JP4063397B2 - Pneumatic radial tire - Google Patents

Description

【００５６】
【表２】

【００５７】
実施例１〜６のタイヤ及び比較例１、２のタイヤを供試タイヤとし、前記リム及び空気圧を用いて下記２項目の試験を下記試験条件の下で実施した。
（１）キャンバースラストＦｃの測定：フラットベルト式室内試験機を用い、ベルト速度を６０km/hとし、このベルトに各供試タイヤをキャンバー角度５°の下で最大負荷能力６５０kgの７０％に相当する荷重４５０kgf で押圧し、キャンバースラストＦｃを測定する。測定結果は比較例１、２をそれぞれのグループで１００とする指数にて表し、値は小なる程良い。
（２）実車による直進走行安定性のテスト：個々の供試タイヤを国産乗用車２５００ｃｃクラスのＦＲ車の全輪に装着し、前席に２名乗車し轍を形成した乾燥アスファルトのテスト路面を１００km/hの速度で走行したときのワンダリング発現度合い、すなわち直進走行安定性をテストドライバのフィーリングにより１０点満点で評価した。評点は大きいほど良い。
以上の２項目のテスト結果をタイヤグループ毎に表１、２の右側に示す。
【００５８】
表１及び表２が示すテスト結果から、まず実施例１〜６のタイヤはいずれも、比較例１、２のタイヤに比しキャンバースラストＦｃ発生量が著しく低減し、実車による乾燥轍路面走行試験における直進走行安定性が格段に優れていることがわかり、また、残存面取り部Ｙのみを有する構成の実施例１及び実施例４の各タイヤでも比較例１、２のタイヤに比しキャンバースラストＦｃ発生量の著しい低減と直進走行安定性の一層の向上とを達成することができることがわかる。
【００５９】
【発明の効果】
この出願の請求項１〜６に記載した発明によれば、轍に代表されるような両側に登り勾配の傾斜面を有する凹部が形成されている路面走行でのワンダリング現象の発生が抑制され、その結果高速での直進走行安定性に優れる、特に偏平率が６０％以下の高性能ラジアルタイヤと呼ばれる空気入りラジアルタイヤを提供することができる。
【図面の簡単な説明】
【図１】この発明の一実施形態例のタイヤの左半断面図である。
【図２】図１に示すタイヤトレッド部の一実施形態例のフットプリントによる接地形状転写図である。
【図３】図１に示すタイヤトレッド部の別の実施形態例のフットプリントによる接地形状転写図である。
【図４】図２に示す接地形状転写図を得るタイヤの同図上のＶ I−Ｖ I線に沿う断面図である。
【図５】図３に示す接地形状転写図を得るタイヤの同図上のＶ−Ｖ線に沿う断面図である。
【図６】図１に示すタイヤの傾斜路面走行時に発生するせん断力及び復元モーメントの説明図である。
【図７】図１に示すタイヤの傾斜路面走行中のせん断力発生状態を示す説明図である。
【図８】傾斜路面を走行するタイヤの正面図又は背面図である。
【図９】図８に示すタイヤの断面図である。
【図１０】図７に示すタイヤをキャンバー角度１０°で平板にを押圧したときのフットプリントの接地部縁取り図である。
【図１１】図７に示すタイヤのフットプリントの接地部縁取り図である。
【符号の説明】
１ 空気入りラジアルタイヤ
２ ビード部
３ サイドウォール部
４ トレッド部
４ｔ 踏面
５ ビードコア
６ カーカス
６−１、６−２ カーカスプライ
７ ベルト
８ トレッドゴム
１０ 直状中央主溝
１１ 直状側方主溝
１２ 傾斜溝
１３ 傾斜枝溝
１４ 子午断面への投影長さを有する溝
１４ｅ 溝縁
１５ サイプ
１８ 分断陸部
１８−１、１８−２、１８−３ 細分陸部
ＣＷ 接地幅
Ｃｅ 接地幅端
Ｄ タイヤ回転方向
Ｒｓ ショルダ領域
Ｙ 残存面取り部
Ｍ 溝１４の切込み方向の溝幅中央を連ねる線
ＶＬ 垂線
α 線Ｍの垂線ＶＬに対する傾斜角度
Ｉ_S 傾斜路面
Ｓ 平板表面
Ｆｃ キャンバースラスト
Ｆｙ 横力
Ｓcr、Ｓｂ せん断力
Ｆxd タイヤ回転方向と反対方向せん断力
Ｍｚ 復元モーメント[0001]
BACKGROUND OF THE INVENTION
    The present invention relates to a pneumatic radial tire, and more particularly to a pneumatic radial tire for use in a vehicle such as a passenger car, a truck, and a bus. In particular, the present invention has an inclined portion, for example, a concave portion such as a saddle, in a direction crossing the traveling direction. Pneumatic radial tires that improve the straight running stability by suppressing the so-called wandering phenomenon, which is a driver's unpredictable tire behavior that occurs when traveling on the road at high speed, and has a particularly small flatness Related to high performance radial tires.
[0002]
[Prior art]
    Pneumatic radial tires, especially high-performance radial tires, have high lateral rigidity to generate lateral force commensurate with the centrifugal force of the vehicle that occurs when the vehicle turns due to the recent increase in output of vehicles. Therefore, the tire must have a tire shape that reduces the flatness ratio and suppresses the height of the sidewalls to make the contact width of the tread as wide as possible. is doing.
[0003]
[Problems to be solved by the invention]
    High-performance radial tires exhibit excellent handling stability when running on flat roads, but when traveling at high speeds on road surfaces with sloping surfaces such as saddle recesses, the tires are subject to the degree of inclination of the recesses on the road surface. As a result of inhomogeneous forces acting, complex behavior is exhibited.
[0004]
    For example, a tire having a small flatness, particularly a radial tire for a passenger car having a flatness of 60% or less, refers to FIG. 8 showing the front or back of the tire 20 traveling on the inclined road surface Is, and the climbing gradient received from the inclined road surface Is. The camber thrust Fc in the direction (indicated by the arrow) generates a lateral force Fy having a component force in the direction of the axis XX of the tire 20, and the lateral force Fy causes the vehicle to apply a force to run up the inclined road surface Is. Therefore, it will impair the straight running stability. In general, when the slope of the inclined road surface Is is the same, the value of the lateral force Fy is larger as the tire has a smaller flatness. Reference symbol Fr is a reaction force to the tire 20 perpendicular to the inclined road surface Is.
[0005]
    The reason why the camber thrust Fc is generated in the tire 20 traveling on the inclined road surface Is is as follows. That is, as shown in FIG. 9 with the tire 20 shown in FIG. 8 as a cross section, the running tire 20 has an upward slope on the inclined road surface Is due to a load W acting in a direction perpendicular to the rotational axis XX. The closer to the side, the stronger it is pressed by the road surface Is, and the lower side of the climb slope, rather than the road surface Is.
[0006]
    As a result, the deflection deformation amount of the sidewall portion 21 of the tire 20 that presses the upward slope upward side of the inclined road surface Is under the vertical load W applied to the tire 20 is the deflection deformation amount of the downward slope sidewall portion 21. The large bending deformation on the upper side of the climbing slope is significantly larger than that of the carcass ply in the direction of the arrow A, and the belt 22 near the carcass ply that is deformed by the deformation is bent in the direction of the arrow B. Since deformation occurs, shear deformation occurs in the tread rubber 23 portion that covers the belt 22 portion that undergoes bending deformation. As a result, the tread rubber 23 of the tire 20 as a whole climbs on the inclined road surface Is, a shearing force in the direction of arrow C is generated, and the resultant force of the shearing force on the entire contact surface is nothing but the camber thrust Fc. .
[0007]
    In other words, as described above, when the tread portion of the running tire 20 gets on the inclined road surface Is, the tire 20 generates a camber thrust Fc in the upward gradient direction of the inclined road surface Is, and the driver is driven by the lateral force Fy component. Regardless of the intention of the vehicle, the vehicle traveling at high speed exhibits a so-called wandering phenomenon in which the vehicle rapidly climbs up the inclined road surface Is, and the straight running stability of the vehicle is significantly impaired.
[0008]
    In order to improve this wandering, it has been proposed to chamfer the edge of the tread part or to apply a large number of sipe (slit) processes, thereby reducing the camber thrust Fc. This is only a countermeasure, and it must be said that a high-performance radial tire with a flatness ratio of 60% or less is inadequate, and a tire capable of exhibiting highly straight running stability suitable for a high-performance radial tire. What is desired is the current situation.
[0009]
    So thisapplicationClaims 1 to 16The pneumatic radial which is excellent in straight running stability at a high speed by suppressing the occurrence of wandering phenomenon on road running in which concave portions having slopes with upward slopes are formed on both sides like a kite. An object is to provide a tire, particularly a high-performance radial tire having a flatness ratio of 60% or less.
[0010]
[Means for Solving the Problems]
    To achieve the above purpose, thisapplicationThe invention described in claim 1 includes a pair of bead portions, a pair of sidewall portions, and a toroid-like tread portion that is continuous with both sidewall portions, and these portions are reinforced across bead cores embedded in the bead portions. In a pneumatic radial tire comprising a radial carcass having one or more plies and a belt for reinforcing a tread portion on an outer periphery of the radial carcass, and having a tread pattern for specifying a rotation direction.
    In the ground contact state of the tread portion in which the tire filled with air pressure corresponding to the maximum load capacity of the tire is pressed perpendicularly to the flat plate under a load load corresponding to 70% of the maximum load capacity,
    At least a partial region including the tread portion end of the tread portion shoulder region separating a distance of 10% or more of the tread portion contact width from the end of the contact width has a projection length onto a plane including the rotation axis of the tire.WhatA plurality of grooves opening at the end of the tread portion, and a land portion divided in the tread circumferential direction by these grooves, and
    At least part of the land, including the tread edge, of each split land only on the side that comes into contact with the ground later under the rolling load of the tire has a remaining chamfer along the groove edge.And
  The remaining chamfered portion is gradually chamfered from the position closest to the tire equator surface toward the end of the tread portion.Pneumatic radial tire characterized byInis there.
[0011]
    Here, the maximum load capacity of the tire is the maximum load of the load capacity (kg) listed in the “pneumatic-load capacity table” for each tire type described in JATMA YEAR BOOK (1998 edition). Air pressure (kPa or kgf / cm) that indicates the capacity (in bold), and the air pressure corresponding to the maximum load capacity is also listed in the “Air Pressure-Load Capacity Table” above.²) Value shall be used. The ground contact width also follows the definition of “ground contact width” described in “2. Definition of terms” in “General information” of JATMA YEAR BOOK (1998 edition). In addition, the rim used to fill the tire with air pressure and apply the load is the same for each tire type and tire size listed in the “Trim Applicable Rim” table described in JATMA YEAR BOOK (1998 edition). Applicable rim. The above description is the same below, and the various items described in JATMA YEAR BOOK (1998 edition) are hereinafter simply abbreviated as JATMA standards.
[0012]
In order to achieve the above object, the invention described in claim 2 of the present application has a pair of bead portions and a pair of sidewall portions, and a toroidal tread portion connected to both sidewall portions. In a pneumatic radial tire comprising a radial carcass having one or more plies reinforced between bead cores each embedded in a bead portion, and a belt for reinforcing a tread portion on an outer periphery of the radial carcass, and having a tread pattern for specifying a rotation direction ,
In the ground contact state of the tread portion in which the tire filled with air pressure corresponding to the maximum load capacity of the tire is pressed perpendicularly to the flat plate under a load load corresponding to 70% of the maximum load capacity,
At least a partial region including the tread portion end of the tread portion shoulder region that separates the distance of 10% or more of the tread portion contact width from the end of the tread portion has a projected length onto a plane including the rotation axis of the tire. And a plurality of grooves that are open to each other, and land portions that are divided in the tread circumferential direction by these grooves, and
At least part of the land portion including the tread portion end of each divided land portion only on the side to be grounded later under the load load rolling of the tire has a remaining chamfered portion along the groove edge,
  A line connecting the center of the groove width in the groove depth direction in a groove cross section by a plane perpendicular to the flat plate surface and including a straight line of the groove width direction of the partial groove or the entire groove including the end of the tread portion of each of the plurality of grooves. Is inclined at an angle of 3 ° or more from the surface of the tread portion toward the bottom of the groove with respect to a perpendicular line with the midpoint of the line segment connecting both ends of the groove edge on the straight line in the groove width direction, and the inclination direction is the tire rotation direction. It is a pneumatic radial tire characterized by being in the opposite direction.
[0013]
    In this case, it is desirable that the upper limit of the inclination angle with respect to the perpendicular to the line segment connecting both ends of the groove edge is 20 ° in terms of maintaining good uneven wear resistance.
  By the way, the above-mentioned straight line in the groove width direction means a normal line or a perpendicular line extending from the center of the groove width in the tread portion grounding surface and an extension line thereof. The same applies hereinafter.
[0014]
    Claim 1And 2As a preferred embodiment of the invention described in claim 1.3As described in the invention described above, the surface of the remaining chamfered portion has at least one of an arc shape and a linear shape in a cross section including a straight line in the groove width direction of the groove and perpendicular to the flat plate surface. To do.
[0015]
    Claims here2 and 3The structure developed from the invention described in claim4As described in the invention described above, the inclination angle of the line connecting the center of the groove width in the groove depth direction in the groove cross section with respect to the perpendicular increases gradually from the position closest to the tire equatorial plane toward the tread portion end. .
[0016]
    In order to achieve the above purpose,applicationClaims5The invention described in 1 includes a pair of bead portions and a pair of sidewall portions, and a toroidal tread portion continuous with both sidewall portions, and each ply is reinforced between bead cores embedded in the bead portions. A pneumatic radial tire including a radial carcass and a belt that reinforces a tread portion on the outer periphery of the radial carcass and having a tread pattern with a rotational direction designation.
    In the ground contact state of the tread portion in which the tire filled with air pressure corresponding to the maximum load capacity of the tire is pressed perpendicularly to the flat plate under a load load corresponding to 70% of the maximum load capacity,
    At least a partial region including the tread portion end of the tread portion shoulder region separating a distance of 10% or more of the tread portion contact width from the end of the contact width has a projection length onto a plane including the rotation axis of the tire.WhatA plurality of grooves opening at the end of the tread portion, and a land portion divided in the tread circumferential direction by these grooves, and
    A line connecting the center of the groove width in the groove cutting direction in a groove cross section by a plane perpendicular to the flat plate surface including the groove width direction straight line of the partial groove or the entire groove including the tread end of each of the plurality of grooves. Inclined in the direction opposite to the tire rotation direction from the tread surface to the groove bottom with respect to a normal line with the midpoint of the line segment connecting both ends of the groove edge on the straight line in the groove width direction. A pneumatic radial tire characterized by being gradually increased from an inclined position closest to to a tread portion end.
[0017]
    Here, the maximum load capacity of the tire, the air pressure corresponding to the maximum load capacity, the contact width, and the rim used to fill the tire with air pressure and apply the load are all in accordance with the above-mentioned JATMA standard and the straight line in the groove width direction. Follow previous definition.
[0018]
    Claim5Of the invention described inSuitableIn an embodiment, the claims6As in the invention described in the above, the inclination angle from the groove bottom of the line connecting the center of the groove width in the groove cutting direction with respect to the vertical line with the midpoint of the line segment connecting both ends of the groove edge on the straight line in the groove width direction as described above. 3 ° or more. The upper limit of the inclination angle is preferably 20 ° in order to maintain good uneven wear resistance.
[0019]
    Claims 1 to above6Regarding the groove and the matters related to the groove described in the above, the groove mentioned here is a wide groove, that is, a groove as a general name, a narrower groove than this groove, that is, a narrow groove as a general name, and narrower than this narrow groove. The sipe (slit) as a general term for the width is a general term. Therefore, the groove refers to at least one of a wide groove (groove), a narrow groove, and a sipe, and is combined with each of these single arrangements. Both the case of mixed arrangement is acceptable.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
    Hereinafter, an example of an embodiment of the present invention will be described with reference to FIGS.
    FIG. 1 is a left half sectional view of a pneumatic radial tire according to an embodiment of the present invention.
    FIG. 2 is a grounding shape transfer diagram by a footprint of an embodiment of the tire tread portion shown in FIG.
    FIG. 3 is a ground shape transfer diagram of the footprint of another embodiment of the tire tread portion shown in FIG.
    FIG. 4 is a diagram of the tire obtained from the ground contact shape transfer diagram shown in FIG.I V−I VThere is a sectional view along the line,
    FIG. 5 is a cross-sectional view taken along line VV of the tire of the ground shape transfer diagram shown in FIG.
[0021]
    In FIG. 1, a pneumatic radial tire 1 (hereinafter referred to as a tire 1) includes a pair of bead portions 2 (only one side is shown), a pair of sidewall portions 3 (only one side is shown), and a pair of sidewall portions 3. And has a tread portion 4 that is continuous in a shape.,One ply or more that reinforces each of the parts 2, 3, and 4 between the bead cores 5 embedded in the bead part 3, and the illustrated example is a carcass 6 that is a rubber coating of a radial array cord of two plies 6-1 and 6-2. And a belt 7 that reinforces the tread portion 3 on the outer periphery of the carcass 6, and further includes a tread rubber 8 on the outer peripheral side of the belt 7. The illustrated example is a tire 1 for a passenger car. An organic fiber cord, for example, a polyester cord is applied to the carcass 6, and the belt 7 has a two-layer steel cord crossing layer and the outermost layer is a spiral winding of nylon cord. Apply with ply.
[0022]
    The tire 1 is assembled to an applicable rim (not shown) specified by the JATMA standard, filled with air pressure corresponding to the maximum load capacity specified by the JATMA standard, and the assembly of the tire 1 and the applicable rim (not shown) is flat. The flat plate is pressed against the flat plate under a load of a load W corresponding to 70% of the maximum load capacity in the vertical direction.
[0023]
    At that time, for example, a slow-drying paint is applied to the tread surface 4t of the tread portion 4, and a paper having a relatively high tensile strength, a relatively thick paper, and a paint-transferable paper such as Kent paper is flattened. A so-called footprint is used which can accurately reproduce the ground contact state of the tread portion 4 tread surface 4t as if it were printed using means for fixing on the top. The ground transfer shape shown in FIGS. 2 and 3 is obtained by trimming the transfer portion of the footprint.
[0024]
    In the following description, the tread portion 4 in the ground contact state under the load W is applied to one straight line passing through the tire equator plane E using the ground contact shape transfer diagram of the tread 4t shown in FIGS. Having a central central groove 10 and a straight side main groove 11 directed to one on both sides thereof, and extending on both sides of the central main groove 10 so as to spread toward each other in a “C” shape. An inclined groove 12 that opens to the side main groove 11, an inclined branch groove 13 that branches from the inclined groove 12 and extends in the same direction as the inclined groove 12, and opens to the side main groove 11, and opens to the side main groove 11. And a plurality of grooves 14 opened at the end of the tread portion 4. The groove 14 will be described later.
[0025]
    As is clear from the above, this tire 1 is premised on having a tread pattern for designating the rotation direction, and the rotation direction in the tire 1 is indicated by an arrow D in FIGS. 2 and 3 are transfer diagrams of the ground contact shape, and in the load-load rolling of the tire 1, the lower side of FIGS. The tread portion 4 in the tire 1 shown in FIG. 3 has two to three sipes 15 between a plurality of adjacent grooves 14, and these sipes 15 will also be described later.
[0026]
    Here, the ground contact width CW of the tread portion 4 defined by the JATMA standard is the maximum linear distance in the axial direction of the tire 1 on the contact surface with the flat plate, and a distance L of 10% or more of the ground contact width CW from the ground width end Ce. In the shoulder region Rs of the separated tread portion 4, the tread rubber 8 in at least a partial region including the end of the tread portion 4 of the region Rs (the shoulder region Rs in the illustrated example) is open at the end of the tread portion 4 in the example illustrated in FIG. 2. In the example shown in FIG. 3, it is assumed that the groove 14 also has an opening 14 at the end of the tread portion 4 and a groove or sipe 15 that is significantly narrower than the groove 14. The groove 14 and the sipe 15 are tires. A plane (a meridional section) including one rotational axis, for example, one straight line P_L
  It is assumed that the array has a projection length onto a plane represented by. The sipe 15 can be replaced with a narrow groove.
[0027]
    The adjacent grooves 14 divide the tread rubber 8 in the circumferential direction of the tread surface 4t to form a land portion 18, and in the example shown in FIG. 3, the sipe 15 further subdivides and subdivides the land portion 18 formed by dividing the adjacent groove 14. Land portions 18-1, 18-2 and 18-3 are formed. The land portion 18 shown in FIGS. 2 and 3 is an example in which the land portions 18-1, 18-2, and 18-3 including the subdivided land portions 18-1, 18-2, and 18-3 are blocked by the grooves 14 and sipes 15 that open to the side main grooves 11. It is not necessary to be a block, and it can be a rug-like land portion, and an optimum land shape can be freely selected based on the use of tires and required performance.
[0028]
    First, referring to FIG. 4, at least the land portion 18 (the subdivided land portions 18-1, 18-2, 18-3, etc. in FIG. 3 are all of the land portion 18 and the subdivided land portions 18-1, 18-2). The land portion including the end Ce of the tread portion 4 only on the side to be grounded later, that is, only on the kicking side, under the load-load rolling of the tire 1 with the direction of the arrow D as the rotation direction. The part has a remaining chamfered portion Y (a portion surrounded by a circle) along the edge of the groove 14 in the ground contact state of the tread portion 4 in which the load 1 corresponding to 70% of the maximum load capacity is applied to the tire 1 And Therefore, the remaining chamfered portion Y does not exist at least in the above-mentioned grounding state at the edge of the groove 14 in the land portion on the side to be grounded first under rolling load load of the tire 1. The remaining chamfered portion Y is preferably adapted to continue from the position closest to the tire equator surface E to the tread portion 4 side opening end. As shown in FIG.I V−I VThe line is a straight line in the groove width direction with respect to the groove 14.
[0029]
    As shown in the figure, the surface shape of the remaining chamfered portion Y is an arc having a radius of curvature r, a composite arc having a plurality of curvature radii, a straight line, and a composite curve of a circular arc and a straight line are not shown. It can be freely selected depending on the required characteristics. The portion indicated by the two-dot chain line in FIG. 4 illustrates the shape when the load W applied to the tire 1 is removed, and the remaining chamfered portion in the ground contact state described above at the kick-out land portion at this time It is natural to provide a chamfered portion to be Y.
[0030]
    Although the illustration of the land portion 18 shown in FIG. 3 is omitted, it has the remaining chamfered portion Y, and each of the subdivided land portions 18-1 and 18-2 also has the remaining chamfered portion on at least a part of the land portion on the kicking side. It is possible to provide the part Y. 2 and 3 may be replaced by the sipe 15 or the narrow groove, and therefore, the remaining chamfered portion Y is naturally provided.
[0031]
    Next, referring to FIG. 5, a line M connecting the center of the groove width in the cutting direction of the groove 14 is shown in FIG. 3 in the cross section of the partial groove portion or the entire groove of the groove 14 including the end Ce of the tread portion 4. The tire is inclined with respect to the vertical line VL with the midpoint of the line segment connecting the groove edge both ends 14e on the VV line shown as shown in FIG. 1 is inclined in the direction opposite to the rotation direction D. The line M may be any of a straight line, a curved line, and a combined curve of a straight line and a curved line. In FIG. 5, the sipe 15 is not shown.
[0032]
    The inclination angle α of the line M with respect to the vertical line VL is constant at the inclination angle α when the line M is a straight line, but at a predetermined cutting position when the line M is a curve or a compound curve as shown in FIG. , And in FIG. 5, this is the inclination angle α at the position corresponding to the tread 4t._T In the groove bottom Gb, the inclination angle α_B In the case where the line M is not a straight line, the angle of inclination α is seen from the same cut position of the groove 14 and the inclination angle α increases from the inclination line M closest to the tire equatorial plane E toward the end of the tread portion 4 where the groove 14 opens. It shall be gradually increased. The two-dot chain line portion shown in FIG. 5 also illustrates the shape when the load W on the tire 1 is removed, and as is clear from this, the groove 14 is inclined only in the state of air pressure filling described above. The inclined groove has an inclination angle smaller than α, and the inclination angle gradually increases as described above.
[0033]
    Although the groove 14 has been described above, the same inclination angle α in the same inclination direction as the groove 14 also for the sipe 15 shown in FIG._A (Not shown), and the inclination angle α is the same as the groove 14._A That gradually increases toward the end of the tread 4 where the sipe 15 opens_A (Not shown). The same applies even if the groove 14 is a narrow groove.
[0034]
    As described above, the conventional tire 20 having a small flatness rate, particularly the tire 20 having a flatness rate of 60% or less, has an inclined road surface I having an ascending slope as shown in FIGS._S When traveling on the road, the inclined road surface I is caused by the vertical load W applied to the tire 20._S The tread rubber 23 becomes stronger as the slope becomes higher above the slope._S It is pressed by the slope, and the slope I_S It ’s even floating. As a result, the slope I under the load W_S As described above, the lateral force Fy acts on the tire 20 traveling in the upward gradient direction. This slope I_S FIG. 10 shows a ground contact shape corresponding to the ground contact state of the upper tread portion tread 23t.
[0035]
    FIG. 10 is a border diagram of the ground contact portion when the tire 20 filled with the air pressure described above is pressed against the flat plate at a camber angle of 10 ° under a load W load corresponding to 70% of the maximum load capacity. FIG. 11 shows the ground contact state of the horizontal flat road surface of the tire 20 under the same conditions as those of the ground contact portion edge diagram shown in FIG. The symbol E shown in FIGS. 10 and 11 is an equator line corresponding to a line on the tire equator plane. 10 shows a generally trapezoidal shape when viewed in overall, and shows that only the tread portion tread 23t on one side is grounded from the tire equator line E, while the grounding portion shown in FIG. It can be seen that the border view has a generally oval shape with the tire equator line E as the central axis when viewed in overalls.
[0036]
    The above-mentioned ground contact state of the tread portion tread is the same in the case of the tire 1, so that the slope I under the load W is loaded._S Similarly, the lateral force Fy acts on the tire 1 traveling in the uphill direction in the climbing direction, but for the reasons described below, the inclined road surface I_S Referring to FIG. 6, which is shown as a diagram connecting the outermost borders of the footprint of the running tire 1, the tire 1 passes through the mass point of its mass and extends around the central axis Z extending in the acting direction of the concentrated load load W on the tire 1. Tire 1 on inclined road surface I_S The tire 1 is significantly different from the conventional tire 20 in that a restoring moment Mz that attempts to rotate in the downward gradient direction is generated.
[0037]
    That is, first, referring to FIG. 4 below, the divided land portion 18 of the tread portion 4 is crushed and deformed by the contact pressure caused by the load W. However, the vulcanized rubber having a predetermined composition, here, the tread rubber 8 has an incompressible characteristic, and therefore tends to expand on the ground contact surface at the time of crushing deformation. This is particularly noticeable at the groove edge of the groove 14.
[0038]
    However, since the movement of the surface of the land portion 18 (the tread surface 4t) on which the partial load ΔW acts is restricted by the frictional contact with the road surface (S), the expansion deformation is suppressed. as a result,The shearing force Scr in the opposite direction parallel to the tire equator plane E and facing each other in the vicinity of the groove edges of the two adjacent grooves 14 acts on the dividing land 18. However, when the divided land portion 18 has the remaining chamfered portion Y only on the groove edge on the one groove 14 side and the sharp edge portion on the groove edge on the other groove 14 side when the tread portion 4 is in contact with the ground, The rubber crushing reaction force of the remaining chamfered portion Y is reduced as compared with the rubber crushing reaction force of the sharp edge portion of the groove, and the balance of the shearing force Scr in the opposite direction is lost. Scr is further reduced as compared with the shearing force Scr indicated by the solid line arrow on the sharp groove edge side, whereby each dividing land portion 18 generates a shearing force ΔFxd in the direction opposite to the rotation direction D of the tire 1 as a whole.
[0039]
    The total shearing force Fxd of the grounded parting land part 18 of the shearing force ΔFxd generated in each parting land part 18 described above is the same on both sides of the equatorial plane E when the tread part 4 is in contact with the horizontal flat road surface. Since the same amount is generated in the direction, no rotational moment is generated around the central axis Z of the tire 1 (see FIG. 6), and it merely serves as a driving force generation source of the tire.
[0040]
    However, when the tire 1 travels on the sloping road surface Is, the tread portion 4 becomes a single ground as in the case of FIG. 10 with the camber angle, and each of the ground contact portions in FIG. The shearing force ΔFxd of the divided land portion 18 is generated only on the tread portion 4 only on one side from the tire equatorial plane E, which is also only on the shoulder side including the contact width end Ce, and the total shearing force Fxd of the shearing force ΔFxd only on one side is The total shearing force Fxd that acts as a driving force generation source and is generated in the shoulder region Rs as a result is that the tire 1 is inclined around the center axis Z of the tire 1 as shown in FIG._S A restoring moment Mz that attempts to rotate in the downward gradient direction is generated.
[0041]
    The restoring moment Mz works to cancel the lateral force Fy, and the vector amount of the lateral force Fy is reduced, is almost zero, or is slightly negative depending on the case, whereby the tire 1 has a tread portion 4 on the inclined road surface Is. Even if a part of the vehicle rides on the road, the tire 1 will not behave against the driver's intention so as to run up the inclined road surface Is, and as a result, the straight running stability of the road surface in which a concave portion such as a saddle road surface is formed is Remarkably improved.
[0042]
    Next, referring to FIG. 5, the line M connecting the center of the groove width in the cutting direction of the groove 14 in the ground contact state of the tread portion 4 is inclined with respect to the perpendicular VL in the direction opposite to the rotation direction D of the tire 1. It is necessary to incline in the same direction with no load applied, so that the inclination of the line M is increased by applying the load W to the tire 1, in other words, the dividing land portion 18 is increased in inclination. Try to fall and deform.
[0043]
    However, in this case as well, the movement of the surface of the land portion 18 (the tread surface 4t) on which the partial load ΔW acts is constrained by frictional contact with the road surface (S). It is suppressed at the place. This suppression is greater in the vicinity of the groove edge 14e of the groove wall surface forming an obtuse angle with respect to the road surface (S), and a shearing force Sb as a reaction force of this suppression is brought to the divided land portion 18, and the direction of the shearing force Sb is as shown in FIG. The direction of rotation of the tire 1 is opposite to that indicated by an arrow in FIG.
[0044]
    In this case, the inclination angle α of the line M connecting the center of the groove width in the cutting direction of the groove 14 with respect to the perpendicular VL has a characteristic that the shear force Sb increases as the value increases, and therefore the inclination angle α (α_T , Α_B ) Gradually increases from the inclined position closest to the tire equatorial plane E toward the end of the tread portion 4, including the case where the line M connecting the center of the groove width of the groove 14 is a curve or a compound curve. Since the shearing force Sb that is larger in the parting land part 18 closer to is generated, the action point of ΣSb = ΔFxd of each parting land part 18 is shifted closer to the end of the tread part 4.
[0045]
    As a result, the point of action of the total shearing force Fxd, which is the sum of the shearing forces ΔFxd of the divided land portions 18 within the contact surface, is also located farther from the central axis Z of the tire 1 shown in FIG. There is an advantage that the surrounding restoring moment Mz becomes a larger value. Based on this restoring moment Mz, the straight running stability improvement of the tire 1 in running on the recess forming road surface is the same as described above.
[0046]
    A structure in which at least a part of the land portion 18 of the dividing land portion 18 only on the kicking side described above has the remaining chamfered portion Y along the groove edge of the groove 14 and a line M connecting the center of the groove width in the cutting direction of the groove 14 are perpendicular. It inclines in the direction opposite to the rotation direction D of the tire 1 with respect to VL, and the inclination angle α (α_T , Α_B ) Are gradually independent from the configuration of the tire equatorial plane E closest to the end of the tread portion 4 and are independent of each other, and have the effect of improving the straight running stability of the tire 1 on the recess-formed road surface. A configuration combining the configurations also has an even more effective straight running stability improvement effect.
[0047]
    Although the groove 14 has been described above, the same effect can be obtained with the sipe 15, and it is a matter of course that the same effect can be obtained even if the groove 14 is replaced with a narrow groove. The tire 1 is filled with air pressure corresponding to the maximum load capacity, the load W corresponding to 70% of the maximum load capacity is applied, and the specific shoulder region of the tread portion 4 is set to 10% or more of the ground contact width. This is set as a condition close to the use condition in the actual vehicle.
[0048]
    Here, when the surface of the remaining chamfered portion Y is an arc having a radius of curvature r in the cross section shown in FIG. 4, although not shown, in the case of a taper cut straight line toward the groove 14, a composite curve of these arcs and straight lines is used. Either of the cases is acceptable. Further, it is effective that the remaining chamfered portion Y gradually increases the chamfering degree from the position closest to the tire equator plane E toward the end of the tread portion 4, and in this way, the total shearing force Fxd generated in the shoulder region Rs is increased. The point of action shifts from the center axis Z (see FIG. 6) of the tire 1 to the outside of the tire 1, and therefore a larger restoring moment Mz can be obtained, which is advantageous.
[0049]
    The radius of curvature r of the remaining chamfered portion Y and the maximum cutting height into the groove 14 are in the range of 0.5 to 3 mm. Because if it is less than 0.5 mm, the above-mentioned effect cannot be obtained in practice, and if it exceeds 3 mm, the ground contact area of the dividing land 18 is excessively reduced, and the effect is excessively reduced.
[0050]
    Further, an inclination angle α (α that inclines the line M connecting the center of the groove width of the groove 14 in the direction opposite to the rotation direction D of the tire 1._T , Α_B ) Is 3 ° or more, and the inclination angle α (α_T , Α_B ) Is preferably as large as possible, but the contact pressure distribution in the shoulder region Rs decreases as it goes toward the contact width end Ce. Therefore, the shoulder region Rs originally tends to be prone to uneven wear, so that it exceeds the limit. Inclination angle α (α_T , Α_B ) Is not preferable, and the inclination angle α (α_T , Α_B ) Is limited to 20 °. This inclination angle α (α_T , Α_B The point within the range of 3 ° to 20 ° is also applied when the configuration having the remaining chamfered portion Y is combined with the above configuration in which the line M is inclined in the direction opposite to the rotation direction D of the tire 1.
[0051]
【Example】
    A radial ply tire for passenger cars, the size of which is 235 / 45ZR17, and the structure is shown in FIG. 1. A carcass 6 that is rubber-coated with a 2-ply radial arrangement polyester cord, a two-ply steel cord cross layer, and a nylon cord cap ply A belt 7 with a layer. Example 13The tire 1 has a tread pattern corresponding to the footprint shown in FIG.4~6The tire 1 has a tread pattern corresponding to the footprint shown in FIG. Example 16In each of the tires, the remaining chamfered portion Y of the dividing land portion 18 has an arc having a cross section of the radius of curvature r, the line M connecting the center of the groove width of the groove 14 is a straight line, and the direction opposite to the tire rotation direction D at an inclination angle α Those that incline, and those of these composite types.
[0052]
    In all the above footprints, the tire 1 is assembled to the standard rim 8JJ of the applicable rims defined by the JATMA standard (1998 version), and the maximum load capacity described in the JATMA standard (1998 version) is 650 kg (mass). Is the ground contact shape of the tread portion 4 when a load of 450 kgf corresponding to 70% of the maximum load capacity of 650 kg (mass) is applied.
[0053]
    Example 13For the tire group, a comparative tire 1 having a tread pattern according to the footprint shown in FIG.4~6Comparative tire 2 provided with a tread pattern according to the footprint shown in FIG.
[0054]
    Examples 1 to6Each tire has a radius of curvature of the cross section of the remaining chamfer Y.r isIncreasing gradually from 0.5 to 2.5 mm, inclination angle α of line M = 10 ° constant, inclination angle of line MButAlthough gradually increasing at 5 to 20 °, the tires were divided into each type, and some example tires were combined with these types. The presence or absence of each of the curvature radius r and the inclination angle α of the cross section of the remaining chamfered portion Y is described in Examples 13And the group of Comparative Example 1 is shown in Table 1, Examples4~6The groups of Comparative Example 2 are shown in Table 2.
[0055]
[Table 1]

[0056]
[Table 2]

[0057]
    Example 16These tires and the tires of Comparative Examples 1 and 2 were used as test tires, and the following two tests were performed under the following test conditions using the rim and air pressure.
  (1) Measurement of camber thrust Fc: Using a flat belt type indoor testing machine, the belt speed is 60 km / h, and each test tire is equivalent to 70% of the maximum load capacity of 650 kg at a camber angle of 5 °. Press with a load of 450 kgf to measure the camber thrust Fc. The measurement result is represented by an index in which Comparative Examples 1 and 2 are set to 100 for each group, and the smaller the value, the better.
  (2) Straight running stability test with actual vehicle: 100km of dry asphalt test road surface with individual test tires mounted on all the wheels of a domestic passenger car 2500cc class FR car and two passengers on the front seat to form a saddle The degree of wandering when traveling at a speed of / h, that is, straight running stability, was evaluated to a maximum of 10 points based on the feeling of a test driver. The higher the score, the better.
    The test results of the above two items are shown on the right side of Tables 1 and 2 for each tire group.
[0058]
    From the test results shown in Tables 1 and 2, Example 16TiresIsBoth,Compared to the tires of Comparative Examples 1 and 2, the amount of Camber thrust Fc generated was significantly reduced, and it was found that the straight running stability in the dry saddle road running test with an actual vehicle was remarkably superior.Also,Example 1 and Example having a configuration having only the remaining chamfered portion Y4It can be seen that each of the tires can achieve a significant reduction in the amount of camber thrust Fc generated and a further improvement in straight running stability as compared with the tires of Comparative Examples 1 and 2.
[0059]
【The invention's effect】
    thisapplicationClaims 1 to 16According to the invention described in (1), the occurrence of wandering phenomenon on the road surface in which the concave portions having the inclined surfaces with the upward slopes are formed on both sides as represented by the eaves is suppressed, and as a result, the vehicle travels straight at high speed. It is possible to provide a pneumatic radial tire which is excellent in stability, particularly called a high performance radial tire having a flatness ratio of 60% or less.
[Brief description of the drawings]
FIG. 1 is a left half sectional view of a tire according to an embodiment of the present invention.
FIG. 2 is a grounding shape transfer diagram by a footprint of one embodiment of the tire tread portion shown in FIG. 1;
FIG. 3 is a ground shape transfer diagram of a footprint of another embodiment of the tire tread portion shown in FIG. 1;
4 is a diagram of a tire obtained from the ground contact shape transfer diagram shown in FIG.V I−V IIt is sectional drawing which follows a line.
5 is a cross-sectional view taken along line VV of the tire of the ground shape transfer diagram shown in FIG. 3;
6 is an explanatory diagram of a shearing force and a restoring moment generated when the tire shown in FIG. 1 travels on an inclined road surface.
7 is an explanatory diagram showing a state in which a shear force is generated during running on the inclined road surface of the tire shown in FIG. 1. FIG.
FIG. 8 is a front view or a rear view of a tire traveling on an inclined road surface.
9 is a cross-sectional view of the tire shown in FIG.
10 is an edge drawing of the grounding portion of the footprint when the tire shown in FIG. 7 is pressed against a flat plate at a camber angle of 10 °. FIG.
11 is a border view of the ground contact portion of the tire footprint shown in FIG. 7. FIG.
[Explanation of symbols]
    1 Pneumatic radial tire
    2 Bead section
    3 Side wall
    4 Tread
    4t tread
    5 Bead core
    6 Carcass
    6-1, 6-2 Carcass ply
    7 Belt
    8 Tread rubber
    10 Straight central main groove
    11 Straight side main groove
    12 Inclined groove
    13 Inclined branch
    14 Groove with projection length on meridional section
    14e Groove edge
    15 Sipe
    18 minutes landing
    18-1, 18-2, 18-3 Subdivision
    CW Grounding width
    Ce Ground width end
    D Tire rotation direction
    Rs shoulder region
    Y Remaining chamfer
    M Line connecting the groove width center in the cutting direction of the groove 14
    VL perpendicular
    Inclination angle of α line M to perpendicular VL
    I_S   Ramp surface
    S Flat plate surface
    Fc Camber Thrust
    Fy lateral force
    Scr, Sb Shear force
    Fxd Shear force opposite to tire rotation direction
    Mz Restoring moment

Claims (6)

A pair of bead portions and a pair of sidewall portions, a toroidal tread portion connected to both sidewall portions, and a radial carcass of one or more plies that reinforces each portion between bead cores embedded in the bead portions; and In a pneumatic radial tire comprising a belt that reinforces the tread portion on the outer periphery of the radial carcass and having a tread pattern for specifying the rotation direction,
In the ground contact state of the tread portion in which the tire filled with air pressure corresponding to the maximum load capacity of the tire is pressed perpendicularly to the flat plate under a load load corresponding to 70% of the maximum load capacity,
At least a partial region including the tread portion end of the tread portion shoulder region separating a distance of 10% or more of the tread portion contact width from the end of the contact width has a projection length onto a plane including the rotation axis of the tire. A plurality of grooves opened at the ends, and land portions divided in the tread circumferential direction by these grooves, and each of the divided land portions only on the side to be grounded later under the rolling load of the tire. , at least a part land portion including a tread portion end, have a remaining chamfer along the groove edge,
The remaining chamfer pneumatic radial tire characterized that you increasing chamfered degree As toward the tread portion edge from the position closest to the tire equatorial plane. A pair of bead portions and a pair of sidewall portions, a toroidal tread portion connected to both sidewall portions, and a radial carcass of one or more plies that reinforces each portion between bead cores embedded in the bead portions; and In a pneumatic radial tire comprising a belt that reinforces the tread portion on the outer periphery of the radial carcass and having a tread pattern for specifying the rotation direction,
In the ground contact state of the tread portion in which the tire filled with air pressure corresponding to the maximum load capacity of the tire is pressed perpendicularly to the flat plate under a load load corresponding to 70% of the maximum load capacity,
At least a partial region including the tread portion end of the tread portion shoulder region separating a distance of 10% or more of the tread portion contact width from the end of the contact width has a projection length onto a plane including the rotation axis of the tire. A plurality of grooves opening at the ends, and land portions divided in the tread circumferential direction by these grooves, and
At least part of the land portion including the tread portion end of each divided land portion only on the side to be grounded later under the load load rolling of the tire has a remaining chamfered portion along the groove edge,
A line connecting the center of the groove width in the groove depth direction in a groove cross section by a plane perpendicular to the flat plate surface and including a straight line of the groove width direction of the partial groove or the entire groove including the end of the tread portion of each of the plurality of grooves. Is inclined at an angle of 3 ° or more from the surface of the tread portion toward the bottom of the groove with respect to a perpendicular line with the midpoint of the line segment connecting both ends of the groove edge on the straight line in the groove width direction, and the inclination direction is the tire rotation direction. Pneumatic radial tire characterized by being in the opposite direction. 3. The tire according to claim 1, wherein the surface of the remaining chamfered portion has at least one of an arc shape and a linear shape in a cross section by a plane perpendicular to the flat plate surface including a groove width direction straight line of the groove. Inclination angle relative to the normal of a line contiguous with the groove width center of the groove depth direction of the groove cross section, a tire according to claim 2 or 3 gradually increases as the toward the tread portion edge from the position closest to the tire equatorial plane. A pair of bead portions and a pair of sidewall portions, a toroidal tread portion connected to both sidewall portions, and a radial carcass of one or more plies that reinforces each portion between bead cores embedded in the bead portions; and In a pneumatic radial tire comprising a belt that reinforces the tread portion on the outer periphery of the radial carcass and having a tread pattern for specifying the rotation direction,
In the ground contact state of the tread portion in which the tire filled with air pressure corresponding to the maximum load capacity of the tire is pressed perpendicularly to the flat plate under a load load corresponding to 70% of the maximum load capacity,
At least a partial region including the tread portion end of the tread portion shoulder region separating a distance of 10% or more of the tread portion contact width from the end of the contact width has a projection length onto a plane including the rotation axis of the tire. A groove width of a partial groove or a whole groove including a plurality of grooves opened at the ends and a land portion divided in the tread circumferential direction by these grooves, and including the tread end of each of the plurality of grooves. The line connecting the center of the groove width in the groove cutting direction in the groove cross section of the plane including the direction straight line and perpendicular to the flat plate surface is the foot of the midpoint of the line segment connecting both ends of the groove edge on the groove width direction straight line. Inclined in the direction opposite to the tire rotation direction from the tread surface to the groove bottom with respect to the vertical line, and the inclination angle gradually increases from the inclined position closest to the tire equatorial plane toward the tread edge. Pneumatic radial tire . Claim with respect to the perpendicular to the foot of the midpoint of the line segment between the groove edge ends on the groove width direction line, the inclination angle from the groove bottom of the line contiguous with the groove width center of the groove cutting direction is less than 3 ° 5 The tire described in 2.

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