Operation control method for rough terrain work vehicle and rough terrain work vehicle

Abstract

The operation control method of this rough terrain work vehicle (1) includes mounting an inclination sensor (7) for detecting an inclination angle on the rough terrain work vehicle 1, causing a control unit (51) to monitor the inclination angle of the rough terrain work vehicle (1) based on the detection value of the inclination sensor (7), and causing the control unit (51) to execute an automatic parking brake control process for automatically operating or releasing the parking brake (44) according to the monitored travel instruction signal, brake instruction signal, and inclination angle.

Description

Technical Field

[0001] The present invention relates to a driving control method for an uneven ground working vehicle and an uneven ground working vehicle. More specifically, the present invention relates to a driving control method for an uneven ground working vehicle for safely driving the uneven ground working vehicle on uneven ground, and an uneven ground working vehicle in which driving control for such safe driving is performed.

Background Art

[0002] On uneven ground with many slopes, an uneven ground working vehicle that travels and works on the uneven ground, such as transporting heavy objects, is used. Many work vehicles including such uneven ground working vehicles have a hydraulic pump that moves a swash plate according to the input solenoid current for the pump and outputs hydraulic pressure according to the movement of the swash plate, a hydraulic motor that converts the fluid energy transmitted hydraulically from the hydraulic pump into rotational energy and outputs rotation, and a parking brake that applies a braking force to the rotation of the hydraulic motor. A hydrostatic continuously variable transmission (hereinafter simply referred to as "HST") and a control unit that controls the operation of the HST are mounted. In recent years, in work vehicles equipped with an HST, various driving controls for the HST have been proposed for safe driving (see, for example, Patent Document 1).

[0003] In the transmission of the work vehicle disclosed in Patent Document 1, when a start operation is performed on the HST and the brake mechanism (parking brake) while the work vehicle is stopped, the movable swash plate of the HST is tilted from the neutral state, and at the same time, the braking force on the drive wheels of the brake mechanism is gradually released, and after a predetermined time has elapsed, the braking force of the brake mechanism is completely released. According to the driving control for the transmission of the work vehicle disclosed in Patent Document 1, when the work vehicle is stopped, brake control is performed, and when the brake mechanism is released and the vehicle is put into a starting state in a state where the movable swash plate of the HST is shaken and tilted (a state where the solenoid current for the pump is not zero), it is possible to prevent the work vehicle from starting to move in a direction unintended by the operator.

Prior Art Documents

Patent Document

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The work vehicle according to the present invention is an uneven ground work vehicle equipped with an HST. In an uneven ground work vehicle, it often starts and stops running on a sloping ground. At that time, due to the characteristics of the HST, if the parking brake is not applied on a sloping ground, there is a risk of running away to the lower side of the slope. Conventionally, in order to prevent this runaway to the lower side of the slope, an operator has manually applied the parking brake, and there is a demand for a driving control for suppressing the runaway to the lower side of the slope to replace the operation compensated by the skill of this operator.

[0006] An object of the present invention has been made in view of this point, and in order to safely operate an uneven ground work vehicle that often travels and stops on a sloping ground, a driving control method for an uneven ground work vehicle capable of suppressing runaway to the lower side of the slope is provided. Another object of the present invention is to provide an uneven ground work vehicle capable of suppressing runaway to the lower side of the slope and enabling safe driving at the start and stop of traveling on a sloping ground.

Means for Solving the Problems

[0007] To solve the above problems, the driving control method for an uneven ground work vehicle according to the present invention is an engine that generates power, driving wheels that rotate in contact with the ground and transmit propulsion force to the ground, A hydraulic pump that converts the rotational energy input from the engine into fluid energy and outputs hydraulic pressure, a hydraulic motor that converts the fluid energy transmitted hydraulically from the hydraulic pump into rotational energy and outputs rotational power, and a parking brake that applies a braking force to the rotation of the hydraulic motor, and a hydrostatic continuously variable transmission that outputs rotational power to the drive wheels at a rotational direction and rotational speed corresponding to the operator's travel direction instruction and travel speed instruction. A travel instruction device that is operated by the operator to give the travel direction instruction and the travel speed instruction, and outputs a travel instruction signal in response to the operation. A parking brake instruction device that is operated by the operator to instruct the operation / release of the parking brake, and outputs a parking brake instruction signal in response to the operation. A control unit that monitors the travel instruction signal and the parking brake instruction signal, and controls the operation of the hydrostatic continuously variable transmission based on the travel instruction signal and the parking brake instruction signal. A method for controlling the operation of an uneven terrain work vehicle equipped with the above. Mounting an inclination sensor on the uneven terrain work vehicle to detect an inclination angle. The control unit monitors the inclination angle of the uneven terrain work vehicle based on the detection value of the inclination sensor. The control unit executes an automatic parking brake control process that automatically activates or releases the parking brake according to the monitored travel instruction signal, the brake instruction signal, and the inclination angle. The automatic parking brake control process includes: Selecting the control process content to be executed according to the current situation of the uneven terrain work vehicle from a plurality of different pre - defined control process contents. Judging the operating state including whether the uneven terrain work vehicle is before starting travel or before stopping travel based on the travel instruction signal and the parking brake instruction signal. When it is judged that the operating state is before starting travel, select the control process content for starting travel as the control process content to be performed thereafter. When it is determined that the operating state is before the vehicle stops, as the control processing content to be performed thereafter, the control processing content for vehicle stop is selected. Among the control processing content for vehicle start and the control processing content for vehicle stop, the inclination state of the rough terrain work vehicle is determined based on the inclination angle. In response to the determined inclination state of the rough terrain work vehicle, the control content including the timing of activation or release of the parking brake is made different.

[0008] In this operation control method of the rough terrain work vehicle, The automatic parking brake control processing further When determining the inclination state of the rough terrain work vehicle, the running direction signal is also referred to to determine whether the rough terrain work vehicle is in an uphill state or a downhill state in combination with the inclination direction. When it is determined that the vehicle is in the uphill state, as the control processing content to be performed thereafter, the control processing content for the uphill state is selected. When it is determined that the vehicle is in the downhill state, as the control processing content to be performed thereafter, it is preferable to select the control processing content for the downhill state.

[0009] Also, in this operation control method of the rough terrain work vehicle, The automatic parking brake control processing further It is determined whether the operator has instructed the activation of the parking brake or the release of the parking brake from the parking brake instruction signal. When it is determined that the operator has instructed the activation of the parking brake, as the control processing content to be performed thereafter, the control processing content for the parking brake activation instruction state is selected. When it is determined that the operator has instructed the release of the parking brake, as the control processing content to be performed thereafter, it is preferable to select the control processing content for the parking brake release instruction state.

[0010] Also, in this operation control method of the rough terrain work vehicle, including mounting a display device for transmitting traveling information to the operator, when the parking brake is operating and the parking brake indicating device is outputting the parking brake indicating signal, the display device displays that the parking brake has been operated in a first display form, when the parking brake is operating and the parking brake indicating device is not outputting the parking brake indicating signal, it is desirable that the control unit displays that the parking brake has been operated in a second display form different from the first display form on the display device.

[0011] Also, in the operation control method of this rough terrain work vehicle, including mounting a timer, the automatic parking brake control process is, among the control process contents for starting travel, when the control unit acquires the travel instruction signal, it measures the elapsed time since the acquisition of the travel instruction signal, when the parking brake that was operating before the elapsed time reached a predetermined set elapsed time is released, it is preferable to gradually increase the rotational output to the drive wheels to the rotational output set based on the travel instruction signal between the time when the parking brake was released and when the set elapsed time has elapsed.

[0012] Also, in the operation control method of this rough terrain work vehicle, the automatic parking brake control process further includes, among the control process contents for the uphill state, judging whether the operator has instructed a slow stop or an emergency stop from the travel instruction signal, when it is judged that the operator has instructed an emergency stop, it is preferable to delay the timing of operating the parking brake compared to when it is judged that the operator has instructed a slow stop.

[0013] Also, in the operation control method of this rough terrain work vehicle, The control unit is caused to determine whether the rough terrain work vehicle is in a climbing driving state at or above a set angle based on the monitored travel instruction signal, the brake instruction signal, and the inclination angle, and when it is determined that the vehicle is in a climbing driving state at or above the set angle, an anti-stall control process is executed to automatically control the travel speed with reference to a predetermined table so as not to stall the engine. It is preferable that this is further included.

[0014] Also, in this operation control method of the rough terrain work vehicle, it includes mounting an engine accelerator dial that is operated by the operator and receives an engine instruction rotational speed that instructs the rotational speed of the engine in response to the operation. The control unit is caused to determine whether the rough terrain work vehicle is in a descending driving state at or above a set angle based on the monitored travel instruction signal, the brake instruction signal, and the inclination angle, and when it is determined that the vehicle is in a descending driving state at or above the set angle, an over-rotation prevention control process is executed to automatically control the engine so that it does not over-rotate, with the rotational speed determined by referring to the engine instruction rotational speed instructed by the operator as the target rotational speed so as to suppress an increase in the engine rotational speed. It is preferable that this is further included.

[0015] Also, in this operation control method of the rough terrain work vehicle, the engine instruction rotational speed instructed by the operator includes a first instruction rotational speed and a second instruction rotational speed having a higher rotational speed than the first instruction rotational speed, and these are selectable. When the first instruction rotational speed is selected, as the over-rotation prevention control process, the rotational speed determined by referring to the first instruction rotational speed is set as the target rotational speed, and the engine is automatically controlled so that it does not over-rotate. When the second instruction rotational speed is selected, as the over-rotation prevention control process, the rotational speed determined by referring to the second instruction rotational speed is set as the target rotational speed, and the engine is automatically controlled so that it does not over-rotate. This is preferable.

[0016] Also, in this operation control method of the rough terrain work vehicle, including mounting a timer, In the over-rotation prevention control process, when the time during which the monitored tilt angle is smaller than the set tilt angle continues for a set continuous time or longer, the rotation of the engine is caused to reach the engine indicated rotational speed indicated by the operator, and the over-rotation prevention control process is terminated. This is preferable.

[0017] In order to solve the above problems, an uneven ground working vehicle according to the present invention is an uneven ground working vehicle that travels on uneven ground, an engine that generates power, drive wheels that rotate in contact with the ground and transmit propulsion force to the ground, a hydraulic pump that converts the rotational energy input from the engine into fluid energy and outputs hydraulic pressure, a hydraulic motor that converts the fluid energy hydraulically transmitted from the hydraulic pump into rotational energy and outputs rotation, and a parking brake that applies a braking force to the rotation of the hydraulic motor. A hydrostatic continuously variable transmission that is disposed between the engine and the drive wheels and outputs rotational power to the drive wheels at a rotational direction and rotational speed corresponding to the operator's traveling direction instruction and traveling speed instruction, a traveling instruction device that is operated by the operator in order for the operator to give the traveling direction instruction and the traveling speed instruction, and outputs a traveling instruction signal in response to the operation, a parking brake instruction device that is operated by the operator in order for the operator to instruct the operation / release of the parking brake, and outputs a parking brake instruction signal in response to the operation, a tilt sensor that detects a tilt angle, is electrically connected to the hydrostatic continuously variable transmission, the traveling instruction device, the parking brake instruction device, and the tilt sensor, and controls the operation of the hydrostatic continuously variable transmission based on the traveling instruction signal and the parking brake instruction signal. a control unit; a storage unit that stores the control processing content by the control unit, The control unit has an automatic parking brake control processing function that automatically activates or releases the parking brake according to the driving instruction signal, the brake instruction signal, and the inclination angle in accordance with the control processing content stored in the storage unit. The automatic parking brake control processing function selects the control processing content to be executed according to the current situation of the rough terrain work vehicle from among a plurality of different pre-specified control processing contents stored in the storage unit. Based on the driving instruction signal and the parking brake instruction signal, it determines the driving state including whether the rough terrain work vehicle is before starting or before stopping. When it is determined that the driving state is before starting, as the control processing content to be performed thereafter, it selects the control processing content for starting driving. When it is determined that the driving state is before stopping, as the control processing content to be performed thereafter, it selects the control processing content for stopping driving. Among the control processing content for starting driving and the control processing content for stopping driving, it determines the inclination state of the rough terrain work vehicle based on the inclination angle. It is characterized by a function that includes varying the control content including the timing of activating or releasing the parking brake according to the determined inclination state of the rough terrain work vehicle.

[0018] In this rough terrain work vehicle, The automatic parking brake control processing function further When determining the inclination state of the rough terrain work vehicle, it also refers to the driving instruction signal to jointly determine the inclination direction of whether the rough terrain work vehicle is in an uphill state or a downhill state. When it is determined that it is in the uphill state, as the control processing content to be performed thereafter, it selects the control processing content for the uphill state. When it is determined that it is in the downhill state, as the control processing content to be performed thereafter, it preferably selects the control processing content for the downhill state, which includes this function.

[0019] In this rough terrain work vehicle, The automatic parking brake control processing function further determines whether the operator has instructed the operation of the parking brake or the release of the parking brake from the parking brake instruction signal, when it is determined that the operation of the parking brake has been instructed, as the control processing content to be performed thereafter, the control processing content for the parking brake operation instruction state is selected, when it is determined that the release of the parking brake has been instructed, as the control processing content to be performed thereafter, the control processing content for the parking brake release instruction state is selected, and it is preferably a function including this.

[0020] In this rough terrain work vehicle, it further includes a display device for transmitting driving information to the operator, the automatic parking brake control processing function when the parking brake is operating and the parking brake instruction device outputs the parking brake instruction signal, the control unit displays on the display device that the parking brake has operated in a first display form, when the parking brake is operating and the parking brake instruction device does not output the parking brake instruction signal, the control unit preferably displays on the display device that the parking brake has operated in a second display form different from the first display form.

[0021] In this rough terrain work vehicle, it is equipped with a timer, in the control processing content for starting travel, when the control unit acquires the travel instruction signal, the automatic parking brake control processing function measures the elapsed time since the acquisition of the travel instruction signal, when the parking brake that is operating is released before the elapsed time elapses a predetermined set elapsed time, the rotational output to the drive wheels is gradually increased to the rotational output set based on the travel instruction signal until the set elapsed time elapses from the time when the parking brake is released, which is preferable.

[0022] In this rough terrain work vehicle, The automatic parking brake control processing function further Among the control processing contents for the uphill state, It is determined whether the operator has instructed a slow stop or an emergency stop from the travel instruction signal, When it is determined that the vehicle is in the state of instructing an emergency stop, the timing of operating the parking brake is delayed compared to the case where it is determined that the vehicle is in the state of instructing a slow stop. It is preferable that the function includes this.

[0023] In this rough terrain work vehicle, The control unit determines whether the rough terrain work vehicle is in an uphill running state at a set angle or more based on the travel instruction signal, the brake instruction signal, and the inclination angle. When it is determined that the vehicle is in an uphill running state at a set angle or more, it has an anti-stall control processing function that automatically controls the travel speed with reference to a predetermined table so as not to stall the engine. It is preferable that the function includes this.

[0024] In this rough terrain work vehicle, It is provided with an engine accelerator dial that is operated by the operator and receives an engine instruction rotation speed that instructs the rotation speed of the engine in response to the operation. The control unit determines whether the rough terrain work vehicle is in a downhill running state at a set angle or more based on the travel instruction signal, the brake instruction signal, and the inclination angle. When it is determined that the vehicle is in a downhill running state at a set angle or more, the rotation speed determined with reference to the engine instruction rotation speed instructed by the operator is set as the target rotation speed so as to suppress an increase in the engine rotation speed, and it has an over-rotation prevention control processing function that automatically controls the engine so as not to over-rotate. It is preferable that the function includes this.

[0025] In this rough terrain work vehicle, An instruction rotation speed selection device that is operated by the operator and, in response to the operation, selects one of a first instruction rotation speed and a second instruction rotation speed having a higher rotation speed than the first instruction rotation speed as the engine instruction rotation speed is provided. When the first instruction rotation speed is selected, the over-rotation prevention control processing function automatically controls the engine so as not to over-rotate, with the rotation speed determined by referring to the first instruction rotation speed as the target rotation speed. When the second instruction rotation speed is selected, the over-rotation prevention control processing function automatically controls the engine so as not to over-rotate, with the rotation speed determined by referring to the second instruction rotation speed as the target rotation speed. This is preferable.

[0026] In this rough terrain work vehicle, A timer is provided. When the time during which the monitored inclination angle is smaller than the set inclination angle continues for the set continuous time, the over-rotation prevention control processing function causes the rotation of the engine to reach the engine instruction rotation speed indicated by the operator and ends the over-rotation prevention control processing. This is preferable.

Effect of the Invention

[0027] According to the present invention, it is possible to provide a driving control method for a rough terrain work vehicle that can suppress runaway to the lower side of an incline in order to safely drive a rough terrain work vehicle that frequently travels and stops on an incline. Further, according to the present invention, it is possible to provide a rough terrain work vehicle in which driving control capable of suppressing runaway to the lower side of an incline is performed before stopping while traveling on an incline.

Brief Description of the Drawings

[0028]

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Mode for Carrying Out the Invention

[0029] (Configuration of the rough terrain work vehicle 1) FIG. 1 is a configuration diagram of the rough terrain work vehicle 1 according to the embodiment. First, with reference to FIG. 1, the configuration of the rough terrain work vehicle 1 as an example of a rough terrain work vehicle to which the present invention is applied will be described.

[0030] The rough terrain work vehicle 1 is called a forwarder and is a transportation device used in forestry to transport heavy objects such as felled trees on rough terrain with many slopes. As shown in FIG. 1, the rough terrain work vehicle 1 includes an engine 2 that generates rotational power, drive wheels 3 that rotate on the ground and transmit propulsion force to the ground, an HST 4 (hydrostatic continuously variable transmission 4) that converts the rotational power generated by the engine 2 into an appropriate torque value, rotational speed, and rotational direction and transmits it to the drive wheels 3, and a controller 5 that controls each part of the rough terrain work vehicle 1 including the engine 2 and the HST 4. Further, the rough terrain work vehicle 1 includes an operator input device 6 for inputting instructions from the operator to the controller 5, an inclination sensor 7 for detecting the inclination angle of the vehicle body, and a display device 8 for transmitting information such as traveling information and vehicle body information to the operator.

[0031] The engine 2 has an internal combustion engine that generates power and an output shaft for outputting the power generated by the internal combustion engine. The engine 2 rotationally drives the output shaft at a predetermined rotational speed according to an instruction from an engine controller 5A in the controller 5 described later.

[0032] The drive wheels 3 are provided on the left and right sides of the vehicle body and are in contact with the ground. The drive wheels 3 include a sprocket 31 that rotates when the rotational output of the HST 4 described later is transmitted, and a rubber belt that is wound around a plurality of pulleys and interlocks with the sprocket 31. Further, the drive wheels 3 have a crawler 32 that rotates greatly so that the inner surface interlocks with the sprocket 31 and surrounds a plurality of pulleys, and transmits propulsion force from the outer surface in contact with the ground to the ground to make the vehicle body travel. The drive wheels 3 can switch between forward and reverse by changing the rotational direction, and can change the direction of the vehicle body by making different rotations on the left and right.

[0033] The HST4 has a closed circuit filled with oil inside. The HST4 is a continuously variable transmission arranged between the engine 2 and the drive wheels 3, and transmits the power from the engine 2 to the drive wheels 3 hydraulically. The HST4 is provided corresponding to each of the left and right drive wheels 3. The HST4 has a hydraulic pump 41 and a hydraulic motor 42. The hydraulic pump 41 is connected to the output shaft of the engine 2, and the rotational output of the engine 2 is inputted to convert rotational energy into fluid energy and output hydraulic pressure. The hydraulic motor 42 is connected to the hydraulic pump 41 by a hydraulic hose so as to form a closed circuit, and converts the fluid energy hydraulically transmitted from the hydraulic pump 41 into rotational energy and outputs rotational power to the drive wheels 3.

[0034] A plurality of solenoid valves 43 for pumps (shown as one set for each hydraulic pump 41 in FIG. 1) are provided for the hydraulic pump 41 to change the hydraulic flow and transmission pressure transmitted to the hydraulic motor 42 by moving a pump swash plate (not shown). The solenoid valve 43 for pumps is driven by a solenoid current for pumps inputted according to an instruction from the control unit 51 of the controller 5 described later to operate the hydraulic pump 41. The HST4 can change the transmission pressure from the hydraulic pump 41 to the hydraulic motor 42 according to the solenoid current for pumps that drives the solenoid valve 43 for pumps, and change the rotational output (rotation speed and rotation direction) from the hydraulic motor 42 to the drive wheels 3.

[0035] Also, the HST4 has left and right parking brakes 44 and a solenoid valve 45 for parking brakes connected to the left and right parking brakes 44 by a hydraulic hose. The left and right parking brakes 44 are attached to the left and right hydraulic motors 42 respectively, and apply braking force to the rotation of each hydraulic motor 42. The solenoid valve 45 for parking brakes is driven by a solenoid current for brakes inputted according to an instruction from the control unit 51 of the controller 5 described later to operate the parking brake 44. The HST4 outputs rotational power to the drive wheels 3 at a rotation direction and rotation speed corresponding to the operator's travel direction instruction and travel speed instruction according to an instruction from the control unit 51 of the controller 5 described later.

[0036] The controller 5 is a computer control device. The controller 5 includes at least an engine controller 5A that controls the operation of the engine 2 and a vehicle body controller 5B that controls the operation of the vehicle body. The controller 5 has the engine controller 5A and the vehicle body controller 5B electrically connected to each other via a harness, and they cooperate to perform the driving control of the rough terrain work vehicle 1. The controller 5 includes a control unit 51 that controls the control of each part electrically connected via the harness, and a storage unit 52 that stores the control processing contents performed by the control unit 51 and stores the data required during control.

[0037] The engine 2 is electrically connected to the engine controller 5A. The engine controller 5A controls the rotation of the engine 2 according to an instruction from the control unit 51. The pump solenoid valve 43 and the parking brake solenoid valve 45 of the HST 4 are electrically connected to the vehicle body controller 5B. The vehicle body controller 5B controls the rotational output of the left and right hydraulic motors 42 of the HST 4 and the parking brake 44 according to an instruction from the control unit 51. Further, an operator input device 6, an inclination sensor 7, and a display device 8, which will be described later, are electrically connected to the vehicle body controller 5B via a harness.

[0038] A travel instruction signal acquired by the operator input device 6, an operation instruction signal including a parking brake instruction signal acquired by the operator input device 6, and a vehicle body information signal acquired from sensors including the inclination sensor 7 are input to the control unit 51. The control unit 51 issues control instructions including control instructions for controlling the pump solenoid current and the brake solenoid current according to the control procedure stored in the storage unit 52 based on the travel instruction signal, the operation instruction signal, and the vehicle body information signal. Thereby, the controller 5 can receive an operation instruction from the operator, cause the rough terrain work vehicle 1 to travel, and present operation information to the operator on the display device 8.

[0039] Here, in the storage unit 52, as control processing contents for causing the control unit 51 to perform driving control of the rough terrain work vehicle 1, according to the current state of the rough terrain work vehicle 1, at least the magnitude or input timing of the solenoid current for the pump, or the input timing of the solenoid current for the brake for operating or releasing the parking brake 44 is made different, and a plurality of control processing contents are stored. Thereby, the control unit 51 has an automatic parking brake control processing function 53, an anti-stall control processing function 54, and an over-rotation prevention control processing function 55.

[0040] The automatic parking brake control processing function 53 is a function for automatically operating or releasing the parking brake according to the running instruction signal, the brake instruction signal, and the inclination angle according to the control processing contents stored in the storage unit 52. The anti-stall control processing function 54 determines whether the rough terrain work vehicle 1 is in a climbing running state at or above a set angle based on the running instruction signal, the brake instruction signal, and the inclination angle according to the control processing contents stored in the storage unit 52. When it is determined that the vehicle is in a climbing running state at or above the set angle, it is a function for automatically controlling the running speed by reducing the solenoid current for the pump with reference to a predetermined table so as not to stall the engine. The over-rotation prevention control processing function 55 determines whether the rough terrain work vehicle 1 is in a descending running state at or above a set angle based on the running instruction signal, the brake instruction signal, and the inclination angle. When it is determined that the vehicle is in a descending running state at or above the set angle, with the rotation speed determined by referring to the engine instruction rotation speed indicated by the operator so as to suppress an increase in the engine rotation speed as the target rotation speed, it is a function for automatically controlling so that the engine 2 does not over-rotate by controlling the solenoid current for the pump corresponding to this target rotation speed.

[0041] In this way, the control unit 51 not only receives the operation instructions from the operator through each function and operates the rough terrain work vehicle 1 according to the operation instructions, but also performs automatic intervention according to the current situation of the rough terrain work vehicle 1 to automatically control a part of the operation of the rough terrain work vehicle 1 so that it can be operated more safely. The current situation of the rough terrain work vehicle 1 includes the inclination angle of the vehicle body of the rough terrain work vehicle 1. Details of the automatic operation control content performed when the rough terrain work vehicle 1 is automatically operation-controlled by each function of the control unit 51 will be described later as the operation method of the rough terrain work vehicle 1.

[0042] Next, the operator input device 6 is an input device for the operator to give operation instructions. As shown in FIG. 1, the rough terrain work vehicle 1 includes, as the operator input device 6, left and right travel levers 61 for respectively instructing the rotation direction and rotation speed of the left and right crawlers 32, a parking brake switch 62 for manually operating the parking brake 44, a 1st / 2nd speed change switch 63 for manually switching the gear ratio (1st speed / 2nd speed), and an engine accelerator dial 64 for manually instructing the engine indicated rotational speed. Each operator input device 6 outputs an operation instruction signal to the vehicle body controller 5B that is electrically connected according to its operation status. For example, the left and right travel levers 61 that function as travel instruction devices are operated by the operator to give travel direction instructions and travel speed instructions, and in response to this operation, a travel instruction signal is output as an operation instruction signal. Also, for example, the parking brake switch 62 that functions as a parking brake instruction device is operated by the operator to give an instruction to operate / release the parking brake 44, and in response to this operation, a parking brake instruction signal is output as an operation instruction signal.

[0043] The inclination sensor 7 is a sensor that detects the inclination angle. The inclination sensor 7 detects the inclination angle of the rough terrain work vehicle 1 and outputs the detected value as a vehicle body information signal to the vehicle body controller 5B that is electrically connected.

[0044] The display device 8 is, for example, a monitor provided in the driver's cab. The display device 8 displays the engine speed, the remaining fuel amount, the inclination state of the vehicle body, etc., based on the output signal from the vehicle body controller 5B which is electrically connected.

[0045] In the rough terrain work vehicle 1 configured as described above, when an operation instruction is given by the operator via the operator input device 6, the control unit 51 that has received the operation instruction issues a control instruction according to the control processing content stored in the storage unit 52, and the HST 4 travels by transmitting the power of the engine 2 to the drive wheels 3 in response to the control instruction. In this control processing content, an operation control procedure for operating the rough terrain work vehicle 1 in accordance with the operator's operation instruction is defined. However, as described above, in order to enable safer operation, a procedure for the control unit 51 to automatically intervene according to the current situation of the rough terrain work vehicle 1 and automatically control a part of the operation of the rough terrain work vehicle 1 is also defined. Hereinafter, the operation control method performed in the rough terrain work vehicle 1 will be described in detail.

[0046] (Operation control method of the rough terrain work vehicle 1) FIG. 2 is an explanatory diagram of the solenoid current for the pump (hereinafter referred to as "SOL current") in the rough terrain work vehicle 1 according to the embodiment. FIG. 2(a) shows the relationship between the inclination of the travel lever 61 and the SOL current. FIG. 2(b) is a graph showing the relationship between the vehicle body inclination angle θ when traveling on a sloping ground and the SOL current. FIGS. 3 to 9 are flowcharts showing a part of the operation control method of the rough terrain work vehicle 1 according to the embodiment. FIG. 3 shows the operation control method immediately after the start of control. FIG. 4 shows the control ST1 for starting flat ground travel. FIG. 5 shows the control ST2 for starting sloping ground travel. FIG. 6 shows the control ST3 for stopping flat ground travel. FIG. 7 shows the control ST4 for stopping sloping ground travel. FIG. 8 shows the control ST5 for ascending slope travel. FIG. 9 shows the control ST6 for descending slope travel. Hereinafter, with reference to these figures, the operation control method of the rough terrain work vehicle 1 will be described.

[0047] <Outline of the operation control method> In the driving control method of the rough terrain work vehicle 1, the control unit 51 monitors the inclination angle of the rough terrain work vehicle 1 based on the travel instruction signal and the brake instruction signal from the operator input device 6, and the detection value of the inclination sensor 7. Then, based on the acquired travel instruction signal, brake instruction signal, and the inclination angle of the rough terrain work vehicle 1, etc., the control unit 51 selects the control processing content from a plurality of different pre-defined control processing contents stored in the storage unit 52, and performs the driving control of the rough terrain work vehicle 1.

[0048] More specifically, the control unit 51 executes an automatic parking brake control process (the control process shown in FIGS. 3 to 7) that automatically activates or releases the parking brake 44 based on the travel instruction signal, the brake instruction signal, and the inclination angle by means of the automatic parking brake control processing function 53. Also, the control unit 51 executes an anti-stall control process (S45) that automatically controls the travel speed so as not to stall the engine in the uphill travel state based on the travel instruction signal, the brake instruction signal, and the inclination angle by means of the anti-stall control processing function 54. Further, the control unit 51 executes an over-rotation prevention control process (S47) that automatically controls to suppress the increase in the engine speed in the downhill travel state based on the travel instruction signal, the brake instruction signal, and the inclination angle by means of the over-rotation prevention control processing function 55.

[0049] <Instruction by the operator> Here, before explaining each control processing content, the relationship between the instruction by the operator and the SOL current output will be explained. The operator instructs the travel speed and the travel direction (the rotation direction and rotation speed of the left and right crawlers 32) by operating the travel lever 61 in order to drive the rough terrain work vehicle 1. Also, the operator instructs the activation / deactivation of the parking brake 44 by turning on / off the parking brake switch 62. Further, the operator instructs whether to set the gear ratio to the first speed or the second speed by switching the first / second speed change switch 63. Also, the operator manually instructs the engine speed of the engine 2 by rotating the engine accelerator dial 64.

[0050] In the operation of the travel lever 61, as shown in Fig. 2(a), by tilting the travel lever 61 from the neutral position to the forward side (the side that instructs the crawler 32 to rotate forward) or the reverse side (the side that instructs the crawler 32 to rotate backward), a travel instruction signal corresponding to the tilting amount is input to the vehicle body controller 5B. Then, the control unit 51 controls the magnitude of the SOL current according to the travel instruction signal, and the hydraulic pump 41 is driven according to the SOL current so as to transmit power to the drive wheels 3.

[0051] For example, as shown in Fig. 2(a), when the travel lever 61 is in the neutral position, the control unit 51 instructs to input the SOL current of 0 mA or the minimum set SOL current L0 (hereinafter simply referred to as "L0") to the pump solenoid valve 43, and the rotation of the drive wheels 3 stops. Also, when the travel lever 61 is tilted to the maximum, the control unit 51 instructs to input the SOL current of the maximum set SOL current Lmax (hereinafter simply referred to as "Lmax") to the pump solenoid valve 43, and the rotation of the drive wheels 3 becomes the fastest. Further, when the travel lever 61 is tilted between the neutral position and the maximum tilted position, the control unit 51 instructs to input the SOL current of a magnitude between L0 and Lmax to the pump solenoid valve 43 according to the tilt, and the rotation of the drive wheels 3 also changes accordingly. Note that the magnitude of the SOL current, the tilt of the operation lever, and the tilt angle of the vehicle body may be shown separately as positive and negative for forward and reverse, but the expressions comparing the magnitudes of the SOL current, the tilt of the operation lever, and the tilt angle of the vehicle body are expressions comparing the absolute values.

[0052] In the operation control according to this embodiment, as shown in FIG. 2(b), between L0 and Lmax, the minimum SOL current L1 (hereinafter simply referred to as "L1") corresponding to the minimum vehicle body tilt angle θ1 for determining a sloped ground is set. Then, the SOL current L2 (hereinafter simply referred to as "L2") corresponding to the vehicle body tilt angle θ2 between the minimum vehicle body tilt angle θ1 for determining a sloped ground and the maximum vehicle body tilt angle θmax corresponding to Lmax is calculated, for example, in a proportional relationship and changes according to the current tilt angle of the vehicle body. In the operation control according to this embodiment, L0, L1, and L2 are used as parameters for determining the state of the vehicle body when selecting the control process to be performed thereafter. Hereinafter, with reference to FIGS. 3 to 9 as well, the control process content and its flow by the control unit 51 in the operation control method of the rough terrain work vehicle 1 according to the embodiment will be described in detail.

[0053] <Contents of control process by control unit 51> In the operation control by the control unit 51, as shown in FIG. 3, first, an operation state determination (S1) is performed to determine whether the rough terrain work vehicle 1 is in a stopped state (A) or a traveling state (B). In the operation state determination (S1), the following (1) to (3) are confirmed. (1) Based on the solenoid current for the brake, whether the parking brake 44 is in an operating state or a released state (2) Whether the parking brake switch 62 is ON or OFF (3) Based on the SOL current, whether the travel lever 61 is in a neutral state (SOL current ≤ L0) or a tilted state (SOL current > L0)

[0054] In the driving state determination (S1), when the parking brake 44 is in the operating state, the parking brake switch 62 is ON, and the travel lever 61 is in the neutral state, the control unit 51 determines that the driving state is the stop state (A) before starting travel. Further, the control unit 51 selects the control processing content for starting travel as the control processing content to be performed thereafter, and proceeds to the confirmation (S2) of the vehicle body tilt angle for starting travel. On the other hand, in the driving state determination (S1), when the parking brake 44 is in the released state, the parking brake switch 62 is OFF, and the travel lever 61 is in the tilted state, the control unit 51 determines that the driving state is the driving state (B) before stopping travel. Further, the control unit 51 selects the control processing content for stopping travel as the control processing content to be performed thereafter, and proceeds to the confirmation (S3) of the vehicle body tilt angle for stopping travel.

[0055] In the confirmation (S2) of the vehicle body tilt angle for starting travel and the confirmation (S3) of the vehicle body tilt angle for stopping travel, the control unit 51 calculates the vehicle body tilt angle from the detection value of the tilt sensor 7. Further, based on the calculated vehicle body tilt angle, it is determined whether the land leveling work vehicle 1 is on flat ground or on a sloped ground. That is, based on the vehicle body tilt angle, the tilt state of the land leveling work vehicle 1 is determined. Thereafter, the control unit 51 varies the control content including the timing of operating or releasing the parking brake 44 in accordance with the determined tilt state of the land leveling work vehicle 1.

[0056] Specifically, in the confirmation of the vehicle body tilt angle for starting travel (S2), when the vehicle body tilt angle |θ| is less than or equal to the minimum vehicle body tilt angle |θ1| for determining a sloping ground, it is determined to be flat ground. When the vehicle body tilt angle |θ| is greater than the minimum vehicle body tilt angle |θ1| for determining a sloping ground, it is determined to be sloping ground. If it is determined to be flat ground, the driving control by the control unit 51 proceeds to the flat ground travel start control ST1. If it is determined to be sloping ground, the driving control by the control unit 51 proceeds to the sloping ground travel start control ST2. Similarly, in the confirmation of the vehicle body tilt angle for stopping travel (S3), when the vehicle body tilt angle |θ| is less than or equal to the minimum vehicle body tilt angle |θ1| for determining a sloping ground, it is determined to be flat ground. When the vehicle body tilt angle |θ| is greater than the minimum vehicle body tilt angle |θ1| for determining a sloping ground, it is determined to be sloping ground. If it is determined to be flat ground, the driving control by the control unit 51 proceeds to the flat ground travel stop control ST3. If it is determined to be sloping ground, the driving control by the control unit 51 proceeds to the sloping ground travel stop control ST4.

[0057] <Control for starting flat ground travel> In the flat ground travel start control ST1, as shown in FIG. 4, a travel instruction confirmation (S4) is performed. In the travel instruction confirmation (S4), the following (1) to (3) are confirmed. (1) Has the operation to turn off the parking brake switch 62 been performed? (2) Has the operation of tilting the travel lever 61 been performed and the SOL current become L0 or more? (3) Or otherwise?

[0058] If, in the travel instruction confirmation (S4), the operation to turn off the parking brake switch 62 has been performed, wait until the operation of tilting the travel lever 61 is performed and the SOL current becomes L0 or more (S5), and then automatically release the parking brake 44 (S6). Thereby, the travel of the rough terrain work vehicle 1 is started, and the driving control by the control unit 51 is returned to the travel state (B) shown in FIG. 3.

[0059] When an operation is performed to tilt the travel lever 61 in the travel instruction confirmation (S4) and the SOL current becomes L0 or more, an operation to turn off the parking brake switch 62 is awaited (S7), and the parking brake 44 is automatically released (S8). As a result, the travel of the rough terrain work vehicle 1 is started, and the operation control by the control unit 51 is returned to the travel state (B) shown in FIG. 3.

[0060] If otherwise determined in the travel instruction confirmation (S4), the control is returned to the stop state (A) shown in FIG. 3.

[0061] <Control for starting travel on sloped ground> In the control ST2 for starting travel on sloped ground, as shown in FIG. 5, a travel instruction confirmation (S9) is performed. In the travel instruction confirmation (S9), the following (1) to (3) are confirmed. (1) Has an operation been performed to turn off the parking brake switch 62? (2) Has an operation been performed to tilt the travel lever 61 and has the SOL current become L0 or more? (3) Or otherwise?

[0062] If an operation is performed to turn off the parking brake switch 62 in the travel instruction confirmation (S9), an operation to tilt the travel lever 61 is awaited until the SOL current becomes L0 or more (S10), and a slope - ascending / descending determination (S11) is performed to determine whether the rough terrain work vehicle 1 is in the slope - ascending state or the slope - descending state from the tilting direction of the travel lever 61. If it is determined that the vehicle is in the slope - ascending state in the slope - ascending / descending determination (S11), an operation to tilt the travel lever 61 is awaited until the SOL current becomes L2 or more (S12), the parking brake 44 is automatically released (S13), the travel of the rough terrain work vehicle 1 is started, and the process proceeds to the slope - ascending travel control ST5. On the other hand, if it is determined that the vehicle is in the slope - descending state in the slope - ascending / descending determination (S11), an operation to tilt the travel lever 61 is awaited until the SOL current becomes L0 or more (S14), and the parking brake 44 is automatically released (S15). As a result, the travel of the rough terrain work vehicle 1 is started, and the process proceeds to the slope - descending travel control ST6.

[0063] Also, when an operation of tilting the travel lever 61 is performed in the travel instruction confirmation (S9) and the SOL current becomes L0 or more, a slope - up / down determination (S16) is performed to determine whether the rough - terrain work vehicle 1 is in the slope - up state or the slope - down state from the tilting direction of the travel lever 61. When it is determined in the slope - up / down determination (S16) that the vehicle is in the slope - up state, after waiting for an operation of tilting the travel lever 61 until the SOL current becomes L2 or more (S17), waiting for an operation to turn off the parking brake switch 62 (S18), the parking brake 44 is automatically released (S19). Thereby, the travel of the rough - terrain work vehicle 1 is started, and the control proceeds to the slope - up travel control ST5. On the other hand, when it is determined in the slope - up / down determination (S16) that the vehicle is in the slope - down state, after waiting for an operation of tilting the travel lever 61 until the SOL current becomes L0 or more (S20), waiting for an operation to turn off the parking brake switch 62 (S21), the parking brake 44 is automatically released (S22), the travel of the rough - terrain work vehicle 1 is started, and the control proceeds to the slope - down travel control ST6.

[0064] Also, when it is otherwise determined in the travel instruction confirmation (S9), the control returns to the stopped state (A) shown in FIG. 3.

[0065] Thus, in the slope - up / down start control ST2, when it is determined in the slope - up / down determination (S11, S16) that the vehicle is in the slope - up state, different from the flat - ground or slope - down state, by performing control to automatically release the parking brake 44 after increasing the output, the runaway of the vehicle body to the lower side of the inclination, which is likely to occur at the start of travel on a slope, is suppressed.

[0066] <Flat - ground travel stop control> In the flat - ground travel stop control ST3, as shown in FIG. 6, a stop instruction confirmation (S23) is performed. In the stop instruction confirmation (S23), the following (1) to (3) are confirmed. (1) Has an operation to turn on the parking brake switch 62 been performed? (2) An operation to return the travel lever 61 to the neutral position has been performed and the SOL current has become less than L0. (3) Or otherwise?

[0067] When an operation to turn on the parking brake switch 62 is performed in the Stop Instruction Confirmation (S23), the parking brake 44 is automatically activated and the output of the SOL current is stopped (S24). That is, the control unit 51 activates the parking brake 44 in conjunction with the operation of turning on the parking brake switch 62. This is one of the control process contents for the parking brake activation instruction state when it is determined that the operator has instructed the activation of the parking brake 44. Thereby, the running of the rough terrain work vehicle 1 is stopped and the control is returned to the stop state (A) shown in FIG. 3.

[0068] Also, when an operation to set the travel lever 61 to neutral is performed in the Stop Instruction Confirmation (S23) and the SOL current becomes less than L0, the output of the SOL current is stopped (S25), and a Parking Brake State Confirmation (S26) is performed to check whether the parking brake switch 62 is ON or OFF. If the parking brake switch 62 is OFF in the Parking Brake 44 State Confirmation (S26), after waiting for a set time of several seconds (S27), the parking brake 44 is automatically activated (S28). That is, the control unit 51 activates the parking brake 44 even when the parking brake switch 62 is OFF. This is one of the control process contents for the parking brake release instruction state when it is determined that the operator has instructed the release of the parking brake 44.

[0069] At this time, in the stopped state with the parking brake switch 62 remaining OFF, when an operation of the travel lever 61 is received, it immediately enters the flat ground travel restart waiting state (C) where travel is possible, and proceeds to the flat ground travel start control ST1.

[0070] Also, when the parking brake switch 62 is ON in the parking brake 44 state confirmation (S26), the parking brake 44 is immediately automatically actuated (S29) to stop the running of the rough terrain work vehicle 1. That is, the control unit 51 actuates the parking brake 44 in conjunction with the ON operation of the parking brake switch 62. This is one of the control processing contents for the parking brake actuation instruction state when it is determined that the operator has instructed the actuation of the parking brake 44. Then, thereafter, the control is returned to the stop state (A) shown in FIG. 3. Also, when it is otherwise determined in the stop instruction confirmation (S23), the control is returned to the running state (B) shown in FIG. 3.

[0071] <Incline Travel Stop Control> In the incline travel stop control ST4, as shown in FIG. 7, a slope up / down determination (S30) is performed to determine whether the rough terrain work vehicle 1 is in the slope up state or the slope down state from the tilt direction of the travel lever 61.

[0072] When it is determined in the slope up / down determination (S30) that the vehicle is in the slope up state, a parking brake state confirmation (S31) is performed to check whether the parking brake switch 62 is ON or OFF. When the parking brake switch 62 is ON in the parking brake 44 state confirmation (S31), the parking brake 44 is immediately automatically actuated (S32) to stop the running of the rough terrain work vehicle 1, and the control is returned to the stop state (A) shown in FIG. 3. That is, the control unit 51 actuates the parking brake 44 in conjunction with the ON operation of the parking brake switch 62. This is one of the control processing contents for the parking brake actuation instruction state when it is determined that the operator has instructed the actuation of the parking brake 44.

[0073] On the other hand, when the parking brake switch 62 is OFF in the parking brake 44 state confirmation (S31), a stop condition determination (S33) is performed to confirm whether a slow stop or an emergency stop is instructed. In the stop condition determination (S33), when the state where the SOL current is less than or equal to the magnitude of the SOL current (L2 + α) obtained by adding the set value α to L2 continues for a predetermined time or more, it is determined as a slow stop, and otherwise as an emergency stop. When it is determined as a slow stop in the stop condition determination (S33), the parking brake 44 is automatically actuated (S34). That is, the control unit 51 actuates the parking brake 44 even when the parking brake switch 62 is OFF. This is one of the control process contents for the parking brake release instruction state when it is determined that the operator has instructed the release of the parking brake 44. At this time, in the stopped state with the parking brake switch 62 OFF, when an operation of the travel lever 61 is received, it immediately enters the slope travel restart waiting state (D) where travel is possible, and proceeds to the slope travel start control ST2.

[0074] On the other hand, when it is determined as an emergency stop in the stop condition determination (S33), after waiting for a set time of several seconds to elapse (S35), the parking brake 44 is automatically actuated (S36). That is, the control unit 51 actuates the parking brake 44 even when the parking brake switch 62 is OFF. This is one of the control process contents for the parking brake release instruction state when it is determined that the operator has instructed the release of the parking brake 44. At this time, in the stopped state with the parking brake switch 62 OFF, when an operation of the travel lever 61 is received, it immediately enters the slope travel restart waiting state (D) where travel is possible, and proceeds to the slope travel start control ST2.

[0075] Also, when it is determined that the vehicle is in the downhill state in the uphill / downhill determination (S30), a stop instruction confirmation (S37) is performed. In the stop instruction confirmation (S37), the following (1) to (3) are confirmed. (1) Has an operation been performed to turn on the parking brake switch 62? (2) Has an operation been performed to set the travel lever 61 to neutral and the SOL current become less than L0? (3) Or otherwise?

[0076] When the operation to turn on the parking brake switch 62 is performed in the stop instruction confirmation (S37), the parking brake 44 is automatically actuated and the output of the SOL current is stopped (S38). That is, the control unit 51 actuates the parking brake 44 in conjunction with the ON operation of the parking brake switch 62. This is one of the control process contents for the parking brake actuation instruction state when it is determined that the operator is in a state of instructing the actuation of the parking brake 44. Thereby, the running of the rough terrain work vehicle 1 is stopped and the control is returned to the stop state (A) shown in FIG. 3.

[0077] Also, when the operation to neutralize the travel lever 61 is performed in the stop instruction confirmation (S37) and the SOL current becomes less than L0, the output of the SOL current is stopped (S39), and a parking brake state confirmation (S40) is performed to check whether the parking brake switch 62 is ON or OFF. When the parking brake switch 62 is OFF in the parking brake 44 state confirmation (S40), after waiting for the set time of several seconds (S41), the parking brake 44 is automatically actuated (S42). That is, the control unit 51 actuates the parking brake 44 even when the parking brake switch 62 is OFF. This is one of the control process contents for the parking brake release instruction state when it is determined that the operator is in a state of instructing the release of the parking brake 44. At this time, in the stop state where the parking brake switch 62 remains OFF, when an operation of the travel lever 61 is received, it immediately enters the inclined ground travel restart waiting state (D) for starting the inclined ground travel, and proceeds to the inclined ground travel start control ST2.

[0078] Also, when the parking brake switch 62 is ON in the parking brake 44 state confirmation (S40), the parking brake 44 is immediately automatically actuated (S43). That is, the control unit 51 actuates the parking brake 44 in conjunction with the ON operation of the parking brake switch 62. This is one of the control process contents for the parking brake actuation instruction state when it is determined that the operator is in a state of instructing the actuation of the parking brake 44. Thereby, the running of the rough terrain work vehicle 1 is stopped and the control is returned to the stop state (A) shown in FIG. 3.

[0079] Also, when it is otherwise determined in the stop instruction confirmation (S37), the control returns to the traveling state (B) shown in FIG. 3.

[0080] The above is the description of the automatic parking brake control process that suppresses runaway to the lower side of the slope at the start and stop of traveling by performing control to automatically activate and release the parking brake 44 at the start and stop of traveling.

[0081] In the driving control by the control unit 51 in the present embodiment, further, in the uphill traveling state, when going uphill with the travel lever 61 tilted largely, in order to prevent the load on the engine 2 from increasing and the engine from stalling easily, an anti-stall control process is performed in the uphill traveling control ST5. Also, in the downhill traveling control ST6 in the downhill traveling state, in order to prevent the hydraulic motor 42 from rotating the engine side of the hydraulic pump 41 and the rotational speed of the engine 2 from increasing and becoming unable to steer, an over-rotation prevention control process is performed in the downhill traveling control ST6.

[0082] (Anti-stall control process) In the uphill traveling control ST5, as shown in FIG. 8, it is determined whether or not the anti-stall control start condition is satisfied (S44). If it is satisfied, the anti-stall control process is performed (S45), and the control returns to the traveling state (B) shown in FIG. 3. If it is not satisfied, the control returns to the traveling state (B) shown in FIG. 3 without performing the anti-stall control process. As an example, the anti-stall control start condition (S44) is a state where the uphill inclination angle is equal to or greater than the set angle, or a state where the vehicle is traveling in second gear according to an instruction from the first / second speed change switch 63. Note that the set angle used in the anti-stall control start condition (S44) is a different index value from the index value for determining whether the vehicle body is on flat ground or a sloped ground in the confirmation of the vehicle body inclination angle (S2)(S3), and preferably, an index value larger than the index value for determining whether the vehicle body is on flat ground or a sloped ground is set.

[0083] In the anti-stall control process (S45), a table is provided in advance that defines the rate at which the engine speed is to be reduced for each tilt angle in order to suppress the increase in the engine speed. During control, the control unit 51 refers to the table and multiplies the rate at which the engine speed corresponding to the tilt angle calculated based on the detection value of the tilt sensor 7 is to be reduced, and performs control to lower the SOL current input to the pump solenoid valve 43.

[0084] (Overspeed prevention control process) In the control ST6 for downhill driving, as shown in FIG. 9, it is determined whether or not the overspeed prevention control start condition is satisfied (S46). When the overspeed prevention control start condition is satisfied, the overspeed prevention control process is performed (S47), and the control is returned to the driving state (B) shown in FIG. 3. When the overspeed prevention control start condition is not satisfied, the control is returned to the driving state (B) shown in FIG. 3 without performing the overspeed prevention control process.

[0085] As an example, the overspeed prevention control start condition (S46) is a state where the downhill tilt angle is equal to or greater than the set angle, or a state where the actual rotation speed of the engine 2 continues to run for a preset time or more in a state where it is greater than a preset rotation speed set in advance by the engine accelerator dial 64 by a preset rotation speed or more. Note that the set angle used in the overspeed prevention control start condition (S46) is a different index value from the index value of the set angle for determining whether the vehicle body is on flat ground or sloping ground in the confirmation of the vehicle body tilt angle (S2) (S3), and preferably an index value greater than the index value for determining whether the vehicle body is on flat ground or sloping ground is set.

[0086] In the over-rotation prevention control process (S47), a table is provided in advance to define the reduction output ratio of the SOL current corresponding to the limit value of the engine speed for each inclination angle so as to suppress the increase in the engine speed. During control, the control unit 51 refers to the table and multiplies by the ratio corresponding to the inclination angle calculated based on the detection value of the inclination sensor 7 to reduce the SOL current. Further, in the over-rotation prevention control process (S47), when the actual rotation speed becomes a predetermined number of rotations greater than the engine indicated rotation speed or exceeds a preset rotation speed, it is also preferable to add processes such as sounding a warning sound or holding the SOL current at 0 until the parking brake 44 is activated.

[0087] (Function and Effect) The operation control method of the rough terrain work vehicle 1 according to the present embodiment mounts an inclination sensor 7 for detecting the inclination angle on the rough terrain work vehicle 1, and causes the control unit 51 to execute an automatic parking brake control process for automatically activating or releasing the parking brake 44 according to the monitored travel instruction signal, brake instruction signal, and inclination angle. This automatic parking brake control process selects the control process content to be executed according to the current situation of the rough terrain work vehicle 1 from a plurality of predefined control process contents. In this operation control method, the control process content for starting travel or the control process content for starting travel selected by determining the operation state including whether the rough terrain work vehicle 1 is before starting travel or before stopping travel, the inclination state of the rough terrain work vehicle 1 is determined based on the inclination angle, and the control content including the timing of activation or release of the parking brake 44 is made different according to the determined inclination state of the rough terrain work vehicle 1. That is, according to the operation control method of the rough terrain work vehicle 1, it is possible to automatically control the parking brake 44 at appropriate timings for each of them to suppress runaway to the lower inclination side at the start and stop of travel where runaway to the lower inclination side is likely to occur, and as a result, it is possible to safely operate the rough terrain work vehicle 1 which often travels and stops on inclined ground.

[0088] Also, in the operation control method of this rough terrain work vehicle 1, in the automatic parking brake control process, further, it is determined whether the rough terrain work vehicle 1 is in an uphill state or a downhill state, and the control process content to be performed thereafter is selected, and the control content including the timing of the operation or release of the parking brake 44 is made different. Thereby, according to the operation control method of the rough terrain work vehicle 1, in the uphill state and the downhill state where the way of running away to the lower side of the slope is different, the parking brake 44 can be automatically controlled at an appropriate timing for each to suppress the running away to the lower side of the slope.

[0089] Also, in the operation control method of this rough terrain work vehicle 1, in the automatic parking brake control process, further, it is determined whether the parking brake switch 62 is ON or OFF (whether the operator has instructed the operation of the parking brake 44 or the release of the parking brake 44). And when it is determined that the state is one in which the operation of the parking brake 44 is instructed, as the control process content to be performed thereafter, the control process content for the parking brake operation instruction state is selected. Also, when it is determined that the state is one in which the release of the parking brake 44 is instructed, as the control process content to be performed thereafter, the control process content for the parking brake release instruction state is selected. The control content for the parking brake operation instruction state and the control content for the parking brake release instruction state differ in the control content including the timing of the operation or release of the parking brake 44. Thereby, according to the operation control method of the rough terrain work vehicle 1, in the state where the parking brake switch 62 is ON or OFF, the parking brake 44 can be automatically controlled at an appropriate timing for each to suppress the running away to the lower side of the slope.

[0090] Also, in the operation control method of this rough terrain work vehicle 1, in the automatic parking brake control process, further, among the control process contents for the uphill state, it is determined whether the operator has instructed a slow stop or an emergency stop from the travel instruction signal. When it is determined that the vehicle is in the state of being instructed to make an emergency stop, the timing of operating the parking brake 44 is delayed compared to the case where it is determined that the vehicle is in the state of being instructed to make a slow stop. Thereby, it is possible to control the parking brake 44 so as not to become too much of an emergency brake automatically and suppress the runaway to the lower side of the slope.

[0091] Also, in the operation control method of the rough terrain work vehicle 1, the control unit 51 determines whether the rough terrain work vehicle 1 is in an uphill travel state at a set angle or more in addition to the automatic parking brake control process. When it is determined that the vehicle is in an uphill travel state at a set angle or more, an anti-stall control process is executed to automatically control the travel speed with reference to a predetermined table so as not to stall the engine. Thereby, according to the operation control method of the rough terrain work vehicle 1, it becomes difficult for the engine to stall during travel on a slope (uphill travel state) other than at the start and stop of travel, and as a result, the rough terrain work vehicle 1, which often travels on a slope, can be safely operated.

[0092] Also, in the operation control method of the rough terrain work vehicle 1, the control unit 51 determines whether the rough terrain work vehicle 1 is in a downhill travel state at a set angle or more in addition to the automatic parking brake control process. When it is determined that the vehicle is in a downhill travel state at a set angle or more, an over-rotation prevention control process is executed to automatically control the engine 2 so that it does not over-rotate, with the rotation speed determined by referring to the engine instruction rotation speed instructed by the operator as the target rotation speed. Thereby, according to the operation control method of the rough terrain work vehicle 1, the increase in the engine rotation speed is suppressed during travel on a slope (downhill travel state) other than at the start and stop of travel, and as a result, the rough terrain work vehicle 1, which often travels on a slope, can be safely operated.

[0093] The rough terrain work vehicle 1 according to this embodiment is operated by the above-described operation control method for the rough terrain work vehicle 1. Therefore, according to the rough terrain work vehicle 1, the effects of the above-described operation control method for the rough terrain work vehicle 1 can be enjoyed, and at the start and stop of traveling when running away to the lower side of the slope is likely to occur, the parking brake 44 is automatically controlled at a timing suitable for each, and running away to the lower side of the slope is suppressed and safe operation can be performed.

[0094] (Other forms) As described above, the present invention has been described based on the above-described embodiments, but the present invention is not limited to the above-described embodiments. It can be implemented in various modes without departing from the gist thereof, and for example, the following modifications are also possible.

[0095] (1) The number of components, the form, position, control order, waiting time, speed, number of gear shifts, etc. of the operator input device described in the above embodiment are examples, and can be changed within a range that does not impair the effects of the present invention.

[0096] (2) In the above-described embodiment, the SOL current L2 corresponding to the vehicle body tilt angle θ2 is calculated in a proportional relationship and has been described as changing according to the current tilt angle of the vehicle body, but the present invention is not limited thereto. The SOL current L2 corresponding to the vehicle body tilt angle θ2 may change according to the current tilt angle of the vehicle body. For example, the SOL current L2 may be calculated from a relational expression other than the proportional relational expression using the vehicle body tilt angle θ2 as a parameter.

[0097] (3) In the above-described embodiment, as an example of the rough terrain work vehicle, a forwarder used for transporting heavy objects such as felled trees in forestry has been described as an example, but the present invention is not limited to the forwarder. The present invention can also be applied to rough terrain work vehicles other than forwarders that assume traveling on rough terrain with slopes, such as forest work vehicles, dumpers, crawler carriers, rough terrain carriers, and forest carriers.

[0098] (4) Next, in the operation control method of the above rough terrain work vehicle, the operation state of the parking brake 44 may be displayed on the display device 8. In this case, when the parking brake 44 is operating and the parking brake switch 62 (parking brake indicating device) is outputting a parking brake indication signal, the control unit 51 (automatic parking brake control processing function 53) displays on the display device 8 that the parking brake 44 has operated in a first display form. Also, when the parking brake 44 is operating and the parking brake switch 62 is not outputting a parking brake indication signal, the control unit 51 (automatic parking brake control processing function 53) displays on the display device 8 that the parking brake 44 has operated in a second display form different from the first display form. FIG. 10 is a flowchart when the display device 8 displays that the parking brake 44 has operated. In this example, the state where the parking brake 44 is operating is indicated by an icon 70. The letter "P" is shown in the center of the icon 70.

[0099] As shown in FIG. 10, the control unit 51 monitors the release output of the parking brake 44 (S60). When the parking brake 44 is not outputting a release output, that is, when the parking brake 44 is operating, it monitors whether the parking brake switch 62 is ON or OFF (S61).

[0100] And when the parking brake switch 62 is ON (when the parking brake switch 62 is outputting a parking brake indication signal), the control unit 51 displays on the display device 8 that the parking brake 44 has operated in a first display form. That is, when the control unit 51 operates the parking brake 44 in conjunction with the ON operation of the parking brake switch 62 while the parking brake 44 is operating, the control unit 51 displays the icon 70 in the first display form on the display device 8. In the above example, S24 and S29 in the flat ground travel stop control ST3 and S32, S38, and S43 in the sloped ground travel stop control ST4 correspond to this case. The first display form in this example is a display form in which the letter "P" is white on a red background.

[0101] On the other hand, when the parking brake switch 62 is OFF (when the parking brake switch 62 is not outputting a parking brake instruction signal) and the control unit 51 activates the parking brake 44, the icon 7 is displayed in the second display form (S64). That is, when the parking brake 44 is operating and the parking brake switch 62 is OFF, the control unit 51 displays the icon 70 in the second display form on the display device 8. In the above example, S28 in the flat ground travel stop control ST3, and S34, S36, and S42 in the inclined ground travel stop control ST4 correspond to this case. The second display form in this example is a display form in which the character "P" is displayed in red on a white background. In this way, the operator can visually determine whether the parking brake 44 was activated by turning the parking brake switch 62 ON while it was operating, or whether it automatically activated while the parking brake switch 62 was in the OFF state.

[0102] Note that when the parking brake 44 is outputting a release output, that is, when the parking brake 44 is not operating, the icon 70 is displayed in the third display form (S65). The third display form in this example is a display form in which the entire icon 70 is gray.

[0103] (Modification Example 1) When the automatic parking brake control process is in the control process content for starting travel, if the control unit 51 acquires a travel instruction signal, it measures the elapsed time since acquiring the travel instruction signal. If the parking brake 44 is released before the elapsed time reaches a predetermined set elapsed time, then during the period from when the parking brake 44 is released until the set elapsed time elapses, the rotational output to the drive wheels may be gradually increased step by step to the rotational output set based on the travel instruction signal. That is, the rough terrain work vehicle is equipped with a timer 71, and in the control process content for starting travel, when the control unit acquires a travel instruction signal, the automatic parking brake control function 53 measures the elapsed time since acquiring the travel instruction signal using the timer 71. If the parking brake is released before the elapsed time reaches a predetermined set elapsed time, then during the period from when the parking brake is released until the set elapsed time elapses, the rotational output to the drive wheels may be gradually increased step by step to the rotational output set based on the travel instruction signal. Here, the timer 71 is shown by a dotted line in FIG. 1. Note that gradually increasing step by step includes, for example, gradually increasing in proportion to the passage of time. By doing so, the start of movement of the rough terrain work vehicle can be made smooth.

[0104] FIG. 11 is a flowchart when the rotation of the engine 2 is gradually increased step by step to the engine indicated rotational speed from the time when the parking brake 44 is released. FIG. 12 is a flowchart when controlling the timing of releasing the parking brake 44 with reference to the travel lever 61 and the parking brake switch 62. FIG. 13 is a flowchart when controlling the timing of releasing the parking brake 44 with reference to the travel lever 61 and the parking brake switch 62 and according to the determination of going uphill / downhill.

[0105] As shown in FIG. 12, in the flat ground travel start control ST1, a travel instruction confirmation (S4) is performed. In the travel instruction confirmation (S4), the following (1) to (3) are confirmed. (1) Has an operation been performed to turn off the parking brake switch 62? (2) Has an operation been performed to tilt the travel lever 61 and has the SOL instruction value, which is the indicated value of the SOL current, become L0 or more? (3) Otherwise

[0106] Here, the SOL instruction value can be obtained based on the travel instruction signal output according to the tilting amount when the travel lever 61 is tilted.

[0107] In the travel instruction confirmation (S4), when it is confirmed that the operation of turning off the parking brake switch 62 has been performed, the travel lever 61 is tilted (S5). When the SOL instruction value becomes L0 or more, the parking brake 44 is automatically released (S6). In this example, as shown in FIG. 11, when the operation of tilting the travel lever 61 is performed and the SOL instruction value becomes L0 or more (S71), the parking brake 44 is released (S72). At this time, the elapsed time from the start of the lever operation is confirmed (S73). When the elapsed time has not elapsed for 0.5 seconds (set elapsed time), the SOL output value is gradually increased from 0 mA to the SOL instruction value in proportion to the passage of time from 0 seconds to 0.5 seconds, and then the SOL current corresponding to the SOL instruction value is output (S74). That is, when the control unit 51 acquires the travel instruction signal, the SOL current value is gradually increased to the SOL current value corresponding to the SOL instruction value from the time when the parking brake 44 is released until the set elapsed time elapses, so that the rotational output to the drive wheels is gradually increased to the rotational output set based on the travel instruction signal. In this example, the SOL current value is increased in proportion to the passage of time, so that the rotational output to the drive wheels is increased in proportion to the passage of time. Thereby, the travel of the rough terrain work vehicle 1 is started, and the operation control by the control unit 51 is returned to the travel state (B) shown in FIG. 3.

[0108] On the other hand, when the operation of turning off the parking brake switch 62 has elapsed for 0.5 seconds (set elapsed time) from the start of the lever operation (S73), the SOL current corresponding to the SOL instruction value is output (S75). Thereby, the travel of the rough terrain work vehicle 1 is started, and the operation control by the control unit 51 is returned to the travel state (B) shown in FIG. 3.

[0109] Also, when it is confirmed in the travel instruction confirmation (S4) that the operation of tilting the travel lever 61 has been performed and the SOL instruction value has become L0 or more, after waiting for the operation of turning off the parking brake switch 62 (S7), the parking brake 44 is released (S8). In this example, as shown in FIG. 11, when the operation of tilting the travel lever 61 is performed and the SOL instruction value becomes L0 or more (S71), after the operation of turning off the parking brake switch 62 is performed (not shown in FIG. 11), the parking brake 44 is released (S72: S8 in FIG. 12). At this time, the elapsed time from the start of the lever operation is confirmed (S73). If the elapsed time has not elapsed for 0.5 seconds (set elapsed time), the SOL output value is gradually increased from 0 mA to the SOL instruction value in proportion to the passage of time between 0 seconds and 0.5 seconds, and then the SOL current corresponding to the SOL instruction value is output (S74). That is, when the control unit 51 acquires the travel instruction signal, the SOL current value is gradually increased to the SOL current value corresponding to the SOL instruction value during the period from the time when the parking brake 44 is released until the set elapsed time elapses, so that the rotational output to the drive wheels is gradually increased to the rotational output set based on the travel instruction signal. Thereby, the travel of the rough terrain work vehicle 1 is started, and the operation control by the control unit 51 is returned to the travel state (B) shown in FIG. 3.

[0110] On the other hand, when the operation of turning off the parking brake switch 62 has elapsed for 0.5 seconds (set elapsed time) from the start of the lever operation (S73), the SOL current corresponding to the SOL instruction value is output (S75). Thereby, the travel of the rough terrain work vehicle 1 is started, and the operation control by the control unit 51 is returned to the travel state (B) shown in FIG. 3.

[0111] Next, in the slope travel start control ST2 shown in FIG. 13, a travel instruction confirmation (S9) is performed. In the travel instruction confirmation (S9), the following (1) to (3) are confirmed. (1) Has the operation of turning off the parking brake switch 62 been performed? (2) Has the operation of tilting the travel lever 61 been performed and the SOL current become L0 or more? (3) Or otherwise?

[0112] When it is confirmed in the traveling direction confirmation (S9) that the operation to turn off the parking brake switch 62 has been performed, if the operation to tilt the travel lever 61 is performed and the SOL current (output value) becomes L0 or more, a slope - up / down determination (S11) is performed to determine whether the rough - terrain work vehicle 1 is in the slope - up state or the slope - down state from the tilting direction of the travel lever 61. Here, when it is determined in the slope - up / down determination (S11) that the vehicle is in the slope - up state, if the operation to tilt the travel lever 61 is performed and it is confirmed that the SOL instruction value is L2 or more, the parking brake 44 is released. In this example, as shown in FIG. 11, the operation to tilt the travel lever 61 is performed and the SOL instruction value becomes L2 or more (S71), and the parking brake 44 is released (S72). At this time, the elapsed time from the start of the lever operation is confirmed (S73). If the elapsed time has not passed 0.5 seconds (set elapsed time), the SOL output value is gradually increased from 0 mA to the SOL instruction value in proportion to the passage of time between 0 seconds and 0.5 seconds, and then the SOL current corresponding to the SOL instruction value is output (S74). That is, when the control unit 51 acquires the travel instruction signal, until the set elapsed time elapses after the parking brake 44 is released, the SOL current value is gradually increased to the SOL current value corresponding to the SOL instruction value, so that the rotational output to the drive wheels is gradually increased to the rotational output set based on the travel instruction signal. Thereby, the travel of the rough - terrain work vehicle 1 is started, and the operation control by the control unit 51 is returned to the slope - up travel control ST5.

[0113] On the other hand, when it is determined in the ramp-up / ramp-down determination (S11) that the vehicle is in the ramp-down state, if an operation of tilting the travel lever 61 is performed and it is confirmed that the SOL instruction value is equal to or greater than L0, the parking brake 44 is released. In this example, as shown in FIG. 11, an operation of tilting the travel lever 61 is performed and the SOL instruction value becomes equal to or greater than L0 (S71), and the parking brake 44 is released (S72). At this time, the elapsed time since the start of the lever operation is confirmed (S73). If the elapsed time has not elapsed for 0.5 seconds (set elapsed time), the SOL output value is gradually increased from 0 mA to the SOL instruction value in proportion to the passage of time between 0 seconds and 0.5 seconds, and then the SOL current corresponding to the SOL instruction value is output (S74). That is, when the control unit 51 acquires the travel instruction signal, the SOL current value is gradually increased to the SOL current value corresponding to the SOL instruction value during the period from the time when the parking brake 44 is released until the set elapsed time elapses, so that the rotational output to the drive wheels is gradually increased to the rotational output set based on the travel instruction signal. As a result, the travel of the rough terrain work vehicle 1 is started, and the operation control by the control unit 51 is returned to the ramp-down travel control ST6.

[0114] Also, when it is confirmed in the travel instruction confirmation (S9) that an operation of tilting the travel lever 61 has been performed and the SOL instruction value has become L0 or more, a slope-up / slope-down determination (S16) is performed to determine whether the rough terrain work vehicle 1 is in a slope-up state or a slope-down state based on the tilting direction of the travel lever 61. When it is determined in the slope-up / slope-down determination (S16) that the vehicle is in a slope-up state, when an operation of tilting the travel lever 61 is performed and the SOL instruction value becomes L2 or more (S17), an operation of waiting for the parking brake switch 62 to be turned OFF (S18) is performed, and then the parking brake 44 is released (S19). In this example, as shown in FIG. 11, when an operation of tilting the travel lever 61 is performed and the SOL instruction value becomes L2 or more (S71), and after an operation of turning the parking brake switch 62 OFF is performed (not shown in FIG. 11), the parking brake 44 is released (S72). At this time, the elapsed time from the time when the lever operation was started is confirmed (S73). If the elapsed time has not passed 0.5 seconds (set elapsed time), the SOL output value is gradually increased from 0 mA to the SOL instruction value in proportion to the passage of time between 0 seconds and 0.5 seconds, and then the SOL current corresponding to the SOL instruction value is output (S74). That is, when the control unit 51 acquires a travel instruction signal, the SOL current value is gradually increased to the SOL current value corresponding to the SOL instruction value during the period from the time when the parking brake 44 is released until the set elapsed time has passed, so that the rotational output to the drive wheels is gradually increased to the rotational output set based on the travel instruction signal. As a result, the travel of the rough terrain work vehicle 1 is started, and the operation control by the control unit 51 is returned to the slope-up travel control ST5.

[0115] When it is determined in the slope climbing / descending determination (S16) that the vehicle is in the descending state, an operation to tilt the travel lever 61 is performed. When the SOL instruction value becomes L0 or more (S20), an operation to turn off the parking brake switch 62 is awaited (S21), and then the parking brake 44 is released (S22). In this example, as shown in FIG. 11, when an operation to tilt the travel lever 61 is performed and the SOL instruction value becomes L02 or more (S71), after an operation to turn off the parking brake switch 62 is performed (not shown in FIG. 11), the parking brake 44 is released (S72). At this point, the elapsed time from the start of the lever operation is confirmed (S73). If the elapsed time has not exceeded 0.5 seconds (set elapsed time), the SOL output value is gradually increased from 0 mA to the SOL instruction value in proportion to the passage of time between 0 seconds and 0.5 seconds, and then the SOL current corresponding to the SOL instruction value is output (S74). That is, when the control unit 51 acquires a travel instruction signal, the SOL current value is gradually increased to the SOL current value corresponding to the SOL instruction value between the time when the parking brake 44 is released and the set elapsed time has passed, so that the rotational output to the drive wheels is gradually increased to the rotational output set based on the travel instruction signal. As a result, the travel of the rough terrain work vehicle 1 is started, and the operation control by the control unit 51 is returned to the descending travel control ST6.

[0116] (Modification 2) Next, in the over-rotation prevention control process in the downhill driving control ST6, it may be possible to set whether the operator performs the over-rotation prevention control process. Also, the operator may be able to set the downhill speed to a first speed and a second speed faster than the first speed, and perform the over-rotation prevention control process (S46) based on the set speed. In this case, the operator sets, as the engine indicated rotational speed, a first indicated rotational speed and a second indicated rotational speed having a rotational speed higher than the first indicated rotational speed, using the engine accelerator dial 64. Further, the rough terrain work vehicle 1 is operated by the operator, and includes an indicated rotational speed selection device 56 that receives the operation and selects one of the first indicated rotational speed and the second indicated rotational speed as the engine indicated rotational speed. When the first indicated rotational speed is selected, the over-rotation prevention control processing function 55 automatically controls the engine 2 so as not to over-rotate, with the rotational speed determined by referring to the first indicated rotational speed as the target rotational speed. Also, when the second indicated rotational speed is selected, the over-rotation prevention control processing function 55 automatically controls the engine 2 so as not to over-rotate, with the rotational speed determined by referring to the second indicated rotational speed as the target rotational speed.

[0117] In this example, the display device 8 is a touch panel capable of touch input. That is, as shown in FIG. 1, the display device 8 also serves as an input device (indicated rotational speed selection device 56). Then, the control unit 51 displays on the display device 8 whether to perform the over-rotation prevention control process, whether to set the downhill speed to the first speed or the second speed, and allows the operator to make a selection. Also, a branch condition shown in FIG. 14 is added between ST6 and S46 in FIG. 9. FIG. 14 is a flowchart of the over-rotation prevention control process with the branch condition added. Here, as the input device (indicated rotational speed selection device 56), a mechanical button for selecting whether to perform the over-rotation prevention control process, whether to set the downhill speed to the first speed or the second speed, may be provided near the display device 8.

[0118] As shown in FIG. 14, in the branch condition added to the overspeed prevention control process, first, it is checked whether the overspeed prevention control process is effective (S81). When the operator sets the overspeed prevention control process not to be performed, regardless of whether the overspeed prevention control start condition is satisfied or not, the control unit 51 returns the operation control to the traveling state (B) shown in FIG. 3 without performing the overspeed prevention control process.

[0119] When the overspeed prevention control process is effective, the downhill speed selected by the operator is checked (S82). When the operator selects the first speed as the downhill speed, the first indicated rotational speed is selected as the engine indicated rotational speed. And when the overspeed prevention control start condition (S46 in FIG. 9) is satisfied, as the overspeed prevention control process, the rotational speed determined with reference to the first indicated rotational speed is set as the target rotational speed, and the engine 2 is automatically controlled so as not to overspeed (S83). Also, when the operator selects the second speed as the downhill speed, the second indicated rotational speed having a higher rotational speed than the first indicated rotational speed is selected as the engine indicated rotational speed. And when the overspeed prevention control start condition (S46 in FIG. 9) is satisfied, as the overspeed prevention control process, the rotational speed determined with reference to the second indicated rotational speed is set as the target rotational speed, and the engine 2 is automatically controlled so as not to overspeed (S84). Here, when the operator sets the downhill speed to the second speed, the traveling speed of the rough terrain work vehicle 1 during the overspeed prevention control process (S47) becomes faster compared to the case where the operator sets the downhill speed to the first speed.

[0120] (Modification Example 3) Also, in the overspeed prevention control process, when returning from the sloping ground to the flat ground, the rotational speed of the engine 2 restricted by the overspeed prevention control process may be gradually returned. That is, the overspeed prevention control process function 55 can be configured such that when the time during which the monitored inclination angle becomes smaller than the set inclination angle continues for the set continuous time, the rotation of the engine 2 is made to reach the engine indicated rotational speed indicated by the operator and the overspeed prevention control process is terminated. FIG. 15 is a flowchart in the case of returning the rotational speed of the engine 2 restricted in the overspeed prevention control process.

[0121] In this case, as shown in FIG. 15, when the over-rotation prevention control start condition is satisfied, it is determined whether the uneven ground working vehicle 1 is in a downhill state or not based on the tilting direction of the travel lever 61 (S85). If it is not in the downhill state, the control is returned to the traveling state (B).

[0122] If it is determined that the vehicle is in the downhill state, it is determined whether the inclination angle of the vehicle body is greater than or equal to the first inclination angle, or whether the actual rotational speed of the engine 2 is greater than the indicated rotational speed by a predetermined number of rotations (S86). In this example, the indicated rotational speed is the engine indicated rotational speed indicated by the engine accelerator dial 64. Therefore, when the downhill speed is set to the first speed, the indicated rotational speed is the first indicated rotational speed, and when the downhill speed is set to the second speed, the indicated rotational speed is the second indicated rotational speed. The predetermined number of rotations is a value smaller than the engine indicated rotational speed. Here, if the inclination angle of the vehicle body is smaller than the first inclination angle, the control is returned to the traveling state (B). Also, if the actual rotational speed of the engine 2 is less than the rotational speed obtained by adding the set rotational speed to the indicated rotational speed, the control is returned to the traveling state (B).

[0123] If the inclination angle of the vehicle body is greater than or equal to the first inclination angle, or if the actual rotational speed of the engine 2 is greater than or equal to the rotational speed obtained by adding the set rotational speed to the indicated rotational speed, it is further confirmed whether the actual rotational speed of the engine 2 exceeds a predetermined comparison rotational speed (S87). The comparison rotational speed is a value greater than the set rotational speed. Also, the comparison rotational speed is a value greater than the engine indicated rotational speed (the first indicated rotational speed and the second indicated rotational speed) indicated by the operator using the engine accelerator dial 64. Here, if the actual rotational speed of the engine 2 exceeds the comparison rotational speed, the stop state (A) is set. The stop state (A) continues until the travel lever 61 is returned to the neutral position by the operator.

[0124] When the actual rotational speed of engine 2 is less than or equal to the comparison rotational speed, check the setting of the downhill speed (S88). When the downhill speed is set to the first speed, fix the indicated rotational speed to the first indicated rotational speed, and increase or decrease the output upper limit value of the SOL current value as necessary so that the gap between the actual rotational speed of engine 2 and the first indicated rotational speed becomes less than or equal to a certain value (S89). When the downhill speed is set to the second speed, fix the indicated rotational speed to the second indicated rotational speed, and increase or decrease the output upper limit value of the SOL current value as necessary so that the gap between the actual rotational speed of engine 2 and the second indicated rotational speed becomes less than or equal to a certain value (S90).

[0125] Here, the over-rotation prevention control processing function 55 monitors whether the state where the inclination angle of the vehicle body is less than the second inclination angle (set inclination angle) has continued for a set continuation time or more (S91). The second inclination angle is a value smaller than the first inclination angle. The set continuation time is several seconds. And when the over-rotation prevention control processing function 55 detects that the state where the inclination angle of the vehicle body is less than the second inclination angle has continued for a set continuation time or more, gradually return the fixing of the indicated rotational speed of engine 2 to the indicated rotational speed and end the over-rotation prevention control (S92). That is, when the state where the inclination angle of the vehicle body is less than the second inclination angle continues for a set continuation time or more, the over-rotation prevention control processing function 55 (control unit 51) determines that the rough terrain work vehicle 1 has returned from the inclined ground to the flat ground. Then, gradually return the rotational speed of engine 2 restricted by the over-rotation prevention control processing to the indicated rotational speed. Thereby, the rotation of engine 2 is made to reach the engine indicated rotational speed indicated by the operator, and the over-rotation prevention control processing is ended. Then, return the operation control by the control unit 51 to the traveling state (B) shown in FIG. 3.

Claims

1. An engine for generating power; The drive wheels rotate on the ground to transmit propulsive force to the ground, a hydrostatic continuously variable transmission having a hydraulic pump that converts rotational energy input from the engine into fluid energy and hydraulically outputs the fluid energy, a hydraulic motor that converts the fluid energy hydraulically transmitted from the hydraulic pump into rotational energy and rotates the energy, and a parking brake that applies a braking force to the rotation of the hydraulic motor, and outputs rotation to the drive wheels in a rotation direction and at a rotation speed according to a travel direction instruction and a travel speed instruction given by an operator; a driving instruction device that is operated by the operator so that the operator can instruct the driving direction and the driving speed, and that outputs a driving instruction signal in response to the operation; A parking brake instruction device that is operated by the operator to instruct the operator to activate / release the parking brake and outputs a parking brake instruction signal in response to the operation; a control unit that monitors the travel instruction signal and the parking brake instruction signal, and controls operation of the hydrostatic continuously variable transmission based on the travel instruction signal and the parking brake instruction signal, Equipping the rough terrain work vehicle with an inclination sensor for detecting an inclination angle; causing the control unit to monitor a tilt angle of the rough terrain work vehicle based on a detection value of the tilt sensor; and executing an automatic parking brake control process in which the control unit automatically activates or releases the parking brake in accordance with the monitored driving instruction signal, the monitored brake instruction signal, and the monitored tilt angle. The automatic parking brake control process includes: A control process content to be executed is selected from a plurality of different control process contents defined in advance according to a current state of the rough terrain working vehicle, determining an operating state including whether the rough terrain work vehicle is about to start traveling or to stop traveling, based on the travel instruction signal and the parking brake instruction signal; When it is determined that the driving state is before the start of running, a control process for starting running is selected as a control process to be performed thereafter; When it is determined that the driving state is before the driving stop, a control process for stopping the driving is selected as a control process to be performed thereafter; determining an inclination state of the rough terrain working vehicle based on the inclination angle in the control process content for starting the traveling and the control process content for stopping the traveling; A driving control method for an all-terrain work vehicle, characterized in that the control content, including the timing of application or release of the parking brake, is changed in response to the determined inclination state of the all-terrain work vehicle.

2. 2. The method for controlling an off-road vehicle according to claim 1, The automatic parking brake control process further includes: When determining the inclination state of the rough terrain working vehicle, the travel instruction signal is also referenced to determine the inclination direction of the rough terrain working vehicle, i.e., whether the rough terrain working vehicle is in an uphill state or a downhill state; When it is determined that the vehicle is in the uphill state, a control process for the uphill state is selected as a control process to be performed thereafter. When it is determined that the vehicle is in a downhill condition, a control process for a downhill condition is selected as the control process to be performed thereafter.

3. 2. The method for controlling an off-road vehicle according to claim 1, The automatic parking brake control process further includes: determining whether the operator has instructed to activate the parking brake or to release the parking brake from the parking brake instruction signal; When it is determined that the parking brake operation is instructed, a control process content for a parking brake operation instruction state is selected as a control process content to be performed thereafter; This is a driving control method for an off-road vehicle, in which, when it is determined that the parking brake is in a state in which release is instructed, control processing content for a parking brake release instructed state is selected as the control processing content to be performed thereafter.

4. 2. The method for controlling an off-road vehicle according to claim 1, and mounting a display device for conveying driving information to the operator; When the parking brake is applied, if the parking brake instruction device outputs the parking brake instruction signal, the display device displays in a first display form that the parking brake has been applied; A driving control method for an off-road vehicle, comprising: when the parking brake is engaged and the parking brake instruction device is not outputting the parking brake instruction signal, displaying on the display device in a second display form different from the first display form that indicates that the parking brake has been engaged.

5. 2. The method for controlling an off-road vehicle according to claim 1, Including having a timer, The automatic parking brake control process includes: In the control process for starting the traveling, when the control unit acquires the traveling instruction signal, the control unit measures the elapsed time from the acquisition of the traveling instruction signal, A driving control method for an off-road vehicle, comprising: when the parking brake, which is applied, is released before the elapsed time has reached a predetermined set elapsed time, gradually increasing the rotational output to the drive wheels to a rotational output that is set based on the travel instruction signal, during the period from the point at which the parking brake is released until the set elapsed time has elapsed.

6. 3. The method for controlling an off-road vehicle according to claim 2, The automatic parking brake control process further includes: In the control process for the uphill state, determining whether the operator has instructed a gradual stop or a sudden stop from the travel instruction signal; In this driving control method for an off-road vehicle, when it is determined that the vehicle is in a state in which a sudden stop has been instructed, the timing of activating the parking brake is delayed compared to when it is determined that the vehicle is in a state in which a gradual stop has been instructed.

7. 7. The method for controlling an off-road vehicle according to claim 1, The driving control method for an all-terrain work vehicle further includes having the control unit determine, based on the monitored driving instruction signal, the brake instruction signal, and the inclination angle, whether the all-terrain work vehicle is in an uphill driving state at an angle equal to or greater than a set angle, and, if it determines that the all-terrain work vehicle is in an uphill driving state at an angle equal to or greater than the set angle, execute an anti-stall control process that automatically controls the driving speed by referring to a specified table to prevent the engine from stalling.

8. 7. The method for controlling an off-road vehicle according to claim 1, an engine accelerator dial is mounted on the engine control unit and receives an engine instruction speed command that is operated by the operator and commands the engine speed in response to the operation; The driving control method for an off-road work vehicle further includes having the control unit determine whether the off-road work vehicle is in a downhill driving state at an angle of more than a set angle based on the monitored driving instruction signal, the brake instruction signal, and the inclination angle, and if it determines that the off-road work vehicle is in a downhill driving state at an angle of more than the set angle, execute an over-speed prevention control process that automatically controls the engine to prevent over-speeding by setting a speed determined by reference to the engine instruction speed instructed by the operator as a target speed, so as to suppress an increase in engine speed.

9. 9. The method for controlling an off-road vehicle according to claim 8, a first instructed engine speed and a second instructed engine speed that is higher than the first instructed engine speed are selectable as the instructed engine speed instructed by the operator, When the first commanded rotation speed is selected, the over-rotation prevention control process automatically controls the engine so as not to over-rotate by setting a rotation speed determined by referring to the first commanded rotation speed as the target rotation speed. A driving control method for an off-road vehicle, characterized in that when the second indicated rotation speed is selected, the over-rev prevention control process automatically controls the engine to not over-rev, by setting a rotation speed determined by reference to the second indicated rotation speed as the target rotation speed.

10. 9. The method for controlling an off-road vehicle according to claim 8, Including having a timer, This driving control method for an off-road vehicle is characterized in that, in the over-rev prevention control process, if the time during which the monitored inclination angle remains smaller than a set inclination angle continues for a set duration or longer, the engine rotation is caused to reach the engine indicated rotation speed indicated by the operator, and the over-rev prevention control process is terminated.

11. An off-road vehicle that travels on rough ground, An engine for generating power; The drive wheels rotate on the ground to transmit propulsive force to the ground, a hydrostatic continuously variable transmission having a hydraulic pump that converts rotational energy input from the engine into fluid energy and hydraulically outputs the fluid energy, a hydraulic motor that converts the fluid energy hydraulically transmitted from the hydraulic pump into rotational energy and rotates the hydraulic energy, and a parking brake that applies a braking force to the rotation of the hydraulic motor, the hydrostatic continuously variable transmission being disposed between the engine and the drive wheels and outputting rotation to the drive wheels in a rotation direction and at a rotation speed according to a travel direction instruction and a travel speed instruction given by an operator; a driving instruction device that is operated by the operator so that the operator can instruct the driving direction and the driving speed, and that outputs a driving instruction signal in response to the operation; A parking brake instruction device that is operated by the operator to instruct the operator to activate / release the parking brake and outputs a parking brake instruction signal in response to the operation; A tilt sensor for detecting a tilt angle; a control unit electrically connected to the hydrostatic continuously variable transmission, the driving instruction device, the parking brake instruction device, and the tilt sensor, and configured to control the operation of the hydrostatic continuously variable transmission based on the driving instruction signal and the parking brake instruction signal; A storage unit that stores the control process content by the control unit, The control unit has an automatic parking brake control processing function that automatically activates or releases the parking brake in accordance with the travel instruction signal, the brake instruction signal, and the inclination angle in accordance with the control processing content stored in the memory unit, the automatic parking brake control processing function is for selecting a control processing content to be executed according to a current situation of the rough terrain work vehicle from among a plurality of different control processing contents defined in advance and stored in the storage unit, determining an operating state including whether the rough terrain work vehicle is about to start traveling or to stop traveling, based on the travel instruction signal and the parking brake instruction signal; When it is determined that the driving state is before the start of running, a control process for starting running is selected as a control process to be performed thereafter; When it is determined that the driving state is before the driving stop, a control process for stopping the driving is selected as a control process to be performed thereafter; determining an inclination state of the rough terrain working vehicle based on the inclination angle in the control process content for starting the traveling and the control process content for stopping the traveling; This off-road work vehicle is characterized by having a function that varies the control content, including the timing of activation or release of the parking brake, in accordance with the determined inclination state of the off-road work vehicle.

12. The off-road working vehicle according to claim 11, The automatic parking brake control processing function further includes: When determining the inclination state of the rough terrain working vehicle, the travel instruction signal is also referenced to determine the inclination direction of the rough terrain working vehicle, i.e., whether the rough terrain working vehicle is in an uphill state or a downhill state; When it is determined that the vehicle is in the uphill state, a control process for the uphill state is selected as a control process to be performed thereafter. When it is determined that the vehicle is in a downhill state, the control process contents to be performed thereafter are selected to be suitable for a downhill state.

13. The off-road working vehicle according to claim 11, The automatic parking brake control processing function further includes: determining whether the operator has instructed to activate the parking brake or to release the parking brake from the parking brake instruction signal; When it is determined that the parking brake operation is instructed, a control process content for a parking brake operation instruction state is selected as a control process content to be performed thereafter; An off-road work vehicle having a function that includes, when it is determined that the parking brake is in a state in which release is instructed, selecting control processing content for a parking brake release instructed state as the control processing content to be performed thereafter.

14. The off-road working vehicle according to claim 11, A display device for conveying driving information to the operator is further provided, The automatic parking brake control processing function includes: When the parking brake is operated, if the parking brake instruction device outputs the parking brake instruction signal, the control unit displays, on the display device, in a first display form that the parking brake has been operated, When the parking brake is engaged and the parking brake instruction device does not output the parking brake instruction signal, the control unit displays on the display device that the parking brake has been engaged in a second display form different from the first display form.

15. The off-road working vehicle according to claim 11, Equipped with a timer, The automatic parking brake control processing function, when the control unit acquires the driving instruction signal in the control processing content for starting driving, measures the elapsed time from when the control unit acquires the driving instruction signal, When the parking brake, which is operating, is released before the elapsed time has reached a predetermined set elapsed time, the off-road work vehicle gradually increases the rotational output to the drive wheels up to the rotational output that is set based on the travel instruction signal during the period from the time the parking brake is released until the set elapsed time has passed.

16. The off-road working vehicle according to claim 12, The automatic parking brake control processing function further includes: In the control process for the uphill state, determining whether the operator has instructed a gradual stop or a sudden stop from the travel instruction signal; This off-road work vehicle has a function including delaying the timing of activating the parking brake when it is determined that the vehicle is in a state in which a sudden stop has been instructed, compared to when it is determined that the vehicle is in a state in which a gradual stop has been instructed.

17. 17. The off-road work vehicle according to any one of claims 11 to 16, The control unit determines whether the rough terrain work vehicle is in an uphill driving state at an angle equal to or greater than a set angle based on the driving instruction signal, the brake instruction signal, and the inclination angle, and if it determines that the vehicle is in an uphill driving state at an angle equal to or greater than the set angle, the control unit has an anti-stall control processing function that automatically controls the driving speed by referring to a specified table to prevent the engine from stalling.

18. 17. The off-road work vehicle according to any one of claims 11 to 16, an engine accelerator dial that is operated by the operator and receives an engine instruction speed that indicates an engine speed in response to the operation; The control unit determines whether the rough terrain work vehicle is in a downhill driving state at an angle of more than a set angle based on the driving instruction signal, the brake instruction signal, and the inclination angle, and if it determines that the vehicle is in a downhill driving state at an angle of more than the set angle, the control unit has an over-revving prevention control processing function that automatically controls the engine to prevent over-revving by setting a target engine speed determined by reference to the engine instruction speed specified by the operator, in order to suppress an increase in engine speed.

19. 19. The off-road vehicle according to claim 18, a command rotation speed selection device that is operated by the operator and selects, as the command engine rotation speed, one of a first command engine rotation speed and a second command engine rotation speed that is higher than the first command engine rotation speed in response to the operation by the operator, The over-rev prevention control processing function, when the first instructed rotation speed is selected, automatically controls the engine so as not to over-rev by setting a rotation speed determined by reference to the first instructed rotation speed as a target rotation speed, and, when the second instructed rotation speed is selected, automatically controls the engine so as not to over-rev by setting a rotation speed determined by reference to the second instructed rotation speed as a target rotation speed.

20. 19. The off-road vehicle according to claim 18, Equipped with a timer, The over-rev prevention control processing function of this off-road work vehicle is characterized in that, when the time during which the monitored inclination angle remains smaller than a set inclination angle continues for a set duration, the engine rotation is increased to the engine indicated speed indicated by the operator, and the over-rev prevention control processing is terminated.