Working machine

Patent metadata

Field	Value
Publication number	US-11788255-B2
Application number	US-202117360398-A
Country	US
Kind code	B2
Filing date	Jun 28, 2021
Priority date	Jun 30, 2020
Publication date	Oct 17, 2023
Grant date	Oct 17, 2023

Abstract

A working machine includes a prime mover, a traveling pump driven by a power of the prime mover to deliver operation fluid, a traveling motor rotated by the operation fluid delivered from the traveling pump to have a rotation speed stage shiftable between a first speed stage and a second speed stage higher than the first speed stage, a traveling switching valve shiftable between a first state where the rotation speed stage of the traveling motor is set to the first speed stage and a second state where the rotation speed stage of the traveling motor is set to the second speed stage, an actuation valve configured to change a pilot pressure of a pilot fluid to control a flow of operation fluid delivered from the traveling pump, and a controller configured to control the pilot pressure of the pilot fluid output from the actuation valve so that a value of the pilot pressure differs depending on whether the set rotation speed stage of the traveling motor is the first speed stage or the second speed stage.

First claim

What is claimed is:

1. A working machine comprising:
a prime mover;
a traveling pump driven by a power of the prime mover to deliver operation fluid;
a traveling motor rotated by the operation fluid delivered from the traveling pump to have a rotation speed stage shiftable between a first speed stage and a second speed stage higher than the first speed stage;
a traveling switching valve shiftable between a first state where the rotation speed stage of the traveling motor is set to the first speed stage and a second state where the rotation speed stage of the traveling motor is set to the second speed stage;
an actuation valve configured to change a pilot pressure of a pilot fluid to control a flow of operation fluid delivered from the traveling pump; and
a controller configured to control the pilot pressure of the pilot fluid output from the actuation valve so that a value of the pilot pressure differs depending on whether the set rotation speed stage of the traveling motor is the first speed stage or the second speed stage.

2. The working machine according to claim 1 , wherein
the controller controls the pilot pressure based on whether the set rotation speed stage of the traveling motor is the first speed stage or the second speed stage.

3. The working machine according to claim 2 , wherein
when the rotation speed stage of the traveling motor is set to the first speed stage, the controller controls, based on a rotation speed of the prime mover, a first-speed pilot pressure that is the pilot pressure corresponding to the traveling motor having the rotation speed state set to the first speed stage, and
when the rotation speed stage of the traveling motor is set to the second speed stage, the controller controls, based on the rotation speed of the prime mover, a second-speed pilot pressure that is the pilot pressure corresponding to the traveling motor having the rotation speed stage set to the second speed stage.

4. The working machine according to claim 3 , wherein
the controller controls the second-speed pilot pressure to be lower than the first-speed pilot pressure.

5. The working machine according to claim 1 , comprising:
an accelerator configured to determine a target rotation speed of the prime mover; and
a rotation detector configured to detect an actual rotation speed of the prime mover, wherein
the controller controls the pilot pressure according to a dropping rotation speed that is a difference between the target rotation speed and the actual rotation speed.

6. The working machine according to claim 5 , wherein
the controller adjusts the pilot pressure when the dropping rotation speed is equal to or higher than a first threshold.

7. The working machine according to claim 5 , wherein
the controller determines the pilot pressure based on the actual rotation speed when the dropping rotation speed is equal to or higher than a second threshold.

8. The working machine according to claim 1 , wherein
when the rotation speed stage of the traveling motor is set to the first speed stage, the controller controls, based on an actual rotation speed of the prime mover, a first-speed pilot pressure, which is the pilot pressure corresponding to the traveling motor having the rotation speed stage set to the first speed stage, and
when the rotation speed stage of the traveling motor is set to the second speed stage, the controller controls, based on the actual rotation speed of the prime mover, a second-speed pilot pressure, which is the pilot pressure corresponding to the traveling motor having the rotation speed stage set to the second speed stage, to be lower than the first-speed pilot pressure.

9. The working machine according to claim 8 , comprising:
an accelerator configured to determine a target rotation speed of the prime mover; and
a rotation detector configured to detect an actual rotation speed of the prime mover, wherein
the controller includes:
a storage storing a first line determining the first-speed pilot pressure based on the actual rotation speed when the set rotation speed stage of the traveling motor is the first speed stage, a second line determining the second-speed pilot pressure based on the actual rotation speed when the set rotation speed stage of the traveling motor is the second speed stage, and a third line determining the first-speed pilot pressure and the second-speed pilot pressure based on the actual rotation speed regardless of whether the set rotation speed stage of the traveling motor is the first speed stage or the second speed stage; and
a determination unit configured to determine the pilot pressure based on any one of the first line, the second line, and the third line stored on the storage.

10. The working machine according to claim 9 , wherein
the determination unit determines the pilot pressure based on either the first line or the second line when a dropping rotation speed is equal to or higher than a third threshold, the dropping rotation speed being a difference between the target rotation speed determined by the accelerator and the actual rotation speed detected by the rotation detector.

11. The working machine according to claim 1 , wherein
the controller controls the pilot pressure to reduce an operation amount of operating the actuation valve before or after the rotation speed stage of the traveling motor is shifted to either the first speed stage or the second speed stage.

12. The working machine according to claim 1 , wherein
the controller reduces a rotation speed of the prime mover before or after the rotation speed stage of the traveling motor is shifted to either the first speed stage or the second speed stage.

13. The working machine according to claim 1 , further comprising:
an accelerator configured to determine a target rotation speed of the prime mover; and
a rotation detector configured to detect an actual rotation speed of the prime mover, wherein
the controller controls the pilot pressure in a PI control or a PID control based on a dropping rotation speed that is a difference between the target rotation speed and the actual rotation speed.

14. The working machine according to claim 13 , wherein
in the PI control or the PID control, the controller uses a control gain that differs depending on whether the set rotation speed stage of the traveling motor is the first speed stage or the second speed stage.

15. The working machine according to claim 14 , wherein
in the PI control or the PID control, the controller uses a proportional gain that differs depending on whether the set rotation speed stage of the traveling motor is the first speed stage or the second speed stage.

16. The working machine according to claim 15 , wherein
in the PI control or the PID control, the controller uses a differential gain that differs depending on whether the set rotation speed stage of the traveling motor is the first speed stage or the second speed stage.

17. A working machine comprising:
a prime mover;
a traveling pump driven by a power of the prime mover and to deliver operation fluid;
a traveling motor rotated by the operation fluid delivered from the traveling pump to have a rotation speed stage shiftable between a first speed stage and a second speed stage higher than the first speed stage;
a machine body on which the prime mover, the traveling pump, and the traveling motor are mounted;
a traveling switching valve shiftable between a first state where the rotation speed stage of the traveling motor is set to the first speed stage and a second state where the rotation speed stage of

Assignees

• Kubota Kk

Inventors

• Fukuda Yuji
• Hamamoto Ryota
• Tomita Jun
• Abe Daiki

Classifications

• E02F9/2253 Primary

  Controlling the travelling speed of vehicles, e.g. adjusting travelling speed according to implement loads, control of hydrostatic transmission · CPC title

• E02F9/2246

  Control of prime movers, e.g. depending on the hydraulic load of work tools · CPC title

• E02F9/2267

  Valves or distributors (position of valves arrangements on upper-structures E02F9/0875) · CPC title

• E02F9/2285

  Pilot-operated systems · CPC title

• E02F9/2296

  Systems with a variable displacement pump · CPC title