Cylinder driving system and energy regenerating method thereof

An energy regenerating method for a cylinder driving system, said method comprising:

• controlling a rotation speed and a rotation direction of a hydraulic pump by an electric motor, wherein the pump comprises three suction/discharge ports including:
• (i) a first port for supplying oil to a bottom chamber of a hydraulic cylinder and for draining oil from said bottom chamber, (ii) a second port for draining oil from a head chamber of said hydraulic cylinder and for supplying oil to said head chamber, and (iii) a third port for draining oil from a tank and for supplying oil to said tank, wherein a suction rate in said first port is a sum of respective discharge rates in said second port and said third port, and a discharge rate in said first port is a sum of respective suction rates in said second port and said third port;
• and
• recovering regenerated energy during regenerative braking of said hydraulic pump via said electric motor.

A cylinder driving system, comprising:

• (i) a hydraulic cylinder;
• (ii) a hydraulic pump which comprises:
• a plurality of cylinder holes including a first group of cylinder holes and a second group of cylinder holes;
• a first port which is adapted to communicate with both the first group and the second group of cylinder holes so as to supply oil to a bottom chamber of the hydraulic cylinder and drain oil from the bottom chamber of the hydraulic cylinder;
• a second port which is adapted to communicate with only the first group of the plurality of cylinder holes so as to drain oil from a head chamber of the hydraulic cylinder and supply oil to the head chamber of the hydraulic cylinder;
• and
• a third port which is adapted to communicate with only the second group of the plurality of cylinder holes so as to drain oil from a tank and supply oil to the tank;
• wherein a flow rate of the first port is a sum of respective flow rates of the second port and the third port;
• and
• (iii) an electric motor for controlling a rotation speed and a rotation direction of said hydraulic pump;
• wherein regenerated energy is recovered via the electric motor during regenerative braking of the hydraulic pump.