Working machine

Patent metadata

Field	Value
Publication number	US-12247374-B2
Application number	US-202218075917-A
Country	US
Kind code	B2
Filing date	Dec 6, 2022
Priority date	Dec 28, 2021
Publication date	Mar 11, 2025
Grant date	Mar 11, 2025

Abstract

A working machine includes a controller that performs shift shock reduction control when shift-down switching from a second state to a first state, in which a motor speed can be increased up to a first maximum speed lower than a second maximum speed available in the second state, is performed. The controller includes a first processor configured to, based on a drop amount that is a difference between target and actual numbers of revolutions of a prime mover, compute a first reduction amount for reducing an amount of hydraulic fluid supply from a traveling pump to a traveling motor, a second processor configured to compute a second reduction amount based on a degree of straight traveling of a machine body, and a reduction controller configured to, based on the first or second reduction amount, whichever is larger in absolute value, perform the shift shock reduction control.

First claim

What is claimed is:

1. A working machine, comprising:
a prime mover;
a traveling pump to operate by power of the prime mover and deliver a hydraulic fluid;
a traveling motor to rotate using the hydraulic fluid delivered by the traveling pump;
a machine body in which the prime mover, the traveling pump, and the traveling motor are provided;
a traveling switching valve operable to switch between a first state allowing a rotation speed of the traveling motor to increase up to a first maximum speed, and a second state allowing the rotation speed of the traveling motor to increase up to a second maximum speed higher than the first maximum speed;
a traveling manipulator including an operation valve to change hydraulic fluid pressure acting on the traveling pump in response to operation of an operation member; and
a controller configured or programmed to perform shift shock reduction control of reducing an amount of hydraulic fluid supply from the traveling pump to the traveling motor when shift-down switching from the second state to the first state is performed, the controller including
a first processor configured or programmed to, based on a drop amount that is a difference between a target number of revolutions of the prime mover and an actual number of revolutions of the prime mover, compute a first reduction amount for reducing the amount of hydraulic fluid supply from the traveling pump to the traveling motor in the shift shock reduction control;
a second processor configured or programmed to, based on a degree of straight traveling of the machine body, compute a second reduction amount for reducing the amount of hydraulic fluid supply from the traveling pump to the traveling motor in the shift shock reduction control; and
a reduction controller configured or programmed to, based on a reduction amount that is either the first reduction amount computed by the first processor or the second reduction amount computed by the second processor, whichever is larger in absolute value, perform the shift shock reduction control.

2. The working machine according to claim 1 , wherein
the first processor is configured or programmed to, based on the drop amount that is the difference between the target number of revolutions of the prime mover and the actual number of revolutions of the prime mover, compute the first reduction amount that is an amount of reduction in number of revolutions of the prime mover in the shift shock reduction control,
the second processor is configured or programmed to, based on the degree of straight traveling of the machine body, compute the second reduction amount that is an amount of reduction in the number of revolutions of the prime mover in the shift shock reduction control, and
the reduction controller is configured or programmed to perform the shift shock reduction control of reducing the amount of hydraulic fluid supply from the traveling pump to the traveling motor by reducing the number of revolutions of the prime mover based on the first reduction amount computed by the first processor or the second reduction amount computed by the second processor, whichever is larger in absolute value.

3. The working machine according to claim 2 , wherein
the reduction controller is configured or programmed to set, as a reduced value of the number of revolutions of the prime mover in the shift shock reduction control, a value obtained by subtracting the reduction amount from the actual number of revolutions of the prime mover.

4. The working machine according to claim 3 , wherein
in a reduction interval till the actual number of revolutions of the prime mover reaching the reduced value, the reduction controller is configured or programmed to set a first rate of reduction in the actual number of revolutions of the prime mover to be constant from a starting point of the reduction interval to an ending point of the reduction interval.

5. The working machine according to claim 3 , wherein
in a reduction interval till the actual number of revolutions of the prime mover reaching the reduced value, the reduction controller is configured or programmed to set a second rate of reduction in the actual number of revolutions of the prime mover in an interval from a starting point of the reduction interval to some midpoint therein to be higher than a third rate of reduction in the actual number of revolutions of the prime mover in an interval from said some midpoint to an ending point of the reduction interval.

6. The working machine according to claim 3 , wherein
the reduction controller is configured or programmed to vary timing of switching the traveling switching valve from the second state to the first state according to the drop amount.

7. The working machine according to claim 3 , further comprising:
a selector switch configured to issue a shift command for either shift-up switching or shift-down switching; and
an accelerator configured to set the target number of revolutions of the prime mover, wherein
when the selector switch issues the shift command for the shift-down switching, the reduction controller is configured or programmed to reduce the actual number of revolutions of the prime mover toward a reduced value set based on the reduction amount, and switch the traveling switching valve to either the first state or the second state in accordance with the shift command.

8. The working machine according to claim 3 , wherein
the reduction controller is configured or programmed to set the reduction amount to be larger as the drop amount is smaller and set the reduction amount to be smaller as the drop amount is larger.

9. The working machine according to claim 2 , wherein
the reduction controller is configured or programmed to vary timing of switching the traveling switching valve from the second state to the first state according to the drop amount.

10. The working machine according to claim 2 , further comprising:
a selector switch configured to issue a shift command for either shift-up switching or shift-down switching; and
an accelerator configured to set the target number of revolutions of the prime mover, wherein
when the selector switch issues the shift command for the shift-down switching, the reduction controller is configured or programmed to reduce the actual number of revolutions of the prime mover toward a reduced value set based on the reduction amount, and switch the traveling switching valve to either the first state or the second state in accordance with the shift command.

11. The working machine according to claim 2 , wherein
the reduction controller is configured or programmed to set the reduction amount to be larger as the drop amount is smaller and set the reduction amount to be smaller as the drop amount is larger.

12. The working machine according to claim 1 , further comprising:
an actuation valve connected to the operation valve upstream of or downstream of the operation valve and configured to control hydraulic fluid pressure acting from the operation valve on the traveling pump; wherein
the controller is configured or programmed to perform the shift shock reduction control of reducing the amount of hydraulic fluid supply from the traveling pump to the traveling motor by reducing the opening of the actuation valve by outputting a control signal to the actuation valve when the shift-down switching is performed,
the first processor is configured or programmed to, based on a drop amount that is a difference between a target number of revolutions of the prime mover and an actual number of revolutions of the prime mover, compute a first reduction amount that is an amount of reduction in opening of the actuation valv

Assignees

• Kubota Kk

Inventors

• Hamamoto Ryota
• Ueda Kazuki
• Abe Daiki

Classifications

• E02F9/2246

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

• E02F9/2285

  Pilot-operated systems · CPC title

• E02F9/2267

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

• E02F9/2292

  Systems with two or more pumps · CPC title

• E02F9/2253 Primary

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