Method of quantifying the utilization of a maximum grip potential of a tire
A method of quantifying the utilization of a maximum grip potential of a tire running on the ground. At two distinct azimuth angles, at least two respective values are determined for a differential extension of the tread of the tire or for a shear of the tread that is homogeneous with said differential extension. The utilization is quantified with the help of a function of the two determined values.
1. A method of quantifying the utilization of a maximum grip potential of a tire running on the ground, comprising the steps of:
determining at least two values for a differential extension of the tread of the tire or for a shear of the tread that is homogeneous with said differential extension, respectively at two distinct azimuth angles; and
wherein the value of the differential extension or of the shear, as determined at a given azimuth angle θ is written Δ(θ), and said utilization is quantified with the help of a value S that is defined as follows:
S
=
(
(
Δ
(
θ
1
)
-
Δ
(
θ
2
)
)
-
O
-
P
slip
·
(
Δ
(
θ
1
)
+
Δ
(
θ
2
)
)
(
P
grip
-
P
slip
)
·
(
Δ
(
θ
1
)
+
Δ
(
θ
2
)
)
where P grip , P slip , and O are predetermined constants, and θ 1 and θ 2 are the two distinct azimuth angle values.
2. The method according to claim 1 , wherein the two azimuth angles define an acute angular sector containing the contact area of the tread with the ground.
3. The method according to claim 2 , wherein the angular sector is about 50°.
4. The method according to claim 1 , wherein P slip =0.
5. The method according to claim 1 , wherein the quantification of said utilization is also a function of a length of the contact area of the tread with the ground.
6. The method according to claim 1 , wherein, when the determined values are shear values, each shear value of the tread is determined substantially in an equatorial plane of the tread.
7. The method according to claim 1 , wherein the differential extension corresponds to the difference between two extension values of the tread measured substantially symmetrically about an equatorial plane of the tire.
8. The method according to claim 7 , wherein the measured extension values are extension values in a direction that is substantially circumferential relative to the tire.
9. The method according to claim 1 , wherein the extension or the shear of the tread is determined respectively by means of at least one extension or shear sensor, preferably implanted between a carcass ply and inside rubber of the tire or on a face of the inside rubber that is in contact with the air inside the tire.
10. The method according to claim 1 , wherein said utilization is quantified with the help of a function of the difference between the two determined values, and of the sum of said two determined values.