Truck tire underinflation detection and control system

A truck tire/wheel assembly detection system in which the moving thermal dynamics of a truck are measured before cooling off, by passing over and around contact or non-contact thermometers directed toward the tire/wheel assembly and transmits the approximate temperature of each tire/wheel assembly to a computer which will compares the output data and identifies each abnormally overheated tire/wheel assembly and print out location on rig and other information that may be required. A modem controlled by the computer is used to advise other interested parties of rig condition at this check out point.

This invention relates generally to a method of detecting underinflated 
tires as well as brake drag and axle bearing failure on over road 
vehicles, but particularly to a novel system for very rapidly detecting 
which tire on a multi-axled trucking rig has lost pressure. 
BACKGROUND OF THE INVENTION 
Tire underinflation has always been a serious concern to the trucking 
people as well as the Federal and State Highway people. An underinflated 
tire, usually caused by a slow leak resulting from a malfunctioning air 
valve, causes shorter tire life, more fuel expenditure and increased wear 
on the highway surface. All parties involved in use and care of the 
highway system would benefit from a practical solution that yields a 
timely warning of underinflated tires for the following reasons: 
A. Truck fleets would save on fuel, tires, labor and road "downtime". 
B. Federal and State highway authorities agree that proper and practical 
tire pressure control would assist in the maintenance of road surface 
condition, extend the life of the road systems and decrease road repair 
expenses. The reason is that a slow leak in one tire of a dual tire 
arrangement increases the dynamic impact characteristics on the road. The 
greater the transfer of load from "leaker" to the good tire the greater 
the potential damage to good tire and road surface. The current weigh 
stations enforce the law with respect to axle loading and rating of tires 
for specific axle loading; however, there is no provision for checking the 
working tires as a support system with respect to said axle loading. 
Information with respect to the effective tire foot print area supporting 
a given load is most important, since it defines unit pressure exerted on 
the road service by the support members. It is our belief that this 
passive system will complement the present weigh station system. The need 
has existed for years for a passive system which would INDICATE 
underinflated tires on a moving rig without any DIRECT human contact with 
the vehicle. This passive system alerts the driver of a pending or 
existing underinflation problem. The setting of alarm levels of pressure 
loss should be decided between highway management and trucking management 
since these parameters must reflect the necessary trade-offs of the actual 
practical field operation. 
C. The public would appreciate the higher quality of road surface and the 
cost savings on road construction and repair. 
There have been a number of designs to detect the underinflation tire 
problems in heavy "over the road" vehicles. To this point none have sold 
successfully because of a combination of high initial cost, increased 
operational and maintenance costs and unsatisfactory field experiences. 
The reason for the high costs is that all prior systems have directed 
their attention to mounting the sensor devices on each individual tire of 
the vehicle. It is time to revisit the low pressure tire problem with a 
new evaluation of how to solve the problem. It is necessary to accept 
certain basic facts as follows: 
1. It must be recognized that successful commercial fleets are well 
maintained and that few trucks leave the company garage area with low 
tires, brake drag or bad bearings. 
2. It must be recognized that modern drivers are better trained and are 
working with much better equipment than in the past. Todays drivers are 
equivalent to mid-level managers in a manufacturing corporation and handle 
their work with a great degree of competence. 
3. It must be recognized that the manufacturers have made great strides in 
the design of modern tires, brakes and axle bearings. The incidence of 
catastrophic tire/wheel failures are quite rare. 
4. It must be recognized that over ninety five per cent of the problems of 
a tire/wheel assembly result from the slow tire leaks usually caused by 
unseating and damage to the tire valve. Unfortunately, the best 
maintenance department cannot protect the rig from the results of such 
slow tire leaks while long haul vehicles are miles away from the 
maintenance base for prolonged periods of time. In a profitable trucking 
operation, the time a big rig is away from home maintenance center is at 
least 85% to 90% of rig life. It is during this dynamic road time that 
symptoms of a tire pressure problem are the most apparent and can be 
corrected before additional vehicle operational costs and damage to road 
surface are incurred. This system will also reduce needless tire pressure 
checking with the air pressure gauge which is very often the cause of the 
slow leaking tire/wheel assembly. 
OBJECT OF INVENTION 
The object of this invention is to provide a system which can detect an 
underinflated tire/wheel assembly on a stationary vehicle or a moving 
vehicle passing through a check lane. Another object of this invention is 
to provide a system which will increase profits to trucking interests as 
well as to increase highway surface life. It is a win win situation for 
all parties concerned with the use, management and condition of the 
nation's highway system e.g. the trucking business, the Federal & State 
Highway Departments and the public. 
The proposed system is a noninvasive practical passive system which will 
operate on the basis that the low tire is an exception rather than the 
rule, but also that the low tire condition accounts for over 95% of 
tire/wheel problems. Therefore, the design goal is to locate a specific 
DYNAMIC anomaly in tire mount area which correlates with possible 
tire/wheel assembly failure modes. This invention employs a passive system 
which observes the anomaly of temperature variations in the tire/wheel 
assembly derived from the energy dynamics of an "over the road" rig 
generating the temperature rise alert of a slow leak tire condition; or an 
overheated wheel caused by unusual mechanical friction. This preventative 
step will allow time to correct a faulty condition so that the vehicle 
proceeds without loss of a tire or "road downtime" costs and possibly 
inflict damage to road surface. It should be stressed that this system is 
workable only because modern equipment and maintenance allow a standard to 
be set because of the normal operation of a large percentage of tires on 
any given rig. This standard allows meaningful analysis of the temperature 
variation relative to excess heat development in underinflated tire/wheel 
assembly as compared to the normal operating tire/wheel assemblies. It 
should also be stressed that the system defined herein is obviously only 
one of many possible system configurations.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
As shown in the drawing, a tractor-trailer rig 10 has entered a check point 
and will immediately (BEFORE COOL Off) proceed to pass over and around 
non-contact thermometers 14, 16 and 18 which are aimed toward the hub and 
sidewall of the tire of each tire/wheel assembly 12 and positioned to 
measure the temperature of each tire and/or wheel as it passes. A standard 
non-contact thermometer, such as Raynger PM manufactured by Raytek Inc., 
is used and requires approximately one second to read the temperature of 
all wheels per axle from a wide range of distances. In the system 
disclosed herein, it is the initial plan to use a range of 3 to 15 feet 
for a total read out time for a 10 wheel vehicle (moving at 2-3 MPH) of 
approximately 20 seconds. This time may be decreased by having the 
thermometers 14-18 track the tire/wheel targets when the rolling tire 
activates a switch signal on a given axle as the vehicle moves forward 
and/or increase sensor pattern readout points. There are applications in 
which user could elect to utilize a hand held contact type thermometer 
read out; e.g. individual fleets checking incoming equipment immediately 
on arrival at home maintenance center. This action would save a fleet 
considerable money currently being spent on manual air gauge tire pressure 
checking labor costs, and decrease the many slow leaks introduced by the 
very use of the air gauge. The less a properly seated air valve seal is 
disturbed the better. 
The temperature output from each thermometer 14-18 is fed into a computer 
20 for processing into a format which would name specifically the axle 
number, the side of the rig, and which tire/wheel assembly has an 
abnormally high temperature. It will also be able to show average 
tire/wheel temperature as well as peak temperature plus any other 
information desired by highway management people as well as the individual 
fleet managers. Should field track tests show that after a certain number 
of miles the wheel metal hub thermal conductivity results in the duals 
reaching temperature equilibrium then the thermometer arrangement would 
change to use either a combination of 14 & 18 or the center bi-directional 
mount 16. In either case, the specific axle and specific side would be 
indicated and the driver would use an air gauge to find the specific 
underinflated tire on the dual wheel which he would do in any case to 
verify that low tire pressure is actually the cause and not other 
mechanical drag problems e.g. bearing or brake drag. 
It should be noted that all tire/wheel units 12 on the same rig have 
undergone the same ambient temperature, same elevation, same speed and 
road conditions. Therefore a significant difference or differences of 
temperature on a tire/wheel unit 12 on the same rig from norm would point 
to a problem. The computer 20 is coupled to a printer 22 which prints out 
specific tire/wheel assembly and a caution to instruct driver to air the 
tire before proceeding. (An airing facility should be set up for this 
purpose) If the tire is moderately hot and should be watched a caution 
print out is prepared for driver. The temperature levels of alarm and 
necessary actions should be set up by management personnel utilizing fleet 
and tire manufacturers inputs. The computer 20 is therefore provided with 
a modem for notifying subsequent check point of the truck identification 
and the particular tire/wheel that was given a caution printout. The 
system is symbiotic to all parties concerned and there is a real incentive 
for driver to heed the caution tag. Consideration should be given to 
sending copy of all caution or "stop and air" instructions to the 
management of the involved rig. This action is not "big brother" syndrome; 
since it could also furnish fleet management valuable information for 
their analysis that the driver print out would not need to contain.