Parker's Central Tire Inflation System (CTIS) offers improved mobility when operating vehicles in severe off-road or soft soil conditions. Ideally suited for the agriculture and military markets, this automatic tire pressure adjustment system allows the driver to optimize tire inflation pressure from the cab while operating on varying terrains with the simple push of a button. Reducing tire pressure results in a bigger tire footprint, providing increased flotation and traction when operating in soft soil terrain. Although often used in conjunction with all-wheel drive, non-all-wheel drive vehicles with CTIS can actually outperform all-wheel drive in many soft soil conditions.
Operating vehicles with reduced tire inflation pressure is approved by tire manufacturers when operating at reduced vehicle speeds. Contrary to common perception, operating at reduced tire inflation pressure can extend tire life due to reduced susceptibility to tire punctures and tread chunking. CTIS also results in increased fuel economy due to the improved rolling resistance as the tire floats on the surface rather than creating ruts in soft soil or sand.
Each wheel end is equipped with a CTIS wheel valve. The wheel valve connects the tire to the CTIS control system whenever it is actively measuring or changing tire pressure. Otherwise, the wheel valve is closed, isolating the tire from the system, thus ensuring that the tire will not leak down. This eliminates the need for manually operated shut off valves when the vehicle is inactive for extended periods of time. This feature also provides extended air seal life when the vehicle is in motion and tire pressure adjustment is not occurring. Parker offers wheel valves in a variety of sizes and configurations including valves with hose connections as well as flush-mount hose-less versions for use with wheels that have integral air passages. Located on the vehicle chassis or undercarriage, Parker’s CTIS pneumatic control unit consists of electro-pneumatic valves and pressure sensors required to monitor and control the pneumatic system.
CTIS provides independent wheel-end control ensuring fail-safe operation in the event of damage to the vehicle or wheel end. The CTIS wheel valve is completely sealed to the atmosphere at the wheel end ensuring reliable deepwater forwarding capability. Tire venting while deflating is routed back through the pneumatic control unit rather than at the wheel end. The CTIS electronic control unit provides decision making and logic execution. The electronic circuitry is completely sealed in an aluminum enclosure resulting in a rugged environmentally robust package.
Vehicle mobility is improved by reducing tire inflation pressure resulting in a larger tire footprint. This bigger footprint improves traction, reduces wheel slip and allows the vehicle to float across the soft terrain instead of compacting the soil and causing rutting. When returning to improved terrain conditions, a simple push of a button on the driver interface automatically inflates the tires to the appropriate pressure utilizing the onboard air compressor.
Its unique wheel valve design provides the best in class deflate performance while incorporating the non piloted remote venting control strategy preferred by most vehicle manufacturers. CTIS can deflate tire pressures significantly lower than the competition while operating reliably over a wide range of temperatures and altitudes. The CTIS is insensitive to vehicle installation variables such as wheel-end, the backpressure, and air seal flow. This results in enhanced fault tolerance as wheel valve shutoff is assured even with kinked, contaminated or restricted airlines. This is a patented wheel valve design that gets the job done faster, resulting in industry precedent-setting deflation rates. The operator interface provides the ability to select four terrain modes:
Mud, sand, and snow
Pressing any of the terrain buttons results in the system checking all tire pressures and then automatically adjusting them to pressure targets. A green light on the driver interface will flash while pressure changes are being made and then turn solid indicating that target tire pressures have been reached. The operator can also select from three load levels: no-load, partial load and full load optimizing tire pressure for load improves fuel economy, vehicle stability and ride comfort.
The CTIS monitors tire pressure at regular intervals and offers a run-flat mode which reduces this interval to almost continuously monitor pressure. This is useful when an increased threat for puncture exists. CTIS will return to normal pressure check intervals after a predetermined time has expired.
The system also monitors vehicle speed and provides both an over-speed warning and an automatic terrain mode bumper to ensure safe operation operators can run in an overspeed condition for a short period of time, for example, to preselect for an impending terrain change continue to over-speed will result in the amber warning led on the selected terrain button beginning to flash. If the vehicle speed is not reduced within an additional time, CTIS will automatically bump up the terrain mode to a more appropriate setting and inflate the tires to the new target pressure. This staged approach allows the operator to pre-select terrains as needed while protecting tires from damage.
Watch the video to learn more and see a vehicle in action:
Article contributed by Ryan Mills, project engineer, Parker Hannifin's Pneumatics Division.
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