JP4354683B2

JP4354683B2 - Tire for agricultural machinery

Info

Publication number: JP4354683B2
Application number: JP2002309949A
Authority: JP
Inventors: 一之遠藤
Original assignee: Bridgestone Corp
Current assignee: Bridgestone Corp
Priority date: 2001-11-12
Filing date: 2002-10-24
Publication date: 2009-10-28
Anticipated expiration: 2022-10-24
Also published as: JP2003205709A

Description

【０００１】
【発明の属する技術分野】
この発明は、泥濘地や湿田等で使用される農業機械に供するタイヤに関するものである。
【０００２】
【従来の技術】
トラクターや田植え機などの農業機械に装着されるタイヤは、泥濘地や湿田等の圃場を走行する際のトラクションが重視されるために、特許文献１に記載されるタイヤを典型例とする、ラグパターンを有することが、通例である。すなわち、図１に示すように、タイヤのトレッド１の周方向に間隔を置いて比較的に高さの高いラグ２を八の字状に配置したラグパターンに成るものが一般的である。
【０００３】
かような比較的に大きなラグを有する農業機械用タイヤにおいて、燃費向上などを所期して軽量化をはかる場合、大きな比重を占めるラグの軽量化が有効である。ここで、ラグはトラクションを得るために所定の高さが必要であるところから、ラグの軽量化は、その幅を狭くすることが順当な策となるが、ラグ剛性が低くなって、タイヤ転動時のラグの動きが大きくなる不利をまねく。すなわち、ラグの摩耗進展速度が速くなって、タイヤ寿命が低下したり、ラグの部分的摩耗が進行して偏摩耗を引き起こすことになる。
【０００４】
さらに、ラグ剛性が低くなると、舗装路の走行においては、タイヤ１回転当りの転がり周長が該タイヤの本来の周長より小さく変化する。これは、ラグの剛性が低くなって、舗装路走行において、ラグが倒れ込み変形を起こすためである。かように、タイヤ本来、換言すると設計通りの転がり周長での走行が、舗装路において達成されない場合、特に４輪駆動の車両に装着した場合に、前、後輪で転がり周長の変化が生じると、いずれかのタイヤにスリップが発生し、偏摩耗やノッキングを引き起こす原因となる。
【０００５】
また、ラグのバットレス部の端面に、図２に示すように、主に意匠の観点から凹所３を設ける場合があり、この凹所３はラグの重量削減にも有効である。しかしながら、凹所３はラグのバットレス部端面の輪郭形状と相似して設けられのが通例であり、凹所３を囲む縁取りがあるため、タイヤを圃場で使用する際に、凹所３、とりわけ走行時にラグの背面側となる部分３ａに泥が付着し易く、圃場外に持ち出される問題をまねく。
【０００６】
【特許文献１】
特開平１１−１１５４１７号公報
【０００７】
【発明が解決しようとする課題】
そこで、この発明は、農業機械用タイヤの軽量化、特にラグの軽量化を、偏摩耗や上記の転がり周長の変化をまねくことなしに達成する、方途について提案することを目的とする。
【０００８】
【課題を解決するための手段】
この発明の要旨構成は、次のとおりである。
(1)タイヤの赤道からトレッド端側へ、タイヤの赤道に対して傾いた向きに延びるラグを、トレッドの周方向に間隔を置いて複数配置した農業機械用タイヤであって、ラグは、タイヤの赤道からトレッド端側へ少なくとも１つの折曲部を介して延在し、かつタイヤの赤道側の端部および折曲部を除く部分の幅を狭くして成り、ラグのバットレス部の端面に、該端面内を起点としてラグの蹴り出し側に拡開して蹴り出し側のラグ溝に連通する、凹所を有することを特徴とする農業機械用タイヤ。
【００１０】
(2)上記(1)において、ラグのタイヤの赤道側の端部および折曲部に隣接する部分の幅が、端部および折曲部での幅の50〜90％であることを特徴とする農業機械用タイヤ。
【００１１】
(3)上記(1)または(2)において、凹所のタイヤ径方向の開口幅はラグ溝側が起点側の1.3 〜2.5 倍であることを特徴とする農業機械用タイヤ。
【００１２】
(4)上記(1)、(2) または(3)において、ラグの踏み込み側始端がタイヤの赤道から離間した位置にあることを特徴とする農業機械用タイヤ。
【００１３】
(5)上記(1)ないし(4)のいずれかにおいて、ラグのタイヤの赤道側の端面はラグの延在方向と交差する向きを有することを特徴とする農業機械用タイヤ。
【００１４】
(6)上記(1)ないし(4)のいずれかにおいて、ラグのタイヤの赤道側の端部は、タイヤの回転軸に対して平行の先端壁面を有し、該先端壁面はタイヤの回転軸を含む面に対して25〜45°の角度で傾斜してなることを特徴とする農業機械用タイヤ。
【００１５】
【発明の実施の形態】
図３に、この発明に従う農業機械用タイヤのトレッド要部を周方向に展開した面を示す。この農業機械用タイヤは、そのトレッド１のタイヤ赤道面Ｏを境とする、トレッド半部のそれぞれにおいて、トレッドの周方向に間隔を置いて複数のラグ４を配置して成る。
【００１６】
各ラグ４は、タイヤの赤道Ｏからトレッド端Ｅ側へ、タイヤの赤道Ｏに対して傾いた向きに延び、かつタイヤの赤道Ｏからトレッド端Ｅ側へ少なくとも１つ、図示例で２つの折曲部５ａおよび５ｂを介して延在する。
【００１７】
さらに、ラグ４において、タイヤの赤道Ｏ側の端部４ａおよび折曲部５ａ，５ｂを除く部分の幅を、図４に点線で示すように、端部４ａおよび折曲部５ａ，５ｂ対比で狭くすることが肝要である。
【００１８】
ここで、ラグ高さが同一の場合、ラグ剛性とラグ幅とは基本的に比例の関係にあるため、図４に示したように、点線部の面積減少によってラグ剛性が低下することが予想される。そして、上記の転がり周長の変化に影響を与える、タイヤ転動時のラグの変形（動き）量は、ラグ剛性に反比例するため、面積減少によるラグ剛性の低下はラグの変形量の増加、強いては上記タイヤ性能の低下に繋がる。
【００１９】
ところが、このラグの変形量は、端部４ａおよび折曲部５ａ，５ｂの各部分での剛性に大きく影響を受けること、さらにラグがタイヤの赤道Ｏからトレッド端Ｅまで連続していることから、図３または図４に示したように、ラグ４の幅を狭くする部分を端部４ａおよび折曲部５ａ，５ｂを除く部分とすれば、ラグの変形量の増大をまねくことなく、ラグの面積減少を実現できることを新たに見出した。すなわち、この発明に従って、端部４ａおよび折曲部５ａ，５ｂを除く部分の幅を狭くすることによって、ラグ全体の変形量を従来並みに抑えた上でラグの軽量化を達成することができたのである。
【００２０】
なお、ラグの幅狭とする部分、具体的にはラグ４の端部４ａおよび折曲部５ａ，５ｂに隣接する部分の幅は、端部４ａおよび折曲部５ａ，５ｂの各幅の50〜90％であることが好ましい。すなわち、図３に示すように、端部４ａでの幅ａ₁ とこれに隣接する部分の幅ｂ₁ との間でａ₁ ：ｂ₁ ＝100 ：50〜90を満足させ、同様に折曲部５ａでの幅ａ₂ とこれに隣接する部分の幅ｂ₂ との間でａ₂ ：ｂ₂ ＝100 ：50〜90および折曲部５ｂでの幅ａ₃ とこれに隣接する部分の幅ｂ₃ との間でａ₃ ：ｂ₃ ＝100 ：50〜90をそれぞれ満足させることが有利である。
【００２１】
なぜなら、上記端部４ａおよび折曲部５ａ，５ｂの各部において隣接する部分の幅が各部対比で50％未満では、必要とするラグ剛性を確保することが難しくなり、一方同90％をこえると、ラグの軽量化並びにコストダウンをはかることが難しくなる。
【００２２】
ここで、上記したラグの幅とは、ラグを折曲部を境として区分した際、その各区分毎、つまり図示例では３つの区分におけるラグの延在方向Ｌ₁ ，Ｌ₂ ，Ｌ₃（図４参照）と直交する向きの幅を意味する。そして、端部４ａおよび折曲部５ａ，５ｂの各幅は、各部における最大幅とし、一方端部および折曲部に隣接する部分の幅は、その隣接する部分における最小幅とする。ここで、上記延在方向は、端部および折曲部を境とした各区分における、ラグの踏み込み側の辺、例えば図４における４ｃ、４ｄおよび４ｅの各辺を基準とし、つまりこれら辺と平行線を延在方向とする。なお、基準となるラグの踏み込み側の辺が曲線の場合は、端部および折曲部を結ぶ線分を、それぞれの辺とする。
【００２３】
次に、この発明の農業機械用タイヤでは、図５に示すように、ラグ４のバットレス部の端面４ｂに、該端面内を起点としてラグ４の蹴り出し側に拡開して蹴り出し側のラグ溝６に連通する領域をえぐって成る、凹所７を設けて、ラグの更なる軽量化に併せて、タイヤに意匠性を付与する。
【００２４】
すなわち、タイヤの転動に伴って土中に入ったラグ４のバットレス面には、タイヤの回転によって土からの接線力をタイヤ周方向に受けるため、ラグの端面４ｂに設けた凹所に、先に図２に示したように縁取りがあると、段差部分（図２中の３ａ部分）に垂直方向の力が加わるため、泥土が付着する核となる。
【００２５】
これに対して、この発明に従って設けた凹所７は、図５に示したように、凹所７の終端がラグ溝６に連通し、上記した従来における段差部分が存在しない、換言すると泥土が付着する核がないため、凹所への泥土の付着を回避できる。
【００２６】
ここで、凹所７のタイヤ径方向の開口幅について、起点側をｃおよび同ラグ溝６側をｄとしたとき、ｄ：1.3 〜1.7 ｃであることが有利である。すなわち、ラグ溝６側の開口幅ｄが起点側の開口幅ｃと同等程度であると、タイヤ転動中に生じるタイヤ径方向の力によって凹所のタイヤ周方向の２辺（図５において上下辺に対応）の縁にも上記の垂直方向の力が加わる結果、泥付着の核となる。この現象は、上記２辺の縁に垂直方向の力が加わるのを防止すれば回避することが可能であり、そのためには、ｄ：1.3 〜1.7 ｃとすることが推奨される。
【００２７】
また、ラグ４の踏み込み側始端、つまり図３における始端４ｓがタイヤの赤道Ｏから離間した位置にあることが、タイヤの転動時、特に泥濘地での使用時にラグ間に泥が付着するのを防止する上で有利である。
【００２８】
さらに、ラグ４のタイヤの赤道Ｏ側の端部、つまり踏み込み側の端部４ａはラグの延在方向と交差する向きを有することが、上記の泥付着の防止性能を維持しつつ、ラグの踏み込み側端部付近の陸部剛性を確保するのに有効である。
【００２９】
ところで、ラグの踏み込み側の端部は、その輪郭に沿った形状の先端壁面を有するのが一般的であり、図３に示した例では、端部４ａの先端壁面は進行方向に突出した山型を呈している。湿田や畑等を走行する際、かような山型先端壁面を有する端部４ａでは、山型先端壁面の進行方向に突出した部分で土が振り分けられて、その両側へと逃げてしまう結果、タイヤが土中に僅かではあるが沈みこむ傾向がある。そして、この沈みこみによって、農業機械用タイヤの牽引力が低下することが新たに判明した。
【００３０】
すなわち、タイヤの沈下量が大きくなると、タイヤの前進に伴う排土量も大きくなって走行抵抗が増加するため、実質的な牽引力の低下をまねくのである。
【００３１】
そこで、図７に示すように、図３に示したラグ４の踏み込み側の端部４ａにおいて、まずタイヤの回転軸に対して平行の先端壁面８を設けることによって、タイヤを湿田や畑等で進行させた際、土が端部４ａの両側に逃れられない構造を与える。すなわち、タイヤの回転軸に対して平行の先端壁面８は、タイヤの進行方向に正対して地面と接触するため、土を先端壁面８の下敷きにして押し固めることができる。この固められた土の上にラグが乗る結果、上記の沈みこみは回避され、牽引力の向上が達成される。
【００３２】
なお、タイヤの回転軸に対して平行の先端壁面８は、図７にて先端壁面８を点線で示すように、端部４ａにおける少なくとも踏み込み側の最先端部分に対応させて設ける必要がある。具体的には、図７（ｃ）に示すように、端部４ａのタイヤの赤道Ｏから離間した境界点Ｐ（図７の例では、端部４ａとその隣接域との間の変曲点）を始点とする先端壁面８の幅ｔが、点Ｐからタイヤの赤道Ｏまでの距離Ｔの30〜80％程度にわたることが好ましい。
【００３３】
勿論、端部４ａの全域にわたってタイヤの回転軸に対して平行の先端壁面８を設けてもよい。例えば、図８に示すラグパターンは、端部４ａの全域がタイヤの回転軸に対して平行であり、この場合は端部４ａの全域にわたってタイヤの回転軸に対して平行の先端壁面８を設けることによって、その幅の拡がりをもって、沈み込みの抑制に対して最上の効果を得ることができる。この図８の例においても、先端壁面８の幅ｔが、点Ｐからタイヤの赤道Ｏまでの距離Ｔの30〜80％程度にわたることが好ましい。
【００３４】
また、踏み込み側の端部４ａ付近は、ラグ相互の間隔が最も狭いために土が詰まり易い部分であり、土が詰まるとラグパターンによるグリップ力の低下から牽引力の低下を招くことになる。ここに、上記の先端壁面８を設けるに当たって、図７(b) および図８(b) に示す、タイヤの回転軸を含む面に対する先端壁面の傾斜角度αを25〜45°の範囲とすることが、土の排出性を改善する上で有利である。
【００３５】
すなわち、先端壁面８のタイヤの回転軸を含む面に対する傾斜角度と、牽引力およびトレッドセンター付近での泥詰まり量との関係を、それぞれ図９および図１０に示すように、両性能を満足するには傾斜角度αを25〜45°の範囲とすればよいことがわかる。なお、泥詰まり量については、傾斜角度αが40〜50°の範囲で優れた結果が得られているが、傾斜角度αが45°を超えて水平に近づくに連れて、ラグによるエッジ効果が損なわれる結果、総合的な牽引力が低下するため、45°以下とすることが好ましい。さらに、軽量化の効果をも考慮すると、傾斜角度αは30°またはその前後５°程度とすることが有利である。
【００３６】
【実施例】
図１（従来例）図３（発明例１）、図７（発明例２）および図８（発明例３）に示したところに従って、下記に示す種々の仕様の下に、サイズが9.5 −24の後輪用の農業機械用タイヤをそれぞれ試作した。なお、その他の構造は、当該サイズの農業機械用タイヤの一般に従って作製した。
【００３７】

【００３８】
かくして得られた各タイヤを標準リムに組み込み、表１に示す内圧および負荷荷重に調整した後、25馬力トラクターの後輪に装着しまたはドラム試験に供し、表１に示す条件に従って各項目の評価を行った。また、前輪には、サイズが６−14の農業機械用タイヤを共通して使用した。その結果を、従来タイヤの結果を100 としたときの指数にて表１に併記する。
【００３９】
【表１】

【００４０】
【発明の効果】
この発明によれば、農業機械用タイヤとしての基本性能を阻害することなしに、軽量化を実現することができる。
【図面の簡単な説明】
【図１】従来の農業機械用タイヤのトレッドパターンを示す図である。
【図２】従来の農業機械用タイヤのラグを示す斜視図である。
【図３】この発明の農業機械用タイヤのトレッドパターンを示す図である。
【図４】この発明の農業機械用タイヤのトレッドパターンを示す図である。
【図５】この発明の農業機械用タイヤのラグを示す斜視図である。
【図６】ラグの偏摩耗の評価手法を説明する図である。
【図７】この発明の農業機械用タイヤの他のトレッドパターンを示す図である。
【図８】この発明の農業機械用タイヤの別のトレッドパターンを示す図である。
【図９】先端壁面のタイヤの回転軸を含む面に対する傾斜角度と牽引力との関係を示す図である。
【図１０】先端壁面のタイヤの回転軸を含む面に対する傾斜角度と泥詰まり量との関係を示す図である。
【符号の説明】
１トレッド
２ラグ
３凹所
４ラグ
４ａ端部
４ｂ端面
５ａ，５ｂ折曲部
６ラグ溝
７凹所
８先端壁面[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a tire for use in agricultural machinery used in mudlands, wetlands, and the like.
[0002]
[Prior art]
Since tires attached to agricultural machines such as tractors and rice planting machines attach importance to traction when traveling in fields such as muddy grounds and wet fields, the tires described in Patent Document 1 are typical examples. It is customary to have a pattern. That is, as shown in FIG. 1, it is common to have a lag pattern in which lugs 2 having a relatively high height are arranged in an eight-letter shape at intervals in the circumferential direction of a tread 1 of a tire.
[0003]
In the agricultural machine tire having such a relatively large lug, it is effective to reduce the weight of the lug that occupies a large specific gravity in order to reduce the weight for the purpose of improving the fuel efficiency. Here, since the lug needs to have a predetermined height to obtain traction, it is an appropriate measure to reduce the weight of the lug. This leads to the disadvantage that the movement of the lag during movement increases. That is, the wear progressing speed of the lug is increased and the tire life is reduced, or partial wear of the lug is advanced to cause uneven wear.
[0004]
Further, when the lug rigidity is lowered, in running on a paved road, the rolling circumference per one rotation of the tire changes smaller than the original circumference of the tire. This is because the rigidity of the lug is lowered, and the lug falls down and deforms when traveling on a paved road. Thus, in other words, in the case where the tire itself, in other words, running at the rolling circumference as designed is not achieved on a paved road, especially when mounted on a four-wheel drive vehicle, there is a change in the rolling circumference at the front and rear wheels. When this occurs, slip occurs in any of the tires, causing uneven wear and knocking.
[0005]
Further, as shown in FIG. 2, a recess 3 may be provided on the end face of the buttress portion of the lug mainly from the viewpoint of design, and this recess 3 is also effective in reducing the weight of the lug. However, the recess 3 is usually provided similar to the contour shape of the end face of the buttress portion of the lug, and since there is a rim surrounding the recess 3, the recess 3, especially when the tire is used in a field, Mud tends to adhere to the portion 3a on the back side of the lug during traveling, leading to a problem of being taken out of the field.
[0006]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-115417
[Problems to be solved by the invention]
Therefore, an object of the present invention is to propose a way to achieve weight reduction of agricultural machinery tires, in particular, weight reduction of lugs without improper wear and change in the rolling circumference.
[0008]
[Means for Solving the Problems]
The gist configuration of the present invention is as follows.
(1) An agricultural machine tire in which a plurality of lugs extending from the equator of the tire to the tread end side in a direction inclined with respect to the equator of the tire are arranged at intervals in the circumferential direction of the tread. of extending through at least one bent portion from the equator to the tread end side, and Ri formed by narrowing the width of the portion excluding the end portion and the bent portion of the equator side of the tire, the end surface of the buttress portion of the lug And an agricultural machine tire characterized by having a recess that expands from the end face to the lug kick-out side and communicates with the lug groove on the kick-out side .
[0010]
(2) In the above (1), the width of the lug tire adjacent to the equator-side end portion and the bent portion is 50 to 90% of the width at the end portion and the bent portion. Agricultural machinery tires.
[0011]
(3) The agricultural machine tire according to (1) or (2), wherein the opening width in the tire radial direction of the recess is 1.3 to 2.5 times the lug groove side from the starting side.
[0012]
(4) The tire for agricultural machinery according to (1), (2) or (3) above, wherein the starting end of the lug is located at a position separated from the equator of the tire.
[0013]
(5) The agricultural machine tire according to any one of (1) to (4), wherein an end surface on the equator side of the lug tire has a direction intersecting with an extending direction of the lug.
[0014]
(6) In any one of the above (1) to (4), the end portion of the lug on the equator side of the tire has a tip wall surface parallel to the rotation axis of the tire, and the tip wall surface is the rotation axis of the tire. A tire for agricultural machinery, wherein the tire is inclined at an angle of 25 to 45 ° with respect to a surface including.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
In FIG. 3, the surface which developed the tread principal part of the tire for agricultural machines according to this invention to the circumferential direction is shown. The agricultural machine tire is formed by arranging a plurality of lugs 4 at intervals in the tread circumferential direction in each of the tread halves with the tire equatorial plane O of the tread 1 as a boundary.
[0016]
Each lug 4 extends from the tire equator O to the tread end E side in a direction inclined with respect to the tire equator O, and at least one fold in the illustrated example from the tire equator O to the tread end E side. It extends through the

curved portions

5a and 5b.
[0017]
Further, in the lug 4, the width of the portion excluding the end portion 4a and the

bent portions

5a and 5b on the equator O side of the tire is compared with the end portion 4a and the

bent portions

5a and 5b as shown by dotted lines in FIG. It is important to make it narrow.
[0018]
Here, when the lug height is the same, the lug rigidity and the lug width are in a proportional relationship, and as shown in FIG. Is done. And since the amount of deformation (movement) of the lug at the time of rolling of the tire, which affects the change in the rolling circumference, is inversely proportional to the lug stiffness, the decrease in the lug stiffness due to the area reduction increases the deformation amount of the lug, If it is strong, it will lead to the deterioration of the tire performance.
[0019]
However, the deformation amount of the lug is greatly influenced by the rigidity of the end 4a and the

bent portions

5a and 5b, and the lug is continuous from the tire equator O to the tread end E. As shown in FIG. 3 or FIG. 4, if the portion that narrows the width of the lug 4 is a portion excluding the end portion 4a and the

bent portions

5a and 5b, the lug can be increased without increasing the deformation amount of the lug. It was newly found that the reduction of the area can be realized. That is, according to the present invention, by reducing the width of the portion excluding the end portion 4a and the

bent portions

5a and 5b, the weight of the lug can be reduced while suppressing the deformation amount of the entire lug to the conventional level. It was.
[0020]
Note that the width of the portion of the lug that is narrow, specifically the portion adjacent to the end 4a and the

bent portions

5a, 5b of the lug 4, is 50% of the width of each of the end 4a and the bent portions 5a, 5b. -90% is preferred. That is, as shown in FIG. 3, a ₁ : b ₁ = 100: 50 to 90 is satisfied between the width a ₁ at the end 4a and the width b _{1 of} the portion adjacent thereto, and bending is similarly performed. A ₂ : b ₂ = 100: 50 to 90 between the width a ₂ at the portion 5a and the width b _{2 of} the portion adjacent thereto, and the width a ₃ at the bent portion 5b and the width of the portion adjacent thereto a between _{_{_{b 3 3: b 3 = 100}}} : they are advantageous to 50-90 a satisfy, respectively.
[0021]
This is because, if the width of the adjacent portions of the end portion 4a and the

bent portions

5a and 5b is less than 50% in comparison with each portion, it becomes difficult to ensure the required lug rigidity, while exceeding 90%. It is difficult to reduce the weight of the lug and reduce the cost.
[0022]
Here, the width of the lug described above means that when the lug is divided with the bent portion as a boundary, the lug extending directions L ₁ , L ₂ , L ₃ ( This means the width in the direction orthogonal to (see FIG. 4). And each width | variety of the edge part 4a and bending

part

5a, 5b shall be the maximum width in each part, and the width | variety of the part adjacent to an edge part and a bending part shall be the minimum width in the adjacent part. Here, the extending direction is based on the side on the side where the lug is depressed, for example, each side of 4c, 4d and 4e in FIG. The parallel line is the extending direction. In addition, when the reference | standard side of the step of the lug is a curve, the line segment which connects an edge part and a bending part is made into each side.
[0023]
Next, in the agricultural machine tire according to the present invention, as shown in FIG. 5, the lug 4 is expanded to the end surface 4b of the buttress portion of the lug 4 from the end surface to the kicking side of the lug 4 and A recess 7 is provided around the region communicating with the lug groove 6, and design is imparted to the tire along with further weight reduction of the lug.
[0024]
That is, the buttress surface of the lug 4 that has entered the soil with the rolling of the tire receives a tangential force from the soil in the tire circumferential direction due to the rotation of the tire. Therefore, in the recess provided in the end surface 4b of the lug, If there is an edge as shown in FIG. 2, a vertical force is applied to the step portion (3a portion in FIG. 2), which becomes a core to which mud adheres.
[0025]
On the other hand, as shown in FIG. 5, the recess 7 provided in accordance with the present invention communicates with the lug groove 6 at the end of the recess 7 and does not have the above-described stepped portion, in other words, mud Since there is no adhering nucleus, mud adherence to the recess can be avoided.
[0026]
Here, the opening width of the recess 7 in the tire radial direction is preferably d: 1.3 to 1.7 c, where c is the starting side and d is the lug groove 6 side. That is, if the opening width d on the lug groove 6 side is approximately the same as the opening width c on the starting side, two sides (in FIG. As a result of the above vertical force also being applied to the edge of the edge (corresponding to the side), it becomes the core of mud adhesion. This phenomenon can be avoided by preventing a vertical force from being applied to the edges of the two sides. For this purpose, d: 1.3 to 1.7 c is recommended.
[0027]
Further, the start side of the lug 4 on the step side, that is, the start end 4s in FIG. 3 is located away from the equator O of the tire, so that mud adheres between the lugs when the tire rolls, particularly when used in a muddy area. It is advantageous in preventing the above.
[0028]
Further, the end of the lug 4 on the equator O side of the tire, that is, the end 4a on the stepping side has a direction intersecting with the extending direction of the lug, while maintaining the above-described performance of preventing mud adhesion. This is effective for securing the rigidity of the land near the stepped side end.
[0029]
By the way, the end of the lug stepping side generally has a tip wall surface having a shape along the contour thereof. In the example shown in FIG. 3, the tip wall surface of the end 4a protrudes in the traveling direction. Presents a mold. When traveling in a wetland or a field, the end portion 4a having such a mountain-shaped tip wall surface distributes soil at the portion protruding in the traveling direction of the mountain-shaped tip wall surface, and escapes to both sides thereof. Tires tend to sink slightly in the soil. And it was newly found that the traction force of agricultural machinery tires is reduced by this sinking.
[0030]
That is, as the amount of tire subsidence increases, the amount of soil with the advance of the tire also increases and the running resistance increases, resulting in a substantial decrease in traction force.
[0031]
Therefore, as shown in FIG. 7, at the end portion 4a on the stepping side of the lug 4 shown in FIG. When advanced, a structure is provided in which the soil cannot escape to both sides of the end portion 4a. That is, the tip wall surface 8 parallel to the tire rotation axis is in contact with the ground in the tire traveling direction, so that the soil can be pressed and solidified under the tip wall surface 8. As a result of the lag riding on the solidified soil, the above-mentioned sinking is avoided and an improvement in traction force is achieved.
[0032]
In addition, it is necessary to provide the front end wall surface 8 parallel to the rotation axis of the tire so as to correspond to at least the most distal portion on the stepping side in the end portion 4a, as indicated by the dotted line in FIG. Specifically, as shown in FIG. 7 (c), the boundary point P (in the example of FIG. 7, the inflection point between the end 4a and its adjacent region) that is separated from the tire equator O at the end 4a. It is preferable that the width t of the tip wall surface 8 starting from) extends about 30 to 80% of the distance T from the point P to the equator O of the tire.
[0033]
Of course, you may provide the front end wall surface 8 parallel to the rotating shaft of a tire over the whole region of the edge part 4a. For example, in the lug pattern shown in FIG. 8, the entire region of the end 4a is parallel to the tire rotation axis, and in this case, the tip wall surface 8 parallel to the tire rotation axis is provided over the entire region of the end 4a. Therefore, the best effect can be obtained with respect to the suppression of subsidence with the expansion of the width. Also in the example of FIG. 8, it is preferable that the width t of the tip wall surface 8 covers about 30 to 80% of the distance T from the point P to the equator O of the tire.
[0034]
Further, the vicinity of the stepped side end portion 4a is a portion where the gap between the lugs is the narrowest, so that the soil is easily clogged. When the soil is clogged, the traction force is reduced due to the decrease in the gripping force due to the lag pattern. In providing the tip wall surface 8 here, the inclination angle α of the tip wall surface with respect to the plane including the rotation axis of the tire shown in FIGS. 7 (b) and 8 (b) is in the range of 25 to 45 °. However, it is advantageous in improving soil discharge.
[0035]
That is, the relationship between the inclination angle of the tip wall surface 8 with respect to the surface including the rotation axis of the tire, the traction force and the amount of mud clogging in the vicinity of the tread center, as shown in FIG. 9 and FIG. It can be seen that the inclination angle α should be in the range of 25 to 45 °. As for the amount of mud clogging, excellent results have been obtained when the inclination angle α is in the range of 40 to 50 °. However, as the inclination angle α exceeds 45 ° and approaches to the horizontal, the edge effect due to the lug becomes effective. As a result of the damage, the overall traction force decreases, and therefore, the angle is preferably 45 ° or less. Further, considering the effect of weight reduction, it is advantageous that the inclination angle α is 30 ° or about 5 ° before and after that.
[0036]
【Example】
According to what is shown in FIG. 1 (conventional example), FIG. 3 (invention example 1), FIG. 7 (invention example 2) and FIG. 8 (invention example 3), the size is 9.5-24 under various specifications shown below. Tires for agricultural machinery for rear wheels were prototyped. In addition, the other structure was produced according to the general of the tire for agricultural machines of the said size.
[0037]

[0038]
Each tire obtained in this way was incorporated into a standard rim, adjusted to the internal pressure and load shown in Table 1, and then mounted on the rear wheel of a 25 horsepower tractor or subjected to a drum test. Evaluation of each item was performed according to the conditions shown in Table 1. Went. Moreover, the tire for agricultural machinery of size 6-14 was used in common for the front wheel. The results are also shown in Table 1 as an index when the result of the conventional tire is set to 100.
[0039]
[Table 1]

[0040]
【The invention's effect】
According to this invention, weight reduction can be realized without impairing basic performance as a tire for agricultural machinery.
[Brief description of the drawings]
FIG. 1 is a view showing a tread pattern of a conventional agricultural machine tire.
FIG. 2 is a perspective view showing a lug of a conventional agricultural machine tire.
FIG. 3 is a view showing a tread pattern of an agricultural machine tire according to the present invention.
FIG. 4 is a diagram showing a tread pattern of an agricultural machine tire according to the present invention.
FIG. 5 is a perspective view showing a lug of an agricultural machine tire according to the present invention.
FIG. 6 is a diagram for explaining a method for evaluating uneven wear of lugs.
FIG. 7 is a view showing another tread pattern of an agricultural machine tire according to the present invention.
FIG. 8 is a view showing another tread pattern of the agricultural machine tire of the present invention.
FIG. 9 is a diagram showing a relationship between an inclination angle of a tip wall surface with respect to a surface including a rotation axis of a tire and traction force.
FIG. 10 is a diagram showing a relationship between an inclination angle of a tip wall surface with respect to a surface including a rotation axis of a tire and an amount of mud clogging.
[Explanation of symbols]
1 tread 2 lug 3 recess 4 lug 4a end

4b end surface

5a, 5b bent part 6 lug groove 7 recess 8 tip wall

Claims

Agricultural machinery tire in which a plurality of lugs extending from the tire equator to the tread end side in a direction inclined with respect to the tire equator are arranged at intervals in the circumferential direction of the tread. It extends through at least one bent portion to the tread end side, and Ri formed by narrowing the width of the portion excluding the end portion and the bent portion of the equator side of the tire,
An agricultural machine tire characterized by having a recess on an end face of a buttress portion of a lug, which expands from the end face to the lug kick-out side and communicates with the lug groove on the kick-out side .

2. The agricultural machine according to claim 1, wherein the width of a portion adjacent to the end portion and the bent portion of the equator side of the lug tire is 50 to 90% of the width at the end portion and the bent portion. tire.

The tire for agricultural machinery according to claim 1 or 2, wherein the opening width in the tire radial direction of the recess is 1.3 to 2.5 times the lug groove side from the starting side.

4. The agricultural machine tire according to claim 1, 2, or 3, wherein the starting side of the lug is located at a position separated from the equator of the tire.

In any one of claims 1 to 4, agricultural machines tire equatorial side end surface of the tire lugs, characterized in that it has a direction crossing the extending direction of the lug.

5. The equator-side end portion of the lug tire according to claim 1 has a tip wall surface parallel to the rotation axis of the tire, and the tip wall surface with respect to a plane including the rotation axis of the tire. An agricultural machine tire characterized by being inclined at an angle of 25 to 45 °.