Method for controlling work vehicles, control program for work vehicles, control system for work vehicles, and work system

Abstract

The present invention provides a control method for work vehicles, a control program for work vehicles, a control system for work vehicles, and a work system that can improve the operability when an operator adjusts the vehicle speed. [Solution] The control method for a work vehicle comprises a running gear, a sub-transmission, and an accelerator control unit. The running gear travels at a vehicle speed that changes according to the rotational speed and gear ratio of the prime mover. The sub-transmission can switch the speed range of the running gear. The accelerator control unit accepts operations to adjust the vehicle speed G3. When the accelerator control unit is operated while the speed range is in a specific range, the control method performs a first control in which only the rotational speed G1 is changed among the rotational speed G1 and gear ratio G2 in a first specific section from the first vehicle speed (first value V1) to the first intermediate vehicle speed (first intermediate value V11) within the vehicle speed range when accelerating and decelerating the running gear from the first vehicle speed (first value V1) to the second vehicle speed (second value V2).

Description

Technical Field

[0005] ,

[0001] The present invention relates to a control method for a work vehicle related to the travel control of a work vehicle, a control program for a work vehicle, a control system for a work vehicle, and a work system.

Background Art

[0002] As related art, for example, in on-road travel such as towing or transporting work equipment, work vehicles such as tractors that can travel relatively fast are known (see, for example, Patent Document 1). A work vehicle according to the related art includes a transmission (hydraulic continuously variable transmission) that changes the power from a prime mover (engine) mounted on a traveling body, a sub-transmission mechanism that transmits the variable speed drive output from the transmission, and a shift pedal that changes the transmission ratio of the transmission.

[0003] A control system for a work vehicle according to the related art (a control system for a work vehicle) includes engine control means for maintaining the rotational speed of the prime mover at the rotational speed set by a throttle lever, and travel control means for controlling the rotational speed of the prime mover and the transmission ratio of the transmission based on the depression amount of the shift pedal. Thereby, while performing an operation of changing the rotational speed of the prime mover and an operation of changing the vehicle speed of the vehicle body with a simple operation such as a shift pedal, the travel operation of the work vehicle is approximated to the travel operation in an automobile with a continuously variable transmission mechanism, thereby reducing the operator's fatigue etc.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0006] The object of the present invention is to provide a control method for a work vehicle, a control program for a work vehicle, a control system for a work vehicle, and a work system that can improve the operability when an operator adjusts the vehicle speed. [Means for solving the problem]

[0007] A control method for a work vehicle according to one aspect of the present invention is a control method for a work vehicle comprising a running gear, a sub-transmission, and an accelerator operating unit. The running gear travels at a vehicle speed that changes according to the rotational speed and gear ratio of the prime mover. The sub-transmission is capable of switching the speed range of the running gear. The accelerator operating unit accepts operations for adjusting the vehicle speed. When the accelerator operating unit is operated while the speed range is in a specific range, the control method performs a first control in which, in a first specific section from the first vehicle speed to the first intermediate vehicle speed within the vehicle speed range when accelerating and decelerating the running gear from the first vehicle speed to the second vehicle speed, only the rotational speed is changed among the rotational speed and the gear ratio.

[0008] A control program for a work vehicle according to one aspect of the present invention is a program that causes one or more processors to execute a control method for the work vehicle.

[0009] A control system for a work vehicle according to one aspect of the present invention is used in a work vehicle comprising a running gear, a sub-transmission, and an accelerator operating unit, and further comprises a running control unit. The running gear travels at a vehicle speed that changes according to the rotational speed and gear ratio of the prime mover. The sub-transmission is capable of switching the speed range of the running gear. The accelerator operating unit receives an operation to adjust the vehicle speed. When the accelerator operating unit is operated while the speed range is in a specific range, the running control unit performs a first control in which only the rotational speed is changed among the rotational speed and gear ratio in a first specific section from the first vehicle speed to the first intermediate vehicle speed within the vehicle speed range when accelerating and decelerating the running gear from a first vehicle speed to a second vehicle speed.

[0010] A work system according to one aspect of the present invention comprises a control system for a work vehicle and the body of the work vehicle. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a control method for a work vehicle, a control program for a work vehicle, a control system for a work vehicle, and a work system that can improve the operability when an operator adjusts the vehicle speed. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a schematic side view showing the external appearance of a work vehicle according to Embodiment 1. [Figure 2] Figure 2 is a schematic block diagram of the work system according to Embodiment 1. [Figure 3] Figure 3 is an explanatory diagram showing an overview of the first and second controls of the work vehicle control system according to Embodiment 1. [Figure 4] Figure 4 shows an example of the first control during acceleration of the running gear by the control system for a work vehicle according to Embodiment 1. [Figure 5] Figure 5 shows an example of the first control during deceleration of the travel device by the control system for work vehicles according to Embodiment 1. [Figure 6]Figure 6 shows an example of the second control during acceleration of the running gear by the control system for work vehicles according to Embodiment 1. [Modes for carrying out the invention]

[0013] The embodiments of the present invention will be described below with reference to the attached drawings. The following embodiments are examples that embody the present invention and are not intended to limit the technical scope of the present invention.

[0014] (Embodiment 1) [1] Overall structure First, the overall configuration of the work system 100 according to this embodiment will be described with reference to Figures 1 and 2. The control system 2 for the work vehicle according to this embodiment (hereinafter also simply referred to as "control system 2") constitutes the work system 100 together with the body 11 of the work vehicle 10. A work machine 12 is mounted on the body 11. In other words, the work system 100 comprises the control system 2 for the work vehicle and the body 11 of the work vehicle 10.

[0015] In this embodiment, the control system 2 is mounted on the body 11 of the work vehicle 10. In other words, the work vehicle 10 has a body 11. The body 11 is configured to be able to be fitted with a work implement 12. In Figure 1, the schematic outline of the work implement 12 is shown by dashed lines.

[0016] In this embodiment, for the sake of explanation, the vertical direction when the work vehicle 10 is in a usable state is defined as the up-down direction D1. The forward-backward direction D2 and left-right direction D3 are defined based on the direction as seen from the operator (driver) sitting in the machine body 11 (driver's unit 5) of the work vehicle 10. The left side of the left-right direction D3 refers to the left side when the machine body 11 is traveling forward (moving forward), and the right side of the left-right direction D3 refers to the right side when the machine body 11 is traveling forward (moving forward). However, these directions are not intended to limit the direction of use (direction during use) of the work vehicle 10.

[0017] The work vehicle 10 moves within the target area F1 (see FIG. 1) and performs some work within the target area F1 by means of the work implement 12. The "work" referred to in the present disclosure is the work performed by the work implement 12 on the target area F1, and includes, for example, various agricultural operations such as tilling, leveling, seeding, fertilizing, pesticide spraying, planting (paddy field planting) or harvesting, as well as various operations such as construction work. In this embodiment, as an example, the work performed by the work vehicle 10 shall be tilling work.

[0018] The work implement 12 performs work within the target area F1 when the body 11 of the work vehicle 10 moves within the target area F1. In this embodiment, as an example, the work implement 12 shall be a tilling machine such as a rotary tiller or a plow that performs tilling work.

[0019] This type of work implement 12 includes a directly mounted work implement directly attached to the three-point hitch, and a trailed work implement towed by the body 11. In this embodiment, as an example, the work implement 12 is a directly mounted rotary tiller that is removably attached to the body 11 of the work vehicle 10. Here, the work implement 12 is attached to the rear side of the body 11 (the side opposite to the forward direction of the body 11). That is, the (directly mounted) work implement 12 is connected to the rear side of the body 11 and performs work while moving forward together with the body 11 when the body 11 moves forward. In this embodiment, the work implement 12 is included in the components of the work vehicle 10, but since the work implement 12 is removable from the body 11, it may not be included in the components of the work vehicle 10.

[0020] As used in this disclosure, the "work vehicle" refers to a vehicle that performs various operations in a target area F1 such as a farm field. As an example, it is an agricultural machine (agricultural implement) such as a tractor, seeder, rice transplanter, spreader, sprayer, transplanter, and harvester. The work vehicle 10 may be, for example, a construction machine (construction implement). In this embodiment, unless otherwise specified, the case where the work vehicle 10 is a tractor equipped with a rotary tiller as the working implement 12 will be described as an example. That is, the work vehicle 10 is constituted by connecting a (direct-mounted) rotary tiller as the working implement 12 to a tractor as the vehicle body 11. In this work vehicle 10, by driving the vehicle body 11 in a target area F1 such as a farm field, tilling work in the target area F1 becomes possible.

[0021] As described above, in this embodiment, the vehicle body 11 is a kind of vehicle that moves by traveling in the target area F1. Here, the vehicle body 11 includes a pair of left and right front wheels 111 as steering wheels, and a pair of left and right rear wheels 112 as drive wheels, and travels in the target area F1 with these four wheels (a pair of front wheels 111 and a pair of rear wheels 112).

[0022] As used in this disclosure, the "target area" is an area where various operations such as tilling, leveling, seeding, fertilizing, pesticide spraying, planting (rice transplanting), or harvesting are performed while the work vehicle 10 moves, and includes paddy fields, fields, orchards, and pastures. For example, when a paddy field or field where crops (agricultural products) such as rice, wheat, soybeans, or buckwheat are grown is the target area F1, the crops grown in the target area F1 are agricultural products. Further, when trees are grown in a nursery, the nursery becomes the target area F1, and when trees that become timber are grown in a forest as in forestry, the forest becomes the target area F1. In this case, the crops grown in the target area F1 are trees or the like. In this embodiment, unless otherwise specified, the work vehicle 10 is used for tilling work in a farm field (target area F1), and the case where the target area F1 is a paddy field for growing rice will be described as an example. Also, the target area F1 is not limited to a farm field. For example, if the work vehicle 10 is a construction machine, the site where the construction machine performs work becomes the target area F1.

[0023] Furthermore, the work vehicle 10 can travel not only within the target area F1 (in this case, the field) but also on roads outside the target area F1, such as off-field routes. Off-field routes are, for example, inter-field connecting roads that connect multiple target areas F1 (fields). Inter-field connecting roads may be farm roads, forest roads, public roads, private roads, or expressways, and may be roads exclusively for the work vehicle 10 or roads that are accessible to general vehicles (passenger cars, etc.).

[0024] In the work vehicle 10 according to this embodiment, the machine body 11 has a driver's compartment 5 for the operator (driver) to sit in. In addition to the driver's seat in the driver's compartment 5, the driver's compartment 5 is equipped with an operating device 15 (see Figure 2) operated by the operator. The operating device 15 includes, for example, a steering wheel, an operating lever, and an operating pedal. The work vehicle 10 is configured to be manually driven by the operator manually operating the operating device 15. Therefore, the work vehicle 10 performs work while driving through the target area F1 by the operator sitting in the driver's seat (manual driving).

[0025] The types of driver's units 5 for the work vehicle 10 include cabin type, canopy type, and lops type. The cabin type driver's unit 5 is equipped with a cabin 50, and the driver's seat is located in the interior space of the cabin 50. The canopy type driver's unit 5 is equipped with a canopy (roof), and the driver's seat is located in the space below the canopy. The lops type driver's unit 5 is not equipped with a cabin 50 or canopy, and the driver's seat is located in an open space above. In this embodiment, the case in which the driver's unit 5 is equipped with a cabin type is described as an example.

[0026] However, the work vehicle 10 is not limited to being driven by a manual operator seated in the driver's unit 5 (manual driving), but may also be capable of operating by automatic driving (autonomous driving, etc.). Furthermore, the work vehicle 10 may be an unmanned vehicle that drives automatically, or it may be operated by remote control of an operator.

[0027] In this disclosure, "autonomous driving" includes "autonomous driving," in which the work vehicle 10 drives autonomously without operator intervention, and "semi-autonomous driving," in which only steering is automated, such as in straight-line assist. "Autonomous driving" is a driving mode in which, for example, the front wheels 111 are automatically steered and vehicle speed and other controls are also automatically performed so that the work vehicle 10 drives along a target path. "Straight-line assist" is a driving mode in which, for example, the front wheels 111 are automatically steered, and vehicle speed and other controls are performed by the operator, so that the work vehicle 10 drives along a straight path parallel to a reference straight line (reference line).

[0028] In other words, "semi-autonomous driving" means that the work vehicle 10 cannot move without operator intervention, but the burden of steering is reduced for the operator, and it is possible to drive along a target path such as a straight line, leading to improved work efficiency. Furthermore, in both autonomous driving and semi-autonomous driving, the front wheels 111 are automatically steered, so it can be said to be a form of "automatic steering mode". In automatic steering mode, the front wheels 111 are automatically steered by an automatic steering mechanism including a steering motor. That is, instead of the operator operating the steering wheel, automatic steering is achieved by changing the direction of the front wheels 111 with the output of the steering motor.

[0029] In addition to the driver's unit 5 and the body 11 having four wheels (front wheels 111 and rear wheels 112), the work vehicle 10 is equipped with a running gear 13, steering gear 14, operating gear 15, display device 16, and prime mover 17, as shown in Figure 2.

[0030] A work implement coupling section, consisting of a three-point linkage mechanism, is provided at the rear of the machine body 11. A work implement 12 can be attached to the work implement coupling section. Power generated by the prime mover 17 can be transmitted to the towed work implement 12 via a transmission and a power take-off shaft (PTO shaft) located at the rear of the machine body 11. Here, since the work implement 12 is detachably connected to the work implement coupling section, it is also possible to connect a device other than the work implement 12 to the machine body 11.

[0031] In this embodiment, the implement 12 is a directly mounted rotary tiller, so tilling can be performed on the field, which is the target area F1, when the machine body 11 is moving forward. The implement 12 has a variable relative position (relative height) in the vertical direction D1 with respect to the machine body 11. As a result, the height of the implement 12 is variable when the field surface, which is the ground surface of the target area F1, is used as a reference. For example, by raising the implement 12 to a height away from the ground surface of the target area F1, the work vehicle 10 can also travel in a non-working state without performing work with the implement 12.

[0032] As shown in Figure 2, the running gear 13 includes a transmission 131, a sub-transmission 132, and a brake mechanism 133. The running gear 13 transmits power from the prime mover 17 to the rear wheels 112 (a pair of left and right drive wheels), and drives the rear wheels 112 to move the work vehicle 10 forward or backward. Specifically, the running gear 13 outputs power from the prime mover 17 to the rear wheels 112 via the transmission 131 and the sub-transmission 132. In this embodiment, the rear wheels 112 are ordinary wheels, but it is not limited to this, and for example, the rear wheels 112 may be crawler type machines 11 with crawler tracks.

[0033] The transmission 131 is the main transmission of the running gear 13, and is a device that changes the output of the prime mover 17 at an arbitrary gear ratio. The gear ratio of the transmission 131 is variable (changeable). In this disclosure, the "gear ratio" of the transmission 131 means the ratio of the rotational speed of the output shaft of the transmission 131 to the rotational speed of the output shaft of the prime mover 17.

[0034] The transmission 131 may employ, for example, a hydrostatic continuously variable transmission (HST) or an integrated hydrostatic mechanical transmission (I-HMT). Alternatively, the transmission 131 may employ a continuously variable transmission such as an HMT (Hydraulic Mechanical Transmission), which is an example of a hydraulic mechanical continuously variable transmission, or a belt-type continuously variable transmission. Furthermore, instead of a continuously variable transmission, an electronically controlled stepped transmission having multiple hydraulic transmission clutches and multiple electromagnetic transmission valves that control the flow of oil to them may be used as the transmission 131.

[0035] The auxiliary transmission 132 is a device that can switch the speed range of the running gear 13 between multiple speed ranges. The auxiliary transmission 132 is located after the transmission 131 and further shifts the output of the transmission 131 to an arbitrary speed range and outputs it to the left and right pair of rear wheels 112. In this embodiment, as an example, the auxiliary transmission 132 is a gear-type transmission and selects one of three speed ranges, "C," "1st," and "2nd," according to the operation of the auxiliary transmission lever 152 (see Figure 2).

[0036] Each time the speed range of the sub-transmission 132 switches from "C" to "1st gear" and then from "1st gear" to "2nd gear" in response to the operation of the sub-transmission lever 152, the speed range of the running gear 13 increases (becomes faster). The low-speed stages "C" and "1st gear" are used for tasks such as tilling, and "2nd gear" is not used for work. Here, "C" means a "very low speed stage" that is even slower than "1st gear," and is called "C" after the initial letter (C) of "Creep."

[0037] With the above configuration, the vehicle speed of the running gear 13 (vehicle speed of the work vehicle 10) is determined by the rotational speed of the prime mover 17, the gear ratio of the transmission 131, and the speed range of the auxiliary transmission 132. For example, if the rotational speed of the prime mover 17 and the speed range of the auxiliary transmission 132 are constant, and the gear ratio of the transmission 131 becomes high (high speed), the vehicle speed will be high. Also, if the gear ratio of the transmission 131 and the speed range of the auxiliary transmission 132 are constant, and the rotational speed of the prime mover 17 becomes low (low speed), the vehicle speed will be low.

[0038] Furthermore, the work vehicle 10 is equipped with a transmission case that houses the transmission 131 and the auxiliary transmission 132, etc. The transmission case is located below the driver's compartment 5 (cabin 50).

[0039] The brake mechanism 133 slows down or stops the machine 11. The brake mechanism 133 applies brakes to a pair of braking wheels (rear wheels 112) through two systems: operation of a braking operation unit 153 (see Figure 2), such as a brake pedal, and automatic control. In other words, the brake mechanism 133 slows down or stops the machine 11 while it is moving by braking the rear wheels 112, which are a pair of braking wheels.

[0040] An example of automatic control of the brake mechanism 133 is an "auto brake" that applies a braking action to the inner rear wheel 112 when the steering angle exceeds a predetermined angle. With such an auto brake, the work vehicle 10 can keep the turning radius small, making it easier to perform tight turns such as a U-turn (for example, changing direction at the headland of the target area F1).

[0041] The steering device 14 is a device that steers the front wheels 111 (a pair of left and right steering wheels). The steering device 14 steers the front wheels 111 in response to the operator's operation of the steering wheel included in the control device 15. The pair of front wheels 111 have a reference posture in a plan view where they are facing in the front-rear direction D2, that is, a posture where the axis of rotation is aligned with the left-right direction D3, and the steering device 14 steers them so that they tilt to the left or right from the reference posture. In other words, the steering device 14 steers the front wheels 111 by changing the direction of the pair of front wheels 111. In this embodiment, the operator operates the steering wheel when manually steering, but this is not the only method; for example, the operator may operate an operating lever or the like to perform manual steering.

[0042] With the running gear 13 and steering gear 14, the aircraft 11 can move within the target area F1 in the longitudinal direction D2 and the lateral direction D3. For example, when the aircraft 11 is moving forward due to the rear wheels 112 being driven by the running gear 13, if the angle of the front wheels 111 is changed by the steering gear 14, the aircraft 11 will turn in the lateral direction D3, changing the direction of travel of the aircraft 11.

[0043] As shown in Figure 2, the operating device 15 includes an accelerator operating unit 151, a sub-transmission lever 152, and a brake operating unit 153. The operating device 15 is located in the driver's unit 5 and receives input from the operator.

[0044] The accelerator control unit 151 receives input for adjusting the vehicle speed of the running gear 13. The accelerator control unit 151 basically receives input for adjusting the rotational speed of the prime mover 17. The accelerator control unit 151 is, for example, an operating pedal (accelerator pedal) located at the operator's feet. The vehicle speed of the running gear 13 (rotational speed of the prime mover 17) is adjusted according to the amount of input (depression) of the accelerator control unit 151, and basically, the larger the input of the accelerator control unit 151, the faster the vehicle speed of the running gear 13 (rotational speed of the prime mover 17).

[0045] The auxiliary transmission lever 152 accepts operations to switch the speed range of the auxiliary transmission 132. The auxiliary transmission lever 152 is, for example, an operating lever located within the operator's reach. The speed range of the running gear 13 ("C gear", "1st gear", or "2nd gear") is determined according to the position of the auxiliary transmission lever 152.

[0046] The braking control unit 153 accepts operations to activate the brake mechanism 133 and decelerate (or stop) the work vehicle 10 while it is in motion. The braking control unit 153 is, for example, an operating pedal (brake pedal) located at the operator's feet. The effectiveness (braking force) of the brake mechanism 133 is adjusted according to the amount of operation (amount of depression) of the braking control unit 153, and basically, the greater the amount of operation of the braking control unit 153, the greater the braking force of the running gear 13.

[0047] In addition, the operating device 15 may include levers, pedals, switches, etc., that are operated by the operator.

[0048] The display device 16 is located in the control unit 5 and is a user interface for presenting information to the operator, such as a liquid crystal display or an organic EL display that displays various types of information. The display device 16 presents various types of information to the operator through display. Furthermore, the display device 16 accepts various operations from the operator by outputting electrical signals corresponding to the operator's operations, for example. This allows the operator to view the display screen shown on the display device 16 and operate the display device 16 as needed.

[0049] The prime mover 17 is a power source that supplies power to at least the running gear 13. The prime mover 17 is located at the front of the machine body 11, covered by a bonnet 114 (see Figure 1). The prime mover 17 is the drive source for the work vehicle 10, and is, for example, a diesel engine. However, the prime mover 17 of the work vehicle 10 is not limited to a diesel engine, but may be an engine such as a gasoline engine, an electric motor, or a hybrid system of an engine and an electric motor.

[0050] Furthermore, the prime mover 17 drives the hydraulic pump by supplying power not only to the running gear 13 but also to the hydraulic pump. The hydraulic pump supplies hydraulic fluid to various hydraulic devices (hydraulic cylinders, hydraulic clutches, etc.) to operate the hydraulic systems.

[0051] The control system 2 controls various parts of the work vehicle 10. The control system 2 is configured to communicate with devices installed on various parts of the machine body 11. Here, the control system 2 may exchange various types of information (data) directly with each device, or it may do so indirectly via a relay or the like.

[0052] The control system 2 primarily consists of a computer system having one or more processors such as a CPU (Central Processing Unit) and one or more memories such as ROM (Read Only Memory) and RAM (Random Access Memory), and performs various processes (information processing). In this embodiment, the control system 2 is an integrated controller that controls the entire work vehicle 10, and consists of, for example, an electronic control unit (ECU). However, the control system 2 may be provided separately from the integrated controller.

[0053] In addition to the above-described configuration, the work vehicle 10 is further equipped with a battery, fuel tank, and various sensors. The battery supplies power to various parts of the work vehicle 10, such as the control system 2.

[0054] [2] Control system configuration Next, the configuration of the control system 2 according to this embodiment will be described in detail with reference to Figure 2.

[0055] In this embodiment, the control system 2, as shown in Figure 2, includes a driving control unit 21, a steering control unit 22, a work control unit 23, and a storage unit 24.

[0056] The travel control unit 21 controls the prime mover 17 and the travel gear 13. The travel control unit 21 adjusts at least the rotational speed of the prime mover 17, as well as the gear ratio (of the transmission 131) and the speed range (of the sub-transmission 132) in the travel gear 13. This allows the travel control unit 21 to adjust the speed of the work vehicle 10 (travel gear 13). The travel control unit 21 can also control the brake mechanism 133 of the travel gear 13 to decelerate or stop the machine 11 while it is in motion.

[0057] The steering control unit 22 controls the steering device 14. The steering control unit 22 has two operating modes: an automatic steering mode and a manual steering mode, and is configured to be switchable between the automatic steering mode and the manual steering mode. The manual steering mode is a mode in which the operator performs steering by operating the steering wheel. At least during autonomous driving or semi-autonomous driving, the steering control unit 22 operates in automatic steering mode and controls the steering device 14 to bring the steering angle of the steering wheels 111 closer to the target steering angle, on behalf of the operator.

[0058] The work control unit 23 controls the work machine 12. At least during autonomous driving, the work control unit 23 controls the work machine 12 based on the current position of the vehicle 11 on the target path. Specifically, if the work vehicle 10 is traveling along a work path on the target path in which work is to be performed by the work machine 12, the work control unit 23 sets the work machine 12 to the work position and performs work with the work machine 12. On the other hand, if the work vehicle 10 is traveling along a non-work path on the target path in which work is not to be performed by the work machine 12, the work control unit 23 raises the work machine 12 to the non-work position and stops work with the work machine 12.

[0059] The memory unit 24 is a non-volatile memory that stores various data such as control programs for the work machine and target path information related to the target route. In other words, the driving control unit 21 and the steering control unit 22 can, for example, perform autonomous driving along the target route based on the target route information stored in the memory unit 24.

[0060] [3] Control method for work vehicles The following describes an example of a control method for the work vehicle 10, primarily performed by the control system 2 (hereinafter simply referred to as the "control method"), with reference to Figures 3 to 6.

[0061] The control method according to this embodiment is executed by a control system 2, which mainly consists of a computer system; in other words, it is implemented by a control program for work vehicles (hereinafter simply referred to as the "control program"). That is, the control program according to this embodiment is a computer program that causes one or more processors to execute each process related to the control method.

[0062] Here, the control system 2 executes the following various processes related to the control method when a specific preset start operation is performed to execute the control program. The start operation is, for example, the operation to start the prime mover 17 by turning on the key of the work vehicle 10. On the other hand, the control system 2 terminates the following various processes related to the control method when a specific preset end operation is performed. The end operation is, for example, the operation to stop the prime mover 17 by turning off the key of the work vehicle 10.

[0063] In the control system 2 according to this embodiment, when the speed range of the auxiliary transmission 132 is in a specific range, the driving control unit 21 can adjust both the rotational speed of the prime mover 17 and the gear ratio of the transmission 131 according to the operation of the accelerator control unit 151 alone. Basically, the driving control unit 21 adjusts the rotational speed of the prime mover 17 and the gear ratio of the transmission 131 according to the amount of operation of the accelerator control unit 151, so that the vehicle speed of the work vehicle 10 (and its driving device 13) increases as the amount of operation (pressing) of the accelerator control unit 151 increases. As a result, the operator can adjust the vehicle speed of the work vehicle 10 (and its driving device 13) by operating only the accelerator control unit 151, similar to how the vehicle speed is controlled by the accelerator pedal in a typical automobile, making it easy to control the vehicle speed of the work vehicle 10.

[0064] In this embodiment, as an example, the "specific range" is "2nd gear" among "C gear," "1st gear," and "2nd gear." In other words, both the rotational speed (of the prime mover 17) and the gear ratio (of the transmission 131) are adjusted according to the operation of the accelerator control unit 151 only when the speed range of the sub-transmission 132 is "2nd gear."

[0065] With this configuration, for example, when driving on the road with the speed range of the sub-transmission 132 set to "2nd gear," both the rotational speed (of the prime mover 17) and the gear ratio (of the transmission 131) can be adjusted according to the operation of the accelerator control unit 151, but only in specific situations. This leads to improved operability of the work vehicle 10.

[0066] However, the "specific range" is not limited to "2nd gear," but may be any one or two of the speed ranges used for driving (on roads, etc.), "C gear," "1st gear," and "2nd gear." For example, the "specific range" may be "1st gear" used for work. In this case, if the speed range of the auxiliary transmission 132 is set to "1st gear" in response to the operation of the auxiliary transmission lever 152, both the rotational speed (of the prime mover 17) and the gear ratio (of the transmission 131) can be adjusted according to the operation of the accelerator control unit 151.

[0067] Incidentally, when the rotational speed (of the prime mover 17) and the gear ratio (of the transmission 131) are controlled simultaneously in accordance with the amount of operation (pressure) of the accelerator control unit 151, depending on the operation of the accelerator control unit 151, the prime mover 17 may become overloaded, causing engine stall or shocks during acceleration and deceleration. Therefore, there are issues with the operability when the operator adjusts the vehicle speed.

[0068] Therefore, in the control method according to this embodiment, the control of the driving control unit 21 when the speed range of the sub-transmission 132 is in a specific range (for example, "2nd gear") is adopted as the control described below (first control, etc.), thereby improving the operability when the operator adjusts the vehicle speed.

[0069] That is, in the present embodiment, as shown in FIG. 3, when the speed range of the sub-transmission 132 is within a specific range, the traveling control unit 21 can individually adjust the rotational speed (of the prime mover 17) and the gear ratio (of the transmission 131) according to the operation of the accelerator operation unit 151. FIG. 3 schematically shows two control patterns, the first control and the second control, when the vertical axis represents the rotational speed and the horizontal axis represents the gear ratio.

[0070] In particular, the control of the traveling control unit 21 when the speed range of the sub-transmission 132 is within a specific range (for example, "second speed") is based on the "first control" shown in the upper part of FIG. 3. In the first control, the rotational speed (of the prime mover 17) and the gear ratio (of the transmission 131) do not change simultaneously but change individually both when the traveling device 13 is accelerating and when it is decelerating.

[0071] Specifically, in the first control, when the operation amount (depression amount) of the accelerator operation unit 151 increases and the traveling device 13 is accelerated from the vehicle speed V1 to the vehicle speed V2 (>V1) (solid line arrow in the figure), the traveling control unit 21 first increases only the rotational speed (P11), and then increases only the gear ratio (P12). Further, in the first control, when the operation amount (depression amount) of the accelerator operation unit 151 decreases and the traveling device 13 is decelerated from the vehicle speed V2 to the vehicle speed V1 (<V2) (broken line arrow in the figure), the traveling control unit 21 first decreases only the rotational speed (P21), and then decreases only the gear ratio (P22).

[0072] FIG. 4 shows an example of the changes in the rotational speed G1 (of the prime mover 17), the gear ratio G2 (of the transmission 131), and the vehicle speed G3 (of the traveling device 13) when the operation amount (depression amount) of the accelerator operation unit 151 increases, that is, when the traveling device 13 is accelerating, according to the first control with the horizontal axis being the time axis. Specifically, the operation of the traveling control unit 21 when the vehicle speed G3 is increased from the first value V1 to the second value V2 (>V1) as the accelerator operation unit 151 is depressed in a state where the operation amount of the accelerator operation unit 151 is minimum and both the rotational speed G1 and the gear ratio G2 are at their minimum values will be described.

[0073] That is, according to the first control, when the accelerator operation unit 151 is depressed, the travel control unit 21 first raises the rotational speed G1 to a target value R1 corresponding to the operation amount of the accelerator operation unit 151. At this time, the gear ratio G2 is fixed, and only with the increase in the rotational speed G1, the vehicle speed G3 increases. When the rotational speed G1 reaches the target value R1 at time point t1, the vehicle speed G3 reaches the first intermediate value V11 (V1 < V11 < V2). After time point t1, while the travel control unit 21 fixes the rotational speed G1 (to the target value R1), it raises the gear ratio G2 according to the operation amount of the accelerator operation unit 151. At this time, until the vehicle speed G3 reaches the second value V2, the vehicle speed G3 further increases with the increase in the gear ratio G2. After the vehicle speed G3 reaches the second value V2 at time point t2, the travel control unit 21 fixes the rotational speed G1 and the gear ratio G2 and maintains the vehicle speed G3 at the second value V2.

[0074] In other words, in the first control, among the vehicle speed ranges (V1~V2) when accelerating the traveling device 13 from the first vehicle speed (the first value V1) to the second vehicle speed (the second value V2), in the first specific section (until time point t1) from the first vehicle speed (the first value V1) to the first intermediate vehicle speed (the first intermediate value V11), only the rotational speed G1 among the rotational speed G1 and the gear ratio G2 is changed. And in the first control, among the vehicle speed ranges (V1~V2) when accelerating the traveling device 13 from the first vehicle speed (the first value V1) to the second vehicle speed (the second value V2), in the second specific section (time points t1~t2) from the second intermediate vehicle speed (the first intermediate value V11) to the second vehicle speed (the second value V2), only the gear ratio G2 among the rotational speed G1 and the gear ratio G2 is changed.

[0075] In short, in the acceleration operation example shown in FIG. 4, the first value V1 is an example of the first vehicle speed, and the second value V2 is an example of the second vehicle speed. Further, the first intermediate value V11 is an example of the first intermediate vehicle speed, and the first intermediate value V11 is also an example of the second intermediate vehicle speed. That is, the first intermediate vehicle speed and the second intermediate vehicle speed are equal (have the same value). <​Further, FIG. 5 shows an example of changes in the rotational speed G1 (of the prime mover 17), the gear ratio G2 (of the transmission 131), and the vehicle speed G3 (of the traveling device 13) during the first control when the operation amount (depression amount) of the accelerator operation unit 151 decreases, that is, when the traveling device 13 decelerates, with the horizontal axis being the time axis. Specifically, in a state where the operation amount of the accelerator operation unit 151 is maximum and both the rotational speed G1 and the gear ratio G2 are stable, the operation of the traveling control unit 21 when the vehicle speed G3 is decreased from the second value V2 to the first value V1 (<V2) as the depression of the accelerator operation unit 151 is loosened will be described.

[0077] That is, according to the first control, after time t1, when the depression of the accelerator operation unit 151 is loosened, the traveling control unit 21 first decreases the rotational speed G1 to the target value R1 corresponding to the operation amount of the accelerator operation unit 151. At this time, the gear ratio G2 is fixed, and the vehicle speed G3 decreases only with the decrease in the rotational speed G1. At the time t2 when the rotational speed G1 reaches the target value R1, the vehicle speed G3 reaches the first intermediate value V11 (V1 < V11 < V2). After time t2, the traveling control unit 21 fixes the rotational speed G1 (at the target value R1) while decreasing the gear ratio G2 according to the operation amount of the accelerator operation unit 151. At this time, until the vehicle speed G3 reaches the first value V1, the vehicle speed G3 further decreases as the gear ratio G2 decreases. After time t3 when the vehicle speed G3 reaches the first value V1, the traveling control unit 21 fixes the rotational speed G1 and the gear ratio G2 and maintains the vehicle speed G3 at the first value V1.

[0078] In other words, in the first control, in the vehicle speed range (V2 to V1) when decelerating the traveling device 13 from the first vehicle speed (second value V2) to the second vehicle speed (first value V1), in the first specific section (time t1 to t2) from the first vehicle speed (second value V2) to the first intermediate vehicle speed (first intermediate value V11), only the rotational speed G1 among the rotational speed G1 and the gear ratio G2 is changed. And in the first control, in the vehicle speed range (V2 to V1) when decelerating the traveling device 13 from the first vehicle speed (second value V2) to the second vehicle speed (first value V1), in the second specific section (time t2 to t3) from the second intermediate vehicle speed (first intermediate value V11) to the second vehicle speed (first value V1), only the gear ratio G2 among the rotational speed G1 and the gear ratio G2 is changed.

[0079] In short, in the deceleration example shown in Figure 5, the second value V2 is an example of the first vehicle speed, and the first value V1 is an example of the second vehicle speed. Furthermore, the first intermediate value V11 is an example of the first intermediate vehicle speed, and the first intermediate value V11 is also an example of the second intermediate vehicle speed. In other words, the first intermediate vehicle speed and the second intermediate vehicle speed are equal (they are equivalent).

[0080] As described above, the control method according to this embodiment is a control method for a work vehicle 10 comprising a running gear 13, a sub-transmission 132, and an accelerator operating unit 151. The running gear 13 travels at a vehicle speed that changes according to the rotational speed and gear ratio of the prime mover 17. The sub-transmission 132 can switch the speed range of the running gear 13. The accelerator operating unit 151 accepts operations to adjust the vehicle speed. When the accelerator operating unit 151 is operated while the speed range is in a specific range, this control method performs a first control in which only the rotational speed is changed among the rotational speed and gear ratio in a first specific section from the first vehicle speed to the first intermediate vehicle speed within the vehicle speed range when accelerating and decelerating the running gear 13 from the first vehicle speed to the second vehicle speed.

[0081] In this disclosure, "acceleration and deceleration" includes at least one of acceleration and deceleration. In other words, in the first control, during acceleration, in which the vehicle speed is increased from a first vehicle speed (for example, a first value V1) to a second vehicle speed (for example, a second value V2), and during deceleration, in which the vehicle speed is decreased from a first vehicle speed (for example, a second value V2) to a second vehicle speed (for example, a first value V1), only the rotational speed is changed among the rotational speed and gear ratio in a first specific section from the first vehicle speed to a first intermediate vehicle speed (for example, a first intermediate value V11).

[0082] With this configuration, during acceleration and / or deceleration, only the rotational speed changes among the rotational speed and gear ratio during a first specific section, at least until the vehicle speed reaches a first intermediate vehicle speed. Therefore, in the first specific section, it is easier to avoid the engine stalling due to high load on the prime mover 17 or shocks during acceleration and deceleration, compared to when both rotational speed and gear ratio change simultaneously. As a result, the operability when the operator adjusts the vehicle speed is improved.

[0083] In this embodiment, the first control is performed both during acceleration and deceleration of the running gear 13. This improves the operability of the operator when adjusting the vehicle speed during both acceleration and deceleration, thus further improving the operability of the operator when adjusting the vehicle speed compared to the case where the first control is performed only during either acceleration or deceleration.

[0084] Furthermore, in the control method according to this embodiment, in the vehicle speed range when accelerating and decelerating from the second vehicle speed to the first vehicle speed, in the second specific section from the second intermediate vehicle speed (for example, the first intermediate value V11) to the second vehicle speed, only the gear ratio is changed among the rotational speed and gear ratio. As a result, in the second specific section, compared to when both the rotational speed and gear ratio are changed simultaneously, it is easier to avoid the prime mover 17 becoming overloaded and causing engine stall or shocks during acceleration and deceleration. Therefore, the operability when the operator adjusts the vehicle speed is further improved.

[0085] By the way, in the control method according to this embodiment, when the speed range of the sub-transmission 132 is in a specific range (for example, "2nd gear"), a second control is employed in addition to the first control described above for the control of the driving control unit 21.

[0086] In the "Second Control" shown in the lower part of FIG. 3, the rotational speed (of the prime mover 17) and the gear ratio (of the transmission 131) do not change individually but change simultaneously only under certain specific conditions. Here, the specific conditions are that the rotational speed is less than a specific rotational speed and the gear ratio is greater than a specific gear ratio. In FIG. 3, the vehicle speed when the rotational speed is less than the specific rotational speed and the gear ratio is greater than the specific gear ratio is defined as vehicle speed V3.

[0087] Specifically, in the second control, when the operation amount (depression amount) of the accelerator operation unit 151 increases and the traveling device 13 is accelerated from vehicle speed V3 toward vehicle speed V2 (>V3) (solid arrow in the figure), the traveling control unit 21 decreases the gear ratio while increasing the rotational speed (P11), and then increases only the gear ratio (P12). Further, in the second control, when the operation amount (depression amount) of the accelerator operation unit 151 decreases and the traveling device 13 is decelerated from vehicle speed V2 toward vehicle speed V3 (<V2) (dashed arrow in the figure), the traveling control unit 21 decreases only the rotational speed (P2).

[0088] FIG. 6 shows an example of changes in the rotational speed G1 (of the prime mover 17), the gear ratio G2 (of the transmission 131), and the vehicle speed G3 (of the traveling device 13) when the operation amount (depression amount) of the accelerator operation unit 151 increases, that is, when the traveling device 13 is accelerated, according to the second control with the horizontal axis being the time axis. Specifically, as the depression of the accelerator operation unit 151 is released, only the rotational speed G1 decreases by the first control and the gear ratio remains high. As the accelerator operation unit 151 is depressed, the operation of the traveling control unit 21 when increasing the vehicle speed G3 from the third value V3 to the second value V2 (>V3) will be described.

[0089] In other words, according to the second control, from time t1 onward, when the accelerator pedal 151 is pressed, the driving control unit 21 first increases the rotational speed G1 to a target value R1 corresponding to the amount of operation of the accelerator pedal 151. At this time, the gear ratio G2 decreases, and the vehicle speed G3 is kept constant due to the increase in rotational speed G1 and the decrease in the gear ratio. At time t2, when the rotational speed G1 reaches the target value R1, the vehicle speed G3 remains at vehicle speed V3. From time t2 onward, the driving control unit 21 fixes the rotational speed G1 (at the target value R1) while increasing the gear ratio G2 according to the amount of operation of the accelerator pedal 151. At this time, the vehicle speed G3 increases in accordance with the increase in the gear ratio G2 until the vehicle speed G3 reaches the second value V2. From the point t3 onward, when the vehicle speed G3 reaches the second value V2, the driving control unit 21 fixes the rotational speed G1 and the gear ratio G2, and maintains the vehicle speed G3 at the second value V2.

[0090] In other words, in the second control, during the period until the rotational speed G1 reaches the target value R1 (times t1 to t2), the rotational speed G1 is increased and the gear ratio G2 is decreased. Then, in the second control, during the period after the rotational speed G1 reaches the target value R1 (times t2 to t3), only the gear ratio G2 is increased.

[0091] In short, the control method according to this embodiment performs a second control (in place of the first control) when the speed range is within a specific range, the rotational speed is less than a specific rotational speed, and the gear ratio is greater than a specific gear ratio. The second control is a control that increases the rotational speed while decreasing the gear ratio when the accelerator pedal 151 is operated to increase the rotational speed. This makes it easier to avoid engine stalling when the accelerator pedal 151 is accelerated (i.e., pressed down) while the rotational speed is reduced by the first control, by increasing the rotational speed while the gear ratio remains high.

[0092] In particular, in this embodiment, the second control changes the rotational speed and gear ratio to maintain a constant vehicle speed. This avoids the unnatural feeling of operation caused by a decrease in vehicle speed when the accelerator pedal 151 is pressed down (i.e., accelerated).

[0093] Incidentally, whether or not to implement the second control that reduces the gear ratio when the rotational speed increases is determined based on, for example, the rotational speed, vehicle speed, load factor of the prime mover 17, and the rate of change of the amount of operation of the accelerator control unit 151, immediately before the acceleration operation of the accelerator control unit 151 (immediately before time t1 in Figure 6). For example, if the load factor of the prime mover 17 is lower than the determination threshold, engine stall is less likely to occur due to increasing the rotational speed even if the gear ratio remains high, so the gear ratio may be maintained when the rotational speed increases.

[0094] Furthermore, if the load factor of the prime mover 17 is lower than the judgment threshold and there is no problem in reducing the rotational speed of the prime mover 17, the fuel efficiency may be improved by reducing the rotational speed of the prime mover 17. In this case, since the vehicle speed may feel unnatural if the amount of operation of the accelerator control unit 151 does not decrease, it is preferable to maintain a constant vehicle speed by increasing the gear ratio while reducing the rotational speed.

[0095] Furthermore, at least a portion of the first specific section and the second specific section may overlap during either the acceleration or deceleration of the running gear 13. That is, in the example of acceleration shown in Figure 4, by setting the first intermediate vehicle speed higher (higher speed) than the second intermediate vehicle speed, a portion of the first specific section (first vehicle speed to first intermediate vehicle speed) and the second specific section (second intermediate vehicle speed to second vehicle speed) overlap. On the other hand, in the example of deceleration shown in Figure 5, by setting the first intermediate vehicle speed lower (lower speed) than the second intermediate vehicle speed, a portion of the first specific section (first intermediate vehicle speed to first vehicle speed) and the second specific section (second vehicle speed to second intermediate vehicle speed) overlap.

[0096] As a result, in the overlapping section between the first and second specific sections, both the rotational speed and the gear ratio will change. Therefore, the transition between the first and second specific sections can be made smoother compared to when there is no overlapping section. Conversely, a blank section may be interposed between the first and second specific sections during at least one of the acceleration and deceleration phases of the running gear 13, in which neither the rotational speed nor the gear ratio changes.

[0097] Furthermore, in the control method according to this embodiment, when the speed range is within a specific range and the amount of operation of the braking operation unit 153, which receives an operation for braking the work vehicle 10, is greater than a specific amount, a third control is performed to reduce the rotational speed while lowering the gear ratio. In other words, when the amount of operation of the braking operation unit 153 is large and the brake mechanism 133 performs relatively sudden braking, the vehicle speed of the work vehicle 10 also decreases significantly (decels). In this case, the vehicle speed can be rapidly reduced by lowering the rotational speed of the prime mover 17 while also lowering the gear ratio (instead of the first control).

[0098] [4] Modified form The following lists some modifications of Embodiment 1. The modifications described below can be combined and applied as appropriate.

[0099] The control system 2 in this disclosure includes a computer system. The computer system mainly consists of one or more processors and one or more memories as hardware. The functions of the control system 2 in this disclosure are realized when the processor executes a program (a control program for work vehicles) recorded in the memory of the computer system. The program may be pre-recorded in the memory of the computer system, provided via a telecommunications line, or provided on a non-temporary recording medium such as a memory card, optical disk, or hard disk drive that can be read by the computer system. Furthermore, some or all of the functional parts included in the control system 2 may be composed of electronic circuits.

[0100] Furthermore, it is not essential for control system 2 to have at least some of its functions integrated into a single enclosure; the components of control system 2 may be distributed across multiple enclosures. Conversely, functions that are distributed across multiple devices in Embodiment 1 may be integrated into a single enclosure. Moreover, at least some of the functions of control system 2 may be implemented by the cloud (cloud computing) or the like.

[0101] [Notes on the invention] The following is an overview of the invention extracted from the above-described embodiments. Note that each configuration and processing function described below can be selected and combined as desired.

[0102] <Note 1> A running gear that operates at a vehicle speed that changes depending on the engine speed and gear ratio, A sub-transmission capable of switching the speed range of the aforementioned traction device, A control method for a work vehicle comprising an accelerator operating unit that receives operations for adjusting the vehicle speed, When the accelerator pedal is operated while the speed range is within a specific range, a first control is performed in which only the rotational speed is changed among the rotational speed and the gear ratio in a first specific section from the first vehicle speed to the first intermediate vehicle speed within the vehicle speed range in which the running gear accelerates and decelerates from the first vehicle speed to the second vehicle speed. A method for controlling work vehicles.

[0103] <Note 2> When the speed range is within the specified range, the rotational speed is less than the specified rotational speed, and the gear ratio is greater than the specified gear ratio, if the accelerator control unit is operated to increase the rotational speed, a second control is performed to increase the rotational speed while decreasing the gear ratio. The control method for the work vehicle described in Appendix 1.

[0104] <Note 3> In the second control, the rotational speed and the gear ratio are changed to maintain the vehicle speed at a constant level. The control method for the work vehicle described in Appendix 2.

[0105] <Note 4> In the vehicle speed range when accelerating or decelerating from the second vehicle speed to the first vehicle speed, in the second specific section from the second intermediate vehicle speed to the second vehicle speed, only the gear ratio among the rotational speed and the gear ratio is changed. A control method for the work vehicle described in any of the appendices 1 to 3.

[0106] <Note 5> During acceleration and deceleration of the aforementioned running gear, at least a portion of the first specific section and the second specific section overlap. Control method for the work vehicle described in Appendix 4.

[0107] <Note 6> The first control is performed both during acceleration and deceleration of the traveling device. A control method for the work vehicle described in any of the appendices 1 to 5.

[0108] <Note 7> When the speed range is within the specified range, and the amount of operation of the braking operation unit that receives operation for braking the work vehicle is greater than a specified amount, a third control is performed to reduce the rotational speed while reducing the gear ratio. A control method for the work vehicle described in any of the appendices 1 to 6.

[0109] <Note 8> The control method for the work vehicle described in any of the appendices 1 to 7, A control program for a work vehicle to be executed by one or more processors. [Explanation of Symbols]

[0110] 1. Control system for work vehicles 10 Work Vehicles 11 aircraft 13. Running gear 17. Engine 21 Driving Control Unit 100 work systems 131 Transmission 132 Sub-transmission 151 Accelerator control unit 153 Brake operation section G1 rotation speed G2 gear ratio G3 vehicle speed V1 First value (first vehicle speed, second vehicle speed) V2 Second value (second vehicle speed, first vehicle speed) V11 First Intermediate Value (First Intermediate Vehicle Speed, Second Intermediate Vehicle Speed)

Claims

1. A running gear that operates at a vehicle speed that changes depending on the engine speed and gear ratio, A sub-transmission capable of switching the speed range of the aforementioned traction device, A control method for a work vehicle comprising an accelerator operating unit that receives operations for adjusting the vehicle speed, When the accelerator pedal is operated while the speed range is within a specific range, a first control is performed in which only the rotational speed is changed among the rotational speed and the gear ratio in a first specific section from the first vehicle speed to the first intermediate vehicle speed within the vehicle speed range in which the running gear accelerates and decelerates from the first vehicle speed to the second vehicle speed. A method for controlling work vehicles.

2. When the speed range is within the specified range, the rotational speed is less than the specified rotational speed, and the gear ratio is greater than the specified gear ratio, if the accelerator control unit is operated to increase the rotational speed, a second control is performed to increase the rotational speed while decreasing the gear ratio. A method for controlling a work vehicle according to claim 1.

3. In the second control, the rotational speed and the gear ratio are changed to maintain the vehicle speed at a constant level. A method for controlling a work vehicle according to claim 2.

4. In the vehicle speed range when accelerating or decelerating from the second vehicle speed to the first vehicle speed, in the second specific section from the second intermediate vehicle speed to the second vehicle speed, only the gear ratio among the rotational speed and the gear ratio is changed. A method for controlling a work vehicle according to any one of claims 1 to 3.

5. During acceleration and deceleration of the aforementioned running gear, at least a portion of the first specific section and the second specific section overlap. A method for controlling a work vehicle according to claim 4.

6. The first control is performed both during acceleration and deceleration of the traveling device. A method for controlling a work vehicle according to any one of claims 1 to 3.

7. When the speed range is within the specified range, and the amount of operation of the braking operation unit that receives operation for braking the work vehicle is greater than a specified amount, a third control is performed to reduce the rotational speed while reducing the gear ratio. A method for controlling a work vehicle according to any one of claims 1 to 3.

8. A method for controlling a work vehicle according to any one of claims 1 to 3, A control program for a work vehicle to be executed by one or more processors.

9. A running gear that operates at a vehicle speed that changes depending on the engine speed and gear ratio, A sub-transmission capable of switching the speed range of the aforementioned traction device, Used in a work vehicle equipped with an accelerator operating unit that accepts operations for adjusting the vehicle speed, When the accelerator pedal is operated while the speed range is within a specific range, the vehicle includes a driving control unit that performs a first control, which changes only the rotational speed among the rotational speed and the gear ratio in a first specific section from the first vehicle speed to the first intermediate vehicle speed within the vehicle speed range when accelerating and decelerating the vehicle from the first vehicle speed to the second vehicle speed. Control system for work vehicles.

10. A control system for a work vehicle according to claim 9, The above-mentioned work vehicle body comprises, Work system.

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