JP3750166B2 - Transmission - Google Patents

Description

【００２８】
この走行変速装置は、油圧クラッチ機構の主変速部３２の伝動上手側と下手側にシンクロメッシュ機構の前後進変速部３１と副変速部３３をそれぞれ配設した構成となっている。このため、シンクロメッシュ機構である前後進変速部３１や副変速部３３部のシフトチェンジをする際に油圧クラッチ機構である副変速部３２で動力を切ることにより、クラッチを別に設けることなく、スムースなシフトチェンジが可能となっている。
【００２９】
また、油圧クラッチ機構はシンクロメッシュ機構に比べて高価かつ油路構成が複雑であるが、この油圧クラッチ機構を３か所の変速部のうちの１か所にだけ取り入れているだけであるので、全体を低コストで作ることができ、しかも全体の油路構成が簡単である。
【００３０】
変速位置の切り替えは前記変速レバー１７で行う。図６に示すように、変速レバー１７はガイド溝１８に沿って前後に回動させられるようになっていて、その回動範囲の後側から前側へ順に「超低」、「ロータリ」、「代かき・プラウ」、「中立」、「走行」の各操作位置が設けられている。「超低」はクリープ作業等の超低速で作業を行う時のモード、「ロータリ」はロータリ耕耘作業時のモード、「代かき・プラウ」は代かき作業もしくはプラウ作業時のモード、「中立」は走行停止のモード、「走行」は路上走行時のモードであって、変速レバー１７で作業（または路上走行）モードを選択すると、それに適した複数段（４〜６段）の変速可能領域が設定される。更に、変速レバー１７のグリップには指操作する増速ボタン１７ａ及び減速ボタン１７ｂが設けられており、これら変速ボタン１７ａ，１７ｂによって前記変速可能領域内で増減速する。
【００３１】
例えば、「ロータリ」の変速可能領域は第５段〜第１０段であり、変速レバー１７で「ロータリ」を選択すると始めに第７段の変速位置になる。そして、第７段を起点として、増速ボタン１７ａを１度押すごとに変速段数が１段づつ上り、減速ボタン１７ｂを１度押すごとに変速段数が１段づつ下がる。各モードの変速可能領域と起点変速段数は図７に示す通りである。
【００３２】
【発明の効果】
本発明にかかる変速装置は、油圧クラッチ機構による変速部の伝動上手側と下手側にシンクロメッシュ機構による変速部をそれぞれ配設し、油圧クラッチ機構による変速部の動力を切ってシンクロメッシュ機構による変速部をシフトチェンジする構成とすることにより、３か所の変速部のうちの１か所に油圧クラッチ機構を採用するだけでスムースなシフトチェンジが可能となると共に、高価な油圧クラッチ機構の数を最小限に抑え低コスト化が図れるようになった。
【図面の簡単な説明】
【図１】トラクタの全体側面図である。
【図２】伝動機構図である。
【図３】走行変速装置の前後進変速部及びＰＴＯ正逆転装置の断面図である。
【図４】走行変速装置の主変速部の断面図である。
【図５】走行変速装置の副変速部の断面図である。
【図６】変速レバーの斜視図である。
【図７】変速位置における主変速と副変速の組み合わせ、及び走行速度を表す図である。
【符号の説明】
１ トラクタ
２ 前輪
３ 後輪
８ ミッションケース
１７ 変速レバー
１７ａ 増速ボタン
１７ｂ 減速ボタン
３１ 前後進変速部（シンクロメッシュ機構による変速部）
３２ 主変速部（油圧クラッチ機構による変速部）
３３ 副変速部（シンクロメッシュ機構による変速部）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a transmission for a traveling vehicle such as a tractor.
[0002]
[Prior art]
A tractor transmission device includes a forward / reverse transmission unit, a main transmission unit, and a sub-transmission unit. The forward / reverse transmission unit switches between forward and reverse, and there are many combinations of main transmission by the main transmission unit and sub-transmission by the sub-transmission unit. A shift position of 16 stages (for example, 16 stages) is set. In a conventional tractor, there are a structure in which each of these transmission portions is configured with a synchromesh mechanism and a structure with a hydraulic clutch mechanism.
[0003]
[Problems to be solved by the invention]
The synchromesh mechanism is advantageous in that the structure is simpler and less expensive than the hydraulic clutch mechanism. On the other hand, in order to smoothly synchronize the rotation of the transmission side and the driven side, A clutch that cuts off the transmission on the lower side is necessary, and the operation process at the time of shift change increases by providing the clutch, so that there is a difficulty that a quick shift change cannot be performed.
[0004]
On the other hand, the configuration using the hydraulic clutch mechanism can instantaneously turn on and off the transmission from the transmission side to the transmission side, so that the shift change can be performed quickly and smoothly without providing a separate clutch. However, the structure of the hydraulic clutch mechanism has a complicated structure because an oil passage for sending hydraulic oil must be provided in the transmission shaft. Also, when the transmission parts are arranged side by side, the longitudinal length of the entire transmission is long. There is a problem that becomes longer. Furthermore, it is a big problem that the cost is high if all the transmission parts are hydraulic clutch mechanisms.
[0005]
In view of the above circumstances, it is an object of the present invention to provide a relatively low-cost and compact transmission device that realizes no clutching to enable quick shifting, and that is also suitable for medium-to-small tractors. To do.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the present invention is configured as follows. That is, in the transmission according to the present invention, the rotational power of the engine (10) overlaps with the synchromesh type front / rear transmission unit (31) via the main clutch (30), and the front / rear position overlaps with the front / rear transmission unit in a side view. Rotational power transmitted to the PTO forward / reverse gear (37) provided in this manner and transmitted to the synchromesh type front / rear transmission (31) is the first, second, third, fourth, After being transmitted to the main transmission section (32) constituted by a hydraulic clutch that can be shifted in four stages, a synchromesh sub-transmission section that can be shifted in four stages of high speed, medium speed, low speed, and ultra-low speed ( 33), and the 16 shift positions of the combination of the main transmission unit and the sub transmission unit are divided into a shiftable region suitable for traveling and a shiftable region suitable for other work. The selection of these areas Configured to perform at over (17), the shift position of the main transmission section comprising a shift starting point in each region after selected in the speed-change lever as a second speed or third speed, shift lever shift position of the region This is characterized in that it can be selected by operating the acceleration / deceleration buttons (17a, 17b) provided on the grip.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a tractor provided with the transmission of the present invention will be described.
[0008]
A tractor 1 shown in FIG. 1 is a front and rear four-wheel drive vehicle, and includes front wheels 2 and 2 and rear wheels 3 and 3 at four corners of the fuselage. The front axle case 5 that supports the axles of the front wheels 2 and 2 is attached to the lower side of the front frame 7, and the rear axle cases 6 and 6 that support the rear wheels 3 and 3 are attached to the rear side surface of the transmission case 8. Yes. The front axle case 5 is pivotally attached to the front frame 7 at the center in the left-right direction so as to be swingable left and right around an axial center fixed in the front-rear direction, and the front wheels 2 and 2 are moved up and down by the unevenness of the ground. Yes.
[0009]
An engine 10 is detachably mounted on the center upper side of the front frame 7. 11 is a radiator, 12 is a cooling fan, 13 is a fan belt, and these are arranged in front of the engine 10. A bonnet 14 covers the front and sides of the engine 10 and auxiliary equipment (not shown).
[0010]
Reference numeral 16 denotes a handle. When the handle is rotated left and right, the front wheels 2 and 2 are steered to the left and right. Reference numeral 17 denotes a speed change lever which is operated to change speed. Fenders 21 and 21 are attached from the front to the upper side of the left and right rear wheels 3 and 3, and a seat 22 is provided between the left and right fenders 21 and 21. The driver's foot at the bottom of the seat 22 is a substantially flat floor 23.
[0011]
At the rear of the machine body, lift arms 27, 27 that are turned up and down by a lifting hydraulic cylinder 26 are provided. The lift arms 27, 27 are connected at their distal ends to intermediate portions of the lower links 27a, 27a for mounting the work implements by lift rods 27b, 27b, and by raising and lowering the lift arms 27, 27, A work machine such as a rotary tiller mounted on the rear ends of the lower links 27a and 27a is moved up and down. Also, one lift rod 27b (right side in the illustrated example) is a hydraulic cylinder for tilting left and right, and the horizontal tilt of the work implement is adjusted by extending and contracting the hydraulic cylinder. Incidentally, Rowarinku 27a, fitted with a top link 27 c upwardly and the left and right central portion of 27a, to support the working machine Rowarinku 27a, the three-point link mechanism composed of 27a and top link 27 c.
[0012]
FIG. 2 is a transmission mechanism diagram of the tractor, and FIGS. 3 to 5 are cross-sectional views showing the structure of the main part. First, an outline of the transmission mechanism will be described.
[0013]
The rotational power of the engine 10 is input to the mission case 8. A main clutch 30 is provided at the entrance of the mission case 8 so that transmission can be turned on and off. The power that has passed through the main clutch 30 is branched into two systems: a driving force for driving the front wheels and the rear wheels, and a PTO driving force for taking out external power. The travel driving force is transmitted to the rear wheel differential device 34 through a travel transmission device including a forward / reverse transmission unit 31, a main transmission unit 32, and an auxiliary transmission unit 33, and drives the left and right rear wheels 3 and 3. Further, the power after shifting by the traveling transmission device is taken out to the front portion of the transmission case 8 via the 4WD switching device 35 and then transmitted to the front wheel differential device 36 in the front axle case 5 by the front wheel transmission shaft 5a. The left and right front wheels 2 and 2 are driven. On the other hand, the PTO driving force is taken out to the PTO shaft 39 protruding rearward from the rear surface portion of the mission case 8 via the PTO forward / reverse rotation device 37 and the PTO transmission device 38. A transmission shaft to various working machines (not shown) is detachably connected to the projecting portion of the PTO shaft 39.
[0014]
Next, the structure of each transmission unit of the traveling transmission apparatus will be described.
The forward / reverse transmission unit 31 is a transmission unit that selectively switches the rotation of the main clutch shaft S1 to the forward / reverse transmission shaft S3 in the normal rotation or reverse rotation direction to transmit. A gear G1 attached to the rear end portion of the main clutch shaft S1 meshes with the gear G2 of the relay shaft S2, and the gear G2 meshes with a forward gear G3 that is rotatably fitted to the forward / reverse transmission shaft S3 by a needle bearing. . Further, a gear G4 is attached to the relay shaft S2 in addition to the gear G2, and the gear G4 is rotatably fitted to the forward / reverse transmission shaft S3 by a needle bearing via the counter gear G5 of the counter shaft S4. Is engaged with the reverse gear G6. Therefore, the forward gear G3 and the reverse gear G6 rotate in opposite directions.
[0015]
The forward gear G3 and the reverse gear G6 are transmission-coupled to the forward / reverse transmission shaft S3 by a synchromesh mechanism. That is, the hub 41 is fitted by spline to the forward / reverse transmission shaft S3, the sleeve 42 is fitted by spline to the outer periphery of the hub 41, and the key 43 is fitted in the groove formed in the sleeve 42. Rings 44, 44 are provided on both sides in the axial direction of the key 43 so as to face the conical portions 45, 45 of the forward gear G3 or the reverse gear G6. When the sleeve 42 is moved in one of the axial directions by a shifter 46 operated by a hydraulic cylinder (not shown) provided outside the transmission case 8, one of the rings 44 is moved to the conical portion 45 of the drive gear by being pushed by the key 43. Due to the friction, the rotation of the ring 44 is transmitted to the conical portion 45, and the rotational speeds of the gear and the forward / reverse transmission shaft S3 are synchronized. When the sleeve 42 is further moved, the spline portion of the sleeve 42 meshes with the spline portion of the gear, so that the forward / reverse transmission shaft S3 and the gear are completely transmission-coupled.
[0016]
When the forward / reverse transmission shaft S3 and the forward gear G3 are transmission-coupled, a “forward” shift is established, and when the forward / reverse transmission shaft S3 and the reverse gear G4 are transmission-coupled, a “reverse” shift is established. Since the to smoothly synchronize the rotation of the drive gear side and the rotation of the hub-side is required to cut off the power from the transmission upstream side or downstream side, to shift change by the main transmission section 32 to the "neutral".
[0017]
The gear G2 of the relay shaft S2 also meshes with the forward rotation gear G7 that is rotatably fitted to the outer periphery of the forward / reverse transmission shaft S5, and the counter gear G5 of the counter shaft S4 is rotatable about the outer periphery of the forward / reverse transmission shaft S5. The PTO driving force is transmitted to the PTO forward / reverse rotation device 37. The PTO forward / reverse device 37 is configured such that these gears G7, G8 and a hub 48 fitted to the forward / reverse transmission shaft S5 by a spline can be transmitted and connected by a sleeve 49 slidable in the axial direction. When the hub 48 is connected in transmission, the forward / reverse transmission shaft S5 rotates in the forward direction, and when the reverse gear G8 and the hub 48 are connected in transmission, the forward / reverse transmission shaft S5 rotates in the reverse direction, and the forward rotation gear G7 and the reverse gear G8 In either case, if the hub 48 is not connected in transmission, the forward / reverse transmission shaft S5 stops rotating.
[0018]
The main transmission unit 32 is a transmission unit that selectively transmits gears in four stages from a main transmission drive shaft S6 provided to rotate integrally with the forward / reverse transmission shaft S3 to a main transmission driven shaft S7 provided in parallel therewith. It is. A first speed drive gear G9, a second speed drive gear G10, a third speed drive gear G11, and a fourth speed drive gear G12 are rotatably fitted to the main speed change drive shaft S6, and are connected to the main speed change driven shaft S7. Is integrally attached in a state where the first-speed driven gear G13, the second-speed driven gear G14, the third-speed driven gear G15, and the fourth-speed driven gear G16 are always meshed with the pair of drive gears G9 to G12. The transmission ratios of these four pairs of main transmission gears increase in the order of the fourth gear, the third gear, the third gear, and the first gear.
[0019]
The drive gears G9 to G12 are connected to the main transmission drive shaft S6 by main transmission clutches C ₁ , C ₂ , C ₃ and C ₄ of a wet multi-plate hydraulic clutch mechanism. That is, two drive drums 51, 51 are assembled to the main transmission drive shaft S6 so as to rotate integrally by a spline, and a clutch boss 52 integrally formed with the first-speed drive gear G9 is formed on the inner peripheral portion of one drive drum. A clutch boss 52 formed integrally with the second-speed drive gear G10 is incorporated, and an inner periphery of the other drive drum is formed integrally with the clutch boss 52 formed integrally with the third-speed drive gear G11 and the fourth-speed drive gear G12. .. And a friction plate 53 on the drive drum side and a friction plate 54 on the clutch boss side are alternately arranged in parallel. On both sides of the partition walls 51a and 51a of the drive drums 51 and 51, pistons 55 for turning on and off the main transmission clutch are disposed, and a part of the lubricating oil filled in the transmission case 8 is hydraulically pumped ( The piston 55 is operated by supplying pressure to the oil chamber 56 between the partition wall 51a and the piston 55 through an oil passage provided in the main transmission drive shaft S6. The friction plates 53, ... and the friction plates 54, ... on the clutch boss side are pressure-bonded to engage the main transmission clutch.
[0020]
Main shift rotation of the drive shaft S6 when the first-speed main transmission clutches C ₁ to input is transmitted to the main speed-change driven shaft S7 via the first speed gear G9, G13 becomes "first speed" shift, second-speed main transmission When the clutch C ₂ to input rotation of the main transmission drive shaft S6 is become main shift "second speed" is transmitted to the driven shaft S7 shifted through the second speed gear G10, G14, enter the main third-speed shift clutch C ₃ When the main speed change drive shaft S6 in rotation first gear G11, via G15 is transmitted to the main speed-change driven shaft S7 becomes "third speed" shift, the main transmission drive when you turn the main for fourth gear shift clutch C ₄ When the rotation of the shaft S6 is transmitted to the main transmission driven shaft S7 through the fourth speed gears G12 and G16, and the main transmission clutch is in the disengaged state, transmission to the travel drive system thereafter. This is a “neutral” shift. Since the friction plate on the driving drum side and the friction plate on the clutch boss side are instantaneously pressed and separated by hydraulic pressure, the shift change of the main transmission unit 32 is made quickly and smoothly.
[0021]
The sub-transmission unit 33 is a transmission unit that selectively transmits the rotation of the main transmission driven shaft S7 to the sub-transmission shaft S8 coaxial with the main transmission driven shaft S7 in four stages. A high speed gear G17 is formed integrally with the cylindrical portion S7a of the main transmission driven shaft S7, and a boss G17a meshing with the high speed gear G17 with internal teeth is provided to rotate integrally. The high speed gear G17 meshes with a gear G18 that is rotatably fitted to a cylindrical shaft S10 provided around the PTO transmission shaft S9, and a gear G19 that is integral with the gear G18 is rotatably fitted to the auxiliary transmission shaft S8. It meshes with the speed gear G20. Further, the high speed gear G17 meshes with a gear G21 provided integrally with the relay shaft S11, and another gear G22 provided integrally with the relay shaft S11 meshes with a low speed gear G23 that is rotatably fitted to the auxiliary transmission shaft S8. ing. Further, another gear G24 formed integrally with the low speed gear G23 meshes with a gear G25 that is splined to the cylindrical shaft S10, and a gear G26 formed integrally with the cylindrical shaft S10 is connected to the auxiliary transmission shaft S8. It meshes with an ultra-low speed gear G27 that is rotatably fitted. Therefore, the auxiliary transmission gears G17, G20, G23, and G27 always rotate integrally, and the rotation speed increases in the order of the high speed gear G17, the medium speed gear G20, the low speed gear G23, and the super low speed gear G27.
[0022]
Further, a gear G28 that is fitted to the auxiliary transmission shaft S8 by a spline is meshed with a gear G29 that is fitted to the cylinder shaft S10 by a spline, and the gear G29 is meshed with a gear G30 of the 4WD switching device transmission shaft S12. A drive pinion G31 that is transmitted to the rear wheel differential device 34 is integrally formed at the rear end portion of the auxiliary transmission shaft S8.
[0023]
Similarly to the relationship between the forward gear G3 and the reverse gear G6 of the forward / reverse transmission unit and the forward / reverse transmission shaft S3, the auxiliary high speed gears G18, G20, G23, G27 are connected to the auxiliary transmission shaft S8 by a synchromesh mechanism. The To describe only the synchromesh mechanism, 61 is a hub, 62 is a sleeve, 63 is a key, 64 is a ring, 65 is a conical portion of an auxiliary transmission gear, and 66 is a shifter.
[0024]
When the high speed gear G18 is transmission-coupled to the sub-transmission shaft S8, a “high-speed” shift is established. When the medium-speed gear G20 is transmission-coupled to the sub-transmission shaft S8, a “medium-speed” shift is established. A “low speed” shift is established, and when the super low speed gear G27 is transmission-coupled to the auxiliary transmission shaft S8, a “super low speed” shift is obtained. Since the to smoothly synchronize the rotation of the rotation drive gear hub it is necessary to cut off the power from the transmission upstream side or downstream side, to shift change by the main transmission section 32 to the "neutral".
[0025]
In the 4WD switching device 34, the average rotational speed (peripheral speed) of the front wheels 2, 2 and the rear wheels 3, 3 is substantially constant, and the average rotational speed of the front wheels 2, 2 is The "front wheel speed-up 4WD" state where the peripheral speed ratio is almost twice the average rotational speed of the rear wheels 3 and 3, and the front wheels 2 and 2 are turned off and only the rear wheels 3 and 3 are driven. This is a device for switching to the “rear wheel 2WD” state, and has a structure using a wet multi-plate hydraulic clutch type transmission mechanism, similar to the forward / reverse transmission unit 31 and the auxiliary transmission unit 33. The PTO transmission 37 is a device that changes the PTO driving force in four stages, and has a structure using a dog clutch type transmission mechanism.
[0026]
As described above, the tractor travel transmission device includes the forward / reverse transmission unit 31, the main transmission unit 32, and the sub-transmission unit 33. The forward / reverse transmission unit 31 switches between forward and reverse, and the main transmission unit 32 All 16 shift positions are selected by a combination of the main shift and the sub shift by the sub shift unit 33. Table 1 shows the combinations of the main speed change and the sub speed change.
[0027]
[Table 1]

[0028]
This travel transmission has a configuration in which a forward / reverse transmission portion 31 and a sub-transmission portion 33 of a synchromesh mechanism are provided on the upper and lower transmission sides of a main transmission portion 32 of a hydraulic clutch mechanism, respectively. Therefore, when shifting the forward / reverse transmission portion 31 or the sub-transmission portion 33 that is the synchromesh mechanism, the power is turned off by the sub-transmission portion 32 that is the hydraulic clutch mechanism, so that a smooth clutch is not provided. Shift change is possible.
[0029]
In addition, the hydraulic clutch mechanism is more expensive and complicated in the oil passage structure than the synchromesh mechanism, but this hydraulic clutch mechanism is only incorporated in one of the three speed change parts. can make the total cost, yet is simple oil passage structure of the whole.
[0030]
The shift position is switched by the shift lever 17. As shown in FIG. 6, the transmission lever 17 can be rotated back and forth along the guide groove 18, and “ultra-low”, “rotary”, “ The operation positions of “pitching / plow”, “neutral”, and “travel” are provided. "Ultra low" is a mode when working at ultra-low speed such as creep work, "Rotary" is a mode during rotary tillage work, "Skipaki / plow" is a mode during plow work or plow work, "Neutral" is traveling The stop mode, “travel”, is a mode when traveling on the road, and when the work (or travel on the road) mode is selected with the shift lever 17, a multi-stage (4-6 speed) shiftable region suitable for the mode is set. The Further, a speed increasing button 17a and a speed reducing button 17b operated by a finger are provided on the grip of the speed changing lever 17, and the speed increasing and decreasing speeds are increased and decreased within the speed changeable region by these speed changing buttons 17a and 17b.
[0031]
For example, the shiftable region of “rotary” is the fifth to the tenth, and when “rotary” is selected with the shift lever 17, the shift position of the seventh step is first set. Then, starting from the seventh step, the shift step number increases by one step each time the acceleration button 17a is pressed once, and the shift step number decreases by one step each time the deceleration button 17b is pressed. FIG. 7 shows the speed changeable region and the number of starting shift stages in each mode.
[0032]
【The invention's effect】
The transmission according to the present invention includes a transmission unit using a synchromesh mechanism on the transmission upper side and lower side of a transmission unit using a hydraulic clutch mechanism, respectively, and the power of the transmission unit using the hydraulic clutch mechanism is turned off to perform the transmission using the synchromesh mechanism. By adopting a configuration that shifts parts, it is possible to make a smooth shift change simply by adopting a hydraulic clutch mechanism at one of the three speed changing parts, and to reduce the number of expensive hydraulic clutch mechanisms. The cost can be reduced to a minimum.
[Brief description of the drawings]
FIG. 1 is an overall side view of a tractor.
FIG. 2 is a transmission mechanism diagram.
FIG. 3 is a cross-sectional view of a forward / reverse transmission portion and a PTO forward / reverse device of a traveling transmission device.
FIG. 4 is a cross-sectional view of a main transmission portion of the travel transmission.
FIG. 5 is a cross-sectional view of a sub-transmission unit of the travel transmission.
FIG. 6 is a perspective view of a transmission lever.
FIG. 7 is a diagram illustrating a combination of a main shift and a sub shift at a shift position, and a traveling speed.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Tractor 2 Front wheel 3 Rear wheel 8 Mission case 17 Shift lever 17a Speed increase button 17b Deceleration button 31 Forward / reverse speed change part (speed change part by synchromesh mechanism)
32 Main transmission (transmission using a hydraulic clutch mechanism)
33 Sub-transmission unit (transmission unit with synchromesh mechanism)

Claims (1)

The PTO forward / reverse rotation device provided so that the rotational power of the engine (10) overlaps with the synchromesh type front / rear transmission unit (31) through the main clutch (30) and the front / rear position overlaps with the front / rear transmission unit in a side view. 37), and the rotational power transmitted to the synchromesh front / rear transmission unit (31) is a hydraulic clutch capable of shifting to the first, second, third, and fourth speeds on the rear side. After being transmitted to the main transmission unit (32) configured in the above, the transmission is transmitted to the synchromesh sub-transmission unit (33) capable of shifting to four stages of high speed, medium speed, low speed, and ultra-low speed. The shift positions of all 16 stages by the combination of the main transmission unit and the sub-transmission unit are divided into a shiftable region suitable for traveling and a shiftable region suitable for other work, and selection of these regions is made a single The shift lever (17) is configured to The shift position of the main transmission section comprising a shift starting point in each region after selecting lever as second speed or third speed, acceleration and deceleration buttons provided a shift position of the region to the grip of the shift lever (17a, 17b) A transmission characterized in that it can be selected by operating.

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