Hydraulic system, flow control method thereof and working machine

Abstract

The invention belongs to the technical field of hydraulic transmission, and discloses a hydraulic system, a flow control method of the hydraulic system and an operation machine.The flow control method comprises the steps that the valve position of each reversing control valve is determined according to the position of a valve element of the reversing control valve of each execution unit; according to the valve position of each reversing control valve, the action to be executed by the hydraulic system at present is determined; according to a first preset mapping relation between the target action and the flow required for executing the target action, the flow required for executing the current action of the hydraulic system is determined; and the rotating speed of the hydraulic pump is adjusted so that the output flow of the hydraulic pump can be matched with the required flow of the hydraulic system. The method can realize flow matching adjustment of the system at low cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydraulic transmission, and in particular relates to a hydraulic system and a flow control method thereof, and an operating machine. Background Art

[0002] Hydraulic systems are a widely used form of power transmission in modern machinery. The matching of their input and output flows directly impacts the system's energy efficiency. Current mainstream technologies rely on two control strategies to achieve this flow matching: First, a flow control mechanism based on proportional valve opening. This approach employs a proportional valve between the pump and the actuator, ensuring the pump maintains a constant output flow. The flow to the actuator is adjusted by varying the flow area of ​​the proportional valve's orifice. Second, pressure-compensated control employs a load feedback mechanism. This dynamically adjusts the pump output by sensing the load pressure in real time. The former generates significant throttling losses when implementing flow control, resulting in high energy consumption and low efficiency. While the latter improves energy efficiency through closed-loop control, it requires the integration of numerous sophisticated components, such as pressure sensors, electronic controllers, and variable displacement pumps. This increases the complexity of the hydraulic circuit and significantly increases costs, making it difficult to implement in low- and mid-range markets or small and medium-sized equipment. Summary of the Invention

[0003] In response to the above-mentioned defects or shortcomings, the present invention provides a hydraulic system and its flow control method, and an operating machine, aiming to solve the technical problem that the flow matching and adjustment scheme of the existing hydraulic system is difficult to achieve both low cost and low energy consumption.

[0004] To achieve the above object, the present invention provides a flow control method for a hydraulic system, the flow control method comprising: S100: Determine the valve position of each reversing control valve according to the position of the valve core of each reversing control valve of each execution unit; S200: Determine the action to be currently performed by the hydraulic system according to the valve position of each reversing control valve; S300: Determining the required flow rate of the hydraulic system to perform the current action based on a first preset mapping relationship between "target action - flow rate required to perform the target action"; S400: Adjust the speed of the hydraulic pump so that the output flow of the hydraulic pump matches the required flow of the hydraulic system.

[0005] In an embodiment of the present invention, before the step of S100: determining the valve position of each reversing control valve according to the position of the valve core of the reversing control valve of each execution unit, the flow control method further includes: S001: Monitor the position of the valve core of the reversing control valve of each execution unit.

[0006] In an embodiment of the present invention, the position of the valve core is monitored by a Hall sensor.

[0007] In an embodiment of the present invention, the hydraulic pump is driven by an engine, and the step of adjusting the rotational speed of the hydraulic pump so that the output flow of the hydraulic pump matches the required flow of the hydraulic system in step S400 specifically includes: S410: Determining a required speed of the hydraulic pump corresponding to the required flow rate based on a second preset mapping relationship between “pump speed-pump output flow rate”; S420: Determining a target gear of the engine corresponding to the required speed based on a third preset mapping relationship between “pump speed-engine gear”; S430: Adjust the engine to the target gear.

[0008] In an embodiment of the present invention, before determining the target gear of the engine corresponding to the required speed, the following steps are required: S411: Establishing a third preset mapping relationship according to the transmission parameters between the engine and the hydraulic pump.

[0009] To achieve the above-mentioned objectives, the present invention also provides a hydraulic system, wherein the hydraulic system includes an oil pumping unit, several execution units, a detection unit and a control unit, the oil pumping unit includes a hydraulic pump and a driving device for driving the hydraulic pump to rotate, each execution unit includes an execution element and a reversing control valve for controlling the operation of the execution element, the detection unit is used to detect the position of the valve core of each reversing control valve, and the control unit is communicatively connected to the detection unit and is used to execute the flow control method described above.

[0010] In an embodiment of the present invention, the detection unit includes a position detection device for respectively detecting the position of the valve core of the reversing control valve, and the control unit is communicatively connected to the position detection device and is specifically configured as follows: Acquiring a position detection signal of a position detection device; According to the type of the position detection signal and the preset comparison relationship, the valve position of the corresponding reversing control valve is determined.

[0011] In an embodiment of the present invention, the position detection device may be a Hall sensor.

[0012] In an embodiment of the present invention, the position detection device may also be one of a proximity switch, a contact switch, a position switch, and a displacement sensor.

[0013] In an embodiment of the present invention, the hydraulic pump may be a fixed displacement pump, and the driving device may be an engine.

[0014] In an embodiment of the present invention, the control unit includes an ECU controller for controlling a gear position of the engine.

[0015] To achieve the above objectives, the present invention further provides a working machine, wherein the working machine includes the hydraulic system described above.

[0016] Through the above technical solution, the hydraulic system and flow control method thereof provided by the embodiment of the present invention have the following beneficial effects: From a system architecture perspective, this hydraulic system only requires the installation of a detection unit for detecting the valve core position on the reversing control valve, and then injecting the corresponding control algorithm into the controller. Very few components are required, and no complex feedback oil circuits or precision components are required. This greatly reduces the cost and difficulty of upgrading and modifying operating machinery. It has excellent compatibility and can adapt to the upgrade of almost all small and medium-sized operating machinery on the market. From a control perspective, this method first determines the action to be performed by the hydraulic system by detecting the valve core position of the reversing control valve. Then, based on the action to be performed by the hydraulic system, the required flow rate of the system can be determined. Finally, the speed of the hydraulic pump is adjusted according to the required flow rate. Although the flow matching adjustment can only achieve approximate flow matching adjustment, the control logic is simple, the components relied on are relatively few, and it can be used in conjunction with a throttle valve to achieve more precise flow adjustment, with very little throttling loss when used together. In this way, for low-end or small and medium-sized products, it can not only realize the installation of low-energy flow matching adjustment function, but also effectively control costs. In addition, this method is open-loop control. Compared with the hysteresis delay of the traditional pressure / flow feedback closed-loop control mechanism, this method can achieve rapid response of flow regulation and higher control efficiency.

[0017] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings are used to provide an understanding of the present invention and constitute a part of the specification. Together with the following detailed description, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings: Figure 1 is a method step diagram of a flow control method for a hydraulic system according to an embodiment of the present invention; Figure 2 is a specific step diagram of step S300 according to an embodiment of the present invention; Figure 3 is a diagram of specific steps before step S320 according to an embodiment of the present invention; Figure 4 is a diagram of specific steps before step S100 according to an embodiment of the present invention; Figure 5 is a hydraulic principle diagram of a hydraulic system according to an embodiment of the present invention; Figure 64 is a system control architecture diagram of a hydraulic system according to an embodiment of the present invention.

[0019] Description of Reference Numerals 11. Actuator; 12. Directional control valve; 2. Oil pump unit; 21. Hydraulic pump; 22. Engine; 3. Detection unit; 4. Control unit; 41. ECU controller. DETAILED DESCRIPTION

[0020] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0021] The hydraulic system and flow control method thereof of the present invention will be described below with reference to the accompanying drawings.

[0022] When operating machinery performs different actions, the demand for hydraulic flow varies. If effective input-output flow matching and adjustment is not performed, the hydraulic system is likely to experience slow response and excessive movement speed, making it difficult to meet the requirements of refined operations. Therefore, it is necessary to design an input-output flow matching and adjustment mechanism.

[0023] Common flow matching mechanisms on the market typically rely on proportional valve opening to adjust the flow rate. This mechanism adjusts the output flow rate by varying the valve opening area. While this type of mechanism is simple and low-cost, it can also result in significant throttling losses, leading to high energy consumption.

[0024] There are also some more intelligent and more precise flow control methods on the market, such as load feedback flow control mechanisms based on variable pumps or servo pumps. This type of control method requires the integration of a large number of precision components, resulting in a complex structure and very high cost, which limits its promotion in the low- and mid-end markets or small and medium-sized equipment.

[0025] In view of this, the present invention discloses a novel hydraulic system and a flow control method thereof.

[0026] like Figure 5 and Figure 6 As shown, the hydraulic system includes an oil pump unit 2 and several execution units for performing actions. Each execution unit includes an actuator 11 and a reversing control valve 12 for controlling the operation of the actuator 11. The reversing control valve 12 is connected between the output oil circuit of the hydraulic pump 21 and the execution unit. The reversing control valve 12 is provided with a detection unit 3 for detecting its own valve position. The reversing control valve 12 is used to control the conduction or cutoff of the output oil circuit and the corresponding actuator.

[0027] like Figure 1 As shown, the flow control method based on the above hydraulic system includes: S100: Determine the valve position of each reversing control valve 12 according to the position of the valve core of each reversing control valve 12 of each execution unit; S200: Determine the action to be currently performed by the hydraulic system according to the valve position of each reversing control valve 12; S200: Determining the required flow rate of the hydraulic system to perform the current action based on a first preset mapping relationship between “target action and flow rate required to perform the target action”; S300: Adjusting the rotation speed of the hydraulic pump 21 so that the output flow of the hydraulic pump 21 matches the required flow of the hydraulic system.

[0028] The hydraulic system and flow control method thereof in the present invention are mainly used in operating machinery, such as truck-mounted cranes, excavators, loaders, tractors, etc.

[0029] Taking the boom-type aerial work platform as an example, the actuator 11 of the boom-type aerial work platform mainly includes the boom telescopic drive cylinder, the boom boom drive cylinder, the slewing drive motor, and the platform lifting drive cylinder. When the platform needs to extend or retract the boom, the reversing control valve 12 between the telescopic drive cylinder and the output oil circuit of the hydraulic pump 21 will switch from the shut-off valve position to the on-valve position. Similarly, when the platform needs to control the boom boom, the vehicle body rotation, or the platform lifting, the corresponding reversing control valve 12 needs to switch valve positions. Therefore, when the platform is operating, it only needs to obtain the valve position status of each reversing control valve 12 to determine the current action to be performed by the hydraulic system.

[0030] Different platform actions require different flow rates. During equipment commissioning, a first preset mapping relationship between different actions and the required flow rates can be calculated in advance. For example, the first preset mapping relationship could be: the flow rate required for boom extension or luffing alone is Q1, the flow rate required for boom extension and platform raising and lowering simultaneously is Q2, and the flow rate required for slewing and retracting simultaneously is Q3. Once the hydraulic system's current action is known, the required flow rate for the current action can be determined based on the first preset mapping relationship.

[0031] The second preset mapping relationship between the rotational speed of the hydraulic pump 21 and the output flow of the hydraulic pump 21 is a factory-known parameter. Therefore, after knowing the required flow of the system, it is only necessary to adjust the rotational speed of the hydraulic pump 21 accordingly to achieve output flow-required flow matching.

[0032] In summary, from the perspective of system architecture, this hydraulic system only requires the installation of a detection unit for detecting the valve core position on the reversing control valve, and then injecting the corresponding control algorithm into the controller. Very few components are required, and no complex feedback oil circuits or precision components are required. This greatly reduces the cost and difficulty of upgrading and modifying operating machinery. It has excellent compatibility and can adapt to the upgrade of almost all small and medium-sized operating machinery on the market. From the control level, this method first determines the action to be performed by the hydraulic system by detecting the valve core position of the reversing control valve. Then, based on the action to be performed by the hydraulic system, the required flow rate of the system can be determined. Finally, the speed of the hydraulic pump is adjusted according to the required flow rate. Although only an approximate flow matching adjustment can be achieved during flow matching adjustment, the control logic is simple, the components relied on are relatively few, and it can be used in conjunction with a throttle valve to achieve more precise flow adjustment. When used in conjunction, the throttling loss is very small. In this way, for low-end or small and medium-sized products, it can not only realize the installation of low-energy flow matching adjustment function, but also effectively control costs. In addition, this method is open-loop control. Compared with the hysteresis delay of the traditional pressure / flow feedback closed-loop control mechanism, this method can achieve rapid response of flow regulation and higher control efficiency.

[0033] In an embodiment of the present invention, the hydraulic pump 21 can be driven by either the engine 22 or the motor. The speed of the hydraulic pump 21 can be adjusted by adjusting the gear position of the engine 22 gearbox or the speed of the motor.

[0034] With the development of new energy technologies, the construction machinery sector is gradually transitioning towards electrification and intelligentization. However, at this stage, especially in the mid- and low-end markets, traditional power systems are still dominated by a fuel engine 22 driving a metering pump. This phenomenon is mainly due to its significant cost and size advantages: the combination of engine 22 and metering pump has a simple structure and a small overall size. Compared with variable displacement pumps or servo pumps, metering pumps are technologically mature and have low manufacturing costs. Therefore, this combination can effectively reduce the production cost of the entire machine and is highly compact, meeting the needs of the mid- and low-end markets or small and medium-sized equipment.

[0035] In the hydraulic system where the engine 22 drives the metering pump, the mainstream solution mostly uses a proportional valve to perform flow matching and adjustment of the hydraulic system. However, as mentioned above, this adjustment method has defects such as high energy consumption and low system efficiency. Although the existing technology has a more effective load feedback flow adjustment mechanism, it is necessary to modify the metering pump and introduce a complex feedback mechanism, which is costly. Therefore, the mid- and low-end markets or small and medium-sized equipment on the market will hardly consider this modification solution.

[0036] This method simplifies the method of obtaining the required flow and adopts a simpler and more direct open-loop control. While being able to retain the quantitative pump and achieve low-energy flow matching adjustment of the system, it also makes up for the dilemma of the hydraulic system with a quantitative pump driven by the engine 22, which cannot achieve both cost and energy saving.

[0037] Specifically, if Figure 2 As shown, for a hydraulic system with a fixed displacement pump driven by the engine 22, after the required flow rate of the system is known, the following method steps can be performed: S410: Determine the required speed of the hydraulic pump 21 corresponding to the required flow rate based on a second preset mapping relationship between “pump speed-pump output flow rate”; S420: Determining a target gear of the engine 22 corresponding to the required speed based on a third preset mapping relationship between the pump speed and the gear of the engine 22; S430: Adjust the engine 22 to the target gear.

[0038] like Figure 3 As shown, before determining the target gear of the engine 22 corresponding to the required speed, the following steps are required: S411 : Establishing a third preset mapping relationship according to the transmission parameters between the engine 22 and the hydraulic pump 21 .

[0039] A third preset mapping relationship between the gear position of engine 22 and the external output speed of engine 22 can also be obtained through pre-calculation. For example, in the case where engine 22 is connected to hydraulic pump 21 via a transmission, the speed of engine 22 is maintained at 2000 rpm when operating under rated conditions. The transmission is capable of adjusting to 10 gear positions, which allow the output speed of engine 22 to be adjusted in steps between 500 and 3500 rpm. In first gear, the external output speed of engine 22 is in the range of [500, 800 rpm]; in second gear, the external output speed of engine 22 is in the range of [800, 1100 rpm]; in third gear, the external output speed of engine 22 is in the range of [1100, 1400 rpm]; and so on.

[0040] After determining the system's required flow rate, the required speed of hydraulic pump 21 corresponding to that flow rate can be found using the second preset mapping relationship. The speed of hydraulic pump 21 is actually the output speed of engine 22 after passing through the gearbox. Determining the required speed of hydraulic pump 21 also determines the required speed gear of engine 22. For example, if the required speed of hydraulic pump 21 is 1500 rpm, which falls within the four-gear range of [1400, 1700), then adjusting the gear of engine 22 to fourth gear will ensure that the output flow of hydraulic pump 21 roughly meets the load's operating requirements, with only a small amount of flow overflowing.

[0041] Of course, the engine 22 and the metering pump can also be connected in a coaxial direct connection, in which case the engine 22 can directly shift gears by itself.

[0042] In an embodiment of the present invention, the hydraulic system further includes a control unit 4 , which is communicatively connected to the detection unit 3 and is configured to execute the flow control method described above.

[0043] In an embodiment of the present invention, the first preset mapping relationship, the second preset mapping relationship, and the third preset mapping relationship can be obtained in advance through live testing, and the preset mapping relationships can be stored in advance in the memory of the control unit 4. When performing control, the control unit 4 only needs to retrieve the data in the memory and compare it, and then generate a corresponding speed control strategy based on the comparison results.

[0044] In an embodiment of the present invention, the detection unit 3 includes a position detection device for respectively detecting the valve core position of each reversing control valve 12, and the control unit 4 is communicatively connected to the position detection device and is specifically configured as follows: Acquiring a position detection signal of a position detection device; According to the type of the position detection signal and the preset comparison relationship, the valve position of the corresponding reversing control valve 12 is determined.

[0045] Correspondingly, such as Figure 4 As shown, in an embodiment of the present invention, before the step of S100: determining the valve position of each reversing control valve according to the position of the valve core of the reversing control valve of each execution unit, the flow control method further includes: S001: Monitor the position of the valve core of the reversing control valve of each execution unit.

[0046] Existing directional control valves almost always change their valve position by switching the position of the valve core relative to the valve body. Therefore, in the present system and method, the position of the valve core of the directional control valve 12 can be directly detected to determine the corresponding valve position of the directional control valve 12. For example, for a two-position, two-way directional control valve 12, when the valve core is in the left position, it is configured to be in the on state, and when in the right position, it is configured to be in the off state. The position detection signal type can include 0 and 1, with 0 representing off and 1 representing on. Based on the type of the position detection signal and a preset comparison relationship, the corresponding valve position of the directional control valve 12 can be determined.

[0047] Of course, if Figure 5As shown, the directional control valve 12 can also be a multi-way directional control valve with three, four, or even more integrated valve positions. The directional control valve 12 can be used with multiple position detection devices. For example, if two position detection devices are located at the axial ends of the valve core, the detection signal type can be a combination of left 0, left 1, right 0, and right 1. For example, a detection signal of left 1 and right 0 indicates that the directional control valve 12 is in the left valve position, while a signal of left 0 and right 0 indicates that the directional control valve 12 is in the center position. This signal combination can determine the status of a directional control valve with a large number of valve positions.

[0048] In an embodiment of the present invention, the position detection device can be a highly integrated, compact device such as a Hall effect sensor or a displacement sensor. Taking a Hall effect sensor as an example, a Hall effect sensor primarily detects changes in magnetic field intensity or polarity. This type of device is compact and can be integrated with the valve core of the reversing control valve 12, adapting to the narrow space within the valve body. Furthermore, due to its non-contact sensing, the Hall effect sensor is free of mechanical wear, has a long lifespan, and is highly resistant to oil, dirt, and vibration. Furthermore, the valve core moves at a relatively high speed during reversing, and the Hall effect sensor has a high detection sensitivity, making it well-suited for position detection during high-speed movement of the valve core.

[0049] In the embodiment of the present invention, such devices can also be installed on the valve body. When the reversing control valve 12 is produced, standardized assembly is achieved by reserving interfaces on the valve body.

[0050] In an embodiment of the present invention, the position detection device may also be a larger device such as a proximity switch, a contact switch, or a position switch. The position detection device may be installed near the valve core or on an operating handle that is transmission-connected to the reversing control end of the valve core.

[0051] In an embodiment of the present invention, each reversing control valve 12 may be detected using multiple position detecting devices, or different types of position detecting devices.

[0052] like Figure 6 As shown, in this embodiment of the present invention, the control unit 4 includes a main controller and an ECU controller 41 for controlling the gear position of the engine 22. The ECU controller 41 is primarily used to control the gear position of the engine 22 or the transmission, thereby adjusting the output speed of the engine 22. The ECU controller 41 can communicate with the position detection device via serial communication, CAN communication, LIN communication, or other means. The electrical signal generated by the position detection device can be directly transmitted to the ECU controller 41, resulting in faster signal transmission, higher dynamic control response, and greater operational efficiency.

[0053] To achieve the above object, the present invention further provides a working machine, wherein the working machine includes the hydraulic system described above. Since the working machine adopts all the technical solutions of the above embodiments, it has at least the beneficial effects brought by the above embodiments, which will not be repeated here.

[0054] In summary, this method constructs an accurate mapping data model based on the relationship between the flow rate requirements and the required speed of the hydraulic pump 21 during the operation of each actuator 11, pre-measured under actual operating conditions. Therefore, during control, the system action to be executed is determined by real-time monitoring of the operation of the reversing control valve 12. Combined with the above model, the flow rate required to execute the current action and the required speed of the hydraulic pump 21 can be easily and intuitively determined. This facilitates subsequent matching of the output flow of the hydraulic pump 21 with the required flow rate of the actuator 11, achieving energy-saving regulation. Furthermore, for hydraulic systems where an engine 22 drives a fixed displacement pump, multi-gear staged control of the engine 22 can provide the fixed displacement pump with variable adjustment capabilities, facilitating low-cost upgrades to existing fixed displacement pump hydraulic systems. Furthermore, this method can optimize the gear position of the engine 22 by setting multiple gears based on the engine 22's optimal speed operating range (e.g., the aforementioned 2000 rpm). This not only ensures that the engine 22 operates continuously within its efficient operating range, but also improves the economic efficiency of each power component, further achieving energy savings for the system.

[0055] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0056] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection, or communication; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0057] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0058] Although the embodiments of the present invention have been described above, it is understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A flow control method for a hydraulic system, characterized in that: The flow control method of the hydraulic system comprises: Determining the valve position of each reversing control valve (12) according to the position of the valve core of each execution unit; Determining the action currently to be performed by the hydraulic system according to the valve position of each reversing control valve (12); determining the required flow rate of the hydraulic system to perform the current action according to a first preset mapping relationship between "target action - flow rate required to perform the target action"; The rotation speed of the hydraulic pump (21) is adjusted so that the output flow of the hydraulic pump (21) matches the required flow of the hydraulic system.

2. The flow control method of the hydraulic system according to claim 1, characterized in that: Before the step of determining the valve position of each reversing control valve (12) according to the position of the valve core of each execution unit, the flow control method further includes: The position of the valve core of the reversing control valve (12) of each of the execution units is monitored.

3. The flow control method of the hydraulic system according to claim 2, characterized in that: The position of the valve core is monitored by a Hall sensor.

4. The flow control method of the hydraulic system according to claim 1, characterized in that: The hydraulic pump (21) is driven by the engine (22), and the steps of adjusting the rotation speed of the hydraulic pump (21) so that the output flow of the hydraulic pump (21) matches the required flow of the hydraulic system specifically include: Determining the required speed of the hydraulic pump (21) corresponding to the required flow rate according to a second preset mapping relationship between "pump speed-pump output flow rate"; Determining a target gear of the engine (22) corresponding to the required speed based on a third preset mapping relationship between "pump speed-engine (22) gear"; The engine (22) is adjusted to the target gear position.

5. The flow control method of the hydraulic system according to claim 4, characterized in that: Before determining the target gear of the engine (22) corresponding to the required speed, the flow control method further includes: The third preset mapping relationship is established according to the transmission parameters between the engine (22) and the hydraulic pump (21).

6. A hydraulic system, characterized in that: The hydraulic system comprises: An oil pump unit (2) comprising a hydraulic pump (21) and a driving device for driving the hydraulic pump (21) to rotate; A plurality of execution units, each execution unit comprising an execution element (11) and a reversing control valve (12) for controlling the operation of the execution element (11); A detection unit (3) for detecting the position of the valve core of each of the reversing control valves (12); A control unit (4) is communicatively connected to the detection unit (3) and is used to execute the flow control method according to any one of claims 1 to 5.

7. The hydraulic system according to claim 6, characterized in that The detection unit (3) includes a position detection device for detecting the position of the valve core of the reversing control valve (12), and the control unit (4) is communicatively connected to the position detection device and is specifically configured as follows: Acquiring a position detection signal of the position detection device; According to the type of the position detection signal and in accordance with a preset comparison relationship, the valve position of the corresponding reversing control valve (12) is determined.

8. The hydraulic system according to claim 7, characterized in that: The position detection device is a Hall sensor.

9. The hydraulic system according to claim 7, characterized in that The position detection device is one of a proximity switch, a contact switch, a position switch, and a displacement sensor.

10. The hydraulic system according to claim 6, characterized in that The hydraulic pump (21) is a fixed displacement pump, and the driving device is an engine (22).

11. The hydraulic system according to claim 10, characterized in that The control unit (4) includes an ECU controller (41) for controlling the gear position of the engine (22).

12. A working machine, characterized in that: Comprising a hydraulic system according to any one of claims 6 to 11.

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