JP2529725Y2 - Front wheel speed-up operation device for agricultural tractor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION INDUSTRIAL APPLICATION FIELD The present invention relates to a front wheel speed-up operation device for an agricultural tractor that speeds up front wheels in order to make a sharp turn at a large turning.

Conventional technology Conventionally, in a front wheel speed increasing device in an agricultural tractor,
A system capable of switching from the front wheel acceleration standby position to the front wheel acceleration position is already known as described in Japanese Utility Model Laid-Open No. 58-171724.

In the above-described conventional front wheel speed-up operation device, the switching from the front wheel speed-up standby position to the front wheel speed-up position can be performed by itself, but the front wheel non-drive position, the front wheel speed-up position, or the front wheel speed-up position can be changed. A separate device for switching to the high speed position was required, and the overall configuration was extremely complicated.

In view of the problems of the prior art, the present invention has a single drive state switch that switches to the front wheel non-drive position, the standard position, the front wheel acceleration standby position, and the front wheel acceleration position to switch the front wheel drive state. The member is provided to be reciprocally movable, and the driving state switching member is interlockedly connected to the manual operation tool, and by operating the manual operation tool, the front wheel non-drive position, the standard position, and the front wheel acceleration standby position are respectively set. The front wheels can be switched sequentially, and the front wheels can be automatically speeded up simply by switching the manual operation tool to the front wheel acceleration standby position and turning the switching body as it is. If the solidification phenomenon of the connecting device due to the coating film, dust, or load lock occurs by operating in the direction opposite to the operation direction opposite to the operation direction to the position, and smoothing the switching operation Operation It is an object to provide a front-wheel acceleration operating position in agricultural tractors les can be reliably prevented.

Means for Solving the Problems According to the present invention, in order to interpose a front wheel transmission N in a front wheel transmission system in a transmission case, the drive to the front wheels is rejected so that the rotation of the front wheels is idle. Driving position, standard position for transmitting driving force to the front wheels in a constant speed driving state in which the front wheels are driven at the same speed as the rear wheels, and front wheel acceleration for increasing the front wheels with respect to the rear wheels in the constant speed driving state In the standby position, the front wheel acceleration standby position, the front wheels are moved to the respective front wheel acceleration positions in which the front wheels are driven in an increased speed state relative to the rear wheels in conjunction with the turning operation of the aircraft, and the front wheel drive state is switched. One drive state switching member
A manual operation tool 71 rotatably supported by a transmission case that is provided so as to be capable of reciprocatingly moving, and that sequentially switches the drive state switching member 35 to the front wheel non-drive position, the standard position, and the front wheel acceleration standby position. When the operation mechanism S from the manual operation tool 71 to the drive state switching member 35 is connected to the transmission case, a rotatable cylindrical rotary operation body 62 that is pivotally supported by the transmission case.
And the rotary operation body 62 is connected to the artificial operation tool 71 side, and a rotatable shaft-like rotary driven body 61 that is protruded through the transmission case coaxially with the rotation operation body 62 is provided. The rotating operation body 62 and the rotating driven body 61 are provided with engaging portions 66, 68 which mesh with each other with a predetermined play gap 70 in the rotating direction, and the rotating driven body is provided between the engaging portions 66, 68. A resilient pressure mechanism 69 for urging the rotation of the rotation driven member 61 in one direction is provided. On the other hand, a protruding portion of the rotation driven member 61 facing the transmission case is interlocked to the drive state switching member 35 via a connection mechanism P. , Artificial operation tool 71
The drive state switching member 35 and the rotating driven body 61 are moved relative to the front wheels with respect to the rear wheels in a state in which the front wheel is positioned at the front wheel acceleration standby position, and in conjunction with the turning operation of the aircraft at or above a preset front wheel turning angle. The manual operation device is configured such that the manual operation device 71 and the rotary operating body 62 can be automatically switched to be preferentially operated while maintaining the front wheel acceleration standby position at the front wheel speed increase standby position at the front wheel speed increase position where the speed increases. 71 is penetrated by a lever guide 82 provided on the body formed by a plurality of holes for guiding and holding at each of the above positions and a groove communicating therewith, and is provided to be freely movable up and down. On the opposite side of the operation direction of the tool 71 from the front wheel non-drive position to the standard position, a flexible portion having a length that allows operation against the urging direction of the resilient mechanism 69 is formed.

The front wheel non-drive position, standard position,
When switching to any of the front wheel acceleration standby positions,
The rotating non-moving body 61 interlockingly connected to the driving state switching member 35 via the linking mechanism P and the driving state switching member 35 via the linking mechanism P is integrally rotated, and the driving state switching member 35 of the front wheel transmission N is driven by the artificial operating tool 71 A front wheel non-drive position where the rotation of the front wheels is idle according to the operation position, a standard position where the front wheels transmit the driving force to the front wheels in a constant speed drive state where the front wheels are driven at the same speed as the rear wheels, or a rear wheel On the other hand, it is converted to a front wheel acceleration standby position at which front wheels can be accelerated. Then, at this front wheel acceleration standby position, when the body is rotated more than the preset front wheel turning angle, the front wheel transmission N is switched to the front wheel acceleration position to reduce the rear wheel speed. The speed of the front wheels is increased to the front wheel speed-up drive state, and the aircraft turns sharply. In the meantime, the range of the rotational play constituted by a predetermined play gap 70 provided between the rotary operated body 61 on the side of the artificial operation tool 71 and the rotating driven body 61 against the resilient mechanism 69 via the linkage mechanism P Therefore, the artificial operation tool 71 maintains the set position at which the vehicle enters the front wheel acceleration standby position in the front wheel drive state.

The operating mechanism S for switching the driving state switching member 35 to each of the front wheel non-driving position, the standard position, and the front wheel acceleration standby position includes a plurality of holes for guiding and holding the artificial operating tool 71 at each of the positions. It is penetrated through a lever guide 82 provided on the body formed with a groove communicating therewith so as to be movable up and down, and the lever guide 82 has an operation direction from the front wheel non-drive position of the switching lever 71 to the standard position. On the opposite side, there is a flexible part with a length that allows operation against the biasing direction of the repression mechanism 69, so that the rotating operation body and the rotating driven body are unpredictable due to paint film or dust, and due to load lock. Even if solidification occurs, the above operation of the switching lever cancels that state.

An embodiment of the present invention will be described with reference to an embodiment shown in the drawings. FIG. 1 exemplifies a mechanism of a traveling transmission system of an agricultural tractor, where 1 is a main transmission unit, 2 is a forward / reverse transmission unit, and 3,4.
Reference numeral denotes a subtransmission unit, and power is transmitted from the subtransmission unit 4 to the rear wheel shaft 5 via a rear wheel differential device 6.
Reference numeral 7 denotes a differential pinion shaft of the rear wheel differential 6, and reference numeral 8 denotes an engine.

A front wheel power take-out gear 9 is spline-fitted to the differential pinion shaft 7, and a counter gear 11 loosely fitted to a reduction shaft 10 of the auxiliary transmission portion 4 meshes with a passive gear 13 of a differential device 12, and The device 12 and the front wheel differential 14 are linked via a front wheel drive shaft 15. The differential device 12 is a differential case 18 described later.
And a drive shaft switching member (sleeve) 35 slidably disposed on the cylindrical portion 20 of the differential case 18 having a brake shaft 32 in which one side gear 31 in the differential case 18 is spline-fitted. By reciprocating each, the differential case 18 and the side gear 31 rotate integrally and the front wheel is driven at the same speed as the rear wheel. In the front wheel non-drive position in which the drive to the front wheels is cut off and the rotation of the front wheels is idled, and in the standard position where the differential case 18 and the side gear 31 rotate integrally and the front wheels are driven at the same speed as the rear wheels, By locking the rotation of the brake shaft 32 and the front wheel acceleration standby position enabling the front wheel to increase the speed of the wheel, the front wheel drive shaft 15 spline-fitted to the other side gear 30 in the differential case 18 is accelerated. Front wheels increase with front wheels speeding up with respect to rear wheels The front wheel drive state is switched so as to be in the high speed state. The driving state switching mechanism M is configured by a manual operation tool (switching lever) 71, which will be described later, that switches the driving state switching member 35 to each of the above positions. The drive state switching mechanism M and the differential device
The front wheel transmission N is constituted by 12, and is interposed in the front wheel transmission system in the transmission case.

16 is a front wheel shaft, 17 is a rear transmission case, and 17 'is a front transmission case, each of which is filled with lubricating oil.

The differential device 12 is configured as shown in FIGS. That is, the passive gear 13 of the differential device 12 is fixed to the differential case 18 with a plurality of bolts 19, and the differential case
The cylindrical portion 20 extending to the front and rear of the cover 18 is mounted on the front of the rear transmission case 17 via bearings 21 and 22.
A pinion 28 and a pinion 29 are attached to both ends of a shaft 27 which is supported by a support 25 attached to the rear wall 23 and fixed to the differential case 18 by pins 26.
0, 31 mesh from the front and rear, the front wheel drive shaft 15 is spline-fitted to the front side gear 30, and the rear side gear
A brake shaft 32 is spline-fitted to 31.

Balls 34 are fitted in a plurality of holes 33 formed in the cylindrical portion 20 of the differential case 18 constituting the differential device 12,
The plurality of balls 34 are pressed by the tapered portion 36 of the sleeve 35 fitted on the cylindrical portion 20 so as not to fall off. The brake shaft 32 is provided with a conical recess 37 corresponding to the hole 33 of the cylindrical portion 20. By moving the sleeve 35 forward, the ball 34 is pressed by the taper portion 36 and the ball 34 is pressed into the conical recess 37. Then, the cylindrical portion 20 and the brake shaft 32 are configured to rotate integrally. The brake shaft 32 is provided with a brake device 38, 39 is a piston thereof, and the piston 39 is a cylinder portion formed in the support 25.
40 is slidably provided. Reference numeral 41 denotes a mating plate, which is attached to the sleeve 42, and a return spring 43 is interposed between the sleeve 42 and the piston 39. Reference numeral 44 denotes a desk plate. The desk plate 44 is attached to a spline boss 45 that is spline-fitted to the brake shaft 32 so as to rotate integrally with the desk plate 44. The desk plate 44 is interposed between the mating plates 41. .

On the other hand, reference numeral 46 denotes a shift rail.
The cover 23 and the support hole 47 on the support 25 side are circular. A mounting hole 49 forming an oil passage 48 near the rear portion of the support hole 47 is connected to a hydraulic circuit described later via a joint 50 and a pipe 51, and is connected to the front portion of the support hole 47 and the cylinder 40 of the brake device 38. The space is communicated by an oil passage 52. The inner diameter of the rear portion of the support hole 47 is larger than the outer diameter of the shift rail 46, and the operating oil is allowed to flow freely, and at a position corresponding to the oil passages 48 and 52 of the shift rail 46. Are formed with cutout surfaces 53, 53 extending slightly inward from the inner end surface of the support 25, and a portion behind the cutout surfaces 53, 53 forms a spool portion 54. And spool part 5
4. The notched surfaces 53, 53 and the oil passages 48, 52 constitute a control valve V that automatically operates by hydraulic pressure. The tip of the fork 55 is fitted to the circumferential groove of the sleeve 35 on the shift rail 46. At the base of the fork 55, a concave groove 57 for letting out hydraulic oil is formed. 58 is a spacer,
The spacer 58 regulates the forward movement position of the fork 55.

By the way, the connecting mechanism P for operating the fork 55 fitted in the drive state switching member (sleeve) 35 is configured as shown in FIGS. That is, in the portion constituting the linking mechanism P, the distal end of the arm 60 is fitted into the receiving groove 59 at the base of the fork 55, and the base is spline-fitted to the rotating shaft 61 on the driven body side. The cylinder 62 on the operation side into which the driving shaft 61 is inserted is inserted into a hole in the side wall of the rear transmission case 17, and the holding plate 64 fitted in the circumferential groove 63 is bolted 65.
It is fixed by tightening. An uneven claw 66 is formed on an outer end surface of the cylinder body 62 on the operation body side, and an uneven claw 68 is formed on an end surface of a boss 67 fixed to an end of the rotation shaft 61. , 68, one recessed part is made deeper than the other recessed part.
The concave and convex claws 66 and the concave and convex claws 68 are engaged with each other by engaging the bent portions at both ends of the joint 69 with the rotational urging force. The concave portions of the concave and convex claws 66 and 68 are wider than the convex portions. A predetermined play gap 70 is formed which can rotate.

On the other hand, reference numeral 71 denotes a switching lever constituting the operation mechanism S, and the switching lever 71 is freely rotatable up and down around a fulcrum 72 on the rear transmission case 17 side,
The lever is operated to switch between a front wheel non-drive position A, a front wheel drive position B, and a front wheel acceleration standby position C. An arm 73 is welded to the cylinder 62, and the arm 73 and a base arm 74 of the switching lever 71 are connected by a rod 75. An operating unit arm 76 is removably inserted into and removed from a receiving end 74a of the base arm 74 of the switching lever 71 to form a series of switching levers 71, and a grip portion 77 is provided at the distal end of the operating unit arm 76. A large diameter portion 78 is formed at the intermediate portion. Further, a compression spring 79 is interposed between the large diameter portion 78 and the receiving member 74a, and is urged in a direction in which the operation portion arm 76 projects with respect to the base arm 74.
The length of the rod 75 can be adjusted by nuts 80 and 81.

82 is a lever guide, and this lever guide 82
The switching lever 71 is provided at a position corresponding to the large-diameter portion 78 with the operating portion arm 76 protruding. As shown in FIG. 7, the lever guide 82 has three round holes 83, 84, 85 in three stages in the vertical direction.
Grooves 86 and 87 connecting 84 and 85 are formed, and the upper round hole 8
3 is formed with a long upper part, and has round holes 83, 84, 8
Reference numeral 5 denotes a portion through which the large-diameter portion 78 of the operation portion arm 76 passes, and grooves 86 and 87 through which the large-diameter portion 78 does not pass and through which the operation arm 76 can pass. The length of the portion 83a elongated above the upper round hole 83 corresponds to the play gap 70 existing between the concave and convex claws 66, 68. Reference numeral 88 denotes a mounting hole for the lever guide 82.

FIG. 8 shows a hydraulic control circuit. In this hydraulic control circuit, a hydraulic pump 90 driven by the power of the engine 8 sucks the oil in the rear transmission case 17 and is operated by a relief valve 91, a pipe 92, a priority valve (separation valve with sequence) 93 and a pipe 94. The pressure is fed to the main circuit, which is distributed to a work machine horizontal control cylinder 96 that constantly controls the posture and height of the work machine by an externally mounted valve 95, and a work machine lift cylinder 97. The priority valve 93 distributes hydraulic oil to the pipe 51 via an electromagnetic valve 98 built therein, and is attached to the upper side of the rear transmission case 17. In the figure, 99 is the rear wheel of the agricultural tractor, 100 is the front wheel, and 101 is the steering wheel.

 Next, the operation of the present invention will be described.

When the agricultural tractor travels by driving only the rear wheel 99, the switching lever 71 of the operating mechanism S is set to the position A (front wheel non-drive position) shown in FIG. 6 is raised to the position shown by the solid line. However, since the concave and convex claws 66 and 68 are engaged with the ridges engaged by the rotational urging action of the resilient mechanism 69, the cylindrical body 62, the rotating shaft 61,
The arm 60, the fork 55, and the shift rail 46 are at the position shown by the solid line A in FIG. 6, the sleeve 35 is at the position shown in FIG.
The rotation of 20 is not transmitted to the brake shaft 32, and the front wheel 100 is kept in a non-drive state. In this state, the spool 54 formed at the rear end of the shift rail 46 is at the position shown in FIG.

When the front wheel 100 is also driven at the time of work, the switch lever 71 is held down by the grip portion 77 and is pushed down to be aligned with the second round hole 84 from the top, and the pushing is released. Is set at the B position (front wheel drive position), the arm 73 rotates downward through the rod 75, and the concave and convex claws 66 integrated with the cylindrical body 62 push the concave and convex claws 68 and rotate by a predetermined angle.
This allows the arm 60 to be moved
Is rotated in the same direction as the rotation direction of the cylindrical body 62, and the fork 55
The shift rail 46 is moved to the position B in FIG. 6 and the state shown in FIG. 10-1 via the shaft, and the ball 34 is pushed into the conical recess 37 at the front of the sleeve 35, so that the brake shaft 32 and the differential case 18 are connected. The wheels rotate together, and the front wheels 100 are driven at a standard speed.

Further, when turning the airframe or when starting the work, if the switching lever 71 is operated to set it at the position C (front wheel acceleration standby position) in FIG. Further, the concave / convex pawl 66 pushes the concave / convex pawl 68 to rotate it by a predetermined angle, whereby the arm 60 pivots and the shift rail 46 is moved via the fork 55 to the position C in FIG. The state moves to the state shown in the figure, and the spool portion 54 closes the small-diameter portion of the support hole 47 serving as a communication hole for the oil passage 52 to the cylinder portion 40 of the brake device 38. In this state,
Ball at the rear of sleeve 35 moved with fork 55
34 is still pushed into the conical recess 37, and the front wheel drive state in which the brake shaft 32 and the differential case 18 rotate integrally is maintained. Therefore, the cylinder for lifting and lowering the work equipment
After operating the 97 and raising the implement, the steering handle 10
When a detector (not shown) detects that the steering angle of the front wheel 100 has become greater than or equal to a predetermined value, the electromagnetic wave of the priority valve 93 inserted into the hydraulic circuit shown in FIG. When the valve 98 is turned on, the hydraulic oil pumped by the hydraulic pump 90 passes through the support hole through the pipe 51 and the joint 50.
47, and pushes out the shift rail 46 to the position D where the base of the fork 55 contacts the spacer 58 (No. 10-3).
Figure). In this process, the rear tapered portion 36 of the sleeve 35 is used.
Only prevents the ball 34 from slipping out, and the differential case 18 and the brake shaft 32 are not interlocked.Hydraulic oil flows into the cylinder 40 of the brake device 38 via the oil passage 52, and the piston 39 As the mating plate 41 of the brake device 38 comes into pressure contact with the desk plate 44, the brake shaft 32 stops, and the front wheel drive shaft 15 is driven at twice the speed. In this state, the arm 60 follows the fork 55 and rotates to the position D in FIG. 6, and the concave and convex claws 68 of the boss 67 fixed to the end of the rotating shaft 61 rotate within the range of the play gap 70. do it,
The cylinder 62 and its linking mechanism P are stopped.

When the steering handle 101 is turned back and the detector (not shown) is turned off after the turning of the body is completed, the solenoid valve 98 of the priority valve 93 is switched to the state shown in FIG. Instead, the pipe 51 communicates with the rear transmission case 17, and the piston 39 is returned by the return spring 43, so that the hydraulic oil of the cylinder section 40 flows out of the oil passage 52 to the pipe 51 via the support hole 47 and the joint 50, The shift rail 46 is moved backward (11th-
Returning to the position shown in FIG. 2), the hydraulic oil flows directly from the inner end of the support hole 47 into the rear transmission case 17 through the gap formed by the cutout surfaces 53, 53, and then sets the switching lever 71 to the A position. Then, the base of the fork 55 comes into contact with the inner end surface of the support 25, and the remaining hydraulic oil flows back into the rear transmission case 17 from the groove 57. When the vehicle is traveling straight with the switching lever 71 set to the C position, the detector (not shown) is turned off even if the turning angle of the front wheel 100 is greater than a set value. So it does not turn at double speed.

Incidentally, the lever guide 82 of the operating mechanism S has a round hole 83 extending upward so that the switching lever 71 can be further operated from the front wheel non-drive position A in a direction against the rotational bias of the repression mechanism 69. Since the divided portion 83a is formed, the rotating shaft 6
1 and between the uneven claws 66, 68 of the cylindrical body 62, etc., due to paint film and dust,
Further, even if the solidification occurs unexpectedly due to the load lock, the state can be easily eliminated by operating the switching lever 71 from the position A to the position A 'further above.

Effects of the Invention As described above, the present invention provides a front wheel transmission system in a transmission case in which a front wheel transmission N is interposed. A non-drive position, a standard position for transmitting a driving force to the front wheels in a constant-speed drive state in which the front wheels are driven at the same speed as the rear wheels, and a front-wheel increase enabling the front wheels to increase in speed with respect to the rear wheels in the constant-speed drive state. Quick standby position,
A single drive for switching the front wheel drive state by moving to the front wheel acceleration position where the front wheels are driven to the rear wheel in an accelerated state relative to the rear wheels in conjunction with the turning operation of the aircraft at the front wheel acceleration standby position. A state switching member 35 is provided so as to be reciprocally movable, and the driving state switching member 35 is rotatably supported on a transmission case side which sequentially switches the front wheel non-drive position, the standard position, and the front wheel acceleration standby position. In order to interlock and connect to the artificial operation tool 71, a rotatable cylindrical rotary operation body 62 that is pivotally supported through the transmission case side during the operation mechanism S from the artificial operation tool 71 to the drive state switching member 35. The rotation operation body 62 is connected to the artificial operation tool 71 side, and a rotatable shaft-like rotation driven body 61 is provided concentrically with the rotation operation body 62 and penetrates into the transmission case. A predetermined play gap 70 is provided between the rotation operating body 62 and the rotation driven body 61 in the rotation direction. Provided with an engagement portion 66, 68 mesh with each other have, rotating the body between the engagement portion 66, 68
A resilient pressure mechanism 69 for urging the rotation of the rotation driven member 61 in one direction is provided. On the other hand, a protruding portion of the rotation driven member 61 facing the transmission case is interlocked to the drive state switching member 35 via a connection mechanism P. In a state where the artificial operation tool 71 is located at the front wheel acceleration standby position, and in conjunction with the turning operation of the aircraft at a predetermined turning angle of the front wheel or more, the drive state switching member 35 and the rotating driven body 61 are moved. The artificial operation device 71 and the rotary operation body 62 are configured to be preferentially operated and automatically switched to the front wheel acceleration position where the front wheel is accelerated with respect to the rear wheel, while maintaining the manual operation tool 71 and the rotary operation body 62 at the front wheel acceleration standby position. At the same time, the manipulator 71 is penetrated by a lever guide 82 provided on the body formed by a plurality of holes for guiding and holding the artificial operation tool 71 at each of the above-described positions and a groove communicating therewith, and is provided so as to be vertically movable. From the front wheel non-drive position of the manual operation device 71 to the standard position On the side opposite to the operation direction of the front end, a flexible portion having a length that allows operation against the biasing direction of the resilient mechanism 69 is configured, so that the front wheel non-drive position, the standard position, and the front wheel acceleration standby position And a single driving state switching member for switching to the front wheel acceleration position is reciprocated in conjunction with the operation of the manual operation tool, thereby easily switching from the front wheel non-drive position to the front wheel acceleration standby position. By switching the artificial operation device to the front wheel acceleration standby position and turning the fuselage as it is, the front wheel can be automatically set to the front wheel acceleration position, and the artificial operation device can be set to the front wheel non-drive position. By operating in the direction opposite to the oppressing mechanism opposite to the operation direction to the standard position, even if the solidification phenomenon of the connecting device due to paint film, dust, or load lock occurs unexpectedly, this can be resolved. , To facilitate switching operation Thus, an operation delay can be reliably prevented.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS The drawings show an embodiment of the present invention, FIG. 1 is a configuration diagram showing a configuration of a traveling power transmission system, FIG. 2 is an exploded sectional view of a front wheel drive unit, and FIG. FIG. 4 is a partial cross-sectional view of the same, FIG. 5 is a side view of the operation mechanism, and FIG.
Fig. 7 is a partial sectional view of the same, Fig. 7 is a front view of a lever guide, Fig. 8 is a circuit diagram of a hydraulic system, Fig. 9 is an overall side view of the agricultural tractor, Figs. 10-1 and 10-2. FIG. 10 and FIG. 10-3 are cross-sectional views for explaining the operation of the control valve. In the figure, A is a front wheel non-drive position, B is a front wheel drive position, C is a front wheel acceleration standby position, D is a front wheel acceleration position, N is a front wheel transmission, M is a drive state switching mechanism, P is a linking mechanism, Is an operating mechanism, 12 is a differential device, 35 is a drive state switching member (sleeve), 61 is a rotating driven body, 62 is a rotating operating body, 69 is a resilient mechanism, 70 is a predetermined play gap, 71 is an artificial operating tool ( (Switch lever), 82 is a lever guide, 100 is a front wheel.

Claims (1)

(57) [Scope of request for utility model registration] 1. A front wheel non-driving position in which a drive to the front wheels is cut off and a rotation of the front wheels is idled in order to interpose a front wheel transmission N in a front wheel transmission system in a transmission case. A standard position for transmitting the driving force to the front wheels in a constant-speed driving state driven at the same speed as the wheels, a front-wheel acceleration standby position for enabling the front wheels to increase in speed with respect to the rear wheels in the constant-speed driving state, and a front-wheel increase. A single drive state switching member for switching the front wheel drive state by moving to each of the front wheel speed increase positions where the front wheels are driven in an increased speed state relative to the rear wheels in conjunction with the rotation operation of the aircraft at the speed standby position.
A manual operation tool 71 rotatably supported by a transmission case that is provided so as to be capable of reciprocatingly moving, and that sequentially switches the drive state switching member 35 to the front wheel non-drive position, the standard position, and the front wheel acceleration standby position. When the operation mechanism S from the manual operation tool 71 to the drive state switching member 35 is connected to the transmission case side, a rotatable cylindrical rotary operation body is supported.
62, the rotary operation body 62 is connected to the artificial operation tool 71 side, and a rotatable shaft-like rotary driven body 61 that is projected coaxially with the rotary operation body 62 into the transmission case. Provided,
The rotary operating body 62 and the rotary driven body 61 are provided with engaging portions 66 and 68 that mesh with each other with a predetermined play gap 70 in the rotational direction, and the rotary driven body 61 is provided between the engaging portions 66 and 68. A resilient pressure mechanism 69 for urging the rotation in one direction, and the other
The protruding portion facing the inside of the transmission case is interlockingly connected to the drive state switching member 35 via a connecting mechanism P to
The drive state switching member 35 and the rotary driven body 61 are moved relative to the rear wheels in a state where the front wheel 71 is positioned at the front wheel acceleration standby position, and interlocked with the turning operation of the aircraft at a predetermined turning angle of the front wheels or more. At the front wheel speed-up position where the front wheel speeds up, the artificial operation tool 71 and the rotary operation body 62 are configured to be preferentially operated while being kept at the front wheel speed-up standby position and can be automatically switched, and the manual operation is performed. The tool 71 is penetrated by a lever guide 82 provided on the body formed by a plurality of holes for guiding and holding the tool at each of the above positions and a groove communicating therewith, and is provided so as to be vertically movable. On the opposite side of the operation direction of the operating tool 71 from the front wheel non-drive position to the standard position, a flexible portion having a length that allows operation against the urging direction of the resilient mechanism 69 is formed. Front wheel speed-up operation device for agricultural tractors.