Work vehicle and method for controlling work vehicle

Patent metadata

Field	Value
Publication number	US-12312003-B2
Application number	US-202217844071-A
Country	US
Kind code	B2
Filing date	Jun 20, 2022
Priority date	Aug 5, 2021
Publication date	May 27, 2025
Grant date	May 27, 2025

Abstract

A method for controlling a work vehicle includes driving a first hydraulic pump and a second hydraulic pump by an engine to supply hydraulic fluid to a first hydraulic motor and a second hydraulic motor, respectively, to drive a first traveling device and a second traveling device, respectively. An operation state of a direction input device to operate a traveling direction of the work vehicle is detected. Based on the operation state detected, whether or not a traveling state of the work vehicle is a turning state. When it is determined that the traveling state is the turning state, a rotation command to decrease a target rotational speed of the engine from a first rotational speed to a second rotational speed is output.

First claim

What is claimed is:

1. A method for controlling a work vehicle, comprising:
driving a first hydraulic pump and a second hydraulic pump by an engine of the work vehicle to supply hydraulic fluid to a first hydraulic motor and a second hydraulic motor, respectively, to drive a first traveling device and a second traveling device, respectively, to advance the work vehicle, the first traveling device and the second traveling device facing each other;
detecting an operation state of a direction input device to operate a traveling direction of the work vehicle;
determining whether or not a traveling state of the work vehicle is a turning state based on the operation state that is detected;
outputting a rotation command to decrease a target rotational speed of the engine from a first rotational speed to a second rotational speed when it is determined that the traveling state is the turning state; and
controlling pilot pressures of pilot oil supplied to the first hydraulic pump and the second hydraulic pump to be target pilot pressures, displacement volumes of the first hydraulic pump and the second hydraulic pump to which the target pilot pressures are applied respectively being maximized when substantially no load is applied to the first hydraulic motor and the second hydraulic motor.

2. The control method according to claim 1 , further comprising:
determining the first rotational speed based on an amount of operation of a speed input device different from the direction input device of the work vehicle; and
outputting the rotation command to set the target rotational speed of the engine of the work vehicle to the first rotational speed, when the first rotational speed is lower than a first threshold speed that is predetermined, even if it is determined that the traveling state is the turning state.

3. The control method according to claim 2 , wherein the second rotation speed is a value obtained by multiplying the first rotational speed by a predetermined ratio.

4. The control method according to claim 2 , further comprising:
measuring a pitch angle which is a tilt angle of the work vehicle in a front-back direction of the work vehicle when it is determined that the traveling state is the turning state; and
determining the second rotational speed is determined in accordance with the pitch angle.

5. The control method according to claim 2 , further comprising:
measuring a roll angle which is a tilt angle of the work vehicle in a left-right direction of the work vehicle when it is determined that the traveling state is the turning state; and
determining the second rotational speed in accordance with the roll angle.

6. The control method according to claim 4 , wherein the second rotational speed is determined to be equal to the first rotational speed when the pitch angle is less than a predetermined first threshold angle.

7. The control method according to claim 6 ,
wherein when the pitch angle is equal to or greater than the first threshold angle and less than a second threshold angle larger than the first threshold angle, the second rotational speed is determined to be a value obtained by multiplying the first rotational speed by a first ratio that is predetermined, and
wherein when the pitch angle is equal to or greater than the second threshold angle, the second rotational speed is determined to be a value obtained by multiplying the first rotational speed by a second ratio which is predetermined and is smaller than the first ratio.

8. The control method according to claim 3 , further comprising:
detecting a rotational speed of the engine, wherein the rotation command to set the target rotational speed to the first rotational speed is output when the rotational speed of the engine which is detected is equal to or lower than a second threshold speed which is predetermined and lower than the first threshold speed.

9. The control method according to claim 1 , further comprising:
detecting a temperature of the hydraulic fluid, wherein the rotation command to set the target rotational speed to the first rotational speed is output when the temperature is less than a predetermined threshold temperature.

10. The control method according to claim 1 , wherein the rotation command to set the target rotational speed to the first rotational speed is output neither when a height of an arm of the work vehicle with respect to a vehicle body of the work vehicle is equal to or greater than a predetermined threshold height nor when the operation is performed.

11. The control method according to claim 1 , further comprising:
determining whether or not the traveling state has become a straight advancing state after the traveling state has become the turning state, wherein when it is determined that the traveling state has become the straight advancing state, the rotation command to set the target rotational speed of the engine to the first rotational speed is output.

12. The control method according to claim 11 , wherein when it is determined that the traveling state is neither the straight advancing state nor the turning state, the rotation command to increase the target rotational speed of the engine from the second rotational speed to the first rotational speed is output.

13. The control method according to claim 12 , wherein when a time for which at least one of a hydraulic pressure of a hydraulic circuit connecting the first hydraulic pump and the first hydraulic motor and a hydraulic pressure of a hydraulic circuit connecting the second hydraulic pump and the second hydraulic motor continues to be equal to or greater than a threshold pressure exceeds a threshold time, the rotation conmmand to further increase the target rotational speed from the second rotational speed to the first rotational speed is output.

14. The control method according to claim 1 , wherein, when a time for which at least one of a hydraulic pressure of a hydraulic circuit connecting the first hydraulic pump and the first hydraulic motor and a hydraulic pressure of a hydraulic circuit connecting the second hydraulic pump and the second hydraulic motor continues to be equal to or greater than a threshold pressure exceeds a threshold time, the rotation command to further increase the target rotational speed from the second rotational speed to the first rotational speed is output.

15. The control method according to claim 1 , wherein it is determined that the traveling state is the turning state when a degree of a first displacement according to which movement in the left-right direction is instructed is not less than a first displacement value and a degree of a second displacement according to which movement in the front-rear direction is instructed is less than a second displacement value, the first displacement and the second displacement being a displacement from a neutral position of the direction input device.

16. The control method according to claim 15 , wherein it is determined that the traveling state is the turning state,
when a first pilot pressure applied to a first port of the first hydraulic pump to drive the first hydraulic pump forward is substantially equal to a fourth pilot pressure applied to a fourth port of the second hydraulic pump to drive the second hydraulic pump backward, and an average of the first pilot pressure and the fourth pilot pressure is greater than a larger value of a second pilot pressure applied to a second port of the first hydraulic pump to drive the first hydraulic pump backward and a third pilot pressure applied to a third port of the second hydraulic pump to drive the second hydraulic pump for

Assignees

• Kubota Kk

Inventors

• Abe Daiki
• Hamamoto Ryota
• Bunryo Yuki

Classifications

• B62D11/005

  Hydraulic control systems · CPC title

• E02F9/2296

  Systems with a variable displacement pump · CPC title

• E02F9/2292

  Systems with two or more pumps · CPC title

• E02F9/225

  Control of steering, e.g. for hydraulic motors driving the vehicle tracks (steering in general B62D) · CPC title

• E02F3/3414

  the arms being pivoted at the rear of the vehicle chassis, e.g. skid steer loader · CPC title