Mowing vehicle

Abstract

To efficiently perform a mowing work by suppressing grass which is left from mowing even when a high load is applied to a mowing motor in a mowing vehicle.SOLUTION: A mowing vehicle includes a mowing device. The mowing device includes a mowing blade which is driven by a plurality of mowing motors. When it is detected that a load of at least one mowing motor in the plurality of mowing motors is a high load, a control device performs control so as to operate the mowing motor of the high load in accordance with a high load response output map. The high load response output map is specified in such a manner that a border rotation speed when switching from an upper limit torque fixed region in which an upper limit torque value is fixed to an upper limit torque reduced region in which the upper limit torque value is reduced with an increase in the rotation speed of the mowing motor is lower than an upper limit rotation speed of the upper limit torque fixed region in output characteristics of the mowing motor which are determined from the mowing motor and a maximum voltage that can be outputted from the mowing motor.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a grass cutting vehicle. [Background technology]

[0002] BACKGROUND ART Conventionally, in a mowing vehicle such as a lawn mower equipped with a mowing device, a configuration has been known in which multiple mowing motors, which are electric motors, drive multiple mowing blades, and mowing work is performed by the multiple mowing blades.

[0003] Patent Document 1 describes a lawnmower vehicle equipped with a mower unit (lawnmower) that mows the lawn with multiple lawnmower blades driven by multiple blade motors (grass-cutting motors). In this configuration, the temperature of the blade motor is detected, and if the detected temperature is higher than a threshold, the blade motor is controlled to run the vehicle at an exceptional speed lower than the target traveling speed using exceptional speed control. Exceptional speed control involves running the vehicle at an exceptional speed lower than the target traveling speed, which is determined by the amount of operation of a steering lever. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-195360 Summary of the Invention [Problem to be solved by the invention]

[0005] In grasslands, the mowing load acting on each mowing motor is often not uniform due to differences in the type and density of plants growing there, and there may be situations where one mowing motor is subjected to an excessive load compared to the other motors.

[0006] In the case of a riding vehicle equipped with a grass cutting device having multiple electrically driven grass cutting blades, if an excessive load is applied to one of the multiple grass cutting motors, the load may exceed the torque that the grass cutting motor can output, causing the heavily loaded grass cutting motor to suddenly stall and stop. If this happens, and the grass cutting motor stops completely, the grass will remain uncut for the amount of grass that the vehicle continued to run with the grass cutting motor stopped. If the driver notices this, they must make a U-turn and return to the area where the grass remains uncut to continue working.

[0007] In particular, because the operating noise of the mowing motors, which are electric motors, is low, if only some of the multiple mowing motors stop, it is difficult for the driver to notice that they have stopped.

[0008] In the configuration described in Patent Document 1, if the temperature of the blade motor rises above a threshold value, the rotation speed of the blade motor may be changed, but even if the temperature does not rise above the threshold value, the high-load mowing motor may suddenly stop, which may result in some grass being left uncut.

[0009] The object of the present invention is to provide a mowing vehicle equipped with a mowing device having a plurality of electrically driven mowing blades, which is less likely to stop suddenly even when a high load is applied to the mowing motor, thereby reducing the amount of grass left uncut and enabling efficient mowing work. [Means for solving the problem]

[0010] The mowing vehicle according to the present invention is a mowing vehicle equipped with a mowing device and a control device, wherein the mowing device includes a plurality of mowing motors which are electric motors for mowing, and mowing blades driven by the plurality of mowing motors, and the control device is configured to operate the high-load mowing motor in accordance with a high-load output map which is an output map that defines the relationship between the upper limit torque value that the mowing motor can output and the rotation speed of the mowing motor when it detects that the load on at least one of the plurality of mowing motors is high. and the high-load response output map is defined so that the boundary rotation speed when switching from a constant upper limit torque region, in which the upper limit torque value is constant regardless of the rotation speed of the grass mowing motor, to a decreasing upper limit torque region, in which the upper limit torque value decreases as the rotation speed of the grass mowing motor increases, is lower than the upper limit rotation speed of the constant upper limit torque region in the output characteristics of the grass mowing motor, which is determined from the grass mowing motor and the maximum voltage that can be output to the grass mowing motor, when the high-load response control is not executed.

[0011] In a brush mowing vehicle according to the present invention, when at least one of a plurality of mowing motors driven at a rated rotational speed is under a high load, the motor's torque increases to balance the load, but its rotational speed decreases in accordance with the upper torque reduction region of the high-load output map. This allows the time it takes for the mowing motor to stall after its rotational speed decreases in accordance with the high-load output map, even under a high load, longer than when a conventional high-load output map is not used. This makes it easier for the driver to notice a high load on the mowing motor from a change in the sound emitted by the mowing device. This allows the driver to quickly eliminate a high load on the mowing motor by reducing the vehicle's traveling speed by operating a speed indicator, such as a control lever, to adjust the vehicle's traveling speed. Therefore, even when a high load is applied to the mowing motor, further torque increases after the torque reaches the upper torque constant region, reducing the likelihood of the mowing motor stalling and stopping suddenly. This prevents the mowing work from continuing when areas of the grass remain uncut, allowing for efficient mowing work.

[0012] In the mowing vehicle according to the present invention, the threshold rotational speed may be set so as to substantially match the minimum rotational speed of the mowing motor required for mowing work using the mowing blade.

[0013] With the above configuration, when the mowing motor is under high load, the rotation speed of the mowing motor can be reduced to a lower speed. This makes it easier for the driver of the vehicle to notice that the load on the mowing motor is increasing. This allows for more efficient mowing work.

[0014] In the mowing vehicle according to the present invention, the lower limit torque of the upper limit torque decreasing region may be configured to be 65% or more and 75% or less of the torque value of the upper limit torque constant region.

[0015] With the above configuration, the relationship between the upper limit torque of the high-load output map and the rotational speed of the mowing motor can be made closer to the relationship between engine torque and engine rotational speed when the mowing device is driven by conventional engine power, which makes it less likely that a driver switching from a mowing vehicle that uses conventional engine power to drive the mowing device will feel uncomfortable.

[0016] In the mowing vehicle of the present invention, the control device may be configured to detect that the load on the mowing motor is high when the detected torque corresponding to the rotational speed of at least one of the mowing motors exceeds the upper limit torque corresponding to the rotational speed of the mowing motor in the high-load output map.

[0017] Furthermore, in the mowing vehicle of the present invention, the control device may be configured so that when some of the multiple mowing motors are subjected to a high load, causing an increase in the torque of the mowing motor and a decrease in the rotational speed of the mowing motor in accordance with the high-load output map, the control device matches the rotational speed of the remaining mowing motors that are not subjected to a high load to the rotational speed of the mowing motor that is subjected to a high load.

[0018] According to the above configuration, when some of the multiple mowing motors are under high load, the mowing area becomes more uniform and looks better than when only the rotation speed of some of the mowing motors, for example one of the mowing motors, is reduced.

[0019] Furthermore, the brush mowing vehicle according to the present invention may be configured to include a travel motor that drives the wheels, and an operating device that indicates a target rotational speed of the travel motor depending on the operating position, wherein the control device controls the drive of the travel motor in accordance with the target rotational speed, and when a high load is detected on at least one of the plurality of brush mowing motors and an increase in torque of the brush mowing motor and a decrease in rotational speed of the brush mowing motor occur in accordance with the high load output map, the degree of increase in the target rotational speed of the travel motor in response to a change in the operating position may be reduced in accordance with the rate at which the rotational speed of the heavily loaded brush mowing motor decreases.

[0020] With the above configuration, when a high load occurs on at least one mowing motor, the rotational speed of the mowing motor decreases in accordance with the high-load output map in response to the increased load on the mowing motor, and the vehicle speed also decreases. This makes it easier for the driver to notice early on that a high load has occurred on the mowing motor. This further reduces the likelihood of mowing work continuing when grass is left uncut, allowing for more efficient mowing work. In addition, because the amount of grass clippings supplied to the mowing motor is relatively reduced, the mowing motor can quickly escape from a high-load state.

[0021] Furthermore, in the above configuration, when at least one of the plurality of mowing motors changes from a high-load state to a state in which all of the mowing motors are not high-load, the rotational speeds of all of the mowing motors may be returned to the normal rotational speed, and the degree of increase in the target rotational speed of the traveling motor in response to a change in the operating position of the operating tool may be returned to the normal degree.

[0022] According to the above configuration, an electric grass cutting vehicle can be provided that allows the driver to drive the wheels and grass cutting device efficiently and easily with an operating feel similar to that of an engine-powered grass cutting vehicle in which the wheels and grass cutting device are driven by engine power and the high load on the grass cutting device is removed. [Effects of the Invention]

[0023] According to the mowing vehicle of the present invention, even when a high load is applied to the mowing motor, the motor is less likely to stop suddenly, allowing for efficient mowing work. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a perspective view of a grass mowing vehicle according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic configuration diagram of the grass cutting vehicle of FIG. 1 as seen from above. [Figure 3A] FIG. 2 is a block diagram showing a control system for the mowing vehicle of FIG. 1. [Figure 3B] FIG. 3B is a detailed block diagram illustrating the control configuration of multiple deck motors extracted from FIG. 3A. [Figure 4] 10 is a diagram showing the relationship between the output characteristics of the deck motor, which is a mowing motor, in the high-load response output map and the conventional output characteristics of the deck motor when high-load response control is not executed in an embodiment. FIG. [Figure 5] 10 is a diagram showing an example of the relationship between the forward operation amount of the left and right operating levers and the rotation speed of the traveling motor on the same side as the operating lever in the left-right direction in the embodiment. FIG. [Figure 6] 5 is a flowchart showing an example of a method for controlling a deck motor in an embodiment. [Figure 7] FIG. 3B is a view corresponding to FIG. 3A, showing a mowing vehicle according to another embodiment of the present invention. [Figure 8] 10 is a flowchart showing an example of a method for controlling a deck motor in another embodiment. [Figure 9] 9 is a diagram showing a part of the process of a plurality of deck inverter control devices when the control process of FIG. 8 is executed by a plurality of deck inverter control devices. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0025] An embodiment of the present invention will be described in detail below with reference to the drawings. In the following, a case will be described in which the mowing vehicle is equipped with a lawnmower as the mowing device, but the mowing vehicle may also be equipped with a mowing device for mowing weeds other than grass. In the following, a case will be described in which the lawnmower is provided between the front and rear wheels, but the mowing device may be provided in front of the front wheels. In the following, a case will be described in which the vehicle has two rear wheels driven by two motors, but the vehicle may also have two front wheels driven by two motors. In the following, a case will be described in which a left-right lever-type operator having two operating levers, one on the left and one on the right, is used; however, this is merely an example; the steering wheel may be used as a turning indicator, and an accelerator pedal provided in front of the seat may be used as a driving indicator. In the following, like elements will be designated by the same reference numerals in all drawings, and redundant description will be omitted or simplified.

[0026] 1 to 7 show an embodiment. In the drawings described below, the front-rear direction is indicated by X, the left-right direction is indicated by Y, and the up-down direction is indicated by Z. Furthermore, the front side is indicated by Fr, the left side is indicated by Lh, and the up side is indicated by Up. X, Y, and Z are perpendicular to each other.

[0027] FIG. 1 is a perspective view of a mowing vehicle 10 according to an embodiment. FIG. 2 is a schematic diagram of the mowing vehicle 10. FIG. 3A is a block diagram showing a control system 80 for the mowing vehicle 10. In the following description, the mowing vehicle 10 will be referred to as the vehicle 10. The vehicle 10 is a riding self-propelled lawnmower suitable for mowing grass. The vehicle 10 is equipped with two wheels (left and right) on the left and right (FIG. 2), two front wheels (caster wheels 15 and 16) on the left and right, and a lawnmower 18. The vehicle 10 is also equipped with a left traveling motor 30 and a right traveling motor 31 (FIGS. 2 and 3A) for driving the left and right wheels 12 and 13. The vehicle 10 is also equipped with three deck motors 63a, 63b, and 63c (FIG. 2) that are mowing motors, two operation levers 22 and 23 on the left and right, a battery 34 (FIGS. 2 and 3A), and a main control device 40 (FIG. 3A). The left traveling motor 30, the right traveling motor 31, and the deck motors 63a, 63b, and 63c are all electric motors, constituting an all-electric grass cutting vehicle. Hereinafter, the deck motors 63a, 63b, and 63c may be collectively referred to as the deck motor 63.

[0028] The left wheel 12 and the right wheel 13 are rear wheels supported on both the left and right rear sides of a main frame 20, which is the vehicle body, and are also main drive wheels. The main frame 20 is formed into a beam structure or the like using metal such as steel. The main frame 20 includes side plate portions 20a, 20b extending substantially in the front-to-rear direction at both left and right ends, and a connecting portion 20c connecting the left and right side plate portions 20a, 20b. A driver's seat 21, where the driver sits as a user, is fixed to the upper side between the rear ends of the left and right side plate portions 20a, 20b.

[0029] Left and right operating levers 22, 23 are arranged separately on the left and right sides of the driver's seat 21, and each moves forward and backward to specify the rotation direction and rotation speed of the corresponding left wheel 12 or right wheel 13. Specifically, two guide panels 26, 27 are fixed to the main frame 20 on the left and right sides of the driver's seat 21, and the two left and right operating levers 22, 23 are supported by the main frame 20 so as to protrude upward from each of the two guide panels 26, 27. The two left and right operating levers 22, 23 correspond to vehicle speed indicators that the driver uses to adjust the vehicle's traveling speed, and also correspond to operating devices that specify the target rotation speed of the traveling motors 30, 31 depending on the operating positions.

[0030] The left operating lever 22 has the function of instructing acceleration / deceleration, stopping, and forward / reverse rotation of the left traveling motor 30. The right operating lever 23 has the function of instructing acceleration / deceleration, stopping, and forward / reverse rotation of the right traveling motor 31. The tip of each operating lever 22, 23 is grasped by the driver and used to instruct the direction and speed of rotation of the left wheel 12 and the right wheel 13. The left operating lever 22 is operated to instruct the drive state of the left wheel 12. The right operating lever 23 is operated to instruct the drive state of the right wheel 13. Each operating lever 22, 23 is approximately L-shaped and has a grip portion 24 formed at the upper end that extends in the left-right direction. The grip portion 24 is grasped and operated by the driver. The lower end of each operating lever 22, 23 can swing around an axis along the left-right direction. When each of the operating levers 22, 23 is tilted forward with respect to the N position, which is a neutral position close to the upright position, as a reference, the traveling motor 30 (or 31) on the same side as the operating lever 22 (or 23) is rotated at a target number of rotations per unit time (sec ) as a target rotation speed corresponding to forward movement. -1 The target rotation speed may be a target number of rotations per minute (min -1 ) can also be set.

[0031] The operating levers 22, 23 indicate that the target rotation speed increases as the amount of tilt increases. When the operating levers 22, 23 are tilted rearward relative to the N position, they indicate that the traveling motor 30 (or 31) on the same side as the operating lever 22 (or 23) is to be driven at a target rotation speed corresponding to reverse, and the target rotation speed increases as the amount of tilt increases. When the operating levers 22, 23 are moved to the N position, they indicate that the driving of the traveling motor 30 (or 31) on the same side as the operating lever 22 (or 23) is to be stopped. Thus, each operating lever 22, 23, when operated by the user, indicates the target rotation speed of the corresponding traveling motor 30, 31, thereby indicating forward, reverse, or stop of the vehicle.

[0032] The tilt positions of the two left and right operating levers 22, 23 in the front-rear direction are detected by left and right lever position sensors (not shown). Each lever sensor includes, for example, a potentiometer. The detection signals of each lever sensor are sent to the main control device 40 (FIG. 3A).

[0033] The two left and right caster wheels 15, 16 are steering wheels supported on the front end of the main frame 20 and are also front wheels. Each caster wheel 15, 16 is provided spaced apart in the longitudinal direction of the vehicle 10 from the left wheel 12 and the right wheel 13. Each caster wheel 15, 16 can freely rotate 360 ​​degrees or more around an axis in the vertical direction (the up and down direction in FIG. 1). The number of caster wheels is not limited to two per vehicle, and only one, or three or more, may be provided per vehicle.

[0034] As shown in FIG. 2 , the left traveling motor 30 is connected to the left wheel 12 via a left gear mechanism 80a supported on the rear side of the main frame 20 and a left axle 120. The right traveling motor 31 is connected to the right wheel 13 via a right gear mechanism 80b supported on the rear side of the main frame 20 and a right axle 121. The left traveling motor 30 and the right traveling motor 31 are supported on the left and right sides, respectively, at the rear side of the main frame 20. The drive of each traveling motor 30, 31 is controlled by the main control device 40 in response to the operation of the corresponding operating levers 22, 23. As a result, the two left and right traveling motors 30, 31 are connected to the two left and right wheels 12, 13, respectively, and are driven independently of each other. The left traveling motor 30 drives the left wheel 12, and the right traveling motor 31 drives the right wheel 13.

[0035] The left traveling motor 30 is connected to a battery 34 (FIG. 2) via a left traveling inverter 84, and is supplied with power from the battery 34. The right traveling motor 31 is connected to a battery 34 via a right traveling inverter 86, and is supplied with power from the battery 34. The left traveling motor 30 and the right traveling motor 31 are, for example, three-phase motors. As shown in FIG. 2, the battery 34 is fixed to the upper or lower surface of the main frame 20 behind the driver's seat 21.

[0036] As shown in Figures 1 and 2, the lawnmower 18 is supported on the lower side of the main frame 20 in the longitudinal middle. This positions the lawnmower 18 between the caster wheels 15, 16 and the left and right wheels 12, 13 in the front-to-rear direction. The lawnmower 18 includes three lawnmower blades 18a, 18b, and 18c (Figure 2), which are rotary lawnmower tools and are located inside the mower deck 19, which serves as a cover. The upper sides of the lawnmower blades 18a, 18b, and 18c are covered by the mower deck 19. Each of the lawnmower blades 18a, 18b, and 18c has multiple blade elements that rotate around an axis oriented vertically (the direction from the front to the back of the paper in Figure 2). This allows the blade elements to rotate and cut the grass to cut it. The cut grass is discharged from an exhaust duct 18d located on either the left or right side of the mower deck 19.

[0037] Each of the three lawnmower blades 18a, 18b, 18c is connected to a corresponding one of the three deck motors 63, which are mowing motors. A battery 34 is connected to each deck motor 63 via a deck inverter 88a, 88b, 88c (FIG. 3A), which is an inverter for the corresponding deck motor 63, and power is supplied from the battery 34. The driving of a deck inverter circuit (described below) of each deck inverter 88a, 88b, 88c is controlled by the main controller 40 in response to the operation of the work unit start switch 33. This drives each deck motor 63. Each deck motor 63 is, for example, a three-phase motor. Hereinafter, the deck inverters 88a, 88b, 88c may be collectively referred to as the deck inverter 88.

[0038] The overall configuration of the vehicle 10 has been described above. Next, using FIG. 3A , a vehicle control system 80 will be described, which includes the three deck motors 63 that drive the lawnmower 18 and the main control device 40. The main control device 40 is connected to a start switch 35, a working unit start switch 33, two left and right lever sensors 50, 51, two left and right travel inverters 84, 86, a deck inverter 88, and two left and right motor speed sensors 54, 55. The start switch 35 and the working unit start switch are located on or near one of the guide panels 26 (or 27) that guide one of the two left and right operating levers 22, 23. The start switch 35 is operable by the user, and upon operation, power is supplied from the battery 34 to the main control device 40, activating the main control device 40. The working unit start switch 33 is operable by the user, and upon operation, switches the lawnmower 18 between operating and stopping. When the working unit start switch 33 commands the lawn mower 18 to start, i.e., when it is turned on, the main control device 40 controls the deck inverter 88 described below to operate the deck motor 63 so that it continues to rotate at the rated rotation speed Vr, which is the target rotation speed during standard mowing work.

[0039] The control system 80 includes an operation unit 32 including a start switch 35, a working unit start switch 33, and two left and right operation levers 22, 23, two left and right lever sensors 50, 51, two left and right travel motors 30, 31 and travel inverters 84, 86, two left and right motor speed sensors 54, 55, three deck motors 63 and deck inverter 88, three deck motor speed sensors 52, a current detection unit 90 and a torque calculation unit 91 for detecting the torque of each deck motor 63, and a main control device 40. Although Fig. 3A shows only one deck motor 63, deck inverter 88, deck motor speed sensor 52, and current detection unit 90, in reality, three deck motors 63 are provided as shown in Fig. 2, and therefore the control system 80 is provided with three deck inverters 88, deck motor speed sensors 52, and current detection units 90 correspondingly.

[0040] The left traveling inverter 84 drives the left traveling motor 30, and the right traveling inverter 86 drives the right traveling motor 31. Each traveling inverter 84, 86 has a traveling inverter circuit including, for example, three arms, each having two switching elements electrically connected in series, and a traveling inverter control device that controls the traveling inverter circuit.

[0041] The operation of each of the traveling inverters 84, 86 is controlled by the main controller 40. As a result, the left traveling motor 30 is controlled by the main controller 40 via the left traveling inverter 84. The right traveling motor 31 is controlled by the main controller 40 via the right traveling inverter 86.

[0042] Furthermore, the left traveling inverter control device of the left traveling inverter 84 receives as input the detected value of the rotation speed of the left traveling motor 30 from the left motor speed sensor 54. The right traveling inverter control device of the right traveling inverter 86 receives as input the detected value of the rotation speed of the right traveling motor 31 from the right motor speed sensor 55. The two left and right motor speed sensors 54, 55 detect the respective rotation speeds of the two left and right traveling motors 30, 31. The detected rotation speed values ​​of each motor speed sensor 54, 55 are output to the main control device 40.

[0043] Figure 3B is a block diagram showing in detail the control configuration of the three deck motors 63a, 63b, and 63c extracted from Figure 3A. As shown in Figure 3B, the three deck inverters 88a, 88b, and 88c have deck inverter control devices 92a, 92b, and 92c and deck inverter circuits 93a, 93b, and 93c, respectively.

[0044] Each deck inverter 88 drives a corresponding deck motor 63. The deck inverter controllers 92a, 92b, 92c of each deck inverter 88 control the corresponding deck inverter circuits 93a, 93b, 93c, and the deck inverter controllers 92a, 92b, 92c have the same basic configurations as the traveling inverter circuits and traveling inverter controllers of each traveling inverter 84, 86, respectively.

[0045] The operation of each deck inverter 88 is controlled by the main controller 40, as described below. The detected rotation speed value of the deck motor 63 is input from the deck motor speed sensor 52 to the deck inverter controllers 92a, 92b, 92c of each deck inverter 88. Each deck motor speed sensor 52 detects the rotation speed of the corresponding deck motor 63. The deck inverter controllers 92a, 92b, 92c output the detected rotation speed value of the deck motor speed sensor 52 to the main controller 40.

[0046] The current detection unit 90 detects the current flowing from the deck inverter 88 to the deck motor 63. For example, the current detection unit 90 calculates the current value of the deck motor 63 from a current value acquired from a three-phase or two-phase electric wire connecting the coil wire of the three-phase deck motor 63 and the three-phase deck inverter.

[0047] The torque calculation unit 91 receives the current value detected by the current detection unit 90 and calculates the torque of the deck motor 63 from that current value. At this time, the torque can be calculated from the current value using a map that shows the relationship between the current value and the torque or a predetermined calculation formula. In this way, the torque of the deck motor 63 is indirectly detected. The torque of each deck motor 63 calculated by the torque calculation unit 91 is output to the main control device 40 as the detected torque of each deck motor 63. Note that the function of the torque calculation unit 91 may be included in the main control device 40.

[0048] The main controller 40 detects the operating point of each deck motor 63a, 63b, 63c based on the detected torque and rotational speed values ​​of the deck motors 63a, 63b, 63c. The main controller 40 controls each deck motor 63 so that it is driven at a rated rotational speed, which is a predetermined target rotational speed, unless at least some of the deck motors 63 are in a high-load state. At this time, each deck motor 63 is controlled by the main controller 40 via inverter controllers 92a, 92b, 92c of the deck inverter 88. As a result, each lawnmower blade 18a, 18b, 18c is rotated and driven by the corresponding deck motor 63.

[0049] 3A, the power supply path from the battery 34 is indicated by a thick solid line, and the signal transmission path is indicated by a thin solid line.

[0050] The main control device 40 includes a calculation unit such as a CPU and a storage unit such as a memory, and is configured, for example, by a microcomputer. The main control device 40 acquires the operating positions of the two control levers 22, 23 from the detection signals of the two left and right lever sensors 50, 51, and sets the target rotation speeds of the left traveling motor 30 and the right traveling motor 31 according to the operating positions of the respective control levers 22, 23.

[0051] The main control device 40 can perform either straight running or turning by setting the target rotation speeds of the two left and right traveling motors 30, 31 according to the operating positions of the two left and right operating levers 22, 23. In this way, the main control device 40 controls the driving of the traveling motors 30, 31 according to the target rotation speeds set according to the operating positions of the two left and right operating levers 22, 23.

[0052] Furthermore, when the main control device 40 detects that the load on at least one of the multiple deck motors 63 is high, it executes high load response control to operate the high load deck motor 63 in accordance with the high load response output map.

[0053] 4 shows the relationship between the output characteristics of the deck motor 63 in the high-load output map and the conventional output characteristics of the deck motor 63 when high-load control is not executed in this embodiment. The high-load output map is a map in which output characteristics are set for operating the deck motor 63 so as to prevent the deck motor 63 from suddenly stopping when a high load is applied to the deck motor 63, and is stored in advance in the storage unit of the main control device 40.

[0054] Here, the conventional output characteristics of the deck motor 63 when high-load response control is not executed are represented by line M1 in FIG. 4, which is made up of a thick solid line portion α2 and thick dashed line portions α1 and β1. Line M1 represents the upper limit torque value that can be output by the deck motor 63, which is set corresponding to the rotation speed of the deck motor 63. This output characteristic has upper limit torque constant regions α1 and α2 and an upper limit torque decrease region β1 connected to an inflection point P1 that corresponds to the upper limit rotation speed of the upper limit torque constant regions α1 and α2. In the upper limit torque constant regions α1 and α2, the upper limit torque value is constant regardless of the rotation speed of the deck motor 63. On the other hand, in the upper limit torque decrease region β2, the upper limit torque value decreases linearly as the rotation speed of the deck motor increases. In the output characteristics, the upper limit torque constant regions α1 and α2 are determined by the deck motor 63 and the maximum voltage that can be output to the deck motor 63 from the battery 34, which is the power source, via the deck inverter 88. Therefore, the rotation speed V1 at the inflection point P1, which is the upper limit rotation speed of the upper limit constant torque regions α1 and α2, is also determined by the deck motor 63 and the maximum voltage that can be output to the deck motor 63.

[0055] In this conventional output characteristic, the maximum rotation speed of the deck motor 63 can be set to be equal to or lower than the upper limit rotation speed V1 of the upper limit torque constant region α2, where the upper limit torque value is constant regardless of the rotation speed of the deck motor 63, and the setting can be such that the upper limit torque Tmax is always output from zero speed to the maximum rotation speed.

[0056] On the other hand, the output characteristics of the high-load output map used in this embodiment are represented by line M2, which is made up of thick solid lines α2 and β2 in FIG. 4 . Like line M1, this output characteristic is represented by the upper limit torque value of the deck motor 63, which is set corresponding to the rotation speed of the deck motor 63. The upper limit torque value in this output characteristic has an upper limit torque constant region α2, which is set on the low rotation speed side and where the upper limit torque is constant at Tmax, and an upper limit torque decrease region β2, which is set on the high rotation speed side. Line M2, which represents the output characteristics of this embodiment, switches between the upper limit torque constant region α2 and the upper limit torque decrease region β2 at an inflection point P2 in accordance with changes in the rotation speed of the deck motor 63. The meanings of the upper limit torque constant region α2 and the upper limit torque decrease region β2 are similar to those of the upper limit torque constant region α1 and the upper limit torque decrease region β1. In this embodiment, the boundary rotation speed at inflection point P2 is specified to be lower than the upper limit rotation speed V1 corresponding to inflection point P1 of the upper limit torque constant regions α1 and α2 in the conventional output characteristic. More specifically, the boundary rotation speed at the inflection point P2 is specified to be approximately equal to the minimum rotation speed Vmin of the deck motor 63 required for mowing work using the lawnmower blades 18a, 18b, 18c. Furthermore, in this embodiment, in the output characteristics of the high-load output map, the lower limit torque Tmin of the upper limit torque decrease region β2 may be set to be 65% to 75% of the torque value Tmax of the upper limit torque constant region α2, and more preferably, to be approximately 70% of the torque value Tmax.

[0057] 4 is used to operate each deck motor 63 according to the output characteristics of that map when a high load is applied to the deck motor 63. Specifically, the main control device 40 detects that the load on the deck motor 63 is high when the detected torque corresponding to the rotation speed of at least one deck motor 63 exceeds the upper limit torque corresponding to the rotation speed of the deck motor 63 in the high load output map.

[0058] 4, in this embodiment, consider a case where the working unit start switch 33 is turned on to cause the deck motor 63 to rotate at a preset rated rotation speed Vr, and the vehicle is traveling without entering a grassy area, for example, and no workload is applied to the deck motor 63. In this case, the deck motor 63 is driven at operating point PA1 with the minimum torque necessary to continue rotating the lawnmower blades 18a, 18b, 18c at the rated rotation speed Vr.

[0059] Next, when the amount of grass cut by the lawnmower blades 18a, 18b, 18c is the standard amount, the deck motor 63 moves along arrow a1 to operating point PA2 and operates at operating point PA2. In this case, the deck motor 63 performs mowing work by outputting a rated torque Tr determined by the rated rotation speed Vr. In this state, the amount of torque change until the upper limit torque value Tmax is reached is A2.

[0060] For example, if the mowing load increases due to an increase in the amount of grass cut by the lawnmower blades 18a, 18b, and 18c, the torque increases accordingly. This torque exceeds the torque value corresponding to the rotational speed in the upper torque reduction region β2 of the high-load output map characteristic M2, and a high load on the deck motor 63 is detected. At this time, the rotational speed of the deck motor 63 decreases along the line of the upper torque reduction region β2 of the high-load output map characteristic M2 in the direction of arrow a2. The operating point of the deck motor 63 moves to PA3 within the upper torque reduction region β2 until it corresponds to the increased mowing load. As a result, the deck motor 63 settles at a rotational speed V2 that is lower than the rated rotational speed Vr and a torque T2 that is higher than the rated torque Tr, and mowing operation continues. The torque change (Tmax - T2) until the upper torque limit Tmax is reached is A2a, but there is still some margin of error before the upper torque limit Tmax is reached.

[0061] On the other hand, unlike the embodiment, in the case of the conventional output characteristic M1 that does not use the output characteristic M2 of the high-load output map, when the deck motor 63 is at the rated rotation speed Vr, it is at the operating point PA4, and mowing operation is performed at a torque Tra that is even greater than the torque T2. At this time, the torque change amount (Tmax - Tra) until the upper limit torque value Tmax is reached is A1. From this state, if the mowing load increases and there is an increase in load equal to the increase in load between the operating points PA2 and PA3, the rotation speed drops to near V1, the torque increases to a value equivalent to the upper limit torque value Tmax, and the torque change amount until the upper limit torque value Tmax is reached is approximately zero. Therefore, if the mowing load increases any further, the deck motor 63 will stall and stop.

[0062] In this embodiment, because it takes a long time for the deck motor 63 to stall after its rotational speed drops from the rated rotational speed Vr, the operator can easily sense a change in the motor sound emitted from the lawnmower 18 and realize that a high load is acting on the deck motor 63. In other words, with conventional deck motor output map characteristics, the operator may not notice that the deck motor has suddenly stopped and continue working, leaving some grass uncut. In contrast, according to this embodiment, the rotational speed of the deck motor 63 acting under a high load drops, and although the appearance of the cut grass may deteriorate, mowing can continue. If the operator notices this and reduces the traveling speed to reduce the mowing load, that deck motor will return to the same set rotation speed as the other deck motors.

[0063] Furthermore, in this example, the boundary rotation speed of the inflection point P2 of the high-load output map M2 is set to approximately coincide with the minimum rotation speed Vmin of the deck motor 63 required for mowing work using the lawnmower blades 18a, 18b, and 18c. This allows the rotation speed of the deck motor 63 to be reduced to a lower speed when the deck motor 63 is under a high load. This makes it even easier for the driver of the vehicle to notice an increase in the load on the deck motor 63. This allows for more efficient mowing work.

[0064] Furthermore, if the lower limit torque Tmin of the upper limit torque decrease region β2 in the output characteristics of the high-load output map is set to be 65% to 75% of the torque value Tmax of the upper limit torque constant region α2, the relationship between the upper limit torque of the high-load output map and the rotational speed of the deck motor can be made closer to the relationship between engine torque and engine rotational speed when the mowing device is driven by power from a conventional engine. This makes it less likely that a driver who switches from a mowing vehicle that drives a mowing device by power from a conventional engine will feel uncomfortable when driving the mowing vehicle of this embodiment.

[0065] Furthermore, in this embodiment, when some of the multiple deck motors 63 are subjected to a high load, causing the torque of the deck motors 63 to increase and the rotational speed to decrease in accordance with the high load output map, the main control device 40 preferably controls the rotational speed of the remaining deck motors 63 that are not subjected to a high load to match the rotational speed of the deck motors 63 that are subjected to a high load.

[0066] As a result, in an embodiment, when some of the multiple deck motors 63, for example, one deck motor 63, are under high load, the rotation speeds of all deck motors 63 are reduced compared to when the rotation speed of only one deck motor 63 is reduced, making the cutting area uniform and improving its appearance.

[0067] Furthermore, in this embodiment, when the main control device 40 detects that the load on at least one of the multiple deck motors 63 is high and, in accordance with the high-load output map, causes an increase in the torque of the deck motor 63 and a decrease in the rotational speed of the deck motor 63, the main control device 40 decreases the rate at which the target rotational speed of the travel motors 30, 31 is increased in response to changes in the operating positions of the left and right operating levers 22, 23, in accordance with the rate at which the rotational speed of the deck motor 63 experiencing a high load is decreased. This makes it easier for the operator to quickly notice that a high load has occurred on the deck motor 63, as described below. This further reduces the likelihood of continuing mowing work with some grass remaining uncut, allowing for more efficient mowing work. Furthermore, by minimizing the deceleration of the travel speed, the deck motor 63 can be quickly released from a state in which a high load is applied, improving work efficiency.

[0068] Fig. 5 is a diagram showing an example of the relationship between the amount of forward operation of the left and right operating levers 22, 23 and the rotation speed of the traveling motors 30, 31 on the same side in the left-right direction as the operating levers 22, 23 in the embodiment. L1 in Fig. 5 is an operating lever motor speed relationship line that shows the relationship between the amount of forward operation of the operating levers 22, 23 and the rotation speed of the traveling motors 30, 31 when no high load is applied to the deck motor 63. On the other hand, L2 in Fig. 5 is an operating lever motor speed relationship line that is applied when a high load is detected on the deck motor 63 and the rotation speed of the deck motor 63 decreases in response to an increase in the torque of the deck motor 63.

[0069] In the example shown in Figure 5, when the rotation speed of the high-load deck motor 63 is reduced by K% in accordance with the high-load output map, the degree of increase in the target rotation speed of the travel motors 30, 31 in response to changes in the operating positions of the left and right operating levers 22, 23 is reduced by K% in accordance with the rate of reduction in the rotation speed of the high-load deck motor 63.

[0070] As a result, in this embodiment, when a high load occurs on some of the deck motors 63, the rotation speeds of all of the deck motors 63 decrease in response to the increase in load on the deck motor 63 with the high load, and the vehicle speed also decreases. This makes it easier for the driver to notice early on that a high load has occurred on the deck motor 63. This further reduces the likelihood of mowing work being continued when grass is left uncut, allowing for more efficient mowing work.

[0071] In this example, when a high load occurs on some of the deck motors 63, the rotation speeds of all of the deck motors 63 are reduced in accordance with the increase in load on the highly loaded deck motors 63, and the vehicle speed is also reduced. On the other hand, as another example of the embodiment, when a high load occurs on some of the deck motors 63, and the torque of the deck motors 63 increases and the rotation speed of the deck motors 63 decreases in accordance with the high load output map, it is also possible to configure the system to perform only one of the following: match the rotation speed of the remaining deck motors 63 that are not heavily loaded to the rotation speed of the highly loaded deck motor 63; and reduce the rate of increase in the target rotation speed of the traveling motors 30, 31 that corresponds to a change in the operating position of the left and right operating levers 22, 23 in accordance with the rate of decrease in the rotation speed of the highly loaded deck motor 63.

[0072] Furthermore, in the embodiment, when at least one deck motor 63 of the multiple deck motors 63 changes from a high load state to a state where none of the deck motors 63 are under high load, the main control device 40 returns the rotation speed of all deck motors 63 to the normal rotation speed, and also returns the rate of increase in the target rotation speed of the travel motors 30, 31 in response to changes in the operating positions of the operating levers 22, 23 to the normal rate. This configuration makes it easier for the driver to drive a vehicle in which the wheels and mowing equipment are driven by the engine, with an operating feel similar to when the mowing equipment is no longer under mowing load.

[0073] FIG. 6 is a flowchart showing an example of a method for controlling the deck motor 63 in an embodiment. The control process in FIG. 6 is executed by the main control device 40 acting as the main control device and controlling each of the deck inverter control devices 92a, 92b, and 92c. A program for executing the control process in FIG. 6 is stored in advance in the main control device 40. The main control device 40 may be a control device integrated with each of the deck inverter control devices 92a, 92b, and 92c. First, in step S10 in FIG. 6, the working unit start switch 33, which is a switch for the deck motor 63, is turned on, and lawn mowing work begins. This causes the main control device 40 to rotate each deck motor 63 at the rated rotation speed Vr (FIG. 4), which is the set rotation speed.

[0074] Next, in step S11, it is determined whether or not it has been detected that the torque of at least one deck motor 63 exceeds the line of the upper limit torque reduction region β2, which represents the upper limit torque corresponding to a set rotation speed such as the rated rotation speed Vr of the high-load output map, and that the load of at least one deck motor 63 is high. If the determination result in step S11 is affirmative (YES), in step S12, the main control device 40 reduces the rotation speed of the deck motor 63 that is experiencing a high load so that the operating point of the deck motor 63 experiencing a high load is located on the upper limit line of the high-load output map, and controls the rotation speed of the deck motor 63 experiencing a high load so that the torque increases in response to an increase in the mowing load on the upper limit line and the rotation speed of the deck motor 63 experiencing a high load decreases. For example, if it has been detected that the deck motor 63 is operating at operating point c1 in FIG. 4, the main control device 40 reduces the rotation speed of the deck motor 63 to move it to operating point c2, and then moves the operating point in the direction of arrow a2 along the line of the upper limit torque reduction region β2 so that a torque corresponding to the increase in the mowing load is obtained, thereby reducing the rotation speed of the deck motor 63.

[0075] Next, in step S13, the main control device 40 reduces the rotation speed of the deck motor 63 that is not heavily loaded to the same rotation speed as the deck motor 63 that is heavily loaded. After step S13, the process proceeds to step S14. In step S14, the main control device 40 reduces the rotation speed of the travel motors 30, 31 in accordance with the rate of change in the rotation speed of the deck motor 63. Specifically, the main control device 40 reduces the rate of increase in the target rotation speed of the travel motors 30, 31 in response to a change in the operating position of the control levers 22, 23 in accordance with the rate of decrease in the rotation speed of the heavily loaded deck motor 63. For example, if the rotation speed of the heavily loaded deck motor 63 decreases by 20% from the rated rotation speed Vr, the main control device 40 controls the rotation speed of the travel motors 30, 31 to be reduced by 20% when the operating levers 22, 23 are in the same operating position.

[0076] Next, in step S15, main controller 40 determines whether or not working unit start switch 33, which is the switch for deck motor 63, has been turned off. If the determination result in S15 is affirmative (YES), all deck motors 63 are stopped in step S19, and the process ends.

[0077] On the other hand, if the determination result in step S15 is negative (NO), then in step S16, the main control device 40 determines whether the torque of at least one deck motor 63 has exceeded the upper limit torque Tmax ( FIG. 4 ) of the high-load output map. If the determination result in S16 is positive (YES), an overload has occurred in at least one deck motor 63, causing it to stall and stop. Therefore, an emergency stop is issued to all deck motors 63, including the other deck motors 63, stopping all deck motors 63 and terminating the process. In this way, by stopping all deck motors 63 when an overload has occurred in at least one deck motor 63, the operator is more likely to notice the occurrence of an overload in a deck motor 63 early due to a change in the sound of the lawnmower 18. This prevents the lawnmower 18 from continuing to travel with grass remaining uncut, allowing for more efficient mowing work.

[0078] On the other hand, if the determination result in S16 is negative (NO), the process returns to step S11 and the process is repeated. If the determination result in step S11 is negative, a high load has not been detected in any of the deck motors 63, so in step S17, each deck motor 63 is set to the rated rotation speed (for example, 3000 min -1 ) is rotated.

[0079] Next, in step S18, as in step S15, main control device 40 determines whether working unit activation switch 33 has been turned off. If the determination result in S18 is affirmative (YES), the process proceeds to step S19. On the other hand, if the determination result in S18 is negative (NO), the process returns to step S11, and the process is repeated.

[0080] According to the vehicle 10 of the above embodiment, even when a high load is applied to the deck motor 63, sudden stops are unlikely to occur, so grass can be efficiently mowed while reducing the amount of grass left uncut.

[0081] FIG. 7 is a diagram corresponding to FIG. 3A of a brush mowing vehicle according to another embodiment. Unlike the configuration shown in FIG. 3B, the configuration of this example differs in that some control processing is performed between multiple deck inverter controllers 94a, 94b, and 94c without the main controller 40. Therefore, each of the multiple deck inverter controllers 94a, 94b, and 94c is connected to the remaining two deck inverter controllers 94a, 94b, and 94c via signal lines to enable signal input and output. A high-load output map is pre-stored in the memory of each deck inverter controller 94a, 94b, and 94c, and the detected torque and rotation speed of the corresponding deck motor 63 are input to the memory. Each deck inverter controller 94a, 94b, and 94c detects that the load on the deck motor 63 is high when the detected torque corresponding to the rotation speed of the corresponding deck motor 63 exceeds the upper limit torque corresponding to the rotation speed of the deck motor 63 in the high-load output map. When a high load on the deck motor 63 is detected, the corresponding deck inverter controller 94a, 94b, 94c executes high-load response control in accordance with the high-load response output map to operate the high-load deck motor 63. In this example, the multiple deck inverter controllers 94a, 94b, 94c correspond to the controllers that primarily execute the high-load response control.

[0082] Figure 8 is a flowchart showing an example of a method for controlling the deck motor 63 in another example of the embodiment. A program for executing the control process of Figure 8 is stored in advance in the memory of each deck inverter control device 94a, 94b, 94c. First, in step S30 of Figure 8, the working unit start switch 33, which is a switch for the deck motor 63, is turned on to start mowing work and drive each deck motor 63 to rotate at the rated rotation speed Vr. At this time, the on signal of the working unit start switch 33 may be input to the deck inverter control device via the main control device 40.

[0083] Next, in step S31, each deck inverter control device 94a, 94b, 94c determines whether the detected torque of the corresponding deck motor 63 exceeds the line of the upper limit torque reduction region β2, which represents the upper limit torque corresponding to the set rotation speed of the high-load output map, and whether the load of at least one deck motor 63 is high. If the determination result in step S31 is affirmative (YES), in step S32, the deck inverter control device 94a, 94b, 94c reduces the rotation speed so that the operating point of the deck motor 63 with a high load is located on the upper limit line of the high-load output map, and increases the torque on the upper limit line in response to an increase in the mowing load, while also reducing the rotation speed of the deck motor 63 with a high load.

[0084] Next, in step S33, the deck inverter control devices 94a, 94b, 94c output commands to the other deck inverter control devices 94a, 94b, 94c to reduce the rotation speed of the deck motor 63 corresponding to the other deck inverter control device to the same rotation speed as the highly loaded deck motor 63. In response to this, as will be described later, the other deck inverter control devices 94a, 94b, 94c reduce the rotation speed of the corresponding deck motor 63 to the rotation speed indicated by the command.

[0085] Next, in step S34, the deck inverter control devices 94a, 94b, 94c output a command to the main control device 40 to reduce the rotation speeds of the traveling motors 30, 31 in accordance with the rate of change in the rotation speed of the deck motor 63. Specifically, the deck inverter control devices 94a, 94b, 94c output a command to reduce the rate of increase in the target rotation speeds of the traveling motors 30, 31, which is responsive to changes in the operating positions of the control levers 22, 23, in accordance with the rate of decrease in the rotation speed of the highly loaded deck motor 63. In response to this, the main control device 40 reduces the rotation speeds of the traveling motors 30, 31 to the rotation speed indicated by the command.

[0086] Next, in step S35, the deck inverter control devices 94a, 94b, 94c determine whether or not the working unit start switch 33, which is the switch for the deck motor 63, has been turned off. If the determination result in S35 is affirmative (YES), the corresponding deck motor 63 is stopped in step S41, and the process ends.

[0087] On the other hand, if the determination result in step S35 is negative (NO), in step S36, the deck inverter control devices 94a, 94b, 94c determine whether the detected torque of the corresponding deck motor 63 has exceeded the upper limit torque Tmax of the high-load output map. If the determination result in S36 is positive (YES), an excessive load has occurred in at least one deck motor 63, causing it to stop in a stalled state. Therefore, a command to stop the corresponding deck motor 63 is issued to the other deck inverter control devices 94a, 94b, 94c so as to bring all deck motors 63 to an emergency stop, and the process ends.

[0088] On the other hand, if the determination result in S36 is negative (NO), the process returns to step S31 and the process is repeated. Also, if the determination result in step S31 is negative, it is determined in step S37 whether or not a command to reduce the rotation speed of the deck motor 63 has been input from the other deck inverter control devices 94a, 94b, 94c.

[0089] If the judgment result of S37 is positive (YES), in step S38, the deck inverter control devices 94a, 94b, 94c perform processing to reduce the rotational speed of the corresponding deck motor 63 to the rotational speed indicated by the command, i.e., the same rotational speed as the rotational speed of the high-load deck motor 63.

[0090] On the other hand, if the determination result in S37 is negative (NO), in step S39, the deck inverter controllers 94a, 94b, 94c drive the corresponding deck motors 63 to rotate at the rated rotation speed.

[0091] After the processing of S38 and S39 is completed, in step S40, it is determined whether the working unit start switch 33 has been turned off, and if the determination result of S40 is positive (YES), the corresponding deck motor 63 is stopped in step S41, and the processing ends.

[0092] On the other hand, if the determination result in step S40 is negative (NO), the process returns to step S11 and the process is repeated.

[0093] Figure 9 is a diagram showing part of the processing of the multiple deck inverter control devices 94a, 94b, and 94c when the control processing of Figure 8 is executed by the multiple deck inverter control devices 94a, 94b, and 94c. Figure 9 shows a case where the deck motor 63 is divided into deck motors A, B, and C, and a high load is applied to deck motor A. The deck inverter control devices 94a, 94b, and 94c will be explained by dividing them into deck inverter control device CA that controls deck motor A, and deck inverter control devices CB and CC that control deck motors B and C, respectively. Note that when two deck motors 63 are simultaneously under high load, for example, deck motors A and B will be on the side generating the high load, and deck motor C will be on the side not receiving the high load.

[0094] According to the execution of the control method of this example, when it is detected that the load on the deck motor A is high, as shown in SA1 of Figure 9, the deck inverter control device AC reduces the rotational speed so that the operating point of the deck motor A is positioned on the upper limit line of the high load corresponding output map, and on the upper limit line, increases the torque in response to the increase in the cutting load, while controlling the rotational speed of the highly loaded deck motor 63 to be reduced.

[0095] Next, the deck inverter control device AC outputs a command to the deck inverter control devices BC and CC to reduce the rotation speed of the other deck motors B and C so that the rotation speed becomes the same as that of the deck motor A.

[0096] On the other hand, the deck inverter control devices BC and CC on the deck motors B and C that are not under high load control the deck motors B and C to rotate at the rated rotation speed, which is the set rotation speed, until they receive a command from another deck inverter control device. On the other hand, when the deck inverter control devices BC and CC receive a command from the deck inverter control device CA to reduce the rotation speed of the deck motors B and C, they control the rotation speed of the deck motors B and C to change it to the rotation speed indicated by the command. In this example, the other configurations and operations are the same as those in Figures 1 to 6.

[0097] In the above embodiment, the upper limit torque reduction region in the high load output map is described as a region in which the upper limit torque value decreases linearly as the rotation speed increases, but the upper limit torque reduction region may also be configured as a region in which the upper limit torque value decreases in a curved manner as the rotation speed increases.

[0098] In addition, in the above embodiment, the lawn mower 18 is described as having three deck motors 63 and three lawn mower blades 18a, 18b, 18c driven by the three deck motors 63, but the number of mowing motors and mowing blades may be two or four or more.

[0099] In the above embodiment, the left and right wheels are independently driven, with the left wheel driven by the left electric motor and the right wheel driven by the right electric motor. However, the present invention can also be applied to a vehicle in which both wheels are driven by a common electric motor.

[0100] The present disclosure is further illustrated by the following embodiments. Configuration 1: A grass cutting vehicle equipped with a grass cutting device and a control device, The mowing device is The mowing apparatus includes a plurality of mowing motors, which are electric motors for mowing grass, and a mowing blade driven by the plurality of mowing motors, The control device when it is detected that the load of at least one of the plurality of mowing motors is high, high load response control is executed to operate the mowing motor with a high load in accordance with a high load response output map, which is an output map that defines the relationship between the upper limit torque value that can be output by the mowing motor and the rotation speed of the mowing motor; the high load response output map is defined so that the boundary rotation speed at which the region switches from a constant upper limit torque region, in which the upper limit torque value is constant regardless of the rotation speed of the mowing motor, to a decreasing upper limit torque region, in which the upper limit torque value decreases as the rotation speed of the mowing motor increases, is lower than the upper limit rotation speed of the constant upper limit torque region in the output characteristics of the mowing motor, which is determined from the mowing motor and the maximum voltage that can be output to the mowing motor, when the high load response control is not executed. Mowing vehicle. Configuration 2: the boundary rotation speed is set so as to substantially coincide with the minimum rotation speed of the mowing motor required for mowing work using the mowing blade; 2. The grass-cutting vehicle according to claim 1. Configuration 3: The lower limit torque of the upper limit torque decrease region is 65% or more and 75% or less of the torque value of the upper limit torque constant region. 3. The grass cutting vehicle according to claim 1 or 2. Configuration 4: the control device detects that the mowing motor is under high load when the detected torque corresponding to the rotational speed of the at least one mowing motor exceeds an upper limit torque corresponding to the rotational speed of the mowing motor in the high load output map. 4. The grass cutting vehicle according to any one of configurations 1 to 3. Configuration 5: when some of the plurality of mowing motors are subjected to a high load, causing an increase in the torque of the mowing motor and a decrease in the rotational speed of the mowing motor in accordance with the high-load output map, the control device matches the rotational speed of the remaining mowing motors that are not subjected to a high load to the rotational speed of the mowing motor that is under a high load. 5. The grass cutting vehicle according to any one of configurations 1 to 4. Configuration 6: a traction motor that drives the wheels; an operating tool for indicating a target rotation speed of the traveling motor depending on an operating position thereof, the control device controls the drive of the travel motor in accordance with the target rotation speed, and when it is detected that at least one of the plurality of mowing motors is under a high load and an increase in the torque of the mowing motor and a decrease in the rotation speed of the mowing motor occur in accordance with the high load output map, the control device reduces the rate at which the target rotation speed of the travel motor is increased in accordance with the change in the operating position in accordance with the rate at which the rotation speed of the mowing motor under a high load is decreased. 6. The grass cutting vehicle according to any one of configurations 1 to 5. Configuration 7: when at least one of the plurality of mowing motors changes from a high-load state to a state in which none of the mowing motors is under high load, the control device returns the rotational speeds of all of the mowing motors to their normal rotational speeds, and returns the rate of increase in the target rotational speed of the traveling motor, which is responsive to the change in the operating position of the operating tool, to its normal rate. 7. The grass-cutting vehicle according to claim 6. [Explanation of symbols]

[0101] 10 grass mowing vehicle (vehicle), 12 left wheel, 13 right wheel, 15, 16 caster wheels, 18 lawn mowing device, 18a to 18c lawn mower blade, 18d exhaust duct, 19 mower deck, 20 main frame, 20a, 20b side plate portion, 20c connecting portion, 21 driver's seat, 22, 23 operation lever, 24 grip portion, 26, 27 guide panel, 30 left travel motor, 31 right travel motor, 32 operation portion, 33 work unit start switch, 34 battery, 35 start switch, 40 control device, 50, 51 lever sensor, 52 deck motor speed sensor, 54 left motor speed sensor, 55 right motor speed sensor, 63a, 63b, 63c deck motor, 80 control system, 80a, 80b gear mechanism, 84 left travel inverter, 86 Right driving inverter, 88a, 88b, 88c deck inverter, 90 current detection unit, 91 torque calculation unit, 92a, 92b, 92c, 94a, 94b, 94c deck inverter control device, 93a, 93b, 93c deck inverter circuit, 120, 121 axles.

Claims

1. A grass cutting vehicle equipped with a grass cutting device and a control device, The mowing device is The mowing apparatus includes a plurality of mowing motors, which are electric motors for mowing grass, and a mowing blade driven by the plurality of mowing motors, The control device when it is detected that the load on at least one of the plurality of mowing motors is high, high load response control is executed to operate the mowing motor under high load in accordance with a high load response output map which is an output map that defines the relationship between the upper limit torque value that can be output by the mowing motor and the rotation speed of the mowing motor; the high load response output map is defined so that the boundary rotation speed at which the region switches from a constant upper limit torque region, in which the upper limit torque value is constant regardless of the rotation speed of the mowing motor, to a decreasing upper limit torque region, in which the upper limit torque value decreases as the rotation speed of the mowing motor increases, is lower than the upper limit rotation speed of the constant upper limit torque region in the output characteristics of the mowing motor, which is determined from the mowing motor and the maximum voltage that can be output to the mowing motor, when the high load response control is not executed. Mowing vehicle.

2. the boundary rotation speed is set so as to substantially coincide with the minimum rotation speed of the mowing motor required for mowing work using the mowing blade; The mowing vehicle according to claim 1 .

3. a lower limit torque in the upper limit torque decreasing region is 65% or more and 75% or less of the torque value in the upper limit torque constant region; The grass-mowing vehicle according to claim 1 or 2.

4. the control device detects that the load on the mowing motor is high when the detected torque corresponding to the rotation speed of the at least one mowing motor exceeds an upper limit torque corresponding to the rotation speed of the mowing motor in the high load output map. The mowing vehicle according to claim 1 .

5. when some of the plurality of mowing motors are subjected to a high load, causing an increase in the torque of the mowing motor and a decrease in the rotational speed of the mowing motor in accordance with the high load output map, the control device matches the rotational speed of the remaining mowing motors that are not subjected to a high load to the rotational speed of the mowing motor that is subjected to a high load. The mowing vehicle according to claim 1 .

6. a traction motor that drives the wheels; an operating tool for indicating a target rotation speed of the traveling motor depending on an operating position thereof, the control device controls the drive of the travel motor in accordance with the target rotational speed, and when it is detected that the load on at least one of the plurality of mowing motors is high and an increase in the torque of the mowing motor and a decrease in the rotational speed of the mowing motor occur in accordance with the high-load output map, the control device reduces the rate at which the target rotational speed of the travel motor increases in accordance with the change in the operating position in accordance with the rate at which the rotational speed of the mowing motor under high load decreases. The mowing vehicle according to claim 1 .

7. when at least one of the plurality of mowing motors changes from a high-load state to a state in which none of the mowing motors is under high load, the control device returns the rotational speeds of all of the mowing motors to normal rotational speeds, and returns the rate of increase in the target rotational speed of the traveling motor, which is responsive to the change in the operating position of the operating tool, to normal.

7. The grass cutting vehicle according to claim 6.

Images