Work machine and control method

Patent metadata

Field	Value
Publication number	US-11719335-B2
Application number	US-202017432350-A
Country	US
Kind code	B2
Filing date	Apr 2, 2020
Priority date	Apr 11, 2019
Publication date	Aug 8, 2023
Grant date	Aug 8, 2023

Abstract

An HST circuit has a hydraulic pump that converts a drive force of an engine into energy of oil, and a hydraulic motor that converts the energy of the oil converted by the hydraulic pump into drive energy. Pressure sensors detect a pressure of the oil within the HST circuit. A variable charge pump replenishes the oil into the HST circuit. A controller controls a capacity of the variable charge pump based on the pressure of the oil within the HST circuit detected by the pressure sensors.

First claim

The invention claimed is:

1. A work machine comprising:
a motive power source;
a closed circuit having a pump that converts a drive force of the motive power source into energy of a fluid and a motor that converts the energy of the fluid converted by the pump into drive energy;
a pressure sensor that detects a pressure of the fluid within the closed circuit;
a variable charge pump that replenishes the fluid into the closed circuit; and
a controller that controls a capacity of the variable charge pump based on the pressure of the fluid within the closed circuit detected by the pressure sensor, wherein the controller controls the capacity of the variable charge pump to be set to a first capacity when the pressure of the fluid detected by the pressure sensor is a first pressure, and controls the capacity of the variable charge pump to be set to a second capacity smaller than the first capacity when the pressure of the fluid detected by the pressure sensor is a second pressure smaller than the first pressure.

2. The work machine according to claim 1 , wherein the controller controls the capacity of the variable charge pump to be changed steplessly based on the pressure of the fluid detected by the pressure sensor.

3. The work machine according to claim 1 , further comprising a rotation sensor that detects a number of rotations of the motive power source, wherein
the controller controls the capacity of the variable charge pump based on the number of rotations of the motive power source detected by the rotation sensor and the pressure of the fluid detected by the pressure sensor.

4. The work machine according to claim 1 , wherein the controller sets a minimum capacity of the variable charge pump based on a towing force of the work machine.

5. The work machine according to claim 4 , wherein
the closed circuit has a first flow path that connects the pump and the motor, and a second flow path that connects the pump and the motor and is different from the first flow path, and
the pressure sensor includes a first pressure sensor that detects a pressure of the fluid in the first flow path, and a second pressure sensor that detects a pressure of the fluid in the second flow path.

6. The work machine according to claim 1 , further comprising an inclination angle sensor that detects an inclination angle of the work machine, wherein
the controller sets a minimum capacity of the variable charge pump based on the inclination angle of the work machine detected by the inclination angle sensor.

7. The work machine according to claim 1 , further comprising a travel lever that selects one state of forward travel, backward travel, and neutral in traveling of the work machine, wherein
the controller sets a minimum capacity of the variable charge pump based on the state selected by the travel lever.

8. The work machine according to claim 1 , further comprising
a work tool; and
an actuator that drives the work tool, wherein
the variable charge pump is connected to provide a pilot pressure to a drive circuit for the actuator.

9. The work machine according to claim 8 , further comprising a pilot pressure sensor that detects the pilot pressure, wherein
the controller sets a minimum capacity of the variable charge pump based on the pilot pressure detected by the pilot pressure sensor.

10. A control method for a work machine, the work machine having a motive power source, and a closed circuit having a pump that converts a drive force of the motive power source into energy of a fluid and a motor that converts the energy of the fluid converted by the pump into drive energy, the control method comprising:
detecting a pressure of the fluid within the closed circuit; and
controlling a capacity of a variable charge pump that replenishes the fluid into the closed circuit, based on the detected pressure of the fluid within the closed circuit, wherein, in controlling the capacity of the variable charge pump, the capacity of the variable charge pump is controlled to be set to a first capacity when the detected pressure of the fluid is a first pressure, and the capacity of the variable charge pump is controlled to be set to a second capacity smaller than the first capacity when the detected pressure of the fluid is a second pressure smaller than the first pressure.

11. The control method for the work machine according to claim 10 , wherein, in controlling the capacity of the variable charge pump, the capacity of the variable charge pump is controlled to be changed steplessly based on the detected pressure of the fluid.

12. The control method for the work machine according to claim 10 , further comprising detecting a number of rotations of the motive power source, wherein
in controlling the capacity of the variable charge pump, the capacity of the variable charge pump is controlled based on the detected number of rotations of the motive power source and the detected pressure of the fluid.

13. The control method for the work machine according to claim 10 , further comprising detecting a towing force of the work machine, wherein
in controlling the capacity of the variable charge pump, a minimum capacity of the variable charge pump is set based on the detected towing force of the work machine.

14. The control method for the work machine according to claim 13 , wherein
the closed circuit has a first flow path that connects the pump and the motor, and a second flow path that connects the pump and the motor and is different from the first flow path, and
detecting the pressure of the fluid within the closed circuit includes detecting at least one of a pressure of the fluid in the first flow path and a pressure of the fluid in the second flow path.

15. The control method for the work machine according to claim 10 , further comprising detecting an inclination angle of the work machine, wherein
in controlling the capacity of the variable charge pump, a minimum capacity of the variable charge pump is set based on the detected inclination angle of the work machine.

16. The control method for the work machine according to claim 10 , further comprising detecting one travel state of forward travel, backward travel, and neutral in traveling of the work machine, wherein
in controlling the capacity of the variable charge pump, a minimum capacity of the variable charge pump is set based on the detected travel state.

17. The control method for the work machine according to claim 10 , wherein
the work machine further has a work tool, and an actuator that drives the work tool,
the variable charge pump is connected to provide a pilot pressure to a drive circuit for the actuator,
the control method further comprises detecting the pilot pressure, and
in controlling the capacity of the variable charge pump, a minimum capacity of the variable charge pump is set based on the detected pilot pressure.

Assignees

• Komatsu Mfg Co Ltd

Inventors

• Nakashima Akira
• Kamikawa Shinobu

Classifications

• F16H61/4078 Primary

  Fluid exchange between hydrostatic circuits and external sources or consumers · CPC title

• E02F9/22

  Hydraulic or pneumatic drives {(for dipper or bucket arm position control E02F3/43, for blade position control for graders E02F3/844; for turntables E02F9/121; for fork-lift trucks B66F9/22)} · CPC title

• F15B11/08

  with only one servomotor · CPC title

• F15B11/167

  using pilot pressure to sense the demand · CPC title

• F15B13/042

  operated by fluid pressure {(F15B13/0401, F15B13/0416 take precedence)} · CPC title