Specification
Title of Invention: Tractor
Technical field
[0001]
　The present invention relates to a tractor equipped with a three-point link mechanism for mounting a working device so that it can be raised and lowered.
Background technology
[0002]
　For example, the tractor disclosed in Japanese Patent Application Laid-Open No. 2018-042530 (Patent Document 1) is provided with a three-point link mechanism, and the three-point link mechanism is operated by a hydraulic unit ("hydraulic lifting device" in the document). be done. When the working device is attached to a three-point link mechanism and is towed by a vehicle body to perform ground work, the working device is configured to be able to move up and down according to the towing load. A load receiving portion (a “load detection member” in the literature) that receives the traction load from the working device is provided. Transmits the amount of operation for swing operation of the link mechanism. In addition, an interlocking swing arm (“swing member” in the literature) that can swing in conjunction with the load receiving portion is provided. When the load receiving portion swings by a predetermined amount or more, the interlocking swing arm swings, and the amount of swinging of the load receiving portion is amplified by the interlocking swing arm, thereby improving the operational sensitivity of the three-point link mechanism.
prior art documents
patent literature
[0003]
Patent Document 1: Japanese Patent Application Laid-Open No. 2018-042530
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0004]
　In the tractor disclosed in Japanese Patent Application Laid-Open No. 2018-042530, the interlocking swing arm does not swing unless the load receiving portion swings by a predetermined amount or more. In other words, unless the pulling load reaches a predetermined amount or more, the operational sensitivity of the three-point link mechanism is not improved. Therefore, there is room for improvement in improving the operation sensitivity.
[0005]
　SUMMARY OF THE INVENTION An object of the present invention is to provide a tractor capable of controlling the lifting and lowering of a working device with high sensitivity in accordance with the towing load.
Means to solve problems
[0006]
　A tractor according to the present invention includes a three-point link mechanism that is vertically swingably connected to a rear portion of a vehicle body and that mounts a work device so that it can be lifted and lowered, a hydraulic unit that can swing the three-point link mechanism, and the work device. a load receiving portion that swings according to the traction load of the work device when performing ground work while being towed by the vehicle body; A link mechanism for transmitting an operation amount is provided, and is provided on the uppermost side of the link mechanism and interlocks with the swinging motion of the load receiving portion with a swinging axis different from the swinging shaft center of the load receiving portion. The load receiving portion is provided with a first portion that presses the interlocking swing arm, and the interlocking swing arm is in contact with the first portion to contact the first portion. A second part pressed by the first part is provided, and a contact position between the first part and the second part is changeable.
[0007]
　According to the present invention, the load receiving portion and the interlocking swing arm swing about their respective swing axes, and the contact position between the first portion and the second portion can be changed. Therefore, by changing the contact position, the link mechanism can amplify the swing amount of the load receiving portion. Further, since the interlocking swing arm is provided on the uppermost side of the link mechanism, the interlocking swing arm swings when the load receiving portion starts swinging. Since the contact position between the first part and the second part can be changed in this state, the link mechanism can amplify the swing amount of the load receiving part from the stage when the load receiving part starts to swing. Therefore, the operational sensitivity of the three-point link mechanism is improved as compared with a configuration in which the interlocking swing arm does not swing unless the load receiving portion swings by a predetermined amount or more. As a result, a tractor capable of controlling the lifting and lowering of the work implement with high sensitivity according to the towing load is realized.
[0008]
　In the present invention, one of the first part and the second part is a rocking member, and the other of the first part and the second part is a plurality of rocking members capable of receiving and locking the rocking member. It is preferable that, in the engaging portion formed with recesses, the swinging member is provided with a positioning mechanism for positioning a swinging angle when engaging with the plurality of recesses.
[0009]
　According to this configuration, the combination of the swinging member and the engaging portion constitutes the combination of the first portion and the second portion, and the swinging member engages with the concave portion of the engaging portion. Further, when the swinging member engages with any one of the plurality of recesses, the swinging angle of the swinging member is held by the positioning mechanism. Therefore, the contact position between the first part and the second part is held without shifting to an unintended position. As a result, the interlocking swing arm can more preferably amplify the amount of swing of the load receiving portion.
[0010]
　In the present invention, it is preferable that the positioning mechanism can position the swing member at an angle orthogonal to the swing angle of the load receiving portion.
[0011]
　With this configuration, the angle at which the swing member is positioned includes an angle orthogonal to the swing angle of the load receiving portion. That is, the swinging range of the swinging member is set to a range close to an angle orthogonal to the swinging angle of the load receiving portion. Therefore, the swing member can firmly receive the reaction force from the locking portion. As a result, the rocking member can suitably press the engaging portion. It should be noted that the "perpendicular angle" in the present invention is not limited to a strict perpendicular angle, and includes an approximately perpendicular angle.
[0012]
　本発明において、前記揺動部材の遊端部に、前記複数の凹部への係入が可能なピンが設けられ、前記係止部に、前記複数の凹部が連続で並ぶように前記複数の凹部を包含する共通凹部が形成され、前記ピンは、前記共通凹部を通過して前記複数の凹部の何れか一つに係入すると好適である。
[0013]
　本構成によると、共通凹部に複数の凹部が形成され、この複数の凹部に揺動部材のピンが係入する。また、ピンが前記共通凹部を通過して前記複数の凹部の何れか一つに係入するため、共通凹部がピンと複数の凹部との隙間空間として形成されている。このことから、作業者が揺動部材の揺動角度を変更する際、共通凹部の隙間空間でピンが揺動する構成が可能となり、揺動角度変更操作が一層容易になる。
[0014]
　本発明において、前記リンク機構に、前記負荷受け部が前記牽引負荷の大きい側に揺動するほど、前記リンク機構のうちの下手側の機構の変位量が大きくなるように動作する感度変更部が備えられていると好適である。
[0015]
　作業装置の牽引負荷が大きくなるほど、負荷受け部の揺動量が大きくなる。作業装置の牽引負荷が大きくなると、牽引負荷を低減させるために、作業装置が積極的に上昇制御されることが望ましい。本構成であれば、負荷受け部の揺動量が大きくなるほど、リンク機構のうちの下手側の機構の変位量が大きくなる。これにより、作業装置が積極的に上昇制御されて牽引負荷が速やかに低減され、牽引負荷の上昇に起因する作業装置の破損やエンジンのストールが好適に防止される。
[0016]
　本発明において、前記リンク機構のうち前記連動揺動アームよりも下手側に、前記第１部及び前記第２部によるリンク比変化率よりも小さなリンク比変化率にリンク比を変更するリンク比変更部が備えられていると好適である。
[0017]
　本構成によって、油圧ユニットに対する操作量の微調整が可能となる。
図面の簡単な説明
[0018]
1 is a right side view of a tractor equipped with a working device; FIG.
2 is a right side view showing the draft control mechanism; FIG.
3 is a plan view showing a draft control mechanism; FIG.
4 is a rear view showing a draft control mechanism; FIG.
5] Fig. 5 is an exploded perspective view showing assembly of the load receiving portion and the interlocking swing mechanism. [Fig.
6 is an exploded perspective view showing assembly of the link mechanism; FIG.
7 is a sectional view taken along the line VV of FIG. 4, showing the link mechanism; FIG.
8 is a cross-sectional view taken along the line VV in FIG. 4 showing the movement of the link mechanism in comparison with FIG. 7;
9 is an enlarged side view showing a rocking member (first part) and a locking part (second part); [0029] FIG.
10 is a plan view cross-sectional view showing a swinging member (first part), a locking part (second part), a first coil spring, and a second coil spring; [0027] FIG.
11 is a right side view showing rocking between the load receiving portion and the interlocking rocking mechanism; FIG.
12 is a right side view showing swinging between the load receiving portion and the interlocking swinging mechanism; FIG.
13 is a right side view showing rocking of the load receiving portion and the interlocking rocking mechanism; FIG.
MODE FOR CARRYING OUT THE INVENTION
[0019]
　EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing this invention is demonstrated based on drawing. The direction indicated by the arrow "F" in FIG. 1 is the forward direction of travel of the tractor, and the direction indicated by the arrow "U" is above the tractor. In addition, the terms “left” and “right” in this specification refer to the right and left of the tractor when viewed forward in the traveling direction.
[0020]
　The tractor shown in FIG. A pair of rear fenders 8 are provided.
[0021]
　A pair of left and right front wheels 1 are pivotally supported by a front frame 3 arranged in the front part of the vehicle body, and positioned laterally outside of the front frame 3 of the vehicle body. The intermediate frame 4 is arranged behind the front frame 3 . A clutch housing 5 is arranged between the front frame 3 and the intermediate frame 4 , and the front frame 3 and the intermediate frame 4 are connected to the clutch housing 5 . A transmission case 6 is connected to the rear end of the intermediate frame 4 . The clutch housing 5 and the transmission case 6 are also used as a body frame of the tractor. That is, a front frame 3 , an intermediate frame 4 , a clutch housing 5 and a transmission case 6 are provided as body frames of the tractor.
[0022]
　An engine E is mounted and supported on the rear portion of the front frame 3, and a clutch housing 5 is connected to the lower rear end of the engine E. As shown in FIG. A pair of left and right rear wheels 2 are pivotally supported by the transmission case 6 so as to be located outside the transmission case 6 on the left and right sides.
[0023]
　Although not shown, the clutch housing 5 contains a main clutch and the like, the intermediate frame 4 has a transmission shaft, and the transmission case 6 contains a main transmission, an auxiliary transmission, and the like. The power of the engine E is transmitted to a pair of left and right front wheels 1 and a pair of left and right rear wheels 2 via a main clutch, a transmission shaft, a main transmission, an auxiliary transmission, and the like.
[0024]
　The operation unit 7 is arranged at the rear part of the vehicle body and is configured so that an operator can get on it. A driving unit 7 is provided with a steering wheel 10 and a driver's seat 11 . An operator can sit on the driver's seat 11 . A steering wheel 10 is provided in front of a driver's seat 11 , and an operator manually operates the steering wheel 10 to steer a pair of left and right front wheels 1 . Rear fenders 8 are arranged on the left and right sides of the driver's seat 11, respectively, on the outer sides of the vehicle body, and the rear fenders 8 cover the left and right rear wheels 2 from above. The transmission case 6 is arranged below the driver's seat 11 . The driver's seat 11 is positioned between the pair of left and right rear wheels 2 in a plan view and a front-rear direction view.
[0025]
　A three-point link mechanism 12 is connected to the rear portion of the transmission case 6 so as to be capable of swinging up and down. The working device 15 shown in FIG. 1 is a plow. The work device 15 may be, for example, a rotary tillage device, a disk harrow, a cultivator, a subsoiler, or the like.
[0026]
　A three-point link mechanism 12 is provided with a single top link 13 and left and right lower links 14 . The lower link 14 is connected to the lower rear portion of the transmission case 6 so as to be able to swing about the swing axis Y1. A load receiving portion 30 is connected to the rear upper portion of the transmission case 6, and the top link 13 is connected to the load receiving portion 30 so as to be able to swing about the swing axis Y2. The load receiving portion 30 will be described later.
[0027]
　The three-point link mechanism 12 is vertically driven by a hydraulically driven lift arm 16 . Specifically, one end of the link member 19 is pivotally connected to the tip of the lift arm 16 with a pin, and the other end of the link member 19 is pivotally connected to the lower link 14 with a pin.
[0028]
　リフトアーム１６は、不図示の油圧アクチュエータの駆動に基づいて、揺動軸芯Ｘまわりに上下揺動可能に構成されている。そして、リフトアーム１６の上下揺動に伴ってロアリンク１４が上下揺動する。作業装置１５と連結されたトップリンク１３も、ロアリンク１４の上下揺動と連係して上下揺動する。作業装置１５は、トップリンク１３とロアリンク１４との夫々に相対揺動可能に連結され、トップリンク１３とロアリンク１４との夫々の上下揺動と連係して作業装置１５は上下に昇降する。
[0029]
　作業者が高さ設定レバー２３を操作すると、油圧アクチュエータに対する作動油の給排が行われてリフトアーム１６が揺動し、作業装置１５が上下昇降する。作動油の給排は不図示のスプールの動作によって制御される。作業装置１５の上下昇降と連動してフィードバックリンク機構（不図示）が動作する。フィードバックリンク機構は、高さ設定レバー２３の操作量と、リフトアーム１６の揺動角度と、に基づいて油圧アクチュエータに対する作動油の給排量を調節する。作業装置１５が制御目標高さに到達すると、油圧アクチュエータに対する作動油の給排が停止して、左右のリフトアーム１６の上下揺動が停止する。このように、３点リンク機構１２は作業装置１５を昇降可能に取付ける。本実施形態で示された油圧アクチュエータ及びスプールは、本発明の『油圧ユニット』に相当する。即ち、３点リンク機構１２を揺動操作可能な油圧ユニットが備えられている。
[0030]
〔ドラフト制御機構について〕
　本実施形態では、作業装置１５の作業高さは、作業装置１５の対地作業時の作業負荷や耕深に基づいて調整可能に構成されている。例えば３点リンク機構１２に作業装置１５としてプラウが連結された場合、プラウによる対地作業が行われる際に、プラウは地面から反力を受け、この反力が牽引負荷となる。牽引負荷が大きくなり過ぎるとプラウが破損したりエンジンＥがストールしたりする虞がある。このため、プラウ等の作業装置１５を牽引負荷に応じて上下昇降し、牽引負荷を一定に調整する機構、即ちドラフト制御機構が、本実施形態のトラクタに備えられている。以下、ドラフト制御機構に関して説明する。
[0031]
　図２乃至図６に示されるように、ドラフト機構に、負荷受け部３０と、リンク機構（連動揺動アーム３１、連結リンク部３２、耕深調整カム３４、連動揺動部３５、連係ロッド３６）と、が備えられている。なお、ドラフト機構としての負荷受け部３０及びリンク機構を見易くするため、図２乃至図４には、リフトアーム１６は図示されていないが、リフトアーム１６の揺動軸芯Ｘは図示されている。
[0032]
　負荷受け部３０は、作業装置１５がトラクタの車体に牽引されながら対地作業を行う場合に作業装置１５の牽引負荷に応じて揺動する。リンク機構は、負荷受け部３０の揺動量に応じて、油圧ユニット（上述した不図示の油圧アクチュエータ及びスプールを含む）に、３点リンク機構１２の揺動操作のための操作量を伝達する。本発明のリンク機構として、連動揺動アーム３１と、連結リンク部３２と、耕深調整カム３４と、連動揺動部３５と、連係ロッド３６と、が備えられている。
[0033]
　負荷受け部３０に、ブラケット３０Ａと、受け部材３０Ｂと、支点ピン３０Ｃと、連係ピン３０Ｄと、第１コイルバネ３０Ｅと、第２コイルバネ３０Ｆと、揺動禁止部材３０Ｇと、が備えられている。ブラケット３０Ａはトランスミッションケース６の後部に連結固定される。トップリンク１３は受け部材３０Ｂに連結されている。
[0034]
　ブラケット３０Ａの下部と受け部材３０Ｂの下部との夫々に、支点ピン３０Ｃを挿通可能な丸孔が機体横向きに穿孔され、ブラケット３０Ａと受け部材３０Ｂとの夫々の下部における当該丸孔を支点ピン３０Ｃが機体横向きに貫通する。つまり、支点ピン３０Ｃは、ブラケット３０Ａと受け部材３０Ｂとを揺動軸芯Ｐまわりに相対揺動可能なように枢支連結し、受け部材３０Ｂは、機体横向きの揺動軸芯Ｐまわりに前後揺動可能である。
[0035]
　受け部材３０Ｂの上下中央部分に、丸孔３０ｏが機体横向きに穿孔されている。また、ブラケット３０Ａの上下中央部分に、長孔３０ｐが機体横向きに穿孔されている。長孔３０ｐの長手方向は機体前後方向に沿っている。受け部材３０Ｂの上下中央部分の丸孔３０ｏと、長孔３０ｐと、を連係ピン３０Ｄが貫通する。連係ピン３０Ｄの長手方向両端部は、受け部材３０Ｂよりも外側に位置する。そして、連係ピン３０Ｄの長手方向端部に、スナップピンが係止して、連係ピン３０Ｄはブラケット３０Ａ及び受け部材３０Ｂに対して抜け止めされている。
[0036]
　連係ピン３０Ｄは、丸孔３０ｏに対して相対変位不能であって、かつ、長孔３０ｐの長手方向に沿ってスライド可能である。このことから、受け部材３０Ｂは、長孔３０ｐの長手方向の範囲で前後揺動可能である。
[0037]
　A storage tube portion 30L is formed on the upper portion of the bracket 30A. 30 L of storage cylinder parts are formed in the cylindrical shape of the body front-back direction. A first coil spring 30E is housed in the housing tube portion 30L (see FIG. 10). A gap is formed between the upper portion of the bracket 30A and the upper portion of the receiving member 30B. The first coil spring 30E is provided in this gap, and both end portions in the extending direction of the first coil spring 30E contact the bracket 30A and the receiving member 30B, respectively. The receiving member 30B is biased by the first coil spring 30E so as to swing backward.
[0038]
　A second coil spring 30F is provided on the opposite side of the bracket 30A to the side where the first coil spring 30E is located. The elastic modulus of the second coil spring 30F is smaller than the elastic modulus of the first coil spring 30E. Although the details will be described later, when the first coil spring 30E expands and the elastic energy of the first coil spring 30E is released, the second coil spring 30F contracts and the elastic energy of the second coil spring 30F increases.
[0039]
　Three upper and lower mounting holes 30s are formed in the rear portion of the bracket 30A, and one end of the top link 13 is connected to one of the plurality of mounting holes 30s via a pin so as to be able to swing vertically. Of the three upper and lower mounting holes 30 s , the portion connected to the top link 13 serves as the pivot axis Y2 of the top link 13 .
[0040]
　The end of the top link 13 opposite to the side connected to the bracket 30A is connected to the upper portion of the work device 15 . Therefore, a tensile force acts on the top link 13 from the work device 15 when the work device 15 is raised or when the work device 15 is not performing work on the ground. Also, in this state, a tensile force acts on the receiving member 30B from the top link 13, and the receiving member 30B swings to the rearmost side.
[0041]
　When a plow is connected to the three-point link mechanism 12 as the working device 15 and plowing work is performed by the plow, the deeper the plowing depth, the stronger the reaction force from the ground to the plow. This reaction force is a traction load, and the upward component of the reaction force acts on the top link 13 as a pressing force. This pressing force is transmitted to the receiving member 30B via the top link 13. As shown in FIG. When this pressing force is greater than the resultant force of the elastic forces of the first coil spring 30E and the second coil spring 30F, the receiving member 30B resists the resultant force of the elastic forces of the first coil spring 30E and the second coil spring 30F. swing forward.
[0042]
　When the receiving member 30B swings forward, the first coil spring 30E contracts. The elastic force of the first coil spring 30E increases in proportion to the contraction amount of the first coil spring 30E. Therefore, the front side of the receiving member 30B is tilted at a swinging angle at which the pressing force acting on the receiving member 30B due to the traction load of the working device 15 and the resultant force of the elastic forces of the first coil spring 30E and the second coil spring 30F are balanced. to stop rocking. Accordingly, as the traction load of the work device 15 due to the work on the ground increases, the pressing force acting on the receiving member 30B increases, so that the receiving member 30B swings further forward. Accordingly, the receiving member 30B is configured to be capable of detecting the traction load of the working device 15. As shown in FIG.
[0043]
　揺動禁止部材３０Ｇは、受け部材３０Ｂの揺動を禁止する部材である。詳述はしないが、揺動禁止部材３０Ｇは、ブラケット３０Ａの左上部に設けられた前後方向の揺動軸芯Ｖ（図４参照）まわりに揺動可能に構成されている。揺動禁止部材３０Ｇの上部にハンドルが設けられている。揺動軸芯Ｖと当該ハンドルとの間に、ブラケット３０Ａの上端部と、受け部材３０Ｂの上端部と、の間の領域に介在可能な水平の板部分が形成されている。作業者が当該ハンドルを左右に操作すると、当該水平の板部分が上下に揺動する。受け部材３０Ｂが最も後側に揺動した状態で、揺動禁止部材３０Ｇが図４における時計回りに揺動すると、当該水平の板部分は、ブラケット３０Ａの上端部と、受け部材３０Ｂの上端部と、の隙間の全領域に亘って介在し、受け部材３０Ｂの前側への揺動を規制する。これにより、受け部材３０Ｂが揺動できなくなる。揺動禁止部材３０Ｇが図４における反時計回りに揺動すると、当該水平の板部分が、ブラケット３０Ａの上端部と、受け部材３０Ｂの上端部と、の間の領域から離れ、受け部材３０Ｂが前後に揺動できるようになる。
[0044]
　負荷受け部３０に、増幅調整部３０Ｈが備えられている。また、ブラケット３０Ａに、連動揺動アーム３１が前後揺動可能なようにピンで枢支連結されている。連動揺動アーム３１は、リンク機構のうちの最も上手側に備えられている。連動揺動アーム３１は、機体横向きの揺動軸芯Ｑ１まわりに前後揺動可能なように、ブラケット３０Ａの右側部に連結されている。増幅調整部３０Ｈは受け部材３０Ｂの右側部にボルト固定されている。連動揺動アーム３１は、負荷受け部３０の揺動軸芯Ｐと異なる揺動軸芯Ｑ１で負荷受け部３０の揺動と連動して揺動する。
[0045]
　増幅調整部３０Ｈは受け部材３０Ｂと一体的に揺動し、受け部材３０Ｂが前方へ揺動すると、連動揺動アーム３１と増幅調整部３０Ｈとが当接し、連動揺動アーム３１が揺動する。詳細に関しては後述するが、連動揺動アーム３１は、受け部材３０Ｂの前後揺動よりも大きく揺動することによって、受け部材３０Ｂの揺動量を増幅可能に構成されている。また、詳細に関しては後述するが、増幅調整部３０Ｈは、連動揺動アーム３１の揺動量を調整可能に構成されている。
[0046]
　受け部材３０Ｂのうち、増幅調整部３０Ｈに対して前上方の部分に当接ボルト３０ｋが連結されている。受け部材３０Ｂが最も後側に揺動された状態で、当接ボルト３０ｋと連動揺動アーム３１とが当接し、連動揺動アーム３１と増幅調整部３０Ｈとは離間する。受け部材３０Ｂが前方へ揺動すると、当接ボルト３０ｋと連動揺動アーム３１とが当接した状態で、連動揺動アーム３１が揺動軸芯Ｑ１まわりに揺動する。このとき、受け部材３０Ｂが前側に揺動するほど、連動揺動アーム３１と増幅調整部３０Ｈとの離間距離は小さくなる。そして、受け部材３０Ｂが更に前方へ揺動し、連動揺動アーム３１と増幅調整部３０Ｈとが当接すると、当接ボルト３０ｋと連動揺動アーム３１とが離間する。
[0047]
　上述したように、リフトアーム１６（図１参照、以下同じ）は油圧アクチュエータに対する作動油の給排によって上下揺動し、作動油の給排は不図示のスプールの動作によって制御される。連結リンク部３２と、耕深調整カム３４と、連動揺動部３５と、連係ロッド３６と、の夫々は、受け部材３０Ｂの揺動動作を、当該スプールへ伝達するためリンク機構である。
[0048]
　As shown in FIGS. 2 to 6, one end of a connecting link portion 32 is pivotally connected to the lower end portion of the interlocking swing arm 31 by a pin member 33 so as to be relatively swingable. A plowing depth adjusting cam 34 is pivotally connected to the end portion by a pin so as to be relatively rockable. A support member 37 is connected to the right side of the transmission case 6, and two cylindrical members 37A and 37B protrude from the support member 37 laterally outward of the vehicle body. The plowing depth adjusting cam 34 is supported by the cylindrical member 37B so as to be able to swing back and forth around the swing axis Z1 in the lateral direction of the machine body.
[0049]
　As shown in FIGS. 6 to 8, the connecting link portion 32 has a first link member 32A, a second link member 32B, a coil spring member 32C, and a connecting pin 32D. The first link member 32A is formed by welding a flat plate member and a bolt member. One longitudinal ends of the flat plate member and the bolt member are connected by welding. Of the flat plate member of the first link member 32A, the end opposite to the side welded to the bolt member is pivotally connected to the second link member 32B by a connecting pin 32D so as to be relatively swingable. The second link member 32B is a flat plate member. The end of the second link member 32B opposite to the side pivotally connected to the first link member 32A is pivotally connected to the tillage depth adjusting cam 34 by a pin so as to be relatively rockable.
[0050]
　A pair of nuts are engaged with the upper and lower end regions of the bolt member of the first link member 32A, and the coil spring member 32C and the pin member 33 are externally inserted between the pair of nuts. 32 C of coil spring members are arrange|positioned above the pin member 33, ie, the side in which the 2nd link member 32B is located. The pin member 33 is fitted onto the bolt member of the first link member 32A, is inserted into one of a plurality of insertion holes 31h formed in the lower end of the interlocking swing arm 31, and is inserted into the insertion hole 31h. with snap pins. That is, the lower end of the bolt member of the first link member 32A and the lower end of the interlocking swing arm 31 are connected by the pin member 33 so as to be swingable.
[0051]
　One end of a tension spring 38 is hooked to the plowing depth adjusting cam 34 , and the other end of the tension spring 38 is hooked to a hook member 39 . The hook member 39 is supported by the cylindrical member 37A. The columnar member 37A is located on the front side of the machine body relative to the tillage depth adjusting cam 34, and the tension spring 38 exerts a tensile force on the tillage depth adjusting cam 34 and the columnar member 37A. Therefore, the plowing depth adjusting cam 34 is urged to swing forward. The lower end of the swing arm 23A of the height setting lever 23 and the lower end of the swing arm 24A of the tillage depth lever 24 are fitted onto the cylindrical member 37A. The longitudinal direction of the columnar member 37A extends along the swing axis Y3 in the lateral direction of the machine body. Each of the lower end portion of the swing arm 23A and the lower end portion of the swing arm 24A is a swing base end portion. That is, the height setting lever 23 and the plowing depth lever 24 can swing back and forth around the swing axis Y3.
[0052]
　耕深調整カム３４にカム部３４ａが形成されている。また、連動揺動部３５の長手方向中央領域にローラー３５Ａが設けられ、カム部３４ａとローラー３５Ａとが当接可能である。カム部３４ａは、前側ほど揺動軸芯Ｚ１から離れるように傾斜する。このことから、カム部３４ａの前側領域とローラー３５Ａとが当接すると、カム部３４ａの後側領域とローラー３５Ａとが当接する場合と比較して、連動揺動部３５の揺動する度合いが大きくなる。耕深調整カム３４は、本発明の『感度変更部』に相当する。
[0053]
　図７及び図８に示されるように、耕深調整カム３４が揺動軸芯Ｚ１まわりに後方へ揺動し、カム部３４ａとローラー３５Ａとが当接すると、ローラー３５Ａがカム部３４ａに沿って移動しながら、連動揺動部３５が後方へ揺動する。連動揺動部３５が後方へ揺動すると、カム部３４ａとローラー３５Ａとがカム部３４ａの前側領域で当接するため、耕深調整カム３４の揺動角度の変化量に対して、連動揺動部３５の揺動角度の変化量が大きくなる。即ち、感度変更部としての耕深調整カム３４は、負荷受け部３０が牽引負荷の大きい側に揺動するほど、リンク機構のうちの下手側の機構の変位量が大きくなるように動作する。
[0054]
　耕深調整カム３４に、ロータリ耕耘装置のコントロールケーブル用の連結部３４ｂが形成され、連結部３４ｂにコントロールケーブルの一端部が連結可能である。ロータリ耕耘装置のコントロールケーブルに関しては、特開２０１８－０４２５３０号公報の図１６及び図１７に記載されている。連結部３４ｂは、連動揺動部３５を挟んでカム部３４ａの位置する側と反対側に位置する。ロータリ耕耘装置の自動耕深制御において、ロータリ耕耘装置に設けられた接地体の上下揺動によって、コントロールケーブルを介して連結部３４ｂが引っ張られて、耕深調整カム３４が前後揺動する。連結部３４ｂにコントロールケーブルが連結される場合、一般的に、揺動禁止部材３０Ｇが下方に揺動操作され、受け部材３０Ｂの前側への揺動が規制される。この場合、図７に示されるように、第１リンク部材３２Ａと第２リンク部材３２Ｂとが連接ピン３２Ｄを介して屈曲自在なように構成されているため、受け部材３０Ｂが揺動不能な場合であっても、耕深調整カム３４は揺動可能である。
[0055]
　連動揺動部３５の遊端部に複数の挿通孔３５ｈが形成され、この複数の挿通孔３５ｈの１つの箇所に連係ロッド３６の後端部がピンで枢支連結されている。連動揺動部３５が後方へ揺動すると、連係ロッド３６が後方へ変位する。図示はしないが、作動油の給排量を調節するスプールを操作するリンク機構が、連係ロッド３６の前端部と連結され、連係ロッド３６が後方へ変位すると、スプールが操作されて作動油が油圧アクチュエータに供給され、リフトアーム１６が上方へ揺動する。
[0056]
　連動揺動部３５の揺動基端部は、ブラケット２４Ｂの遊端部に揺動可能にピンで枢支連結され、連動揺動部３５は揺動軸芯Ｚ２まわりに前後揺動可能である。円柱部材３７Ａの位置する箇所において、揺動アーム２４Ａとブラケット２４Ｂとの夫々の揺動基端部が溶接によって連結されている。また、耕深調整カム３４は揺動アーム２４Ａと当接可能である。耕深調整カム３４が後方へ揺動すると、カム部３４ａとローラー３５Ａとが接近し、連動揺動部３５は後方に揺動操作され易くなる。つまり、耕深調整カム３４が後側に揺動されると、リフトアーム１６は上方に揺動操作され易くなる。
[0057]
　連動揺動部３５の揺動箇所にトーションバネ４０が巻き掛けられている。トーションバネ４０は、連動揺動部３５の揺動基端部における下向き部分と、ブラケット２４Ｂの遊端部における下向き部分と、の夫々に係止されている。連動揺動部３５は、トーションバネ４０によって前側に揺動するように付勢されている。
[0058]
　作業装置１５からの押圧力を受けて受け部材３０Ｂが前側に揺動すると、連動揺動アーム３１が当接ボルト３０ｋまたは増幅調整部３０Ｈと当接し、連動揺動アーム３１が図７及び図８の側面視において時計回りに揺動する。連動揺動アーム３１の揺動と連動して連結リンク部３２が後側へ引っ張られる。このとき、図８に示されるように、第１リンク部材３２Ａと第２リンク部材３２Ｂとが引っ張られて真っ直ぐ延びるため、連結リンク部３２から耕深調整カム３４へ引張力が作用する。そして、連結リンク部３２が後方へ変位するとともに耕深調整カム３４が後方へ揺動する。
[0059]
　As the plowing depth adjusting cam 34 swings, the cam portion 34a and the roller 35A approach each other. Then, when the cam portion 34a and the roller 35A come into contact with each other, the interlocking swing portion 35 swings backward while the roller 35A moves along the cam portion 34a. Then, the connecting rod 36 swingably connected to the interlocking swinging portion 35 is pulled and displaced rearward. Hydraulic oil is supplied to the hydraulic actuator by moving the spool, and the lift arm 16 swings upward in conjunction with the swinging motion of the interlocking swinging portion 35 to raise the position of the working device 15 .
[0060]
　In the case where the working device 15 is a plow, when the position of the plow rises, the reaction force applied from the ground to the plow decreases, so the pressing force acting on the receiving member 30B from the plow via the top link 13 also decreases. Then, when the pressing force acting on the receiving member 30B and the elastic force of the first coil spring 30E are balanced, the receiving member 30B, the interlocking swing arm 31, the tillage depth adjusting cam 34, and the interlocking swing portion 35 , stop swinging, and the connecting rod 36 is no longer displaced. By operating the spool by the feedback link mechanism described above, supply and discharge of hydraulic oil to the hydraulic actuator is stopped, and the vertical swing of the left and right lift arms 16 is stopped.
[0061]
　When the pressing force ceases to act on the receiving member 30B, the receiving member 30B stops at the rearmost end of the front-rear swing range based on the front-rear length of the long hole 30p. At this time, since the space between the first link member 32A and the second link member 32B in the connecting link portion 32 is loosened, even if the interlocking swing arm 31 swings, the plowing depth adjusting cam 34 does not move the interlocking swing arm 31. It is no longer linked with the swing. A coil spring member 32C is externally inserted to the first link member 32A in the connecting link portion 32 . As a result, even if the receiving member 30B swings sharply from the swinging state toward the front side to the rearmost end, and the interlocking swinging arm 31 also swings sharply, the sharp swinging causes The impact is absorbed by the expansion and contraction of the coil spring member 32C. Therefore, the problem that the tillage depth adjusting cam 34 and the interlocking swinging portion 35 swing unnecessarily due to the impact is avoided. At this time, the plowing depth adjusting cam 34 swings forward due to the elastic force of the tension spring 38 . Further, the interlocking swinging portion 35 swings forward by the elastic force of the torsion spring 40 .
[0062]
[Regarding the Amplification Adjusting Part]
　As described above, the interlocking swing arm 31 is constructed so as to be able to amplify the amount of swing of the receiving member 30B. Further, the amplification adjustment portion 30H is bolted to the receiving member 30B, and the amplification adjustment portion 30H and the interlocking swing arm 31 are configured to be able to contact each other.
[0063]
　The interlocking swing arm 31 extends vertically. When the contact point between the amplification adjustment section 30H and the interlocking swing arm 31 in the vertical direction is changed, the amount of swinging of the interlocking swing arm 31 changes even if the amount of swinging of the receiving member 30B is the same. The amplification adjusting section 30H is configured such that the point of contact with the interlocking swing arm 31 can be adjusted in the vertical direction.
[0064]
　As shown in FIGS. 9 to 13, the amplification adjustment section 30H is provided with a bracket member 50 and a swing member 51. As shown in FIG. Long holes 50a are formed in the upper and lower ends of the flat surface of the bracket member 50, and the pair of upper and lower long holes 50a extend in the vertical direction. A bolt is inserted through the pair of upper and lower elongated holes 50a. That is, the bracket member 50 is bolted to the receiving member 30B so as to enable vertical positioning adjustment. A projecting cylindrical portion 50b is formed in the region between the pair of upper and lower elongated holes 50a, and the projecting cylindrical portion 50b projects to the side opposite to the side where the receiving member 30B is located. A screw groove that can be engaged with a nut is formed in the protruding tip of the protruding cylindrical portion 50b.
[0065]
　The swing member 51 is configured to be swingable relative to the bracket member 50 . A bolt insertion hole 51 b is drilled in the rocking base end of the rocking member 51 . The projecting cylindrical portion 50b is inserted through the bolt insertion hole 51b, and the nut is engaged with the distal end portion of the projecting cylindrical portion 50b. Thereby, the rocking member 51 is configured to be vertically rockable about the rocking axis Q2. The rocking member 51 corresponds to the "first part" in the present invention. That is, the load receiving portion 30 is provided with a swing member 51 as a first portion that presses the interlocking swing arm 31 .
[0066]
　An engagement pin 51a is provided at the free end of the swing member 51. As shown in FIG. The engagement pin 51a is formed in a columnar shape extending in the lateral direction of the machine body. The engaging pin 51a may be fixed by welding to the free end of the swing member 51, or may be connected to the free end of the swing member 51 with a bolt. The engaging pin 51a corresponds to the "pin" of the present invention.
[0067]
　第１部としての揺動部材５１と接触して、揺動部材５１によって押圧される『第２部』が、連動揺動アーム３１に備えられている。本実施形態では、この第２部は係止部５２である。係止部５２に、揺動部材５１を受け入れ係止可能な複数の凹部が形成されている。『複数の凹部』として、連動揺動アーム３１のうち、揺動軸芯Ｑ１よりも上側の部分に、第１凹入部５２ａと第２凹入部５２ｂと第３凹入部５２ｃとが上下に並ぶ状態で設けられている。
[0068]
　第１凹入部５２ａ、第２凹入部５２ｂ、第３凹入部５２ｃのうち、第１凹入部５２ａが揺動軸芯Ｑ１から最も遠く、第３凹入部５２ｃが揺動軸芯Ｑ１から最も近い。第１凹入部５２ａと第２凹入部５２ｂと第３凹入部５２ｃとの夫々は、円柱形状の係入ピン５１ａと対応して円弧状に湾曲するように形成されている。これにより、第１凹入部５２ａと第２凹入部５２ｂと第３凹入部５２ｃとの夫々は係入ピン５１ａを受け入れ係止可能に構成されている。即ち、係入ピン５１ａは、第１凹入部５２ａと第２凹入部５２ｂと第３凹入部５２ｃとの夫々への係入が可能である。
[0069]
　連動揺動アーム３１のうち、第１凹入部５２ａの上方部分と、第３凹入部５２ｃの下方部分と、の夫々に上下一対の突出部分５２ｄ，５２ｅが形成され、この上下一対の突出部分５２ｄ，５２ｅは、連動揺動アーム３１の他の部分より揺動部材５１の位置する側に突出する。この上下一対の突出部分５２ｄ，５２ｅの間に係入ピン５１ａが位置し、係入ピン５１ａは、この上下一対の突出部分５２ｄ，５２ｅの上下範囲内で揺動軸芯Ｑ２まわりに揺動可能となっている。この上下一対の突出部分５２ｄ，５２ｅの間に、第１凹入部５２ａと第２凹入部５２ｂと第３凹入部５２ｃとが上下に並ぶ状態で設けられている。この上下一対の突出部分５２ｄ，５２ｅと、第１凹入部５２ａと、第２凹入部５２ｂと、第３凹入部５２ｃと、に亘って入り江のように囲まれた領域は本発明の『共通凹部』に相当する。即ち、係止部５２に、複数の凹部が連続で並ぶように複数の凹部を包含する共通凹部が形成されている。そして、係入ピン５１ａは、共通凹部を通過して複数の凹部の何れか１つに係入する。
[0070]
　揺動部材５１が上下に揺動することによって、揺動部材５１は、係入ピン５１ａと第１凹入部５２ａとが係合可能な状態と、係入ピン５１ａと第２凹入部５２ｂとが係合可能な状態と、係入ピン５１ａと第３凹入部５２ｃとが係合可能な状態と、に切換え可能に構成されている。このように、第１部としての揺動部材５１と、第２部としての係止部５２と、の接触位置が変更可能に構成されている。
[0071]
　揺動部材５１に、第１凹入部５２ａと第２凹入部５２ｂと第３凹入部５２ｃとの何れかに係入する際の揺動角度を位置決めする『位置決め機構』が備えられている。本実施形態の位置決め機構はデテント機構である。位置決め機構に、ボール５１ｏと、コイルバネ部材５１ｐと、デテント凹部５０ｐ，５０ｑ，５０ｒと、が備えられている。
[0072]
　A handle arm 51c is connected to a portion of the swinging member 51 adjacent to the engaging pin 51a on the side where the bolt insertion hole 51b is located. The handle arm 51c protrudes to the side opposite to the side where the receiving member 30B is located. A handle 51d is connected rearward to the projecting tip of the handle arm 51c.
[0073]
　The handle arm 51c is cylindrical. As shown in FIG. 10, a cylindrical hole is bored in the handle arm 51c along the longitudinal direction of the handle arm 51c, and a detent mechanism ball 51o and a coil spring member 51p are inserted into this cylindrical hole. It is As shown in FIGS. 9 and 10, the bracket member 50 has three detent recesses 50p, 50q, and 50r formed along the swing track of the handle arm 51c. A ball 51o for the detent mechanism is engaged with one of the detent recesses 50p, 50q, 50r. When the ball 51o is engaged with the detent recess 50p, the engaging pin 51a and the first recess 52a can be engaged. When the ball 51o is engaged with the detent recess 50q, the engaging pin 51a and the second recess 52b can be engaged. When the ball 51o is engaged with the detent recess 50r, the engaging pin 51a and the third recess 52c can be engaged. In this manner, the swing member 51 is configured to swing up and down in three stages.
[0074]
　The positioning mechanism in this embodiment can position the swing member 51 at an angle orthogonal to the swing angle of the load receiving portion 30 . When the ball 51o is engaged with the detent recess 50q, a straight line extending between the swing axis P and the swing axis Q2, a straight line extending between the center of the engaging pin 51a and the swing axis Q2 in the side view of the machine body, are orthogonal or substantially orthogonal (see FIG. 12). That is, the angle at which the swinging member 51 is positioned (the swinging angle at which the positioning mechanism positions the swinging member 51 ) includes an angle orthogonal to the swinging angle of the load receiving portion 30 . Each of the detent recesses 50p and the detent recesses 50r is distributed vertically with respect to the detent recesses 50q. Therefore, the swing member 51 can firmly receive the reaction force from the locking portion 52 .
[0075]
　When the pressing force does not act on the receiving member 30B, the receiving member 30B stops at the rearmost end of the front-rear swing range based on the front-rear length of the long hole 30p. At this time, the interlocking swing arm 31 contacts the contact bolt 30k of the receiving member 30B and is separated from the swing member 51. As shown in FIG. Therefore, when the pressing force does not act on the receiving member 30B, the operator can easily switch the swinging member 51 between the above three stages.
[0076]
　上述したように、受け部材３０Ｂが前方へ揺動すると、最初は、当接ボルト３０ｋと連動揺動アーム３１との当接によって、連動揺動アーム３１が揺動する。受け部材３０Ｂは揺動軸芯Ｐまわりに揺動し、連動揺動アーム３１は揺動軸芯Ｑ１まわりに揺動する。揺動部材５１と揺動軸芯Ｐとの離間距離は、第１凹入部５２ａ、第２凹入部５２ｂ、第３凹入部５２ｃの夫々と揺動軸芯Ｑ１との離間距離よりも離れている。このことから、当接ボルト３０ｋと連動揺動アーム３１とが当接した状態で受け部材３０Ｂが前方へ揺動すると、第１凹入部５２ａ、第２凹入部５２ｂ、第３凹入部５２ｃの夫々の変位量は、揺動部材５１の変位量よりも小さい。このため、当接ボルト３０ｋと連動揺動アーム３１とが当接した状態で受け部材３０Ｂが前方へ揺動すると、係入ピン５１ａは第１凹入部５２ａ、第２凹入部５２ｂ、第３凹入部５２ｃの夫々に接近する。そして、係入ピン５１ａが、第１凹入部５２ａ、第２凹入部５２ｂ、第３凹入部５２ｃの何れかと当接すると、当接ボルト３０ｋと連動揺動アーム３１とが離間する。
[0077]
　図１１乃至図１３に示されるように、揺動部材５１と連動揺動アーム３１との当接点が、第１凹入部５２ａと、第２凹入部５２ｂと、第３凹入部５２ｃと、の何れかで異なると、受け部材３０Ｂの揺動量が同じであっても連動揺動アーム３１の揺動量が変化する。図１１に、係入ピン５１ａと第１凹入部５２ａとの当接状態が示されている。図１２に、係入ピン５１ａと第２凹入部５２ｂとの当接状態が示されている。図１３に、係入ピン５１ａと第３凹入部５２ｃとの当接状態が示されている。なお、図１１乃至図１３の何れにおいても、揺動禁止部材３０Ｇは受け部材３０Ｂの揺動を規制しない状態に操作済みである。
[0078]
　第２凹入部５２ｂは第１凹入部５２ａよりも揺動軸芯Ｑ１に近い。このため、図１２に示されるように、係入ピン５１ａと第２凹入部５２ｂとが当接する場合の連動揺動アーム３１の揺動量（Ｄ２で示されている）は、係入ピン５１ａと第１凹入部５２ａとが当接する場合の連動揺動アーム３１の揺動量（Ｄ１で示されている）よりも多い。このため、係入ピン５１ａと第２凹入部５２ｂとが当接する場合、トップリンク１３は、係入ピン５１ａと第１凹入部５２ａとが当接する場合よりも大きく上下揺動する。
[0079]
　第３凹入部５２ｃは第２凹入部５２ｂよりも揺動軸芯Ｑ１に近い。このため、図１３に示されるように、係入ピン５１ａと第３凹入部５２ｃとが当接する場合の連動揺動アーム３１の揺動量（Ｄ３で示されている）は、係入ピン５１ａと第２凹入部５２ｂとが当接する場合の連動揺動アーム３１の揺動量（Ｄ２で示されている）よりも多い。このため、係入ピン５１ａと第３凹入部５２ｃとが当接する場合、トップリンク１３は、係入ピン５１ａと第２凹入部５２ｂとが当接する場合よりも大きく上下揺動する。このように、受け部材３０Ｂの前後揺動が大きく増幅されるほど、リフトアーム１６は大きく上下揺動する。
[0080]
　In addition, the angular velocity and the angular acceleration when the interlocked swing arm 31 swings also change in proportion to the change in the amount of swing of the interlocked swing arm 31 . That is, the angular velocity and angular acceleration of the interlocking swing arm 31 when the engaging pin 51a and the second recessed portion 52b abut each other is the same as the interlocking swing arm when the engaging pin 51a and the first recessed portion 52a abut. faster than 31 angular velocities and angular accelerations. The angular velocity and angular acceleration of the interlocking swing arm 31 when the engaging pin 51a and the third recessed portion 52c are in contact are the same as those of the interlocking swing arm 31 when the engaging pin 51a and the second recessed portion 52b are in contact. faster than 31 angular velocities and angular accelerations. As the angular velocity and angular acceleration of the interlocking swing arm 31 increase, the angular velocity and angular acceleration when the tillage depth adjusting cam 34 and the interlocking swing section 35 swing also increase. As the angular velocity and angular acceleration of the interlocking oscillating portion 35 increase, the speed and acceleration when the linking rod 36 is displaced also increase, so the spool for controlling the supply and discharge of hydraulic oil is also operated at high speed. The faster the spool is actuated, the more nimble the hydraulic actuator for the lift arm 16 will be, thereby increasing the responsiveness of the lift arm 16 and increasing the angular velocity at which the lift arm 16 swings. In other words, the greater the amplitude of the back-and-forth swing of the receiving member 30B by the interlocking swing arm 31, the faster the angular velocity and angular acceleration when the lift arm 16 swings.
[0081]
　In this way, by changing the contact point between the swing member 51 and the locking portion 52, the link ratio between the receiving member 30B and the interlocking swing arm 31 can be changed. In the present embodiment, four insertion holes 31h are formed in the lower end portion of the interlocking swing arm 31, and three insertion holes 35h are formed in the free end portion of the interlocking swinging portion 35. As shown in FIG. The insertion hole 31h corresponds to the "link ratio changing portion" of the present invention. The insertion hole 35h also corresponds to the "link ratio changing portion" of the present invention.
[0082]
　One of the four insertion holes 31h is selected, and the pin member 33 is inserted through this one. When the selected position of the insertion hole 31h changes, the amount by which the connecting link portion 32 is displaced changes, and the amount by which the connecting link portion 32 is displaced increases in the lower insertion holes 31h. That is, the link ratio between the interlocking swing arm 31 and the connecting link portion 32 is configured to be changeable by the four insertion holes 31h. Here, the receiving member 30B and the interlocking swing arm when the abutting position between the swinging member 51 and the engaging portion 52 is changed to the upper and lower adjacent positions in accordance with the switching operation of the swinging member 51 by the operator. 31 is defined as the first link ratio change rate. Further, the change rate of the link ratio between the interlocking swing arm 31 and the connecting link portion 32 when the connecting portion with the connecting link portion 32 among the four insertion holes 31h is changed to the adjacent insertion hole 31h is calculated as follows: Defined as 2-link ratio change rate. The second link ratio change rate is less than the first link ratio change rate.
[0083]
　One of the three insertion holes 35h is selected, and the rear end of the connecting rod 36 is pivotally connected to this one position with a pin. When the selected position of the insertion hole 35h changes, the amount by which the connecting rod 36 is displaced changes, and the amount by which the connecting rod 36 is displaced increases in the insertion hole 31h on the free end side. That is, the link ratio between the interlocking swinging portion 35 and the linking rod 36 is configured to be changeable by the three insertion holes 35h. Here, the rate of change in the link ratio between the interlocking swinging portion 35 and the linking rod 36 when the linking portion of the three insertion holes 35h with the linking rod 36 is changed to the adjacent insertion hole 35h is expressed as the third Defined as link ratio change rate. The third link ratio change rate is smaller than the above first link ratio change rate.
[0084]
　That is, a link ratio changing portion that changes the link ratio to a link ratio change rate smaller than the link ratio change rate by the swing member 51 and the locking portion 52 is provided on the downstream side of the interlocking swing arm 31 in the link mechanism, Insertion holes 31h and 35h are provided.
[0085]
[Regarding Coil Spring Acting on Receiving Member]
　As shown in FIG. 10, a second coil spring 30F is provided on the opposite side of the bracket 30A to the side where the first coil spring 30E is located. The mounting structure of the second coil spring 30F will be described below.
[0086]
　A cylindrical housing portion 30L is formed on the upper portion of the bracket 30A, and a first coil spring 30E is housed in the cylindrical housing portion 30L. A front-rear through-hole 30q is drilled at the radially central portion of the front portion of the cylindrical storage portion 30L. A hollow boss member 60 is connected to the front portion of the cylindrical storage portion 30L. A thread groove is formed on the outer circumference of the front portion of the boss member 60, and the nut 63 is engaged with this thread groove. A spacer is provided between the rear end portion of the boss member 60 and the nut 63, but this spacer may be composed of a plurality of washers (flat washers or spring washers). The nut 63 protrudes forward from the bracket 30A, and the position of the nut 63 is adjusted by the spacer. In short, the longitudinal position of the nut 63 may be adjusted according to the length of the second coil spring 30F. The nut 63 and the spacer may be integrated, or the nut 63 may be a double nut without the spacer. Also, the boss member 60 and the nut 63 may be one integrally formed member, or the boss member 60 may have a configuration in which no screw groove is formed on the outer periphery of the front portion thereof.
[0087]
　受け部材３０Ｂのうち、第１コイルバネ３０Ｅ当接する領域に、前方に突出する突出部３０ｔが溶接固定され、この突出部３０ｔにロッド６１が上下揺動可能に枢支連結される。ロッド６１は、第１コイルバネ３０Ｅの内周空間を貫通する。貫通孔３０ｑに内嵌した状態のボス部材６０の中空孔をロッド６１が貫通し、ロッド６１の突出先端部がブラケット３０Ａよりも前側に突出する。
[0088]
　第２コイルバネ３０Ｆは、ブラケット３０Ａよりも機体前側でロッド６１に外挿されている。第２コイルバネ３０Ｆのうち、受け部材３０Ｂの位置する側と反対側の端部に、第２コイルバネ３０Ｆの外径よりも大径の平座金６２がロッド６１に外挿される。
[0089]
　ロッド６１の突出先端部にはネジ溝が形成されている。平座金６２の両面部の夫々はナット締めされ、平座金６２は一対のナットで挟持されている。第２コイルバネ３０Ｆの長さに合わせて平座金６２の前後位置が調整可能に構成されて良い。また、ナット６３は、第２コイルバネ３０Ｆの外径よりも大きな対辺径となるように形成されている。即ち、第２コイルバネ３０Ｆの延び方向の両端部は、ナット６３と、平座金６２と、の夫々に当接する。また、ボス部材６０のネジ溝部分と、平座金６２を挟持するナットと、は第２コイルバネ３０Ｆの内径よりも若干小さな外径となるように形成されている。このため、ボス部材６０のネジ溝部分と、平座金６２を挟持するナットと、が第２コイルバネ３０Ｆの内周部分とガタつくことなく当接する。
[0090]
　As the receiving member 30B rocks back and forth, the rod 61 moves back and forth while rocking relative to the receiving member 30B. At this time, as the receiving member 30B swings, the rod 61 is displaced in the vertical direction. Therefore, the hollow hole of the boss member 60 is formed with a diameter sufficiently larger than the cross-sectional diameter of the rod 61 .
[0091]
　When the receiving member 30B swings back and forth, the separation distance between the bracket 30A and the receiving member 30B changes, and the nut 63 supported by the bracket 30A and the flat washer 62 supported by the receiving member 30B via the rod 61 move. , also changes. As a result, the first coil spring 30E expands and contracts. Further, when the receiving member 30B swings back and forth, the rod 61 is displaced back and forth, the distance between the nut 63 and the flat washer 62 changes, and the second coil spring 30F expands and contracts.
[0092]
　When the first coil spring 30E expands and the elastic energy of the first coil spring 30E decreases, the second coil spring 30F contracts and the elastic energy of the second coil spring 30F increases. When the pressing force suddenly stops acting on the receiving member 30B, the elastic energy of the first coil spring 30E is released at once. It is conceivable that abrupt rocking may occur up to the extreme end of the range of motion. Even in such a case, as the receiving member 30B swings backward, the second coil spring 30F contracts and elastic energy is stored in the second coil spring 30F. This suppresses rapid extension of the first coil spring 30E. As a result, the impact when the linking pin 30D comes into contact with the rearmost end of the long hole 30p is reduced. Also, chattering of the receiving member 30B caused by the contact is suppressed.
[0093]
[Other Embodiments]
　The present invention is not limited to the configurations exemplified in the above-described embodiments, and other representative embodiments of the present invention will be exemplified below.
[0094]
(1) In the above-described embodiment, the load receiving portion 30 is provided with the swing member 51 as the "first portion", and the interlocking swing arm 31 is provided with the locking portion 52 as the "second portion". but not limited to this embodiment. For example, the load receiving portion 30 may be provided with a component corresponding to the locking portion 52 and the interlocking swing arm 31 may be provided with a component corresponding to the swing member 51 . In short, one of the first part and the second part is the rocking member 51, and the other of the first part and the second part is formed with a plurality of recesses capable of receiving and locking the rocking member 51. It may be the locking portion 52 .
[0095]
(2) In the above-described embodiment, the locking portion 52 as the "second part" is configured as a part of the interlocking swing arm 31, but the interlocking swinging arm 31 and the locking portion 52 are separated. may be configured as
[0096]
(3) In the above-described embodiment, the load receiving portion 30 is provided with the swinging member 51 as the "first portion", but the first portion may not be a swinging member. 51a may slide up and down. In other words, it is sufficient that the contact position between the "first part" and the "second part" can be changed.
[0097]
(4) The connecting link portion 32 shown in the above embodiment has a first link member 32A, a second link member 32B, a coil spring member 32C, and a connecting pin 32D, but is not limited to this embodiment. . For example, the connecting link portion 32 may be composed of a chain or a wire. That is, the chain or wire as the connecting link portion 32 may be pulled by the interlocking swing arm 31 to be tense, and the chain or wire may pull the plowing depth adjusting cam 34 to swing. In this embodiment, the chain or wire slackens when pressure is no longer applied to the receiving member 30B. Therefore, even if the interlocking swing arm 31 swings, the plowing depth adjusting cam 34 does not interlock with the swinging of the interlocking swing arm 31, as in the above-described embodiment.
[0098]
(5) In the above-described embodiment, three recessed portions (first recessed portion 52a, second recessed portion 52b, and third recessed portion 52c) are formed in the locking portion 52 as the "second portion". In the present invention, the "plurality of recesses" may be two, or may be four or more. Alternatively, the engaging portion 52 may have a configuration in which no concave portion is formed, and a flat surface portion is formed in the engaging portion 52 so that the contact position between the swing member 51 and the flat surface portion of the engaging portion 52 can be changed. May be.
[0099]
(6) In the above-described embodiment, the upper portion of the first recessed portion 52a and the lower portion of the third recessed portion 52c are each formed with a pair of upper and lower protruding portions. The first recessed portion 52a, the second recessed portion 52b, and the third recessed portion 52c are arranged vertically to form a "common recessed portion", but the invention is not limited to this embodiment. For example, the "common recess" may not be formed, and the upper portion of the first recessed portion 52a and the lower portion of the third recessed portion 52c may not be formed with a pair of upper and lower protrusions, and may simply be formed with a plurality of protrusions. A configuration in which the concave portions are arranged in a line along the longitudinal direction of the interlocking swing arm 31 may be employed. Alternatively, the “common recess” may be formed as one recess corresponding to the swing range of the swing member 51 .
[0100]
(7) In the above-described embodiment, the receiving member 30B swings back and forth, but the receiving member 30B may swing up and down. In this case, the interlocking swing arm 31 may extend in the front-rear direction of the fuselage, and a plurality of concave portions may be arranged along the longitudinal direction of the interlocking swing arm 31 .
[0101]
(8) In the above-described embodiment, four insertion holes 31h are formed in the lower end portion of the interlocking swing arm 31, and three insertion holes 35h are formed in the free end portion of the interlocking swinging portion 35. , is not limited to this embodiment. One of the insertion hole 31h and the insertion hole 35h may be provided at a plurality of locations, and the other of the insertion hole 31h and the insertion hole 35h may be provided at only one location. Also, the number of insertion holes 31h and 35h can be changed as appropriate.
[0102]
(9) In the above-described embodiment, when the operator switches the swinging member 51 in three steps, the engagement pin 51a is positioned between the first recessed portion 52a and the second recessed portion 52b, Alternatively, the interlocking swing arm 31 may slightly swing due to contact with the protrusion between the second recessed portion 52b and the third recessed portion 52c. Even in such a case, the first link member 32A and the second link member 32B of the connecting link portion 32 are loosened swingably and cannot be pulled straight. That is, even if the interlocking swing arm 31 swings slightly due to the swinging of the swinging member 51 by the work vehicle, the play of the connecting link portion 32 prevents the swinging of the interlocking swing arm 31 from interlocking. It may be a configuration. Further, when the operator switches the swinging member 51 in three stages, the engaging pin 51a is moved to the convex portion between the first recessed portion 52a and the second recessed portion 52b or the second recessed portion 52b. and the third recessed portion 52c.
[0103]
　It should be noted that the configurations disclosed in the above-described embodiments (including other embodiments, the same shall apply hereinafter) can be applied in combination with configurations disclosed in other embodiments unless there is a contradiction. Moreover, the embodiments disclosed in this specification are merely examples, and the embodiments of the present invention are not limited to these, and can be modified as appropriate without departing from the scope of the present invention.
Industrial applicability
[0104]
　INDUSTRIAL APPLICABILITY The present invention can be applied to a tractor equipped with a three-point link mechanism for mounting a working device so that it can be raised and lowered.
Code explanation
[0105]
　12: Three-point link mechanism
　15: Working device
　30: Load receiving portion
　31: Interlocking swing arm (link mechanism)
　31h: Insertion hole (link ratio changing portion)
　32: Connection link portion (link mechanism)
　34: Plowing depth adjustment cam (Link mechanism, sensitivity change portion)
　35: Interlocking swing portion (link mechanism)
　35h: Insertion hole (link ratio change portion)
　36: Coupling rod (link mechanism)
　50p: Detent concave portion (positioning mechanism)
　50q: Detent concave portion (positioning mechanism) Mechanism)
　50r: Detent recess (positioning mechanism)
　51: Swing member (first part)
　51o: Ball (positioning mechanism)
　51p: Coil spring member (positioning mechanism)
　52: Locking part (second part, common recess)
　52a: First recessed portion (plurality of recesses)
　52b: Second recessed portion (plurality of recesses)
　52c: Third recessed portion (plurality of recesses)
　P: Swing axis
　Q1: Swing axis

[Claim 1]
　A three-point link mechanism, which is connected to the rear part of the vehicle body so as to be able to swing vertically and mounts the working device so as to be able to move up and down,
　a hydraulic unit capable of swinging the three-point link mechanism, and the
　working device while being pulled by the vehicle body. A load receiving portion that swings according to the traction load of the work device when ground work is performed, and
　a link that transmits an operation amount for the swinging operation to the hydraulic unit according to a swing amount of the load receiving portion. and an interlocking rocking mechanism that rocks in conjunction with the rocking of the load receiving portion on a rocking axis different from the rocking axis of the load receiving portion , provided on
　the uppermost side of the link mechanism. A moving arm is provided, the
　load receiving portion is provided with a first portion that presses the
　interlocking swing arm, and the interlocking swing arm contacts the first portion and is pressed by the first portion. A tractor comprising a second
　part, wherein a contact position between the first part and the second part is changeable.
[Claim 2]
　One of the first part and the second part is a swinging member, and the other of
　the first part and the second part is formed with a plurality of recesses capable of receiving and locking the swinging member.
　2. The tractor according to claim 1, further comprising a positioning mechanism for positioning a swinging angle of said swinging member when engaging said plurality of recesses.
[Claim 3]
　The tractor according to claim 2, wherein the positioning mechanism can position the swing member at an angle perpendicular to the swing angle of the load receiving portion.
[Claim 4]
　A pin that can be engaged with the plurality of recesses is provided at the free end of the swinging member, and the
　locking portion includes the plurality of recesses so that the plurality of recesses are continuously arranged. 4. A tractor according to claim 2 or 3, wherein recesses are formed and
　said pin passes through said common recess to engage any one of said plurality of recesses.
[Claim 5]
　The link mechanism is provided with a sensitivity changer that operates so that the displacement amount of the mechanism on the lower side of the link mechanism increases as the load receiving portion swings toward the side where the traction load is greater. A tractor according to any one of claims 1 to 4.
[Claim 6]
　A link ratio changing section for changing the link ratio to a link ratio change rate smaller than the link ratio change rate by the first section and the second section is provided on the downstream side of the interlocking swing arm in the link mechanism. A tractor according to any one of claims 1 to 5.