JP2007269061A - Pto transmitting structure for tractor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To compactly compose a PTO transmitting structure which prevents inertia rotating force of a working device from being reversely transmitted to a traveling system even if the working device is attached to either one of a rear PTO shaft or a mid PTO shaft, and easily carries out power interruption in a selected PTO mode, in the PTO transmitting structure for a tractor equipped with the rear PTO shaft in a machine body rear portion and the mid PTO shaft in a machine body lower portion. <P>SOLUTION: In a PTO system receiving engine power, a PTO mode selecting mechanism 66 switching/selecting output pattern to the rear PTO shaft 12 and the mid PTO shaft 13 is arranged. A one-way clutch 46 and the PTO clutch 47 are arranged on a transmission upper side of a PTO mode selecting mechanism 66. Preferably, the one-way clutch 46 is arranged on an upper side of transmission. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a PTO transmission structure for a tractor having a rear PTO shaft and a mid PTO shaft.

  In the PTO transmission structure, when the main clutch is disengaged, the reverse driving force due to the inertial rotation of the working device driven by the rear PTO shaft or the mid PTO shaft is transmitted to the traveling transmission system to avoid the body moving. For this reason, a one-way clutch that permits the preceding rotation on the driven side is often interposed in the PTO transmission system.

For example, Patent Document 1 discloses a PTO transmission structure configured to transmit PTO power that has passed through a one-way clutch to the rear PT0 axis, the mid PTO axis, or both via PTO mode selection means. Patent Document 2 discloses a PTO transmission structure in which a one-way clutch is interposed in each of a transmission system for a rear PTO shaft and a transmission system for a mid PTO shaft.
JP-A-5-162551 (FIG. 5) Japanese Patent Laid-Open No. 7-277017

  In the conventional structure described above, by introducing the one-way clutch, it is possible to avoid the reverse driving force due to the inertial rotation of the working device driven by the rear PTO shaft or the mid PTO shaft being transmitted to the traveling transmission system and moving the airframe. In addition, it is possible to arbitrarily select driving of only the rear PTO axis, driving of only the mid PTO axis, and driving of both PTO axes. However, the power transmission in any selected PTO mode is interrupted. There was room for improvement.

  In the PTO transmission structure shown in Patent Document 1, a neutral position is provided in the operation region of the shift sleeve in the PTO mode selection means, and the PTO mode is selected and functions as a PTO clutch. When power transmission is performed again after power transmission is interrupted, it is necessary to perform a mode selection operation each time, which makes the operation cumbersome. In the middle of moving the shift sleeve to the neutral position, it may pass through the selected position of the PTO mode that has not been selected, and may drive the PTO shaft that has been paused for a moment.

  In the PTO transmission structure shown in Patent Document 2, power transmission is intermittently performed by operating the shift gear provided in each of the transmission system of the rear PTO shaft and the transmission system of the mid PTO shaft, and the PTO mode is operated by operating patterns of the two shift gears. For example, in the PTO mode in which both the rear PTO shaft and the mid PTO shaft are driven, it is necessary to operate two shift gears in order to stop driving. The operation becomes troublesome.

  The present invention has been made paying attention to such points, and the inertial rotational force of the work device is transmitted back to the traveling system regardless of whether the work device is attached to either the rear PTO shaft or the mid PTO shaft. The main purpose is to form a compact PTO transmission structure that can prevent power failure and easily perform power interruption in the selected PTO mode.

The transmission structure of the tractor according to the first invention is a tractor PTO transmission structure having a rear PTO shaft at the rear of the fuselage and a mid PTO shaft at the bottom of the fuselage,
The PTO transmission shaft that receives engine power is provided with a PTO mode selection mechanism that switches and selects the output form to the rear PTO shaft and the mid PTO shaft, and a one-way clutch and PTO on the transmission upper side of the PTO mode selection mechanism. A clutch is provided.

According to the above configuration, the one-way clutch prevents the reverse driving force due to the inertial rotation of the connected working devices from being reversely transmitted to the traveling system regardless of which PTO mode is selected by the PTO mode selection mechanism.
Even if any PTO mode is selected by the PTO mode selection mechanism, the power can be interrupted while maintaining the PTO mode by the PTO clutch.

  Therefore, according to the first invention, it is possible to prevent the inertial rotational force of the working device from being transmitted back to the traveling system regardless of whether the working device is attached to either the rear PTO shaft or the mid PTO shaft. Easy power interruption in selected PTO mode

The transmission structure of the tractor according to the second invention is the above-mentioned first invention,
The one-way clutch is provided in the transmission of the PTO clutch.

  According to the above configuration, by disengaging the PTO clutch, the subsequent inertial rotation of the PTO transmission system can be prevented from being transmitted to the one-way clutch, and the one-way clutch can be made smaller.

The transmission structure of the tractor according to the third invention is the above first or second invention,
The one-way clutch, PTO clutch, and PTO mode selection mechanism are continuously arranged on the same axis.

  According to the above configuration, the transmission members in the one-way clutch, the PTO clutch, and the PTO mode selection mechanism can be shared. For example, when the one-way clutch is a good transmission of the PTO clutch, the one-way clutch and the PTO clutch can be made compact in the axial direction by changing the driven-side transmission member of the one-way clutch to the drive-side transmission member of the PTO clutch. It becomes possible to deploy. The same applies to the PTO clutch and the PTO mode selection mechanism. By making the driven transmission member of the PTO clutch the drive side transmission member of the PTO mode selection mechanism, the PTO clutch and the PTO mode selection mechanism can be made compact in the axial direction. It becomes possible to deploy.

The transmission structure of the tractor according to the fourth invention is the above-mentioned third invention,
The PTO clutch and the PTO mode selection mechanism are mounted and supported on a common transmission shaft.

  According to the above configuration, the PTO clutch and the PTO mode selection mechanism can be pre-assembled on a common transmission shaft, which is effective for planting that improves the assembly workability of the entire transmission structure.

The transmission structure of the tractor according to the fifth invention is the above fourth invention,
The PTO clutch is configured to be hydraulically operated, and an oil passage for operating the clutch is formed inside the transmission shaft, and the oil passage and an operation valve disposed outside the case are supported by the bearing for supporting the transmission shaft. It is connected in communication via an internal oil passage on the wall.

  According to the above configuration, the operation of turning on and off the PTO clutch is light enough to operate the operation valve, and even frequent PTO clutch operations can be performed quickly and lightly without fatigue.

  FIG. 1 shows an entire side surface of a four-wheel drive agricultural tractor as an example of a work machine. This agricultural tractor has a structure in which a body body is configured by connecting a clutch housing 2 connected to a rear portion of an engine 1 and a transmission case 3 via a housing frame 4 made of sheet metal. A front axle case 7 having a steering front wheel 6 is supported in a freely rolling manner on a front frame 5 extending forward from the lower part of the engine 1, and a rear wheel 8 is mounted on the rear part of the transmission case 3. Yes.

  The transmission case 3 is configured by connecting a front case 3f, a mid case 3m, and a differential case 3d, and a speed reduction case 3e is pivotally supported via a rear wheel 8 on the left and right sides of the differential case 3d. A cylinder case 10 having a lift arm 9 is connected to an upper portion of the differential case 3d, and a three-point link mechanism 11 for connecting a work device is moved up and down by a hydraulically driven lift arm 9. The rear PTO shaft 12 projects rearward from the rear surface of the differential case 3d, and the mid PTO shaft 13 projects forward from the lower portion of the midcase 3m.

  The transmission structure is shown in FIGS. The upper part of the clutch housing 2 is equipped with a single plate dry-type main clutch 14, and a main gear transmission portion 15 and a forward / reverse switching portion 16 are incorporated in the front case 3f. A sub-gear transmission 17 is incorporated.

  The main gear transmission unit 15 is configured to shift the engine power input to the input shaft 18 in three stages and transmit it to the intermediate shaft 19, and the forward / reverse switching unit 16 corrects the transmission power of the intermediate shaft 19. It is configured to rotate or reversely transmit to the output shaft 20 so that a main shift of three forward speeds and three reverse speeds can be performed in the front case 3f.

  More specifically, a small-diameter free-wheeling gear G1 and a large-diameter free-wheeling gear G2 are mounted on the input shaft 18 of the main gear transmission unit 15, and a medium-diameter shift gear is interposed between the small-diameter and large-diameter free-wheeling gears G1 and G2. G3 is splined, and on the other hand, the intermediate shaft 19 can be engaged with the large-diameter gear G4 and the small-diameter gear G5 that are always meshed with the small-diameter idle gear G1 and the large-diameter idle gear G2, respectively, and the shift gear G3. A medium-diameter gear G6 is fixed. By shifting the shift gear G3 to the front position and engaging the boss of the small-diameter free gear G1 with a spline, the intermediate shaft 19 is driven at low speed (first speed) via the small-diameter free gear G1 and the large-diameter gear G4. Transmission is performed, and the shift gear G3 is shifted to the front and rear intermediate positions and directly meshed with the medium diameter gear G6, so that the intermediate shaft 19 is transmitted with medium speed (second speed) and the shift gear 3 is shifted to the rear position. Then, by spline engagement with the boss portion of the large-diameter idle gear G2, high-speed (third speed) power transmission is made to the intermediate shaft 19 via the large-diameter idle gear G2 and the small-diameter gear G5. .

  The output shaft 20 includes a forward transmission idle gear G8 that is always engaged with the gear G7 of the intermediate shaft 19, and a reverse transmission idle gear that is always engaged with the gear G9 of the intermediate shaft 19 via the reverse gear G10. G11 is provided, and the shift sleeve S, which is spline-fitted to the output shaft 20, is shifted and selectively engaged with the boss portion of the normal rotation transmission idle gear G8 or the reverse rotation transmission idle gear G11. Thus, the transmission power of the intermediate shaft 19 is forwardly or reversely transmitted to the output shaft 20.

  The sub-gear transmission 17 performs a three-stage shift between the transmission shaft 21 butt-connected to the output shaft 20 and the final output shaft 22 arranged in parallel thereto, and the rear end of the final output shaft 22 The differential mechanism D is driven via the bevel pinion gear Gp provided to the left and right rear wheels 8 and is differentially driven.

  More specifically, a large-diameter loosely fitted gear G12 and a small-diameter loosely fitted gear G13 are attached to the front and rear of the transmission shaft 21, and a shift gear G14 that is shifted between the small-diameter and large-diameter loosely fitted gears G12 and G13 is provided. A spline is attached. On the other hand, the final output shaft 22 has a small diameter gear G15 that always meshes with the large diameter loose fitting gear 12, a large diameter gear G16 that always meshes with the small diameter loose fitting gear G13, and a medium diameter that can be directly meshed with the shift gear G14. The gear G17 is fixed. By shifting the shift gear G14 rearward and engaging the boss portion with the boss portion of the small-diameter free-fit gear G13, transmission at the gear ratio of the small-diameter free-fit gear G13 and the large-diameter gear G16 results in "low speed". Then, by shifting the shift gear G14 to the front and rear intermediate position and directly meshing with the medium diameter gear G17, "medium speed" is brought about by transmission in the gear ratio between the shift gear G14 and the medium diameter gear G17. By shifting the shift gear G14 forward and engaging the boss portion with the boss portion of the large diameter loosely fitted gear G12, "high speed" is achieved by transmission at the gear ratio between the large diameter loosely fitted gear 12 and the small diameter gear G15. It is brought about.

  An output gear G18 for power transmission to the front wheels 6 is fixed to the front end portion of the final output shaft 22 that is shifted as described above, and the front wheel drive transmission is extended across the front case 3f and the midcase 3m. A shaft 23 is penetratingly supported, and the power extracted from the front wheel drive transmission shaft 23 is transmitted to the front axle case 7 via a front wheel transmission structure described later. A shift gear G19 is spline-fitted to the rear end of the front wheel drive transmission shaft 23. The shift gear G19 is shifted forward and meshed with the output gear G18 of the final transmission shaft 22, so that the rear wheel drive speed can be increased. A four-wheel drive state in which the front wheel drive power at the synchronized speed is extracted from the front wheel drive transmission shaft 23 is brought about, and the shift gear G19 is shifted rearward to release the occlusion with the output gear G18. And the rear two-wheel drive state by only the rear wheel 8 is brought about.

  As shown in FIG. 2, the clutch housing 2 is provided with a dry clutch chamber a that houses the main clutch 14, and a wet (oil bath lubrication) transmission chamber b that is isolated from the clutch chamber a. A main transmission shaft 25 for transmitting engine power to the input shaft 18 of the main gear transmission 15 is inserted and supported in the upper part of the chamber b, and is taken forward from the front wheel drive transmission shaft 23 in the lower part of the transmission chamber b. A front wheel transmission mechanism 26 that receives the power for driving the front wheels is provided. The front wheel transmission mechanism 26 includes an input shaft 28 concentrically connected to the front wheel drive transmission shaft 23 via an intermediate transmission shaft 27 and a transmission shaft 29 parallel thereto. The transmission shaft 29 is shifted in two steps by turning on and off the provided transmission clutch 30, and this transmission power is transmitted to the front wheel drive shaft 31 provided at the lower end of the case and taken out from the front wheel drive shaft 31 to the front. It is configured to transmit the two-stage shift power to the front axle case 7.

  The input shaft 28 is provided with a large-diameter gear G20 and a small-diameter gear G21, and the transmission shaft 29 is provided with a small-diameter idle gear G22 and a large-diameter idle gear G23 that are always meshed with the large-diameter and small-diameter gears G20 and G21. Is provided. As shown in FIG. 5, the transmission clutch 30 provided on the transmission shaft 29 is a multi-plate type between a clutch drum 32 fixed to the transmission shaft 25 and a spline boss portion 33 provided continuously with the small-diameter free-wheeling gear G22. The friction transmission portion 34 is moved forward and backward by the pressure oil supplied and discharged through the in-shaft oil passage and the built-in spring 36 by interposing the friction transmission portion 34. The clutch is engaged or disengaged by pressing or releasing the pressure contact.

  A shift member 37 externally fitted to the boss portion of the clutch drum 32 is integrated with the piston member 35 via a connecting pin 38 penetrating the clutch drum 32, and shifts as the piston member 35 moves forward and backward. The member 37 is shifted integrally.

  In a state in which the supply of pressure oil to the transmission clutch 30 is cut off, as shown in FIG. 5, the piston member 35 is displaced backward to the left in the drawing by the internal spring 36, and the transmission clutch 30 enters the "disengaged" state. At the same time, a shift member 37 integrated with the piston member 35 is engaged and connected to the large-diameter idle gear G23 on the side surface, and the power of the input shaft 28 is used for the small-diameter gear G21, the large-diameter idle gear G23, the shift member 37, and After being decelerated and transmitted to the transmission shaft 29 via the clutch drum 32, it is taken out from the front end of the transmission shaft 29 and transmitted to the front axle case 7 via the front wheel drive shaft 31. In this case, the front wheels 6 are driven at a peripheral speed equivalent to (or slightly faster than) the rear wheel peripheral speed, so that a standard four-wheel drive mode appears.

  As shown in FIG. 6, when the pressure member is supplied, the piston member 35 moves to the right in the drawing against the spring 36 and presses the friction transmission 34 to bring the transmission clutch 30 into the “on” state. The shift member 37 integrated with the piston member 35 is released from the large-diameter idle gear G23, and the power of the input shaft 28 causes the large-diameter gear G20, the small-diameter idle gear G22, the friction transmission portion 34, and the clutch drum. After being transmitted to the transmission shaft 25 through 32, the transmission is transmitted to the front axle case 7 via the front wheel drive shaft 31. In this case, the front wheels 6 are driven at a peripheral speed that is approximately twice the peripheral speed of the rear wheels, so that the front wheel acceleration drive mode appears.

  As shown in the hydraulic circuit diagram of FIG. 7, the pressure oil supply / discharge oil passage of the speed change clutch 30 is provided with a front wheel control valve V 1 that is switched in conjunction with the steering of the front wheels 6, and automatic shifting of the front wheels 6. An automatic shift selection valve V2 for selecting on / off and a check valve V3 that is switched in conjunction with the shift operation of the auxiliary gear transmission 17 are arranged in series, and the pressure from the hydraulic pump OP driven by the engine power is provided. The oil is supplied to the front wheel shift hydraulic circuit c after passing through the power steering unit 39 and the oil cooler 40.

  As shown in FIGS. 5 and 6, the front wheel control valve V <b> 1, the automatic transmission selection valve V <b> 2, and the check valve V <b> 3 are each configured as a rotary valve, and these valves V <b> 1, V <b> 2, V <b> 3 are connected to the rear part of the clutch housing 2. The single valve casing 41 is assembled. While the front wheel control valve V1 and the check valve V3 are arranged in parallel, the automatic transmission selection valve V2 positioned between them has a spool shaft center of the other valves V1, V2. It is arranged to be orthogonal to.

  The front wheel control valve V1 is mechanically linked to the steering mechanism 42 of the front wheel 6 and shuts off the oil passage when the front wheel 6 is in a straight traveling state, so that the front wheel 6 is more than a set angle (for example, 35 °) from the straight traveling position. When the vehicle is steered to the left or right, the front wheel control valve V1 is rotated to open the oil passage. The automatic transmission selection valve V2 is linked to the switching lever 43, and the oil passage is opened at the automatic transmission “ON” position and the oil passage is blocked at the automatic transmission “OFF” position. Further, the check valve V3 is linked to a sub-transmission lever 44 that switches the sub-gear transmission unit 17 that changes the traveling speed to three stages, and the sub-gear transmission unit 17 is set to “low speed” or “medium speed”. The oil passage is opened in the operated state, and the oil passage is blocked in the state in which the auxiliary gear transmission 17 is operated at “high speed”.

  Accordingly, the automatic transmission selection valve V2 is selected to the automatic transmission "on" position to open the oil passage, and the auxiliary gear transmission 17 is operated to "low speed" or "medium speed", so that the state check valve V3 is Only when the oil passage is open, the front wheel control valve V1 is switched in conjunction with the steering of the front wheel 6 or more, and pressure oil is supplied to the transmission clutch 30 to drive the front wheel 6 at an increased speed. A smooth small turn is performed. Even if the automatic transmission selection valve V2 is selected at the automatic transmission "ON" position, if the auxiliary gear transmission 17 is at "high speed", the front wheel automatically increases even if the front wheel 6 is steered beyond the set angle. Speed is never executed. Further, if the automatic transmission selection valve V2 is selected at the automatic transmission “off” position and the oil passage is closed, naturally, the front wheel automatic acceleration is not performed even by the steering of the front wheel 6.

  Next, the PTO transmission structure will be described.

  The rear end of the input shaft 18 that is passed through and supported at the upper part of the front case 3f and the transmission shaft 45 that is supported across the front case 3f and the midcase 3m are concentrically arranged and arranged at the abutting portion. The input shaft 18 and the transmission shaft 45 are interlocked and connected through a provided one-way clutch 46 and a PTO clutch 47. A relay transmission shaft 48 is concentrically connected to the rear end of the transmission shaft 45, and a small diameter gear G24 provided at the rear end portion of the relay transmission shaft 48 and a large diameter gear G25 provided on the rear PTO shaft 11 are engaged. The rear PTO shaft 11 is driven at a constant speed independently of the traveling system.

  As shown in FIGS. 3 and 8, the one-way clutch 46 is splined to the rear end portion of the input shaft 18 so as to be slidable back and forth, and is slidably biased rearward by a spring 49. And a driven-side transmission member 51 that is loosely fitted and attached to the front portion of the transmission shaft 45 so as not to be displaceable in the axial direction. The clutch member 50 and the transmission member 51 are opposed to each other at the butt-opposing end. Occlusal interlocking is performed via a joint portion 52. The inclined claw engaging portion 52 allows the driven-side transmission member 51 to rotate in the rotational direction of the input shaft 18 with respect to the clutch member 50 while the clutch member 50 is pushed and displaced forward against the spring 49. The claw inclination direction is set, and the input shaft 18 is prevented from being rotated by reverse driving from the PTO transmission system. That is, when a working device having a large rotational inertia is driven to rotate by PTO power, the input shaft 18 is driven by the rotational inertia of the working device even if the main clutch 14 is disengaged and the traveling is stopped and the transmission to the PTO transmission system is stopped. It is avoided that the vehicle is driven and the running is continued.

  The clutch member 50 and the transmission member 51 constituting the one-way clutch 46 are supported by a bearing wall 3fw provided at the rear portion of the front case 3f via a bearing 53, and the inclined claw engaging portion 52 is connected to the bearing 53. The inner fitting is supported on the inner periphery, and the occlusion and the detachment operation are performed in a state of being reliably aligned.

  The PTO clutch 47 includes a drum-shaped transmission member (hereinafter referred to as a clutch drum) 51 that is loosely supported by the front portion of the transmission shaft 45, a driven-side clutch sleeve 54 that is externally attached to the transmission shaft 45, and a clutch Friction release direction (left side in FIG. 8) of the multi-plate friction transmission portion 55 interposed between the drum 51 and the clutch sleeve 54, the piston member 56 for clutch operation fitted in the clutch drum 51, and the piston member 56 It is constituted by a spring 57 and the like that urges the spring. The transmission shaft 45 is provided with an oil passage e, and the pressure oil supplied through the oil passage e is displaced to the right in FIG. The transmission 55 is pressed and brought into a “clutch engaged” state. The pressure oil supply is released and the piston member 56 is displaced to the left in FIG. The resulting “clutch disengagement” state is provided.

  The oil passage e of the transmission shaft 45 is connected in communication with an operation valve V4 attached to the outer surface of the case via an internal oil passage f of a bearing wall 3mw provided in the middle of the front and rear of the mid case 3m. The PTO clutch 47 is turned on and off by switching operation with a PTO clutch lever 58 provided in the driving section. The operation valve V4 belongs to a hydraulic system that drives the lift arm 9.

  A PTO brake 60 is provided at a position behind the PTO clutch 47 to block inertia rotation on the lower side of the transmission in conjunction with the “clutch disengagement” operation. The PTO brake 60 includes a friction plate 61 fitted on the clutch sleeve 54 by a spline, a receiving plate 62 for receiving the friction plate 61 from the rear, and a braking plate 64 fixed to the front case 3f via a stay 63. When the PTO clutch 47 is turned off and the piston member 56 is urged and moved to the left by the spring 57, the clutch sleeve 54 moves in the same direction as the piston member 56, and the friction plate 61 The clutch sleeve 54 is braked by being sandwiched between the receiving plate 62 and the brake plate 64.

  As shown in FIG. 3, a mid PTO case 65 is connected to the lower surface of the mid case 3m so as to project and support the mid PTO shaft 13 toward the front, and PTO power is transmitted to the rear PTO shaft 12 and the mid PTO shaft. The PTO mode selection mechanism 66 that switches and selects the form to be taken out from the PTO clutch 47 is provided on the lower transmission side of the PTO clutch 47.

  The transmission system to the mid PTO shaft 13 includes a power take-off gear G26 loosely fitted on the rear portion of the transmission shaft 45 and a gear G27 integrally formed with the mid PTO shaft 13 via the relay gears G28, G29, and G30. The relay gear G28 is loosely fitted on the front wheel drive transmission shaft 23, the relay gear G29 is loosely supported on the transmission shaft 21 of the traveling system, and the relay gear G30 is a mid case. It is loosely supported by a support shaft 67 mounted on a 3 m lower wall.

  The PTO mode selection mechanism 66 shifts a shift member 68 fitted in the spline to the rear portion of the clutch sleeve 54 in the PTO clutch 47 to move back and forth, thereby transmitting power only to the rear PTO shaft 12 and the rear PTO shaft 12. And a mode for transmitting power to both the mid PTO shaft 13 and a mode for transmitting power only to the mid PTO shaft 13.

  As shown in FIG. 9, when the shift member 68 is shifted to the foremost position, the shift member 68 is engaged with only the spline portion 45 a provided on the transmission shaft 45, and the shift member 68 is engaged with the shift member 68 via the PTO clutch 47. The transmitted power is transmitted only to the rear PTO shaft 12 via the relay transmission shaft 48.

  As shown in FIG. 8, when the shift member 68 is shifted to the front and rear intermediate position, the shift member 68 is splined over the spline portion 45a of the transmission shaft 45 and the boss portion of the power take-out gear G26. The power transmitted to the shift member 68 via the clutch 47 is transmitted to the rear PTO shaft 12 via the relay transmission shaft 48 and is also transmitted to the mid PTO shaft 13.

  As shown in FIG. 10, when the shift member 68 is shifted to the rearmost position, the shift member 68 is splined only to the boss portion of the power take-out gear G26, and is connected to the shift member 68 via the PTO clutch 47. The transmitted power is transmitted to the mid PTO shaft 13 only.

  Here, the transmission mode in which only the mid PTO shaft 13 is driven by the PTO mode selection mechanism 66 is selected for the shaft coupling sleeve 69 that is externally splined across the PTO transmission shaft 45 and the relay transmission shaft 48. At this time, the rear PTO shaft 12, which has become free, is configured to be prevented from rotating together.

  The shaft connecting sleeve 69 is splined so that it can shift forward and backward, and its operating system is linked so that the shaft connecting sleeve 69 is shifted in the reverse direction in synchronization with the shift member 68 for selecting the PTO mode. ing. That is, as shown in FIGS. 11 and 12, an operation shaft 70 provided with an eccentric operation pin 70a engaged with the shift member 68, and an operation shaft 71 provided with an operation arm 71a engaged with the shaft connection sleeve 69. Is inserted through the side wall of the midcase 3m, and an operation pin 70b provided at the outer end of the operation shaft 70 and a PTO mode selection lever 72 arranged to swing back and forth around the fulcrum p are connected via a rod 73. The linkage lever 71b extended from the outer end portion of the operation shaft 71 and the operation pin 70b are linked to each other through a long hole, and the shift member 68 and the shaft are pivoted by a forward / backward swing operation of the PTO mode selection lever 72. The connecting sleeve 69 is shifted in the opposite direction.

  Therefore, the transmission mode in which the shift member 68 is shifted to the foremost position and the front-rear intermediate position and only the rear PTO shaft 12 is driven, or the transmission mode in which both the rear PTO shaft 12 and the mid PTO shaft 13 are driven is selected. In this state, the shaft coupling sleeve 69 is at the rearmost position or the front-rear intermediate position of the shift range, and the shaft coupling sleeve 69 at this time functions as a mere shaft joint. As shown in FIG. 10, when the shift member 68 is shifted to the rearmost position and the transmission mode in which only the mid PTO shaft 13 is driven is selected, the shaft connecting sleeve 69 is interlocked with the rearward shift of the shift member 68. Is moved forward, and the front end engaging claw 69a of the shaft coupling sleeve 69 is engaged from the rear with the rib 74 formed on the rear surface of the bearing wall 3mw in the mid case 3m, so that the PTO system of the PTO system which is in a freely rotating state is brought about. The rotation of the transmission shaft 45 and the relay transmission shaft 48 is prevented.

  [Another Example]

  (1) As shown in FIGS. 13 and 14, instead of the front case 3 f that performs forward / rearward multi-stage shifting, a hydrostatic pump equipped with a variable displacement hydraulic pump P and a constant displacement hydraulic motor M is provided. A step transmission (HST) may be connected to the mid case 3m to implement a continuously variable forward / reverse shift. In this case, the one-way clutch 46 is provided at the abutting portion between the rear penetrating end and the PTO transmission shaft 45 through the input shaft 18 as a pump shaft.

  (2) The one-way clutch 46 may be a roller type in addition to the meshing type described above.

  (3) The PTO clutch 47 may be a pawl clutch that is shifted in an artificial manner or a hydraulic manner.

  (4) It is also possible to implement the PTO clutch 47 in a form in which the one-way clutch 46 is well transmitted.

  (5) The PTO mode selection mechanism 66 may be configured as a two-mode switching type that transmits only to either the rear PTO shaft 12 or the mid PTO shaft 13.

Overall side view of tractor Vertical side view of front wheel transmission structure Longitudinal side view showing the entire transmission structure Schematic showing the gear train of the entire transmission structure Longitudinal side view of front wheel speed change mechanism in standard four-wheel drive mode Longitudinal side view of front wheel speed change mechanism in front wheel acceleration drive mode Hydraulic circuit diagram Vertical side view of PTO transmission structure Vertical side view of PTO transmission structure Vertical side view of PTO transmission structure Side view showing operation structure of PTO mode selection mechanism Front view showing the operation structure of the PTO mode selection mechanism Vertical side view showing the entire transmission structure of another embodiment Schematic showing the gear train of the entire transmission structure of another embodiment

Explanation of symbols

12 Rear PTO shaft 13 Mid PTO shaft 45 Transmission shaft 46 One-way clutch 47 PTO clutch 66 PTO mode selection mechanism 3mw Bearing wall e Oil passage f Internal oil passage V4 Operation valve

Claims (5)

A tractor PTO transmission structure with a rear PTO shaft at the rear of the fuselage and a mid PTO shaft at the bottom of the fuselage,
The PTO transmission shaft that receives engine power is provided with a PTO mode selection mechanism that switches and selects the output form to the rear PTO shaft and the mid PTO shaft, and a one-way clutch and PTO on the transmission upper side of the PTO mode selection mechanism. PTO transmission structure of tractor characterized by having a clutch   The tractor PTO transmission structure according to claim 1, wherein the one-way clutch is provided in a good transmission of the PTO clutch.   The tractor PTO transmission structure according to claim 1, wherein the one-way clutch, the PTO clutch, and the PTO mode selection mechanism are continuously arranged on the same axis.   The tractor PTO transmission structure according to claim 3, wherein the PTO clutch and the PTO mode selection mechanism are mounted and supported on a common transmission shaft.   The PTO clutch is configured to be hydraulically operated, and an oil passage for operating the clutch is formed inside the transmission shaft, and the oil passage and an operation valve disposed outside the case are supported by the bearing for supporting the transmission shaft. The tractor PTO transmission structure according to claim 4, wherein the tractor PTO transmission structure is connected through a wall internal oil passage.

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