Working machine

Abstract

To provide a working machine capable of appropriate vehicle speed control even when the working condition momentarily changes.SOLUTION: A working machine includes: a drive wheel unit rotated by electric motors 41, 42 for traveling; a working device rotated by an electric motor 43 for working; a vehicle speed setting tool for setting a desired vehicle speed; a rotation speed detection unit 55 for detecting the rotation speed of the working device; a rotation speed change behavior calculation unit 58 for calculating the change behavior of the rotation speed over time; a vehicle speed control unit 59 for generating a vehicle speed control signal on the basis of the desired vehicle speed and the change behavior; and a traveling motor control unit 52 for driving the electric motors 41, 42 for traveling on the basis of the vehicle speed control signal.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a work machine that performs work while traveling, and that is equipped with a drive wheel unit that is rotated by an electric motor for traveling, and a work device that is rotated by an electric motor for work. [Background technology]

[0002] Patent Document 1 describes a work machine as described above, in which the number of revolutions of the blade (a type of working speed) is controlled to increase or decrease in response to an increase or decrease in the ground speed of the blade relative to the ground.

[0003] Furthermore, Patent Document 2 describes a grass cutter that cuts grass by rotating the cutting blade while traveling. With this grass cutter, when the cutting blade rotation speed (a type of working speed) decreases due to an increase in the rotation load of the cutting blade while cutting grass at the maximum speed that can be changed, the maximum speed is changed to reduce the vehicle speed and the rotation load of the cutting blade in order to avoid inconvenience caused by the decrease in the cutting blade rotation speed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-136305 A [Patent Document 2] JP 2018-196354 A Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Documents 1 and 2, when the working speed decreases, vehicle speed control is performed to reduce the vehicle speed. However, the working condition of the working machine may change instantaneously, and if the vehicle speed is changed every time a change in the working speed is detected, good work results may not be obtained. In addition, frequent changes in vehicle speed cause discomfort to the driver.

[0006] In view of the above circumstances, there is a demand for a work machine that is capable of appropriate vehicle speed control even when the work conditions change momentarily. [Means for solving the problem]

[0007] The working machine according to the present invention, which performs work while traveling, comprises a drive wheel unit rotated by a traveling electric motor, a working device rotated by a working electric motor, a vehicle speed setting device for setting a desired vehicle speed, a rotation speed detection unit for detecting the rotation speed of the working device, a rotation speed change behavior calculation unit for calculating the change behavior of the rotation speed over time, a vehicle speed control unit for generating a vehicle speed control signal based on the desired vehicle speed and the change behavior, and a traveling motor control unit for driving the traveling electric motor based on the vehicle speed control signal.

[0008] According to this configuration, when a load is applied to the work electric motor and the work speed of the work implement decreases, the rotation speed change behavior calculation unit calculates the change behavior over time of the detected rotation speed of the work implement. The vehicle speed control unit generates a vehicle speed control signal based on the desired vehicle speed set by the vehicle speed setting device and the change behavior calculated by the rotation speed change behavior calculation unit. Since the change behavior over time of the rotation speed of the work implement is taken into consideration in generating this vehicle speed control signal, appropriate vehicle speed control is possible even when the work condition changes instantaneously. Here, appropriate vehicle speed control does not mean vehicle speed acceleration / deceleration control that is simply proportional to the increase or decrease in the rotational speed of the work implement, but vehicle speed acceleration / deceleration control that is synchronized with the change over time in the rotational speed of the work implement.

[0009] The present invention also proposes that an actual vehicle speed calculation unit is provided for calculating an actual vehicle speed, and the vehicle speed control unit generates the vehicle speed control signal based on the desired vehicle speed, the change behavior, and the actual vehicle speed. In this configuration, when generating a vehicle speed control signal for changing the current vehicle speed, the actual vehicle speed, which is the actual vehicle speed at that time, is taken into consideration along with the desired vehicle speed and the change behavior, making it possible to perform appropriate vehicle speed control.

[0010] In the present invention, it is also proposed that the rotation speed change behavior calculation unit distinguishes between an abrupt change behavior that shows a high rate of change in the rotation speed and a slow change behavior that shows a rate of change lower than the rate of change of the abrupt change behavior, and the vehicle speed control unit generates the vehicle speed control signal that brings about different vehicle speed changes for the abrupt change behavior and the slow change behavior. In this configuration, when an abrupt change behavior that shows a high rate of change in the rotation speed of the working device occurs and when a slow change behavior that shows a low rate of change in the rotation speed of the working device occurs and the like occurs, a vehicle speed change control is performed according to each change behavior. At that time, the vehicle speed change control when the abrupt change behavior occurs and the vehicle speed change control when the slow change behavior occurs may be performed in different vehicle speed control forms that show independent vehicle speed change rates. For example, in the vehicle speed change control for the abrupt change behavior, in order to quickly recover from a sudden drop in the rotation speed of the working device due to a sudden increase in the work load, a vehicle speed change (deceleration) is performed according to the rate of change over time of the abrupt change behavior. As a result, the work load is reduced and the rotation speed of the working device returns to the original rotation speed.

[0011] The vehicle speed change control when a sudden change occurs and the vehicle speed change control when a slow change occurs may be performed in the same vehicle speed control form. For example, in both the sudden change behavior and the slow change behavior of the rotation speed of the working tool, the vehicle speed control that changes the vehicle speed slowly is performed according to the rotation speed change behavior, thereby suppressing the sudden change in vehicle speed that makes the driver uncomfortable.

[0012] The distinction between the rapid change behavior and the gradual change behavior regarding the rotation speed of the working device can be made in various forms as follows. (1) Distinguish between rapid change behavior and slow change behavior based on the rate of change of rotation speed over a given period of time. (2) The rapid change behavior and the slow change behavior are distinguished based on the integrated value of the rate of change of the rotation speed for each unit time, which is calculated over time. (3) When the rotation speed detection signal is treated as a waveform signal and frequency analyzed over a specified time range, a sudden decrease (increase) in the rotation speed causes the frequency spectrum to shift significantly to the lower frequency side (wider frequency side), whereas a slow decrease (increase) in the rotation speed causes the distribution of the frequency components to shift slightly to the lower frequency side (wider frequency side). The amount of this shift and the shape of the frequency spectrum curve are used to distinguish between sudden and slow change behaviors. In terms of electronic control, generating a vehicle speed control signal using the frequency spectrum curve as an input parameter for vehicle speed change control is also one method of vehicle speed change control in response to sudden and slow change behaviors.

[0013] When the work machine is traveling unmanned, it is not necessary to take into consideration vehicle speed fluctuations that cause discomfort to the driver (an example of inappropriate vehicle speed fluctuations).For this reason, the present invention is provided with an unmanned automatic driving mode in which the work machine is traveled for work without a driver, and the rotation speed change behavior calculation unit calculates an abrupt change behavior that exhibits a high rate of change in the rotation speed and a slow change behavior that exhibits a rate of change that is lower than the rate of change of the abrupt change behavior, and when the unmanned automatic driving mode is being executed, the vehicle speed control unit generates the vehicle speed control signal that brings about an abrupt vehicle speed change corresponding to the abrupt change behavior, and generates the vehicle speed control signal that brings about a slow vehicle speed change corresponding to the slow change behavior.

[0014] When a driver or passenger is on board the work machine, it is proposed that the acceleration control of the machine (vehicle speed increase control) and the deceleration control of the machine (vehicle speed decrease control) are separate control forms. For example, it is preferable that the vehicle speed increase is performed slowly so as not to cause discomfort to the passenger. However, since the vehicle speed decrease may be performed for emergency evacuation, it is preferable that the vehicle speed decrease is performed suddenly. For this reason, in an embodiment of the present invention, it is proposed that the vehicle speed control unit divides the vehicle speed control relationship, which indicates the relationship between the desired vehicle speed and the changing behavior, which are input parameters, and the vehicle speed control signal, which is an output parameter, into an acceleration relationship used during acceleration and a deceleration relationship used during deceleration. As a specific embodiment, it is preferable that the acceleration relationship and the deceleration relationship are independently adjustable.

[0015] The above-mentioned control of the vehicle speed change following the rotation change of the working device is preferably applied to a grass cutting device equipped with a rotary blade. This is because a grass cutting device equipped with a rotary blade is prone to an increase in the load on the working electric motor due to entanglement of cut grass. Therefore, in a preferred embodiment of the present invention, the working device is a grass cutting device having a rotary blade. [Brief description of the drawings]

[0016] [Figure 1] 1 is an overall side view of an electric grass cutter, which is an example of an electric work vehicle. [Diagram 2] FIG. 2 is an overall plan view of the electric grass cutter. [Diagram 3] FIG. 2 is a schematic diagram showing a power system and a control system of the electric grass cutter. [Figure 4] FIG. 2 is a functional block diagram showing a control function section of a control unit. [Diagram 5] FIG. 4 is a schematic diagram showing the flow of a control system for controlling a vehicle speed and a working rotation speed. [Figure 6] FIG. 2 is a schematic diagram of a hardware-based electronic circuit as a specific example of a vehicle speed control unit. [Figure 7] 4 is a schematic flowchart of vehicle speed control. [Figure 8] FIG. 11 is a functional block diagram showing another embodiment of vehicle speed control that depends on the work rotation speed. [Figure 9] 5 is a time chart showing vehicle speed control when the mower rotation speed is reduced while the vehicle is being driven. [Figure 10] FIG. 4 is a schematic diagram illustrating map control used in vehicle speed control. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] In this specification, unless otherwise specified, "front" means forward in the longitudinal direction (driving direction) of the vehicle body, and "rear" means rearward in the longitudinal direction (driving direction) of the vehicle body. Furthermore, left-right or lateral means the transverse direction (vehicle width direction) of the vehicle body that is perpendicular to the longitudinal direction of the vehicle body. "Up" or "down" refers to the positional relationship in the vertical direction of the vehicle body, and indicates the relationship in terms of height above ground. In the figures, "front" is indicated by "F", "rear" by "B", "left" by "L", "right" by "R", "up" by "U" and "down" by "D".

[0018] Next, one embodiment of an electric working vehicle according to the present invention will be described. Here, the electric working vehicle is an electric grass cutter. As shown in Fig. 1 and Fig. 2, this electric grass cutter is equipped with a pair of left and right front wheels 11 supported at the front of the vehicle body 1, a pair of left and right rear wheels 12 as a drive wheel unit supported at the rear of the vehicle body 1, and a grass cutter 3 as a working device supported between the front wheels 11 and the rear wheels 12 under the vehicle body 1. A battery storage section 60 for storing a battery 6 is provided between the left and right rear wheels 12. Furthermore, the vehicle body 1 is provided with a driver's seat 13, a rope frame 14, etc.

[0019] The vehicle body 1 includes a frame 10 consisting of right and left longitudinal beams extending in the front-rear direction and a cross beam connecting the longitudinal beams. The lower end of a ROPS frame 14 is connected to the frame 10.

[0020] The front wheels 11 are caster type wheels, and the rear wheels 12 are drive wheels. A left running motor 41 and a right running motor 42 are disposed inside each rear wheel 12 as electric motors for running (running motors). The power of the left running motor 41 and the right running motor 42 is transmitted to the rear wheels 12 via a reduction gear mechanism 16. Each rear wheel 12 is driven independently.

[0021] An instrument panel 7 is disposed to the right of the driver's seat 13. Shift levers 17 are disposed on both sides of the driver's seat 13 as vehicle speed setting devices for setting a desired vehicle speed. When the right shift lever 17 is operated to the neutral position, the right traveling motor 42 is stopped. When the right shift lever 17 is operated to the forward side, the right traveling motor 42 rotates forward, and when the right shift lever 17 is operated to the reverse side, the right traveling motor 42 rotates reverse. Similarly, when the left speed change lever 17 is operated to the neutral position, forward side, or reverse side, the left traveling motor 41 operates in the same manner as the above-mentioned right traveling motor 42. In other words, by operating the right and left speed change levers 17, the right and left rear wheels 12 are driven forward or reverse independently of each other, and the vehicle body 1 moves forward or reverse and turns right or left.

[0022] As shown in Fig. 1, the grass cutting device 3, which is an example of a working device, includes a mower deck 30 and a cutting blade 31 supported rotatably about a vertical axis inside the mower deck 30. The cutting blade 31 is a rotary blade, and is rotated by a mower motor 43, which is an electric motor for working. The mower deck 30 is suspended from the frame 10 by a link mechanism 34 so as to be freely raised and lowered.

[0023] The power system and control system of the electric grass cutter are shown in Fig. 3. The mower motor 43 is provided on the rear wall of the mower deck 30. The mower motor 43 rotates the rotating shaft 32 to which the cutting blade 31 is attached via a belt transmission mechanism 33. A left traveling motor 41 is provided as an electric motor for traveling in order to rotate the left rear wheel 12, and a right traveling motor 42 is provided as an electric motor for traveling in order to rotate the right rear wheel 12.

[0024] The left traveling motor 41, the right traveling motor 42, and the mower motor 43 are supplied with power from an inverter 4. The inverter 4 includes a traveling motor inverter 4A that supplies power to the left traveling motor 41 and the right traveling motor 42, and a mower motor inverter 4B that supplies power to the mower motor 43. The inverter 4 is driven and controlled based on a control signal from a control unit 5. The inverter 4 is connected to a battery 6 as a power source.

[0025] As shown in FIG. 4, the control unit 5 includes, as control function sections, an input / output processing section 51, a driving motor control section 52, a mower motor control section 53, an equipment control section 54, a rotation speed detection section 55, an actual vehicle speed calculation section 56, and a vehicle speed control unit 57.

[0026] The input / output processing unit 51 is connected to a detection device group 9A, an installed device group 9B, an inverter 4, and the like.

[0027] 3, the detection device group 9A includes sensors (such as potentiometers) such as a left running motor sensor 91 that detects the rotation speed of the left running motor 41, a right running motor sensor 92 that detects the rotation speed of the right running motor 42, a mower motor sensor 93 that detects the rotation speed of the mower motor 43, a left shift sensor 94 that detects the amount of operation of the left shift lever 17, and a right shift sensor 95 that detects the amount of operation of the right shift lever 17. The equipment device group 9B includes the instrument panel 7, lights, a buzzer, etc.

[0028] As sensor signals related to vehicle speed control, the rotation speed of the cutting blade 31 (the rotation speed of the mower motor 43), the operation amount of the left shift lever 17, and the operation amount of the right shift lever 17 are sent from the detection device group 9A to the control unit 5.

[0029] The traveling motor control unit 52 generates a motor control signal based on a vehicle speed control signal from a vehicle speed control unit 57, and drives the inverter 4 to independently control the driving of the left traveling motor 41 and the right traveling motor 42.

[0030] The mower motor control unit 53, which serves as a work motor control unit, generates a motor control signal based on a preset default work rotation speed, and drives the inverter 4 to drive and control the mower motor 43. If a work rotation speed setting device for arbitrarily setting the work rotation speed is provided, it is also possible to drive and control the mower motor 43 based on the work rotation speed set by the work rotation speed setting device.

[0031] The equipment control unit 54 is capable of managing the operation of the equipment group 9B, as well as converting various pieces of information to be notified to the driver into notification signals and driving notification devices such as buzzers and speakers.

[0032] The rotation speed detection unit 55 detects the rotation speed of the mower motor 43 corresponding to the rotation speed of the cutting blade 31 as the working speed based on a rotation speed sensor signal from a mower motor sensor 93 that detects the rotation speed of the mower motor 43 .

[0033] The actual vehicle speed calculation unit 56 calculates the running speed of the vehicle body 1, i.e., the actual vehicle speed, based on sensor signals indicating the rotational speed of the left running motor 41 detected by the left running motor sensor 91 and the rotational speed of the right running motor 42 detected by the right running motor sensor 92, both of which are included in the detection device group 9A.

[0034] The vehicle speed control unit 57 does not simply control the drive of the left traveling motor 41 and the right traveling motor 42 based on the amount of operation of the left shift lever 17 and the amount of operation of the right shift lever 17, but takes into consideration the change in the rotation speed of the mower motor 43 (the rotation speed of the working device) over time. For this reason, the vehicle speed control unit 57 includes a rotation speed change behavior calculation unit 58 and a vehicle speed control unit 59, as shown in FIG.

[0035] The rotation speed change behavior calculation unit 58 receives the actual rotation speed (working rotation speed) of the cutting blade 31 detected by the rotation speed detection unit 55 and the set rotation speed set as the control target rotation speed. The rotation speed change behavior calculation unit 58 has a function of calculating the change behavior of the rotation speed (actual rotation speed) over time, and therefore provides the vehicle speed control unit 59 with a deviation between the set rotation speed and the time-dependent rotation speed (change behavior) derived from the change behavior of the rotation speed over time as a parameter for changing the vehicle speed. Furthermore, the rotation speed change behavior calculation unit 58 calculates (distinguishes) a sudden change behavior indicating a sudden change in the rotation speed and a slow change behavior indicating a slow change in the rotation speed, and provides the vehicle speed control unit 59 with a change behavior state signal indicating whether the current change behavior is a sudden change behavior or a slow change behavior. This change behavior state signal also includes information indicating whether the vehicle is in an accelerating state (positive change rate behavior) or a decelerating state (negative change rate behavior).

[0036] The vehicle speed control unit 59 generates a vehicle speed control signal (output parameter) to be given to the travel motor control unit 52 based on the left operation amount and the right operation amount, the desired vehicle speed (input parameter) determined by the left operation amount and the right operation amount, and the change behavior (input parameter) calculated by the rotation speed change behavior calculation unit 58. In this embodiment, the actual vehicle speed calculated by the actual vehicle speed calculation unit 56 is given to the vehicle speed control unit 59, and the vehicle speed control unit 59 generates a vehicle speed control signal having a vehicle speed change rate calculated based on the desired vehicle speed, the change behavior, and the actual vehicle speed. By adding the actual vehicle speed as a vehicle speed change parameter, it becomes possible to generate a vehicle speed control signal that takes into account the degree of acceleration / deceleration of the vehicle speed change (vehicle speed change rate) realized by the generated vehicle speed control signal.

[0037] When the rotation speed of the cutting blade 31 decreases when the cutting blade 31 enters a dense grass field, for example, the vehicle speed control unit 57 can operate in various vehicle speed change control modes as shown below in order to restore the decrease in rotation speed. Only one of these vehicle speed change control modes (a), (b), (c), (d), (e), and (f) may be adopted, or a plurality of them may be adopted and made selectable.

[0038] (a) The vehicle speed control unit 57 outputs a vehicle speed control signal that brings about different changes in vehicle speed depending on whether the vehicle is undergoing a sudden change or a gradual change. (b) The vehicle speed control unit 57 outputs a vehicle speed control signal that brings about a gradual change in vehicle speed in response to both the sudden change behavior and the gradual change behavior. (c) If the vehicle is equipped with an unmanned automatic driving mode for performing work driving without a driver, during unmanned automatic driving, the vehicle speed control unit 57 generates a vehicle speed control signal that brings about a sudden change in vehicle speed in response to a sudden change in behavior, and outputs a vehicle speed control signal that brings about a slow change in vehicle speed in response to a slow change in behavior. (d) When the vehicle is provided with an unmanned automatic driving mode for performing unmanned work travel, the rotation speed change behavior calculation unit 58 stops operating. In other words, the vehicle speed control unit 57 outputs a vehicle speed control signal generated without taking into account the rotation speed change behavior. (e) The vehicle speed control unit 57 can determine the unmanned automatic driving mode, the manned automatic driving mode, and the manual driving mode according to the switch state of the driving mode selection switch included in the detection device group 9A. That is, the driver or the manager can set one of the unmanned automatic driving mode, the manned automatic driving mode, and the manual driving mode by operating the driving mode selection switch. The function of the driving mode selection switch can be substituted by one of the functions of the remote control of this electric grass cutter or a function of an app installed in a mobile communication device carried by the driver, etc. In the unmanned automatic driving mode, the vehicle speed control unit 57 can perform vehicle speed control without considering vehicle speed fluctuations that cause discomfort to the driver, and in the manned automatic driving mode, the vehicle speed control can perform vehicle speed control without vehicle speed fluctuations that cause discomfort to the driver. Even in the manual driving mode, it is possible to perform vehicle speed control without vehicle speed fluctuations that cause discomfort to the driver. (f) In the vehicle speed control unit 57, the vehicle speed control relationship indicating the relationship between the desired vehicle speed and changing behavior as input parameters and the vehicle speed control signal as output parameter is divided into an acceleration relationship used during acceleration and a deceleration relationship used during deceleration. When the changing behavior indicates acceleration, the vehicle speed control unit 57 outputs a vehicle speed control signal generated using the acceleration relationship, and when the changing behavior indicates deceleration, the vehicle speed control unit 57 outputs a vehicle speed control signal generated using the deceleration relationship. The acceleration relationship and the deceleration relationship can be adjusted independently.

[0039] The above description of the vehicle speed control unit 57 is for the purpose of explanation and is an abstract description. In an actual embodiment, the vehicle speed control unit 57 is configured with a hardware-based electronic circuit or a software-based electronic circuit. An image of such an electronic circuit is shown in FIG. 6. Whether the vehicle speed control unit 57 is configured with a hardware-based electronic circuit or a software-based electronic circuit, the above description is used to explain the respective operations. For example, the time-dependent data processing in FIG. 6 corresponds to the function of the rotation speed change behavior calculation unit 58, the acceleration calculation processing / principle calculation processing corresponds to the function described in (f) above, and the vehicle speed correction corresponds to the function of the vehicle speed control unit 59.

[0040] This electric grass mower can be automatically operated in an unmanned automatic driving mode or a manned automatic driving mode, and the vehicle speed control unit 57 can perform different vehicle speed control depending on the automatic driving mode. The flowchart in FIG. 7 shows that different vehicle speed controls are performed depending on the set automatic driving mode. In this vehicle speed control routine, first, it is determined whether the set automatic driving mode is the unmanned automatic driving mode or the manned automatic driving mode (#01). This determination can be made from the state of the driving mode selection switch.

[0041] If the determination result is the manned automatic driving mode (#02), that is, if a driver is sitting in the driver's seat 13, vehicle speed control that depends on the rotation speed change behavior is performed to avoid a sudden change in vehicle speed due to a sudden change in the mower rotation speed (#03). If the determination result is the unmanned automatic driving mode (#04), that is, if no one is in the driver's seat 13, vehicle speed control that does not depend on the rotation speed change behavior is performed (#05). In either case, this vehicle speed control is performed until the electric grass mower is stopped (No branch at #06), and when the operation is stopped (Yes branch at #06), this routine ends.

[0042] Next, the vehicle speed control in the unmanned automatic driving mode and the manned automatic driving mode will be explained in more detail with reference to Figures 8, 9, and 10. Figure 8 is a functional block diagram showing the functional parts of the vehicle speed control constructed in the vehicle speed control unit 57 by hardware, software, or both. Figure 9 is a time chart showing the vehicle speed control when the mower rotation speed is reduced during manned driving. Figure 10 is a schematic diagram explaining the map control used in the vehicle speed control.

[0043] As shown in Fig. 8, a deviation calculator 71 inputs a set mower rotation speed (target rotation speed) which is the rotation speed of the mower motor 43, and an actual work rotation speed (actual mower rotation speed), and outputs the difference between them as a deviation. A PD controller 72 outputs a control amount based on the input deviation. The control amount is further calculated by a saturation calculator 73, and the calculation result is input to a control amount converter 74 as a control amount.

[0044] The control amount conversion unit 74 cooperates with the vehicle speed control unit 59, and when the unmanned automatic driving mode is set, the mower load is reduced by a sudden change in vehicle speed in response to a sudden change in the mower rotation speed. When the manned automatic driving mode is set, that is, when a person is on board the vehicle body 1, the mower load is reduced by a gradual change in vehicle speed in response to a sudden change in the mower rotation speed.

[0045] The control amount conversion unit 74 in this embodiment includes a conversion calculation unit 74a, a control map 74b, and a map selection unit 74c. The control amount input via the saturation calculator 73 is converted into a converted control amount by the conversion calculation unit 74a and output. At that time, the conversion calculation unit 74a uses the control map 74b. The control map 74b derives a map output value from a map input value provided by the conversion calculation unit 74a and provides it to the conversion calculation unit 74a. The conversion calculation unit 74a calculates a converted control amount from this map output value and provides it to the vehicle speed control unit 59. The vehicle speed control unit 59 generates a vehicle speed control signal from the converted control amount and provides it to the travel motor control unit 52. As shown in FIG. 10, the map selection unit 74c selects and sets the control map 74b to be used depending on whether the set driving mode is an unmanned automatic driving mode (unmanned driving) or a manned automatic driving mode (manned driving). In one example of a specific control map 74b for the manned automatic driving mode, if the map input value is "100", the map output value representing the control gain is "0.3", and if the map input value is "30", the map output value representing the control gain is "1". Between the map input value of "100" and "30", the map output value is a sequentially increasing value from "0.3" to "1", and between the map input value of "30" and "1", the map output value is constant at "1". In the unmanned automatic driving mode, regardless of the value of the map input value, the map output value is always fixed to "1". In this embodiment, deceleration and acceleration are performed by applying a gain to the control amount that defines the vehicle speed.

[0046] The time chart of FIG. 9 shows how the vehicle speed changes with the change in the mower rotation speed by the control amount conversion unit 74 and the vehicle speed control unit 59. In this time chart, the vehicle speed changes with the change in the mower rotation speed in the manned automatic driving mode are shown by a thick solid line. To summarize the time chart in the manned automatic driving mode, when the mower becomes overloaded, the mower rotation speed, which is the mower motor rotation speed, decreases, and this is detected, and the deviation is amplified by the PD controller 72, taking into account the frequency, and is saturated to become the control amount. A large value of the control amount means that the "amount of change is large" and the "speed of change is fast". Since the control amount is large, the gain becomes a small value, and the vehicle speed drops sharply (see the deceleration section in FIG. 9). When the vehicle speed drops, the load on the mower motor 43 becomes lighter, and the mower rotation speed gradually returns to the target rotation speed. As a result, the deviation becomes "0" and the control amount also becomes "0", but the map output value does not immediately become "1", but gradually returns to "1" along a predetermined inclined line (see the return section in FIG. 9). When the map output value becomes "1", the vehicle speed corresponds to the left operation amount and right operation amount of the shift lever 17. In the figure, the change in the gain value and the change in the vehicle speed are shown linearly (linearly), but of course, the change may be a nonlinear change, that is, a change represented by a curve. Furthermore, in FIG. 9, for comparison, the state of the change in the vehicle speed in the unmanned automatic driving mode is also shown by a thick dotted line. That is, in the unmanned automatic driving mode, the vehicle speed is reduced in response to a decrease in the mower rotation speed due to an overload of the mower, and when the mower rotation speed returns to normal, the vehicle speed also returns to normal accordingly. Therefore, the mower speed is reduced, the vehicle speed is reduced, the mower speed is restored, and the vehicle speed is restored, all with virtually no delay, which may result in a sudden change in vehicle speed. However, since the vehicle is unmanned, rapid vehicle speed control is prioritized.

[0047] [Another embodiment] (1) The functional block diagrams shown in Figures 4 and 5 are drawn for explanatory purposes, and specific functional units (e.g., rotation speed detection unit 55, actual vehicle speed calculation unit 56) may be provided outside of control unit 5. In addition, each functional unit (e.g., vehicle speed control unit 57) may be divided or integrated as desired. (2) In the above-described embodiment, an electric grass cutter is given as an example of an electric work vehicle. However, the above-described power supply device can also be installed on other electric work machines, electric tractors, electric harvesters, electric construction machines, and the like.

[0048] In addition, the configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, provided no contradiction arises. Furthermore, the embodiments disclosed in this specification are illustrative, and the embodiments of the present invention are not limited thereto, and can be appropriately modified within the scope that does not deviate from the purpose of the present invention. [Industrial Applicability]

[0049] The present invention is applicable not only to grass cutters, but also to crop harvesters, snow removal machines, and the like. [Explanation of symbols]

[0050] 1: Body 3: Grass cutting equipment (work equipment) 4: Inverter 4A: Inverter for driving motor 4B: Mower motor inverter 5: Control unit 9A: Detection equipment group 9B: Equipment group 11: Front wheel 12: Rear wheel 17: Gear shift lever (vehicle speed setting device) 30: Moore Deck 31:Kariblade 41: Left driving motor (electric motor for driving) 42: Right driving motor (electric motor for driving) 43: Mower motor (electric motor for work) 52: Travel motor control unit 53: Mower motor control unit 54: Equipment control section 55: Rotation speed detection unit 56: Actual vehicle speed calculation section 57: Vehicle speed control unit 58: Rotation speed change behavior calculation unit 59: Vehicle speed control unit

Claims

1. A working machine that performs work while traveling, A drive wheel unit rotated by an electric motor for traveling; A working device rotated by an electric working motor; A vehicle speed setting device for setting a desired vehicle speed; A rotation speed detection unit that detects a rotation speed of the working device; A rotation speed change behavior calculation unit that calculates a change behavior of the rotation speed over time; a vehicle speed control unit that generates a vehicle speed control signal based on the desired vehicle speed and the changing behavior; a travel motor control unit that drives the travel electric motor based on the vehicle speed control signal.

2. The work machine according to claim 1 , further comprising an actual vehicle speed calculation unit that calculates an actual vehicle speed, the vehicle speed control unit generating the vehicle speed control signal based on the desired vehicle speed, the changing behavior, and the actual vehicle speed.

3. the rotation speed change behavior calculation unit calculates an abrupt change behavior indicating a high rate of change of the rotation speed and a slow change behavior indicating a rate of change lower than the rate of change of the abrupt change behavior, The work machine according to claim 1 , wherein the vehicle speed control unit generates the vehicle speed control signal that brings about different changes in vehicle speed depending on whether the vehicle speed is changed suddenly or slowly.

4. the rotation speed change behavior calculation unit calculates an abrupt change behavior indicating a high rate of change of the rotation speed and a slow change behavior indicating a rate of change lower than the rate of change of the abrupt change behavior, The work machine according to claim 1 , wherein the vehicle speed control unit generates the vehicle speed control signal that results in independent vehicle speed change rates for the sudden change behavior and the gradual change behavior.

5. It is equipped with an unmanned automatic driving mode that allows unmanned work driving, the rotation speed change behavior calculation unit calculates an abrupt change behavior indicating a high rate of change of the rotation speed and a slow change behavior indicating a rate of change lower than the rate of change of the abrupt change behavior, 2. The work machine according to claim 1, wherein, when the unmanned automatic driving mode is being executed, the vehicle speed control unit generates the vehicle speed control signal that brings about a sudden change in vehicle speed corresponding to the sudden change behavior, and generates the vehicle speed control signal that brings about a slow change in vehicle speed corresponding to the slow change behavior.

6. 2. The work machine according to claim 1, wherein the vehicle speed control unit divides a vehicle speed control relationship indicating a relationship between the desired vehicle speed and the changing behavior as input parameters and the vehicle speed control signal as an output parameter into an acceleration relationship used during acceleration and a deceleration relationship used during deceleration.

7. 7. The work machine according to claim 6, wherein the acceleration relationship and the deceleration relationship are adjustable independently of each other.

8. The working machine according to any one of claims 1 to 7, wherein the working implement is a grass cutting implement having a rotary blade.

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