JP3611448B2

JP3611448B2 - Driving transmission structure of work vehicle

Info

Publication number: JP3611448B2
Application number: JP15283798A
Authority: JP
Inventors: 昌義中田
Original assignee: Kubota Corp
Current assignee: Kubota Corp
Priority date: 1998-06-02
Filing date: 1998-06-02
Publication date: 2005-01-19
Anticipated expiration: 2018-06-02
Also published as: JPH11342755A

Description

【０００１】
【発明の属する技術分野】
本発明は、作業車の走行伝動構造に関する。
【０００２】
【従来の技術】
コンバインや農用トラクタ等の作業車においては、走行用として複数の変速位置を備えた有段式の第１変速装置と、複数の変速位置を備えた有段式の第２変速装置とを直列に配置したものがある。これにより、第１変速装置の変速位置の段数と第２変速装置の変速位置の段数とを乗じたものが、全体としての変速位置の段数となるのであり、全体としても変速位置が多数設定されることになる。
【０００３】
前述のような第１及び第２変速装置を備えた作業車において、例えば第１変速装置が３段の変速位置（１，２，３速位置）を備え、第２変速装置が高低２段の変速位置（低速及び高速位置）を備えている場合、第２変速装置の低速位置において第１変速装置を１，２，３速位置に変速操作し、次に第２変速装置を高速位置に変速操作して、再び第１変速装置を１，２，３速位置に変速操作することになり、全体として６段の変速位置を備えることになる。
【０００４】
この場合、例えば第１変速装置の１，２，３速位置の伝動比Ａ１，Ａ２，Ａ３を、伝動比Ａ１（１．０）、伝動比Ａ２（２．０）、伝動比Ａ３（３．０）に設定して、第２変速装置の低速及び高速位置の伝動比Ｌ，Ｈを、伝動比Ｌ（１．０）、伝動比Ｈ（４．０）に設定したとする。
従って、図６に示すように、６段の変速位置（（１）Ａ１×Ｌ、（２）Ａ２×Ｌ、（３）Ａ３×Ｌ、（４）Ａ１×Ｈ、（５）Ａ２×Ｈ、（６）Ａ３×Ｈ）の伝動比は、（１）Ａ１×Ｌ＝１．０、（２）Ａ２×Ｌ＝２．０、（３）Ａ３×Ｌ＝３．０、（４）Ａ１×Ｈ＝４．０、（５）Ａ２×Ｈ＝８．０、（６）Ａ３×Ｈ＝１２．０となる。
【０００５】
【発明が解決しようとする課題】
前述の［従来の技術］に記載のように、第２変速装置の低速位置において第１変速装置を１，２，３速位置に変速操作し、第２変速装置を高速位置において第１変速装置を１，２，３速位置に変速操作するように構成した場合、図６に示すように、変速位置（（３）Ａ３×Ｌ）での伝動比（３．０）よりも、一段高速側である変速位置（（４）Ａ１×Ｈ）での伝動比（４．０）が大きくなるようにする為に、第２変速装置の高速位置の伝動比Ｈ（４．０）を、第２変速装置の低速位置の伝動比Ｌ（１．０）よりも充分に大きなものに設定する必要がある。
【０００６】
前述のように第２変速装置の高速位置の伝動比Ｈ（４．０）が充分に大きなものに設定されてしまうと、図６に示すように変速位置（（４）Ａ１×Ｈ）よりも高速側である変速位置（（５）Ａ２×Ｈ、（６）Ａ３×Ｈ）の伝動比（８．０、１２．０）が、第２変速装置の高速位置の伝動比Ｈ（４．０）によってさらに大きなものとなってしまう。
これにより作業者が低速側から高速側に変速操作していく場合、変速位置（（４）Ａ１×Ｈ）から、変速位置（（５）Ａ２×Ｈ、（６）Ａ３×Ｈ）に変速操作される際に、急に増速される状態となるので、作業者が違和感を感じることがある。
本発明は、走行用として複数の変速位置を備えた有段式の第１及び第２変速装置を備えた作業車において、作業者が違和感を感じることなく滑らかな変速操作が行えるように構成することを目的としている。
【０００７】
【課題を解決するための手段】
［Ｉ］上記目的を達成するために講じた本発明による作業車の走行伝動構造の技術手段は、複数の変速位置を備えた有段式の第１変速装置と、複数の変速位置を備えた有段式の第２変速装置とを直列に配置し、
前記第１及び第２変速装置を通って変速操作された動力の伝動比において、前記第２変速装置が所定の変速位置であり前記第１変速装置が所定の変速位置である伝動比と、前記第２変速装置が前記所定の変速位置であり前記第１変速装置が前記所定の変速位置よりも高速側の変速位置である伝動比との間に、
前記第２変速装置が前記所定の変速位置よりも高速側の変速位置であり前記第１変速装置が前記所定の変速位置である伝動比が位置するように、前記第１及び第２変速装置の変速位置を設定すると共に、
人為的に操作される単一の変速操作具と、前記変速操作具の高速側及び低速側への操作に基づいて伝動比が順番に高速側及び低速側に設定されるように、前記第１及び第２変速装置を変速操作する変速操作手段を備えてあり、
さらに、前記変速操作手段の操作範囲に設定される変速領域のうち、高速領域で隣接する変速段間での伝動比の変化率が、低速領域で隣接する変速段間での伝動比の変化率よりも小となるように、前記前記第１変速装置及び第２変速装置における各伝動比を設定したことである。
これによって、例えば第１変速装置が３段の変速位置（１，２，３速位置）を備え、第２変速装置が高低２段の変速位置（低速及び高速位置）を備えている場合、［従来の技術］に記載の構成であると、例えば図６の横軸に示すように変速段数が少ない第２変速装置の変速位置を基礎として、変速段数の多い第１変速装置が変速操作される状態となる。これに対し請求項１の特徴によると、例えば図５の横軸に示すように［従来の技術］の構成とは逆に、変速段数の多い第１変速装置の変速位置を基礎として、変速段数の少ない第２変速装置が変速操作される状態となる。
【０００８】
これにより請求項１の特徴によると、例えば図５に示すように第１変速装置の１，２，３速位置の伝動比Ａ１，Ａ２，Ａ３を、伝動比Ａ１（１．０）、伝動比Ａ２（５．１）、伝動比Ａ３（９．２）に設定して、第２変速装置の低速及び高速位置の伝動比Ｌ，Ｈを、伝動比Ｌ（１．０）、伝動比Ｈ（１．３）に設定したとする。
従って、請求項１の特徴によると例えば図５に示すように、６段の変速位置（（１）Ａ１×Ｌ、（２）Ａ１×Ｈ、（３）Ａ２×Ｌ、（４）Ａ２×Ｈ、（５）Ａ３×Ｌ、（６）Ａ３×Ｈ）の伝動比は、（１）Ａ１×Ｌ＝１．０、（２）Ａ１×Ｈ＝１．３、（３）Ａ２×Ｌ＝５．１、（４）Ａ２×Ｈ＝６．６、（５）Ａ３×Ｌ＝９．２、（６）Ａ３×Ｈ＝１２．０となる。
【０００９】
これにより、請求項１の特徴によると例えば図５に示すように、第２変速装置の高速位置の伝動比Ｈ（１．３）を、第２変速装置の低速位置の伝動比Ｌ（１．０）よりも充分に大きなものに設定しなくても、６段の変速位置（（１）Ａ１×Ｌ、（２）Ａ１×Ｈ、（３）Ａ２×Ｌ、（４）Ａ２×Ｈ、（５）Ａ３×Ｌ、（６）Ａ３×Ｈ）の伝動比を、順番に高速側に設定することができる。
従って、第２変速装置の高速位置の伝動比Ｈ（１．３）を、第２変速装置の低速位置の伝動比Ｌ（１．０）よりも充分に大きなものに設定しなくてもよい点により、［従来の技術］に記載の構成及び図６に比べて、例えば図５に示すように急に増速されると言う状態（急に減速されると言う状態）を伴うことなく、比較的滑らかに低速側から高速側（高速側から低速側）に変速操作される状態を得ることができる。
【００１０】
［ＩＩ］請求項２の特徴によると、請求項１の場合と同様に前項［Ｉ］に記載の「作用」を備えており、これに加えて以下のような「作用」を備えている。
請求項２の特徴のように、第１変速装置を複数の摩擦クラッチを備えた摩擦クラッチ型式に構成すると、第１変速装置の変速操作時において摩擦クラッチを少し滑らせながら伝動状態に操作すると言うような操作が容易に行えるので、第１変速装置から下手側に急速に動力が伝達される状態を避けることができる。
【００１１】
［ＩＩＩ］請求項３の特徴によると、請求項１又は２の場合と同様に前項［Ｉ］［ＩＩ］に記載の「作用」を備えており、これに加えて以下のような「作用」を備えている。
伝動比の異なる複数の伝動ギヤにシフト部材を択一的に咬合させることによって変速操作されるギヤ変速型式に第２変速装置を構成した場合、請求項３の特徴のようにシフト部材をアクチュエータによって操作するように構成すると、作業者にとってシフト部材を楽に操作することができるのであり、シフト部材を伝動ギヤに咬合させる操作を、容易に制御することができるようになる。
【００１２】
【発明の実施の形態】
図１は作業車の一例である農用のコンバインの走行用のミッションケース１の内部を示しており、エンジン（図示せず）からの動力が伝動ベルト（図示せず）を介して、ミッションケース１の入力プーリー２に伝達され、ギヤシフト型式の第２変速装置４、油圧クラッチ型式の第１変速装置３及びサイドクラッチ５を介して、右及び左のクローラ走行装置６に伝達される。
【００１３】
入力プーリー２が固定された入力軸９に対し、伝動軸７及び出力プーリー８を備えた出力軸２０が配置されて、伝動軸７に伝動ギヤ２９，３０が固定されており、入力軸９に固定された伝動ギヤ３１が伝動軸７の伝動ギヤ２９に咬合している。出力軸２０にシフトギヤ３２がスプライン構造にてスライド自在に外嵌されており、シフトギヤ３２を伝動軸７の伝動ギヤ２９，３０に咬合させることによって、出力プーリー８から刈取部（図示せず）に伝達される動力を、高低２段に変速操作することができる。
【００１４】
次に第２変速装置４について説明する。
図１に示すように、入力軸９に対し伝動軸１０が配置されて、入力軸９に相対回転自在に外嵌された低速ギヤ１１及び高速ギヤ１２が、伝動軸１０に固定された低速ギヤ１３及び高速ギヤ１４に咬合しており、低速ギヤ１１及び高速ギヤ１２の間において、入力軸９にシフト部材１７がスプライン構造にてスライド自在に外嵌されている。
【００１５】
以上の構造により、シフト部材１７を低速ギヤ１１に咬合させると（低速状態）、入力軸９の動力が低速状態で伝動軸１０から第１変速装置３に伝達され、シフト部材１７を高速ギヤ１２に咬合させると（高速状態）、入力軸９の動力が高速状態で伝動軸１０から第１変速装置３に伝達されるのであり、第２変速装置４により高低の２段の変速操作が行える。
【００１６】
次に、油圧クラッチ型式（摩擦クラッチ型式）の第１変速装置３について説明する。
図１に示すように、伝動軸１０と平行に伝動軸１５，１６が配置され、伝動軸１５に前進１速ギヤ２５及び前進３速ギヤ２７が相対回転自在に外嵌されて、伝動軸１０に固定された第１出力ギヤ１８及び第２出力ギヤ１９に、前進１速及び前進３速ギヤ２５，２７が咬合しており、前進１速及び前進３速ギヤ２５，２７と伝動軸１５との間に、摩擦式で油圧多板式の前進１速クラッチ２１及び前進３速クラッチ２３が設けられている。
【００１７】
伝動軸１６に前進２速ギヤ２６及び後進ギヤ２８が相対回転自在に外嵌され、伝動軸１０の低速ギヤ１３及び伝動軸１５の前進１速ギヤ２５に、前進２速及び後進ギヤ２６，２８が咬合しており、前進２速及び後進ギヤ２６，２８と伝動軸１６との間に、摩擦式で油圧多板式の前進２速クラッチ２２及び後進クラッチ２４が設けられている。これにより、前進１速〜後進クラッチ２１〜２４に択一的に作動油を供給し伝動側に操作することにより、第１変速装置３において前進３段後進１段の変速操作が行える。
以上のように、第２変速装置４及び第１変速装置３を通って変速操作された動力が、伝動軸１５，１６の中央部に形成された出力ギヤ１５ａ，１６ａから、後述する伝動ギヤ３４、サイドギヤ３５及び駆動軸３７を介して右及び左のクローラ走行装置６に伝達される。
【００１８】
図３及び図１に示すように、サイドクラッチ５が設けられる伝動軸３３に、大径の伝動ギヤ３４が支持されており、伝動軸１５，１６の中央部に形成された出力ギヤ１５ａ，１６ａが、伝動ギヤ３４に咬合している。伝動軸３３の両端のサイドブレーキ３６が配置されて、伝動軸３３における伝動ギヤ３４とサイドブレーキ３６との間に、一対のサイドギヤ３５がスライド自在に外嵌されている。サイドギヤ３５がバネ４０により、伝動ギヤ３４のボス部３４ａの咬合部３４ｂへの咬合側に付勢されて、クローラ走行装置６における駆動軸３７の駆動ギヤ３８がサイドギヤ３５に常時咬合しており、サイドギヤ３５等によりサイドクラッチ５が構成されている。
【００１９】
伝動ギヤ３４のボス部３４ａの内側に、リング状のピストン部材３９がスライド自在に配置されており、ピストン部材３９、伝動ギヤ３４のボス部３４ａ及び伝動軸３３の中央のフランジ部３３ｄで囲まれたリング状の油室が形成されている。伝動軸３３に油路３３ａが形成されており、油路３３ａの端部から斜めに形成された油路３３ｂが油室に接続されている。
【００２０】
これにより、通常は右及び左のサイドギヤ３５が伝動ギヤ３４の咬合部３４ｂに咬合して（図３の右のサイドギヤ３５の状態参照）、伝動ギヤ３４の動力が右及び左のクローラ走行装置６に伝達されており、機体は直進している。次に、油路３３ａ，３３ｂを介して例えば左の油室に作動油を供給すると、図３に示すように左のピストン部材３９により、左のサイドギヤ３５が紙面左方に押し操作されて、左のサイドギヤ３５が伝動ギヤ３４の咬合部３４ｂから離れるのであり、左のピストン部材３９が油路３３ｃに達して油室と油路３３ｃとが連通すると、この位置で左のピストン部材３９及びサイドギヤ３５が停止する。
この位置は、左のサイドギヤ３５が伝動ギヤ３４の咬合部３４ｂから離れるのに対し、左のサイドブレーキ３６を押圧入り操作しないサイドクラッチ５の切り位置である。従って、左のクローラ走行装置６への動力が遮断されて、左のクローラ走行装置６が自由回転する状態となって、機体は左に緩やかに旋回する。
【００２１】
次に油路３３ｃの下手側を絞り操作すると油室の圧力が上昇して、左のピストン部材３９により左のサイドギヤ３５が、サイドクラッチ５の切り位置からさらに紙面左方に押し操作されて、左のサイドブレーキ３６を押圧入り操作する。これにより、左のサイドブレーキ３６により左のクローラ走行装置６に制動が掛かり、機体は左に信地旋回する。
【００２２】
次に、第１及び第２変速装置３，４の変速操作の構成について説明する。
図２に示すように、第２変速装置４のシフト部材１７をスライド操作する複動型の油圧シリンダ４１が備えられており、第１変速装置３の前進１速〜後進クラッチ２１〜２４及び第２変速装置４の油圧シリンダ４１に作動油を給排操作するロータリ式の変速制御弁４２が、ミッションケース１に内装されている。変速制御弁２３は中立位置Ｎ、前進１速位置Ｆ１〜前進６速位置Ｆ６、後進１速位置Ｒ１及び後進２速位置Ｒ２を備えており、円筒状に形成されたスプール４２ａ（図４参照）の内部に、ピストン４３ａ及びバネ４３ｂによって構成されたアキュムレータ４３が備えられている。
【００２３】
ミッションケース１の潤滑油が作動油としてポンプ４４に吸引され、ポンプ４４からの作動油が油路４７を介して変速制御弁４２に供給されて、変速制御弁４２からの作動油が、油路４８（又は油路４９）を介して油圧シリンダ４１の油室４１ａ（又は油室４１ｂ）に供給されており、油圧シリンダ４１の油室４１ｂ（又は油室４１ａ）の作動油が、油路４９（又は油路４８）を介して、変速制御弁４２に戻されミッションケース１に戻されている。
【００２４】
油圧シリンダ４１の油室４１ａ（又は油室４１ｂ）の作動油が、油路５０を介して変速制御弁４２に戻されて、変速制御弁４２の内部油路５１を介してアキュムレータ４３に供給されており、アキュムレータ４３からの作動油が変速制御弁４２の内部油路５２及び油路５３を介して、前進１速〜後進クラッチ２１〜２４のうちの一つに供給される。
【００２５】
図４に示すように、変速制御弁４２のスプール４２ａの端部にギヤ部４２ｂが形成されて、ギヤ部４２ｂがミッションケース１の外側に突出している。ミッションケース１の上部の横軸芯Ｐ１周りに、扇型の操作ギヤ４５が揺動自在に支持されて、操作ギヤ４５に変速レバー４６が固定されており、操作ギヤ４５がスプール４２ａのギヤ部４２ｂに咬合している。以上の構造によって、変速レバー４６を図４の紙面左右方向に操作すると、操作ギヤ４５によりスプール４２ａが回転操作されて、スプール４２ａが図２に示す中立位置Ｎ、前進１速位置Ｆ１、前進２速位置Ｆ２、前進３速位置Ｆ３、前進４速位置Ｆ４、前進５速位置Ｆ５、前進６速位置Ｆ６、並びに、後進１速位置Ｒ１、後進２速位置Ｒ２に操作される。
【００２６】
次に、変速制御弁４２における前進１速位置Ｆ１〜後進２速位置Ｒ２について説明する。
図２に示す状態は変速制御弁４２を中立位置Ｎに操作している状態であり、作動油が油圧シリンダ４１の油室４１ａに供給されて、油圧シリンダ４１によりシフト部材１７が、図２の紙面右方にスライド操作されて低速ギヤ１１に咬合しており、前進１速位置Ｆ１〜後進クラッチ２４の作動油がミッションケース１に戻されて、前進１速クラッチ２１〜後進クラッチ２４が伝動遮断側に操作されている。これにより、動力が低速状態で第２変速装置４から第１変速装置３に伝達されているが、第１変速装置３の前進１速クラッチ２１〜後進クラッチ２４が伝動遮断側に操作されているので、動力が第１変速装置３において遮断された状態となって、機体は停止している。
【００２７】
前述のように変速制御弁４２を中立位置Ｎに操作している状態から前進１速位置Ｆ１に操作すると、第２変速装置４の低速状態において、変速制御弁４２から前進１速クラッチ２１に作動油が供給され、前進１速クラッチ２１が伝動側に操作されて、機体が発進する。この場合、第２変速装置４の低速状態において、前進１速クラッチ２１が伝動遮断側から伝動側に操作されるので、前進１速クラッチ２１がある程度滑って、発進時のショックが前進１速クラッチ２１に吸収されながら、機体がショック少なく滑らかに発進する。
【００２８】
変速制御弁４２を前進２速位置Ｆ２に操作すると、前進１速クラッチ２１が伝動側に操作された状態において、油圧シリンダ４１の油室４１ｂに作動油が供給されて、油圧シリンダ４１によりシフト部材１７が、図２の紙面左方にスライド操作されて高速ギヤ１２に咬合し、第２変速装置４が高速状態となる。
変速制御弁４２を前進３速位置Ｆ３に操作すると、油圧シリンダ４１の油室４１ａに作動油が供給されて、油圧シリンダ４１によりシフト部材１７が、図２の紙面右方にスライド操作されて低速ギヤ１１に咬合し、第２変速装置４が低速状態となり、前進２速クラッチ２２に作動油が供給されて、前進２速クラッチ２２が伝動側に操作される。
【００２９】
変速制御弁４２を前進４速位置Ｆ４に操作すると、前進２速クラッチ２２が伝動側に操作された状態において、油圧シリンダ４１の油室４１ｂに作動油が供給されて、油圧シリンダ４１によりシフト部材１７が、図２の紙面左方にスライド操作されて高速ギヤ１２に咬合し、第２変速装置４が高速状態となる。
変速制御弁４２を前進５速位置Ｆ５に操作すると、油圧シリンダ４１の油室４１ａに作動油が供給されて、油圧シリンダ４１によりシフト部材１７が、図２の紙面右方にスライド操作されて低速ギヤ１１に咬合し、第２変速装置４が低速状態となり、前進３速クラッチ２３に作動油が供給されて、前進３速クラッチ２３が伝動側に操作される。
変速制御弁４２を前進６速位置Ｆ６に操作すると、前進３速クラッチ２３が伝動側に操作された状態において、油圧シリンダ４１の油室４１ｂに作動油が供給されて、油圧シリンダ４１によりシフト部材１７が、図２の紙面左方にスライド操作されて高速ギヤ１２に咬合し、第２変速装置４が高速状態となる。
【００３０】
前述のように変速制御弁４２を中立位置Ｎに操作している状態から後進１速位置Ｒ１に操作すると、第２変速装置４の低速状態において、変速制御弁４２から後進クラッチ２４に作動油が供給され、後進クラッチ２４が伝動側に操作されて機体が発進する。この場合、第２変速装置４の低速状態において、後進クラッチ２４が伝動遮断側から伝動側に操作されるので、後進クラッチ２４がある程度滑って、発進時のショックが後進クラッチ２４に吸収されながら、機体がショック少なく滑らかに発進する。
変速制御弁４２を後進２速位置Ｆ２に操作すると、後進クラッチ２４が伝動側に操作された状態において、油圧シリンダ４１の油室４１ｂに作動油が供給されて、油圧シリンダ４１によりシフト部材１７が、図２の紙面左方にスライド操作されて高速ギヤ１２に咬合し、第２変速装置４が高速状態となる。
【００３１】
［発明の実施の別形態］図１及び図２の構成においては、第２変速装置４が高低の２段に変速操作可能に構成されているが、この第２変速装置４を高中低の３段に変速操作可能に構成してもよい。図１及び図２の構成においては、第１変速装置３が前進３段に変速操作可能に構成されているが、この第１変速装置３を前進４段に変速操作可能に構成してもよい。
【００３２】
前述のように第１及び第２変速装置３，４を構成した場合、第１変速装置の１，２，３，４速位置を伝動比Ａ１，Ａ２，Ａ３，Ａ４に設定し、第２変速装置の低速、中速及び高速位置を伝動比Ｌ，Ｍ，Ｈに設定すると、第１及び第２変速装置３，４による１２段の変速位置の伝動比が、以下のような順番で高速になっていくように設定する。
（１）Ａ１×Ｌ＜（２）Ａ１×Ｍ＜（３）Ａ１×Ｈ＜（４）Ａ２×Ｌ＜（５）Ａ２×Ｍ＜（６）Ａ２×Ｈ＜（７）Ａ３×Ｌ＜（８）Ａ３×Ｍ＜（９）Ａ３×Ｈ＜（１０）Ａ４×Ｌ＜（１１）Ａ４×Ｍ＜（１２）Ａ４×Ｈ。
【００３３】
【発明の効果】
請求項１の特徴によると、走行用として複数の変速位置を備えた有段式の第１及び第２変速装置を備えた作業車において、第２変速装置の低速側の変速比に対して第２変速装置の高速側の変速比を、あまり大きなものに設定しなくても、比較的滑らかに低速側から高速側（高速側から低速側）に変速操作される状態を得ることができるようになるので、作業者が違和感を感じることなく滑らかな変速操作が行えるようになって、作業車の走行性能を向上させることができた。
【００３４】
請求項２の特徴によると、請求項１の場合と同様に前述の請求項１の「発明の効果」を備えており、この「発明の効果」に加えて以下のような「発明の効果」を備えている。
請求項２の特徴のように、第１変速装置を摩擦クラッチ型式に構成することにより、変速操作がショック少なく滑らかに行えるようになって、作業車の乗り心地を向上させることができた。
【００３５】
請求項３の特徴によると、請求項１又は２の場合と同様に前述の請求項１又は２の「発明の効果」を備えており、この「発明の効果」に加えて以下のような「発明の効果」を備えている。
請求項３の特徴によると、伝動比の異なる複数の伝動ギヤにシフト部材を択一的に咬合させることによって変速操作されるギヤ変速型式に第２変速装置を構成した場合、アクチュエータによってシフト部材が楽に操作されるようになり、変速操作時の操作性を向上させることができた。さらに、シフト部材の操作をアクチュエータにより容易に制御することができるようになるので、作業車の機能性を高めることができるようになる。
【図面の簡単な説明】
【図１】ミッションケースの内部を示す概略正面図
【図２】変速制御弁、アキュムレータ、前進１速〜後進クラッチ及び油圧シリンダ等の油圧回路図
【図３】サイドギヤ付近の縦断正面図
【図４】変速制御弁のスプール及び変速レバーの操作ギヤの連係状態を示す側面図
【図５】変速位置と伝動比との関係を示す図
【図６】従来の技術における変速位置と伝動比との関係を示す図
【符号の説明】
３第１変速装置
４第２変速装置
１１，１２伝動ギヤ
１７シフト部材
２１，２２，２３，２４摩擦クラッチ
４１アクチュエータ
４２変速操作手段
４６変速操作具[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a traveling transmission structure for a work vehicle.
[0002]
[Prior art]
In a working vehicle such as a combine or an agricultural tractor, a stepped first transmission having a plurality of shift positions for traveling and a stepped second transmission having a plurality of shift positions are connected in series. There is something arranged. As a result, the product of the number of shift positions of the first transmission and the number of shift positions of the second transmission is the number of shift positions as a whole, and a large number of shift positions are set as a whole. Will be.
[0003]
In a work vehicle including the first and second transmissions as described above, for example, the first transmission has three speed positions (1, 2, and 3rd speed positions), and the second transmission has high and low two speeds. If the shift position (low speed and high speed position) is provided, the first transmission is shifted to the first, second and third speed positions at the low speed position of the second transmission, and then the second transmission is shifted to the high speed position. By operating, the first transmission device is again shifted to the first, second and third speed positions, so that six shift positions are provided as a whole.
[0004]
In this case, for example, the transmission ratios A1, A2, and A3 of the first, second, and third speed positions of the first transmission are set to the transmission ratio A1 (1.0), the transmission ratio A2 (2.0), and the transmission ratio A3 (3. It is assumed that the transmission ratios L and H at the low speed and high speed positions of the second transmission are set to the transmission ratio L (1.0) and the transmission ratio H (4.0).
Therefore, as shown in FIG. 6, there are six shift positions ((1) A1 × L, (2) A2 × L, (3) A3 × L, (4) A1 × H, (5) A2 × H, The transmission ratio of (6) A3 × H) is (1) A1 × L = 1.0, (2) A2 × L = 2.0, (3) A3 × L = 3.0, (4) A1 × H = 4.0, (5) A2 × H = 8.0, and (6) A3 × H = 12.0.
[0005]
[Problems to be solved by the invention]
As described in [Prior Art] above, the first transmission is shifted to the first, second and third speed positions at the low speed position of the second transmission, and the first transmission is operated at the high speed position. Is configured to be shifted to the first, second, and third speed positions, as shown in FIG. 6, one step higher than the transmission ratio (3.0) at the shift position ((3) A3 × L). In order to increase the transmission ratio (4.0) at the shift position ((4) A1 × H), the transmission ratio H (4.0) at the high speed position of the second transmission is set to the second It is necessary to set it to be sufficiently larger than the transmission ratio L (1.0) at the low speed position of the transmission.
[0006]
As described above, if the transmission ratio H (4.0) at the high speed position of the second transmission is set to a sufficiently large value, the speed change position ((4) A1 × H) as shown in FIG. The transmission ratio (8.0, 12.0) of the shift position ((5) A2 × H, (6) A3 × H) on the high speed side is the transmission ratio H (4.0 of the high speed position of the second transmission). ) Makes it even bigger.
Thus, when the operator shifts from the low speed side to the high speed side, the shift operation is performed from the shift position ((4) A1 × H) to the shift position ((5) A2 × H, (6) A3 × H). When this is done, the speed is suddenly increased, so the operator may feel uncomfortable.
The present invention is configured so that a smooth shift operation can be performed without causing the operator to feel uncomfortable in a work vehicle including stepped first and second transmissions having a plurality of shift positions for traveling. The purpose is that.
[0007]
[Means for Solving the Problems]
[I] The technical means of the traveling transmission structure for a work vehicle according to the present invention taken to achieve the above object includes a stepped first transmission having a plurality of shift positions and a plurality of shift positions. A stepped second transmission is arranged in series ,
In the transmission ratio of the motive power shifted through the first and second transmissions, the transmission ratio in which the second transmission is a predetermined transmission position and the first transmission is a predetermined transmission position; Between the transmission ratio in which the second transmission is the predetermined shift position and the first transmission is the shift position on the higher speed side than the predetermined shift position,
The first and second transmissions are arranged such that the second transmission is at a higher speed shift position than the predetermined shift position and the transmission ratio is at which the first transmission is at the predetermined shift position. While setting the shift position,
The first shift operation tool that is artificially operated, and the transmission ratio is set to the high speed side and the low speed side in order based on the operation to the high speed side and the low speed side of the shift operation tool. And a shift operation means for shifting the second transmission.
Further, among the shift regions set in the operation range of the shift operation means, the rate of change of the transmission ratio between adjacent gears in the high speed region is the rate of change of the transmission ratio between adjacent gears in the low speed region. Each transmission ratio in the first transmission and the second transmission is set so as to be smaller .
Thus, for example, when the first transmission device has three shift positions (1, 2 and 3rd speed positions) and the second transmission device has two shift positions (low speed and high speed positions), [ With the configuration described in the “Prior Art”, for example, as shown on the horizontal axis in FIG. 6, the first transmission with a large number of gears is shifted based on the shift position of the second transmission with a small number of gears. It becomes a state. On the other hand, according to the feature of claim 1, for example, as shown on the horizontal axis of FIG. 5, the number of shift stages is based on the shift position of the first transmission with a large number of shift stages, as opposed to the configuration of [Prior Art]. The second transmission device with a small amount of gears is in a state where the gear shift operation is performed.
[0008]
Thus, according to the feature of claim 1, for example, as shown in FIG. 5, the transmission ratios A1, A2 and A3 of the first, second and third speed positions of the first transmission are set to the transmission ratio A1 (1.0), the transmission ratio. A2 (5.1) and transmission ratio A3 (9.2) are set, and transmission ratios L and H at the low speed and high speed positions of the second transmission are set to transmission ratio L (1.0) and transmission ratio H ( It is assumed that 1.3) is set.
Therefore, according to the feature of claim 1, for example, as shown in FIG. 5, there are six shift positions ((1) A1 × L, (2) A1 × H, (3) A2 × L, (4) A2 × H , (5) A3 × L, (6) A3 × H) are (1) A1 × L = 1.0, (2) A1 × H = 1.3, (3) A2 × L = 5 0.1, (4) A2 × H = 6.6, (5) A3 × L = 9.2, and (6) A3 × H = 12.0.
[0009]
Thus, according to the feature of claim 1, for example, as shown in FIG. 5, the transmission ratio H (1.3) at the high speed position of the second transmission is set to the transmission ratio L (1. Even if it is not set to a value sufficiently larger than (0), the six shift positions ((1) A1 × L, (2) A1 × H, (3) A2 × L, (4) A2 × H, ( 5) The transmission ratio of A3 × L and (6) A3 × H) can be set in order on the high speed side.
Therefore, the transmission ratio H (1.3) at the high speed position of the second transmission need not be set sufficiently larger than the transmission ratio L (1.0) at the low speed position of the second transmission. Compared with the configuration described in [Prior Art] and FIG. 6, for example, a comparison is made without accompanying a state of sudden increase in speed (state of sudden deceleration) as shown in FIG. 5, for example. Thus, it is possible to obtain a state where the gear shifting operation is smoothly performed from the low speed side to the high speed side (from the high speed side to the low speed side).
[0010]
[II] According to the feature of claim 2, as in the case of claim 1, the “action” described in the preceding item [I] is provided, and in addition to this, the following “action” is provided.
If the first transmission is configured as a friction clutch type having a plurality of friction clutches as in the feature of claim 2, it is said that the first clutch is operated in a transmission state while sliding the friction clutch slightly during the shifting operation of the first transmission. Since such an operation can be easily performed, it is possible to avoid a state in which power is rapidly transmitted from the first transmission to the lower side.
[0011]
[III] According to the feature of claim 3, as in the case of claim 1 or 2, the “action” described in the preceding paragraph [I] [II] is provided, and in addition, the following “action” is provided. It has.
When the second transmission is configured in a gear transmission type in which a shift operation is performed by selectively engaging a shift member with a plurality of transmission gears having different transmission ratios, the shift member is configured by an actuator as in the feature of claim 3. When configured to operate, the shift member can be easily operated for the operator, and the operation of engaging the shift member with the transmission gear can be easily controlled.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows the inside of a mission case 1 for traveling an agricultural combine that is an example of a work vehicle. Power from an engine (not shown) is transmitted via a transmission belt (not shown) to the mission case 1. Is transmitted to the right and left crawler travel devices 6 via the gear shift type second transmission device 4, the hydraulic clutch type first transmission device 3 and the side clutch 5.
[0013]
An output shaft 20 including a transmission shaft 7 and an output pulley 8 is arranged with respect to the input shaft 9 to which the input pulley 2 is fixed, and transmission gears 29 and 30 are fixed to the transmission shaft 7. The fixed transmission gear 31 is engaged with the transmission gear 29 of the transmission shaft 7. A shift gear 32 is slidably fitted on the output shaft 20 in a spline structure, and the shift gear 32 is engaged with the transmission gears 29 and 30 of the transmission shaft 7 so that the output pulley 8 cuts a cutting portion (not shown). The transmitted power can be shifted in two steps of high and low.
[0014]
Next, the second transmission 4 will be described.
As shown in FIG. 1, a transmission shaft 10 is arranged with respect to the input shaft 9, and a low-speed gear 11 and a high-speed gear 12 that are externally fitted to the input shaft 9 so as to be relatively rotatable are fixed to the transmission shaft 10. 13 and the high speed gear 14, and a shift member 17 is slidably fitted on the input shaft 9 in a spline structure between the low speed gear 11 and the high speed gear 12.
[0015]
With the above structure, when the shift member 17 is engaged with the low speed gear 11 (low speed state), the power of the input shaft 9 is transmitted from the transmission shaft 10 to the first transmission 3 in the low speed state, and the shift member 17 is transmitted to the high speed gear 12. (The high speed state), the power of the input shaft 9 is transmitted from the transmission shaft 10 to the first transmission device 3 at a high speed state, and the second transmission device 4 can perform two-step shift operation.
[0016]
Next, the first transmission 3 of the hydraulic clutch type (friction clutch type) will be described.
As shown in FIG. 1, transmission shafts 15 and 16 are arranged in parallel with the transmission shaft 10, and a forward first speed gear 25 and a forward third speed gear 27 are externally fitted to the transmission shaft 15 so as to be relatively rotatable. The first output gear 18 and the second output gear 19 fixed to the first output gear 18 and the second output gear 19 are engaged with the first forward gear 3 and the third forward gear 25, 27. Between them, a friction type hydraulic multi-plate forward first speed clutch 21 and a forward third speed clutch 23 are provided.
[0017]
A forward second-speed gear 26 and a reverse gear 28 are externally fitted to the transmission shaft 16 so as to be relatively rotatable, and a forward second-speed and reverse gears 26, 28 are connected to the low-speed gear 13 of the transmission shaft 10 and the forward first-speed gear 25 of the transmission shaft 15. Between the forward second speed and reverse gears 26, 28 and the transmission shaft 16, a friction type hydraulic multi-plate forward second speed clutch 22 and a reverse clutch 24 are provided. As a result, the first forward gear to the reverse clutches 21 to 24 can be alternatively supplied with hydraulic oil and operated to the transmission side, whereby the first speed change device 3 can perform a shift operation of three forward speeds and one reverse speed.
As described above, the power shifted through the second transmission device 4 and the first transmission device 3 is transmitted from the output gears 15a and 16a formed at the center of the transmission shafts 15 and 16 to a transmission gear 34 described later. Then, it is transmitted to the right and left crawler traveling devices 6 through the side gear 35 and the drive shaft 37.
[0018]
As shown in FIGS. 3 and 1, a large-diameter transmission gear 34 is supported on the transmission shaft 33 provided with the side clutch 5, and output gears 15 a and 16 a formed at the center of the transmission shafts 15 and 16. Is engaged with the transmission gear 34. Side brakes 36 at both ends of the transmission shaft 33 are arranged, and a pair of side gears 35 are slidably fitted between the transmission gear 34 and the side brake 36 on the transmission shaft 33. The side gear 35 is biased by the spring 40 toward the occlusion side of the boss portion 34a of the transmission gear 34 to the occlusion portion 34b, and the drive gear 38 of the drive shaft 37 in the crawler traveling device 6 is always engaged with the side gear 35. The side clutch 5 is constituted by the side gear 35 and the like.
[0019]
A ring-shaped piston member 39 is slidably disposed inside the boss portion 34 a of the transmission gear 34, and is surrounded by the piston member 39, the boss portion 34 a of the transmission gear 34, and the flange portion 33 d at the center of the transmission shaft 33. A ring-shaped oil chamber is formed. An oil passage 33a is formed in the transmission shaft 33, and an oil passage 33b formed obliquely from the end of the oil passage 33a is connected to the oil chamber.
[0020]
As a result, the right and left side gears 35 are normally engaged with the occlusal portion 34b of the transmission gear 34 (see the state of the right side gear 35 in FIG. 3), and the power of the transmission gear 34 is controlled to the right and left crawler travel devices 6. The aircraft is going straight. Next, when hydraulic oil is supplied to, for example, the left oil chamber via the oil passages 33a and 33b, the left side gear 35 is pushed to the left by the left piston member 39 as shown in FIG. The left side gear 35 is separated from the occlusal portion 34b of the transmission gear 34. When the left piston member 39 reaches the oil passage 33c and the oil chamber and the oil passage 33c communicate with each other, the left piston member 39 and the side gear are located at this position. 35 stops.
This position is a disengagement position of the side clutch 5 in which the left side brake 36 is not pressed and operated while the left side gear 35 is separated from the occlusal portion 34 b of the transmission gear 34. Therefore, the power to the left crawler traveling device 6 is cut off, and the left crawler traveling device 6 enters a state of free rotation, so that the aircraft slowly turns to the left.
[0021]
Next, when the lower side of the oil passage 33c is squeezed, the pressure in the oil chamber rises, and the left side gear 35 is further pushed to the left from the cut position of the side clutch 5 by the left piston member 39, The left side brake 36 is pressed and operated. As a result, the left crawler travel device 6 is braked by the left side brake 36, and the aircraft turns to the left.
[0022]
Next, the configuration of the shifting operation of the first and second transmission devices 3 and 4 will be described.
As shown in FIG. 2, a double-acting hydraulic cylinder 41 that slides the shift member 17 of the second transmission 4 is provided, and the first transmission 3 to the reverse clutches 21 to 24 and the first transmission 3 of the first transmission 3 are provided. A rotary type shift control valve 42 for supplying and discharging hydraulic oil to and from a hydraulic cylinder 41 of the two-speed transmission 4 is housed in the transmission case 1. The shift control valve 23 includes a neutral position N, a forward first speed position F1 to a forward sixth speed position F6, a reverse first speed position R1, and a reverse second speed position R2, and a spool 42a formed in a cylindrical shape (see FIG. 4). Is provided with an accumulator 43 constituted by a piston 43a and a spring 43b.
[0023]
The lubricating oil in the transmission case 1 is sucked into the pump 44 as hydraulic oil, the hydraulic oil from the pump 44 is supplied to the transmission control valve 42 via the oil passage 47, and the hydraulic oil from the transmission control valve 42 is supplied to the oil passage. 48 (or oil passage 49) is supplied to the oil chamber 41 a (or oil chamber 41 b) of the hydraulic cylinder 41, and the hydraulic oil in the oil chamber 41 b (or oil chamber 41 a) of the hydraulic cylinder 41 is supplied to the oil passage 49. It is returned to the transmission control valve 42 via the (or oil passage 48) and returned to the mission case 1.
[0024]
The hydraulic oil in the oil chamber 41 a (or oil chamber 41 b) of the hydraulic cylinder 41 is returned to the transmission control valve 42 through the oil passage 50 and supplied to the accumulator 43 through the internal oil passage 51 of the transmission control valve 42. The hydraulic oil from the accumulator 43 is supplied to one of the forward first speed to the reverse clutches 21 to 24 through the internal oil passage 52 and the oil passage 53 of the transmission control valve 42.
[0025]
As shown in FIG. 4, a gear portion 42 b is formed at the end of the spool 42 a of the transmission control valve 42, and the gear portion 42 b protrudes outside the transmission case 1. A fan-shaped operation gear 45 is swingably supported around the horizontal axis P1 at the top of the transmission case 1, and a transmission lever 46 is fixed to the operation gear 45. The operation gear 45 is a gear portion of the spool 42a. Bites 42b. With the above structure, when the speed change lever 46 is operated in the left-right direction in FIG. 4, the spool 42a is rotated by the operation gear 45, and the spool 42a is in the neutral position N, forward first speed position F1, forward 2 shown in FIG. It is operated to a speed position F2, a forward third speed position F3, a forward fourth speed position F4, a forward fifth speed position F5, a forward sixth speed position F6, a reverse first speed position R1, and a reverse second speed position R2.
[0026]
Next, the first forward speed position F1 to the second reverse speed position R2 of the shift control valve 42 will be described.
The state shown in FIG. 2 is a state in which the shift control valve 42 is operated to the neutral position N. The hydraulic oil is supplied to the oil chamber 41a of the hydraulic cylinder 41, and the shift member 17 is moved by the hydraulic cylinder 41 to the position shown in FIG. It is slid rightward on the paper surface and meshed with the low speed gear 11, the hydraulic oil from the first forward speed position F <b> 1 to the reverse clutch 24 is returned to the transmission case 1, and the forward first speed clutch 21 to the reverse clutch 24 are cut off from transmission. Is being operated on the side. Thus, power is transmitted from the second transmission 4 to the first transmission 3 in a low speed state, but the forward first speed clutch 21 to the reverse clutch 24 of the first transmission 3 are operated to the transmission cutoff side. Therefore, the power is cut off in the first transmission 3, and the aircraft is stopped.
[0027]
As described above, when the shift control valve 42 is operated from the neutral position N to the forward first speed position F1, the shift control valve 42 operates the forward first speed clutch 21 in the low speed state of the second transmission 4. Oil is supplied, the forward first speed clutch 21 is operated to the transmission side, and the aircraft starts. In this case, since the forward first speed clutch 21 is operated from the transmission cut-off side to the transmission side in the low speed state of the second transmission 4, the forward first speed clutch 21 slips to some extent, and the shock at the time of start is a forward first speed clutch. The aircraft will start smoothly with little shock while being absorbed by 21.
[0028]
When the shift control valve 42 is operated to the forward second speed position F2, hydraulic oil is supplied to the oil chamber 41b of the hydraulic cylinder 41 in a state where the forward first speed clutch 21 is operated to the transmission side, and the hydraulic cylinder 41 shifts the shift member. 17 is slid to the left in FIG. 2 to engage with the high speed gear 12, and the second transmission 4 is in a high speed state.
When the shift control valve 42 is operated to the forward third speed position F3, hydraulic oil is supplied to the oil chamber 41a of the hydraulic cylinder 41, and the shift member 17 is slid to the right in FIG. The second transmission 4 is brought into a low speed state by meshing with the gear 11, hydraulic oil is supplied to the forward second speed clutch 22, and the forward second speed clutch 22 is operated to the transmission side.
[0029]
When the shift control valve 42 is operated to the forward fourth speed position F4, hydraulic oil is supplied to the oil chamber 41b of the hydraulic cylinder 41 in a state where the forward second speed clutch 22 is operated to the transmission side, and the hydraulic cylinder 41 shifts the shift member. 17 is slid to the left in FIG. 2 and meshes with the high speed gear 12 so that the second transmission 4 is in a high speed state.
When the shift control valve 42 is operated to the forward fifth speed position F5, hydraulic oil is supplied to the oil chamber 41a of the hydraulic cylinder 41, and the shift member 17 is slid to the right in the drawing of FIG. The second transmission 4 is brought into a low speed state by meshing with the gear 11, hydraulic oil is supplied to the forward third speed clutch 23, and the forward third speed clutch 23 is operated to the transmission side.
When the shift control valve 42 is operated to the forward sixth speed position F6, the hydraulic oil is supplied to the oil chamber 41b of the hydraulic cylinder 41 in a state where the forward third speed clutch 23 is operated to the transmission side, and the hydraulic cylinder 41 shifts the shift member. 17 is slid to the left in FIG. 2 and meshes with the high speed gear 12 so that the second transmission 4 is in a high speed state.
[0030]
As described above, when the shift control valve 42 is operated from the neutral position N to the reverse first speed position R1, hydraulic oil is transferred from the shift control valve 42 to the reverse clutch 24 in the low speed state of the second transmission 4. Then, the reverse clutch 24 is operated to the transmission side and the aircraft starts. In this case, since the reverse clutch 24 is operated from the transmission cutoff side to the transmission side in the low speed state of the second transmission 4, the reverse clutch 24 slips to some extent, and the shock at the start is absorbed by the reverse clutch 24. The aircraft starts smoothly with little shock.
When the shift control valve 42 is operated to the second reverse speed position F2, hydraulic oil is supplied to the oil chamber 41b of the hydraulic cylinder 41 in a state where the reverse clutch 24 is operated to the transmission side, and the shift member 17 is moved by the hydraulic cylinder 41. 2 is slid to the left in FIG. 2 to engage with the high speed gear 12, and the second transmission 4 is in a high speed state.
[0031]
[Embodiment of the Invention] In the configuration of FIGS. 1 and 2, the second transmission device 4 is configured to be capable of shifting operation in two steps of high and low. You may comprise so that gear shifting operation can be carried out to a stage. In the configuration of FIGS. 1 and 2, the first transmission 3 is configured to be capable of shifting operation in three forward speeds. However, the first transmission device 3 may be configured to be capable of shifting operation in four forward speeds. .
[0032]
When the first and second transmissions 3 and 4 are configured as described above, the first, second, third, and fourth speed positions of the first transmission are set to the transmission ratios A1, A2, A3, and A4, and the second transmission is performed. When the low, medium, and high speed positions of the device are set to transmission ratios L, M, and H, the transmission ratios of the 12-speed shift positions by the first and second transmissions 3 and 4 are increased in the following order. Set to become.
(1) A1 * L <(2) A1 * M <(3) A1 * H <(4) A2 * L <(5) A2 * M <(6) A2 * H <(7) A3 * L <( 8) A3 * M <(9) A3 * H <(10) A4 * L <(11) A4 * M <(12) A4 * H.
[0033]
【The invention's effect】
According to the first aspect of the present invention, in the work vehicle including the stepped first and second transmissions having a plurality of shift positions for traveling, the speed change ratio on the low speed side of the second transmission is A state in which a speed change operation from the low speed side to the high speed side (from the high speed side to the low speed side) can be obtained relatively smoothly without setting the gear ratio on the high speed side of the two-transmission device to be too large. As a result, the smooth shifting operation can be performed without the operator feeling uncomfortable, and the traveling performance of the work vehicle can be improved.
[0034]
According to the feature of claim 2, as in the case of claim 1, the “effect of the invention” of the above-mentioned claim 1 is provided. In addition to the “effect of the invention”, the following “effect of the invention” is provided. It has.
According to the second aspect of the present invention, by configuring the first transmission as a friction clutch type, the speed change operation can be performed smoothly with little shock, and the riding comfort of the work vehicle can be improved.
[0035]
According to the feature of claim 3, the “effect of the invention” of claim 1 or 2 is provided as in the case of claim 1 or 2, and in addition to the “effect of invention”, the following “ The effect of the invention is provided.
According to the third aspect of the present invention, when the second transmission is configured in a gear transmission type in which a shift operation is performed by selectively engaging a shift member with a plurality of transmission gears having different transmission ratios, the shift member is moved by an actuator. It became easier to operate and improved operability during shifting operations. Furthermore, since the operation of the shift member can be easily controlled by the actuator, the functionality of the work vehicle can be enhanced.
[Brief description of the drawings]
FIG. 1 is a schematic front view showing the inside of a mission case. FIG. 2 is a hydraulic circuit diagram of a shift control valve, an accumulator, a forward first speed to a reverse clutch, a hydraulic cylinder, and the like. FIG. 5 is a side view showing a linkage state between the spool of the speed change control valve and the operation gear of the speed change lever. FIG. 5 is a view showing the relation between the speed change position and the transmission ratio. Figure showing symbols [Explanation of symbols]
3 First transmission 4 Second transmission 11, 12 Transmission gear 17 Shift members 21, 22, 23, 24 Friction clutch 41 Actuator 42 Shift operation means 46 Shift operation tool

Claims

A stepped first transmission having a plurality of shift positions and a stepped second transmission having a plurality of shift positions are arranged in series,
In a transmission ratio of power shifted through the first and second transmissions, a transmission ratio in which the second transmission is a predetermined transmission position and the first transmission is a predetermined transmission position; between the second transmission is predetermined a shift position of the first transmission is transmission ratio is a lever position of the high-speed side than the predetermined shift position,
Wherein as second transmission is transmission ratio high speed side of a gear position the first transmission is a predetermined gear position than the predetermined shift position is located, the first and second transmission While setting the shift position,
The first shift operation tool that is artificially operated, and the transmission ratio is set to the high speed side and the low speed side in order based on the operation to the high speed side and the low speed side of the shift operation tool. And a shift operation means for shifting the second transmission .
Further, among the shift regions set in the operation range of the shift operation means, the rate of change of the transmission ratio between adjacent gears in the high speed region is the rate of change of the transmission ratio between adjacent gears in the low speed region. A traveling transmission structure for a work vehicle in which transmission ratios in the first transmission and the second transmission are set to be smaller .

A plurality of friction clutches having different transmission ratios are arranged, and the first transmission is configured as a friction clutch type in which a speed change operation is performed by operating one of the plurality of friction clutches to the transmission side. The traveling transmission structure for a work vehicle according to claim 1.

The second speed change device is configured in a gear transmission type that is operated to shift by selectively engaging a shift member with a plurality of transmission gears having different transmission ratios, and the shift member is operated based on a shift command, The traveling transmission structure for a work vehicle according to claim 1, further comprising an actuator that selectively engages the plurality of transmission gears.