Vehicle weight and cargo load determination using tire pressure

Details Vehicle weight and cargo load determination using tire pressure Vehicle weight and cargo load determination using tire pressure

2000-05-09

2002-09-10

Hoff, Marc S. (Department: 2857)

Data processing: measuring, calibrating, or testing

Measurement system

Weight

C702S033000, C702S098000, C702S101000, C702S113000, C702S130000, C702S129000

Reexamination Certificate

active

06449582

ABSTRACT:

FIELD OF INVENTION
This invention relates to the method and apparatus for determining the weight of the vehicle and/or the cargo load based on the tire pressure and temperature.
BACKGROUND OF THE INVENTION
Many different systems have been designed to measure the tire pressures of a vehicle and relay this information to the operator, see for example U.S. Pat. No. 5,675,314 issue Oct. 7 1997 to Chaklader or U.S. Pat. No. 5,289,160 issued Feb. 22, 1994 to Fiorletta. U.S. Pat. No. 4,909,074 issued Mar. 20, 1990 to Gerresheim et al. describes a specific application of sensed tire pressure wherein curves based on atmospheric temperature are used to determine safe driving conditions for the tires under the then current atmospheric conditions.
U.S. Pat. No. 5,081,443 issued Jan. 14, 1992 to Breit describes a specific tire pressure and temperature sensor and system wherein the tire pressure and temperature are both monitored as well as other outside and cab conditions. The measured tire temperature and pressure are used for two different and unrelated functions; the temperature is used to monitor the brake function while the pressure is used to monitor the weight of the cargo. The concept of measuring the weight of the vehicle based on the tire pressure has also been described in Japanese patent no. JP10267739 published Oct. 9, 1998. Inventor Tsukasa teaches that the tire pressure may be used to determine the weight of or load on a vehicle. None of the existing systems compensate for tire temperature which can significantly alter the tire pressure in determining the weight of the vehicle based on the tire pressures and thus a significant error can be included in the measured load weight obtained by practicing the teachings of the above patents of Breit and Tsukasa.
BRIEF DESCRIPTION OF THE PRESENT INVENTION
It is an object of the present invention to provide a more accurate system for measuring the weight of the vehicle and/or of its load based tire pressure. More specifically, it is an object of the present invention to provide a more accurate system for measuring the weight of the vehicle and/or of its load based tire pressure. Broadly, the present invention relates to a method for measuring the weight of a vehicle based on change in tire pressure comprising, measuring tire pressure and temperature of at least a significant number of tires on a vehicle, determining a temperature standardized pressure P(s) based on a selected standard temperature for each tire, totaling said temperature standardized pressures for said tires P
(S)TOTAL
and determining total weight W
TOTAL
of said vehicle based on
W
TOTAL
=C
F
(&Dgr;
P
(S)TOTAL
)
Where W
TOTAL
=total weight of said vehicle
&Dgr;P
(S)TOTAL
=total or summation of all of said temperature standardized tire
pressures P
(S)
less the summation P
I(S)TOTAL
of the initial tire pressures P
I
measured with no load on the tires converted to temperature standardized
pressures P
I(S)
and summed to provide a summation of initial pressures
P
I(S)TOTAL
C
F
=a conversion factor of weight/unit change of standardized tire pressures.
Preferably, said method further comprises determining the weight of the vehicle alone W
V
and determining the weight of cargo W
C
based on
W
C=
W
TOTAL
−W
V
Preferably, said weight of the vehicle alone W
V
is determined by initially measuring initial tire pressure P
I
of each said tire under conditions of no load, determining said temperature standardized initial pressure P
I(S)
for said selected standard temperature for each of said tires, measuring pressure P
V
in said tires when said tires are subject only to the weight of the vehicle W
(V)
and determining a standardized pressure P
V(S)
for each said tire based on P
V
in said tires and determining weight of said vehicle W
V
based on the equation
W
V
=C
F
(
P
V(S)TOTAL
−P
I(S)TOTAL
)=
C
F
(&Dgr;
P
V(S)TOTAL
)
Wherein W
V
=Vehicle weight
P
I(S)TOTAL
=is the sum or total of said initial standardized pressures P
I(S)
for said tires under no load
P
V(S)TOTAL
=the sum or total of said temperature standardized pressures
P
V(S)
of said tires
&Dgr;P
V(S)TOTAL
=the change in total of the temperature standardized tire pressures based measured with only the weight of the vehicle over initial temperature standardized pressures under no load i.e. P
V(S)TOTAL
−P
I(S)TOTAL
C
F
=said conversion factor of unit weight/unit change of standardized tire pressures.
Preferably, said conversion factor C
F
is determined by measuring said weight of the vehicle alone W
V
, initially measuring initial tire pressure P
I
of each said tire under conditions of no load, determining said temperature standardized initial pressure P
I(S)
for said selected standard temperature for each of said tires, measuring pressure P
V
in said tires when said tires are subject only to said weight of the vehicle alone W
(V)
and determining a standardized pressure P
V(S)
for each said tire based on P
V
in said tires and determining said conversion factor C
F
based on the equation
C
F
=W
V
/(
P
V(S)TOTAL
−P
I(S)TOTAL
)=
W
V
/(&Dgr;
P
V(S)TOTAL
)
Wherein W
V
=Vehicle weight
P
I(S)TOTAL
=is the sum or total of said initial standardized pressures P
I(S)
for said tires under no load
P
V(S)TOTAL
=the sum or total of said temperature standardized pressures P
V(S)
of said tires
&Dgr;P
V(S)TOTAL
=the change in total of the temperature standardized tire pressures based measured with only the weight of the vehicle over initial temperature standardized pressures under no load i.e. P
V(S)TOTAL
−P
I(S)TOTAL
C
F
=said conversion factor of weight/unit change of standardized tire pressures.
Preferably, said determining said weight of cargo W
C
is based on the equation
W
C
=C
F
[P
T(S)TOTAL
−(
P
V(S)TOTAL
)]=
C
F
(&Dgr;
P
C(S)TOTAL
)
Wherein W
C
=weight of the cargo
P
V(S)TOTAL
=the total of said temperature standardized pressures P
V(S)
of said tires measure when only load on the tire is the vehicle (i.e. no load on the vehicle)
P
T(S)TOTAL
=the total of said temperature standardized pressures P
T(S)
of said tires measured under full load (i.e. vehicle plus cargo).
&Dgr;P
C(S)TOTAL
=the change in total of the temperature standardized tire pressures P
T(S)TOTAL
−P
V(S)TOTAL
due to the weight of the cargo and
C
F
=said conversion factor of unit weight/unit change of standardized tire pressures.
Preferably, said determining said weight of cargo W
C
is based on the equation
C
FT
&Dgr;P
(ST)TOTAL
=C
F1
(&Dgr;
P
(S1)
)+
C
F2
(&Dgr;
P
(S2)
)+
C
F3
(&Dgr;
P
(S3)
)+ - - - +
C
Fn
(&Dgr;
P
(Sn)
)
Where &Dgr;P
(ST)TOTAL
=total of the temperature corrected changes in individual tire pressures.
C
FT
=a conversion factor based on change in weight/unit change of standardized tire pressures based on the weighted average of C
F1
, C
F2
, C
F3
- - - C
F1
and is in effect equivalent to
C
FT
=[C
F1
(&Dgr;P
(S1)
)+C
F2
(&Dgr;P
(S2)
)+C
F3
(&Dgr;P
(S3)
)+ - - - +C
Fn
(&Dgr;P
(Sn)
)]/&Dgr;P
(ST)TOTAL
C
F1
, C
F2
, C
F3
- - - C
Fn
are predetermined specific values of a conversion factor C
F
for each of the tires 1, 2, 3 - - - n respectively.
Preferably, said weight of the vehicle alone W
V
is determined by initially measuring initial tire pressure P
I
of each said tire under conditions of no load, determining said temperature standardized initial pressure P
I(S)
for said selected standard temperature for each of said tires, measuring pressure P
V
in said tires when said tires are subject only to the weight of the vehicle W
(V)
and determining a standardized pressure P
V(S)
for each said tire based on P
V
in said tires and determining weight of said vehicle W
V
based on the equation
W
V
=[C
F1
(
P
V(S1)
)+
C
F2
+(
P
V(S2)
)+
C
F3
(
P
V(S3)
)+ - - - +
C
Fn
(
P
V(Sn)
)]

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