JP2004116757A

JP2004116757A - Travel controller for work vehicle

Info

Publication number: JP2004116757A
Application number: JP2002285040A
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; Mikio Okada; 岡田　幹夫; Futoshi Ikeda; 池田　太
Original assignee: Kubota Corp
Current assignee: Kubota Corp
Priority date: 2002-09-30
Filing date: 2002-09-30
Publication date: 2004-04-15

Abstract

PROBLEM TO BE SOLVED: To provide a travel controller for a work vehicle providing proper linear traveling at a vehicle speed command value commanded by a vehicle speed command means in a linear traveling state, and proper turning in a turning radius commanded by a turning command means in a turning state. SOLUTION: In the linear traveling state, control is carried out so that a shift position of an operated body 29 of a continuously variable transmission of a reference side is in target shift position, and an output rotational speed of a continuously variable transmission of a following side is a target rotational speed. In the turning state, control is carried out so that the shift position of the operated body 29 of the continuously variable transmission of the reference side is in a target shift position, and an output rotational speed of a continuously variable transmission in an opposite side is a target rotational speed so that a speed ratio corresponding to the turning radius is provided. The shift position of the operated body 29 of the continuously variable transmission of the reference side is operated so that at least accelerating is avoided when changing from linear traveling to turning. 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、直進及び旋回を指令自在で且つ旋回するときの旋回半径の大きさを指令自在な旋回指令手段と、直進走行用の車速指令値を指令する車速指令手段と、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走行制御を実行する制御手段とが備えられている作業車の走行制御装置に関する。
【０００２】
【従来の技術】
上記構成の作業車の走行制御装置は、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、各電動モータにより一対の無段変速装置の被操作体としてのトラニオンレバーを操作する構成とし、前記制御手段としてのコントローラが、前記走行制御として、直進状態においては、前記一対の回転センサの検出値夫々と前記車速指令値とが等しくなるように変速操作手段を作動させ、前記走行制御として、旋回状態においては、旋回指令手段としてのパワステレバーの旋回用の操作角度が大になり指令される旋回半径が小さくなるほど、旋回中心側の無段変速装置を減速させて一対の無段変速装置の回転速度の比率を変化させる形態で、各別に設定される目標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したものがあった（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４、図６）
【０００４】
【発明が解決しようとする課題】
上記従来構成においては、旋回指令手段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、左右一対の無段変速装置の夫々の出力回転速度が各別に設定されている目標回転速度になるように変速操作手段の作動を制御する構成であるから、以下に説明するような不利な点があった。
【０００５】
作業車が走行している場合に走行負荷の変動等に起因してエンジンの回転速度が変動することがあるが、エンジンの回転速度が変動すると前記各無段変速装置の出力回転速度が変化することになる。このように出力回転速度が変化すると、前記各無段変速装置の出力回転速度が上記したような各別に設定された目標回転速度になるように変速操作手段の作動が制御されるが、無段変速装置の変速操作に対して出力回転速度の検出には少し時間遅れが生じ、又、目標回転速度への変速に遅れが生じることがある。そうすると、例えば、走行負荷の変動によってエンジン回転速度が低下して無段変速装置の出力回転速度が低下すると、上記したように目標回転速度になるように変速操作手段の作動が制御されることによって元の出力回転速度に戻そうとするが、制御が実行されたときに走行負荷が低めの走行負荷に戻ってエンジン回転速度が元の回転速度に復帰していると、結果的に出力回転速度が高速になり過ぎてしまうので、再度、制御が実行されるといった、所謂、ハンチング現象が起きて、左右の無段変速装置の出力回転速度が不安定な状態で変動するおそれがある。
【０００６】
しかし、上記従来構成においては、このように無段変速装置の出力回転速度が変動するおそれがあるにもかかわらず、例えば直進状態においては、一対の無段変速装置の出力回転速度が夫々前記車速指令値になるように制御されるので、直進走行するときの左右両側の走行装置の走行速度が安定せず車体がふらついた状態となって、車体が車速指令手段にて指令された車速指令値にて適正に直進走行することが出来なくなるおそれがある。
【０００７】
又、旋回状態においても、一対の無段変速装置の回転速度の比率が旋回指令手段にて指令される旋回半径に対応する速度比率になる形態で、左右一対の無段変速装置の夫々の出力回転速度が各別に設定された目標回転速度になるように変速操作手段の作動を制御する構成であるから、左右両側の走行装置の走行速度が安定せず、車体が旋回指令手段により指令された旋回半径で適正に旋回走行することが出来なくなるおそれがある。
【０００８】
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、直進状態では車速指令手段にて指令された車速指令値にて適正に直進走行することが可能となり、しかも、旋回状態では旋回指令手段にて指令された旋回半径にて適正に旋回走行することが可能となる作業車の走行制御装置を提供する点にある。
【０００９】
【課題を解決するための手段】
請求項１に記載の作業車の走行制御装置は、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、直進及び旋回を指令自在で且つ旋回するときの旋回半径の大きさを指令自在な旋回指令手段と、直進走行用の車速指令値を指令する車速指令手段と、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走行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、
前記一対の無段変速装置の夫々における変速用の被操作体の変速位置を各別に検出する一対の変速位置検出手段と、前記一対の無段変速装置の出力回転速度を各別に検出する一対の変速出力検出手段とが備えられ、
前記制御手段が、前記走行制御として、
直進状態においては、前記一対の無段変速装置のうち基準用の条件を満たす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他方の無段変速装置を追従側の無段変速装置として基準側の無段変速装置における前記被操作体の変速位置が前記車速指令値に対応する目標変速位置になるように前記変速操作手段を作動させる変速位置調整処理と、前記基準側の無段変速装置の出力回転速度を基準回転速度として前記追従側の無段変速装置の出力回転速度が前記基準回転速度との関連にて定められた目標回転速度になるように前記変速操作手段を作動させる速度追従処理の夫々を実行するように構成され、且つ、
旋回状態においては、前記一対の無段変速装置のうちの旋回中心から離れる側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前記被操作体の変速位置が前記目標変速位置になるように前記変速操作手段を作動させる変速位置調整処理と、前記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、前記旋回指令手段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前記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と、前記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前記変速操作手段を作動させる回転速度調整処理とを夫々実行し、かつ、前記変速位置調整処理において、前記車速指令手段による前記車速指令値に応じた増減速操作が行われていない状態で前記旋回指令手段の指令状態が前記直進を指令する状態から前記旋回を指令する状態に切り換えられたときに、旋回中心から離れる側の無段変速装置における前記被操作体の変速位置を、少なくとも増速を回避するように前記旋回指令手段の指令状態が切り換えられる直前における位置に固定させる変速位置固定操作を実行するよう構成されていることを特徴とする。
【００１０】
すなわち、直進状態においては、一対の無段変速装置のうち基準用の条件を満たす基準側の無段変速装置における被操作体の変速位置が車速指令値に対応する目標変速位置になるように変速操作手段を作動させる。前記基準用の条件としては、例えば被操作体の変速位置が前記目標変速位置に近い側のものを基準とするような条件等がある。又、そのとき、追従側の無段変速装置の出力回転速度が基準側の無段変速装置の出力回転速度である基準回転速度との関連にて定められた目標回転速度になるように変速操作手段を作動させる。この目標回転速度は基本的には基準回転速度と同じ値であるが、制御用の不感帯を有する所定の幅を有する値でもよい。
【００１１】
このように、基準側の無段変速装置は被操作体の変速位置が目標変速位置になるように制御されるので、例えば、走行負荷の変動等によって出力回転速度が変化しても被操作体の変速位置に対する目標変速位置は変化しない。そして、追従側の無段変速装置は、基準側の無段変速装置の出力回転速度と同じか又はほぼ同じになるように速度調整される。つまり、走行負荷の変動等によりエンジン回転速度が変動するような場合には、左右一対の無段変速装置は出力回転速度が変化するものの、左右一対の無段変速装置はほぼ同じような速度で追従しながら変化することになり、左右の走行装置は走行速度が大きく変動することがなく、適正に直進走行することが可能となる。
【００１２】
そして、旋回状態においては、一対の無段変速装置のうち旋回中心から離れる側に位置する基準側の無段変速装置に対しては、その被操作体の変速位置が目標変速位置になるように変速操作手段を作動させ、反対側の無段変速装置に対しては出力回転速度が目標回転速度になるように変速操作手段を作動させる。そのとき、反対側の無段変速装置の目標回転速度は、基準側の無段変速装置の出力回転速度を基準として、一対の無段変速装置夫々の出力回転速度の速度比率が旋回指令手段にて指令される旋回半径に対応する速度比率に対応する値として求められることになる。従って、一対の無段変速装置夫々の出力回転速度の速度比率が旋回指令手段にて指令される旋回半径に対応する速度比率になるように調整されて、旋回走行が行われることになる。
【００１３】
このように、速度比率の基準となる側の無段変速装置は、被操作体の変速位置が目標変速位置になるように制御されるので、例えば、走行負荷の変動等によって出力回転速度が変化しても被操作体の変速位置に対する目標変速位置は変化しない。そして、反対側の無段変速装置の出力回転速度は、基準側の無段変速装置の出力回転速度を基準として、旋回指令手段にて指令される旋回半径に対応する速度比率になるように速度調整される。つまり、走行負荷の変動等によりエンジン回転速度が変動するような場合においては、左右一対の無段変速装置は出力回転速度が変化するものの、左右一対の無段変速装置は、ほぼ同じような速度比率を維持して追従しながら変化することになり、誤差の少ない状態で旋回指令手段にて指令された旋回半径にて適正に旋回走行することが可能となる。
【００１４】
ところで、車速指令手段による車速指令値に応じた増減速操作が行われていない状態で旋回指令手段の指令状態が直進を指令する状態から旋回を指令する状態に切り換えられたときに、一対の無段変速装置のうち旋回中心から離れる側に位置する無段変速装置が基準側の無段変速装置となるが、切り換えられる直前まで行われていた直進走行状態にて旋回中心から離れる側に位置する無段変速装置が追従側の無段変速装置として制御され、しかも、その無段変速装置の被操作体の変速位置が前記目標変速位置に比べて中立位置側つまり低速側に位置している状態で上記したような速度追従処理が行われていることがある。
そのような状態で直進を指令する状態から旋回を指令する状態になり、旋回中心から離れる側に位置する無段変速装置が基準側の無段変速装置に切り換えられると、その無段変速装置の被操作体の変速位置が前記目標変速位置になるように位置調整されるので、出力回転速度が操縦者の意思に反して増速してしまい、操縦者に違和感を与えるおそれがある。
【００１５】
そこで、旋回中心から離れる側の無段変速装置における被操作体の変速位置を、旋回指令手段の指令状態が切り換えられる直前における位置に固定させる変速位置固定操作を実行することにより、上記したような増速を回避するようにしている。
【００１６】
従って、直進状態から旋回状態に切り換わったときにおいて不測に車体が増速する不利を回避しながら、直進状態では車速指令手段にて指令された車速指令値にて適正に直進走行することが可能となり、しかも、旋回状態では旋回指令手段にて指令された旋回半径にて適正に旋回走行することが可能となる作業車の走行制御装置を提供できるに至った。
【００１７】
請求項２に記載の作業車の走行制御装置は、請求項１において、前記制御手段が、前記旋回指令手段が前記直進状態を指令する状態に切り換わり、且つ、左右の無段変速装置の出力回転速度が同一又はほぼ同一になると、前記変速位置固定操作を停止するように構成されていることを特徴とする。
【００１８】
すなわち、前記直進状態を指令する状態に切り換わり、且つ、左右の無段変速装置の出力回転速度が同一又はほぼ同一になると、前記変速位置固定操作を停止して変速位置調整処理及び速度追従処理夫々を実行することになる。このように前記直進状態を指令する状態に切り換わり、且つ、左右の無段変速装置の出力回転速度が同一又はほぼ同一になると、旋回状態において旋回中心から離れる側に位置していた無段変速装置の被操作体の変速位置が前記目標変速位置になるように位置調整されることがあっても、大きく増速が行われることはなく操縦者に違和感を与えるおそれがなく、車速指令手段にて指令された車速指令値にて適正に直進走行することができる。
【００１９】
請求項３記載の作業車の走行制御装置は、請求項１又は２において、前記制御手段が、前記旋回指令手段にて指令される旋回方向が異なる方向に変更されると、前記変速位置固定操作を停止するように構成されていることを特徴とする。
【００２０】
すなわち、前記旋回指令手段にて指令される旋回方向が異なる方向に変更されると、前記変速位置固定操作を停止して前記回転速度調整処理を実行することになる。旋回方向が異なる方向に変更されると、基準側の無段変速装置が反対側の無段変速装置に変化することになり、そのときまで前記変速位置固定操作が行われていた無段変速装置は前記回転速度調整処理が実行される状態になるので、前記変速位置固定操作を停止しても大きく増速が行われることはなく操縦者に違和感を与えるおそれがなく、適正に旋回走行することができる。
【００２１】
請求項４記載の作業車の走行制御装置は、請求項１〜３のいずれかにおいて、前記制御手段が、前記車速指令手段にて指令される車速指令値が変更されると、前記変速位置固定操作を停止するように構成されていることを特徴とする。
【００２２】
すなわち、前記車速指令手段にて指令される車速指令値が変更されると、前記変速位置固定操作を停止して、基準側の無段変速装置が変更された車速指令値にて走行するように変速位置調整処理を実行することになる。前記車速指令手段にて指令される車速指令値が変更されるときは操縦者の意思によって増速又は減速を行うときであるから、前記変速位置固定操作を停止することで、指令された車速指令値になるように増減速させることができるのである。
【００２３】
【発明の実施の形態】
以下、本発明に係る作業車の走行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。
【００２４】
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。
【００２５】
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。
【００２６】
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。
【００２７】
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。
【００２８】
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。
【００２９】
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。
【００３０】
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。
【００３１】
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直進走行用の車速指令値としての目標車速を指令し、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。
【００３２】
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。
【００３３】
そして、直進及び旋回を行うべく前記走行用操作機構３０を作動させる走行制御を実行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、走行制御として、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夫々実行する構成となっている。
【００３４】
前記直進制御について簡単に説明すると、図５に示すように、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夫々のトラニオン軸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の変速位置が共に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を作動させる変速操作処理を実行する。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、前記一対の無段変速装置のうち基準用の条件を満たす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他方の無段変速装置を追従側の無段変速装置として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を作動させる変速位置調整処理と、基準側の無段変速装置の出力回転速度を基準回転速度として追従側の無段変速装置の出力回転速度が基準回転速度との関連にて定められた目標回転速度になるように走行用操作機構３０を作動させる速度追従処理の夫々を実行するように構成されている。
【００３５】
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。
【００３６】
説明を加えると、制御装置３１は、一対の無段変速装置１１Ｒ、１１Ｌのうちの旋回中心から離れる側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を作動させる変速位置調整処理と、前記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と、反対側の無段変速装置の出力回転速度が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とを夫々実行し、かつ、前記変速位置調整処理において、主変速レバー２４による目標車速に応じた増減速操作が行われていない状態で旋回レバー２６の指令状態が直進を指令する状態から旋回を指令する状態に切り換えられたときに、旋回中心から離れる側の無段変速装置におけるトラニオン軸２９の変速位置を、少なくとも増速を回避するように旋回レバー２６の指令状態が切り換えられる直前における位置に固定させる変速位置固定操作を実行するよう構成されている。
【００３７】
そして、制御装置３１は、旋回レバー２６が直進状態を指令する状態に切り換わり、且つ、左右の無段変速装置１１Ｒ、１１Ｌの出力回転速度が同一又はほぼ同一になると、前記変速位置固定操作を停止するように構成されている。又、旋回レバー２６にて指令される旋回方向が異なる方向に変更されると、前記変速位置固定操作を停止するように構成されている。更には、主変速レバー２４にて指令される目標車速が変更されると、前記変速位置固定操作を停止するように構成されている。
【００３８】
以下、フローチャートに基づいて制御装置３１の走行制御の処理動作について具体的に説明する。
図７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ると旋回制御を実行し、旋回レバーが直進指令位置にあり旋回が指令されていなければ直進制御を実行する（ステップ１、２、３）。
【００３９】
次に、前記直進制御について説明する。
図８に示すように、左右一対の無段変速装置１１Ｒ、１１Ｌ夫々におけるトラニオン軸２９の変速位置が共に主変速レバー２４にて指令される目標車速に対応する目標変速位置に到達していなければ、変速位置センサ４６，４７にて検出される左右一対の無段変速装置１１Ｒ、１１Ｌ夫々のトラニオン軸２９の変速位置が共に目標変速位置になるように走行用操作機構３０を作動させる変速操作処理を実行する（ステップ４、５）。
【００４０】
そして、少なくともいずれか一方の無段変速装置夫々におけるトラニオン軸２９の変速位置が目標変速位置に到達すると、一対の無段変速装置のうち左側の無段変速装置のトラニオン軸２９の変速位置が、右側の無段変速装置１１Ｒのトラニオン軸２９の変速位置よりも中立域から遠い側に位置する場合には、前記基準用の条件が満たされているものとして、左側の無段変速装置１１Ｌを基準側の無段変速装置とし、反対側の中立域に近い側に位置する右側の無段変速装置１１Ｒを追従制御する無段変速装置として、変速位置センサ４７にて検出される左側の無段変速装置１１Ｌ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（ステップ６，７）。又、その左側の無段変速装置１１Ｌにおける出力速度を回転速度センサ４５にて検出して同期用目標速度として設定して、追従制御する無段変速装置としての右側の無段変速装置１１Ｒに対しては、回転速度セン４４サにて検出される実回転速度と前記同期用目標速度との偏差が小さくなるように走行用操作機構３０を作動させる速度追従処理を実行する（ステップ８）。具体的には、前記実回転速度と前記同期用目標速度との偏差が小さくなるように比例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、対応する油圧シリンダの作動を制御するのである。
【００４１】
ステップ６において一対の無段変速装置のうち右側の無段変速装置１１Ｒのトラニオン軸２９の変速位置が左側の無段変速装置１１Ｌのトラニオン軸２９の変速位置よりも中立域から遠い側に位置する場合には、右側の無段変速装置１１Ｒを基準側の無段変速装置とし、反対側の中立域に近い側に位置する左側の無段変速装置１１Ｌを追従制御する無段変速装置として，上記ステップ７、８と同様な処理を実行する（ステップ９、１０）。
【００４２】
次に前記旋回制御について説明する。
図９に示すように、この旋回制御においては、先ず、抑え込み処理を実行する（ステップ１１）。図１０、図１１を参照しながら抑え込み処理について説明する。主変速レバー２４の移動操作に伴う増減速操作が行われていない状態で、旋回レバー２６が右側に傾倒していれば旋回レバー２６にて指令される旋回方向が右抑え込みフラグが作用する方向とは異なる方向に変更されたものとして右抑え込みフラグをオフして（ステップ２１、２２、２３）、左側の無段変速装置１１Ｌが増速を起こすおそれがある所定条件が成立していれば左抑え込みフラグをオンする（ステップ２４、２５）。この所定条件とは、右側の無段変速装置１１Ｒにおけるトラニオン軸２９が目標変速位置近傍にあり、左側の無段変速装置１１Ｌにおけるトラニオン軸２９が目標変速位置から外れておりしかも中立域の近傍になく、また、左右の無段変速装置１１Ｒ、１１Ｌ夫々の出力回転速度の速度差が３０ｒｐｍ未満であれば、所定条件が成立しているものとする。
【００４３】
又、旋回レバー２６が右側に傾倒していない状態、つまり、旋回レバー２６が中立位置にあり直進状態を指令する状態に切り換わり、且つ、左右の無段変速装置１１Ｒ、１１Ｌの出力回転速度が同一又はほぼ同一になると、具体的には、左右の無段変速装置１１Ｒ、１１Ｌの出力回転速度の速度差が１０ｒｐｍ未満であれば、左抑え込みフラグをオフする（ステップ２６、２７）
【００４４】
次に、旋回レバー２６が左側に傾倒していれば旋回レバー２６にて指令される旋回方向が左抑え込みフラグが作用する方向とは異なる方向に変更されたものとして左抑え込みフラグをオフして（ステップ２８、２９）、右側の無段変速装置１１Ｒが増速を起こすおそれある所定条件が成立していれば右抑え込みフラグをオンする（ステップ３０、３１）。この所定条件とは、左側の無段変速装置１１Ｌにおけるトラニオン軸２９が目標変速位置近傍にあり、右側の無段変速装置１１Ｒにおけるトラニオン軸２９が目標変速位置から外れておりしかも中立域の近傍になく、また、左右の無段変速装置１１Ｒ、１１Ｌ夫々の出力回転速度の速度差が３０ｒｐｍ未満であれば、所定条件が成立しているものとする。
【００４５】
又、旋回レバー２６が左側に傾倒していない状態、つまり、旋回レバー２６が中立位置にあり直進状態を指令する状態に切り換わり、且つ、左右の無段変速装置１１Ｒ、１１Ｌの出力回転速度が同一又はほぼ同一になると、具体的には、左右の無段変速装置１１Ｒ、１１Ｌの出力回転速度の速度差が１０ｒｐｍ未満であれば、右抑え込みフラグをオフする（ステップ３２、３３）
【００４６】
そして、主変速レバー２４の位置が変化して増減速操作が行われると、左抑え込みフラグ及び右抑え込みフラグはいずれもオフさせるが（ステップ３４、３５）、主変速レバー２４の位置が変化していなければ、左抑え込みフラグがオン状態であれば左側の無段変速装置１１Ｌのトラニオン軸２９の抑え込み操作を実行する（ステップ３６，３７）。具体的には、そのトラニオン軸２９の変速位置を旋回レバー２６の指令状態が切り換えられる直前における位置に固定させるのである。又、右抑え込みフラグがオン状態であればステップ３７と同様に右側の無段変速装置１１Ｒのトラニオン軸２９の抑え込み操作を実行する（ステップ３８，３９）。このようなトラニオン軸２９の抑え込み操作が変速位置固定操作に対応する。
【００４７】
そして、このような抑え込み処理が行われた後、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１２）、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、そのとき、左抑え込みフラグがオンしていなければ（ステップ１３）、その左側の無段変速装置１１Ｌ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変速操作を行うべく走行用操作機構３０を作動させる（ステップ１４）。具体的には、トラニオン軸２９の実変速位置と目標変速位置との偏差が小さくなるように比例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、油圧シリンダ３３Ｒの作動を制御するのである。ステップ１３にて左抑え込みフラグがオンしていれば、前記抑え込み処理において左抑え込みフラグがオフするまで、ステップ１４を実行せずに左側の無段変速装置１１Ｌのトラニオン軸２９の変速位置を旋回レバー２６の指令状態が切り換えられる直前における位置に固定させることになる。
【００４８】
次に、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１５）。
【００４９】
図６に示すように、旋回レバー２６の操作位置に対する左右の無段変速装置１１Ｒ、１１Ｌの速度比率の関係が予め設定されて記憶されており、この関係と、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６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。
【００５０】
この図から明らかなように、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。しかも、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形態の複数（図６に示す例では４種類）の旋回モードが選択可能に構成されている。そして、旋回モードを切り換えるため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曲線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。
【００５１】
図９に示す４種類の旋回モードについて説明すると、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。
【００５２】
そして、上記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１６）。具体的には、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。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。
【００５３】
前記ステップ１２にて旋回方向として左方向が指令されていると判断された場合には、右側の無段変速装置１１Ｒを基準側の無段変速装置として制御される対象が左右反対になるが、ステップ１３〜１６と同様な処理を実行する（ステップ１７〜２０）。上記ステップ１１〜１４、１７、１８の夫々の処理が前記変速位置調整処理に対応することになる。
【００５４】
〔別実施形態〕
次に、別実施形態を列記する。
【００５５】
（１）上記実施形態では、旋回レバーが前記直進状態を指令する状態に切り換わり、且つ、左右の無段変速装置の出力回転速度が同一又はほぼ同一になったとき、旋回レバーにて指令される旋回方向が異なる方向に変更されたとき、主変速レバーにて指令される車速指令値が変更されたときの夫々において、前記変速位置固定操作を停止するように構成したが、これらの各条件のいずれか１つの条件が成立したときに前記変速位置固定操作を停止するようにしてもよく、停止用の条件としては、これらのものに限らず他の条件を設定してもよい。
【００５６】
（２）上記実施形態では、直進状態において、前記一対の無段変速装置のうちトラニオン軸の変速位置が中立域から遠い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定めるよう構成するものを例示したが、このような構成に代えて、前記一対の無段変速装置のうち前記被操作体の変速位置が前記停止用変速位置から近い側に位置する無段変速装置を前記基準側の無段変速装置として定める構成としたり、前記制御目標位置に至った無段変速装置を前記基準側の無段変速装置として定める構成とする等、各種の形態で実施してもよい。
【００５７】
（３）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。
【００５８】
（４）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。
【００５９】
（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縦断背面図
【図３】操作構造の構成を示す概略図
【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】旋回レバーの位置と速度比率との関係を示す図
【図７】制御動作のフローチャート
【図８】制御動作のフローチャート
【図９】制御動作のフローチャート
【図１０】制御動作のフローチャート
【図１１】制御動作のフローチャート
【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
２９　　　　　　　被操作体
３０　　　　　　　変速操作手段
３１　　　　　　　制御手段
４４、４５　　　　変速出力検出手段
４６、４７　　　　変速位置検出手段[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, A turning command means for freely commanding a turning radius when turning, a vehicle speed commanding means for commanding a vehicle speed command value for straight running, and operating the speed change operating means for performing straight running and turning. The present invention relates to a travel control device for a work vehicle, which is provided with control means for performing travel control.
[0002]
[Prior art]
The traveling control device for a working vehicle having the above configuration is applied to, for example, a working vehicle such as a combine, and conventionally, there is the following configuration.
That is, a pair of electric motors are provided as shift operation means using a hydrostatic stepless transmission as the pair of stepless transmissions, and each electric motor serves as an operated body of the pair of stepless transmissions. The trunnion lever is configured to be operated, and the controller as the control unit is configured to control the shift operation unit so that, in the straight traveling state, the detection values of the pair of rotation sensors and the vehicle speed command value are equal in the straight running state. In the turning state, the stepless speed change device on the turning center side is decelerated as the operation angle for turning the power steering lever as the turning command means increases and the commanded turning radius decreases in the turning state. In this manner, the ratio of the rotational speeds of the pair of continuously variable transmissions is changed, and a pair of continuously variable transmissions is driven by each of the electric motors so that the target rotational speed is set individually. Was something configured to actuate the transmission (e.g., see Patent Document 1.).
[0003]
[Patent Document 1]
JP-A-8-172871 (pages 3 to 5, FIGS. 4 and 6)
[0004]
[Problems to be solved by the invention]
In the above-described conventional configuration, the output rotational speeds of the pair of left and right continuously variable transmissions are set to target rotational speeds that are individually set so as to have a speed ratio corresponding to the turning radius commanded by the turning commanding means. Since the operation of the shift operation means is controlled so as to be as described above, there are disadvantages as described below.
[0005]
When the work vehicle is traveling, the rotational speed of the engine may fluctuate due to fluctuations in the traveling load, etc., and when the rotational speed of the engine fluctuates, the output rotational speed of each of the continuously variable transmissions changes. Will be. When the output rotation speed changes in this manner, the operation of the speed change operation means is controlled so that the output rotation speed of each of the continuously variable transmissions becomes the target rotation speed set individually as described above. There may be a slight time delay in detecting the output rotational speed with respect to the shift operation of the transmission, and a delay in shifting to the target rotational speed. Then, for example, when the engine rotation speed is reduced due to a change in the running load and the output rotation speed of the continuously variable transmission is reduced, the operation of the shift operation means is controlled so as to reach the target rotation speed as described above. When the control is executed, the running load returns to a lower running load and the engine speed returns to the original speed. Becomes too high, so-called hunting phenomenon that the control is executed again may occur, and the output rotational speeds of the left and right continuously variable transmissions may fluctuate in an unstable state.
[0006]
However, in the above-described conventional configuration, in spite of the possibility that the output rotational speed of the continuously variable transmission may fluctuate, for example, in a straight traveling state, the output rotational speeds of the pair of continuously variable transmissions are respectively equal to the vehicle speed. Since the vehicle speed is controlled to be the command value, the traveling speeds of the traveling devices on both the left and right sides when traveling straight ahead become unstable and the vehicle body fluctuates, and the vehicle speed command value is commanded by the vehicle speed command means. The vehicle may not be able to travel straight ahead properly.
[0007]
Further, even in the turning state, the output of each of the pair of left and right continuously variable transmissions is set so that the rotation speed ratio of the pair of continuously variable transmissions becomes a speed ratio corresponding to the turning radius commanded by the turning command means. Since the operation of the speed change operation means is controlled so that the rotation speed becomes the target rotation speed set individually, the traveling speeds of the traveling devices on both the left and right sides are not stabilized, and the vehicle body is commanded by the turning command means. There is a possibility that the vehicle may not be able to turn properly at the turning radius.
[0008]
The present invention has been made by paying attention to such a point, and an object of the present invention is to enable the vehicle to travel properly straight ahead with the vehicle speed command value commanded by the vehicle speed command means in the straight traveling state, and further, in the turning state. It is an object of the present invention to provide a traveling control device for a working vehicle that can appropriately perform a turning operation with a turning radius commanded by turning command means.
[0009]
[Means for Solving the Problems]
The traveling control device for a work vehicle according to claim 1, wherein a pair of continuously variable transmissions that steplessly change the traveling speed of each of the pair of left and right traveling devices, and a speed change operation of each of the pair of continuously variable transmissions. Flexible speed change operation means, turn command means for freely commanding straight ahead and turn, and a command for the size of a turning radius when turning, vehicle speed command means for commanding a vehicle speed command value for straight ahead traveling, Control means for executing travel control for activating the speed change operation means to perform a turn,
A pair of shift position detecting means for separately detecting a shift position of a shift operated body in each of the pair of continuously variable transmissions, and a pair of shift position detecting means for separately detecting an output rotation speed of the pair of continuously variable transmissions. Shift output detection means,
The control means, as the travel control,
In the straight traveling state, one of the pair of continuously variable transmissions that satisfies the reference condition is set as the reference side continuously variable transmission, and the other continuously variable transmission is set as the following side continuously variable transmission. A shift position adjusting process for operating the shift operation means such that a shift position of the operated body in the reference-side continuously variable transmission is a target shift position corresponding to the vehicle speed command value; Using the output rotation speed of the stepped transmission as a reference rotation speed, operating the shift operation means such that the output rotation speed of the follower-side continuously variable transmission becomes a target rotation speed determined in relation to the reference rotation speed. Configured to execute each of the speed following processes to be performed, and
In the turning state, the continuously variable transmission on the side away from the center of rotation of the pair of continuously variable transmissions is defined as the reference continuously variable transmission, and the shift position of the operated body in the reference continuously variable transmission is set. And a speed ratio between an output rotation speed of the continuously variable transmission on the reference side and an output rotation speed of the continuously variable transmission on the opposite side. A target speed setting process for determining a target rotation speed of the continuously variable transmission on the opposite side so as to have a speed ratio corresponding to a turning radius instructed by the rotation instructing means; and a continuously variable transmission on the opposite side. And a rotation speed adjustment process for operating the shift operation means so that the output rotation speed of the vehicle becomes the target rotation speed, and in the shift position adjustment process, the vehicle speed instruction by the vehicle speed instruction means is performed. When the command state of the turning command means is switched from the state of commanding the straight running to the state of commanding the turning in a state where the acceleration / deceleration operation according to the above is not performed, the stepless speed change on the side away from the turning center. The apparatus is configured to execute a shift position fixing operation for fixing a shift position of the operated body in the device to a position immediately before a command state of the turning command means is switched so as to avoid at least an increase in speed. And
[0010]
In other words, in the straight traveling state, the shift is performed such that the shift position of the operated body in the reference-side continuously variable transmission that satisfies the reference condition among the pair of continuously variable transmissions is the target shift position corresponding to the vehicle speed command value. Activate the operating means. The reference condition includes, for example, a condition in which the shift position of the operated body is closer to the target shift position than the target shift position. At this time, the speed change operation is performed so that the output rotational speed of the continuously variable transmission on the following side becomes the target rotational speed determined in relation to the reference rotational speed which is the output rotational speed of the continuously variable transmission on the reference side. Activate the means. The target rotation speed is basically the same value as the reference rotation speed, but may be a value having a predetermined width having a dead zone for control.
[0011]
As described above, since the reference continuously variable transmission is controlled such that the shift position of the operated body becomes the target shift position, for example, even if the output rotational speed changes due to a change in the running load or the like, the operated body is controlled. The target shift position does not change with respect to the shift position. Then, the speed of the continuously variable transmission on the following side is adjusted so as to be equal to or substantially equal to the output rotational speed of the continuously variable transmission on the reference side. In other words, when the engine rotational speed fluctuates due to a change in running load or the like, the output rotational speed of the pair of left and right continuously variable transmissions changes, but the pair of left and right continuously variable transmissions has approximately the same speed. The right and left traveling devices do not vary greatly in traveling speed, and can travel straight ahead properly.
[0012]
In the turning state, the shift position of the operated body is set to the target shift position for the reference-side continuously variable transmission that is located on the side away from the center of rotation of the pair of continuously variable transmissions. The speed change operation means is operated, and the speed change operation means is operated so that the output rotation speed becomes the target rotation speed for the continuously variable transmission on the opposite side. At that time, the target rotational speed of the continuously variable transmission on the opposite side is based on the output rotational speed of the continuously variable transmission on the reference side, and the speed ratio of the output rotational speed of each of the pair of continuously variable transmissions to the turning command means. Is obtained as a value corresponding to the speed ratio corresponding to the turning radius commanded by the command. Therefore, the turning traveling is performed by adjusting the speed ratio of the output rotational speed of each of the pair of continuously variable transmissions to the speed ratio corresponding to the turning radius commanded by the turning command means.
[0013]
In this way, the continuously variable transmission on the reference side of the speed ratio is controlled such that the shift position of the operated body is at the target shift position. However, the target shift position relative to the shift position of the operated body does not change. The output rotational speed of the continuously variable transmission on the opposite side is set to a speed ratio corresponding to the turning radius commanded by the turning command means with reference to the output rotational speed of the reference continuously variable transmission. Adjusted. In other words, when the engine rotational speed fluctuates due to a change in running load or the like, the output rotational speed of the pair of left and right continuously variable transmissions changes, but the pair of left and right continuously variable transmissions has substantially the same speed. The ratio changes while following the ratio while maintaining the ratio, and it is possible to appropriately turn with the turning radius commanded by the turning command means in a state with a small error.
[0014]
By the way, when the command state of the turn command means is switched from a state of commanding straight ahead to a state of commanding a turn in a state where the acceleration / deceleration operation according to the vehicle speed command value by the vehicle speed command means is not performed, a pair of non-turn signals is provided. The continuously variable transmission that is located on the side away from the turning center of the stepped transmission is the reference-side continuously variable transmission, but is located on the side that is away from the turning center in the straight running state that was performed immediately before switching. A state in which the continuously variable transmission is controlled as a follower-side continuously variable transmission, and the shift position of the operated body of the continuously variable transmission is located on the neutral position side, that is, on the low-speed side with respect to the target shift position. In some cases, the speed following process is performed as described above.
In such a state, the state changes from the state of commanding straight ahead to the state of commanding turning, and when the continuously variable transmission located on the side away from the turning center is switched to the reference continuously variable transmission, Since the shift position of the operated body is adjusted so as to be the target shift position, the output rotation speed is increased against the intention of the driver, and the driver may feel uncomfortable.
[0015]
Therefore, by executing a shift position fixing operation for fixing the shift position of the operated body in the continuously variable transmission on the side away from the turning center to a position immediately before the command state of the turning command means is switched, as described above. It tries to avoid speeding up.
[0016]
Therefore, while avoiding the disadvantage of unexpectedly increasing the vehicle speed when the vehicle is switched from the straight traveling state to the turning state, the vehicle can travel straight ahead properly with the vehicle speed command value commanded by the vehicle speed command means in the straight traveling state. In addition, it is possible to provide a traveling control device for a work vehicle that can appropriately perform a turning traveling with a turning radius commanded by turning command means in a turning state.
[0017]
According to a second aspect of the present invention, in the traveling control device for a working vehicle according to the first aspect, the control unit switches to a state in which the turning command unit instructs the straight traveling state, and outputs the left and right continuously variable transmissions. When the rotation speeds are the same or substantially the same, the shift position fixing operation is stopped.
[0018]
That is, when the state is switched to the state in which the straight traveling state is commanded and the output rotational speeds of the left and right continuously variable transmissions are the same or substantially the same, the shift position fixing operation is stopped, and the shift position adjusting process and the speed following process are performed. Each will run. As described above, when the state is switched to the state in which the straight traveling state is commanded and the output rotational speeds of the left and right continuously variable transmissions are the same or substantially the same, the continuously variable transmission that is located on the side away from the turning center in the turning state. Even if the shift position of the operated body of the device is adjusted so as to be the target shift position, the speed is not greatly increased and there is no fear of giving an uncomfortable feeling to the operator, and the vehicle speed command means The vehicle can travel straight ahead properly with the commanded vehicle speed.
[0019]
According to a third aspect of the present invention, in the traveling control device for a work vehicle according to the first or second aspect, when the control unit changes the turning direction commanded by the turning command unit to a different direction, the shift position fixing operation is performed. Is stopped.
[0020]
That is, when the turning direction commanded by the turning command means is changed to a different direction, the shift position fixing operation is stopped and the rotation speed adjustment processing is executed. When the turning direction is changed to a different direction, the continuously variable transmission on the reference side changes to the continuously variable transmission on the opposite side, and the continuously variable transmission in which the shift position fixing operation has been performed up to that time. Is in a state in which the rotation speed adjustment process is executed, so that even if the shift position fixing operation is stopped, the speed is not greatly increased, and there is no possibility of giving a sense of incongruity to the operator. Can be.
[0021]
According to a fourth aspect of the present invention, in the traveling control device for a work vehicle according to any one of the first to third aspects, when the control means changes a vehicle speed command value commanded by the vehicle speed command means, the shift position is fixed. The operation is stopped.
[0022]
That is, when the vehicle speed command value instructed by the vehicle speed command means is changed, the shift position fixing operation is stopped, and the reference side continuously variable transmission runs at the changed vehicle speed command value. The shift position adjustment processing will be executed. The vehicle speed command value instructed by the vehicle speed command means is changed when the speed is increased or decelerated by the driver's intention. Therefore, by stopping the shift position fixing operation, the commanded vehicle speed command is issued. It can be accelerated or decelerated to a value.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a case where an embodiment of a traveling 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.
[0024]
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.
[0025]
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.
[0026]
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.
[0027]
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, respectively. 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.
[0028]
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. .
[0029]
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.
[0030]
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.
[0031]
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 instructs a target vehicle speed as a vehicle speed command value for a straight running that increases as the vehicle speed increases, and instructs 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.
[0032]
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.
[0033]
A control device 31 using a microcomputer is provided as control means for executing travel control for operating the travel operation mechanism 30 to perform straight traveling and turning. The control device 31 includes a main shift lever as travel control. In addition to executing the straight traveling control for operating the traveling operation mechanism 30 so that the vehicle body travels straight at the target vehicle speed instructed at 24, the traveling operation mechanism 30 is operated to perform the turning commanded by the turning lever 26. It is configured to execute the turning control respectively.
[0034]
Briefly describing the straight running control, as shown in FIG. 5, in a state where the turning lever 26 is operated to the straight running command position and the straight running is commanded, the main speed change lever 24 is located substantially in the middle of the operable range. When the vehicle is operated to the neutral position, the vehicle is stopped, and when the vehicle is operated to swing from the neutral position to the forward side, a target vehicle speed at which the traveling speed to the forward side is continuously increased to a high speed is commanded, and the vehicle moves backward from the neutral position. When the vehicle is operated to the side, a target vehicle speed at which the traveling speed to the reverse side is increased steplessly is commanded accordingly.
When the trunnion shaft 29 of each of the pair of left and right continuously variable transmissions 11R and 11L is separated from the target shift position corresponding to the target vehicle speed, the shift of the trunnion shaft 29 of each of the pair of left and right continuously variable transmissions 11R and 11L is changed. A shift operation process for operating the traveling operation mechanism 30 so that both the positions become the target shift positions corresponding to the target vehicle speed is executed. When the trunnion shaft 29 of any one of the continuously variable transmissions reaches the target shift position, one of the pair of continuously variable transmissions that satisfies the reference condition is connected to the reference continuously variable transmission. The traveling operation mechanism 30 is arranged such that the transmission position of the trunnion shaft 29 in the reference-side continuously variable transmission is the target transmission position corresponding to the target vehicle speed, and the other continuously variable transmission is the follower continuously variable transmission. And the target rotation speed determined by the output rotation speed of the follower-side continuously variable transmission in relation to the reference rotation speed, with the output rotation speed of the reference-side continuously variable transmission as the reference rotation speed. Each of the speed following processes for operating the traveling operation mechanism 30 to achieve the speed is configured to be executed.
[0035]
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.
[0036]
In addition, the control device 31 sets the continuously variable transmission on the side away from the turning center of the pair of continuously variable transmissions 11R and 11L as the reference side continuously variable transmission in the reference side continuously variable transmission. A shift position adjusting process for operating the traveling operation mechanism 30 so that the shift position of the trunnion shaft 29 becomes a target shift position corresponding to the target vehicle speed, and a shift position adjusting process on the opposite side to the output rotational speed of the reference side continuously variable transmission. A target speed setting process for obtaining a target rotation speed of the continuously variable transmission on the opposite side so that a speed ratio with the output rotation speed of the stepped transmission becomes a speed ratio corresponding to a turning radius instructed by the turning lever 26; And a rotation speed adjustment process for operating the traveling operation mechanism 30 so that the output rotation speed of the continuously variable transmission on the opposite side becomes the target rotation speed. When the command state of the turning lever 26 is switched from a state of commanding straight-ahead to a state of commanding turning in a state where the acceleration / deceleration operation according to the target vehicle speed by the lever 24 is not performed, there is nothing on the side away from the turning center. The shift position fixing operation for fixing the shift position of the trunnion shaft 29 in the step transmission to at least the position immediately before the command state of the turning lever 26 is switched so as to avoid increasing the speed is executed.
[0037]
Then, when the turning lever 26 is switched to a state in which the straight traveling state is commanded, and the output rotational speeds of the left and right continuously variable transmissions 11R and 11L become the same or substantially the same, the control device 31 performs the shift position fixing operation. It is configured to stop. When the turning direction commanded by the turning lever 26 is changed to a different direction, the shift position fixing operation is stopped. Further, when the target vehicle speed commanded by the main shift lever 24 is changed, the shift position fixing operation is stopped.
[0038]
Hereinafter, the processing operation of the traveling control of the control device 31 will be specifically described based on a flowchart.
As shown in FIG. 7, when the turning lever 26 is operated to swing from the straight-moving command position to the right or left turning command range and turning is commanded, turning control is executed. If the command has not been issued, the straight running control is executed (steps 1, 2, 3).
[0039]
Next, the straight traveling control will be described.
As shown in FIG. 8, if the shift position of the trunnion shaft 29 in each of the pair of left and right continuously variable transmissions 11 R and 11 L has not reached the target shift position corresponding to the target vehicle speed commanded by the main shift lever 24. A shift operation process for operating the traveling operation mechanism 30 so that the shift positions of the pair of left and right continuously variable transmissions 11R and 11L detected by the shift position sensors 46 and 47 are both the target shift positions. Is executed (steps 4 and 5).
[0040]
Then, when the shift position of the trunnion shaft 29 in at least one of the continuously variable transmissions reaches the target shift position, the shift position of the trunnion shaft 29 of the left continuously variable transmission of the pair of continuously variable transmissions is If the right side of the continuously variable transmission 11R is located farther from the neutral region than the shift position of the trunnion shaft 29 of the right continuously variable transmission 11R, it is determined that the reference condition is satisfied, and the left continuously variable transmission 11L is The continuously variable transmission on the left side, which is detected by the shift position sensor 47, is a continuously variable transmission that follows and controls the continuously variable transmission 11R on the right side, which is located closer to the neutral region on the opposite side. The traveling operation mechanism 30 is operated so that the gear position of the trunnion shaft 29 in the device 11L becomes the target gear position (steps 6 and 7). Further, the output speed of the left continuously variable transmission 11L is detected by the rotation speed sensor 45 and set as the synchronization target speed, so that the output of the right continuously variable transmission 11R as the continuously variable transmission for following control is controlled. Specifically, a speed follow-up process for operating the traveling operation mechanism 30 is performed so that the deviation between the actual rotation speed detected by the rotation speed sensor 44 and the target speed for synchronization is reduced (step 8). Specifically, the solenoid valve 34A for oil supply and the solenoid valve 34B for oil discharge in the traveling operation mechanism 30 are switched and controlled by proportional control so that the deviation between the actual rotation speed and the target speed for synchronization is reduced. The operation of the corresponding hydraulic cylinder is controlled.
[0041]
In step 6, the transmission position of the trunnion shaft 29 of the right continuously variable transmission 11R of the pair of continuously variable transmissions is located farther from the neutral region than the transmission position of the trunnion shaft 29 of the left continuously variable transmission 11L. In this case, the continuously variable transmission 11R on the right side is defined as the continuously variable transmission on the reference side, and the continuously variable transmission 11L on the left side, which is located on the opposite side close to the neutral region, is defined as the continuously variable transmission that performs tracking control. The same processing as steps 7 and 8 is executed (steps 9 and 10).
[0042]
Next, the turning control will be described.
As shown in FIG. 9, in the turning control, first, a restraining process is executed (step 11). The suppression process will be described with reference to FIGS. If the acceleration / deceleration operation accompanying the movement operation of the main transmission lever 24 is not performed and the turning lever 26 is tilted to the right, the turning direction instructed by the turning lever 26 will be the direction in which the right restraint flag operates. Is changed to a different direction, the right holding flag is turned off (steps 21, 22, and 23). If a predetermined condition that the left continuously variable transmission 11L may increase in speed is satisfied, the left holding is performed. The flag is turned on (steps 24 and 25). The predetermined condition is that the trunnion shaft 29 in the right continuously variable transmission 11R is near the target shift position, the trunnion shaft 29 in the left continuously variable transmission 11L is out of the target shift position, and is near the neutral range. If the difference between the output rotation speeds of the left and right continuously variable transmissions 11R and 11L is less than 30 rpm, it is assumed that the predetermined condition is satisfied.
[0043]
In addition, the state in which the turning lever 26 is not tilted to the right, that is, the state in which the turning lever 26 is in the neutral position and switches to a state in which a straight traveling state is commanded, and the output rotational speed of the left and right continuously variable transmissions 11R and 11L is reduced. If they are the same or almost the same, specifically, if the speed difference between the output rotational speeds of the left and right continuously variable transmissions 11R and 11L is less than 10 rpm, the left restraint flag is turned off (steps 26 and 27).
[0044]
Next, if the turning lever 26 is tilted to the left, it is determined that the turning direction commanded by the turning lever 26 has been changed to a direction different from the direction in which the left holding flag operates, and the left holding flag is turned off ( Steps 28 and 29), if the predetermined condition that the right continuously variable transmission 11R may cause an increase in speed is satisfied, the right restraint flag is turned on (steps 30 and 31). The predetermined condition is that the trunnion shaft 29 in the left continuously variable transmission 11L is near the target shift position, the trunnion shaft 29 in the right continuously variable transmission 11R is out of the target shift position, and is near the neutral range. If the difference between the output rotation speeds of the left and right continuously variable transmissions 11R and 11L is less than 30 rpm, it is assumed that the predetermined condition is satisfied.
[0045]
In addition, the state in which the turning lever 26 is not tilted to the left, that is, the state in which the turning lever 26 is in the neutral position and switches to a state in which a straight traveling state is commanded, and the output rotational speed of the left and right continuously variable transmissions 11R and 11L is reduced. If they are the same or substantially the same, specifically, if the speed difference between the output rotational speeds of the left and right continuously variable transmissions 11R and 11L is less than 10 rpm, the right restraint flag is turned off (steps 32 and 33).
[0046]
When the position of the main shift lever 24 is changed and the acceleration / deceleration operation is performed, both the left hold flag and the right hold flag are turned off (steps 34 and 35), but the position of the main shift lever 24 has changed. Otherwise, if the left restraint flag is on, the restraint operation of the trunnion shaft 29 of the left continuously variable transmission 11L is executed (steps 36 and 37). Specifically, the shift position of the trunnion shaft 29 is fixed to the position immediately before the command state of the turning lever 26 is switched. If the right restraint flag is on, the restraint operation of the trunnion shaft 29 of the right continuously variable transmission 11R is executed as in step 37 (steps 38 and 39). Such a pressing operation of the trunnion shaft 29 corresponds to a shift position fixing operation.
[0047]
Then, after such a restraining process is performed, for example, when a turn is commanded to the right (step 12), the left side of the continuously variable transmission that is located on the side away from the center of the turn. Assuming that the continuously variable transmission 11L is a reference continuously variable transmission, at this time, if the left hold-down flag is not turned on (step 13), the transmission position of the trunnion shaft 29 in the left continuously variable transmission 11L is the target transmission position. The traveling operation mechanism 30 is operated so as to perform the speed change operation (step 14). Specifically, switching control of the refueling solenoid valve 34A and the oil draining solenoid valve 34B in the traveling operation mechanism 30 is performed by proportional control so that the deviation between the actual shift position of the trunnion shaft 29 and the target shift position is reduced. Thus, the operation of the hydraulic cylinder 33R is controlled. If the left restraint flag is turned on in step 13, the step S14 is not executed until the left restraint flag is turned off in the restraining process, and the gear position of the trunnion shaft 29 of the left continuously variable transmission 11L is turned. 26 is fixed to the position immediately before the command state is switched.
[0048]
Next, the output rotation speed of the left continuously variable transmission 11L is detected by the rotation speed sensor 45, and the output rotation speed of the left continuously variable transmission 11L is compared with the output rotation speed of the right continuously variable transmission 11R. A target rotation speed setting process is performed to determine a target rotation speed of the right continuously variable transmission 11R so that the speed ratio becomes a speed ratio corresponding to a turning radius commanded by the turning lever 26 (step 15).
[0049]
As shown in FIG. 6, the relationship between the operation position of the turning lever 26 and the speed ratio of the left and right continuously variable transmissions 11R and 11L is preset and stored, and this relationship and the command based on the operating position of the turning lever 26 are stored. Based on the information, the target rotational speed of the continuously variable transmission 11R on the right side is determined. 6, the output rotation speed V of the continuously variable transmission located on the reference side, that is, the side distant 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.
[0050]
As is clear from this figure, as the speed ratio of the turning lever 26 to the operating position increases, the larger the amount of movement of the turning lever 26 from the neutral position, the more gradually the operating position of the turning lever 26 changes per unit amount. A quadratic function that changes the amount of change in the turning radius with respect to a change per unit amount of the operating position of the turning lever to the larger side as the amount of movement in the direction away from the neutral position increases in a form that changes to the larger side. Is set as In addition, a plurality of (four in the example shown in FIG. 6) turning modes having different speed ratios when the turning lever 26 is operated to the maximum operation position where the moving amount of the turning lever 26 is the largest can be selected. A mode changeover switch 42 for switching the turning mode is provided, and a changeover command by the mode changeover switch 42 is given to the control device 31, and the control device 31 determines which curve based on the changeover command. It is determined whether or not the target rotation speed is to be obtained by using it.
[0051]
The four types of turning modes shown in FIG. 9 will be described. 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 the output of the continuously variable transmission on the opposite side. A mode (L1) in which the rotational speed is reduced to about 1/3 of the rotational speed V, a mode (L2) in which the output rotational speed of the continuously variable transmission on the turning center side becomes zero, A mode in which the output rotational speed of the continuously variable transmission is a speed that is about 逆 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 (L3). The output rotational speed of the continuously variable transmission on the turning center side is substantially the same as 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 mode (L4) is set respectively.
[0052]
Then, a deviation between the target rotational speed obtained as described above and the current output rotational 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 16). More specifically, the refueling solenoid valve 34A and the respective oil discharging solenoids in the traveling operation mechanism 30 are controlled by PI control so that the deviation between the target rotation speed and the current output rotation speed of the continuously variable transmission 11R on the right side is reduced. By controlling the switching of the 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.
[0053]
When it is determined in step 12 that the left direction is commanded as the turning direction, the right and left continuously variable transmission 11R are controlled as the reference-side continuously variable transmission, but the right and left are opposite. The same processing as in steps 13 to 16 is executed (steps 17 to 20). The processes in steps 11 to 14, 17, and 18 correspond to the shift position adjustment process.
[0054]
[Another embodiment]
Next, another embodiment will be described.
[0055]
(1) In the above embodiment, when the turning lever is switched to the state in which the straight traveling state is commanded and the output rotational speeds of the left and right continuously variable transmissions are the same or substantially the same, the command is given by the turning lever. When the turning direction is changed to a different direction, the shift position fixing operation is stopped when the vehicle speed command value commanded by the main shift lever is changed, respectively. The shift position fixing operation may be stopped when any one of the conditions is satisfied. The conditions for stopping may be other conditions than those described above.
[0056]
(2) In the above embodiment, in the straight traveling state, the continuously variable transmission in which the transmission position of the trunnion shaft is located farther from the neutral region among the pair of continuously variable transmissions is determined as the reference side continuously variable transmission. Although the configuration is exemplified, instead of such a configuration, the continuously variable transmission in which the shift position of the operated body is located on the side closer to the stop transmission position among the pair of continuously variable transmissions is described above. The present invention may be embodied in various forms such as a configuration determined as a reference-side continuously variable transmission, or a configuration determined as the reference-side continuously variable transmission that has reached the control target position.
[0057]
(3) 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.
[0058]
(4) In the above-described 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.
[0059]
(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 longitudinal rear view showing a transmission structure.
FIG. 3 is a schematic diagram showing a configuration of an operation structure.
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 diagram showing a relationship between a position of a turning lever and a speed ratio.
FIG. 7 is a flowchart of a control operation.
FIG. 8 is a flowchart of a control operation.
FIG. 9 is a flowchart of a control operation.
FIG. 10 is a flowchart of a control operation.
FIG. 11 is a flowchart of a control operation.
[Explanation of symbols]
1R, 1L traveling device
11R, 11L continuously variable transmission
24 Vehicle speed command means
26 Turn command means
29 Operated body
30 Speed change operation means
31 Control means
44, 45 shift output detecting means
46, 47 shift position detecting means

Claims

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, a shift operation means capable of individually performing a shift operation of the pair of continuously variable transmissions, and a command for directing straight and turning. And turning command means for commanding the magnitude of the turning radius when turning, vehicle speed command means for commanding a vehicle speed command value for straight running, and running control for operating the speed change operating means for performing straight running and turning. A traveling control device for a work vehicle, the control device comprising:
A pair of shift position detecting means for separately detecting a shift position of a shift operated body in each of the pair of continuously variable transmissions, and a pair of shift position detecting means for separately detecting an output rotation speed of the pair of continuously variable transmissions. Shift output detection means,
The control means, as the travel control,
In the straight traveling state, one of the pair of continuously variable transmissions that satisfies the reference condition is set as the reference side continuously variable transmission, and the other continuously variable transmission is set as the following side continuously variable transmission. A shift position adjusting process for operating the shift operation means such that a shift position of the operated body in the reference-side continuously variable transmission is a target shift position corresponding to the vehicle speed command value; Using the output rotation speed of the stepped transmission as a reference rotation speed, operating the shift operation means such that the output rotation speed of the follower-side continuously variable transmission becomes a target rotation speed determined in relation to the reference rotation speed. Configured to execute each of the speed following processes to be performed, and
In the turning state, the continuously variable transmission on the side away from the center of rotation of the pair of continuously variable transmissions is defined as the reference continuously variable transmission, and the shift position of the operated body in the reference continuously variable transmission is set. And a speed ratio between an output rotation speed of the continuously variable transmission on the reference side and an output rotation speed of the continuously variable transmission on the opposite side. A target speed setting process for determining a target rotation speed of the continuously variable transmission on the opposite side so as to have a speed ratio corresponding to a turning radius instructed by the rotation instructing means; and a continuously variable transmission on the opposite side. And a rotation speed adjustment process for operating the shift operation means so that the output rotation speed of the vehicle becomes the target rotation speed, and in the shift position adjustment process, the vehicle speed instruction by the vehicle speed instruction means is performed. When the command state of the turning command means is switched from the state of commanding the straight traveling to the state of commanding the turning in a state where the acceleration / deceleration operation according to the above is not performed, the continuously variable shift on the side away from the turning center. A work vehicle configured to execute a shift position fixing operation for fixing a shift position of the operated body in the device to a position immediately before the command state of the turning command means is switched so as to avoid at least acceleration. Travel control device.

The control means,
The shift position fixing operation is stopped when the turning command means is switched to a state in which the straight traveling state is commanded and the output rotational speeds of the left and right continuously variable transmissions are the same or substantially the same. The travel control device for a work vehicle according to claim 1.

The control means,
The traveling control device for a work vehicle according to claim 1 or 2, wherein the shift position fixing operation is stopped when a turning direction commanded by the turning command means is changed to a different direction.

The control means,
The traveling control of the work vehicle according to any one of claims 1 to 3, wherein the shift position fixing operation is stopped when a vehicle speed command value instructed by the vehicle speed command means is changed. apparatus.