Design and Testing of an Automatic Tire Inflation System for Drive Axles on Class 8 Tractors

An Automatic Tire Inflation System (ATIS) specifically designed for commercial use on trailer axles is currently being installed and utilized successfully by trucking companies, the military and owner/operators throughout the U.S.

A need exists for an ATIS specifically designed for the drive axles of Class 8 over-the- road tractors. The addition of an ATIS for drive axles will expand automatic tire monitoring capability to all heavily loaded tires of the over-the-road truck/trailer rig. An ATIS for drive axles has been designed, fabricated and tested. Testing and evaluation of the prototype ATIS drive axle system indicates the system can be successfully installed on a typical tractor rig and operated for an extended period without problems. The testing included a 50,000 mile evaluation of the ATIS installed in a laboratory test fixture. The test fixture used stock axle parts and operated at 65 MPH. Environmental testing was conducted at temperatures ranging from -20 to +200 degrees F. A 100,000 mile (162,000 km) road test will be conducted by Southwest Research over a specified road course to complete the evaluation of the DRAXIS unit. The road test will be conducted after completion of laboratory testing.

The commercial drive axle ATIS differs from the current military CTIS design in that the entire system is installed external of the hub and outside the bearing area and is designed to operate at current highway speeds. The commercial ATIS requires only removal of the axle shaft and hub/brake drum assembly and spreading of the brake shoes for installation. The bearings, seal and ABS equipment remain in or attached to the hub and are not disturbed.

Design Features include:

1. 1.
   Supply air is distributed to the tires through a rotary air coupling that is external of the bearings and can be installed without disturbing the axle shaft, hub or bearing components.
2. 2.
   The system results in no additional frictional heat load in the bearing area. OEM axle manufacturers expressed concern that additional heat load in bearing areas could lead to early failure of bearings and seals.
3. 3.
   The drive axle ATIS can be operated in conjunction with or independently of the trailer ATIS.
4. 4.
   System components can be installed at the OEM level or field installed on an existing axle.