Excavator pump control direct drive distributed hydraulic system and control method

Abstract

This invention discloses a pump-controlled direct-drive distributed hydraulic system and control method for an excavator, comprising: a first port of a variable hydraulic pump connected to the inlet of a first pilot-operated check valve via an oil circuit; the outlet of the first pilot-operated check valve connected to the rodless chamber via an oil circuit; a rod chamber connected to the inlet of a second pilot-operated check valve via an oil circuit; the outlet of the second pilot-operated check valve connected to the second port of the variable hydraulic pump via an oil circuit; the rodless chamber of the hydraulic cylinder sequentially connected to the inlet of the first check valve, the outlet of the first check valve to the outlet of the second check valve, and the inlet of the second check valve to the rod chamber of the hydraulic cylinder; the outlets of the first and second check valves connected to the control ports of the first and second pilot-operated check valves via a first directional valve; this invention can eliminate throttling losses in the hydraulic system.

Description

Technical Field

[0001] This invention belongs to the field of excavator hydraulic control technology, specifically relating to an excavator pump-controlled direct-drive distributed hydraulic system and control method. Background Technology

[0002] Excavators play a vital role in engineering construction and continue to grow in popularity, with the electrification of excavators accelerating. Currently, most electric excavators adopt a configuration that is a conversion from hydraulic to electric, where an electric motor replaces the engine as the power source. Their hydraulic systems still use centralized valve-controlled hydraulic systems, utilizing a single fixed-displacement pump to provide power to the hydraulic system through a multi-way valve. When performing complex actions, in order to meet the power requirements of different actuators, the system pressure needs to be throttled and regulated through the multi-way valve, resulting in energy loss in the system and causing low overall system efficiency and severe heat generation.

[0003] With the development of servo motor control technology, using hydraulic pumps to directly control actuators has become a direction and development trend for improving the efficiency of hydraulic systems. Pump-controlled direct drive eliminates the need for control valves, reduces throttling losses in the hydraulic system, and avoids control valve malfunctions.

[0004] However, existing technologies have not fully realized pump-controlled direct drive (e.g., a distributed direct drive excavator hydraulic system with servo motor driven dual variable pumps, application number CN201810342465.3), and there are still some throttling losses in hydraulic valves; in addition, some existing systems (e.g., a distributed direct drive excavator hydraulic system with motor driven dual fixed displacement pumps and dual accumulators, application number CN201810709211.0) have one actuator driven by two variable pumps, which increases the system cost. Summary of the Invention

[0005] The purpose of this invention is to provide a pump-controlled direct-drive distributed hydraulic system and control method for excavators, which eliminates the throttling loss of the hydraulic system and simultaneously recovers the gravitational potential energy of the excavator to improve its endurance.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the present invention provides a pump-controlled direct-drive distributed hydraulic system for an excavator, including a hydraulic cylinder for driving the boom, bucket, or stick, and a cylinder drive unit.

[0008] The hydraulic cylinder drive unit includes a servo motor and a variable hydraulic pump connected by a transmission connection. The servo motor is electrically connected to an energy storage battery. The first port of the variable hydraulic pump is connected to the inlet of a first hydraulically controlled check valve through an oil circuit. The outlet of the first hydraulically controlled check valve is connected to the rodless chamber of the hydraulic cylinder through an oil circuit. The rod chamber of the hydraulic cylinder is connected to the inlet of a second hydraulically controlled check valve through an oil circuit. The outlet of the second hydraulically controlled check valve is connected to the second port of the variable hydraulic pump through an oil circuit.

[0009] The rodless chamber of the hydraulic cylinder is sequentially connected to the inlet of the first check valve, the outlet of the first check valve is sequentially connected to the outlet of the second check valve, and the inlet of the second check valve is sequentially connected to the rod chamber of the hydraulic cylinder.

[0010] The oil outlet of the first check valve and the oil outlet of the second check valve are connected to the control oil port of the first hydraulic check valve and the control oil port of the second hydraulic check valve through the first reversing valve.

[0011] Furthermore, it also includes a third control check valve, a fourth control check valve, and an accumulator; the inlet ports of the third and fourth control check valves are connected to the accumulator; the first port of the variable hydraulic pump is connected to the outlet port of the third control check valve via an oil circuit, and the first port of the variable hydraulic pump is connected to the control port of the fourth control check valve via an oil circuit; the second port of the variable hydraulic pump is connected to the outlet port of the fourth control check valve via an oil circuit, and the second port of the variable hydraulic pump is connected to the control port of the third control check valve via an oil circuit.

[0012] Furthermore, the oil outlet of the first hydraulic check valve is connected to the oil inlet of the third control check valve and the oil inlet of the fourth control check valve through the first relief valve.

[0013] Furthermore, the oil inlet of the second hydraulic check valve is connected to the oil inlet of the third control check valve and the oil inlet of the fourth control check valve through the second relief valve.

[0014] Furthermore, the oil outlets of the first overflow valve and the second overflow valve are connected to the control ports of the first hydraulic check valve and the second hydraulic check valve via the first directional valve.

[0015] Furthermore, the first directional valve is configured as a two-position three-way solenoid valve. When the first directional valve exits the first working position, the oil outlet of the first check valve and the oil outlet of the second check valve are connected to the control oil ports of the first hydraulically controlled check valve and the second hydraulically controlled check valve. When the first directional valve exits the second working position, the oil outlet of the first relief valve and the oil outlet of the second relief valve are connected to the control oil ports of the first hydraulically controlled check valve and the second hydraulically controlled check valve.

[0016] Furthermore, it also includes a travel drive unit, which is equipped with a high-speed motor, a fixed-displacement hydraulic pump, and a travel hydraulic motor; the high-speed motor drives the fixed-displacement hydraulic pump to move; the fixed-displacement hydraulic pump drives the travel hydraulic motor to move; and the travel hydraulic motor drives the excavator's travel mechanism to move.

[0017] Furthermore, the outlet of the fixed-displacement hydraulic pump is connected to the inlet of the traveling hydraulic motor, and the outlet of the traveling hydraulic motor is connected to the inlet of the fixed-displacement hydraulic pump; the inlet and outlet of the traveling hydraulic motor are connected to the oil tank through a second directional valve; the second directional valve is set as a three-position three-way solenoid valve. When the second directional valve is in the first position, the inlet of the traveling hydraulic motor is connected to the oil tank; when the second directional valve is in the second position, the connection between the inlet of the traveling hydraulic motor and the oil tank, and between the inlet of the traveling hydraulic motor and the oil tank, are both interrupted; when the second directional valve is in the third position, the outlet of the traveling hydraulic motor is connected to the oil tank.

[0018] Furthermore, a third overflow valve and a cooler are provided on the oil line between the second reversing valve and the oil tank.

[0019] Furthermore, the walking drive unit also includes a fourth relief valve and a fifth relief valve; the oil outlet of the fixed displacement hydraulic pump is sequentially connected to the oil inlet of the fourth relief valve, and the oil outlet of the fourth relief valve is sequentially connected to the oil inlet of the fixed displacement hydraulic pump; the oil inlet of the fixed displacement hydraulic pump is sequentially connected to the oil inlet of the fifth relief valve, and the oil outlet of the fifth relief valve is sequentially connected to the oil outlet of the fixed displacement hydraulic pump.

[0020] Furthermore, the walking drive unit also includes a replenishing oil pump, the oil inlet of which is connected to the oil tank; the oil outlet of the replenishing oil pump is connected to the oil inlet of the third check valve and the oil inlet of the fourth check valve through an oil circuit; the oil outlet of the third check valve is connected to the oil inlet of the walking hydraulic motor, and the oil outlet of the fourth check valve is connected to the oil inlet of the fixed displacement hydraulic pump.

[0021] In a second aspect, the present invention provides a control method for a pump-controlled direct-drive distributed hydraulic system for an excavator, comprising:

[0022] When the hydraulic cylinder is in the extended state and the load direction is the same as the hydraulic cylinder's movement direction, the first directional valve controls the oil outlet of the first check valve to connect with the oil outlet of the second check valve. The control ports of the first and second hydraulically controlled check valves are then connected. High-pressure hydraulic oil in the rod chamber of the hydraulic cylinder enters the control port of the second hydraulically controlled check valve, which then opens in the reverse direction. The high-pressure hydraulic oil in the rod chamber of the hydraulic cylinder flows to the variable displacement hydraulic pump. The high-pressure hydraulic oil drives the variable displacement hydraulic pump to move forward, driving the hydraulic oil flow. The hydraulic oil passes through the first port of the variable displacement hydraulic pump, through the first hydraulically controlled check valve, and enters the rodless chamber of the hydraulic cylinder. The variable displacement hydraulic pump drives the servo motor to rotate, generating electricity which is stored in the energy storage battery.

[0023] When the hydraulic cylinder is in the extended state and the load direction is opposite to the hydraulic cylinder's movement direction, the servo motor is controlled to drive the variable hydraulic pump to move forward, driving the hydraulic oil to flow. The hydraulic oil enters the rodless chamber of the hydraulic cylinder from the first port of the variable hydraulic pump through the first hydraulically controlled check valve. The first directional valve controls the outlet of the first check valve to connect with the outlet of the second check valve, connecting the control ports of the first and second hydraulically controlled check valves. The high-pressure hydraulic oil in the rodless chamber of the hydraulic cylinder enters the control port of the second hydraulically controlled check valve, and the second hydraulically controlled check valve opens in the reverse direction, allowing the hydraulic oil in the rod chamber of the hydraulic cylinder to flow back to the variable hydraulic pump.

[0024] When the hydraulic cylinder is in the retracted state and the load direction is opposite to the hydraulic cylinder's movement direction, the servo motor is controlled to drive the variable hydraulic pump to move in the opposite direction, driving the hydraulic oil to flow. The hydraulic oil enters the rod chamber of the hydraulic cylinder through the second port of the variable hydraulic pump and the second hydraulically controlled check valve. The first directional valve controls the outlet of the first check valve to connect with the outlet of the second check valve, connecting the control ports of the first and second hydraulically controlled check valves. The high-pressure hydraulic oil in the rod chamber of the hydraulic cylinder enters the control port of the first hydraulically controlled check valve, and the first hydraulically controlled check valve opens in the reverse direction, allowing the hydraulic oil in the rodless chamber of the hydraulic cylinder to flow back to the variable hydraulic pump.

[0025] When the hydraulic cylinder is in the retracted state and the load direction is the same as the hydraulic cylinder's movement direction, the first directional valve controls the oil outlet of the first check valve to connect with the oil outlet of the second check valve. The control oil ports of the first and second hydraulically controlled check valves are connected. The high-pressure hydraulic oil in the rodless chamber of the hydraulic cylinder enters the control oil port of the first hydraulically controlled check valve. The first hydraulically controlled check valve opens in the reverse direction, and the high-pressure hydraulic oil in the rodless chamber of the hydraulic cylinder flows to the variable hydraulic pump. The high-pressure hydraulic oil drives the variable hydraulic pump to move in the reverse direction, driving the hydraulic oil to flow. The hydraulic oil enters the rod chamber of the hydraulic cylinder through the second oil port of the variable hydraulic pump and the second hydraulically controlled check valve. The variable hydraulic pump drives the servo motor to rotate, generating electricity and storing it in the energy storage battery.

[0026] Furthermore, the excavator's pump-controlled direct-drive distributed hydraulic system also includes a third control check valve, a fourth control check valve, and an accumulator; the inlet ports of the third and fourth control check valves are connected to the accumulator; the first port of the variable hydraulic pump is connected to the outlet port of the third control check valve via an oil circuit, and the first port of the variable hydraulic pump is connected to the control port of the fourth control check valve via an oil circuit; the second port of the variable hydraulic pump is connected to the outlet port of the fourth control check valve via an oil circuit, and the second port of the variable hydraulic pump is connected to the control port of the third control check valve via an oil circuit.

[0027] When the hydraulic cylinder is in the extended state and the load direction is the same as the hydraulic cylinder movement direction, the high-pressure hydraulic oil at the second oil port of the variable hydraulic pump enters the control oil port of the third hydraulic control check valve. The third hydraulic control check valve opens in the reverse direction, and the accumulator replenishes hydraulic oil to the hydraulic cylinder through the third hydraulic control check valve.

[0028] When the hydraulic cylinder is in the extended state and the load direction is opposite to the hydraulic cylinder movement direction, the high-pressure hydraulic oil at the first oil port of the variable hydraulic pump enters the control oil port of the fourth hydraulic control check valve. The fourth hydraulic control check valve opens in the reverse direction, and the accumulator replenishes hydraulic oil to the hydraulic cylinder through the fourth hydraulic control check valve.

[0029] When the hydraulic cylinder is in the retracted state and the load direction is opposite to the hydraulic cylinder movement direction, the high-pressure hydraulic oil at the second port of the variable hydraulic pump enters the control port of the third hydraulic control check valve, and the third hydraulic control check valve opens in the reverse direction to replenish hydraulic oil to the accumulator.

[0030] When the hydraulic cylinder is in the retracted state and the load direction is the same as the hydraulic cylinder's movement direction, the high-pressure hydraulic oil at the first port of the variable hydraulic pump enters the control port of the fourth hydraulic control check valve, and the fourth hydraulic control check valve opens in the reverse direction to replenish hydraulic oil to the accumulator.

[0031] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0032] This invention utilizes a pump-controlled hydraulic system to replace the traditional valve-controlled hydraulic system, thereby reducing throttling losses. It also employs a distributed system instead of a centralized system to eliminate throttling losses caused by load differences in the centralized system. Furthermore, it uses a servo motor to drive a variable displacement pump, expanding the flow control range of the hydraulic system and reducing overflow losses.

[0033] This invention enables the potential energy of the load to be converted into electrical energy and stored in the power battery by opening the hydraulically controlled check valve, thus realizing the recovery of the excavator's gravitational potential energy. The hydraulically controlled check valve is open when working, and when the actuator needs to maintain the load, it can be closed by the control valve to achieve the load holding function. The recovery of the excavator's gravitational potential energy improves its endurance. Attached Figure Description

[0034] Figure 1 This is a structural diagram of a pump-controlled direct-drive distributed hydraulic system for an excavator provided in Embodiment 1;

[0035] Figure 2 This is the first working condition control principle diagram of the hydraulic cylinder drive unit provided in Embodiment 2;

[0036] Figure 3 This is the second working condition control principle diagram of the hydraulic cylinder drive unit provided in Embodiment 2;

[0037] Figure 4 This is the control principle diagram of the third working condition of the hydraulic cylinder drive unit provided in Embodiment 2;

[0038] Figure 5 This is the control principle diagram of the fourth working condition of the hydraulic cylinder drive unit provided in Embodiment 2;

[0039] Figure 6 This is the control principle diagram of the walking drive unit provided in Embodiment 2.

[0040] In the diagram, 01 is the hydraulic cylinder drive unit, 1 is the servo motor, 2 is the variable hydraulic pump, 3 is the third hydraulically controlled check valve, 4 is the first hydraulically controlled check valve, 5 is the first directional valve, 6 is the first relief valve, 7 is the first check valve, 8 is the rodless chamber, 9 is the rod chamber, 10 is the second check valve, 11 is the second relief valve, 12 is the second hydraulically controlled check valve, 13 is the accumulator, and 14 is the fourth hydraulically controlled check valve.

[0041] 02 is the walking drive unit, 21 is the fixed displacement hydraulic pump, 22 is the walking hydraulic motor, 23 is the second directional valve, 24 is the third relief valve, 25 is the cooler, 26 is the fourth relief valve, 27 is the fifth relief valve, 28 is the replenishing pump, 29 is the third check valve, 210 is the fourth check valve, and 211 is the high-speed motor. Detailed Implementation

[0042] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0043] It should be noted that in the description of this invention, the terms "front," "rear," "left," "right," "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used only for the convenience of describing the invention and do not require the invention to be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention. The terms "front," "rear," "left," "right," "upper," and "lower" used in the description of this invention refer to the directions shown in the accompanying drawings, while the terms "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0044] Example 1

[0045] like Figure 1 As shown, a pump-controlled direct-drive distributed hydraulic system for an excavator includes hydraulic cylinders for driving the boom, bucket, or stick, as well as a cylinder drive unit.

[0046] The hydraulic cylinder drive unit 01 includes a servo motor 1 and a variable hydraulic pump 2 connected by transmission. The servo motor 1 is electrically connected to an energy storage battery. The first oil port of the variable hydraulic pump 2 is connected to the oil inlet of the first hydraulic control check valve 4 through an oil circuit. The oil outlet of the first hydraulic control check valve 4 is connected to the rodless chamber 8 of the hydraulic cylinder through an oil circuit. The rod chamber 9 of the hydraulic cylinder is connected to the oil inlet of the second hydraulic control check valve 12 through an oil circuit. The oil outlet of the second hydraulic control check valve 12 is connected to the second oil port of the variable hydraulic pump 2 through an oil circuit.

[0047] The rodless chamber 8 of the hydraulic cylinder is sequentially connected to the inlet of the first check valve 7, the outlet of the first check valve 7 is connected to the outlet of the second check valve 10, and the inlet of the second check valve 10 is connected to the rod chamber 9 of the hydraulic cylinder. The outlet of the first check valve 7 and the outlet of the second check valve 10 are connected to the control port of the first hydraulic control check valve 4 and the control port of the second hydraulic control check valve 12 through the first directional valve 5.

[0048] The inlet of the third control check valve 3 and the inlet of the fourth control check valve 14 are connected to the accumulator 13; the first port of the variable hydraulic pump 2 is connected to the outlet of the third control check valve 3 through an oil circuit, and the first port of the variable hydraulic pump 2 is connected to the control port of the fourth control check valve 14 through an oil circuit; the second port of the variable hydraulic pump 2 is connected to the outlet of the fourth control check valve 14 through an oil circuit, and the second port of the variable hydraulic pump 2 is connected to the control port of the third control check valve 3 through an oil circuit.

[0049] The outlet of the first hydraulic check valve 4 is connected to the inlet of the third control check valve 3 and the inlet of the fourth control check valve 14 via the first relief valve 6. The inlet of the second hydraulic check valve 12 is connected to the inlet of the third control check valve 3 and the inlet of the fourth control check valve 14 via the second relief valve 11. The outlets of the first relief valve 6 and the second relief valve 11 are connected to the control ports of the first hydraulic check valve 4 and the second hydraulic check valve 12 via the first directional valve 5.

[0050] The first directional valve 5 is configured as a two-position three-way solenoid valve. When the first directional valve 5 exits the first working position, the oil outlet of the first check valve 7 and the oil outlet of the second check valve 10 are connected to the control oil ports of the first hydraulic check valve 4 and the second hydraulic check valve 12. When the first directional valve 5 exits the second working position, the oil outlet of the first relief valve 6 and the oil outlet of the second relief valve 11 are connected to the control oil ports of the first hydraulic check valve 4 and the second hydraulic check valve 12.

[0051] The variable hydraulic pump is controlled according to the working conditions to drive the hydraulic system actuator. The variable hydraulic pump can also be used as a motor to recover the potential energy of the hydraulic cylinder and drive the servo motor to reverse and generate electricity. Since the excavator's working hydraulic cylinder is an asymmetrical cylinder, the accumulator 13 is connected to the low-pressure circuit of the hydraulic system to replenish and supply oil, so as to match the oil suction and discharge of the variable hydraulic pump with the required flow of the hydraulic cylinder. The first directional valve 5, the first check valve 7 and the second check valve 10 ensure the opening and closing of the circuit and realize the load holding function of the working cylinder. The first relief valve 6 and the second relief valve 11 are used as safety valves of the cylinder drive unit 01 to ensure system safety.

[0052] The excavator pump-controlled direct-drive distributed hydraulic system also includes a travel drive unit 02, which is equipped with a high-speed motor 211, a fixed-displacement hydraulic pump 21, and a travel hydraulic motor 22. The high-speed motor 211 drives the fixed-displacement hydraulic pump 21 to move; the fixed-displacement hydraulic pump 21 drives the travel hydraulic motor 22 to move; and the travel hydraulic motor 22 drives the excavator's travel mechanism to move.

[0053] The outlet of the fixed-displacement hydraulic pump 21 is connected to the inlet of the traveling hydraulic motor 22, and the outlet of the traveling hydraulic motor 22 is connected to the inlet of the fixed-displacement hydraulic pump 21. The inlet and outlet of the traveling hydraulic motor 22 are connected to the oil tank via a second directional valve 23. The second directional valve 23 is configured as a three-position three-way solenoid valve. When the second directional valve 23 is in the first position, the inlet of the traveling hydraulic motor 11 is connected to the oil tank. When the second directional valve 23 is in the second position, the connection between the inlet of the traveling hydraulic motor 11 and the oil tank, and between the inlet of the traveling hydraulic motor 11 and the oil tank, are both interrupted. When the second directional valve 23 is in the third position, the outlet of the traveling hydraulic motor 11 is connected to the oil tank. A third overflow valve 24 and a cooler 25 are provided on the oil line between the second directional valve 23 and the oil tank.

[0054] The walking drive unit 02 also includes a fourth relief valve 26 and a fifth relief valve 27; the oil outlet of the fixed displacement hydraulic pump 21 is sequentially connected to the oil inlet of the fourth relief valve 26, and the oil outlet of the fourth relief valve 26 is sequentially connected to the oil inlet of the fixed displacement hydraulic pump 21; the oil inlet of the fixed displacement hydraulic pump 21 is sequentially connected to the oil inlet of the fifth relief valve 27, and the oil outlet of the fifth relief valve 27 is sequentially connected to the oil outlet of the fixed displacement hydraulic pump 21.

[0055] The walking drive unit also includes a replenishing oil pump 28, the oil inlet of which is connected to the oil tank; the oil outlet of the replenishing oil pump 28 is connected to the oil inlet of the third check valve 29 and the oil inlet of the fourth check valve 210 through an oil circuit; the oil outlet of the third check valve 29 is connected to the oil inlet of the walking hydraulic motor 22, and the oil outlet of the fourth check valve 210 is connected to the oil inlet of the fixed displacement hydraulic pump 21.

[0056] The walking drive unit drives the fixed displacement hydraulic pump 21 through the high-speed motor 211 to drive the walking hydraulic motor 22. The oil replenishment pump 28 replenishes oil to the walking drive unit through the check valve. The oil in the walking drive unit returns to the oil tank through the second reversing valve and the cooler for cooling, ensuring the continuous operation of the system.

[0057] Example 2

[0058] like Figures 2 to 6 As shown, a control method for a pump-controlled direct-drive distributed hydraulic system for an excavator is disclosed. The control method is applied to the pump-controlled direct-drive distributed hydraulic system described in Example 1, and includes:

[0059] like Figure 2As shown, when the hydraulic cylinder is in the extended state and the load direction is the same as the hydraulic cylinder's movement direction, it is considered that the hydraulic cylinder is in the first working condition. The first reversing valve 5 controls the oil outlet of the first check valve 7 to connect with the oil outlet of the second check valve 10, which is the control oil port of the first hydraulic control check valve 4 and the control oil port of the second hydraulic control check valve 12. The high-pressure hydraulic oil in the rod chamber 9 of the hydraulic cylinder enters the control oil port of the second hydraulic control check valve 12. The second hydraulic control check valve 12 opens in the reverse direction, and the high-pressure hydraulic oil in the rod chamber 9 of the hydraulic cylinder flows to the variable hydraulic pump 2. The high-pressure hydraulic oil drives the variable hydraulic pump 2 to move in the forward direction, driving the hydraulic oil to flow. The hydraulic oil enters the rodless chamber 8 of the hydraulic cylinder from the first oil port of the variable hydraulic pump 2 through the first hydraulic control check valve 4. The variable hydraulic pump 2 drives the servo motor 1 to rotate, generating electricity and storing it in the energy storage battery.

[0060] High-pressure hydraulic oil from the second port of the variable hydraulic pump 2 enters the control port of the third hydraulic control check valve 3. The third hydraulic control check valve 3 opens in reverse, and the accumulator 13 replenishes hydraulic oil to the hydraulic cylinder through the third hydraulic control check valve 3.

[0061] like Figure 3 As shown, when the hydraulic cylinder is in the extended state and the load direction is opposite to the hydraulic cylinder's movement direction, it is recorded as the hydraulic cylinder being in the second working condition. The servo motor 1 is controlled to drive the variable hydraulic pump 2 to move in the forward direction, driving the hydraulic oil to flow. The hydraulic oil enters the rodless chamber 8 of the hydraulic cylinder from the first oil port of the variable hydraulic pump 2 through the first hydraulic control check valve 4. The first directional valve 5 controls the oil outlet of the first check valve 7 to connect with the oil outlet of the second check valve 10, connecting the control oil port of the first hydraulic control check valve 4 and the control oil port of the second hydraulic control check valve 12. The high-pressure hydraulic oil in the rodless chamber 8 of the hydraulic cylinder enters the control oil port of the second hydraulic control check valve 12, and the second hydraulic control check valve 12 opens in the reverse direction. The hydraulic oil in the rod chamber 9 of the hydraulic cylinder flows back to the variable hydraulic pump 2.

[0062] High-pressure hydraulic oil from the first port of the variable hydraulic pump 2 enters the control port of the fourth hydraulic control check valve 14. The fourth hydraulic control check valve 14 opens in reverse, and the accumulator 13 replenishes hydraulic oil to the hydraulic cylinder through the fourth hydraulic control check valve 14.

[0063] like Figure 4As shown, when the hydraulic cylinder is in the retracted state and the load direction is opposite to the hydraulic cylinder's movement direction, it is recorded as the hydraulic cylinder being in the third working condition. The servo motor 1 is controlled to drive the variable hydraulic pump 2 to move in the opposite direction, driving the hydraulic oil to flow. The hydraulic oil enters the rod chamber 9 of the hydraulic cylinder through the second oil port of the variable hydraulic pump 2 and the second hydraulic control check valve 12. The first directional valve 5 controls the oil outlet of the first check valve 7 to connect with the oil outlet of the second check valve 10 to the control oil port of the first hydraulic control check valve 4 and the control oil port of the second hydraulic control check valve 12. The high-pressure hydraulic oil in the rod chamber of the hydraulic cylinder enters the control oil port of the first hydraulic control check valve 4, and the first hydraulic control check valve 4 opens in the reverse direction. The hydraulic oil in the rodless chamber 8 of the hydraulic cylinder flows back to the variable hydraulic pump 2.

[0064] High-pressure hydraulic oil from the second port of the variable hydraulic pump 2 enters the control port of the third hydraulic control check valve 3, and the third hydraulic control check valve 3 opens in reverse to replenish hydraulic oil to the accumulator 13.

[0065] like Figure 5 As shown, when the hydraulic cylinder is in the retracted state and the load direction is the same as the hydraulic cylinder's movement direction, it is recorded as the hydraulic cylinder being in the fourth working condition. The first directional valve 5 controls the oil outlet of the first check valve 7 to connect with the oil outlet of the second check valve 10, which in turn connects to the control ports of the first hydraulically controlled check valve 4 and the second hydraulically controlled check valve 12. High-pressure hydraulic oil in the rodless chamber 8 of the hydraulic cylinder enters the control port of the first hydraulically controlled check valve 4, causing the first hydraulically controlled check valve 4 to open in the reverse direction. The high-pressure hydraulic oil in the rodless chamber 8 of the hydraulic cylinder flows to the variable hydraulic pump 2, which drives the variable hydraulic pump 2 to move in the reverse direction, causing the hydraulic oil to flow. The hydraulic oil passes through the second port of the variable hydraulic pump 2 and then through the second hydraulically controlled check valve 12 before entering the rod chamber 9 of the hydraulic cylinder. The variable hydraulic pump 2 drives the servo motor 1 to rotate, generating electricity which is stored in the energy storage battery.

[0066] High-pressure hydraulic oil from the first port of the variable hydraulic pump 2 enters the control port of the fourth hydraulic control check valve 4, and the fourth hydraulic control check valve 4 opens in reverse to replenish hydraulic oil to the accumulator 13.

[0067] In this implementation, by opening the hydraulic check valve, the potential energy of the load can be converted into electrical energy and stored in the power battery, thus realizing the recovery of the excavator's gravitational potential energy. The hydraulic check valve is open when working, and when the actuator needs to maintain the load, it can be closed by the control valve to achieve the load holding function. The recovery of the excavator's gravitational potential energy improves its endurance.

[0068] like Figure 6As shown, the high-speed motor 211 drives the fixed-displacement hydraulic pump 21 to move; the fixed-displacement hydraulic pump 21 drives the travel hydraulic motor 22 to move, and the travel hydraulic motor 22 drives the excavator's travel mechanism to move; the replenishing pump 28 replenishes oil to the travel drive unit through a one-way valve, and the oil in the travel drive unit returns to the oil tank for cooling through the second reversing valve and the cooler; the fourth overflow valve 26 and the fifth overflow valve 27 are used as safety valves for the cylinder drive unit 01 to ensure the continuous operation of the system.

[0069] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A pump-controlled direct-drive distributed hydraulic system for excavators, characterized in that, Includes hydraulic cylinders and cylinder drive units used to drive the boom, bucket, or stick; The hydraulic cylinder drive unit includes a servo motor and a variable hydraulic pump connected by a transmission connection. The servo motor is electrically connected to an energy storage battery. The first port of the variable hydraulic pump is connected to the inlet of a first hydraulically controlled check valve through an oil circuit. The outlet of the first hydraulically controlled check valve is connected to the rodless chamber of the hydraulic cylinder through an oil circuit. The rod chamber of the hydraulic cylinder is connected to the inlet of a second hydraulically controlled check valve through an oil circuit. The outlet of the second hydraulically controlled check valve is connected to the second port of the variable hydraulic pump through an oil circuit. The rodless chamber of the hydraulic cylinder is sequentially connected to the inlet of the first check valve, the outlet of the first check valve is sequentially connected to the outlet of the second check valve, and the inlet of the second check valve is sequentially connected to the rod chamber of the hydraulic cylinder. The oil outlet of the first check valve and the oil outlet of the second check valve are connected to the control oil port of the first hydraulic check valve and the control oil port of the second hydraulic check valve through the first reversing valve. It also includes a third control check valve, a fourth control check valve, and an accumulator; the inlet ports of the third and fourth control check valves are connected to the accumulator; the first port of the variable hydraulic pump is connected to the outlet port of the third control check valve via an oil circuit, and the first port of the variable hydraulic pump is connected to the control port of the fourth control check valve via an oil circuit; the second port of the variable hydraulic pump is connected to the outlet port of the fourth control check valve via an oil circuit, and the second port of the variable hydraulic pump is connected to the control port of the third control check valve via an oil circuit. The oil outlet of the first hydraulic check valve is connected to the oil inlet of the third control check valve and the oil inlet of the fourth control check valve through the first relief valve; the oil inlet of the second hydraulic check valve is connected to the oil inlet of the third control check valve and the oil inlet of the fourth control check valve through the second relief valve. The oil outlet of the first relief valve and the oil outlet of the second relief valve are connected to the control oil port of the first hydraulic check valve and the control oil port of the second hydraulic check valve through the first reversing valve. The first directional valve is configured as a two-position three-way solenoid valve. When the first directional valve is in the first working position, the oil outlet of the first check valve and the oil outlet of the second check valve are connected to the control oil ports of the first hydraulic check valve and the second hydraulic check valve. When the first directional valve is in the second working position, the oil outlet of the first relief valve and the oil outlet of the second relief valve are connected to the control oil ports of the first hydraulic check valve and the second hydraulic check valve.

2. The excavator pump-controlled direct-drive distributed hydraulic system according to claim 1, characterized in that, It also includes a travel drive unit, which is equipped with a high-speed motor, a fixed-displacement hydraulic pump and a travel hydraulic motor; the high-speed motor drives the fixed-displacement hydraulic pump to move; the fixed-displacement hydraulic pump drives the travel hydraulic motor to move; and the travel hydraulic motor drives the excavator's travel mechanism to move.

3. The excavator pump-controlled direct-drive distributed hydraulic system according to claim 2, characterized in that, The outlet of the fixed-displacement hydraulic pump is connected to the inlet of the traveling hydraulic motor, and the outlet of the traveling hydraulic motor is connected to the inlet of the fixed-displacement hydraulic pump. The inlet and outlet of the traveling hydraulic motor are connected to the oil tank through a second directional valve. The second directional valve is set as a three-position three-way solenoid valve. When the second directional valve is in the first position, the inlet of the traveling hydraulic motor is connected to the oil tank. When the second directional valve is in the second position, the connection between the inlet of the traveling hydraulic motor and the oil tank, and between the inlet of the traveling hydraulic motor and the oil tank, is interrupted. When the second directional valve is in the third position, the outlet of the traveling hydraulic motor is connected to the oil tank.

4. The excavator pump-controlled direct-drive distributed hydraulic system according to claim 3, characterized in that, A third overflow valve and a cooler are provided on the oil line between the second reversing valve and the oil tank.

5. The excavator pump-controlled direct-drive distributed hydraulic system according to claim 2, characterized in that, The walking drive unit also includes a fourth relief valve and a fifth relief valve; the oil outlet of the fixed displacement hydraulic pump is sequentially connected to the oil inlet of the fourth relief valve, and the oil outlet of the fourth relief valve is sequentially connected to the oil inlet of the fixed displacement hydraulic pump; the oil inlet of the fixed displacement hydraulic pump is sequentially connected to the oil inlet of the fifth relief valve, and the oil outlet of the fifth relief valve is sequentially connected to the oil outlet of the fixed displacement hydraulic pump.

6. The excavator pump-controlled direct-drive distributed hydraulic system according to claim 2, characterized in that, The walking drive unit also includes a replenishing oil pump, the oil inlet of which is connected to the oil tank; the oil outlet of the replenishing oil pump is connected to the oil inlet of the third check valve and the oil inlet of the fourth check valve through an oil circuit; the oil outlet of the third check valve is connected to the oil inlet of the walking hydraulic motor, and the oil outlet of the fourth check valve is connected to the oil inlet of the fixed displacement hydraulic pump.

7. The control method for the pump-controlled direct-drive distributed hydraulic system of an excavator according to any one of claims 1 to 6, characterized in that, include: When the hydraulic cylinder is in the extended state and the load direction is the same as the hydraulic cylinder's movement direction, the first directional valve controls the oil outlet of the first check valve to connect with the oil outlet of the second check valve. The control ports of the first and second hydraulically controlled check valves are then connected. High-pressure hydraulic oil in the rod chamber of the hydraulic cylinder enters the control port of the second hydraulically controlled check valve, which then opens in the reverse direction. The high-pressure hydraulic oil in the rod chamber of the hydraulic cylinder flows to the variable displacement hydraulic pump. The high-pressure hydraulic oil drives the variable displacement hydraulic pump to move forward, driving the hydraulic oil flow. The hydraulic oil passes through the first port of the variable displacement hydraulic pump, through the first hydraulically controlled check valve, and enters the rodless chamber of the hydraulic cylinder. The variable displacement hydraulic pump drives the servo motor to rotate, generating electricity which is stored in the energy storage battery. When the hydraulic cylinder is in the extended state and the load direction is opposite to the hydraulic cylinder's movement direction, the servo motor is controlled to drive the variable hydraulic pump to move forward, driving the hydraulic oil to flow. The hydraulic oil enters the rodless chamber of the hydraulic cylinder from the first port of the variable hydraulic pump through the first hydraulically controlled check valve. The first directional valve controls the outlet of the first check valve to connect with the outlet of the second check valve, connecting the control ports of the first and second hydraulically controlled check valves. The high-pressure hydraulic oil in the rodless chamber of the hydraulic cylinder enters the control port of the second hydraulically controlled check valve, and the second hydraulically controlled check valve opens in the reverse direction, allowing the hydraulic oil in the rod chamber of the hydraulic cylinder to flow back to the variable hydraulic pump. When the hydraulic cylinder is in the retracted state and the load direction is opposite to the hydraulic cylinder's movement direction, the servo motor is controlled to drive the variable hydraulic pump to move in the opposite direction, driving the hydraulic oil to flow. The hydraulic oil enters the rod chamber of the hydraulic cylinder through the second port of the variable hydraulic pump and the second hydraulically controlled check valve. The first directional valve controls the outlet of the first check valve to connect with the outlet of the second check valve, connecting the control ports of the first and second hydraulically controlled check valves. The high-pressure hydraulic oil in the rod chamber of the hydraulic cylinder enters the control port of the first hydraulically controlled check valve, and the first hydraulically controlled check valve opens in the reverse direction, allowing the hydraulic oil in the rodless chamber of the hydraulic cylinder to flow back to the variable hydraulic pump. When the hydraulic cylinder is in the retracted state and the load direction is the same as the hydraulic cylinder's movement direction, the first directional valve controls the oil outlet of the first check valve to connect with the oil outlet of the second check valve. The control oil ports of the first and second hydraulically controlled check valves are connected. The high-pressure hydraulic oil in the rodless chamber of the hydraulic cylinder enters the control oil port of the first hydraulically controlled check valve. The first hydraulically controlled check valve opens in the reverse direction, and the high-pressure hydraulic oil in the rodless chamber of the hydraulic cylinder flows to the variable hydraulic pump. The high-pressure hydraulic oil drives the variable hydraulic pump to move in the reverse direction, driving the hydraulic oil to flow. The hydraulic oil enters the rod chamber of the hydraulic cylinder through the second oil port of the variable hydraulic pump and the second hydraulically controlled check valve. The variable hydraulic pump drives the servo motor to rotate, generating electricity and storing it in the energy storage battery.

8. The control method according to claim 7, characterized in that, The excavator's pump-controlled direct-drive distributed hydraulic system also includes a third control check valve, a fourth control check valve, and an accumulator; the inlet ports of the third and fourth control check valves are connected to the accumulator; the first port of the variable hydraulic pump is connected to the outlet port of the third control check valve via an oil circuit, and the first port of the variable hydraulic pump is connected to the control port of the fourth control check valve via an oil circuit; the second port of the variable hydraulic pump is connected to the outlet port of the fourth control check valve via an oil circuit, and the second port of the variable hydraulic pump is connected to the control port of the third control check valve via an oil circuit. When the hydraulic cylinder is in the extended state and the load direction is the same as the hydraulic cylinder movement direction, the high-pressure hydraulic oil at the second oil port of the variable hydraulic pump enters the control oil port of the third hydraulic control check valve. The third hydraulic control check valve opens in the reverse direction, and the accumulator replenishes hydraulic oil to the hydraulic cylinder through the third hydraulic control check valve. When the hydraulic cylinder is in the extended state and the load direction is opposite to the hydraulic cylinder movement direction, the high-pressure hydraulic oil at the first oil port of the variable hydraulic pump enters the control oil port of the fourth hydraulic control check valve. The fourth hydraulic control check valve opens in the reverse direction, and the accumulator replenishes hydraulic oil to the hydraulic cylinder through the fourth hydraulic control check valve. When the hydraulic cylinder is in the retracted state and the load direction is opposite to the hydraulic cylinder movement direction, the high-pressure hydraulic oil at the second port of the variable hydraulic pump enters the control port of the third hydraulic control check valve, and the third hydraulic control check valve opens in the reverse direction to replenish hydraulic oil to the accumulator. When the hydraulic cylinder is in the retracted state and the load direction is the same as the hydraulic cylinder's movement direction, the high-pressure hydraulic oil at the first port of the variable hydraulic pump enters the control port of the fourth hydraulic control check valve, and the fourth hydraulic control check valve opens in the reverse direction to replenish hydraulic oil to the accumulator.

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