Electric work vehicle

Abstract

The present invention provides an electric work vehicle comprising: a first electric motor 30 that drives a work device 4; a second electric motor 40 that drives a front wheel 2 or a rear wheel 3; and a controller 80 that controls the first electric motor 30 and the second electric motor 40. When the load of the first electric motor 30 exceeds a first threshold value C1, the controller 80 reduces the speed of output rotation of the second electric motor 40. The electric work vehicle has a first mode M1 in which, when the load of the first electric motor 30 is not more than the first threshold value C1 but exceeds a second threshold value C2, an increase in the speed of the second motor 40 is restricted. Thus, the electric work vehicle makes it possible to perform work comfortably.

Description

Electric work vehicle

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

[0002] Conventionally, a work electric motor for driving a work device for mowing lawn grass and a traveling electric motor for driving drive wheels are provided. When an excessive load is applied to the work electric motor, a technique for reducing the rotational output of the traveling electric motor or the work electric motor is known (Patent Document 1).

[0003] Japanese Unexamined Patent Application Publication No. 2023-182153

[0004] In the means of Patent Document 1, the target vehicle speed is basically determined by a manual operation tool such as a shift lever, and the rotational speed of the work electric motor is set according to the target vehicle speed. When a load exceeding a predetermined value of the work electric motor is detected, the rotational output of the traveling electric motor or the work electric motor is decelerated to prevent an overload on the work electric motor. However, when the traveling electric motor is decelerated, depending on the work load situation, the vehicle speed may frequently change and the riding comfort may deteriorate, making it impossible to work comfortably.

[0005] Therefore, an object of the present invention is to provide an electric work vehicle that can work comfortably.

[0006] To solve the above problems, the electric work vehicle of the present invention includes a first electric motor (30) for driving a work device (4), a second electric motor (40) for driving a front wheel (2) or a rear wheel (3), and a controller (80) for controlling the first electric motor (30) and the second electric motor (40). When the load of the first electric motor (30) exceeds a first threshold value (C1), the controller (80) decelerates the output rotation of the second electric motor (40). The electric work vehicle is provided with a first mode (M1) for restricting the speed increase of the second electric motor (40) when the load of the first electric motor (30) is below the first threshold value (C1) and exceeds a second threshold value (C2).

[0007] According to the present invention, by providing a region in which the acceleration of the second electric motor (40) is restricted in a load region lower than a first threshold (C1), which is the load on the first electric motor (30) that decelerates the second electric motor (40), it is possible to suppress the load on the first electric motor (30) from reaching the first threshold (C1) and also suppress the increase in load, thereby suppressing fluctuations in vehicle speed and enabling comfortable operation.

[0008] This is a perspective view of the work vehicle from the front left. This is a perspective view of the front of the power room from the rear left. This is a perspective view of the rear of the power room from the rear left. This is a transmission diagram of the output rotation of the electric motor. This is a connection diagram of the controller. This is an explanatory diagram of the first to third thresholds in high load mode. This is a control time chart of the power saving mode, showing (A) output torque, (B) average output torque, and (C) the first electric motor instructed rotation speed.

[0009] As shown in Figure 1, the electric work vehicle has a pair of front wheels 2 on the lower front part of the machine frame 1, and a pair of rear wheels 3 on the lower rear part of the machine frame 1.

[0010] A work device 4 for mowing grass is provided at the front of the machine frame 1, and a control unit 5 for the operator is provided at the rear of the work device 4. A safety frame (rops) 6 for protecting the operator is provided at the rear of the control unit 5, and a grass collection container 7 for storing the mowed grass is provided at the rear of the safety frame 6, and an electric room 8 is provided below the grass collection container 7 to house a first electric motor 30 for driving the work device 4, a battery 60, etc.

[0011] A steering column 10 supporting the steering wheel is provided in front of the cockpit of the control unit 5. A touch panel monitor displaying the output rotation speed of the first electric motor 30 is provided at the top of the steering column 10, and the lower part is fixed to the front of the floor.

[0012] A brake pedal 11 for reducing the rotational speed of the front wheels 2 is provided on the left side of the steering column 10 on the floor, and an accelerator pedal 12 for increasing or decreasing the output rotational speed of the second electric motor 40 for driving the front wheels 2 is provided on the right side. The amount of depression of the accelerator pedal 12 is measured by an angle sensor 12S such as a potentiometer attached to its base.

[0013] The area above the front wheel 2 is covered by a fender 13, and a gear shift lever 14 for operating an inverter device 35 that increases or decreases the output rotation of the first electric motor 30 is provided on the fender 13 located to the right of the driver's seat.

[0014] Furthermore, a control switch 27 for starting load control is provided behind the gear shift lever 14, and a mode switch 26 for selecting and setting the power consumption of the first electric motor 30 and the control mode of the second electric motor 40 is provided to the left of the control switch 27.

[0015] The rear of the work device 4 and the front of the grass collection container 7 are connected by a chute 16 that extends in the front-to-back direction, and a blower 17 is provided in the middle of the chute 16 in the front-to-back direction to transport the cut grass inside the chute 16 to the grass collection container 7.

[0016] A pair of left and right link arms 18 are provided on the front of the left and right walls of the grass collection container 7. The front of the link arms 18 are fixed to the safety frame 6 so as to be able to swing from side to side, and the safety frame 6 and the link arms 18 are connected by a lifting component 19 such as a hydraulic cylinder, and the rear of the lower wall of the grass collection container 7 is resting on the horizontal frame 21A of the support frame 21, which will be described later. This allows the lifting component 19 to be driven to raise and lower the grass collection container 7.

[0017] As shown in Figures 2 and 3, the front motor compartment 8A of the motor compartment 8 is equipped with a first motor 30 and a second motor 40, while the rear motor compartment 8B is equipped with a battery 60 for storing power supplied to the first motor 30 and the other motors. An inverter device 35 for driving the first motor 30 is provided behind the first motor 30 at a predetermined distance in the front-rear direction, and an inverter device 45 for driving the second motor 40 is provided behind the second motor 40 at a predetermined distance in the front-rear direction. The inverter devices 35 and 45 are also provided in front of the battery 60 at a predetermined distance in the front-rear direction. This allows for easy routing of each motor 30, 40 and the inverter devices 35 and 45.

[0018] As shown in Figure 4, the output rotation of the first electric motor 30 is transmitted to the input shaft 57A, and the output rotation of the input shaft 57A is transmitted to the rotating shaft 58A after being increased or decreased in speed.

[0019] The output rotation of the rotating shaft 58A is accelerated or decelerated before being transmitted to the output shaft 33, and the output rotation of the output shaft 33 is transmitted to the hydraulic pump 51. This allows the first electric motor 30 to be driven, which in turn drives the hydraulic pump 51.

[0020] The output rotation of the rotating shaft 58A is accelerated or decelerated before being transmitted to the rotating shaft 58B, and the output rotation of the rotating shaft 58B is transmitted to the output shaft 31 via the clutch 55. The output rotation of the output shaft 31 is transmitted to the work device 4. This allows the first electric motor 30 to be driven, thereby driving the work device 4.

[0021] The output rotation of the rotating shaft 58A is accelerated or decelerated before being transmitted to the rotating shaft 58C, and the output rotation of the rotating shaft 58C is transmitted to the output shaft 32 via the clutch 56. The output rotation of the output shaft 32 is transmitted to the blower 17. This allows the first electric motor 30 to be driven, which in turn drives the blower 17.

[0022] The output rotation of the second electric motor 40 is transmitted to the input shaft 57B, and the output rotation of the input shaft 57B is accelerated or decelerated before being transmitted to the output shafts 41 and 42.

[0023] The output rotation of the output shaft 41 is transmitted to the drive shaft 43 for the front wheels via the differential gear 54, and the output rotation of the drive shaft 43 is transmitted to the front wheels 2. This allows the second electric motor 40 to be driven and the front wheels 2 to rotate. In addition, the output rotation of the output shaft 42 can also be transmitted to the rear wheels 3 via the 4WD clutch and differential gear, etc.

[0024] As shown in Figure 5, the controller 80 of the work vehicle is formed from a processing unit 81 consisting of a CPU and the like, a storage unit 82 consisting of ROM, RAM, a hard disk drive, flash memory and the like, and a communication unit 83 for data communication with the outside.

[0025] The processing unit 81 calculates output values ​​to be output to the inverter device 45 based on the amount the accelerator pedal 12 is pressed, calculates output values ​​to be output to the inverter device 45 based on the amount the gear shift lever 14 is operated, and calculates output values ​​to be output to the inverter device 35 based on the rotational speed of the first electric motor 30, which is set for each mode selected by the mode switch 26 and selected according to the situation.

[0026] The memory unit 82 saves the mode that was selected by the mode switch 26 immediately before the work vehicle stopped. This allows the vehicle to be restarted in the mode selected immediately before stopping without having to select a mode again with the mode switch 26.

[0027] The input side of the controller 80 is connected via a predetermined input interface circuit to an angle sensor 12S for measuring the amount the accelerator pedal 12 is pressed, a dial 25 which serves as a rotation speed control device for arbitrarily setting the output rotation speed of the first electric motor 30 for work, a mode switch 26 for changing the control modes of the first electric motor 30 and the second electric motor 40, and an inverter device 35 that drives the first electric motor 30.

[0028] On the output side of the controller 80, an inverter device 35 that drives the first electric motor 30 for work and an inverter device 45 that drives the second electric motor 40 for travel are connected via a predetermined output interface circuit.

[0029] In this embodiment, the mode switch 26 allows selection of a first mode, high-load mode M1; a second mode, power-saving mode M2; and a third mode, manual mode M3. In high-load mode M1, the first electric motor 30 is controlled to maintain a third rotational speed N3, which is higher than the first rotational speed N1 and second rotational speed N2 selected in power-saving mode M2. In manual mode M3, the first electric motor 30 maintains a rotational speed selected by the operator using the dial 25.

[0030] As shown in Figure 6, in high-load mode M1, three threshold values ​​are set for the load of the first electric motor 30. The controller 80 outputs the third rotational speed N3, which is the set rotational speed for high-load mode M1, to the inverter device 35. The first electric motor 30, which is a three-phase AC motor, detects the rotational speed and feeds it back to the inverter device 35, and is controlled to maintain the third rotational speed N3. Based on the output current value at this time, the output torque of the first electric motor 30 is calculated, and this output torque is filtered with a low-pass filter and evaluated as the load.

[0031] In electric work vehicles, overload of the first electric motor 30 occurs when the amount of grass cut and collected exceeds the cutting capacity and grass collection capacity. To prevent this overload, a configuration is adopted in which, when the load of the first electric motor 30 exceeds a first threshold C1, the second electric motor 40 is decelerated at a preset deceleration rate. With this configuration, the vehicle speed is reduced until the load falls below the first threshold C1, preventing clogging of the work device 4 and chute 16 with cut grass and avoiding interruptions to work. As a result, work efficiency is improved and power consumption is reduced, making it possible to extend the continuous working time.

[0032] If the load is greater than the second threshold C2 but less than or equal to the first threshold C1, the acceleration of the second electric motor 40 is restricted. This prevents the load from exceeding the first threshold C1, thus preventing clogging of the mowed grass. Furthermore, it also prevents deceleration caused by the load exceeding the first threshold C1, suppressing fluctuations in vehicle speed and allowing for comfortable operation.

[0033] If the load is below the second threshold C2, and the second electric motor 40 is moving at a lower speed than the value indicated by the accelerator pedal 12, the second electric motor 40 is increased in speed. This allows the speed to be increased in accordance with the value indicated by the accelerator pedal 12 when the load is not high, thereby increasing the work speed and improving work efficiency. In addition, when the vehicle is running at a fixed set speed, known as cruise control, the speed is increased to the set speed.

[0034] In addition to the above control, if the load is greater than the third threshold C3, the load difference at predetermined time intervals is monitored, and if the difference is greater than a predetermined value, the second electric motor 40 is decelerated until the difference falls below the predetermined value. This suppresses the increase in load when the fluctuation range of the load increase is large, thereby preventing the system from reaching an overload state and preventing clogging of the mowed grass. Furthermore, by suppressing sudden load increases and overload states, malfunctions of the electric work vehicle can be prevented. In this embodiment, the third threshold C3 is a lower value than the second threshold C2, but it is not limited to this, and may be a higher value than the second threshold C2, or the same value. Also, in order to prevent the system from reaching an overload state, it is desirable that the third threshold C3 is a lower value than the first threshold C1.

[0035] As described above, in high-load mode M1, the first electric motor 30 is driven at a third rotational speed N3, which is higher than the rotational speed set in power-saving mode M2, allowing for powerful operation of high-load tasks. In addition, the vehicle speed is adjusted by detecting the load on the first electric motor 30, so even inexperienced operators can work like skilled operators, preventing clogs in the mowed grass. Furthermore, the speed increase is restricted according to the load, suppressing fluctuations in vehicle speed for comfortable operation. Moreover, by suppressing sudden increases in load, clogging can be effectively prevented, allowing for comfortable operation without interruption.

[0036] As shown in Figure 7, in power-saving mode M2, the rotational speed of the first electric motor 30 is changed based on the load on the first electric motor 30. In other words, when the load is small, the motor operates at the first rotational speed N1 to suppress power consumption and noise, and when the load is large, it operates at a second rotational speed N2, which is higher than the first rotational speed N1.

[0037] Specifically, in power-saving mode M2, the inverter device 35 calculates the output torque of the first electric motor 30 based on the output current value when the rotational speed of the first electric motor 30 is maintained at the first rotational speed N1 or the second rotational speed N2. The average value of this output torque at predetermined time intervals is evaluated as the load. The output torque diagram (Figure 7(A)) is a graph showing the fluctuation of the output torque over time. The average output torque values ​​TQ1 to TQ3 are calculated at predetermined time intervals t (for example, 5 seconds) (Figure 7(B)).

[0038] When the load exceeds the fourth threshold C4 while the first electric motor 30 is set to a first rotational speed N1, the set rotational speed of the first electric motor 30 is increased to the second rotational speed N2. For example, the average load torque TQ1 over elapsed time t0 to t1 is calculated, and if the average load torque TQ1 is equal to or greater than the fourth threshold C4, the set rotational speed of the first electric motor 30 is increased from the first rotational speed N1 to the second rotational speed N2. At this time, angular acceleration may be controlled by setting the rotational speed to take a predetermined time (t1'-t1) to increase from the first rotational speed N1 to the second rotational speed N2.

[0039] When the load falls below the fifth threshold C5 while the first electric motor 30 is set to the second rotational speed N2, the set rotational speed of the first electric motor 30 is reduced to the first rotational speed N1. For example, the average load torque TQ3 over elapsed time t2 to t3 is calculated, and if the average load torque TQ3 is below the fifth threshold C5, the set rotational speed of the first electric motor 30 is reduced from the second rotational speed N2 to the first rotational speed N1. At this time, the angular acceleration may be controlled by setting the time to take a predetermined amount of time (t3'-t3) to reduce the rotational speed from the second rotational speed N2 to the first rotational speed N1. The time taken to increase the set rotational speed of the first electric motor 30 (t1'-t1) and the time taken to decrease it (t3'-t3) may be the same or different.

[0040] The fourth threshold C4 and the fifth threshold C5 may be the same value, but they may also be set to different values ​​with a predetermined difference by introducing a hysteresis width. For example, the average load torque TQ2 over time t1 to t2 is lower than the fourth threshold C4 but higher than the fifth threshold C5, so the second rotational speed N2 is maintained. Setting the fifth threshold C5 to a value lower than the fourth threshold C4 prevents frequent changes in the rotational speed of the first electric motor 30 when the load is near the threshold. Also, determining the load using the average output torque at predetermined time intervals t also prevents frequent changes in the rotational speed of the first electric motor 30.

[0041] As described above, in power-saving mode M2, the first electric motor 30 is driven at a first rotational speed N1 or second rotational speed N2, which is lower than the rotational speed set in high-load mode M1, thus reducing power consumption during operation. In particular, when the workload is low, the system is configured to operate at the first rotational speed N1, which is lower than the second rotational speed N2, thereby suppressing power consumption and enabling continuous operation for long periods. When the workload increases, the system operates at the second rotational speed N2 as needed, allowing for comfortable operation from low to medium loads while consuming less power than in high-load mode M1.

[0042] In manual mode M3, the first electric motor 30 is operated at a rotational speed arbitrarily set by the dial 25, and vehicle speed control is not performed by controlling the rotational speed of the first electric motor 30 or the second electric motor 40 in accordance with the load. This allows, for example, a skilled worker to set the optimal rotational speed of the first electric motor 30 and manually adjust the vehicle speed while sensing the load.

[0043] By configuring the high-load mode M1, power-saving mode M2, and manual mode M3 as described above to be switchable via the mode switch 26, it is possible to work comfortably according to various situations and needs, such as the workload and the operator's skill level.

Claims

1. An electric work vehicle comprising: a first electric motor (30) for driving a work device (4); a second electric motor (40) for driving a front wheel (2) or a rear wheel (3); and a controller (80) for controlling the first electric motor (30) and the second electric motor (40), wherein the controller (80) reduces the output rotation of the second electric motor (40) when the load of the first electric motor (30) exceeds a first threshold (C1), and has a first mode (M1) for restricting the acceleration of the second electric motor (40) when the load of the first electric motor (30) is less than or equal to the first threshold (C1) but exceeds a second threshold (C2).

2. The electric work vehicle according to claim 1, wherein the controller (80) reduces the output rotation of the second electric motor (40) when the load exceeds a third threshold (C3) which is set to a value lower than the first threshold (C1), and when the load fluctuation of the first electric motor (30) is greater than a predetermined load fluctuation value.

3. The electric work vehicle according to claim 2, further comprising a second mode (M2) wherein the controller (80) is set to drive the first electric motor (30) at a predetermined second rotational speed (N2) that is higher than the first rotational speed (N1) when the load is above a fourth threshold (C4) when the first electric motor (30) is being driven at a predetermined first rotational speed (N1), and when the first electric motor (30) is being driven at the second rotational speed (N2), the controller (80) is set to drive the first electric motor (30) at the first rotational speed (N1) when the load is below a fifth threshold (C5) which is set to be below the fourth threshold (C4).

4. The electric work vehicle according to claim 3, wherein the load to be evaluated in the second mode (M2) is the average value of the output torque of the first electric motor (30) over a predetermined time interval (t).

5. An electric work vehicle according to claim 4, further comprising: a rotation speed control device (25) for arbitrarily setting the output rotation of the first electric motor (30); the first electric motor (30) being driven to maintain a rotation speed arbitrarily set by the rotation speed control device (25); the second electric motor (40) having a third mode (M3) in which the rotation speed is varied only according to an instruction value from a vehicle speed control device (12) operated by the driver; and a mode switch (26) for switching between the first mode (M1), the second mode (M2), and the third mode (M3).

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