Working vehicle

Abstract

To provide a working vehicle capable of performing a shift operation of a PTO-based power transmitting system by electronic control using a switch.SOLUTION: A working vehicle has a PTO shaft to extract power of a prime mover to an outside, and comprises: a first PTO transmission shaft to which power from the prime mover is transmitted; a second PTO transmission shaft that transmits power to the PTO shaft; a first gear train and a second gear train, which transmit power from the first PTO transmission shaft to the second PTO transmission shaft; and a synchromesh type switching mechanism that switches power transmission from the first PTO transmission shaft to the second PTO transmission shaft between a first mode where the power transmission is performed via the first gear train and a second mode where the power transmission is performed via the second gear train.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a work vehicle.

Background Art

[0002] Conventionally, a work vehicle disclosed in Patent Document 1 is known.

[0003] The work vehicle disclosed in Patent Document 1 includes a PTO shaft for taking out the power of the prime mover to the outside, and a PTO system power transmission system (PTO transmission direction downstream side transmission structure 350) for transmitting the power of the prime mover to the PTO shaft. The PTO system power transmission system has a PTO speed change mechanism (PTO multi-stage speed change mechanism 370).

[0004] The PTO speed change mechanism includes a first gear train and a second gear train that transmit power from a first PTO transmission shaft to which the power of the prime mover is transmitted to a second PTO transmission shaft that transmits power to the PTO shaft, and the power transmission from the first PTO transmission shaft to the second PTO transmission shaft is configured to be switched to either a first state performed via the first gear train or a second state performed via the second gear train.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, conventionally, there has been a desire to perform the speed change operation of the PTO system power transmission system by electronic control using a switch.

[0007] In view of the above problems, an object of the present invention is to provide a work vehicle capable of performing a speed change operation of a PTO system power transmission system by electronic control using a switch.

Means for Solving the Problems

[0008] A work vehicle according to one aspect of the present invention is a work vehicle provided with a PTO shaft for extracting the power of a prime mover to the outside, and includes a first PTO transmission shaft to which the power from the prime mover is transmitted, a second PTO transmission shaft that transmits power to the PTO shaft, a first gear train and a second gear train that transmit power from the first PTO transmission shaft to the second PTO transmission shaft, and a synchromesh type switching mechanism that switches the power transmission from the first PTO transmission shaft to the second PTO transmission shaft to either a first state that is performed via the first gear train or a second state that is performed via the second gear train.

[0009] A shift fork that performs a switching operation of the switching mechanism so as to switch to either the first state or the second state, an operating mechanism that operates the shift fork so as to perform the switching operation of the switching mechanism by the shift fork, a switch that outputs an operation signal for operating the operating mechanism, and a control device that outputs a control signal for operating the operating mechanism when an operation signal from the switch is acquired may be provided.

[0010] The first gear train transmits power to the PTO shaft when the rotational speed of the prime mover is a first rotational speed, and the second gear train transmits power to the PTO shaft when the rotational speed of the prime mover is a second rotational speed different from the first rotational speed. The gear ratios of the first gear train and the second gear train may be set to gear ratios such that the rotational speed of the PTO shaft is substantially equal whether the rotational speed of the prime mover is the first rotational speed or the second rotational speed.

[0011] When the control device acquires an operation signal from the switch, the control device may switch the rotational speed of the prime mover to either the first rotational speed or the second rotational speed, and output a control signal to the operating mechanism so as to switch to either the first state or the second state corresponding to the first rotational speed and the second rotational speed.

[0012] The operating mechanism may include a shift cylinder that moves the shift fork to perform the switching operation, and a shift valve that is controlled by the control signal to operate the shift cylinder.

[0013] The shift cylinder includes a cylinder body and a piston rod that protrudes and retracts with respect to the cylinder body, and the shift fork may have a connecting portion that is connected to the piston rod via a connecting pin. It may have a connecting portion connected via a connecting pin.

[0014] It is provided with a detection sensor that detects the position of the shift fork. The shift fork is movable between a first operation position and a second operation position, and has a detection portion for the detection sensor to detect that the shift fork is in the first operation position or the second operation position. The first operation position is a position where the switching mechanism switches the power transmission from the first PTO transmission shaft to the second PTO transmission shaft to the first state, and the second operation position may be a position where the switching mechanism switches the power transmission from the first PTO transmission shaft to the second PTO transmission shaft to the second state.

Advantages of the Invention

[0015] According to the above work vehicle, in order to switch the power transmission from the first PTO transmission shaft to the second PTO transmission shaft to either the first state via the first gear train or the second state via the second gear train, by configuring it to be performed by a synchromesh type switching mechanism, the shift operation of the PTO system power transmission system can be configured to be performed by electronic control using a switch.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0017] Hereinafter, an embodiment of the present invention will be described with appropriate reference to the drawings.

[0018] FIG. 1 shows a side view of a work vehicle 1 of the present embodiment. In the present embodiment, a tractor is exemplified as the work vehicle 1. Hereinafter, the work vehicle 1 will be described assuming it is a tractor, but the work vehicle 1 is not limited to a tractor.

[0019] As shown in FIG. 1, the tractor 1 includes a driver's seat 2 on which an operator sits.

[0020] In the following description, the front side (in the direction of arrow A1 in FIG. 1) of the operator sitting on the driver's seat 2 will be described as the front, and the rear side (in the direction of arrow A2 in FIG. 1) of the operator will be described as the rear. Also, the left side (the near side in FIG. 1) of the operator will be described as the left, and the right side (the far side in FIG. 1) of the operator will be described as the right.

[0021] Also, an explanation will be given with the direction indicated by the arrow K1 in FIG. 1 as the front-rear direction. Further, the horizontal direction orthogonal to the front-rear direction K1 is referred to as the vehicle body width direction. Further, in the vehicle body width direction, the direction from the central portion of the tractor 1 toward the right portion or the left portion is referred to as the outer side in the vehicle body width direction. Further, in the vehicle body width direction, the direction from the right portion or the left portion of the tractor 1 toward the central portion of the tractor 1 is referred to as the inner side in the vehicle body width direction.

[0022] As shown in FIG. 1, the tractor 1 includes a vehicle body 3, front wheels 4 disposed on the left and right of the front portion of the vehicle body 3, rear wheels 5 disposed on the left and right of the rear portion of the vehicle body 3, and a driver's cab 7 disposed above the vehicle body 3 and including a steering wheel 6, a driver's seat 2, and the like. The front wheels 4 are steerable wheels. Further, in the present embodiment, the front wheels 4 and the rear wheels 5 are drivable drive wheels. Note that the drive wheels may be only the rear wheels 5 or only the front wheels 4. The front wheels 4 and the rear wheels 5 constitute a traveling device that supports the vehicle body 3 so as to be travelable.

[0023] As shown in FIG. 1, the vehicle body 3 includes an engine (prime mover) 8 as a power source, a front frame connected to the engine 8 and protruding forward from the engine 8, and a power transmission case 10 connected to the rear portion of the engine 8 and extending rearward from the engine 8. A PTO shaft 9 for taking out the power of the engine 8 to the outside is disposed at the rear portion of the power transmission case 10 (vehicle body 3).

[0024] In the present embodiment, the engine 8 is a diesel engine. The engine 8 may be a gasoline engine. Further, the power source may be a prime mover other than the engine. For example, it may be an electric motor.

[0025] As shown in FIG. 2, the power transmission case 10 includes a flywheel housing 11 connected to the rear portion of the engine 8, a clutch housing 12 connected to the rear portion of the flywheel housing 11, a continuously variable transmission case 13 connected to the rear portion of the clutch housing 12, and a transmission case 14 connected to the rear portion of the continuously variable transmission case 13.

[0026] The flywheel housing 11 houses a flywheel 15 that rotates integrally with the crankshaft of the engine 8. The clutch housing 12 houses a main clutch 16 that intermittently transmits the power of the engine 8 transmitted through the flywheel 15. The continuously variable transmission case 13 houses a hydraulic pump (referred to as an HST pump) 18 and a hydraulic motor (referred to as an HST motor) 19, which are components of a continuously variable transmission (HST: hydrostatic continuously variable transmission) 17. The transmission case 14 houses a traveling transmission mechanism (see FIG. 3) 20 that shifts the power output from the continuously variable transmission 17 and transmits it to the drive wheels.

[0027] FIG. 3 shows a power transmission system 21 that transmits the power of the engine 8. The power transmission system 21 includes a transmission mechanism 22 that branches and transmits the power of the engine 8, a traveling power transmission system 23 that transmits the power of the engine 8 to the drive wheels (front wheels 4 and rear wheels 5), and a PTO power transmission system 24 that transmits the power of the engine 8 to the PTO shaft 9.

[0028] As shown in FIG. 3, the transmission mechanism 22 includes an input gear 25 and a pair of transmission gears 26 and 27. The power of the engine 8 that has passed through the flywheel 15 and the main clutch 16 is transmitted to the input gear 25. The input gear 25 meshes with the pair of transmission gears 26 and 27 and transmits power to the pair of transmission gears 26 and 27. The first transmission gear 26, which is one of the pair of transmission gears 26 and 27, rotates integrally with the first transmission shaft 29. The second transmission gear 27, which is the other of the pair of transmission gears 26 and 27, rotates integrally with the second transmission shaft 30.

[0029] As shown in FIG. 3, the traveling power transmission system 23 includes a continuously variable transmission 17 to which the power from the engine 8 is transmitted, and a traveling transmission mechanism 20 that shifts the power output from the continuously variable transmission 17 and transmits it to the drive wheels.

[0030] As shown in FIG. 3, the traveling transmission mechanism 20 includes a planetary gear mechanism 47, a forward and reverse switching mechanism 48, and a sub-transmission mechanism 49.

[0031] The planetary gear mechanism 47 includes a sun gear 47a, a plurality of planetary gears 47b provided around the sun gear 47a, a carrier 47c that rotatably supports each planetary gear 47b, a ring gear 47d that meshes with the plurality of planetary gears 47b, and an output shaft 47e that outputs power.

[0032] The rotational power output from the motor shaft 33 of the HST motor 19 is input to the sun gear 47a. The rotational power of the second transmission shaft 30 is input to the carrier 47c. The planetary gear mechanism 47 combines the driving force from the continuously variable transmission 17 and the driving force from the engine 8 that does not receive the speed change action of the continuously variable transmission 17, and outputs the combined driving force from the output shaft 47e to the input shaft 48a of the forward and reverse switching mechanism 48.

[0033] The forward and reverse switching mechanism 48 outputs the driving force transmitted to the input shaft 48a from either the forward output gear train 48b that transmits forward driving force or the reverse gear train 48c that transmits reverse driving force. The forward and reverse switching mechanism 48 has a switching clutch 48d that switches the power transmission state between a state of transmitting forward driving force and a state of transmitting reverse driving force.

[0034] The sub-speed change mechanism 49 switches the power output from the output shaft 48e of the forward and reverse switching mechanism 48 to either a low speed state, a medium speed state, or a high speed state and outputs it. The power output from the sub-speed change mechanism 49 is transmitted to the rear wheels 5 via the rear wheel differential mechanism 50. Also, the power output from the sub-speed change mechanism 49 is transmitted to the front wheels 4 via the front wheel power take-off gear train 51, the clutch mechanism 52, the front wheel power transmission shaft 53, the front wheel differential mechanism 54, and the like.

[0035] As shown in FIG. 3, the PTO system power transmission system 24 includes a PTO clutch 56, a PTO speed change mechanism 57, a final transmission shaft 58, and an intermediate gear train 59. The PTO system power transmission system 24 is housed inside the transmission case 14.

[0036] The PTO clutch 56 intermittently transmits the power from the first transmission shaft 29 (engine 8). It is a device. The PTO clutch 56 transmits power to the PTO speed change mechanism 57 in the clutch connected state. The PTO clutch 56 is constituted by, for example, a wet multi-plate hydraulic clutch that becomes the clutch connected state by supplying oil (hydraulic oil) and becomes the clutch disengaged state by discharging the oil. Further, oil is supplied or discharged to the PTO clutch 56 via an electromagnetic switching valve 60 which is an electromagnetic type switching valve. That is, the power interruption operation of the PTO clutch 56 is performed by the electromagnetic switching valve 60.

[0037] As shown in FIG. 6, the electromagnetic switching valve 60 is connected to a control device 61 and is controlled by the control device 61.

[0038] The PTO speed change mechanism 57 changes the speed of the power transmitted via the PTO clutch 56. The PTO speed change mechanism 57 has a first PTO transmission shaft 62, a second PTO transmission shaft 63, a first gear train 64 and a second gear train 65, and a switching mechanism 66.

[0039] Power from the first transmission shaft 29 (engine 8) is transmitted to the first PTO transmission shaft 62 via the PTO clutch 56. The second PTO transmission shaft 63 transmits power to the PTO shaft 9. The first gear train 64 and the second gear train 65 transmit power from the first PTO transmission shaft 62 to the second PTO transmission shaft 63.

[0040] The first gear train 64 has a drive side gear 64a that rotates integrally with the first PTO transmission shaft 62, and a driven side gear 64b that meshes with the drive side gear 64a and is fitted to the second PTO transmission shaft 63 so as to be relatively rotatable. The second gear train 65 has a drive side gear 65a that rotates integrally with the first PTO transmission shaft 62, and a driven side gear 65b that meshes with the drive side gear 65a and is fitted to the second PTO transmission shaft 63 so as to be relatively rotatable.

[0041] The first gear train 64 transmits power to the PTO shaft 9 when the rotational speed of the engine 8 is the first rotational speed. The second gear train 65 transmits power to the PTO shaft 9 when the rotational speed of the engine 8 is a second rotational speed different from the first rotational speed. In the present embodiment, the second rotational speed is higher than the first rotational speed. Therefore, the second gear train 65 decelerates the rotational power of the first PTO transmission shaft 62 more than the first gear train 64 and transmits it to the second PTO transmission shaft 63.

[0042] Also, the gear ratios of the first gear train 64 and the second gear train 65 are set to gear ratios such that the rotational speed of the PTO shaft 9 is substantially equal whether the rotational speed of the engine 8 is the first rotational speed or the second rotational speed. By switching the rotational speed of the engine 8 from the first rotational speed to the second rotational speed, the output horsepower output from the PTO shaft 9 can be increased without changing the rotational speed of the PTO shaft 9.

[0043] The switching mechanism 66 is a synchromesh type switching mechanism that switches the power transmission from the first PTO transmission shaft 62 to the second PTO transmission shaft 63 either to a first state that passes through the first gear train 64 or to a second state that passes through the second gear train 65.

[0044] As shown in FIG. 4, the switching mechanism 66 is disposed between the driven-side gear (referred to as the first driven-side gear) 64b of the first gear train 64 and the driven-side gear (referred to as the second driven-side gear) 65b of the second gear train 65. The first driven-side gear 64b is provided with a first spline portion 67 and a conical first cone portion 68. The second driven-side gear 65b is provided with a second spline portion 69 and a conical second cone portion 70.

[0045] The switching mechanism 66 includes a coupling 71, a shifter 72, a synchronizer key 73, and a pair of synchronizer rings 74A, 74B.

[0046] The coupling 71 is fitted rotatably integrally with the second PTO transmission shaft 63. The shifter 72 is formed in a cylindrical shape and is fitted to the outer peripheral portion of the coupling 71 by spline fitting. Therefore, the shifter 72 is rotatable integrally with the coupling 71 and is movable in the axial direction of the second PTO transmission shaft 63 with respect to the coupling 71.

[0047] A plurality of synchronizer keys 73 are provided and are respectively fitted into a plurality of key grooves formed in the outer peripheral portion of the coupling 71. The protruding portion 73a of the synchronizer key 73 is fitted into the groove of the shifter 72 and the synchronizer key 73 is pressed against the shifter 72 by a spring.

[0048] One of the pair of synchronizer rings 74A, 74B (referred to as the first synchronizer ring) ) 74A has a spline portion 74a on the outer periphery and is disposed on the outer periphery of the first cone portion 68. The other of the pair of synchronizer rings 74A, 74B (referred to as the second synchronizer ring) 74B has a spline portion 74b on the outer periphery and is disposed on the outer periphery of the second cone portion 70.

[0049] Next, the operation of the switching mechanism 66 will be described.

[0050] When a force in the direction of moving the shifter 72 to the first driven gear 64b is applied and the shifter 72 starts to move to the first driven gear 64b, the synchronizer key 73 pressed by the shifter 72 presses the first synchronizer ring 74A against the first cone portion 68. Due to the frictional force generated between the first synchronizer ring 74A and the first cone portion 68, the rotation of the coupling 71 and the synchronizer key 73 starts to be transmitted to the first synchronizer ring 74A and the first driven gear 64b.

[0051] When the shifter 72 attempts to move further, the engagement between the shifter 72 and the synchronizer key 73 disengages, and only the shifter 72 moves. The first synchronizer ring 74A and the shifter 72 come into contact at the chamfered portions of their respective splines. As a result, the frictional force in the rotational direction received by the first synchronizer ring 74A is also added to the force pushing the first synchronizer ring 74A, and the resultant force presses the first synchronizer ring 74A against the first cone portion 68. Thereby, the first driven gear 64b reaches the same rotational speed as the shifter 72. That is, the rotational speeds of the first driven gear 64b and the shifter 72 are synchronized.

[0052] When the rotations of the shifter 72 and the first driven gear 64b match (synchronize), the shifter 72 meshes with the first synchronizer ring 74A and the first spline portion 67 in sequence. Thereby, the rotational power of the first PTO transmission shaft 62 is transmitted to the second PTO transmission shaft 63 via the first driving gear → the first driven gear 64b → the shifter 72 → the coupling 71.

[0053] When moving the shifter 72 to the second driven gear 65b, the operation is the same as above, so the description is omitted.

[0054] As shown in FIG. 3, the final transmission shaft 58 rotates integrally with the PTO shaft 9. The relay gear train 59 transmits the power output from the PTO transmission mechanism 57 to the final transmission shaft 58.

[0055] As shown in FIG. 3, the PTO system power transmission system 24 has a power take-off gear 75. The power take-off gear 75 is rotatably attached to the final transmission shaft 58 integrally. The rotational power of the power take-off gear 75 is transmitted to the power take-off portion 102 via the gear transmission mechanism 76. The power take-off portion 102 can transmit power to a work implement such as a mid-mount mower attached to the lower part of the tractor 1 in an intermittent manner.

[0056] As shown in FIG. 5, the tractor 1 is provided with a shift fork 77 that performs a switching operation of a switching mechanism 66 to switch the power transmission from the first PTO transmission shaft 62 to the second PTO transmission shaft 63 to either the first state or the second state.

[0057] As shown in FIGS. 5, 6, 7, and 8, the shift fork 77 has a boss portion 78, a main body portion 79, a connecting portion 80, and a detection portion 81. The boss portion 78 is slidably supported by a support rod 82. The support rod 82 is arranged in parallel with the second PTO transmission shaft 63 (see FIG. 6). Therefore, the shift fork 77 is movable in the axial direction of the second PTO transmission shaft 63. Both axial ends of the support rod 82 are supported by the transmission case 14.

[0058] The main body portion 79 is formed in a bifurcated shape and engages with the engagement groove 72a of the shifter 72. Since the main body portion 79 engages with the shifter 72, the shift fork 77 and the shifter 72 are integrally movable. The boss portion 78 is formed at the base of the main body portion 79. The connecting portion 80 is formed at the base of the main body portion 79. The connecting portion 80 is formed to protrude rightward from the base. The connecting portion 80 is located below the boss portion 78. The connecting portion 80 has a connecting hole 83 that opens rightward.

[0059] The detection portion 81 is formed at the upper part of an extension portion 84 that extends upward from the boss portion 78. The detection portion 81 has a first engagement portion 81a, a second engagement portion 81b, and a recess 81c on the right side surface. The first engagement portion 81a is provided at the front of the detection portion 81. The second engagement portion 81b is provided at the rear of the detection portion 81. The recess 81c is provided between the first engagement portion 81a and the second engagement portion 8 1b.

[0060] As shown in FIGS. 5, 6, and 7, the tractor 1 includes an operating mechanism 85 for operating the shift fork 77 to perform the switching operation of the switching mechanism 66 by the shift fork 77. The operating mechanism 85 is arranged to the right of the shift fork 77 as shown in FIGS. 5 and 6.

[0061] As shown in FIG. 6, the operation mechanism 85 includes a shift valve 86, a main body 87, and a shift cylinder 88. The shift valve 86 is constituted by an electromagnetic valve. The shift valve 86 is connected to the control device 61. The shift valve 86 is operationally controlled by a control signal output from the control device 61.

[0062] The main body 87 houses the shift valve 86. An oil passage is formed in the main body 87 to guide oil (hydraulic oil) supplied from a hydraulic pump installed in the tractor 1 to the shift valve 86 and the shift cylinder 88. The main body 87 is attached to the outer surface of the right side wall 14a of the transmission case 14 (see FIG. 5).

[0063] The shift cylinder 88 moves the shift fork 77 to perform the switching operation of the switching mechanism 66. As shown in FIG. 6, the shift cylinder 88 includes a cylinder body 89, a piston 90, and a piston rod 91. The cylinder body 89 is provided on the left part of the main body 87. The cylinder body 89 is integrally formed with the main body 87. That is, the main body 87 and the cylinder body 89 are integral. The cylinder body 89 is inserted into the inside of the transmission case 14 through an opening 92 formed in the right side wall 14a of the transmission case 14.

[0064] The cylinder body 89 is formed with a cylinder chamber 89a and a rod insertion hole 89b that communicates with the front portion of the cylinder chamber 89a and opens forward. The piston 90 is movable in the cylinder chamber 89a in the front-rear direction K1 (a direction parallel to the axis of the first PTO transmission shaft 62). The piston rod 91 is connected to the front surface side of the piston 90 and passes through the rod insertion hole 89b. A pin insertion hole 93 is formed in the tip side of the piston rod 91. A connecting pin 94 is inserted through the pin insertion hole 93 and the connecting hole 83 of the shift fork 77. The piston rod 91 and the shift fork 77 are connected by the connecting pin 94. By controlling the supply and discharge of oil to the cylinder chamber 89a by the shift valve 86, the piston rod 91 protrudes and retracts with respect to the cylinder body 89. When the piston rod 91 protrudes and retracts, the shift fork 77 moves.

[0065] As shown in FIGS. 9 and 10, the piston 90 can be switched between a first shift position X1 (FIG. 9) and a second shift position X2 (FIG. 10) by the shift valve 86.

[0066] As shown in FIG. 9, the first shift position X1 is a position where the shift fork 77 is moved to the first operation position Y1 and the shifter 72 is engaged with the first spline portion 67 of the first driven gear 64b. That is, the first shift position X1 is a position where the power transmission from the first PTO transmission shaft 62 to the second PTO transmission shaft 63 is switched to the first state. In other words, the first operation position Y1 of the shift fork 77 is a position where the switching mechanism 66 switches the power transmission from the first PTO transmission shaft 62 to the second PTO transmission shaft 63 to the first state.

[0067] As shown in FIG. 10, the second shift position X2 is the position where the shift fork 77 is moved to the second operation position Y2, and is the position where the shifter 72 is engaged with the second spline portion 69 of the second driven gear 65b. That is, the second shift position X2 is the position where the power transmission from the first PTO transmission shaft 62 to the second PTO transmission shaft 63 is switched to the second state. In other words, the second operation position Y2 of the shift fork 77 is the position where the switching mechanism 66 switches the power transmission from the first PTO transmission shaft 62 to the second PTO transmission shaft 63 to the second state.

[0068] As shown in FIGS. 5, 6, 7, and 8, the tractor 1 includes a detection mechanism 95 that detects the position of the shift fork 77. The detection mechanism 95 has a detection sensor 96 and a pushing member 97. As shown in FIG. 5, the detection sensor 96 is held by a holding portion 98 formed on the side wall 14a of the transmission case 14. The pushing member 97 is interposed between the detection sensor 96 and the detection portion 81 of the shift fork 77. The pushing member 97 is supported by a support portion (not shown) provided on the transmission case 14 so as to be movable in the vehicle width direction.

[0069] When the pushing member 97 abuts against the first engaging portion 81a of the shift fork 77, the detection sensor 96 detects that the pushing member 97 pushes the contact 96a of the detection sensor 96, whereby the shift fork 77 is engaged with the first spline portion 67 of the shifter 72 (the first operation position Y1). Further, when the pushing member 97 abuts against the second engaging portion 81b of the shift fork 77, the detection sensor 96 detects that the pushing member 97 pushes the contact 96a of the detection sensor 96, whereby the shift fork 77 is engaged with the second spline portion 69 of the shifter 72 (the second operation position Y2).

[0070] Therefore, the shift fork 77 is movable between the first operation position Y1 and the second operation position Y2, and has a detection portion 81 for the detection sensor 96 to detect that the shift fork 77 is in the first operation position Y1 or the second operation position Y2.

[0071] Note that the detection mechanism 95 may be composed of only the detection sensor 96. In this case, the contact 96a of the detection sensor 96 is brought into contact with the detection unit 81.

[0072] As shown in FIG. 6, the tractor 1 is provided with a shift switch 99. The shift switch 99 is disposed near the driver's seat 2. The shift switch 99 is for outputting at least an operation signal for operating the operation mechanism 85. In the present embodiment, the shift switch 99 outputs an operation signal for switching the rotational speed of the engine 8 and operating the operation mechanism 85. The shift switch 99 is connected to the control device 61. The control device 61 can acquire the operation signal output from the shift switch 99. Further, an ECU (engine control unit) 100 for controlling the rotational speed of the engine 8 is connected to the control device 61.

[0073] The shift switch 99 is constituted by a rotary switch that is rotationally operated manually by the operator. The shift switch 99 is switchable to a first position 101a, a second position 101b, and a third position 101c.

[0074] When the shift switch 99 is switched to (operated to) the first position 101a, the control device 61 acquires the operation signal from the shift switch 99 and outputs a control signal (first control signal) to the ECU 100 and the operation mechanism 85 (shift valve 86). When the ECU 100 acquires the first control signal, it switches the rotational speed of the engine 8 to the first rotational speed and fixes it at the first rotational speed. When the operation mechanism 85 (shift valve 86) acquires the first control signal, it operates the shift cylinder 88 to move the shift fork 77 to the first operation position Y1, and switches the switching mechanism 66 so that the power transmission from the first PTO transmission shaft 62 to the second PTO transmission shaft 63 is in the first state.

[0075] When the transmission switch 99 is switched to the second position 101b (operated), the control device 61 acquires an operation signal from the transmission switch 99 and outputs a control signal (second control signal) to the ECU 100 and the operation mechanism 85 (transmission valve 86). When the ECU 100 acquires the second control signal, it switches the rotational speed of the engine 8 to the second rotational speed and fixes it at the second rotational speed. When the operation mechanism 85 (transmission valve 86) acquires the second control signal, it operates the shift cylinder 88 to move the shift fork 77 to the second operation position Y2, and switches the switching mechanism 66 so that the power transmission from the first PTO transmission shaft 62 to the second PTO transmission shaft 63 is in the second state.

[0076] When the transmission switch 99 is switched to the third position 101c, the control device 61 acquires an operation signal from the transmission switch 99 and outputs a control signal (third control signal) to the ECU 100. When the ECU 100 acquires the third control signal, it does not fix the rotational speed of the engine 8 to a specific rotational speed. In this case, the rotational speed of the engine 8 is controlled to the rotational speed set by the operation of an accelerator member manually operated by the operator, for example. Also, when the control device 61 switches the transmission switch 99 to the third position 101c, it does not output a control signal to the operation mechanism 85 (transmission valve 86). That is, the switching mechanism 66 does not switch to the neutral position.

[0077] Note that, for example, when the transmission switch 99 is switched to the third position 101c, the electromagnetic switching valve 60 can acquire the third control signal, and the PTO clutch 56 can be switched to the clutch-disengaged state by the electromagnetic switching valve 60. Also, the PTO clutch 56 can be switched between the clutch-engaged state and the clutch-disengaged state by an operation of an operator different from the operation of the transmission switch 99.

[0078] A preferred embodiment of the present invention provides the work vehicle 1 described in the following items. (Item 1) A work vehicle 1 having a PTO shaft 9 for extracting the power of the prime mover 8 to the outside, including a first PTO transmission shaft 62 to which the power from the prime mover 8 is transmitted, a second PTO transmission shaft 63 for transmitting power to the PTO shaft 9, a first gear train 64 and a second gear train 65 for transmitting power from the first PTO transmission shaft 62 to the second PTO transmission shaft 63, and a synchromesh type switching mechanism 66 for switching the power transmission from the first PTO transmission shaft 62 to the second PTO transmission shaft 63 to either a first state performed via the first gear train 64 or a second state performed via the second gear train 65.

[0079] According to the work vehicle 1 according to this item 1, by configuring the synchromesh type switching mechanism 66 to switch the power transmission from the first PTO transmission shaft 62 to the second PTO transmission shaft 63 to either a first state performed via the first gear train 64 or a second state performed via the second gear train 65, the gear shifting operation of the PTO system power transmission system can be performed by electronic control using a switch. (Item 2) A shift fork 77 for performing a switching operation of the switching mechanism 66 to switch to either the first state or the second state, an operating mechanism 85 for operating the shift fork 77 to perform the switching operation of the switching mechanism 66 by the shift fork 77, a switch 99 for outputting an operation signal for operating the operating mechanism 85, and a control device 61 for outputting a control signal for operating the operating mechanism 85 when an operation signal from the switch 99 is acquired. The work vehicle 1 according to item 1 is provided with these components.

[0080] According to the work vehicle 1 according to this item 2, by operating the operating mechanism 85 with a control signal output from the control device 61 by operating the switch 99, and operating the shift fork 77 by the operating mechanism 85 to perform the switching operation of the switching mechanism 66, the gear shifting operation of the PTO system power transmission system can be performed by electronic control using a switch. (Item 3) The first gear train 64 transmits power to the PTO shaft 9 when the rotational speed of the prime mover 8 is the first rotational speed, and the second gear train 65 transmits power to the PTO shaft 9 when the rotational speed of the prime mover 8 is a second rotational speed different from the first rotational speed. The gear ratios of the first gear train 64 and the second gear train 65 are set to gear ratios such that the rotational speed of the PTO shaft 9 is substantially equal whether the rotational speed of the prime mover 8 is the first rotational speed or the second rotational speed. The work vehicle 1 according to item 1 or 2.

[0081] According to the work vehicle 1 according to this item 3, by switching the rotational speed of the engine 8 from the lower rotational speed of the first rotational speed and the second rotational speed to the higher rotational speed, the output horsepower output from the PTO shaft 9 can be increased without changing the rotational speed of the PTO shaft 9. (Item 4) When the control device 61 acquires the operation signal from the switch 99, it switches the rotational speed of the prime mover 8 to either the first rotational speed or the second rotational speed, and outputs a control signal to the operation mechanism 85 so as to switch to either the first state or the second state corresponding to the first rotational speed and the second rotational speed. The work vehicle 1 according to item 3 which quotes item 2.

[0082] According to the work vehicle 1 according to this item 4, by operating the switch 99, the switching between the first state and the second state can be automatically performed in conjunction with the switching between the first rotational speed and the second rotational speed. (Item 5) The operation mechanism 85 includes a shift cylinder 88 that moves the shift fork 77 to perform the switching operation, and a shift valve 86 that is controlled by the control signal to operate the shift cylinder 88. The work vehicle 1 according to item 2, item 3 which quotes item 2, or item 4.

[0083] According to the work vehicle 1 according to this item 5, a shift cylinder for moving the shift fork 77 The switching between the first state and the second state can be automatically performed by the damper 88 and the shift valve 86 that operates the shift cylinder 88. (Item 6) The shift cylinder 88 has a cylinder body 89 and a piston rod 91 that protrudes and retracts with respect to the cylinder body 89. The shift fork 77 has a connecting portion 80 that is connected to the piston rod 91 via a connecting pin 94. The work vehicle 1 according to Item 5.

[0084] According to the work vehicle 1 according to this Item 6, the movement operation of the shift fork 77 can be performed by the shift cylinder 88. (Item 7) The work vehicle 1 according to Item 2, Item 3, Item 4, Item 5, or Item 6 that includes a detection sensor 96 that detects the position of the shift fork 77. The shift fork 77 is movable to a first operation position Y1 and a second operation position Y2, and has a detection portion 81 for the detection sensor 96 to detect that the shift fork 77 is at the first operation position Y1 or the second operation position Y2. The first operation position Y1 is a position where the switching mechanism 66 switches the power transmission from the first PTO transmission shaft 62 to the second PTO transmission shaft 63 to the first state. The second operation position Y2 is a position where the switching mechanism 66 switches the power transmission from the first PTO transmission shaft 62 to the second PTO transmission shaft 63 to the second state.

[0085] According to the work vehicle 1 according to this Item 7, it is possible to detect whether the power transmission from the first PTO transmission shaft 62 to the second PTO transmission shaft 63 is in the first state or the second state.

[0086] As described above, although one embodiment of the present invention has been described, it should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Explanation of Reference Numerals

[0087] 1 Work vehicle 8 Prime mover 9 PTO shaft 61 Control device 62 First PTO drive shaft 63 Second PTO drive shaft 64 First gear train 65 Second gear train 66 Switching mechanism 77 Shift fork 80 Connecting part 81 Detection unit 85 Operating mechanism 86 Shift valve 88 Shift cylinder 89 Cylinder body 91 Piston rod 94 Connecting pin 96 Detection sensor 99 Switch (shift switch) Y1 First operating position Y2 Second operating position

Claims

1. A work vehicle equipped with a PTO shaft for extracting the power of the prime mover to the outside, a first PTO transmission shaft to which the power from the prime mover is transmitted, a second PTO transmission shaft for transmitting power to the PTO shaft, a first gear train and a second gear train for transmitting power from the first PTO transmission shaft to the second PTO transmission shaft, a synchromesh type switching mechanism for switching the power transmission from the first PTO transmission shaft to the second PTO transmission shaft to either a first state performed via the first gear train or a second state performed via the second gear train, A work vehicle equipped with the above.

2. A shift fork for performing a switching operation of the switching mechanism so as to switch to either the first state or the second state, an operating mechanism for operating the shift fork so as to perform the switching operation of the switching mechanism by the shift fork, a switch for outputting an operation signal for operating the operating mechanism, a control device for outputting a control signal for operating the operating mechanism when an operation signal from the switch is acquired, The work vehicle according to claim 1, comprising the above.

3. The first gear train transmits power to the PTO shaft when the rotational speed of the prime mover is a first rotational speed, The second gear train transmits power to the PTO shaft when the rotational speed of the prime mover is a second rotational speed different from the first rotational speed, The gear ratios of the first gear train and the second gear train are set to gear ratios such that the rotational speed of the PTO shaft is substantially equal whether the rotational speed of the prime mover is the first rotational speed or the second rotational speed. The work vehicle according to claim 1 or 2.

4. When the control device acquires an operation signal from the switch, it switches the rotational speed of the prime mover to either the first rotational speed or the second rotational speed, and outputs a control signal to the operating mechanism so as to switch to either the first state or the second state corresponding to the first rotational speed and the second rotational speed. The work vehicle according to claim 3, which quotes claim 2.

5. The operating mechanism has a shift cylinder for moving the shift fork to perform the switching operation, and a shift valve controlled by the control signal to operate the shift cylinder. The work vehicle according to claim 2.

6. The shift cylinder has a cylinder body and a piston rod that protrudes and retracts with respect to the cylinder body, The work vehicle according to claim 5, wherein the shift fork has a connecting portion connected to the piston rod via a connecting pin.

7. comprising a detection sensor for detecting the position of the shift fork, the shift fork is movable to a first operation position and a second operation position, and has a detection portion for the detection sensor to detect that the shift fork is in the first operation position or the second operation position, the first operation position is a position where the switching mechanism switches the power transmission from the first PTO transmission shaft to the second PTO transmission shaft to the first state, the second operation position is a position where the switching mechanism switches the power transmission from the first PTO transmission shaft to the second PTO transmission shaft to the second state, the work vehicle according to claim 2.

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