(19)
(11)EP 3 686 036 A1

(12)EUROPEAN PATENT APPLICATION

(43)Date of publication:
29.07.2020 Bulletin 2020/31

(21)Application number: 20150154.1

(22)Date of filing:  03.01.2020
(51)Int. Cl.: 
B60C 11/03  (2006.01)
(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR
Designated Extension States:
BA ME
Designated Validation States:
KH MA MD TN

(30)Priority: 15.01.2019 JP 2019004578

(71)Applicant: Sumitomo Rubber Industries, Ltd.
Kobe-shi, Hyogo-ken 651-0072 (JP)

(72)Inventor:
  • UEYAMA, Kiyotaka
    Kobe-shi, Hyogo 651-0072 (JP)

(74)Representative: Manitz Finsterwald Patent- und Rechtsanwaltspartnerschaft mbB 
Martin-Greif-Strasse 1
80336 München
80336 München (DE)

  


(54)TIRE TREAD BAND


(57) Provided is a tire that can allow achievement of both steering stability and ride comfort.
A tread portion 2 has an outer tread end Teo that is positioned on an outer side of a vehicle when mounted to the vehicle, a plurality of circumferential grooves 3 that extend continuously in a tire circumferential direction, and a plurality of land portions 4 that are defined by the circumferential grooves 3. The circumferential grooves 3 include an outer circumferential groove 3A that extends adjacently to a tire equator C in a region closer to the outer tread end Teo than the tire equator C is. The land portions 4 include an outer shoulder land portion 4A that is defined between the outer circumferential groove 3A and the outer tread end Teo so as to continuously extend therebetween in a tire axial direction, and that has the largest width in the tire axial direction among the land portions 4. The outer shoulder land portion 4A has a first outer lateral groove 5 that extends inward in the tire axial direction and terminates in the outer shoulder land portion 4A. An angle of the first outer lateral groove 5 relative to the tire axial direction at a terminating position in the outer shoulder land portion 4A is 0 to 20°.




Description

BACKGROUND OF THE INVENTION


Field of the Invention



[0001] The present invention relates to a tire including a tread portion that has an asymmetric tread pattern and that has a designated mounting direction to a vehicle.

Description of the Background Art



[0002] To date, various tires each including a tread portion that has an asymmetric tread pattern and that has a designated mounting direction to a vehicle, have been known. For example, Japanese Laid-Open Patent Publication No. 2009-040156 suggests a tire in which an outer shoulder region is formed as outer block rows by tilted outer main grooves that extend transversely across the outer shoulder region between a ground contact edge and a longitudinal main groove in an outer side region disposed on the outer side of the vehicle.

[0003] In the tire disclosed in Japanese Laid-Open Patent Publication No. 2009-040156, achievement of both dry grip performance and wet performance is attempted by three longitudinal main grooves being disposed and stiffness being improved in the outer shoulder region. However, in the tire disclosed in Japanese Laid-Open Patent Publication No. 2009-040156, input from a road surface is increased according to the improvement of the stiffness of the tread portion, so that a problem that ride comfort is degraded may arise.

[0004] The present invention has been made in view of the aforementioned circumstances, and a main object of the present invention is to provide a tire that allows achievement of both steering stability and ride comfort.

SUMMARY OF THE INVENTION



[0005] The present invention is directed to a tire that includes a tread portion which has an asymmetric tread pattern and which has a designated mounting direction to a vehicle. The tread portion has an outer tread end that is positioned outward of a tire equator on an outer side of the vehicle when mounted to the vehicle, an inner tread end that is positioned inward of the tire equator on an inner side of the vehicle when mounted to the vehicle, a plurality of circumferential grooves that extend continuously in a tire circumferential direction, and a plurality of land portions that are defined by the circumferential grooves. The circumferential grooves include an outer circumferential groove that extends adjacently to the tire equator in a region closer to the outer tread end than the tire equator is. The land portions include an outer shoulder land portion that is defined between the outer circumferential groove and the outer tread end so as to continuously extend therebetween in a tire axial direction, and that has the largest width in the tire axial direction among the land portions. The outer shoulder land portion has a first outer lateral groove that extends inward from the outer tread end in the tire axial direction and terminates in the outer shoulder land portion. An angle of the first outer lateral groove relative to the tire axial direction at a terminating position in the outer shoulder land portion is 0 to 20°.

[0006] In the tire of the present invention, the circumferential grooves preferably include a first inner circumferential groove that extends adjacently to the inner tread end in a region closer to the inner tread end than the tire equator. The land portions preferably include an inner shoulder land portion that is defined between the first inner circumferential groove and the inner tread end, and does not have grooves and sipes that extend continuously in the tire circumferential direction and grooves that extend transversely in the tire axial direction. The inner shoulder land portion preferably has an inner lateral groove that extends inward from the inner tread end in the tire axial direction and terminates in the inner shoulder land portion.

[0007] In the tire of the present invention, the circumferential grooves preferably include a second inner circumferential groove that extends adjacently to the tire equator in a region closer to the inner tread end than the tire equator. The land portions preferably include a crown land portion that is defined between the outer circumferential groove and the second inner circumferential groove. In the crown land portion, a first length L1, in the tire axial direction, of a region closer to the outer circumferential groove than the tire equator is preferably greater than a second length L2, in the tire axial direction, of a region closer to the second inner circumferential groove than the tire equator.

[0008] In the tire of the present invention, a difference (L1-L2) between the first length L1 and the second length L2 is preferably 20% to 80% of a width Wc of the crown land portion.

[0009] In the tire of the present invention, a width Wo of the outer shoulder land portion is preferably 25% to 40% of a tread width between the outer tread end and the inner tread end.

[0010] In the tire of the present invention, a length Lo1, in the tire axial direction, of the first outer lateral groove is preferably 40% to 60% of the width Wo of the outer shoulder land portion.

[0011] In the tire of the present invention, the outer shoulder land portion preferably has a second outer lateral groove that extends outward from the outer circumferential groove in the tire axial direction and terminates in the outer shoulder land portion.

[0012] In the tire of the present invention, a length Lo2, in the tire axial direction, of the second outer lateral groove is preferably 25% to 75% of a difference (Wo-Lo1) between the width Wo of the outer shoulder land portion and the length Lo1, in the tire axial direction, of the first outer lateral groove.

[0013] In the tire of the present invention, the circumferential grooves preferably include a second inner circumferential groove that extends adjacently to the tire equator in a region closer to the inner tread end than the tire equator. The land portions preferably include a crown land portion that is defined between the outer circumferential groove and the second inner circumferential groove. The crown land portion preferably includes a first crown lateral groove that extends inward from the outer circumferential groove in the tire axial direction, and terminates in the crown land portion. An opening of the first crown lateral groove to the outer circumferential groove is preferably disposed on an extension of the second outer lateral groove.

[0014] In the tire of the present invention, the circumferential grooves include the outer circumferential groove that extends adjacently to the tire equator in a region closer to the outer tread end than the tire equator, and the land portions include the outer shoulder land portion that is defined between the outer circumferential groove and the outer tread end so as to continuously extend therebetween in the tire axial direction, and has the largest width in the tire axial direction among the land portions. The land portions having such a structure can allow stiffness to become high on the outer side of the vehicle, allow cornering power during cornering to be improved, and allow steering stability to be improved by the tire.

[0015] In the tire of the present invention, the outer shoulder land portion has the first outer lateral groove that extends inward from the outer tread end in the tire axial direction and terminates in the outer shoulder land portion. An angle of the first outer lateral groove relative to the tire axial direction at a terminating position in the outer shoulder land portion is 0 to 20°. The outer shoulder land portion having such a structure can allow input from a road surface to be regulated by the first outer lateral groove while maintaining stiffness, and allow ride comfort to be improved by the tire. Therefore, the tire of the present invention can allow both steering stability and ride comfort to be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS



[0016] 

FIG. 1 is a development of a tread portion of a tire according to one embodiment of the present invention;

FIG. 2 is an enlarged development of an outer shoulder land portion;

FIG. 3 is an enlarged development of an inner shoulder land portion; and

FIG. 4 is an enlarged development of a middle land portion and a crown land portion.


DESCRIPTION OF THE PREFERRED EMBODIMENTS



[0017] One embodiment of the present invention will be described below in detail with reference to the drawings.

[0018] FIG. 1 is a development of a tread portion 2 of a tire 1 according to the present embodiment. As shown in FIG. 1, the tire 1 of the present embodiment includes the tread portion 2 which has an asymmetric tread pattern and which has a designated mounting direction to a vehicle.

[0019] The tire 1 is preferably used as, for example, a pneumatic tire for a passenger car. The tire 1 is not limited to a pneumatic tire for a passenger car. The tire 1 can be used as various tires including, for example, a heavy duty pneumatic tire and a non-pneumatic tire which is not filled with pressurized air.

[0020] The tread portion 2 of the present embodiment includes an outer tread end Teo that is positioned outward of a tire equator C on the outer side of a vehicle when the tire 1 is mounted to the vehicle, and an inner tread end Tei that is positioned inward of the tire equator C on the inner side of the vehicle when the tire 1 is mounted to the vehicle.

[0021] In the description herein, the "outer tread end Teo" and the "inner tread end Tei" are tire-axially outermost ground contact positions in the case of the tire 1 in a normal state being in contact with a plane at a camber angle of 0° under a normal load. The center position, in the tire axial direction, between the outer tread end Teo and the inner tread end Tei is the tire equator C.

[0022] The "normal state" represents a state in which the tire 1 is mounted on a normal rim and is inflated with air to a normal internal pressure, and no load is applied to the tire 1 when the tire 1 is a pneumatic tire. In the description herein, unless otherwise specified, dimensions of components of the tire 1, and the like are represented as values measured in the normal state.

[0023] The "normal rim" represents a rim that is defined by a standard, in a standard system including the standard with which the tire 1 complies, for each tire, and is, for example, the "standard rim" in the JATMA standard, the "Design Rim" in the TRA standard, or the "Measuring Rim" in the ETRTO standard.

[0024] The "normal internal pressure" represents an air pressure that is defined by a standard, in a standard system including the standard with which the tire 1 complies, for each tire, and is the "maximum air pressure" in the JATMA standard, the maximum value recited in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, or the "INFLATION PRESSURE" in the ETRTO standard.

[0025] The "normal load" represents a load that is defined by a standard, in a standard system including the standard with which the tire 1 complies, for each tire, and is "maximum load capacity" in the JATMA standard, the maximum value recited in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, or the "LOAD CAPACITY" in the ETRTO standard.

[0026] The tread portion 2 preferably includes a plurality of circumferential grooves 3 that extend continuously in the tire circumferential direction, and a plurality of land portions 4 that are defined by the circumferential grooves 3. In the present embodiment, each of the plurality of land portions 4 does not have grooves and sipes that extend continuously in the tire circumferential direction and grooves that extend transversely in the tire axial direction. The land portions 4 having such a structure has a high stiffness and can allow steering stability to be improved by the tire 1. In the description herein, the sipe has opposing wall surfaces that are brought into contact with each other when the tire 1 contacts with the ground, and the groove forms a gap between opposing wall surfaces also when the tire 1 contacts with the ground.

[0027] The circumferential grooves 3 of the present embodiment include one outer circumferential groove 3A that extends adjacently to the tire equator C in a region closer to the outer tread end Teo than the tire equator C is. In the tread portion 2 of the present embodiment, only the outer circumferential groove 3A is a groove that extends continuously in the tire circumferential direction in a region closer to the outer tread end Teo than the tire equator C. The circumferential grooves 3 having such a structure can allow a preferable drainage performance to be assured and allow wet performance of the tire 1 to be improved.

[0028] The land portions 4 of the present embodiment include an outer shoulder land portion 4A that extends continuously in the tire axial direction and is defined between the outer circumferential groove 3A and the outer tread end Teo. That is, the outer shoulder land portion 4A does not have grooves and sipes that extend continuously in the tire circumferential direction. The outer shoulder land portion 4A preferably has the largest width in the tire axial direction among the land portions 4. The land portions 4 having such a structure can allow stiffness to become high on the outer side of the vehicle and allow cornering power during cornering to be improved, and thus allow steering stability to be improved by the tire 1.

[0029] The outer shoulder land portion 4A preferably has first outer lateral grooves 5 that extend inward from the outer tread end Teo in the tire axial direction, and terminate in the outer shoulder land portion 4A. The outer shoulder land portion 4A having such a structure can allow a groove volume of each first outer lateral groove 5 to be reduced, allow pattern noise during rolling to be lowered, and allow noise performance of the tire 1 to be improved.

[0030] An angle θ1 of the first outer lateral groove 5 relative to the tire axial direction at a terminating position in the outer shoulder land portion 4A is preferably 0 to 20°. The first outer lateral groove 5 having such a structure can allow input from a road surface to be regulated while maintaining stiffness of the outer shoulder land portion 4A, and allow ride comfort to be improved by the tire 1. Therefore, the tire 1 of the present embodiment can allow achievement of both steering stability and ride comfort.

[0031] In a more preferable mode, the circumferential grooves 3 include a first inner circumferential groove 3B that extends adjacently to the inner tread end Tei in a region closer to the inner tread end Tei than the tire equator C, and a second inner circumferential groove 3C that extends adjacently to the tire equator C in a region closer to the inner tread end Tei than the tire equator C. The tread portion 2 having such a structure has two inner circumferential grooves disposed inward of the tire equator C on the inner side of the vehicle. Therefore, drainage performance is favorable on the inner side of the vehicle, and wet performance of the tire 1 can be further improved.

[0032] A groove width W1 of the outer circumferential groove 3A and a groove width W3 of the second inner circumferential groove 3C are preferably each greater than a groove width W2 of the first inner circumferential groove 3B. The circumferential grooves 3 having such a structure can allow drainage performance around the tire equator C to become good and allow achievement of both drainage performance and stiffness of the tread portion 2. Therefore, the tire 1 of the present embodiment allows achievement of both wet performance and steering stability.

[0033] The groove width W1 of the outer circumferential groove 3A is preferably 4% to 10% of a tread width TW. The outer circumferential groove 3A having such a structure can allow achievement of both stiffness and drainage performance on the outer side of the vehicle, and allow achievement of both steering stability and wet performance of the tire 1. The tread width TW is a distance in the tire axial direction between the outer tread end Teo and the inner tread end Tei in the normal state.

[0034] The groove width W2 of the first inner circumferential groove 3B is preferably 2% to 8% of the tread width TW. The groove width W3 of the second inner circumferential groove 3C is preferably 4% to 10% of the tread width TW. The first inner circumferential groove 3B and the second inner circumferential groove 3C having such structures can allow achievement of both stiffness and drainage performance on the inner side of the vehicle and allow achievement of both steering stability and wet performance of the tire 1.

[0035] The land portions 4 of the present embodiment include an inner shoulder land portion 4B that is defined between the first inner circumferential groove 3B and the inner tread end Tei, and that does not have grooves and sipes that extend continuously in the tire circumferential direction and grooves that extend transversely in the tire axial direction. Furthermore, the land portions 4 preferably include a middle land portion 4C that is defined between the first inner circumferential groove 3B and the second inner circumferential groove 3C, and a crown land portion 4D that is defined between the outer circumferential groove 3A and the second inner circumferential groove 3C. Each of the outer shoulder land portion 4A, the middle land portion 4C, and the crown land portion 4D of the present embodiment does not have grooves and sipes that extend continuously in the tire circumferential direction, and grooves that extend transversely in the tire axial direction. The land portions 4 having such a structure have a high stiffness and can allow steering stability to be improved by the tire 1.

[0036] A width Wo, in the tire axial direction, of the outer shoulder land portion 4A is preferably greater than a width Wi, in the tire axial direction, of the inner shoulder land portion 4B, a width Wm, in the tire axial direction, of the middle land portion 4C, and a width Wc, in the tire axial direction, of the crown land portion 4D. The outer shoulder land portion 4A having such a structure can allow stiffness to become high on the outer side of the vehicle, allow cornering power during cornering to be improved, and allow steering stability to be further improved by the tire 1.

[0037] The width Wo of the outer shoulder land portion 4A is preferably 25% to 40% of the tread width TW. When the width Wo is less than 25% of the tread width TW, stiffness is reduced on the outer side of the vehicle, and steering stability may not be improved by the tire 1. When the width Wo is greater than 40% of the tread width TW, stiffness becomes excessively high on the outer side of the vehicle, and ride comfort provided by the tire 1 may be degraded.

[0038] The width Wi of the inner shoulder land portion 4B is preferably 11% to 22% of the tread width TW. The width Wm of the middle land portion 4C is preferably 12% to 24% of the tread width TW. The inner shoulder land portion 4B and the middle land portion 4C having such structures can allow stiffness on the inner side of the vehicle to be maintained in an appropriate range, and allow both steering stability and ride comfort to be achieved by the tire 1.

[0039] The width Wc of the crown land portion 4D is preferably 10% to 20% of the tread width TW. The crown land portion 4D having such a structure can allow stiffness near the tire equator C to be maintained in an appropriate range, and allow both steering stability and ride comfort to be achieved by the tire 1.

[0040] FIG. 2 is an enlarged development of the outer shoulder land portion 4A. As shown in FIG. 2, a length Lo1, in the tire axial direction, of each first outer lateral groove 5 is preferably 40% to 60% of the width Wo of the outer shoulder land portion 4A. When the length Lo1 is less than 40% of the width Wo, stiffness of the outer shoulder land portion 4A becomes excessively high, and ride comfort provided by the tire 1 may be degraded. When the length Lo1 is greater than 60% of the width Wo, stiffness of the outer shoulder land portion 4A is reduced and a groove volume is increased, so that steering stability and noise performance may not be improved by the tire 1.

[0041] The outer shoulder land portion 4A of the present embodiment has a second outer lateral groove 6 that extends outward from the outer circumferential groove 3A in the tire axial direction and terminates in the outer shoulder land portion 4A. The outer shoulder land portion 4A having such a structure can allow stiffness to become appropriate, and allow well-balanced improvement of steering stability, ride comfort, and noise performance.

[0042] A length Lo2, in the tire axial direction, of each second outer lateral groove 6 is preferably 25% to 75% of a difference (Wo-Lo1) between the width Wo of the outer shoulder land portion 4A and the length Lo1, in the tire axial direction, of the first outer lateral groove 5. When the length Lo2 is less than 25% of the difference (Wo-Lo1), stiffness of the outer shoulder land portion 4A cannot be regulated, and ride comfort may not be improved by the tire 1. When the length Lo2 is greater than 75% of the difference (Wo-Lo1), stiffness of the outer shoulder land portion 4A is reduced and the groove volume is increased, so that steering stability and noise performance may not be improved by the tire 1.

[0043] An angle θ2 of the second outer lateral groove 6 relative to the tire axial direction is preferably 0 to 20°. The angle θ2 of the second outer lateral groove 6 is preferably almost equal to the angle θ1 of the first outer lateral groove 5. The second outer lateral groove 6 having such a structure and the first outer lateral groove 5 can allow stiffness of the outer shoulder land portion 4A to be in an appropriate range, and allow well-balanced improvement of steering stability, ride comfort, and noise performance to be achieved by the tire 1.

[0044] The outer shoulder land portion 4A of the present embodiment has outer sipes 7 that connect between the first outer lateral grooves 5 and the outer circumferential groove 3A. For example, the outer sipes 7 extend linearly. Each outer sipe 7 preferably extends at an angle equal to the angle θ1 relative to the tire axial direction, at the terminating position in the outer shoulder land portion 4A. The outer sipes 7 having such a structure can allow stiffness of the outer shoulder land portion 4A to be in an appropriate range, and allow both steering stability and ride comfort to be achieved by the tire 1.

[0045] FIG. 3 is an enlarged development of the inner shoulder land portion 4B. As shown in FIG. 3, the inner shoulder land portion 4B preferably has inner lateral grooves 8 that extend inward from the inner tread end Tei in the tire axial direction and terminate in the inner shoulder land portion 4B. The inner lateral groove 8 having such a structure has a small groove volume and can allow pattern noise during rolling to be lowered, thereby allowing noise performance of the tire 1 to be improved.

[0046] A length Li, in the tire axial direction, of each inner lateral groove 8 is preferably 50% to 70% of the width Wi of the inner shoulder land portion 4B. When the length Li is less than 50% of the width Wo, stiffness of the inner shoulder land portion 4B becomes excessively high, and ride comfort provided by the tire 1 may be degraded. When the length Li is greater than 70% of the width Wo, stiffness of the inner shoulder land portion 4B is reduced and the groove volume is increased, so that steering stability and noise performance may not be improved by the tire 1.

[0047] An angle θ3 of the inner lateral groove 8 relative to the tire axial direction at the terminating position in the inner shoulder land portion 4B is preferably 0 to 20°. The inner lateral groove 8 having such a structure can allow stiffness, in the tire axial direction, of the inner shoulder land portion 4B to be improved, and can also have a reduced groove volume, thereby allowing steering stability and noise performance to be improved by the tire 1.

[0048] FIG. 4 is an enlarged development of the middle land portion 4C and the crown land portion 4D. As shown in FIG. 4, the middle land portion 4C preferably has middle lateral grooves 9 that extend inward from the first inner circumferential groove 3B in the tire axial direction and terminate in the middle land portion 4C. The middle lateral grooves 9 having such a structure can allow stiffness of the middle land portion 4C to be in an appropriate range, and allow well-balanced improvement of steering stability, ride comfort, and noise performance to be achieved by the tire 1.

[0049] A length Lm, in the tire axial direction, of each middle lateral groove 9 is preferably 40% to 60% of the width Wm of the middle land portion 4C. When the length Lm is less than 40% of the width Wm, stiffness of the middle land portion 4C becomes excessively high, and ride comfort provided by the tire 1 may be degraded. When the length Lm is greater than 60% of the width Wm, stiffness of the middle land portion 4C is reduced and the groove volume is increased, so that steering stability and noise performance may not be improved by the tire 1.

[0050] The middle land portion 4C preferably has middle sipes 10 that continuously extend from the first inner circumferential groove 3B to the second inner circumferential groove 3C. For example, the middle sipes 10 and the middle lateral grooves 9 alternate in the tire circumferential direction. The middle sipes 10 having such a structure can allow stiffness of the middle land portion 4C to be in an appropriate range, and allow both steering stability and ride comfort to be achieved by the tire 1.

[0051] In the crown land portion 4D, a first length L1, in the tire axial direction, of a region closer to the outer circumferential groove 3A than the tire equator C is preferably greater than a second length L2, in the tire axial direction, of a region closer to the second inner circumferential groove 3C than the tire equator C. The crown land portion 4D having such a structure can allow stiffness to become high on the outer side of the vehicle, and allow cornering power during cornering to be improved, so that steering stability can be further improved by the tire 1.

[0052] A difference (L1-L2) between the first length L1 and the second length L2 is preferably 20% to 80% of the width Wc of the crown land portion 4D. When the difference (L1-L2) is less than 20% thereof, stiffness of the outer shoulder land portion 4A becomes excessively high, and ride comfort provided by the tire 1 may be degraded. When the difference (L1-L2) is greater than 80% thereof, stiffness of the outer shoulder land portion 4A is reduced, and steering stability may not be improved by the tire 1.

[0053] The crown land portion 4D preferably includes first crown lateral grooves 11 that extend inward from the outer circumferential groove 3A in the tire axial direction, and terminate in the crown land portion 4D. For example, the first crown lateral grooves 11 extend linearly. The first crown lateral grooves 11 having such a structure can allow stiffness of the crown land portion 4D to be regulated, and allow steering stability to be improved by the tire 1.

[0054] In the present embodiment, an opening 11a of each first crown lateral groove 11 to the outer circumferential groove 3A is disposed on the extension of the second outer lateral groove 6. The first crown lateral groove 11 is preferably tilted relative to the tire axial direction in the direction opposite to the direction of the second outer lateral groove 6. The first crown lateral grooves 11 having such a structure and the second outer lateral grooves 6 can allow stiffness on the outer side of the vehicle to be in an appropriate range, and allow well-balanced improvement of steering stability, ride comfort, and noise performance to be achieved by the tire 1.

[0055] A length Lc1, in the tire axial direction, of the first crown lateral groove 11 is preferably 10% to 30% of the first length L1. When the length Lc1 is less than 10% of the first length L1, stiffness of the crown land portion 4D may not be regulated and steering stability may not be improved by the tire 1. When the length Lc1 is greater than 30% of the first length L1, stiffness of the crown land portion 4D is reduced and the groove volume is increased, so that steering stability and noise performance may not be improved by the tire 1.

[0056] The crown land portion 4D of the present embodiment includes second crown lateral grooves 12 that extend inward from the second inner circumferential groove 3C in the tire axial direction, and terminate in the crown land portion 4D. For example, the second crown lateral grooves 12 and the first crown lateral grooves 11 alternate in the tire circumferential direction. The second crown lateral grooves 12 having such a structure and the first crown lateral grooves 11 can allow stiffness of the crown land portion 4D to be in an appropriate range, and allow well-balanced improvement of steering stability, ride comfort, and noise performance to be achieved by the tire 1.

[0057] A length Lc2, in the tire axial direction, of the second crown lateral groove 12 is preferably 30% to 50% of the second length L2. When the length Lc2 is less than 30% of the second length L2, stiffness of the crown land portion 4D may not be regulated, and steering stability may not be improved by the tire 1. When the length Lc2 is greater than 50% of the second length L2, stiffness of the crown land portion 4D is reduced and the groove volume is increased, so that steering stability and noise performance may not be improved by the tire 1.

[0058] Although the preferred embodiments of the present invention have been described above in detail, the present invention is not limited to the embodiments described above, and various modifications can be devised to implement the present invention.

[Examples]



[0059] A sample of a pneumatic tire having a basic pattern shown in FIG. 1 was produced based on the specifications indicated in Table 1. The tires produced as the samples were mounted to all the wheels of a test vehicle, and steering stability and ride comfort were evaluated. Specifications common to the sample tires and a test method were as follows.

<Common specifications>



[0060] Test vehicle: four-wheel-drive vehicle, as a passenger car, having an engine displacement of 3.8 liters
Size of tire for front wheel: 255/40R20
Size of tire for rear wheel: 285/3 5R20
Size of rim for front wheel: 20×10J
Size of rim for rear wheel: 20×10.5J
Air pressure for front wheel: 210 kPa
Air pressure for rear wheel: 200 kPa

<Steering stability>



[0061] One test driver got in the test vehicle and drove on a circuit test course, and the test driver made sensory evaluation for responsiveness of the vehicle to steering at a low speed (40 to 80 km/h) and a high speed (100 to 120 km/h). The results are indicated as indexes with the index of comparative example being 100. The greater the value of the index is, the more excellent steering stability is.

<Ride comfort>



[0062] One test driver got in the test vehicle and drove on a test course of a road under vibration, and the test driver made sensory evaluation for ride comfort at 40 km/h. The results are indicated as indexes with the index of comparative example being 100. The greater the value of the index is, the more excellent ride comfort is.

[0063] The test results are indicated in Table 1.
[Table 1]
 Comp. Ex.Example 1Example 2Example 3Example 4Example 5Example 6Example 7Example 8Example 9
Angle θ1(°) of first outer lateral groove 45 10 10 10 10 10 10 10 10 10
First outer lateral groove length Lo1/outer land portion width Wo (%) 100 35 40 50 60 65 50 50 50 50
(First length L1-second length L2)/ crown land portion width Wc (%) 40 40 40 40 40 40 10 20 80 90
Steering stability (index) 100 125 122 120 110 105 105 115 110 105
Ride comfort (index) 100 100 104 106 106 107 108 107 104 101


[0064] According to the test results, it is confirmed that the tires of examples allowed steering stability to be improved while maintaining ride comfort which was equivalent to or better than that in the comparative example, and allowed achievement of both steering stability and ride comfort.


Claims

1. A tire comprising
a tread portion which has an asymmetric tread pattern and which has a designated mounting direction to a vehicle, wherein
the tread portion has an outer tread end that is positioned outward of a tire equator on an outer side of the vehicle when mounted to the vehicle, an inner tread end that is positioned inward of the tire equator on an inner side of the vehicle when mounted to the vehicle, a plurality of circumferential grooves that extend continuously in a tire circumferential direction, and a plurality of land portions that are defined by the circumferential grooves,
the circumferential grooves include an outer circumferential groove that extends adjacently to the tire equator in a region closer to the outer tread end than the tire equator is,
the land portions include an outer shoulder land portion that is defined between the outer circumferential groove and the outer tread end so as to continuously extend therebetween in a tire axial direction, and that has the largest width in the tire axial direction among the land portions,
the outer shoulder land portion has a first outer lateral groove that extends inward from the outer tread end in the tire axial direction and terminates in the outer shoulder land portion, and
an angle of the first outer lateral groove relative to the tire axial direction at a terminating position in the outer shoulder land portion is 0 to 20°.
 
2. The tire according to claim 1, wherein
the circumferential grooves include a first inner circumferential groove that extends adjacently to the inner tread end in a region closer to the inner tread end than the tire equator,
the land portions include an inner shoulder land portion that is defined between the first inner circumferential groove and the inner tread end, and does not have grooves and sipes that extend continuously in the tire circumferential direction and grooves that extend transversely in the tire axial direction, and
the inner shoulder land portion has an inner lateral groove that extends inward from the inner tread end in the tire axial direction and terminates in the inner shoulder land portion.
 
3. The tire according to claim 1 or 2, wherein
the circumferential grooves include a second inner circumferential groove that extends adjacently to the tire equator in a region closer to the inner tread end than the tire equator,
the land portions include a crown land portion that is defined between the outer circumferential groove and the second inner circumferential groove, and
in the crown land portion, a first length L1, in the tire axial direction, of a region closer to the outer circumferential groove than the tire equator is greater than a second length L2, in the tire axial direction, of a region closer to the second inner circumferential groove than the tire equator.
 
4. The tire according to claim 3, wherein a difference (L1-L2) between the first length L1 and the second length L2 is 20% to 80% of a width Wc of the crown land portion.
 
5. The tire according to any one of claims 1 to 4, wherein a width Wo of the outer shoulder land portion is 25% to 40% of a tread width between the outer tread end and the inner tread end.
 
6. The tire according to any one of claims 1 to 5, wherein a length Lo1, in the tire axial direction, of the first outer lateral groove is 40% to 60% of the width Wo of the outer shoulder land portion.
 
7. The tire according to any one of claims 1 to 6, wherein the outer shoulder land portion has a second outer lateral groove that extends outward from the outer circumferential groove in the tire axial direction and terminates in the outer shoulder land portion.
 
8. The tire according to claim 7, wherein a length Lo2, in the tire axial direction, of the second outer lateral groove is 25% to 75% of a difference (Wo-Lo1) between the width Wo of the outer shoulder land portion and the length Lo1, in the tire axial direction, of the first outer lateral groove.
 
9. The tire according to claim 7 or 8, wherein
the circumferential grooves include a second inner circumferential groove that extends adjacently to the tire equator in a region closer to the inner tread end than the tire equator,
the land portions include a crown land portion that is defined between the outer circumferential groove and the second inner circumferential groove,
the crown land portion includes a first crown lateral groove that extends inward from the outer circumferential groove in the tire axial direction, and terminates in the crown land portion, and
an opening of the first crown lateral groove to the outer circumferential groove is disposed on an extension of the second outer lateral groove.
 




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REFERENCES CITED IN THE DESCRIPTION



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Patent documents cited in the description