Fault detection method for central tire inflation system

Claim 2

Claim 2. The method of claim 1 wherein said reference range is defined by a low reference pressure corresponding to the lowest expected atmospheric pressure at at least the highest expected operating altitude and a high reference pressure corresponding to the highest expected atmospheric pressure at no higher than the lowest expected operating altitude.

Claim 3

Claim 3. The method of claim 2 wherein said range is about 16.5-to-8.0 psia.

Claim 4

Claim 4. The method of claim 1 wherein said CTIS includes means for sensing operating altitude and for adjusting said range in accordance with sensed altitude.

Claim 5

Claim 5. The method of claim 2 including signaling the presence of a system fault condition.

Claim 6

Claim 6. A diagnostic method for sensing unacceptable operating conditions in an on-board CTIS for measuring and controlling the inflation pressure of an inflatable vehicle tire, said CTIS measuring inflation pressure of said tire by fluidly connecting the interior pressurized chamber of said tire to means associated with said conduit for allowing the pressure in said conduit to stabilize at a pressure equal to pressure in said interior pressurized chamber and then sensing the pressure in said conduit; said method characterized by: fluidly isolating said conduit and then fluidly connecting the interior chamber of said tire to means, allowing the conduit to assume a substantially equilibrium condition while taking a sensing of the pressurization in said conduit; comparing said sensed pressurization to reference value corresponding to said pressurization at conditions of minimum acceptable tire inflation, and if said sensed pressure is less than said reference value, signalling the presence of an unacceptable condition and preventing further control of the inflation pressurization of said tires.

Claim 7

Claim 7. The method of claim 5 wherein said reference value is about 20 psia.

Claim 8

Claim 8. A diagnostic method for sensing unacceptable operating conditions in an on-board CTIS of the type comprising a control valve assembly (70) for selectively pressurizing and venting a controlled fluid conduit (20), a tank (74) for accumulating pressurized air, means for selecting fluidly connecting and isolating said control valve assembly and said tank, two-position pressure switch means (74A) communicating with the pressurized interior of said tank and movable from a first position (open) to a second position (closed) if the pressurization in said tank exceeds a first reference value and movable from said second position to a first position if the pressurization in said tank is less than a second reference value, said first reference value being greater than said second reference value, said pressure switch means generating a signal indicative of the position thereof, means for sensing vehicle speed and generating a signal indicative thereof, and control means for receiving input signals and processing said input signals to generate command output signals, said control means effective to generate command output signals prohibiting fluid communication between said tank and said control valve upon receiving an input signal indicating said pressure switch is in the first position thereof, said method characterized by: sensing the position of said two-position pressure switch; sensing the speed of the vehicle; if said two-position pressure switch remains in the first position thereof for at least a preselected period of time while vehicle speed exceeds a reference speed, preventing further operation of the CTIS.

Claim 9

Claim 9. The method of claim 8 wherein said tank is an air brake wet tank fluidly connected to the vehicle air brake system.

Claim 10

Claim 10. The method of claim 9 wherein said tank is fluidly connected to an on-board air compressor, the output of which compressor is directly related to the speed of the vehicle.

Claim 11

Claim 11. The method of claim 9 wherein said second reference pressure is the minimum acceptable pressure for operation of said air brake system.

Claim 12

Claim 12. The method of claim 8 wherein said control means includes a digital microprocessor.

Claim 13

Claim 13. A diagnostic method for sensing unacceptable operating conditions in an on-board CTIS for measuring and controlling the inflation pressure of vehicle inflatable tires, said CTIS of the type comprising a control valve assembly (70) for selectively pressurizing and venting a controlled fluid conduit (20), means (80) for measuring the pressure in said conduit, means for selectively fluidly connecting said inflatable tires to said fluid conduit, means effective to cause said conduit to assume the pressure in said inflatable tire during pressure measurement operations, a tank for accumulating pressurized air, means (72) for providing pressurized air to said tank means for selecting fluidly connecting and isolating said control valve assembly and said tank, two-position pressure switch means (74A) communicating with the pressurized interior of said tank and movable from a first position to a second position if the pressurization in said tank exceeds a first reference value and movable from said second position to a first position if the pressurization in said tank is less than a second reference value, said first reference value being greater than said second reference value, said pressure switch means generating a signal indicative of the position thereof, means for sensing vehicle speed and generating a signal indicative thereof and control means for receiving input signals and processing said input signals to generate command output signals, said control unit effective to generate command output signals prohibiting fluid communication between said tank and said control valve upon receiving an input signal indicating said pressure switch is in the first position thereof, said CTIS effective to increase inflation pressure by repeated cycles comprising connecting said tires and said tank to said conduit if the pressure switch is in the second position and to isolate said tank from said conduit if the pressure switch is in the first position thereof; said method characterized by: during tire inflation operations, sensing and memorizing tire pressures during the portions of each inflation cycle when the tank is isolated from the conduit; determining if tire pressure is increasing or decreasing with respect to time; and if tire pressure is decreasing with respect to time, preventing further control of the inflation pressure of said tires.

Claim 14

Claim 14. The method of claim 11 wherein said tank is an air brake wet tank fluidly connected to the vehicle air brake system.

Claim 15

Claim 15. The method of claim 14 wherein said tank is fluidly connected to an on-board air compressor, and said second reference pressure is the minimum acceptable pressure for operation of said air brake system.