JP2018127018A

JP2018127018A - Pneumatic tire

Info

Publication number: JP2018127018A
Application number: JP2017019451A
Authority: JP
Inventors: 晴隆井上; Harutaka Inoue
Original assignee: Yokohama Rubber Co Ltd
Current assignee: Yokohama Rubber Co Ltd
Priority date: 2017-02-06
Filing date: 2017-02-06
Publication date: 2018-08-16
Anticipated expiration: 2037-02-06
Also published as: JP6838412B2

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire which can excellently maintain tire performance represented by steering stability and wear resistance even when the groove area of a tread part is increased considering snow performance when a tire chain is installed.SOLUTION: The pneumatic tire has a tread part 1 comprising a main groove 11 extending in a tire circumferential direction, a circumferential direction narrow groove 21 extending in the tire circumferential direction outside a tire width direction further than the main groove 11, and a plurality of lug grooves 22 extending outwards in the tire width direction from the circumferential direction narrow groove 21. A T-shaped, bottom-raised part 25 is formed at a location where the circumferential direction narrow groove 21 and the lug groove 22 are connected. The bottom-raised part 25 has a circumferential direction extending part 25A that is wider than the groove width of the lug groove 22 within circumferential direction narrow groove 21, and also has a width direction extending part 25B connecting to the circumferential direction extending part 25A within the lug groove 22.SELECTED DRAWING: Figure 2

Description

本発明は、サマータイヤ又はオールシーズンタイヤとして好適な空気入りタイヤに関し、更に詳しくは、チェーン装着時のスノー性能を考慮してトレッド部の溝面積を増加させた場合であっても、操縦安定性や耐摩耗性に代表されるタイヤ性能を良好に維持することを可能にした空気入りタイヤに関する。 The present invention relates to a pneumatic tire suitable as a summer tire or an all-season tire. More specifically, even when the groove area of the tread portion is increased in consideration of snow performance when the chain is mounted, the steering stability is improved. Further, the present invention relates to a pneumatic tire that can maintain good tire performance represented by wear resistance.

空気入りタイヤは、トレッド部にタイヤ周方向に延びる複数本の主溝とタイヤ幅方向に延びる複数本のラグ溝を備えており、そのトレッドパターンに基づいて所望のタイヤ性能を適切に発揮するように構成されている。特に、サマータイヤやオールシーズンタイヤにおいては、操縦安定性や耐摩耗性を十分に確保することが求められている。 The pneumatic tire is provided with a plurality of main grooves extending in the tire circumferential direction and a plurality of lug grooves extending in the tire width direction in the tread portion so that desired tire performance is appropriately exhibited based on the tread pattern. It is configured. In particular, for summer tires and all-season tires, it is required to ensure sufficient steering stability and wear resistance.

このようなサマータイヤやオールシーズンタイヤにおいて、チェーン装着時のスノー性能を考慮してトレッド部の溝面積を増加させる場合がある。例えば、トレッド部における主溝よりもタイヤ幅方向外側のショルダー領域にタイヤ周方向に延びる周方向細溝を追加し、その周方向細溝に対してラグ溝を連通させた構造が提案されている。このようなトレッドパターンでは、ショルダー領域の溝面積とエッジ成分が多くなるためチェーン装着時のスノー性能を高めることができる。 In such summer tires and all-season tires, the groove area of the tread portion may be increased in consideration of snow performance when the chain is attached. For example, a structure has been proposed in which a circumferential narrow groove extending in the tire circumferential direction is added to a shoulder region on the outer side in the tire width direction from the main groove in the tread portion, and a lug groove is communicated with the circumferential narrow groove. . In such a tread pattern, since the groove area and the edge component of the shoulder region are increased, the snow performance when the chain is attached can be improved.

しかしながら、上述のようにチェーン装着時のスノー性能を考慮してトレッド部の溝面積を増加させた場合、トレッド部に区画された陸部の剛性が低下するため、操縦安定性や耐摩耗性が悪化することになる。これに対して、ラグ溝の長手方向の一部に底上げ部を設けることにより陸部の剛性を確保することが提案されているが（例えば、特許文献１〜３参照）、その補強効果は必ずしも十分ではない。 However, when the groove area of the tread part is increased in consideration of the snow performance when the chain is mounted as described above, the rigidity of the land part divided into the tread part is lowered, so that steering stability and wear resistance are reduced. It will get worse. On the other hand, it has been proposed to secure the rigidity of the land portion by providing a bottom raised portion in a part in the longitudinal direction of the lug groove (see, for example, Patent Documents 1 to 3), but the reinforcing effect is not necessarily limited. Not enough.

特許第４６６５６２６号公報Japanese Patent No. 4665626 特開２０１６−３７２７７号公報JP 2016-37277 A 特開２０１６−５５８１６号公報JP-A-2006-55816

本発明の目的は、チェーン装着時のスノー性能を考慮してトレッド部の溝面積を増加させた場合であっても、操縦安定性や耐摩耗性に代表されるタイヤ性能を良好に維持することを可能にした空気入りタイヤを提供することにある。 An object of the present invention is to maintain good tire performance represented by steering stability and wear resistance even when the groove area of the tread portion is increased in consideration of snow performance when the chain is mounted. It is to provide a pneumatic tire that enables the above.

上記目的を達成するための本発明の空気入りタイヤは、トレッド部に、タイヤ周方向に延びる主溝と、該主溝よりもタイヤ幅方向外側でタイヤ周方向に延びる周方向細溝と、該周方向細溝からタイヤ幅方向外側に向かって延びる複数本のラグ溝とを備えた空気入りタイヤにおいて、
前記周方向細溝と前記ラグ溝とが連結された部位にＴ字状の底上げ部が形成されており、該底上げ部は前記周方向細溝内に前記ラグ溝の溝幅よりも広い周方向延長部分を有すると共に前記ラグ溝内に前記周方向延長部分に連なる幅方向延長部分を有することを特徴とするものである。 In order to achieve the above object, a pneumatic tire according to the present invention includes, in a tread portion, a main groove extending in the tire circumferential direction, a circumferential narrow groove extending in the tire circumferential direction on the outer side in the tire width direction than the main groove, In a pneumatic tire provided with a plurality of lug grooves extending from the circumferential narrow groove toward the outer side in the tire width direction,
A T-shaped bottom raising portion is formed at a portion where the circumferential narrow groove and the lug groove are connected, and the bottom raising portion has a circumferential direction wider than the groove width of the lug groove in the circumferential narrow groove. It has an extension part and has a width direction extension part connected to the circumferential direction extension part in the lug groove.

本発明では、トレッド部における主溝よりもタイヤ幅方向外側の領域にタイヤ周方向に延びる周方向細溝を追加し、その周方向細溝に対してラグ溝を連通させた構造を採用することにより、当該領域の溝面積とエッジ成分を確保し、チェーン装着時のスノー性能を高めることが可能になる。その一方で、周方向細溝とラグ溝とが連結された部位にはＴ字状の底上げ部が形成されており、その底上げ部が周方向細溝内にラグ溝の溝幅よりも広い周方向延長部分を有すると共にラグ溝内に周方向延長部分に連なる幅方向延長部分を有しているので、これら周方向細溝及びラグ溝に隣接する陸部の剛性を十分に確保し、操縦安定性や耐摩耗性に代表されるタイヤ性能を良好に維持することができる。 In the present invention, a structure in which a circumferential narrow groove extending in the tire circumferential direction is added to a region on the outer side in the tire width direction from the main groove in the tread portion, and a structure in which the lug groove communicates with the circumferential narrow groove is adopted. As a result, it is possible to secure the groove area and the edge component of the region and improve the snow performance when the chain is mounted. On the other hand, a T-shaped bottom raised portion is formed at a portion where the circumferential narrow groove and the lug groove are connected, and the bottom raised portion has a circumferential width wider than the width of the lug groove in the circumferential narrow groove. Since it has a direction extension part and a width direction extension part connected to the circumferential direction extension part in the lug groove, the rigidity of the land part adjacent to the circumferential direction narrow groove and the lug groove is sufficiently secured, and the steering stability The tire performance represented by the property and the wear resistance can be maintained well.

本発明において、底上げ部の周方向延長部分のタイヤ周方向の長さａはラグ溝の幅ｂの１１０％〜３００％であり、底上げ部の周方向延長部分の高さｄは周方向細溝の深さｃの２０％〜８０％であることが好ましい。また、底上げ部のタイヤ幅方向の長さｅは周方向細溝の幅ｆの１１０％〜５００％であり、底上げ部の幅方向延長部分の高さｈはラグ溝の深さｇの２０％〜８０％であることが好ましい。このような関係を満足することにより、摩耗時において溝面積が極端に減少することを回避しながら、陸部の剛性を十分に確保し、所望のタイヤ性能を発揮することができる。 In the present invention, the length a in the tire circumferential direction of the circumferentially extended portion of the bottom raised portion is 110% to 300% of the width b of the lug groove, and the height d of the circumferentially extended portion of the bottom raised portion is the circumferential narrow groove. The depth c is preferably 20% to 80%. The length e in the tire width direction of the bottom raised portion is 110% to 500% of the width f of the circumferential narrow groove, and the height h of the widthwise extension portion of the bottom raised portion is 20% of the depth g of the lug groove. It is preferable that it is -80%. By satisfying such a relationship, it is possible to sufficiently ensure the rigidity of the land portion and to exhibit desired tire performance while avoiding an extremely reduced groove area during wear.

本発明において、主溝とは、溝幅が３．０ｍｍ〜２５．０ｍｍの範囲にあり、溝深さが４．０ｍｍ〜２０．０ｍｍの範囲にあり、ウエアインジケータ−を有する溝である。また、周方向細溝とは、溝幅が０．５ｍｍ〜２．９ｍｍの範囲にあり、溝深さが１．０ｍｍ〜１５．０ｍｍの範囲にある。 In the present invention, the main groove is a groove having a wear indicator in which the groove width is in the range of 3.0 mm to 25.0 mm, the groove depth is in the range of 4.0 mm to 20.0 mm. The circumferential narrow groove has a groove width in the range of 0.5 mm to 2.9 mm and a groove depth in the range of 1.0 mm to 15.0 mm.

本発明の実施形態からなる空気入りタイヤを示す子午線断面図である。It is meridian sectional drawing which shows the pneumatic tire which consists of embodiment of this invention. 本発明の実施形態からなる空気入りタイヤのトレッドパターンを示す展開図である。It is an expanded view which shows the tread pattern of the pneumatic tire which consists of embodiment of this invention. 本発明の空気入りタイヤのトレッド部に形成された周方向細溝及びラグ溝の輪郭を示す斜視図である。It is a perspective view which shows the outline of the circumferential direction fine groove formed in the tread part of the pneumatic tire of this invention, and a lug groove. 本発明の空気入りタイヤのトレッド部に形成された周方向細溝及びラグ溝の輪郭を示す平面図である。It is a top view which shows the outline of the circumferential direction fine groove formed in the tread part of the pneumatic tire of this invention, and a lug groove. 本発明の空気入りタイヤのトレッド部に形成された周方向細溝及びラグ溝の輪郭をタイヤ幅方向の外側から見た状態を示す側面図である。It is a side view which shows the state which looked at the outline of the circumferential direction fine groove and lug groove formed in the tread part of the pneumatic tire of this invention from the outer side of the tire width direction. 本発明の空気入りタイヤのトレッド部に形成された周方向細溝及びラグ溝の輪郭をタイヤ周方向の一方側から見た状態を示す側面図である。It is a side view which shows the state which looked at the outline of the circumferential direction fine groove and lug groove formed in the tread part of the pneumatic tire of this invention from the one side of the tire circumferential direction.

以下、本発明の構成について添付の図面を参照しながら詳細に説明する。図１〜図２は本発明の実施形態からなる空気入りタイヤを示す、図３〜図６はそのトレッド部に形成された周方向細溝及びラグ溝の輪郭を示すものである。 Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. 1 to 2 show a pneumatic tire according to an embodiment of the present invention, and FIGS. 3 to 6 show outlines of circumferential narrow grooves and lug grooves formed in the tread portion.

図１に示すように、本実施形態の空気入りタイヤは、タイヤ周方向に延在して環状をなすトレッド部１と、該トレッド部１の両側に配置された一対のサイドウォール部２，２と、これらサイドウォール部２のタイヤ径方向内側に配置された一対のビード部３，３とを備えている。 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.

一対のビード部３，３間には２層のカーカス層４が装架されている。このカーカス層４は、タイヤ径方向に延びる複数本の補強コードを含み、各ビード部３に配置されたビードコア５の廻りにタイヤ内側から外側へ折り返されている。カーカス層４の補強コードとしては、ナイロンやポリエステル等の有機繊維コードが好ましく使用される。ビードコア５の外周上には断面三角形状のゴム組成物からなるビードフィラー６が配置されている。 A two-layer carcass layer 4 is mounted between the pair of bead portions 3 and 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded from the inside of the tire to the outside around the bead core 5 disposed in each bead portion 3. As the reinforcing cord of the carcass layer 4, an organic fiber cord such as nylon or polyester is preferably used. 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.

一方、トレッド部１におけるカーカス層４の外周側には複数層のベルト層７が埋設されている。これらベルト層７はタイヤ周方向に対して傾斜する複数本の補強コードを含み、かつ層間で補強コードが互いに交差するように配置されている。ベルト層７において、補強コードのタイヤ周方向に対する傾斜角度は例えば１０°〜４０°の範囲に設定されている。ベルト層７の補強コードとしては、スチールコードが好ましく使用される。ベルト層７の外周側には、高速耐久性の向上を目的として、補強コードをタイヤ周方向に対して例えば５°以下の角度で配列してなる少なくとも１層のベルトカバー層８が配置されている。ベルトカバー層８の補強コードとしては、ナイロンやアラミド等の有機繊維コードが好ましく使用される。 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 reinforcing cords inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords cross each other between the layers. In the belt layer 7, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in a range of, for example, 10 ° to 40 °. A steel cord is preferably used as the reinforcing cord of the belt layer 7. For the purpose of improving high-speed durability, at least one belt cover layer 8 in which reinforcing cords are arranged at an angle of, for example, 5 ° or less with respect to the tire circumferential direction is disposed on the outer peripheral side of the belt layer 7. Yes. As the reinforcing cord of the belt cover layer 8, an organic fiber cord such as nylon or aramid is preferably used.

なお、上述したタイヤ内部構造は空気入りタイヤにおける代表的な例を示すものであるが、これに限定されるものではない。 In addition, although the tire internal structure mentioned above shows the typical example in a pneumatic tire, it is not limited to this.

図２に示すように、トレッド部１には、タイヤ周方向に延びる３本の主溝１１，１２，１３が形成されている。これら主溝１１〜１３によりトレッド部１には４列の陸部２０，３０，４０，５０が区分されている。トレッド部１において、陸部２０は一方のショルダー領域に位置し、陸部３０，４０はセンター領域に位置し、陸部５０は他方のショルダー領域に位置している。 As shown in FIG. 2, the tread portion 1 is formed with three main grooves 11, 12, 13 extending in the tire circumferential direction. The main grooves 11 to 13 divide the tread portion 1 into four rows of land portions 20, 30, 40, and 50. In the tread portion 1, the land portion 20 is located in one shoulder region, the land portions 30 and 40 are located in the center region, and the land portion 50 is located in the other shoulder region.

一方のショルダー領域に位置する陸部２０には、タイヤ周方向に延びる周方向細溝２１と、該周方向細溝２１からタイヤ幅方向外側に向かって延びる複数本のラグ溝２２とが形成されている。また、陸部２０における周方向細溝２１よりもタイヤ幅方向外側の部位にはタイヤ幅方向に延びる複数本のサイプ２３が形成されており、これらサイプ２３とラグ溝２２とがタイヤ周方向に沿って交互に配置されている。更に、陸部２０において周方向細溝２１と主溝１１とで挟まれた部位には、一端が主溝１１に連通し、他端が閉止した複数本の補助溝２４が形成されている。 The land portion 20 located in one shoulder region is formed with a circumferential narrow groove 21 extending in the tire circumferential direction and a plurality of lug grooves 22 extending outward from the circumferential narrow groove 21 in the tire width direction. ing. Further, a plurality of sipes 23 extending in the tire width direction are formed on the land portion 20 on the outer side in the tire width direction than the circumferential narrow grooves 21, and the sipes 23 and the lug grooves 22 are arranged in the tire circumferential direction. Alternatingly arranged along. Furthermore, a plurality of auxiliary grooves 24 whose one end communicates with the main groove 11 and whose other end is closed are formed in a portion of the land portion 20 sandwiched between the circumferential narrow groove 21 and the main groove 11.

センター領域に位置する一方の陸部３０には、タイヤ周方向に延びる周方向細溝３１と、一端が主溝１１又は１２に連通し、他端が閉止した複数本の補助溝３４が形成されている。また、センター領域に位置する他方の陸部４０には、屈曲しながら陸部４０を横断する複数本の補助溝４４が形成されている。 One land portion 30 located in the center region is formed with a circumferential narrow groove 31 extending in the tire circumferential direction and a plurality of auxiliary grooves 34 with one end communicating with the main groove 11 or 12 and the other end closed. ing. The other land portion 40 located in the center region is formed with a plurality of auxiliary grooves 44 that cross the land portion 40 while being bent.

他方のショルダー領域に位置する陸部５０には、主溝１３に対して非連通であってタイヤ幅方向に延びる複数本のラグ溝５２が形成されている。また、陸部５０にはタイヤ幅方向に延びる複数本のサイプ５３が形成されており、これらサイプ５３とラグ溝５２とがタイヤ周方向に沿って交互に配置されている。更に、陸部５０には、一端が主溝１３に連通し、他端が閉止した複数本の補助溝５４が形成されている。 The land portion 50 located in the other shoulder region is formed with a plurality of lug grooves 52 that are not in communication with the main groove 13 and extend in the tire width direction. A plurality of sipes 53 extending in the tire width direction are formed on the land portion 50, and the sipes 53 and the lug grooves 52 are alternately arranged along the tire circumferential direction. Further, the land portion 50 is formed with a plurality of auxiliary grooves 54 having one end communicating with the main groove 13 and the other end closed.

上述のように、トレッド部１に、タイヤ周方向に延びる主溝１１と、該主溝１１よりもタイヤ幅方向外側でタイヤ周方向に延びる周方向細溝２１と、該周方向細溝２１からタイヤ幅方向外側に向かって延びる複数本のラグ溝２２とを備えた空気入りタイヤにおいて、周方向細溝２１とラグ溝２３とが連結された部位にはＴ字状の底上げ部２５が形成されている。図３〜図６に示すように、底上げ部２５は、周方向細溝２１内にラグ溝２２の溝幅よりも広い周方向延長部分２５Ａを有すると共に、ラグ溝２２内に周方向延長部分２５Ａに連なる幅方向延長部分２５Ｂを有している。 As described above, the tread portion 1 includes a main groove 11 extending in the tire circumferential direction, a circumferential narrow groove 21 extending in the tire circumferential direction outside the main groove 11 in the tire width direction, and the circumferential narrow groove 21. In a pneumatic tire provided with a plurality of lug grooves 22 extending outward in the tire width direction, a T-shaped bottom raised portion 25 is formed at a portion where the circumferential narrow grooves 21 and the lug grooves 23 are connected. ing. As shown in FIGS. 3 to 6, the bottom raised portion 25 has a circumferentially extending portion 25 </ b> A wider than the groove width of the lug groove 22 in the circumferential narrow groove 21, and a circumferentially extending portion 25 </ b> A in the lug groove 22. It has the width direction extension part 25B which continues to.

このようにトレッド部１における主溝１１よりもタイヤ幅方向外側のショルダー領域にタイヤ周方向に延びる周方向細溝２１を設け、その周方向細溝２１に対して複数本のラグ溝２２を連通させた構造を採用することにより、トレッド部１のショルダー領域の溝面積とエッジ成分を確保し、チェーン装着時のスノー性能を高めることができる。その一方で、周方向細溝２１とラグ溝２２とが連結された部位にはＴ字状の底上げ部２５が形成されており、その底上げ部２５が周方向細溝２１内にラグ溝２２の溝幅よりも広い周方向延長部分２５Ａを有すると共にラグ溝２２内に周方向延長部分２５Ａに連なる幅方向延長部分２５Ｂを有しているので、これら周方向細溝２１及びラグ溝２２に隣接する陸部２０の剛性を十分に確保することができる。つまり、周方向細溝２１とラグ溝２２とが連結された部位に配置されたＴ字状の底上げ部２５が周方向細溝２１の幅方向の変形とラグ溝２２の幅方向の変形を一体的に抑制することにより、陸部２０の剛性を効果的に増大させることができる。これにより、操縦安定性や耐摩耗性に代表されるタイヤ性能を良好に維持することができる。 Thus, the circumferential narrow groove 21 extending in the tire circumferential direction is provided in the shoulder region on the outer side in the tire width direction than the main groove 11 in the tread portion 1, and the plurality of lug grooves 22 are communicated with the circumferential narrow groove 21. By adopting such a structure, the groove area and the edge component of the shoulder region of the tread portion 1 can be secured, and the snow performance when the chain is attached can be enhanced. On the other hand, a T-shaped bottom raising portion 25 is formed at a portion where the circumferential narrow groove 21 and the lug groove 22 are connected, and the bottom raising portion 25 is formed in the circumferential narrow groove 21 with the lug groove 22. Since it has a circumferentially extending portion 25A wider than the groove width and a widthwise extending portion 25B connected to the circumferentially extending portion 25A in the lug groove 22, it is adjacent to the circumferential narrow groove 21 and the lug groove 22. Sufficient rigidity of the land portion 20 can be ensured. In other words, the T-shaped bottom raised portion 25 disposed at the portion where the circumferential narrow groove 21 and the lug groove 22 are connected integrally deforms the circumferential narrow groove 21 in the width direction and the lug groove 22 in the width direction. By suppressing it effectively, the rigidity of the land portion 20 can be effectively increased. Thereby, the tire performance represented by steering stability and abrasion resistance can be maintained favorably.

上記空気入りタイヤにおいて、底上げ部２５の周方向延長部分２５Ａのタイヤ周方向の長さａはラグ溝２２の幅ｂの１１０％〜３００％であり、底上げ部２５の周方向延長部分２５Ａの高さｄは周方向細溝２１の深さｃの２０％〜８０％であると良い。このような関係を満足することにより、摩耗時において溝面積が極端に減少することを回避しながら、陸部２０の剛性を十分に確保し、所望のタイヤ性能を発揮することができる。 In the pneumatic tire, the circumferential length a of the circumferentially extending portion 25A of the bottom raised portion 25 is 110% to 300% of the width b of the lug groove 22, and the height of the circumferentially extended portion 25A of the bottom raised portion 25 is high. The length d is preferably 20% to 80% of the depth c of the circumferential narrow groove 21. By satisfying such a relationship, the rigidity of the land portion 20 can be sufficiently ensured and desired tire performance can be exhibited while avoiding an extremely reduced groove area during wear.

ここで、周方向延長部分２５Ａのタイヤ周方向の長さａがラグ溝２２の幅ｂの１１０％よりも小さいと陸部２０の剛性を増大させる効果が低下し、逆にラグ溝２２の幅ｂの３００％よりも大きいとウエット性能を低下させる要因となる。また、周方向延長部分２５Ａの高さｄが周方向細溝２１の深さｃの２０％よりも小さいと陸部２０の剛性を増大させる効果が低下し、逆に周方向細溝２１の深さｃの８０％よりも大きいとウエット性能を低下させる要因となる。なお、周方向延長部分２５Ａのタイヤ周方向の長さａは周方向延長部分２５Ａの頂面の長さである。 Here, if the length a in the tire circumferential direction of the circumferentially extending portion 25A is smaller than 110% of the width b of the lug groove 22, the effect of increasing the rigidity of the land portion 20 is reduced, and conversely the width of the lug groove 22 If it is larger than 300% of b, it will be a factor of reducing the wet performance. Further, if the height d of the circumferentially extending portion 25A is smaller than 20% of the depth c of the circumferential narrow groove 21, the effect of increasing the rigidity of the land portion 20 is reduced, and conversely the depth of the circumferential narrow groove 21 is reduced. If it is larger than 80% of the thickness c, it will cause a decrease in wet performance. The length a in the tire circumferential direction of the circumferentially extending portion 25A is the length of the top surface of the circumferentially extending portion 25A.

また、上記空気入りタイヤにおいて、底上げ部２５のタイヤ幅方向の長さｅは周方向細溝２１の幅ｆの１１０％〜５００％であり、底上げ部２５の幅方向延長部分２５Ｂの高さｈはラグ溝２２の深さｇの２０％〜８０％であると良い。このような関係を満足することにより、摩耗時において溝面積が極端に減少することを回避しながら、陸部２０の剛性を十分に確保し、所望のタイヤ性能を発揮することができる。 In the pneumatic tire, the length e of the bottom raised portion 25 in the tire width direction is 110% to 500% of the width f of the circumferential narrow groove 21, and the height h of the widthwise extended portion 25 </ b> B of the bottom raised portion 25. Is preferably 20% to 80% of the depth g of the lug groove 22. By satisfying such a relationship, the rigidity of the land portion 20 can be sufficiently ensured and desired tire performance can be exhibited while avoiding an extremely reduced groove area during wear.

ここで、底上げ部２５のタイヤ幅方向の長さｅが周方向細溝２１の幅ｆの１１０％よりも小さいと陸部２０の剛性を増大させる効果が低下し、逆に周方向細溝２１の幅ｆの５００％よりも大きいとウエット性能を低下させる要因となる。また、幅方向延長部分２５Ｂの高さｈがラグ溝２２の深さｇの２０％よりも小さいと陸部２０の剛性を増大させる効果が低下し、逆にラグ溝２２の深さｇの８０％よりも大きいとウエット性能を低下させる要因となる。なお、底上げ部２５のタイヤ幅方向の長さｅは底上げ部２５の頂面の長さである。 Here, if the length e of the bottom raised portion 25 in the tire width direction is smaller than 110% of the width f of the circumferential narrow groove 21, the effect of increasing the rigidity of the land portion 20 is reduced, and conversely the circumferential narrow groove 21. If the width is larger than 500% of the width f, the wet performance will be reduced. Further, if the height h of the width direction extension portion 25B is smaller than 20% of the depth g of the lug groove 22, the effect of increasing the rigidity of the land portion 20 is reduced, and conversely, the depth g of the lug groove 22 is 80. If it is larger than%, it will cause a decrease in wet performance. The length e in the tire width direction of the bottom raised portion 25 is the length of the top surface of the bottom raised portion 25.

タイヤサイズ１８５／６５Ｒ１５で、図２に示すトレッドパターンを有する空気入りタイヤにおいて、周方向細溝での底上げ部の有無、ラグ溝での底上げ部の有無、ラグ溝の幅ｂに対する底上げ部の周方向延長部分のタイヤ周方向の長さａの比率（ａ／ｂ×１００％）、周方向細溝の深さｃに対する底上げ部の周方向延長部分の高さｄの比率（ｄ／ｃ×１００％）、周方向細溝の幅ｆに対する底上げ部のタイヤ幅方向の長さｅの比率（ｅ／ｆ×１００％）、ラグ溝の深さｇに対する底上げ部の幅方向延長部分の高さｈの比率（ｈ／ｇ×１００％）を表１のように設定した従来例、比較例１〜２及び実施例１〜６のタイヤを製作した。 In the pneumatic tire having the tread pattern shown in FIG. 2 with a tire size of 185 / 65R15, the presence or absence of a raised portion in the circumferential narrow groove, the presence or absence of the raised portion in the lug groove, the circumference of the raised portion with respect to the width b of the lug groove The ratio of the length a in the tire circumferential direction of the directional extension portion (a / b × 100%), the ratio of the height d of the circumferential extension portion of the bottom raised portion to the depth c of the circumferential narrow groove (d / c × 100) %), The ratio of the length e in the tire width direction of the bottom raised portion to the width f of the circumferential narrow groove (e / f × 100%), the height h of the widthwise extension portion of the bottom raised portion to the depth g of the lug groove Tires of conventional examples, comparative examples 1 and 2 and examples 1 to 6 in which the ratio (h / g × 100%) was set as shown in Table 1 were manufactured.

比較例１のタイヤは、周方向細溝とラグ溝とが連結された部位において周方向細溝内に底上げ部を局所的に設けたものである。比較例２のタイヤは、周方向細溝とラグ溝とが連結された部位においてラグ溝内に底上げ部を局所的に設けたものである。実施例１〜６のタイヤは、周方向細溝とラグ溝とが連結された部位において周方向細溝及びラグ溝に跨るＴ字状の底上げ部を局所的に設けたものである。 In the tire of Comparative Example 1, a bottom raised portion is locally provided in the circumferential narrow groove at a portion where the circumferential narrow groove and the lug groove are connected. In the tire of Comparative Example 2, a bottom raised portion is locally provided in the lug groove at a portion where the circumferential narrow groove and the lug groove are connected. In the tires of Examples 1 to 6, a T-shaped bottom-up portion that spans the circumferential narrow groove and the lug groove is locally provided at a portion where the circumferential narrow groove and the lug groove are connected.

これら試験タイヤについて、下記試験方法により、スノー性能、ウエット路面での制動性能（０％摩耗時、５０％摩耗時）、ドライ路面での操縦安定性、耐摩耗性を評価し、その結果を表１に併せて示した。 For these test tires, the following test methods were used to evaluate snow performance, braking performance on wet road surfaces (at 0% wear and 50% wear), steering stability on dry road surfaces, and wear resistance. Also shown in FIG.

スノー性能：
各試験タイヤをリムサイズ１５×６Ｊのホイールに組み付けて前輪駆動車に装着し、空気圧を２２０ｋＰａ（前輪）／２１０ｋＰａ（後輪）とし、前輪のタイヤにチェーンを装着し、テストドライバーによる雪上での走行試験を実施し、スノー性能について官能評価を行った。評価結果は、従来例を１００とする指数にて示した。この指数値が大きいほどスノー性能が優れていることを意味する。 Snow performance:
Each test tire is assembled to a wheel with a rim size of 15 × 6J and mounted on a front-wheel drive vehicle. The air pressure is 220 kPa (front wheel) / 210 kPa (rear wheel). A test was conducted and a sensory evaluation was performed on snow performance. The evaluation results are shown as an index with the conventional example being 100. A larger index value means better snow performance.

ウエット路面での制動性能：
各試験タイヤをリムサイズ１５×６Ｊのホイールに組み付けて前輪駆動車に装着し、空気圧を２２０ｋＰａ（前輪）／２１０ｋＰａ（後輪）とし、水深１ｍｍのテストコースにおいて１００ｋｍ／ｈの走行状態からブレーキを掛けて制動距離を測定した。評価結果は、測定値の逆数を用い、従来例を１００とする指数にて示した。この指数値が大きいほどウエット路面での制動性能が優れていることを意味する。このような評価はタイヤが０％摩耗状態（新品時）及び５０％摩耗状態であるときにそれぞれ実施した。 Braking performance on wet surfaces:
Each test tire is assembled to a wheel with a rim size of 15 × 6J and mounted on a front-wheel drive vehicle. Braking distance was measured. The evaluation results are shown as an index with the conventional example being 100, using the reciprocal of the measured value. The larger the index value, the better the braking performance on the wet road surface. Such an evaluation was performed when the tire was in a 0% worn state (when new) and a 50% worn state, respectively.

ドライ路面での操縦安定性：
各試験タイヤをリムサイズ１５×６Ｊのホイールに組み付けて前輪駆動車に装着し、空気圧を２２０ｋＰａ（前輪）／２１０ｋＰａ（後輪）とし、テストドライバーによるドライ路面からなるテストコースでの走行試験を実施し、操縦安定性について官能評価を行った。評価結果は、従来例を１００とする指数にて示した。この指数値が大きいほどドライ路面での操縦安定性が優れていることを意味する。 Steering stability on dry roads:
Each test tire is mounted on a wheel with a rim size of 15 × 6J and mounted on a front-wheel drive vehicle. The air pressure is 220 kPa (front wheel) / 210 kPa (rear wheel), and a running test is performed on a test course consisting of a dry road surface by a test driver. The sensory evaluation was conducted on the handling stability. The evaluation results are shown as an index with the conventional example being 100. The larger the index value, the better the steering stability on the dry road surface.

耐摩耗性：
各試験タイヤをリムサイズ１５×６Ｊのホイールに組み付けて前輪駆動車に装着し、空気圧を２２０ｋＰａ（前輪）／２１０ｋＰａ（後輪）とし、テストドライバーによるドライ路面からなるテストコースでの走行試験を実施し、ショルダー陸部の摩耗量と走行距離を測定し、摩耗量１ｍｍ当たりの走行距離を求めた。評価結果は、従来例を１００とする指数にて示した。この指数値が大きいほど耐摩耗性が優れていることを意味する。 Abrasion resistance:
Each test tire is mounted on a wheel with a rim size of 15 × 6J and mounted on a front-wheel drive vehicle. The air pressure is 220 kPa (front wheel) / 210 kPa (rear wheel), and a running test is performed on a test course consisting of a dry road surface by a test driver. The wear amount and travel distance of the shoulder land portion were measured, and the travel distance per 1 mm of wear amount was obtained. The evaluation results are shown as an index with the conventional example being 100. A larger index value means better wear resistance.

この表１から判るように、実施例１〜６のタイヤは、従来例との対比において、チェーン装着時のスノー性能を改善したトレッドパターンを採用するにあたって、操縦安定性や耐摩耗性を改善することができた。これに対して、比較例１のタイヤでは、底上げ部が周方向細溝内だけに配置されているため操縦安定性や耐摩耗性の改善効果が不十分であった。また、比較例２のタイヤでは、底上げ部がラグ溝内だけに配置されているため操縦安定性や耐摩耗性の改善効果が不十分であった。 As can be seen from Table 1, the tires of Examples 1 to 6 improve the handling stability and wear resistance when adopting the tread pattern with improved snow performance when the chain is mounted in comparison with the conventional example. I was able to. On the other hand, in the tire of Comparative Example 1, since the bottom raised portion is disposed only in the circumferential narrow groove, the effect of improving steering stability and wear resistance was insufficient. Moreover, in the tire of Comparative Example 2, since the bottom raised portion is disposed only in the lug groove, the effect of improving steering stability and wear resistance was insufficient.

１トレッド部
２サイドウォール部
３ビード部
１１，１２，１３主溝
２０，３０，４０，５０陸部
２１，３１周方向細溝
２２，５２ラグ溝
２３，５３サイプ
２４，３４，４４，５４補助溝
２５底上げ部
２５Ａ周方向延長部分
２５Ｂ幅方向延長部分 DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 11, 12, 13 Main groove 20, 30, 40, 50 Land part 21, 31 Circumferential thin groove 22, 52 Lug groove 23, 53 Sipe 24, 34, 44, 54 Auxiliary Groove 25 Bottom raising part 25A Circumferentially extending portion 25B Widthwise extending portion

Claims

トレッド部に、タイヤ周方向に延びる主溝と、該主溝よりもタイヤ幅方向外側でタイヤ周方向に延びる周方向細溝と、該周方向細溝からタイヤ幅方向外側に向かって延びる複数本のラグ溝とを備えた空気入りタイヤにおいて、
前記周方向細溝と前記ラグ溝とが連結された部位にＴ字状の底上げ部が形成されており、該底上げ部は前記周方向細溝内に前記ラグ溝の溝幅よりも広い周方向延長部分を有すると共に前記ラグ溝内に前記周方向延長部分に連なる幅方向延長部分を有することを特徴とする空気入りタイヤ。 In the tread portion, a main groove extending in the tire circumferential direction, a circumferential narrow groove extending in the tire circumferential direction outside the main groove in the tire width direction, and a plurality of grooves extending outward from the circumferential narrow groove in the tire width direction In pneumatic tires with lug grooves,
A T-shaped bottom raising portion is formed at a portion where the circumferential narrow groove and the lug groove are connected, and the bottom raising portion has a circumferential direction wider than the groove width of the lug groove in the circumferential narrow groove. A pneumatic tire having an extension portion and a width direction extension portion connected to the circumferential extension portion in the lug groove.

前記底上げ部の周方向延長部分のタイヤ周方向の長さａが前記ラグ溝の幅ｂの１１０％〜３００％であり、前記底上げ部の周方向延長部分の高さｄが前記周方向細溝の深さｃの２０％〜８０％であることを特徴とする請求項１に記載の空気入りタイヤ。 The circumferential length a of the circumferentially extending portion of the bottom raised portion is 110% to 300% of the width b of the lug groove, and the height d of the circumferentially extending portion of the raised bottom portion is the circumferential narrow groove. The pneumatic tire according to claim 1, wherein the tire has a depth c of 20% to 80%.

前記底上げ部のタイヤ幅方向の長さｅが前記周方向細溝の幅ｆの１１０％〜５００％であり、前記底上げ部の幅方向延長部分の高さｈが前記ラグ溝の深さｇの２０％〜８０％であることを特徴とする請求項１又は２に記載の空気入りタイヤ。 The length e of the bottom raised portion in the tire width direction is 110% to 500% of the width f of the circumferential narrow groove, and the height h of the width extended portion of the bottom raised portion is the depth g of the lug groove. The pneumatic tire according to claim 1 or 2, which is 20% to 80%.