JP2004114797A

JP2004114797A - Turning control apparatus for working vehicle

Info

Publication number: JP2004114797A
Application number: JP2002279345A
Authority: JP
Inventors: Yukifumi Yamanaka; 山中　　之史; Yoshihiro Ueda; 上田　　吉弘; Shigeki Hayashi; 林　繁樹; Yuji Kato; 加藤　裕治; Futoshi Ikeda; 池田　太; Katsuhide Kato; 加藤　　勝秀
Original assignee: Kubota Corp
Current assignee: Kubota Corp
Priority date: 2002-09-25
Filing date: 2002-09-25
Publication date: 2004-04-15

Abstract

<P>PROBLEM TO BE SOLVED: To provide a turning control apparatus for a working vehicle enabling small turning with a small turning radius without a widened range of moving operation and specifically gentle turning with fine adjustment and eliminating disadvantages such as shocks to a car body caused by abrupt change in a running state of a running device. <P>SOLUTION: A pair of continuous variable transmissions 11R,11L to vary running speed of left and right running devices individually and continuously are respectively speed variably mounted in the turning control apparatus. The relation between a moving amount of a turning lever 26 from a straight-forward command position and a turning radius is determined in correspondence to a quadratic function to enlarge the turning radius as the moving amount widens and to change to the larger side a variation amount of the turning radius per a unit amount of the moving amount over a whole range. An operation mechanism 30 for running is actuated to attain a target turning radius obtained based on an operational position of the turning lever 26 and the relation with the secondary function. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、左右一対の走行装置の走行速度を各別に無段階に変速する一対の無段変速装置と、その一対の無段変速装置を各別に変速操作自在な変速操作手段と、前記直進状態を指令する直進指令位置及び前記旋回状態を指令する旋回指令用操作領域の全範囲にわたり移動操作自在で、且つ、前記旋回状態として、前記旋回指令操作領域において直進指令位置から離れる方向への移動量が大きいほど旋回半径が小さい旋回状態を指令する旋回指令手段と、前記旋回指令手段の指令情報に基づいて直進及び旋回を行うべく前記変速操作手段を作動させる旋回制御を実行する制御手段とが備えられている作業車の旋回制御装置に関する。
【０００２】
【従来の技術】
上記構成の作業車の旋回制御装置は、例えばコンバイン等の作業車に適用されるものであり、従来では、次のような構成のものがあった。
つまり、前記一対の無段変速装置として静油圧式の無段変速装置を用いて、変速操作手段として一対の電動モータが設けられ、一対の無段変速装置夫々の出力回転速度を一対の回転センサにて検出して、これらの回転センサの検出値が夫々目標とする出力回転速度になるように各電動モータにより一対の無段変速装置を作動させるように構成され、しかも、これらの無段変速装置の伝動下手側に動力伝達を入り切り自在な操向クラッチと各走行装置を制動自在な操向ブレーキとが備えられる構成のものがあり、前記旋回制御として、次のような処理を実行する構成のものがあった。つまり、旋回モードとして、緩旋回モード、ブレーキ旋回モード、スピン旋回モードがあり、そのうちの緩旋回モードでは、旋回指令手段としてのパワステレバーの直進指令位置から離れる方向への移動量が大きく大きい旋回半径を指令するほど、左右一対の無段変速装置のうち旋回中心から離れる側の無段変速装置の出力回転速度を基準として旋回中心側の無段変速装置を無段階に減速させる形態で、且つ、パワステレバーの操作位置の単位量あたりの変化に対する旋回半径の変化量が全操作範囲にわたって一定となる形態で、一対の無段変速装置の回転速度の比率を変化させることにより旋回するときの旋回半径を小さくさせるように変速操作手段の作動を制御するように構成したものがあった。尚、ブレーキ旋回モードでは、パワステレバーの旋回用の操作角度が大になると旋回中心側の走行装置に対して操向クラッチを切り且つ操向ブレーキを作動させる状態で旋回を行い、スピン旋回モードでは、操向クラッチの切り及び操向ブレーキの作動に加えて、パワステレバーの旋回用の操作角度が大になると、旋回中心側の走行装置が逆回転する状態に切り換わるようになっている（例えば、特許文献１参照。）。
【０００３】
【特許文献１】
特開平８−１７２８７１号公報（第３頁―第５頁、図７、図８）
【０００４】
【発明が解決しようとする課題】
上記従来構成では、旋回指令手段の操作位置の移動に伴って旋回半径を無段階に滑らかに変更させることができる利点があるものの、旋回指令手段の操作位置の単位量あたりの変化に対する旋回半径の変化量が全操作範囲にわたって一定となる形態で一対の無段変速装置の回転速度の比率を変化させることにより旋回半径を小さくさせる構成であるから、旋回指令手段を旋回指令用操作領域における直進指令位置から離れる方向へ少しだけ移動操作させるようにしても旋回状態が大きく変化してしまうので、直進状態から微調節しながら緩やかに旋回を行うことが適正に行えないものになる不利がある。
例えばコンバイン等のように植付け作物を収穫するような作業車であれば、車体を作物の植付け列に沿わせるために旋回操作を行うような場合において、旋回状態を微調節しながら緩やかな旋回を行う必要があるが、上記従来構成においては、旋回指令手段を旋回指令用操作領域における直進指令位置から離れる方向へ少しだけ移動操作させても旋回半径が大きく変化してしまうので、このような微調節による旋回操作が行い難いものとなる。
【０００５】
尚、このような不利を回避するためには、旋回指令手段を操作したときに旋回指令用操作領域の全範囲にわたって微調節できるように、旋回状態を緩やかに変化させる形態にすることが考えられるが、このように構成すると、旋回指令手段を最大操作位置まで操作してもそのときに旋回半径が充分小さくならず、小さい旋回半径で小回り旋回を行い難いものとなる。
上記従来技術では、小さい旋回半径にさせるためには、旋回モードを緩旋回モードからブレーキ旋回モードやスピン旋回モードに切り換えることで対応可能であるが、作業走行中にこのような旋回モードの切り換えを行うのは煩わしいものとなる不利があり、しかも、ブレーキ旋回モードやスピン旋回モードに切り換えた状態では、旋回指令手段を旋回指令用操作領域における直進指令位置から離れる方向へ移動させた場合に、その移動操作の途中において旋回中心側の走行装置の走行状態が急に変化して車体にショックが発生し操縦者の乗り心地が悪化するといった不利もある。
【０００６】
又、上記不利を回避するための別の方法として、前記旋回指令用操作領域における旋回指令手段が移動操作可能な範囲を広くさせて、旋回指令手段の操作位置の単位量当たりの変化に対する旋回半径の変化量を旋回指令用操作領域の全域にわたり小さいものにすることも考えられるが、この構成では、直進状態から小さい旋回半径の旋回状態に操作するような場合に、旋回指令手段を大きく移動操作させる必要があり、旋回のための操作が煩わしいものとなる不利がある。
【０００７】
本発明はかかる点に着目してなされたものであり、その目的は、旋回指令手段の旋回指令用操作領域における移動操作範囲を不必要に広くさせることなく旋回指令手段の移動量を大きくさせたときに小さい旋回半径の旋回状態にさせることができ、しかも、旋回指令手段の移動量が少ない状態では微調節しながら緩やかに旋回を行うことが可能となり、更には、旋回指令用操作領域の全領域において旋回指令手段を移動操作させても走行装置の走行状態が急に変化して車体にショックが発生するといった不利の生じ難い作業車の旋回制御装置を提供する点にある。
【０００８】
【課題を解決するための手段】
請求項１に記載の作業車の旋回制御装置は、左右一対の走行装置の走行速度を各別に無段階に変速する一対の無段変速装置と、その一対の無段変速装置を各別に変速操作自在な変速操作手段と、前記直進状態を指令する直進指令位置及び前記旋回状態を指令する旋回指令用操作領域の全範囲にわたり移動操作自在で、且つ、前記旋回状態として、前記旋回指令操作領域において直進指令位置から離れる方向への移動量が大きいほど旋回半径が小さい旋回状態を指令する旋回指令手段と、前記旋回指令手段の指令情報に基づいて直進及び旋回を行うべく前記変速操作手段を作動させる旋回制御を実行する制御手段とが備えられているものであって、前記制御手段が、前記旋回制御として、前記旋回指令手段の前記旋回指令操作領域における直進指令位置から離れる方向への移動量と前記旋回半径との関係を、前記旋回指令操作領域における直進指令位置から離れる方向への移動量が大になるほど旋回半径が小さくなり、且つ、前記旋回指令操作領域の全範囲にわたって、前記旋回指令操作領域における直進指令位置から離れる方向への移動量が大になるほど、前記旋回指令手段の操作位置の単位量あたりの変化に対する旋回半径の変化量を大側に変化させる二次関数に対応する関係として定めて、この二次関数に対応する関係として定められる前記旋回指令操作領域における直進指令位置から離れる方向への移動量と旋回半径との関係、及び、前記旋回指令手段の操作位置に基づいて、その旋回指令手段の操作位置に対応する目標旋回半径を求めて、旋回半径がその目標旋回半径になるように前記変速操作手段を作動させるように構成されていることを特徴とする。
【０００９】
すなわち、旋回指令手段により旋回状態が指令されると、上記したように二次関数に対応する関係として定められる旋回指令操作領域における直進指令位置から離れる方向への移動量と旋回半径との関係、及び、旋回指令手段の操作位置に基づいて、その旋回指令手段の操作位置に対応する目標旋回半径を求める。つまり、旋回指令手段の旋回指令操作領域における直進指令位置から離れる方向への移動量が大になるほど旋回半径が小さくなり、しかも、旋回指令操作領域の全範囲にわたって、前記移動量が大になるほど、旋回指令手段の操作位置の単位量あたりの変化に対する旋回半径の変化量を大側に変化させる二次関数にて定められる値として目標旋回半径が求められる。そして、旋回半径がその目標旋回半径になるように前記変速操作手段を作動させるのである。
【００１０】
前記旋回指令手段の旋回指令操作領域における直進指令位置から離れる方向への移動量が少ない状態であれば、旋回指令手段の操作位置の単位量あたりの変化に対する旋回半径の変化量が小さいので、旋回指令手段を操作させても旋回半径が大きく変化することがないので、直進指令位置から離れる方向へ少しだけ移動操作させるようにしても旋回状態が大きく変化することがなく、直進状態から微調節しながら緩やかに旋回を行うことを適正に行い易いものになる。
【００１１】
又、旋回指令操作領域の全範囲にわたって、前記移動量が大になるほど、旋回指令手段の操作位置の単位量あたりの変化に対する旋回半径の変化量を大側に変化させる二次関数にて定められる値として目標旋回半径が求められるので、操作位置の単位量あたりの変化に対する旋回半径の変化量が一定に設けられるものに比べて、旋回指令用操作領域における移動操作範囲が同じであっても旋回指令手段を最大操作位置まで移動させたときの旋回半径を小さい旋回半径にさせることが可能であり、しかも、旋回指令操作領域の全範囲にわたって二次関数にて定められる値として目標旋回半径が求められるので、旋回指令手段を旋回指令操作領域の全範囲にわたって移動させても、その移動途中において目標旋回半径が急激に変化することがなく旋回半径が滑らかに変化することになるので、旋回操作の途中において旋回中心側の走行装置の走行状態が急に変化して車体にショックが発生することがない。
【００１２】
従って、旋回指令手段の旋回指令用操作領域における移動操作範囲を不必要に広くさせることなく旋回指令手段の移動量を大きくさせたときに小さい旋回半径の旋回状態にさせることができ、しかも、旋回指令手段の移動量が少ない状態では微調節しながら緩やかに旋回を行うことが可能となり、更には、旋回指令用操作領域の全領域において旋回指令手段を移動操作させても走行装置の走行状態が急に変化して車体にショックが発生するといった不利の生じ難い作業車の旋回制御装置を提供できるに至った。
【００１３】
請求項２に記載の作業車の旋回制御装置は、請求項１において、前記制御手段が、前記二次関数に対応する関係として定められる前記旋回指令手段の前記旋回指令操作領域における直進指令位置から離れる方向への移動量と前記旋回半径との関係に相当する数式情報と、前記旋回指令手段の指令情報に基づいて、前記目標旋回半径を求めるように構成されていることを特徴とする。
【００１４】
このように前記旋回指令手段における前記移動量と前記旋回半径との関係が数式情報にて定められているので、制御手段は、旋回指令手段の指令情報をこの数式に当てはめて演算によって簡単に目標旋回半径を求めることができ、例えば、前記移動量と前記旋回半径との関係をマップデータのような多くのデータ数を有する情報として記憶する構成に比べて、制御構成が簡素になる利点があるとともに、数式に基づいて演算するだけの処理でよく処理に要する時間も短くなるので、制御応答性を向上できる利点もある。
【００１５】
請求項３記載の作業車の旋回制御装置は、請求項２において、前記制御手段が、前記二次関数に対応する関係として定められる前記旋回指令手段の前記旋回指令操作領域における直進指令位置から離れる方向への移動量と前記旋回半径との関係として、前記旋回指令手段の操作位置が同じであるときのその操作位置に対応する旋回半径が異なる複数種のものを記憶して、その記憶している複数種の関係のうちのいずれか一つを選択する人為操作式の選択手段にて選択された関係に基づいて、その旋回指令手段の操作位置に対応する目標旋回半径を求めて旋回半径がその目標旋回半径になるように前記変速操作手段を作動させるように構成されていることを特徴とする。
【００１６】
すなわち、前記旋回指令手段の前記移動量と前記旋回半径との関係として、前記旋回指令手段の操作位置が同じであるときのその操作位置に対応する旋回半径が異なる複数種のものが記憶されており、そのうちのいずれか１つが人為操作式の選択手段にて選択されることになる。そして、選択された関係に基づいて目標旋回半径を求めて、旋回半径がその目標旋回半径になるように変速操作手段を作動させるのである。
【００１７】
つまり、作業車の作業状況として想定される複数の作業状況や、操作者の旋回操作に対する熟練度の違い等に対応させて、そのときに適合した旋回操作内容で旋回を行うことが可能なように予め複数の関係を定めて記憶しておき、適宜、作業者が判断して人為操作式の選択手段にて選択することで、そのときの実際の作業状況や操作者の旋回操作に対する熟練度の違い等に応じた旋回操作内容で旋回を行うことができる。
【００１８】
請求項４記載の作業車の旋回制御装置は、請求項３において、前記複数種の関係が、前記旋回指令手段が前記旋回指令用操作領域のうち前記移動量が最も大きい最大操作位置に操作されたときの旋回半径が互いに異なる形態のものとして設定されていることを特徴とする。
【００１９】
すなわち、前記旋回指令手段が最大操作位置に操作されたときの旋回半径が互いに異なる形態の複数種の関係として設定されるので、作業状況や、操作者の旋回操作に対する熟練度の違い等に応じて適切なものに設定しておくと、操作者が小さい旋回半径にて旋回させる必要であると感じて、例えば、旋回指令手段を大きな操作力で移動操作させた場合に途中の操作位置にまで操作させる積もりであっても誤って最大操作位置にまで操作させるようなことがあっても、その最大操作位置に操作されたときの旋回半径を操作者が適正なものとして任意に変更設定された旋回半径として設定することができるので、常に適切な旋回半径で旋回操作を行うことが可能となる。
【００２０】
請求項５記載の作業車の旋回制御装置は、請求項１〜４のいずれかにおいて、前記制御手段が、前記旋回制御として、前記一対の走行装置のうち旋回中心に対して離れる側に位置する走行装置が車速指令手段にて指令される目標車速に対応する走行速度に維持され、且つ、旋回中心側に位置する走行装置が前記旋回指令手段の前記旋回指令操作領域における直進指令位置から離れる方向への移動量が大きくなるほど走行速度が減速する形態で、前記変速操作手段を作動させるよう構成されていることを特徴とする。
【００２１】
すなわち、旋回中心側に位置する走行装置が減速して旋回するので、旋回半径を小さくして小回り旋回させることが可能な状態となり、しかも、旋回中心に対して離れる側に位置する走行装置が車速指令手段にて指令される目標車速に対応する走行速度に維持されるので、例えば、旋回指令手段にて直進が指令されて車速指令手段にて指令される目標車速にて直進走行している状態から、旋回指令手段にて旋回が指令される状態に切り換わったような場合、又は、旋回走行している状態から直進走行に切り換わったような場合であっても、旋回中心に対して離れる側に位置する走行装置の走行速度がほとんど変化しないので速度変化によるショック等が少なく走行安定性が向上するものとなる。
【００２２】
【発明の実施の形態】
以下、本発明に係る作業車の旋回制御装置の実施形態を作業車の一例としてのコンバインに適用した場合について図面に基づいて説明する。
【００２３】
図１に作業車の一例であるコンバインの全体側面が示されており、このコンバインは、走行装置の一例である左右一対のクローラ式走行装置１Ｒ、１Ｌの駆動で走行する走行機体２の前部に、植立穀稈を刈り取って後方に向けて搬送する刈取搬送装置３を昇降可能に連結し、走行機体２に、刈取搬送装置３からの刈取穀稈を受け取って脱穀処理並びに選別処理を実行する脱穀装置４と、脱穀装置４からの穀粒を貯留する穀粒タンク５とを搭載するとともに、穀粒タンク５の前方箇所に搭乗運転部６を形成することによって構成されている。
【００２４】
図２に示すように、このコンバインは、エンジン７からの動力を、ベルトテンション式の主クラッチ８を介してミッションケース９の入力軸１０に伝達し、この入力軸１０から走行用の一対の無段変速装置１１Ｒ、１１Ｌに分配伝達し、走行用の一方の無段変速装置１１Ｌによる変速後の動力を左側のギヤ式の副変速装置１３Ｌを介して左側のクローラ式走行装置１Ｌに伝達し、走行用の他方の無段変速装置１１Ｒによる変速後の動力を、右側のギヤ式の副変速装置１３Ｒを介して右側のクローラ式走行装置１Ｒに伝達するようにして走行駆動用の伝動機構を構成している。一方、エンジン７からの動力が作業用の無段変速装置１２にも供給され、その作業用の無段変速装置１２による変速後の動力を、ベルトテンション式の刈取クラッチ１４を介して刈取搬送装置３に伝達するようにして刈取作業用の伝動機構を構成している。左右のギヤ式の副変速装置１３Ｒ、１３Ｌは、前記各無段変速装置１１Ｒ、１１Ｌの変速後の動力を高低２段に切り換え自在に構成されている。又、搭乗運転部６には、前後方向に揺動操作可能な単一の副変速レバー２５が設けられ、この副変速レバー２５は、図示しない連係機構を介してギヤ式の副変速機構１３Ｒ、１３Ｌに連係されており、副変速レバー２５の操作によって、走行用の各無段変速装置１１Ｒ、１１Ｌによる変速後の動力を高低２段に変速できるようになっている。
【００２５】
走行用の各無段変速装置１１Ｒ、１１Ｌは、アキシャルプランジャ形式で可変容量型のピストンポンプ１９とピストンモータ２０とを夫々備えて静油圧式の無段変速装置として構成され、作業用の無段変速装置１２も同様に、アキシャルプランジャ形式で可変容量型のピストンポンプ２１とピストンモータ２２とを備えて静油圧式無段変速装置として構成され、左右のクローラ式走行装置１Ｒ、１Ｌ夫々の走行方向を前進方向並びに後進方向に切り換え且つ走行速度を無段階に変速することができる構成となっている。
【００２６】
そして、図３に示すように、走行用の各無段変速装置１１Ｒ、１１Ｌを各別に変速操作する変速操作手段としての油圧式の走行用操作機構３０と、作業用の無段変速装置１２を変速操作する油圧式の作業用操作機構３６とが夫々備えられている。前記走行用操作機構３０は、走行用の各無段変速装置１１Ｒ、１１Ｌの夫々におけるトラニオン軸２９（被操作体の一例）に連動連結された一対の複動型の油圧シリンダ３３Ｒ、３３Ｌと、これらの各油圧シリンダ３３Ｒ、３３Ｌに対する正逆方向夫々の操作に対応する一対の油室に作動油を供給する状態と供給を停止する状態とに切り換え自在な一対の２位置切換式の給油用電磁弁３４Ａと、前記一対の油室から作動油を排出する状態と排出を停止する状態とに切り換え自在な一対の２位置切換式の排油用電磁弁３４Ｂとを備えて構成されている。前記各油圧シリンダ３３Ｒ、３３Ｌは、内装されるバネの付勢力により中立位置に復帰付勢される構成となっている。
【００２７】
前記作業用操作機構３６も同様に、作業用の無段変速装置１２におけるトラニオン軸３７に連動連結されるとともに、内装されるバネの付勢力により中立位置に復帰付勢される構成の複動型の油圧シリンダ４０と、この油圧シリンダ４０に対する正逆方向夫々の操作に対応する一対の油室に作動油を供給する状態と供給を停止する状態とに切り換え自在な一対の２位置切換式の給油用電磁弁４１Ａと、前記一対の油室から作動油を排出する状態と排出を停止する状態とに切り換え自在な一対の２位置切換式の排油用電磁弁４１Ｂとを備えて構成されている。
【００２８】
前記各給油用電磁弁３４Ａ、４１Ａは、バネの付勢力によってスプールを給油停止状態に移動付勢する構成となっており、ソレノイドによる電磁力によってバネの付勢力に抗してスプールを移動操作して作動油を供給する状態に切り換える構成となっており、又、前記各排油用電磁弁３４Ｂ、４１Ｂは、バネの付勢力によってスプールを排出状態に移動付勢される構成となっており、ソレノイドによる電磁力によってバネの付勢力に抗してスプールを移動操作して作動油の排出を停止する状態に切り換わる構成となっている。
【００２９】
上記したような無段変速装置１１Ｒ、１１Ｌの変速動作の概略について説明を加えると、図４に示すように、トラニオン軸２９の変速位置が中立域にあれば変速出力（走行速度）は零となり、トラニオン軸２９の変速位置がその中立域から所定方向に回動操作されると前進方向への走行速度が無段階に増速操作され、トラニオン軸２９が中立域から所定方向と反対方向に回動操作されると後進方向への走行速度が無段階に増速操作される構成となっている。
【００３０】
搭乗運転部６には、走行停止を指令する停止用指令位置としての中立位置を含む所定操作範囲内で車体前後方向に沿って移動自在で、且つ、中立位置からの前方側への移動操作量が大きくなるほど高速となる目標車速を指令し、中立位置からの後方側への移動操作量が大きくなるほど高速となる目標車速を指令するレバー操作式の人為操作具としての単一の主変速レバー２４、及び、左右方向に沿って所定の左右操作範囲にわたり揺動操作可能な旋回指令手段としての単一の旋回レバー２６などが装備されている。そして、図３に示すように、主変速レバー２４の操作位置を検出する変速レバーセンサ２７と、旋回レバー２６の操作位置を検出する操作位置検出手段としての旋回レバーセンサ２８とが夫々設けられ、それらは共に回転式のポテンショメータにて構成されている。
【００３１】
又、走行用の一対の無段変速装置１１Ｒ、１１Ｌには、それらの出力回転速度を各別に検出する変速出力検出手段としての回転速度センサ４４、４５と、夫々の無段変速装置１１Ｒ、１１Ｌの変速位置、すなわち、一対の油圧シリンダ３３Ｒ、３３Ｌによる夫々のトラニオン軸２９の操作角度を検出する変速位置検出手段としての回転式のポテンショメータにて構成される変速位置センサ４６、４７とが夫々備えられている。尚、作業用の無段変速装置１２にも同様に回転速度センサ５１が設けられる。
【００３２】
そして、前記走行用操作機構３０の動作を制御する制御手段としてのマイクロコンピュータ利用の制御装置３１が備えられ、この制御装置３１は、主変速レバー２４にて指令される目標車速で車体を直進走行させるべく走行用操作機構３０を作動させる直進制御を実行するとともに、旋回レバー２６にて指令された旋回を行うべく走行用操作機構３０を作動させる旋回制御を実行する構成となっている。
【００３３】
前記直進制御について簡単に説明すると、旋回レバー２６が直進指令位置に操作されて直進が指令されている状態で、主変速レバー２４が操作可能範囲のほぼ中間に位置する中立位置に操作されると走行停止状態となり、中立位置から前進側へ揺動操作されるとそれに伴って前進側への走行速度が無段階で高速となる目標車速が指令され、中立位置から後進側へ操作されるとそれに伴って後進側への走行速度が無段階で高速となる目標車速が指令される。そして、左右一対の無段変速装置１１Ｒ、１１Ｌの夫々トラニオン軸２９が目標車速に対応する目標変速位置から離れているときは、左右一対の無段変速装置１１Ｒ、１１Ｌ夫々のトラニオン軸２９を目標車速に対応する目標変速位置になるように走行用操作機構３０を作動させる。そして、いずれかの無段変速装置のトラニオン軸２９が目標変速位置に至ると、いずれか一方の無段変速装置はトラニオン軸２９が目標変速位置に維持されるように制御されるが、他方の無段変速装置はその出力回転速度が、前記一方の無段変速装置の出力回転速度と同じ速度になるように速度同期処理が行われる。
【００３４】
次に、旋回制御について説明すると、制御装置３１は、主変速レバー２４が操作されて所定速度で走行しているときに、旋回レバー２６が直進指令位置から左右いずれかの旋回指令範囲に揺動操作されると、前記直進指令位置から離れる側に操作されるほど旋回半径が小さくなる旋回状態となるように走行用操作機構３０を作動させるように構成されている。
説明を加えると、制御装置３１は、前記旋回制御として、一対の無段変速装置１１Ｒ、１１Ｌのうちのいずれか一方の無段変速装置を基準側の無段変速装置として、その基準側の無段変速装置におけるトラニオン軸２９の変速位置が目標変速位置になるように走行用操作機構３０を作動させる変速位置調整処理、基準側の無段変速装置の出力回転速度と反対側の無段変速装置の出力回転速度との速度比率が、旋回レバー２６にて指令される旋回半径に対応する速度比率となるように反対側の無段変速装置の目標回転速度を求める目標速度設定処理、及び、反対側の無段変速装置の出力回転速度が前記目標回転速度になるように走行用操作機構３０を作動させる回転速度調整処理の夫々を実行するように構成されている。
【００３５】
しかも、制御装置３１は、前記旋回制御として、旋回レバー２６の旋回指令操作領域における直進指令位置から離れる方向への移動量と旋回半径に対応する速度比率との関係を、前記旋回指令操作領域における直進指令位置から離れる方向への移動量が大になるほど旋回半径が小さい速度比率となり、且つ、前記旋回指令操作領域の全範囲にわたって、旋回指令操作領域における直進指令位置から離れる方向への移動量が大になるほど、旋回レバー２６の操作位置の単位量あたりの変化に対する旋回半径（速度比率）の変化量を大側に変化させる二次関数に対応する関係として定めて、この二次関数に対応する関係として定められる旋回指令操作領域における直進指令位置から離れる方向への移動量と旋回半径に対応する速度比率との関係、及び、旋回レバー２６の操作位置に基づいて、その旋回レバー２６の操作位置に対応する目標旋回半径としての目標速度比率を求めて、旋回半径に対応する実際の速度比率がその目標速度比率になるように走行用操作機構３０を作動させるように構成されている。
【００３６】
更に、制御装置３１は、上述したように前記二次関数に対応する関係として定められる旋回レバーの旋回指令操作領域における直進指令位置から離れる方向への移動量と旋回半径に対応する速度比率との関係は、具体的には、数式情報として記憶して設定されており、制御装置３１は、旋回レバーの指令情報とのこの数式情報とに基づいて、目標旋回半径に対応する目標速度比率を求めるように構成されている。
【００３７】
以下、フローチャートに基づいて制御装置３１の旋回制御の処理動作について具体的に説明する。
図６に示すように、旋回レバー２６が直進指令位置から左右いずれかの旋回指令範囲に揺動操作されて旋回が指令され、例えば右方向に旋回が指令されている場合には（ステップ１、２）、旋回中心に対して離れる側に位置する無段変速装置である左側の無段変速装置１１Ｌを基準側の無段変速装置として、その基準側の無段変速装置におけるトラニオン軸２９の変速位置が目標変速位置になるように走行用操作機構３０を作動させる変速位置調整処理を実行する（ステップ３）。
【００３８】
この変速位置調整処理について説明を加えると、図７に示すように、先ず、左側の無段変速装置１１Ｌにおけるトラニオン軸２９に対する目標変速位置を計算にて求める（ステップ３１）。このとき、主変速レバー２４にて指令されている目標車速に対応するトラニオン軸２９の変速位置を前記目標変速位置として設定するようになっている。
【００３９】
次に、この目標変速位置と、変速位置センサ４７にて検出される現在のトラニオン軸２９の変速位置との偏差を求めて、その位置偏差が小さくなるように走行用操作機構３０を作動させてトラニオン軸２９の変速位置を変更調整する（ステップ３２、３３）。具体的には、走行用操作機構３０における給油用電磁弁３４Ａ及び各排油用電磁弁３４Ｂを切り換え制御して油圧シリンダ３３Ｒの作動を制御するのである。
【００４０】
次に、上記したようにして変速位置調整が行われる左側の無段変速装置１１Ｌの出力回転速度を回転速度センサ４５にて検出して、左側の無段変速装置１１Ｌの出力回転速度と右側の無段変速装置１１Ｒの出力回転速度との速度比率が、旋回レバー２６にて指令される旋回半径に対応する速度比率となるように右側の無段変速装置１１Ｒの目標回転速度を求める目標回転速度設定処理を実行する（ステップ４）。
【００４１】
つまり、旋回レバー２６の操作位置に対する旋回半径に対応する値としての左右の無段変速装置１１Ｒ、１１Ｌの速度比率の関係が、例えば図８に示すような相関関係となるように、それらの関係に相当する数式情報が予め設定されて記憶されている。そして、その数式情報と、旋回レバー２６の操作位置による指令情報とに基づいて、右側の無段変速装置１１Ｒの目標回転速度を求めるのである。
図８に示す関係について説明を加えると、この図は、旋回レバー２６の操作位置の変化に対して、基準側すなわち旋回中心に対して離れる側に位置する無段変速装置の出力回転速度Ｖを基準として、旋回中心側に位置する無段変速装置の速度比率の変化を示している。ステップ４では、右側の無段変速装置１１Ｒが旋回中心側に位置する無段変速装置であるから、この速度比率から右側の無段変速装置１１Ｒの目標回転速度を求めることになる。
【００４２】
図８に示すように、旋回レバー２６の操作位置に対する速度比率が、旋回レバー２６による中立位置からの移動量が大になるほど、旋回レバー２６の操作位置の単位量当たりの変化に対して漸次大側に変化する形態で、且つ、中立位置から離れる方向への移動量が大になるほど、旋回レバーの操作位置の単位量あたりの変化に対する旋回半径の変化量を大側に変化させる二次関数として設定されている。
その数式情報について具体的に説明すると、基準側すなわち旋回中心に対して離れる側に位置する無段変速装置の出力回転速度Ｖを基準として、旋回中心側に位置する無段変速装置の速度Ｖｏを表す数式として、下記数１に示されるような数式に基づいて演算にて求められることになる。ここで、Ｘは、旋回レバー２６の中立位置から離れる方向への移動量であり、ａ，ｂ，ｃは予め実験データ等に基づいて求められる係数である。
【００４３】
【数１】
Ｖｏ＝Ｖ―（ａＸ^２＋ｂＸ＋ｃ）
【００４４】
そして、旋回レバー２６の直進指令位置から離れる方向への移動量と速度比率との関係として、旋回レバー２６の操作位置が同じであるときのその操作位置に対応する速度比率が異なる複数種のものであって、且つ、旋回レバー２６の移動量が最も大きい最大操作位置に操作されたときの速度比率が互いに異なる旋回モードとなるような複数（図８に示す例では４種類）のものを記憶しており、その記憶している複数種の関係のうちのいずれか一つを選択して演算に使用することができる構成となっている。具体的には、つまり、図８に示すような関係が得られるように、実験結果に基づいて、前記係数ａ，ｂ，ｃを適宜変更させた複数の数式が予め設定されて記憶されており、そのうちのいずれか１つの数式を選択して使用するようになっている。そして、複数の関数のうちのいずれかに切り換えるための人為操作式の選択手段としてのモード切換スイッチ４２が設けられており、このモード切換スイッチ４２による切換指令が制御装置３１に与えられて、制御装置３１は、その切換指令に基づいていずれの関数を利用して目標回転速度を求めるかを決定するようになっている。
【００４５】
図８示す４種類の旋回モードについて説明を加えると、旋回レバー２６が最大操作位置にまで操作されたときに、旋回中心側の無段変速装置の出力回転速度が反対側の無段変速装置の出力回転速度Ｖの約１／３の速度にまで減速されるモード（Ｌ１）、旋回中心側の無段変速装置の出力回転速度が零となるまで減速されるモード（Ｌ２）、旋回中心側の無段変速装置の出力回転速度が反対側の無段変速装置の駆動回転方向とは逆回転方向で反対側の無段変速装置の出力回転速度Ｖの約１／３の速度になるモード（Ｌ３）、旋回中心側の無段変速装置の出力回転速度が反対側の無段変速装置の駆動回転方向とは逆回転方向で反対側の無段変速装置の出力回転速度Ｖと同程度の速度になるモード（Ｌ４）が夫々設定されている。
【００４６】
そして、上述したようにして求められた目標回転速度と現在の右側の無段変速装置１１Ｒの出力回転速度との偏差を求めて、その偏差が小さくなるように、つまり、右側の無段変速装置１１Ｒの出力回転速度が前記目標回転速度になるように走行用操作機構３０を作動させる回転速度調整処理を実行する（ステップ５）。具体的には、前記目標回転速度と現在の右側の無段変速装置１１Ｒの出力回転速度との偏差が小さくなるようにＰＩ制御によって走行用操作機構３０における給油用電磁弁３４Ａ及び各排油用電磁弁３４Ｂを切り換え制御して、出力回転速度が目標回転速度になるようにトラニオン軸２９の変速位置を変更調整するのである。このようにして、左右の走行装置１Ｒ、１Ｌが前記速度比率にて回転駆動されて、旋回レバー２６にて指令された旋回半径にて車体が旋回走行するのである。
【００４７】
ステップ２で旋回方向として左方向が指令されている場合には、右側の無段変速装置１１Ｒを基準側の無段変速装置として、ステップ３〜５と同様な変速位置調整処理、目標速度設定処理、及び、回転速度調整処理の夫々を実行することになる（ステップ６、７、８）。
【００４８】
〔別実施形態〕
次に、別実施形態を列記する。
【００４９】
（１）上記実施形態では、旋回制御において、旋回中心に対して離れる側に位置する走行装置が主変速レバーにて指令される目標車速に対応する走行速度に維持されるように、目標車速に対応するトラニオン軸の変速位置を目標変速位置として設定するように構成したが、このような構成に限らず、目標車速に対して例えば０．８〜１．２程度の所定の比率を掛けた車速に対応するトラニオン軸の変速位置を目標変速位置として設定するようにしてもよい。
【００５０】
（２）上記実施形態では、前記二次関数に対応する関係として定められる旋回レバーおける直進指令位置から離れる方向への移動量と旋回半径（速度比率）との関係に相当するものを数式情報として複数のものを記憶してそのうちのいずれか１つをモード切換スイッチにて選択して使用する構成としたが、このような構成に代えて次のような構成としてもよい。
前記関係を数式情報として記憶するものに代えて、前記移動量と旋回半径との関係をマップデータとして記憶させておき、そのマップデータに基づいて目標旋回半径を求めるようにしてもよく、複数の関数を固定状態で設定して記憶させる構成ではなく、切換スイッチに代えて可変抵抗等を用いて旋回レバーの移動量が最も大きい最大操作位置に操作されたときの旋回半径が無段階に変化するように変更調整することが可能な構成としてもよい。又、複数の関係の中からいずれか１つを選択して使用するものに代えて、１種類の関係だけを設定して常にその１種類の関係に基づいて目標旋回半径を求めるものでもよい。
【００５１】
（３）上記実施形態では、前記変速位置調整処理において、旋回中心に対して離れる側に位置する無段変速装置を基準側の無段変速装置としたが、このような構成に限らず、旋回中心側に位置する無段変速装置を基準側の無段変速装置として変速位置調整処理を実行するようにしてもよい。
【００５２】
（４）上記実施形態では、無段変速装置のトラニオン軸を操作するアクチュエータとして、油圧シリンダを例示したが、油圧モータや電動モータ等他のアクチュエータを用いてもよい。
【００５３】
（５）上記実施形態では、一対の無段変速装置として、静油圧式無段変速装置を用いたが、このような構成に代えて、例えば、ベルト式無段変速装置やテーパコーン型の無段変速装置と走行方向を前後で切り換えるための前後進切換機構とを組み合わせる構成としてもよい。又、このような構成と合わせて、前記車速指令手段として、所定操作範囲の一端側が走行停止を指令する停止指令位置になり、所定操作範囲の他端側が高速側の上限値になるように構成するものでもよい。
【００５４】
（６）上記実施形態では、作業車としてコンバインを例示したが、本発明はコンバインに限らず、人参収穫機や大根収穫機など他の農作業車でもよく、又、農作業車に限らず建設機械等の作業車でもよい。
【図面の簡単な説明】
【図１】コンバインの全体側面図
【図２】伝動構造を示す概略構成図
【図３】制御ブロック図
【図４】変速位置と変速出力との関係を示す図
【図５】主変速レバー操作位置と目標車速との関係を示す図
【図６】制御動作のフローチャート
【図７】制御動作のフローチャート
【図８】旋回レバーの位置と速度比率との関係を示す図
【符号の説明】
１Ｒ、１Ｌ　　　　走行装置
１１Ｒ、１１Ｌ　　無段変速装置
２４　　　　　　　車速指令手段
２６　　　　　　　旋回指令手段
３０　　　　　　　変速操作手段
３１　　　　　　　制御手段
４２　　　　　　　選択手段[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a pair of continuously variable transmissions for continuously changing the traveling speed of a pair of left and right traveling devices in a stepless manner, a shift operation means capable of individually performing a speed change operation of the pair of continuously variable transmissions, and And the amount of movement in the direction away from the straight-moving command position in the turning command operation area in the turning command operation area as the turning state. The turning command means for commanding a turning state in which the turning radius is smaller as the turning angle is larger, and the control means for executing turning control for operating the speed change operating means to perform straight ahead and turning based on the command information of the turning command means. The present invention relates to a turning control device for a working vehicle.
[0002]
[Prior art]
The turning control device for a work vehicle having the above-described configuration is applied to a work vehicle such as a combine, for example. Conventionally, there is the following configuration.
That is, a hydrostatic type continuously variable transmission is used as the pair of continuously variable transmissions, and a pair of electric motors are provided as the shift operation means. The output rotation speed of each of the pair of continuously variable transmissions is determined by a pair of rotation sensors. And a pair of continuously variable transmissions are operated by the respective electric motors so that the detection values of these rotation sensors become the respective target output rotational speeds. There is a configuration in which a steering clutch capable of freely turning on and off power transmission and a steering brake capable of braking each traveling device are provided on the lower side of transmission of the device, and the following processes are executed as the turning control. There was one. In other words, the turning mode includes a gentle turning mode, a brake turning mode, and a spin turning mode. In the gentle turning mode, the turning radius of the power steering lever as the turning command means in the direction away from the straight traveling command position is large and large. In the form of a stepless deceleration of the continuously variable transmission on the turning center side based on the output rotation speed of the continuously variable transmission on the side away from the center of rotation of the pair of left and right continuously variable transmissions, and The turning radius when turning by changing the ratio of the rotation speed of the pair of continuously variable transmissions in a form in which the change amount of the turning radius with respect to the change per unit amount of the operating position of the power steering lever is constant over the entire operation range. There is a configuration in which the operation of the speed change operation means is controlled so as to reduce the speed. In the brake turning mode, when the turning angle of the power steering lever becomes large, the turning is performed in a state where the steering clutch is disengaged and the steering brake is operated for the traveling device on the turning center side, and in the spin turning mode. In addition to the disengagement of the steering clutch and the operation of the steering brake, when the operation angle for turning the power steering lever becomes large, the traveling device on the turning center side is switched to the state of reverse rotation (for example, And Patent Document 1.).
[0003]
[Patent Document 1]
JP-A-8-172871 (pages 3 to 5, FIGS. 7 and 8)
[0004]
[Problems to be solved by the invention]
In the above-described conventional configuration, although there is an advantage that the turning radius can be smoothly changed steplessly with the movement of the operation position of the turning command means, the turning radius of the turning command means with respect to a change per unit amount of the operating position of the turning command means. Since the turning radius is reduced by changing the ratio of the rotation speeds of the pair of continuously variable transmissions so that the amount of change is constant over the entire operation range, the turning command means is used to direct the straight traveling command in the turning command operation area. Even if a slight movement operation is performed in the direction away from the position, the turning state greatly changes, so that there is a disadvantage that it is not possible to perform a gentle turning while finely adjusting from a straight traveling state.
For example, in the case of a work vehicle such as a combine harvester that harvests planted crops, in the case where a turning operation is performed to make the vehicle body follow the planting row of the crop, a gentle turning while finely adjusting the turning state is performed. However, in the above-described conventional configuration, even if the turning command means is slightly moved in a direction away from the straight-moving command position in the turning command operation area, the turning radius greatly changes. The turning operation by the adjustment becomes difficult.
[0005]
In order to avoid such disadvantages, it is conceivable to adopt a mode in which the turning state is gradually changed so that fine adjustment can be made over the entire range of the turning command operation area when the turning command means is operated. However, with this configuration, even if the turning command means is operated to the maximum operation position, the turning radius does not become sufficiently small at that time, and it becomes difficult to make a small turn with a small turning radius.
In the above prior art, a small turning radius can be dealt with by switching the turning mode from the gentle turning mode to the brake turning mode or the spin turning mode. There is a disadvantage that it is troublesome to perform, and furthermore, in a state where the mode is switched to the brake turning mode or the spin turning mode, when the turning command means is moved in a direction away from the straight-moving command position in the turning command operation area, the There is also a disadvantage that the traveling state of the traveling device on the turning center side suddenly changes during the moving operation, causing a shock to the vehicle body and deteriorating the ride comfort of the driver.
[0006]
Further, as another method for avoiding the disadvantage, a range in which the turning command means can perform a moving operation in the turning command operation area is widened, and a turning radius with respect to a change per unit amount of an operation position of the turning command means is given. It is conceivable that the amount of change of the turning command is small over the entire turning command operation area. However, in this configuration, when the turning operation is performed from a straight traveling state to a turning state with a small turning radius, the turning command means is largely moved and operated. It is disadvantageous that the turning operation is troublesome.
[0007]
The present invention has been made in view of such a point, and an object of the present invention is to increase the movement amount of the turning command means without unnecessarily widening the moving operation range in the turning command operation area of the turning command means. Sometimes, a turning state with a small turning radius can be achieved, and in a state where the amount of movement of the turning command means is small, it is possible to perform a gentle turn while making fine adjustments. Another object of the present invention is to provide a turning control device for a work vehicle which is less likely to cause disadvantages such as a sudden change in the running state of the running device even when the turning command means is moved and operated in a region and a shock to the vehicle body.
[0008]
[Means for Solving the Problems]
The turning control device for a working vehicle according to claim 1, wherein a pair of continuously variable transmissions for continuously changing the traveling speed of the pair of left and right traveling devices in a stepless manner, and a speed change operation for each of the pair of continuously variable transmissions. Free shift operation means, and can freely move over the entire range of a straight-moving command position for commanding the straight-moving state and a turning command operating area for commanding the turning state, and as the turning state, in the turning command operating area. Turning command means for commanding a turning state in which the turning radius is smaller as the amount of movement in the direction away from the straight-moving command position is larger; and operating the shift operation means for performing straight-turning and turning based on command information from the turning command means. Control means for executing a turning control, wherein the control means performs the turning control as the turning control in a straight line in the turning command operation area of the turning command means. The relationship between the amount of movement in the direction away from the command position and the turning radius is determined as follows: the larger the amount of movement in the direction away from the straight command position in the turning command operation area, the smaller the turning radius becomes, and Over the entire range of the area, the larger the amount of movement in the direction away from the straight-moving command position in the turning command operation area, the larger the amount of change in the turning radius with respect to the change per unit amount of the operating position of the turning command means. Determined as the relationship corresponding to the quadratic function to be changed, the relationship between the amount of movement in the direction away from the straight ahead command position and the turning radius in the turning command operation area defined as the relationship corresponding to the quadratic function, and A target turning radius corresponding to the operation position of the turning command means is obtained based on the operating position of the turning command means, and the turning radius becomes the target turning radius. Characterized in that it is configured to actuate the shift operation means as.
[0009]
That is, when the turning state is commanded by the turning command means, the relationship between the amount of movement in the direction away from the straight-moving command position and the turning radius in the turning command operation area defined as the relationship corresponding to the quadratic function as described above, Further, based on the operation position of the turning command means, a target turning radius corresponding to the operation position of the turning command means is obtained. In other words, the larger the amount of movement of the turn command means in the direction of the turn command operation area in the direction away from the straight travel command position, the smaller the turning radius becomes, and the larger the amount of movement becomes over the entire range of the turn command operation area, The target turning radius is obtained as a value determined by a quadratic function that changes the amount of change of the turning radius with respect to a change per unit amount of the operation position of the turning command means to a larger side. Then, the shift operation means is operated so that the turning radius becomes the target turning radius.
[0010]
If the amount of movement of the turn command means in the turn command operation area in the direction away from the straight ahead command position is small, the change amount of the turning radius with respect to a change per unit amount of the operation position of the turn command means is small. Even if the commanding means is operated, the turning radius does not greatly change.Therefore, even if the turning operation is slightly performed in a direction away from the straight-ahead command position, the turning state does not greatly change. In this case, it is easy to appropriately perform a gentle turn.
[0011]
Further, over the entire range of the turning command operation area, the larger the amount of movement is, the larger the amount of change in the turning radius with respect to a change per unit amount of the operating position of the turning command means is determined by a quadratic function that changes the amount of change. Since the target turning radius is obtained as a value, the turning operation can be performed even if the moving operation range in the turning command operation area is the same as compared with the case where the turning radius change amount with respect to the change per unit amount of the operation position is provided constant. The turning radius when the command means is moved to the maximum operation position can be reduced to a small turning radius, and the target turning radius is determined as a value determined by a quadratic function over the entire range of the turning command operation area. Therefore, even if the turning command means is moved over the entire range of the turning command operation area, the target turning radius does not suddenly change during the movement. Since times radius will vary smoothly, the traveling state of the traveling device of the turning center side in the middle of the turning operation is a shock to the vehicle body changes suddenly do not occur.
[0012]
Therefore, when the amount of movement of the turning command means is increased without unnecessarily widening the moving operation range in the turning command operation area of the turning command means, a turning state with a small turning radius can be achieved. In the state where the movement amount of the command means is small, it is possible to make a gentle turn while finely adjusting.Furthermore, even when the turn command means is moved and operated in the entire area of the operation area for the turn command, the traveling state of the traveling device is not changed. It has become possible to provide a turning control device for a work vehicle that is unlikely to cause disadvantages such as a sudden change and a shock on the vehicle body.
[0013]
According to a second aspect of the present invention, in the work vehicle turning control device according to the first aspect, the control means determines a position corresponding to the quadratic function from a straight ahead command position in the turning command operation area of the turning command means. It is characterized in that the target turning radius is obtained based on mathematical formula information corresponding to the relationship between the amount of movement in the separating direction and the turning radius and command information of the turning command means.
[0014]
As described above, since the relationship between the movement amount and the turning radius in the turning command means is determined by the mathematical formula information, the control means applies the command information of the turning command means to this formula to easily calculate the target by calculation. The turning radius can be obtained, and for example, there is an advantage that the control configuration is simplified as compared with a configuration in which the relationship between the movement amount and the turning radius is stored as information having a large number of data such as map data. At the same time, the time required for the process can be shortened by only the process of calculating based on the mathematical expression, and thus there is an advantage that the control responsiveness can be improved.
[0015]
According to a third aspect of the present invention, in the turning control device for a work vehicle according to the second aspect, the control means moves away from a straight-moving command position in the turning command operation area of the turning command means defined as a relation corresponding to the quadratic function. As the relationship between the amount of movement in the direction and the turning radius, a plurality of types having different turning radii corresponding to the operating position when the operating position of the turning command means is the same are stored and stored. The target turning radius corresponding to the operation position of the turning command means is obtained based on the relation selected by the manually operated selecting means for selecting any one of the plural kinds of relations. The shift operating means is operated so as to have the target turning radius.
[0016]
That is, as the relationship between the amount of movement of the turning command means and the turning radius, a plurality of types of turning radii corresponding to the operating positions of the turning command means different when the operating position is the same are stored. Therefore, any one of them is selected by the manually operated selecting means. Then, a target turning radius is obtained based on the selected relationship, and the shift operation means is operated so that the turning radius becomes the target turning radius.
[0017]
In other words, it is possible to make a turn with a turning operation content adapted at that time in correspondence with a plurality of work conditions assumed as the work conditions of the work vehicle, a difference in the skill level of the operator for the turning operation, and the like. A plurality of relationships are defined and stored in advance, and the operator can appropriately judge and select the relationship with a manually operated selection means, thereby realizing the actual work situation at that time and the skill level of the operator for the turning operation. The turning can be performed with the turning operation content according to the difference between the turning operation and the like.
[0018]
According to a fourth aspect of the present invention, in the work vehicle turning control device according to the third aspect, the plurality of types of relationships are such that the turning command means is operated to a maximum operation position where the movement amount is the largest in the turning command operation area. The turning radii at the time of turning are set to be different from each other.
[0019]
That is, since the turning radius when the turning command means is operated to the maximum operation position is set as a plurality of types of relations different from each other, the turning radius depends on the work situation, the difference in the skill level of the turning operation of the operator, and the like. The operator feels that it is necessary to make a turn with a small turning radius, for example, when the turning command means is moved with a large operating force, it is necessary to reach an intermediate operating position. The turning radius when operated to the maximum operation position was arbitrarily changed and set by the operator as appropriate, even if it was intended to be operated and even if it was accidentally operated to the maximum operation position. Since the turning radius can be set, the turning operation can always be performed with an appropriate turning radius.
[0020]
According to a fifth aspect of the present invention, in the turning control device for a work vehicle according to any one of the first to fourth aspects, the control unit is located on a side of the pair of traveling devices that is away from a turning center as the turning control. A direction in which the traveling device is maintained at a traveling speed corresponding to the target vehicle speed commanded by the vehicle speed commanding means, and the traveling device located on the turning center side moves away from the straight-moving command position in the turning command operation area of the turning commanding means. The shift operation means is configured to operate in such a manner that the traveling speed decreases as the amount of movement increases.
[0021]
That is, since the traveling device located on the turning center side decelerates and turns, it is possible to make a small turning radius with a small turning radius, and the traveling device located on the side away from the turning center has the vehicle speed. Since the vehicle travel speed is maintained at a speed corresponding to the target vehicle speed commanded by the commanding means, for example, a state in which the vehicle is traveling straight ahead at the target vehicle speed commanded by the turning speed commanding means and the vehicle speed commanding means. From the turning center even if the state is switched to a state where turning is commanded by the turning command means, or if the state is changed from straight running to straight running. Since the traveling speed of the traveling device located on the side hardly changes, shock or the like due to the speed change is small, and the traveling stability is improved.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a case where an embodiment of a turning control device for a work vehicle according to the present invention is applied to a combine as an example of a work vehicle will be described with reference to the drawings.
[0023]
FIG. 1 shows an overall side view of a combine as an example of a working vehicle. The combine is a front part of a traveling body 2 driven by a pair of left and right crawler traveling devices 1R and 1L as an example of a traveling device. In addition, the harvesting and transporting device 3 that cuts the planted grain culm and transports the harvested grain backward is connected so as to be able to move up and down, and the traveling body 2 receives the harvested grain culm from the harvesting and transporting device 3 and executes threshing and sorting processes. And a grain tank 5 for storing the grains from the threshing apparatus 4, and a boarding operation unit 6 is formed in front of the grain tank 5.
[0024]
As shown in FIG. 2, the combine transmits power from an engine 7 to an input shaft 10 of a transmission case 9 via a belt-tension type main clutch 8, and from the input shaft 10, a pair of traveling The transmission is distributed to the step transmissions 11R and 11L, and the power after shifting by one of the continuously variable transmissions 11L is transmitted to the left crawler type traveling device 1L via the left gear type auxiliary transmission 13L. A transmission drive mechanism is configured to transmit power after shifting by the other continuously variable transmission 11R to the right crawler type traveling device 1R via the right gear type auxiliary transmission 13R. are doing. On the other hand, the power from the engine 7 is also supplied to the continuously variable transmission 12 for work, and the power after the speed change by the continuously variable transmission 12 for work is transferred to the reaping conveyance device via the belt tension type reaping clutch 14. The transmission mechanism for mowing work is constituted so as to transmit the power to the transmission mechanism 3. The left and right gear type auxiliary transmissions 13R, 13L are configured to be capable of switching the power after shifting of each of the continuously variable transmissions 11R, 11L between high and low gears. Further, the boarding operation unit 6 is provided with a single sub-transmission lever 25 capable of swinging in the front-rear direction. The sub-transmission lever 25 is connected to a gear-type sub-transmission mechanism 13R via a linkage mechanism (not shown). 13L, the power after shifting by the continuously variable transmissions 11R and 11L for traveling can be shifted between high and low by operating the auxiliary transmission lever 25.
[0025]
Each of the continuously variable transmissions 11R and 11L for traveling is configured as a hydrostatic continuously variable transmission including an axial plunger type variable displacement type piston pump 19 and a piston motor 20, respectively. Similarly, the transmission 12 is configured as a hydrostatic stepless transmission including an axial plunger type and a variable displacement type piston pump 21 and a piston motor 22, and the traveling directions of the left and right crawler traveling devices 1R and 1L, respectively. Can be switched between the forward direction and the reverse direction, and the traveling speed can be continuously changed.
[0026]
Then, as shown in FIG. 3, a hydraulic traveling operation mechanism 30 as a shift operation means for performing a shift operation of each of the continuously variable transmissions 11R and 11L for traveling, and a continuously variable transmission 12 for work. A hydraulic work operation mechanism 36 for performing a speed change operation is provided. The traveling operation mechanism 30 includes a pair of double-acting hydraulic cylinders 33R and 33L that are operatively connected to the trunnion shaft 29 (an example of an operated body) in each of the traveling continuously variable transmissions 11R and 11L. A pair of two-position switching type oil supply electromagnetics that can be switched between a state in which hydraulic oil is supplied to a pair of oil chambers and a state in which supply of hydraulic oil is stopped corresponding to operations in the forward and reverse directions on these hydraulic cylinders 33R, 33L. It is provided with a valve 34A and a pair of two-position switching type oil discharge electromagnetic valves 34B that are switchable between a state in which the hydraulic oil is discharged from the pair of oil chambers and a state in which the discharge is stopped. Each of the hydraulic cylinders 33R and 33L is configured to be urged to return to the neutral position by the urging force of a spring installed therein.
[0027]
Similarly, the work operation mechanism 36 is linked to the trunnion shaft 37 of the work continuously variable transmission 12 and is urged to return to the neutral position by the biasing force of the internal spring. Hydraulic cylinder 40 and a pair of two-position switching type refueling that can be switched between a state in which hydraulic oil is supplied to a pair of oil chambers corresponding to operations in the forward and reverse directions with respect to the hydraulic cylinder 40 and a state in which supply is stopped. Electromagnetic valve 41A and a pair of two-position switching type oil discharge electromagnetic valves 41B that can be switched between a state in which hydraulic oil is discharged from the pair of oil chambers and a state in which discharge is stopped. .
[0028]
Each of the refueling solenoid valves 34A and 41A is configured to move and bias the spool to a refueling stop state by a biasing force of a spring, and moves the spool against the biasing force of the spring by an electromagnetic force of a solenoid. The hydraulic oil discharging solenoid valves 34B and 41B are configured to move and bias the spool to a discharging state by the biasing force of a spring. The configuration is such that the operation is switched to a state in which the discharge of the hydraulic oil is stopped by moving the spool against the urging force of the spring by the electromagnetic force of the solenoid.
[0029]
The outline of the shift operation of the continuously variable transmissions 11R and 11L described above will be described. As shown in FIG. 4, if the shift position of the trunnion shaft 29 is in the neutral range, the shift output (running speed) becomes zero. When the transmission position of the trunnion shaft 29 is rotated in the predetermined direction from the neutral region, the traveling speed in the forward direction is steplessly increased, and the trunnion shaft 29 is rotated in the direction opposite to the predetermined direction from the neutral region. When it is operated dynamically, the traveling speed in the reverse direction is increased steplessly.
[0030]
The boarding operation unit 6 is capable of moving along the vehicle front-rear direction within a predetermined operation range including the neutral position as a stop command position for instructing the traveling stop, and moving forward from the neutral position. The single main transmission lever 24 as a lever-operated artificial operation tool for instructing a target vehicle speed that increases as the vehicle speed increases, and instructing a target vehicle speed that increases as the amount of backward movement from the neutral position increases. And a single swing lever 26 as swing command means capable of swinging over a predetermined left and right operation range along the left and right directions. As shown in FIG. 3, a shift lever sensor 27 for detecting the operating position of the main shift lever 24 and a turning lever sensor 28 as operating position detecting means for detecting the operating position of the turning lever 26 are provided, respectively. They are both constituted by rotary potentiometers.
[0031]
The pair of continuously variable transmissions 11R and 11L for traveling have rotation speed sensors 44 and 45 as shift output detecting means for detecting their output rotational speeds individually, and the respective continuously variable transmissions 11R and 11L. Shift position sensors 46, 47, which are rotary potentiometers as shift position detecting means for detecting the operation angle of the respective trunnion shafts 29 by the pair of hydraulic cylinders 33R, 33L. Have been. The work continuously variable transmission 12 is also provided with a rotation speed sensor 51.
[0032]
A control device 31 using a microcomputer as control means for controlling the operation of the traveling operation mechanism 30 is provided. The control device 31 travels straight through the vehicle body at a target vehicle speed commanded by the main shift lever 24. In addition to executing the straight-ahead control for operating the traveling operation mechanism 30 so as to perform the turning operation, the turning control for operating the traveling operation mechanism 30 to perform the turning commanded by the turning lever 26 is executed.
[0033]
Briefly describing the straight-ahead control, if the main shift lever 24 is operated to a neutral position substantially at the center of the operable range in a state where the turning lever 26 is operated to the straight-ahead command position and the straight-ahead is commanded. When the vehicle is in the traveling stop state and the swing operation is performed from the neutral position to the forward side, the target vehicle speed at which the traveling speed to the forward side becomes steplessly high is instructed accordingly, and when the vehicle is operated from the neutral position to the reverse side, At the same time, a target vehicle speed at which the traveling speed to the reverse side is increased steplessly is instructed. When the trunnion shafts 29 of the pair of left and right continuously variable transmissions 11R and 11L are separated from the target shift position corresponding to the target vehicle speed, the trunnion shafts 29 of the pair of left and right continuously variable transmissions 11R and 11L are moved to the target. The traveling operation mechanism 30 is operated so as to reach the target shift position corresponding to the vehicle speed. When the trunnion shaft 29 of one of the continuously variable transmissions reaches the target shift position, one of the continuously variable transmissions is controlled such that the trunnion shaft 29 is maintained at the target shift position, while the other one is controlled. The speed synchronizing process is performed so that the output rotation speed of the continuously variable transmission is the same as the output rotation speed of the one continuously variable transmission.
[0034]
Next, the turning control will be described. When the main transmission lever 24 is operated and the vehicle is traveling at a predetermined speed, the control device 31 swings the turning lever 26 from the straight traveling command position to the right or left turning command range. When operated, the traveling operation mechanism 30 is configured to operate so that the turning state is such that the turning radius becomes smaller as the operation is performed further away from the straight ahead command position.
In addition, the control device 31 performs one of the pair of continuously variable transmissions 11R and 11L as the reference side continuously variable transmission as the reference side continuously variable transmission as the turning control. Shift position adjustment processing for operating the traveling operation mechanism 30 so that the shift position of the trunnion shaft 29 in the step transmission is at the target shift position, the stepless transmission that is opposite to the output rotational speed of the reference stepless transmission. Target speed setting processing for obtaining the target rotation speed of the continuously variable transmission on the opposite side so that the speed ratio with the output rotation speed of the rotation speed corresponds to the turning radius commanded by the turning lever 26, and Each of the rotation speed adjustment processes for operating the traveling operation mechanism 30 so that the output rotation speed of the continuously variable transmission on the side becomes the target rotation speed is executed.
[0035]
In addition, the control device 31 determines, as the turning control, the relationship between the moving amount of the turning lever 26 in the direction away from the straight-moving command position in the turning command operation region and the speed ratio corresponding to the turning radius in the turning command operation region. As the amount of movement in the direction away from the straight command position increases, the turning radius becomes a smaller speed ratio, and over the entire range of the turning command operation area, the amount of movement in the direction away from the straight command position in the turning command operation area is reduced. The larger the larger, the larger the change amount of the turning radius (speed ratio) with respect to the change per unit amount of the operating position of the turning lever 26 is defined as a relationship corresponding to a quadratic function that changes to a larger side, and corresponds to this quadratic function. The relationship between the amount of movement in the direction away from the straight ahead command position and the speed ratio corresponding to the turning radius in the turn command operation area defined as the relationship, Further, based on the operation position of the turning lever 26, a target speed ratio as a target turning radius corresponding to the operating position of the turning lever 26 is obtained, and the actual speed ratio corresponding to the turning radius becomes the target speed ratio. Thus, the driving operation mechanism 30 is configured to operate.
[0036]
Further, as described above, the control device 31 determines whether the amount of movement of the turning lever away from the straight-moving command position in the turning command operation area defined as the relationship corresponding to the quadratic function is equal to the speed ratio corresponding to the turning radius. The relationship is specifically stored and set as mathematical formula information, and the control device 31 obtains a target speed ratio corresponding to a target turning radius based on the command information of the turning lever and this formula information. It is configured as follows.
[0037]
Hereinafter, the processing operation of the turning control of the control device 31 will be specifically described based on a flowchart.
As shown in FIG. 6, when the turning lever 26 is operated to swing from the straight-moving command position to the right or left turning command range, turning is commanded. For example, when turning is commanded rightward (step 1, 2) The speed of the trunnion shaft 29 in the reference-side continuously variable transmission is set as the reference of the continuously variable transmission 11L on the left side, which is the continuously variable transmission located on the side away from the turning center. A shift position adjustment process for operating the traveling operation mechanism 30 so that the position becomes the target shift position is executed (step 3).
[0038]
To explain the shift position adjustment processing, as shown in FIG. 7, first, a target shift position with respect to the trunnion shaft 29 in the left continuously variable transmission 11L is calculated (step 31). At this time, the shift position of the trunnion shaft 29 corresponding to the target vehicle speed commanded by the main shift lever 24 is set as the target shift position.
[0039]
Next, a deviation between the target shift position and the current shift position of the trunnion shaft 29 detected by the shift position sensor 47 is obtained, and the traveling operation mechanism 30 is operated so as to reduce the position deviation. The shift position of the trunnion shaft 29 is changed and adjusted (steps 32 and 33). Specifically, the operation of the hydraulic cylinder 33R is controlled by switching control of the oil supply solenoid valve 34A and the oil drainage solenoid valve 34B in the traveling operation mechanism 30.
[0040]
Next, the output rotation speed of the left continuously variable transmission 11L for which the shift position adjustment is performed as described above is detected by the rotation speed sensor 45, and the output rotation speed of the left continuously variable transmission 11L is compared with the right rotation speed. A target rotation speed for obtaining the target rotation speed of the right continuously variable transmission 11R such that the speed ratio with the output rotation speed of the continuously variable transmission 11R becomes a speed ratio corresponding to the turning radius commanded by the turning lever 26. A setting process is executed (step 4).
[0041]
In other words, the relationship between the speed ratios of the left and right continuously variable transmissions 11R and 11L as values corresponding to the turning radius with respect to the operating position of the turning lever 26 is such that, for example, a correlation as shown in FIG. 8 is obtained. Is set and stored in advance. Then, the target rotational speed of the right continuously variable transmission 11R is obtained based on the mathematical formula information and the command information based on the operation position of the turning lever 26.
8, the output rotation speed V of the continuously variable transmission located on the reference side, that is, on the side away from the center of rotation, in response to a change in the operation position of the rotation lever 26, is shown. The change in the speed ratio of the continuously variable transmission located on the turning center side is shown as a reference. In step 4, since the right continuously variable transmission 11R is the continuously variable transmission located on the turning center side, the target rotational speed of the right continuously variable transmission 11R is determined from this speed ratio.
[0042]
As shown in FIG. 8, the speed ratio of the turning lever 26 to the operating position gradually increases as the amount of movement of the turning lever 26 from the neutral position increases with respect to a change in the operating position of the turning lever 26 per unit amount. Side, and as the amount of movement in the direction away from the neutral position increases, the quadratic function that changes the amount of change of the turning radius with respect to the change per unit amount of the operating position of the turning lever to the large side Is set.
The mathematical formula information will be specifically described. Based on the output rotation speed V of the continuously variable transmission located on the reference side, that is, the side distant from the turning center, the speed Vo of the continuously variable transmission located on the turning center side is calculated. The expression is obtained by calculation based on the expression shown in the following Expression 1. Here, X is an amount of movement of the turning lever 26 in a direction away from the neutral position, and a, b, and c are coefficients obtained in advance based on experimental data and the like.
[0043]
(Equation 1)
Vo = V- (aX ² + BX + c)
[0044]
As the relationship between the amount of movement of the turning lever 26 in the direction away from the straight-moving command position and the speed ratio, a plurality of types having different speed ratios corresponding to the operating position when the operating position of the turning lever 26 is the same. And a plurality (four in the example shown in FIG. 8) of turning modes having different speed ratios when operated to the maximum operation position where the moving amount of the turning lever 26 is the largest. The configuration is such that any one of the plurality of types of stored relationships can be selected and used for calculation. Specifically, a plurality of mathematical expressions in which the coefficients a, b, and c are appropriately changed based on the experimental results are stored in advance so that the relationship shown in FIG. 8 is obtained. Any one of the formulas is selected and used. Further, a mode changeover switch 42 is provided as a manually operated selection means for switching to any one of the plurality of functions, and a changeover command by the mode changeover switch 42 is given to the control device 31 to perform control. The device 31 determines which function is to be used to determine the target rotational speed based on the switching command.
[0045]
When the turning lever 26 is operated to the maximum operation position, the output rotation speed of the continuously variable transmission on the turning center side is changed to that of the continuously variable transmission on the opposite side when the turning lever 26 is operated to the maximum operation position. A mode (L1) in which the output rotation speed is reduced to about １／ of the output rotation speed V, a mode (L2) in which the output rotation speed of the continuously variable transmission on the turning center side becomes zero (L2), A mode (L3) in which the output rotational speed of the continuously variable transmission is a speed that is about ３ of the output rotational speed V of the continuously variable transmission on the opposite side in the direction opposite to the drive rotation direction of the continuously variable transmission on the opposite side. ), The output rotation speed of the continuously variable transmission on the turning center side is opposite to the drive rotation direction of the continuously variable transmission on the opposite side, and is substantially the same as the output rotation speed V of the continuously variable transmission on the opposite side. Mode (L4) is set respectively.
[0046]
Then, a difference between the target rotation speed obtained as described above and the current output rotation speed of the right continuously variable transmission 11R is determined, and the deviation is reduced, that is, the right continuously variable transmission 11R. A rotation speed adjustment process for operating the traveling operation mechanism 30 so that the output rotation speed of the 11R becomes the target rotation speed is executed (step 5). More specifically, the solenoid valve 34A for refueling and the oil replenishment valve in the driving operation mechanism 30 are controlled by the PI control so that the deviation between the target rotational speed and the current output rotational speed of the continuously variable transmission 11R on the right side is reduced. By controlling the switching of the solenoid valve 34B, the shift position of the trunnion shaft 29 is changed and adjusted so that the output rotation speed becomes the target rotation speed. In this way, the left and right traveling devices 1R and 1L are rotationally driven at the above-mentioned speed ratio, and the vehicle body turns with the turning radius commanded by the turning lever 26.
[0047]
If the left direction is commanded as the turning direction in step 2, the right-side continuously variable transmission 11R is set as the reference-side continuously variable transmission, and the same shift position adjustment processing and target speed setting processing as in steps 3 to 5 are performed. , And the rotation speed adjustment processing are executed (steps 6, 7, 8).
[0048]
[Another embodiment]
Next, another embodiment will be described.
[0049]
(1) In the above embodiment, in the turning control, the target vehicle speed is adjusted so that the traveling device located on the side away from the turning center is maintained at the traveling speed corresponding to the target vehicle speed commanded by the main shift lever. Although the shift position of the corresponding trunnion shaft is set as the target shift position, the present invention is not limited to such a structure, and the vehicle speed obtained by multiplying the target vehicle speed by, for example, a predetermined ratio of about 0.8 to 1.2 is applied. May be set as the target shift position.
[0050]
(2) In the above-described embodiment, a mathematical expression information corresponding to the relationship between the amount of movement of the turning lever in the direction away from the straight-ahead command position and the turning radius (speed ratio) determined as the relationship corresponding to the quadratic function is used. Although a plurality of items are stored and any one of them is selected and used by the mode switch, the following configuration may be used instead of such a configuration.
Instead of storing the relationship as mathematical information, the relationship between the movement amount and the turning radius may be stored as map data, and the target turning radius may be obtained based on the map data. Instead of a configuration in which a function is set and stored in a fixed state, the turning radius when the turning lever is moved to the maximum operation position where the moving amount of the turning lever is the largest is changed steplessly using a variable resistor or the like instead of the changeover switch. It is good also as a structure which can be changed and adjusted like this. Instead of selecting and using one of a plurality of relationships, only one type of relationship may be set and the target turning radius may always be obtained based on the one type of relationship.
[0051]
(3) In the above-described embodiment, in the shift position adjusting process, the continuously variable transmission located on the side away from the turning center is the reference continuously variable transmission. The shift position adjustment process may be executed by setting the continuously variable transmission located at the center side as the reference continuously variable transmission.
[0052]
(4) In the above embodiment, the hydraulic cylinder is exemplified as the actuator for operating the trunnion shaft of the continuously variable transmission. However, another actuator such as a hydraulic motor or an electric motor may be used.
[0053]
(5) In the above embodiment, a hydrostatic stepless transmission is used as the pair of stepless transmissions. Instead of such a configuration, for example, a belt-type stepless transmission or a taper cone-type stepless transmission is used. The transmission may be combined with a forward / reverse switching mechanism for switching the traveling direction between forward and backward. In addition to such a configuration, the vehicle speed command means is configured such that one end of a predetermined operation range is a stop command position for instructing stop of traveling, and the other end of the predetermined operation range is an upper limit value on a high speed side. You may do.
[0054]
(6) In the above embodiment, the combine vehicle is exemplified as the work vehicle. However, the present invention is not limited to the combine vehicle, but may be another agricultural work vehicle such as a ginseng harvester or a radish harvester. Work vehicle.
[Brief description of the drawings]
FIG. 1 is an overall side view of a combine.
FIG. 2 is a schematic configuration diagram showing a transmission structure.
FIG. 3 is a control block diagram.
FIG. 4 is a diagram showing a relationship between a shift position and a shift output.
FIG. 5 is a diagram showing a relationship between a main shift lever operation position and a target vehicle speed.
FIG. 6 is a flowchart of a control operation.
FIG. 7 is a flowchart of a control operation.
FIG. 8 is a diagram showing a relationship between a position of a turning lever and a speed ratio.
[Explanation of symbols]
1R, 1L traveling device
11R, 11L continuously variable transmission
24 Vehicle speed command means
26 Turn command means
30 Speed change operation means
31 Control means
42 Selection means

Claims

A pair of continuously variable transmissions that steplessly change the traveling speed of each of the pair of left and right traveling devices,
A shift operating means capable of shifting the pair of continuously variable transmissions separately,
It is free to move over the entire range of the straight-moving command position for commanding the straight-moving state and the turning command operation area for commanding the turning state, and in the turning state, in a direction away from the straight-moving command position in the turning command operating area. Turning command means for commanding a turning state in which the turning radius is small as the moving amount of the turning is large;
A control means for performing a turning control for operating the speed change operating means to perform a straight running and a turning based on the command information of the turning command means;
The control means includes:
The relationship between the amount of movement of the turning command means in the direction away from the straight-moving command position in the turning command operation area and the turning radius is determined as the moving amount in the direction away from the straight-moving command position in the turning command operation area increases. The smaller the turning radius, and the larger the amount of movement in the direction away from the straight-moving command position in the turning command operation area over the entire range of the turning command operation area, the more the per-unit amount of the operation position of the turning command means. Is defined as a relationship corresponding to a quadratic function that changes the amount of change of the turning radius with respect to the change to a large side,
Based on the relationship between the amount of movement in the direction away from the straight-ahead command position and the turning radius in the turning command operation area determined as a relationship corresponding to this quadratic function, and the turning position of the turning command means, A turning control device for a working vehicle configured to determine a target turning radius corresponding to an operation position of the means and to operate the shift operation means so that the turning radius becomes the target turning radius.

The control means,
Mathematical information corresponding to the relationship between the amount of movement of the turning command means defined in a relationship corresponding to the quadratic function in a direction away from the straight-moving command position in the turning command operation area and the turning radius, and the turning command means The turning control device for a work vehicle according to claim 1, wherein the target turning radius is obtained based on the command information.

The control means,
The operation position of the turning command means is the same as the relation between the amount of movement of the turning command means defined in the relation corresponding to the quadratic function in the turning command operation area in the direction away from the straight-moving command position and the turning radius. Is stored in a plurality of types having different turning radii corresponding to the operation position at the time of the operation position, and the artificially operated selection means for selecting any one of the plurality of types of the stored relationships. A method for determining a target turning radius corresponding to an operation position of the turning command means based on the selected relationship, and operating the speed change operating means so that the turning radius becomes the target turning radius. 3. The turning control device for a working vehicle according to 2.

The plurality of types of relationships are set such that the turning radii when the turning command means is operated to the maximum operation position where the movement amount is the largest in the turning command operation area are different from each other. 3. The turning control device for a working vehicle according to claim 3.

The control means includes:
Of the pair of traveling devices, the traveling device located on the side away from the turning center is maintained at the traveling speed corresponding to the target vehicle speed commanded by the vehicle speed commanding means, and the traveling device located on the turning center side is 5. The speed change operation means according to claim 1, wherein the speed change operation means is operated in such a manner that a traveling speed is reduced as an amount of movement of the turn command means in a direction away from a straight traveling command position in the turn command operation area increases. The turning control device for a work vehicle according to claim 1.