Work vehicle

Abstract

To provide a work vehicle which enables a steering device to be operated with a steering wheel to steer front wheels even when driving of an electric motor for driving rear wheels is stopped.SOLUTION: In a work vehicle, an electric motor (30) for driving rear wheels (3) is stored in an engine hood (4) and a steering wheel (11) is provided on the front side of a driver's seat (10) of a steering part (5). Further, a steering device (45) which steers front wheels (2) in response to an operation of the steering wheel (11) is provided. When the electric motor (30) is driven, a hydraulic oil is supplied to the steering device (45) through a pump (39) driven by the electric motor (30). When driving of the electric motor (30) is stopped, the hydraulic oil in the steering device (45) is not drained to the pump (39).SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a work vehicle equipped with a steering device operated by a steering wheel. [Background technology]

[0002] A conventional technology is known in which a pump is driven by an engine that drives the rear wheels, and hydraulic oil is sent to a steering device operated by a steering wheel (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2024-5666 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the electrified work vehicle in which the engine of Patent Document 1 is replaced with an electric motor, when the electric motor that drives the rear wheels is stopped to stop the work vehicle from moving, there is a problem in that hydraulic oil is discharged from the steering device toward the pump, making it impossible to operate the steering device with the steering wheel.

[0005] SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a work vehicle in which the front wheels can be steered by operating the steering device with the steering wheel even when the drive of the electric motor that drives the rear wheels is stopped. [Means for solving the problem]

[0006] The present invention, which has solved the above problems, is as follows. That is, the invention described in claim 1 is a work vehicle having a pair of left and right front wheels (2) and rear wheels (3) on the underside of a vehicle body (1), a hood (4) on the upper side of the vehicle body (1), and a control section (5) on which an operator rides on the rear side of the hood (4), The work vehicle is characterized in that an electric motor (30) for driving rear wheels (3) is stored in the hood (4), a steering wheel (11) is provided in front of a driver's seat (10) of the control section (5), and a steering device (45) for steering the front wheels (2) in response to operation of the steering wheel (11). When the electric motor (30) is operating, hydraulic oil is supplied to the steering device (45) via a pump (39) driven by the electric motor (30), and when the operation of the electric motor (30) is stopped, the hydraulic oil in the steering device (45) is not discharged to the pump (39).

[0007] The invention described in claim 2 is the work vehicle described in claim 1, in which a clutch (41) is provided between the electric motor (30) and the pump (39), and when the electric motor (30) is driven, the clutch (41) rotates in one direction, and when the driving of the electric motor (30) is stopped, the clutch (41) does not rotate in the opposite direction to the one direction.

[0008] The invention described in claim 3 is the work vehicle described in claim 2, in which a counter gear (40) is provided between the electric motor (30) and the clutch (41), and when the electric motor (30) is driven, the counter gear (40) rotates, and when the driving of the electric motor (30) is stopped, an electromagnetic brake (40A) of the counter gear (40) is activated to stop the rotation of the counter gear (40).

[0009] The invention of claim 4 is the work vehicle of claim 1, wherein a first solenoid valve (80B) is provided between a first pipe (71) connecting the pump (39) and the steering device (45), and when the electric motor (30) is driven, the pump (39) and the steering device (45) are connected via the first solenoid valve (80B), and when the driving of the electric motor (30) is stopped, the communication between the pump (39) and the steering device (45) is cut off via the first solenoid valve (80B).

[0010] The invention of claim 5 is the work vehicle of claim 4, wherein a second solenoid valve (84) is provided in a second pipe (83) that connects a portion of the first pipe (71) between the first solenoid valve (80B) and the steering device (45) to an oil tank (38) that stores working oil, and when the electric motor (30) starts to drive, the working oil in the first pipe (71) is drained into the oil tank (38) over a predetermined time via the second solenoid valve (84).

[0011] The invention of claim 6 is the work vehicle of claim 1, wherein a check valve (81) is provided between the first pipe (71) connecting the pump (39) and the steering device (45), and the check valve (81) supplies hydraulic oil from the pump (39) to the steering device (45) and prevents hydraulic oil from being discharged from the steering device (45) to the pump (39).

[0012] The invention of claim 7 is the work vehicle of claim 6, wherein a second solenoid valve (84) is provided in a second pipe (83) that connects a portion of the first pipe (71) between the check valve (81) and the steering device (45) to an oil tank (38) that stores working oil, and when the electric motor (30) starts to drive, the working oil in the first pipe (71) is drained into the oil tank (38) via the second solenoid valve (84) over a predetermined time. [Effects of the Invention]

[0013] According to the invention of claim 1, the electric motor (30) for driving the rear wheels (3) is stored in the hood (4), a steering wheel (11) is provided in front of the driver's seat (10) of the control section (5), and a steering device (45) for steering the front wheels (2) in response to operation of the steering wheel (11) is provided, and when the electric motor (30) is driven, hydraulic oil is supplied to the steering device (45) via a pump (39) driven by the electric motor (30), and when the driving of the electric motor (30) is stopped, the hydraulic oil in the steering device (45) is not discharged to the pump (39). Therefore, even when the driving of the electric motor (30) is stopped, the steering device (45) can be operated with the steering wheel (11) to send the hydraulic oil remaining in the steering device (45) to a piston, thereby allowing the front wheels (2) to be steered.

[0014] According to the invention of claim 2, in addition to the effect of the invention of claim 1, a clutch (41) is provided between the electric motor (30) and the pump (39). When the electric motor (30) is driven, the clutch (41) rotates in one direction, and when the driving of the electric motor (30) is stopped, the clutch (41) does not rotate in the opposite direction. Therefore, when the driving of the electric motor (30) is stopped, it is possible to further prevent the hydraulic oil in the steering device (45) from being discharged into the pump (39).

[0015] According to the invention of claim 3, in addition to the effect of the invention of claim 2, a counter gear (40) is provided between the electric motor (30) and the clutch (41), and when the electric motor (30) is driven, the counter gear (40) rotates, and when the driving of the electric motor (30) is stopped, the electromagnetic brake (40A) of the counter gear (40) is activated to stop the rotation of the counter gear (40). Therefore, when the driving of the electric motor (30) is stopped, it is possible to further prevent the hydraulic oil in the steering device (45) from being discharged to the pump (39).

[0016] According to the invention of claim 4, in addition to the effect of the invention of claim 1, a first solenoid valve (80B) is provided between the first pipe (71) connecting the pump (39) and the steering device (45), and when the electric motor (30) is driven, the pump (39) and the steering device (45) are connected via the first solenoid valve (80B), and when the electric motor (30) is stopped, the pump (39) and the steering device (45) are disconnected via the first solenoid valve (80B). Therefore, when the electric motor (30) is stopped, it is possible to further prevent the hydraulic oil in the steering device (45) from being discharged to the pump (39). Also, it is possible to reduce the number of parts by removing parts such as the clutch (41) and the counter gear (40).

[0017] According to the invention of claim 5, in addition to the effect of the invention of claim 4, the second pipe (83) connecting a portion of the first pipe (71) between the first solenoid valve (80B) and the steering device (45) to the oil tank (38) storing the working oil is provided with the second solenoid valve (84). When the electric motor (30) starts to operate, the working oil in the first pipe (71) is discharged to the oil tank (38) via the second solenoid valve (84) over a predetermined time period. As a result, the back pressure of the working oil acting on the pump (39) is reduced, and the electric motor (30) can be started smoothly.

[0018] According to the invention of claim 6, in addition to the effect of the invention of claim 1, a check valve (81) is provided between the first pipe (71) connecting the pump (39) and the steering device (45), and the check valve (81) supplies hydraulic oil from the pump (39) to the steering device (45) and prevents the hydraulic oil from being discharged from the steering device (45) to the pump (39). Therefore, when the driving of the electric motor (30) is stopped, it is possible to more effectively prevent the hydraulic oil in the steering device (45) from being discharged to the pump (39). Also, it is possible to reduce the number of parts by removing parts such as the clutch (41) and the counter gear (40).

[0019] According to the seventh aspect of the invention, in addition to the effect of the sixth aspect of the invention, the second solenoid valve (84) is provided in the second pipe (83) connecting the portion of the first pipe (71) between the check valve (81) and the steering device (45) to the oil tank (38) that stores the working oil. When the electric motor (30) starts to operate, the working oil in the first pipe (71) is discharged to the oil tank (38) via the second solenoid valve (84) over a predetermined time period. As a result, the back pressure of the working oil applied to the pump (39) is reduced, and the electric motor (30) can be started smoothly. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 2 is a perspective view of the work vehicle as viewed from the front right. [Figure 2] FIG. 2 is a perspective view of the main part of the work vehicle as viewed from the front right. [Figure 3] FIG. 2 is a perspective view of the main part of the work vehicle as viewed from the left front. [Figure 4] FIG. 2 is a perspective view of the front main portion of the work vehicle as viewed from the left front. [Figure 5] FIG. 2 is an explanatory diagram of an electric motor and a gear pump. [Figure 6] FIG. 6 is an enlarged view of a main part of FIG. 5. [Figure 7] FIG. 2 is a perspective view of the front wheel steering device as seen from the front left. [Figure 8] 1 is a transmission diagram of the output rotation of a prime mover. [Figure 9] 1 shows a hydraulic circuit according to a first embodiment. [Figure 10] 4 is a hydraulic circuit according to a second embodiment. [Figure 11] 10 is a hydraulic circuit according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] As shown in FIGS. 1 to 3, a work vehicle such as a tractor has a pair of left and right front wheels 2 provided at the front lower part of a vehicle body 1, and a pair of left and right rear wheels 3 provided at the rear lower part of the vehicle body 1.

[0022] A bonnet 4 that houses the electric motor 30 is provided at the front upper part of the vehicle body 1, a control section 5 on which an operator sits is provided behind the bonnet 4, safety frames (ROPS) 6F, 6B that protect the operator are provided at the front and rear of the control section 5, and a PTO shaft 7 that extends in the front-to-rear direction and to which the output rotation of the electric motor 30 is transmitted is provided at the rear lower side of the control section 5. A work machine such as a manure spreader that spreads compost on a field is connected to the PTO shaft 7.

[0023] A steering wheel 11 for steering the front wheels 2 is provided in front of a driver's seat 10 in the control section 5. A clutch pedal 14 is provided on the left side of the lower part of a steering column 13, which houses a steering shaft 12 that supports the steering wheel 11, and an accelerator pedal 15 is provided on the right side.

[0024] The vehicle body 1 is formed from a body frame 20 and a transmission case 21 that extends rearward from the rear of the body frame 20 and houses a hydraulic continuously variable transmission 50 that increases or decreases the output rotation transmitted from the electric motor 30, a transmission gear box 52 that increases or decreases the output rotation transmitted from the continuously variable transmission 50, and the like.

[0025] A front case 22 extending in the left-right direction is provided at the front of the body frame 20 and houses a differential gear 57 and a drive shaft 58 that drive the front wheels 2, and a rear case 23 extending in the left-right direction is provided at the rear of the transmission case 21 and houses a differential gear 53 and a drive shaft 54 ​​that drive the rear wheels 3.

[0026] An electric motor 30 that drives the rear wheels 3 and a gear pump (referred to as a "pump" in the claims) 39 is provided between the left and right walls of the vehicle frame 20, and a support base 31 is provided on the upper side of the vehicle frame 20. A battery case 32 that houses a battery that supplies power to the electric motor 30, and an inverter case 33 that houses an inverter device that drives the electric motor 30, are mounted on the support base 31. The support base 31 is supported on the vehicle frame 20 via a vertical frame (not shown) that extends upward from the vehicle frame 20.

[0027] As shown in Fig. 4, a cooling device 36 including a radiator, a fan, etc., is provided in front of the battery case 32 and the inverter case 33. This allows cooled air to be blown toward the inverter case 33, preventing the inverter housed in the inverter case 33 from becoming too hot. The frame 35 is formed from a left vertical frame extending upward from the left wall of the body frame 20, a right vertical frame extending upward from the right wall of the body frame 20, and a horizontal frame connecting the upper parts of the left vertical frame and the right vertical frame.

[0028] As shown in Figures 2 and 3, an oil tank 38 for storing hydraulic oil is provided below the support base 31, and a gear pump 39 for supplying hydraulic oil to a steering device 45 operated by the steering wheel 11 is provided on the right wall of the oil tank 38.

[0029] 5 and 6, the output rotation of electric motor 30 is transmitted to gear pump 39 via a counter gear 40 that is supported on a shaft that is disposed parallel to the output shaft of electric motor 30 and extends in the fore-and-aft direction, and a clutch 41. As a result, when electric motor 30 is driven, that is, when the work vehicle is traveling, the output rotation of electric motor 30 is transmitted to gear pump 39, and hydraulic oil can be sent from gear pump 39 to steering device 45.

[0030] An electromagnetic brake 40A that stops rotation about the support shaft is attached to the counter gear 40. As a result, when the driving of the electric motor 30 is stopped, that is, when the work vehicle is stopped, the rotation of the counter gear 40 is stopped, preventing the hydraulic oil in the steering device 45 from being discharged into the oil tank 38 via the gear pump 39, allowing the steering wheel 11 to be operated to steer the front wheels 2.

[0031] It is also preferable to use a one-way clutch for clutch 41. This prevents hydraulic oil in steering device 45 from being discharged into oil tank 38 via gear pump 39 even if electromagnetic brake 40A malfunctions, allowing front wheels 2 to be steered by operating steering wheel 11. The one-way clutch rotates when electric motor 30 is driven, and stops rotating when electric motor 30 is stopped.

[0032] As shown in Figure 7, the steering device 45 is attached to the top of the steering shaft 12, and hydraulic oil is supplied from the steering device 45 to the cylinder 57A of the differential gear 57 housed in the front case 22 via a pair of flexible left and right oil tubes 46L, 46R.

[0033] 8, the output rotation of the electric motor 30 is output to the output shaft 30A. The output rotation of the output shaft 30A is transmitted to the gear pump 39 via the clutch 41, and is also transmitted to the continuously variable transmission 50. The output rotation transmitted to the continuously variable transmission 50 is increased or decreased in speed and its output rotation direction is switched by the continuously variable transmission 50, and then output from the first output shaft 50A and the second output shaft 50B.

[0034] The output rotation of the first output shaft 50A is transmitted to a speed change gear box 52 via a clutch 51. The clutch 51 is switched between engagement and disengagement by stepping on the clutch pedal 14, and the output rotation transmitted to the speed change gear box 52 is increased or decreased in speed change gear box 52 and the output rotation direction is switched thereafter, and then output from an output shaft 52A.

[0035] The output rotation of the output shaft 52A is transmitted via a bevel gear to a differential gear 53 for the rear wheels. The output rotation transmitted to the differential gear 53 is output from the differential gear 53 to drive shafts 54 extending to the left and right, and then transmitted to a pair of left and right rear wheels 3 via a pair of left and right wheels.

[0036] The output rotation of output shaft 52A is transmitted via gears to rotary shaft 55. The output rotation transmitted to rotary shaft 55 is then transmitted to a differential gear 57 for the front wheels via a four-wheel drive clutch 56. The clutch 56 is switched between engagement and disengagement by operating a four-wheel drive lever (not shown) provided on the steering unit 5, and the output rotation transmitted to differential gear 57 is output from differential gear 57 to drive shafts 58 extending to the left and right, and then transmitted to a pair of left and right front wheels 2 via a pair of left and right wheels.

[0037] The output rotation of the second output shaft 50B is transmitted to a PTO transmission gearbox 61 via a PTO clutch 60. The clutch 60 is switched between engagement and disengagement by operating a PTO lever (not shown) provided on the control unit 5, and the output rotation transmitted to the PTO transmission gearbox 61 is increased or decreased in the PTO transmission gearbox 61 before being transmitted to the PTO shaft 7. The clutch 60 is made up of a forward / reverse clutch that switches the direction of output rotation, and a connecting clutch that connects and disconnects a clutch provided downstream of the forward / reverse clutch.

[0038] <Hydraulic circuit of the first embodiment> As shown in FIG. 9 , hydraulic oil stored in the oil tank 38 is supplied to a gear pump 39 driven by the electric motor 30 via a flexible oil tube 70. The oil tube 70 is provided with a filter 70A that removes impurities from the hydraulic oil and a solenoid valve 80A. The solenoid valve 80A is a two-port normally open solenoid valve, and when the work vehicle stops traveling, the coil of the solenoid valve 80A is excited, disabling communication between the ports. This prevents hydraulic oil in the steering device 45 from being discharged from the steering device 45 to the oil tank 38 via the solenoid valve 80A when the work vehicle stops traveling, i.e., when the electric motor 30 stops operating. This maintains hydraulic oil in the steering device 45, and allows the front wheels 2 to be steered via the steering device 45 by operating the steering wheel 11, even when the electric motor 30 is stopped operating.

[0039] The hydraulic oil discharged from the gear pump 39 is supplied to the solenoid valve 73 of the steering device 45 via a flexible oil tube (referred to as the "first pipe" in the claims) 71. A solenoid valve 80B is provided in the oil tube 71. The solenoid valve (referred to as the "first solenoid valve" in the claims) 80B is a two-port normally open solenoid valve, and when the work vehicle stops traveling, the coil of the solenoid valve 80B is excited, thereby releasing communication between the ports. This prevents the hydraulic oil in the steering device 45 from being discharged from the steering device 45 to the oil tank 38 via the solenoid valve 80B when the work vehicle stops traveling, i.e., when the drive of the electric motor 30 stops. Therefore, hydraulic oil is maintained in the steering device 45, and the front wheels 2 can be steered via the steering device 45 by operating the steering wheel 11, even when the drive of the electric motor 30 is stopped.

[0040] The coil of the solenoid valve 73 is excited by an Orbitroll (registered trademark, the same applies hereinafter) 74 which operates in accordance with the operating direction of the steering wheel 11. The solenoid valve 73 is a 4-port 3-position solenoid valve.

[0041] When the steering wheel 11 is not rotated, the pair of left and right coils of the solenoid valve 73 are excited, and the hydraulic oil in the solenoid valve 73 is not sent to the oil tubes 46L, 46R, stopping the piston of the cylinder 57A, thereby allowing the work vehicle to travel straight ahead.

[0042] When the steering wheel 11 is rotated counterclockwise, the left coil of the solenoid valve 73 is demagnetized and the right coil is excited, and the hydraulic oil in the solenoid valve 73 is sent to the oil tube 46L, moving the piston of the cylinder 57A to the right and turning the front wheels 2 to the right. This allows the work vehicle to turn right.

[0043] When the steering wheel 11 is rotated clockwise, the left coil of the solenoid valve 73 is excited and the right coil is de-energized, and the hydraulic oil in the solenoid valve 73 is sent to the oil tube 46R, moving the piston of the cylinder 57A to the left and turning the front wheels 2 to the left. This allows the work vehicle to turn left.

[0044] In the steering device 45, a relief valve 75A is provided in an oil tube 75 connected to an oil tube 71 and an oil tube 72. This makes it possible to prevent a large amount of hydraulic oil from being supplied from the gear pump 39 to the solenoid valve 73 via the oil tube 71, etc. A two-port normally open solenoid valve (not shown) is provided in the oil tube 72, and when the driving of the electric motor 30 stops, the coil of the two-port normally open solenoid valve is excited to release communication between the ports.

[0045] In addition, in the steering device 45, a check valve 76A is provided in an oil tube 76 connected to the oil tube 71 and the oil tube 72. This prevents the hydraulic oil discharged from the cylinder 57A via the solenoid valve 73 or the like from being sent to the gear pump 39 via the oil tube 71.

[0046] <Hydraulic circuit of second embodiment> A hydraulic circuit according to the second embodiment is shown in Fig. 10. The same members as those in the hydraulic circuit according to the first embodiment are given the same reference numerals and the description thereof will be omitted.

[0047] 10, the hydraulic oil stored in the oil tank 38 is supplied to the gear pump 39 driven by the electric motor 30 via an oil tube 70. The oil tube 70 is provided with a filter 70A.

[0048] The hydraulic oil discharged from the gear pump 39 is supplied to the solenoid valve 73 of the steering device 45 via an oil tube 71. A check valve 81 is provided in the oil tube 71. This prevents the hydraulic oil in the steering device 45 from being discharged from the steering device 45 to the oil tank 38 via the check valve 81 when the work vehicle stops traveling, i.e., when the drive of the electric motor 30 stops. Therefore, hydraulic oil is maintained in the steering device 45, and the front wheels 2 can be steered via the steering device 45 by operating the steering wheel 11, even when the drive of the electric motor 30 is stopped.

[0049] <Hydraulic circuit of the third embodiment> A hydraulic circuit according to the third embodiment is shown in Fig. 11. The same members as those in the hydraulic circuit according to the first embodiment are given the same reference numerals and the description thereof will be omitted.

[0050] 11, the hydraulic oil stored in the oil tank 38 is supplied to the gear pump 39 driven by the electric motor 30 via an oil tube 70. The oil tube 70 is provided with a filter 70A.

[0051] The hydraulic oil discharged from the gear pump 39 is supplied to the solenoid valve 73 of the steering device 45 via an oil tube 71. A check valve 82 is provided in the oil tube 71. This prevents the hydraulic oil in the steering device 45 from being discharged from the steering device 45 to the oil tank 38 via the check valve when the work vehicle stops traveling, i.e., when the drive of the electric motor 30 stops. Therefore, hydraulic oil is maintained in the steering device 45, and the front wheels 2 can be steered via the steering device 45 by operating the steering wheel 11, even when the drive of the electric motor 30 is stopped.

[0052] A flexible oil tube (referred to as "second piping" in the claims) 83 that connects the oil tube 71 to the oil tank 38 is provided downstream of the check valve 82 in the oil tube 71, and a solenoid valve 84 such as an unloading valve is provided in the oil tube 83. The solenoid valve (referred to as "second solenoid valve" in the claims) 84 is a two-port normally closed solenoid valve. When the work vehicle starts traveling, i.e., when the electric motor 30 is driven to start the gear pump 39, the coil of the solenoid valve 84 is excited for a preset time, thereby opening up communication between the ports. As a result, the hydraulic oil in the oil tube 71 downstream of the check valve 82 is drained to the oil tank 38 via the solenoid valve 84, reducing the back pressure applied by the hydraulic oil to the gear pump 39 and enabling smooth start-up of the gear pump 39. This eliminates the need to attach a starter motor to the gear pump 39. The check valve 82 can also be replaced with a solenoid valve 80B.

[0053] As an alternative to providing the oil tube 83 and the solenoid valve 84, the back pressure applied to the gear pump 39 from the hydraulic oil can be reduced by rotating the electric motor 30 in the reverse direction after the clutch 51 is disengaged. [Explanation of symbols]

[0054] 1. Body 2 front wheels 3 rear wheels 4. Bonnet 5 Control Unit 10 cockpit 11. Steering wheel 30 Electric motor 38 Oil Tank 39 Gear pump (pump) 40 Counter gear 40A electromagnetic brake 41 Clutch 45 Steering gear 71 Oil tube (first piping) 80B Solenoid valve (first solenoid valve) 83 Oil tube (second piping) 84 Solenoid valve (second solenoid valve)

Claims

1. A work vehicle having a pair of left and right front wheels (2) and rear wheels (3) on the underside of a vehicle body (1), a hood (4) on the upper side of the vehicle body (1), and a control section (5) on which a worker rides on the rear side of the hood (4), The bonnet (4) houses an electric motor (30) for driving the rear wheels (3), A steering wheel (11) is provided in front of a cockpit (10) of the control section (5), a steering device (45) for steering the front wheels (2) in response to operation of the steering wheel (11); When the electric motor (30) is driven, hydraulic oil is supplied to the steering device (45) through a pump (39) driven by the electric motor (30); A work vehicle characterized in that, when the driving of the electric motor (30) is stopped, the hydraulic oil in the steering device (45) is not discharged to the pump (39).

2. A clutch (41) is provided between the electric motor (30) and the pump (39), When the electric motor (30) is driven, the clutch (41) rotates in one direction, 2. A work vehicle according to claim 1, wherein the clutch does not rotate in a direction opposite to one direction when the electric motor is stopped.

3. A counter gear (40) is provided between the electric motor (30) and the clutch (41), When the electric motor (30) is driven, the counter gear (40) rotates, 3. A work vehicle according to claim 2, wherein when the driving of the electric motor (30) is stopped, an electromagnetic brake (40A) of the counter gear (40) is activated to stop the rotation of the counter gear (40).

4. a first electromagnetic valve (80B) is provided between a first pipe (71) connecting the pump (39) and a steering device (45); When the electric motor (30) is driven, the pump (39) is connected to the steering device (45) via the first solenoid valve (80B), 2. The work vehicle according to claim 1, wherein when the driving of the electric motor (30) is stopped, communication between the pump (39) and the steering device (45) is interrupted via the first solenoid valve (80B).

5. a second solenoid valve (84) is provided in a second pipe (83) connecting a portion of the first pipe (71) between the first solenoid valve (80B) and the steering device (45) to an oil tank (38) for storing working oil; 5. A work vehicle according to claim 4, wherein when the electric motor (30) starts to drive, the hydraulic oil in the first pipe (71) is drained into the oil tank (38) via the second solenoid valve (84) for a predetermined time.

6. a check valve (81) is provided between the first pipe (71) connecting the pump (39) and the steering device (45); 2. A work vehicle according to claim 1, wherein the check valve (81) allows hydraulic oil to be supplied from the pump (39) to the steering device (45) and prevents hydraulic oil from being discharged from the steering device (45) to the pump (39).

7. a second solenoid valve (84) is provided in a second pipe (83) connecting a portion of the first pipe (71) between the check valve (81) and the steering device (45) to an oil tank (38) for storing working oil; 7. A work vehicle according to claim 6, wherein when the electric motor (30) starts to drive, the hydraulic oil in the first pipe (71) is drained into the oil tank (38) via the second solenoid valve (84) for a predetermined period of time.

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