Patent ID: 11866911
Assignee: KUBOTA CORPORATION
Field: Civil engineering (Other fields)
Classification: CPC E  F | IPC E  F

Claim 13:
14. A work vehicle comprising:
an engine;
a hydraulic pump to be driven by the engine to supply hydraulic fluid;
an oil passage connected to the hydraulic pump through which the hydraulic fluid flows;
a hydraulic motor provided in the oil passage to be rotated by the hydraulic fluid; and
a fan connected to the hydraulic motor to rotate together with the hydraulic motor;
a variable relief valve connected to the oil passage and having a solenoid, the variable relief valve being configured to control a flow rate of the hydraulic fluid flowing through the oil passage in accordance with a current flowing through the solenoid; and
circuitry configured to control the magnitude of the current flowing through the solenoid to control a rotational speed of the fan,
the circuitry being configured to supply, when the engine is started, a first current that has a first magnitude to the solenoid such that the hydraulic fluid flows through the oil passage by a first flow rate to rotate the fan connected to the oil passage,
the circuitry being configured to supply, when a rotational speed of the engine becomes larger than a first rotational speed threshold value, a second current that has a second magnitude larger than the first magnitude such that the hydraulic fluid flows through the oil passage by a second flow rate smaller than the first flow rate to reduce the rotational speed of the fan, and
the circuitry being configured to supply, when the rotational speed of the engine is greater than the second rotational speed threshold value and the temperature of the hydraulic fluid exceeds the first threshold temperature, a fifth current that has a fifth magnitude equal to or smaller than the first magnitude to the solenoid of the variable relief valve to close the variable relief valve such that hydraulic fluid output from the hydraulic pump flows through the oil passage by a third flow rate which is larger than the first flow rate and which increases as the rotational speed of the engine increases.