Control oil passage, hydraulic system, working arm and construction machine

Abstract

This invention provides a control oil circuit, hydraulic system, boom, and engineering machinery. The control oil circuit includes a load feedback loop and a flow regulating valve connected in parallel with the load oil circuit. When the control oil circuit is in its first operating state, the variable displacement pump operates, and the load feedback loop feeds back the load pressure to the variable displacement pump, allowing it to adjust its displacement based on the load pressure. When the control oil circuit is in its second operating state, the fixed displacement pump operates, and the load feedback loop feeds back the load pressure to the flow regulating valve, adjusting the displacement distribution between the flow regulating valve and the load oil circuit. This control oil circuit allows for the selection of either a single variable displacement pump or a single fixed displacement pump for different operating conditions, and also enables the matching of appropriate hydraulic circuits when both pumps are operating, achieving global optimization.

Description

Technical Field

[0001] This invention relates to the field of engineering machinery technology, and in particular to a control oil circuit, a hydraulic system equipped with the control oil circuit, a working arm equipped with the hydraulic system, and an engineering machine equipped with the working arm. Background Technology

[0002] In concrete operations, hydraulic systems are typically used to drive the actuators at various joints of a robotic arm, enabling them to perform corresponding actions and thus control the robotic arm to complete the task. Currently, the placing system of commonly used concrete machinery is driven and controlled by a "pump-valve combination hydraulic control system" within the hydraulic system. There are two common types of pump-valve combination hydraulic control systems: ① Combining a variable displacement pump with a load-sensitive multi-way valve (PSV).

[0003] ② The fixed displacement pump is combined with a multi-way valve (PSL) with a three-way flow control valve.

[0004] Since both of the above-mentioned pump-valve combination hydraulic control systems have their optimal operating conditions and limitations, each system can only meet some operating condition requirements and it is difficult to achieve global optimization. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a control oil circuit, a hydraulic system provided with the control oil circuit, a working arm provided with the hydraulic system, and an engineering machine provided with the working arm. Through the control oil circuit, a fixed displacement pump or a variable displacement pump can be selected to work according to the actual working conditions, and a suitable hydraulic circuit can be matched to achieve global optimization.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A control oil circuit includes a load feedback loop and a flow regulating valve for parallel connection with the load oil circuit; In the first operating state, the load feedback loop can feed back the load pressure to the variable pump, so that the variable pump can adjust its own displacement based on the load pressure. In the second operating state, the load feedback loop can feed back the load pressure to the flow regulating valve to adjust the flow regulating valve and the displacement distribution of the load oil circuit.

[0007] Optionally, the control oil circuit described above may also include an unloading valve: The unloading valve is a switch valve. When it is in the connected state, it can connect the load feedback loop to the oil tank. When it is closed, it can provide feedback on the load pressure.

[0008] Optionally, the control oil circuit described above may also include a switching valve; When the switching valve is in the first working position, the control oil circuit is in the first working state; When the switching valve is in the second working position, the control oil circuit is in the second working state.

[0009] Optionally, in the above control oil circuit, the switching valve is provided with a first interface, a second interface, and a third interface; When the switching valve is in the first working position, the first interface and the third interface are connected. When the switching valve is in the second working position, the second interface and the third interface are connected.

[0010] Optionally, the above-mentioned control oil circuit is provided with a load oil circuit supply port and a load oil circuit return port; The flow regulating valve is a proportional valve, wherein: the oil inlet and non-spring end interface of the proportional valve are both connected to the oil supply port of the load oil circuit; The oil outlet of the proportional valve is connected to the oil return port of the load oil circuit. The non-spring end interface and the first interface are sequentially connected in series downstream of the oil supply port of the load oil circuit and are connected in parallel with the load oil circuit. The third interface is connected to the spring end interface of the flow regulating valve; The second interface is used to connect in parallel with the variable pump control port and is connected to the load feedback loop to receive the load pressure of the load feedback loop.

[0011] Optionally, in the above-mentioned control oil circuit, an overflow valve is provided at the spring end interface of the flow regulating valve; And / or, the control oil circuit is further provided with a pressure reducing valve, and the non-spring end interface, the first interface, and the pressure reducing valve are connected in series.

[0012] Optionally, in the above control oil circuit, the switching valve is a solenoid valve or a manual valve with memory function.

[0013] Optionally, in the above-mentioned control oil circuit, the switching valve is a plate valve or a cartridge valve.

[0014] A hydraulic system includes a variable displacement pump, a fixed displacement pump, and the aforementioned control circuit, wherein: The variable pump and the fixed pump are connected in parallel upstream of the load oil supply port of the control oil circuit.

[0015] Optionally, in the above hydraulic system, the variable pump and the fixed pump are respectively connected to the first drive device and the second drive device.

[0016] Optionally, in the above hydraulic system, a first check valve is provided between the outlet of the variable pump and the oil supply port of the load oil circuit; A second check valve is provided between the outlet of the metering pump and the oil supply port of the load oil circuit.

[0017] A working arm includes multiple joints, each or multiple joints being provided with an actuator, the actuator including a hydraulic cylinder and a plate-type multi-way valve for controlling the movement of the hydraulic cylinder; the working arm also includes a hydraulic system as described above for supplying hydraulic oil to the plate-type multi-way valve.

[0018] An engineering machine is equipped with a working arm as described above.

[0019] In the control oil circuit, hydraulic system, working arm, and engineering machinery provided by this invention, the load feedback loop can not only feed back the load pressure to the variable pump in the first working state (i.e. when the variable pump is working) so that the variable pump can adjust its own displacement based on the load pressure, but also feed back the load pressure to the flow control valve in the second working state (i.e. when the fixed displacement pump is working) so as to adjust the displacement distribution between the flow control valve and the load oil circuit. Thus, it is possible to select the variable pump to drive alone or the fixed displacement pump to drive alone according to different working conditions. Moreover, it is also possible to match a suitable hydraulic circuit for the fixed displacement pump and the variable pump when they are working to achieve global optimization. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the control oil circuit provided in an embodiment of the present invention.

[0022] Figure 2 A simplified structural diagram of the switching valve provided in an embodiment of the present invention.

[0023] Figure 3 A schematic diagram of the basic path of the PSV-type circuit (thick line in the figure) in the hydraulic system provided for the embodiments of the present invention.

[0024] Figure 4 A basic path diagram of a PSL-type circuit (thick lines in the figure) in a hydraulic system provided for an embodiment of the present invention.

[0025] Figure 5 A schematic diagram of the hydraulic system of the boom provided in an embodiment of the present invention. Detailed Implementation

[0026] In order to ensure the reliability of large-scale engineering machinery operations, it is necessary to arrange two sets of power systems, namely "variable pump + fixed pump", so that the variable pump can be used to drive the machinery alone or the fixed pump can be used to drive the machinery alone, depending on different working conditions.

[0027] To meet the above requirements, embodiments of the present invention disclose a control oil circuit, a hydraulic system equipped with the control oil circuit, a working arm equipped with the hydraulic system, and an engineering machine equipped with the working arm. Through the control oil circuit, a fixed displacement pump or a variable displacement pump can be selected to work according to the actual working conditions, and a suitable hydraulic circuit can be matched to achieve global optimization.

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] First, please see Figures 1 to 4 The control oil circuit provided in this embodiment of the invention includes a load feedback loop LS and a flow regulating valve 5, wherein: The load feedback loop LS, i.e., the dynamic pressure feedback loop, is related to the load (see [reference]). Figure 5 The multi-way valve in the system can detect and provide feedback on load pressure; see details below. Figure 1 and Figure 5 The oil circuit connected to the oil inlet above the unloading feed valve 6; The flow regulating valve 5 is connected in parallel with the load oil circuit. The starting position of the load oil circuit can be found in [reference needed]. Figure 3 and Figure 4 The large right-pointing arrow at point P (i.e., the oil supply port of the load oil circuit, or simply the oil supply port) and the large left-pointing arrow at point R (i.e., the oil return port of the load oil circuit, or simply the oil return port); When the control oil circuit is in the first working state, the variable pump 7 in the hydraulic system works, and the load feedback circuit LS feeds back the load pressure to the variable pump 7 so that the variable pump 7 can adjust the displacement in real time according to the load pressure. At this time, a PSV type circuit is formed in the control oil circuit, that is, a safety valve control circuit, which can adjust the oil supply hydraulic pressure and displacement in real time according to the load conditions in the actual working conditions. When the control oil circuit is in the second working state, the fixed displacement pump 8 in the hydraulic system works, and the load feedback loop LS feeds back the load pressure to the flow regulating valve 5 so as to regulate the hydraulic pressure and displacement of the load oil circuit through the flow regulating valve 5. At this time, since the flow regulating valve 5 is connected in parallel with the load oil circuit, the oil supply to the oil circuit where the flow regulating valve 5 is located can be increased / decreased while the displacement of the fixed displacement pump 8 remains unchanged. Thus, the oil supply to the load oil circuit can be decreased / increased. It can be seen that a PSL type circuit, i.e., a proportional valve control circuit, is formed in the control oil circuit at this time, which can adjust the hydraulic pressure and displacement in the load oil circuit in real time according to the load conditions in the actual working conditions.

[0030] As can be seen, the control oil circuit and hydraulic system provided in the embodiments of the present invention can not only select a variable pump to drive alone or a fixed pump to drive alone according to different working conditions, but also match a suitable hydraulic circuit for the fixed pump and variable pump when they are working to achieve global optimization.

[0031] For specific implementation details, please refer to [link / reference]. Figure 1 and Figure 5 The aforementioned control oil circuit is equipped with an unloading valve 6. The unloading valve 6 is a switching valve; in its open state, it connects the load feedback loop LS to the oil tank, and in its closed state, it provides load pressure feedback. Specifically, as... Figure 1 As shown, the unloading valve 6 can be set to open when energized (i.e., in the connected state) and close when de-energized. When the unloading valve 6 is energized, the load feedback loop LS feeds the load pressure back to the X port of the variable pump 7; when the unloading valve 6 is de-energized, the load feedback loop LS connects the load pressure to the oil tank to achieve unloading.

[0032] In specific implementation, a switching valve 4 is installed in the aforementioned control oil circuit. When the switching valve 4 is in the first working position (i.e. Figure 1 and Figure 2 When the switching valve 4 is in the upper position (i.e., the control oil circuit is in the first working state, and the variable pump 7 is working); when the switching valve 4 is in the second working position (i.e., the upper position), the control oil circuit is in the first working state, and the variable pump 7 is working; ... Figure 1 and Figure 2 When the switch valve 4 is in the lower position (as in the middle position), the control oil circuit is in the second working state, and the metering pump 8 operates. Specifically, the switching valve 4 can be a two-position three-way solenoid valve. Alternatively, in other specific embodiments, a manual valve with memory function can also be used as the switching valve 4. Moreover, the switching valve 4 can be a plate valve, a cartridge valve (e.g., a threaded cartridge valve), or other control valves capable of achieving the above-mentioned switching function.

[0033] Please see Figure 1 and Figure 3 Taking a two-position three-way valve as an example, the switching valve 4 is equipped with a first port e, a second port g, and a third port f: when the switching valve 4 is in the first working position (i.e. Figure 1 and Figure 2When the first interface e and the third interface f are in the upper position, a PSV-type circuit is formed in the control oil circuit, and the variable pump 7 operates; when the switching valve 4 is in the second operating position (i.e., Figure 1 and Figure 2 When the lower position is connected, the second interface g and the third interface f are connected, forming a PSL-type loop in the control oil circuit, and the metering pump 8 works.

[0034] For specific implementation details, please refer to [link / reference]. Figure 1 The flow regulating valve 5 is preferably a proportional valve, such as a three-way proportional valve that can adjust the flow rate according to the pressure difference between the two sides. Specifically: the inlet c and the non-spring end interface h of the proportional valve are both connected to the load oil circuit supply port P; the outlet d of the proportional valve is connected to the load oil circuit return port R; the non-spring end interface h and the first interface e are sequentially connected in series downstream of the supply port P and in parallel with the load oil circuit; the third interface f is connected to the spring end interface k of the flow regulating valve 5; the second interface g is connected in parallel with the variable pump control port x and is connected to the load feedback loop LS to receive the load pressure fed back by the load feedback loop LS.

[0035] As can be seen from the above connection relationship, the load feedback loop LS in the control oil circuit is directly connected to the second interface g of the switching valve 4, so that when the variable pump 7 is working, the load pressure can be fed back to the control oil port x of the variable pump 7, so that the variable pump 7 can adjust its own displacement in real time according to the load pressure; and since the load feedback loop LS in the control oil circuit is connected to the spring end interface k of the flow regulating valve 5, the load pressure can be fed back to the flow regulating valve 5 when the fixed displacement pump 8 is working, and the valve core of the flow regulating valve 5 is controlled to be in different positions, so that the variable pump 7 can adjust the hydraulic pressure and flow in the load oil circuit in real time according to the load pressure.

[0036] In practice, the working process of this control oil circuit is as follows: (i) When switching valve 4 is in the first working position, the first port e and the third port f of switching valve 4 are connected, and the second port g is closed. At this time, the pressure oil at port P flows through the lower oil passage (i.e. Figure 1 The oil path below point M reaches the non-spring end interface h of the flow regulating valve 5, and then passes through the upper oil path (i.e. Figure 1 The oil circuit on the left side of point M and the switching valve 4 reach the spring end interface k of the flow regulating valve 5, thus making the oil pressure on both sides of the flow regulating valve 5 equal, i.e. Figure 1 The oil pressure at port h and port k are equal. At this time, the valve core of flow control valve 5 is pushed to the open position by the spring force, and flow control valve 5 is in the open position (i.e., Figure 3 (the lower-level component), losing its flow regulation function; (ii) When the switching valve 4 is in the second working position, the second port g and the third port f of the switching valve 4 are connected. Furthermore, since the second port g is connected to the load feedback loop LS, the load pressure sensed by the load feedback loop LS can be fed back to the spring end port k of the flow regulating valve 5. At this time, the non-spring end port h of the flow regulating valve 5 is the oil supply pressure at port P, and the spring end port k of the flow regulating valve 5 is the load pressure fed back from the load feedback loop LS. Therefore, the oil pressures on both sides of the flow regulating valve 5 are unequal, and the flow regulating valve 5 is in the on position (i.e., Figure 2 (The upper position in the middle). At this time, the inlet and outlet oil ports of the flow regulating valve 5 (i.e., Figure 2 The oil inlet c and oil outlet d) are connected to the oil supply port P and the oil return port R respectively; and the control port X of the variable pump loses its function, so the variable pump does not start.

[0037] For specific implementation details, please refer to [link / reference]. Figure 1 In the aforementioned control oil circuit, a relief valve 9 is installed at the spring end interface k of the flow regulating valve 5; a pressure reducing valve 10 is also installed in the control oil circuit, with the non-spring end interface h, the first interface e, and the pressure reducing valve 10 connected in series. Therefore, in the pump-valve combination hydraulic control system provided in this embodiment of the invention, a switching valve 4 is installed in parallel on the oil circuit between the flow regulating valve 5 and the pressure reducing valve 10. The three ports (e, f, g) of the switching valve 4 are respectively connected to one end of the flow regulating valve 5, one end of the pressure reducing valve 10, and the load feedback loop (LS). Figure 1 The X port in the diagram is connected to the control port of the variable pump control valve (the control port of the variable pump control valve can be considered as the...). Figure 1 (X in the middle).

[0038] In practice, the variable displacement pump 7 and the fixed displacement pump 8 are connected by different power sources, and each is connected in parallel to the inlet of the multi-way valve head after passing through a check valve. Please refer to [link to relevant documentation]. Figure 3 In the hydraulic system provided by this invention, the variable displacement pump 7 and the fixed displacement pump 8 are connected in parallel at the oil supply port P of the load oil circuit, and are respectively connected to the first drive device and the second drive device. Preferably, a first check valve 11 is provided between the outlet of the variable displacement pump 7 and the oil supply port P, and a second check valve 12 is provided between the outlet of the fixed displacement pump 8 and the oil supply port P. It can be seen that the variable displacement pump and the fixed displacement pump are connected to different power sources. Alternatively, in other embodiments, the variable displacement pump and the fixed displacement pump can be arranged in other ways, as long as it can be ensured that the variable displacement pump and the fixed displacement pump can be driven independently.

[0039] In summary, the embodiments of the present invention provide a novel control oil circuit that can fully combine the control functions of the PSV type circuit (or load-sensitive multi-way valve) and the PSL type circuit (or multi-way valve with three-way flow regulating valve). By combining the two functions in a single multi-way valve control oil circuit through principle and structural design, the machine can use the PSV type circuit multi-way valve control function when the variable pump provides power and the PSL type circuit multi-way valve control function when the fixed pump provides power, without having to back up two independent multi-way valve control oil circuits in the system.

[0040] This invention also provides a working arm, such as a concrete placing system robot, i.e., a boom, or a robotic arm, which has actuators at one or more joints. Each actuator includes a hydraulic cylinder and a multi-way valve for controlling the movement of the hydraulic cylinder. Furthermore, the concrete placing system robot is also equipped with a hydraulic system as described above for supplying hydraulic oil to the multi-way valve.

[0041] Please see details. Figure 3 The robotic arm is equipped with the aforementioned actuators at multiple joints, and the multi-way valves in these actuators are arranged in parallel to form multiple working links 2. Furthermore, the concrete placing system robotic arm also includes a head link 1 (or oil inlet link) and a tail link 3. The aforementioned pump-valve combination hydraulic control system is located in the head link 1, and a switching valve 4 is used to change the working mode of the head link, allowing the multi-way valve control oil circuit to have both PSL and PSV working states.

[0042] In practical implementation, the plate-type multi-way valve can be set as a one-piece cast multi-way valve without losing the aforementioned control mechanism form. The head-connector 1 can use different structures depending on the type of hydraulic pump (fixed displacement pump / variable displacement pump).

[0043] As can be seen, the present invention improves the control oil circuit of the boom drive multi-way valve oil inlet connection (head connection). The control mode of the oil inlet connection can be changed according to the system working state (i.e. whether the variable pump or the fixed pump is providing flow to the system at this time).

[0044] Specifically, please see Figure 3 and Figure 4 : When the hydraulic system is in variable pump operation mode, switching valve 4 is in the upper position. At this time, the control oil circuit enters the PSV type circuit operation mode. Since the g port of switching valve 4 is disconnected, the load feedback circuit LS (i.e., Figure 1The load pressure oil fed back from the oil inlet of the unloading valve 6 (connected to the oil circuit) enters the swashplate control mechanism of the variable pump 7 through port X. At this time, the pressure oil at port P passes through the upper and lower oil circuits and the switching valve 4 to reach both sides of the flow regulating valve 5. At this time, the oil pressure on both sides of the flow regulating valve 5 is equal, so its valve core is pushed to the open position under the action of spring force, and the flow regulating valve 5 loses its function. At this time, the control oil circuit and the variable pump 7 form a PSV type circuit to drive the operation.

[0045] In practical implementation, the working principle of the PSV type circuit is as follows: Under normal standby conditions, the variable pump outputs its own pressure of approximately 14-25 bar, which is also the system pressure. At this time, the pump has no load feedback, its displacement is at its minimum, and there is almost no flow output. When any valve in the working connection is activated, the load pressure at ports A and B is transmitted to the variable pump signal port through the load feedback loop LS and the shuttle valve. At this time, the pump swashplate changes, the flow output begins to increase, and the pressure begins to rise until the required flow at ports A and B is controlled. When the displacement of the handle rod and the main valve core changes, the pump also changes accordingly to achieve on-demand flow output and achieve energy saving.

[0046] Specifically, please see Figure 3 and Figure 5 : When the hydraulic system is in the working state of the fixed displacement pump, the switching valve 4 is switched to the lower position. At this time, the control oil circuit enters the working state of the PSL type circuit. Since the g port of the switching valve 4 is connected, the load pressure oil fed back by the load feedback circuit LS reaches the spring end of the flow regulating valve 5 through the f port of the switching valve 4. At this time, the upper oil port of the P port pressure oil is disconnected by the switching valve, and only the lower oil circuit reaches the non-spring end of the flow regulating valve 5. At this time, the flow regulating valve 5 starts to work, and the X port loses its function. At this time, the control oil circuit and the fixed displacement pump 8 form a PSL type circuit to drive the operation.

[0047] In practical implementation, the working principle of the PSL type circuit is as follows: In normal standby mode, the pilot oil from port P is directed to one side of the valve core of flow control valve 5, opening the valve core and overcoming the 9 bar force of the spring. P and R are connected, and the system pressure is approximately 9 bar. When any valve in the working connection is activated, the load pressure at ports AB is transmitted to the spring chamber of flow control valve 5 through the load feedback loop LS and the shuttle valve. At this time, the valve core opening of flow control valve 5 decreases, and the system pressure rises until the forces at both ends of the valve core are balanced, and the pressure stabilizes. Excess flow returns to the oil tank through port R.

[0048] In summary, embodiments of the present invention also provide an engineering machine equipped with the working arm described above.

[0049] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0050] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0051] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A control oil passage characterized by, It includes a load oil circuit supply port (P), a load oil circuit return port (R), a load feedback loop (LS), a switching valve (4), and a flow regulating valve (5) for parallel connection with the load oil circuit. The inlet (c) and outlet (d) of the flow regulating valve (5) are respectively connected to the load oil circuit supply port (P) and the load oil circuit return port (R). In the first working state, the switching valve (4) is in the first working position so that the flow regulating valve (5) is in the cut-off position. The load feedback loop (LS) can be connected to the variable pump control port (x) of the variable pump (7) to feed back the load pressure to the variable pump (7) so that the variable pump (7) can adjust its own displacement based on the load pressure. In the second working state, the switching valve (4) is in the second working position so that the load feedback loop (LS) is connected to the control end of the flow regulating valve (5). The flow regulating valve (5) is in the connected position. The load feedback loop (LS) can feed back the load pressure to the flow regulating valve (5) to adjust the displacement distribution of the flow regulating valve (5) and the load oil circuit.

2. The control oil passage according to claim 1, characterized by, Also includes unloading valve (6): The unloading valve (6) is a switching valve. When it is in the connected state, it can connect the load feedback loop (LS) to the oil tank. When it is in the closed state, it can provide feedback on the load pressure.

3. The control oil passage according to claim 1, characterized by The switching valve (4) is provided with a first port (e), a second port (g) and a third port (f); When the switching valve (4) is in the first working position, the first interface (e) and the third interface (f) are connected; When the switching valve (4) is in the second working position, the second interface (g) and the third interface (f) are connected.

4. The control oil passage according to claim 3, characterized by The flow regulating valve (5) is a proportional valve, wherein: The oil inlet (c) and non-spring end interface (h) of the proportional valve are both connected to the oil supply port (P) of the load oil circuit. The oil outlet (d) of the proportional valve is connected to the oil return port (R) of the load oil circuit; The non-spring end interface (h) and the first interface (e) are connected in series downstream of the load oil circuit supply port (P) and are connected in parallel with the load oil circuit. The third interface (f) is connected to the spring end interface (k) of the flow regulating valve (5); The second interface (g) is used to connect in parallel with the variable pump control port (x) and is connected to the load feedback loop (LS) to receive the load pressure fed back by the load feedback loop (LS).

5. The control oil passage according to claim 4, characterized by An overflow valve (9) is provided at the spring end interface (k) of the flow regulating valve (5). And / or, the control oil circuit is also provided with a pressure reducing valve (10), and the non-spring end interface (h), the first interface (e), and the pressure reducing valve (10) are connected in series.

6. The control oil circuit according to claim 1, characterized in that, The switching valve (4) is a solenoid valve or a manual valve with memory function; And / or, the switching valve (4) is a plate valve or a cartridge valve.

7. A hydraulic system characterized by, Includes a variable displacement pump (7), a fixed displacement pump (8), and a control circuit as described in any one of claims 1 to 6, wherein: The variable pump (7) and the fixed pump (8) are connected in parallel upstream of the load oil supply port (P) of the control oil circuit.

8. The hydraulic system according to claim 7, characterized in that, A first check valve (11) is provided between the outlet of the variable pump (7) and the oil supply port (P) of the load oil circuit. A second check valve (12) is provided between the outlet of the metering pump (8) and the oil supply port (P) of the load oil circuit.

9. A working arm comprising multiple joints, wherein each or multiple joints are respectively provided with an actuator, said actuator comprising a hydraulic cylinder and a plate-type multi-way valve for controlling the movement of said hydraulic cylinder, characterized in that, It also includes the hydraulic system as described in claim 7 or 8, for supplying hydraulic oil to the plate-type multi-way valve.

10. An engineering machinery, characterized in that, It is equipped with the working arm as described in claim 9.

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