JP2004330856A

JP2004330856A - Ride-on type working vehicle

Info

Publication number: JP2004330856A
Application number: JP2003128790A
Authority: JP
Inventors: Makoto Kubotsu; 誠窪津
Original assignee: Kubota Corp
Current assignee: Kubota Corp
Priority date: 2003-05-07
Filing date: 2003-05-07
Publication date: 2004-11-25
Anticipated expiration: 2023-05-07
Also published as: JP4083067B2

Abstract

<P>PROBLEM TO BE SOLVED: To suppress damaging of a working place by a rear wheel in a turning center side at the time of turning, when a ride-on type working vehicle intends to turn with a small turning radius by greatly steering a right or left front wheel to the right or left side, in the ride-on type working vehicle. <P>SOLUTION: When the front wheel 1 is steered in a range between a straight-ahead position A0 and right and left first setting angles A1, a first transmission state wherein power is transmitted to the right and left rear wheels 2 is established. When the front wheel 1 is steered between the right and left first setting angle A1 and right and left second setting angle A2, an interrupting state wherein power to the rear wheel 2 in the turning center side is interrupted and the rear wheel 2 in the turning center side comes to be in a freely rotating state is established. When the front wheel 1 is steered in a range between the right and left second setting angles A2 and right and left steering limits A3, a second transmission state wherein power of lower speed than the power transmitted to the right and left rear wheels 2 in the first transmission state is transmitted to the rear wheel 2 in the turning center side, is established. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、乗用型作業車の走行系の構造に関する。
【０００２】
【従来の技術】
乗用型作業車においては、例えば特許文献１に開示されているように、右及び左の後輪への動力を伝動及び遮断自在な右及び左のサイドクラッチ（特許文献１の図９，１２，１３中の９６）を備えて、右及び左の前輪が右又は左に操向操作されると、旋回中心側のサイドクラッチが遮断操作されるように、右及び左の前輪と右及び左のサイドクラッチとを連係したものがある。このように旋回中心側のサイドクラッチが遮断操作されて、旋回中心側の後輪が自由回転するように構成すると、旋回中心側の後輪が旋回に伴って適度に回転しながら前進する状態となって、旋回時に旋回中心側の後輪によって作業地が荒らされる状態が少なくなる。
【０００３】
【特許文献１】
特開２００１−９５３３５号公報（図９，１２，１３）
【０００４】
【発明が解決しようとする課題】
特許文献１の構造において、右及び左の前輪を右又は左に大きく操向操作して小さい旋回半径で旋回しようとした場合、特に走行抵抗の大きな作業地では（例えば凹凸の激しい地面や深い水田等）、旋回中心側の後輪が回転せずに殆どその場で横に向きを変えるような状態になることがある。このように、旋回中心側の後輪が回転せずに殆どその場で横に向きを変えるような状態になると、旋回時に旋回中心側の後輪によって作業地が荒らされる状態になることがある。
【０００５】
本発明は、乗用型作業車において、右及び左の前輪を右又は左に操向操作すると、旋回中心側の後輪への動力が遮断されて、旋回中心側の後輪が自由回転状態となるように構成した場合、右及び左の前輪を右又は左に大きく操向操作して小さい旋回半径で旋回しようとした際に、旋回時に旋回中心側の後輪によって作業地が荒らされる状態を少なくすることを目的としている。
【０００６】
【課題を解決するための手段】
［Ｉ］
請求項１の特徴によると、操向操作自在な右及び左の前輪と、右及び左の後輪とを備えて、直進位置から右及び左の第１設定角度を設定し、右及び左の第１設定角度よりも右及び左の操向限度側に右及び左の第２設定角度を設定している。右及び左の前輪が直進位置と右及び左の第１設定角度との間の範囲に操向操作されると、右及び左の後輪に動力が伝達される第１伝動状態が設定される。右及び左の前輪が右の第１設定角度と右の第２設定角度との間の範囲、又は左の第１設定角度と左の第２設定角度との間の範囲に操向操作されると、旋回中心側の後輪への動力が遮断されて、旋回中心側の後輪が自由回転状態となる遮断状態が設定される。右及び左の前輪が右の第２設定角度と右の操向限度との間の範囲、又は左の第２設定角度と左の操向限度との間の範囲に操向操作されると、第１伝動状態で右及び左の後輪に伝達される動力よりも低速の動力が旋回中心側の後輪に伝達される第２伝動状態が設定される。
【０００７】
これにより、請求項１の特徴によると、右及び左の前輪が直進位置と右及び左の第１設定角度との間の範囲に操向操作されると、右及び左の後輪に動力が伝達される（第１伝動状態）。これにより、機体は直進又は緩やかに右又は左に向きを変える。
次に右又は左に旋回する場合、右及び左の前輪が右の第１設定角度と右の第２設定角度との間の範囲、又は左の第１設定角度と左の第２設定角度との間の範囲に操向操作されると、旋回中心側の後輪への動力が遮断されて、旋回中心側の後輪が自由回転状態となる（遮断状態）。これにより、旋回中心側の後輪が旋回に伴って適度に回転しながら前進する状態となって、旋回時に旋回中心側の後輪によって作業地が荒らされる状態が少なくなる。
【０００８】
次に右又は左に小さい旋回半径で旋回する場合、右及び左の前輪が右の第２設定角度と右の操向限度との間の範囲、又は左の第２設定角度と左の操向限度との間の範囲に操向操作されると、第１伝動状態で右及び左の後輪に伝達される動力よりも低速の動力が旋回中心側の後輪に伝達される（第２伝動状態）。これにより、旋回中心側の後輪が回転せずに殆どその場で横に向きを変えようとしても、低速の動力が旋回中心側の後輪に伝達されて、旋回中心側の後輪が少しずつ回転して前進しながら横に向きを変えるような状態となるので、旋回中心側の後輪が回転せずに殆どその場で横に向きを変えるような状態になり難い。
【０００９】
［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。
右及び左の後輪への伝動構造を構成する場合、請求項２の特徴によると、一つの伝動系から右の伝動系及び左の伝動系を分岐させて、右の伝動系から右の第１伝動状態の伝動系及び右の第２伝動状態の伝動系を分岐させ、左の伝動系から左の第１伝動状態の伝動系及び左の第２伝動状態の伝動系を分岐させて、右の第１及び第２伝動状態の伝動系を右の後輪に接続し、左の第１及び第２伝動状態の伝動系を左の後輪に接続している。右及び左の第１及び第２伝動状態の伝動系を伝動及び遮断状態に操作自在な切換機構を備えている。
【００１０】
請求項２の特徴によると、右及び左の第１伝動状態の伝動系を伝動状態に操作し右及び左の第２伝動状態の伝動系を遮断状態に操作すると、一つの伝動系の動力が右及び左の伝動系、右及び左の第１伝動状態の伝動系を介して、右及び左の後輪に伝達される（前項［Ｉ］に記載の第１伝動状態）。
次に前述の状態において、例えば切換機構により右の第１及び第２伝動状態の伝動系を遮断状態に操作すると、右（旋回中心側）の後輪が自由回転状態となる（前項［Ｉ］に記載の遮断状態）。
次に前述の状態において、例えば切換機構により右の第１伝動状態の伝動系を遮断状態に操作し右の第２伝動状態の伝動系を伝動状態に操作すると、右及び左の第１伝動状態の伝動系を介して右及び左の後輪に伝達される動力よりも低速の動力が、右（旋回中心側）の後輪に伝達される（前項［Ｉ］に記載の第２伝動状態）。
【００１１】
以上のように、請求項２の特徴によると、右及び左の後輪への伝動構造を構成する場合、一つの伝動系から右の伝動系及び左の伝動系を分岐させて、右の伝動系から右の第１伝動状態の伝動系及び右の第２伝動状態の伝動系を分岐させ、左の伝動系から左の第１伝動状態の伝動系及び左の第２伝動状態の伝動系を分岐させているので、右及び左の第１及び第２伝動状態の伝動系が比較的短いものとなる。
【００１２】
［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。
請求項３の特徴によると、右及び左の前輪が右の第２設定角度と右の操向限度との間の範囲、又は左の第２設定角度と左の操向限度との間の範囲に操向操作された状態において、第１伝動状態の右及び左の後輪への伝動速度と第２伝動状態の旋回中心側への後輪の伝動速度との比が、旋回中心から旋回外側の後輪までの距離と旋回中心から旋回中心側の後輪までの距離との比に略等しくなるように構成している。このように、旋回中心から旋回外側の後輪までの距離及び旋回中心から旋回中心側の後輪までの距離に基づいて、第２伝動状態の旋回中心側への後輪の伝動速度を適切なものに設定することができる。
【００１３】
【発明の実施の形態】
［１］
図１及び図２に示すように、右及び左の前輪１、右及び左の後輪２を備えた機体の後部に、リンク機構３及びリンク機構３を昇降駆動する油圧シリンダ４が備えられ、リンク機構３の後部に苗植付装置５が支持されて、乗用型作業車の一例である乗用型田植機が構成されている。
【００１４】
図１及び図２に示すように、苗植付装置５は、伝動ケース６、伝動ケース６の後部に回転駆動自在に支持された植付ケース７、植付ケース７の両端に備えられた一対の植付アーム８、接地フロート９及び苗のせ台１０等を備えて構成されている。これにより、苗のせ台１０が左右に往復横送り駆動されるのに伴って、植付ケース７が回転駆動され、苗のせ台１０の下部から植付アーム８が交互に苗を取り出して田面に植え付ける。
【００１５】
図１及び図２に示すように、運転座席１１の後側に肥料を貯留するホッパー１２及び繰り出し部１３が備えられ、運転座席１１の下側にブロア１４が備えられている。接地フロート９に作溝器１５が備えられて、繰り出し部１３と作溝器１５とに亘ってホース１６が接続されている。これにより、前述のような苗の植え付けに伴って、ホッパー１２から肥料が所定量ずつ繰り出し部１３によって繰り出され、ブロア１４の送風により肥料がホース１６を通って作溝器１５に供給されるのであり、作溝器１５を介して肥料が田面に供給される。
【００１６】
［２］
次に、右及び左の前輪１、右及び左の後輪２の支持構造について説明する。
図１，３，４に示すように、機体の前部にミッションケース１７が備えられ、ミッションケース１７の前部に連結された支持フレーム１８に、エンジン１９が支持されている。ミッションケース１７の後部に平板状の支持フレーム２０が連結され、角パイプ状の右及び左の機体フレーム２１が支持フレーム２０に連結されて後方に延出されており、右及び左の機体フレーム２１の後部に平板状の支持部材２２が連結されて、支持部材２２にリンク機構３、油圧シリンダ４、運転座席１１、ホッパー１２、繰り出し部１３及びブロア１４が支持されている。
【００１７】
図１，３，４に示すように、ミッションケース１７の右及び左の横側面から前車軸ケース２３が延出され、前車軸ケース２３の端部に円筒状の支持部２３ａが斜め前方下方（縦軸芯Ｐ１参照）に向いて備えられている。右及び左の前輪１を支持する前輪支持部２４が、前車軸ケース２３の支持部２３ａに縦軸芯Ｐ１周りに回転自在及び縦軸芯Ｐ１の方向にスライド自在に支持されており、前車軸ケース２３の支持部２３ａの内部にサスペンションバネ４０が備えられて、サスペンションバネ４０により前輪支持部２４が支持されている。これにより、右及び左の前輪１が、サスペンションバネ４０により独立に弾性的に上下動自在に支持されている。
【００１８】
図３及び図５に示すように、ミッションケース１７の下部にピットマンアーム２５が縦軸芯Ｐ２周りに揺動自在に支持され後向きに延出されて、前輪支持部２４とピットマンアーム２５とに亘ってタイロッド２６が接続されている。図１及び図２に示すように、ピットマンアーム２５を揺動操作する操縦ハンドル２７が備えられており、操縦ハンドル２７によりピットマンアーム２５を揺動操作することにより、右及び左の前輪１を操向操作する。
【００１９】
図１，３，４に示すように、後車軸ケース２８が一体的に形成されて、後車軸ケース２８に右及び左の後輪２が支持されている。後車軸ケース２８の前部に右及び左の支持アーム２９が連結されて前方に延出されており、支持フレーム２０に支持された支持軸３０の両端に、右及び左の支持アーム２９の前端がゴムブッシュ３１を介して上下に揺動自在に接続されている。後車軸ケース２８と支持部材２２とに亘って、右及び左のサスペンションバネ３２が接続されている。左の機体フレーム２１に支持軸３３が前後向きに固定され、ラテラルロッド３４がゴムブッシュ（図示せず）を介して上下に揺動自在に支持軸３３に接続され、後車軸ケース２８に前向きに固定された支持軸２８ａに、ラテラルロッド３４の端部がゴムブッシュ（図示せず）を介して上下に揺動自在に接続されている。
【００２０】
これにより、後車軸ケース２８が右及び左のサスペンションバネ３２により上下動及びローリング自在に支持されるのであり、右及び左の支持アーム２９により後車軸ケース２８の前後方向の位置が決められ、ラテラルロッド３４により後車軸ケース２８の左右方向の位置が決められる。図３，４，７に示すように、硬質ゴム製のストッパー５５が右及び左の機体フレーム２１に固定されており、後車軸ケース２８が上昇してストッパー５５に接当することにより、後車軸ケース２８の上下方向の位置が決められる。
【００２１】
図１及び図４に示すように、エンジン１９の動力がミッションケース１７に伝達され変速操作されて、前車軸ケース２３から右及び左の前輪１に伝達されている。エンジン１９の動力がミッションケース１７の出力軸３５、伝動軸３６及び自在継手３７を介して後車軸ケース２８の入力軸３８に伝達され、後車軸ケース２８から右及び左の後輪２に伝達されている。
【００２２】
［３］
次に、後車軸ケース２８における右及び左の後輪２への伝動構造について説明する。
図６に示すように、後車軸ケース２８に伝動軸３９が備えられて、入力軸３８に固定されたベベルギヤ３８ａが、伝動軸３９に固定されたベベルギヤ３９ａに咬合している。後車軸ケース２８に出力軸５０が備えられ、出力軸５０に固定されたベベルギヤ５０ａが伝動軸３９のベベルギヤ３９ａに咬合している。出力軸５０に出力アーム（図示せず）が備えられ、出力アームと繰り出し部１３の入力部（図示せず）とに亘ってプッシュプルワイヤ（図示せず）が接続されている。これにより、入力軸３８の動力が出力軸５０及びプッシュプルワイヤを介して繰り出し部１３に伝達されて、前項［１］に記載のように、ホッパー１２から肥料が所定量ずつ繰り出し部１３によって繰り出される。
【００２３】
図６，８，９（イ）に示すように、伝動軸３９の右及び左の端部において、右及び左の第２伝動ギヤ４２が伝動軸３９に相対回転自在に外嵌されており、右及び左の第２伝動ギヤ４２はギヤ部４２ａ及び咬合部４２ｂを備えている。右及び左の第１伝動ギヤ４１が右及び左の第２伝動ギヤ４２に相対回転自在に外嵌されており、右及び左の第１伝動ギヤ４１は内向きの第１ギヤ部４１ａ及び外向きの第２ギヤ部４１ｂを備えている。右及び左のシフトギヤ４３がスプライン構造により一体回転及びスライド自在に伝動軸３９に外嵌されており、右及び左のシフトギヤ４３はギヤ部４３ａ及び咬合部４３ｂを備えている。右及び左のシフトギヤ４３を右及び左の第２伝動ギヤ４２から離れる側に付勢するバネ４４が、伝動軸３９に外嵌されている。
【００２４】
図６及び図８に示すように、後車軸ケース２８に中間の伝動軸４５、右及び左の後輪２を支持する車軸４６が備えられて、伝動軸４５に固定された伝動ギヤ４７，４８が右及び左の第１伝動ギヤ４１の第２ギヤ部４１ｂ、右及び左の第２伝動ギヤ４２のギヤ部４２ａに咬合しており、車軸４６に固定された伝動ギヤ４９が伝動軸４５のギヤ部４５ａに咬合している。
【００２５】
図６，７，８に示すように、後車軸ケース２８に操作軸５１が回転自在に支持され、シフトギヤ４３の端部に接当するスリーブ５２が伝動軸３９に相対回転自在に外嵌されており、操作軸５１に固定された操作ピン５１ａがスリーブ５２の端部に接当している。後車軸ケース２８から操作軸５１が下方に突出して、操作軸５１の突出部に操作アーム５１ｂが備えられており、図５，６，７，８に示すように、ピットマンアーム２５と操作軸５１の操作アーム５１ｂとに亘って連係ロッド５３が接続されている。これによって、操縦ハンドル２７によりピットマンアーム２５が揺動操作されて、右及び左の前輪１が操向操作されると、連係ロッド５３により操作軸５１が回転操作されて、操作軸５１の操作ピン５１ａ及びスリーブ５２を介して、右及び左のシフトギヤ４３がスライド操作される。
【００２６】
［４］
次に、右及び左の前輪１を直進位置Ａ０と右及び左の第１設定角度Ａ１との間の範囲、右の第１設定角度Ａ１と右の第２設定角度Ａ２との間の範囲、左の第１設定角度Ａ１と左の第２設定角度Ａ２との間の範囲に操向操作した場合について説明する。
図５に示すように、右及び左の前輪１に対して、直進位置Ａ０、右及び左の第１設定角度Ａ１、右及び左の第２設定角度Ａ２、右及び左の操向限度Ａ３が設定されている。この場合、右及び左の第２設定角度Ａ２が右及び左の操向限度Ａ３に近いものに設定されており、右の第２設定角度Ａ２と右の操向限度Ａ３との間の範囲、左の第２設定角度Ａ２と左の操向限度Ａ３との間の範囲が狭いものに設定されている（右及び左の第２設定角度Ａ２が右及び左の操向限度Ａ３に非常に接近した状態）。
【００２７】
図６，８，９（イ）に示す状態は、右及び左の前輪１が直進位置Ａ０に操向操作された状態であり、右及び左のシフトギヤ４３のギヤ部４３ａが右及び左の第１伝動ギヤ４１の第１ギヤ部４１ａに咬合している状態である。これにより、入力軸３８の動力が伝動軸３９、右及び左のシフトギヤ４３、右及び左の第１伝動ギヤ４１、伝動ギヤ４７、伝動軸４５、車軸４６を介して右及び左の後輪２に伝達されている。右及び左の前輪１が直進位置Ａ０と右及び左の第１設定角度Ａ１との間の範囲に操向操作されていても、前述の状態となる。これにより、機体は直進又は緩やかに右又は左に向きを変える。
【００２８】
右及び左の前輪１が左の第１設定角度Ａ１と左の第２設定角度Ａ２との間の範囲に操向操作されると、ピットマンアーム２５により左の連係ロッド５３が引き操作されて、図９（ロ）に示すように、左のシフトギヤ４３が左の第２伝動ギヤ４２に向けてスライド操作され、左のシフトギヤ４３のギヤ部４３ａが左の第１伝動ギヤ４１の第１ギヤ部４１ａから離れて（左のシフトギヤ４３の咬合部４３ｂは左の第２伝動ギヤ４２の咬合部４２ｂに咬合していない）、左の後輪２への動力が遮断され、左の後輪２が自由回転状態となる。右のシフトギヤ４３のギヤ部４３ａは右の第１伝動ギヤ４１の第１ギヤ部４１ａに咬合したままであり、入力軸３８の動力が右の第１伝動ギヤ４１及び伝動ギヤ４７を介して右の後輪２に伝達されている。
【００２９】
右及び左の前輪１が右の第１設定角度Ａ１と右の第２設定角度Ａ２との間の範囲に操向操作されると、ピットマンアーム２５により右の連係ロッド５３が引き操作されて、右のシフトギヤ４３が右の第２伝動ギヤ４２に向けてスライド操作され、右のシフトギヤ４３のギヤ部４３ａが右の第１伝動ギヤ４１の第１ギヤ部４１ａから離れて（右のシフトギヤ４３の咬合部４３ｂは右の第２伝動ギヤ４２の咬合部４２ｂに咬合していない）、右の後輪２への動力が遮断され、右の後輪２が自由回転状態となる。左のシフトギヤ４３のギヤ部４３ａは左の第１伝動ギヤ４１の第１ギヤ部４１ａに咬合したままであり、入力軸３８の動力が左の第１伝動ギヤ４１及び伝動ギヤ４７を介して左の後輪２に伝達されている。
【００３０】
以上のように、右及び左の前輪１が右の第１設定角度Ａ１と右の第２設定角度Ａ２との間の範囲、又は左の第１設定角度Ａ１と左の第２設定角度Ａ２との間の範囲に操向操作されると、右及び左の前輪１、旋回外側の後輪２に動力が伝達された状態で、旋回中心側の後輪２への動力が遮断されて、旋回中心側の後輪２が自由回転状態となり、右又は左への旋回が行われる。これにより、旋回中心側の後輪２が旋回に伴って適度に回転しながら前進する状態となって、旋回時に旋回中心側の後輪２によって田面が荒らされる状態が少なくなる。
【００３１】
［５］
次に、右及び左の前輪１を右の第２設定角度Ａ２と右の操向限度Ａ３との間の範囲、左の第２設定角度Ａ２と左の操向限度Ａ３との間の範囲に操向操作した場合について説明する。
右及び左の前輪１が左の第２設定角度Ａ２と左の操向限度Ａ３との間の範囲に操向操作されると、ピットマンアーム２５により左の連係ロッド５３がさらに引き操作されて、図９（ハ）に示すように、左のシフトギヤ４３が左の第２伝動ギヤ４２に向けてさらにスライド操作され、左のシフトギヤ４３の咬合部４３ｂが左の第２伝動ギヤ４２の咬合部４２ｂに咬合して、入力軸３８の動力が伝動軸３９、左のシフトギヤ４３、左の第２伝動ギヤ４２、伝動ギヤ４８、伝動軸４５、車軸４６を介して左の後輪２に伝達される。右のシフトギヤ４３のギヤ部４３ａは右の第１伝動ギヤ４１の第１ギヤ部４１ａに咬合したままであり、入力軸３８の動力が右の第１伝動ギヤ４１及び伝動ギヤ４７を介して右の後輪２に伝達されている。
【００３２】
右及び左の前輪１が右の第２設定角度Ａ２と右の操向限度Ａ３との間の範囲に操向操作されると、ピットマンアーム２５により右の連係ロッド５３がさらに引き操作されて、右のシフトギヤ４３が右の第２伝動ギヤ４２に向けてさらにスライド操作され、右のシフトギヤ４３の咬合部４３ｂが右の第２伝動ギヤ４２の咬合部４２ｂに咬合して、入力軸３８の動力が伝動軸３９、右のシフトギヤ４３、右の第２伝動ギヤ４２、伝動ギヤ４８、伝動軸４５、車軸４６を介して右の後輪２に伝達される。左のシフトギヤ４３のギヤ部４３ａは左の第１伝動ギヤ４１の第１ギヤ部４１ａに咬合したままであり、入力軸３８の動力が左の第１伝動ギヤ４１及び伝動ギヤ４７を介して左の後輪２に伝達されている。
【００３３】
この場合、前項［４］及び図９（イ）に示すように、入力軸３８の動力が右（左）の第１伝動ギヤ４１及び伝動ギヤ４７を介して右（左）の後輪２に伝達される状態での伝動比（伝動速度）Ｂ１よりも、図９（ハ）に示すように、入力軸３８の動力が右（左）の第２伝動ギヤ４２及び伝動ギヤ４８を介して右（左）の後輪２に伝達される状態での伝動比（伝動速度）Ｂ２が低速になるように設定されている。
【００３４】
さらに、図１０に示すように、右及び左の前輪１が右の第２設定角度Ａ２と右の操向限度Ａ３との間の範囲、又は左の第２設定角度Ａ２と左の操向限度Ａ３との間の範囲に操向操作された状態において、伝動比（伝動速度）Ｂ１、伝動比（伝動速度）Ｂ２、旋回中心Ｃから旋回外側の後輪２までの距離Ｌ１、旋回中心Ｃから旋回中心側の後輪２までの距離Ｌ２とにおいて、
Ｂ１／Ｂ２≒Ｌ１／Ｌ２
となるように、伝動比（伝動速度）Ｂ１と伝動比（伝動速度）Ｂ２との比が、距離Ｌ１と距離Ｌ２との比に略等しくなるように構成されている。
【００３５】
［発明の実施の第１別形態］
前述の［発明の実施の形態］に代えて、図１１及び図１２（イ）に示すように構成してもよい。
図１１及び図１２（イ）に示すように、右及び左の第１伝動ギヤ４１において第１ギヤ部４１ａを廃止し、右及び左のシフトギヤ４３においてギヤ部４３ａを廃止して、右及び左の第１伝動ギヤ４１と右及び左のシフトギヤ４３との間に摩擦板５４を配置している。これ以外の構造は、前述の［発明の実施の形態］と同じである。
【００３６】
これにより、図１１及び図１２（イ）に示すように、右及び左の前輪１が直進位置Ａ０に操向操作されると、バネ４４によって右及び左のシフトギヤ４３により摩擦板５４が押圧されて、入力軸３８の動力が伝動軸３９、右及び左のシフトギヤ４３、摩擦板５４、右及び左の第１伝動ギヤ４１、伝動ギヤ４７、伝動軸４５、車軸４６を介して右及び左の後輪２に伝達される。右及び左の前輪１が直進位置Ａ０と右及び左の第１設定角度Ａ１との間の範囲に操向操作されていても、前述の状態となる。
【００３７】
右及び左の前輪１が左の第１設定角度Ａ１と左の第２設定角度Ａ２との間の範囲に操向操作されると、ピットマンアーム２５により左の連係ロッド５３が引き操作されて、左のシフトギヤ４３が左の第２伝動ギヤ４２に向けてスライド操作され、左のシフトギヤ４３が摩擦板５４を押圧しなくなり（左のシフトギヤ４３の咬合部４３ｂは左の第２伝動ギヤ４２の咬合部４２ｂに咬合していない）、左の後輪２への動力が遮断されて、左の後輪２が自由回転状態となる。右のシフトギヤ４３は摩擦板５４を押圧したままであり、入力軸３８の動力が右の第１伝動ギヤ４１及び伝動ギヤ４７を介して右の後輪２に伝達されている。
【００３８】
右及び左の前輪１が右の第１設定角度Ａ１と右の第２設定角度Ａ２との間の範囲に操向操作されると、ピットマンアーム２５により右の連係ロッド５３が引き操作されて、右のシフトギヤ４３が右の第２伝動ギヤ４２に向けてスライド操作され、右のシフトギヤ４３が摩擦板５４を押圧しなくなり（右のシフトギヤ４３の咬合部４３ｂは右の第２伝動ギヤ４２の咬合部４２ｂに咬合していない）、右の後輪２への動力が遮断されて、右の後輪２が自由回転状態となる。左のシフトギヤ４３は摩擦板５４を押圧したままであり、入力軸３８の動力が左の第１伝動ギヤ４１及び伝動ギヤ４７を介して左の後輪２に伝達されている。
【００３９】
右及び左の前輪１が左の第２設定角度Ａ２と左の操向限度Ａ３との間の範囲に操向操作されると、図１２（ロ）に示すようにピットマンアーム２５により左の連係ロッド５３がさらに引き操作されて、左のシフトギヤ４３が左の第２伝動ギヤ４２に向けてさらにスライド操作され、左のシフトギヤ４３の咬合部４３ｂが左の第２伝動ギヤ４２の咬合部４２ｂに咬合して、入力軸３８の動力が伝動軸３９、左のシフトギヤ４３、左の第２伝動ギヤ４２、伝動ギヤ４８、伝動軸４５、車軸４６を介して左の後輪２に伝達される。右のシフトギヤ４３は摩擦板５４を押圧したままであり、入力軸３８の動力が右の第１伝動ギヤ４１及び伝動ギヤ４７を介して右の後輪２に伝達されている。
【００４０】
右及び左の前輪１が右の第２設定角度Ａ２と右の操向限度Ａ３との間の範囲に操向操作されると、ピットマンアーム２５により右の連係ロッド５３がさらに引き操作されて、右のシフトギヤ４３が右の第２伝動ギヤ４２に向けてさらにスライド操作され、右のシフトギヤ４３の咬合部４３ｂが右の第２伝動ギヤ４２の咬合部４２ｂに咬合して、入力軸３８の動力が伝動軸３９、右のシフトギヤ４３、右の第２伝動ギヤ４２、伝動ギヤ４８、伝動軸４５、車軸４６を介して右の後輪２に伝達される。左のシフトギヤ４３は摩擦板５４を押圧したままであり、入力軸３８の動力が左の第１伝動ギヤ４１及び伝動ギヤ４７を介して左の後輪２に伝達されている。
【００４１】
［発明の実施の第２別形態］
前述の［発明の実施の形態］及び［発明の実施の第１別形態］に代えて、図１３（イ）に示すように構成してもよい。
図１３（イ）に示すように、右及び左の第１伝動ギヤ４１において第１ギヤ部４１ａを廃止し、右及び左のシフトギヤ４３においてギヤ部４３ａを廃止して、右及び左の第１伝動ギヤ４１と右及び左のシフトギヤ４３との間に摩擦板５４を配置している。右及び左の第２伝動ギヤ４２において咬合部４２ｂを廃止し、右及び左の第２伝動ギヤ４２にリング状の受け板４２ｃを固定している。右及び左のシフトギヤ４３において咬合部４３ｂを廃止し、右及び左のシフトギヤ４３の端部４３ｃをリング状の平面状に構成している。この場合、図５に示す右及び左の第２設定角度Ａ２と右及び左の操向限度Ａ３とが同じ位置となる。これ以外の構造は、前述の［発明の実施の形態］と同じである。
【００４２】
これにより、図１３（イ）に示すように、右及び左の前輪１が直進位置Ａ０に操向操作されると、バネ４４によって右及び左のシフトギヤ４３により摩擦板５４が押圧されて、入力軸３８の動力が伝動軸３９、右及び左のシフトギヤ４３、摩擦板５４、右及び左の第１伝動ギヤ４１、伝動ギヤ４７、伝動軸４５、車軸４６を介して右及び左の後輪２に伝達される。右及び左の前輪１が直進位置Ａ０と右及び左の第１設定角度Ａ１との間の範囲に操向操作されていても、前述の状態となる。
【００４３】
右及び左の前輪１が左の第１設定角度Ａ１と左の第２設定角度Ａ２との間の範囲に操向操作されると、ピットマンアーム２５により左の連係ロッド５３が引き操作されて、左のシフトギヤ４３が左の第２伝動ギヤ４２に向けてスライド操作され、左のシフトギヤ４３が摩擦板５４を押圧しなくなり（左のシフトギヤ４３の端部４３ｃは左の第２伝動ギヤ４２の受け板４２ｃに押圧されていない）、左の後輪２への動力が遮断されて、左の後輪２が自由回転状態となる。右のシフトギヤ４３は摩擦板５４を押圧したままであり、入力軸３８の動力が右の第１伝動ギヤ４１及び伝動ギヤ４７を介して右の後輪２に伝達されている。
【００４４】
右及び左の前輪１が右の第１設定角度Ａ１と右の第２設定角度Ａ２との間の範囲に操向操作されると、ピットマンアーム２５により右の連係ロッド５３が引き操作されて、右のシフトギヤ４３が右の第２伝動ギヤ４２に向けてスライド操作され、右のシフトギヤ４３が摩擦板５４を押圧しなくなり（右のシフトギヤ４３の端部４３ｃは右の第２伝動ギヤ４２の受け板４２ｃに押圧されていない）、右の後輪２への動力が遮断されて、右の後輪２が自由回転状態となる。左のシフトギヤ４３は摩擦板５４を押圧したままであり、入力軸３８の動力が左の第１伝動ギヤ４１及び伝動ギヤ４７を介して左の後輪２に伝達されている。
【００４５】
右及び左の前輪１が左の第２設定角度Ａ２（左の操向限度Ａ３）に操向操作されると、図１３（ロ）に示すように、ピットマンアーム２５により左の連係ロッド５３がさらに引き操作されて、左のシフトギヤ４３が左の第２伝動ギヤ４２に向けてさらにスライド操作され、左のシフトギヤ４３の端部４３ｃが左の第２伝動ギヤ４２の受け板４２ｃに押圧されて、入力軸３８の動力が伝動軸３９、左のシフトギヤ４３（端部４３ｃ）、左の第２伝動ギヤ４２（受け板４２ｃ）、伝動ギヤ４８、伝動軸４５、車軸４６を介して左の後輪２に伝達される。右のシフトギヤ４３は摩擦板５４を押圧したままであり、入力軸３８の動力が右の第１伝動ギヤ４１及び伝動ギヤ４７を介して右の後輪２に伝達されている。
【００４６】
右及び左の前輪１が右の第２設定角度Ａ２（右の操向限度Ａ３）に操向操作されると、ピットマンアーム２５により右の連係ロッド５３がさらに引き操作されて、右のシフトギヤ４３が右の第２伝動ギヤ４２に向けてさらにスライド操作され、右のシフトギヤ４３の端部４３ｃが右の第２伝動ギヤ４２の受け板４２ｃに押圧されて、入力軸３８の動力が伝動軸３９、右のシフトギヤ４３（端部４３ｃ）、右の第２伝動ギヤ４２（受け板４２ｃ）、伝動ギヤ４８、伝動軸４５、車軸４６を介して右の後輪２に伝達される。左のシフトギヤ４３は摩擦板５４を押圧したままであり、入力軸３８の動力が左の第１伝動ギヤ４１及び伝動ギヤ４７を介して左の後輪２に伝達されている。
【００４７】
［発明の実施の第３別形態］
前述の［発明の実施の形態］及び［発明の実施の第１別形態］、［発明の実施の第２別形態］において、右及び左の連係ロッド５３に融通用のバネ（図示せず）を備えてもよい。このように構成すると、右の第２設定角度Ａ２と右の操向限度Ａ３との間の範囲、左の第２設定角度Ａ２と左の操向限度Ａ３との間の範囲が広くなるようにすることができる（右及び左の第２設定角度Ａ２が、右及び左の操向限度Ａ３から右及び左の第１設定角度Ａ１側に比較的離れた状態となるようにすることができる）。
本発明は乗用型田植機ばかりではなく、機体の後部に直播装置を備えた乗用型直播機や、機体の後部に薬剤散布装置を備えた乗用型管理機にも適用できる。
【００４８】
【発明の効果】
請求項１の特徴によると、乗用型作業車において、右及び左の前輪を右又は左に操向操作すると、旋回中心側の後輪への動力が遮断されて、旋回中心側の後輪が自由回転状態となるように構成した場合、右及び左の前輪を右又は左に大きく操向操作して小さい旋回半径で旋回しようとした際に、旋回中心側の後輪が少しずつ回転して前進しながら横に向きを変えるような状態となり、旋回中心側の後輪が回転せずに殆どその場で横に向きを変えるような状態になり難いようにすることができて、旋回時に旋回中心側の後輪によって作業地が荒らされる状態を少なくすることができて、乗用型作業車の旋回性能を向上させることができた。
請求項１の特徴によると、右及び左の前輪を右又は左に操向操作すると、旋回中心側の後輪への動力が遮断されて、旋回中心側の後輪が自由回転するように構成し、旋回時に旋回中心側の後輪によって作業地が荒らされる状態が少なくなると言う利点をそのまま備えている。
【００４９】
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の特徴によると、右及び左の後輪への伝動構造を構成する場合、右及び左の第１及び第２伝動状態の伝動系が比較的短いものとなるので、構造の簡素化の面で有利なものとなった。
【００５０】
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、右及び左の前輪が右の第２設定角度と右の操向限度との間の範囲、又は左の第２設定角度と左の操向限度との間の範囲に操向操作された状態において、旋回中心から旋回外側の後輪までの距離及び旋回中心から旋回中心側の後輪までの距離に基づき、第２伝動状態の旋回中心側への後輪の伝動速度を適切なものに設定することができるようになって、乗用型作業車の旋回性能を向上させることができた。
【図面の簡単な説明】
【図１】乗用型田植機の全体側面図
【図２】乗用型田植機の全体平面図
【図３】前車軸ケース及び後車軸ケースの付近の側面図
【図４】前車軸ケース及び後車軸ケースの付近の平面図
【図５】ピットマンアーム及び後車軸ケースの付近の平面図
【図６】後車軸ケースの横断平面図
【図７】後車軸ケースの付近の縦断側面図
【図８】後車軸ケースにおける左のサイドギヤの付近の横断平面図
【図９】右及び左の前輪が直進位置と右及び左の第１設定角度との間の範囲、左の第１設定角度と左の第２設定角度との間の範囲、左の第２設定角度と左の操向限度との間の範囲に操向操作された状態における左のサイドギヤの付近の横断平面図
【図１０】右及び左の前輪が左の第２設定角度と左の操向限度との間の範囲に操向操作された状態における右及び左の前輪、右及び左の後輪の状態を示す平面図
【図１１】発明の実施の第１別形態において、後車軸ケースにおける左のサイドギヤの付近の横断平面図
【図１２】発明の実施の第１別形態において、右及び左の前輪が直進位置と右及び左の第１設定角度との間の範囲、左の第２設定角度と左の操向限度との間の範囲に操向操作された状態における左のサイドギヤの付近の横断平面図
【図１３】発明の実施の第２別形態において、右及び左の前輪が直進位置と右及び左の第１設定角度との間の範囲、左の第２設定角度（左の操向限度）に操向操作された状態における左のサイドギヤの付近の横断平面図
【符号の説明】
１右及び左の前輪
２右及び左の後輪
３５，３６，３８一つの伝動系
３９右の伝動系、左の伝動系
４１，４７右の第１伝動状態の伝動系、左の第１伝動状態の伝動系
４２，４８右の第２伝動状態の伝動系、左の第２伝動状態の伝動系
４３切換機構
Ａ０直進位置
Ａ１右及び左の第１設定角度
Ａ２右及び左の第２設定角度
Ａ３右及び左の操向限度
Ｂ１第１伝動状態の右及び左の後輪への伝動速度
Ｂ２第２伝動状態の旋回中心側の後輪への伝動速度
Ｌ１旋回中心から旋回外側の後輪までの距離
Ｌ２旋回中心から旋回中心側の後輪までの距離[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a structure of a traveling system of a riding work vehicle.
[0002]
[Prior art]
In a riding type work vehicle, for example, as disclosed in Patent Literature 1, right and left side clutches capable of transmitting and disconnecting power to right and left rear wheels (see FIGS. 9, 12, and 12 of Patent Literature 1). 13), when the right and left front wheels are steered to the right or left, the right and left front wheels and right and left front wheels are disengaged so that the side clutch on the turning center side is disengaged. Some are linked to a side clutch. In this way, when the side clutch on the turning center side is disengaged and the rear wheel on the turning center side is freely rotated, the rear wheel on the turning center side advances while rotating appropriately with the turn. As a result, the situation in which the work area is roughened by the rear wheel on the turning center side during turning is reduced.
[0003]
[Patent Document 1]
JP 2001-95335 A (FIGS. 9, 12, 13)
[0004]
[Problems to be solved by the invention]
In the structure of Patent Document 1, when the right and left front wheels are largely steered to the right or left to make a turn with a small turning radius, particularly in a work place having a large running resistance (for example, a ground having a large unevenness or a deep paddy field). Etc.), the rear wheel on the turning center side may turn sideways almost immediately without rotating. As described above, if the turning center-side rear wheel turns sideways almost immediately without rotating, the work area may be roughened by the turning center-side rear wheel during turning. .
[0005]
According to the present invention, in a riding type work vehicle, when the right and left front wheels are steered to the right or left, power to a turning center side rear wheel is shut off, and the turning center side rear wheel enters a free rotation state. When the right and left front wheels are largely steered to the right or left to turn with a small turning radius, the state in which the working ground is roughened by the turning center side rear wheel at the time of turning. It is intended to reduce.
[0006]
[Means for Solving the Problems]
[I]
According to the features of claim 1, the vehicle includes right and left front wheels that can be steered and right and left rear wheels, and sets right and left first set angles from a straight traveling position. The right and left second set angles are set on the right and left steering limit sides of the first set angle. When the right and left front wheels are steered to a range between the straight traveling position and the right and left first set angles, a first transmission state in which power is transmitted to the right and left rear wheels is set. . The right and left front wheels are steered to a range between a right first set angle and a right second set angle, or a range between a left first set angle and a left second set angle. Then, the power to the rear center wheel on the turning center is shut off, and the shutoff state in which the rear wheel on the turning center side is in a free rotation state is set. When the right and left front wheels are steered to a range between the right second set angle and the right steering limit, or a range between the left second set angle and the left steering limit, In the first transmission state, a second transmission state is set in which power lower than the power transmitted to the right and left rear wheels is transmitted to the turning center side rear wheel.
[0007]
Thus, according to the features of claim 1, when the right and left front wheels are steered to a range between the straight traveling position and the right and left first set angles, power is applied to the right and left rear wheels. Power is transmitted (first transmission state). As a result, the aircraft turns straight or slowly turns right or left.
Next, when turning right or left, the right and left front wheels are in a range between the first right setting angle and the second right setting angle, or the first left setting angle and the second left setting angle are different from each other. When the steering operation is performed in the range between, the power to the turning center-side rear wheel is cut off, and the turning center-side rear wheel enters a free rotation state (cutoff state). As a result, the turning center-side rear wheel moves forward while rotating appropriately while turning, and the state in which the work center is roughened by the turning center-side rear wheel during turning is reduced.
[0008]
Next, when turning with a small turning radius to the right or left, the right and left front wheels are in a range between the right second set angle and the right steering limit, or the left second set angle and the left steer. When the steering operation is performed in the range between the limit and the limit, the power transmitted to the turning center side rear wheel is lower than the power transmitted to the right and left rear wheels in the first transmission state (second transmission). Status). As a result, even if the turning wheel on the turning center side tries to turn sideways almost immediately without rotating, low-speed power is transmitted to the turning wheel on the turning center side, and the rear wheel on the turning center side is slightly Since the vehicle turns sideways and turns forward while turning forward, the rear wheel on the turning center side hardly turns and turns sideways almost on the spot.
[0009]
[II]
According to the feature of the second aspect, similar to the case of the first aspect, the "operation" described in the above [I] is provided, and in addition, the following "operation" is provided.
When the transmission structure to the right and left rear wheels is configured, according to the feature of claim 2, the right transmission system and the left transmission system are branched from one transmission system, and the right transmission system is divided into the right transmission system and the right transmission system. The transmission system in the first transmission state and the transmission system in the second transmission state on the right are branched, and the transmission system in the first transmission state on the left and the transmission system in the second transmission state on the left are branched from the left transmission system. The first and second transmission state transmission systems are connected to the right rear wheel, and the left first and second transmission state transmission systems are connected to the left rear wheel. There is provided a switching mechanism operable to set the right and left transmission systems in the first and second transmission states to the transmission and cutoff states.
[0010]
According to the feature of claim 2, when the right and left transmission systems in the first transmission state are operated in the transmission state and the right and left transmission systems in the second transmission state are operated in the cutoff state, the power of one transmission system is reduced. The power is transmitted to the right and left rear wheels via the right and left transmission systems and the right and left transmission systems in the first transmission state (the first transmission state described in [I] above).
Next, in the above-described state, for example, when the transmission system in the first and second transmission states on the right side is operated to be in the cutoff state by the switching mechanism, the rear wheel on the right (the turning center side) is in a free rotation state (the preceding item [I]). Cut-off state).
Next, in the state described above, for example, when the transmission system in the first transmission state on the right is operated to be in the cut-off state and the transmission system in the second transmission state on the right is operated in the transmission state by the switching mechanism, the first transmission state in the right and left states is obtained. Power transmitted to the right and left rear wheels via the transmission system is transmitted to the right (turn center side) rear wheel (the second transmission state described in [I] above). .
[0011]
As described above, according to the second aspect of the present invention, when the transmission structure to the right and left rear wheels is configured, the right transmission system and the left transmission system are branched from one transmission system to form the right transmission system. The transmission system in the first transmission state on the right and the transmission system in the second transmission state on the right are branched from the system, and the transmission system in the first transmission state on the left and the transmission system in the second transmission state on the left are separated from the left transmission system. Because of the branch, the transmission systems in the first and second transmission states on the right and left are relatively short.
[0012]
[III]
According to the feature of the third aspect, similar to the case of the first or second aspect, the present invention has the “action” described in the preceding items [I] and [II], and additionally has the following “action”. I have.
According to the features of claim 3, the right and left front wheels range between a right second set angle and a right steering limit, or a range between a left second set angle and a left steering limit. In the state where the steering operation is performed, the ratio of the transmission speed to the right and left rear wheels in the first transmission state and the transmission speed of the rear wheels to the turning center side in the second transmission state is determined from the turning center to the turning outside. The distance from the rear wheel to the rear wheel and the distance from the turning center to the rear wheel on the turning center side are substantially equal to each other. As described above, the transmission speed of the rear wheel to the turning center side in the second transmission state is appropriately set based on the distance from the turning center to the rear wheel outside the turning and the distance from the turning center to the rear wheel on the turning center side. Can be set to something.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
[1]
As shown in FIGS. 1 and 2, a link mechanism 3 and a hydraulic cylinder 4 that drives the link mechanism 3 up and down are provided at the rear of the body including right and left front wheels 1 and right and left rear wheels 2. A seedling planting device 5 is supported at the rear of the link mechanism 3 to constitute a riding rice transplanter that is an example of a riding work vehicle.
[0014]
As shown in FIGS. 1 and 2, the seedling planting device 5 includes a transmission case 6, a planting case 7 rotatably supported at a rear portion of the transmission case 6, and a pair of ends provided at both ends of the planting case 7. , A grounding float 9, a seedling rest 10, and the like. As a result, the planting case 7 is driven to rotate as the seedling rest 10 is reciprocally traversely moved left and right, and the planting arm 8 alternately takes out the seedlings from the lower part of the seedling rest 10 and places it on the rice field. Plant.
[0015]
As shown in FIGS. 1 and 2, a hopper 12 and a feeding portion 13 for storing fertilizer are provided on the rear side of the driver's seat 11, and a blower 14 is provided below the driver's seat 11. The ground float 9 is provided with a groove generator 15, and a hose 16 is connected between the feeding portion 13 and the groove generator 15. As a result, the fertilizer is fed from the hopper 12 by a predetermined amount at the time of the seedling planting as described above by the feeding unit 13, and the fertilizer is supplied to the groove generator 15 through the hose 16 by the blower 14. Yes, fertilizer is supplied to the rice field via the groove generator 15.
[0016]
[2]
Next, the support structure of the right and left front wheels 1 and the right and left rear wheels 2 will be described.
As shown in FIGS. 1, 3, and 4, a transmission case 17 is provided at a front portion of the body, and an engine 19 is supported by a support frame 18 connected to the front portion of the transmission case 17. A flat support frame 20 is connected to a rear portion of the transmission case 17, and right and left body frames 21 each having a square pipe shape are connected to the support frame 20 and extend rearward. A plate-shaped support member 22 is connected to the rear part, and the link member 3, the hydraulic cylinder 4, the driver's seat 11, the hopper 12, the feeding portion 13, and the blower 14 are supported by the support member 22.
[0017]
As shown in FIGS. 1, 3, and 4, the front axle case 23 extends from the right and left lateral sides of the transmission case 17, and a cylindrical support portion 23a is provided at an end of the front axle case 23 obliquely downward and forward ( (See the vertical axis P1). A front wheel support portion 24 for supporting the right and left front wheels 1 is supported by a support portion 23a of the front axle case 23 so as to be rotatable around the vertical axis P1 and slidably in the direction of the vertical axis P1. A suspension spring 40 is provided inside the support portion 23 a of the case 23, and the front wheel support portion 24 is supported by the suspension spring 40. Thus, the right and left front wheels 1 are independently elastically supported by the suspension spring 40 so as to be vertically movable.
[0018]
As shown in FIGS. 3 and 5, a pitman arm 25 is supported at the lower portion of the transmission case 17 so as to be swingable around a longitudinal axis P2 and extends rearward, and extends between the front wheel support portion 24 and the pitman arm 25. Tie rod 26 is connected. As shown in FIGS. 1 and 2, a steering handle 27 for swinging the pitman arm 25 is provided. By swinging the pitman arm 25 with the steering handle 27, the right and left front wheels 1 are steered. Operation.
[0019]
As shown in FIGS. 1, 3, and 4, a rear axle case 28 is integrally formed, and the right and left rear wheels 2 are supported by the rear axle case 28. Right and left support arms 29 are connected to the front portion of the rear axle case 28 and extend forward, and the front ends of the right and left support arms 29 are provided at both ends of the support shaft 30 supported by the support frame 20. Are connected via a rubber bush 31 so as to be swingable up and down. The right and left suspension springs 32 are connected across the rear axle case 28 and the support member 22. A support shaft 33 is fixed to the left body frame 21 in the front-rear direction, and a lateral rod 34 is connected to the support shaft 33 via a rubber bush (not shown) so as to be swingable up and down. The end of the lateral rod 34 is connected to the fixed support shaft 28a via a rubber bush (not shown) so as to be vertically swingable.
[0020]
As a result, the rear axle case 28 is supported by the right and left suspension springs 32 so as to be able to move up and down and freely roll. The right and left support arms 29 determine the position of the rear axle case 28 in the front-rear direction. The position of the rear axle case 28 in the left-right direction is determined by the rod 34. As shown in FIGS. 3, 4, and 7, a hard rubber stopper 55 is fixed to the right and left body frames 21, and the rear axle case 28 rises and comes into contact with the stopper 55, whereby the rear axle is The vertical position of the case 28 is determined.
[0021]
As shown in FIGS. 1 and 4, the power of the engine 19 is transmitted to the transmission case 17 to perform a speed change operation, and is transmitted from the front axle case 23 to the right and left front wheels 1. The power of the engine 19 is transmitted to the input shaft 38 of the rear axle case 28 via the output shaft 35, the transmission shaft 36 and the universal joint 37 of the transmission case 17, and transmitted from the rear axle case 28 to the right and left rear wheels 2. ing.
[0022]
[3]
Next, a transmission structure of the rear axle case 28 to the right and left rear wheels 2 will be described.
As shown in FIG. 6, a transmission shaft 39 is provided in the rear axle case 28, and a bevel gear 38 a fixed to the input shaft 38 is engaged with a bevel gear 39 a fixed to the transmission shaft 39. An output shaft 50 is provided on the rear axle case 28, and a bevel gear 50 a fixed to the output shaft 50 is engaged with the bevel gear 39 a of the transmission shaft 39. The output shaft 50 is provided with an output arm (not shown), and a push-pull wire (not shown) is connected between the output arm and an input section (not shown) of the feeding section 13. Thereby, the power of the input shaft 38 is transmitted to the feeding unit 13 via the output shaft 50 and the push-pull wire, and the fertilizer is fed by the feeding unit 13 from the hopper 12 by a predetermined amount as described in the above item [1]. It is.
[0023]
As shown in FIGS. 6, 8, and 9 (a), right and left second transmission gears 42 are externally fitted to the transmission shaft 39 so as to be relatively rotatable at right and left ends of the transmission shaft 39. The right and left second transmission gears 42 include a gear portion 42a and an engagement portion 42b. The right and left first transmission gears 41 are fitted to the right and left second transmission gears 42 so as to be rotatable relative to each other, and the right and left first transmission gears 41 are connected to the inward first gear portion 41a and the outside. A second gear portion 41b is provided. The right and left shift gears 43 are externally fitted to the transmission shaft 39 so as to rotate integrally and slidably with a spline structure, and the right and left shift gears 43 include a gear portion 43a and an engagement portion 43b. A spring 44 for urging the right and left shift gears 43 away from the right and left second transmission gears 42 is externally fitted to the transmission shaft 39.
[0024]
As shown in FIGS. 6 and 8, a rear axle case 28 is provided with an intermediate transmission shaft 45 and an axle 46 for supporting the right and left rear wheels 2, and transmission gears 47 and 48 fixed to the transmission shaft 45. Are engaged with the second gear portion 41b of the right and left first transmission gears 41 and the gear portion 42a of the right and left second transmission gears 42, and the transmission gear 49 fixed to the axle 46 is attached to the transmission shaft 45. It is engaged with the gear portion 45a.
[0025]
As shown in FIGS. 6, 7, and 8, the operation shaft 51 is rotatably supported by the rear axle case 28, and the sleeve 52 that contacts the end of the shift gear 43 is rotatably fitted to the transmission shaft 39. The operation pin 51 a fixed to the operation shaft 51 is in contact with the end of the sleeve 52. The operating shaft 51 projects downward from the rear axle case 28, and an operating arm 51b is provided on a protruding portion of the operating shaft 51. As shown in FIGS. The link rod 53 is connected to the operation arm 51b. Thereby, when the pitman arm 25 is swung by the steering handle 27 and the right and left front wheels 1 are steered, the operating shaft 51 is rotated by the link rod 53 and the operating pin of the operating shaft 51 is operated. The right and left shift gears 43 are slid via the sleeve 51a and the sleeve 52.
[0026]
[4]
Next, the right and left front wheels 1 are moved in a range between the straight traveling position A0 and the right and left first set angles A1, a range between the right first set angle A1 and the right second set angle A2, A case where the steering operation is performed in a range between the first set angle A1 on the left and the second set angle A2 on the left will be described.
As shown in FIG. 5, with respect to the right and left front wheels 1, the straight traveling position A0, the right and left first set angles A1, the right and left second set angles A2, and the right and left steering limits A3 are set. Is set. In this case, the right and left second set angles A2 are set close to the right and left steering limits A3, and a range between the right second set angle A2 and the right steering limits A3; The range between the left second set angle A2 and the left steering limit A3 is set to be narrow (the right and left second set angles A2 are very close to the right and left steering limits A3). State).
[0027]
The states shown in FIGS. 6, 8, and 9 (a) are states in which the right and left front wheels 1 are steered to the straight traveling position A0, and the gear portions 43a of the right and left shift gears 43 are the right and left first gears. This is a state where the first transmission gear 41 is engaged with the first gear portion 41a. Thereby, the power of the input shaft 38 is transmitted to the right and left rear wheels 2 via the transmission shaft 39, the right and left shift gears 43, the right and left first transmission gears 41, the transmission gear 47, the transmission shaft 45, and the axle 46. Has been transmitted to. The above-described state is obtained even when the right and left front wheels 1 are steered in a range between the straight traveling position A0 and the right and left first set angles A1. As a result, the aircraft turns straight or slowly turns right or left.
[0028]
When the right and left front wheels 1 are steered to a range between the left first set angle A1 and the left second set angle A2, the pitman arm 25 pulls the left link rod 53, As shown in FIG. 9B, the left shift gear 43 is slid toward the left second transmission gear 42, and the gear portion 43a of the left shift gear 43 is shifted to the first gear portion of the left first transmission gear 41. 41a (the biting portion 43b of the left shift gear 43 does not bite with the biting portion 42b of the left second transmission gear 42), power to the left rear wheel 2 is cut off, and the left rear wheel 2 It is in a free rotation state. The gear portion 43a of the right shift gear 43 remains engaged with the first gear portion 41a of the right first transmission gear 41, and the power of the input shaft 38 is transmitted through the right first transmission gear 41 and the transmission gear 47 to the right. Is transmitted to the rear wheel 2.
[0029]
When the right and left front wheels 1 are steered to a range between the right first set angle A1 and the right second set angle A2, the pitman arm 25 pulls the right link rod 53, The right shift gear 43 is slid toward the right second transmission gear 42, and the gear portion 43a of the right shift gear 43 is separated from the first gear portion 41a of the right first transmission gear 41 (the shift gear 43 of the right shift gear 43). The engaging portion 43b is not engaged with the engaging portion 42b of the right second transmission gear 42), the power to the right rear wheel 2 is shut off, and the right rear wheel 2 enters a free rotation state. The gear portion 43a of the left shift gear 43 remains engaged with the first gear portion 41a of the left first transmission gear 41, and the power of the input shaft 38 is transmitted through the left first transmission gear 41 and the transmission gear 47 to the left. Is transmitted to the rear wheel 2.
[0030]
As described above, the right and left front wheels 1 are in the range between the right first set angle A1 and the right second set angle A2, or the left first set angle A1 and the left second set angle A2. When the steering operation is performed in the range between, the power to the right and left front wheels 1 and the rear wheel 2 outside the turning is transmitted, and the power to the rear center wheel 2 on the turning center side is cut off. The rear wheel 2 on the center side is in a free rotation state, and turns right or left. As a result, the turning center-side rear wheel 2 moves forward while rotating appropriately while turning, and the state where the rice paddle surface is roughened by the turning center-side rear wheel 2 during turning is reduced.
[0031]
[5]
Next, the right and left front wheels 1 are set to a range between the right second set angle A2 and the right steering limit A3, and a range between the left second set angle A2 and the left steering limit A3. A case where the steering operation is performed will be described.
When the right and left front wheels 1 are steered to a range between the left second set angle A2 and the left steering limit A3, the left link rod 53 is further pulled by the pitman arm 25, and As shown in FIG. 9C, the left shift gear 43 is further slid toward the left second transmission gear 42, and the bite 43b of the left shift gear 43 is turned into the bite 42b of the left second transmission gear 42. And the power of the input shaft 38 is transmitted to the left rear wheel 2 via the transmission shaft 39, the left shift gear 43, the left second transmission gear 42, the transmission gear 48, the transmission shaft 45, and the axle 46. . The gear portion 43a of the right shift gear 43 remains engaged with the first gear portion 41a of the right first transmission gear 41, and the power of the input shaft 38 is transmitted through the right first transmission gear 41 and the transmission gear 47 to the right. Is transmitted to the rear wheel 2.
[0032]
When the right and left front wheels 1 are steered to a range between the right second set angle A2 and the right steering limit A3, the right link rod 53 is further pulled by the pitman arm 25, and The right shift gear 43 is further slid toward the right second transmission gear 42, and the engagement portion 43 b of the right shift gear 43 engages with the engagement portion 42 b of the right second transmission gear 42, and the power of the input shaft 38 is changed. Is transmitted to the right rear wheel 2 via the transmission shaft 39, the right shift gear 43, the right second transmission gear 42, the transmission gear 48, the transmission shaft 45, and the axle 46. The gear portion 43a of the left shift gear 43 remains engaged with the first gear portion 41a of the left first transmission gear 41, and the power of the input shaft 38 is transmitted through the left first transmission gear 41 and the transmission gear 47 to the left. Is transmitted to the rear wheel 2.
[0033]
In this case, the power of the input shaft 38 is transmitted to the right (left) rear wheel 2 via the right (left) first transmission gear 41 and the transmission gear 47, as shown in the preceding section [4] and FIG. As shown in FIG. 9C, the power of the input shaft 38 is shifted to the right (left) via the right (left) second transmission gear 42 and the transmission gear 48 more than the transmission ratio (transmission speed) B1 in the transmitted state. (Left) The transmission ratio (transmission speed) B2 when transmitted to the rear wheel 2 is set to be low.
[0034]
Further, as shown in FIG. 10, the right and left front wheels 1 are in the range between the right second set angle A2 and the right steering limit A3, or the left second set angle A2 and the left steering limit. In the state where the steering operation is performed in a range between A3 and A3, the transmission ratio (transmission speed) B1, the transmission ratio (transmission speed) B2, the distance L1 from the turning center C to the rear wheel 2 outside the turning center, and the distance from the turning center C At a distance L2 to the rear wheel 2 on the turning center side,
B1 / B2 ≒ L1 / L2
Thus, the ratio between the transmission ratio (transmission speed) B1 and the transmission ratio (transmission speed) B2 is substantially equal to the ratio between the distance L1 and the distance L2.
[0035]
[First Embodiment of the Invention]
Instead of the above-described [Embodiment of the invention], a configuration as shown in FIGS. 11 and 12 (A) may be adopted.
As shown in FIGS. 11 and 12A, the first gear portion 41a is eliminated in the right and left first transmission gears 41, and the gear portion 43a is eliminated in the right and left shift gears 43. A friction plate 54 is arranged between the first transmission gear 41 and the right and left shift gears 43. The other structure is the same as that of the above-mentioned [Embodiment of the invention].
[0036]
As a result, as shown in FIGS. 11 and 12 (a), when the right and left front wheels 1 are steered to the straight traveling position A0, the friction plates 54 are pressed by the right and left shift gears 43 by the springs 44. The power of the input shaft 38 is transmitted through the transmission shaft 39, the right and left shift gears 43, the friction plate 54, the right and left first transmission gears 41, the transmission gear 47, the transmission shaft 45, and the right and left The power is transmitted to the rear wheel 2. The above-described state is obtained even when the right and left front wheels 1 are steered in a range between the straight traveling position A0 and the right and left first set angles A1.
[0037]
When the right and left front wheels 1 are steered to a range between the left first set angle A1 and the left second set angle A2, the left link rod 53 is pulled by the pitman arm 25, The left shift gear 43 is slid toward the left second transmission gear 42, and the left shift gear 43 no longer presses the friction plate 54 (the engagement portion 43b of the left shift gear 43 engages with the left second transmission gear 42). The power to the left rear wheel 2 is cut off, and the left rear wheel 2 enters a free rotation state. The right shift gear 43 keeps pressing the friction plate 54, and the power of the input shaft 38 is transmitted to the right rear wheel 2 via the right first transmission gear 41 and the transmission gear 47.
[0038]
When the right and left front wheels 1 are steered to a range between the right first set angle A1 and the right second set angle A2, the pitman arm 25 pulls the right link rod 53, The right shift gear 43 is slid toward the right second transmission gear 42, so that the right shift gear 43 no longer presses the friction plate 54 (the engagement portion 43b of the right shift gear 43 is engaged with the right second transmission gear 42). The power to the right rear wheel 2 is cut off, and the right rear wheel 2 enters a free rotation state. The left shift gear 43 keeps pressing the friction plate 54, and the power of the input shaft 38 is transmitted to the left rear wheel 2 via the left first transmission gear 41 and the transmission gear 47.
[0039]
When the right and left front wheels 1 are steered to a range between the left second set angle A2 and the left steering limit A3, the pitman arm 25 links the left and right as shown in FIG. The rod 53 is further pulled, the left shift gear 43 is further slid toward the left second transmission gear 42, and the bite 43b of the left shift gear 43 is brought into contact with the bite 42b of the left second transmission gear 42. The power of the input shaft 38 is transmitted to the left rear wheel 2 via the transmission shaft 39, the left shift gear 43, the left second transmission gear 42, the transmission gear 48, the transmission shaft 45, and the axle 46. The right shift gear 43 keeps pressing the friction plate 54, and the power of the input shaft 38 is transmitted to the right rear wheel 2 via the right first transmission gear 41 and the transmission gear 47.
[0040]
When the right and left front wheels 1 are steered to a range between the right second set angle A2 and the right steering limit A3, the right link rod 53 is further pulled by the pitman arm 25, and The right shift gear 43 is further slid toward the right second transmission gear 42, and the engagement portion 43 b of the right shift gear 43 engages with the engagement portion 42 b of the right second transmission gear 42, and the power of the input shaft 38 is changed. Is transmitted to the right rear wheel 2 via the transmission shaft 39, the right shift gear 43, the right second transmission gear 42, the transmission gear 48, the transmission shaft 45, and the axle 46. The left shift gear 43 keeps pressing the friction plate 54, and the power of the input shaft 38 is transmitted to the left rear wheel 2 via the left first transmission gear 41 and the transmission gear 47.
[0041]
[Second Alternative Embodiment of the Invention]
Instead of the above-described [Embodiment of the invention] and [First alternative embodiment of the invention], a configuration as shown in FIG.
As shown in FIG. 13A, the first gear portion 41a is abolished in the right and left first transmission gears 41, and the gear portion 43a is abolished in the right and left shift gears 43. A friction plate 54 is arranged between the transmission gear 41 and the right and left shift gears 43. In the right and left second transmission gears 42, the occlusion portion 42b is eliminated, and the ring-shaped receiving plate 42c is fixed to the right and left second transmission gears 42. In the right and left shift gears 43, the occlusion portion 43b is eliminated, and the end 43c of the right and left shift gears 43 is formed in a ring-shaped plane. In this case, the right and left second set angles A2 and the right and left steering limits A3 shown in FIG. 5 are at the same position. The other structure is the same as that of the above-mentioned [Embodiment of the invention].
[0042]
Thus, as shown in FIG. 13A, when the right and left front wheels 1 are steered to the straight traveling position A0, the friction plates 54 are pressed by the right and left shift gears 43 by the springs 44, and the input is performed. The power of the shaft 38 is transmitted to the right and left rear wheels 2 via the transmission shaft 39, the right and left shift gears 43, the friction plates 54, the right and left first transmission gears 41, the transmission gear 47, the transmission shaft 45, and the axle 46. Is transmitted to Even if the right and left front wheels 1 are steered in a range between the straight traveling position A0 and the right and left first set angles A1, the above-described state is obtained.
[0043]
When the right and left front wheels 1 are steered to a range between the left first set angle A1 and the left second set angle A2, the pitman arm 25 pulls the left link rod 53, The left shift gear 43 is slid toward the left second transmission gear 42, and the left shift gear 43 no longer presses the friction plate 54 (the end 43c of the left shift gear 43 receives the left second transmission gear 42). The power to the left rear wheel 2 is cut off, and the left rear wheel 2 enters a free rotation state. The right shift gear 43 keeps pressing the friction plate 54, and the power of the input shaft 38 is transmitted to the right rear wheel 2 via the right first transmission gear 41 and the transmission gear 47.
[0044]
When the right and left front wheels 1 are steered to a range between the right first set angle A1 and the right second set angle A2, the pitman arm 25 pulls the right link rod 53, The right shift gear 43 is slid toward the right second transmission gear 42, and the right shift gear 43 no longer presses the friction plate 54 (the end 43c of the right shift gear 43 receives the right second transmission gear 42). The power to the right rear wheel 2 is cut off, and the right rear wheel 2 enters a free rotation state. The left shift gear 43 keeps pressing the friction plate 54, and the power of the input shaft 38 is transmitted to the left rear wheel 2 via the left first transmission gear 41 and the transmission gear 47.
[0045]
When the right and left front wheels 1 are steered to the left second set angle A2 (left steering limit A3), the left link rod 53 is moved by the pitman arm 25 as shown in FIG. By further pulling, the left shift gear 43 is further slid toward the left second transmission gear 42, and the end 43 c of the left shift gear 43 is pressed by the receiving plate 42 c of the left second transmission gear 42. The power of the input shaft 38 is transmitted to the rear left via the transmission shaft 39, the left shift gear 43 (end portion 43c), the left second transmission gear 42 (the receiving plate 42c), the transmission gear 48, the transmission shaft 45, and the axle 46. It is transmitted to the wheel 2. The right shift gear 43 keeps pressing the friction plate 54, and the power of the input shaft 38 is transmitted to the right rear wheel 2 via the right first transmission gear 41 and the transmission gear 47.
[0046]
When the right and left front wheels 1 are steered to the second right set angle A2 (right steering limit A3), the pitman arm 25 further pulls the right link rod 53 to cause the right shift gear 43 to move. Is further slid toward the right second transmission gear 42, the end 43c of the right shift gear 43 is pressed by the receiving plate 42c of the right second transmission gear 42, and the power of the input shaft 38 is transmitted to the transmission shaft 39. The power is transmitted to the right rear wheel 2 via the right shift gear 43 (end portion 43c), the right second transmission gear 42 (the receiving plate 42c), the transmission gear 48, the transmission shaft 45, and the axle 46. The left shift gear 43 keeps pressing the friction plate 54, and the power of the input shaft 38 is transmitted to the left rear wheel 2 via the left first transmission gear 41 and the transmission gear 47.
[0047]
[Third Alternative Embodiment of the Invention]
In the above-described [Embodiment of the invention], [First alternative embodiment of the invention], and [Second alternative embodiment of the invention], a spring (not shown) for accommodating the right and left linkage rods 53 is provided. May be provided. With this configuration, the range between the right second set angle A2 and the right steering limit A3 and the range between the left second set angle A2 and the left steering limit A3 are widened. (The right and left second set angles A2 can be relatively far from the right and left steering limits A3 to the right and left first set angles A1). .
The present invention can be applied not only to a riding type rice transplanter but also to a riding type direct sowing machine having a direct sowing device at the rear of the body, and a riding type management machine having a medicine spraying device at the back of the body.
[0048]
【The invention's effect】
According to the first aspect of the present invention, in the riding type work vehicle, when the right and left front wheels are steered to the right or left, power to the turning center side rear wheel is shut off, and the turning center side rear wheel is turned off. When configured to be in a free rotation state, when the right and left front wheels are steered to the right or to the left by a large turning operation to turn with a small turning radius, the turning wheel on the turning center side rotates little by little. The vehicle turns sideways while moving forward, and the rear wheel on the turning center side does not rotate and hardly turns sideways on the spot. The state in which the work area was roughened by the rear wheel on the center side could be reduced, and the turning performance of the passenger work vehicle could be improved.
According to the feature of the first aspect, when the right and left front wheels are steered to the right or left, power to the turning center side rear wheel is shut off, and the turning center side rear wheel freely rotates. In addition, there is provided an advantage that the state in which the work place is roughened by the rear wheel on the turning center side during turning is reduced.
[0049]
According to the feature of the second aspect, the "effect of the invention" of the above-mentioned claim 1 is provided similarly to the case of the first aspect, and in addition to the "effect of the invention", the following "effect of the invention" It has.
According to the second aspect of the present invention, when the transmission structure to the right and left rear wheels is configured, the transmission systems in the first and second transmission states of the right and left are relatively short, so that the structure is simplified. In terms of
[0050]
According to the feature of the third aspect, similar to the case of the first or second aspect, the present invention has the "effect of the invention" of the first or second aspect, and in addition to the "effect of the invention", the following " Effect of the Invention ".
According to the features of claim 3, the right and left front wheels range between a right second set angle and a right steering limit, or a range between a left second set angle and a left steering limit. In the state where the steering operation is performed, the transmission of the rear wheel to the turning center side in the second transmission state is performed based on the distance from the turning center to the rear wheel outside the turning center and the distance from the turning center to the rear wheel on the turning center side. The speed can be set to an appropriate speed, and the turning performance of the riding work vehicle can be improved.
[Brief description of the drawings]
FIG. 1 is an overall side view of a riding rice transplanter.
FIG. 2 is an overall plan view of a riding rice transplanter.
FIG. 3 is a side view of the vicinity of a front axle case and a rear axle case.
FIG. 4 is a plan view of the vicinity of a front axle case and a rear axle case.
FIG. 5 is a plan view of the vicinity of a pitman arm and a rear axle case.
FIG. 6 is a cross-sectional plan view of the rear axle case.
FIG. 7 is a vertical side view of the vicinity of the rear axle case.
FIG. 8 is a cross-sectional plan view near the left side gear in the rear axle case.
FIG. 9 is a view showing a range in which the right and left front wheels are in the straight traveling position and the right and left first set angles, a range between the first left set angle and the second left set angle, and a left second set angle; Cross-sectional plan view near the left side gear in a state where the steering operation is performed in a range between the set angle and the left steering limit.
FIG. 10 shows states of the right and left front wheels and the right and left rear wheels in a state where the right and left front wheels are steered to a range between the second set angle on the left and the left steering limit. Plan view shown
FIG. 11 is a cross-sectional plan view showing the vicinity of a left side gear in a rear axle case according to the first alternative embodiment of the present invention;
FIG. 12 is a view showing a state in which the right and left front wheels are in a range between the straight traveling position and the right and left first set angles, the second left set angle and the left steering limit in the first alternative embodiment of the present invention; Cross-sectional plan view of the vicinity of the left side gear in a state where the steering operation is performed in the range between
FIG. 13 is a view showing the right and left front wheels in a range between the straight traveling position and the right and left first set angles, and the second set angle on the left (left steering limit) according to the second embodiment of the present invention; Plan view of the vicinity of the left side gear in a state where the steering operation is performed
[Explanation of symbols]
1 Right and left front wheels
2 Right and left rear wheels
35,36,38 One transmission system
39 Right transmission system, left transmission system
41, 47 Transmission system in right first transmission state, transmission system in left first transmission state
42, 48 Transmission system in right second transmission state, transmission system in left second transmission state
43 Switching mechanism
A0 Straight ahead position
A1 Right and left first set angles
A2 Right and left second set angles
A3 Right and left steering limits
B1 Transmission speed to the right and left rear wheels in the first transmission state
B2 Transmission speed to the rear wheel on the turning center side in the second transmission state
L1 Distance from turning center to rear wheel outside turning
L2 Distance from turning center to rear wheel on the turning center side

Claims

操向操作自在な右及び左の前輪と、右及び左の後輪とを備えて、
直進位置から右及び左の第１設定角度を設定し、前記右及び左の第１設定角度よりも右及び左の操向限度側に右及び左の第２設定角度を設定すると共に、
右及び左の前輪が直進位置と前記右及び左の第１設定角度との間の範囲に操向操作されると、右及び左の後輪に動力が伝達される第１伝動状態が設定され、
右及び左の前輪が前記右の第１設定角度と右の第２設定角度との間の範囲、又は前記左の第１設定角度と左の第２設定角度との間の範囲に操向操作されると、旋回中心側の後輪への動力が遮断されて、旋回中心側の後輪が自由回転状態となる遮断状態が設定され、
右及び左の前輪が前記右の第２設定角度と右の操向限度との間の範囲、又は前記左の第２設定角度と左の操向限度との間の範囲に操向操作されると、前記第１伝動状態で右及び左の後輪に伝達される動力よりも低速の動力が旋回中心側の後輪に伝達される第２伝動状態が設定されるように構成してある乗用型作業車。With right and left front wheels that can be steered and right and left rear wheels,
Setting the right and left first set angles from the straight ahead position, and setting the right and left second set angles on the right and left steering limit sides than the right and left first set angles,
When the right and left front wheels are steered to a range between the straight traveling position and the right and left first set angles, a first transmission state in which power is transmitted to the right and left rear wheels is set. ,
The right and left front wheels are steered to a range between the right first set angle and the right second set angle, or a range between the left first set angle and the left second set angle. When this is done, the power to the turning center-side rear wheel is shut off, and a shut-off state in which the turning center-side rear wheel enters a free rotation state is set,
The right and left front wheels are steered to a range between the right second set angle and the right steering limit, or a range between the left second set angle and the left steering limit. And a second transmission state in which a lower power than the power transmitted to the right and left rear wheels in the first transmission state is transmitted to the rear wheel on the turning center side. Type work vehicle.

一つの伝動系から右の伝動系及び左の伝動系を分岐させて、前記右の伝動系から右の第１伝動状態の伝動系及び右の第２伝動状態の伝動系を分岐させ、前記左の伝動系から左の第１伝動状態の伝動系及び左の第２伝動状態の伝動系を分岐させて、
前記右の第１及び第２伝動状態の伝動系を右の後輪に接続し、前記左の第１及び第２伝動状態の伝動系を左の後輪に接続すると共に、
前記右及び左の第１及び第２伝動状態の伝動系を伝動及び遮断状態に操作自在な切換機構を備えて、
前記切換機構により右及び左の第１伝動状態の伝動系を伝動状態に操作し右及び左の第２伝動状態の伝動系を遮断状態に操作して第１伝動状態を設定し、
前記切換機構により右及び左の第１及び第２伝動状態の伝動系を遮断状態に操作して遮断状態を設定し、
前記切換機構により右又は左の第１伝動状態の伝動系を遮断状態に操作し右又は左の第２伝動状態の伝動系を伝動状態に操作して第２伝動状態を設定するように構成してある請求項１に記載の乗用型作業車。The right transmission system and the left transmission system are branched from one transmission system, and the right transmission system in the first transmission state and the right transmission system in the second transmission state are branched from the right transmission system. The transmission system of the first transmission state on the left and the transmission system of the second transmission state on the left are branched from the transmission system of
The right first and second transmission state transmission systems are connected to the right rear wheel, and the left first and second transmission state transmission systems are connected to the left rear wheel,
The right and left first and second transmission states of the transmission system are provided with a switching mechanism operable to be in a transmission and cutoff state,
The first transmission state is set by operating the right and left first transmission state transmission systems by the switching mechanism to the transmission state, and operating the right and left second transmission state transmission systems to the cutoff state by the switching mechanism,
The switching mechanism operates the transmission systems of the first and second transmission states on the right and the left to a cutoff state to set a cutoff state,
The switching mechanism is configured to set the second transmission state by operating the right or left transmission system in the first transmission state to the cutoff state and operate the transmission system in the right or left second transmission state to the transmission state. The riding work vehicle according to claim 1, wherein

右及び左の前輪が前記右の第２設定角度と右の操向限度との間の範囲、又は前記左の第２設定角度と左の操向限度との間の範囲に操向操作された状態において、前記第１伝動状態の右及び左の後輪への伝動速度と第２伝動状態の旋回中心側への後輪の伝動速度との比が、旋回中心から旋回外側の後輪までの距離と旋回中心から旋回中心側の後輪までの距離との比に略等しくなるように構成してある請求項１又は２に記載の乗用型作業車。The right and left front wheels are steered to a range between the right second set angle and the right steering limit, or a range between the left second set angle and the left steering limit. In the state, the ratio of the transmission speed to the right and left rear wheels in the first transmission state and the transmission speed of the rear wheel to the turning center side in the second transmission state is from the turning center to the rear outside wheel. 3. The riding work vehicle according to claim 1, wherein the ratio is substantially equal to a ratio of the distance to a distance from the turning center to the rear wheel on the turning center side.