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Claims  |
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What is claimed is:
1. A method for estimating a tire wear life which comprises:
a step of obtaining a friction energy value of the tire Ewf in free
rolling, a friction energy value of the tire Ewa in a state in which the
tire is provided with a toe angle, a friction energy value of the tire Ews
in a state in which a side force is applied to the tire, a friction energy
value of the tire Ewd in a state in which a driving force is applied to
the tire, and a friction energy value of the tire Ewb in a state in which
a braking force is applied to the tire;
a step of obtaining a friction energy value ew of a rubber sample made of
the same material as the material used in a tire tread portion under a
severity approximately the same as the severity in actual use of the tire
and a wear depth W per given driving distance;
a step of obtaining a rubber index Gi which is a value obtained by dividing
the friction energy ew by the wear depth W, i.e., ew/W, and a friction
energy Ew expressed by the following formula:
Ew=Ewf+Ewa+Ews+Ewb+Ewd
and
a step of estimating the tire wear life on the basis of a value including a
product of the rubber index Gi and a reciprocal of Ew (1/Ew), i.e., Gi/Ew.
2. A method for estimating a tire wear life according to claim 1, wherein
the value containing the product Gi/Ew is a value selected from the
product Gi/Ew or a value obtained by multiplying the product Gi/Ew by a
remaining groove depth remaining before the groove depth reaches a limit
for disposal of the tire.
3. A method for estimating a tire wear life according to claim 1, which
further comprises:
a step of expressing the friction energy Ews, the friction energy Ewd and
the friction energy Ewb, using an input force in a transverse direction
Fy, a force in a forward direction Fx+ generated by the driving force, a
force in a backward direction Fx- generated by the braking force,
undetermined coefficients S, D and B and exponents ns, nd and nb, by the
following formulae:
Ews=S.times.Fy.sup.ns
Ewd=D.times.Fx+.sup.nd
Ewb=B.times.FX-.sup.nb
a step of determining the undetermined coefficients S, D and B and the
exponents ns, nd and nb in advance on the basis of values of the friction
energy Ews, the friction energy Ewd and the friction energy Ewb measured
under application of a given value of the input force in the transverse
direction Fy, a given value of the force in the forward direction Fx+ and
a given value of the force in the backward direction Fx-, respectively;
a step of determining values of the input force in the transverse direction
Fy, the force in the forward direction Fx+ and the force in the backward
direction Fx- on the basis of RMS values of the distribution of
acceleration in a transverse direction at a center of gravity position of
a vehicle and the distribution of acceleration in a longitudinal direction
at a center of gravity position of the vehicle in actual use of the
vehicle; and
a step of obtaining the friction energy Ews, the friction energy Ewd and
the friction energy Ewb on the basis of the determined values of the input
force in the transverse direction Fy, the force in the forward direction
Fx+ and the force in the backward direction Fx- in accordance with the
above formulae in which the coefficients and the exponents have been
determined.
4. A method for estimating a tire wear life according to claim 2, which
further comprises:
a step of expressing the friction energy Ews, the friction energy Ewd and
the friction energy Ewb, using an input force in a transverse direction
Fy, a force in a forward direction Fx+ generated by the driving force, a
force in a backward direction Fx- generated by the braking force,
undetermined coefficients S, D and B and exponents ns, nd and nb, by the
following formulae:
Ews=S.times.Fy.sup.ns
Ewd=D.times.Fx+.sup.nd
Ewb=B.times.FX-.sup.nb
a step of determining the undetermined coefficients S, D and B and the
exponents ns, nd and nb in advance on the basis of values of the friction
energy Ews, the friction energy Ewd and the friction energy Ewb measured
under application of a given value of the input force in the transverse
direction Fy, a given value of the force in the forward direction Fx+ and
a given value of the force in the backward direction Fx-, respectively;
a step of determining values of the input force in the transverse direction
Fy, the force in the forward direction Fx+ and the force in the backward
direction Fx- on the basis of RMS values of the distribution of
acceleration in a transverse direction at a center of gravity position of
a vehicle and the distribution of acceleration in a longitudinal direction
at a center of gravity position of the vehicle in actual use of the
vehicle; and
a step of obtaining the friction energy Ews, the friction energy Ewd and
the friction energy Ewb on the basis of the determined values of the input
force in the transverse direction Fy, the force in the forward direction
Fx+ and the force in the backward direction Fx- in accordance with the
above formulae in which the coefficients and the exponents have been
determined.
5. A method for estimating a tire wear life according to claim 1, which
further comprises:
a step of expressing the friction energy Ews, the friction energy Ewd and
the friction energy Ewb, using an input force in a transverse direction
Fy, a force in a forward direction Fx+ generated by the driving force, a
force in a backward direction Fx- generated by the braking force,
undetermined coefficients S, D and B and exponents ns, nd and nb, by the
following formulae:
Ews=S.times.Fy.sup.ns
Ewd=D.times.Fx+.sup.nd
Ewb=B.times.FX-.sup.nb
a step of setting each of the exponents ns, nd and nb at a specific value
between 1.5 and 3 and determining the undetermined coefficients S, D and B
in advance on the basis of values of the friction energy Ews, the friction
energy Ewd and the friction energy Ewb measured under application of an
input force in the transverse direction Fy, a force in the forward
direction Fx+ and a force in the backward direction Fx-, respectively;
a step of determining values of the input force in the transverse direction
Fy, the force in the forward direction Fx+ and the force in the backward
direction Fx- on the basis of RMS values of the distribution of
acceleration in a transverse direction at a center of gravity position of
a vehicle and the distribution of acceleration in a longitudinal direction
at a center of gravity position of the vehicle in actual use of the
vehicle; and
a step of obtaining the friction energy Ews, the friction energy Ewd and
the friction energy Ewb on the basis of the determined values of the input
force in the transverse direction Fy, the force in the forward direction
Fx+ and the force in the backward direction Fx- in accordance with the
above formulae in which the coefficients and the exponents have been
determined.
6. A method for estimating a tire wear life according to claim 2, which
further comprises:
a step of expressing the friction energy Ews, the friction energy Ewd and
the friction energy Ewb, using an input force in a transverse direction
Fy, a force in a forward direction Fx+ generated by the driving force, a
force in a backward direction Fx- generated by the braking force,
undetermined coefficients S, D and B and exponents ns, nd and nb, by the
following formulae:
Ews=S.times.Fy.sup.ns
Ewd=D.times.Fx+.sup.nd
Ewb=B.times.FX-.sup.nb
a step of setting each of the exponents ns, nd and nb at a specific value
between 1.5 and 3 and determining the undetermined coefficients S, D and B
in advance on the basis of values of the friction energy Ews, the friction
energy Ewd and the friction energy Ewb measured under application of an
input force in the transverse direction Fy, a force in the forward
direction Fx+ and a force in the backward direction, respectively Fx-;
a step of determining values of the input force in the transverse direction
Fy, the force in the forward direction Fx+ and the force in the backward
direction Fx- on the basis of RMS values of the distribution of
acceleration in a transverse direction at a center of gravity position of
a vehicle and the distribution of acceleration in a longitudinal direction
at a center of gravity position of the vehicle in actual use of the
vehicle; and
a step of obtaining the friction energy Ews, the friction energy Ewd and
the friction energy Ewb on the basis of the determined values of the input
force in the transverse direction Fy, the force in the forward direction
Fx+ and the force in the backward direction Fx- in accordance with the
above formulae in which the coefficients and the exponents have been
determined.
7. A method for estimating a tire wear life according to claim 1, which
further comprises:
a step of dividing the friction energy Ews into a friction energy Ews+
generated in a rightward turn of a vehicle to which the tire is mounted
and a friction energy Ews- generated in a leftward turn of the vehicle to
which the tire is mounted on the basis of an Ackerman characteristic and
the toe angle of the vehicle and obtaining each of the friction energy
Ews+ and the friction energy Ews-; and
a step of obtaining the friction energy Ews as a sum of the friction energy
Ews+ and the friction energy Ews-, i.e., Ews++Ews-.
8. A method for estimating a tire wear life according to claim 2, which
further comprises:
a step of dividing the friction energy Ews into a friction energy Ews+
generated in a rightward turn of a vehicle to which the tire is mounted
and a friction energy Ews- generated in a leftward turn of the vehicle to
which the tire is mounted on the basis of an Ackerman characteristic and
the toe angle of the vehicle and obtaining each of the friction energy
Ews+ and the friction energy Ews-; and
a step of obtaining the friction energy Ews as a sum of the friction energy
Ews+ and the friction energy Ews-, i.e., Ews++Ews-.
9. A method for estimating a tire wear life according to claim 7, which
further comprises:
a step of expressing a friction energy Ews+, a friction energy Ews-, the
friction energy Ewd and the friction energy Ewb, using an input force in a
transverse direction Fy+ generated in a rightward turn of a vehicle, an
input force in a transverse direction Fy- generated in a leftward turn of
the vehicle, a force in a forward direction Fx+ generated by the driving
force, a force in a backward direction Fx- generated by the braking force,
undetermined coefficients S1, S2, D and B and exponents ns1, ns2, nd and
nb, by the following formulae:
Ews+=S1.times.Fy+.sup.ns1
Ews-=S2.times.Fy-.sup.ns2
Ewd=D.times.Fx+.sup.nd
Ewb=B.times.FX-.sup.nb
a step of determining the undetermined coefficients S1, S2, D and B and the
exponents ns1, ns2, nd and nb in advance on the basis of values of the
friction energy Ews+, the friction energy Ews-, the friction energy Ewd
and the friction energy Ewb measured under application of a given value of
the input force in the transverse direction Fy+, a given value of the
input force in the transverse direction Fy-, a given value of the force in
the forward direction Fx+ and a given value of the force in the backward
direction Fx-, respectively;
a step of determining values of the input force in the transverse direction
Fy+, the input force in the transverse direction Fy-, the force in the
forward direction Fx+ and the force in the backward direction Fx- on the
basis of RMS values of the distribution of acceleration in a transverse
direction at a center of gravity position of a vehicle and the
distribution of acceleration in a longitudinal direction at a center of
gravity position of the vehicle in actual use of the vehicle; and
a step of obtaining the friction energy Ews+, the friction energy Ews-, the
friction energy Ewd and the friction energy Ewb on the basis of the
determined values of the input force in the transverse direction Fy+, the
input force in the transverse direction Fy-, the force in the forward
direction Fx+ and the force in the backward direction Fx- in accordance
with the above formulae in which the coefficients and the exponents have
been determined.
10. A method for estimating a tire wear life according to claim 8, which
further comprises:
a step of expressing a friction energy Ews+, a friction energy Ews-, the
friction energy Ewd and the friction energy Ewb, using an input force in a
transverse direction Fy+ generated in rightward turn of a vehicle, an
input force in a transverse direction Fy- generated in leftward turn of
the vehicle, a force in a forward direction Fx+ generated by the driving
force, a force in a backward direction Fx- generated by the braking force,
undetermined coefficients S1, S2, D and B and exponents ns1, ns2, nd and
nb, by the following formulae:
Ews+=S1.times.Fy+.sup.ns1
Ews-=S2.times.Fy-.sup.ns2
Ewd=D.times.Fx+.sup.nd
Ewb=B.times.FX-.sup.nb
a step of determining the undetermined coefficients S1, S2, D and B and the
exponents ns1, ns2, nd and nb in advance on the basis of values of the
friction energy Ews+, the friction energy Ews-, the friction energy Ewd
and the friction energy Ewb measured under application of a given value of
the input force in the transverse direction Fy+, a given value of the
input force in the transverse direction Fy-, a given value of the force in
the forward direction Fx+ and a given value of the force in the backward
direction Fx-, respectively;
a step of determining values of the input force in the transverse direction
Fy+, the input force in the transverse direction Fy-, the force in the
forward direction Fx+ and the force in the backward direction Fx- on the
basis of RMS values of the distribution of acceleration in a transverse
direction at a center of gravity position of a vehicle and the
distribution of acceleration in a longitudinal direction at a center of
gravity position of the vehicle in actual use of the vehicle; and
a step of obtaining the friction energy Ews+, the friction energy Ews-, the
friction energy Ewd and the friction energy Ewb on the basis of the
determined values of the input force in the transverse direction Fy+, the
input force in the transverse direction Fy-, the force in the forward
direction Fx+ and the force in the backward direction Fx- in accordance
with the above formulae in which the coefficients and the exponents have
been determined.
11. A method for estimating a tire wear life according to claim 7, which
further comprises:
a step of expressing a friction energy Ews+, a friction energy Ews-, the
friction energy Ewd and the friction energy Ewb, using an input force in a
transverse direction Fy+ generated in rightward turn of a vehicle, an
input force in a transverse direction Fy- generated in leftward turn of
the vehicle, a force in a forward direction Fx+ generated by the driving
force, a force in a backward direction Fx- generated by the braking force,
undetermined coefficients S1, S2, D and B and exponents ns1, ns2, nd and
nb, by the following formulae:
Ews+=S1.times.Fy+.sup.ns1
Ews-=S2.times.Fy-.sup.ns2
Ewd=D.times.Fx+.sup.nd
Ewb=B.times.FX-.sup.nb
a step of setting each of exponents ns1, ns2, nd and nb at a specific value
between 1.5 and 3 and determining the undetermined coefficients S1, S2, D
and B in advance on the basis of values of the friction energy Ews+, the
friction energy Ews-, the friction energy Ewd and the friction energy Ewb
measured under application of a given value of the input force in the
transverse direction Fy+, a given value of the input force in the
transverse direction Fy-, a given value of the force in the forward
direction Fx+ and a given value of the force in the backward direction
Fx-, respectively;
a step of determining values of the input force in the transverse direction
Fy+, the input force in the transverse direction Fy-, the force in the
forward direction Fx+ and the force in the backward direction Fx- on the
basis of RMS values of the distribution of acceleration in a transverse
direction at a center of gravity position of a vehicle and the
distribution of acceleration in a longitudinal direction at a center of
gravity position of the vehicle in actual use of the vehicle; and
a step of obtaining the friction energy Ews+, the friction energy Ews-, the
friction energy Ewd and the friction energy Ewb on the basis of the
determined values of the input force in the transverse direction Fy+, the
input force in the transverse direction Fy-, the force in the forward
direction Fx+ and the force in the backward direction Fx- in accordance
with the above formulae in which the coefficients and the exponents have
been determined.
12. A method for estimating a tire wear life according to claim 8, which
further comprises:
a step of expressing a friction energy Ews+, a friction energy Ews-, the
friction energy Ewd and the friction energy Ewb, using an input force in a
transverse direction Fy+ generated in rightward turn of a vehicle, an
input force in a transverse direction Fy- generated in leftward turn of
the vehicle, a force in a forward direction Fx+ generated by the driving
force, a force in a backward direction Fx- generated by the braking force,
undetermined coefficients S1, S2, D and B and exponents ns1, ns2, nd and
nb, by the following formulae:
Ews+=S1.times.Fy+.sup.ns1
Ews-=S2.times.Fy-.sup.ns2
Ewd=D.times.Fx+.sup.nd
Ewb=B.times.FX-.sup.nb
a step of setting each of exponents ns1, ns2, nd and nb at a specific value
between 1.5 and 3 and determining the undetermined coefficients S1, S2, D
and B in advance on the basis of values of the friction energy Ews+, the
friction energy Ews-, the friction energy Ewd and the friction energy Ewb
measured under application of a given value of the input force in the
transverse direction Fy+, a given value of the input force in the
transverse direction Fy-, a given value of the force in the forward
direction Fx+ and a given value of the force in the backward direction
Fx-, respectively;
a step of determining values of the input force in the transverse direction
Fy+, the input force in the transverse direction Fy-, the force in the
forward direction Fx+ and the force in the backward direction Fx- on the
basis of RMS values of the distribution of acceleration in a transverse
direction at a center of gravity position of a vehicle and the
distribution of acceleration in a longitudinal direction at a center of
gravity position of the vehicle in actual use of the vehicle; and
a step of obtaining the friction energy Ews+, the friction energy Ews-, the
friction energy Ewd and the friction energy Ewb on the basis of the
determined values of the input force in the transverse direction Fy+, the
input force in the transverse direction Fy-, the force in the forward
direction Fx+ and the force in the backward direction Fx- in accordance
with the above formulae in which the coefficients and the exponents have
been determined.
13. A method for estimating a tire wear life according to claim 1, wherein
the tire wear life is estimated at a plurality of portions of the tire.
14. A method for estimating a tire wear life according to claim 2, wherein
the tire wear life is estimated at a plurality of portions of the tire.
15. A method for estimating a tire wear life according to claim 1, wherein
the friction energy Ew is expressed as a value per unit area and unit
distance of driving standardized using a rolling radius of the tire.
16. A method for estimating a tire wear life according to claim 2, wherein
the friction energy Ew is expressed as a value per unit area and unit
distance of driving standardized using a rolling radius of the tire.
17. A method for estimating a tire wear life according to claim 1, wherein,
on the basis of the measured value of the rubber index Gi and the friction
energy Ew, an expected value of an amount of wear is expressed by a
formula:
expected value of an amount of wear=Ew/Gi.
18. A method for estimating a tire wear life according to claim 7, wherein,
on the basis of a measured value of the rubber index Gi and the friction
energies Ewf, Ewa, Ews+, Ews-, Ewd, and Ewb, an expected value of an
amount of wear is expressed by a formula:
expected value of an amount of
wear={(Ewf)+(Ewa)+(Ews+)+(Ews-)+(Ewd)+(Ewb)}/Gi
=Ew/Gi.
19. A method for estimating a tire wear life according to claim 8, wherein,
on the basis of a measured value of the rubber index Gi and the friction
energies Ewf, Ewa, Ews+, Ews-, Ewd, and Ewb, an expected value of an
amount of wear is expressed by a formula:
expected value of an amount of
wear={(Ewf)+(Ewa)+(Ews+)+(Ews-)+(Ewd)+(Ewb)}/Gi
=Ew/Gi.
20. A method for estimating a tire wear life which comprises:
a step of pressing at least one of a road surface simulation member and a
rotatable rubber test piece against the other of the road surface
simulation member and the rotatable rubber test piece such that the road
surface simulation member and the rubber test piece are in a pressed
state, and driving the rubber test piece to rotate;
a step of measuring a radius (Rr) of the rubber test piece at the side
thereof which presses the side of pressing the road surface simulation
member when the rubber test piece is pressed against the road surface
simulation member and rotated and/or when the road surface simulation
member is pressed against the rubber test piece;
a step of adjusting, on the basis of the measured radius of the rubber test
piece, the slip rate of the rubber test piece such that the rubber test
piece is rotated at a slip rate which is in the range of 0.5% to 5%;
a step of rotating the rubber test piece freely with respect to the road
surface simulation member;
a step of measuring a longitudinal force when the rubber test piece is
rotated at a slip rate which is in the range of 0.5% to 5% and a
longitudinal force when the rubber test piece is rotated freely with
respect to the road surface simulation member, the longitudinal force
being defined as a force in a direction tangential to the plane of contact
between the road surface simulation member and the rubber test piece; and
a step of obtaining a degree of rubber wear (V) from values including a
friction energy (ew) obtained on the basis of each of the detected
longitudinal forces and the slip rate.
21. A method for estimating a tire wear life according to claim 20, further
comprising:
a step of obtaining a mass value of the rubber test piece before the rubber
test piece is rotated at the slip rate;
a step of obtaining a mass value of the rubber test piece after the rubber
test piece is rotated at the slip rate; and
a step of computing the degree of rubber wear (V) as a wear depth in the
radial direction per unit friction energy (W/ew) using a wear depth in the
radial direction (W) and the friction energy (ew), the wear depth in the
radial direction (W) being obtained from an amount of wear of the rubber
test piece (W.sub.0), the density of the rubber test piece (.rho.), and
the total length (A) over which the road surface simulation member
contacts the rubber test piece in a pressed state when the rubber test
piece is rotated at the slip rate for a predetermined time, the amount of
wear of the rubber test piece (W.sub.0) being obtained on the basis of the
measured mass value of the rubber test piece before the rubber test piece
is rotated at the slip rate and the measured mass value of the rubber test
piece after the rubber test piece is rotated at the slip rate.
22. A method for estimating a tire wear life according to claim 21, further
comprising:
a step of obtaining a friction energy (ew.sub.t) of a tire which is mounted
onto a vehicle and formed of the same material as the material of the
rubber test piece; and
a step of obtaining a degree of rubber wear of the tire (Wt) on the basis
of the friction energy of the tire (ew.sub.t) and the degree of rubber
wear (V).
23. A method for estimating a tire wear life which comprises:
a step of obtaining a friction energy value of the tire Ewf in free
rolling, a friction energy of the tire Ewa in a state in which the tire is
provided with a toe angle;
a step of obtaining a friction energy value of the tire Ews' in a state in
which a side force is applied to the tire, a friction energy of the tire
Ewd' in a state in which a driving force is applied to the tire, and a
friction energy of the tire Ewb' in a state in which a braking force is
applied to the tire, said friction energy values Ews', Ewd', Ewb' being
each obtained in a state in which the camber angle, the toe angle and the
load are provided in consideration of the condition changing between a
static state and a dynamic state when the tire is used;
a step of obtaining a friction energy vasue ew of a rubber sample made of
the same material as the material used in a tire tread portion under a
seventy approximately the same as the severity in actual use of the tire
and a wear depth W per given driving distance;
a step of obtaining a rubber index Gi which is a value obtained by dividing
the friction energy ew by the wear depth W, i.e., ew/W, and a friction
energy Ew' expressed by the following formula:
Ew'=Ewf+Ewa+Ews'+Ewb'+Ewd'
and
a step of estimating the tire wear life on the basis of a value including a
product of the rubber index Gi and a reciprocal of Ew (1/Ew), i.e., Gi/Ew.
24. A method for estimating a tire wear life according to claim 23, which
further comprises:
a step of expressing the friction energy Ews', the friction energy Ewd' and
the friction energy Ewb', using an input force in a transverse direction
Fy, a force in a forward direction Fx+ generated by the driving force, a
force in a backward direction Fx- generated by the braking force,
undetermined coefficients S, D and B and exponents ns, nd and nb, by the
following formulae;
Ews'=S.times.Fy.sup.ns
Ewd'=D.times.Fx+.sup.nd
Ewb'=B.times.FX-.sup.nb
a step of determining the undetermined coefficients S, D and B and the
exponents ns, nd and nb in advance on the basis of values of the friction
energy Ews', the friction energy Ewd' and the friction energy Ewb'
measured under application of a given value of the input force in the
transverse direction Fy, a given value of the force in the forward
direction Fx+ and a given value of the force in the backward direction
Fx-, respectively;
a step of determining values of the input force in the transverse direction
Fy, the force in the forward direction Fx+ and the force in the backward
direction Fx--on the basis of RMS value of the distribution of
acceleration in a transverse direction at a center of gravity position of
a vehicle and the distribution of acceleration in a longitudinal direction
at a center of gravity position of the vehicle in actual use of the
vehicle; and
a step of obtaining the friction energy Ews', the friction energy Ewd' and
the friction energy Ewb' on the basis of the determined values of the
input force in the transverse direction Fy, the force in the forward
direction Fx+ and the force in the backward direction Fx- in accordance
with the above formulae in which the coefficients and the exponents have
been determined.
25. A method for estimating a tire wear life according to claim 23, which
further comprises:
a step of expressing the friction energy Ews', the friction energy Ewd' and
the friction energy Ewb', using an input force in a transverse direction
Fy, a force in a forward direction Fx+ generated by the driving force, a
force in a backward direction Fx- generated by the braking force,
undetermined coefficients S, D and B and exponents ns, nd and nb, by the
following formulae:
Ews'=S.times.Fy.sup.ns
Ewd'=D.times.Fx+.sup.nd
Ewb'=B.times.FX-.sup.nb
a step of setting each of the exponents ns, nd and nb at a specific value
between 1.5 and 3 and determining the undetermined coefficients S, D and B
in advance on the basis of values of the friction energy Ews', the
friction energy Ewd' and the friction energy Ewb' measured under
application of an input force in the transverse direction Fy, a force in
the forward direction Fx+ and a force in the backward direction Fx-,
respectively;
a step of determining values of the input force in the transverse direction
Fy, the force in the forward direction Fx+ and the force in the backward
direction Fx- on the basis of RMS values of the distribution of
acceleration in a transverse direction at a center of gravity position of
a vehicle and the distribution of acceleration in a longitudinal direction
at a center of gravity position of the vehicle in actual use of the
vehicle; and
a step of obtaining the friction energy Ews', the friction energy Ewd' and
the friction energy Ewb' on the basis of the determined values of the
input force in the transverse direction Fy, the force in the forward
direction Fx+ and the force in the backward direction Fx- in accordance
with the above formulae in which the coefficients and the exponents have
been determined.
26. A method for estimating a tire wear life according to claim 23, which
further comprises;
a step of dividing the friction energy Ews' into a friction energy Ews+'
generated in a rightward turn of a vehicle to which the tire is mounted
and a friction energy Ews-' generated in a leftward turn of the vehicle to
which the tire is mounted on the basis of an Ackerman characteristic and
the toe angle of the vehicle and obtaining each of the friction energy
Ews+' and the friction energy Ews-'; and
a step of obtaining the friction energy Ews' as a sum of the friction
energy Ews+' and the friction energy Ews-', i.e., Ews+'+Ews-'.
27. A method for estimating a tire wear life according to claim 23, wherein
the tire wear life is estimated at a plurality of portions of the tire.
28. A method for estimating a tire wear life according to claim 23, wherein
the friction energy Ew' is expressed as a value per unit area and unit
distance of driving standardized using a rolling radius of the tire.
29. A method or estimating a tire wear life according to claim 23, wherein,
on the basis of the measured value of the rubber index Gi and the friction
energy Ew', an expected value of an amount of wear is expressed by a
formula:
expected value of an amount of wear=Ew'/Gi.
30. A method for estimating a tire wear life according to claim 26, which
further comprises:
a step of expressing a friction energy Ews+', a friction energy Ews-', the
friction energy Ewd' and the friction energy Ewb', using an input force in
a transverse direction Fy+ generated in a rightward turn of a vehicle, an
input force in a transverse direction Fy- generated in a leftward turn of
the vehicle, a force in a forward direction Fx+ generated by the driving
force, a force in a backward direction Fx- generated by the braking force,
undetermined coefficients S1, S2, D and B and exponents ns1, ns2, nd and
nb, by the following formulae:
Ews+'=S1.times.Fy+.sup.ns1
Ews-'=S2.times.Fy-.sup.ns2
Ewd'=D.times.Fx+.sup.nd
Ewb'=B.times.FX-.sup.nb
a step of determining the undetermined coefficients S1, S2, D and B and the
exponents ns1, ns2, nd and nb in advance on the basis of values of the
friction energy Ews+', the friction energy Ews-', the friction energy Ewd'
and the friction energy Ewb' measured under application of a given value
of the input force in the transverse direction Fy+, a given value of the
input force in the transverse direction Fy-, a given value of the force in
the forward direction Fx+ and a given value of the force in the backward
direction Fx-, respectively;
a step of determining values of the input force in the transverse direction
Fy+, the input force in the transverse direction Fy-, the force in the
forward direction Fx+ and the force in the backward direction Fx- on the
basis of RMS values of the distribution of acceleration in a transverse
direction at a center of gravity position of a vehicle and the
distribution of acceleration in a longitudinal direction at a center of
gravity position of the vehicle in actual use of the vehicle; and
a step of obtaining the friction energy Ews+', the friction energy Ews-',
the friction energy Ewd' and the friction energy Ewb' on the basis of the
determined values of the input force in the transverse direction Fy+, the
input force in the transverse direction Fy-, the force in the forward
direction Fx+ and the force in the backward direction Fx- in accordance
with the above formulae in which the coefficients and the exponents have
been determined.
31. A method for estimating a tire wear life according to claim 26, which
further comprises:
a step of expressing a friction energy Ews+', a friction energy Ews-', the
friction energy Ewd' and the friction energy Ewb', using an input force in
a transverse direction Fy+ generated in rightward turn of a vehicle, an
input force in a transverse direction Fy- generated in leftward turn of
the vehicle, a force in a forward direction Fx+ generated by the driving
force, a force in a backward direction Fx- generated by the braking force,
undetermined coefficients S1, S2, D and B and exponents ns1, ns2, nd and
nb, by the following formulae:
Ews+'=S1.times.Fy+.sup.ns1
Ews-'=S2.times.Fy-.sup.ns2
Ewd'=D.times.Fx+.sup.nd
Ewb'=B.times.FX-.sup.nb
a step of setting each of exponents ns1, ns2, nd and nb at a specific value
between 1.5 and 3 and determining the undetermined coefficients S1, S2, D
and B in advance on the basis of values of the friction energy Ews+', the
friction energy Ews-', the friction energy Ewd' and the friction energy
Ewb' measured under application of a given value of the input force in the
transverse direction Fy+, a given value of the input force in the
transverse direction Fy-, a given value of the force in the forward
direction Fx+ and a given value of the force in the backward direction
Fx-, respectively;
a step of determining values of the input force in the transverse direction
Fy+, the input force in the transverse direction Fy-, the force in the
forward direction Fx+ and the force m the backward direction Fx- on the
basis of RMS values of the distribution of acceleration in a transverse
direction at a center of gravity position of a vehicle and the
distribution of acceleration in a longitudinal direction at a center of
gravity position of the vehicle in actual use of the vehicle; and
a step of obtaining the friction energy Ews+', the friction energy Ews-',
the friction energy Ewd' and the friction energy Ewb' on the basis of the
determined values of the input force in the transverse direction Fy+, the
input force in the transverse direction Fy-, the force in the forward
direction Fx+ and the force in the backward direction Fx- in accordance
with the above formulae in which the coefficients and the exponents have
been determined.
32. A method for estimating a tire wear life according to claim 26,
wherein, on the basis of a measured value of the rubber index Gi and the
friction energies Ewf, Ewa, Ews+', Ews-', Ewd', and Ewb', an expected
value of an amount of wear is expressed by a formula:
expected value of an amount of wear
={(Ewf)+(Ewa)+(Ews+')+(Ews-')+(Ewd')+(Ewb')}/Gi
=Ew'/Gi. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for estimating a tire wear life,
and more particularly, to a method for estimating a tire wear life which
enables estimating the tire wear lie or the degree of wear of rubber in
actual use.
2. Description of the Related Art
Heretofore, the wear life of a tire used for vehicles has been estimated
from the condition of wear (the degree of wear or the amount of wear)
after a vehicle mounting the tire whose wear life is to be estimated is
actually driven for a specific distance (as for the definition of the word
"wear life", refer to page 13 of the specification).
However, this method has a drawback in that the test is quite
time-consuming because the distance to be driven by the vehicle for the
test must be great in order to get an accurate measurement of the amount
of wear of the tire required for a highly precise estimation.
To overcome the above drawback, in the technology disclosed in Japanese
Patent Application Publication (hereinafter, referred to as JP-B) 1-56374,
at least two pairs of test tires are mounted to a vehicle used for the
test and are driven on roads in a manner such that the rotation speeds of
the two tires are different between the pairs by a desired extent so that
the wear of the tire due to the driving force and due to the braking force
can be evaluated simultaneously.
As the formula for estimating the amount of wear of a tire, Schallamach's
formula of the amount of wear is known. In accordance with this
theoretical formula, the amount of wear M of a tire per unit distance of
driving is considered to be proportional to the friction energy and can be
expressed by the following formula (1):
M=.gamma..rho.F.sup.2 /C (1)
In formula (1), .gamma. represents the degree of wear of a tire, .rho.
represents resilience, F represents an external force applied to the tire
and C represents the rigidity of the tire against a force in the
longitudinal direction or the transverse direction thereof When the
rigidity C is expressed move specifically by the rigidity in the
longitudinal direction, (in the driving direction) Cd, and the rigidity in
the direction of braking Cb, and the rigidity in the transverse direction
Cs, Schallamach's formula of the amount of wear is expressed by the
following formula (2):
M=.gamma..rho.F.sup.2 /(Cd+Cb+Cs)
=.gamma..rho.(Fx+.sup.2 /Cd+Fx-.sup.2 /Cb+Fy.sup.2 /Cs) (2)
In the above formula, Fx+ represents a force in the forward direction
generated by a driving force, Fx- represents a force in the backwards
direction generated by a braking force and Fy represents an input force in
the transverse direction.
However, the technology described in the specification of JP-B 1-56374 has
a drawback in that at least one actual road test must be conducted for a
long time and thus it still takes a long time to estimate the tire wear
life, although the time required for the test can be decreased in
comparison with the time required for methods of estimation using only one
pair of tires in one run of the road test.
Moreover, Schallamach's formula of the amount of wear has a drawback in
that, although the formula takes rigidities in the direction of driving,
in the direction of braking and in the transverse direction into
consideration, accurate estimation of tire wear life of a tire mounted to
a vehicle in actual use is still difficult when factors taken into
consideration are limited to these parameters.
When driving a vehicle in actual use, there are more diverse factors
affecting the wear of a tire such as the properties of the rubber of the
tire tread portion, tire tread patterns and structures, and input forces
experienced by a tire in the actual use of the tire by the customers
(during driving in the conditions of actual road use of the vehicle).
Therefore, in the actual driving condition of a vehicle which is affected
by so many diverse factors, it is obviously difficult to accurately
estimate the wear of a tire using Schallamach's formula of the amount of
wear in which only rigidities in the direction of driving, in the
direction of braking and in the transverse direction are considered.
SUMMARY OF THE INVENTION
The present invention has been made to overcome the above problems and has
an objective of providing a method for estimating the tire wear life which
enables accurate estimation of the tire wear life in a short time.
To achieve the above object, in the first aspect of the method for
estimating the tire wear life of the present invention, a friction energy
of the tire Ewf in free rolling, a friction energy of the tire Ewa when
the tire is mounted with a toe angle, a friction energy of the tire Ews
under application of a side force to the tire, a friction energy of the
tire Ewd under application of a driving force to the tire and a friction
energy of the tire Ewb under application of a braking force to the tire
are obtained. In addition, a friction energy ew of a rubber sample made of
the same material as the material used in the tire tread portion under a
severity substantially the same as the severity in the actual use of the
tire and a wear depth W per given driving distance are also obtained.
The tire wear life is estimated on the basis of a value including a product
of a rubber index Gi and a reciprocal of a friction energy Ew (1/Ew),
i.e., Gi/Ew. The rubber index Gi is a value obtained by dividing the
friction energy ew by the wear depth W, i.e., ew/W. The friction energy Ew
is expressed by the following formula:
Ew=Ewf+Ewa+Ews+Ewb+Ewd
In accordance with the first aspect of the present invention, the friction
energy of the tire Ewf in free rolling and the friction energy of the tire
Ewa when the tire is mounted with a toe angle are used as the factors for
estimating the tire wear life in addition to the friction energy of the
tire Ews under application of a side force (force in the transverse
direction) to the tire, the friction energy of the tire Ewd under
application of a driving force to the tire and the friction energy of the
tire Ewb under application of a braking force to the tire. Therefore, the
tire wear life can be estimated more accurately in comparison with the
estimation of the tire wear life in accordance with the Schallamach's
formula of the amount of wear in which rigidity in the direction of
driving, in the direction of braking and in the transverse direction alone
are taken into consideration.
In this aspect, the rubber index Gi is measured under a severity which is
approximately the same as the severity in the actual use of the tire and
used for estimation of the tire wear life. Therefore, the tire wear life
can be estimated more accurately in comparison with the estimation using
the friction resistance index obtained by the conventional Lambourn
abrasion tester specified in Japanese Industrial Standard K 6264.
In the second aspect of the present invention, it is preferable that the
value including the product Gi/Ew is a value selected from the product
Gi/Ew or a value obtained by multiplying the product Gi/Ew by a remaining
groove depth remaining before the groove depth reaches the limit for
disposal of the tire.
As the remaining groove depth remaining before the groove depth reaches the
limit for disposal of the tire, it is preferable that a value obtained by
subtracting the value which is considered to be the limit for disposal of
the tire, for example 1.6 (mm), from the groove depth NSD is used.
In the third aspect of the present invention, using an input force in a
transverse direction Fy, a force in a forward direction Fx+ generated by
the driving force, a force in a backward direction Fx- generated by the
braking force, undetermined coefficients S, D and B and exponents ns, nd
and nb, the friction energy Ews, the friction energy Ewd and the friction
energy Ewb are expressed by the following formulae:
Ews=S.times.Fy.sup.ns
Ewd=D.times.Fx+.sup.nd
Ewb=B.times.FX-.sup.nb
The undetermined coefficients S, D and B and the exponents ns, nd and nb
are obtained in advance on the basis of values of the friction energy Ews,
the friction energy Ewd and the friction energy Ewb measured under
application of a given value of the input force in the transverse
direction Fy, a given value of the force in the forward direction Fx+ and
a given value of the force in the backward direction Fx-, respectively.
Values of the input force in the transverse direction Fy, the force in the
forward direction Fx+ and the force in the backward direction Fx- are
determined on the basis of RMS values of the distribution of acceleration
in the transverse direction at the center of gravity position of the
vehicle and the distribution of acceleration in the longitudinal direction
at the center of gravity position of the vehicle in the actual use of the
vehicle. The friction energy Ews, the friction energy Ewd and the friction
energy Ewb are obtained on the basis of the determined values of the input
force in the transverse direction Fy, the force in forward direction Fx+
and the force in the backward direction Fx- in accordance with the above
formulae.
In accordance with the third aspect of the present invention, the
estimation reflects input forces in the actual use of the tire because the
friction energy Ews, the friction energy Ewd and the friction energy Ewb
are obtained on the basis of RMS values of the distribution of
acceleration in the transverse direction at the center of gravity position
of the vehicle or the distribution of acceleration in the longitudinal
direction at the center of gravity position of the vehicle in the actual
use of the tire. Therefore, the tire wear life can be estimated more
accurately in comparison with estimations which do not reflect input
forces in the actual use of the tire.
In the fourth aspect of the present invention, the exponents ns, nd and nb
which are obtained on the basis of measured values in the third aspect are
each set at a fixed value in the range of 1.5 to 3 and preferably in the
range of 2 to 3. The undetermined coefficients S, D and B are obtained in
advance on the basis of values of the friction e | | |
