Patent ID: 8468818

Claim:
An HST cooling circuit, comprising: an HST hydraulic circuit that is formed through a closed circuit connection of a variable displacement hydraulic pump and at least first and second variable displacement hydraulic motors; a charge pump that replenishes the HST hydraulic circuit with hydraulic oil; a cooling circuit that comprises a first oil line that is connected to a drain port of the variable displacement hydraulic pump and to a drain port for oil inflow of the first hydraulic motor, a second oil line that is connected to a drain port for oil outflow of the first hydraulic motor and to a drain port for oil inflow of the second hydraulic motor, and a third oil line that is connected to a drain port for oil outflow of the second hydraulic motor and to a reservoir, wherein through the cooling circuit an excess of the hydraulic oil that has been replenished from the charge pump to the HST hydraulic circuit is returned to the reservoir through at least, and in the order of, the drain port of the variable displacement hydraulic pump, the first hydraulic motor, and the second hydraulic motor; a hydraulic source that supplies hydraulic oil to an hydraulic device other than the first and second hydraulic motors; and a merge circuit through which a portion of hydraulic oil from the hydraulic source is merged into the second oil line that lies downstream of the first hydraulic motor and upstream of the second hydraulic motor in the cooling circuit.