Electric work vehicles

Abstract

To provide an electric work vehicle that can accelerate responsively by changing the acceleration according to the work mode, making it easier to perform appropriate tasks. [Solution] An electric lawnmower according to one embodiment comprises a vehicle body, a work implement mounted on the vehicle body, a travel motor that drives the drive wheels of the vehicle body, a work motor that drives the work implement, and a control device that receives an input for the vehicle body's travel speed and allows selection of multiple work modes. The control device performs load control, which reduces the vehicle speed of the vehicle body when the load of the work motor exceeds a specified value, and increases the vehicle speed to the specified speed when the load of the work motor falls below a specified value and the vehicle speed is slower than the specified speed. The acceleration during acceleration in load control is varied for each of the multiple work modes.

Description

Technical Field

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

Background Art

[0002] Conventionally, an electric work vehicle capable of selecting an applicable work mode to be actually applied from a plurality of work modes that determine the rotational speed of a work device with respect to the vehicle speed is known (see, for example, Patent Document 1). Such an electric work vehicle controls a traveling electric motor and a work electric motor based on the operation amount of an artificial vehicle speed operation tool and the applicable work mode.

[0003] When the motor load of the work electric motor increases to a predetermined value or more, the electric work vehicle performs a load reduction process, which is a process of reducing the rotational speed, a process of reducing the vehicle speed, or both processes.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, in an electric work vehicle that rotates a work motor at a target rotational speed to control a work machine and the rotational speed of the work electric motor is determined for each work mode, when working in a work mode intended to keep the battery consumption at a low torque (predetermined torque), when the acceleration increases, the torque of the work motor immediately reaches the predetermined torque. In this case, the electric work vehicle performs control to reduce the vehicle speed when the torque increases, and the speed does not stabilize and the riding comfort is poor. However, when trying to perform work while maintaining a high torque by making the acceleration constant, the operation becomes slow when the acceleration is small.

[0006] The present invention has been made in view of the above, and aims to provide an electric work vehicle that can accelerate responsively by changing the acceleration according to the work mode, thereby facilitating the performance of appropriate work. [Means for solving the problem]

[0007] To solve the above-mentioned problems and achieve the objective, the system comprises a vehicle body (2), a work implement (4) mounted on the vehicle body (2), a travel motor (40) that drives the drive wheels of the vehicle body (2), a work motor (30) that drives the work implement (4), and a control device (70) that receives an input for the travel speed of the vehicle body (2) and allows selection of multiple work modes (30). The control device (70) performs load control, which reduces the vehicle speed of the vehicle body (2) when the load of the work motor (30) exceeds a specified value, and increases the vehicle speed of the vehicle body (2) to the specified speed when the load of the work motor (30) falls below the specified value, and changes the acceleration during acceleration in the load control for each of the multiple work modes. [Effects of the Invention]

[0008] According to the electric lawnmower of this embodiment, by changing the acceleration according to the work mode, it is possible to accelerate quickly and perform appropriate work. [Brief explanation of the drawing]

[0009] [Figure 1] This is a perspective view of the electric work vehicle from the front left. [Figure 2] This is a perspective view of the front of the power unit, seen from the rear left side. [Figure 3] This is a perspective view of the rear of the power unit, seen from the rear left side. [Figure 4] This is a floor plan of the electrical room. [Figure 5] This is a perspective view of the work motor and travel motor from the rear left side. [Figure 6] This is a plan view of the work motor and the travel motor. [Figure 7]It is a rear view of the working motor and the traveling motor. [Figure 8] It is a perspective view of the battery seen from the rear left side. [Figure 9] It is a plan view of the electric chamber with the battery mounted. [Figure 10] It is a plan view of the working motor, the traveling motor, and the inverter device. [Figure 11] It is a left side view of the working motor, the traveling motor, and the inverter device. [Figure 12] It is a transmission diagram of the output rotation of the working motor and the traveling motor. [Figure 13] It is a connection diagram of the control device. [Figure 14] It is an explanatory diagram of the working mode selected by the mode switch. [Figure 15] It is an explanatory diagram of the power wiring and the output wiring. [Figure 16] It is an explanatory diagram for explaining the specified value of the load of the working motor.

Mode for Carrying out the Invention

[0010] Hereinafter, the electric work vehicle according to the embodiment of the present invention will be specifically described with reference to the drawings. Note that the components in the following embodiments include those that can be replaced by those skilled in the art, or those that are substantially the same, that is, those within the so-called equivalent range. Furthermore, the present invention is not limited to the above embodiments, and can be variously modified and implemented without departing from the gist of the present invention.

[0011] First, the overall configuration of the electric work vehicle 100 will be described with reference to FIG. 1. FIG. 1 is a perspective view of the electric work vehicle 100 seen from the front left side.

[0012] As shown in FIG. 1, the electric work vehicle 100 includes a traveling vehicle body 101, a working machine 4, and a grass collection container 7. The traveling vehicle body 101 includes a body frame 1, front wheels 2, rear wheels 3, a control unit 5, a safety frame 6, a steering column 10, an accelerator pedal 12, and a shift lever 14.

[0013] The body frame 1 forms the body skeleton of the traveling vehicle body 101. In the electric work vehicle 100, a pair of left and right front wheels 2 are provided at the front part on the lower side of the body frame 1, and a pair of left and right rear wheels 3 are provided at the rear part on the lower side of the body frame 1.

[0014] At the front part of the body frame 1, a working machine 4 for mowing the lawn grass growing in the field is mounted. At the rear side of the working machine 4, a control section 5 for an operator to board is provided. At the rear side of the control section 5, a safety frame (ROPS) 6 for protecting the operator is provided. At the rear side of the safety frame 6, a grass collecting container 7 for storing the mowed lawn grass is provided. At the lower side of the grass collecting container 7, an electric room 8 for arranging a traveling motor 40 for driving the front wheels 2, a battery 50, etc. is provided.

[0015] In front of the driver's seat of the control section 5, a steering column 10 for supporting a steering wheel is provided. At the upper part of the steering column 10, a monitor for displaying the output rotation speed etc. of the traveling motor 40 is provided, and the lower part is fixed to the front part of the floor.

[0016] On the left side of the steering column 10 on the floor, a brake pedal 11 for decelerating the rotation speed of the front wheels 2 is provided, and on the right side, an accelerator pedal 12 for increasing and decreasing the output rotation speed of the traveling motor 40 for driving the front wheels 2 is provided. Note that the depression amount of the accelerator pedal 12 is measured by an angle sensor 12S (see FIG. 13) mounted on the base of the accelerator pedal 12.

[0017] Above the front wheels 2 is covered by a fender 13. On the fender 13 located on the right side of the driver's seat, a shift lever 14 for operating an inverter device 35 for increasing and decreasing the output rotation of a working motor 30 for driving the working machine 4 is provided. On the right side of the shift lever 14, a mode switch 15 for setting the power consumption of the working motor 30, the maximum output rotation and the angular acceleration of the traveling motor 40 is provided. Note that the operation amount of the shift lever 14 is measured by an angle sensor 14S (see FIG. 13) mounted on the base of the shift lever 14.

[0018] The rear of the work machine 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 (see Figure 12) is provided in the middle of the chute 16 in the front-to-back direction to exhaust air into the chute 16.

[0019] A pair of left and right link arms 18 are provided at the front of the left and right walls of the grass collection container 7. The front of each link arm 18 is pivotably fixed to the safety frame 6, and the safety frame 6 and the link arms 18 are connected by a lifting component 19 such as a hydraulic cylinder. The rear of the lower wall of the grass collection container 7 is mounted on the lateral frame 21A (see Figure 2) of the support frame 21 (see Figure 3), which will be described later. This allows the lifting component 19 to be driven to raise and lower the grass collection container 7.

[0020] Next, the configuration of the motor room 8 will be described with reference to Figures 2 to 4. Figure 2 is a perspective view of the front of the motor room 8 from the rear left. Figure 3 is a perspective view of the rear of the motor room 8 from the rear left. Figure 4 is a plan view of the motor room 8.

[0021] As shown in Figures 2 and 3, the front motor compartment 8A of the motor compartment 8 is equipped with a work motor 30 and a travel motor 40, while the rear motor compartment 8B is equipped with a battery 50 that stores the power supplied to the work motor 30, the travel motor 40, etc.

[0022] In a plan view, the work motor 30 is located on the left side of the left-right centerline of the machine frame 1, and the travel motor 40 is located on the right side of the left-right centerline of the machine frame 1. This suppresses the weight difference between the weight applied to the left side of the left-right centerline of the machine frame 1 and the weight applied to the right side of the left-right centerline of the machine frame 1, thereby improving steering performance.

[0023] In a side view, a support frame 20 extending upward from the aircraft frame 1 is provided in the partition between the front motor compartment 8A and the rear motor compartment 8B, and a support frame 21 extending upward from the aircraft frame 1 is provided at the rear end of the rear motor compartment 8B.

[0024] The support frame 20 is formed by a left vertical frame 20L extending upward from the middle left portion of the aircraft frame 1, a right vertical frame 20R extending upward from the middle right portion of the aircraft frame 1, and a horizontal frame 20A extending in the left-right direction that connects the upper parts of the left vertical frame 20L and the right vertical frame 20R.

[0025] The support frame 21 is formed by a left longitudinal frame 21L extending upward from the left rear end of the aircraft frame 1, a right longitudinal frame 21R extending upward from the right rear end of the aircraft frame 1, a transverse frame 21A extending in the left-right direction and connecting the upper parts of the left longitudinal frame 21L and the right longitudinal frame 21R, and a transverse frame 21B extending in the left-right direction and connecting the intermediate parts of the left longitudinal frame 21L and the right longitudinal frame 21R. The left part of the transverse frame 21B extends to the left of the left longitudinal frame 21L, and the right part extends to the right of the right longitudinal frame 21R.

[0026] The middle section of the left vertical frame 20L and the left end of the horizontal frame 21B are connected by the left front-rear frame 22L, which extends in the front-rear direction, and the middle section of the right vertical frame 20R and the right end of the horizontal frame 21B are connected by the right front-rear frame 22R, which extends in the front-rear direction. This allows the rear of the battery 50 to be positioned above the drive shaft 46 of the rear wheel 3, preventing large deformations from occurring in the aircraft frame 1.

[0027] The upper part of the left vertical frame 20L and the middle part of the left vertical frame 23L located at the rear of the control unit 5 are connected by a left front-rear frame 24L that extends in the front-rear direction, and the upper part of the right vertical frame 20R of the support frame 20 and the middle part of the right vertical frame (not shown) located at the rear of the control unit 5 are connected by a right front-rear frame 24R (see Figure 10) that extends in the front-rear direction.

[0028] As shown in Figure 4, the longitudinal direction of the work motor 30 is aligned with the front-to-back direction. The travel motor 40 is located adjacent to the right side of the work motor 30, and the longitudinal direction of the travel motor 40 is aligned with the front-to-back direction.

[0029] A radiator 60 for cooling the water used to cool the work motor 30 and other components is provided on the outside of the left wall of the power chamber 8, and a fan 61 for blowing outside air towards the power chamber 8 is provided between the radiator 60 and the work motor 30. A circular opening (not shown) is formed on the left wall of the power chamber 8 opposite the fan 61. This suppresses the temperature rise of the work motor 30 and other components, preventing malfunctions of the work motor 30 and other components. The fan 61 can also be provided on the left side of the radiator 60.

[0030] Next, the configuration of the work motor 30 and the travel motor 40 will be described with reference to Figures 5 to 7. Figure 5 is a perspective view of the work motor 30 and the travel motor 40 from the rear left. Figure 6 is a plan view of the work motor 30 and the travel motor 40. Figure 7 is a rear view of the work motor 30 and the travel motor 40.

[0031] As shown in Figures 5 to 7, the output shaft 30A of the work motor 30 (see Figure 12) is connected to a reduction gear 31 located on the lower side of the work motor 30. The output shaft 31A of the reduction gear 31 extends forward and is connected to a work clutch 32 (see Figure 12) located between the reduction gear 31 and the transmission path of the work machine 4.

[0032] The output shaft 40A of the drive motor 40 (see Figure 12) is connected to a reduction gear 41 located on the front side of the drive motor 40. The output shaft 41A of the reduction gear 41 extends forward, and the output shaft 41B extends rearward and is connected to a 4WD clutch 43, which switches between front-wheel drive and four-wheel drive and is located between the reduction gear 41 and the transmission path of the rear wheels 3.

[0033] Next, the configuration of the battery 50 will be described with reference to Figures 8 and 9. Figure 8 is a perspective view of the battery 50 from the rear left side. Figure 9 is a plan view of the motor room 8 on which the battery 50 is mounted.

[0034] As shown in Figure 8, the battery 50 is formed from four battery modules 50A. The upper parts of the four battery modules 50A are connected by a pair of left and right angle-shaped mounting frames 51 that extend in the front-to-back direction and are spaced apart in the left-to-right direction, and the lower parts are connected by a pair of left and right square pipe-shaped mounting frames 52 that extend in the front-to-back direction and are spaced apart in the left-to-right direction.

[0035] The front portion of the mounting frame 51 extends forward of the battery 50, and the rear portion extends backward of the battery 50. The mounting frame 52 extends from the front end to the rear end of the battery 50.

[0036] As shown in Figure 9, the front part of the mounting frame 51 is detachably fixed to the horizontal frame 20A of the support frame 20 by fastening members such as bolts, and the rear part is detachably fixed to the horizontal frame 21A of the support frame 21 by fastening members such as bolts.

[0037] The left mounting frame 52 is mounted on the left front / rear frame 22L (see Figure 10), and the right mounting frame 52 is mounted on the right front / rear frame 22R (see Figure 10).

[0038] The front and rear of the mounting frame 51 are formed with openings 51A (see Figure 8) through which a suspension hook can be inserted when replacing the battery 50. This allows the battery 50 to be easily attached to and detached from the support frame 20 and support frame 21, and the battery 50 to be easily replaced.

[0039] Next, the configuration of the work motor 30, the travel motor 40, and the inverter devices 35 and 45 will be described with reference to Figures 10 and 11. Figure 10 is a plan view of the work motor 30, the travel motor 40, and the inverter devices 35 and 45. Figure 11 is a left side view of the work motor 30, the travel motor 40, and the inverter devices 35 and 45.

[0040] As shown in Figures 10 and 11, an inverter device 35 that drives the work motor 30 is provided on the rear side of the work motor 30 at a predetermined distance in the front-rear direction, and an inverter device 45 that drives the travel motor 40 is provided on the rear side of the travel motor 40 at a predetermined distance in the front-rear direction. Furthermore, the inverter devices 35 and 45 are provided on the front side of the battery 50 at a predetermined distance in the front-rear direction. This makes it easy to arrange the work motor 30 and travel motor 40 and the inverter devices 35 and 45. In addition, air blown from the fan 61 (see Figure 9) can pass through the gap between the work motor 30 and travel motor 40 and the inverter devices 35 and 45, allowing for efficient cooling of the work motor 30 and travel motor 40 and the inverter devices 35 and 45.

[0041] Next, the transmission configuration of the output rotation of the work motor 30 and the travel motor 40 will be described with reference to Figure 12. Figure 12 is a transmission diagram of the output rotation of the work motor 30 and the travel motor 40.

[0042] As shown in Figure 12, the output rotation of the output shaft 30A of the work motor 30 is reduced by the reduction gear 31 and then output from the output shafts 31A and 31B of the reduction gear 31.

[0043] The output rotation of the output shaft 31A is transmitted to the work PTO 33 via the work clutch 32 to drive the work implement 4. The output rotation of the output shaft 31B is transmitted to the hydraulic pump 34, which pumps oil to supply to the lifting components 19, etc.

[0044] Furthermore, the output rotation of the output shaft 30A of the work motor 30 is transmitted to the blower PTO 37 via the blower clutch 36 to drive the blower 17.

[0045] The output rotation of the output shaft 40A of the travel motor 40 is reduced by the reduction gear 41, and then output from the output shafts 41A and 41B of the reduction gear 41.

[0046] The output rotation of the output shaft 41A is transmitted to the differential gear 42 for the front wheels to drive the front wheels 2, the output rotation of the output shaft 41B is transmitted to the differential gear 44 for the rear wheels via the 4WD clutch 43, and the output rotation of the differential gear 44 is transmitted to the drive shaft 46 to drive the rear wheels 3.

[0047] Next, the control configuration of the electric work vehicle 100 will be described with reference to Figure 13. Figure 13 is a connection diagram of the control device 70.

[0048] As shown in Figure 13, the control device 70 of the electric work vehicle 100 is formed from a processing unit 71 consisting of a CPU and the like, a storage unit 72 consisting of ROM, RAM, hard disk drive, flash memory and the like, and a communication unit 73 for data communication with the outside.

[0049] The processing unit 71 calculates output values ​​to be output to the inverter device 45 based on the amount the accelerator pedal 12 is pressed, and calculates output values ​​to be output to the inverter device 35 based on the amount the gear shift lever 14 is operated, and so on.

[0050] Furthermore, the processing unit 71 performs load control, which reduces the vehicle speed of the vehicle body 101 when the load of the work motor 30 exceeds a specified value, and increases the vehicle speed of the vehicle body 101 to the instructed speed if the vehicle speed is slower than the instructed speed when the load of the work motor 30 falls below the specified value. The specified value is a set value set for each work mode. The instructed speed is a target vehicle speed determined according to the amount the accelerator pedal 12 is pressed. The vehicle speed of the vehicle body 101 is, for example, the vehicle speed detected by the rotational speed of the drive motor 40. The processing unit 71 calculates an output value to output to the inverter device 45 so that the vehicle speed becomes the target speed in load control.

[0051] The memory unit 72 saves the work mode that was selected by the mode switch 15 immediately before the electric work vehicle 100 stopped. This allows the vehicle to be restarted in the work mode selected immediately before stopping without having to re-select a mode with the mode switch 15.

[0052] The communication unit 73 transmits and receives data with a portable controller (not shown).

[0053] On the input side of the control device 70, an angle sensor 12S for measuring the amount of depression of the accelerator pedal 12 which increases or decreases the output rotation of the travel motor 40, an angle sensor 14S for measuring the amount of operation of the shift lever 14 which increases or decreases the output rotation of the work motor 30, and a mode switch 15, etc., are connected via a predetermined input interface circuit.

[0054] On the output side of the control device 70, an inverter device 35 for driving the work motor 30 and an inverter device 45 for driving the travel motor 40 are connected via a predetermined output interface circuit.

[0055] Next, the control configuration of the electric work vehicle 100 will be described with reference to Figure 14. Figure 14 is an explanatory diagram of the work modes selected by the mode switch 15.

[0056] As shown in Figure 14, in this embodiment, the mode switch 15 can be used to select one of Power mode, Mid mode, or Eco mode. In Power mode, the acceleration setting condition for the travel motor 40 is high acceleration a P It is pre-set. In Mid mode, the acceleration condition for the travel motor 40 is medium acceleration a M It is pre-set. In Eco mode, the acceleration setting condition for the travel motor 40 is low acceleration a E Set this in advance.

[0057] Next, the configuration of the power wiring and output wiring will be explained with reference to Figure 15. Figure 15 is an explanatory diagram of the power wiring P1-P3 and output wiring S1-S4.

[0058] As shown in Figure 15, power from the battery 50 is supplied to the control device 70 via power wiring P1, to the inverter devices 35 and 45 via power wiring P2, and to the work motor 30 and the travel motor 40 via power wiring P3.

[0059] The output value of the control device 70 is input to the inverter device 35 via output wiring S1, and the output value of the inverter device 35 is input to the work motor 30 via output wiring S2. In addition, the output value of the control device 70 is input to the inverter device 45 via output wiring S3, and the output value of the inverter device 45 is input to the travel motor 40 via output wiring S4. In other words, the output rotations of the work motor 30 and the travel motor 40 are controlled individually by the inverter devices 35 and 45, respectively, so that the output rotation of the work motor 30 is not affected by the output rotation of the travel motor 40, and the output rotation of the travel motor 40 is not affected by the output rotation of the work motor 30.

[0060] Next, the control performed by the electric work vehicle 100 will be explained with reference to Figure 16. Figure 16 is an explanatory diagram illustrating the specified load value of the work motor 30.

[0061] The control device 70 controls the generated torque using a drive current or detected current (or power). The drive current (power) is correlated with the generated torque, and by using this current for control, the need for additional torque sensors and other equipment is eliminated.

[0062] As described above, the electric work vehicle 100 is driven by two motors: a work motor 30 and a travel motor 40. The control device 70 detects the torque generated by the current of the work motor 30 and controls the vehicle speed using the travel motor 40. In this electric work vehicle 100, during work, the work motor 30 maintains the rotational speed of the blade, etc., by receiving the load during work, and the generated torque, etc., can be directly detected by the drive current of the work motor 30, allowing the work motor 30 to be controlled. This improves the accuracy of load detection and load control, enabling more efficient work. The drive current is the current flowing through the power wiring P2 between the battery 50 and the inverter device 45.

[0063] As shown in Figure 16, the control device 70 sets specified load values ​​K1 to K3 for the work motor 30 in relation to the rotational speed of the work motor 30, and controls the torque generated by the work motor 30. In the electric work vehicle 100 of the present invention, since specified load values ​​K1 to K3 are set in relation to the rotational speed of the work motor 30, the specified load values ​​K1 to K3 can be set according to the work load generated by high rotational speed instructions and low rotational speed instructions, leading to effective energy-saving operation. This makes it possible to suppress power consumption as much as possible. Note that the specified load values ​​K1 to K3 shown in Figure 16 are not particularly limited, and for example, the gradient of the specified values ​​K1 to K3 may be arbitrarily changed at high rotational speeds.

[0064] The control device 70 sets default load values ​​K1 to K3 for each of the multiple work modes. For example, in Power mode, a default load value K1 is set; in Mid mode, a default load value K2 is set; and in Eco mode, a default load value K3 is set. In each work mode, the control device 70 performs load control, which reduces the vehicle speed of the traveling vehicle 101 when the load of the work motor 30 exceeds the default values ​​K1 to K3, and increases the vehicle speed of the traveling vehicle 101 to the instructed speed if the vehicle speed is slower than the instructed speed when the load of the work motor 30 falls below the default values ​​K1 to K3. The control device 70 changes the acceleration during acceleration in load control for each of the multiple work modes (for example, Power mode, Mid mode, Eco mode). By changing the acceleration during acceleration for each work mode, it is possible to set the power consumption to be reduced or the work efficiency to be prioritized according to preference.

[0065] Furthermore, the control device 70 sets the acceleration during speed increase in load control to be higher the higher the specified load values ​​K1 to K3 of the work motor 30, and sets the acceleration during speed increase in load control to be lower the lower the specified load values ​​K1 to K3 of the work motor 30 (see Figure 14). In the electric work vehicle 100 of the present invention, the specified load values ​​K1 to K3 are set by the work mode setting when operating, so the operator can choose their preference, such as wanting to work at a suitable vehicle speed under high load even if it is slightly less energy-efficient. In addition, it is possible to minimize power consumption as much as possible.

[0066] The electric work vehicle 100 may also be configured with a single motor drive for the work motor 30 and the travel motor 40. The control device 70 detects the generated torque etc. based on the drive current of the single motor and controls the vehicle speed with a continuously variable transmission for the travel system. In such an electric work vehicle 100, even if there are load fluctuations in the travel system in response to the work load such as grass cutting, the continuously variable transmission mechanism of the travel system does not increase the vehicle speed, so operation with less power loss of the motor can be expected. In addition, the system can be configured with one motor, making it an inexpensive system that can operate with good energy efficiency.

[0067] Next, we will describe other features of the electric work vehicle 100 and their effects.

[0068] The control device 70 may instruct the work motor 30 to set a specified rotational speed (hereinafter referred to as the PTO specified rotational speed) and perform a maximum torque limit (limiting the torque to the maximum capacity of the work motor 30) to maintain the PTO specified rotational speed. If the torque generated during operation is less than or equal to the limit torque and greater than or equal to a specified torque, the control device 70 performs control to suppress the increase in the vehicle speed (hereinafter referred to as speed increase suppression control).

[0069] Conventionally, when working with a lawnmower or the like, if a load exceeding the capacity (limit torque) of the work motor 30 occurs, the rotational speed of the work motor 30 drops sharply, and clogging or other problems occur in the work implement 4, resulting in maximum power consumption during that time, leading to wasted power consumption and work loss. In the electric work vehicle 100 of the present invention, the increase in vehicle speed is suppressed when a high torque within the maximum capacity (limit torque) of the work motor 30 is generated, so if the grass density of the work target is constant, the work load does not increase and stable work can be performed efficiently. As a result, work can be performed with less wasted power consumption, leading to energy-saving operation.

[0070] Furthermore, the control device 70 may change the gradient of the speed change when increasing the speed within a predetermined range of load less than or equal to a specified load value K1, a predetermined range of load less than or equal to a specified load value K2, and a predetermined range of load less than or equal to a specified load value K3, more gradually than usual. In the electric work vehicle 100 of the present invention, even if the operator operates the accelerator pedal 12 abruptly, it is possible to prevent abrupt changes in the load when the load increases on the speed-increasing side depending on the magnitude of the load. Therefore, discomfort during work is eliminated, and the operator can recognize that the load is increasing through the phenomenon of slower speed changes, leading to smoother operation. This makes it possible to suppress abrupt speed changes to loads that would require speed-increasing restrictions.

[0071] Furthermore, if the control device 70 experiences a decrease in the actual PTO rotation speed relative to the PTO instruction rotation speed, it may prioritize deceleration over acceleration suppression control when controlling the vehicle speed. In the electric work vehicle 100 of this invention, when the work load increases due to changes in grass height or the degree of wetness of the grass, appropriate deceleration can be performed, leading to continued work with less clogging. This makes it possible to respond to situations where the load cannot be reduced without reducing the vehicle speed in the event of abrupt load fluctuations.

[0072] The control device 70 may, when it detects a load equivalent to the limiting torque, prioritize deceleration over acceleration suppression control to control the vehicle speed. In the electric work vehicle 100 of this invention, appropriate deceleration can be performed when the work load increases due to changes in grass height or the degree of wetness of the grass, leading to continued work with less clogging. This makes it possible to respond to situations where the load cannot be reduced without reducing the vehicle speed in the event of abrupt load fluctuations.

[0073] The electric work vehicle 100 may vary its vehicle speed in conjunction with the operation of the forward and reverse pedals (not shown). The control device 70 may configure the actual speed instruction to change with a predetermined delay (late limit processing) in response to the instruction to operate the forward and reverse pedals. Speed ​​control based on load fluctuations (suppression of acceleration, mitigation of acceleration, deceleration control) is controlled by changing the constant amount of change within a predetermined time used for late limit processing according to the conditions. In the electric work vehicle 100 of this invention, the program configuration can be simplified by changing the constants such as late limit processing, which are composed of driving based on pedal operation, according to the conditions. This simplifies the algorithm of the driving system program.

[0074] The control device 70 refers to the graph shown in Figure 16 (hereinafter also referred to as the current map) prepared for the three-phase AC motor being driven, and estimates and controls the generated torque based on the instantaneous detected current and detected rotational speed. In the electric work vehicle 100 of this invention, torque is estimated from the detected current and rotational speed values ​​during operation by referring to the data in the graph, so there is no need for extra torque sensors or the like.

[0075] <Load control for electric farm machinery> Next, we will explain the load control of the electric work vehicle 100.

[0076] The electric work vehicle 100 is an electric lawnmower that operates using a three-phase AC motor as its drive source. The work motor 30 is driven based on a current map that is pre-set as the motor characteristics. When the electric work vehicle 100 is driven in a mode that changes the drive current to maintain the instructed rotational speed (speed control), it is configured to estimate the instantaneous load based on the current map using the actual rotational speed when driven with the instructed drive current.

[0077] In the electric work vehicle 100 of this invention, the generated torque is estimated by comparing the drive current detected when the work motor 30 is driven with speed control and the motor rotation speed at that time with a current map that has been created in advance, thereby detecting the actual equivalent load. This makes it possible to appropriately estimate the load on the work motor 30. The current map is a mapping of current instruction values ​​for each rotation speed that has been pre-mapped for the motor used and stored in the ECU or the like.

[0078] Furthermore, the control device 70 may restrict the actual speed command from increasing even if the indicated speed is increasing, when the rate of change of the generated torque changes to the high-load side at a gradient greater than specified. In the electric work vehicle 100 of the present invention, the speed command of the travel motor 40 is restricted from increasing even when the indicated speed is increasing, so that the total amount of grass entering the cutting unit (work machine 4) does not increase easily, which helps to prevent clogging and other problems.

[0079] Furthermore, the control device 70 may have multiple thresholds set for the increasing gradient of the generated torque. For example, the control device 70 may set multiple thresholds such as setting the actual speed command to decelerate when the increasing gradient is steep, and instructing the actual speed command to maintain speed when the increasing gradient is gentler than the steep increasing gradient. In the electric work vehicle 100 of the present invention, by setting multiple thresholds, the total amount of grass is reduced by deceleration in the case of a steep increasing gradient that could lead to clogging. And, if the increasing gradient is gentle, but increasing the speed would increase the total amount of grass and could lead to clogging, the speed is maintained, allowing operation without excessive acceleration or deceleration.

[0080] Furthermore, the control device 70 may apply a torque limit to the drive of the work motor 30 based on the generated torque. If the rotational speed of the work motor 30 drops below a specified rotational speed due to the torque limit, the control device 70 stops the drive of the work motor 30. In the electric work vehicle 100 of the present invention, if the rotational speed drops due to the torque limit, it is possible to suppress the accumulation of a large amount of grass in the work machine 4 if the operation continues as is. In addition, even if grass clogging occurs, it is kept to a minimum, so the grass clogging work can be done in a short time and work efficiency is improved.

[0081] Furthermore, when the control device 70 stops the drive of the work motor 30, it may also stop the drive of the travel motor 40. In the electric work vehicle 100 of this invention, if the rotational speed is reduced due to torque limiting, continuing work as is can prevent a large amount of grass from clogging the work implement 4. Also, even if grass clogging occurs, it can be kept to a minimum, so that grass clogging removal work can be done in a short time and work efficiency can be improved.

[0082] As described above, the electric work vehicle 100 according to this embodiment includes a vehicle body 101, a work machine 4 mounted on the vehicle body 101, a travel motor 40 that drives the drive wheels of the vehicle body 101, a work motor 30 that drives the work machine 4, and a control device 70 that receives the instructed speed of travel of the vehicle body 101 and allows selection of multiple work modes. The control device 70 performs load control, which reduces the vehicle speed of the vehicle body 101 when the load of the work motor 30 exceeds a specified value K1 to K3, and increases the vehicle speed of the vehicle body 101 to the instructed speed when the vehicle speed is slower than the instructed speed when the load of the work motor 30 falls below the specified value K1 to K3, and changes the acceleration during acceleration in load control for each of the multiple work modes. With the electric work vehicle 100 configured in this way, by changing the acceleration during acceleration for each work mode, it is possible to set the power consumption to be reduced or the work efficiency to be prioritized according to preference.

[0083] Furthermore, in the electric work vehicle 100, the specified load values ​​K1 to K3 for the work motor 30 differ for each of the multiple work modes. The control device 70 sets the acceleration during speed increase in load control higher the higher the specified load values ​​K1 to K3 for the work motor 30, and sets the acceleration during speed increase in load control lower the lower the specified load values ​​K1 to K3 for the work motor 30. With the electric work vehicle 100 configured in this way, when the specified load values ​​K1 to K3 are low (to reduce power consumption and work for a long time), the specified load values ​​K1 to K3 are reached immediately during acceleration, preventing frequent fluctuations in vehicle speed and unstable behavior. Also, when the specified load values ​​K1 to K3 are high and there is a margin, the operation may feel sluggish when accelerating slowly, so the operation can be made agile when accelerating sharply.

[0084] Further effects and modifications can be readily derived by those skilled in the art. Therefore, broader aspects of the present invention are not limited to the specific details and representative embodiments expressed and described above. Accordingly, various modifications are possible without departing from the spirit or scope of the overall concept of the invention as defined by the appended claims and their equivalents. [Explanation of Symbols]

[0085] 2 Front wheels 3 Rear wheels 4. Work equipment 30 Working motors 40. Driving motor 70 Control device 100 Electric Work Vehicles 101 Running vehicle K1 Standard Value K2 Standard Value K3 Standard Value

Claims

1. The vehicle body and A work machine mounted on the aforementioned vehicle body, A drive motor that drives the drive wheels of the aforementioned vehicle body, A work motor that drives the aforementioned work machine, The vehicle includes a control device that receives input for the instructed speed of the vehicle body and allows selection of multiple work modes. The control device is Load control is performed such that when the load of the work motor exceeds a specified value, the vehicle speed of the traveling vehicle is reduced, and when the load of the work motor falls below the specified value, the vehicle speed of the traveling vehicle is increased to the specified speed if it is slower than the specified speed. An electric work vehicle that changes the acceleration during speed increase in load control for each of the aforementioned multiple work modes.

2. The specified load value for the work motor differs for each of the aforementioned multiple work modes. The control device is The electric work vehicle according to claim 1, wherein the higher the specified value of the load of the work motor, the higher the acceleration during speed increase in the load control is set, and the lower the specified value of the load of the work motor, the lower the acceleration during speed increase in the load control is set.

Images