JP7808972B2 - electric work vehicle - Google Patents

Description

This invention is a battery-powered electric work vehicle whose running power is provided by a motor driven by electricity supplied from a battery.

Patent Document 1 discloses an electric work vehicle that uses a motor instead of an engine as a power source. The transmission is equipped with a continuously variable transmission called an HMT (Hydraulic Mechanical Transmission), and a transmission consisting of a clutch and a gear-type transmission mechanism.

Patent Document 2 discloses a battery-powered electric work vehicle equipped with a work implement, a battery, a motor driven by power supplied from the battery, a transmission, and a traveling device (front and rear wheels). The transmission is equipped with a continuously variable transmission called an HST (Hydraulic Static Transmission), which changes the speed of the driving force received from the motor and transmits it to the left and right rear wheels. The motor basically rotates at a constant speed, and changing the swash plate angle of the HST changes the rotational speed of the rear wheels, and therefore the vehicle speed. As a result, a transmission mechanism using a clutch can be omitted.

JP 2013-141955 A Japanese Patent Application Laid-Open No. 2021-104768

With the aim of achieving a carbon-neutral society in which greenhouse gas emissions are reduced to zero overall, electric work vehicles that use electric motors instead of engines as their power source, as shown in Patent Document 1 and Patent Document 2, have been attracting attention in recent years. Unlike engines, electric motors have the advantage of maintaining constant torque across most of the rotational range, allowing them to output stable rotational power from low to high speeds.

However, most drivers of electric work vehicles are accustomed to driving engine-powered work vehicles, which use an engine as the power source and change gears by operating a clutch. For this reason, with electric work vehicles such as those described above, the vehicle's behavior when operating the clutch or changing gears is different from that of engine-powered work vehicles, causing a sense of discomfort. To address this discomfort for drivers who find it bothersome, there is a demand for an electric work vehicle that allows them to experience driving conditions similar to those of an engine-powered work vehicle equipped with a conventional gear change mechanism when changing the power output from the transmission.

An electric work vehicle according to the present invention comprises an electric motor, a traveling device, a transmission that transmits power from the electric motor to a work device via the traveling device and a PTO shaft , a control unit that controls the behavior of the electric motor, and a manual operating tool that issues a change command to the control unit to request a change in output power from the transmission to the PTO shaft ,
The control unit controls the electric motor based on the change command, through a simulated operation of the electric motor, so as to give the driver a sense of the behavior of the vehicle body during a change operation in an engine-powered working vehicle.

With this configuration, when the driver operates the manual operating device that issues a change command to the control unit to change the output power from the transmission (such as slowing down, increasing speed, or switching the PTO on or off), the electric motor behaves in a manner that mimics the behavior of an engine-powered work vehicle when such a change is made. Whether this manual operating device is a dummy operating device that does not directly change the output power from the transmission, or a real operating device that actually changes the output power from the transmission, by operating this manual operating device, the driver can experience driving and working conditions similar to those of an engine-powered work vehicle equipped with a conventional transmission mechanism when making changes.

Even in an electric work vehicle not equipped with a clutch-based transmission mechanism, it is possible to simulate the vehicle body behavior experienced when changing transmission output power through clutch operation in an engine-powered work vehicle equipped with a conventional clutch transmission mechanism by operating a pseudo-clutch operating device. In this case, if the change operating device for changing the transmission output power also functions as a pseudo-clutch operating device, there is no need to physically provide a pseudo-clutch operating device, which is convenient. Therefore, in one preferred embodiment of the present invention, the manual operating device is a change operating device for changing the transmission output power, and the change operating device also functions as a pseudo-clutch operating device. The change command issued by the change operating device also includes a pseudo-clutch operating command, and the control unit controls the electric motor based on the change command and the pseudo-clutch operating command. In this configuration, for example, when the driver operates the change operating device to change the vehicle speed, a pseudo-clutch operating command is given to the control unit along with a gear change command as a change command. The control unit performs gear shift control based on the gear shift command, and also controls the electric motor based on the pseudo clutch operation command to simulate the vehicle body behavior that occurs during clutch gear shifting (gear shifting involving clutch operation) in an engine-powered work vehicle equipped with a clutch gear shifting mechanism. In some cases, the change operation tool and pseudo clutch operation tool may be provided separately.

In an engine-powered work vehicle equipped with a conventional clutch transmission mechanism, the vehicle body behavior experienced during clutch shifting varies from person to person, and preferred behavior also varies from person to person. For this reason, it is preferable to provide multiple simulated behavior modes that create simulated vehicle body behavior (electric motor behavior) based on a pseudo-clutch operation command, and select one based on the driver's preference and driving conditions. Of course, it is also preferable to be able to select a mode that does not simulate vehicle body behavior based on a pseudo-clutch operation command. For this reason, in one preferred embodiment of the present invention, the control unit is provided with multiple different simulated behavior modes for simulating the behavior of the electric motor based on the change command.

Some electric work vehicles use a motor instead of an engine as a power source, but the transmission is equipped with a transmission consisting of a conventional clutch and gear-type speed change mechanism. Applying the present invention to such electric work vehicles will also achieve the above-described effects. Therefore, in one preferred embodiment of the present invention, the manual operating device includes a speed change device that operates a speed change mechanism equipped in the transmission, the change command from the speed change device is a speed change command, and the control unit controls the electric motor based on the speed change command and sends a control signal to the actuator of the speed change mechanism. Furthermore, in another preferred embodiment of the present invention, the manual operating device includes a clutch operating device that operates a clutch equipped in the transmission, the change command from the clutch operating device is a clutch operation command, and the control unit controls the electric motor based on the clutch operation command and sends a control signal to the actuator of the clutch.

Furthermore, many of the work devices attached to work vehicles are driven by power (PTO power) branched off from the transmission, and are equipped with a PTO clutch that switches this PTO power transmission on and off. In engine-powered work vehicles, operating the PTO clutch causes a momentary load fluctuation in the engine, so the driver often feels the vehicle behavior and performs the appropriate work based on that. Therefore, even when operating such a PTO clutch, vehicle behavior familiar to engine-powered work vehicles is required. For this reason, in one preferred embodiment of the present invention, the manual operation device includes a PTO clutch operation device that operates the PTO clutch equipped on the transmission, and the control unit controls the electric motor and sends a control signal to the PTO clutch actuator based on the change command from the PTO clutch operation device.

FIG. 2 is a left side view of the tractor. FIG. 2 is a left side view showing the arrangement of an inverter and the like. FIG. 2 is a diagram illustrating a flow of power transmission. FIG. 2 is a diagram illustrating a configuration of a transmission. FIG. 2 is a functional block diagram showing a configuration related to an operation control system. FIG. 2 is a functional block diagram showing a configuration related to a pseudo clutch control system.

The following description will explain the embodiments of the present invention with reference to the drawings. In the following description, unless otherwise specified, the direction of arrow F in the drawings will be referred to as "front," the direction of arrow B as "rear," the direction of arrow L as "left," and the direction of arrow R as "right." Furthermore, the direction of arrow U in the drawings will be referred to as "up," and the direction of arrow D as "down."

[Overall configuration of the tractor]
As shown in Fig. 1, the tractor includes left and right front wheels 10, left and right rear wheels 11, and a cover member 12 as a traveling device.

The tractor also includes a machine frame 2 and a driving section 3. The machine frame 2 is supported by left and right front wheels 10 and left and right rear wheels 11.

The cover member 12 is located at the front of the aircraft. The driver's unit 3 is located behind the cover member 12. In other words, the cover member 12 is located in front of the driver's unit 3.

The driver's unit 3 has a protective frame 30, a driver's seat 31, and a steering wheel 32. The driver can sit in the driver's seat 31, allowing the driver to get into the driver's unit 3. The left and right front wheels 10 are steered by operating the steering wheel 32. The driver can perform various driving operations using the driver's unit 3.

The tractor is equipped with a battery 4, which is a traction battery. The cover member 12 is configured to be able to swing around an opening/closing axis Q that runs along the left-right direction of the vehicle body. This allows the cover member 12 to be opened and closed. When the cover member 12 is in the closed state, the battery 4 is covered by the cover member 12.

As shown in FIG. 2, the tractor is equipped with an inverter 14 and an electric motor (hereinafter simply referred to as the motor) M. The battery 4 supplies power to the inverter 14. The inverter 14 converts DC power from the battery 4 into AC power and supplies it to the motor M. The motor M is then driven by the AC power supplied from the inverter 14.

As shown in Figures 2 and 3, the tractor is equipped with a transmission 16 that transmits power from a motor M to the front wheels 10 and left and right rear wheels 11, which serve as the travel device. A hydrostatic continuously variable transmission (hereinafter referred to as HST 15) is located in the front stage of the transmission 16. The HST 15 has an HST pump 15a and an HST motor 15b. The HST pump 15a is driven by rotational power from the motor M. When the HST pump 15a is driven, rotational power is output from the HST motor 15b. The HST 15 is configured so that the rotational power between the HST pump 15a and the HST motor 15b can be changed forward and backward and continuously.

The rotational power output from the HST motor 15b is distributed to the left and right rear wheels 11 via a gear transmission mechanism 16A located in the middle of the transmission 16 and a rear wheel differential gear mechanism 16B located in the middle of the transmission 16. Because this tractor is a four-wheel drive type, the rotational power from the gear transmission mechanism 16A of the transmission 16 is distributed to the left and right front wheels 10 via the front wheel drive shaft 9 and the front wheel differential gear mechanism.

As shown in Figure 2, the tractor also has a mid-PTO shaft 17 and a rear PTO shaft 18. The rotational power output from the motor M is distributed in the transmission 16 to the HST pump 15a, mid-PTO shaft 17, and rear PTO shaft 18. This causes the mid-PTO shaft 17 and rear PTO shaft 18 to rotate.

The rotational power of the mid-PTO shaft 17 or rear PTO shaft 18 drives the working device attached to the mid-PTO shaft 17 or rear PTO shaft 18. For example, as shown in FIG. 2, in this embodiment, a brush cutting device 19 is connected to the mid-PTO shaft 17, and the brush cutting device 19 is driven by the rotational power of the mid-PTO shaft 17.

If a work implement is connected to the mid-PTO shaft 17 or rear PTO shaft 18, the work implement is driven by the rotational power of the mid-PTO shaft 17 or rear PTO shaft 18. For example, as shown in FIG. 2, in this embodiment, a brush cutter 19 is connected to the mid-PTO shaft 17. The brush cutter 19 is driven by the rotational power of the mid-PTO shaft 17. Also, although not shown, when plowing work is performed, a tiller is connected to the rear PTO shaft 18.

[Transmission structure]
4, the transmission 16 includes a gear transmission mechanism 16A, which is a speed change mechanism, a rear wheel differential gear mechanism 16B, and a PTO mechanism 16C. The PTO mechanism 16C includes a first shaft 21, a first gear mechanism 22, a second gear mechanism 23, a second shaft 24, a third gear mechanism 25, a first clutch 26, and a second clutch 27. The first clutch 26 and the second clutch 27 function as PTO clutches, and each of them is configured to be able to change its state between an ON state in which power is transmitted and a OFF state in which power is not transmitted.

The output shaft MA of the motor M is connected to the first shaft 21. The first shaft 21 is connected to the rotating shaft of the HST pump 15a. When the first clutch 26 is engaged, rotational power is transmitted from the first shaft 21 to the first gear mechanism 22. When the second clutch 27 is engaged, rotational power is transmitted from the first shaft 21 to the second shaft 24.

The rotational power transmitted to the first gear mechanism 22 is transmitted to the mid PTO shaft 17 via the second gear mechanism 23. The rotational power transmitted to the second shaft 24 is transmitted to the rear PTO shaft 18 via the third gear mechanism 25.

The rotational power transmitted to the HST pump 15a is hydraulically changed in the HST 15 and output from the HST motor 15b. The rotational power output from the HST motor 15b is transmitted to the gear transmission mechanism 16A via the third shaft 28. The rotational power transmitted to the gear transmission mechanism 16A is changed in speed by the gear transmission mechanism 16A and distributed to the front drive shaft 9 and the rear differential gear mechanism 16B. The left and right front wheels 10 are driven by the rotational power transmitted to the front drive shaft 9. The left and right rear wheels 11 are driven by the rotational power transmitted to the rear differential gear mechanism 16B.

[Operation control system]
As shown in Figure 5, this tractor is equipped with a control unit 5 that controls the behavior of the motor M and changes in the transmission state of the transmission 16, and manual operators 40 that issue change commands to the control unit 5 requesting changes in the output power from the transmission 16. The manual operators 40 include an accelerator operator 41, a work operator 43, and a travel operator 42. The manual operators 40 are not particularly limited, and may be, for example, levers or buttons. The manual operators 40 are provided, for example, in the driving section 3.

The control unit 5 has a motor control unit 51, a driving control unit 52, and an operation control unit 53.

When the accelerator operating device 41 is manually operated, a signal corresponding to that operation is sent to the motor control unit 51. The motor control unit 51 controls the inverter 14 based on that signal, thereby controlling the output rotation speed of the motor M. In other words, the motor control unit 51 controls the output rotation speed of the motor M in response to the manual operation of the accelerator operating device 41.

If the travel operating device 42 is a speed change device that adjusts the pump swash plate angle of the HST 15, when this speed change device is manually operated, a signal corresponding to that operation is sent to the travel control unit 52. The travel control unit 52 controls the pump swash plate angle of the HST pump 15a based on that signal. When the pump swash plate angle changes, the gear ratio in the HST 15 changes. In other words, the travel control unit 52 controls the gear state of the HST 15 in response to the manual operation of the travel operating device 42.

When the pump swash plate 58 is in the neutral position, the HST 15 is in a state where rotational power is not output from the HST motor 15b. The HST 15 outputs rotational power in the forward and reverse directions to the left and right front wheels 10 and the left and right rear wheels 11 according to the angle of the pump swash plate 58. In other words, the HST 15 is configured to be able to output rotational power in the forward and reverse directions to the left and right front wheels 10 and the left and right rear wheels 11 according to the manual operation of the travel operating device 42.

If the travel operating device 42 is a speed change operating device that switches between the high-speed and low-speed speed change sections of the gear transmission mechanism 16A, the speed change operating device of the gear transmission mechanism 16A is controlled in response to manual operation of the travel operating device 42. Note that a speed change operating device is a type of change operating device used to change the output power of the transmission 16.

When the work operating tool 43, which functions as a PTO clutch operating tool, is manually operated, a signal corresponding to that operation is sent to the work control unit 53. Based on that signal, the work control unit 53 sends control signals to the actuators of the first clutch 26 and the second clutch 27, controlling the on/off states of the first clutch 26 and the second clutch 27. In this way, the work control unit 53 switches the state of the mid PTO shaft 17 and the rear PTO shaft 18 between a rotating state and a non-rotating state.

[Pseudo clutch control]
6, the motor control unit 51 includes a pseudo-clutch behavior control unit 511 and a pseudo-behavior table 512. The pseudo-clutch behavior control unit 511 controls the motor M so that it behaves like a pseudo-clutch, based on a change command requesting a change in the output power from the transmission 16, in this case a change in the rotational speed, by the traveling operation device 42 and the work operation device 43, which are the manual operation device 40.

The pseudo-clutch behavior is the vehicle behavior of this tractor that is induced by controlling the motor M to simulate the vehicle behavior (acceleration/deceleration, etc.) that may occur in an engine-powered work vehicle during gear change operations when the travel operating device 42 changes gears on the HST 15 or the gear transmission mechanism 16A, or when the work operating device 43 switches power transmission to the PTO mechanism 16C. While gear changes in the HST 15 do not involve clutch operation, the simulated vehicle behavior that occurs during gear change operations that do not involve clutch operation is also considered pseudo-clutch behavior.

For example, if the travel operating device 42 is a gear change operating device that changes the gear position of the gear transmission mechanism 16A, this gear change operating device also functions as a pseudo-clutch operating device. In other words, the change command generated by operating this gear change operating device includes a gear change command and a pseudo-clutch operating command. Based on the gear change command, the travel control unit 52 of the control unit 5 drives the gear change actuator of the gear transmission mechanism 16A to change the gear position of the gear transmission mechanism 16A to the desired gear position. At the same time, the pseudo-clutch behavior control unit 511 of the control unit 5 controls the motor M to simulate the vehicle body behavior that may occur during gear change operations in an engine-powered work vehicle.

Furthermore, if the work operating device 43 is a PTO switching device that switches power transmission for the PTO mechanism 16C using the first clutch 26 or the second clutch 27, this PTO switching device also functions as a pseudo-clutch operating device. In other words, the change command generated by operating this PTO switching device includes a switching command and a pseudo-clutch operating command. Based on the switching command, the travel control unit 52 of the control unit 5 drives the clutch actuator of the first clutch 26 or the second clutch 27 of the PTO mechanism 16C to create the desired transmission of rotational power from the PTO mechanism 16C. At the same time, the pseudo-clutch behavior control unit 511 of the control unit 5 controls the motor M to simulate the vehicle behavior that may occur in an engine-powered work vehicle when power transmission is changed in the PTO mechanism 16C.

When an engine control program that causes motor M to behave in a manner that simulates these vehicle characteristics is created as a simulated behavior mode, the vehicle body behavior that occurs when an operation that changes the power output of the transmission 16 is performed on an engine-powered work vehicle is first experimentally determined. An engine control program that causes motor M to behave in a manner that produces the vehicle body behavior determined here is then created as a simulated behavior mode.

The vehicle behavior that occurs when power transmission is changed in the PTO mechanism 16C varies depending on the type of work device to which rotational power is transmitted by the PTO mechanism 16C. Different vehicle behaviors also occur depending on the gear position switched in the gear transmission mechanism 16A. Furthermore, the preferred vehicle behavior simulated by the motor M and experienced by the driver varies depending on the driver. For this reason, the simulated behavior table 512 stores multiple different simulated behavior modes for simulating the behavior of the electric motor. The simulated clutch behavior control unit 511 selects an appropriate simulated behavior mode based on rules preset in accordance with the driver's operation, and controls the simulated behavior of the motor M based on the selected simulated behavior mode. The simulated behavior table 512 is not necessary when there is only one simulated behavior mode to simplify the configuration, or when a configuration is adopted in which different simulated behavior modes are created by changing parameters within a single simulated behavior mode.

[Another embodiment]
(1) In the above-described embodiment, the HST 15 is provided as a continuously variable transmission in the transmission 16, but the present invention is not limited to this. Other belt-type continuously variable transmissions or planetary gear-type continuously variable transmissions may be used. Furthermore, the continuously variable transmission may be omitted, and the transmission 16 may be configured solely with a gear-type stepped device.

(2) In the above-described embodiment, the manual operating device 40 was connected to the control unit 5 using a by-wire system, but it may also be connected to the object of operation via a mechanical link. Even in this case, for manual operating devices 40 that require the motor M to simulate the behavior of the operating device during a change operation, a signal indicating the operation content is sent to the control unit 5.

The configurations disclosed in the above-described embodiments (including other embodiments, the same applies hereinafter) can be applied in combination with configurations disclosed in other embodiments, provided no contradictions arise. Furthermore, the embodiments disclosed in this specification are merely examples, and the present invention is not limited to these embodiments. They can be modified as appropriate within the scope of the purpose of the present invention.

This invention can be used not only in tractors, but also in various electric work vehicles such as combine harvesters, rice transplanters, and construction machines.

4: Battery 14: Inverter 16: Transmission 16A: Gear transmission mechanism 16C: PTO mechanism 19: Grass cutting device 40: Manual operation device 41: Accelerator operation device 42: Travel operation device 43: Work operation device 5: Control unit 51: Motor control unit 511: Pseudo clutch behavior control unit 512: Pseudo behavior table

Claims (5)

An electric motor;
Running gear and
a transmission that transmits power from the electric motor to the working device via the traveling device and the PTO shaft ;
a control unit for controlling the behavior of the electric motor;
a manual operating tool that issues a change command to the control unit to change the output power from the transmission to the PTO shaft ,
The control unit controls the electric motor based on the change command, through a simulated operation of the electric motor, to give the driver a sense of the behavior of the vehicle body during a change operation in an engine-powered work vehicle. 2. The electric work vehicle according to claim 1, wherein the manual operating device is a change operating device for changing the output power of the transmission, the change operating device also functions as a pseudo- command operating device, the change command by the change operating device also includes a pseudo- operation command, and the control unit controls the electric motor based on the change command and the pseudo-operation command. An electric work vehicle as described in claim 1 or 2, wherein the control unit is provided with a plurality of different simulated behavior modes for simulating the behavior of the electric motor based on the change command. 4. The electric work vehicle according to claim 1, wherein the manual operation device includes a speed change device that switches between a high-speed and low-speed stage shifting section of a gear transmission mechanism equipped in the transmission, the change command by the speed change device is a speed change command , and the control unit controls the electric motor based on the speed change command through a simulated operation of the electric motor so as to give the driver an impression of the behavior of the vehicle body during a speed change operation in an engine-powered work vehicle, and sends a control signal to a speed change actuator of the speed change mechanism. 5. The electric work vehicle according to claim 1, wherein the manual operation device includes a PTO clutch operation device that operates a PTO clutch equipped on the transmission, and the control unit controls the electric motor based on the change command from the PTO clutch operation device , through a simulated operation of the electric motor, so as to give the driver an impression of the behavior of the vehicle body during a change operation in an engine-powered work vehicle, and sends a control signal to an actuator of the PTO clutch.