Self inflating tyre system is an automatic mechanism for maintaining proper level of pressure inside the vehicle tyres.Or in other words it is an automatic inflation or deflation system used in tyres.This system reduces the wear of the tread of the tyre and increases driving comfort. It also increases fuel efficiency and ensures safe driving.The main self inflating systems used are CTIS and TMS systems.
Tyre-inflation systems have three general goals:
- Detect when the air pressure in a particular tyre has dropped - This means they have to constantly (or intermittently) monitor the air pressure in each tyre.
- Notify the driver of the problem
- Inflate 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 needed.
- Parts of Any Self-inflating System
- They all use some type of valve to isolate individual tyres to prevent airflow from all tyres when one is being checked or inflated.
- They have a method for sensing the tyre pressures. This is addressed in most cases with central sensors that relay information to an electronic control unit and then to the driver.
- They have an air source, which is usually an existing inboard 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 tyre inflation.
- There 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 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 conduit.
- There has to be a pressure relief vent to vent air from the tyre without risking damage to the hub or rear-axle seals
Central Tyre Inflation System (CTIS)
The idea behind the CTIS is to provide control over the air pressure in each tyre as a way to improve performance on different surfaces. For example, lowering the air pressure in a tyre creates a 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 surface. This is important on work sites and in agricultural fields. By giving the driver direct control over the air pressure in each tyre, maneuverability is greatly improved.
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 inflation automatically based on the selected pressure the driver has set.
There are two main manufacturers of the CTIS: U.S.-based Dana Corporation and France-based Syegon (a division of GIAT). Dana Corporation has two versions, the CTIS for military use (developed by PSI) and the Tyre Pressure Control System (TPCS) for commercial, heavy machinery use. In the next section, we'll take a look at the inner workings of a basic CTIS setup.
Here is a look at the overall system:
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 tyres can be balanced. Part of the wheel valve's job is to isolate the tyre 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 tyres.
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 tyre 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 tyre-pressure readings to the ECU.
An operator control panel allows the driver to select tyre-pressure modes to match current conditions. This dash-mounted panel displays current tyre pressures, selected modes and system status. When the driver selects a tyre-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), tyre pressure should be higher to prevent tyre 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 tyres 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.
Design and Fabrication of Automatic Tyre Inflation System-Mechanical Project
(Buy Project) 22.TYRE INFLATION & DEFLATION SYSTEM FOR FOUR WHEELER
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