Hydraulic driving circuit with motor displacement limitation control

A hydraulic driving circuit comprising:

• a first hydraulic circuit including a bidirectional tilting type variable displacement hydraulic pump driven by a primer mover, a pilot pump rotated by the prime mover, a restrictor for generating a differential pressure corresponding to a discharge of said pilot pump, a pump displacement control means for controlling a displacement of said variable displacement hydraulic pump in accordance with the differential pressure generated by said restrictor, a forward/reverse change-over valve for controlling the direction of discharge of said variable displacement hydraulic pump by changing over the direction in which the differential pressure input to said pump displacement control means acts, a variable displacement hydraulic motor connected to said variable displacement hydraulic pump in a closed circuit, and a motor displacement control means for controlling a displacement of said variable displacement hydraulic motor;
• a second hydraulic circuit for driving a loader attachment using a discharge pressure of a loader attachment hydraulic pump driven by said prime mover;
• an accelerator pedal for controlling a speed of said prime mover;
• and
• a motor displacement limitation means for limiting a maximum value of the displacement of said variable displacement hydraulic motor in accordance with a load pressure in said second hydraulic circuit.