Hydraulic system and working machine

Abstract

The invention belongs to the technical field of operation machinery and provides a hydraulic system and operation machinery. The hydraulic system comprises a working loop, a power unit, a first oil pump, a second oil pump and a control unit. The power unit comprises a power source and a power distribution device, the power distribution device is provided with an input end, a first output end and a second output end, the power source is connected with the input end, the first output end and the second output end correspond to different transmission ratios, the first oil pump is connected with the first output end, and the second oil pump is connected with the second output end. Due to the fact that the first output end and the second output end correspond to different transmission ratios, the first oil pump and the second oil pump can carry out differential output according to different requirements of different subsystem oil ways for flow and pressure, the first oil pump and the second oil pump are driven through the same power source, and compared with a traditional multi-independent-pump driving scheme, the driving efficiency is improved. The number of power sources is reduced, and the space utilization rate is increased.

Description

Technical Field

[0001] This invention belongs to the field of work machinery technology, specifically relating to a hydraulic system and work machinery. Background Technology

[0002] As construction machinery develops towards high performance and multi-functionality, its hydraulic systems are becoming increasingly complex. Each subsystem (such as travel, rotation, and operation) often has different pressure and flow requirements. Traditional solutions that rely on a single large electric motor or engine to drive a pump for oil supply are difficult to meet these diverse working conditions simultaneously. Therefore, using multiple electric pumps for individual and adaptive oil supply has become the mainstream trend in technological development.

[0003] However, most common multi-pump oil supply solutions currently employ a simple stacking approach: "one hydraulic subsystem is equipped with one independently operating electric pump." While this approach achieves basic functionality, it significantly increases system costs, results in a bulky spatial layout, and leads to low energy efficiency. Summary of the Invention

[0004] To address the aforementioned deficiencies or shortcomings, this invention provides a hydraulic system and a working machine, aiming to solve the technical problem that existing working machines require a large number of pump units to meet the differentiated flow requirements of each sub-hydraulic system, resulting in a bulky system and high costs.

[0005] To achieve the above objectives, the present invention provides a hydraulic system comprising a working circuit, a power unit, a first oil pump, a second oil pump, and a control unit. The power unit includes a power source and a power distribution device. The power distribution device has an input terminal, a first output terminal, and a second output terminal. The power source is connected to the input terminal, and the first and second output terminals correspond to different transmission ratios. The first oil pump is connected to the first output terminal, and the second oil pump is connected to the second output terminal. The control unit is used to control at least one of the first and second oil pumps to supply oil to the working circuit.

[0006] In this embodiment, the power unit further includes a first clutch, and the first oil pump is connected to the first output end through the first clutch.

[0007] In this embodiment, the power unit further includes a second clutch, and the second oil pump is connected to the second output end through the second clutch.

[0008] In this embodiment, the working circuit includes a first working circuit and a second working circuit. The first working circuit includes a first main valve and a first actuator, and the second working circuit includes a second main valve and a second actuator. The oil inlet of the first main valve is connected to the pump port of the first oil pump, and the oil inlet of the second main valve is connected to the pump port of the second oil pump.

[0009] In this embodiment, the hydraulic system further includes a merging oil circuit, which is connected to the pump port oil circuit of the first oil pump and the pump port oil circuit of the second oil pump respectively. A merging valve for controlling the on / off state is provided on the merging oil circuit.

[0010] In this embodiment, the displacement of the first oil pump is greater than that of the second oil pump, the upper limit of the allowable speed of the first oil pump is less than that of the second oil pump, the first transmission ratio between the input end and the first output end is greater than the second transmission ratio between the output end and the second output end; a first check valve is also provided on the confluence oil line, which is configured to open when the hydraulic oil output by the second oil pump flows to the pump port oil line of the first oil pump and close in the reverse direction.

[0011] In this embodiment, a second check valve is provided on the oil inlet of the first oil pump and the oil inlet of the second oil pump respectively. The second check valve is used to control the corresponding oil pump to output in one direction. The confluence oil circuit is connected to the oil outlet side of the second check valve.

[0012] In this embodiment, the operating speed of the power source is adjustable, the first main valve is an on / off directional valve, and the second main valve is a proportional directional valve.

[0013] In this embodiment, the hydraulic system further includes a first overflow oil passage connecting the pump port of the first oil pump to the oil tank, and a first overflow valve is provided on the first overflow oil passage. The pressure of the first overflow valve is adjustable, or the opening pressure of the first overflow valve is fixed. The hydraulic system further includes a second overflow oil passage connecting the pump port of the second oil pump to the oil tank, and a second overflow valve is provided on the second overflow oil passage. The pressure of the second overflow valve is adjustable, or the opening pressure of the second overflow valve is fixed.

[0014] To achieve the above objectives, the present invention also provides a working machine, wherein the working machine includes the hydraulic system described above.

[0015] Through the above technical solutions, the hydraulic system provided by the embodiments of the present invention has the following beneficial effects: Different transmission ratios allow the first and second output terminals to operate at different speeds, enabling the first and second oil pumps to provide differentiated outputs based on the varying flow and pressure requirements of different subsystem oil circuits. Furthermore, since the first and second oil pumps are driven by the same power source, compared to traditional multi-independent pump drive schemes, the number of power sources is reduced, improving space utilization and providing crucial support for the compact and lightweight design of the entire machine. In addition, this system employs a transmission architecture where one power source drives multiple oil pumps, offering high versatility and flexibility in power source selection.

[0016] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0017] The accompanying drawings are provided to illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a hydraulic schematic diagram of the hydraulic system according to an embodiment of the present invention.

[0018] Explanation of reference numerals in the attached figures 1. Power unit; 11. Power source; 12. Power distribution device; 13. First clutch; 14. Second clutch; 2. First working circuit; 21. First oil pump; 22. First actuator; 23. First main valve; 3. Second working circuit; 31. Second oil pump; 32. Second actuator; 33. Second main valve; 4. Combining oil circuit; 41. Combining valve; 42. First check valve; 51. First overflow oil circuit; 52. First overflow valve; 53. Second overflow oil circuit; 54. Second overflow valve; 61. Second check valve; 62. Pressure sensor; 71. Oil tank; 72. Cooler. Detailed Implementation

[0019] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0020] The hydraulic system of the present invention will now be described with reference to the accompanying drawings.

[0021] The hydraulic system of construction machinery typically consists of multiple subsystems. Taking an excavator as an example, its hydraulic system includes a travel drive subsystem, a steering drive subsystem, a swing drive subsystem, and a working device control subsystem, each forming an independent working circuit. The pressure and flow required by these subsystems differ significantly during operation. For instance, precise control of the excavator's stick requires a stable, low flow rate, while controlling the digging travel requires a high flow rate.

[0022] To cope with the complex flow and pressure requirements of each subsystem, existing technologies generally adopt an architecture of "one motor and pump per subsystem," meaning that each critical subsystem is equipped with its own independent motor and pump. This architecture is essentially a mechanical superposition of multiple simple single-pump systems. The use of a large number of repetitive motors, pumps, and their accessories not only leads to a sharp increase in raw material and procurement costs, but also results in a large amount of scattered hardware being piled up in the limited installation space of the equipment (such as the turntable or chassis), severely encroaching on the layout space of other critical components and forcing the entire machine to become bloated.

[0023] In view of this, the present invention provides a hydraulic system, such as Figure 1 As shown, the hydraulic system includes a working circuit, a power unit 1, a first oil pump 21, and a second oil pump 31.

[0024] The power unit 1 includes a power source 11 and a power distribution device 12. The power distribution device 12 has an input terminal, a first output terminal, and a second output terminal. The power source 11 is connected to the input terminal, the first output terminal and the second output terminal correspond to different transmission ratios, the first oil pump 21 is connected to the first output terminal, and the second oil pump 31 is connected to the second output terminal.

[0025] Different transmission ratios allow the first and second output terminals to operate at different speeds, enabling the first oil pump 21 and the second oil pump 31 to provide differentiated outputs based on the varying flow and pressure requirements of different subsystem oil circuits. Since the first oil pump 21 and the second oil pump 31 are driven by the same power source 11, compared to traditional multi-independent pump drive schemes, the number of power sources 11 is reduced, improving space utilization and providing crucial support for the compact and lightweight design of the entire machine. Furthermore, the hydraulic system in this embodiment employs a transmission architecture where one power source 11 drives multiple oil pumps, offering high versatility and flexibility in power source 11 selection. This architecture can not only be driven by an electric motor but also seamlessly integrate with various operating machines powered by engines. In other words, the power source in this embodiment can be either an electric motor or an engine.

[0026] In this embodiment, the power distribution device 12 may be a gearbox, transfer case, multi-output shaft gearbox, reducer, etc.

[0027] like Figure 1 As shown, in this embodiment, the power unit 1 may further include a first clutch 13, and the first oil pump 21 is connected to the first output end through the first clutch 13. Through the first clutch 13, the start and stop control of the first oil pump 21 can be realized without stopping the power source 11.

[0028] Similarly, in this embodiment, the power unit 1 may also include a second clutch 14, through which the second oil pump 31 is connected to the second output terminal. The second clutch 14 allows for start-stop control of the second oil pump 31 without shutting down the power source 11.

[0029] In this embodiment, the number of first output terminals and second output terminals can be one or more, the number of first oil pumps 21 corresponds one-to-one with the number of first output terminals, and the number of second oil pumps 31 corresponds one-to-one with the number of second output terminals. By using more output terminals, the functionality of the hydraulic system can be further enhanced.

[0030] In this embodiment, the hydraulic system also includes a control unit. The control unit is used to control at least one of the first oil pump 21 and the second oil pump 31 to supply oil to the working circuit. In some embodiments, the control unit can specifically control the disconnection or engagement of the transmission between the first oil pump 21 and the first output terminal, and between the second oil pump 31 and the second output terminal, to achieve start-stop control of the first oil pump 21 and the second oil pump 31, thereby achieving joint or selective oil supply to the working circuit by the first oil pump 21 and the second oil pump 31. In other embodiments, the control unit can also specifically control the hydraulic components in the working circuit to achieve joint or selective oil supply to the actuators in the working circuit by the first oil pump 21 and the second oil pump 31. For example, by controlling the hydraulic valves in the working circuit, one of the first oil pump 21 and the second oil pump 31 can supply oil to the actuators in the working circuit, while the oil output by the other pump flows directly back to the oil tank, etc.

[0031] In this embodiment, the control unit may include an electronic control unit, such as an electric handle or a controller with an interactive interface (such as an electronic control screen), which can respond to user operations, generate control commands, and act on relevant actuators, such as electric valves, electro-hydraulic valves, and electromagnetic clutches, to achieve control functions. Alternatively, the control unit may also be a mechanical control unit, such as a mechanical handle or pedal, which acts on relevant actuators, such as friction clutches and hydraulic valves, through mechanical transmission to achieve control functions.

[0032] In this embodiment, the first oil pump 21 and the second oil pump 31 supply oil to the working circuit. This can mean that the first oil pump 21 and the second oil pump 31 supply oil to different working circuits, or it can mean that the first oil pump 21 and the second oil pump 31 supply oil to the same working circuit.

[0033] For example, the working circuit may include a first working circuit 2 and a second working circuit 3. The first working circuit 2 includes a first main valve 23 and a first actuator 22, and the second working circuit 3 includes a second main valve 33 and a second actuator 32. Under normal operating conditions, the first actuator 22 and the second actuator 32 have different requirements for flow rate and pressure. By connecting the inlet of the first main valve 23 to the pump port of the first oil pump 21, and the inlet of the second main valve 33 to the pump port of the second oil pump 31, the effect of different oil pumps driven by a single power source 11 can be achieved to output hydraulic oil differently to different working circuits.

[0034] like Figure 1As shown, in this embodiment, the hydraulic system also includes a confluence oil circuit 4, which is connected to the pump port oil circuit of the first oil pump 21 and the pump port oil circuit of the second oil pump 31. A confluence valve 41 for controlling the on / off state is provided on the confluence oil circuit 4. The control unit can control the confluence valve 41 to open or close. When the flow demand of one of the working circuits is too high, and the oil supply from a single oil pump is insufficient to meet the rapid pressure build-up requirement, the first oil pump 21 and the second oil pump 31 can be combined to supply oil to the corresponding working circuit through the confluence oil circuit 4. In other words, this system achieves faster start-up response of the working circuits by performing combined control of multiple oil pumps driven by the same power source.

[0035] In this embodiment, since there is a difference in the oil pressure output by the first oil pump 21 and the second oil pump 31, in order to avoid mutual interference between the two oil pumps with different output pressures when they merge, such as... Figure 1 As shown, a second check valve 61 can also be installed on both the oil inlet of the first oil pump 21 and the oil inlet of the second oil pump 31, with the confluence oil passage 4 connected to the outlet side of the second check valve 61. The second check valve 61 prevents higher-pressure oil from flowing back into the lower-pressure oil pump, protecting the oil pump from impact.

[0036] In this embodiment, to accommodate the different flow and pressure requirements of each working circuit, the first oil pump 21 can be configured as a low-speed, high-displacement pump, and the second oil pump 31 can be configured as a high-speed, low-displacement pump. Correspondingly, the first actuator 22 in the first working circuit 2 is an actuator with high flow requirements, and the second actuator 32 in the second working circuit 3 has a lower flow requirements than the first actuator 22 under normal operating conditions.

[0037] The low-speed, high-displacement first oil pump 21 can stably output a large flow rate, meeting the rapid response and action of the first actuator 22 with large flow rate requirements. Meanwhile, the high-speed, low-displacement second oil pump 31, due to its low inertia and fast response, combined with its ample speed adjustment range, can enhance the micro-motion operation capability of the second actuator 32 with small flow rate requirements.

[0038] like Figure 1 As shown, in this embodiment, in order to match the difference in operating speed between the first oil pump 21 and the second oil pump 31, the first transmission ratio between the input terminal and the first output terminal can be set to be greater than the second transmission ratio between the output terminal and the second output terminal, that is, the speed output by the first output terminal is less than the output speed of the second output terminal. The transmission ratio is calculated using the formula i = Nin / Nout, where Nin refers to the speed at the output terminal and Nout refers to the speed at the output terminal.

[0039] like Figure 1As shown, in this embodiment, a first check valve 42 may also be provided on the confluence oil circuit 4. The first check valve 42 is configured to open when the hydraulic oil output by the second oil pump 31 flows to the pump port oil circuit of the first oil pump 21 and to close in the reverse direction.

[0040] Under specific operating conditions, when the instantaneous flow demand of the first actuator 22 exceeds the supply capacity of the first oil pump 21, the confluence oil circuit 4 can be opened, allowing the second oil pump 31 to supplement the flow to the first working circuit 2, thereby increasing the working response speed and movement rate of the first working circuit 2. The first check valve 42 prevents pressure fluctuations or high-pressure oil in the first working circuit 2 from flowing back into the second working circuit 3 during confluence, ensuring the independence of the second working circuit 3's operation.

[0041] Furthermore, the operating speed of the power source 11 can be adjusted. For the first actuator 22 with high flow rate requirements, a directional control valve with only on / off switching function can be used for directional control. For the actuator with low flow rate requirements, a proportional directional control valve can be used for control. In other words, when the first oil pump 21 is a low-speed, high-displacement pump and the second oil pump 31 is a high-speed, low-displacement pump, the first main valve 23 can be set as a directional control valve with oil circuit on / off switching function, and the second main valve 33 can be set as a proportional directional control valve. At this time, the working flow rate of the first actuator 22 can be adjusted by changing the speed of the power source 11, and the working oil quantity of the second actuator 32 can be adjusted by both pump control and valve control.

[0042] This adjustment method effectively avoids the huge pressure loss and hydraulic shock caused by throttling of large-flow oil, increasing the operational stability and energy utilization efficiency of the first working circuit 2. Since the output capacity of the second oil pump 31 is limited, the flow rate of the second actuator 32 can be controlled by coordinating the opening of the proportional directional valve and the rotational speed of the power source 11. This not only achieves a high degree of matching between the supply and demand flow of the second actuator 32, but also reduces the energy consumption of the second working circuit 3 and improves the micro-motion operation performance of the second actuator 32.

[0043] In this embodiment, in order to control the merging and splitting of the first working circuit 2 and the second working circuit 3 at appropriate times, the control unit can be configured as follows: Obtain the first action command from the first actuator 22 to drive the load to perform work; According to the first action command, the first oil pump 21 is connected to the first output terminal, the second oil pump 31 is connected to the second output terminal, and the confluence valve 41 is opened so that the first oil pump 21 and the second oil pump 31 merge to supply oil to the first actuator.

[0044] The execution of the first actuator 22 to drive the load to do work may include commands such as extending the hydraulic cylinder and winding the rope by the winch.

[0045] Taking the first actuator 22 as the boom cylinder of an excavator as an example, when the boom is stationary and the operator needs to control the boom to lift, the control unit receives the first action command for the boom cylinder to extend, generated by the operating handle. For the boom to move from rest, the oil pump needs to input a large amount of oil into the first working circuit 2 to quickly build up pressure. However, relying solely on the first oil pump 21 for oil supply would take several seconds to build up pressure, resulting in a delay in the boom's movement. Therefore, after receiving the first action command, the control unit can connect the first oil pump 21 to the first output terminal and the second oil pump 31 to the second output terminal, and control the confluence valve 41 to open, so that the first oil pump 21 and the second oil pump 31 combine to supply oil to the first actuator. Through the auxiliary oil supply of the second oil pump 31, the time for the boom to move from rest is reduced.

[0046] In this embodiment, the confluence valve 41 can also be a proportional valve, and the confluence flow rate of the second oil pump 31 can be controlled by controlling the opening ratio of the confluence valve 41.

[0047] In this embodiment, controlling the opening of the confluence valve 41 according to the first action command can be achieved by adjusting the opening degree of the confluence valve 41 to its maximum according to the first action command. By confluencing at the maximum opening degree, the throttling effect of the confluence valve 41 can be reduced, thereby accelerating the pressure build-up of the first working circuit 2.

[0048] In this embodiment, after the opening of the control confluence valve 41 is adjusted to the maximum, the control unit is further configured to: Detect whether the first actuator 22 is driven; If the first actuator 22 is driven, the control confluence valve 41 will gradually reduce its opening within a preset time period until it is completely closed.

[0049] The hydraulic system may also include a pressure sensor 62 for detecting the pressure in the oil inlet of the first actuator 22. The detection data from the pressure sensor 62 can indicate whether the first actuator 22 is being driven.

[0050] When the first actuator 22 is not yet driven, theoretically, the oil inlet pressure of the first actuator 22 is gradually increasing, and the derivative of the pressure, Der_P, is greater than 0. When Der_P ≤ 0, it indicates that the first actuator 22 has overcome the static friction and started to move, and the oil inlet pressure will decrease from the peak pressure, indicating that the first actuator 22 has been driven. By giving a preset closing delay time, within this time, the opening of the confluence valve 41 is gradually reduced from the maximum value to 0. When the confluence function is closed, the load of the second oil pump 31 is gradually transferred to the first oil pump 21, ensuring the smooth operation of the system.

[0051] like Figure 1As shown, in this embodiment, the hydraulic system also includes a first overflow oil passage 51 connecting the pump port oil passage of the first oil pump 21 to the oil tank 71. The first overflow oil passage 51 is provided with a first overflow valve 52. The pressure of the first overflow valve 52 is adjustable, or the opening pressure of the first overflow valve 52 is fixed.

[0052] The hydraulic system also includes a second overflow oil passage 53 connecting the pump port oil passage of the second oil pump 31 to the oil tank 71. A second overflow valve 54 is installed on the second overflow oil passage 53. The pressure of the second overflow valve 54 is adjustable, or the opening pressure of the second overflow valve 54 is fixed. The overflow oil passage ensures system safety and prevents overpressure operation. Furthermore, by setting the overflow pressure of the overflow valve to be adjustable, an alternative pressure relief path is provided for the working circuit.

[0053] Specifically, when the pressures of the first relief valve 52 and the second relief valve 54 are adjustable, the output end can be directly connected to the corresponding oil pump using a coupling. At this time, whether the first oil pump 21 and the second oil pump 31 participate in the working circuit can be determined by controlling whether the corresponding relief valve is opened or closed. When the relief valve is open, the oil circuit at the pump port of the corresponding oil pump is depressurized, and the oil pump is in an idling state.

[0054] In this embodiment, after the confluence valve 41 is completely closed, the control unit can also detect whether the second main valve 33 is in the working position. If it is in the working position, the control unit controls the second oil pump 31 to supply oil to the second actuator 32. If it is not in the working position, the control unit can control the second oil pump 31 to stop participating in the system operation.

[0055] like Figure 1 As shown, in this embodiment, controlling the second oil pump 31 to stop participating in the system operation can be done by disconnecting the second oil pump 31 from the second output terminal, or by adjusting the opening pressure of the second overflow valve to close to 0.

[0056] In this embodiment, the control unit can also control the rotational speed of the power source 11 according to the desired rotational speed indicated by the operation command. For example, when the operator moves the control handle of the first actuator 22 to the first position Angle1, the controller can control the power source 11 to operate at a rotational speed of n=k1·Angle1, where k1 is the conversion parameter between the position of the control handle and the rotational speed of the power source 11.

[0057] In this embodiment, the first actuator 22 and the second actuator 32 can be a hydraulic cylinder or a motor, respectively.

[0058] In this embodiment, the first oil pump 21 and the second oil pump 31 can be fixed displacement pumps with fixed displacement. Fixed displacement pumps have lower cost and better durability. Of course, the first oil pump 21 and the second oil pump 31 can also be variable displacement pumps.

[0059] like Figure 1 As shown, in this embodiment, a cooler 72 is also provided on the return oil line of the oil tank 71. When each working circuit is depressurized, the oil first passes through the cooler 72 and then flows back to the oil tank 71. By setting up the cooler 72, the oil returning to the tank is cooled.

[0060] To achieve the above objectives, the present invention also provides a working machine, wherein the working machine includes the hydraulic system described above. In some examples, the working machine may be construction machinery, emergency equipment, agricultural machinery, or a working robot, etc. Since the working machine adopts all the technical solutions of the above embodiments, it at least possesses the beneficial effects brought by the above embodiments, and will not be repeated here.

[0061] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0062] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0063] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0064] Although embodiments of the present invention have been described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A hydraulic system, characterized in that, The hydraulic system includes: Working circuit; The power unit (1) includes a power source (11) and a power distribution device (12). The power distribution device (12) is provided with an input terminal, a first output terminal and a second output terminal. The power source (11) is connected to the input terminal, and the first output terminal and the second output terminal correspond to different transmission ratios. The first oil pump (21) is connected to the first output terminal; The second oil pump (31) is connected to the second output terminal; A control unit is used to control at least one of the first oil pump (21) and the second oil pump (31) to supply oil to the working circuit.

2. The hydraulic system according to claim 1, characterized in that, The power unit (1) also includes a first clutch (13), and the first oil pump (21) is connected to the first output end through the first clutch (13).

3. The hydraulic system according to claim 1 or 2, characterized in that, The power unit (1) also includes a second clutch (14), and the second oil pump (31) is connected to the second output end through the second clutch (14).

4. The hydraulic system according to claim 1 or 2, characterized in that, The working circuit includes a first working circuit (2) and a second working circuit (3). The first working circuit (2) includes a first main valve (23) and a first actuator (22). The second working circuit (3) includes a second main valve (33) and a second actuator (32). The oil inlet of the first main valve (23) is connected to the oil pump port of the first oil pump (21), and the oil inlet of the second main valve (33) is connected to the oil pump port of the second oil pump (31).

5. The hydraulic system according to claim 4, characterized in that, The hydraulic system also includes a merging oil circuit (4), which is connected to the pump port oil circuit of the first oil pump (21) and the pump port oil circuit of the second oil pump (31) respectively. The merging oil circuit (4) is provided with a merging valve (41) for controlling the on and off.

6. The hydraulic system according to claim 5, characterized in that, The displacement of the first oil pump (21) is greater than that of the second oil pump (31), the upper limit of the allowable speed of the first oil pump (21) is less than that of the upper limit of the allowable speed of the second oil pump (31), and the first transmission ratio between the input end and the first output end is greater than the second transmission ratio between the output end and the second output end. The confluence oil circuit (4) is also provided with a first check valve (42), which is configured to open and close in the reverse direction when the hydraulic oil output by the second oil pump (31) flows to the pump port oil circuit of the first oil pump (21).

7. The hydraulic system according to claim 5, characterized in that, A second check valve (61) is provided on the oil port of the first oil pump (21) and the oil port of the second oil pump (31). The second check valve is used to control the corresponding oil pump to output to the outside in one direction. The confluence oil circuit (4) is connected to the oil outlet side of the second check valve (61).

8. The hydraulic system according to claim 4, characterized in that, The operating speed of the power source (11) is adjustable, the first main valve (23) is an on / off directional valve, and the second main valve (33) is a proportional directional valve.

9. The hydraulic system according to claim 1 or 2, characterized in that, The hydraulic system also includes a first overflow oil passage (51) connecting the pump port oil passage of the first oil pump (21) to the oil tank (71). The first overflow oil passage (51) is provided with a first overflow valve (52). The pressure of the first overflow valve (52) is adjustable, or the opening pressure of the first overflow valve (52) is fixed. The hydraulic system also includes a second overflow oil passage (53) connecting the pump port oil passage of the second oil pump (31) to the oil tank (71). The second overflow oil passage (53) is provided with a second overflow valve (54). The pressure of the second overflow valve (54) is adjustable, or the opening pressure of the second overflow valve (54) is fixed.

10. A type of operating machinery, characterized in that, The operating machinery includes a hydraulic system according to any one of claims 1 to 9.

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