Work vehicle and control method for work vehicle

Patent metadata

Field	Value
Publication number	US-11326324-B2
Application number	US-201916627096-A
Country	US
Kind code	B2
Filing date	Jan 21, 2019
Priority date	Feb 23, 2018
Publication date	May 10, 2022
Grant date	May 10, 2022

Abstract

The controller determines whether the vehicle is in a shuttle motion from the operating position of the forward/reverse travel operating member and the actual traveling direction of the vehicle. The controller determines a target braking force when the vehicle is in the shuttle motion. The controller determines at least one of a target displacement of the travel pump and a target displacement of the travel motor based on the target braking force.

First claim

What is claimed is:

1. A work vehicle comprising:
an engine;
a travel pump configured to be driven by the engine;
a hydraulic circuit connected to the travel pump;
a travel motor connected to the travel pump through the hydraulic circuit;
a forward/reverse travel operating member;
a forward/reverse travel operating sensor configured to output a signal indicative of an operating position of the forward/reverse travel operating member;
a traveling direction sensor configured to output a signal indicative of an actual traveling direction of the work vehicle; and
a controller configured to control the travel pump and the travel motor, the controller being configured to
receive the signals from the forward/reverse travel operating sensor and the traveling direction sensor,
determine whether the work vehicle is in a shuttle motion from the operating position of the forward/reverse travel operating member and the actual traveling direction of the work vehicle,
determine a target braking force when the work vehicle is in the shuttle motion, the target braking force being a target value for the total deceleration-inducing force acting on the work vehicle,
store a displacement instruction of the travel pump at a starting time of the shuttle motion,
determine a pump target displacement of the travel pump and a motor target displacement of the travel motor based on the target braking force, the pump target displacement being determined by reducing the displacement instruction of the travel pump at the starting time of the shuttle motion in accordance with the target braking force and an elapsed time from the starting time of the shuttle motion, and
control the travel pump and the travel motor to the pump target displacement and the motor target displacement, respectively.

2. The work vehicle according to claim 1 , further comprising:
an accelerator operating member; and
an accelerator operating sensor configured to output a signal indicative of an operating amount of the accelerator operating member,
the controller being further configured to
receive a signal from the accelerator operating sensor, and
determine the target braking force in response to the operating amount of the accelerator operating member.

3. The work vehicle according to claim 2 , wherein
the controller is further configured to refer to target braking data to determine the target braking force from the operating amount of the accelerator operating member, the target braking data defining a relationship between the operating amount of the accelerator operating member and the target braking force.

4. The work vehicle according to claim 1 , wherein
the controller is further configured to
receive a signal indicating an actual vehicle speed,
determine a target vehicle speed during the shuttle motion from the elapsed time from the starting time of the shuttle motion, the actual vehicle speed, and the target braking force,
calculate a vehicle speed ratio by dividing the target vehicle speed by the actual vehicle speed, and
reduce the displacement instruction by multiplying the displacement instruction by the vehicle speed ratio.

5. The work vehicle according to claim 4 , wherein
the controller is further configured to bring the target vehicle speed during the shuttle motion close to zero in response to the elapsed time from the starting time of the shuttle motion.

6. The work vehicle according to claim 1 , wherein
the travel pump includes a first pump port and a second pump port,
the travel motor includes a first motor port and a second motor port, and
the hydraulic circuit includes a first circuit connecting the first pump port and the first motor port, and a second circuit connecting the second pump port and the second motor port, and
the work vehicle further comprises:
a first pressure sensor configured to output a signal indicative of a hydraulic pressure in the first circuit; and
a second pressure sensor configured to output a signal indicative of a hydraulic pressure in the second circuit,
the controller being further configured to
receive the signal from the first pressure sensor and the signal from the second pressure sensor,
acquire an actual differential pressure between the first circuit and the second circuit from the signal from the first pressure sensor and the signal from the second pressure sensor, and
determine the motor target displacement from the target braking force and the actual differential pressure.

7. The work vehicle according to claim 1 , wherein
the controller is further configured to
receive a signal indicating an actual vehicle speed, and
reduce the target braking force in response to a drop in the actual vehicle speed.

8. The work vehicle according to claim 7 , wherein
the controller is further configured to refer to braking upper limit data to determine an upper limit of the target braking force from the actual vehicle speed, the braking upper limit data defining a relationship between the actual vehicle speed and the upper limit of the target braking force.

9. The work vehicle according to claim 1 , wherein
the controller is further configured to determine that the work vehicle is in the shuttle motion when the operating position of the forward/reverse travel operating member and the actual traveling direction of the work vehicle do not match.

10. The work vehicle according to claim 1 , further comprising:
an inching operating member; and
an inching operating sensor configured to output a signal indicative of an operating amount of the inching operating member,
the controller being further configured to
receive the signal from the inching operating sensor, and
determine the target braking force in response to the operating amount of the inching operating member.

11. The work vehicle according to claim 10 , wherein
the controller is further configured to refer to target braking data to determine the target braking force from the operating amount of the inching operating member, the target braking data defining a relationship between the operating amount of the inching operating member and the target braking force.

12. A method executed by a controller in order to control a work vehicle, the work vehicle comprising an engine, a travel pump configured to be driven by the engine, a hydraulic circuit connected to the travel pump, a travel motor connected to the travel pump through the hydraulic circuit, and a forward/reverse travel operating member, the method comprising:
receiving a signal indicative of an operating position of the forward/reverse travel operating member;
receiving a signal indicative of an actual traveling direction of the work vehicle;
determining that the work vehicle is in a shuttle motion from the operating position of the forward/reverse travel operating member and the actual traveling direction of the work vehicle;
determining a target braking force when the work vehicle is in the shuttle motion, the target braking force being a target value for the total deceleration-inducing force acting on the work vehicle;
storing a displacement instruction of the travel pump at a starting time of the shuttle motion;
determining a pump target displacement of the travel pump and a motor target displacement of the travel motor based on the target braking force, the pump target displacement being determined by reducing the displacement instruction of the travel pump at the starting time of the shuttle motion in accordance with the target braking force and an elapsed time from the starting time of the shuttle motion; and
controlling the travel pump and the travel motor to the pump target displacement

Assignees

• Komatsu Mfg Co Ltd

Inventors

• Oasa Takahisa

Classifications

• F16H2059/708

  Sensing reverse gear, e.g. by a reverse gear switch · CPC title

• F16H2059/6861

  the pressures, e.g. high, low or differential pressures · CPC title

• F16H2059/366

  Engine or motor speed · CPC title

• F16H59/44

  dependent on machine speed {, e.g. the vehicle speed} (F16H59/46 takes precedence) · CPC title

• F16H61/4157

  Control of braking, e.g. preventing pump over-speeding when motor acts as a pump · CPC title