Data processing: structural design – modeling – simulation – and em – Modeling by mathematical expression
Reexamination Certificate
2001-11-15
2004-02-24
Frejd, Russell (Department: 2123)
Data processing: structural design, modeling, simulation, and em
Modeling by mathematical expression
C703S001000, C703S008000, C152S209200, C152S209300, C152S209500, C152S209150, C152S209180, C156S110100, C700S031000
Reexamination Certificate
active
06697772
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to a method for determining preselected performance characteristics of a tread of a tire, comprising ride comfort, noise and handling, and a tire provided with a tread having optimal characteristics with reference to said performance characteristics.
SUMMARY OF THE INVENTION
The subject of this invention is a method which allows to determine a set of performance characteristics of a tread of a tire by means of a single criterion which refers to all the performance characteristics taken into account.
An initial aspect of the invention is a method for determining preselected performance characteristics of a tread of a tire, comprising ride comfort, noise and handling, where a longitudinal direction (x), a transversal direction (y) and a vertical direction (z) are associated with said tread, where said tread has a preselected thickness and a preselected circumferential development and is made from a preselected rubber compound comprising blocks and grooves, each portion of said tread in contact with a road surface having a contact area, where said method comprises the following phases:
a) dividing said tread into a 3-D grid of full cells and empty cells of preselected dimensions (dxdydz),
b) identifying piles of said cells in said grid, each pile of cells having a base area equal to that of one cell (dxdy) and a height (h) equal to said thickness of the tread, said piles of cells being full, empty or partially fully,
c) dividing each contact area into longitudinal and transversal strips of piles of cells, with preselected dimensions in said transversal and longitudinal directions,
d) counting the number of consecutive piles of full cells delimited by two piles of cells which are either partially full or empty, one preceding, the other following said consecutive piles of full cells in each strip and
e) associating a transversal or longitudinal stiffness K with each strip of piles of cells by means of the following linear relationship:
K
=m*n
where n is the number of consecutive piles of full cells and m is an angular coefficient which is determined by means of the following linear relationship:
m=mm*i+c
where mm is an angular coefficient, i is the total number of empty cells present in said two piles of cells which are either partially full or empty delimiting said consecutive piles of full cells and c is a constant, said angular coefficient mm and constant c both depending on the number n of consecutive piles of full cells,
f) assigning a preselected deformation state to each transversal and longitudinal strip of piles of cells,
g) determining at least one single force F, associated with each strip of piles of cells and acting in one of transversal (y) and longitudinal (x) directions by means of said stiffness value K and said deformation state,
h) determining at least one total force F
t
associated with each contact area and acting in one of transversal (y) and longitudinal (x) said directions by summing all the single forces associated with all the transversal and longitudinal strips of piles of cells of said contact area, said total force representing at least one of said performance characteristics,
i) determining the pattern of the total forces F
t
associated with all the contact areas along said circumferential development of the tread and
j) analysing said pattern of total forces F
t
to evaluate whether said total forces assume values such as to optimize at least one preselected performance characteristic of said tread.
According to one embodiment:
k) in said step c), each contact area is divided into transversal strips of piles of cells with dimensions dx ly h, where dx is the length of a cell in said longitudinal direction (x), ly is the width of said strip in said transversal direction (y), measured in a preselected position in said longitudinal direction (x) and delimited by portions of the contour line of the contact area, and h is the thickness of said tread,
l) in said step e), a transversal stiffness K
y
is associated with each transversal strip of piles of cells,
m) in said step g), a single transversal force F
y
=K
y
*y is associated with each transversal strip,
n) in said step h), a total transversal force F
yt
is associated with each contact area and
o) in said step i), a pattern of the total transversal forces F
yt
is obtained for the entire circumferential development of the tread and in said step j) the values assumed by said total transversal forces are evaluated to check whether they have a mean value higher than a preselected limit and a variance lower than a preselected limit to optimize said tread with reference to handling.
According to another embodiment:
p) in said step c), each contact area is divided into longitudinal strips of piles of cells with dimensions dy lx h, where dy is the width of a cell in said transversal direction (y), lx is the length of said strip in said longitudinal direction (x), measured in a preselected position in said transversal direction (y) and delimited by portions of the contour line of the contact area, and h is the thickness of said tread,
q) in said step e), a longitudinal stiffness K
x
, is associated with each longitudinal strip of piles of cells and
r) in said step g), a single longitudinal force F
x
=K
x
*x is associated with each longitudinal strip,
s) in said step h), a total longitudinal force F
xt
is associated with each contact area and
t) in said step i), a pattern of the total longitudinal forces F
xt
is obtained for the entire circumferential development of the tread and in said step j) the values assumed by said total longitudinal forces are evaluated to check whether they have a mean value and variance lower than preselected limits to minimize the noise output by said tread and optimize ride comfort.
Preferably, said method also comprises the following phase:
u) associating a total transversal stiffness K
yt
to each contact area by summing the transversal stiffness values K
y
associated with all transversal strips in said contact area.
Advantageously, said method also comprises the following phase:
v) associating a total longitudinal stiffness K
xt
to each contact area by summing the longitudinal stiffness values K
x
associated with all longitudinal strips in said contact area.
Preferably, the value of said stiffness K
xt
is in the range from 2300 to 2500 N/mm and the value of said stiffness K
yt
is in the range from 2400 to 2600 N/mm.
In turn, the ratio of said stiffness values K
yt
and K
xt
is preferably as follows:
K
yt
/K
xt
=0.98÷1.05.
The method according to this invention has the advantage of being simple and very reliable.
A second aspect of this invention relates to a tire provided with a tread having optimal characteristics as regards preselected performance characteristics, comprising ride comfort, noise and handling, where a longitudinal direction (x), a transversal direction (y) and a vertical direction (z) are associated with said tread, where said tread has a preselected thickness and a preselected circumferential development and is made from a preselected rubber compound and comprises blocks and grooves, each portion of said tread in contact with a road surface having a contact area, where said tread is divisible into a 3-D grid of full cells and empty cells of preselected dimensions (dxdydz), where in said grid piles of said cells are identified, each pile of cells having a base area equal to that of one cell (dxdy) and height (h) equal to said thickness of the tread, said piles of cells being full, empty and partially full, where each contact area is divided into transversal and longitudinal strips of piles of cells having preselected dimensions in said transversal and longitudinal directions, where each strip of piles of cells comprises consecutive piles of full cells delimited by two piles of partially full or empty cells, one preceding and the other following said consecutive piles of full cells, where a transversal or longitudinal stiffness K is a
Esercitato Paolo
Mancosu Federico
Matrascia Giuseppe
Frejd Russell
Pirelli Pneumatici S.p.A.
LandOfFree
Method for determining preselected performance... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for determining preselected performance..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for determining preselected performance... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3290396