Post-valve compensated load sensing system, hydraulic system and crane

Abstract

The present invention discloses a post-valve compensation load-sensitive system, a hydraulic system, and a crane, which relate to the hydraulic field and are used to achieve greater energy conservation. The working oil circuit of the post-valve compensation load-sensitive system includes a load-sensitive pump, a control valve, an actuator, and a pressure compensator; the control valve is located between the load-sensitive pump and the actuator; and the pressure compensator is arranged downstream of the control valve. The load-sensitive oil circuit includes a pump variable mechanism, a flow control valve, and a throttling assembly; the pump variable mechanism is connected to the control end of the load-sensitive pump, and the flow control valve is fluidically connected to the pump variable mechanism; the oil inlet of the throttling assembly is connected to the pilot control end of the pressure compensator. The first overflow branch includes a first reversing valve and a first overflow valve; the first overflow valve is located downstream of the first reversing valve. The oil inlet of the first reversing valve is fluidically connected to the control end of the flow control valve and the oil outlet of the throttling assembly; the oil outlet of the first overflow valve is connected to the return oil. The above-mentioned system is very energy-saving and has low noise.

Description

Technical Field

[0001] The present invention relates to the field of hydraulics, and in particular to a post-valve compensation load sensing system, a hydraulic system and a crane. Background Art

[0002] Crane loading operations primarily involve four main movements: telescopic, luffing, hoisting, and slewing. The crane's hydraulic system controls these four movements, including telescopic, luffing, and primary and secondary hoisting. Specifically, the control of these four movements is integrated into a single multi-way valve. To enhance the coordination of compound movements (two or more movements operating simultaneously), post-valve compensation technology is employed to improve flow distribution accuracy when multiple loads are operating simultaneously. To ensure system installation, a relief valve is also incorporated into the hydraulic system.

[0003] The inventors discovered that crane hydraulic systems typically integrate two or more actuator control valves into a single multi-way valve. Two actuator control valves and the actuator are connected in parallel at the oil outlet of the load-sensing pump. A main relief valve is installed in parallel in the oil line between the load-sensing pump and the control valves of each actuator to limit the maximum pressure of the hydraulic system.

[0004] The inventors discovered that the maximum operating pressures required by various actuators vary, often being less than or equal to the set pressure of the primary relief valve. Therefore, a secondary relief valve is often required to limit the maximum operating pressures of different actuators. When the operating pressure of a particular actuator reaches the set pressure of the secondary relief valve, the relief valve opens, allowing hydraulic oil to overflow, limiting the maximum operating pressure and protecting the actuator. The operation of other actuators is unaffected by the secondary relief valve.

[0005] The inventors have discovered that the prior art has at least the following problems: during the overflow process of the existing hydraulic system, energy loss and overflow noise are very large. Summary of the Invention

[0006] The present invention proposes a post-valve compensation load-sensing system, a hydraulic system and a crane, so as to provide a post-valve compensation load-sensing system with greater energy conservation and noise reduction.

[0007] An embodiment of the present invention provides a post-valve compensation load sensing system, comprising:

[0008] A working oil circuit includes a load sensing pump, a control valve, an actuator, and a pressure compensator; the actuator includes a first working oil port and a second working oil port; the control valve is located between the oil outlet of the load sensing pump and the first and second working oil ports of the actuator to control the operation of the actuator; the pressure compensator is disposed downstream of the control valve;

[0009] A load-sensing oil circuit includes a pump variable mechanism, a flow control valve, and a throttling assembly; the pump variable mechanism is connected to the control end of the load-sensing pump, and the flow control valve is in fluid communication with the pump variable mechanism to control the displacement of the pump variable mechanism and thereby control the displacement of the load-sensing pump; the oil inlet of the throttling assembly is in communication with the pilot control end of the pressure compensator;

[0010] The first overflow branch includes a first reversing valve and a first overflow valve; the first overflow valve is located downstream of the first reversing valve; the first reversing valve is configured to be open when oil is flowing into the first working oil port of the actuator and to be closed when oil is not flowing into the first working oil port of the actuator; wherein the oil inlet of the first reversing valve is in fluid communication with the control end of the flow control valve and the oil outlet of the throttling assembly; the oil outlet of the first overflow valve is in fluid communication with return oil; and

[0011] The system overflow branch includes a system overflow valve; the system overflow valve is arranged between the oil outlet of the load sensing pump and the oil return port of the control valve.

[0012] In some embodiments, the relief pressure of the first relief valve is lower than the relief pressure of the system relief valve.

[0013] In some embodiments, the pilot control end of the first reversing valve is fluidically connected to the first working oil port of the actuator.

[0014] In some embodiments, the pilot control end of the first reversing valve is connected to the first pilot control end of the control valve.

[0015] In some embodiments, the first reversing valve is a solenoid reversing valve.

[0016] In some embodiments, the post-valve compensation load sensing system further comprises:

[0017] The second overflow branch includes a second reversing valve and a second overflow valve; the second overflow valve is located downstream of the second reversing valve; the second reversing valve is constructed to be conductive when oil is flowing into the second working oil port of the actuator and to be cut off when oil is not flowing into the second working oil port of the actuator; wherein the oil inlet of the second reversing valve is fluidically connected to the control end of the flow control valve and the oil outlet of the throttling assembly; the oil outlet of the second overflow valve is connected to the return oil.

[0018] In some embodiments, the pilot control end of the second reversing valve is fluidically connected to the second working oil port of the actuator.

[0019] In some embodiments, the pilot control end of the second reversing valve is connected to the second pilot control end of the control valve.

[0020] In some embodiments, the second reversing valve is a solenoid reversing valve.

[0021] In some embodiments, the throttle assembly includes a throttle orifice.

[0022] An embodiment of the present invention further provides a hydraulic system, comprising the post-valve compensation load-sensing system provided by any technical solution of the present invention.

[0023] An embodiment of the present invention further provides a crane, comprising the hydraulic system provided by any technical solution of the present invention.

[0024] The post-valve compensation load-sensitive system provided by the above technical solution includes a first overflow branch and a system overflow branch. Among them, the system overflow branch uses the oil overflow in the working oil circuit, and has a large flow rate; the first overflow branch uses the oil overflow in the load-sensitive oil circuit, and has a small flow rate. The overflow pressure of the system overflow branch is greater than the overflow pressure of the first overflow branch. When the post-valve compensation load-sensitive system is working normally, if the load pressure is too small, the system overflow branch does not need to work, and the first overflow branch can be directly used to overflow, which can play a role in adjusting the displacement of the load-sensitive pump. In addition, the overflow flow of the first overflow branch is very small, which is very energy-saving and environmentally friendly, and the noise is also very low, which greatly improves the technical level of load pressure control in the post-valve compensation load-sensitive system. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0026] Figure 1 Schematic diagram of the structure of the post-valve compensation load sensing system provided in some embodiments of the present invention.

[0027] Figure 2 Schematic diagram of the structure of a post-valve compensation load sensing system provided in some other embodiments of the present invention.

[0028] Figure 3 A schematic structural diagram of a post-valve compensation load sensing system provided in some further embodiments of the present invention.

[0029] Figure 4 A schematic structural diagram of a post-valve compensation load sensing system provided in some embodiments of the present invention.

[0030] Reference numerals:

[0031] 1. Working oil circuit; 2. Load-sensing oil circuit; 3. First overflow branch; 4. System overflow branch; 5. Second overflow branch;

[0032] 11. Load sensing pump; 12. Control valve; 13. Actuator; 14. Pressure compensator;

[0033] 21. Pump variable mechanism; 22. Flow control valve; 23. Throttle assembly;

[0034] 31. First reversing valve; 32. First overflow valve;

[0035] 41. System overflow valve;

[0036] 51. Second reversing valve; 52. Second overflow valve. DETAILED DESCRIPTION

[0037] The following combination Figures 1 to 4 The technical solution provided by the present invention is described in more detail.

[0038] Explanation of nouns or terms used in this article.

[0039] The load-sensitive hydraulic system is an energy-saving hydraulic system widely used in the field of engineering machinery. It can achieve precise control of flow and pressure, including two control methods: pre-valve compensation and post-valve compensation.

[0040] Load Independent Flow Distribution (LUDV) is a hydraulic system that uses a pressure compensator positioned between the main valve orifice and the load to control flow through the main valve core. If the hydraulic system is saturated, the LUDV system proportionally reduces the flow required by each load, improving flow distribution accuracy when multiple loads are operating simultaneously.

[0041] See also Figure 1An embodiment of the present invention provides a post-valve compensation load-sensing system, comprising a working oil circuit 1, a load-sensing oil circuit 2, a first overflow branch 3, and a system overflow branch 4. The working oil circuit 1 includes a load-sensing pump 11, a control valve 12, an actuator 13, and a pressure compensator 14. The actuator 13 includes a first working oil port A and a second working oil port B. The control valve 12 is located between the oil outlet of the load-sensing pump 11 and the first and second working oil ports A and B of the actuator 13 to control the operation of the actuator 13. The pressure compensator 14 is disposed downstream of the control valve 12. The load-sensing oil circuit 2 includes a pump variable mechanism 21, a flow control valve 22, and a throttle assembly 23. The pump variable mechanism 21 is connected to the control end of the load-sensing pump 11, and the flow control valve 22 is in fluid communication with the pump variable mechanism 21 to control the displacement of the pump variable mechanism 21 and, thereby, the displacement of the load-sensing pump 11. The oil inlet of the throttle assembly 23 is connected to the pilot control end of the pressure compensator 14. The first overflow branch 3 includes a first reversing valve 31 and a first relief valve 32. The first relief valve 32 is located downstream of the first reversing valve 31. The first reversing valve 31 is configured to open when oil is flowing into the first working oil port A of the actuator 13 and to close when oil is not flowing into the first working oil port A of the actuator 13. The oil inlet of the first reversing valve 31 is in fluid communication with the control end of the flow control valve 22 and the oil outlet of the throttle assembly 23. The oil outlet of the first relief valve 32 is connected to the return oil. The system overflow branch 4 includes a system relief valve 41. The system relief valve 41 is located between the oil outlet of the load sensing pump 11 and the return oil port of the control valve 12.

[0042] The load-sensing pump 11 is equipped with a flow control valve 22. This flow control valve 22 has two control terminals: a first control terminal and a second control terminal. A spring is also provided at the first control terminal. The flow control valve 22 uses the spring to set a small pressure differential ΔP. The feedback oil circuit LS, which feeds back from the control valve 12 to the load-sensing pump 11, acts on the first control terminal of the flow control valve 22. The oil pressure P at the outlet of the load-sensing pump 11 acts on the second control terminal. For ease of description, the outlet pressure of the load-sensing pump 11 is represented by P, and the feedback pressure of the feedback oil circuit LS is represented by LS.

[0043] When P-LS>ΔP, the flow control valve 22 switches to the right and is in the left valve position. The hydraulic oil at the outlet of the load sensing pump 11 enters the pump variable mechanism 21, reducing the displacement of the load sensing pump 11.

[0044] When P-LS<ΔP, the flow control valve 22 switches to the left and is in the right valve position. The pressure oil in the pump variable mechanism 21 is connected to the return oil circuit. Under the action of the return spring, the pump variable mechanism 21 increases the displacement of the load sensing pump 11.

[0045] When P-LS=ΔP, the displacement of the load sensing pump 11 is maintained at a certain equilibrium position, and the output flow of the load sensing pump 11 is kept constant.

[0046] The pressure difference between P and LS is generated by the hydraulic oil flowing through the throttle of control valve 12. As the throttle increases, the pressure difference between P and LS decreases. When P - LS < ΔP, the displacement of load-sensing pump 11 increases, and the output flow rate of load-sensing pump 11 increases. The pressure difference between P and LS increases accordingly until P - LS = ΔP, at which point load-sensing pump 11 regains a stable displacement. The reverse is also true. In this way, the output flow rate of load-sensing pump 11 can be automatically controlled based on the opening of control valve 12.

[0047] The displacement of the load-sensing pump 11 is controlled by a pump variable displacement mechanism 21, which is controlled by a flow control valve 22 based on the difference between the pump outlet pressure P and the load feedback pressure LS. The oil outlet of the load-sensing pump 11 is connected to the oil inlet of the control valve 12. A pressure compensator 14 is connected in series between the control valve 12 and the actuator 13. The load pressure LS fed back from the pressure compensator 14 acts on the first control port of the flow control valve 22 of the load-sensing pump 11.

[0048] The first reversing valve 31 of the first overflow branch 3 is connected in parallel to the feedback oil circuit, the first overflow valve 32 is connected in series between the first reversing valve 31 and the return oil circuit, and the pilot control chamber of the first reversing valve 31 is connected to the following oil circuit: the oil circuit between the control valve 12 and the actuator 13.

[0049] A throttle assembly 23, specifically a damping orifice, is provided in the feedback oil path between the first reversing valve 31 and the pressure compensator 14. The throttle assembly 23 is located in the load-sensing oil path LS from the pressure compensator 14 to the load-sensing pump 11. Normally, the first reversing valve 31 is in the disconnected position due to the spring force at its control end. When the pilot control pressure of the first reversing valve 31 exceeds the spring force at its control end, the first reversing valve 31 operates in the connected position. In some embodiments, the first reversing valve 31 is configured such that, as long as the actuator 13 performs a corresponding action, the pilot control pressure of the first reversing valve 31 is greater than zero, and the first reversing valve 31 is in the open state. The corresponding action of the actuator 13 means that, if the first relief branch 3 is configured for action A of the actuator 13, such as cylinder extension, the first reversing valve 31 of the first relief branch 3 is in the open state as long as the cylinder extends. When the pressure feedback from the load-sensing oil circuit LS exceeds the relief pressure of the first relief valve 32, the first relief branch 3 is opened, causing the load-sensing oil circuit LS to overflow, thereby reducing the pressure there. According to the principle described above, when the oil pressure in the load-sensing oil circuit LS is relatively low, P-LS>ΔP, and the displacement of the load-sensing pump 11 decreases. This allows the displacement of the load-sensing pump 11 to be reduced by overflowing the first relief branch 3, even when the system relief branch 4 is not overflowing.

[0050] In some embodiments, the relief pressure of the first relief valve 32 is lower than the relief pressure of the system relief valve 41 .

[0051] The working principle of the post-valve compensation load sensing system pressure control method is as follows:

[0052] When the control valve 12 controls the actuator 13 to work through the first working oil port A, the hydraulic oil from the control valve 12 to the oil port A acts on the pilot control chamber of the first reversing valve 31 at the same time, pushing the first reversing valve 31 to work in the connecting position.

[0053] The load pressure provided by the control valve 12 to the first working oil port A of the actuator 13 passes through the pressure compensator 14 and the throttle assembly 23 at the same time, one path of which is fed back to the first control end of the flow control valve 22 of the load sensing pump 11, and the other path is connected to the first relief valve 32 through the first reversing valve 31.

[0054] When the load pressure provided by the control valve 12 to the first working oil port A of the actuator 13 is lower than the set pressure of the first relief valve 32, the first relief valve 32 is in a closed state, the displacement of the load-sensing pump 11 is controlled by the control valve 12, and all flows pass through the control valve 12 to drive the actuator 13 to work.

[0055] When the load pressure from the control valve 12 to the first working oil port A exceeds the set pressure of the first relief valve 32, the first relief valve 32 opens, connecting the load-sensing oil circuit 2 to the return oil circuit T through the first relief valve 32, achieving relief. When the first relief valve 32 overflows, the flow rate of the load-sensing oil circuit 2 through the throttle assembly 23 increases, causing a pressure drop in the hydraulic oil flowing through the throttle assembly 23. This causes the difference between the outlet pressure P of the load-sensing pump 11 and the load feedback pressure LS to exceed the set pressure of the first control terminal of the flow control valve 22 of the load-sensing pump 11. According to the operating principle of the load-sensing pump 11, the pressure at the oil outlet of the load-sensing pump 11 acts on the pump variable mechanism 21 through the flow control valve 22, reducing the displacement of the load-sensing pump 11 until it reaches a smaller displacement, sufficient to maintain the system pressure set by the first relief valve 32. The system pressure no longer increases, thus limiting the load pressure. Therefore, the flow rate of the load-sensing pump 11 is regulated without requiring the system relief branch 4 to overflow.

[0056] If the first overflow branch 3 is not provided, when the pressure reaches the set pressure of the system overflow valve 41 during the operation of the control valve 12 controlling the actuator 13, the entire pump output flow will be discharged through the system overflow valve 41 for high-pressure overflow. Furthermore, the larger the throttle opening of the control valve 12 (the throttle opening inside the control valve 12), the greater the output flow of the load-sensing pump 11, and the greater the flow overflowing through the system overflow valve 41. During this high-pressure, high-flow overflow, a large amount of heat is generated, resulting in energy waste and a rapid increase in the hydraulic oil temperature. This, in turn, can lead to problems such as reduced reliability and lifespan of the seals of the hydraulic components of the actuator 13, as well as decreased efficiency. Furthermore, overflowing the system overflow valve 41 will generate a large amount of overflow noise, causing noise pollution.

[0057] When the control valve 12 controls the actuator 13 through the second working oil port B, the oil circuit from the control valve 12 to the first working oil port A is connected to the return oil circuit T. The control pressure of the first reversing valve 31 is lower than the reversing pressure. The first reversing valve 31 works in the disconnected position. Therefore, the first relief valve 32 is disconnected from the load-sensing oil circuit LS and does not control the load feedback pressure.

[0058] In the embodiments described above, see Figure 1 In some embodiments, the pilot control end of the first reversing valve 31 is fluidically connected to the first working oil port A of the actuator 13. Alternatively, the pilot control end of the first reversing valve 31 is fluidically connected to the first working oil port A of the actuator 13 and the oil path connecting the control valve 12. As long as oil is flowing into the first working oil port A of the actuator 13, the pilot control end of the first reversing valve 31 can control the valve position of the first reversing valve 31 based on the oil pressure at the first working oil port A of the actuator 13, thereby maintaining the first reversing valve 31 in a conducting state.

[0059] See also Figure 2 In other embodiments, the pilot control end of the first reversing valve 31 is connected to the first pilot control end Xa of the control valve 12. The presence of control oil at the first pilot control end Xa of the control valve 12 indicates that the control valve 12 is in a position where oil flows into the first working oil port A of the actuator 13 and out of the second working oil port B of the actuator 13. At this point, the pilot control end of the first reversing valve 31 can also adjust the valve position of the reversing valve 31 based on the oil pressure at the first pilot control end Xa of the control valve 12, placing the first reversing valve 31 in a conducting state.

[0060] See also Figure 3 In other embodiments, the first reversing valve 31 is an electromagnetic reversing valve. By controlling the electromagnetic conduction state of the first reversing valve 31, the valve position of the first reversing valve 31 is switched between the conduction state and the cut-off state.

[0061] When the post-valve compensation load-sensitive system is working, the hydraulic oil flows out from the oil outlet of the load-sensitive pump 11, flows to the control valve 12, and after the direction of the hydraulic oil is adjusted by the control valve 12, enters the actuator 13. The actuator 13 is, for example, a cylinder. The actuator 13 can have more than two actions. Taking the cylinder as an example, the cylinder has two actions: extension and retraction. In the above-mentioned embodiments, the first overflow branch 3 introduced is used to play an overflow protection role when oil is supplied to the first working oil port A of the actuator 13, such as overflow protection during the extension action. Of course, corresponding overflow protection can also be set for each action. In the embodiments below, the post-valve compensation load-sensitive system also includes a second overflow branch 5, which is used to play an overflow protection role when oil is supplied to the second working oil port B of the actuator 13.

[0062] See also Figure 4 The difference between this embodiment and the above embodiments is that in this embodiment, a first overflow branch 3, a system overflow branch 4 and a second overflow branch 5 are set at the same time.

[0063] First overflow branch 3 provides overflow protection when oil is flowing into first working oil port A of actuator 13, and second overflow branch 5 is inoperative at this time. System overflow branch 4 provides overflow protection when oil is flowing into second working oil port B of actuator 13, and first overflow branch 3 is inoperative at this time.

[0064] The working principle of the first overflow branch 3 is the same as that of the above embodiment, which will not be described in detail here. The specific implementation and working principle of the second overflow branch 5 are introduced here.

[0065] Specifically, the second overflow branch 5 includes a second reversing valve 51 and a second relief valve 52. The second relief valve 52 is located downstream of the second reversing valve 51. The second reversing valve 51 is configured to open when oil is flowing into the second working oil port B of the actuator 13 and to close when oil is not flowing into the second working oil port B of the actuator 13. The oil inlet of the second reversing valve 51 is in fluid communication with the control end of the flow control valve 22 and the oil outlet of the throttle assembly 23. The oil outlet of the second relief valve 52 is connected to the return oil.

[0066] See also Figure 4 The pilot control oil circuit of the first reversing valve 31 is connected to the pipeline from the control valve 12 to the first working oil port A of the actuator 13. The pilot control oil circuit port of the second reversing valve 51 is connected to the pipeline from the second working oil port B of the actuator 13. The oil inlets of the first and second reversing valves 31, 51 are both connected to the LS feedback oil circuit between the throttle combination and the load-sensing pump 11. The oil outlet of the first reversing valve 31 is connected to the oil inlet of the first relief valve 32, and the oil outlet of the second reversing valve 51 is connected to the oil inlet of the second relief valve 52. The oil outlets of the first and second relief valves 32, 52 are connected to the return oil circuit.

[0067] Specifically, the working principle of the second overflow branch 5 is as follows.

[0068] When the control valve 12 controls the actuator 13 to work through the second working oil port B, the hydraulic oil from the control valve 12 to the second working oil port B acts on the pilot control chamber of the second reversing valve 51, pushing the second reversing valve 51 to work in the connecting position.

[0069] The load pressure from the control valve 12 to the second working oil port B passes through the pressure compensator 14 and the throttle assembly 23 at the same time, one path of which is fed back to the first control end of the flow control valve 22 of the load sensing pump 11, and the other path passes through the second reversing valve 51 and is connected to the second overflow valve 52.

[0070] When the load pressure from the control valve 12 to the second working oil port B is less than the set pressure of the second relief valve 52, the second relief valve 52 is in a closed state, the displacement of the load-sensing pump 11 is controlled by the control valve 12, and all flows pass through the control valve 12 to drive the actuator 13 to work.

[0071] When the load pressure from control valve 12 to second working oil port B exceeds the set pressure of second relief valve 52, second relief valve 52 opens, connecting load-sensing oil circuit 2 to return oil circuit T via second relief valve 52, achieving relief. When second relief valve 52 overflows, the flow rate of load-sensing oil circuit 2 through throttle assembly 23 increases, causing a pressure drop in the hydraulic oil flowing through throttle assembly 23. This causes the difference between the outlet pressure P of load-sensing pump 11 and the load feedback pressure LS to exceed the set pressure of the first control terminal of flow control valve 22 of load-sensing pump 11. According to the operating principle of load-sensing pump 11, at this time, the pressure at the outlet of load-sensing pump 11 acts on pump variable mechanism 21 through flow control valve 22, reducing the displacement of load-sensing pump 11 until it reaches a lower displacement, sufficient to maintain the system pressure set by first relief valve 32. The system pressure no longer increases, thus limiting the load pressure. Therefore, flow regulation of load-sensing pump 11 is achieved without requiring overflow of system overflow branch 4.

[0072] In other embodiments, the pilot control end of the second reversing valve 51 is fluidically connected to the second working oil port B of the actuator 13 .

[0073] In yet other embodiments, the pilot control end of the second reversing valve 51 is connected to the second pilot control end of the control valve 12. When control oil is present in the second pilot control end of the control valve 12, the valve position of the control valve 12 causes oil to flow into the second working oil port B of the actuator. The pilot control end of the second reversing valve 51 is connected to the second pilot control end of the control valve 12. Under the action of the pilot control oil in the second pilot control end of the control valve 12, the valve position of the second reversing valve 51 is switched to a conducting state.

[0074] In some embodiments, the second reversing valve 51 is an electromagnetic reversing valve, and the valve position of the second reversing valve 51 is switched between the on and off states by controlling the electromagnetic conduction state of the second reversing valve 51 .

[0075] The above technical solution fully utilizes the working characteristics of the load-sensitive system, and realizes that when the system overflows, the displacement of the hydraulic pump is automatically reduced, the flow output of the hydraulic system is minimized, and the overflow valve is in a small flow overflow state, with low energy loss and low noise. Moreover, the required overflow valve has a small diameter, low cost, and light weight. Compared with the prior art, which uses a system overflow valve 41 to completely unload the flow from the control valve 12 to the actuator 13, the technical solution of the embodiment of the present invention has the advantages of large overflow flow, low energy loss, low heat generation, and low noise pollution. In addition, the first overflow branch 3 and the second overflow branch 5 both use small flow overflow, and the required overflow valve has a small diameter, low cost, and light weight.

[0076] An embodiment of the present invention further provides a hydraulic system, comprising the post-valve compensation load-sensing system provided by any technical solution of the present invention.

[0077] An embodiment of the present invention further provides a crane, comprising the hydraulic system provided by any technical solution of the present invention.

[0078] In addition to the hydraulic system, the crane also includes a telescopic system and a luffing system. The actions of the telescopic system and the luffing system are controlled by the hydraulic system.

[0079] The telescopic system includes the following actions: the crane uses hydraulic cylinders and other devices to drive the boom to extend and retract, thereby controlling the length of the boom.

[0080] The luffing system includes the following actions: the crane drives the boom to rotate around a fixed hinge point through a hydraulic cylinder to achieve changes in the boom angle and amplitude.

[0081] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the protection content of the present invention.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A post-valve compensation load sensing system, characterized in that: include: A working oil circuit (1) includes a load-sensing pump (11), a control valve (12), an actuator (13), and a pressure compensator (14); the actuator (13) includes a first working oil port and a second working oil port; the control valve (12) is located between the oil outlet of the load-sensing pump (11) and the first working oil port and the second working oil port of the actuator (13) to control the action of the actuator (13); the pressure compensator (14) is arranged downstream of the control valve (12); A load-sensitive oil circuit (2) includes a pump variable mechanism (21), a flow control valve (22), and a throttling assembly (23); the pump variable mechanism (21) is connected to the control end of the load-sensitive pump (11), and the flow control valve (22) is fluidically connected to the pump variable mechanism (21) to control the displacement of the pump variable mechanism (21), thereby controlling the displacement of the load-sensitive pump (11); the oil inlet of the throttling assembly (23) is connected to the pilot control end of the pressure compensator (14); A first overflow branch (3) includes a first reversing valve (31) and a first overflow valve (32); the first overflow valve (32) is located downstream of the first reversing valve (31); the first reversing valve (31) is configured to be open when oil is flowing into the first working oil port of the actuator (13) and closed when oil is not flowing into the first working oil port of the actuator (13); wherein the oil inlet of the first reversing valve (31) is in fluid communication with the control end of the flow control valve (22) and the oil outlet of the throttling assembly (23); the oil outlet of the first overflow valve (32) is in fluid communication with return oil; and The system overflow branch (4) includes a system overflow valve (41); the system overflow valve (41) is arranged between the oil outlet of the load sensing pump (11) and the oil return port of the control valve (12).

2. The post-valve compensation load sensing system according to claim 1, characterized in that: The overflow pressure of the first overflow valve (32) is lower than the overflow pressure of the system overflow valve (41).

3. The post-valve compensation load sensing system according to claim 1, characterized in that: The pilot control end fluid of the first reversing valve (31) is connected to the first working oil port of the actuator (13).

4. The post-valve compensation load sensing system according to claim 1, characterized in that: The pilot control end of the first reversing valve (31) is connected to the first pilot control end of the control valve (12).

5. The post-valve compensation load sensing system according to claim 1, characterized in that: The first reversing valve (31) is an electromagnetic reversing valve.

6. The post-valve compensation load sensing system according to claim 1, characterized in that: Also includes: The second overflow branch (5) comprises a second reversing valve (51) and a second overflow valve (52); the second overflow valve (52) is located downstream of the second reversing valve (51); the second reversing valve (51) is configured to be conductive when oil is flowing into the second working oil port of the actuator (13) and to be closed when oil is not flowing into the second working oil port of the actuator (13); wherein the oil inlet of the second reversing valve (51) is fluidically connected to the control end of the flow control valve (22) and the oil outlet of the throttling assembly (23); and the oil outlet of the second overflow valve (52) is connected to return oil.

7. The post-valve compensation load sensing system according to claim 6, characterized in that: The pilot control end fluid of the second reversing valve (51) is connected to the second working oil port of the actuator (13).

8. The post-valve compensation load sensing system according to claim 6, characterized in that: The pilot control end of the second reversing valve (51) is connected to the second pilot control end of the control valve (12).

9. The post-valve compensation load sensing system according to claim 6, characterized in that: The second reversing valve (51) is an electromagnetic reversing valve.

10. The post-valve compensation load sensing system according to claim 1, characterized in that: The throttling assembly (23) comprises a throttling hole.

11. A hydraulic system, characterized in that: The invention comprises the post-valve compensation load sensing system according to any one of claims 1 to 10.

12. A crane, characterized in that: Includes the hydraulic system according to claim 11.

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