Dual-power closed hydraulic system

Abstract

The invention relates to the technical field of closed hydraulic systems, in particular to a dual-power closed hydraulic system which comprises a hydraulic execution element, a first closed pump driven by a first engine and a second closed pump driven by a second engine, and the first closed pump and the second closed pump are communicated with the hydraulic execution element through a three-way switching valve. A double-pump independent oil supply mode can be achieved, when the pressure of a high-pressure pipeline in the closed hydraulic system exceeds a safety value, pressure is released to the oil supplementing tank, the high-pressure overflow valve drains oil to one side of a low-pressure pipeline, and when the pressure of the low-pressure pipeline in the closed hydraulic system is lower than a set value, low-pressure oil is guided back to the oil supplementing tank. After power switching between the first closed pump and the second closed pump, under the cooperation of the external oil supplementing assembly and the control assembly, oil can be driven to be accurately supplemented into the system from the oil supplementing tank in the oil supplementing process, the situation that due to the fact that the oil supplementing pressure is too high, differential pressure loss is caused, and additional heating of the system is caused is avoided, and the power capability of a hydraulic execution element can be guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of closed hydraulic systems, and in particular, to a dual-power closed hydraulic system. Background Art

[0002] In a hydraulic system, the mechanical energy input by a motor or other prime mover is converted into the pressure energy of a liquid to provide pressure oil for an actuator. Under normal conditions, an oil pump supplies oil to the system to automatically maintain the rated pressure of the system. Through the locking of a control valve, the function of maintaining the position of a valve at any position can be achieved. Since a closed circuit is formed by connecting the head and tail of a hydraulic pump and a motor and adopts pump displacement speed regulation, the energy loss of the system is small, which is suitable for occasions with high power and large flow rate.

[0003] For example, Chinese Patent with application number CN 201110122994.0 discloses a switching valve and a dual-power closed hydraulic system with the switching valve, which can enable different power components to provide power for the actuator simultaneously to ensure the working efficiency of the system. And when the power demand is low, some power components can be stopped to save resources, or the power of some power components can be concentrated to supply other actuators; in addition, the control valve can cut off the passage between the corresponding power component and other power components, thereby protecting the power components that are not in the working state and avoiding the leakage of pressure oil from the power components in the non-working state, improving the system efficiency. However, due to the leakage of hydraulic oil in the closed system and the power switching between different power components, oil replenishment operations are required. Moreover, the variable adjustment of one pump in the dual power may cause the flow rate fluctuation of the other pump. Once the oil replenishment pressure is too high, pressure difference loss will be caused, resulting in additional heat generation of the system, and at the same time, the pressure difference between port A and port B of the motor will be reduced, resulting in the reduction of the motor's work capacity. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a dual-power closed hydraulic system to solve the technical problems in the prior art that due to the leakage of hydraulic oil in the closed system and the power switching between different power components, oil replenishment operations are required. Moreover, the variable adjustment of one pump in the dual power may cause the flow rate fluctuation of the other pump. Once the oil replenishment pressure is too high, pressure difference loss will be caused, resulting in additional heat generation of the system, and at the same time, the pressure difference between port A and port B of the motor will be reduced, resulting in the reduction of the motor's work capacity.

[0005] For the above purposes, the present invention provides a dual-power closed hydraulic system, which includes a hydraulic actuator, a first closed pump driven by a first engine, and a second closed pump driven by a second engine. The first closed pump and the second closed pump are connected to the hydraulic actuator through a three-way switching valve. The first closed pump and the second closed pump are both connected with a cleaning valve, and the cleaning valve is connected to a replenishing oil tank. There are high-pressure pipelines and low-pressure pipelines between the hydraulic actuator and the first closed pump and between the hydraulic actuator and the second closed pump. The closed hydraulic system further includes:

[0006] A high-pressure overflow valve provided between the cleaning valve and the hydraulic actuator, and the high-pressure overflow valve discharges oil to the low-pressure pipeline side;

[0007] Oil replenishing check valves respectively bidirectionally provided between the first closed pump and the cleaning valve and between the second closed pump and the cleaning valve. The bidirectionally arranged oil replenishing check valves are respectively communicated with the high-pressure pipeline and the low-pressure pipeline;

[0008] An external oil replenishing component for supplementing the leaked oil to prevent pressure deficit;

[0009] A control component for controlling the output torque of the hydraulic actuator.

[0010] Further, the hydraulic actuator includes a first motor and a second motor. The first motor and the second motor are both fixed-displacement motors, and the output torque of the first motor is greater than that of the second motor.

[0011] Further, the oil drain ports of the first closed pump and the second closed pump are respectively connected to the housings of the first motor and the second motor, and are connected to the replenishing oil tank through an oil drain overflow valve.

[0012] Further, oil return pipes are provided on the housings of the first closed pump and the second closed pump, and are connected to the external oil replenishing component through a three-way switching valve.

[0013] Further, the external oil replenishing component includes:

[0014] A cooling tank provided inside the closed hydraulic system, and a cooler is provided at the side end of the cooling tank;

[0015] An oil suction filter pipeline provided in the cooling tank, the oil suction filter pipeline is connected to the replenishing oil tank, and the end of the oil suction filter pipeline is a filter plug;

[0016] An oil replenishing pump provided between the filter plug and the three-way switching valve, and the oil replenishing pump is communicated between the bidirectionally arranged oil replenishing check valves through an oil replenishing overflow valve;

[0017] Both sides of the oil suction filter pipeline are expansion sections, the middle of the oil suction filter pipeline is a throat constriction section, and a bypass pipeline is provided on the throat constriction section;

[0018] A heat dissipation plate provided at the upper end of the bypass pipeline, and the heat dissipation plate faces the cooler.

[0019] Furthermore, an oil return check valve is provided on the oil return pipe, and both ports of the oil return check valve are respectively communicated with both ports of the cooler.

[0020] Furthermore, the control component is a manual servo valve whose end is connected to a three-way switching valve corresponding to the makeup oil pump, and the manual servo valve is also communicated with the closed pump one to control the output torque of the motor one.

[0021] Furthermore, both the closed pump one and the closed pump two are variable pumps.

[0022] Furthermore, the cleaning valve is an external valve.

[0023] Furthermore, the cleaning valve includes a shuttle valve and a low-pressure overflow valve.

[0024] Advantages of the present invention: During use, a dual-pump independent oil supply mode can be achieved. When the pressure in the high-pressure pipeline of the closed hydraulic system exceeds the safety value, pressure is relieved to the makeup oil tank, and the high-pressure overflow valve drains oil to the low-pressure pipeline side. When the pressure in the low-pressure pipeline of the closed hydraulic system is lower than the set value, the low-pressure oil is guided back to the makeup oil tank. During oil replenishment, since the oil replenishment check valves are respectively arranged bidirectionally between the closed pump one and the cleaning valve, and between the closed pump two and the cleaning valve, it can ensure that unidirectional conduction can be achieved during the oil replenishment process of the high-pressure pipeline, preventing oil from flowing back; after the power switch between the closed pump one and the closed pump two, with the cooperation of the external oil replenishment component and the control component, it enables the oil to be accurately replenished from the makeup oil tank into the system during the oil replenishment process, avoiding differential pressure loss caused by excessive oil replenishment pressure, resulting in additional heat generation in the system, and can ensure the work capacity of the hydraulic actuator. Description of the Drawings

[0025] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are only those of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0026] Figure 1 It is a schematic hydraulic principle diagram provided by the present invention;

[0027] Figure 2 It is a schematic structural diagram of the external oil replenishment component in the dual-power closed hydraulic system provided by the present invention;

[0028] Figure 3 It is a schematic installation diagram of the cooler on the cooling tank in the present invention;

[0029] Figure 4 This is a schematic assembly diagram of the cooling box and the external oil replenishing component of the present invention;

[0030] Figure 5 This is a schematic external structure diagram of the external oil replenishing component in the present invention;

[0031] Figure 6 This is a schematic internal structure diagram of the external oil replenishing component in the present invention.

[0032] The markings in the figure are:

[0033] 1. First engine; 2. Closed pump one; 3. Second engine; 4. Closed pump two; 5. Three-way switching valve; 6. Cleaning valve; 7. Oil replenishing tank; 8. High-pressure overflow valve; 9. Oil replenishing check valve; 10. Motor one; 11. Motor two; 12. Drain overflow valve; 13. Return oil pipe; 14. Cooling box; 15. Cooler; 16. Oil suction filter pipeline; 17. Filter plug; 18. Oil replenishing pump; 19. Expansion section; 20. Throat contraction section; 21. Bypass pipeline; 22. Heat dissipation plate; 23. Return oil check valve; 24. Manual servo valve; 25. Shuttle valve; 26. Low-pressure overflow valve. Specific embodiments

[0034] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to specific embodiments.

[0035] It should be noted that unless otherwise defined, the technical terms or scientific terms used in the present invention should have the ordinary meanings understood by those of ordinary skill in the field to which the present invention belongs. The "first", "second" and similar terms used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. The terms such as "including" or "comprising" mean that the elements or objects appearing before this term cover the elements or objects listed after this term and their equivalents, without excluding other elements or objects. The terms such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The terms such as "upper", "lower", "left", "right" are only used to represent relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0036] In the first aspect of the present invention, a dual-power closed hydraulic system is proposed, as Figure 1-6As shown in the figure, it includes a hydraulic actuator, a closed pump 2 driven by a first engine 1, and a closed pump 4 driven by a second engine 3. The closed pump 2 and the closed pump 4 are connected to the hydraulic actuator through a three-way switching valve 5. The closed pump 2 and the closed pump 4 are both connected with a cleaning valve 6. The cleaning valve 6 is connected to a supplementary oil tank 7. There are high-pressure pipelines and low-pressure pipelines between the hydraulic actuator and the closed pump 2, and between the hydraulic actuator and the closed pump 4. The closed hydraulic system further includes:

[0037] A high-pressure overflow valve 8 provided between the cleaning valve 6 and the hydraulic actuator, and the high-pressure overflow valve 8 discharges oil to the low-pressure pipeline side;

[0038] Oil replenishing one-way valves 9 respectively bidirectionally provided between the closed pump 2 and the cleaning valve 6, and between the closed pump 4 and the cleaning valve 6. The bidirectionally arranged oil replenishing one-way valves 9 are respectively connected to the high-pressure pipeline and the low-pressure pipeline;

[0039] An external oil replenishing component for replenishing the leaked oil to prevent pressure deficit;

[0040] A control component for controlling the output torque of the hydraulic actuator.

[0041] In this embodiment, as Figure 1 shown, the hydraulic actuator includes a first motor 10 and a second motor 11. Both the first motor 10 and the second motor 11 are fixed-displacement motors. The output torque of the first motor 10 is greater than that of the second motor 11. Among them, the first motor 10 is an axial piston fixed-displacement motor with a rated displacement of 250 mL / r and a working pressure range of 0 - 35 MPa; the second motor 11 is a gear fixed-displacement motor with a rated displacement of 160 mL / r and a working pressure range of 0 - 28 MPa.

[0042] In this embodiment, during use, the closed pump 2 and the closed pump 4 are connected to the hydraulic actuator through the three-way switching valve 5, that is, they are connected in parallel to the first motor 10 and the second motor 11. The three-way switching valve 5 is an electromagnetic proportional valve. When its spool is in a state of shifting to the left, the closed pump 2 drives the hydraulic actuator, and the control component can control the output torque of the hydraulic actuator. When the spool is in a state of shifting to the right, the closed pump 4 drives the hydraulic actuator. Thus, a dual-pump independent oil supply mode can be achieved;

[0043] During operation, the safety pressure value is set to 1.3 times the rated pressure of the system. When the pressure in the high-pressure pipeline of the closed hydraulic system exceeds the safety value, i.e., when the pressure is abnormal, it discharges pressure to the supplementary oil tank 7, and the high-pressure overflow valve 8 discharges oil to the low-pressure pipeline side, forming a local circulation loop. When the pressure in the low-pressure pipeline of the closed hydraulic system is lower than the set value, the low-pressure oil is guided back to the supplementary oil tank 7. During oil replenishment, since the oil replenishment check valves 9 are respectively arranged bidirectionally between the first closed pump 2 and the cleaning valve 6, and between the second closed pump 4 and the cleaning valve 6, it can ensure unidirectional conduction during the oil replenishment process of the high-pressure pipeline, prevent oil from flowing back, and supplement oil from the outside when the system has insufficient oil suction, prevent cavitation, and maintain the stable operation of the closed loop;

[0044] After the power switch between the first closed pump 2 and the second closed pump 4, with the cooperation of the external oil replenishment component and the control component, it enables the oil to be accurately replenished from the supplementary oil tank 7 into the system during the oil replenishment process, avoiding differential pressure loss caused by excessive oil replenishment pressure, resulting in additional heat generation of the system, and can ensure the work capacity of the hydraulic actuator.

[0045] In this embodiment, as Figure 1 shown, the oil drain ports of the first closed pump 2 and the second closed pump 4 are respectively connected to the housings of the first motor 10 and the second motor 11, and are connected to the supplementary oil tank 7 through the oil drain overflow valve 12. The oil drain port of the first closed pump 2 is forced to discharge pressure through the oil drain overflow valve 12 to avoid the first closed pump 2 being stuck due to residual pressure.

[0046] In this embodiment, as Figure 1 shown, oil return pipes 13 are provided on the housings of both the first closed pump 2 and the second closed pump 4, and are connected to the external oil replenishment component through the three-way switching valve 5. The oil return structure of the housings of the first closed pump 2 and the second closed pump 4 adopts a three-stage filtration method. Its housing oil drain port is connected to the oil port of the three-way switching valve 5 through a φ16mm oil return pipe 13, and after being guided by the neutral function of the switching valve, it enters the external oil replenishment component in two paths.

[0047] In this embodiment, as Figures 2-6 shown, the external oil replenishment component includes:

[0048] A cooling tank 14 provided inside the closed hydraulic system. The cooling tank 14 is integrally formed by extrusion of aluminum alloy. A cooler 15 is provided at the side end of the cooling tank 14, and the execution end of the cooler 15 is a fan blade structure;

[0049] An oil suction filter pipeline 16 provided inside the cooling tank 14. The oil suction filter pipeline 16 is connected to the supplementary oil tank 7, and the end of the oil suction filter pipeline 16 is a filter plug 17;

[0050] The make-up oil pump 18 is arranged between the filter plug 17 and the three-way switching valve 5. The make-up oil pump 18 is connected between the make-up oil check valves 9 arranged in two directions through the make-up oil overflow valve. When the system leakage suddenly increases, the outlet pressure of the make-up oil pump 18 drops, which can trigger the closing of the make-up oil overflow valve. The oil in the cooling tank 14 is quickly replenished through the oil suction filter pipeline 16 to achieve the purpose of quickly restoring to the set pressure. The fresh oil pumped by the make-up oil pump 18 exchanges with the oil containing a large amount of heat inside the system to ensure that the temperature of the system oil does not become too high;

[0051] Both sides of the oil suction filter pipeline 16 are expansion sections 19, and the middle part of the oil suction filter pipeline 16 is a throat contraction section 20. The included angle at the junction of the expansion section 19 and the throat contraction section 20 is 15°. The length of the expansion section 19 is 120 mm, the inlet diameter is φ90 mm. A bypass pipeline 21 is provided on the throat contraction section 20. The pipeline diameter of the expansion section 19 is 60 mm more than that of the throat contraction section 20. Due to the relatively thick pipeline diameter of the expansion section 19, the flow rate of the oil is reduced, while the pipeline diameter of the throat contraction section 20 is relatively thin, and the flow rate of the oil is quickly increased. Due to the Bernoulli effect, when the oil flows from the expansion section 19 to the throat contraction section 20, it is in an accelerating flow state. Therefore, when the flow rate of the oil in the throat contraction section 20 is the largest, the static pressure is the lowest, so that a pressure difference is formed between the high-pressure area at the inlet of the throat contraction section 20 and the low-pressure area in the middle throat. During the power switching process between the closed-circuit pump one 2 and the closed-circuit pump two 4, since the motor one 10 drives the motor one 10 with a larger output torque, a relatively large leakage amount will occur before the power switching. After the power switching, a relative change occurs in the pressure difference formed between the high-pressure area at the inlet of the throat contraction section 20 and the low-pressure area in the middle throat. According to the change amount of this pressure difference, the oil is driven to be accurately replenished into the system from the make-up oil tank 7 to avoid excessive make-up oil pressure;

[0052] The heat dissipation plate 22 is arranged at the upper end of the bypass pipeline 21. The heat dissipation plate 22 faces the cooler 15. The bypass pipeline 21 can extract the hot oil into the heat dissipation plate 22 and cool it through the cooler 15.

[0053] In this embodiment, as Figure 1 shown, a check valve 23 is provided on the return oil pipe 13. The two ports of the check valve 23 are respectively connected and communicated with the two ports of the cooler 15. The check valve 23 is arranged on the return oil pipe 13 and is 300 mm away from the cooler 15. The opening pressure of the check valve 23 is set to 0.3 MPa, and the valve core material is selected as silicon nitride ceramic to ensure that a bypass oil circuit is automatically established when the pressure difference between the inlet and outlet of the cooler 15 exceeds 0.5 MPa.

[0054] In this embodiment, as Figure 1As shown in the figure, the control component is a manual servo valve 24 with one end connected to a three-way switching valve 5 corresponding to a make-up oil pump 18. The manual servo valve 24 is also connected to a closed-loop pump 1, so as to control the output torque of the closed-loop pump 1. The switching of the manual servo valve 24 controls the closed-loop pump 1, and by adjusting the displacement of the closed-loop pump 1, the output torque of the motor 1 is maintained. The manual servo valve 24 adopts a common three-position four-way spool valve structure, which has a P port, a T port, and A and B working oil ports. Among them, the P port of the manual servo valve 24 is connected to the outlet of the make-up oil pump 18 through a pipeline, the T port is connected to a make-up oil tank 7, the A port is connected to the rodless cavity of the swashplate control cylinder of the closed-loop pump 1 through an oil circuit, and the B port is connected to the rod cavity of the swashplate control cylinder of the closed-loop pump 1 through an oil circuit;

[0055] During operation, the displacement direction of the spool of the manual servo valve 24 is proportional to the mechanical deflection of the operating handle. When the operator turns the handle in the first direction, the P port and the A port of the manual servo valve 24 are conducted, and the pressure oil output by the make-up oil pump 18 enters the rodless cavity of the swashplate control cylinder of the closed-loop pump 1, pushing the piston rod out, thereby increasing the swashplate angle of the closed-loop pump 1 and increasing its displacement; at the same time, the oil in the rod cavity of the swashplate control cylinder of the closed-loop pump 1 returns to the oil tank 7 through the B port. Conversely, when the handle is turned in the opposite direction, the B port is connected to the P port, and the pressure oil enters the rod cavity to reduce the swashplate angle, realizing stepless adjustment of the displacement;

[0056] Furthermore, a throttle hole and a matching one-way valve are arranged in parallel between the T port of the manual servo valve 24 and the control oil port of the three-way switching valve 5. When the three-way switching valve 5 switches the power source, the throttle hole can slow down the control oil pressure fluctuation, and the matching one-way valve opens to quickly relieve pressure when the oil pressure suddenly changes. The dual functions ensure the pressure stability during the switching process. When it is detected that the output torque of the motor 1 is lower than the set value, the operator adjusts the manual servo valve 24 forward, increasing the displacement of the closed-loop pump 1 and raising the pump outlet pressure until it is detected that the actual swashplate angle is consistent with the set value, and the spool returns to the middle position, and the system enters a new equilibrium state, thus realizing the closed-loop stability of the output torque.

[0057] In this embodiment, both the closed-loop pump 1 and the closed-loop pump 2 are variable pumps, and the output flow and direction can be changed by adjusting the corresponding swashplate angles inside, thereby realizing the stepless speed regulation function and improving the response performance and energy-saving efficiency of the system.

[0058] In this embodiment, the cleaning valve 6 is an external valve. The cleaning valve 6 includes a shuttle valve 25 and a low-pressure overflow valve 26. When the pressure in the high-pressure pipeline exceeds the set pressure, the low-pressure overflow valve 26 opens and relieves pressure to the supplementary oil tank 7. When the pressure in the low-pressure pipeline is lower than the set pressure, the shuttle valve 25 switches to the conducting state, guiding the low-pressure hydraulic oil back to the supplementary oil tank 7. Among them, the two oil inlets on both sides of the shuttle valve 25 are respectively connected to the high-pressure pipeline and the low-pressure pipeline. The oil inlet of the low-pressure overflow valve 26 is in parallel with the oil outlet of the shuttle valve 25, and the two are jointly connected to the filter chamber of the supplementary oil tank 7. When the closed-loop pump 1 works alone, the cleaning valve 6 corresponding to the closed-loop pump 2 is in the standby state. If the pressure in the high-pressure pipeline suddenly rises at this time, the low-pressure overflow valve 26 immediately opens to relieve pressure; at the same time, when the pressure in the low-pressure pipeline drops to 0.08 MPa, the shuttle valve 25 automatically switches to the conducting state, guiding the low-pressure hydraulic oil back to the supplementary oil tank 7 and triggering the oil replenishment check valve 9 to open, forming a pressure compensation loop to stabilize the system pressure within the set range.

[0059] Those of ordinary skill in the art should understand that the discussion of any embodiment above is only exemplary and is not intended to imply that the scope of the present invention is limited to these examples; under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and the steps can be implemented in any order, and there are many other variations in different aspects of the present invention as above, which are not provided in detail for the sake of brevity.

[0060] The present invention aims to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A dual-power closed hydraulic system, comprising a hydraulic actuator, a first closed pump (2) driven by a first engine (1), and a second closed pump (4) driven by a second engine (3). The first closed pump (2) and the second closed pump (4) are communicated with the hydraulic actuator through a three-way switching valve (5), and is characterized in that, Both the closed - type pump one (2) and the closed - type pump two (4) are connected with a cleaning valve (6), the cleaning valve (6) is connected with a supplementary oil tank (7), there are high - pressure pipelines and low - pressure pipelines between the hydraulic actuator and the closed - type pump one (2) and between the hydraulic actuator and the closed - type pump two (4) respectively. The closed - type hydraulic system further includes: A high - pressure overflow valve (8) provided between the cleaning valve (6) and the hydraulic actuator, and the high - pressure overflow valve (8) discharges oil to the low - pressure pipeline side; Oil - supplement check valves (9) respectively arranged bidirectionally between the closed - type pump one (2) and the cleaning valve (6) and between the closed - type pump two (4) and the cleaning valve (6), and the bidirectionally arranged oil - supplement check valves (9) are respectively communicated with the high - pressure pipeline and the low - pressure pipeline; An external oil - supplement component for supplementing the leaked oil to prevent pressure deficit; A control component for controlling the output torque size of the hydraulic actuator.

2. The dual-power closed hydraulic system according to claim 1, characterized in that, The hydraulic actuator includes a motor one (10) and a motor two (11), both the motor one (10) and the motor two (11) are fixed - displacement motors, and the output torque of the motor one (10) is greater than the output torque of the motor two (11).

3. The dual-power closed hydraulic system according to claim 2, wherein, The oil - drain ports of the closed - type pump one (2) and the closed - type pump two (4) are respectively connected to the housings of the motor one (10) and the motor two (11), and are connected to the supplementary oil tank (7) through an oil - drain overflow valve (12).

4. A dual-power closed hydraulic system according to claim 2, wherein Return oil pipes (13) are provided on the housings of the closed - type pump one (2) and the closed - type pump two (4) respectively, and are connected to the external oil - supplement component through a three - way switching valve (5).

5. A dual-power closed hydraulic system according to claim 4, characterized in that, The external oil - supplement component includes: A cooling tank (14) arranged inside the closed - type hydraulic system, and a cooler (15) is provided at the side end of the cooling tank (14); An oil - suction filter pipeline (16) arranged inside the cooling tank (14), the oil - suction filter pipeline (16) is connected to the supplementary oil tank (7), and the end of the oil - suction filter pipeline (16) is a filter plug (17); An oil - supplement pump (18) arranged between the filter plug (17) and the three - way switching valve (5), and the oil - supplement pump (18) is communicated between the bidirectionally arranged oil - supplement check valves (9) through an oil - supplement overflow valve; The two sides of the oil - suction filter pipeline (16) are expansion sections (19), the middle part of the oil - suction filter pipeline (16) is a throat contraction section (20), and a bypass pipeline (21) is provided on the throat contraction section (20); A heat - dissipation plate (22) arranged at the upper end of the bypass pipeline (21), and the heat - dissipation plate (22) faces the cooler (15).

6. The dual-power closed hydraulic system according to claim 5, characterized in that, A return - oil check valve (23) is provided on the return - oil pipe (13), and the two ports of the return - oil check valve (23) are respectively communicated with the two ports of the cooler (15).

7. A dual-power closed hydraulic system according to claim 5, characterized in that, The control component is a manual servo valve (24) whose end is connected to the three - way switching valve (5) corresponding to the oil - supplement pump (18), and the manual servo valve (24) is also communicated with the closed - type pump one (2) to control the output torque size of the motor one (10).

8. A dual-power closed hydraulic system according to claim 1, characterized in that, Both the closed - type pump one (2) and the closed - type pump two (4) are variable pumps.

9. The dual-power closed hydraulic system according to claim 1, wherein The cleaning valve (6) is an external - type valve.

10. A dual-power closed hydraulic system according to claim 9, characterized in that, The cleaning valve (6) includes a shuttle valve (25) and a low-pressure overflow valve (26).

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