electric work vehicle

Abstract

The present invention provides an electric work vehicle that can avoid hazards by controlling its speed, such as stopping, decelerating, or maintaining speed. [Solution] The electric work vehicle of the present invention has a work torque map 120 that shows the relationship between the work motor rotation speed Nw and the work motor torque Tw of the work electric motor 30. The work torque map 120 is set with a stop threshold 131 that defines the boundary of the work motor torque Tw when the vehicle is forcibly stopped, a forced deceleration threshold 132 that defines the boundary of the work motor torque Tw when the vehicle speed of the vehicle is forcibly reduced, and a speed increase prohibition threshold 133 that defines the boundary of the work motor torque Tw when speed increase of the vehicle is prohibited. The control device 100 controls the vehicle speed of the vehicle by controlling the travel motor rotation speed Nr of the travel electric motor 40 according to the relationship between the work motor torque Tw at an arbitrary work motor rotation speed Nw and each threshold 131 to 133.

Description

Technical Field

[0001] The present invention relates to an electric work vehicle.

Background Art

[0002] Conventionally, a steering control technique is already known, which switches automatic traveling to manual traveling when a user's steering wheel operation torque exceeds a threshold value corresponding to the vehicle speed during automatic traveling of a work vehicle (see, for example, Patent Document 1 and the like). This type of technique is intended to avoid imminent danger to a work vehicle during automatic operation.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Disclosure of the Invention

Problem to be Solved by the Invention

[0004] However, although the technique of Patent Document 1 is effective for work vehicles during manned automatic operation, it cannot be applied to work vehicles during unmanned automatic traveling. In addition, in consideration of the safety of automatic operation of work vehicles regardless of whether they are manned or unmanned, while steering control techniques are important, it is considered that it is also essential to develop danger avoidance techniques related to vehicle speed such as stopping traveling, decelerating, or maintaining vehicle speed. This type of problem is not limited to conventional work vehicles whose drive source is an engine, but also applies to electric work vehicles whose drive source is an electric motor.

Means for Solving the Problem

[0005] In view of the above problems, it is a technical object of the present invention to provide an electric work vehicle that can avoid danger by controlling vehicle speed such as stopping traveling, decelerating, or maintaining vehicle speed.

[0006] The present invention relates to an electric work vehicle comprising a running unit for moving the vehicle, a work unit provided on the vehicle, a running electric motor for driving the running unit, a work electric motor for driving the work unit, a battery for supplying power to both electric motors, and a control device for controlling various functions, wherein the vehicle has a work torque map showing the relationship between the work motor rotation speed and the work motor torque of the work electric motor, the work torque map includes a stop threshold that defines the boundary of the work motor torque when the vehicle is forcibly stopped, a forced deceleration threshold that defines the boundary of the work motor torque when the vehicle speed of the vehicle is forcibly reduced, and a speed increase prohibition threshold that defines the boundary of the work motor torque when speed increase of the vehicle is prohibited, and the control device controls the vehicle speed of the vehicle by controlling the running motor rotation speed of the running electric motor according to the relationship between the work motor torque at an arbitrary work motor rotation speed and each of the thresholds.

[0007] In the electric work vehicle of the present invention, the control device may stop driving the electric motor for travel and stop the vehicle from moving if the working motor torque at any working motor rotation speed is near one of the threshold values ​​in the threshold value group, and the working motor rotation speed is lower than the rotation speed commanded by the control device for a predetermined period of time or longer.

[0008] In the electric work vehicle of the present invention, when the control device starts driving the travel unit in conjunction with the work unit, it may increase the rotational speed of the travel motor of the travel electric motor at a second upward gradient, which has a smaller gradient angle than the first upward gradient with respect to the amount of operation of the gear shift control device provided on the unit, until the unit reaches a predetermined vehicle speed.

[0009] In the electric work vehicle of the present invention, the control device is capable of performing late limit processing on the amount of operation of the gear shifting device, and the late limit value in the speed-increasing direction under the condition that the driving unit is started to be driven in conjunction with the work unit may be set to be smaller than the late limit value under other conditions.

[0010] In the electric work vehicle of the present invention, the control device is capable of performing automatic driving control that automatically adjusts the vehicle speed of the machine, and the automatic driving control includes at least a time priority mode that shortens the working time for driving the work unit, and the control device may, while performing the automatic driving control in the time priority mode, control the motor to increase the rotational speed of the drive motor by a predetermined increment relative to the current vehicle speed once a predetermined time has elapsed while both the work electric motor and the drive electric motor are driven. [Effects of the Invention]

[0011] Conventionally, the main configuration involved a single engine or electric motor distributing power to both the drive unit and the work unit. Therefore, when prioritizing the torque output of the work unit and reducing the rotational speed of the engine or motor to save energy, the travel speed (vehicle speed) of the drive unit inevitably decreased as well, resulting in a problem where work efficiency could not be improved. In this invention, however, the adoption of a two-motor system, consisting of a work electric motor and a drive electric motor, is effectively utilized to drive and control the work electric motor and the drive electric motor separately, making it possible to drive the work unit in an energy-saving manner without affecting the drive unit.

[0012] Furthermore, according to the present invention, even with a two-motor electric work vehicle, when the workload on the work unit increases, it is possible to prevent an increase in the vehicle speed of the electric work vehicle, forcibly decelerate it, or stop it from moving, thereby preventing various troubles during work and ensuring the stable continuation of various work. Since the above vehicle speed control is executed when a workload occurs that could lead to damage to various gears of the work system, damage to various gears of the work system can be prevented. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic perspective view showing an example of an electric lawnmower. [Figure 2] This is a perspective view of the power unit from the rear left side. [Figure 3]It is a perspective view of the electric chamber seen from the rear right side. [Figure 4] It is a skeleton diagram of the power transmission system of an electric lawn mower. [Figure 5] It is a hydraulic circuit diagram of an electric lawn mower. [Figure 6] It is a skeleton diagram of the cooling system of an electric lawn mower. [Figure 7] It is a functional block diagram of an electric lawn mower [Figure 8] It is an explanatory diagram of a work torque map showing the relationship between the work motor rotation speed and work motor torque of a work electric motor. [Figure 9] It is an explanatory diagram of the first quadrant of the work torque map, and is a diagram explaining the reduction control of the work motor rotation speed. [Figure 10] It is a diagram explaining the increase control of the work motor rotation speed in the first quadrant of the work torque map. [Figure 11] It is a diagram explaining the reduction control of the work motor rotation speed using a no-load torque line in the first quadrant of the work torque map. [Figure 12] It is an explanatory diagram of a case where a speed increase prohibition torque line and a forced deceleration torque line are set in the first quadrant of the work torque map. [Figure 13] It is an explanatory diagram of a case where a stop threshold, a forced deceleration threshold and a speed increase prohibition threshold are set in the first quadrant of the work torque map. [Figure 14] It is a diagram showing the relationship between the shift operation amount of a shift pedal and the travel motor rotation speed of a travel electric motor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, embodiments embodying the present invention will be described with reference to the accompanying drawings. While preferred embodiments of the invention are shown in the drawings, the invention can be embodied in many different forms and is not limited to the embodiments described herein.

[0015] An outline of the electric work vehicle according to the embodiment will be described with reference to FIGS. 1 to 3. In the embodiment, the present invention is applied to an electric lawn mower LM, which is an example of an electric work vehicle. The electric work vehicle is not limited to the electric lawn mower LM, and various types of electric work vehicles such as an electric tractor, an electric rice transplanter, or an electric combine may be adopted. In the following description, when terms indicating a specific direction or position (for example, "left-right", "up-down", etc.) are used, front-rear, left-right, and up-down are expressed based on the forward traveling direction of the electric lawn mower LM. These terms are used for convenience of description, and do not limit the technical scope of the present invention.

[0016] In the embodiment, the body 1 of the electric lawn mower LM is supported by a pair of left and right front wheels 2 and a pair of left and right rear wheels 3, which serve as a traveling unit. The front wheels 2 are mainly wheels for steering and driving. The electric lawn mower LM of the embodiment is configured to be switchable between two-wheel drive (2WD) that drives the front wheels 2 and four-wheel drive (4WD) that drives both the front wheels 2 and the rear wheels 3. It should be noted that the traveling unit is not limited to the front wheels 2 and the rear wheels 3, and may be a pair of left and right traveling crawlers or the like.

[0017] A mower device 4 serving as a working unit is provided at the front portion of the body 1. The mower device 4 is for cutting lawn grass planted in a field or the like. Although detailed illustration is omitted, the mower device 4 includes a pair of left and right rotating cutting blades and a mower lifting cylinder 14 (see FIG. 5). The mower device 4 is configured to move up and down by the expansion and contraction movement of the left and right mower lifting cylinders 14. The working unit of the embodiment includes an electric working unit and a hydraulic working unit. The mower device 4 corresponds to the electric working unit, and the mower lifting cylinder 14 corresponds to the hydraulic working unit.

[0018] A steering section 5 on which a user such as an operator rides is arranged at the front upper portion of the body 1. A safety frame 6 for protecting the user is erected at the rear portion of the steering section 5. A grass collecting container 7 for storing lawn grass cut by the mower device 4 is mounted on the body 1 rearward of the safety frame 6. A portion of the body 1 below the grass collecting container 7 is configured as an electric chamber 8 that accommodates a working electric motor 30, a traveling electric motor 40, a high-voltage battery 50 and the like, which will be described later.

[0019] In the control unit 5, a steering column 10 supporting a steering handle 9 for steering the front wheels is erected in front of the driver's seat where the user sits. Display devices such as an instrument panel (not shown) are located in front of the steering handle 9 on the steering column 10. In the control unit 5, a foot-operated brake pedal 11 for braking the front wheels 2 and rear wheels 3 is provided to the left of the steering column 10. A foot-operated gear shift pedal 12 for increasing or decreasing the speed of the electric lawnmower LM is provided to the right of the steering column 10. The fenders 13 on both the left and right sides of the driver's seat cover the top of the corresponding front wheels 2.

[0020] The rear of the mower device 4 and the front of the grass collection container 7 are connected via a hollow cylindrical chute 16 that extends in the front-to-back direction. A blower 17 is provided at the middle of the chute 16 to create an airflow toward the grass collection container 7 (see Figure 4). In this case, the grass cut by the rotating cutting blades of the mower device 4 is transported and collected into the grass collection container 7 via the chute 16 by the airflow generated by the cutting blades and the airflow from the blower 17. The blower 17 corresponds to the electric working unit.

[0021] A pair of link arms 18 are attached to both the left and right sides of the grass collection container 7. The front of each link arm 18 is supported by a safety frame 6 so as to be able to swing up and down. A lift cylinder 19 is mounted between each link arm 18 and the safety frame 6. The extension and retraction of both the left and right lift cylinders 19 causes the grass collection container 7 to move up and down via the left and right link arms 18.

[0022] A rear gate 15 that can be opened and closed is provided on the rear side of the grass collection container 7. A dump cylinder 20 is provided on the rear side of each link arm 18. The extension and retraction of both left and right dump cylinders 20 causes the grass collection container 7 to tilt diagonally downward and rearward via both left and right link arms 18, and to return to its original grass collection position. When the grass collection container 7 is in the dump position, the rear gate 15 is opened and the grass inside the grass collection container 7 is released. The lift cylinder 19 and dump cylinders 20 correspond to the hydraulic work section.

[0023] As shown in Figures 2 and 3, the front of the motor chamber 8, located below the grass collection container 7 of the machine body 1, is equipped with a work motor 30 that drives the mower device 4, which is the work unit, and a drive motor 40 that drives at least the front wheels 2, which are the drive unit, side by side. In this embodiment, the work motor 30 is located on the left side in the direction of travel, and the drive motor 40 is located on the right side. Needless to say, the relative positions of the work motor 30 and the drive motor 40 can be reversed. It is desirable that the work motor 30 and the drive motor 40 are DC motors with relatively high output.

[0024] A high-voltage battery 50 is provided at the rear of the motor compartment 8 to supply power to the work motor 30 and the drive motor 40. Note that, for the sake of clarity, some components, such as the cover of the motor compartment 8, are not shown in Figures 2 and 3.

[0025] A water-cooling radiator 60 is provided on the left and right outer sides (left outer side in this embodiment) of the front of the power chamber 8. Between the radiator 60 and the work electric motor 30, a radiator fan 61 is provided to draw outside air into the power chamber 8. The radiator 60 air-cools the coolant for the electric motors 30, 40, etc., through heat exchange. The rotation of the radiator fan 61 draws outside air (cooling air) into the power chamber 8 from the outside, and the radiator 60 and both left and right electric motors 30, 40, etc. are air-cooled. On the opposite side of the radiator 60 in the front of the power chamber 8 (right outer side in this embodiment), an auxiliary battery 62 (low-voltage battery) is located to supply power to the radiator fan 61 and the vehicle control unit 100 (VCD), etc., which will be described later.

[0026] Next, the power transmission system of the electric lawnmower LM will be described with reference to Figure 4. The electric lawnmower LM of this embodiment is configured to transmit the output of the working electric motor 30 to the mower device 4, etc., and the output of the driving electric motor 40 to the front wheel 2 or the front and rear wheels 2, 3. In other words, the electric lawnmower LM of this embodiment is a two-motor system configured by distributing the power of the electric motors 30 and 40, which are the drive sources, to work and to drive.

[0027] The working output shaft 30a of the working electric motor 30 is connected to a working reduction shaft 32, which extends parallel to the working output shaft 30a, via a gear-type working reduction mechanism 31, so as to be able to transmit power. The working reduction shaft 32 is connected to a first working PTO shaft 35 so as to be able to transmit power via a first working clutch 33 and a first gear mechanism 34. The mower device 4 is then connected to the first working PTO shaft 35 so as to be able to transmit power. The first working clutch 33 interrupts the transmission of power from the working electric motor 30 to the mower device 4. The output of the working electric motor 30 is transmitted from the working output shaft 30a to the mower device 4 via the working reduction mechanism 31, the working reduction shaft 32, the first working clutch 33, the first gear mechanism 34, and the first working PTO shaft 35, driving the rotating cutting blade pair.

[0028] Furthermore, a charge pump 36 is provided in association with the work reduction mechanism 31 as a hydraulic drive source. The charge pump 36 supplies hydraulic fluid to the lift cylinder 19, dump cylinder 20, mower lifting cylinder 14, etc., to drive them. The output transmitted from the work electric motor 30 to the work reduction mechanism 31 is branched and transmitted to the charge pump 36.

[0029] The working output shaft 30a of the working electric motor 30 is connected to the second working PTO shaft 39 via a second working clutch 37 and a second gear mechanism 38, so as to be able to transmit power. The blower 17 for transporting turfgrass is then connected to the second working PTO shaft 39 so as to be able to transmit power. The second working clutch 37 intercepts the power transmission from the working electric motor 30 to the blower 17. The output of the working electric motor 30 is transmitted from the working output shaft 30a to the blower 17 via the second working clutch 37, the second gear mechanism 38, and the second working PTO shaft 39, driving the blower 17.

[0030] The drive output shaft 40a of the drive electric motor 40 is connected to a drive reduction shaft 42 that extends parallel to the drive output shaft 40a via a gear-type drive reduction mechanism 41, so as to be able to transmit power. The drive reduction shaft 42 extends front and rear on either side of the drive reduction mechanism 41. The front side of the drive reduction shaft 42 is connected to both the left and right front wheels 2 via a front wheel differential gear mechanism 43 so as to be able to transmit power. The rear side of the drive reduction shaft 42 is connected to both the left and right rear wheels 3 via a 4WD clutch 44 and a rear wheel differential gear mechanism 45 so as to be able to transmit power. The 4WD clutch 44 switches the driving mode of the electric lawnmower LM between two-wheel drive (2WD) and four-wheel drive (4WD).

[0031] The output of the electric motor 40 for driving is transmitted from the driving output shaft 40a to the driving reduction shaft 42 via the driving reduction mechanism 41, and then from the driving reduction shaft 42 to the left and right front wheels 2 via the front wheel differential gear mechanism 43, driving the left and right front wheels 2. If four-wheel drive is selected with the 4WD clutch 44, the output is also transmitted from the driving reduction shaft 42 to the left and right rear wheels 3 via the 4WD clutch 44 and the rear wheel differential gear mechanism 45, driving the left and right rear wheels 3.

[0032] Next, the hydraulic circuit structure of the electric lawnmower LM will be described with reference to Figure 5. The hydraulic circuit 70 of the electric lawnmower LM is equipped with a charge pump 36 as a hydraulic drive source driven by a branch output of the electric motor 30 for work. The suction side of the charge pump 36 is connected to an oil pan 71 provided on the machine body 1 via a suction filter 72 for filtering hydraulic fluid. A power steering mechanism 73 that controls the supply and discharge of hydraulic fluid to the steering cylinder 74 for power steering is connected to the discharge side of the charge pump 36. Downstream from the power steering mechanism 73 are a lift switching valve 75 that controls the supply and discharge of hydraulic fluid to both left and right lift cylinders 19, a dump switching valve 76 that controls the supply and discharge of hydraulic fluid to both left and right dump cylinders 20, and a mower lifting switching valve 77 that controls the supply and discharge of hydraulic fluid to the mower lifting cylinder 14. As mentioned above, the steering cylinder 74, lift cylinder 19, dump cylinder 20, and mower lifting cylinder 14 correspond to the hydraulic work section.

[0033] A first clutch control valve 78, which controls the supply and discharge of hydraulic fluid to the clutch cylinder 33a of the first working clutch 33, and a second clutch control valve 79, which controls the supply and discharge of hydraulic fluid to the clutch cylinder 37a of the second working clutch 37, are connected to an oil passage branched from between the charge pump 36 and the power steering mechanism 73. The hydraulic fluid in the oil pan 71 is drawn into the charge pump 36 via the suction filter 72 by the drive of the charge pump 36 and supplied to various parts 73 to 79 of the hydraulic circuit 70. The clutch cylinders 33a and 37a correspond to the hydraulic working parts. The hydraulic circuit 70 also includes relief valves, check valves, oil filters, etc.

[0034] Next, the cooling system of the electric lawnmower LM will be described with reference to Figure 6. The cooling system 80 of the electric lawnmower LM includes a cooling water pump 81 powered by an auxiliary battery 62 and a water-cooling radiator 60. The cooling water pump 81 and the radiator 60 are connected by a closed-loop cooling passage 82, which connects their respective intake and discharge sides. Downstream of the cooling water pump 81 in the closed-loop cooling passage 82, it is divided into two directions: a working cooling passage 83 and a driving cooling passage 84.

[0035] The work cooling passage 83 houses the work MCU 85, which controls the drive of the work electric motor 30, and the work electric motor 30. The drive cooling passage 84 houses an integrated unit 86 including an onboard charger (OBC) and a DC / DC converter, a drive MCU 87, which controls the drive of the drive electric motor 40, and the drive electric motor 40. The downstream ends of the work cooling passage 83 and the drive cooling passage 84 merge again and are connected to the intake side of the radiator 60. The radiator fan 61, which faces the radiator 60, is driven by power from the auxiliary battery 62, similar to the coolant pump 81.

[0036] The coolant pump 81 draws the coolant from the radiator 60 and branches into a work cooling passage 83 and a drive cooling passage 84. In the work cooling passage 83, the coolant passes through the work MCU 85 and the work electric motor 30, cooling them. In the drive cooling passage 84, the coolant passes through the integrated unit 86, the drive MCU 87, and the drive electric motor 40, cooling them. The coolant that has passed through each cooling passage 83 and 84 rejoins and is supplied to the radiator 60, where it is cooled by the cooling air from the radiator fan 61. In this way, the coolant circulates within the closed-loop cooling passage 82.

[0037] Next, the hardware configuration of the electric lawnmower LM will be described with reference to Figure 7. The electric lawnmower LM is equipped with a vehicle control unit 100 (VCD) which is a control device that performs various controls on the electric lawnmower LM. The vehicle control unit 100 is a control device that monitors and manages the entire electric lawnmower LM. Although not shown in the diagram, the vehicle control unit 100 has a processor, memory, storage, communication interface and input / output interface, etc., and can communicate with each other via a communication bus. The vehicle control unit 100 can communicate with external management devices and terminal devices, etc., via the internet network or directly from the communication interface.

[0038] The vehicle control unit 100 is electrically connected via communication lines 103 to a power-on switch 111, a seat switch 112, an eco-mode switch 113, a power-mode switch 114, a user-setting switch 115, a PTO dial 116, a radiator fan 61, a coolant pump 81, a first work clutch 33 (with its electromagnetic solenoid), a second work clutch 37 (with its electromagnetic solenoid), a work MCU 85, a drive MCU 87, an integrated unit 86, and a power distribution unit 117 (PDU).

[0039] The power-on switch 111 instructs the system to start the electric lawnmower LM. The seat switch 112 detects whether a user is seated in the driver's seat. The eco-mode switch 113 sets the output range of the working motor speed Nw (details described later) of the working electric motor 30 to a range prioritizing energy efficiency, which is lower than normal. The power-mode switch 114 sets the output range of the working motor speed Nw to a range prioritizing output, which is higher than normal. The user-setting switch 115 sets the individual no-load torque line 126 (details described later) which shows the torque change when the rotating cutting blade pair is idling without cutting grass under no load. The PTO dial 116 sets the maximum rotational speed of the working motor speed Nw.

[0040] The power distribution unit 117 distributes power from the high-voltage battery 50 to the electric motors 30 for work and the electric motors 40 for driving, and includes a battery monitoring system (BMS) and contactors. The high-voltage battery 50 and the junction box 118 are electrically connected to the power distribution unit 117 via the high-voltage line 101.

[0041] The junction box 118 is responsible for relaying and distributing power via the power distribution unit 117. The junction box 118 is electrically connected to the integrated unit 86 and the charging inlet 119 via the high-voltage line 101. The charging inlet 119 is connected to the charging connector (not shown) of an external power source or an external generator to charge the high-voltage battery 50. Furthermore, the junction box 118 is electrically connected to the work MCU 85 and the work electric motor 30, and to the travel MCU 87 and the travel electric motor 40 via the high-voltage line 101.

[0042] As mentioned above, the LM electric lawnmower is equipped with an auxiliary battery 62 (low-voltage battery) in addition to the high-voltage battery 50. The vehicle control unit 100 (VCD), integrated unit 86, radiator fan 61, and coolant pump 81 are electrically connected to the auxiliary battery 62 via the low-voltage line 102.

[0043] Next, with reference to Figures 8 to 13, the torque control of the work electric motor 30 (which can also be described as torque control of the first work PTO shaft 35 for the mower device 4) will be explained. The work electric motor 30 in this embodiment performs four-quadrant drive of forward and reverse rotation, powering, and braking, enabling it to accelerate and decelerate the rotation of the mower device 4, which is the work unit, in the same way as in the conventional case of engine drive alone. Similarly, the travel electric motor 40 also performs four-quadrant drive of forward and reverse rotation, powering, and braking, enabling it to accelerate and decelerate the front wheel 2 or the front and rear wheels 2, 3, which are the travel unit, in the same way as in the conventional case of engine drive alone.

[0044] Figure 8 is a work torque map 120 showing the relationship between the work motor rotation speed Nw (also known as the PTO rotation speed) and the work motor torque Tw of the work electric motor 30. Here, the four-quadrant drive of the work electric motor 30 will be explained with reference to the work torque map 120. The four quadrants show the relative relationship between the rotation direction of the work output shaft 30a of the work electric motor 30 (which can also be known as the sign of the work motor rotation speed Nw) and the sign of the work motor torque Tw.

[0045] The first quadrant is defined as the case where both the motor rotational speed Nw and the motor torque Tw are positive signs, the second quadrant is the case where the motor rotational speed Nw is negative and the motor torque Tw is positive signs, the third quadrant is the case where both the motor rotational speed Nw and the motor torque Tw are negative signs, and the fourth quadrant is the case where the motor rotational speed Nw is positive and the motor torque Tw is negative signs. The first and third quadrants are called powering, and the second and fourth quadrants are called braking.

[0046] In the relationship between the working motor rotation speed Nw and the working motor torque Tw, in the first quadrant, the pair of rotating cutting blades of the mower device 4 is in a state of increasing forward rotation; in the second quadrant, the pair of rotating cutting blades of the mower device 4 is in a state of decreasing forward rotation (braking); in the third quadrant, the pair of rotating cutting blades of the mower device 4 is in a state of increasing reverse rotation; and in the fourth quadrant, the pair of rotating cutting blades of the mower device 4 is in a state of decreasing reverse rotation (braking).

[0047] The relationship between the working motor rotation speed Nw and the working motor torque Tw is not limited to a map format; for example, it may be represented in a function table format. Furthermore, the driving torque map showing the relationship between the driving motor rotation speed and the driving motor torque of the driving electric motor 40 is the same as the working torque map 120, and a detailed explanation is omitted here.

[0048] In this embodiment, a work torque map 120 is pre-stored in the memory of the vehicle control unit 100. In the work torque map 120 shown in Figures 8 to 13, the work motor rotation speed Nw is plotted on the horizontal axis and the work motor torque Tw is plotted on the vertical axis. The work motor rotation speed Nw of the work electric motor 30 is read by the work MCU 85, and the work motor torque Tw is obtained by calculations performed by the work MCU 85.

[0049] In Figures 8 to 13, the thick dashed lines drawn outside the origin represent the maximum torque line 121, which indicates the instantaneous maximum torque that can be temporarily output when the electric motor 30 is driven, and are specific to the electric motor 30. In Figures 8 to 13, the thick solid lines drawn inside the maximum torque line 121 represent the rated torque line 122, which indicates the rated torque at which the electric motor 30 can be driven stably and continuously. As can be seen from these torque lines 121 and 122, the rated torque is a smaller value than the instantaneous maximum torque.

[0050] In Figure 9 and subsequent figures, for convenience, the operation of the electric motor 30 in the first quadrant will be explained as an example. In the operation torque map 120 of the embodiment, the upper limit of the torque value Tmax (also called the torque upper limit line) for the operation motor rotation speed Nw is set within the region between the maximum torque line 121 and the rated torque line 122. Therefore, the operation motor torque Tw that the electric motor 30 can take is up to the torque upper limit Tmax, and the electric motor 30 will not be driven with an operation motor torque Tw that exceeds the torque upper limit Tmax.

[0051] Furthermore, in the working torque map 120, the upper limit value Nmax (also called the rotation limit line) of the working motor rotation speed Nw is set within the rated output range, which is the area enclosed by the rated torque line 122. Therefore, the working motor rotation speed Nw that the working electric motor 30 can take is limited to the rotation limit value Nmax, and the working electric motor 30 will never be driven at a working motor rotation speed Nw that exceeds the rotation limit value Nmax. In the working torque map 120 of this embodiment, the area enclosed by the rotation limit value Nmax and the torque limit value Tmax is the operating area 123 of the working electric motor 30.

[0052] In the working torque map 120, the lower limit of the working motor rotation speed Nw, Nmin (also known as the rotation lower limit line), is set within the rated output range. The maximum setting range 124 for the PTO dial 116 is between the rotation lower limit Nmin and the rotation upper limit Nmax. In other words, when driving the mower device 4 or the blower 17, the working electric motor 30 is driven in the practical region 123a of the usable region 123, which is between the rotation lower limit Nmin and the rotation upper limit Nmax.

[0053] Generally, when the drive source is an electric motor, the electric motor is completely stopped at a state equivalent to idling when the drive source is an engine. However, as shown in Figure 5, in this embodiment, the charge pump 36 that supplies hydraulic fluid to the hydraulic system of the electric lawnmower LM is driven by the output of the work electric motor 30. Therefore, when the electric lawnmower LM is in operation and it is necessary to immediately supply hydraulic fluid not only to the power steering mechanism 73 and steering cylinder 74, but also to the lift cylinder 19 and clutch cylinders 33a, 37a, etc., there are circumstances that prevent the work electric motor 30 from being completely stopped.

[0054] Upon consideration of this point, it can be seen that, in the embodiment, for example, when driving on a road without performing grass cutting work, it is sufficient for the work electric motor 30 to output just enough power to drive the charge pump 36. Therefore, when driving on a road, the vehicle control unit 100 drives the work electric motor 30 in the pump area 123b of the operating area 123, where the rotational speed is below the lower limit value Nmin.

[0055] In this way, even if the electric motor 30 for the work equipment cannot be completely stopped, as in the embodiment, power consumption by the electric motor 30 for work equipment can be suppressed when the mower device 4 or blower 17 (electric work unit) is not being used, thereby saving energy in the electric lawnmower LM. In other words, a state equivalent to engine idling can be created in the drive configuration of the electric motor 30 for work equipment. This also contributes to improving energy efficiency.

[0056] Furthermore, by changing the various cylinders 14, 19, 20, 33a, 37a, and 74 shown in the hydraulic circuit diagram of Figure 5 to electric types, and by dividing the power transmission system from the electric motor 30 for the work into three systems—the mower device 4, the blower 17, and the cylinder group 14, 19, 20, 33a, 37a, and 74—it becomes possible to completely stop the electric motor 30 for the work depending on the situation while the electric lawnmower LM is in operation.

[0057] In normal mode, with the eco mode switch 113 and power mode switch 114 in the off position, the upper limit of the working motor rotation speed Nw is set to the normal upper limit value Nst, and the range that can be set with the PTO dial 116 is between the rotation lower limit value Nmin and the normal upper limit value Nst. In eco mode, with the eco mode switch 113 in the on position, the upper limit of the working motor rotation speed Nw is set to the eco upper limit value Nec, and the range that can be set with the PTO dial 116 is between the rotation lower limit value Nmin and the eco upper limit value Nec.

[0058] Furthermore, in power mode, when the power mode switch 114 is ON, the upper limit of the working motor rotation speed Nw is set to the rotation upper limit value Nmax, and the range that can be set with the PTO dial 116 becomes the range from the rotation lower limit value Nmin to the rotation upper limit value Nmax, i.e., the maximum setting range 124. In this way, the user can set the maximum rotation speed of the working electric motor 30 (the rotation speed of the rotating cutting blade pair in the mower device 4) based on the condition of the grass planted in the field, etc., thereby enabling energy saving and improved electricity efficiency while fully utilizing the working capacity of the mower device 4.

[0059] The working torque map 120 has a basic no-load torque curve 125 predefined by the manufacturer. The basic no-load torque curve 125 shows the relationship between the working motor rotation speed Nw and the working motor torque Tw when the rotating cutting blade pair of the mower device 4 is running freely, and is set uniformly for electric lawnmowers LM of the same model.

[0060] The working torque map 120 also includes individual no-load torque lines 126. Similar to the basic no-load torque line 125, the individual no-load torque line 126 shows the relationship between the working motor rotation speed Nw and the working motor torque Tw when the rotating cutting blade pair of the mower device 4 is idling, but it is obtained due to individual differences in the electric lawnmower LM. In this embodiment, the user setting switch 115 is turned ON to idle the rotating cutting blade pair of the mower device 4, and the individual no-load torque line 126 is obtained from the result.

[0061] In this case, the individual no-load torque curve 126, which covers even the individual differences of the electric lawnmower LM, is used as the standard for the no-load torque characteristics of the electric motor 30. Of course, the basic no-load torque curve 125 may also be used as the standard for the no-load torque characteristics of the electric motor 30. Having both the basic no-load torque curve 125 and the individual no-load torque curve 126 is preferable because it allows for the determination of whether the individual no-load torque curve 126 indicates an appropriate no-load state by comparing it with the basic no-load torque curve 125.

[0062] Although not shown in the diagram, a second basic no-load torque line, obtained by adding a value equivalent to an additional intercept that takes into account the resistance of grass passage within the chute 16 to the basic no-load torque line 125, may be set to be located above the individual no-load torque line 126. In this way, by referring to the second basic no-load torque line, it is possible to determine whether or not there is resistance of grass passage within the chute 16, and to grasp the smoothness of grass transport from the chute 16 to the grass collection container 7, as well as whether or not there is grass clogging within the chute 16.

[0063] The work torque map 120 includes a work allowable torque line 127. The work allowable torque line 127 defines the limit of the work motor torque Tw that the work electric motor 30 can handle, and is set above the practical region 123a. In Figure 9, the work allowable torque line 127 is a line that slopes diagonally upward to the right, such that the work motor torque Tw decreases as the work motor rotation speed Nw decreases. This is set considering that the required torque increases as the work motor rotation speed Nw increases. Needless to say, in Figure 9, the work allowable torque line 127 is located above the basic no-load torque line 125 and the individual no-load torque line 126.

[0064] As shown in Figure 9, when the work motor torque Tw(a) calculated by the work MCU 85 is near the allowable work torque line 127, and the vehicle control unit 100 determines that it is possible to take a work load L(a) value at a rotational speed Nw(b) that is lower than the work motor rotational speed Nw(a) at that time and in a region below the allowable work torque line 127, it executes control to reduce the work motor rotational speed of the work electric motor 30 from Nw(a) to Nw(b).

[0065] For convenience, in the following explanation, when the motor rotation speed Nw, motor torque Tw, and load L are shown individually, an identifying alphabet may be added in parentheses to each symbol (e.g., motor rotation speed Nw(a), motor torque Tw(b), load L(c)).

[0066] The working load L(a) is obtained from the difference between the working motor torque Tw(a) and the corresponding no-load torque Two(a), and the working load L(b) is obtained from the difference between the working motor torque Tw(b) and the corresponding no-load torque Two(b). In this embodiment, the individual no-load torque line 126 is used as the reference for the no-load torque characteristics of the working electric motor 30, so the no-load torque Two(a) is the value on the individual no-load torque line 126.

[0067] In this case, the working motor torque Tw(b) is calculated such that the working load L(b) = L(a) when the working motor rotation speed is Nw(b), and a current value I corresponding to the working motor torque Tw(b) is supplied to the working electric motor 30. The working motor torque Tw(b) is located below the allowable working torque line 127. The working motor torque Tw is, Tw = V × I × 1000 / (2π / 60 × Nw) This can be calculated from the following formula. Here, V is the voltage value, I is the current value, and Nw is the rotational speed of the work motor. Since the voltage value V of the work electric motor 30, which is powered by the high-voltage line 101, is constant (48V), as can be seen from the formula for work motor torque Tw, the current value I corresponding to work motor torque Tw(b) is smaller than the current value I when work motor torque Tw(a).

[0068] By controlling the motor as described above, it is possible to reduce the rotational speed of the electric motor 30 from Nw(a) to Nw(b) and the torque of the electric motor from Tw(a) to Tw(b) while ensuring that the motor can withstand the actual work load L(a)=L(b). Therefore, power consumption by the electric motor 30 can be suppressed, and the energy efficiency of the electric lawnmower LM can be improved. This also contributes to improved energy efficiency.

[0069] To determine whether the working motor torque Tw(a) is near the allowable working torque line 127, for example, a dead zone of a predetermined width can be set below the allowable working torque line 127, and when the working motor torque Tw(a) takes a value within the dead zone, it can be determined that the working motor torque Tw(a) is near the allowable working torque line 127.

[0070] When the vehicle control unit 100 reduces the rotational speed of the electric motor 30 from Nw(a) to Nw(b), it performs control to maintain the rotational speed of the electric motor 30 at Nw(b) until the electric lawnmower LM travels a predetermined distance or for a predetermined time. Frequent fluctuations in the rotational speed Nw of the electric motor can cause changes in the airflow of the blower 17 and may lead to grass clogging in the chute 16. There is also a concern that it may cause hunting behavior (unstable control operation) of the electric motor 30 and the mower device 4. By adopting the above control, stable behavior of the blower 17 can be ensured, and hunting behavior of the electric motor 30 and the mower device 4 can be prevented.

[0071] The vehicle control unit 100 can perform control to maintain the current vehicle speed of the electric lawnmower LM and prevent further speed increases when the working motor torque Tw at any working motor rotation speed Nw exceeds the allowable working torque line 127. Alternatively, the vehicle control unit 100 may also perform control to forcibly reduce the driving motor rotation speed of the electric driving motor 40 in accordance with the working motor torque Tw when the working motor torque Tw at any working motor rotation speed Nw exceeds the allowable working torque line 127, thereby forcibly decelerating the current vehicle speed of the electric lawnmower LM.

[0072] As described above, the allowable torque curve 127 can be used to determine the drive control of the electric motor 40 for travel based on the working motor torque Tw. When the working motor torque Tw exceeds the allowable torque curve 127, it means that the working load L of the mower device 4 is increasing, for example, because the grass density is high and the mowing resistance is large, or because foreign matter is causing large resistance on the rotating cutting blade pair. If the vehicle speed of the electric lawnmower LM is maintained at high speed in such a state, there is a risk of grass clogging in the chute 16 or failure of the mower device 4. Therefore, by adopting vehicle speed control based on the allowable torque curve 127, even with a two-motor electric lawnmower LM, it is possible to prevent an increase in the vehicle speed of the electric lawnmower LM when the working load L of the mower device 4 is increasing, thereby preventing problems during grass cutting, such as grass clogging in the chute 16 or failure of the mower device 4. As a result, grass cutting work can be continued stably.

[0073] Figure 10 is an explanatory diagram of the work torque map 120, using the driving of the work electric motor 30 in the first quadrant as an example, and is the same as Figure 9. This is shown separately from Figure 9 in order to make the explanation of the control for increasing the work motor torque T easier to understand. As shown in Figure 10, when the work motor torque Tw(a) calculated by the work MCU 85 exceeds the allowable work torque line 127, the vehicle control unit 100 can execute control to increase the work motor rotation speed of the work electric motor 30 from Nw(a) to Nw(c) when it determines that it is possible to take a work load L(a) value in the region where the rotation speed Nw(c) is higher than the current work motor rotation speed Nw(a) and is below the allowable work torque line 127.

[0074] The control described above is the reverse of the control method used to reduce the working motor rotation speed Nw, as explained earlier. In this case, the working load L(a) is obtained from the difference between the working motor torque Tw(a) and the corresponding no-load torque Two(a), and the working load L(c) is obtained from the difference between the working motor torque Tw(c) and the corresponding no-load torque Two(c). A working motor torque Tw(c) is calculated such that the working load L(c) = L(a) when the working motor rotation speed is Nw(c), and a current value I corresponding to the working motor torque Tw(c) is supplied to the working electric motor 30. The working motor torque Tw(c) is located below the allowable working torque line 127. The working motor torque Tw(c) is obtained from the formula explained in the control of reducing the working motor rotation speed Nw. The current value I corresponding to the working motor torque Tw(c) is greater than the current value I when the working motor torque is Tw(a).

[0075] By controlling it as described above, the rotational speed of the electric motor 30 is increased from Nw(a) to Nw(c), which is optimal for the actual work load L(a)=L(c), and the motor torque is increased from Tw(a) to Tw(c), bringing it below the allowable torque line of 127, thereby enabling stable and continuous operation of the electric motor 30.

[0076] Figure 11 is an explanatory diagram of the work torque map 120, using the drive of the work electric motor 30 in the first quadrant as an example, and is the same as Figures 9 and 10. As shown in Figure 11, the vehicle control unit 100 can perform control to reduce the work motor rotation speed to a predetermined rotation speed lower than Nw(d) when the work motor torque Tw(d) calculated by the work MCU 85 is near the no-load torque line. In this case, the individual no-load torque line 126 is used as the no-load torque line. The basic no-load torque line 125 may be used instead of the individual no-load torque line 126. As the predetermined rotation speed lower than the work motor rotation speed Nw(d), for example, the rotation lower limit value Nmin can be used, but other values ​​are also acceptable. For example, the predetermined rotation speed may be reduced to the pump area 123b within the operating area 123, which is below the rotation lower limit value Nmin.

[0077] The working motor torque Tw(min) for a working motor rotational speed Nmin is calculated as a value such that the working load L(min) = L(d), and a current value I corresponding to the working motor torque Tw(min) is supplied to the working electric motor 30. The working motor torque Tw(min) is located above the no-load torque line (in this embodiment, the individual no-load torque line 126). The working motor torque Tw(min) is obtained from the formula explained in the control of reducing the working motor rotational speed Nw. The current value I corresponding to the working motor torque Tw(min) is smaller than the current value I when the working motor torque Tw(d).

[0078] In the example shown in Figure 11, whether the working motor torque Tw(d) is near the no-load torque line can be determined, for example, by setting a dead zone of a predetermined width above the no-load torque line, and when the working motor torque Tw(d) takes a value within the dead zone, it can be determined that the working motor torque Tw(d) is near the allowable working torque line 127.

[0079] The state in which the working motor torque Tw(d) is near the no-load torque line means, for example, when the electric lawnmower LM is turning in an area without grass during mowing. Therefore, by employing a control method to reduce the working motor rotation speed Nw using the no-load torque line as described above, power consumption by the working electric motor 30 can be suppressed when the working load L is not applied to the mower device 4 during mowing, thereby saving energy in the electric lawnmower LM. This also contributes to improving electricity efficiency.

[0080] Subsequently, when the mower device 4 begins mowing the grass and detects an increase in the working motor torque Tw, it is desirable for the vehicle control unit 100 to automatically increase the working motor rotation speed Nw of the working electric motor 30 back to its original rotation speed Nw(d) before the decrease. This is because it allows for a smooth response to changes in conditions during grass cutting and enables stable continuation of the grass cutting operation.

[0081] Figure 12 is an explanatory diagram of the work torque map 120, using the drive of the work electric motor 30 in the first quadrant as an example, and is the same as Figures 9 to 11. As shown in Figure 12, the work torque map 120 may also have a speed increase prohibition torque line 128 and a forced deceleration torque line 129. The speed increase prohibition torque line 128 and the forced deceleration torque line 129 are used to determine the drive control of the travel electric motor 40 based on the work motor torque Tw. The speed increase prohibition torque line 128 and the forced deceleration torque line 129 are set at the top of the practical region 123a, with the forced deceleration torque line 129 located above the speed increase prohibition torque line 128.

[0082] The speed increase prohibition torque line 128 and the forced deceleration torque line 129 are lines that slope diagonally upward to the right in Figure 12, such that the working motor torque Tw decreases as the working motor rotation speed Nw decreases. This is set considering that the required torque increases as the working motor rotation speed Nw increases. Needless to say, in Figure 12, the speed increase prohibition torque line 128 and the forced deceleration torque line 129 are located above the basic no-load torque line 125 and the individual no-load torque line 126. The speed increase prohibition torque line 128 may coincide with the working allowable torque line 127, or they may be set separately.

[0083] When the speed-increase prohibition torque line 128 and the forced deceleration torque line 129 are set in the work torque map 120, the vehicle control unit 100, when the work motor torque Tw at any work motor rotation speed Nw exceeds the speed-increase prohibition torque line 128, maintains the travel motor rotation speed of the travel electric motor 40 (stops increasing it), maintains the current vehicle speed of the electric lawnmower LM, and prohibits speed increase. Then, when the work motor torque Tw at any work motor rotation speed Nw exceeds the forced deceleration torque line 129, the vehicle control unit 100 forcibly reduces the travel motor rotation speed of the travel electric motor 40 in accordance with the work motor torque Tw, forcibly decelerating the current vehicle speed of the electric lawnmower LM.

[0084] When the working motor torque Tw exceeds the speed increase prohibition torque line 128 or the forced reduction torque line 129, it means that the working load L of the mower device 4 is increasing. Therefore, by employing vehicle speed control using the speed increase prohibition torque line 128 and the forced reduction torque line 129, even though it is a two-motor electric lawnmower LM, when the working load L of the mower device 4 increases, it is possible to prevent an increase in the vehicle speed of the electric lawnmower LM, thereby preventing problems during grass cutting work and ensuring stable and continuous grass cutting work.

[0085] It is desirable that the vehicle control unit 100, while the first work clutch 33 is powered, be able to perform control such that the higher the work motor rotation speed Nw, the faster the electric lawnmower LM moves, by correlating the work motor rotation speed Nw with the travel motor rotation speed of the travel electric motor 40, i.e., the vehicle speed of the electric lawnmower LM. The powered state of the first work clutch 33 means that the mower device 4 is being driven. In this case, as the vehicle speed of the electric lawnmower LM increases, the work load L of the mower device 4 associated with cutting grass increases. Therefore, when mowing grass while driving with the mower device 4 in operation, by making the work motor rotation speed Nw proportional to the vehicle speed of the electric lawnmower LM, the mower device 4 can be driven with a work motor rotation speed Nw that matches the work load L. As a result, the work efficiency of the electric lawnmower LM can be improved.

[0086] In this embodiment, the mower device 4 and blower 17 are started to drive by driving the work electric motor 30 and engaging the first work clutch 33 and the second work clutch 37. Here, it is desirable that the vehicle control unit 100 executes control to start driving the drive electric motor 40 when the work motor torque Tw calculated by the work MCU 85 moves upward from the vicinity of the no-load torque line. In other words, priority is given to the driving order of the mower device 4 and blower 17 and the front and rear wheels 2 and 3. Either the individual no-load torque line 126 or the basic no-load torque line 125 may be used as the no-load torque line.

[0087] In this way, the electric motor 40 (front and rear wheels 2 and 3) is driven only after the electric motor 30 (mower device 4 and blower 17) has reached a normal operating state. This prevents the front and rear wheels 2 and 3 from being driven (the electric lawnmower LM from moving) in situations such as when the electric motor 30 has not reached a sufficient rotational speed or when the mower device 4 or blower 17 has malfunctioned, thus preventing problems such as grass clogging.

[0088] Furthermore, in the above-described priority drive control, it is desirable that the vehicle control unit 100, upon detecting that the working motor torque Tw is more than a specified value above the no-load torque line, puts the drive of the electric motor 40 on standby (does not drive) until the working motor torque Tw falls below the specified value. When the working motor torque Tw is more than a specified value above the no-load torque line, it means, for example, that grass has become entangled in the rotating cutting blade pair of the mower device from a previous mowing operation, or that grass has become clogged in the chute 16. By adopting the above control, it is not necessary to run the electric lawnmower LM until the problem such as grass clogging is resolved, and once the problem is resolved, it is possible to smoothly transition to mowing work. It is also possible to turn off the power to the electric lawnmower LM and perform inspection work.

[0089] Furthermore, in the above-described priority drive control, it is desirable for the vehicle control unit 100 to execute various controls after a predetermined time lag following the power connection of the first work clutch 33 and / or the second work clutch 37. When the mower device 4 and blower 17 are started to operate, a large torque exceeding, for example, the allowable torque line 127 may be generated instantaneously. Therefore, by adopting the above control, it is possible to avoid reflecting exceptional situations in the control of the vehicle control unit 100, thereby improving the control performance of the vehicle control unit 100.

[0090] In this embodiment, when stopping the operation of the electric motor 30, it is desirable for the vehicle control unit 100 to first cut off the power to the first work clutch 33, and then, after a predetermined time has elapsed, to cut off the power to the second work clutch 37. In this case, priority is given to the stopping order of the mower device 4 and the blower 17. This is because even after the mower device 4 is stopped, there is still turf in the chute 16 that is being transported, so a grace period is needed to send that turf to the grass collection container 7.

[0091] Furthermore, in the priority stop control described above, if the vehicle control unit 100 detects that the work motor torque Tw is more than a specified value above the no-load torque line after disabling the power of the first work clutch 33 and before disabling the power of the second work clutch 37, it is desirable to maintain the second work clutch 37 in a power-connected state until the work motor torque Tw falls below the specified value. This is preferable because, after stopping the mower device 4, the blower 17 can be driven until any problems such as grass clogging are resolved, thereby transporting the turf grass in the chute 16 to the grass collection container 7.

[0092] In this embodiment, it is desirable that the vehicle control unit 100, upon detecting that the grass collection container 7 is full using a full-fill sensor, executes control to stop both the working electric motor 30 and the driving electric motor 40. If the electric lawnmower LM is operated with the mower device 4 and blower 17 stopped while the grass collection container is full, grass may accumulate near the chute entrance, potentially causing clogging. By stopping both the working electric motor 30 and the driving electric motor 40, the accumulation of grass and subsequent clogging can be prevented.

[0093] Conventionally, the main configuration involved a single engine or electric motor distributing power to the drive unit and the work unit. Therefore, when prioritizing the torque output of the work unit and reducing the rotational speed of the engine or motor to save energy, the travel speed (vehicle speed) of the drive unit inevitably decreased as well, resulting in a problem where work efficiency could not be improved. In this embodiment, the adoption of a two-motor system consisting of a work electric motor 30 and a drive electric motor 40 is effectively utilized, and the work electric motor 30 and the drive electric motor 40 are driven and controlled separately, making it possible to drive the work unit (especially the electric work unit, the mower device 4 and the blower 17) in an energy-saving manner without affecting the drive unit (front and rear wheels 2 and 3).

[0094] Now, Figure 13 is an explanatory diagram of the work torque map 120, using the driving of the work electric motor 30 in the first quadrant as an example, and is the same as Figures 9 to 12. In the example of Figure 13, the work torque map 120 is set to show the range of work motor torque Tw that the work electric motor 30 can take when the mower device 4 is driven (grass cutting work). The work torque map 123c in this embodiment is the area between the speed increase prohibition torque line 128 (which may be the work allowance torque line 127) and the work lower limit torque line 130, which is part of the practical area 123a that lies between the rotation lower limit value Nmin and the rotation upper limit value Nmax. In this case as well, the speed increase prohibition torque line 128 may be set to coincide with the work allowance torque line 127 or to be set separately.

[0095] Furthermore, the work torque map 120 includes a stop threshold 131 that defines the boundary of the work motor torque Tw when the machine 1 is forcibly stopped, a forced deceleration threshold 132 that defines the boundary of the work motor torque Tw when the speed of the machine 1 is forcibly reduced, and a speed increase prohibition threshold 133 that defines the boundary of the work motor torque Tw when speed increase of the machine 1 is prohibited.

[0096] In this embodiment, the rated torque line 122 is applied as the stop threshold 131, the forced deceleration torque line 129 is applied as the forced deceleration threshold 132, and the speed increase prohibition torque line 128 is applied as the speed increase prohibition threshold 133. In other words, each torque line 122, 129, and 128 can be considered a set of thresholds 131, 132, and 133 for any working motor rotation speed Nw. Note that each threshold 131, 132, and 133 may be a constant value. In other words, each torque line 122, 129, and 128 may be a horizontal line without any slope.

[0097] In this case, not only the forced deceleration threshold 132 (forced deceleration torque line 129) and the speed increase prohibition threshold 133 (speed increase prohibition torque line 128), but also the stop threshold 131 (rated torque line 122) are used to determine the drive control of the traction electric motor 40 based on the working motor torque Tw.

[0098] When the stop threshold 131 (rated torque line 122), forced deceleration threshold 132 (forced deceleration torque line 129), and speed increase prohibition threshold 133 (speed increase prohibition torque line 128) are set in the work torque map 120, the vehicle control unit 100 will maintain the drive motor rotation speed of the drive electric motor 40 (stop increasing it) and maintain the current vehicle speed of the electric lawnmower LM, prohibiting further speed increase (see white circle in Figure 13).

[0099] When the working motor torque Tw at any working motor rotation speed Nw exceeds the forced deceleration threshold 132 (forced deceleration torque line 129), the rotation speed of the drive motor 40 is forcibly reduced in accordance with the working motor torque Tw, forcibly decelerating the current vehicle speed of the electric lawnmower LM (see black circle in Figure 13). When the working motor torque Tw at any working motor rotation speed Nw exceeds the stop threshold 131 (rated torque line 122), the drive motor 40 is stopped, and the electric lawnmower LM (machine 1) stops moving (see white triangle in Figure 13).

[0100] When the working motor torque Tw exceeds the stop threshold 131 (rated torque line 122), the forced deceleration threshold 132 (forced deceleration torque line 129), or the speed increase prohibition threshold 133 (speed increase prohibition torque line 128), it means that the working load L of the mower device 4 is increasing.

[0101] Therefore, by employing vehicle speed control using threshold values ​​131, 132, and 133 (torque lines 122, 129, and 128), even though it is a two-motor electric lawnmower LM, when the working load L of the mower device 4 increases, it is possible to prevent the vehicle speed of the electric lawnmower LM from increasing, forcibly decelerate it, or stop it from moving, thereby preventing problems during grass cutting work and ensuring the stable continuation of grass cutting work. Since the above vehicle speed control is executed when a working load L occurs that could lead to damage to various gears of the work system, damage to various gears of the work system can be prevented.

[0102] In the example in Figure 13, the forced deceleration threshold 132 and the speed increase prohibition threshold 133 are different values ​​corresponding to the working motor rotation speed Nw. In this embodiment, the forced deceleration torque line 129, which is the set of forced deceleration thresholds 132, and the speed increase prohibition torque line 128, which is the set of speed increase prohibition thresholds 133, are lines that slope upward to the right, similar to the example in Figure 12, where the working motor torque Tw increases as the working motor rotation speed Nw increases. The reason for this setting is the same as in the example in Figure 12. That is, it takes into account that the required torque increases as the working motor rotation speed Nw increases, thereby ensuring stable operation of the mower device 4.

[0103] Furthermore, as mentioned above, the upper limit of the working motor rotation speed Nw differs depending on the mode, such as eco mode. In this case, in normal mode, the upper limit of the working motor rotation speed Nw is set to the normal upper limit value Nst, in eco mode, the upper limit of the working motor rotation speed Nw is set to the eco upper limit value Nec, and in power mode (also known as boost mode), the upper limit of the working motor rotation speed Nw is set to the rotation upper limit value Nmax. This setting is for the stable operation of the mower device 4.

[0104] Furthermore, as in the embodiment, it is desirable that the upper limits of the stop threshold 131, the forced deceleration threshold 132, and the speed increase prohibition threshold 133 decrease as the upper limit of the working motor rotation speed Nw decreases. In this case, the forced deceleration torque line 129 is located above the speed increase prohibition torque line 128, and the rated torque line 122 is located above the forced deceleration torque line 129. In particular, it is desirable to set the slope of the forced deceleration torque line 129 and the speed increase prohibition torque line 128 so that the difference between them decreases as the working motor rotation speed Nw decreases. That is, it is desirable to set the slope of the forced deceleration torque line 129 to be greater than that of the speed increase prohibition torque line 128. These points are also settings for stable driving of the mower device 4.

[0105] In this embodiment, the electric motor 30 for operation drives the mower device 4 (during grass cutting) with a motor rotation speed Nw and motor torque Tw within the operating range 123c of the working torque map 120. In particular, the motor rotation speed Nw is restricted to a value between the lower rotation limit Nmin and the upper rotation limit Nmax. This also reduces the risk of generating excessive motor torque Tw and contributes to preventing damage to various gears and other components of the work system.

[0106] When the working motor torque Tw at any working motor rotation speed Nw is near one of the thresholds 131, 132, or 133, it is desirable for the vehicle control unit 100 to execute control to stop the driving electric motor 40 and stop the electric lawnmower LM (machine body 1) when the working motor rotation speed Nw remains lower than the commanded rotation speed of the vehicle control unit 100 for a predetermined period of time or longer.

[0107] If the working motor torque Tw is near any of the thresholds in threshold groups 131, 132, and 133, it means that the working load L of the mower device 4 is large. Furthermore, if the actual working motor rotation speed Nw is lower than the commanded rotation speed of the vehicle control unit 100, and this continues for a predetermined time or longer, it can be inferred that a serious high-load condition is occurring, such as grass getting entangled in the mower device 4 or grass clogging in the chute 16. By employing the above-mentioned travel stop control, the grass cutting operation of the mower device 4 can be quickly stopped in the event of a serious high-load condition, and in this case as well, it is highly effective in preventing damage to various gears of the work system.

[0108] Whether the working motor torque Tw is near one of the thresholds in the threshold groups 131, 132, and 133 can be determined, for example, in the case of the stop threshold 131 (rated torque line 122), by setting a dead zone of a predetermined width below the stop threshold 131 (rated torque line 122), and if the working motor torque Tw takes a value within the dead zone, it can be determined that the working motor torque Tw is near the stop threshold 131 (rated torque line 122). The command rotation speed of the vehicle control unit 100 is set by the PTO dial 116 provided on the control unit 5. The length of the predetermined time can also be set as appropriate.

[0109] Furthermore, in the above-described drive stop control, when the drive motor 40 is stopped to stop the electric lawnmower LM (machine body 1), it is desirable to also stop the mower device 4. In this case, the work motor 30 may be stopped, but in consideration of maintaining the operation of the blower 17 and charge pump 36, the first work clutch 33 may be put into a power cut-off state to stop the mower device 4. This helps to reduce power consumption in cases where grass gets entangled in the mower device 4 or grass gets clogged in the chute 16, making it impossible to continue mowing.

[0110] When the above-mentioned drive stop control is combined with the drive stop control of the mower device 4, it is desirable to maintain the drive stop state of the mower device 4 after it has been automatically stopped, unless the user first turns it off using a PTO operating tool (not shown) such as a PTO lever on the control unit 5 and then turns it on. If the mower device 4 starts driving immediately after removing tangled grass or grass blockages in the chute 16 and the workload on the mower device 4 has been relieved, it would be extremely dangerous for the user who performed the removal work. Therefore, the mower device 4 will not be driven (restarted) unless the user first goes through the procedure of turning it off and then on using the PTO operating tool, thus eliminating the danger of sudden operation of the mower device 4 and ensuring user safety.

[0111] After the above-mentioned driving stop control is performed (after the electric lawnmower LM (machine 1) has stopped moving), it is desirable to maintain the stopped state of the electric lawnmower LM (machine 1) until the gear shifting device such as the gear shift pedal 12 provided on the control unit 5 is released (neutralized). After the gear shifting device is released, it is more preferable to have the vehicle control unit 100 control the system so that if the working motor torque Tw at that time is near the no-load torque line, it will accept (permit) subsequent speed increase operations of the gear shifting device.

[0112] In this way, the electric lawnmower LM does not need to be driven until problems such as grass entanglement or blockage are resolved, and once the problem is resolved, the mowing work can be smoothly resumed. In this case, either an individual no-load torque wire 126 or a basic no-load torque wire 125 may be used as the no-load torque wire. Furthermore, when resuming driving after executing the above driving stop control, it is preferable to provide a notification member to inform the user that driving has started again. Conversely, it is also preferable to provide a notification member to inform the user that driving is stopped while driving is being stopped. Adopting these configurations makes it easy for the user to understand the situation and is user-friendly.

[0113] Next, with reference to Figure 14, the manner of interlocking control of the drive motor 40 with respect to the work motor 30 will be described. Figure 14 is a diagram showing the relationship between the gear shift operation amount OP, such as the gear shift pedal 12 which is a gear shift operating device, and the drive motor rotation speed Nr of the drive motor 40. In the embodiment, when the vehicle control unit 100 starts driving at least the front wheels 2 (drive motor 40) in conjunction with the mower device 4 (work motor 30), it is possible to perform control to increase the drive motor rotation speed Nr of the drive motor 40 by a second upward gradient Gec, Gst, Gmax which has a gradient angle smaller than the first upward gradient Gx with respect to the gear shift operation amount OP of the gear shift pedal.

[0114] In the example shown in Figure 14, the basic relationship X between the gear shift operation amount OP and the travel motor rotation speed Nr is set to be linearly proportional throughout the entire range. The basic relationship X is applied, for example, when driving on a road without performing grass cutting work. When the travel motor 40 is started to drive in conjunction with the work electric motor 30, the relationship between the gear shift operation amount OP and the travel motor rotation speed Nr is set to a downward-convex quadratic curve Yec,Yst,Ymax for each mode such as eco mode. This makes the upward slope of the quadratic curve Yec,Yst,Ymax small at the initial stage of gear shifting with the gear shift pedal 12, becoming a second upward slope Gec,Gst,Gmax, and after a predetermined value Nr(p) of the travel motor rotation speed Nr, it is set to increase in proportion to the gear shift operation amount of the gear shift pedal 12. In this case, at the initial stage of gear shifting with the gear shift pedal 12, ΔNr decreases from ΔNrec,ΔNrst,ΔNrmax when the unit rotation speed is linearly proportional to the unit operation amount ΔOP.

[0115] In normal mode, the normal mode relation Yst is applied; in eco mode, the eco mode relation Yec is applied; and in power mode (boost mode), the power mode relation Ymax is applied. In this way, when the drive motor 40 is started in conjunction with the work motor 30, that is, when the machine 1 is started while the mower device 4 is being driven, the increase in vehicle speed can be made gradual. This prevents a sudden increase in the work load L of the mower device 4 due to a sudden increase in vehicle speed, and limits the work load L applied to the work motor 30 when the machine 1 is started. Therefore, fluctuations in the work load L can be made as smooth as possible, ensuring stable and continuous grass cutting work.

[0116] In this embodiment, the relationship between the gear shift operation amount OP and the travel motor rotation speed Nr is expressed as a downward-convex quadratic curve Yec, Yst, Ymax for each mode, such as eco mode, and the lower the travel motor rotation speed Nr, the gentler the second upward gradient Gec, Gst, Gmax becomes. After a predetermined value Nr(p) of the travel motor rotation speed Nr, the second upward gradient Gec, Gst, Gmax increases in proportion to the gear shift operation amount of the gear shift pedal 12. For this reason, at least when starting the machine 1 while driving the mower device 4, the work load L applied to the work electric motor 30 is limited, causing the machine 1 to start moving with slow acceleration contrary to the user's intention. However, after the predetermined value Nr(p) of the travel motor rotation speed Nr, smooth acceleration is obtained, mitigating the user's discomfort with the acceleration.

[0117] In setting the relationship between the gear shift operation amount OP and the travel motor rotation speed Nr, X,Yec,Yst,Ymax, in addition to using a linear straight line X or a downward-convex quadratic curve Y, the slope of the linear straight line X may be changed, the shape of the downward-convex quadratic curve Yec,Yst,Ymax may be changed or made into an upward-convex quadratic curve, or the linear straight line X or the quadratic curve Yec,Yst,Ymax may be changed when the gear shift pedal 12 is used for acceleration and deceleration (release).

[0118] Furthermore, when performing the above-mentioned upward gradient control, it is desirable to disable the speed increase prohibition control using the speed increase prohibition torque wire 128. This is because, at least when starting the machine 1 while driving the mower device 4, using both upward gradient control and speed increase prohibition control may cause the machine 1 to have difficulty accelerating, depending on the acceleration method, potentially reducing the work efficiency of the electric lawnmower LM.

[0119] However, if the working motor torque Tw at any working motor rotation speed Nw exceeds the forced deceleration torque line 129, the vehicle control unit 100 will forcibly reduce the rotation speed of the travel motor 40 in accordance with the working motor torque Tw, even without executing speed increase prohibition control, thereby forcibly decelerating the current vehicle speed of the electric lawnmower LM. This is because it is assumed that the working load L of the mower device 4 is excessive, and continuing in this state is likely to cause grass entanglement or blockage.

[0120] Instead of the example in Figure 14, the vehicle control unit 100 may also be capable of performing late limit processing on the amount of gear shift operation of the gear shift pedal 12. In this case, it is desirable to set the late limit value in the speed increase direction to be smaller than the late limit value under other conditions, at least when starting the machine 1 while driving the mower device 4. The late limit processing is a process that smooths the increase in vehicle speed by adding a predetermined limit to the rate of change of the drive motor rotation speed Nr required of the drive electric motor 40.

[0121] In this case as well, similar to the example in Figure 14, when the drive motor 40 is started in conjunction with the work motor 30, that is, when the machine 1 is started while at least the mower device 4 is being driven, the increase in vehicle speed (acceleration) can be made gradual. This prevents a sudden increase in the work load L of the mower device 4 due to a rapid increase in vehicle speed, and limits the work load L applied to the work motor 30 when the machine 1 is started.

[0122] Furthermore, when performing the above-mentioned late limiting process, it is desirable to disable the speed increase prohibition control using the speed increase prohibition torque line 128, similar to the example in Figure 14. This is because, if late limiting and speed increase prohibition control are used together, depending on the acceleration method, the machine 1 may have difficulty escaping from a slow vehicle speed. Also, in this case, if the work motor torque Tw at an arbitrary work motor rotation speed Nw exceeds the forced deceleration torque line 129, the vehicle control unit 100 will forcibly reduce the rotation speed of the drive motor 40 in accordance with the work motor torque Tw, even without performing speed increase prohibition control, thereby forcibly decelerating the current vehicle speed of the electric lawnmower LM.

[0123] The vehicle control unit 100 of this embodiment is capable of performing automatic driving control that automatically adjusts the vehicle speed of the machine 1 (which can also be called the rotational speed Nr of the driving electric motor 40). The automatic driving control includes at least a time-priority mode aimed at shortening the working time for driving the mower device 4 and the blower 17, which are the working parts. The automatic driving control of this embodiment includes both a time-priority mode and an energy-saving priority mode that suppresses power consumption by the working electric motor 30 and the driving electric motor 40.

[0124] When the vehicle control unit 100 is performing automatic driving control in time priority mode, if the working time during which both the work electric motor 30 and the driving electric motor 40 are driven has elapsed for a predetermined period of time or longer, it is possible to perform control to increase the rotational speed Nr of the driving electric motor 40 by a predetermined amount relative to the current gear shift operation amount of the gear shift pedal 12 (current vehicle speed).

[0125] In this case, the vehicle control unit 100 increases the travel motor rotation speed Nr in predetermined increments, while maintaining the travel motor rotation speed Nr at or below the maximum value Nrmax (9 km / h in the embodiment) and the work motor rotation speed Nw at or below the upper rotation limit Nmax (2600 rpm in the embodiment). Alternatively, the work motor rotation speed Nw may also be increased in predetermined increments in accordance with the travel motor rotation speed Nr.

[0126] In this way, the electric lawnmower LM (machine 1) can be driven at the fastest possible speed to perform the mowing work, allowing the mowing work to be completed in a short time. In response to the increased workload L of the mower device 4, which corresponds to the increased speed of the electric lawnmower LM, it is also possible to drive the mower device 4 with a corresponding motor rotation speed Nw.

[0127] Furthermore, while the vehicle control unit 100 is performing automatic driving control in energy-saving priority mode, if the working electric motor 30 and the driving electric motor 40 have been driven for a predetermined period of time or longer, the vehicle control unit 100 can also perform control to reduce the working motor rotation speed Nw of the working electric motor 30 by a predetermined amount relative to the current working motor rotation speed Nw (current rotation speed of the rotating cutting blade pair). In this case, the vehicle control unit 100 reduces the working motor rotation speed Nw by a predetermined amount while maintaining the working motor rotation speed Nw at or above the lower limit of rotation Nmin (2200 rpm in the embodiment). By reducing the working motor rotation speed Nw as much as possible in this way, energy-saving operation becomes possible.

[0128] The configuration of each part in the present invention is not limited to the illustrated embodiment, and various modifications are possible without departing from the spirit of the present invention. [Explanation of Symbols]

[0129] Gx: First upward gradient, Gec, Gst, Gmax: Second upward gradient, LM: Electric lawnmower, Nw: Working motor rotation speed, Nmin: Lower rotation limit, Nmax: Upper rotation limit, Nst: Normal upper limit, Nec: Eco upper limit, Nr: Travel motor rotation speed, Nr(p): Predetermined value of travel motor rotation speed, OP: Speed ​​change operation amount, Tw: Working motor torque, Two: No-load torque, Yec, Yst, Ymax: Quadratic curve, ΔOP: Unit operation amount, ΔNr, ΔNrec, ΔNrst, ΔNrmax: Unit rotation speed. 30 Electric motor for operation, 33 First operation clutch, 35 First operation PTO shaft, 36 Charge pump, 37 Second operation clutch, 39 Second operation PTO shaft, 40 Electric motor for driving, 50 High-voltage battery, 60 Radiator, 61 Radiator fan, 62 Auxiliary battery, 85 Operation MCU, 86 Integrated unit, 87 Driving MCU, 100 Vehicle control unit (control device), 111 Power-on switch, 112 Seat switch, 113 Eco mode switch, 114 Power mode switch, 115 User setting switch, 116 PTO dial, 120 Operational torque map, 121 Maximum torque line, 122 Rated torque line, 123 Operating range, 123a Practical range, 123b Pump range, 123c Actual operating range, 124 Maximum setting range on PTO dial, 125 Basic no-load torque line, 126 Individual no-load torque line, 127 Allowable working torque line, 128 Speed ​​increase prohibition torque line, 129 Forced deceleration torque line, 130 Lower limit working torque line, 131 Stop threshold, 132 Forced deceleration threshold, 133 Speed ​​increase prohibition threshold

Claims

1. An electric work vehicle comprising a running section for moving the machine, a work section provided on the machine, a driving electric motor for driving the running section, a work electric motor for driving the work section, a battery for supplying power to both electric motors, and a control device for controlling various functions, The aforementioned electric motor has a work torque map that shows the relationship between the motor rotation speed and the motor torque. The aforementioned work torque map includes a stop threshold that defines the boundary of the work motor torque when the machine is forcibly stopped, a forced deceleration threshold that defines the boundary of the work motor torque when the machine's speed is forcibly reduced, and a speed increase prohibition threshold that defines the boundary of the work motor torque when speed increase of the machine is prohibited. The control device controls the rotational speed of the travel motor of the travel electric motor in accordance with the relationship between the work motor torque at an arbitrary work motor rotational speed and each of the threshold values, thereby controlling the vehicle speed of the machine. Electric work vehicle.

2. The control device, when the working motor torque at any working motor rotation speed is near one of the threshold values ​​in the threshold group, stops the driving of the electric motor and stops the machine from moving if the working motor rotation speed remains lower than the commanded rotation speed of the control device for a predetermined period of time or longer. The electric work vehicle described in claim 1.

3. When the control device starts driving the travel unit in conjunction with the work unit, it increases the rotational speed of the travel motor of the travel electric motor at a second upward gradient, which has a smaller gradient angle than the first upward gradient with respect to the amount of operation of the gear shift control device provided on the unit, until the machine reaches a predetermined vehicle speed. An electric work vehicle as described in claim 1 or 2.

4. The control device is capable of performing late limit processing on the amount of operation of the gear shifting device, and the late limit value in the speed-increasing direction under the condition that the drive unit is started in conjunction with the work unit is set to be smaller than the late limit value under other conditions. The electric work vehicle described in claim 3.

5. The control device is capable of performing automatic driving control that automatically adjusts the vehicle speed of the machine, and the automatic driving control includes at least a time priority mode aimed at shortening the working time for driving the work unit. During the execution of the automatic driving control in the time priority mode, the control device controls the motor to increase the rotational speed of the driving motor by a predetermined increment relative to the current vehicle speed once a predetermined working time has elapsed in which both the work motor and the driving motor are driven. The electric work vehicle described in claim 1.

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