Hydraulic Drive Working Vehicle

A hydraulic drive working vehicle comprising a vehicle frame, first and second wheels respectively supported on one side and the other side of the vehicle frame in a vehicle lengthwise direction, a driving power source supported by the vehicle frame, a variable-displacement type hydraulic pump operatively driven by the driving power source, a variable-displacement type first hydraulic motor operatively driving the first wheel, and a fixed-displacement type second hydraulic motor operatively driving the second wheel, wherein the hydraulic pump, the first hydraulic motor and the second hydraulic motor are fluidly connected in series to form a closed circuit through a pump/second-motor line, a second-motor/first-motor line and a first-motor/pump line that establish fluid connections between the hydraulic pump and the second hydraulic motor, between the second hydraulic motor and the first hydraulic motor and between the first hydraulic motor and the hydraulic pump, respectively,

• the hydraulic drive working vehicle further comprising a bypass valve which selectively realizing a first-motor driving mode in which only the first hydraulic motor is driven by fluidly connecting the pump/second-motor line and the second-motor/first-motor line, and a first/second-motor driving mode in which both the first and second hydraulic motors are driven by fluidly disconnecting the both lines, a driving-mode changeover operation member capable of being manually operated for changing over the driving mode, a bypass-valve actuating mechanism for actuating the bypass valve, and a hydraulic-motor actuating mechanism for actuating a capacity adjustment mechanism of the first hydraulic motor,
• wherein the capacity adjustment mechanism is configured so as to change the capacity of the first hydraulic motor within a range including a standard capacity which makes a peripheral speed of the first wheel driven by the first hydraulic motor equal to a peripheral speed of the second wheel driven by the second hydraulic motor,
• wherein the bypass-valve actuating mechanism selectively positions the bypass valve at a first-motor driving position and a first/second-motor driving position that realize the first-motor driving mode and the first/second-motor driving mode, respectively, in accordance with a manual operation on the driving-mode changeover operation member, and
• wherein the hydraulic-motor actuating mechanism actuates the capacity adjusting mechanism such that the capacity of the first hydraulic motor becomes the standard capacity when the bypass valve is positioned at the first/second-motor driving position and is set to a first capacity smaller than the standard capacity when the bypass valve is positioned at the first motor driving position.