Work vehicles

Abstract

To provide a work vehicle that can reduce energy waste and environmental impact in relation to the workload compared to conventional technologies. [Solution] By switching between a first rotational speed mode in which the torque is varied to maintain a first rotational speed (N1) according to the load, and a second rotational speed mode in which the motor (M1) is controlled with a second torque limit value (T2a) corresponding to a second rotational speed (N2) that is lower than a first torque limit value (T1a) corresponding to the first rotational speed (N1), and the torque of the motor (M1) according to the load is controlled so as not to exceed the second torque limit value (T2a), energy waste and environmental burden can be suppressed in relation to the workload compared to conventional technology.

Description

Technical Field

[0001] The present invention relates to a work vehicle that performs work in a field.

Background Art

[0002] In work vehicles such as tractors, rice transplanters, and lawn mowers, electrification is progressing, and work vehicles that use a motor as a drive source for work implements and travel are known. In such a work vehicle, a plurality of battery modules, which are the power sources of the motor, are detachable, and a technique is conventionally known in which a torque command value is output to an inverter device so that a target output is obtained based on a vehicle characteristic table according to the number of mounted battery modules.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] (Problems of the Prior Art) In the technique described in Patent Document 1, a current value (torque command value) is output according to the user's operation and the number of mounted battery modules to obtain a target output. Therefore, when the target output according to the user's operation is an excessive operation with respect to the actual load, an excessive current value will be supplied. Therefore, energy waste occurs, and there is also a concern about environmental load.

[0005] The technical problem of the present invention is to provide a work vehicle capable of suppressing energy waste and environmental load with respect to the load of work as compared with the conventional technique.

Means for Solving the Problems

[0006] To solve the aforementioned technical problems, the invention described in claim 1 is a work vehicle comprising: a vehicle body (10); a work implement (5) supported by the vehicle body (10) for performing work on a field; a motor (M1) for driving the work implement (5); a control unit (200) that switches between a first rotational speed mode, which controls the rotational speed of the motor (M1) to a predetermined first rotational speed (N1) and varies the torque to maintain the first rotational speed (N1) according to the load; and a second rotational speed mode, which controls the motor (M1) with a second torque limit value (T2a) corresponding to a second rotational speed (N2) lower than the first rotational speed (N1) as the upper limit, and controls the torque of the motor (M1) according to the load so as not to exceed the second torque limit value (T2a), according to the input of an operator.

[0007] The invention described in claim 2 is a work vehicle according to claim 1, further comprising a control unit (200) that sets the second torque limit value (T2a) in the second rotation speed mode to a lower value than the first torque limit value (T1a) in the first rotation speed mode.

[0008] The invention described in claim 3 is a work vehicle according to claim 2, comprising: an input unit (SW2) on which an operator can input the rotational speed of the motor (M1); and a control unit (200) that makes the second torque limit value (T2a) corresponding to the upper limit of the second rotational speed (N2) that can be input by the input unit (SW2) in the second rotational speed mode smaller than the first torque limit value (T1a) corresponding to the upper limit of the first rotational speed (N1) that can be input by the input unit (SW2) in the first rotational speed mode.

[0009] The invention described in claim 4 is a work vehicle according to claim 2, comprising a control unit (200) that calculates an estimated load torque (Ta) corresponding to the work load of the work machine (5), and when the difference between the estimated load torque (Ta) and the second torque limit value (T2a) reaches a predetermined margin value (Tb), reduces the current value supplied to the motor (M1) to be less than the current value in the case of the second torque limit value (T2a).

[0010] The invention described in claim 5 is a work vehicle according to claim 4, comprising a second motor (M2) installed separately from the motor (M1) and driving the travel devices (11, 12) of the vehicle body (10), and a control unit (200) that controls the travel speed of the second motor (M2) according to the work load of the work machine (5) based on the work content of the work machine (5).

[0011] The invention described in claim 6 is a work vehicle according to claim 5, further comprising a control unit (200) that, when the work load of the work machine (5) based on the work content of the work machine (5) changes from a heavy load to a light load, prioritizes the recovery of the travel speed of the second motor (M2) over the supply of current to the motor (M1). [Effects of the Invention]

[0012] According to the invention described in claim 1, by switching between a first rotational speed mode in which the torque is varied to maintain a first rotational speed (N1) according to the load, and a second rotational speed mode in which the motor (M1) is controlled with a second torque limit value (T2a) corresponding to a second rotational speed (N2) that is lower than a first torque limit value (T1a) corresponding to the first rotational speed (N1), and the torque of the motor (M1) according to the load is controlled so as not to exceed the second torque limit value (T2a), energy waste and environmental burden can be suppressed in relation to the workload compared to conventional technology.

[0013] According to the invention described in claim 2, in addition to the effects described in claim 1, power consumption can be suppressed in the second rotational speed mode by setting the second torque limit value (T2a) to a lower value than the first torque limit value (T1a).

[0014] According to the invention described in claim 3, in addition to the effects described in claim 2, power consumption can be suppressed in the second rotational speed mode by making the second torque limit value (T2a), which corresponds to the upper limit of the second rotational speed (N2), smaller than the first torque limit value (T1a), which corresponds to the upper limit of the first rotational speed (N1) that can be input by the input unit (SW2).

[0015] According to the invention described in claim 4, in addition to the effects described in claim 2, when the difference between the estimated load torque (Ta) and the second torque limit value (T2a) reaches a margin value (Tb), the current value supplied to the motor (M1) is made smaller than the current value in the case of the second torque limit value (T2a), thereby suppressing unnecessary power consumption.

[0016] According to the invention described in claim 5, in addition to the effects described in claim 4, the travel speed of the work machine (5) can be controlled according to the work load using a second motor (M2) separate from the motor (M1).

[0017] According to the invention described in claim 6, in addition to the effects described in claim 5, when the work load changes from a heavy load to a light load, the travel speed of the second motor (M2) can be prioritized for recovery over the current supply to the motor (M1). [Brief explanation of the drawing]

[0018] [Figure 1] Figure 1 is a side view of a riding lawnmower, which is an example of a work vehicle according to an embodiment of the present invention. [Figure 2] Figure 2 is an explanatory diagram of the main parts of the riding lawnmower shown in Figure 1. [Figure 3] Figure 3 is a functional block diagram of the control means of the embodiment. [Figure 4] Figure 4 is an explanatory diagram of the setting of rotational speed and torque limit value in the embodiment, and is a graph with rotational speed on the horizontal axis and torque value on the vertical axis. [Modes for carrying out the invention]

[0019] Next, while referring to the drawings, examples of embodiments of the present invention will be described, but the present invention is not limited to the following examples. In the description of the embodiments, the left and right directions are referred to as left and right, respectively, toward the forward direction of the machine body, and the forward direction is referred to as front and the backward direction is referred to as rear for explanation. In the following description using the drawings, illustrations other than the members necessary for the explanation are appropriately omitted for ease of understanding.

[0020] Hereinafter, embodiments of the present invention will be described while referring to the drawings.

[0021] In FIGS. 1 and 2, the whole or a part of a riding lawn mower 1 as an example of a work vehicle according to an embodiment of the present invention is shown. The riding lawn mower 1 includes a vehicle body 10 that can travel in the front-rear direction, and front wheels 11, 11 and rear wheels 12, 12 as an example of a traveling device are provided at the front and rear of the vehicle body 10, respectively. Further, a driver's seat 2 is arranged at the front of the vehicle body 10. Below the driver's seat 2, a traveling motor unit 4 as an example of a second motor is arranged. Also, a motor unit (PTO motor unit) 3 as an example of a motor is arranged at the rear of the vehicle body 10.

[0022] The vehicle body 10 has a floor frame 13 that forms a floor portion 21. The driver's seat 2 is arranged behind the floor portion 21 formed above the front of the vehicle body 10. The floor portion 21 is provided with a steering column 22 arranged at the front thereof, a foot pedal 23 for operation arranged on the left and right of the steering column 22, a seat 24 serving as the driver's seat arranged behind the steering column 22, and operation units 25 arranged on the left and right of the seat 24. A steering wheel (handle) 26 for steering is provided on the steering column 22, and a manual lever 27 for operation, an operation panel (not shown), etc. are provided on the operation unit 25. In this riding lawn mower 1, the rear wheels 12, 12 are steered left and right by rotating the steering wheel 26 left and right.

[0023] As an example of a drive source, the motor unit 3 is positioned at the front of the rear of the vehicle body 10. In this embodiment, an electric motor unit 3 is used, but it is also possible to use a hybrid unit that combines an internal combustion engine (gasoline engine or diesel engine) with a motor, or to use only an internal combustion engine. The motor unit 3 incorporates a PTO motor (not shown) and a transmission, and the power from the PTO motor is transmitted to the grass cutting device 5 (described later) after being shifted. Furthermore, the drive motor unit 4 also incorporates a drive motor and a transmission (not shown), and is configured to transmit the power of the drive motor to the front wheels 11, 11 and rear wheels 12, 12 after the power has been shifted and distributed.

[0024] In this embodiment, the riding lawnmower 1 has a structure located below the front of the vehicle body 10 and in front of the front wheels 11, 11. A grass-cutting device 5, which is an example of a work machine, is attached, and a grass collection container 56 is positioned at the rear of the vehicle body 10 and above the motor unit 3.

[0025] The grass cutting device 5 is a device that performs grass cutting work such as grass by rotating a cutting blade inside a cover 51 with an open bottom, and is for example called a rotary mower. The cover 51 of this grass cutting device 5 is rotatably attached to the vehicle body 10 via a support arm 52 and moves up and down. The cutting blade of the grass cutting device 5 is rotated by power transmitted from the motor unit 3.

[0026] The grass collection container 56 is a container for storing the grass cut by the grass cutting device 5, and is commonly referred to as a collector. The grass collection container 56 is a box-shaped structure, such as a cube, and has an openable and closable door 56b on its rear side for discharging the stored grass. The grass collection container 56 is attached via a lifting and dumping mechanism 58 to left and right support frames 57 that are positioned above the motor unit 3 behind the seat 24 and the control unit 25. The lifting and dumping mechanism 58 functions to move the grass collection container 56 to a predetermined position and state when discharging the grass clippings it contains, and consists of a support frame, a link mechanism, a hydraulic cylinder, etc. Safety bars 59 are provided at the upper ends of the left and right support frames 57, with a shape that connects them to each other.

[0027] Furthermore, as shown in Figure 2, the riding lawnmower 1 is equipped with a grass clipping collection unit 53 located between the front wheels 11, 11 and behind the mowing device 5, which collects the cut grass by suction and stores it in a grass collection container 56. The grass clipping collection unit 53 consists of a blower 53a which acts as a suction unit, and a chute (duct) 53b which connects the blower 53a and the grass collection container 56 and acts as a transport unit that passes the grass clippings collected by the blower 53a towards the grass collection container 56.

[0028] In Figure 2, the motor unit 3 is fixedly supported to the lower frame 101 of the vehicle body 10. The battery frame 102 is located at the rear of the lower frame 101. The lower end of the rear frame 103 is rotatably supported at the rear end of the battery frame 102. The rear frame 103 can open and close the inside of the battery frame 102 by rotating about the pivot point at its lower end. The battery 111 is housed inside the battery frame 102. The battery 111 is located at the rear of the vehicle body 10, below the grass collection container 56, and behind the motor unit 3.

[0029] The lower frame 101 supports a motor control device (MSD) 121 that controls the rotation of the motor unit 3. The motor control device 121 is located between the battery frame 102 and the motor unit 3. That is, the motor control device 121 is located near the right-side vertical frame 102a(R), which is the rotation center of the battery frame 102. In other words, the motor control device 121 is located on the right side of the vehicle body 10. Furthermore, in the riding lawnmower 1 of this embodiment, an MCU (Main Control Unit: an example of a control unit) 122, which controls the entire riding lawnmower 1, is positioned between the motor unit 3 and the battery frame 102 as an example of a main control device.

[0030] Furthermore, in the riding lawnmower 1 of this embodiment, a junction box (JB) 123, which concentrates electrical circuits such as power supply and communication, is located above the motor unit 3. The motor control device 121, MCU 122, and junction box 123 are connected to the battery 111 and powered thereby. Therefore, in this embodiment, the terminals on the motor control device 121, MCU 122, and junction box 123 are also located on the right side of the vehicle body 10.

[0031] (Description of the control unit) Figure 3 is a functional block diagram of the control means of the embodiment. In the block diagram of Figure 3, elements unrelated to the description of the embodiments of the present invention are omitted from the illustration and description. In Figure 3, the control unit (MCU, an example of control means) 200 of the embodiment is composed of a small information processing device, a so-called microcomputer. Therefore, the control unit 200 can realize various functions by executing a program stored in ROM or the like.

[0032] The control unit 200 of this embodiment receives signals from sensors such as a mode switching switch (an example of an input unit) SW1 and a rotation speed input switch (an example of an input unit) SW2, as well as from signal output elements such as various switches and buttons. The mode switching switch SW1 is located on the control unit 25 and switches the operating mode of the motor unit 3 and the travel motor unit 4 (the "normal mode" and "eco mode" described later). The rotation speed input switch SW2 is located on the operating unit 25 and is used to input the upper limit of the rotation speed when the motor unit 3 and the travel motor unit 4 are operating. As an example of a display unit, the display monitor, which is an example of an input component, is composed of a so-called touch panel, and input is possible according to the position touched by a finger.

[0033] The control unit 200 of this embodiment outputs control signals to controlled elements such as the PTO motor (an example of a motor) M1 of the motor unit 3 that operates the grass cutting device 5, the grass cutting collection unit 53, the lifting / dumping mechanism 58, the hydraulic pump, etc., and the travel motor (an example of a second motor) M2 of the travel motor unit 4 that operates the travel device (front wheels 11, rear wheels 12).

[0034] The control unit 200 of this embodiment has the following functional modules (program modules). The mode switching means 201 switches between a normal mode, which is an example of a first rotation speed mode, and an eco mode, which is an example of a second rotation speed mode, in response to the input of the mode switching switch SW1.

[0035] The rotation speed input means 202 inputs an upper limit value for the rotation speed of the PTO motor M1 in response to the input of the rotation speed input switch SW2. In the rotation speed input means 202 of this embodiment, it is possible to input an upper limit value for the rotation speed of the PTO motor M1 in normal mode (an example of a first rotation speed) and an upper limit value for the rotation speed of the PTO motor M1 in eco mode (an example of a second rotation speed). In this embodiment, the rotation speed can be set within the same upper limit range as in normal mode, even in eco mode. Furthermore, to be environmentally conscious, it is possible to set the upper limit of the second rotation speed N2, which can be input via the rotation speed input switch SW2 in the second rotation speed mode, to a smaller value than the upper limit of the first rotation speed N1, which can be input via the rotation speed input switch SW2 in the first rotation speed mode. In other words, the operator can set a lower rotation speed in eco mode than in normal mode. Also, in this embodiment, the lower limits of the first rotation speed N1 and the second rotation speed N2 are set to be above the minimum rotation speed required to operate the hydraulic pump, which needs to be operated even when no work is being done in the field.

[0036] The normal mode setting means (an example of a first rotation mode setting means) 203 includes a first rotation speed setting means 203a and a first torque limit value setting means 203b, and sets the normal mode as an example of the first rotation mode. The normal mode setting means 203 of this embodiment switches to the normal mode when an input to select the normal mode is received via the mode switching switch SW1.

[0037] Figure 4 is an explanatory diagram of the setting of rotational speed and torque limit value in the embodiment, and is a graph with rotational speed on the horizontal axis and torque value on the vertical axis. The first rotational speed setting means 203a sets the rotational speed of the PTO motor M1 to the input rotational speed N1 when a rotational speed is input via the rotational speed input means 202. In Figure 4, if no rotational speed is input via the rotational speed input means 202, the rotational speed of the PTO motor M1 (first rotational speed N1) is set to a predetermined first standard rotational speed (standard value, default value) N1a.

[0038] The first torque limit setting means 203b sets the first torque limit value T1a based on the first rotational speed setting means 203a. The first torque limit value T1a is set based on the first rotational speed N1, within the continuous operation region A1 of the PTO motor M1, with a predetermined margin (allowance) relative to the upper limit A1a of the continuous operation region A1. Here, it is preferable to determine a torque value that is less likely to cause damage to the machine, including the speed change mechanism, through experiments, and set that torque value as the first torque limit value T1a. The continuous operation region A1 refers to the region where, under the specified operating environment, the heat generated from the PTO motor M1 is kept within the specified limits, allowing for continuous operation. Outside of the continuous operation region A1, there is a short-time operation region A2 where operation is possible for a short period (e.g., 1 minute) considering the heat generated by the PTO motor M1, and where the output torque is greater than in the continuous operation region A1.

[0039] Furthermore, in this embodiment, if a torque exceeding the first torque limit value T1a is generated during operation in normal mode, the travel speed is reduced by the travel motor control means (205c) described later. Furthermore, in this embodiment, a first speed increase limit value T1b is set, which is a predetermined value smaller than the first torque limit value T1a. In this embodiment, when operating in normal mode, if the torque generated exceeds the first speed increase limit value T1b but does not reach the first torque limit value T1a, the travel motor control means (205c) suppresses the increase in travel speed. That is, even if the accelerator is pressed, the speed does not increase, and the previous travel speed is maintained. It should be noted that this is not limited to cases where the speed does not increase; for example, it is also possible to have a configuration where the speed increase is less than the normal speed increase amount relative to the amount the accelerator is pressed (operation amount) (slow acceleration).

[0040] In the normal mode of the embodiment, the PTO motor M1 is controlled at the first rotational speed N1, and current is supplied to the PTO motor M1 to vary the torque so as to maintain the first rotational speed N1 according to the load generated by the mowing device 5. Therefore, the torque varies according to the total working load of the mowing device 5, the grass collection unit 53, and the like. In the normal mode, the torque can rise up to the upper limit A2a of the short-time operation region A2. That is, when the working load of the mowing device 5 or the like increases, current corresponding to the torque at the upper limit A2a of the short-time operation region A2 is supplied. When the torque generation time within the range of the short-time operation region A2 elapses for a specified short time (for example, 1 minute), the torque is forcibly limited to the upper limit value A1a of the continuous operation region A1 (the supplied current is limited). When forcibly limiting the torque to the upper limit value A1a of the continuous operation region A1, it is not limited to the mode of performing determination and control based on time. For example, it is also possible to forcibly limit the torque when the temperature of the PTO motor M1 reaches a specified temperature.

[0041] The eco-mode setting means (an example of the setting means for the second rotation mode) 204 has a second rotational speed setting means 204a and a second torque limit value setting means 204b, and sets the eco-mode as an example of the second rotation mode. The eco-mode setting means 204 of the embodiment switches to the eco-mode when an input for selecting the eco-mode is made by the mode changeover switch SW1.

[0042] When the rotational speed is input by the rotational speed input means 202, the second rotational speed setting means 204a sets the input rotational speed as the second rotational speed N2 and sets the rotational speed of the PTO motor M1 to the input rotational speed (the second rotational speed N2). When the rotational speed is not input by the rotational speed input means 202, a predetermined second standard rotational speed (standard value, default value) N2a is set as the rotational speed of the PTO motor M1 (the second rotational speed N2). In the embodiment, as an example, the second standard rotational speed N2a is set to the same value as the first standard rotational speed N1a, but it is not limited thereto, and different values are also possible, and it is desirable that N2a < N1a.

[0043] The second torque limit setting means 204b sets the second torque limit T2a based on the second rotational speed setting means 204a. The second torque limit T2a is set to a value smaller than the first torque limit T1a within the continuous operation region A1 of the PTO motor M1, based on the second standard rotational speed N2a. In other words, the second torque limit T2a, which corresponds to the upper limit of the second rotational speed N2 in eco mode, is set to a smaller value than the first torque limit T1a, which corresponds to the upper limit of the first rotational speed N1 in normal mode.

[0044] In particular, in this embodiment, the second torque limit value T2a is set to a lower value than the first speed increase limit value T1b. While it is preferable that the second torque limit value T2a be lower than the first speed increase limit value T1b, it is also possible to set them to the same value, or for the second torque limit value T2a to be larger. Furthermore, in the second torque limit setting means 204b of the embodiment, a second speed increase limit value T2b is also set, which is smaller than the second torque limit value T2a by a predetermined value, similar to the first speed increase limit value T1b.

[0045] Therefore, in this embodiment, when operating in eco mode, if torque exceeding the second torque limit value T2a is generated, the travel motor control means (205c) reduces the travel speed. Also, when operating in eco mode, if torque exceeding the second speed increase limit value T2b but not reaching the second torque limit value T2a is generated, the travel motor control means (205c) suppresses the increase in travel speed.

[0046] In the eco mode of this embodiment, the PTO motor M1 is controlled at a second rotational speed N2, and the torque is varied by supplying current to the PTO motor M1 so that the torque does not exceed the second torque limit value T2a (in other words, so that the maximum torque remains at the second torque limit value T2a) according to the load generated by the grass cutting device 5. Therefore, in eco mode, even if a load exceeding the second torque limit value T2a is applied, the current supplied to the PTO motor M1 is limited to the current corresponding to the second torque limit value T2a, and the rotational speed of the PTO motor M1 will fluctuate (decrease).

[0047] In this embodiment, the control of the normal mode and eco mode is performed when the vehicle body 10 is working while moving forward, that is, when both the PTO motor M1 and the travel motor M2 are rotating in the forward direction, but it is not limited to this. For example, it is also possible to switch between the normal mode and eco mode when working while moving backward (when both the PTO motor M1 and the travel motor M2 are rotating in the reverse direction), when moving forward to remove grass stuck in the grass cutting device 5 and the grass cutting device 5 is rotating in the reverse direction (when the PTO motor M1 is rotating in the reverse direction and the travel motor M2 is rotating in the forward direction), or when moving backward and the grass cutting device 5 is rotating in the forward direction (when the PTO motor M1 is rotating in the forward direction and the travel motor M2 is rotating in the reverse direction), etc.

[0048] The motor control means 205 controls the PTO motor M1 and the travel motor M2 to control the movement and mowing operation of the riding lawnmower 1. The motor control means 205 of this embodiment has the following means 205a to 205f. The torque estimation means 205a calculates an estimated load torque (torque estimate) Ta corresponding to the work load of the grass cutting device 5, etc., based on information such as the supply current value and rotational speed to the PTO motor M1, the temperature of the PTO motor M1 (linked to the operating time), and the slip ratio of the motor. The torque estimate Ta is calculated at predetermined time intervals (sampling intervals).

[0049] The PTO motor control means 205b controls the PTO motor M1. The PTO motor control means 205b controls the PTO motor M1 based on the rotational speeds N1, N2 and torque limit values ​​T1a, T2a set by the normal mode setting means 203 or the eco mode setting means 204. In normal mode, the PTO motor control means 205b increases or decreases the supplied current value in accordance with the increase or decrease of the estimated torque value Ta in order to maintain the first rotational speed N1. In eco mode, the PTO motor control means 205b increases or decreases the supplied current value in accordance with the increase or decrease of the estimated torque value Ta in order to maintain the second rotational speed N2 until the second torque limit value T2a is reached, and once the estimated torque value Ta reaches the second torque limit value T2a, it maintains the current value corresponding to the second torque limit value T2a.

[0050] The travel motor control means 205c controls the travel motor M2. During operation, the travel motor control means 205c controls the travel device (front wheels 11, rear wheels 12) and the travel speed of the vehicle body 10 by controlling the rotation speed and torque of the travel motor M2 so that the travel speed corresponds to the working speed, i.e., the rotation speed N1, N2 of the PTO motor M1. During operation, the travel speed is basically controlled according to the working speed, but if an emergency occurs and the operator operates the foot pedals 23 such as the accelerator or brake, the travel motor M2 is controlled according to the amount the foot pedals 23 are pressed.

[0051] In this embodiment, the control means 205c for the travel motor controls the vehicle to maintain the previous travel speed by suppressing acceleration even when the foot pedal 23 is pressed down, when the torque (estimated torque value Ta) of the PTO motor M1 reaches the acceleration limit values ​​T1b and T2b. Furthermore, in this embodiment, the control means 205c for the travel motor reduces the travel speed regardless of the amount the foot pedal 23 is pressed down when the torque (estimated torque value Ta) of the PTO motor M1 reaches the torque limit values ​​T1a and T2a. The travel speed after deceleration is controlled according to the difference between the torque (estimated torque value Ta) of the PTO motor M1 and the torque limit values ​​T1a and T2a, and the larger the difference, the lower the travel speed after deceleration (the greater the deceleration width and deceleration gradient).

[0052] In the embodiment, an example was given of deceleration occurring when the torque of the PTO motor M1 reaches the torque limit values ​​T1a, T2a, but the embodiment is not limited to this. For example, considering the possibility that the torque of the PTO motor M1 temporarily reaches the torque limit values ​​T1a, T2a, it is also possible to control the motor to decelerate if the state in which the torque of the PTO motor M1 reaches the torque limit values ​​T1a, T2a continues for a predetermined time (for example, 1 minute) or longer.

[0053] The load fluctuation determination means 205d determines whether the workload during work has decreased or not. The light load fluctuation determination means 205d of the embodiment determines, based on the torque estimate value Ta, that the load has become lighter, i.e., that it has changed from a heavy load to a light load, when the current torque estimate value Ta is smaller than the previous torque estimate value Ta'. If it is determined that the load has changed to a light load, the current supplied to the travel motor control means 205c and the PTO motor control means 205b decreases in accordance with the reduced load. Furthermore, if the load changes from a heavy load exceeding the torque limit values ​​T1a and T2a to a light load below the torque limit values ​​T1a and T2a, the current supply to the travel motor M2, which was decelerating, is increased to increase its speed (recover the travel speed), and the current supply to the PTO motor M1 is reduced to match the torque corresponding to the light load.

[0054] Furthermore, to address the possibility that the light load is a temporary phenomenon, it is desirable to prioritize the recovery of the travel speed of the travel motor M2 without reducing the torque of the PTO motor M1. Therefore, for example, it is possible to prioritize the recovery of the travel speed until a light load below the torque limit values ​​T1a and T2a is detected three or more times, and then reduce the torque of the PTO motor M1 after three or more detections. In addition, the speed increase amount and speed increase gradient can be set according to the difference between the estimated torque value Ta at the time of light load and the torque limit values ​​T1a and T2a.

[0055] The torque difference determination means 205e determines, in eco mode, whether the difference between the calculated torque estimate Ta and the second torque limit value T2a (=T2a-Ta) reaches a predetermined margin value Tb.

[0056] The PTO control torque upper limit changing means 205f reduces the current supplied to the PTO motor M1 to less than the current supplied when the second torque limit value T2a is used, when the difference between the estimated torque value Ta and the second torque limit value T2a (T2a-Ta) reaches a margin value Tb. In other words, when operating in eco mode, if the workload acting on the grass cutting device 5, etc. has sufficient margin over the second torque limit value T2a (i.e., the workload is considerably low), the second torque limit value T2a is lowered to reduce the current supplied to the PTO motor M1. Therefore, for example, when the grass cutting device 5 and the grass cutting collection unit 53 are not operated and only the hydraulic pump is operating, the workload becomes very small, so the second torque limit value T2a is lowered by the margin value Tb to reduce the current supplied to the PTO motor M1.

[0057] (Operation of the embodiment) In the riding lawnmower 1 of the embodiment having the above configuration, in addition to the normal mode which is similar to the operation of conventional work vehicles, an eco mode is provided. In eco mode, even if the workload increases, once the second torque limit value T2a is reached, no further current is supplied to the PTO motor M1, and the torque is maintained at the second torque limit value T2a. Therefore, the torque does not increase and the rotational speed of the PTO motor M1 decreases. In accordance with the decrease in the rotational speed of the PTO motor M1, the travel speed of the travel motor M2 is also reduced. In places with a high workload, work is performed at low rotational speed and low speed while suppressing an increase in current consumption. In conventional technology and in normal mode, the torque of the PTO motor M1 increased as the workload increased. Therefore, in normal mode, the current consumption could increase significantly in accordance with the workload, but in eco mode, the increase in current consumption is suppressed. Consequently, the riding lawnmower 1 of this embodiment can suppress energy waste and environmental impact in relation to the workload compared to conventional technology.

[0058] In particular, when the torque of the PTO motor M1 was increased, in conventional motors, the motor's torque could not keep up with the workload (the motor would lose power), causing the motor to lose synchronization. Therefore, the motor losing synchronization ultimately protected the transmission mechanism (transmission case) and transmission mechanism (shaft, rod, etc.) between the motor and the implement (grass cutting device 5). However, with recent improvements and increased performance of motors, the motor's torque is less likely to be overwhelmed by the workload. Therefore, when the workload increases, the transmission mechanism and other components are subjected to load, potentially leading to damage to these components. In contrast, in this embodiment, in normal mode, a torque value that is less likely to cause damage to the machine, including the transmission mechanism, is set as the first torque limit value T1a. Therefore, when torque exceeding the first torque limit value T1a is generated, the travel speed is reduced, and the riding grass cutter 1 is controlled to reduce the workload. Thus, even in normal mode, the torque of the PTO motor M1 is more likely to fall below the first torque limit value T1a. Therefore, damage to the machinery, including the transmission mechanism, is suppressed even in normal mode. Furthermore, in eco mode, the second torque limit value T2a is set to a smaller value than the first torque limit value T1a, further suppressing damage to the machinery, including the transmission mechanism, compared to normal mode.

[0059] Furthermore, in this embodiment, when inputting rotational speed, the input rotational speed is set lower in eco mode than in normal mode. Therefore, even when rotational speed is input, the second torque limit value T2a is set to a value smaller than the first torque limit value T1a, thereby suppressing damage to the machine, including the transmission mechanism.

[0060] Furthermore, in this embodiment, in eco mode, if the estimated torque value Ta has sufficient margin over the second torque limit value T2a, the current value supplied to the PTO motor M1 is further reduced. Therefore, unnecessary current consumption is suppressed. In particular, in this embodiment, a torque estimate value Ta is calculated and used. While torque can also be detected using a torque detector, torque detectors are expensive. Furthermore, if torque is detected only from the current value, changes in rotational speed cannot be taken into account, and there is a problem of variability. In contrast, in this embodiment, the output value (torque estimate value Ta) includes the current value, rotational speed, and motor slip, making estimation easier. In this embodiment, the PTO motor control means 205b (MCU) uses the calculated torque estimate value Ta as a reference, enabling energy-saving operation through time-axis-inclusive inference control. It is also possible to perform control based on values ​​detected using a torque detector.

[0061] Although a riding lawnmower 1 was used as an example of a work vehicle, the invention is not limited to this. It can also be applied to tractors, rice transplanters, combine harvesters, etc. In other words, in configurations where the work equipment is attached to the rear of the vehicle body 10, such as tractors and rice transplanters, the battery 111 and motor unit 3 can be housed in the bonnet portion at the front of the vehicle body 10.

[0062] Furthermore, in the case of work vehicles such as tractors, if seat belts are provided, it is preferable to provide a configuration that detects whether the seat belt is fastened, and to improve safety by not accepting inputs such as mode switching, rotation speed input, driving operations (forward / reverse, gear shifting, etc.), and operation of implements when the seat belt is not fastened. However, when a robot is operating a work vehicle (autonomous driving / automatic work), it is preferable to accept some inputs (forward / reverse switching, PTO on / off, etc.) even when the seat belt is not fastened, as this allows the robot to operate even if the operator is not seated in the driver's seat. The acceptance / rejection of inputs can be done by software processing, or it can be done by hardware processing using a combination of switches. That is, it is also possible to have a hardware configuration in which a switch is turned on when the seat belt is fastened, connecting the signal circuits for forward / reverse switching and PTO on / off, and when the seat belt is unfastened the switch is turned off, disconnecting the signal circuits for forward / reverse switching and PTO on / off.

[0063] Furthermore, although the above embodiment illustrates a configuration in which the PTO motor M1 and the travel motor M2 are separate, i.e., a configuration with two motors, it is not limited to this. It is also possible to use a common motor (one motor). In the case of using one motor, the rotational speed and torque can be controlled by the travel transmission mechanism and the work equipment transmission mechanism, respectively, after the output is branched from the motor. Alternatively, the travel motor M2 can be replaced with an internal combustion engine such as a gasoline engine or diesel engine. [Explanation of Symbols]

[0064] 1. Work vehicles, 5. Work equipment, 10 car bodies, 11,12 Running gear, 200 Control unit, M1 motor, M2 Second motor, N1 First rotational speed, N2 Second rotational speed, SW2 input section, T1a First torque limit value, T2a Second torque limit value, Ta: Estimated value of load torque. Tb margin.

Claims

1. Vehicle body (10) and A work machine (5) is supported by the vehicle body (10) and performs work on the field, A motor (M1) that drives the aforementioned work machine (5), A control unit (200) switches between, in response to operator input, a first rotation speed mode in which the rotation speed of the motor (M1) is controlled to a predetermined first rotation speed (N1) and the torque is varied according to the load to maintain the first rotation speed (N1), and a second rotation speed mode in which the motor (M1) is controlled with a second torque limit value (T2a) corresponding to a second rotation speed (N2) lower than the first rotation speed (N1) as the upper limit, and the torque of the motor (M1) according to the load is controlled so as not to exceed the second torque limit value (T2a). A work vehicle equipped with [a specific feature / equipment].

2. The control unit (200) sets the second torque limit value (T2a) in the second rotation speed mode to a lower value than the first torque limit value (T1a) in the first rotation speed mode. A work vehicle according to claim 1, comprising:

3. The motor (M1) has an input unit (SW2) that allows the operator to input the rotation speed, The control unit (200) makes the second torque limit value (T2a), which corresponds to the upper limit of the second rotation speed (N2), which can be input by the input unit (SW2) in the second rotation speed mode, smaller than the first torque limit value (T1a), which corresponds to the upper limit of the first rotation speed (N1), which can be input by the input unit (SW2) in the first rotation speed mode. A work vehicle according to claim 2, comprising:

4. The control unit (200) calculates an estimated load torque (Ta) corresponding to the work load of the work machine (5), and when the difference between the estimated load torque (Ta) and the second torque limit value (T2a) reaches a predetermined margin value (Tb), it reduces the current value supplied to the motor (M1) to less than the current value in the case of the second torque limit value (T2a). A work vehicle according to claim 2, comprising:

5. A second motor (M2) is installed separately from the aforementioned motor (M1) and drives the running gear (11, 12) of the vehicle body (10), The control unit (200) controls the travel speed of the second motor (M2) according to the workload of the work machine (5) based on the work performed by the work machine (5), A work vehicle according to claim 4, comprising:

6. When the work load of the work machine (5) changes from a heavy load to a light load based on the work content of the work machine (5), the control unit (200) prioritizes restoring the travel speed of the second motor (M2) over supplying current to the motor (M1). A work vehicle according to claim 5, comprising:

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