CN116443731A

CN116443731A - Valve post-compensation load sensitive system, hydraulic system and crane

Info

Publication number: CN116443731A
Application number: CN202310359609.7A
Authority: CN
Inventors: 曹立峰; 焦国旺; 周彬; 朱双双
Original assignee: Xuzhou Heavy Machinery Co Ltd
Current assignee: Xuzhou Heavy Machinery Co Ltd
Priority date: 2023-03-31
Filing date: 2023-03-31
Publication date: 2023-07-18

Abstract

The invention discloses a valve post-compensation load sensitive system, a hydraulic system and a crane, and relates to the field of hydraulic pressure. The working oil way of the valve post-compensation load sensitive system comprises a load sensitive pump, a control valve, an actuating mechanism and a pressure compensator; the control valve is positioned between the load sensitive pump and the actuating mechanism; the pressure compensator is disposed downstream of the control valve. The load sensitive oil circuit comprises a pump variable mechanism, a flow control valve and a throttling component; the pump variable mechanism is connected with the control end of the load sensitive pump, and the flow control valve is in fluid communication with the pump variable mechanism; and an oil inlet of the throttling component is communicated with a pilot control end of the pressure compensator. The first overflow branch comprises a first reversing valve and a first overflow valve; the first relief valve is located downstream of the first reversing valve. 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; and an oil outlet of the first overflow valve is communicated with oil return. The system is very energy-saving and has low noise.

Description

Valve post-compensation load sensitive system, hydraulic system and crane

Technical Field

The invention relates to the field of hydraulic pressure, in particular to a valve post-compensation load sensitive system, a hydraulic system and a crane.

Background

The crane loading operation mainly comprises four main actions of telescoping, luffing, lifting and rotating. The hydraulic system of the crane is used for controlling four actions of telescoping and luffing of the crane and main and auxiliary lifting, and particularly, the control of the four actions is integrated on a multi-way valve. In order to improve the coordination of compound actions (more than two actions work simultaneously), a valve back compensation technology is adopted to improve the flow distribution precision during the simultaneous operation of multiple loads. In order to ensure the system installation, a relief valve is also provided in the hydraulic system.

The inventors have found that two or more actuator control valves are typically integrated into a single multiplex valve in a crane hydraulic system. And the oil outlet of the load sensitive pump is connected with two actuating mechanism control valves and actuating mechanisms in parallel. The main overflow valve is arranged in parallel on an oil path between the load sensitive pump and the control valve of each actuating mechanism, so as to play a role in limiting the maximum pressure of the hydraulic system.

The inventors have found, however, that the maximum operating pressure required for each actuator is not exactly the same, typically less than or equal to the set pressure of the main relief valve, and that a secondary relief valve is typically also required to limit the maximum operating pressure for the different actuators. When the working pressure of the actuating mechanism reaches the set pressure of the secondary overflow valve, the overflow valve is opened, hydraulic oil overflows from the overflow valve, the maximum working pressure is limited, and the actuating mechanism is protected. And when other executing mechanisms work, the influence of the secondary overflow valve is avoided.

The inventors found that there are at least the following problems in the prior art: in the overflow process of the existing hydraulic system, energy loss and overflow noise are very large.

Disclosure of Invention

The invention provides a valve post-compensation load sensitive system, a hydraulic system and a crane, which are used for providing a valve post-compensation load sensitive system with more energy conservation and noise reduction.

An embodiment of the present invention provides a post-valve compensating load-sensing system, comprising:

the working oil circuit comprises a load sensitive pump, a control valve, an actuating mechanism and a pressure compensator; the actuating mechanism comprises a first working oil port and a second working oil port; the control valve is positioned between the oil outlet of the load-sensitive pump and the first working oil port and the second working oil port of the executing mechanism so as to control the action of the executing mechanism; the pressure compensator is arranged downstream of the control valve;

the load sensitive oil circuit comprises a pump variable mechanism, a flow control valve and a throttling component; the pump variable mechanism is connected with the control end of the load-sensitive 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 thus the displacement of the load-sensitive pump; an oil inlet of the throttling assembly is communicated with a pilot control end of the pressure compensator;

the first overflow branch comprises a first reversing valve and a first overflow valve; the first overflow valve is positioned downstream of the first reversing valve; the first reversing valve is configured to be conducted when the first working oil port of the actuating mechanism is filled with oil, and to be cut off when the first working oil port of the actuating mechanism is not filled with oil; 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 communicated with oil return; and

a system overflow branch comprising a system overflow valve; the system overflow valve is arranged between the oil outlet of the load-sensitive pump and the oil return port of the control valve.

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

In some embodiments, the pilot control end of the first reversing valve is in fluid communication with the first hydraulic port of the actuator.

In some embodiments, the pilot control end of the first reversing valve communicates with the first pilot control end of the control valve.

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

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

the second overflow branch comprises a second reversing valve and a second overflow valve; the second overflow valve is positioned downstream of the second reversing valve; the second reversing valve is configured to be conducted when the second working oil port of the actuating mechanism is filled with oil, and to be cut off when the second working oil port of the actuating mechanism is not filled with oil; wherein the oil inlet of the second reversing valve is in fluid communication with the control end of the flow control valve and the oil outlet of the throttling assembly; and an oil outlet of the second overflow valve is communicated with oil return.

In some embodiments, the pilot control end of the second reversing valve is in fluid communication with the second working port of the actuator.

In some embodiments, the pilot control end of the second reversing valve communicates with the second pilot control end of the control valve.

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

In some embodiments, the throttling assembly includes a throttling orifice.

The embodiment of the invention also provides a hydraulic system, which comprises the post-valve compensation load sensitive system provided by any technical scheme of the invention.

The embodiment of the invention also provides a crane, which comprises the hydraulic system provided by any technical scheme of the invention.

The valve post-compensation load sensing system provided by the technical scheme comprises a first overflow branch and a system overflow branch. The system overflow branch adopts oil overflow in the working oil way, so that the flow is large; the first overflow branch adopts oil way overflow in the load sensitive oil way, and the flow is small. The overflow pressure of the overflow branch of the system is larger than that of the first overflow branch. When the valve back compensation load sensitive system works normally, if the load pressure is too small, the system overflow branch is not required to work, the first overflow branch is directly adopted to overflow, the effect of adjusting the displacement of the load sensitive pump can be achieved, the flow of the first overflow branch overflow is very small, the valve back compensation load sensitive system is very energy-saving and environment-friendly, noise is very small, and the technical level of load pressure control in the valve back compensation load sensitive system is greatly improved.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiments of the invention and together with the description serve to explain the invention and do not constitute a limitation on the invention. In the drawings:

fig. 1 is a schematic diagram of a post-valve compensation load-sensing system according to some embodiments of the present invention.

FIG. 2 is a schematic diagram of a post-valve compensation load sensing system according to further embodiments of the present invention.

FIG. 3 is a schematic diagram of a post-valve compensation load sensing system according to still other embodiments of the present invention.

FIG. 4 is a schematic diagram of a post-valve compensation load sensing system according to some embodiments of the present invention.

Reference numerals:

1. a working oil path; 2. load sensitive oil circuit; 3. a first overflow branch; 4. a system overflow branch; 5. a second overflow branch;

11. a load-sensitive pump; 12. a control valve; 13. an actuator; 14. a pressure compensator;

21. a pump variable mechanism; 22. a flow control valve; 23. a throttle assembly;

31. a first reversing valve; 32. a first overflow valve;

41. a system overflow valve;

51. a second reversing valve; 52. and a second relief valve.

Detailed Description

The technical scheme provided by the invention is described in more detail below with reference to fig. 1 to 4.

The terms or terminology used herein are interpreted.

The load sensitive hydraulic system is an energy-saving hydraulic system which is widely applied in the field of engineering machinery, and can realize accurate control of flow and pressure, and comprises two control modes of pre-valve compensation and post-valve compensation.

The post-valve compensation system Load Independent Flow Distribution, abbreviated as LUDV, is a hydraulic system in which a pressure compensator is disposed between a main valve orifice and a load to control the flow through a main valve spool. Under the condition of saturated flow of the hydraulic system, the valve post-compensation system can reduce the flow required by each load according to the proportion, and improves the flow distribution precision when multiple loads work simultaneously.

Referring to fig. 1, an embodiment of the present invention provides a post-valve compensation load-sensing system, which includes a working oil path 1, a load-sensing oil path 2, a first overflow branch 3, and a system overflow branch 4. The working oil circuit 1 comprises a load sensitive pump 11, a control valve 12, an actuator 13 and a pressure compensator 14; the actuating mechanism 13 comprises a first working oil port A and a second working oil port B; the control valve 12 is positioned between the oil outlet of the load-sensitive pump 11 and the first working oil port A and the second working oil port B of the executing mechanism 13 to control the action of the executing mechanism 13; a pressure compensator 14 is provided downstream of the control valve 12. The load sensitive oil passage 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 a control end of the load-sensitive pump 11, and the flow control valve 22 is in fluid communication with the pump variable mechanism 21 to control displacement of the pump variable mechanism 21 and, in turn, the load-sensitive pump 11. The oil inlet of the throttle assembly 23 communicates with the pilot control end of the pressure compensator 14. The first overflow branch 3 comprises a first reversing valve 31 and a first overflow valve 32; the first relief valve 32 is located downstream of the first reversing valve 31; the first reversing valve 31 is configured to be turned on when the first working oil port a of the actuator 13 has oil inlet, and turned off when the first working oil port a of the actuator 13 has no oil inlet; 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 communicated with oil return. The system overflow branch 4 comprises a system overflow valve 41; the system relief valve 41 is arranged between the oil outlet of the load-sensitive pump 11 and the return port of the control valve 12.

The load sensitive pump 11 is provided with a flow control valve 22, the flow control valve 22 comprising two control terminals: the first control end and the second control end. And a spring is also arranged at the first control end. The flow control valve 22 is spring-biased to a small pressure difference Δp, and a feedback path LS from the control valve 12 to the load-sensitive pump 11 acts on the first control end of the flow control valve 22. The oil pressure P of the oil outlet of the load-sensitive pump 11 acts on the second control end, and for convenience of description, the outlet pressure of the load-sensitive pump 11 is denoted by P, and the feedback pressure of the feedback oil path LS is denoted by LS.

When P-LS > DeltaP, the flow control valve 22 commutates to the right, the flow control valve 22 is at the left valve position, and the hydraulic oil at the outlet of the load sensitive pump 11 enters the pump variable mechanism 21, so that the displacement of the load sensitive pump 11 is reduced.

When P-LS < DeltaP, the flow control valve 22 commutates leftwards, the flow control valve 22 is positioned at the right valve position, the pressure oil in the pump variable mechanism 21 is communicated with the return oil way, and the pump variable mechanism 21 increases the displacement of the load-sensitive pump 11 under the action of the return spring.

When P-ls=Δp, the displacement of load-sensitive pump 11 is maintained at a certain equilibrium position and the load-sensitive pump 11 output flow remains constant.

The pressure difference between P and LS is created by the restriction of the hydraulic oil flow through the control valve 12, and when the restriction increases, the pressure difference between P and LS will decrease, and when P-LS < Δp, the displacement of the load-sensitive pump 11 increases and the output flow of the load-sensitive pump 11 increases. The pressure difference between P and LS increases until P-ls=Δp, and load-sensitive pump 11 reaches a stable displacement again. Vice versa, in this way, the output flow rate of the load-sensitive pump 11 can be automatically controlled according to the opening degree of the control valve 12.

The displacement of the load sensitive pump 11 is controlled by a pump variable mechanism 21, the pump variable mechanism 21 being controlled by a flow control valve 22 in accordance with the difference between the pump outlet pressure P and the load feedback pressure LS. The oil outlet of the load-sensitive pump 11 is connected with 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, and the load pressure LS fed back from the pressure compensator 14 acts on the first control end of the flow control valve 22 of the load-sensitive pump 11.

The first reversing valve 31 of the first overflow branch 3 is connected in parallel to the feedback oil path, the first overflow valve 32 is connected in series between the first reversing valve 31 and the oil return path, and the pilot control cavity of the first reversing valve 31 is communicated with the following oil paths: the oil passage from the valve 12 to the actuator 13 is controlled.

A throttle assembly 23 is arranged on the feedback oil path between the first reversing valve 31 and the pressure compensator 14, the throttle assembly 23 is specifically a damping hole, for example, and the throttle assembly 23 is positioned on the load sensitive oil path LS from the pressure compensator 14 to the load sensitive pump 11. The first directional valve 31 is normally in the open position under the spring force of its own control end. When the pilot control pressure of the first directional valve 31 is higher than the control end spring force of the first directional valve 31, the first directional valve 31 operates in the communication position. In some embodiments, the first directional valve 31 is configured such that the pilot control pressure of the first directional valve 31 is greater than 0 and the first directional valve 31 is in a conductive state as long as the actuator 13 performs a corresponding action. The corresponding actuation of the actuator 13 means that if the first overflow branch 3 is configured for an actuation of the actuator 13, such as a cylinder extension, the first directional valve 31 of the first overflow branch 3 is in a conductive state as long as the cylinder has the extension. When the pressure fed back by the load-sensitive oil path LS is greater than the relief pressure of the first relief valve 32, the first relief branch 3 is turned on, and a relief effect is exerted on the load-sensitive oil path LS, so that the pressure of the load-sensitive oil path LS is reduced. According to the principle described above, when the oil pressure of the load-sensitive oil passage LS is relatively small, P-LS > Δp, the displacement of the load-sensitive pump 11 is reduced. This achieves that the displacement of the load-sensitive pump 11 is reduced by the overflow of the first overflow branch 3 without the overflow of the system overflow branch 4.

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

The working principle of the pressure control method of the valve back compensation load sensitive system is as follows:

when the control valve 12 controls the actuator 13 to work through the first working oil port a, 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, so as to push the first reversing valve 31 to work in the communication position.

The control valve 12 provides the load pressure to the first working port a of the actuator 13 through both the pressure compensator 14 and the throttle assembly 23, one of which is fed back to the first control end of the flow control valve 22 of the load-sensitive pump 11 and the other of which is connected to the first relief valve 32 through the first reversing valve 31.

When the load pressure of the first working oil port a provided to the actuator 13 by the control valve 12 is smaller 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-sensitive pump 11 is controlled by the control valve 12, and all the flow passes through the control valve 12 to drive the actuator 13 to work.

When the load pressure from the control valve 12 to the first working port a is greater than the set pressure of the first relief valve 32, the first relief valve 32 is opened, and the load-sensitive oil passage 2 communicates with the return oil passage T through the first relief valve 32, so as to implement relief. When the first relief valve 32 overflows, the flow rate of the load-sensitive oil path 2 flowing through the throttling assembly 23 is increased, and the pressure drop is generated when the hydraulic oil flows through the throttling assembly 23, so that the difference between the outlet pressure P of the load-sensitive pump 11 and the load feedback pressure LS is larger than the set pressure of the first control end of the flow control valve 22 of the load-sensitive pump 11. According to the working principle of the load-sensitive pump 11, the pressure of the oil outlet of the load-sensitive pump 11 acts on the pump variable mechanism 21 through the flow control valve 22, so that the displacement of the load-sensitive pump 11 is reduced until a smaller displacement is achieved, the system pressure set by the first overflow valve 32 can only be maintained, the system pressure is not increased any more, and the purpose of limiting the load pressure is achieved, so that the flow of the load-sensitive pump 11 is regulated under the condition that the overflow of the system overflow branch 4 is not needed.

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 actuator 13 controlled by the control valve 12, the total flow output by the pump will overflow at high pressure through the system overflow valve 41, and the larger the orifice of the control valve 12 (orifice inside the control valve 12), the larger the output flow of the load-sensitive pump 11, and the larger the flow overflowed through the system overflow valve 41. In the process of high-pressure and large-flow overflow, a large amount of heat is generated, so that energy waste is caused, the temperature of hydraulic oil is rapidly increased, and further the problems of reliability and service life reduction, efficiency reduction and the like of the sealing of the hydraulic element of the actuating mechanism 13 are caused. Meanwhile, the overflow of the system overflow valve 41 will generate a large overflow noise, resulting in noise pollution.

When the control valve 12 controls the actuator 13 to work through the second working oil port B, the oil path from the control valve 12 to the first working oil port a is communicated with the oil return path T, the control pressure of the first reversing valve 31 is lower than the reversing pressure, and the first reversing valve 31 works in the disconnected position, so that the first overflow valve 32 is disconnected from the load-sensitive oil path LS, and the load feedback pressure is not controlled.

In the embodiments described above, referring to fig. 1, in some embodiments, the pilot control end of the first directional valve 31 is in fluid communication with the first hydraulic port a of the actuator 13. Alternatively, the pilot control end of the first directional valve 31 is in fluid communication with a communication oil path between the first hydraulic fluid port a of the actuator 13 and the control valve 12. As long as the first working oil port a of the actuator 13 has oil inlet, the pilot control end of the first reversing valve 31 can control the first reversing valve 31 to change the valve position according to the oil pressure of the first working oil port a of the actuator 13, so that the first reversing valve 31 is in a conducting state.

Referring to fig. 2, in other embodiments, the pilot control end of the first directional valve 31 communicates with the first pilot control end Xa of the control valve 12. The first pilot control end Xa of the control valve 12 has control oil, which indicates that the valve position of the control valve 12 is in a state of making the first working oil port a of the actuator 13 feed oil and the second working oil port B of the actuator 13 discharge oil. At this time, the pilot control end of the first directional valve 31 may also adjust the valve position of one directional valve 31 according to the oil pressure of the first pilot control end Xa of the control valve 12, so that the first directional valve 31 is in a conductive state.

Referring to fig. 3, in other embodiments, the first directional valve 31 is an electromagnetic directional 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 on state and the off state.

When the valve back compensation load sensitive system works, hydraulic oil flows out from an oil outlet of the load sensitive pump 11, flows to the control valve 12, and enters the actuating mechanism 13 after the direction of the hydraulic oil is regulated by the control valve 12. The actuator 13 is, for example, an oil cylinder or the like. The actuator 13 may have more than two actions, and the cylinder is exemplified as an extension and retraction action. In the above embodiments, the first overflow branch 3 is used to perform an overflow protection function when the first working oil port a of the actuator 13 is filled with oil, for example, perform an overflow protection function when the actuator is extended. Of course, a corresponding overflow protection may be provided for each action. In the following embodiment, the valve post-compensation load-sensitive system further comprises a second overflow branch 5 for providing overflow protection for the oil inlet of the second working port B of the actuator 13.

Referring to fig. 4, the present embodiment is different from the above embodiments in that the first overflow branch 3, the system overflow branch 4, and the second overflow branch 5 are provided at the same time in the present embodiment.

The first overflow branch 3 plays an overflow protection role when the first working oil port A of the actuating mechanism 13 is filled with oil, and the second overflow branch 5 is not active at the moment. The system overflow branch 4 plays an overflow protection role when the second working oil port B of the actuating mechanism 13 is filled with oil, and the first overflow branch 3 does not play a role at the moment.

The principle of the functioning of the first overflow branch 3 is the same as in the previous embodiments and will not be described here in detail. The specific implementation and the functioning principle of the second overflow branch 5 are described here.

Specifically, the second overflow branch 5 includes a second reversing valve 51 and a second overflow valve 52; the second relief valve 52 is located downstream of the second reversing valve 51; the second switching valve 51 is configured to be turned on when the second working port B of the actuator 13 has oil, and to be turned off when the second working port B of the actuator 13 has no oil. Wherein 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 throttling assembly 23; the oil outlet of the second relief valve 52 communicates with the return oil.

Referring to fig. 4, the pilot control oil passage of the first directional valve 31 communicates with the piping from the control valve 12 to the first working port a of the actuator 13, and the pilot control oil passage of the second directional valve 51 is connected with the piping from the second working port B of the actuator 13. The oil inlets of the first reversing valve 31 and the second reversing valve 51 are connected with an oil path of the LS feedback oil path between the throttling combination and the load sensitive pump 11. The oil outlet of the first reversing valve 31 is communicated with the oil inlet of the first overflow valve 32, the oil outlet of the second reversing valve 51 is connected with the oil inlet of the second overflow valve 52, and the oil outlets of the first overflow valve 32 and the second overflow valve 52 are connected with an oil return path.

Specifically, the second overflow branch 5 operates as follows.

When the control valve 12 controls the actuator 13 to operate through the second working oil port B, 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 to push the second reversing valve 51 to operate at the communication position.

The load pressure from the control valve 12 to the second working port B passes through both the pressure compensator 14 and the throttle assembly 23, one of which is fed back to the first control end of the flow control valve 22 of the load-sensitive pump 11, and the other of which is connected to the second relief valve 52 through the second reversing valve 51.

When the load pressure from the control valve 12 to the second working port B is smaller 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-sensitive pump 11 is controlled by the control valve 12, and all the flow passes through the control valve 12 to drive the actuator 13 to work.

When the load pressure from the control valve 12 to the second working port B is greater than the set pressure of the second relief valve 52, the second relief valve 52 is opened, and the load-sensitive oil passage 2 communicates with the return oil passage T through the second relief valve 52, thereby achieving relief. When the second relief valve 52 overflows, the flow rate of the load-sensitive oil path 2 flowing through the throttling assembly 23 is increased, and the pressure drop is generated when the hydraulic oil flows through the throttling assembly 23, so that the difference between the outlet pressure P of the load-sensitive pump 11 and the load feedback pressure LS is greater than the set pressure of the first control end of the flow control valve 22 of the load-sensitive pump 11. According to the working principle of the load-sensitive pump 11, the pressure of the oil outlet of the load-sensitive pump 11 acts on the pump variable mechanism 21 through the flow control valve 22, so that the displacement of the load-sensitive pump 11 is reduced until a smaller displacement is achieved, the system pressure set by the first overflow valve 32 can only be maintained, the system pressure is not increased any more, and the purpose of limiting the load pressure is achieved, so that the flow of the load-sensitive pump 11 is regulated under the condition that the overflow of the system overflow branch 4 is not needed.

In other embodiments, the pilot control end of the second reversing valve 51 is in fluid communication with the second hydraulic port B of the actuator 13.

In still other embodiments, the pilot control end of the second reversing valve 51 communicates with the second pilot control end of the control valve 12. When the second pilot control end of the control valve 12 has control oil, the valve position of the control valve 12 makes the second working oil port B of the actuator to be filled with oil. The pilot control end of the second directional valve 51 communicates with the second pilot control end of the control valve 12, and the valve position of the second directional valve 51 is switched to the on state by the pilot control oil at the second pilot control end of the control valve 12.

In some embodiments, the second reversing valve 51 is a solenoid reversing valve. By controlling the electromagnetic conduction state of the second reversing valve 51, the valve position of the second reversing valve 51 is switched between the on state and the off state.

According to the technical scheme, the working characteristics of the load sensitive system are fully utilized, when the overflow of the system is realized, the displacement of the hydraulic pump is automatically reduced, the flow output of the hydraulic system is reduced to the maximum extent, the overflow valve is in a micro flow overflow state, the energy loss is small, the noise is small, and in addition, the required overflow valve has small drift diameter, low cost and light weight. Compared with the prior art, the system overflow valve 41 is adopted to completely discharge the flow from the control valve 12 to the actuating mechanism 13, and the technical scheme of the embodiment of the invention has the advantages of larger overflow flow, low energy loss, less heat productivity and less noise pollution. And, first overflow branch road 3, second overflow branch road 5 all adopt low-flow overflow, and the latus rectum of required overflow valve is less, and is with low costs, light in weight.

In addition to the hydraulic system, the crane also comprises a telescopic system and a luffing system. The action of the telescopic system and the amplitude varying system is controlled by the hydraulic system.

The telescopic system comprises the following actions: the crane drives the suspension arm to extend and retract through the hydraulic cylinder and other devices, so that the length of the suspension arm is controlled.

The luffing system is an apparatus comprising: the crane drives the suspension arm to rotate around a certain fixed hinge point through the hydraulic oil cylinder, so that the angle and amplitude of the suspension arm are changed.

In the description of the present invention, it should be understood that the terms "center," "longitudinal," "lateral," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, merely to facilitate description of the present invention and simplify the description, and do not indicate or imply that the device or element being referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the protection of the present invention.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may be modified or some technical features may be replaced with others, which may not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A post-valve compensating load sensing system, comprising:

the working oil way (1) comprises a load sensitive pump (11), a control valve (12), an actuating mechanism (13) and a pressure compensator (14); the actuating mechanism (13) comprises a first working oil port and a second working oil port; the control valve (12) is positioned between the oil outlet of the load-sensitive pump (11) and the first working oil port and the second working oil port of the executing mechanism (13) so as to control the action of the executing mechanism (13); the pressure compensator (14) is arranged downstream of the control valve (12);

the load sensitive oil circuit (2) comprises a pump variable mechanism (21), a flow control valve (22) and a throttling component (23); the pump variable mechanism (21) is connected with the control end of the load sensitive pump (11), and the flow control valve (22) is in fluid communication with the pump variable mechanism (21) so as to control the displacement of the pump variable mechanism (21) and further control the displacement of the load sensitive pump (11); an oil inlet of the throttling assembly (23) is communicated with a pilot control end of the pressure compensator (14);

a first overflow branch (3) comprising 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 conducted when the first working oil port of the actuating mechanism (13) is filled with oil, and to be cut off when the first working oil port of the actuating mechanism (13) is not filled with oil; wherein an oil inlet of the first reversing valve (31) is in fluid communication with a control end of the flow control valve (22) and an oil outlet of the throttling assembly (23); an oil outlet of the first overflow valve (32) is communicated with oil return; and

a system overflow branch (4) comprising a system overflow valve (41); the system overflow valve (41) is arranged between an oil outlet of the load-sensitive pump (11) and an oil return port of the control valve (12).

2. The post-valve compensating load sensing system of claim 1, wherein the relief pressure of the first relief valve (32) is lower than the relief pressure of the system relief valve (41).

3. The post valve compensation load sensing system of claim 1, wherein a pilot control end of the first reversing valve (31) is in fluid communication with a first working port of the actuator (13).

4. The post valve compensation load sensing system of claim 1, wherein a pilot control end of the first reversing valve (31) communicates with a first pilot control end of the control valve (12).

5. The post valve compensation load sensing system of claim 1, wherein the first reversing valve (31) is an electromagnetic reversing valve.

6. The post valve compensation load sensing system of claim 1, further comprising:

a second overflow branch (5) comprising 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 conducted when the second working oil port of the actuating mechanism (13) is filled with oil, and to be cut off when the second working oil port of the actuating mechanism (13) is not filled with oil; wherein an oil inlet of the second reversing valve (51) is in fluid communication with a control end of the flow control valve (22) and an oil outlet of the throttling assembly (23); and an oil outlet of the second overflow valve (52) is communicated with oil return.

7. The post valve compensation load sensing system of claim 6, wherein a pilot control end of the second reversing valve (51) is in fluid communication with a second working port of the actuator (13).

8. The post valve compensation load sensing system of claim 6, wherein a pilot control end of the second reversing valve (51) communicates with a second pilot control end of the control valve (12).

9. The post valve compensation load sensing system of claim 6, wherein the second reversing valve (51) is an electromagnetic reversing valve.

10. The post valve compensation load sensing system of claim 1, wherein the throttle assembly (23) comprises a throttle orifice.

11. A hydraulic system comprising a post-valve compensation load sensing system according to any one of claims 1 to 10.

12. A crane comprising the hydraulic system of claim 11.