electric work vehicle

Abstract

To provide an electric work vehicle capable of changing a vehicle speed while maintaining the rotation speed of power take-off shafts at a target rotation speed.SOLUTION: An electric work vehicle includes: a motor control unit for controlling a motor M; power take-off shafts 17, 18 that can be connected with a work device and transmit rotary power from the motor M to the work device; and a distribution mechanism 20 for distributing the rotary power outputted from the motor M to a hydrostatic continuously variable transmission 15 and the power take-off shafts 17, 18. The hydrostatic continuously variable transmission 15 is configured to shift the speed of the rotary power inputted into the hydrostatic continuously variable transmission 15 and output the rotary power to a travel device. The motor control unit can perform maintenance control for maintaining the output rotation speed of the motor M at a rotation speed corresponding to the target rotation speed of the power take-off shafts 17, 18. The hydrostatic continuously variable transmission 15 is configured to be capable of changing a gear shift state in the hydrostatic continuously variable transmission 15 according to manual operation of a speed change operation tool in the state where the maintenance control is being performed.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an electric work vehicle that includes a battery, a motor that is driven by power supplied from the battery, and a traveling device that is driven by rotational power output from the motor. [Background technology]

[0002] An example of an electric work vehicle like the one described above is already known, as described in Patent Document 1. In this electric work vehicle (referred to as a "tractor" in Patent Document 1), part of the motor's output is transmitted to the work implement (referred to as a "cultivator" in Patent Document 1). This drives the work implement. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-957 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 does not provide a detailed description of the power transmission structure for transmitting the output from the motor to the working device. However, it is conceivable to provide a power take-off shaft that can be connected to the working device and can transmit rotational power from the motor to the working device in the electric work vehicle described in Patent Document 1. With this configuration, the working device can be driven by connecting it to the power take-off shaft.

[0005] However, depending on the configuration of the power transmission structure that transmits the output from the motor to the working device, it is possible that when the speed of the rotational power transmitted to the traveling device is changed in order to change the vehicle speed, the rotation speed of the power take-off shaft will also change.

[0006] An object of the present invention is to provide an electric work vehicle that is capable of changing the vehicle speed while maintaining the rotational speed of the power take-off shaft at a target rotational speed. [Means for solving the problem]

[0007] The present invention is characterized by: an output shaft of the transmission device connected to an input shaft of the traveling device located at a different height; and a power distribution mechanism for distributing the rotational power output from the motor to a hydrostatic continuously variable transmission and the power take-off shaft; and a transmission device for changing the speed of the rotational power output from the hydrostatic continuously variable transmission and outputting it to the traveling device. The motor control unit is capable of maintenance control for maintaining the output rotational speed of the motor at a rotational speed corresponding to a target rotational speed of the power take-off shaft, and the hydrostatic continuously variable transmission is configured to be able to change the speed change state of the hydrostatic continuously variable transmission in response to manual operation of a speed change operating tool while the maintenance control is being executed, and the output shaft of the transmission device is connected to an input shaft of the traveling device located at a different height. The mid-power takeoff shaft is provided in the center of the vehicle in the longitudinal direction, and the transmission is provided behind the motor. The mid-power takeoff shaft extends forward from below the transmission. Electric work vehicle.

[0008] According to this configuration, by manually operating the speed change operating device while maintenance control is being executed, the rotational speed of the power take-off shaft is maintained at the target rotational speed, while the speed of the rotational power output from the hydrostatic continuously variable transmission to the traveling device is changed, thereby changing the vehicle speed.

[0009] That is, with this configuration, it is possible to realize an electric work vehicle that is capable of changing the vehicle speed while maintaining the rotational speed of the power take-off shaft at the target rotational speed.

[0010] Furthermore, in the present invention, it is preferable that the hydrostatic continuously variable transmission has a relief mechanism.

[0011] With this configuration, when a relatively large rotational fluctuation (load fluctuation) is transmitted from the traveling device to the hydrostatic continuously variable transmission due to the influence of ground conditions, etc., the shock caused by the rotational fluctuation is absorbed by the hydraulic relief in the relief mechanism, thereby reducing the shock transmitted to the motor, etc.

[0012] Furthermore, in the present invention, it is preferable that the hydrostatic continuously variable transmission is configured to be able to output rotational power in a forward direction and a reverse direction to the traveling device in response to manual operation of the speed change operating device, and that the traveling device is driven by the rotational power in the forward direction to enable forward travel, and that the traveling device is driven by the rotational power in the reverse direction to enable reverse travel.

[0013] This configuration makes it possible to realize an electric work vehicle that can travel forward and backward without providing a dedicated mechanism for reversing the traveling device in addition to a hydrostatic continuously variable transmission. In other words, an electric work vehicle that can travel forward and backward can be realized with a relatively simple configuration.

[0014] Furthermore, in the present invention, it is preferable that a rotary operating device is provided that accepts an operation to change the rotational state of the power take-off shaft, and when the speed change state of the hydrostatic continuously variable transmission is a state in which no rotational power is output from the hydrostatic continuously variable transmission and the rotary operating device is operated so that the power take-off shaft does not rotate, the motor control unit executes reduction control to reduce the output torque of the motor.

[0015] According to this configuration, when the hydrostatic continuously variable transmission does not output rotational power and the power takeoff shaft does not rotate, the output torque of the motor decreases, which makes it possible to reduce battery power consumption when the hydrostatic continuously variable transmission does not output rotational power and the power takeoff shaft does not rotate.

[0016] Furthermore, in the present invention, it is preferable that the driving of the motor is stopped during the reduction control.

[0017] According to this configuration, the motor is stopped when no rotational power is output from the hydrostatic continuously variable transmission and the power take-off shaft is not rotating, which makes it possible to reduce battery power consumption compared to a configuration in which the motor is not stopped when no rotational power is output from the hydrostatic continuously variable transmission and the power take-off shaft is not rotating.

[0018] Furthermore, in the present invention, it is preferable that a front power take-off shaft is provided as the power take-off shaft provided at the front of the aircraft body.

[0019] With this configuration, power from the motor can be taken off through the front power take-off shaft, so when a work implement such as a front mower or snow removal device is connected to the front of the machine body, it is easy to take power from the motor into the connected work implement. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 2 is a left side view of the tractor. [Figure 2] FIG. 2 is a left side view showing the arrangement of an inverter and the like. [Figure 3] FIG. 2 is a diagram illustrating a flow of power transmission. [Figure 4] FIG. [Figure 5] FIG. 2 is a partially cutaway left side view showing the configuration of the power transmission shaft and the like. [Figure 6] FIG. 2 is a block diagram showing a configuration related to a control unit. [Figure 7] FIG. 2 is a hydraulic circuit diagram showing the configuration of a relief mechanism and the like. [Figure 8] 10 is a flowchart of a reduction control flow. [Figure 9] FIG. 10 is a block diagram showing a configuration related to a control unit in a first alternative embodiment. [Figure 10] 10 is a flowchart of a reduction control flow in a first alternative embodiment. [Figure 11] FIG. 10 is a schematic side view showing a power transmission device of a tractor in another embodiment (8). [Figure 12] FIG. 10 is a schematic side view showing a power transmission device of a tractor in another embodiment (9). DETAILED DESCRIPTION OF THE INVENTION

[0021] An embodiment of the present invention will be described with reference to the drawings. In the following description, unless otherwise specified, the direction of arrow F in the drawings will be referred to as "front," the direction of arrow B as "rear," the direction of arrow L as "left," and the direction of arrow R as "right." Furthermore, the direction of arrow U in the drawings will be referred to as "up," and the direction of arrow D as "down."

[0022] [Overall configuration of the tractor] The tractor of this embodiment will be described below. As shown in Fig. 1, the tractor has left and right front wheels 10, left and right rear wheels 11, and a cover member 12.

[0023] The tractor also includes a machine body frame 2 and a driving section 3. The machine body frame 2 is supported by left and right front wheels 10 and left and right rear wheels 11.

[0024] The cover member 12 is disposed at the front of the vehicle body, and the driving section 3 is provided behind the cover member 12. In other words, the cover member 12 is disposed in front of the driving section 3.

[0025] The driver's section 3 has a protective frame 30, a driver's seat 31, and a steering wheel 32. An operator can sit in the driver's seat 31. This allows the operator to get into the driver's section 3. The left and right front wheels 10 are steered by operating the steering wheel 32. The operator can perform various driving operations in the driver's section 3.

[0026] The tractor is equipped with a traction battery 4. The cover member 12 is configured to be swingable about an opening / closing axis Q that extends in the left-right direction of the vehicle body. This allows the cover member 12 to be opened and closed. When the cover member 12 is in the closed state, the traction battery 4 is covered by the cover member 12.

[0027] As shown in Fig. 2, the tractor includes an inverter 14 and a motor M. The traction battery 4 supplies power to the inverter 14. The inverter 14 converts DC power from the traction battery 4 into AC power and supplies it to the motor M. The motor M is then driven by the AC power supplied from the inverter 14.

[0028] 2 and 3, the tractor is equipped with a hydrostatic continuously variable transmission 15 and a transmission 16. As shown in Fig. 3, the hydrostatic continuously variable transmission 15 has a hydraulic pump 15a and a hydraulic motor 15b.

[0029] The hydraulic pump 15a is driven by rotational power from the motor M. When the hydraulic pump 15a is driven, rotational power is output from the hydraulic motor 15b. The hydrostatic continuously variable transmission 15 is configured so that the speed of the rotational power is changed between the hydraulic pump 15a and the hydraulic motor 15b. The hydrostatic continuously variable transmission 15 is also configured so that the gear ratio can be changed continuously.

[0030] The rotational power output from the hydraulic motor 15b is transmitted to the transmission 16. The rotational power transmitted to the transmission 16 is changed in speed by a gear-type speed change mechanism of the transmission 16 and distributed to the left and right front wheels 10 and the left and right rear wheels 11. In this way, the left and right front wheels 10 and the left and right rear wheels 11 are driven.

[0031] 2 and 3, the tractor is equipped with a mid PTO shaft 17 and a rear PTO shaft 18. The rotational power output from the motor M is distributed to the hydraulic pump 15a, the mid PTO shaft 17, and the rear PTO shaft 18. This causes the mid PTO shaft 17 and the rear PTO shaft 18 to rotate.

[0032] If a working device is connected to the mid PTO shaft 17 or the rear PTO shaft 18, the working device will be driven by the rotational power of the mid PTO shaft 17 or the rear PTO shaft 18. For example, as shown in FIG. 2, in this embodiment, a brush cutting device 19 is connected to the mid PTO shaft 17. The brush cutting device 19 is driven by the rotational power of the mid PTO shaft 17.

[0033] With the above configuration, the tractor of this embodiment is equipped with a driving battery 4, a motor M driven by power supplied from the driving battery 4, and left and right front wheels 10 and left and right rear wheels 11 driven by rotational power output from the motor M.

[0034] The tractor also includes a mid PTO shaft 17 and a rear PTO shaft 18 that can be connected to a work implement and that can transmit rotational power from the motor M to the work implement.

[0035] In addition, in this tractor, the hydrostatic continuously variable transmission 15 is configured to change the speed of the rotational power input to the hydrostatic continuously variable transmission 15 and output it to the left and right front wheels 10 and the left and right rear wheels 11.

[0036] This tractor corresponds to the "electric work vehicle" according to the present invention. The traction battery 4 corresponds to the "battery" according to the present invention. The left and right front wheels 10 and the left and right rear wheels 11 each correspond to the "traveling device" according to the present invention. The mid PTO shaft 17 and the rear PTO shaft 18 each correspond to the "power take-off shaft" according to the present invention. The brush cutting device 19 corresponds to the "working device" according to the present invention.

[0037] [Power transmission mechanism] As shown in Fig. 4, this tractor is equipped with a distribution mechanism 20. The distribution mechanism 20 has a power transmission shaft MB, a first shaft 21, a first gear mechanism 22, a second gear mechanism 23, a second shaft 24, a third gear mechanism 25, a first clutch 26, and a second clutch 27. The first clutch 26 and the second clutch 27 are both configured to be able to change their states between an on state in which they transmit power and a off state in which they do not transmit power.

[0038] An output shaft MA of the motor M is connected to a first shaft 21 via a power transmission shaft MB. The output shaft MA, power transmission shaft MB, and first shaft 21 rotate integrally. The first shaft 21 is connected to a hydraulic pump 15a. When the first clutch 26 is engaged, rotational power is transmitted from the first shaft 21 to the first gear mechanism 22. When the second clutch 27 is engaged, rotational power is transmitted from the first shaft 21 to the second shaft 24.

[0039] With this configuration, the rotational power output from the motor M is distributed from the first shaft 21 to the hydraulic pump 15a, the first gear mechanism 22, and the second shaft 24.

[0040] The rotational power transmitted to the first gear mechanism 22 is transmitted to the mid-PTO shaft 17 via the second gear mechanism 23. This causes the mid-PTO shaft 17 to rotate.

[0041] The rotational power transmitted to the second shaft 24 is transmitted to the rear PTO shaft 18 via the third gear mechanism 25. As a result, the rear PTO shaft 18 rotates.

[0042] As described above, the tractor of this embodiment is provided with a distribution mechanism 20 that distributes the rotational power output from the motor M to the hydrostatic continuously variable transmission 15, the mid PTO shaft 17, and the rear PTO shaft 18.

[0043] With the above configuration, when the motor M is driving to rotate, if the first clutch 26 is engaged, the mid PTO shaft 17 rotates, and when the first clutch 26 is disengaged, the mid PTO shaft 17 does not rotate. Also, when the motor M is driving to rotate, if the second clutch 27 is engaged, the rear PTO shaft 18 rotates, and when the second clutch 27 is disengaged, the rear PTO shaft 18 does not rotate.

[0044] The rotational power transmitted to the hydraulic pump 15a is hydraulically changed in the hydrostatic continuously variable transmission 15 and output from the hydraulic motor 15b. The rotational power output from the hydraulic motor 15b is transmitted via the third shaft 41 to a speed change unit 16a, which is a gear-type speed change mechanism of the transmission 16. The rotational power transmitted to the speed change unit 16a is changed in speed by the speed change unit 16a and distributed to the power transmission shaft X and the rear wheel differential mechanism 43. The rotational power transmitted to the power transmission shaft X is transmitted to the left and right front wheels 10 via the transmission connection unit Z and the power transmission shaft Y. This drives the left and right front wheels 10. The rotational power transmitted to the rear wheel differential mechanism 43 drives the left and right rear wheels 11.

[0045] As shown in Figures 2 and 5, the power transmission shaft X is disposed obliquely forward to transmit power from the transmission 16 through a case W connected to the hydrostatic continuously variable transmission 15. The front wheel input section 10A, through which power is input to the left and right front wheels 10, is disposed at a position lower than the upstream end of the power transmission shaft X in the power transmission direction. By configuring the power transmission shaft X to be connected to the front wheel input section 10A via the transmission connection section Z and the power transmission shaft Y, power is transmitted from the upstream end of the power transmission shaft X in the power transmission direction to the front wheel input section 10A, which is located at a different height from the upstream end. The transmission connection section Z is disposed below the motor M and is surrounded by the vehicle frame 2.

[0046] 2 and 5, the motor M and hydrostatic continuously variable transmission 15 are positioned apart from each other and connected to each other by the power transmission shaft MB, which makes it less likely that resonance will occur. Because the inverter 14 is susceptible to vibrations, it is connected to the vehicle frame 2 and the driving battery 4 is positioned above the inverter 14, making it less likely that vibration will occur near the inverter 14. In addition, by positioning the inverter 14 at a distance from the hydrostatic continuously variable transmission 15, problems caused by vibrations are less likely to occur.

[0047] As shown in Fig. 5, a radiator 80, a DC (Direct Current) converter 81, and an auxiliary battery 82 are disposed in front of the traction battery 4. The radiator 80 and a water pump (not shown) are included in the cooling water path of the tractor. The cooling water is pumped by the water pump, causing the cooling water to circulate through this cooling water path. The cooling water is cooled as it passes through the radiator 80.

[0048] Furthermore, power is sent from the driving battery 4 to a DC-DC converter 81. Then, the DC-DC converter 81 steps down the power from the driving battery 4 and supplies it to an auxiliary battery 82. The auxiliary battery 82 supplies power to various auxiliary devices.

[0049] [Various operating tools] As shown in Fig. 6, this tractor is equipped with an accelerator operation device 51, a rotation operation device 52, a speed change operation device 53, and a control unit 54. The accelerator operation device 51, the rotation operation device 52, and the speed change operation device 53 are not particularly limited, and may be, for example, a lever or a button. Furthermore, the accelerator operation device 51, the rotation operation device 52, and the speed change operation device 53 may be provided in the driving unit 3, for example.

[0050] The control unit 54 has a motor control unit 55 , a working clutch control unit 56 , and a gear change control unit 57 .

[0051] When the accelerator operation device 51 is manually operated, a signal corresponding to the operation is sent to the motor control unit 55. The motor control unit 55 controls the inverter 14 based on the signal, thereby controlling the output rotation speed of the motor M. That is, the motor control unit 55 controls the output rotation speed of the motor M in response to the manual operation of the accelerator operation device 51. The accelerator operation device 51 also accepts an operation to change the output rotation speed of the motor M.

[0052] As described above, the tractor of this embodiment is provided with the motor control unit 55 that controls the motor M.

[0053] When the rotation operating device 52 is manually operated, a signal corresponding to the operation is sent to the work clutch control unit 56. The work clutch control unit 56 controls the on / off states of the first clutch 26 and the second clutch 27 based on the signal. In this way, the work clutch control unit 56 controls the rotation states of the mid PTO shaft 17 and the rear PTO shaft 18. More specifically, the work clutch control unit 56 switches the states of the mid PTO shaft 17 and the rear PTO shaft 18 between a rotating state and a non-rotating state.

[0054] That is, the work clutch control unit 56 controls the rotational states of the mid PTO shaft 17 and the rear PTO shaft 18 in response to manual operation of the rotation operation device 52. In addition, the rotation operation device 52 accepts operations to change the rotational states of the mid PTO shaft 17 and the rear PTO shaft 18.

[0055] As described above, the tractor of this embodiment is provided with the rotation operation device 52 that accepts an operation to change the rotation state of the mid PTO shaft 17 and the rear PTO shaft 18.

[0056] When the gear shift operating device 53 is manually operated, a signal corresponding to the operation is sent to the gear shift control unit 57. The gear shift control unit 57 controls the angle of a pump swash plate 58 of the hydraulic pump 15a based on the signal. When the angle of the pump swash plate 58 changes, the gear ratio of the hydrostatic continuously variable transmission 15 changes. In other words, the gear shift control unit 57 controls the gear shift state of the hydrostatic continuously variable transmission 15 in accordance with the manual operation of the gear shift operating device 53. The gear shift operating device 53 also accepts an operation to change the gear shift state of the hydrostatic continuously variable transmission 15.

[0057] The hydrostatic continuously variable transmission 15 is configured so that when the pump swash plate 58 is in the neutral state, no rotational power is output from the hydraulic motor 15b. The hydrostatic continuously variable transmission 15 is also configured so that it can output rotational power in the forward and reverse directions to the left and right front wheels 10 and the left and right rear wheels 11 according to the angle of the pump swash plate 58. That is, the hydrostatic continuously variable transmission 15 is configured so that it can output rotational power in the forward and reverse directions to the left and right front wheels 10 and the left and right rear wheels 11 according to the manual operation of the speed change operating device 53.

[0058] The tractor of this embodiment can move forward by driving the left and right front wheels 10 and the left and right rear wheels 11 with rotational power in the forward direction. The tractor of this embodiment can also move backward by driving the left and right front wheels 10 and the left and right rear wheels 11 with rotational power in the reverse direction.

[0059] When the tractor of this embodiment is traveling for work, the operator operates the accelerator operation device 51 to set the output rotation speed of the motor M to a rotation speed corresponding to the target rotation speed of the mid PTO shaft 17 or the rear PTO shaft 18. The motor control unit 55 is configured to be able to maintain the output rotation speed of the motor M at the rotation speed set by manual operation of the accelerator operation device 51 while the tractor is traveling for work.

[0060] That is, the motor control unit 55 is capable of maintaining the output rotation speed of the motor M at a rotation speed corresponding to the target rotation speed of the mid PTO shaft 17 or the rear PTO shaft 18.

[0061] Furthermore, even when maintenance control is being executed by the motor control unit 55, the speed change state of the hydrostatic continuously variable transmission 15 can be changed by manually operating the speed change operating device 53. This makes it possible to change the vehicle speed while maintaining the rotation speed of the mid PTO shaft 17 or the rear PTO shaft 18.

[0062] In this way, the hydrostatic continuously variable transmission 15 is configured so that the speed change state of the hydrostatic continuously variable transmission 15 can be changed in response to manual operation of the speed change operating device 53 while maintenance control is being executed.

[0063] The control unit 54 and each element included in the control unit 54, such as the motor control unit 55, may be a physical device such as a microcomputer, or may be a functional unit in software.

[0064] [Hydraulic system] 7, the hydrostatic continuously variable transmission 15 has a hydraulic circuit 60. The hydraulic pump 15a and the hydraulic motor 15b are included in the hydraulic circuit 60. The hydrostatic continuously variable transmission 15 also has an oil pump 61 and a relief mechanism 62.

[0065] The oil pump 61 is connected to the first shaft 21. The oil pump 61 is configured to be driven by rotational power from the first shaft 21. The oil pump 61 supplies oil (hydraulic oil) to the hydraulic circuit 60.

[0066] However, the present invention is not limited to this, and the oil pump 61 may be provided outside the hydrostatic continuously variable transmission 15. Furthermore, the oil pump 61 may be configured to be driven by rotational power from a member other than the first shaft 21.

[0067] The relief mechanism 62 is connected to the hydraulic circuit 60. The relief mechanism 62 is a mechanism that discharges oil (working oil) in the hydraulic circuit 60 to the outside of the hydraulic circuit 60 when the hydraulic pressure in the hydraulic circuit 60 exceeds a predetermined threshold. With this configuration, when the hydraulic pressure in the hydraulic circuit 60 exceeds the predetermined threshold, the oil is discharged from the hydraulic circuit 60 via the relief mechanism 62. In this way, the hydrostatic continuously variable transmission 15 has the relief mechanism 62.

[0068] [Decrease control] 6 is configured to execute reduction control when the speed change state of the hydrostatic continuously variable transmission 15 is a state in which rotational power is not output from the hydrostatic continuously variable transmission 15 and the rotation operating device 52 is operated so that the mid PTO shaft 17 and the rear PTO shaft 18 do not rotate. The reduction control is control to reduce the output torque of the motor M. In this embodiment, the reduction control stops the drive of the motor M.

[0069] In other words, when the speed change state of the hydrostatic continuously variable transmission 15 is a state in which no rotational power is output from the hydrostatic continuously variable transmission 15 and the rotation operating device 52 is operated so that the mid PTO shaft 17 and the rear PTO shaft 18 do not rotate, the motor control unit 55 executes reduction control to reduce the output torque of the motor M.

[0070] The following describes the reduction control. The motor control unit 55 is configured to execute the reduction control in accordance with the reduction control flow shown in Fig. 8. This reduction control flow is executed repeatedly at regular intervals while the motor M is rotating.

[0071] When this lowering control flow is started, first, the process of step S01 is executed. In step S01, as shown in Fig. 6, information indicating the operation state of the rotation operation device 52 is sent from the rotation operation device 52 to the motor control unit 55. Based on the information, the motor control unit 55 determines whether the rotation operation device 52 is being operated so as not to rotate the mid PTO shaft 17 and the rear PTO shaft 18.

[0072] If the rotation operation device 52 is not being operated so that the mid PTO shaft 17 and the rear PTO shaft 18 do not rotate ("No" in step S01 in FIG. 8), this lowering control flow is temporarily ended.

[0073] If the rotation operation device 52 is operated so that the mid PTO shaft 17 and the rear PTO shaft 18 do not rotate ("Yes" in step S01 in FIG. 8), the process proceeds to step S02.

[0074] In step S02, as shown in Fig. 6, information indicating the operation state of the speed change operating device 53 is sent from the speed change operating device 53 to the motor control unit 55. Based on the information, the motor control unit 55 determines whether the speed change state of the hydrostatic continuously variable transmission 15 is a state in which no rotational power is output from the hydrostatic continuously variable transmission 15. More specifically, the motor control unit 55 determines whether the pump swash plate 58 is in a neutral state.

[0075] If the pump swash plate 58 is not in the neutral state ("No" in step S02 in FIG. 8), this reduction control flow is temporarily ended.

[0076] If the pump swash plate 58 is in the neutral state ("Yes" in step S02 in FIG. 8), the process proceeds to step S03.

[0077] In step S03, the above-described reduction control is executed by the motor control unit 55. After that, this reduction control flow ends for the time being.

[0078] Although not particularly limited, after the reduction control is executed, the output torque of the motor M may be restored, for example, when the speed change state of the hydrostatic continuously variable transmission 15 becomes a state in which rotational power is output from the hydrostatic continuously variable transmission 15, or the output torque of the motor M may be restored when the rotation operation device 52 is operated so as to rotate the mid PTO shaft 17 or the rear PTO shaft 18. Note that restoring the output torque to its original value means returning the output torque to the value before the reduction control was executed.

[0079] According to the configuration described above, by manually operating the speed change operating device 53 while maintenance control is being executed, the rotational speed of the mid PTO shaft 17 or the rear PTO shaft 18 is maintained at the target rotational speed, while the speed of the rotational power output from the hydrostatic continuously variable transmission 15 to the left and right front wheels 10 and the left and right rear wheels 11 changes. As a result, the vehicle speed changes.

[0080] That is, according to the configuration described above, a tractor can be realized that is capable of changing the vehicle speed while maintaining the rotation speed of the mid PTO shaft 17 or the rear PTO shaft 18 at the target rotation speed.

[0081] [First Alternative Embodiment] In the above embodiment, a hydrostatic continuously variable transmission 15 is provided.

[0082] However, the present invention is not limited to this. Below, a first alternative embodiment of the present invention will be described, focusing on the differences from the above embodiment. The configuration other than the parts described below is the same as the above embodiment. Furthermore, the same reference numerals are used to designate the same configuration as the above embodiment.

[0083] As shown in Fig. 9, in the first alternative embodiment, a traveling clutch 72 is provided instead of the hydrostatic continuously variable transmission 15. Also, in the first alternative embodiment, a traveling clutch operating device 70 and a traveling clutch control device 71 are provided instead of the speed change operating device 53 and the speed change control device 57. The traveling clutch operating device 70 is not particularly limited, and may be, for example, a lever or a button. Also, the traveling clutch operating device 70 may be provided in the driving unit 3, for example.

[0084] The traveling clutch 72 is configured to be able to change its state between an on state in which power is transmitted and a off state in which power is not transmitted. The power transmission mechanism of the first alternative embodiment is configured so that when the traveling clutch 72 is in the on state, rotational power is transmitted from the first shaft 21 to the third shaft 41 via the traveling clutch 72. When the traveling clutch 72 is in the off state, rotational power from the motor M is not transmitted to the left and right front wheels 10 and the left and right rear wheels 11.

[0085] When the traveling clutch operating device 70 is manually operated, a signal corresponding to the operation is sent to the traveling clutch control unit 71. The traveling clutch control unit 71 controls the on / off state of the traveling clutch 72 based on the signal. That is, the traveling clutch control unit 71 controls the on / off state of the traveling clutch 72 in response to the manual operation of the traveling clutch operating device 70.

[0086] In the first alternative embodiment, the motor control unit 55 is configured to execute the above-mentioned reduction control when the traveling clutch 72 is in the disengaged state and the rotation operating device 52 is operated so that the mid PTO shaft 17 and the rear PTO shaft 18 do not rotate.

[0087] More specifically, the motor control unit 55 in the first alternative embodiment is configured to execute the reduction control in accordance with the reduction control flow shown in Fig. 10. This reduction control flow is repeatedly executed at regular time intervals while the motor M is rotating.

[0088] When this lowering control flow is started, first, the process of step S11 is executed. In step S11, similar to step S01 in Fig. 8, it is determined whether the rotation operating device 52 is being operated so that the mid PTO shaft 17 and the rear PTO shaft 18 do not rotate.

[0089] If the rotation operation device 52 is not being operated so that the mid PTO shaft 17 and the rear PTO shaft 18 do not rotate ("No" in step S11 of FIG. 10), this lowering control flow is temporarily ended.

[0090] If the rotation operation device 52 is operated so that the mid PTO shaft 17 and the rear PTO shaft 18 do not rotate ("Yes" in step S11 of FIG. 10), the process proceeds to step S12.

[0091] 9, in step S12, information indicating the operating state of the traveling clutch operating device 70 is sent from the traveling clutch operating device 70 to the motor control unit 55. Based on the information, the motor control unit 55 determines whether the traveling clutch 72 is in the disengaged state.

[0092] If the running clutch 72 is not in the disengaged state ("No" in step S12 of FIG. 10), this decrease control flow ends for the time being.

[0093] If the running clutch 72 is in the disengaged state ("Yes" in step S12 of FIG. 10), the process proceeds to step S13.

[0094] In step S13, the above-described reduction control is executed by the motor control unit 55. After that, this reduction control flow ends for the time being.

[0095] Other Embodiments (1) The rotation speed corresponding to the target rotation speed of the mid PTO shaft 17 or the rear PTO shaft 18 may be determined in advance, regardless of the manual operation of the accelerator operation device 51. In this case, the accelerator operation device 51 does not need to be provided.

[0096] (2) The rotation operation tool 52 may be connected to the first clutch 26 and the second clutch 27 by a mechanical link. In this case, the work clutch control unit 56 may not be provided.

[0097] (3) The speed change operating device 53 may be connected to the pump swash plate 58 by a mechanical link. In this case, the speed change control unit 57 may not be provided.

[0098] (4) The hydrostatic continuously variable transmission 15 may be configured so as not to be able to output rotational power in the reverse direction.

[0099] (5) In the reduction control, the driving of the motor M does not have to be stopped.

[0100] (6) The motor control unit 55 may be configured not to execute the reduction control.

[0101] (7) Either the mid PTO shaft 17 or the rear PTO shaft 18 does not have to be provided.

[0102] (8) The tractor may be configured as shown in Fig. 11. In the tractor shown in Fig. 11, a first front PTO shaft 91 (corresponding to the "power take-off shaft" and "front power take-off shaft" according to the present invention) is provided at the front of the machine body. The first front PTO shaft 91 takes power from the motor M.

[0103] Specifically, the first front PTO shaft 91 is rotatably supported by a first support portion 92 provided at the front of the body frame 2. A rear portion of the first front PTO shaft 91 is connected to an output portion M2 provided at the motor M via a rotating shaft 93. The rotating shaft 93 is rotatably supported by a second support portion 94 provided at the body frame 2 between the first support portion 92 and the output portion M2. Power output from the output portion M2 of the motor M is transmitted to the first front PTO shaft 91 via the rotating shaft 93.

[0104] In this configuration, the first front PTO shaft 91 is connectable to a work device and can transmit rotational power from the motor M to the work device. Furthermore, with a configuration similar to that of the above embodiment, the motor control unit 55 is capable of maintenance control to maintain the output rotation speed of the motor M at a rotation speed corresponding to the target rotation speed of the first front PTO shaft 91. Furthermore, with a configuration similar to that of the above embodiment, the rotation operating device 52 accepts an operation to change the rotation state of the first front PTO shaft 91. Furthermore, with a configuration similar to that of the above embodiment, when the speed change state of the hydrostatic continuously variable transmission 15 is a state in which no rotational power is output from the hydrostatic continuously variable transmission 15 and the rotation operating device 52 is operated so that the mid PTO shaft 17, the rear PTO shaft 18, and the first front PTO shaft 91 do not rotate, the motor control unit 55 executes reduction control to reduce the output torque of the motor M.

[0105] In this configuration, the output section M2 is included in the distribution mechanism 20. That is, in this configuration, the distribution mechanism 20 distributes the rotational power output from the motor M to the hydrostatic continuously variable transmission 15, the mid PTO shaft 17, the rear PTO shaft 18, and the first front PTO shaft 91.

[0106] (9) The tractor may be configured as shown in Fig. 12. In the tractor shown in Fig. 12, a second front PTO shaft 95 (corresponding to the "power take-off shaft" and "front power take-off shaft" according to the present invention) is provided at the front of the machine body. The second front PTO shaft 95 takes power from the motor M.

[0107] Specifically, the second front PTO shaft 95 is rotatably supported by a first support portion 92 provided at the front of the machine frame 2. The rear portion of the second front PTO shaft 95 is connected to a power take-off portion 96a provided on an input case 96 of the brush mower 19 via a rotating shaft 97. The rotating shaft 97 is rotatably supported by a second support portion 94 provided on the machine frame 2 between the first support portion 92 and the power take-off portion 96a. A universal joint 98 serving as a bending portion that enables the brush mower 19 to be raised and lowered is provided on the rotating shaft 97 at a position between the second support portion 94 and the power take-off portion 96a. Power output by the motor M is transmitted to the second front PTO shaft 95 via the mid-PTO shaft 17, the input case 96, and the rotating shaft 97.

[0108] In this configuration, the second front PTO shaft 95 is connectable to a work device and can transmit rotational power from the motor M to the work device. Furthermore, with a configuration similar to that of the above embodiment, the motor control unit 55 is capable of maintenance control to maintain the output rotation speed of the motor M at a rotation speed corresponding to the target rotation speed of the second front PTO shaft 95. Furthermore, with a configuration similar to that of the above embodiment, the rotation operating device 52 accepts an operation to change the rotation state of the second front PTO shaft 95. Furthermore, with a configuration similar to that of the above embodiment, when the speed change state of the hydrostatic continuously variable transmission 15 is a state in which no rotational power is output from the hydrostatic continuously variable transmission 15 and the rotation operating device 52 is operated so that the mid PTO shaft 17, the rear PTO shaft 18, and the second front PTO shaft 95 do not rotate, the motor control unit 55 executes reduction control to reduce the output torque of the motor M.

[0109] In this configuration, the distribution mechanism 20 distributes the rotational power output from the motor M to the hydrostatic continuously variable transmission 15, the mid PTO shaft 17, the second front PTO shaft 95, and the rear PTO shaft 18. The second front PTO shaft 95 is located downstream of the mid PTO shaft 17 in the flow of power transmission.

[0110] The configurations disclosed in the above-described embodiments (including other embodiments, the same applies hereinafter) can be applied in combination with the configurations disclosed in other embodiments, unless a contradiction arises. Furthermore, the embodiments disclosed in this specification are merely examples, and the present invention is not limited to these, and can be modified as appropriate within the scope of the purpose of the present invention. [Industrial Applicability]

[0111] The present invention can be used not only in tractors but also in various electric work vehicles such as combine harvesters, rice transplanters, and construction machines. [Explanation of symbols]

[0112] 4. Driving battery (battery) 10 Front wheels (running gear) 11 Rear wheels (running gear) 15 Hydrostatic continuously variable transmission 16 Transmission 17 Mid PTO shaft (power take-off shaft) 18 Rear PTO shaft (power take-off shaft) 19 Grass-cutting equipment (work equipment) 20 Distribution mechanism 52 Rotational control device 53 Gear shifting device 55 Motor control unit 62 Relief mechanism 91 No. 1 front PTO shaft (power take-off shaft, front power take-off shaft) 95 Second front PTO shaft (power take-off shaft, front power take-off shaft) Medium motor

Claims

1. An electric work vehicle comprising: a battery; a motor driven by power supplied from the battery; and a traveling device driven by rotational power output from the motor, a motor control unit that controls the motor; a power take-off shaft that can be connected to a working device and that can transmit rotational power from the motor to the working device; a distribution mechanism that distributes the rotational power output from the motor to the hydrostatic continuously variable transmission and the power takeoff shaft; a transmission device that changes the speed of the rotational power output from the hydrostatic continuously variable transmission and outputs it to the traveling device, the motor control unit is capable of performing maintenance control to maintain the output rotation speed of the motor at a rotation speed corresponding to a target rotation speed of the power take-off shaft, the hydrostatic continuously variable transmission is configured to be able to change a speed change state in the hydrostatic continuously variable transmission in response to a manual operation of a speed change operating device while the maintenance control is being executed, The output shaft of the transmission is connected to the input shaft of the traveling device located at a different height, A mid-power takeoff shaft is provided in the center of the aircraft in the longitudinal direction, the transmission is provided behind the motor, In the electric work vehicle, the mid power take-off shaft extends forward from below the transmission.

2. 2. The electric work vehicle according to claim 1, wherein the hydrostatic continuously variable transmission has a relief mechanism.

3. The hydrostatic continuously variable transmission is configured to be able to output rotational power in a forward rotation direction and a reverse rotation direction to the traveling device in response to manual operation of the speed change operating device, The traveling device is driven by rotational power in the forward direction, thereby allowing the vehicle to move forward; 3. The electric work vehicle according to claim 1, wherein the travel device is driven by rotational power in a reverse direction, thereby enabling the vehicle to travel backward.

4. a rotation operating device that accepts an operation to change the rotation state of the power take-off shaft, 4. The electric work vehicle according to claim 1, wherein when the hydrostatic continuously variable transmission is in a speed-changing state where rotational power is not output from the hydrostatic continuously variable transmission and the rotation operating device is operated so as not to rotate the power takeoff shaft, the motor control unit executes reduction control to reduce the output torque of the motor.

5. The electric work vehicle according to claim 4, wherein the drive of the motor is stopped during the reduction control.

6. 6. The electric work vehicle according to claim 1, further comprising a front power take-off shaft provided at the front of the vehicle body as the power take-off shaft.

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