the kinetic energy of the rotating wheels into the reciprocating motion of an air pump inside a hub at the center of the wheel. The compressed air is fed into the tire tube via a special hose, while appropriate air pressure is maintained by emitting surplus air from an air hole in the hose. The process of making this idea a reality, however, was difficult. For example, on very rainy days the pump would send water into the tube; this problem was solved by improvements to the shape of the air hole. The device is said to maintain appropriate air pressure in the tires as long as the bicycle is ridden at least 3 kilometers a month.

Self Inflating Bicycle Tyres For some reason or other we found ourselves over at SmartStuff and noticed they had some very cute green stuff. They’ve even begun to code certain finds under ‘environment’. On this visit we were intrigued by something that they'd originally seen at Red Ferret: the Nakano Air Hub. The "world's first automatic air replacement device for bicycle tires." Energy from the spinning wheel sets up a rotary cam action, that feeds a pump inside the hub, which in turns keep your tyres at the correct air pressure. Without any over-inflation, due a special valve. But there is a catch for real lazy types. The bike must be ridden at least 1.8 miles (3 km) a month to work properly. Currently it’s only available in Japan, on bikes by Bridgestone

CONCLUSION With the improving technology mans life is becoming simpler .Probably the SELF INFLATING TYRES is the best example for this. It wont be long before people stop visiting the air filling stations. I have put forth a simple technology but very useful one.