WO2019171554A1

WO2019171554A1 - Pneumatic tire

Info

Publication number: WO2019171554A1
Application number: PCT/JP2018/009071
Authority: WO
Inventors: 孝志芝井
Original assignee: 横浜ゴム株式会社
Priority date: 2018-03-08
Filing date: 2018-03-08
Publication date: 2019-09-12
Also published as: JPWO2019171554A1; JP6729809B2

Abstract

Provided is a pneumatic tire that can suppress uneven shoulder wear in a tread and improve ride comfort. Maximum ground contact lengths LA1, LB1, and LC1 and maximum ground contact widths WA1, WB1, and WC1, which are respectively obtained when a pneumatic tire filled with 230 kPa of air is grounded under the condition that loads respectively corresponding to 40%, 75%, and 100% of the maximum load carrying capacity are applied to the pneumatic tire, and outside ground contact lengths LA2, LB2, and LC2, which are respectively positioned at 40% of the maximum ground contact widths WA1, WB1, and WC1 from the tire central position outwardly in the tire width direction, satisfy the following relationships: 1.02 ≤ (LB2/LB1)/(LA2/LA1) ≤ 1.25 and 1.00 ≤ (LC2/LC1)/(LB2/LB1) ≤ 1.20. When a tread (1) is divided into a central region Xc having a width corresponding to 53% of the maximum ground contact width WB1 and outside regions Xs that are outside the central region Xc, the groove area Sc of the central region Xc and the groove areas Ss of the outside regions Xs satisfy the following relationship: 1.01 ≤ Sc/Ss ≤ 1.50.

Description

Pneumatic tire

The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire that can suppress uneven shoulder wear of a tread portion and improve riding comfort.

A pneumatic tire is generally disposed in a tire tread portion extending in the tire circumferential direction, a pair of sidewall portions disposed on both sides of the tread portion, and on the inner side in the tire radial direction of the sidewall portions. A pair of bead portions, a carcass layer mounted between the pair of bead portions, and a structure including a plurality of belt layers disposed on the outer side in the tire radial direction of the carcass layer in the tread portion. doing.

Such a pneumatic tire is required to improve the wear characteristics as a permanent problem. As a technique for improving the wear characteristics, for example, it has been proposed to increase the rigidity of the tread portion by increasing the hardness of the cap tread rubber (see, for example, Patent Document 1). However, when the hardness of the cap tread rubber is simply increased, there is a problem that the impact received from the road surface during traveling increases with the increase in rigidity of the tread portion, and the riding comfort (mild feeling) deteriorates. For this reason, it is necessary to achieve both wear characteristics and riding comfort that are in contradiction.

By the way, a technique for improving various performances of a pneumatic tire by defining the contact shape of the pneumatic tire has been proposed (see, for example, Patent Documents 2 to 4). However, these technologies do not achieve both wear characteristics and riding comfort.

Japanese Unexamined Patent Publication No. 2017-203080 Japanese Unexamined Patent Publication No. 6-8710 Japanese Laid-Open Patent Publication No. 8-108710 Japanese Unexamined Patent Application Publication No. 2009-78790

An object of the present invention is to provide a pneumatic tire capable of suppressing uneven shoulder wear of a tread portion and improving riding comfort.

In order to achieve the above object, a pneumatic tire according to the present invention includes a tread portion that extends in the tire circumferential direction to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and the sidewall portions. In a pneumatic tire provided with a pair of bead portions arranged on the inner side in the tire radial direction of
Maximum contact length in the tire circumferential direction when the pneumatic tire is filled with air pressure of 230 kPa and contacted with a load of 40%, 75%, and 100% of the maximum load capacity determined by the standard, respectively. Are LA1, LB1, and LC1, respectively, and the maximum ground contact widths in the tire width direction are WA1, WB1, and WC1, respectively, at positions 40% of the maximum ground contact widths WA1, WB1, and WC1 from the tire center position toward the outside in the tire width direction. When the external contact lengths in the tire circumferential direction are LA2, LB2, and LC2, respectively, the maximum contact lengths LA1, LB1, and LC1 and the external contact lengths LA2, LB2, and LC2 are 1.02 ≦ (LB2 / LB1) / (LA2 /LA1)≦1.25, 1.00 ≦ (LC2 / LC1) / (LB2 / LB1) ≦ 1.20,
When the tread portion is divided into a central region having a width corresponding to 53% of the maximum ground contact width WB1 centered on the tire equator and an outer region in the maximum ground contact width WB1 outside the center region in the tire width direction. The groove area Sc of the central region and the groove area Ss of the outer region satisfy the relationship of 1.01 ≦ Sc / Ss ≦ 1.50.

In the present invention, the groove area Sc of the central region and the groove area Ss of the outer region satisfy the relationship of 1.01 ≦ Sc / Ss ≦ 1.50, and the groove area Sc in the central region is sufficiently secured. The rigidity in the central region of the tread portion can be lowered to ease the input from the road surface, and the riding comfort (mild feeling) can be improved. On the other hand, by reducing the groove area Ss in the outer region, it is possible to secure rigidity in the outer region of the tread portion and suppress shoulder uneven wear of the tread portion. Further, the maximum ground contact lengths LA1, LB1, and LC1 and external ground contact lengths LA2, LB2, and LC2 are 1.02 ≦ (LB2 / LB1) / (LA2 / LA1) ≦ 1.25, 1.00 ≦ (LC2 / LC1) / By satisfying the relationship (LB2 / LB1) ≦ 1.20 and defining the ground contact shape in consideration of load fluctuations, the effect of suppressing shoulder uneven wear and the effect of improving riding comfort can be further enhanced.

In the present invention, it is preferable that the maximum ground contact length LB1 and the external ground contact length LB2 satisfy the relationship of 0.65 ≦ LB2 / LB1 ≦ 0.95. Further, the maximum ground contact lengths LA1, LB1, and LC1 and the external ground contact lengths LA2, LB2, and LC2 satisfy the relationship of (LC2 / LC1) / (LB2 / LB1) ≦ (LB2 / LB1) / (LA2 / LA1). preferable. Thereby, riding comfort can be improved based on the ground contact shape.

In the present invention, a central main groove extending in the tire circumferential direction in the tread portion, an outer main groove extending in the tire circumferential direction at a position on the outer side in the tire width direction from the central main groove, and the tire width from the outer main groove. A tread pattern in which a plurality of outer lateral grooves extending in the tire width direction at positions outside in the direction can be employed.

In this case, in order to ensure rigidity in the outer region of the tread portion and to suppress uneven shoulder wear of the tread portion, it is preferable to adopt the following structure. That is, it is preferable that the inclination angle θsl formed by the side wall of the outer lateral groove with respect to the normal line of the tread surface satisfies the relationship of 0 ° ≦ θsl ≦ 10 °. The groove depth Dsl of the outer lateral groove preferably satisfies the relationship of 0.20 ≦ Dsl / GDs ≦ 0.90 with respect to the groove depth GDs of the outer main groove. The outer lateral groove has a bottom raised portion in a part of the longitudinal direction, and the groove depth Db at the bottom raised portion has a relationship of 0.30 ≦ Db / Dsl ≦ 0.90 with respect to the groove depth Dsl of the outer lateral groove. It is preferable to satisfy. It is preferable that the groove depth GDs of the outer main groove satisfies the relationship 0.80 ≦ GDs / GDc ≦ 1.00 with respect to the groove depth GDc of the central main groove. Further, when a plurality of central lateral grooves extending in the tire width direction are formed in the tread portion at positions inside the outer main groove in the tire width direction, the groove depth Dsl of the outer lateral groove is smaller than the groove depth Dcl of the central lateral groove. It is preferable that the relationship of 0.50 ≦ Dsl / Dcl ≦ 1.00 is satisfied. Furthermore, it is preferable that all of the outer lateral grooves formed outside the outer main groove in the tire width direction have a groove width of 1.0 mm or less.

In the present invention, when the tread portion includes a plurality of belt cords that are inclined with respect to the tire circumferential direction, and a plurality of belt layers in which the belt cords intersect with each other are embedded, It is preferable that the inclination angle α with respect to the tire circumferential direction satisfies the relationship of 21 ° ≦ α ≦ 30 °. By not extremely reducing the inclination angle α of the belt cord at the tire center position, it is possible to suppress the increase in rigidity of the belt layer and improve the riding comfort.

The inclination angle α of the belt cord with respect to the tire circumferential direction at the tire center position and the inclination angle β of the belt cord with respect to the tire circumferential direction at the belt end position satisfy the relationship of 18 ° ≦ β <α ≦ 30 °. Is preferred. By setting the inclination angle β at the belt end position of the belt cord to be small, shoulder uneven wear can be effectively suppressed.

The pneumatic tire of the present invention is preferably a passenger car tire having an aspect ratio of 0.65 or less. ADVANTAGE OF THE INVENTION According to this invention, in the tire for passenger cars in which the improvement of riding comfort is requested | required strictly, it becomes possible to make both partial wear resistance and riding comfort compatible.

において In the present invention, the contact shape of the tread portion is measured under the condition that a predetermined load is applied by placing the tire on a regular rim and placing the tire vertically on a plane in a state filled with a predetermined air pressure. The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based, for example, a standard rim for JATMA, “Design Rim” for TRA, or ETRTO. Then, “Measuring Rim” is set. The air pressure is 230 kPa. Further, the predetermined load is a load of 40%, 75% or 100% of the maximum load capacity defined by each standard for each tire in a standard system including the standard on which the tire is based.

FIG. 1 is a meridian cross-sectional view showing a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a development view showing a tread pattern of the pneumatic tire of FIG. FIG. 3 is a plan view showing a ground contact shape (40% load) of the pneumatic tire of FIG. FIG. 4 is a plan view showing a ground contact shape (75% load) of the pneumatic tire of FIG. FIG. 5 is a plan view showing a ground contact shape (100% load) of the pneumatic tire of FIG. 6 is a cross-sectional view showing a central main groove, an outer main groove, and an outer lateral groove (lug groove) formed in the tread portion of the pneumatic tire of FIG. FIG. 7 is a cross-sectional view showing an outer lateral groove (lag groove) formed in the tread portion of the pneumatic tire of FIG. FIG. 8 is a cross-sectional view showing a central lateral groove (lag groove) formed in the tread portion of the pneumatic tire of FIG. FIG. 9 is a development view showing a tread pattern of a pneumatic tire according to another embodiment of the present invention. 10 is a cross-sectional view showing an outer lateral groove (sipe) formed in the tread portion of the pneumatic tire of FIG. FIG. 11 is a sectional view showing a modification of the outer lateral groove (sipe). FIG. 12 is a development view showing a belt layer constituting the pneumatic tire of the present invention.

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. 1 and 2 show a pneumatic tire according to an embodiment of the present invention. In FIG. 2, CL is a tire center position, Tc is a tire circumferential direction, and Tw is a tire width direction.

As shown in FIG. 1, the pneumatic tire of the present embodiment includes a tread portion 1 that extends in the tire circumferential direction and has an annular shape, and a pair of

sidewall portions

2, 2 disposed on both sides of the tread portion 1. And a pair of

bead portions

3 and 3 disposed inside the sidewall portion 2 in the tire radial direction.

The carcass layer 4 is mounted between the pair of

bead portions

3 and 3. The carcass layer 4 includes a plurality of carcass cords extending in the tire radial direction, and is folded back from the inside of the tire to the outside around the bead core 5 disposed in each bead portion 3. A bead filler 6 made of a rubber composition having a triangular cross-section is disposed on the outer periphery of the bead core 5.

On the other hand, a plurality of belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 7 include a plurality of belt cords inclined with respect to the tire circumferential direction, and are arranged so that the belt cords cross each other between the layers. A steel cord is preferably used as the belt cord constituting the belt layer 7. On the outer peripheral side of the belt layer 7, at least one belt reinforcing layer 8 including a plurality of band cords oriented in the tire circumferential direction is disposed. It is desirable that the belt reinforcing layer 8 has a jointless structure in which at least one band cord is aligned and rubber-coated strip material is continuously wound in the tire circumferential direction. As the band cord constituting the belt reinforcing layer 8, an organic fiber cord such as nylon or aramid is preferably used.

As shown in FIG. 2, the tread portion 1 includes a pair of central

main grooves

11, 11 extending in the tire circumferential direction at positions on both sides of the tire center position CL, and the tire

main body

11, 11 outside the central

main grooves

11, 11. A pair of outer

main grooves

12 and 12 extending in the tire circumferential direction at the position are formed. The central main groove 11 and the outer main groove 12 may have a straight shape or may have a zigzag shape. As a result, a center land portion 20 is defined between the central

main grooves

11 and 11, and a middle land portion 30 is defined between the central main groove 11 and the outer main groove 12. A shoulder land portion 40 is defined in the area.

A plurality of central lateral grooves 31 extending in the tire width direction are formed in each of the middle land portions 30. The central lateral groove 31 includes a central lug groove 31A having a groove width in the range of 1.1 mm to 9.5 mm on the tread surface and a central sipe 31B having a groove width on the tread surface of 1.0 mm or less. . The central lug grooves 31A and the central sipes 31B are alternately arranged along the tire circumferential direction. Further, a circumferential narrow groove 32 extending in the tire circumferential direction and having a zigzag shape is formed on one side of the middle land portion 30.

Each of the shoulder land portions 40 is formed with a plurality of outer lateral grooves 41 extending in the tire width direction. The outer lateral groove 41 includes at least one of an outer lug groove 41A having a groove width on the tread surface of 1.1 mm to 9.0 mm and an outer sipe 41B having a groove width of 1.0 mm or less on the tread surface. Yes. In the form in which both are present, the outer lug grooves 41A and the outer sipes 41B are alternately arranged along the tire circumferential direction.

FIGS. 3 to 5 show the ground contact shapes (40% load, 75% load, 100% load) of the pneumatic tire of FIG. 1, respectively. In the pneumatic tire described above, a tire when the pneumatic tire is filled with 230 kPa of air pressure and is grounded under a condition in which a load of 40%, 75%, and 100% of the maximum load capacity specified by the standard is applied, respectively. The maximum contact length in the circumferential direction is LA1, LB1, LC1 (mm), and the maximum contact width in the tire width direction is WA1, WB1, WC1 (mm), respectively. External contact lengths in the tire circumferential direction at positions 40% of the widths WA1, WB1, and WC1 are LA2, LB2, and LC2 (mm), respectively.

That is, as shown in FIG. 3, the maximum in the tire circumferential direction when the pneumatic tire is filled with 230 kPa of air pressure and contacted with a load of 40% of the maximum load capacity defined in the standard is applied. The contact length is LA1, the maximum contact width in the tire width direction is WA1, and the external contact length in the tire circumferential direction at a position 40% of the maximum contact width WA1 from the tire center position CL toward the outer side in the tire width direction is LA2. . The external ground contact length LA2 is an average value of measured values on both sides of the tire center position CL.

Moreover, as shown in FIG. 4, the maximum in the tire circumferential direction when the pneumatic tire is filled with 230 kPa of air pressure and grounded under a condition where a load of 75% of the maximum load capacity defined by the standard is applied. The contact length is LB1, the maximum contact width in the tire width direction is WB1, and the external contact length in the tire circumferential direction at a position 40% of the maximum contact width WB1 from the tire center position CL toward the outer side in the tire width direction is LB2. . The external contact length LB2 is an average value of measured values on both sides of the tire center position CL.

Further, as shown in FIG. 5, the maximum in the tire circumferential direction when the pneumatic tire is filled with 230 kPa of air pressure and grounded under the condition of applying a load of 100% of the maximum load capacity defined by the standard. The contact length is LC1, the maximum contact width in the tire width direction is WC1, and the external contact length in the tire circumferential direction at the position of 40% of the maximum contact width WC1 from the tire center position CL toward the outer side in the tire width direction is LC2. . The external contact length LC2 is an average value of measured values on both sides of the tire center position CL.

Here, the maximum ground contact lengths LA1, LB1, and LC1 and the external ground contact lengths LA2, LB2, and LC2 satisfy the following relationship.
1.02 ≦ (LB2 / LB1) / (LA2 / LA1) ≦ 1.25
1.00 ≦ (LC2 / LC1) / (LB2 / LB1) ≦ 1.20

Further, as shown in FIG. 4, the tread portion 1 is located within the central region Xc having a width corresponding to 53% of the maximum ground contact width WB1 centered on the tire equator (ie, the tire center position CL) and the maximum ground contact width WB1. When divided into the outer region Xs that is on the outer side in the tire width direction from the central region Xc, the groove area Sc (mm ² ) of the central region Xc and the groove area Ss (mm ² ) of the outer region Xs satisfy the following relationship. .
1.01 ≦ Sc / Ss ≦ 1.50

The groove area Sc of the central region Xc means the total area of the groove components formed in the central region Xc on the tire circumference, and the groove area Ss of the outer region Xs is the groove component formed in the outer region Xs on the tire circumference. It means the total area. When the groove component has a chamfered portion, the area of the chamfered portion is also included in the total area of the groove component.

In the pneumatic tire described above, the groove area Sc of the central region Xc and the groove area Ss of the outer region Xs satisfy the relationship of 1.01 ≦ Sc / Ss ≦ 1.50, and the groove area Sc in the central region Xc is By ensuring sufficiently, the rigidity in the center area | region Xc of the tread part 1 can be made low, the input from a road surface can be eased, and riding comfort (mild feeling) can be improved. On the other hand, by reducing the groove area Ss in the outer region Xs, the rigidity in the outer region Xs of the tread portion 1 can be ensured, and shoulder uneven wear of the tread portion 1 can be suppressed.

Here, if Sc / S is smaller than 1.01, the groove area Sc in the central region Xc is insufficient, so that the effect of improving the riding comfort becomes insufficient. Conversely, if Sc / Ss is larger than 1.50. Since the groove area Ss in the outer region Xs becomes excessive, the effect of suppressing shoulder uneven wear becomes insufficient. In particular, it is desirable to satisfy the relationship of 1.05 ≦ Sc / Ss ≦ 1.30, and further 1.13 ≦ Sc / Ss ≦ 1.30.

In the pneumatic tire described above, the maximum contact lengths LA1, LB1, and LC1 and the external contact lengths LA2, LB2, and LC2 are 1.02 ≦ (LB2 / LB1) / (LA2 / LA1) ≦ 1.25, 1.00. By satisfying the relationship of ≦ (LC2 / LC1) / (LB2 / LB1) ≦ 1.20 and defining the ground contact shape in consideration of load fluctuation, the effect of suppressing shoulder uneven wear and the effect of improving riding comfort are further enhanced. be able to. In other words, in a general vehicle equipped with an engine in front, (LB2 / LB1) / (LA2 / LA1) is set within a predetermined range in consideration of load fluctuations of a rear mounted tire having a relatively small load. Thus, considering the load fluctuations of the front-mounted tire with a relatively large load, (LC2 / LC1) / (LB2 / LB1) is set within a predetermined range, so that the effect of suppressing uneven shoulder wear and the ride comfort can be reduced. The improvement effect can be optimized.

Here, if (LB2 / LB1) / (LA2 / LA1) is less than 1.02, the effect of improving riding comfort is insufficient, and conversely if it is greater than 1.25, the effect of suppressing shoulder uneven wear is ineffective. It will be enough. Similarly, if (LC2 / LC1) / (LB2 / LB1) is smaller than 1.00, the effect of improving riding comfort is insufficient, and conversely if it is larger than 1.20, the effect of suppressing shoulder uneven wear is ineffective. It will be enough. In particular, it is desirable to satisfy the relationship of 1.03 ≦ (LB2 / LB1) / (LA2 / LA1) ≦ 1.15, 1.02 ≦ (LC2 / LC1) / (LB2 / LB1) ≦ 1.10.

In the pneumatic tire, the maximum contact length LB1 and the external contact length LB2 may satisfy the relationship of 0.65 ≦ LB2 / LB1 ≦ 0.95. By controlling the ground contact shape under the condition where a load of 75% of the maximum load capacity is applied, it is possible to exhibit a good riding comfort during steady running. In particular, in the range of 0.70 ≦ LB2 / LB1 ≦ 0.88, the envelope characteristics of the tread portion 1 are improved and the riding comfort is effectively improved.

In the pneumatic tire, the maximum contact lengths LA1, LB1, and LC1 and the external contact lengths LA2, LB2, and LC2 have a relationship of (LC2 / LC1) / (LB2 / LB1) ≦ (LB2 / LB1) / (LA2 / LA1). It is good to be satisfied. Thus, riding comfort can be improved by optimizing the contact shape of the rear and front tires.

As described above, in the tread portion 1, the central main groove 11 extending in the tire circumferential direction, the outer main groove 12 extending in the tire circumferential direction at a position outside the central main groove 11 in the tire width direction, and the outer main groove 12. In a pneumatic tire having a tread pattern in which a plurality of outer lateral grooves 41 extending in the tire width direction are formed at positions outside the tire width direction, the rigidity in the outer region Xs of the tread portion 1 is secured, and the tread portion In order to suppress the shoulder uneven wear of FIG. 1, structures as shown in FIGS. 6 to 8 can be employed.

That is, as shown in FIG. 7, the inclination angle θsl formed by the side wall of the outer lateral groove 41 (particularly, the outer lug groove 41A) with respect to the normal line of the tread surface preferably satisfies the relationship 0 ° ≦ θsl ≦ 10 °. By setting the inclination angle θsl of the outer lateral groove 41 in the above range, the rigidity in the outer region Xs of the tread portion 1 can be ensured. Here, if θsl is smaller than 0 ° and the side wall has an overhang shape, the rigidity in the outer region Xs is lowered. Conversely, if it is larger than 10 °, the drainage is adversely affected. In particular, it is desirable to satisfy the relationship of 1 ° ≦ θsl ≦ 8 °.

As shown in FIG. 6, the groove depth Dsl of the outer lateral groove 41 may satisfy the relationship of 0.20 ≦ Dsl / GDs ≦ 0.90 with respect to the groove depth GDs of the outer main groove 12. Thereby, the rigidity in the outer side area | region Xs of the tread part 1 is securable. Here, if Dsl / GDs is smaller than 0.20, the drainage is adversely affected. Conversely, if Dsl / GDs is larger than 0.90, the rigidity in the outer region Xs decreases.

The outer lateral groove 41 (particularly, the outer lug groove 41A) has a bottom raised portion 42 in a part of its longitudinal direction, and the groove depth Db at the bottom raised portion 42 is 0. 0 relative to the groove depth Dsl of the outer lateral groove 41. The relationship of 30 ≦ Db / Dsl ≦ 0.90 should be satisfied. Here, the bottom raised portion 42 is disposed at a position that opens adjacent to the outer main groove 12. By providing such a raised portion 42, the rigidity in the outer region Xs of the tread portion 1 can be ensured. Here, if Db / Dsl is larger than 0.90, the influence on the rigidity is reduced, and conversely if it is smaller than 0.30, the drainage is adversely affected.

The groove depth GDs of the outer main groove 12 may satisfy the relationship of 0.80 ≦ GDs / GDc ≦ 1.00 with respect to the groove depth GDc of the central main groove 11. Thereby, the rigidity in the outer side area | region Xs of the tread part 1 is securable. Here, if GDs / GDc is smaller than 0.80, the drainage is adversely affected. Conversely, if GDs / GDc is larger than 1.00, it is difficult to ensure the rigidity in the outer region Xs of the tread portion 1. .

When a plurality of central lateral grooves 31 extending in the tire width direction are formed in the tread portion 1 at positions inside the outer main grooves 12 in the tire width direction, the groove depth Dsl of the outer lateral grooves 41 is the groove depth of the central lateral grooves 31. It is preferable that the relationship of 0.50 ≦ Dsl / Dcl ≦ 1.00 is satisfied with respect to Dcl (see FIGS. 7 and 8). Thereby, the rigidity in the outer side area | region Xs of the tread part 1 is securable. Here, if Dsl / Dcl is smaller than 0.50, the drainage is adversely affected. Conversely, if Dsl / Dcl is larger than 1.00, it is difficult to ensure rigidity in the outer region Xs of the tread portion 1. .

FIG. 9 shows a tread pattern of a pneumatic tire according to another embodiment of the present invention. 9, the same components as those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted. In FIG. 9, all of the outer lateral grooves 41 formed on the outer side in the tire width direction with respect to the outer main groove 12 are constituted by outer sipe 41B having a groove width of 1.0 mm or less. Thus, by making all of the outer lateral grooves 41 outer sipe 41B having a groove width of 1.0 mm or less, rigidity in the outer region Xs of the tread portion 1 can be ensured, and shoulder uneven wear can be suppressed. In FIG. 9, all of the central lateral grooves 31 formed on the inner side in the tire width direction from the outer main groove 12 are constituted by a central sipe 31B having a groove width of 1.0 mm or less.

The outer sipe 41B may have a constant groove width from the tread surface to the groove bottom as shown in FIG. 10, or, as shown in FIG. 11, a chamfered portion 43 at the opening to the tread surface. You may have. A similar structure can be adopted for the central sipe 31B.

In the pneumatic tire described above, when the tread portion 1 includes a plurality of belt cords C that are inclined with respect to the tire circumferential direction, and a plurality of belt layers 7 in which the belt cords C cross each other are embedded, As shown in FIG. 12, the inclination angle α of the belt cord C with respect to the tire circumferential direction at the tire center position CL preferably satisfies the relationship of 21 ° ≦ α ≦ 30 °. By not extremely reducing the inclination angle α of the belt cord C at the tire center position CL, the increase in rigidity of the belt layer 7 can be suppressed and the riding comfort can be improved. Here, when the inclination angle α is smaller than 21 °, the effect of improving the riding comfort is lowered due to the increase in rigidity of the belt layer 7. On the other hand, when the inclination angle α is larger than 30 °, the tire characteristics such as steering stability are deteriorated. Not right.

The inclination angle α of the belt cord C with respect to the tire circumferential direction at the tire center position CL and the inclination angle β of the belt cord C with respect to the tire circumferential direction at the belt end position BE have a relationship of 18 ° ≦ β <α ≦ 30 °. It is good to be satisfied. By reducing the inclination angle β of the belt cord C at the belt end position BE, shoulder uneven wear can be effectively suppressed, and the inclination angle α of the belt cord C at the tire center position CL can be reduced. By not extremely reducing the angle, an increase in rigidity of the belt layer 7 in the central region Xc of the tread portion 1 can be suppressed and good riding comfort can be maintained. In particular, the difference between the inclination angle α and the inclination angle β is preferably 3 ° or more. A structure in which the inclination angle β of the belt cord C with respect to the tire circumferential direction at the belt end position BE is smaller than the inclination angle α of the belt cord C with respect to the tire circumferential direction at the tire center position CL is preferable. The belt cord C may be inclined at a constant angle with respect to the tire circumferential direction over the entire width, and the inclination angles α and β may be set to the same value, or α <β.

As shown in FIG. 12, the belt layer 7 has a high angle region Ac on the center side in which the inclination angle of the belt cord C is in the range of α ± 1 ° and a shoulder in which the inclination angle of the belt cord C is in the range of β ± 1 °. The low-angle region As on the side, the width Lc of the high-angle region Ac is ½ or more of the total width L of the belt layer 7, and the width Ls of each low-angle region As is 1 of the total width L of the belt layer 7. It is good that it is / 8 or more. Thus, by setting the high-angle area Ac on the center side and the low-angle area As on the shoulder side of the belt layer 7 as described above, the rigidity distribution of the tread portion 1 can be optimized. Here, when the width Lc of the high angle region Ac is smaller than ½ of the entire width L of the belt layer 7, the function as the belt layer 7 is deteriorated, and the width Ls of the low angle region As is the entire width of the belt layer 7. If it is smaller than 1/8 of L, the rigidity in the tire circumferential direction in the outer region Xs of the tread portion 1 cannot be sufficiently increased. The width Lc of the high angle area Ac and the width Ls of the low angle area As are set based on the total width L of each belt layer 7.

The pneumatic tire described above is suitable as a tire for passenger cars having a flatness ratio of 0.65 or less. In a tire for a passenger car that is required to improve riding comfort, it is possible to achieve both uneven wear resistance and riding comfort.

In the embodiment described above, a tread pattern including four main grooves in the tread portion has been described. However, the present invention includes a tread pattern including three main grooves in the tread portion, and a V-shaped main groove in the tread portion. It is applicable also to the tread pattern which contains.

With a tire size of 205 / 55R16 91V, a carcass layer is mounted between a pair of bead portions, two belt layers are embedded on the outer side in the tire radial direction of the carcass layer in the tread portion, and extend in the tire circumferential direction on the tread portion. A pair of central main grooves, a pair of outer main grooves extending in the tire circumferential direction at a position on the outer side in the tire width direction from the central main grooves, and extending in the tire width direction at a position on the inner side in the tire width direction from the outer main grooves. In a pneumatic tire in which a plurality of central lateral grooves and a plurality of outer lateral grooves extending in the tire width direction at positions outside the outer main grooves in the tire width direction are formed, the tire circumference at the tire cord center position of the belt cord The inclination angle α with respect to the direction, the inclination angle β with respect to the tire circumferential direction at the belt end position of the belt cord, the inclination angle θsl of the side wall of the outer lateral groove, the groove depth GDs of the outer main groove, outside Groove depth Dsl, ratio Dsl / GDs, groove depth Db, ratio Db / Dsl, groove depth GDc of central main groove, ratio GDs / GDc, groove depth Dcl of center lateral groove , Ratio Dsl / Dcl, groove width of outer lateral groove, ratio Sc / Ss of groove area Sc of central region and groove region Ss of outer region, (LB2 / LB1) / (LA2 / LA1), (LC2 / LC1) / ( Tires of Comparative Examples 1 to 3 and Examples 1 to 9 having LB2 / LB1) and LB2 / LB1 (rectangular ratio) set as shown in Table 1 were manufactured.

偏 These test tires were evaluated for uneven wear resistance (shoulder region), riding comfort, and wet performance by the following test methods, and the results are also shown in Table 1.

Uneven wear resistance (shoulder area):
Each test tire is mounted on a wheel with a rim size of 16 × 6.5J and mounted on a friction energy measurement tester, and the average friction energy in the shoulder region of the tread is measured under the conditions of air pressure of 230 kPa and load load of 4.5 kN. did. The measured values are obtained by measuring the frictional energy at a total of four points of 2 locations in the tire width direction × 2 locations in the tire circumferential direction, which are 10 mm intervals in each region, and averaging them. The evaluation results are shown as an index with the comparative example 2 being 100, using the reciprocal of the measured value. The larger the index value, the better the uneven wear resistance.

Ride comfort:
Each test tire is mounted on a wheel with a rim size of 16x6.5J and mounted on a front-wheel drive vehicle with a displacement of 2 liters, filled with the specified air pressure of the vehicle, and a panel at a test course with protrusions on the road surface. A sensory evaluation on riding comfort (mild feeling) was performed in consideration of the input of protrusions. The evaluation results are shown as an index with Comparative Example 1 as 100. A larger index value means better riding comfort.

Wet performance:
Each test tire is mounted on a wheel with a rim size of 16 x 6.5J and mounted on a front-wheel drive vehicle with a displacement of 2 liters. The specified air pressure of the vehicle is filled, and a running test is conducted by a panel on a watered test course. The sensory evaluation on the handling stability on the wet road surface was conducted. The evaluation results are shown as an index with Comparative Example 1 as 100. A larger index value means better wet performance.

As can be seen from Table 1, in comparison with Comparative Example 1, the tires of Examples 1 to 9 were excellent in uneven wear resistance, riding comfort, and wet performance. On the other hand, the tires of Comparative Examples 2 and 3 were not always sufficient in improving these performances.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 8 Belt reinforcement layer 11 Central main groove 12 Outer main groove 31 Central lateral groove 31A Central lug groove 31B Central sipe 41 Outer lateral groove 41A Outer lug groove 41B outer sipe

Claims

An annular tread portion extending in the tire circumferential direction, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the inner side in the tire radial direction of the sidewall portions. In the provided pneumatic tire,
Maximum contact length in the tire circumferential direction when the pneumatic tire is filled with air pressure of 230 kPa and contacted with a load of 40%, 75%, and 100% of the maximum load capacity determined by the standard, respectively. Are LA1, LB1, and LC1, respectively, and the maximum ground contact widths in the tire width direction are WA1, WB1, and WC1, respectively, at positions 40% of the maximum ground contact widths WA1, WB1, and WC1 from the tire center position toward the outside in the tire width direction. When the external contact lengths in the tire circumferential direction are LA2, LB2, and LC2, respectively, the maximum contact lengths LA1, LB1, and LC1 and the external contact lengths LA2, LB2, and LC2 are 1.02 ≦ (LB2 / LB1) / (LA2 /LA1)≦1.25, 1.00 ≦ (LC2 / LC1) / (LB2 / LB1) ≦ 1.20,
When the tread portion is divided into a central region having a width corresponding to 53% of the maximum ground contact width WB1 centered on the tire equator and an outer region in the maximum ground contact width WB1 outside the center region in the tire width direction. The pneumatic tire is characterized in that the groove area Sc of the central region and the groove area Ss of the outer region satisfy a relationship of 1.01 ≦ Sc / Ss ≦ 1.50.
The pneumatic tire according to claim 1, wherein the maximum contact length LB1 and the external contact length LB2 satisfy a relationship of 0.65 ≦ LB2 / LB1 ≦ 0.95.
The maximum ground contact lengths LA1, LB1, and LC1 and the external ground contact lengths LA2, LB2, and LC2 satisfy the relationship of (LC2 / LC1) / (LB2 / LB1) ≦ (LB2 / LB1) / (LA2 / LA1). The pneumatic tire according to claim 1 or 2, characterized by the above.
A central main groove extending in the tire circumferential direction in the tread portion, an outer main groove extending in the tire circumferential direction at a position on the outer side in the tire width direction from the central main groove, and a position on the outer side in the tire width direction from the outer main groove. The pneumatic tire according to any one of claims 1 to 3, wherein a plurality of outer lateral grooves extending in the tire width direction are formed.
The pneumatic tire according to claim 4, wherein an inclination angle θsl formed by a side wall of the outer lateral groove with respect to a normal line of the tread surface satisfies a relationship of 0 ° ≦ θsl ≦ 10 °.
The groove depth Dsl of the outer lateral groove satisfies a relationship of 0.20 ≦ Dsl / GDs ≦ 0.90 with respect to the groove depth GDs of the outer main groove. Pneumatic tire.
The outer lateral groove has a bottom raised portion in a part of its longitudinal direction, and the groove depth Db at the bottom raised portion is 0.30 ≦ Db / Dsl ≦ 0.90 with respect to the groove depth Dsl of the outer lateral groove. The pneumatic tire according to any one of claims 4 to 6, wherein the relationship is satisfied.
The groove depth GDs of the outer main groove satisfies a relationship of 0.80 ≦ GDs / GDc ≦ 1.00 with respect to the groove depth GDc of the central main groove. The pneumatic tire according to Crab.
A plurality of central lateral grooves extending in the tire width direction are formed in the tread portion at a position on the inner side in the tire width direction from the outer main groove, and the groove depth Dsl of the outer lateral groove is set to the groove depth Dcl of the central lateral groove. 9. The pneumatic tire according to claim 4, wherein a relationship of 0.50 ≦ Dsl / Dcl ≦ 1.00 is satisfied.
The pneumatic tire according to any one of claims 4 to 9, wherein all of the outer lateral grooves formed outside the outer main groove in the tire width direction have a groove width of 1.0 mm or less.
The tread portion includes a plurality of belt cords that are inclined with respect to the tire circumferential direction, and a plurality of belt layers in which the belt cords intersect with each other are embedded, and the tire circumferential direction at the tire center position of the belt cord The pneumatic tire according to any one of claims 1 to 10, wherein an inclination angle α with respect to the angle satisfies a relationship of 21 ° ≦ α ≦ 30 °.
The inclination angle α of the belt cord with respect to the tire circumferential direction at the tire center position and the inclination angle β of the belt cord with respect to the tire circumferential direction at the belt end position satisfy a relationship of 18 ° ≦ β <α ≦ 30 °. The pneumatic tire according to claim 11.
The pneumatic tire according to any one of claims 1 to 12, wherein the pneumatic tire is a passenger tire having a flatness ratio of 0.65 or less.