Variable-speed volume-control direct-drive all-electric hydraulic excavator driving and energy recovery system

A variable-speed volume-control direct-drive all-electric hydraulic excavator driving and energy recovery system, comprising:

• a boom hydraulic cylinder (1), an arm hydraulic cylinder (2), a bucket hydraulic cylinder (3), a swing motor (4), a left travel motor (5), a right travel motor (6), a mutual DC bus (7), a main switch (8), a rectifier (9), a smooth capacitor (10), a DC-DC converter (11), and a storage battery (12), wherein a drive control circuit is also included, comprising:
• an A energy source (13), a B energy source (14), a C energy source (15), a boom cylinder control valve group (16), an arm cylinder control valve (17), a swing motor control valve group (18), a bucket control valve (20), a swing control valve (21), a left travel control valve (22), a right travel control valve (23), I-VIII 2-position 2-way valves (24˜31), I and II 2-position 3-way valves (32,33), I and II accumulators (34,35);
• wherein each of the A, the B, and the C energy sources comprises a hydraulic pump (40), a motor generator (39), an inverter (38), an input of the inverter is connected to the mutual DC bus, an output of the inverter is connected to a motor generator driving the inverter, the motor generator is connected with the hydraulic pump driven by the motor generator;
• wherein the control valve group of the boom cylinder, the arm cylinder and the swing motor comprises of A, B, C, D 2-position 2-way valves, wherein first ports of A, D 2-position 2-way valve are connected to an oil tank respectively;
• second ports of A, D 2-position 2-way valve are connected to a first port of the B 2-position 2-way valve and a first port of the C 2-position 2-way valve respectively;
• a second port of the B 2-position 2-way valve and a second port of the C 2-position 2-way valve are connected together;
• a oil passage is drawn from a piping between the A and the B 2-position 2-way valve to be connected with a rod cavity of the boom hydraulic cylinder, a rod cavity of the arm hydraulic cylinder and a first port of the swing motor;
• wherein another oil passage is drawn from a piping between the C and the D 2-position 2-way valve to be connected with a rodless cavity of the boom hydraulic cylinder, a rodless cavity of the arm hydraulic cylinder and a second port of the swing motor;
• wherein a first working port of the hydraulic pump of the A energy source is connected with a first port of the I 2-position 3-way valve;
• a second port and a third port of the I 2-position 3-way valve are connected with the I accumulator and the tank respectively;
• a second working port of the hydraulic pump of the A energy source is connected with a first port of the left travel control valve, a first port of the bucket control valve, a piping between the B 2-position 2-way valve and the C 2-position 2-way valve of the boom cylinder control valve group, a first port of the IV 2-position 2-way valve and a first port of the V 2-position 2-way valve;
• wherein an inlet of the hydraulic pump of the B energy source is connected with the tank, an outlet of which is connected with a second port of the V 2-position 2-way valve;
• wherein an outlet of the hydraulic pump of the B energy source is connected with a piping between the B and C 2-position 2-way valve of the bucket control valve group and swing motor control valve group, a first port of the right travel control valve, and a first port of the VI 2-position 2-way valve;
• the outlet of the hydraulic pump of the B energy source is connected with the II accumulator through the VII 2-position 2-way valve;
• wherein a first working port of the hydraulic pump of the C energy source is connected with a first port of the II 2-position 3-way valve, wherein a second and a third port is connected with the II accumulator and the tank respectively;
• a second working port of the hydraulic pump of the C energy source is connected with a second port of the VI 2-position 2-way valve, a second port of the I and the II 2-position 2-way valve, and a first port of swing control valve;
• wherein a second working port of the hydraulic pump of the C energy source is connected with the II accumulator and a second working port of the hydraulic pump of the A energy source through the VIII 2-position 2-way valve and the IV 2-position 2-way valve respectively;
• a first port of the I 2-position 2-way valve and the II 2-position 2-way valve are connected with the rod cavity of the boom hydraulic cylinder and the arm hydraulic cylinder respectively;
• wherein a second port and a third port of the swing control valve are connected with two ports of the swing motor respectively;
• working ports of the left travel motor and the right travel motor are connected with the left travel control valve and the right travel control valve respectively;
• a first working port of the III 2-position 2-way valve is connected with the rodless cavity of the arm hydraulic cylinder;
• a second working port of the III 2-position 2-way valve is connected with a first working port of the II 2-position 2-way valve;
• wherein control circuits of the boom hydraulic cylinder, the arm hydraulic cylinder and swing motor are all independent-cavity variable-speed pump-control volume direct-drive circuits;
• the A energy source feeds oil to the left travel motor, the bucket hydraulic cylinder and the boom hydraulic cylinder;
• the B energy source feeds oil to the arm hydraulic cylinder, the swing motor and the right travel motor;
• the C energy source feeds oil to the left travel motor, the bucket hydraulic cylinder, the boom hydraulic cylinder, the arm hydraulic cylinder, the swing motor and the right travel motor by on/off control of the IV, V and VI 2-position 2-way valves;
• wherein a redundancy control of the A, the B and the C energy source is that the rod cavity and the rodless cavity of the boom hydraulic cylinder are controlled by the A energy source or the C energy source or the combination of the A and the C energy source and the B energy source or the C energy source or the combination of the B and the C energy source respectively, the rod cavity and the rodless cavity of the arm hydraulic cylinder are controlled by the B energy source or the C energy source or the combination of the B and the C energy source and the B energy source or the C energy source or the combination of the B and the C energy source respectively, and the oil is able to pass through the rod cavity and the rodless cavity of the arm hydraulic cylinder by the on/off control of the III 2-position 2-way valve;
• wherein control circuits of the boom hydraulic cylinder, the arm hydraulic cylinder and the swing motor are active and passive composite energy recovery circuits, wherein when the pressure inside the I and the II accumulator is lower than the pre-set minimal value, potential energy of the boom hydraulic cylinder and the arm hydraulic cylinder and kinetic energy of the swing motor braking is stored in the I or the II accumulator by connecting the IV-VIII 2-position 2-way valves;
• when the pressure inside the I and the II accumulators is higher than the pre-set maximum value, the potential energy of the boom hydraulic cylinder and the arm hydraulic cylinder and the kinetic energy of the swing motor braking is stored in the mutual DC bus as electric energy transferred by the motor generator;
• the energy storage in the I or the II accumulators and DC bus is able to be carried out simultaneously;
• wherein the system energy is past and transferred between the accumulator, the mutual DC bus and the motor generator, which is able to drive a load by control the A, the B and the C energy source;
• wherein a redundancy control of the energy recovery of the A, the B and the C energy source is when the motor generator is recover the energy as a generator the A, the B and the C energy source is able to work separately or in combination to recover the potential energy of the boom hydraulic cylinder and the arm hydraulic cylinder and the kinetic energy of the swing motor braking.