JP2005239009A - Tractor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily maintain an equal speed and speed increase switch mechanism. <P>SOLUTION: A transmission part is provided with a first case and a second case. A PTO speed change mechanism for changing speed of a PTO shaft and a front/rear wheel speed change mechanism for changing speed of front/rear wheels are provided in the first case, and the equal speed and speed increase switch mechanism for accelerating the front wheels is provided in the second case. The second case is detachably attached to the first case, and the equal speed and speed increase switch mechanism in the second case is detachably interlockingly connected to the front wheel speed change mechanism. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a tractor capable of switching a speed increase of a front wheel.

  Conventionally, as one form of a tractor, a transmission unit is linked to a prime mover unit, and a pair of left and right front wheels are linked to the transmission unit via a front wheel side differential unit, while a left and right pair of front wheels are connected via a rear wheel side differential unit. Some have a pair of rear wheels linked together.

In the mission section, a PTO transmission mechanism for shifting the PTO shaft, a front / rear wheel transmission mechanism for shifting the front and rear wheels, and an equal / acceleration switching mechanism for increasing the speed of the front wheels are provided ( For example, see Patent Document 1).
JP 11-334401 A

  However, in the tractor described above, even when only the constant / acceleration switching mechanism is maintained, the mission section must be disassembled, and the maintenance work is complicated.

  In addition, the number of parts of the equal / acceleration switching mechanism is large, and this also causes troublesome maintenance work.

  Therefore, in the present invention, the transmission unit is interlocked and connected to the prime mover unit, and the pair of left and right front wheels are interlocked and connected to the mission unit via the front wheel side differential part, while the pair of left and right sides are connected via the rear wheel side differential part. In the tractor with the rear wheels linked to each other, the transmission section includes a first case and a second case, and a PTO transmission mechanism for shifting the PTO shaft in the first case, and before and after shifting the front and rear wheels. A wheel speed change mechanism is provided, while a speed change mechanism for increasing the speed of the front wheels is provided in the second case, and the second case is detachably attached to the first case and provided in the second case. The equal / acceleration switching mechanism provides a tractor characterized in that it is detachably linked to the front / rear wheel transmission mechanism.

  Further, the present invention provides a front end portion of the output shaft of the front / rear wheel speed change mechanism provided in the first case and extending into the second case, and an output of the equal / speed increase switching mechanism provided in the second case. Before the tip of the shaft is placed on the same axis and brought into a butted state and detachably connected via the boss, and a part of the equal / speed change switching mechanism is formed on the outer peripheral surface of the boss Another feature is that an output gear for increasing the wheel speed is formed.

(1) In the present invention described in claim 1, the transmission section includes a first case and a second case, and a PTO transmission mechanism for shifting the PTO shaft in the first case and the front and rear wheels are shifted. A front / rear wheel speed change mechanism is provided, and a second / case is provided with an equal / acceleration switching mechanism for increasing the speed of the front wheel, and the second case is detachably attached to the first case. The equal / acceleration switching mechanism provided in is detachably linked to the front / rear wheel transmission mechanism.

  In this way, the second case containing the equal / acceleration switching mechanism is detachably attached to the first case, and the equal / acceleration switching mechanism provided in the second case is used as the front / rear wheel transmission mechanism. Because it is detachably linked, when the equality / speed increase switching mechanism is to be maintained, the second case is removed from the first case, and the equal speed increase switching mechanism is connected to the front / rear wheel speed change mechanism. By releasing, maintenance of the equal / acceleration switching mechanism can be easily performed.

  (2) In the present invention described in claim 2, the front end portion of the output shaft of the front / rear wheel speed change mechanism provided in the first case and extending into the second case, and the like provided in the second case, etc. The tip of the input shaft of the speed increasing switching mechanism is placed on the same axis to be in a butted state and is detachably connected through the boss, and the constant speed increasing switching mechanism is connected to the outer peripheral surface of the boss. An output gear for speed increasing the front wheel, which forms a part, is formed.

  In this way, the tip of the output shaft of the front / rear wheel transmission mechanism and the tip of the input shaft of the equal / acceleration switching mechanism are detachably connected via the boss, The speed increase switching mechanism can be easily disconnected from the front and rear wheel transmission mechanisms.

  In addition, the boss that connects the output shaft of the front / rear wheel speed change mechanism and the input shaft of the equal / acceleration switching mechanism forms an output gear for increasing the front wheel on the outer peripheral surface. It is possible to reduce the number of parts of the speed switching mechanism, and to reduce maintenance labor and labor, as well as cost.

  Furthermore, since the tip of the output shaft of the front / rear wheel speed change mechanism and the tip of the input shaft of the equal / acceleration switching mechanism are abutted on the same axis, the equal / acceleration switching mechanism The attachment and detachment can be facilitated, and the front wheel speed increasing mechanism can be made compact.

  And since the equal / speed increase switching mechanism can be easily attached and removed, the front / rear wheel drive four-wheel drive specification is changed to the two-wheel drive specification only for the rear wheel drive by removing the equal / speed increase change mechanism at the time of shipment. It can be easily changed.

  A shown in FIGS. 1 and 2 is a tractor according to the present invention. The tractor A is provided with a prime mover portion 2 on a fuselage frame 1 and a front end of a clutch housing portion 3 extending in the front-rear direction on the prime mover portion 2. The transmission unit 4 is connected to the rear end of the clutch housing 3 and the driving unit 5 is disposed above the clutch housing 3 and the transmission unit 4. A pair of left and right front wheels 7 and 7 are interlocked and connected via a wheel side differential portion 6, while a pair of left and right rear wheels 9 and 9 are interlocked and connected via a rear wheel side differential portion 8 provided at the rear of the mission portion 4. doing.

  The prime mover section 2 closes the engine 10 and the like with a hood 11 so as to be freely opened and closed.

  The clutch housing part 3 is provided with a transmission shaft (not shown) for interlockingly connecting the engine 10 and the transmission part 4 in a clutch housing 12 formed by extending in the front-rear direction, and at the front part of the transmission shaft. A clutch (not shown) is provided.

  As shown in FIG. 4, the mission unit 4 includes a main transmission unit for shifting the front and rear wheels 7, 7, 9, 9 between forward rotation and reverse rotation in the mission case 14. 15, a sub-transmission unit 16 for further shifting the rotational speed changed by the main transmission unit 15, and the rotational speed of the front wheels 7, 7 are switched to a constant speed state or an increased speed state with the rear wheels 9, 9. And a PTO shaft 18 for outputting power to various working machines, and a PTO transmission unit 19 for shifting the rotational speed of the PTO shaft 18.

  The driving unit 5 is positioned behind the bonnet 11 and above the front part of the clutch housing 12 so that the steering column 20 is erected, and a wheel support that forms part of the steering operation mechanism is formed from the upper end of the steering column 20. A shaft 21 is protruded, a steering wheel 22 is attached to the upper end portion of the wheel support shaft 21, and a driver's seat 23 is disposed at a position behind the steering wheel 22 and above the transmission unit 4.

  As shown in FIG. 3, at the left side of the driver's seat 23, a main transmission lever 24 for operating the main transmission unit 15 and a sub transmission lever 25 for operating the sub transmission unit 16 are provided. And a PTO speed change lever 26 for operating the PTO speed change unit 19, while a right side position of the driver's seat 23 is a work for raising and lowering a work machine (not shown) connected to the rear. A machine lifting lever 27 and a tilling depth adjusting lever 28 for adjusting a tilling depth of a tilling device (not shown) connected to the rear are disposed. In FIG. 2, 29 is a clutch pedal, and 30 and 31 are brake pedals.

  In addition, step bodies 193 and 193 are extended from the clutch housing 12 to the left and right sides, respectively, and the lower ends of the front wheel fenders 194 and 194 are connected to the rear ends of the step bodies 193 and 193, respectively.

  The left rear wheel fender 194 is provided with a lever guide body 195, and a main transmission lever guide groove 196 formed by extending straight in the front-rear direction is provided at the front right side of the lever guide body 195. The main transmission lever 24 is inserted into the transmission lever guide groove 196, and the main transmission lever 24 is slidable back and forth along the main transmission lever guide groove 196.

  A sub-transmission lever guide groove 197 formed in a substantially H shape in plan view is provided at the left front portion of the lever guide body 195 and on the left side of the main transmission lever guide groove 196. The auxiliary transmission lever 25 is inserted, and the auxiliary transmission lever 25 is slidable along the auxiliary transmission lever guide groove 197.

  Further, a PTO transmission lever guide groove 198 formed by extending straight in the front-rear direction is provided at the rear portion of the lever guide body 195, and the PTO transmission lever 26 is inserted into the PTO transmission lever guide groove 198, and The PTO speed change lever 26 is slidable along the PTO speed change lever guide groove 198.

  Hereinafter, the structure of the mission unit 4 will be described in more detail with reference to FIGS.

[Description of Mission 4]
In other words, the mission section 4 includes a first case 40 and a second case 41 that form a mission case 14, a PTO transmission mechanism 42 that shifts the PTO shaft 18 in the first case 40, and front and rear wheels 7. , 7, 9 and 9 are provided with a front and rear wheel speed change mechanism 43, while the front case 7 and 7 are switched to a constant speed state or an increased speed state with the rear wheels 9 and 9 in the second case 41, etc. An acceleration switching mechanism 44 is provided.

  The second case 41 is disposed in front of the first case 40, and is detachably attached to the first case 40 from the front via a mounting bolt 45, and is provided in the second case 41. The speed increasing switching mechanism 44 is detachably linked to the front / rear wheel speed changing mechanism 43 from the front.

  In this way, only the second case 41 incorporating the equal / acceleration switching mechanism 44 is detachably attached to the first case 40 from the front, and the equal / acceleration switching mechanism 44 provided in the second case 41 is provided. Is connected to the front / rear wheel speed change mechanism 43 so as to be freely detachable from the front, so that only the second case 41 can be easily moved forward from the first case 40 when maintaining the constant / increase speed switching mechanism 44. Can be removed from the front / rear wheel speed change mechanism 43 and the front / rear wheel speed change mechanism 44 can be easily disconnected from the front and rear to facilitate maintenance of the removed etc. speed increase switching mechanism 44. be able to.

  In addition, since the second case 41 is disposed in front of the first case 40, the minimum ground clearance of the mission case 14 itself can be secured, and the mission case 14 interferes with projections on the ground. Can be prevented as much as possible.

  Furthermore, since the equal / acceleration switching mechanism 44 can be easily attached / detached via the second case 41, the second case 41 can be removed at the time of shipment from the four-wheel drive specification of the front / rear wheel drive. It can be easily changed to a two-wheel drive specification with only drive.

  As shown in FIGS. 4 and 5, the first case 40 is provided with a front wall body 46, an intermediate wall body 47, and a rear wall body 48, and an axial line in the front-rear direction is provided at the center upper portion of the front wall body 46. The input shaft supporting boss part 49 is connected to the input shaft supporting boss part 49 so that the input shaft 50 with the axis line oriented in the front-rear direction is rotatably supported in the input shaft supporting boss part 49. A PTO shaft support boss 51 with the axis line in the front-rear direction is connected to the center upper part, and the PTO shaft 18 with the axis line in the front-rear direction is rotatably supported in the PTO shaft support boss part 51. I am letting.

(Description of PTO transmission mechanism 42)
The PTO speed change mechanism 42 has a front PTO speed change shaft 52 with its axis lined in the front-rear direction between the front wall 46 and the intermediate wall 47 so as to be rotatable. The rear end portion extends rearward from the intermediate wall body 47, and connects the front end portion of the rear PTO transmission shaft 53 with the axis lined in the front-rear direction to the rear end portion via a connecting cylinder 54. The rear end portion of the rear TPO transmission shaft 53 is rotatably supported by the rear wall body 48.

  A PTO transmission 19 is provided at the front of the front PTO transmission shaft 52. The PTO transmission 19 is spline-fitted with a transmission cylinder 55 on the outer peripheral surface of the front PTO transmission shaft 52. A slide engagement body 56 is slidably fitted in the axial direction on the outer peripheral surface of the transmission cylinder 55, and a high speed gear 57 and a reverse rotation gear 58 are rotatably attached to the front position of the slide engagement body 56 while sliding. A low transmission gear 59 is rotatably attached to the rear position of the meshing body 56.

  Further, the high transmission gear 57 is provided with a high transmission meshing piece 60, the reverse rotation gear 58 is provided with a reverse rotation meshing piece 61, and the low transmission gear 59 is provided with a low transmission gearing piece 62. Each of the gears 57, 58, 59 and the front PTO speed change shaft 52 are interlocked by engaging one of the front and rear slide engagement pieces 63, 64 provided on the slide engagement body 56 with the pieces 60, 61, 62. It can be connected.

  An output gear 65 is attached to the rear end portion of the rear PTO transmission shaft 53, while an input gear 66 is attached to the front end portion of the PTO shaft 18, and both gears 65 and 66 are engaged. Reference numeral 67 denotes a cover body that covers the protruding portion of the PTO shaft 18.

  Here, a PTO speed change fork 68 is engaged with the slide engagement body 56, and a base end portion 68a of the PTO speed change fork 68 is horizontally mounted on the front upper part of the first case 40 with its axis line directed in the front-rear direction. It is attached to the PTO speed change fork shaft 69.

  Then, the base end portion of the PTO speed change lever 26 is connected to the PTO speed change fork shaft 69, and the slide engagement body 56 is slid through the PTO speed change fork 68 by operating the PTO speed change lever 26. Any of the front and rear slide engagement pieces 63, 64 provided on the slide engagement body 56 is engaged with any of the engagement pieces 60, 61, 62, and each gear 57, 58, 59 and the front PTO transmission shaft The PTO shaft 18 can be shifted to any one of low speed, neutral speed, high speed, and reverse rotation.

  Further, a first output gear 65 and a second output gear 66 are coaxially attached to the input shaft 50, and the first output gear 65 meshes with a first counter gear 71 attached to a counter shaft 70 described later. The high-speed gear 57 is meshed with the first counter gear 71, and the low-speed gear 59 is meshed with a third counter gear 73 that is integrally connected to the first counter gear 71 via a connecting body 72. On the other hand, the second output gear 65 is engaged with the reverse gear 58.

  The counter shaft 70 is horizontally mounted between the front wall body 46 and the intermediate wall body 47 so that the axis is directed in the front-rear direction, and a first counter gear 71 and a second counter gear 70 are disposed on the front half of the counter shaft 70. The counter gear 74 and the third counter gear 73 are rotatably attached in a state of being integrally connected via the connecting body 72, while the fourth, fifth, sixth, and fourth are attached to the rear half of the counter shaft 70. 7 Counter gears 75, 76, 77, 78 are attached to rotate together with the counter shaft 70, respectively.

(Description of front / rear wheel speed change mechanism 43)
The front / rear wheel speed change mechanism 43 has a main / sub-transmission shaft 80 that pivots between a lower portion of the front wall body 46 and the intermediate wall body 47 so that the main / sub-transmission shaft 80 is turned in the front / rear direction. A main transmission unit 15 is provided in the front half of the shaft 80, and an auxiliary transmission unit 16 is provided in the rear half.

(Main transmission 15)
Then, the main transmission unit 15 is attached to the outer peripheral surface of the front half of the main / sub-transmission shaft 80 by fitting the cylindrical gear support 81 so as to rotate integrally, and the outer peripheral surface of the cylindrical gear support 81 The transmission cylinder 82 is spline-fitted to the center of the slide cylinder 83, and the slide engagement body 83 is fitted to the outer peripheral surface of the transmission cylinder 82 so as to be slidable in the axial direction. While the high transmission gear 84 is rotatably attached, the reverse gear 85 is rotatably attached to the rear position of the slide engagement body 83.

  Here, the high transmission gear 84 is engaged with the first counter gear 71, and the reverse gear 85 is engaged with the low transmission gear 59.

  In addition, the front and rear transmission meshing pieces 86 and 87 are provided on the outer peripheral surface of the transmission cylinder 82, while the front and rear slide engagement pieces 88 and 89 are provided on the inner peripheral surface of the slide coupling body 83, and the slide meshing is performed. A low speed gear 90 is integrally formed on the outer peripheral surface of the body 83.

  The high transmission gear 84 is provided with a high transmission mesh piece 91, and the reverse rotation gear 85 is provided with a reverse rotation engagement piece 92.

  Here, the main transmission fork 93 is engaged with the slide engagement body 83. As shown in FIGS. 6 and 7, the base end portion 93a of the main transmission fork 93 is a main transmission fork shaft 94 described later. It is attached to.

  Then, the base end portion of the main transmission lever 24 is connected to the main transmission fork shaft 94, and the main transmission lever 24 is rotated in the front-rear direction, whereby the slide engagement body 83 is connected via the main transmission fork 93. By sliding, it is possible to switch between high shift, low shift, neutral, and reverse (reverse).

  That is, in the high speed change operation, the front slide engagement piece 88 of the slide engagement body 83 is engaged with the high transmission engagement piece 91 of the high transmission gear 84 and the front transmission engagement piece 86 of the transmission cylinder 82. It is a state and a sushi.

  The low speed shifting operation is performed by engaging the front slide engagement piece 88 of the slide engagement piece 83 with the front and rear transmission engagement pieces 86 and 87 of the transmission cylinder 82, and the low speed gear 90 of the slide engagement piece 83. In this state, the second counter gear 74 is engaged.

  In the neutral operation, the front and rear slide engagement pieces 88 and 89 of the slide engagement piece 83 are not engaged with any of the front and rear transmission engagement pieces 86 and 87 of the transmission cylinder 82. It is.

  In reverse (reverse) operation, the front slide engagement piece 88 of the slide engagement piece 83 is engaged with the rear transmission engagement piece 87 of the transmission cylinder 82, and the rear slide engagement piece 89 of the slide engagement piece 83 is reversely rotated. It is assumed that the state is engaged with 85 reversing engagement pieces 92.

(Sub-transmission unit 16)
The subtransmission unit 16 includes a main transmission gear 95 formed at the rear end of the outer peripheral surface of the transmission cylinder 82, the fourth counter gear 75 meshed with the main transmission gear 95, and a fourth counter. The fifth, sixth, and seventh counter gears 76, 77, and 78 that are coaxially mounted via the gear 75 and the counter shaft 70, and the main and auxiliary transmission shafts 80 to mesh with these gears 76, 77, and 78 The high-speed stage shift gear 96 and the low-speed stage shift gear 97 are slidably attached to the outer peripheral surface of the rear half.

  The high-speed gear shift gear 96 is slidably spline-fitted with a gear body 96a on the outer peripheral surface of the main / sub-transmission shaft 80, and meshed with the main transmission transmission gear 95 on the front surface of the gear body 96a. A fourth transmission gear forming piece 96b is formed, and a third transmission gear forming piece 96c that meshes with the fifth counter gear 76 is formed on the outer peripheral surface of the gear body 96a.

  Here, a high-speed gear shift fork 98 is engaged with the gear main body 96a, and as shown in FIGS. 6 and 7, a base end portion 98a of the high-speed gear shift fork 98 has a high speed gear shift fork described later. It is attached to the switching fork shaft 127.

  Then, the base end portion of the auxiliary transmission lever 25 is engaged with the high speed stage switching fork shaft 127 via the base end portion 98a of the high speed stage transmission fork 98, and the auxiliary transmission lever 25 is rotated in the front-rear direction. By performing the dynamic operation, the high-speed stage shift gear 96 is slid through the high-speed stage shift fork 98 so that the fourth speed, the neutral speed, and the third speed can be switched.

  That is, in the fourth speed change operation, the fourth transmission gear forming piece 96b is engaged with the main transmission transmission gear 95 in the engaged state, and the third transmission gear forming piece 96c is released from the fifth counter gear 76. It is what you make.

  In the neutral operation, the fourth transmission gear forming piece 96b is disengaged from the main transmission gear 95 and the third transmission gear forming piece 96c is disengaged from the fifth counter gear 76.

  The third speed change operation is performed by releasing the engagement of the fourth transmission gear forming piece 96b from the main transmission gear 95 and engaging the third transmission gear forming piece 96c with the fifth counter gear 76. is there.

  The low-speed stage shift gear 97 is formed with a second speed change gear that has a gear body 97a slidably fitted on the outer peripheral surface of the main / sub transmission shaft 80 and slidably engaged with the sixth counter gear 77 on the outer peripheral surface of the gear main body 97a. A piece 97b is formed, and a first transmission gear forming piece 97c that meshes with the seventh counter gear 78 is formed on the outer peripheral surface of the gear body 96a.

  Here, a low-speed gear shift fork 99 is engaged with the gear body 97a, and as shown in FIGS. 6 and 7, the base end portion 99a of the low-speed gear shift fork 99 is a low-speed gear shift fork 99 described later. It is attached to the switching fork shaft 126.

  Then, the base end portion of the auxiliary transmission lever 25 is engaged with the high speed stage switching fork shaft 127 via the base end portion 98a of the high speed stage transmission fork 98, and the auxiliary transmission lever 25 is rotated in the front-rear direction. By performing the dynamic operation, the low-speed stage shift gear 97 is slid through the low-speed stage shift fork 99 so that the second speed, the neutral speed, and the first speed can be switched.

  That is, in the second speed change operation, the second transmission gear forming piece 97b is engaged with the sixth counter gear 77 and the first transmission gear forming piece 97c is released from the seventh counter gear 78. .

  In the neutral operation, the second transmission gear forming piece 97b is disengaged from the sixth counter gear 77, and the first transmission gear forming piece 97c is disengaged from the seventh counter gear 78.

  Further, the first speed change operation is to release the engagement of the second transmission gear forming piece 97b from the sixth counter gear 77 and to engage the first transmission gear forming piece 97c with the seventh counter gear 78. is there.

  The main / sub-transmission shaft 80 has a front end 100 extended forward, and an equal / acceleration switching mechanism 44 described later is detachably linked to the front end 100 while a bevel gear 101 is provided at the rear end. The rear wheel side differential portion 8 is linked and connected to the bevel gear 101.

(Explanation of equal / speed change mechanism 44)
The constant / acceleration switching mechanism 44 is provided in the second case 41 as described above, and the second case 41 is formed in a cap shape with a rear opening, and the axis is directed to the front wall 41a in the front-rear direction. The output shaft support boss portion 102 is connected in communication, and the output shaft support boss portion 102 is rotatably supported by the middle portion of the output shaft 103 with the axis line directed in the front-rear direction, and the rear end portion 111 of the output shaft 103 And the front end portion 100 of the main / sub-transmission shaft 80 are detachably linked to each other.

  The equal / acceleration switching unit 17 slidably fits a cylindrical switching slide body 105 via a ball bearing 104 to the outer peripheral surface of the intermediate portion of the output shaft 103, and the front end of the switching slide body 105 The front tooth portion 106 and the rear tooth portion 107 are formed at the front portion and the rear end portion, respectively, and the speed increasing side tooth portion 108 and the constant speed side tooth portion 109 are respectively provided at the front and rear of the switching slide body 105. It is arranged.

  In this way, the switching slide body 105 is slid forward, and the front tooth portion 106 is engaged with the speed increasing side tooth portion 108, so that the speed increasing switching can be performed, while the switching slide body 105 is moved rearward. It is possible to switch at a constant speed by sliding and meshing the rear tooth portion 107 with the constant speed side tooth portion 109.

  That is, the front end portion 100 of the main / sub transmission shaft 80 of the front / rear wheel speed change mechanism 43 provided in the first case 40 and extended to the second case 41, and the same / increase provided in the second case 41 The rear end portion 111 of the output shaft 103 of the speed switching mechanism 44 is placed on the same axis line to be in a butted state and is detachably spline-fitted and connected via the boss portion 112. On the outer peripheral surface, a front wheel speed increasing output gear 113 forming a part of the constant / speed increasing switching mechanism 44 and the constant speed side tooth portion 109 are integrally formed.

  In this way, the front end 110 of the main / sub transmission shaft 80 of the front / rear wheel transmission mechanism 43 and the front end 111 of the output shaft 103 of the equal / acceleration switching mechanism 44 are attached and detached via the boss 112. Since they are connected freely, the equal / acceleration switching mechanism 44 can be easily disconnected from the front / rear wheel transmission mechanism 43.

  Moreover, the boss 112 that connects the main / sub transmission shaft 80 of the front / rear wheel transmission mechanism 43 and the output shaft 103 of the equal / acceleration switching mechanism 44 has an output gear 113 for front wheel acceleration on the outer peripheral surface. Therefore, it is possible to reduce the number of parts of the equal / acceleration switching mechanism 44, thereby reducing maintenance labor and labor, and cost.

  Further, the front end portion 100 of the main / sub transmission shaft 80 of the front / rear wheel transmission mechanism 43 and the rear end portion 111 of the output shaft 103 of the equal / acceleration switching mechanism 44 are arranged on the same axis. Therefore, the equal / speed increase switching mechanism 44 can be easily attached and detached, and the equal / speed increase switching mechanism 44 can be made compact.

  Further, a boss 114 is rotatably fitted to the front outer peripheral surface of the output shaft 103, and the front wheel speed increasing input gear 115 and the speed increasing side described above are connected to the outer peripheral surface of the boss 114. The tooth portion 108 is integrally formed.

  In addition, a speed increasing shaft 116 with its axis lined in the front-rear direction is pivoted horizontally between the middle part of the front wall 41a of the second case 41 and the front wall body of the first case 40, and the same increase. A speed increasing output gear 117 and a speed increasing input gear 118 are provided at the front and rear of the speed shaft 116, respectively, and the speed increasing input gear 118 is engaged with the front wheel speed increasing output gear 113, while the front wheel speed increasing. The speed increasing output gear 117 is engaged with the speed input gear 115.

  Furthermore, as shown in FIG. 10, a fork shaft 119 for speed change switching is attached to the substantially central portion of the second case 41 so as to be slidable back and forth. A base end portion of the equal / acceleration switching fork 120 is attached to 119, and a distal end portion of the equal / acceleration switching fork 120 is engaged with the switching slide 105.

  A left fork wall of the second case 41 is rotatably provided with a fork operation shaft 121 having an axis line in the left-right direction penetrating the inner side of the second case 41 via a fork operation arm 122. The base end portion of the constant / speed increasing switching fork 120 is interlocked and connected, while the constant / speed increasing switching operation portion 123 is interlocked and connected to the outer end portion of the fork operating shaft 121.

  In addition, the steering operation interlocking mechanism 125 is interlocked and connected to the equal / acceleration switching operation unit 123, and the switching restriction / release means 124 cancels the switching restriction of the equal / acceleration switching operation unit 123. -When the speed change switching operation part 123 is switched to the speed increase side, the steering operation interlocking mechanism 125 is linked to the turning operation by the steering wheel 22 so that the rotational speed of the front wheels 7 and 7 is increased. At the same time, the switching restriction / cancellation means 124 cancels the switching restriction of the equal / increase / increase switching operation section 123 only when the auxiliary transmission section 16 is set to the low speed shift speed stage. Switching to the high speed variable speed stage is regulated.

  Here, for convenience of explanation, first, the arrangement structure of the fork shafts 94, 126, and 127 provided in the main / sub-transmission units 15 and 16 and the equal / acceleration switching unit 17 will be described, and then the switching restriction / release means 124 will be described. A specific description will be given, followed by a specific description of the equal / acceleration switching operation unit 123 and the steering operation interlocking mechanism 125.

(Description of arrangement structure of each fork shaft 94, 126, 127)
That is, the low speed stage switching fork shaft 126 and the high speed stage switching fork shaft 127 that constitute a part of the auxiliary transmission unit 16, and the main speed switching fork shaft 94 that constitutes a part of the main transmission unit 15, As shown in FIGS. 5-7, between the front wall body 46 and the intermediate wall body 47 of the 1st case 40, it can slide in the front-back direction in the parallel state which turned the axis line in the front-back direction. As shown in FIG. 4, the fork shaft 119 for equal / acceleration switching that constitutes a part of the equal / acceleration switching unit 17 is installed on the front wall 41 a of the second case 41 and the first case 40. Between the front wall body 46, it is installed so that sliding (sliding) is possible in the front-back direction.

  Then, as shown in FIG. 5, a high speed stage switching fork shaft 127 is disposed immediately below the low speed stage switching fork shaft 126 as viewed from the front, and immediately below the high speed stage switching fork shaft 127. The main speed change fork shaft 94 is disposed at the lower position, and the equal / increase speed change fork shaft 119 is disposed at the lower right side of the low speed stage change fork shaft 126 so that the low speed stage change fork shaft 126 is provided. The high speed stage switching fork shaft 127 and the equal / increase speed switching fork shaft 119 are arranged so as to form a vertex of a virtual substantially isosceles triangle.

  In FIG. 5, reference numeral 142 denotes a temporary fixing ball for temporarily fixing the high-speed stage switching fork shaft 127 to the switching position, 143 denotes a pressing spring that elastically biases the temporary fixing ball 142 in a pressing state, and 144 denotes a main spring. A temporary fixing ball 145 that temporarily fixes the shift switching fork shaft 128 to the switching position is a pressing spring that elastically biases the temporary fixing ball 144 to a pressed state.

(Description of switching restriction / cancellation means 124)
As shown in FIGS. 6 and 7, the switching restricting / releasing means 124 is a rod-shaped member extending in the vertical direction between the low speed stage switching fork shaft 126 and the equal / speed increasing switching fork shaft 119. The first switching restriction / release body 130 is interposed between the low-speed stage switching fork shaft 126 and the high-speed stage switching fork shaft 127. The rod-shaped second switching restriction / release body 131 extends in the vertical direction. Is interposed.

  These first and second switching restriction / cancellation bodies 130 and 131 are accommodated in first and second communication holes 140 and 141 formed in the front wall body 46 of the first case 40, and adjacent fork shafts 119 and 126 ( 126, 127) is slidable in a direction substantially perpendicular to these.

  In addition, the equal / acceleration engaging recess 132 is formed on the outer peripheral surface of the equal / acceleration switching fork shaft 119, while the first lower-stage engaging recess is formed on the outer peripheral surface of the low-speed stage switching fork shaft 126. The high-speed engagement recesses 134 and the second-speed engagement recesses 135 are formed in parallel along the circumferential direction, and the high-speed stage engagement recesses 137 are formed on the outer peripheral surface of the high-speed stage switching fork shaft 127. It is formed along the circumferential direction.

  In this way, as shown in FIGS. 5 and 7, the lower end portion 133 of the first switching restricting / releasing body 130 which is slidable in the vertical direction with respect to the constant / acceleration engaging recess 132 is retracted. Thus, the upper end portion 136 of the first switching restricting / releasing body 130 advances and engages with either the first speed engaging recess 134 or the second speed engaging recess 135. In this state, the switching restriction of the fork shaft 119 for switching the equal speed / increase speed is released, the switching of the fork shaft 126 for switching the low speed stage is restricted, and the outer peripheral surface of the fork shaft 127 for switching the high speed stage is The lower end portion 138 of the second switching restricting / releasing body 131 is engaged with the high speed step engaging recess 137 formed along the circumferential direction, and switching of the high speed step switching fork shaft 127 is restricted. I am doing so.

  On the other hand, as shown in FIG. 6, the lower end portion 133 of the first switching restricting / releasing body 130 is engaged with the constant / acceleration engaging recess 132, and the low speed stage engaging recesses 134, 135 When the upper end portion 136 of the 1 switching restriction / release body 130 is in the disengaged state, the switching restriction of the constant / increase speed switching fork shaft 119 is made.

  As described above, the switching restriction / cancellation means 124 is used only when the subtransmission unit 16 is set to the low speed stage (first speed or second speed in the present embodiment). When the auxiliary transmission unit 16 is set to a high speed stage (the third speed or the fourth speed in the present embodiment), the equal / speed increase switching unit is enabled. No. 17 is regulated and speed change switching is disabled.

  Therefore, the switching restriction of the equal / acceleration switching operation part 123 is canceled by the switching restriction / cancellation means 124 only when the sub-transmission part 16 is set to the low speed variable speed stage (first speed or second speed). In addition, switching to the high speed variable speed stage (3rd speed or 4th speed) of the sub-transmission unit 16 is restricted, so that the same / increase speed switching is performed even though the vehicle body is in a high speed running state. It is possible to reliably prevent the problem that the part 17 is switched and the front wheels 7 and 7 are accelerated. As a result, it is possible to eliminate the fear of fear for the operator.

  At this time, the low speed stage switching fork shaft 126 and the high speed stage switching fork shaft 127 that constitute a part of the auxiliary transmission unit 16, and the equal and speed switching part that constitutes a part of the equal and speed switching part. A fork shaft 119 is arranged in a parallel state with its axis line oriented in the same direction, and a first switching restriction / release body that constitutes a part of the switching restriction / release means 124 between these adjacent fork shafts 126, 127, 119 By interposing 130 and the second switching restriction / cancellation body 131, the switching restriction of the fork shaft 119 for constant speed / increase speed switching is made so that the switching restriction is ensured with a simple and compact structure. It can be carried out.

(Explanation of equal / acceleration switching operation section 123)
As shown in FIGS. 8 to 11, the equal / acceleration switching operation unit 123 interlocks / releases the aforementioned equal / acceleration switching unit 17 and the steering operation interlocking mechanism 125 linked to the steering operation mechanism. The equivalence / speed increase switching operation unit 123 and the steering operation interlocking mechanism 125 are arranged close to each other on a virtual substantially the same vertical surface facing the left-right direction.

  That is, the equal / acceleration switching operation portion 123 includes a lever stay 150 connected to the left side wall 12a of the clutch housing 12, and a lever support shaft 151 protruding outward from the lever stay 150 toward the left side. While the base end of the equal / acceleration switching lever 153 is connected to the support shaft 151 via the boss 152, the base end of the lever interlocking arm 154 is rotatably fitted to the outer peripheral surface of the boss 152. In addition, a connecting protrusion 155 that protrudes rearward from the base end portion of the lever interlocking arm 154, and a connecting protrusion 156 that protrudes rearward from the base end portion of the constant / acceleration switching lever 153. The connecting pins 157 are linked together. Reference numeral 158 denotes a lever guide piece formed to extend outward from the upper end of the lever stay 150, and reference numeral 159 denotes a lever guide groove.

  Then, the base end portion of the interlocking support shaft 160 whose axis is directed in the left-right direction is coaxially interlockingly connected to the outer end portion of the fork operating shaft 121 of the equal / acceleration switching portion 17 described above. The base end portions of the pair of left and right operating arms 162, 162 are connected to each other through the cylindrical body 161, and arc-shaped interlocking avoidance guide grooves 163, 163 centering on the interlocking support shaft 160 are formed at the distal ends of both the operating arms 162, 162. At the same time, the interlocking engagement grooves 164 and 164 are formed to extend downward from the rear end edges of the interlocking avoidance guide grooves 163 and 163.

  In addition, an interlock avoidance guide groove 165 coinciding with the interlock avoidance guide grooves 163 and 163 is also formed at the tip of the lever interlock arm 154. As shown in FIG. The rear end edge portion 166 is formed to extend rearward from the rear end edge portions 167, 167 of the interlocking avoidance guide grooves 163, 163 formed in the operating arms 162, 162, and the rear end edge portions 166, 167, 167 and the above-described interlocking engagement grooves. 164 and 164 are formed on the same rotation locus with the lever support shaft 151 as the center.

  Furthermore, in the above-mentioned interlocking avoidance guide grooves 163, 163, 165, an interlocking connection pin 168 having an axis line in the left-right direction is penetrated, and a pin is restored between the interlocking connection pin 168 and the lever stay 150. The interlocking connecting pin 168 is urged rearward by the pin restoring spring 169 with the spring 169 interposed.

  In addition, a spring locking piece 170 is suspended from the cylindrical body 161, while a spring locking body 171 is projected from the clutch housing 12 toward the left side, and the spring locking piece 170 and the spring locking body are provided. The arm restoring spring 172 is interposed between the arm 171 and the elastic restoring force of the arm restoring spring 172 so that the arm restoring spring 172 is rotated counterclockwise around the interlocking support shaft 160 as shown in FIG. The operating arms 162 and 162 can be rotated and returned.

  In this way, the constant / increase speed changeover lever 153 has a constant speed operation position (A) erected substantially vertically as shown in FIGS. 11 and 12, and forward as shown in FIGS. The switching operation can be performed by rotating between the tilted speed increasing operation position (b).

  When the constant / acceleration switching lever 153 is operated to the constant speed operation position (A), the interlocking connection pin 168 slides in the interlocking avoidance guide grooves 163, 163, 165 as shown in FIGS. Only the operation arms 162 and 162 are prevented from rotating.

  Further, when the equal / acceleration switching lever 153 is operated to the acceleration operation position (b), the lever interlocking arm 154 rotates counterclockwise around the lever support shaft 151 as shown in FIGS. As shown in FIG. 13, the interlocking connection pin 168 that is rotated and is in contact with the rear end edge 166 of the interlocking avoidance guide groove 165 of the lever interlocking arm 154 is used for interlocking engagement. It is made to move in the grooves 164 and 164.

  In this state, when the interlocking connection pin 168 is pulled forward in conjunction with the steering operation interlocking mechanism 125 interlocked with the steering operation mechanism described later, as shown in FIG. It is rotated counterclockwise around the interlocking support shaft 160, and the turning power is transmitted to the fork operating shaft 121 of the equal / acceleration switching portion 17 via the interlocking support shaft 160, and the equivalent / acceleration switching portion. 17 is switched to the speed increasing side.

(Explanation of steering operation linkage mechanism 125)
As shown in FIGS. 9 and 11, the steering operation interlocking mechanism 125 has a lever swing support shaft 175 projecting from the front portion of the left side wall 12a of the clutch housing 12 toward the left side, and the lever swing support shaft. A boss portion 176 is rotatably fitted to the outer peripheral surface of the shaft 175, and an interlocking arm 177 is protruded upward on the upper left side of the boss portion 176, while a pair of left and right interlocking is provided on the right side of the boss portion 176. The lever bodies 178 and 178 are connected to each other, and each interlocking lever body 178 and 178 is formed with an upper projecting piece 179 and 179 and a lower projecting piece 180 and 180. An operation interlocking body 181 is interposed.

  As shown in FIGS. 9 and 11, the steering operation interlocking body 181 is formed with through holes 184 and 185 penetrating in the front-rear direction in the engaging bodies 182 and 183 interposed between the upper and lower protruding pieces 179, 179, 180, and 180. The front ends of a pair of upper and lower tension rods 186, 187 extending in the front-rear direction are passed through 184, 185, and engaged bodies 188, 189 are provided at the front end sections, and the engaged bodies 182, 183 are engaged with the engaged bodies 188, 189 from the rear. The rear ends of the tension rods 186 and 187 are connected to a connecting body 190, and a connecting tension spring 191 is interposed between the connecting body 190 and the interlocking connecting pin 168.

  Here, the pair of upper and lower tension rods 186, 187, the coupling body 190, and the coupling tension spring 191 are arranged on substantially the same straight line extending in the front-rear direction in a plan view, as shown in FIG. It is made compact by sliding (moving) in the front-rear direction on the line.

  Further, the upper end of the interlocking arm 177 is connected to the rear end of a push-pull rod 192 that forms part of the steering operation mechanism, and the left and right sides of the steering wheel 22 that forms part of the steering operation mechanism. The push / pull rod 192 is pushed and pulled in the front-rear direction in conjunction with the turning operation, and the interlock arm 177 is swung in the front-rear direction around the lever swing support shaft 175 in conjunction with the push-pull rod 192.

  Thus, when the interlocking arm 177 swings in the front-rear direction, the upper and lower protruding pieces 179, 179, 180, 180 swing in the front-rear direction via the boss 176.

  When the upper projecting pieces 179, 179 swing forward, the engaging body 182 provided between the upper projecting pieces 179, 179 engages with the engaged body 188 provided at the front end of the upper pulling rod 186 from behind, The tension rod 186 is pulled and slid forward, and the interlocking connecting pin 168 is pulled and slid forward through the connecting body 190 and the connecting tension spring 191.

  At this time, the downward projecting pieces 180, 180 swing backward, and the engaging body 183 provided between the both downward projecting pieces 180, 180 does not engage with the engaged body 189 provided at the front end portion of the lower pulling rod 187. The tension rod 187 does not slide in the front-rear direction.

  Further, when the downward projecting pieces 180, 180 swing forward, the engaging body 183 provided between the two downward projecting pieces 180, 180 engages with the engaged body 189 provided at the front end portion of the lower pulling rod 187 from behind, The tension rod 187 is pulled and slid forward, and the interlocking connection pin 168 is pulled and slid forward via the connecting body 190 and the connecting tension spring 191.

  At this time, the upper projecting pieces 179 and 179 swing backward, and the engaging body 182 provided between the upper projecting pieces 179 and 179 does not engage with the engaged body 188 provided at the front end of the upper pulling rod 186. The tension rod 186 does not slide back and forth.

  Therefore, as described above, when the equal / acceleration switching lever 153 is operated to the acceleration operation position (b), the steering operation interlocking mechanism can be operated even if the steering wheel 22 is rotated in either the left or right direction. The interlocking connection pin 168 is pulled and slid forward by 125, and both the operating arms 162 and 162 are rotated.

  In addition, as described above, the equal / acceleration switching operation unit 123 and the steering operation interlocking mechanism 125 are arranged close to each other on a virtual substantially the same vertical surface with the surface facing in the left-right direction. It can be arranged compactly, and the number of parts can be reduced and interlocking adjustment can be simplified.

  Here, as shown in FIGS. 1, 2, and 9, the equal / acceleration switching lever 153 protrudes in the vicinity of the rear portion of the left side wall 12 a of the clutch housing 12 and to the left and right sides from the clutch housing 12. The step bodies 193 and 193 that are stretched are arranged so as to protrude upward.

  That is, the equal / acceleration switching lever 153 does not hinder when getting on and off the driving unit 5 via the step body 193, and can be easily operated near the feet even when sitting on the driver's seat 23, Furthermore, since it is disposed in the vicinity of the operating arms 162 and 162 disposed in the vicinity of the constant / increasing speed switching section 17, the equal / increasing speed switching lever 153 and the operating arms 162 and 162 are connected to the equal / increasing speed switching section 17 with each other. It is possible to reduce the number of component parts for interlocking connection to each other as much as possible, thereby improving the interlocking performance and reducing the manufacturing cost.

  In addition, since the equal / acceleration switching lever 153, the operating arms 162 and 162, and the equal / acceleration switching unit 17 are arranged in the vicinity of the left side of the clutch housing 12, they can be arranged close to each other in a compact manner. This makes it possible to reduce the number of parts and simplify the interlock adjustment.

  FIGS. 15 and 16 show the equal / acceleration switching operation unit 123 as the second embodiment. The equivalent / acceleration switching operation unit 123 performs the equal / acceleration switching operation as the first embodiment. A lever interlocking body 200 is provided instead of the lever interlocking arm 154 of the section 123, and the lever interlocking body 200 is displaced in the vertical direction by the equal / acceleration switching lever 153.

  That is, a support cylinder body 202 having an axis line in the vertical direction is provided on a support plate body 201 fixed to the clutch housing 12, and a rod-like support piece 203 extending in the vertical direction is inserted into the support cylinder body 202. A pressing spring 204 is interposed between the upper end of the support piece 203 and the upper end surface of the support cylinder 202 so that the support piece 203 is supported by the support cylinder 202, and the lower end of the support piece 203 is inward. A support arm 205 is formed by extending toward the front, and the lever interlocking body 200 is attached to the tip of the support arm 205.

  The lever interlocking body 200 is formed with interlocking avoidance guide grooves 163 and 163 formed on the operating arm 162 at the front portion and interlocking avoidance guide grooves 165 that coincide with the left and right directions, while being extended vertically at the rear portion. The lower end portion of the speed switching lever 153 is continuously provided.

  In addition, a locking piece 206 is provided at the upper end of the equal / acceleration switching lever 153 so that the locking piece 206 can be locked to a locking receiving body 207 provided in the clutch housing 12. The body 207 is provided with an upper locking receiving portion 208 and a lower locking receiving portion 209.

  In this way, the constant speed operation position where the constant / acceleration switching lever 153 is pulled upward against the elastic biasing force of the pressing spring 204 and the locking piece 206 is locked to the upper locking receiving portion 208 ( In (b), the lever interlocking body 200 is displaced upward, and the interlocking avoidance guide groove 165 formed in the lever interlocking body 200 coincides with the interlocking avoidance guide grooves 163 and 163 formed in the operating arm 162 in the left-right direction. The interlocking connecting pin 168 only slides in these guide grooves 163, 163, 165, and the operating arm 162 is not operated.

  Further, when the locking piece 206 locked to the upper locking receiving portion 208 is moved to the side to release the locking, the equal / acceleration switching lever 153 is pulled downward by the elastic biasing force of the pressing spring 204. Increased speed operation position (b).

  Then, the lever interlocking body 200 is displaced downward, and the interlocking connecting pin 168 engaging with the rear end edge 166 of the interlocking avoiding guide groove 165 formed in the lever interlocking body 200 is formed in the operating arm 162. The interlocking engagement groove 164 is also engaged, and the interlocking avoidance guide grooves 163 and 163 are slid in the same state, and the operating arm 162 is rotated counterclockwise.

  In this way, by operating the equal / acceleration switching lever 153 in the vertical direction so that the equivalent / acceleration switching lever 153 is not displaced in the front / rear direction, it is arranged at the operator's feet, etc. A wide space for the operator's feet can be secured so that the acceleration switching lever 153 does not hinder the operator.

  FIG. 17 shows an equal / acceleration switching operation unit 123 as a third embodiment, and the equivalent / acceleration switching operation unit 123 of the equal / acceleration switching operation unit 123 as the first embodiment described above. The rear end portion of the connecting tension spring 191 is connected to the upper end portion of the operating arm 162 via the connecting pin 210, while the stopper receiving body 211 is extended downward from the lower end portion of the operating arm 162 to receive the stopper receiving portion. A stopper body 212 fixed to the clutch housing 12 is disposed at a rear position of the body 211, and a stopper action body 213 is interposed between the stopper body 121 and the stopper receiving body 211 so as to be freely inserted and removed.

  The stopper acting body 213 is attached to the lower end portion of the equal / acceleration switching lever 153 extending in the vertical direction, and the equivalent / acceleration switching lever 153 can be slid in the vertical direction via the cylindrical guide body 214. There is no. Reference numeral 215 denotes a support body that supports the cylindrical guide body 214, and the support body 215 is fixed to the clutch housing 12.

  In this way, at the constant speed operation position (A) in which the constant / increase speed changeover lever 153 is pushed down, the stopper acting body 213 is disposed between the stopper body 212 and the stopper receiving body 211, and the operating arm 162 Even if a rotating force acts on the stopper body 211, the stopper receiving body 211 comes into contact with the stopper body 212 via the stopper body 213, and the rotation of the operating arm 162 is restricted.

  At this time, the rotational force acting on the operating arm 162 is absorbed by the connecting tension spring 191 being pulled.

  In addition, at the speed increasing operation position (b) in which the equal / speed increasing switching lever 153 is pulled upward, the stopper acting body 213 disposed between the stopper body 212 and the stopper receiving body 211 is displaced upward, When a rotating force is applied to the operating arm 162, the operating arm 162 is rotated counterclockwise.

  In this way, by operating the equal / acceleration switching lever 153 in the vertical direction so that the equivalent / acceleration switching lever 153 is not displaced in the front / rear direction, it is arranged at the operator's feet, etc. A wide space for the operator's feet can be secured so that the acceleration switching lever 153 does not hinder the operator.

The side view of the tractor concerning the present invention. The top view of the tractor. The top view of an operation lever. Sectional side view of a mission section. The front view of a mission part. Explanatory drawing of a switching control / cancellation means (regulated state of equal / acceleration switching unit). Explanatory drawing of a switching restriction | limiting control | release means (regulation cancellation | release state of an equal speed increase switching part). The side view of an equality / speed increase switching operation part and a steering operation interlocking mechanism. The top view of an equality / speed increase switching operation part and a steering operation interlocking mechanism. FIG. 6 is a cross-sectional rear view of the equal / acceleration switching operation unit. Side surface explanatory drawing of the constant / speed increase switching operation part in a constant speed operation state. Side surface explanatory drawing of the equality / speed increase switching operation part which performed turning operation in the constant speed operation state. Side surface explanatory drawing of the equality / speed increase switching operation part in speed increase operation state. Side surface explanatory drawing of the equal / acceleration switching operation part which performed turning operation in the acceleration operation state. Side surface explanatory drawing of the equality / speed increase switching operation part as 2nd Embodiment. Front explanatory drawing of an equivalent / acceleration switching operation unit. Side surface explanatory drawing of the equality / speed increase switching operation part as 3rd Embodiment.

Explanation of symbols

A Tractor 1 Airframe frame 2 Motor part 3 Clutch housing part 4 Mission part 5 Driving part

Claims (2)

The mission unit is linked to the prime mover unit, and a pair of left and right front wheels are linked to the mission unit via the front wheel side differential unit, while a pair of left and right rear wheels are linked to each other via the rear wheel side differential unit. In the tractor,
The mission section includes a first case and a second case, and a PTO transmission mechanism for shifting the PTO shaft and a front / rear wheel transmission mechanism for shifting the front and rear wheels are provided in the first case, In the two cases, a speed change mechanism is provided to speed up the front wheels.
A tractor characterized in that the second case is detachably attached to the first case, and the equal / acceleration switching mechanism provided in the second case is detachably linked to the front / rear wheel transmission mechanism.   A front end portion of the output shaft of the front / rear wheel speed change mechanism provided in the first case and extending into the second case, and a front end portion of the output shaft of the equal / acceleration switching mechanism provided in the second case The front wheel speed increasing output is arranged on the same axis and brought into a butted state and is detachably connected via the boss portion to form a part of the equal speed increasing switching mechanism on the outer peripheral surface of the boss portion. The tractor according to claim 1, wherein a gear is formed.

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