PNEUMATIC RADIAL TIRE FOR A PASSENGER VEHICLE AND METHOD OF USING THE SAME

TECHNICAL FIELD

The present invention relates to a pneumatic radial tire for a passenger vehicle and a method of using the tire.

BACKGROUND ART

Bias tires having relatively narrower sectional widths had been predominantly used in vehicles until around 1960 because vehicles in those days were relatively lightweight, and the speed demanded for the vehicles were lower, resulting a less burden imposed on the tires. However, radial tires are predominant these days and those having larger widths and assuming flat shapes are particularly demanded due to increase in weight and speed of vehicles (see, for example, PTL 1).

However, the increase in a tire width sacrifices the vehicle space and thus degrades comfortability. This is a major problem particularly for electric vehicles that have been put on practical use in anticipation of future, considering situations where ensuring a space around tires has been becoming of great importance, because the electric vehicles are required to secure a space for accommodating driving components such as a motor for controlling a torque for rotating a tire about a drive shaft.

Further, there has been an increasing demand for lower fuel consumption along with increased interest in environmental issues. Here, it has been known to increase a diameter and a width of the tire in order to reduce a rolling resistance value (RR value) of the tire for better fuel efficiency. However, there is a problem that the increase in the diameter and width of the tire leads to an increase in tire weight and air resistance, which rather increases vehicle resistance and causes excessive tire loading capability.

CITATION LIST
Patent Literature

PTL 1: JP H7-40706 A

SUMMARY OF INVENTION
Technical Problem

The present invention aims at solving the problems described above and an object thereof is to provide a pneumatic radial tire for a passenger vehicle that is lightweight with less vehicle resistance and thus ensures excellent comfortability, and to provide a method of using the tire.

Solution to Problem

The inventors diligently studied to solve the aforementioned problems.

As a result, the inventors have found that it is extremely effective, for the purpose of improvement in fuel efficiency and comfortability of a radial tire, to appropriately control reduction in a width of the tire and the increase in a diameter, namely, a relationship between a tire cross-sectional width SW and a tire outer diameter OD.

The present invention has been contrived based on the aforementioned knowledge and a summary thereof is as follows:

(1) A pneumatic radial tire for a passenger vehicle having a carcass, which is composed of a ply of cords radially arranged and toroidally provided between a pair of bead cores, and a bead filler disposed outside the bead cores in a tire radial direction, wherein

when the radial tire is mounted on a rim and applied with internal pressure of at least 250 kPa,

with a tire cross-sectional width SW of smaller than 165 (mm), a ratio of the tire cross-sectional width SW to a tire outer diameter OD, SW/OD, is no more than 0.26,

with the tire cross-sectional width SW of 165 (mm) or larger, the tire cross-sectional width SW and the tire outer diameter OD satisfy a relational expression:

OD≧2.135×SW+282.3, and

a bead filler tire-width-direction cross-sectional area S1 is one to four times the size of a bead core tire-width-direction cross-sectional area S2.

(2) A pneumatic radial tire for a passenger vehicle having a carcass, which is composed of a ply of cords radially arranged and toroidally provided between a pair of bead cores, and a bead filler disposed outside the bead cores in a tire radial direction, wherein

when the radial tire is mounted on a rim and applied with internal pressure of at least 250 kPa, a tire cross-sectional width SW and a tire outer diameter OD satisfy a relational expression:

OD≧−0.0187×SW²+9.15×SW−380, and

a bead filler tire-width-direction cross-sectional area S1 is one to four times the size of a bead core tire-width-direction cross-sectional area S2.

(3) The pneumatic radial tire for a passenger vehicle according to (1) or (2) set forth above, wherein, when BFW represents a width of the bead filler in the tire width direction in a tire radial direction center position of the bead filler and BDW represents a maximum width of the bead core in the tire width direction, the following relational expression:

0.1≦BFW/BDW≦0.5

is satisfied.

(4) The pneumatic radial tire for a passenger vehicle according to any one of (1) to (3) set forth above, wherein, when BFH represents a height of the bead filler in the tire radial direction and SH represents a tire sectional height, the following relational expression:

0.1≦BFH/SH≦0.25

is satisfied.

(5) The pneumatic radial tire for a passenger vehicle according to any one of (1) to (4) set forth above, wherein BFH, the height of the bead filler in the tire radial direction, is no more than 45 mm.

(6) A method of using a pneumatic radial tire for a passenger vehicle, wherein the tire according to (1) or (2) set forth above having the internal pressure of at least 250 kPa is used.

(7) A pneumatic radial tire for a passenger vehicle including a carcass, which is composed of a ply of carcass codes radially arranged and toroidally provided between bead cores embedded in a pair of bead portions, and a pair of sidewall portions connected to the bead portions, wherein

when the tire is mounted on a rim and applied with internal pressure of at least 250 kPa,

with a tire cross-sectional width SW of smaller than 165 (mm), a ratio of the tire cross-sectional width SW to a tire outer diameter OD, SW/OD, is no more than 0.26,

with the tire cross-sectional width SW of 165 (mm) or larger, the tire cross-sectional width SW and the tire outer diameter OD satisfy a relational expression:

OD≧2.135×SW+282.3, and

a ratio Ts/Tb is 15% to 40%, the Ts representing a gauge of the sidewall portion in a maximum width portion of the tire and the Tb representing a bead width of the bead core in a tire radial direction center position.

(8) A pneumatic radial tire for a passenger vehicle including a carcass, which is composed of a ply of carcass codes radially arranged and toroidally provided between bead cores embedded in a pair of bead portions, and a pair of sidewall portions connected to the bead portions, wherein

when the tire is mounted on a rim and applied with internal pressure of at least 250 kPa, a tire cross-sectional width SW and a tire outer diameter OD satisfy a relational expression:

OD≧−0.0187×SW²+9.15×SW−380, and

a ratio Ts/Tb is 15% to 40%, the Ts representing a gauge of the sidewall portion in a tire maximum width portion and the Tb representing a bead width of the bead core in a tire radial direction center position.

(9) The pneumatic radial tire for a passenger vehicle according to (7) or (8) set forth above, wherein the gauge Ts of the sidewall portion in the tire maximum width portion is no less than 1.5 mm.

(10) The pneumatic radial tire for a passenger vehicle according to any one of (7) to (9) set forth above, wherein a diameter Tbc of the bead core is 4 mm to 12 mm.

(11) A method of using a pneumatic radial tire for a passenger vehicle, wherein the tire according to (7) or (8) set forth above having internal pressure of at least 250 kPa is used.

(12) A pneumatic radial tire for a passenger vehicle including a carcass, which is composed of a ply of carcass codes radially arranged and toroidally provided between a pair of bead portions, and a pair of sidewall portions connected to the bead portions, wherein

when the tire is mounted on a rim and applied with internal pressure of at least 250 kPa,

with a tire cross-sectional width SW of smaller than 165 (mm), a ratio of the tire cross-sectional width SW to a tire outer diameter OD, SW/OD, is no more than 0.26,

with the tire cross-sectional width SW of 165 (mm) or larger, the tire cross-sectional width SW and the tire outer diameter OD satisfy a relational expression:

OD≧2.135×SW+282.3, and

a ratio Ts/Tc is 5 to 10, the Ts representing a gauge of the sidewall portion in a tire maximum width portion and Tc representing a diameter of the carcass code.

(13) A pneumatic radial tire for a passenger vehicle including a carcass, which is composed of a ply of carcass codes radially arranged and toroidally provided between a pair of bead portions, and a pair of sidewall portions connected to the bead portions, wherein

when the tire is mounted on a rim and applied with internal pressure of at least 250 kPa, a tire cross-sectional width SW and a tire outer diameter OD satisfy a relational expression:

OD≧−0.0187×SW²+9.15×SW−380, and

a ratio Ts/Tc is 5 to 10, the Ts representing a gauge of the sidewall portion in a tire maximum width portion and Tc representing a diameter of the carcass code.

(14) The pneumatic radial tire for a passenger vehicle according to (12) or (13) set forth above, wherein, when Ta represents a distance in a tire width direction from a surface of the carcass code to a tire outer surface, a ratio Ta/Tc is 3 to 6.

(15) The pneumatic radial tire for a passenger vehicle according to any one of (12) to (14) set forth above, wherein the diameter Tc of the carcass code is 0.4 mm to 0.8 mm.

(16) A method of using a pneumatic radial tire for a passenger vehicle, wherein the tire according to (12) or (13) set forth above having internal pressure of at least 250 kPa is used.

Advantageous Effect of Invention

According to the present invention, a pneumatic radial tire for a passenger vehicle that is lightweight having less vehicle resistance and thus capable of providing excellent comfortability may be provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1(
a) is a side view of a tire, and FIG. 1(b) is a cross-sectional view in a tire circumferential direction illustrating the proximity of a ground-contact surface of the tire;

FIG. 2 is a graph illustrating a relationship between a tire outer diameter OD and a tire deflection amount δ1;

FIGS. 3(
a), (b) are diagrams illustrating tire deformations;

FIGS. 4(
a), (b) are cross-sectional diagrams in a tire width direction illustrating tire deformations;

FIG. 5 is a graph illustrating a relationship between a ground-contact width W and a deflection amount δ2;

FIG. 6 is a diagram illustrating a relationship among a load, internal pressure, and a ground-contact area;

FIG. 7(
a) is a graph illustrating the deflection amount δ1 of the tire having high internal pressure, and FIG. 7(b) is a graph illustrating the ground-contact area when the tire is applied with high internal pressure;

FIGS. 8(
a), (b) are diagrams illustrating vehicle space ensured by the tire with a larger diameter and a narrower width;

FIG. 9 is a graph illustrating a relationship between the tire internal pressure and a tire rolling resistance value (RR value);

FIGS. 10(
a), (b) are graphs illustrating weight and the rolling resistance value of each tire;

FIGS. 11(
a), (b) are graphs illustrating a ground-contact length and the rolling resistance value of each tire;

FIGS. 12(
a), (b) are graphs illustrating the deflection amount δ1 and the ground-contact length of each tire;

FIG. 13 is a graph illustrating a relationship between a ground-contact width and the rolling resistance value of each tire;

FIGS. 14(
a), (b) are graphs illustrating a relationship between SW and OD of test tires and conventional tires;

FIG. 15 is a graph illustrating the weight and the rolling resistance value of each tire;

FIG. 16 is a cross-sectional view in a tire width direction of a pneumatic radial tire for a passenger vehicle according to the present invention;

FIG. 17 is a cross-sectional view in a tire width direction of a pneumatic radial tire for a passenger vehicle according to the present invention;

FIG. 18(
a) is a schematic diagram illustrating a size of a member around sidewall portion, and FIG. 18(b) is a schematic diagram illustrating a size of a member around the bead portion;

FIG. 19 is a cross-sectional diagram in the tire width direction of the pneumatic radial tire for a passenger vehicle according to the present invention;

FIG. 20 is a schematic diagram illustrating a size of a tire member around the sidewall portion;

FIGS. 21(
a), (b) are graphs illustrating results of an evaluation of a tire performance test;

FIGS. 22(
a), (b) are graphs illustrating results of an evaluation of a tire performance test;

FIGS. 23(
a), (b) are graphs illustrating results of an evaluation of a tire performance test;

FIGS. 24(
a), (b) are graphs illustrating results of an evaluation of a tire performance test;

FIGS. 25(
a), (b) are graphs illustrating results of an evaluation of a tire performance test; and

FIGS. 26(
a), (b) are graphs illustrating results of an evaluation of a tire performance test.

DESCRIPTION OF EMBODIMENTS

The following is a description of a process that led to a pneumatic radial tire for a passenger car (hereinafter, referred to as a tire) according to the present invention.

FIG. 1(
a) illustrates a tire crown portion bending upon application of a load. Due to the bending of the crown portion, as schematically illustrated in a parallelogram in FIG. 1(a), tread rubber undergoes shear deformation in a tire circumferential direction, which repeatedly occurs during rotation of the tire, causing energy loss and the increase in tire rolling resistance.

As such, in order to reduce a rolling resistance value, first, reduction in a deflection amount of the tire during ground contact becomes of importance.

FIG. 1(
b) is a cross-sectional view in a circumferential direction of the tire in the proximity of a ground-contact surface thereof. As illustrated in FIG. 1(b), when OD (mm), δ1 (mm), and L (mm) represent a tire outer diameter, a deflection amount, and a ground-contact length in the circumferential direction, respectively, the deflection amount δ1 may be approximately represented by, in a geometrical manner, the following two formulae:

δ1=(OD/2)×(1−cos θ) (Formula 1)

θ≈ tan⁻¹{(L/2)/(OD/2)}≈L/OD (Formula 2)

Also, FIG. 2 is a graph illustrating a relationship between the tire outer diameter OD and the deflection amount δ1 when conventional tires in various sizes are mounted on an application rim and applied with prescribed internal pressure and a maximum load.

Here, the “application rim” for the conventional tire is defined by industrial standards valid in areas where the tire is produced and used, such as JATMA (Japan Automobile Tire Manufacturers Association) YEAR BOOK in Japan, ETRTO (European Tyre and Rim Technical Organization) STANDARD MANUAL in Europe, and TRA (THE TIRE and RIM ASSOCIATION INC.) YEAR BOOK in the United States. Also, the “prescribed internal pressure” is based on a correspondence table of the application rim corresponding to a size of a radial ply tire as defined in the above-mentioned JATMAYEAR BOOK (Japan Automobile Tire Manufacturers Association Standards) and the like, the air pressure, and a load capacity. Further, the term “maximum load” means a maximum load (maximum load capacity) of a single tire in an appropriate size prescribed in the above-mentioned predetermined industrial standards.

From Formulae 1 and 2 set forth above and FIG. 2, it can be seen that, in order to reduce the deflection amount δ1, it is effective to increase the tire outer diameter OD.

That is, in order to reduce the tire rolling resistance from a viewpoint of suppression of the shear deformation of tread rubber in the tire circumferential direction, it is effective to increase a tire diameter.

Further, from the following Formula representing a tire belt tension, it can be seen that the tire belt tension increases along with the increase in the tire diameter.

T=(OD/2)×P (Formula 3)

Along with the increase in the tire belt tension, tire ring rigidity (rigidity for keeping a ring shape of the tire) also increases, which, as illustrated in FIGS. 3(a), (b), promotes deformation eccentrically moving the entire ring (i.e., eccentric deformation) while the tire is maintained in the ring shape. Thereby, deformation of the tread rubber is suppressed, reducing the tire rolling resistance value.

That is, the increase in the tire diameter is effective in reducing the tire rolling resistance value, also from a viewpoint of suppressing deformation of the ring shape of the tire.

Next, the inventors focused on the shear deformation of the tread rubber in the tire width direction.

That is, deflection of the crown portion when the tire contacts the ground, as schematically illustrated by a parallelogram of FIG. 4(a), causes shear deformation of the tread rubber in the tire width direction, which repeatedly occurs during rotation of the tire, causing energy loss and the increase in the rolling resistance.

FIG. 4(
b) is a cross-sectional view of a tire ground-contact surface in the tire width direction. As illustrated in FIG. 4(b), in the cross-section in the tire width direction, each of points E1 and E2 represents a contact end upon application of a maximum load defined for each vehicle wearing the tire, a point F represents a width direction center position, and W (mm) represents a width direction contact width.

Also, in a no-load state, CR (mm) represents a crown radius at each of the points E1 and E2 on a curve including the three points E1, E2, and F approximated by a circular arc in the width-direction cross-section, and O represents a center of a circle made on the basis of the circular arc. Here, in the width-direction cross-section, a line segment OE1 forms an angle γ(°) with respect to a tire equator plane.

Further, when a deflection amount δ2 (mm) (an amount of deflection of ground-contact ends in the width direction) represents a deflection amount upon application of a maximum load defined for each vehicle wearing the tires described above, the δ2 may be approximately expressed by the following formulae in a geometrical manner:

δ2=CR×(1−cos γ) (Formula 4)

γ≈ tan⁻¹{(W/2)/CR}≈W/2CR (Formula 5)

Also, FIG. 5 is a graph illustrating a relationship between the contact width W and the deflection amount δ2 when conventional tires in various sizes are mounted on the application rim and applied with the prescribed internal pressure and the maximum load.

As can be seen from Formulae 4, 5 set forth above and FIG. 5, reduction in the ground-contact width W may reduce the deflection amount δ2. That is, in order to reduce the tire rolling resistance from a viewpoint of suppression of the shear deformation of the tread rubber in the tire width direction, it is effective to reduce a tire width.

The reduction in the tire width is also effective to reduce tire weight.

As described above, it has been found that appropriate regulation of the increase in the tire diameter and the reduction in the tire width enables reduction in the tire rolling resistance value while reducing the tire weight.

As illustrated in FIG. 6, incidentally, when L, W, P, and Lo represent the ground-contact length, the ground-contact width, the internal pressure, and a load on the tire, respectively, a relationship between a ground-contact area of the tire and the applied load satisfies the following relational expression:

Lo≈W×L×P, (Formula 6)

which is derived from an equilibrium-force condition.

Therefore, under a condition with a certain load applied on the tire and certain internal pressure, when the ground-contact width W of the tire is reduced so as to suppress the shear deformation of the tread rubber in the width direction and also to reduce the tire weight as described above, the ground-contact length L increases, as can be seen from the relational expression of a balance of Formula 6 set forth above.

Accordingly, it has been newly found that, according to Formulae 1, 2 set forth above, the increase in the deflection amount δ1 due to the increase in the ground-contact length L leads to the increase in the shear deformation of the tread rubber in the tire circumferential direction.

As such, the inventors have found that, as a method to suppress the increase in the ground-contact length while reducing the width of the tire, it is effective to use the tire with high internal pressure.

That is, based on the relational expression of Formula 6 set forth above, regardless of the reduction in the ground-contact width, the tire with high internal pressure may support an applied load without reducing the ground-contact length.

FIG. 7(
a) is a graph illustrating a relationship between the ground-contact width W and the deflection amount δ1 of a tire of 195/65R15 in size mounted on the application rim and applied with the maximum load. FIG. 7(b) is a graph illustrating a relationship between the ground-contact width W and the ground-contact area of the tire of 195/65R15 in size mounted on the application rim and applied with the maximum load.

As illustrated in FIG. 7(a), when the tire with prescribed internal pressure is used, the ground-contact width reduces and thus the deflection amount δ1 increases, reducing the effect to reduce the shear deformation of the tread rubber in the circumferential direction. As illustrated in FIG. 7(b), also, the ground-contact area remains approximately the same regardless of the reduction in the ground-contact width while the ground-contact length increases.

On the other hand, by using the tire with high internal pressure, the increase in the deflection amount may be suppressed regardless of the reduction in the ground-contact width as illustrated in FIG. 7(a) and, by reducing the ground-contact width, the ground-contact area may also be reduced as illustrated in FIG. 7(b).

Accordingly, the shear deformation of the tread rubber in the circumferential direction when the tire contacts the ground may be suppressed, thus reducing the tire rolling resistance value.

Further, as illustrated in FIGS. 8(a), (b), the reduction in the tire width may ensure a space inside/outside a vehicle; in particular, a space for accommodating driving components in the proximity of an inner side of the tire. Also, the increase in the diameter of the radial tire increases a height of a drive shaft and an under-chassis space, securing spaces for a car trunk and the like and also a space for accommodating driving units.

On the basis of the findings described above, the inventors investigated for specific conditions under which the increase in the tire diameter, the reduction in the tire width, and application of high internal pressure may achieve both the reduction in the tire rolling resistance value and the tire weight.

First, as a referential tire for evaluation, a tire of 195/65R15 in size was prepared, because such a tire has been used for the most common types of vehicles and thus suitable for comparison of tire performance.

Tires in various sizes were also prepared, which were mounted on a rim with a width corresponding to a bead width of the tire and applied with the internal pressure of 220 kPa, or applied with high internal pressure. Then, tests were conducted as described below.

Table 1 shows specifications of each of the tires. Other specifications such as internal structures of the tires that are not shown in Table 1 are similar to those of common tires. Each of the tires includes a carcass composed of a ply of codes radially arranged and toroidally provided between a pair of bead portions.

With regard to the tire size, the inventors studied using tires in various sizes including conventional sizes prescribed in JATMA (the tire standard in Japan), TRA (the tire standard in the United States), ETRTO (the tire standard in EU) and the like, as well as using tires in non-standard sizes.

Especially assuming a sporty application, test tires 27 to 33 with a tire cross-sectional width SW of at least 175 (mm) were also prepared.

Here, the test tires 27 to 33 were compared with a tire of 225/45R17 in size (Reference Tire 2), which is larger than the tire of 195/65R15 in size (Reference Tire 1) by an inch.

TABLE 1

Ratio

Tire Size
SW/OD

Conventional Tire
Conventional Tire 1
145/70R12
0.29

Conventional Tire 2
155/55R14
0.29

Conventional Tire 3
165/60R14
0.30

Conventional Tire 4
175/65R14
0.30

Conventional Tire 5
185/60R15
0.31

Reference Tire 1
195/65R15
0.31

Conventional Tire 6
205/55R16
0.32

Conventional Tire 7
215/60R16
0.32

Conventional Tire 8
225/55R17
0.33

Conventional Tire 9
245/45R18
0.36

Conventional Tire 10
155/65R13
0.29

Reference Tire 2
225/45R17
0.35

Test tire
Test tire 1
165/65R19
0.24

Test tire 2
155/65R18
0.24

Test tire 3
145/65R19
0.22

Test tire 4
135/65R19
0.21

Test tire 5
125/65R19
0.19

Test tire 6
175/55R22
0.23

Test tire 7
165/55R20
0.24

Test tire 8
155/55R19
0.24

Test tire 9
145/55R20
0.22

Test tire 10
135/55R20
0.21

Test tire 11
125/55R20
0.19

Test tire 12
175/45R23
0.24

Test tire 13
165/45R22
0.23

Test tire 14
155/45R21
0.23

Test tire 15
145/45R21
0.22

Test tire 16
135/45R21
0.21

Test tire 17
145/60R16
0.25

Test tire 18
155/60R17
0.25

Test tire 19
165/55R19
0.25

Test tire 20
155/45R18
0.26

Test tire 21
165/55R18
0.26

Test tire 22
175/55R19
0.26

Test tire 23
115/50R17
0.21

Test tire 24
105/50R16
0.21

Test tire 25
135/60R17
0.23

Test tire 26
185/60R20
0.25

Test tire 27
185/50R20
0.27

Test tire 28
195/60R19
0.27

Test tire 29
175/60R18
0.26

Test tire 30
195/55R20
0.27

Test tire 31
215/50R21
0.29

Test tire 32
205/55R20
0.28

Test tire 33
185/45R22
0.26

Each of the tires set forth above was mounted on the rim with the width corresponding to the bead width of the tire to obtain a tire-rim assembly. The tire was then applied with the maximum load prescribed for each vehicle wearing the tire and run at a drum rotation speed of 100 km/h, for measurement of the rolling resistance.

Results of an evaluation are shown as indices relative to that of Reference Tire 1 set to 100. The smaller the index, the smaller the rolling resistance.

Weight of each of the tire was measured and is shown as index relative to that of Reference Tire 1 set to 100 (the smaller the index, the lighter the weight).

Results of an evaluation are shown in Tables 2 and 3 below, based on which the results are further illustrated in FIGS. 10 to 13.

TABLE 2

RR
Internal

Tire

Value
Pressure
W
L
OD
δ1
Weight

220 kPa
(INDEX)
(kPa)
(mm)
(mm)
(mm)
(mm)
(INDEX)

Conventional
Conventional
120
220
111.65
162.8
507.8
12.1
61.3

Tire
Tire 1

Conventional
125
220
119.35
152.3
526.1
10.4
61.9

Tire 2

Conventional
118
220
127.05
143.1
553.6
8.8
71.6

Tire 3

Conventional
109
220
134.75
134.9
583.1
7.5
82.5

Tire 4

Conventional
106
220
142.45
127.6
603
6.5
87.4

Tire 5

Reference
100
220
150.15
121.1
634.5
5.6
100

Tire 1

Conventional
101
220
157.85
115.2
631.9
5.1
98.3

Tire 6

Conventional
93
220
164.65
110.4
664.4
4.5
111.9

Tire 7

Conventional
85
220
170.85
106.4
679.3
4.1
124.7

Tire 8

Conventional
80
220
176.65
102.9
677.7
3.8
129.4

Tire 9

Conventional
90
220
170.8
106.4
634.3
4.4
116.5

Tire 10

Reference
90
220
170.8
106.5
634.3
4.37
116

Tire 2

Test Tire
Test Tire 1
98.9
220
127.1
143.1
697.1
7.1
93

Test Tire 2
106.7
220
119.4
152.3
658.7
8.5
82.5

Test Tire 3
107.5
220
111.7
162.8
671.1
9.5
78.6

Test Tire 4
111.7
220
104
174.9
658.1
11
71.8

Test Tire 5
116
220
96.3
188.9
645.1
13
65.2

Test Tire 6
88.3
220
134.8
134.9
751.3
5.9
99.7

Test Tire 7
99.3
220
128.3
141.7
689.5
7.1
86.3

Test Tire 8
106.8
220
120.5
150.8
653.1
8.4
76.8

Test Tire 9
107.4
220
112.8
161.2
667.5
9.3
73.4

Test Tire 10
111.4
220
105
173.2
656.5
10.9
67.2

Test Tire 11
115.4
220
97.2
187
645.5
12.8
61.2

Test Tire 12
89
220
136.1
133.6
741.7
5.9
92

Test Tire 13
96.3
220
129.6
140.3
707.3
6.8
82.7

Test Tire 14
103.5
220
121.7
149.3
672.9
8
73.9

Test Tire 15
107.2
220
113.9
159.6
663.9
9.2
68.2

Test Tire 16
111
220
106
171.5
654.9
10.7
62.7

Test Tire 17
102.7
220
114.6
158.7
580.4
10.2
65.9

Test Tire 18
100.1
220
122.5
148.4
617.8
8.5
75

Test Tire 19
94.2
220
130.4
139.4
664.1
7
83.1

Test Tire 20
105
220
122.5
148.4
596.7
8.8
65.5

Test Tire 21
96.2
220
130.4
139.4
638.7
7.3
79.9

Test Tire 22
93.6
220
131.3
138.5
675.1
6.2
89.6

Test Tire 23
118
220
92.0
197.6
546.8
16.3
48.2

Test Tire 24
120
220
89.3
203.7
511.4
18.2
41.2

Test Tire 25
113
220
108.0
168.3
593.8
11.3
65.9

Test Tire 26
102
220
138.8
131.0
730
5.7
109.4

Test Tire 27
89.2
220
138.8
131.0
693.0
6.0
104.7

Test Tire 28
90.9
220
146.3
124.3
716.6
5.3
109.5

Test Tire 29
92.9
220
131.3
138.5
667.2
7.0
102.4

Test Tire 30
95.8
220
136.5
133.2
722.5
6.0
106.9

Test Tire 31
81.9
220
150.5
120.8
748.4
4.8
114.1

Test Tire 32
85.4
220
143.5
126.7
733.5
5.4
112.0

Test Tire 33
91.4
220
131.3
138.5
716.3
6.5
102.0

TABLE 3

RR
Internal

Tire

High Internal
Value
Pressure
W
L
OD
δ1
Weight

Pressure
(INDEX)
(kPa)
(mm)
(mm)
(mm)
(mm)
(INDEX)

Conventional
Conventional
108
295
111.71
121.4
507.8
7
61.3

Tire
Tire 1

Conventional
111.3
275
119.4
121.9
526.1
6.8
61.9

Tire 2

Conventional
108.6
260
127.1
121.1
553.6
6.4
71.6

Tire 3

Conventional
103.6
245
134.8
121.2
583.1
6.1
82.5

Tire 4

Conventional
103.9
230
142.5
122.1
603
6
87.4

Tire 5

Reference
100
220
150.2
121.1
634.5
5.6
100

Tire 1

Conventional
101
220
157.9
115.2
631.9
5.1
98.3

Tire 6

Conventional
93
220
164.7
110.4
664.4
4.5
111.9

Tire 7

Conventional
85
220
170.9
106.4
679.3
4.1
115.9

Tire 8

Conventional
80
220
176.7
102.9
677.7
3.8
117.7

Tire 9

Conventional
90
220
170.8
106.4
634.3
4.4
116.5

Tire 10

Reference
90
220
170.8
106.5
634.3
4.37
116

Tire 2

Test Tire 1
92.2
260
127.1
121.1
697.1
5.1
93

Test Tire 2
96
275
119.4
120.6
658.7
5.4
82.5

Test Tire 3
92.4
295
111.7
121.4
671.1
5.4
78.6

Test Tire 4
91.6
315
104
121
658.1
5.4
71.8

Test Tire 5
88.2
340
96.3
121.2
645.1
5.5
65.2

Test Tire 6
84.8
345
134.8
120.7
751.3
4.8
99.7

Test Tire 7
92.6
260
128.3
120.8
689.5
5.2
86.3

Test Tire 8
96.2
275
120.5
121.1
653.1
5.5
76.8

Test Tire 9
92.3
290
112.8
121.1
667.5
5.4
73.4

Test Tire 10
92.4
310
105
121.7
656.5
5.5
67.2

Test Tire 11
87.7
340
97.2
121
645.5
5.5
61.2

Test Tire 12
85.5
250
136.1
120.9
741.7
4.8
92

Test Tire 13
89.7
255
129.6
121
707.3
5.1
82.7

Test Tire 14
93.2
270
121.7
121.2
672.9
5.3
73.9

Test Tire 15
92.2
290
113.9
121.1
663.9
5.4
68.2

Test Tire 16
92.1
310
106
121.3
654.9
5.5
62.7

Test Tire 17
93.9
290
114.6
120.4
580.4
6
65.9

Test Tire 18
92.1
270
122.5
120.9
617.8
5.7
75

Test Tire 19
89.4
255
130.4
120.3
664.1
5.3
83.1

Test Tire 20
92.1
270
122.5
120.9
596.7
5.9
65.5

Test Tire 21
89.4
255
130.4
120.3
638.7
5.5
79.9

Test Tire 22
88.7
250
131.3
121.9
675.1
5.3
89.6

Test Tire 23
86.7
350
92.0
124.2
546.8
6.8
48.2

Test Tire 24
94.1
350
89.3
128.0
511.4
7.66
41.2

Test Tire 25
85.6
300
108.0
123.4
593.8
6.22
65.9

Test Tire 26
73.0
270
138.8
106.7
730
3.84
109.4

Test Tire 27
80.0
270
104.7
106.8
693.0
4.0
104.7

Test Tire 28
81.3
258
109.5
106.7
716.6
3.9
109.5

Test Tire 29
84.7
286
102.4
106.6
667.2
4.2
102.4

Test Tire 30
83.3
277
106.9
105.8
722.5
3.8
106.9

Test Tire 31
75.0
250
114.1
106.3
748.4
3.7
114.1

Test Tire 32
78.7
263
112.0
106.0
733.5
3.8
112.0

Test Tire 33
86.7
285
100.0
106.9
716.3
3.9
102.0

Also, by using the test tires 8, 15, 20, and 31 with various internal pressure, the tests for evaluation of the tire rolling resistance value were conducted in the method described above.

Results of the an evaluation are shown in Table 4 and FIG. 9.

TABLE 4

Internal
Tire Size

Pressure
145/45R21
155/55R19
155/45R18
215/50R21

(kPa)
RR Value (INDEX)

220
106.8
107.2
105
102

250
99
99
97
95

280
96
93
91
88

310
91.8
88.5
87
84

340
88
85
84
81

400
83
79
79
77

From Tables 2 to 4 and FIGS. 9, 10(a), (b), it can be seen that, when the test tires 1 to 26 with the internal pressure of at least 250 kPa are used, both the tire rolling resistance value and the tire weight may be reduced comparing to those of Reference Tire 1. It can also be seen that, when the test tires 27 to 33 with the internal pressure of at least 250 kPa are used, both the tire rolling resistance value and the tire weight may be reduced comparing to those of Reference Tire 2.

Note that the internal pressure is preferably no more than 350 kPa.

Here, the inventors have studied in more detail about sizes of the test tires 1 to 33 that allow reduction in both the tire rolling resistance value and the tire weight.

FIGS. 14(
a), (b) are graphs illustrating a relationship of a cross-sectional width SW (mm) and an outer diameter OD (mm) of the test tires and the conventional tires.

As illustrated in FIG. 14(a), when the cross-sectional width SW is 165 (mm) or smaller, a ratio SW/OD of the test tires are no more than 0.26. That is, it can be seen that, when the internal pressure is set to 250 kPa or more, tires with the ratio SW/OD of no more than 0.26 may reduce both the tire rolling resistance and the tire weight.

As illustrated in FIG. 14(a), also, when the cross-sectional width SW is 165 (mm) or greater, the cross-sectional width SW and the outer diameter OD of the test tire satisfy the following relational expression:

OD≧2.135×SW+282.3

That is, when the cross-sectional width SW is 165 (mm) or greater, the tires with the internal pressure of 250 kPa or more that satisfy the above relational expression may reduce both the tire rolling resistance value and the tire weight.

As illustrated in FIG. 14 (b), further, as a result of fitting using a quadratic curve boundary of a tire size that enables reduction in both the tire rolling resistance value and the tire weight in conjunction with the tire with SW of smaller than 165 (mm) and the tire with SW of 165 (mm) or greater, it was found that a tire that satisfies the following relational expression:

OD≧−0.0187×SW²+9.15×SW−380

may reduce both the tire rolling resistance value and the tire weight.

In order to reduce both the tire rolling resistance value and the tire weight together, SW/OD≦0.26 is preferably satisfied, and SW/OD≦0.24 is particularly preferably satisfied.

Also, from Tables 2, 3 and FIGS. 11(a), (b), it can be seen that applying high internal pressure may suppress the increase in the ground-contact length caused by the reduction in the ground-contact width, such that the ground-contact length becomes similar to that of Reference Tires.

As can be seen in Table 2 and FIG. 12(a), further, when the internal pressure is at 220 kPa, reducing the ground-contact width increases the ground-contact length and the deflection amount δ1. As can be seen in Table 2 and FIG. 12 (b), on the other hand, applying high internal pressure suppresses the increase in the ground-contact length, reducing the deflection amount δ1.

As can be seen in Table 3 and FIG. 13, accordingly, when a tire, which is in size with the tire cross-sectional width SW and the outer diameter OD satisfying SW/OD≦0.26 (SW≦165 (mm)) mounted on a rim with a width corresponding to the bead width of the tire and applied with the maximum load defined for each vehicle wearing the tire, is used to have the ground-contact width of no more than 150 mm, the reduction in both the tire rolling resistance value and the tire weight may be achieved. It can also be seen that, when a tire, which is in size satisfying OD≧2.135×SW+282.3 (SW≧165 (mm)) mounted on the rim with the width corresponding to the bead width of the tire and applied with the maximum load defined for each vehicle wearing the tire, is used to have the ground-contact width of no more than 175 mm, the reduction in both the tire rolling resistance value and the tire weight may be achieved.

Alternatively, when a tire, which is in size satisfying OD≧−0.0187×SW²+9.15×SW−380 mounted on the rim with the width corresponding to the bead width of the tire and applied with the maximum load defined for each vehicle wearing the tire, is used to have the ground-contact width of no more than 175 mm, the reduction in both the tire rolling resistance value and the tire weight may be achieved. Note that, in FIG. 13, INDEX 100 means a tire with the ground-contact width of 150 mm. The smaller the number, the smaller the ground-contact width.

The ground-contact width, from a viewpoint of enhancing the safety and stability of the vehicle by securing a tire axial force, is preferably no less than 90 mm.

At this time, the ground-contact length is preferably 90 to 140 mm.

Upon application of a maximum load defined for each vehicle wearing a tire in size with the tire cross-sectional width SW and the outer diameter OD satisfying SW/OD≦0.26 (SW<165 (mm)) and, simultaneously, OD≧2.135×SW+282.3 when taking a linear expression boundary, or OD≧−0.0187×SW²+9.15×SW−380 when taking a quadratic boundary, a ground-contact area of the tire is preferably no more than 16000 mm². Thereby, reduction in both the tire rolling resistance and the tire weight may be achieved.

Note that, from the viewpoint of enhancing the safety and stability of the vehicle by securing the tire axial force, the ground-contact area is preferably no less than 10000 mm².

In order to see an effect of the high internal pressure, tires in further various sizes applied with different internal pressure were used for evaluation of the tire rolling resistance and the tire weight.

Specifications of each of the tires and results of the evaluation are shown in Table 5 and FIG. 15.

TABLE 5

Internal Pres-
RR Value
Tire Weight

Tire Size
sure (kPa)
(Index)
(Index)

Conventional
145/70R12
220
120
45

Tire
155/55R14
220
125
49

165/60R14
220
118
61

175/65R14
220
109
74

185/60R15
220
106
83

195/65R15
220
100
100

205/55R16
220
101
101

215/55R17
220
93
121

225/55R17
220
85
131

245/45R18
220
80
136

225/45R17
220
90
116.5

Internal Pres-
145/70R19
265
92.5
79

sure Similar
155/55R20
256
93.8
75

to Deflection
165/60R20
250
95.1
93

Amount δ1
175/60R19
250
93.2
92

High Internal
145/70R19
270
90.7
79

Pressure
155/55R20
270
88.9
75

(Case 1)
165/60R20
270
87
93

175/60R19
270
85.5
92

High Internal
145/70R19
320
76.6
79

Pressure
155/55R20
320
75
75

(Case 2)
165/60R20
320
73.4
93

175/60R19
320
72.9
92

As shown in Table 5 and FIG. 15, by using a tire, which is in size satisfying, under a condition with high internal pressure that allows the δ1 to be similar regardless of the reduction in the ground-contact width, SW/OD≦0.26 (SW<165 (mm)) and, simultaneously, OD≧2.135×SW+282.3 (SW≧162 (mm)) (it may also be referred to as a relational expression A) when taking the linear expression boundary, or OD≧−0.0187×SW²+9.15×SW−380 (it may also be referred to as a relational expression B) when taking the quadratic boundary, both the tire rolling resistance and the tire weight may be reduced.

It can also be seen that, by using the tire in size satisfying the relational expression A or the relational expression B described above applied with the internal pressure of no less than 270 kPa, the tire rolling resistance may be significantly reduced and, with the internal pressure of no less than 320 kPa, the tire rolling resistance may be even further reduced.

Here, a preferable tire structure for use with high internal pressure of no less than 250 kPa will be described.

First, the carcass preferably has at least one carcass ply having an end in a high turn-up structure positioning outside a tire maximum width portion in a tire radial direction. More preferably, the end portion has what is called an envelope structure positioning between the carcass and a belt in the tire radial direction.

As for the belt, one with high rigidity is preferably used. More specifically, a belt code with Young's modulus of 45000 MPa or higher is preferably used.

Thereby, the carcass structure and the rigidity of the belt are optimized, ensuring a tire durable with high internal pressure.

Further, an inner liner of the tire preferably has a thickness of no less than 0.6 mm, so as to prevent air leak under a high internal pressure condition.

Here, the inventors have also found these problems specific to a tire with a small width, a large diameter and high internal pressure that the tire with a smaller width as described above has a smaller deflection amount on the ground-contact area, that a belt tension is increased due to the large radial and high internal pressure which increases a vertical spring coefficient, and that the comfortability is degraded. As such, the inventors have diligently studied to solve those problems and acquired a knowledge of a tire structure that may solve the problems.

The following is a description of a structure of a pneumatic radial tire with a small width, a large diameter and high internal pressure for a passenger vehicle that improves the comfortability.

FIG. 16 is cross-sectional view of a tire in the tire width direction according to a first embodiment of the present invention.

FIG. 16 illustrates a half portion of the tire in the tire width direction from a tire equatorial plane CL serving as a boundary.

Note that this tire is in size satisfying the relational expression A or the relational expression B.

As illustrated in FIG. 16, the tire according to the present embodiment includes a belt 3, which is made up of two belt layers 3a, 3b by way of example in the figure at a position radially outside the carcass 2 that is composed of a ply of carcass cords radially arranged and toroidally provided around the bead core 1a embedded in a pair of bead portions 1 of the tire, and a bead filler 4 disposed at a position radially outside the bead core 1a.

Here, the bead filler 4 is a high-rigidity member having 100% modulus at room temperature at, for example, 24 to 31 (MPa) in conformity to JIS K6251 (revised on Dec. 20, 2010).

Here, in the tire of the present embodiment, a tire-width-direction cross-sectional area S1 of the bead filler 4 is 1 to 4 times the size of a tire-width-direction cross-sectional area S2 of the bead core 1a.

Note that, when the tire has a holding bead core structure in which the carcass is held from both inner side and outer side in the tire width direction, a total volume of the bead core inside and outside the carcass in the tire width direction is defined as S2.

The following is a description of an operation and an effect of the present embodiment.

The cross-section of the bead filler 4 within an above-mentioned range enables reduction in the volume of the bead filler, which is the high-rigidity member, and also in the vertical spring coefficient of the tire, thereby improving the comfortability. The tire weight may be reduced also by reducing weight of the bead filler, whereby the tire rolling resistance may be further reduced.

Especially, since the tire with a small width and a large diameter satisfying the relational expression A or the relational expression B has high tension rigidity of the belt and low tension rigidity in the tire side portion compared to that of the belt, limiting the cross-sectional area S1 of the bead filler within the predetermined range as described above is highly effective in reduction of the vertical spring coefficient.

Here, when the tire-width-direction cross-sectional area S1 of the bead filler 4 is larger than 4 times the size of the tire-width-direction cross-sectional area S2 of the bead core 1, the volume of the bead filler made of the high-rigidity member increases, suppressing sufficient reduction in the vertical spring coefficient of the tire and degrading the comfortability.

On the other hand, when the tire-width-direction cross-sectional area S1 of the bead filler 4 is smaller than the tire-width-direction cross-sectional area S2 of the bead core 1a, the rigidity of the bead portion is significantly reduced and a lateral spring coefficient becomes too small to ensure steering stability.

According to the present embodiment, also, as illustrated in FIG. 16, when BFW represents a width of the bead filler 4 in the tire width direction in a tire radial direction center position and BDW represents a maximum width of the bead core 1a in the tire width direction,

0.1≦BFW/BDW≦0.5

is preferably satisfied.

This is because, when the ratio BFW/BDW is no more than 0.5, the volume of the bead filler may be reduced while a height thereof is maintained, which enables the reduction in the vertical spring coefficient while maintaining the rigidity in the tire rotational direction. Accordingly, the comfortability may be improved and the tire weight may be reduced.

Also, when the ratio BFW/BDW is no less than 1.0, the rigidity of the bead portion may be ensured and the vertical spring coefficient may be maintained, thereby further ensuring the steering stability.

According to the present embodiment, further, as illustrated in FIG. 16, when BFH represents a height of the bead filler 4 in the tire radial direction and SH represents a sectional height of the tire (tire cross-sectional height),

0.1≦BFH/SH≦0.25

is preferably satisfied.

This is because, when the above ratio BFH/SH is no more than 0.25, the height of the bead filler, which is made of the high-rigidity member, in the radial direction may be reduced, whereby the vertical spring coefficient of the tire may be effectively reduced and the comfortability may be improved.

Also, when the above ratio BFH/SH is no less than 0.1, the rigidity of the bead portion is ensured and the lateral spring coefficient may be maintained, thereby further ensuring the steering stability.

More specifically, the BFH representing the height of the bead filler in the tire radial direction is preferably 10 mm to 45 mm.

Here, the tire sectional height SH represents a ½ of a difference between an outer diameter of the tire and a diameter of the rim when the tire is mounted on the rim and applied with the internal pressure defined for each vehicle wearing the tire and no load.

FIG. 17 is a cross-sectional view of a tire in the tire width direction according to a second embodiment of the present invention.

FIG. 17 illustrates a half portion of the tire in the tire width direction from the tire equatorial plane CL serving as the boundary.

Note that this tire is in size satisfying the relational expression A or the relational expression B.

As illustrated in FIG. 17, the tire according to the present embodiment includes a belt 3, which is made up of two belt layers 3a, 3b by way of example in the figure at a position radially outside the carcass 2 that is composed of a ply of carcass cords radially disposed and toroidally provided around the bead core 1a embedded in the pair of bead portions 1 of the tire.

The tire according to the present embodiment also includes a sidewall portion 5 connecting to the beat portion 1.

In the illustrated example, the carcass 2 is made up of a carcass main portion 2a and a folding portion 2b.

In the illustrated example, further, the bead filler 4 is disposed radially outside the bead core 1a in the tire radial direction.

FIG. 18(
a) is a schematic diagram illustrating a size of a tire member around a sidewall portion of the tire. FIG. 18(b) is a schematic diagram illustrating a size of the tire member around the bead portion of the tire.

Here, according to the present embodiment, as illustrated in FIGS. 17 and 18(a), (b), when Ts represents a gauge of the sidewall portion 5 in the tire maximum width portion and Tb represents a bead width in a tire radial direction center position of the bead core 1a, a ratio Ts/Tb is 15% to 40%.

Note that the “tire maximum width portion” means a maximum width position in a tire-width-direction cross-section when the tire is mounted on the rim and applied with no load.

The gauge Ts is a sum of thicknesses of all members including rubber, a reinforcing member, the inner liner and the like.

When the tire has a structure in which the bead core is divided into small bead cores by the carcass, Tb represents a distance between a width direction innermost end and an outermost end among all of the small bead cores.

The following is a description of an operation and an effect of the present embodiment.

According to the present embodiment, when the ratio Ts/Tb is within the above range, the rigidity of the tire maximum width portion where great bending deformation occurs during application of a load on the tire is appropriately reduced, thereby reducing the vertical spring coefficient and improving the comfortability.

That is, when the above ratio Ts/Tb exceeds 40%, the gauge of the sidewall portion 5 in the tire maximum width portion is increased, increasing rigidity of the sidewall portion 5 and the vertical spring coefficient. On the other hand, when the above ratio Ts/Tb is smaller than 15%, the lateral spring coefficient becomes too small to ensure the steering stability.

Here, in particular, the gauge Ts of the sidewall portion in the tire maximum width portion is preferably no less than 1.5 mm.

With the gauge Ts of 1.5 mm or more, the rigidity of the tire maximum width portion may be appropriately maintained, preventing reduction in the lateral spring coefficient and further ensuring the steering stability.

On the other hand, in order to further improve the comfortability by effectively reducing the vertical spring coefficient, the gauge Ts of the sidewall portion 5 in the tire maximum width portion is preferably no more than 4 mm.

Also, a diameter Tbc of the bead core 1a (a maximum width of the bead core in the tire width direction) is preferably 4 mm to 12 mm.

With the Tbc of no less than 4 mm, weight reduction may be achieved while ensuring bending rigidity and torsional rigidity on a rim flange. Also, with the Tbc of no more than 12 mm, the steering stability may be ensured while suppressing weight increase.

FIG. 19 is a cross-sectional view of a tire in the tire width direction according to a third embodiment of the present invention.

FIG. 19 illustrates a half portion of the tire in the tire width direction from the tire equatorial plane CL serving as the boundary.

Note that this tire is in size satisfying the relational expression A or the relational expression B described above.

As illustrated in FIG. 19, the tire according to the present embodiment includes the belt 3, which is made up of two belt layers 3a, 3b by way of example in the figure at a position radially outside the carcass 2 that is composed of a ply of carcass cords radially arranged and toroidally provided in a pair of bead portions 1 of the tire.

The tire of the present embodiment also includes the sidewall portion 5 connecting to the bead portion 1.

In the illustrated example, the bead core 1a is embedded in the bead portion 1, and the bead filler 4 is disposed outside the bead core 1a in the tire radial direction.

Further, in the illustrated example, the carcass 2 is made up of the carcass main portion 2a and the folding portion 2b.

FIG. 20 is a schematic diagram illustrating dimensions of the tire member around the sidewall portion of the tire.

Here, in the tire according to the present embodiment, as illustrated in FIG. 19 and FIG. 20, the ratio Ts/Tc is 5 to 10, the Ts representing the gauge of the sidewall portion 5 in the tire maximum width portion and the Tc representing a diameter of the carcass cord.

Note that the “tire maximum width portion” means the maximum width position in the tire-width-direction cross-section when the tire is mounted on the rim and applied with no load.

The following is a description of an operation and an effect of the present embodiment.

According to the present embodiment, when the ratio Ts/Tc is within the above range, the rigidity of the tire maximum width portion where great bending deformation occurs during application of a load on the tire is appropriately reduced, thereby reducing the vertical spring coefficient and improving the comfortability.

That is, when the ratio Ts/Tc exceeds 10, the gauge of the sidewall portion 4 in the tire maximum width portion is increased, increasing rigidity of the sidewall portion 4 and the vertical spring coefficient. On the other hand, when the ratio Ts/Tc is smaller than 5, the lateral spring coefficient becomes too small to ensure steering stability.

Also, in the tire of the present embodiment, as illustrated in FIG. 19 and FIG. 20, when Ta represents a distance in the tire width direction from a surface of the carcass code in the tire maximum width portion to a tire outer surface 6, a ratio Ta/Tc is preferably 3 to 6.

With the ratio Ta/Tc of no more than 6, the gauge of the sidewall portion 4 in the tire maximum width portion may be reduced and the rigidity of the sidewall portion 5 may be reduced, thereby reducing the vertical spring coefficient and further improving the comfortability. Also, with the ratio Ta/Tc of no less than 3, the lateral spring coefficient may be ensured, further ensuring the steering stability.

Note that the term “Ta” represents a distance in the tire maximum width portion from the surface of the carcass code on the width direction outermost side to the tire outer surface.

That is, when the carcass folding portion extends to a radially outer side over the tire maximum width portion, the Ta represents a distance from the surface of the carcass code in the carcass folding portion to the tire outer surface 6.

Here, the diameter Tc of the carcass cord is preferably 0.4 mm to 0.8 mm. With the diameter Tc of the carcass code of no more than 0.8 mm, the gauge Ts of the sidewall portion relative to the diameter Tc may be reduced, reducing the vertical spring coefficient. Also, with the diameter Tc of the carcass code of no less than 0.4 mm, the gauge Ts of the sidewall portion relative to the diameter Tc may be ensured, increasing the lateral spring coefficient and ensuring the steering stability.

EXAMPLES
Example 1

In order to confirm the effect of the tire according to the first embodiment, test tires 34-59 and tires according to Comparative Examples 1 to 10 were produced experimentally. Each of the tires includes a carcass, which is composed of a ply of codes radially arranged and toroidally provided between a pair of bead cores, and a bead filler disposed outside the bead core in the tire radial direction.

The following tests were conducted to evaluate performance of the tires.

Each of the tires were mounted on the rim and, by using the indoor tester, the deflection amount thereof was measured. The vertical spring coefficient and the lateral spring coefficient were measured from a tangential gradient of a load of 4 kN and are shown as indices relative to those of the tire according to Comparative Example 1 set to 100. The greater the number, the higher the spring constant. Note that the vertical spring coefficient is used as an index of comfortability; the smaller the number, the better the comfortability.

Each of the above tires was mounted on the rim to obtain a tire-rim assembly, which was then applied with a maximum load defined for each vehicle wearing the tire, for measurement of the rolling resistance thereof under a condition of a drum rotation speed at 100 km/h.

Results of the evaluation are shown as indices relative to the RR value of the tire according to Comparative Example 1 set to 100. The smaller the index, the smaller the rolling resistance.

By using a flat-belt-type cornering test machine, the cornering power was measured with the load at 4 kN and at a speed of 100 km/h.

For evaluation, the cornering power (CP) is shown as an index relative to that of the tire according to Comparative Example 1 set to 100. The greater the index, the preferably higher the cornering power.

The weight of the tires was measured. For evaluation, the weight is shown as an index relative to that of the tire according to Comparative Example 1 set to 100. The smaller the index, the lighter the weight.

Specifications of each of the tires are shown in Table 6, and results of the evaluation are shown in Table 7 and FIGS. 21(a), (b).

TABLE 6

Internal

Tire Size
Pressure (kPa)
S1/S2
SH (mm)
BFH/SH
BFH (mm)
BFW/BDW

Comparative
195/65R15
220
4.4
126.8
0.32
41
0.5

Example 1

Comparative
195/65R15
220
4.4
126.8
0.32
41
0.3

Example 2

Comparative
195/65R15
220
2.1
126.8
0.15
19
0.5

Example 3

Comparative
195/65R15
220
1.5
126.8
0.15
19
0.3

Example 4

Test Tire 34
165/65R19
220
4.1
107.3
0.32
34
0.5

Test Tire 35
165/65R19
220
2.9
107.3
0.32
34
0.3

Test Tire 36
165/65R19
220
1.9
107.3
0.15
16
0.5

Test Tire 37
165/65R19
220
1.4
107.3
0.15
16
0.3

Test Tire 38
155/45R21
220
2.7
69.8
0.32
22
0.5

Test Tire 39
155/45R21
220
1.9
69.8
0.32
22
0.3

Test Tire 40
155/45R21
220
1.4
69.8
0.15
10
0.5

Test Tire 41
155/45R21
220
1.1
69.8
0.15
10
0.3

Test Tire 42
165/55R20
220
3.5
90.8
0.32
29
0.5

Test Tire 43
165/55R20
220
2.4
90.8
0.32
29
0.3

Test Tire 44
165/55R20
220
1.6
90.8
0.15
14
0.5

Test Tire 45
165/55R20
220
1.2
90.8
0.15
14
0.3

Test Tire 46
165/65R19
220
1
107.3
0.19
20
0.3

Test Tire 47
165/65R19
220
4
107.3
0.33
35
0.3

Comparative
165/65R19
220
0.9
107.3
0.19
20
0.3

Example 5

Comparative
165/65R19
220
4.1
107.3
0.33
35
0.3

Example 6

Test Tire 48
155/45R21
220
1
69.8
0.32
22
0.3

Test Tire 49
155/45R21
220
4
69.8
0.34
24
0.3

Comparative
155/145R21
220
0.9
69.8
0.32
22
0.3

Example 7

Comparative
155/45R21
220
4.1
69.8
0.34
24
0.3

Example 8

Test Tire 50
165/55R20
220
1
90.8
0.2
18
0.3

Test Tire 51
165/55R20
220
4
90.8
0.33
30
0.3

Comparative
165/55R20
220
0.9
90.8
0.2
18
0.3

Example 9

Comparative
165/55R20
220
4.1
90.8
0.33
30
0.3

Example 10

Test Tire 52
165/65R19
220
2.9
107.3
0.32
34
0.1

Test Tire 53
165/65R19
220
2.9
107.3
0.32
34
0.5

Test Tire 54
165/65R19
220
2.9
107.3
0.32
34
0.09

Test Tire 55
165/65R19
220
2.9
107.3
0.32
34
0.51

Test Tire 56
165/65R19
220
1.5
107.3
0.1
11
0.3

Test Tire 57
165/65R19
220
1.5
107.3
0.25
27
0.3

Test Tire 58
165/65R19
220
1.5
107.3
0.09
10
0.3

Test Tire 59
165/65R19
220
1.5
107.3
0.26
28
0.3

TABLE 7

Lateral

Spring

Coefficient/

Ground-
Ground-

Vertical
Lateral
Vertical

Contact
Contact

Spring
Spring
Spring
RR

Length
Width

Coefficient
Coefficient
Coefficient
Value
CP
Weight
L
W
OD

Comparative
100
100
100
100
100
100
100
100
100

Example 1

Comparative
99
96
97
98
98
98
101
100
100

Example 2

Comparative
96
95
99
95
97
95
101
100
100

Example 3

Comparative
95
93
98
93
96
92
102
100
100

Example 4

Test Tire 34
97
109
112
92
110
93
103
85
109.9

Test Tire 35
96
108
113
89
108
90
104
85
109.9

Test Tire 36
95
107
113
87
105
87
103
85
109.9

Test Tire 37
93
105
113
84
105
84
104
85
109.9

Test Tire 38
97
111
114
74
103
74
103
80
106.1

Test Tire 39
95
110
116
72
103
72
104
80
106.1

Test Tire 40
94
108
115
70
102
69
104
80
106.1

Test Tire 41
92
106
115
69
102
67
105
80
106.1

Test Tire 42
97
112
115
93
113
86
104
86
108.7

Test Tire 43
96
110
115
90
114
83
105
86
108.7

Test Tire 44
95
106
112
87
108
80
104
86
108.7

Test Tire 45
93
104
112
85
108
77
105
86
108.7

Test Tire 46
95
105
111
88
106
89
103
85
109.9

Test Tire 47
99
112
113
94
115
95
103
85
109.9

Comparative
93
98
105
87
99
88
103
85
109.9

Example 5

Comparative
105
115
110
97
116
97
103
85
109.9

Example 6

Test Tire 48
94
107
114
71
103
71
104
80
106.1

Test Tire 49
98
114
116
77
110
77
104
80
106.1

Comparative
92
98
107
70
94
70
104
80
106.1

Example 7

Comparative
104
117
113
80
111
79
104
80
106.1

Example 8

Test Tire 50
95
106
112
89
114
82
105
86
108.7

Test Tire 51
99
114
115
95
118
88
105
86
108.7

Comparative
93
99
106
88
99
81
105
86
108.7

Example 9

Comparative
105
117
111
98
122
90
105
86
108.7

Example 10

Test Tire 52
95
104
109
88
108
89
104
85
109.9

Test Tire 53
98
112
114
94
112
95
104
85
109.9

Test Tire 54
93
97
104
87
106
88
104
85
109.9

Test Tire 55
99
115
116
97
116
97
104
85
109.9

Test Tire 56
93
100
108
84
102
86
104
85
109.9

Test Tire 57
97
110
113
89
105
90
104
85
109.9

Test Tire 58
90
91
101
83
101
85
104
85
109.9

Test Tire 59
99
111
112
92
106
92
104
85
109.9

As illustrated in Tables 6, 7 and FIGS. 21 (a), (b), each of the test tires satisfying the relational expression A or the relational expression B and, simultaneously, having S1/S2 within a favorable range is lightweight and has less rolling resistance as well as a small vertical spring coefficient, thus providing excellent comfortability.

Also, the test tires having the ratio BFW/BDW within the favorable range have smaller vertical spring coefficients while ensuring the cornering power.

Further, the test tires having a favorable ratio BFH/SH may reduce the vertical spring coefficient while ensuring the cornering power.

Next, in order to see the effect of high internal pressure of the tire, tests for evaluation of performance of test tires 60 to 71 and tires according to Comparative Examples 11 to 13 with high internal pressure shown below were conducted.

Specifications of each of the tires are shown in Table 8, and results of the evaluation are shown in Table 9 and FIGS. 22(a), (b).

TABLE 8

Internal

Pressure

SH

BFH

Tire Size
(kPa)
S1/S2
(mm)
BFH/SH
(mm)
BFW/BDW

Comparative
195/65R15
220
4.4
126.8
0.32
41
0.5

Example 11

Comparative
195/65R15
240
4.4
126.8
0.32
41
0.5

Example 12

Comparative
195/65R15
250
4.4
126.8
0.32
41
0.3

Example 13

Test Tire 60
165/65R19
240
2.9
107.3
0.32
34
0.3

Test Tire 61
165/65R19
250
2.9
107.3
0.32
34
0.3

Test Tire 62
165/65R19
240
1.4
107.3
0.15
16
0.3

Test Tire 63
165/65R19
250
1.4
107.3
0.15
16
0.3

Test Tire 64
155/45R21
240
1.9
69.8
0.32
22
0.3

Test Tire 65
155/45R21
250
1.9
69.8
0.32
22
0.3

Test Tire 66
155/45R21
240
1.1
69.8
0.15
10
0.3

Test Tire 67
155/45R21
250
1.1
69.8
0.15
10
0.3

Test Tire 68
165/55R20
240
2.4
90.8
0.32
29
0.3

Test Tire 69
165/55R20
250
2.4
90.8
0.32
29
0.3

Test Tire 70
165/55R20
240
1.2
90.8
0.15
14
0.3

Test Tire 71
165/55R20
250
1.2
90.8
0.15
14
0.3

TABLE 9

Lateral

Spring

Coefficient/

Ground-
Ground-

Lateral
Lateral
Vertical

Contact
Contact

Spring
Spring
Spring
RR

Length
Width

Coefficient
Coefficient
Coefficient
Value
CP
Weight
L
W
OD

Comparative
100
100
100
100
100
100
100
100
100

Example 11

Comparative
104
103
99
99
98
100
96
100
100

Example 12

Comparative
106
105
99
96
94
100
93
100
100

Example 13

Test Tire 60
97
110
113
88
105
90
102
85
109.9

Test Tire 61
98
114
116
85
107
90
101
85
109.9

Test Tire 62
94
107
114
82
103
84
103
85
109.9

Test Tire 63
95
111
117
79
105
84
102
85
109.9

Test Tire 64
97
112
115
71
102
72
103
80
106.1

Test Tire 65
98
116
118
68
104
72
102
80
106.1

Test Tire 66
94
108
115
68
101
67
103
80
106.1

Test Tire 67
95
111
117
65
103
67
102
80
106.1

Test Tire 68
97
113
116
89
110
83
103
86
108.7

Test Tire 69
98
117
119
86
112
83
102
86
108.7

Test Tire 70
95
106
112
84
106
77
103
86
108.7

Test Tire 71
96
109
114
81
109
77
102
86
108.7

Comparisons between Tables 9 and 7 and between FIGS. 21 (a), (b) and FIGS. 22(a), (b) show that use of the tire with high internal pressure further reduces the tire rolling resistance and further improves the cornering power.

Example 2

Next, in order to confirm the effect of the tire according to the second embodiment, test tires 72 to 82 and tires according to Comparative Examples 14 to 23 were produced experimentally. Each of the tires includes the carcass, which is composed of a ply of codes radially arranged and toroidally provided between a pair of bead cores, and a pair of sidewall portions connected to the bead portions.

In order to evaluate the performance of these tires, in a manner similar to Example 1, tests were conducted for evaluation of the spring coefficients, the rolling resistance value (RR value), the cornering power, and the tire weight.

Note that, for evaluation, the spring coefficients are shown as indices relative to that of the tire according to Comparative Example 14 set to 100. The greater the value, the higher the spring constant. Also, the rolling resistance value (RR value), for evaluation thereof, is shown as an index relative to that of the tire according to Comparative Example 14 set to 100. The smaller the index, the smaller the rolling resistance. Further, the cornering power, for evaluation thereof, is shown as an index relative to that of the tire according to Comparative Example 14 set to 100. The greater the index, the preferably higher the cornering power. Also, the tire weight, for evaluation thereof, is shown as an index relative to that of the tire according to Comparative Example 14 set to 100. The smaller the value, the lighter the weight.

Specifications of each of the tires are shown in Table 10, and results of the evaluation are shown in Table 11 and FIGS. 23(a), (b).

Note that in Table 10 the term “SH” means a sectional height (a cross-sectional height of the tire).

TABLE 10

Internal

Ts/

Ratio
Pressure
SH
Tb
Ts
Tb
Tbc

Tire Size
SW/OD
(kPa)
(mm)
(%)
(mm)
(mm)
(mm)

Comparative
195/65R15
0.31
220
126.8
67
10
15
10

Example

14

Comparative
195/65R15
0.31
220
126.8
33
5
15
10

Example

15

Comparative
165/65R19
0.24
220
107.3
71
10
14
8

Example

16

Test Tire 72
165/65R19
0.24
220
107.3
29
4
14
8

Comparative
165/55R21
0.23
220
107.3
69
9
13
6

Example

17

Test Tire 73
165/55R21
0.23
220
107.3
27
3.5
13
6

Comparative
155/55R21
0.22
220
85.3
71
10
14
4

Example

18

Test Tire 74
155/55R21
0.22
220
85.3
29
4
14
4

Comparative
155/55R21
0.22
220
85.3
9
1.3
14
4

Example

19

Test Tire 75
155/55R21
0.22
220
85.3
29
4
14
3

107.

Test Tire 76
165/65R19
0.24
220
107.3
15
2.3
15
8

Test Tire 77
165/65R19
0.24
220
40
5.2
13
8

Comparative
165/65R19
0.24
220
107.3
14
1.7
12
8

Example

20

Comparative
165/65R19
0.24
220
107.3
41
6.2
15
8

Example

21

Test Tire 78
155/55R21
0.22
220
85.3
15
2.3
15
4

Test Tire 79
155/55R21
0.22
220
85.3
40
5.2
13
4

Comparative
155/55R21
0.22
220
85.3
14
1.7
12
4

Example

22

Comparative
155/55R21
0.22
220
85.3
41
6.2
15
4

Example

23

Test Tire 80
155/55R21
0.22
220
85.3
15
1.5
10
4

Test Tire 81
155/55R21
0.22
220
85.3
29
4
14
13

Test Tire 82
155/55R21
0.22
220
85.3
17.5
1.4
8
4

TABLE 11

Lateral

Ground-
Ground-

Spring/

Contact
Contact

Vertical
Lateral
Vertical
RR

Length
Width

Spring
Spring
Spring
Value
CP
Weight
L
W
OD

Comparative
100
100
100
100
100
100
100
100
100

Example 14

Comparative
99
97
98
97
98
97
101
100
100

Example 15

Comparative
115
111
96
97
104
93
102
85
109.9

Example 16

Test Tire 72
97
107
110
96
102
90
103
85
109.9

Comparative
130
116
89
85
104
86
103
80
112.7

Example 17

Test Tire 73
97
111
114
84
101
83
104
80
112.7

Comparative
120
111
92
98
109
77
104
86
110.9

Example 18

Test Tire 74
97
104
106
96
105
75
105
86
110.9

Comparative
96
97
101
80
95
72
106
86
110.9

Example 19

Test Tire 75
95
96
101
78
102
74
106
86
110.9

Test Tire 76
97
102
105
94
100
88
103
85
109.9

Test Tire 77
99
109
110
95
106
93
103
85
109.9

Comparative
98
97
99
94
98
86
103
85
109.9

Example 20

Comparative
110
109
99
97
110
98
103
85
109.9

Example 21

Test Tire 78
98
100
102
95
103
73
105
86
110.9

Test Tire 79
99
107
106
97
108
77
105
86
110.9

Comparative
98
97
99
94
98
72
105
86
110.9

Example 22

Comparative
109
106
97
99
110
80
105
86
110.9

Example 23

Test Tire 80
97
97
100
81
102
70
106
86
110.9

Test Tire 81
99
103
104
83
104
73
106
86
110.9

Test Tire 82
95
95
100
80
101
69
106
86
110.9

As shown in Tables 10, 11 and FIGS. 23 (a), (b), each of the test tires satisfying the relational expression A or the relational expression B and, simultaneously, having the ratio Ts/Tb within the favorable range is lightweight and has less rolling resistance as well as smaller vertical spring coefficient, thus providing excellent comfortability.

Also, the test tires having a favorable gauge Ts have excellent cornering power.

Further, the test tires having favorable values of the diameter Tbc of the bead core also have excellent cornering power.

Next, in order to see the effect of the tire with high internal pressure, tests for evaluation of performance of test tires 83 to 88 and tires according to Comparative Examples 24 and 25 with high internal pressure shown below were conducted.

Specifications of each of the tires are shown in Table 12, and results of the evaluation are shown in Table 13 and FIGS. 24(a), (b).

TABLE 12

Internal

Ratio
Pressure

Ts/Tb
Ts
TB
TBC

Tire Size
SW/OD
(kPa)
SH (mm)
(%)
(mm)
(mm)
(mm)

Comparative
195/65R15
0.31
220
126.8
67
10
15
10

Example 14

Comparative
195/65R15
0.31
240
126.8
67
10
15
10

Example 24

Comparative
195/65R15
0.31
250
126.8
67
10
15
10

Example 25

Test Tire 83
165/65R19
0.24
240
107.3
29
4
14
8

Test Tire 84
165/65R19
0.24
250
107.3
29
4
14
8

Test Tire 85
165/55R21
0.23
240
107.3
27
3.5
13
6

Test Tire 86
165/55R21
0.23
250
107.3
27
3.5
13
6

Test Tire 87
155/55R21
0.22
240
85.3
29
4
14
4

Test Tire 88
155/55R21
0.22
250
85.3
29
4
14
4

TABLE 13

Lateral

Ground-
Ground-

Spring/

Contact
Contact

Vertical
Lateral
Vertical

Length
Width

Spring
Spring
Spring
RR Value
CP
Weight
L
W
OD

Comparative
100
100
100
100
100
100
100
100
100

Example 14

Comparative
110
106
94
99
98
100
96
100
100

Example 24

Comparative
115
110
87
96
96
100
93
100
100

Example 25

Test Tire 83
98
109
111
95
103
90
102
85
109.9

Test Tire 84
99
118
119
90
108
90
100
85
109.9

Test Tire 85
98
112
114
83
104
83
103
80
112.7

Test Tire 86
99
119
120
77
110
83
101
80
112.7

Test Tire 87
98
105
107
95
106
75
104
86
110.9

Test Tire 88
99
111
112
90
111
75
100
86
110.9

From Table 13 and FIGS. 24(a), (b), it can be seen that using the tire with high internal pressure may reduce the tire rolling resistance value and improve the cornering power.

Example 3

Next, in order to see the effect of a tire according to Example 3, test tires 89 to 103 and tires according to Comparative Examples 26 to 34 were produced experimentally. Each of the tires includes the carcass, which is composed of a ply of codes radially arranged and toroidally provided between a pair of bead portions, and a pair of sidewall portions connected to the bead portions.

Note that, for evaluation, the spring coefficients are shown as indices relative to those of the tire according to Comparative Example 26 set to 100. The greater the value, the higher the spring constant. Also, the rolling resistance value (RR value), for evaluation thereof, is shown as an index relative to that of the tire according to Comparative Example 26 set to 100. The smaller the index, the smaller the rolling resistance. Further, the cornering power, for evaluation thereof, is shown as an index relative to that of the tire according to Comparative Example 26 set to 100. The greater the index, the preferably higher the cornering power. Also, the tire weight, for evaluation thereof, is shown as an index relative to that of the tire according to Comparative Example 26 set to 100. The smaller the value, the lighter the weight.

Specifications of each of the tires are shown in Table 14, and results of the evaluation are shown in Table 15 and FIGS. 25(a), (b).

TABLE 14

Internal

Pressure
Ts
Ta
Tc

Tire Size
SW/OD
(kPa)
(mm)
(mm)
(mm)
Ts/Tc
Ta/Tc

Comparative
195/65R15
0.31
220
10
6
0.66
15.2
9.1

Example 26

Comparative
195/65R15
0.31
220
5
3
0.66
7.6
4.5

Example 27

Comparative
165/65R19
0.24
220
10
5
0.5
20
10

Example 28

Test Tire 89
165/65R19
0.24
220
4
2.5
0.5
8
5

Comparative
165/55R21
0.23
220
9
5.5
0.5
18
11

Example 29

Test Tire 90
165/55R21
0.23
220
3.5
2.8
0.5
7
5.6

Comparative
155/55R21
0.22
220
10
6
0.55
18.2
10.9

Example 30

Test Tire 91
155/55R21
0.22
220
4
2
0.55
7.3
3.6

Comparative
155/55R21
0.22
220
10
6
0.8
12.5
7.5

Example 31

Test Tire 92
165/65R19
0.24
220
2.5
2.5
0.5
5
5

Test Tire 93
165/65R19
0.24
220
5
2.5
0.5
10
5

Comparative
165/65R19
0.24
220
2.3
2.5
0.5
4.5
5

Example 32

Comparative
165/65R19
0.24
220
6.3
2.5
0.5
12.5
5

Example 33

Test Tire 94
155/55R21
0.22
220
2.8
2
0.55
5
3.6

Test Tire 95
155/55R21
0.22
220
5.5
2
0.55
10
3.6

Comparative
155/55R21
0.22
220
2.5
2
0.55
4.5
3.6

Example 34

Test Tire 96
155/55R21
0.22
220
4
1.7
0.55
7.3
3

Test Tire 97
155/55R21
0.22
220
4
3.3
0.55
7.3
6

Test Tire 98
155/55R21
0.22
220
4
1.4
0.55
7.3
2.5

Test Tire 99
155/55R21
0.22
220
4
3.9
0.55
7.3
7

Test Tire 100
155/55R21
0.22
220
5.1
2.5
0.7
7.3
3.6

Test Tire 101
155/55R21
0.22
220
2.9
1.4
0.4
7.3
3.6

Test Tire 102
155/55R21
0.22
220
5.8
2.9
0.8
7.3
3.6

Test Tire 103
155/55R21
0.22
220
2.6
1.3
0.35
7.3
3.6

TABLE 15

Lateral

Ground-
Ground-

Spring/

Contact
Contact

Vertical
Lateral
Vertical
RR

Length
Width

Spring
Spring
Spring
Value
CP
Weight
L
W
OD

Comparative
100
100
100
100
100
100
100
100
100

Example 26

Comparative
104
84
81
97
86
97
101
100
100

Example 27

Comparative
110
112
101
92
110
93
105
85
109.9

Example 28

Test Tire 89
97
106
107
87
106
90
106
85
109.9

Comparative
120
126
104
74
113
74
103
80
112.7

Example 29

Test Tire 90
99
116
111
73
105
72
103
80
112.7

Comparative
113
114
101
93
110
86
103
86
110.9

Example 30

Test Tire 91
98
110
110
91
107
83
103
86
110.9

Comparative
130
120
92
106
110
93
101
86
110.9

Example 31

Test Tire 92
95
101
106
85
103
88
106
85
109.9

Test Tire 93
99
107
108
89
109
93
106
85
109.9

Comparative
95
94
99
83
97
85
106
85
109.9

Example 32

Comparative
110
108
98
88
111
97
106
85
109.9

Example 33

Test Tire 94
97
103
106
88
104
80
103
86
110.9

Test Tire 95
99
112
113
93
110
86
103
86
110.9

Comparative
96
95
99
92
98
79
103
86
110.9

Example 34

Test Tire 96
98
102
104
88
103
80
103
86
110.9

Test Tire 97
98
109
111
94
107
85
103
86
110.9

Test Tire 98
97
96
99
85
101
78
103
86
110.9

Test Tire 99
99
111
112
97
110
89
103
86
110.9

Test Tire 100
99
113
114
93
112
85
103
86
110.9

Test Tire 101
96
104
108
88
104
81
103
86
110.9

Test Tire 102
99
114
115
95
115
87
103
86
110.9

Test Tire 103
95
98
103
85
102
79
103
86
110.9

As shown in Tables 14, 15 and FIGS. 25(a), (b), each of the test tires satisfying the relational expression A or the relational expression B and, simultaneously, having the ratio Ts/Tc within a favorable range is lightweight and has less rolling resistance as well as small vertical spring coefficient, thus providing excellent comfortability.

Also, the test tires having Ta/Tc in a favorable range have smaller vertical spring coefficients while maintaining approximately the same cornering power.

Further, the test tires having favorable values of the code diameter Tc have further smaller vertical spring coefficients and improved cornering power.

Next, in order to see the effect of the tire having high internal pressure, tests for evaluation of performance of test tires 104 to 109 and tires according to Comparative Examples 35 to 37 with high internal pressure shown below were conducted.

Specifications of each of the tires are shown in Table 16, and results of the evaluation are shown in Table 17 and FIGS. 26(a), (b).

TABLE 16

Internal

Ratio
Pressure
Ts
Ta
Tc

Tire Size
SW/OD
(kPa)
(mm)
(mm)
(mm)
Ts/Tc
Ta/Tc

Comparative
195/65R15
0.31
220
10
6
0.66
15.2
9.1

Example 35

Comparative
195/65R15
0.31
240
10
6
0.66
15.2
9.1

Example 36

Comparative
195/65R15
0.31
250
10
6
0.66
15.2
9.1

Example 37

Test Tire
165/65R19
0.24
240
4
2.5
0.5
8
5

104

Test Tire
165/65R19
0.24
250
4
2.5
0.5
8
5

105

Test Tire
165/55R21
0.23
240
3.5
2.8
0.5
7
5.6

106

Test Tire
165/55R21
0.23
250
3.5
2.8
0.5
7
5.6

107

Test Tire
155/55R21
0.22
240
4
2
0.55
7.3
3.6

108

Test Tire
155/55R21
0.22
250
4
2
0.55
7.3
3.6

109

TABLE 17

Lateral

Ground-
Ground-

Spring/

Contact
Contact

Vertical
Lateral
Vertical
RR

Length
Width

Spring
Spring
Spring
Value
CP
Weight
L
W
OD

Comparative
100
100
100
100
100
100
100
100
100

Example 35

Comparative
110
106
94
99
98
100
97
100
100

Example 36

Comparative
115
110
87
96
96
100
93
100
100

Example 37

Test Tire 104
98
109
111
95
103
90
102
85
109.9

Test Tire 105
99
119
120
89
109
90
100
85
109.9

Test Tire 106
98
111
113
84
103
84
103
80
112.7

Test Tire 107
99
117
118
79
108
84
101
80
112.7

Test Tire 108
98
106
108
94
107
74
104
86
110.9

Test Tire 109
99
110
111
91
110
74
100
86
110.9

From Table 17 and FIGS. 26 (a), (b), it can be seen that, when the tire having high internal pressure is used, the tire rolling resistance value is further reduced and cornering power is further improved.

REFERENCE SIGNS LIST

1 bead portion

1
a bead core

2 carcass

2
a carcass main body

2
b carcass folding portion

3 belt

4 bead filler

5 side wall portion

6 tire outer surface

Number	Date	Country	Kind
2011-185178	Aug 2011	JP	national
2011-185195	Aug 2011	JP	national
2011-185279	Aug 2011	JP	national

PNEUMATIC RADIAL TIRE FOR A PASSENGER VEHICLE AND METHOD OF USING THE SAME

Information

Publication Number

Date Filed

Date Published

Inventors

Original Assignees

CPC

US Classifications

International Classifications

Abstract

Description

Claims

Priority Claims (3)

PCT Information