Work vehicle and control method for work vehicle

Patent metadata

Field	Value
Publication number	US-12503833-B2
Application number	US-202519026509-A
Country	US
Kind code	B2
Filing date	Jan 17, 2025
Priority date	Aug 10, 2022
Publication date	Dec 23, 2025
Grant date	Dec 23, 2025

Abstract

A work vehicle includes a primary pressure control valve configured to control a pilot primary pressure of pilot oil. A secondary pressure control valve is configured to control a pilot secondary pressure of the pilot oil. Control circuitry is configured to control a rotation speed of an engine according to a target rotation speed. The control circuitry is configured to control the primary pressure control valve and the secondary pressure control valve based on a first target value of the pilot primary pressure and a second target value of the pilot secondary pressure.

First claim

What is claimed is:

1 . A work vehicle comprising:
a hydraulic motor configured to drive a traveling device; a hydraulic pump having a pilot port to which pilot pressure of pilot oil is applied, the hydraulic pump being configured to supply hydraulic fluid to the hydraulic motor in accordance with the pilot pressure; an engine configured to drive the hydraulic pump; a rotation speed sensor configured to detect a rotation speed of the engine; a pilot pump configured to be driven by the engine to discharge the pilot oil; an operation lever configured to receive an instruction of a travel direction from a user; an operation valve configured to control the pilot pressure by operation of the operation lever; a first pilot oil passage connecting the pilot pump and the operation valve, the pilot oil being supplied through the first pilot oil passage; a primary pressure control valve provided in the first pilot oil passage and configured to control a pilot primary pressure which is a pressure of the pilot oil in the first pilot oil passage; a second pilot oil passage connecting the operation valve and the pilot port, the pilot oil being supplied through the second pilot oil passage; a secondary pressure control valve connected to the second pilot oil passage and configured to control a pilot secondary pressure which is a pressure of the pilot oil in the second pilot oil passage; and control circuitry configured to control the rotation speed of the engine according to a target rotation speed of the engine, and control the primary pressure control valve and the secondary pressure control valve based on a first target value of the pilot primary pressure and a second target value of the pilot secondary pressure.

2 . The work vehicle according to claim 1 ,
wherein the control circuitry is configured to simultaneously control the primary pressure control valve and the secondary pressure control valve when the rotation speed of the engine detected by the rotation speed sensor becomes lower than the target rotation speed by a predetermined speed difference or more.

3 . The work vehicle according to claim 2 , further comprising:
a discharge oil passage which is branched from the second pilot oil passage and via which the secondary pressure control valve is connected to the second pilot oil passage; and a throttle provided in the second pilot oil passage between the operation valve and the discharge oil passage.

4 . The work vehicle according to claim 1 , further comprising:
a discharge oil passage which is branched from the second pilot oil passage and via which the secondary pressure control valve is connected to the second pilot oil passage; and a throttle provided in the second pilot oil passage between the operation valve and the discharge oil passage.

5 . A control method for a work vehicle, comprising:
detecting a rotation speed of an engine; controlling the engine such that the rotation speed of the engine becomes a target rotation speed; driving a hydraulic pump connected to the engine such that the hydraulic pump discharges hydraulic fluid to a hydraulic motor connected to a traveling device; driving a pilot pump connected to the engine such that the pilot pump discharges pilot oil to a first pilot oil passage; controlling an operation valve connected to the first pilot oil passage according to an instruction of a traveling direction by a user to convert a pilot primary pressure, which is a pressure of the pilot oil provided through the first pilot oil passage, into a pilot secondary pressure to be applied to the pilot oil in a second pilot oil passage connecting the operation valve and a pilot port of the hydraulic pump; controlling a primary pressure control valve provided in the first pilot oil passage to adjust the pilot primary pressure to a first target value; and controlling a secondary pressure control valve connected to the second pilot oil passage to adjust the pilot secondary pressure to a second target value.

6 . The control method according to claim 5 ,
wherein the controlling the primary pressure control valve and the secondary pressure control valve includes simultaneously controlling the primary pressure control valve and the secondary pressure control valve when the rotation speed of the engine detected by the rotation speed sensor becomes lower than the target rotation speed by a predetermined speed difference or more.

Assignees

• Kubota Kk

Inventors

• Nagao Kohei
• Abe Daiki
• Hamamoto Ryota

Classifications

• E02F9/2246

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

• E02F9/2296

  Systems with a variable displacement pump · CPC title

• E02F9/2285

  Pilot-operated systems · CPC title

• E02F9/2292

  Systems with two or more pumps · CPC title

• B60Y2200/411

  Bulldozers, Graders · CPC title