1. A lift hydraulic system, comprising: the hydraulic control system comprises a hydraulic execution element, a reversing valve, a first one-way valve, a hydraulic control one-way valve, a first pressure limiting valve and a pressure regulating valve group, wherein the hydraulic execution element is provided with a first oil cavity and a second oil cavity;

the reversing valve has a first working state and a second working state, and in the first working state, a first oil port of the hydraulic control one-way valve and a control oil port of the first pressure limiting valve are both communicated with an oil outlet of the pump source through the reversing valve; an oil inlet of the first pressure limiting valve is communicated with the first oil cavity, and an oil outlet of the first pressure limiting valve is communicated with an oil return tank through the reversing valve;

in a second working state, the oil inlet of the first one-way valve and the control oil port of the hydraulic control one-way valve are both communicated with the oil outlet of the pump source through the reversing valve, and the oil outlet of the first one-way valve is communicated with the first oil cavity; a first oil port of the hydraulic control one-way valve is communicated with the oil return tank through the reversing valve;

and a second oil port of the hydraulic control one-way valve is communicated with the second oil cavity through a first oil way, and the pressure regulating valve group is arranged on the first oil way.

2. The lifting hydraulic system according to claim 1, wherein the pressure regulating valve set comprises a second pressure limiting valve, an oil inlet of the second pressure limiting valve is communicated with the first oil path, and an oil outlet of the second pressure limiting valve is communicated with the oil return tank.

3. The lift hydraulic system of claim 1, further comprising a first flow restriction valve;

and a first oil port of the first flow limiting valve is communicated with the reversing valve, and a second oil port of the first flow limiting valve is communicated with a first oil port of the hydraulic control one-way valve.

4. The lift hydraulic system of claim 1, wherein the pressure regulating valve block includes a pressure relief valve and a second check valve;

an oil inlet of the pressure reducing valve is communicated with a second oil port of the hydraulic control one-way valve, and an oil outlet of the pressure reducing valve is communicated with the second oil cavity;

the second check valve is connected with the pressure reducing valve in parallel, an oil inlet of the second check valve is communicated with the second oil cavity, and an oil outlet of the second check valve is communicated with a second oil port of the hydraulic control check valve.

5. The lift hydraulic system of claim 1, further comprising a second flow restriction valve;

an oil inlet of the second flow limiting valve is communicated with the reversing valve, and an oil outlet of the second flow limiting valve is communicated with a control oil port of the first pressure limiting valve.

6. The lift hydraulic system of claim 1, further comprising a third flow restriction valve;

an oil inlet of the third flow limiting valve is communicated with the reversing valve, and an oil outlet of the third flow limiting valve is communicated with a control oil port of the hydraulic control one-way valve.

7. The lift hydraulic system of claim 1, further comprising an overflow valve, an oil inlet of the overflow valve being in communication with the reversing valve and an oil outlet of the overflow valve being in communication with the oil return tank.

8. The lift hydraulic system of claim 1, wherein the hydraulic actuator is a cylinder or a motor.

9. A work machine, characterized by comprising a lift hydraulic system according to any one of claims 1 to 8.

10. The work machine of claim 9, wherein the work machine comprises a fire truck, a boom truck, a concrete pump truck, or a crane.

Background

The crane is a common hoisting machine and is used for hoisting and lowering heavy objects, the weight of the counter weight is larger and larger along with the development of the ultra-large crane, and the hydraulic control system of the counter weight oil cylinder directly influences the disassembly and assembly efficiency of the counter weight and the reliability of the counter weight oil cylinder.

When a counterweight oil cylinder extends quickly and reaches a position in the self-disassembling process of a counterweight of the conventional crane, a structural member connected with the counterweight oil cylinder is easy to crack due to overhigh pressure entering a rodless cavity of the counterweight oil cylinder, and a pressure limiting valve communicated with a rod cavity of the counterweight oil cylinder cannot be opened due to overlow pressure entering the counterweight oil cylinder, so that oil cannot return.

Disclosure of Invention

The invention provides a lifting hydraulic system and an operating machine, and aims to overcome the defect that the lifting hydraulic system in the prior art cannot perform graded pressure limiting on a first oil cavity and a second oil cavity of a hydraulic execution element, and realize that the pressure of the first oil cavity and the pressure of the second oil cavity of the hydraulic execution element are both maintained in a normal range.

The invention provides a lifting hydraulic system, comprising: the hydraulic control system comprises a hydraulic execution element, a reversing valve, a first one-way valve, a hydraulic control one-way valve, a first pressure limiting valve and a pressure regulating valve group, wherein the hydraulic execution element is provided with a first oil cavity and a second oil cavity;

the reversing valve has a first working state and a second working state, and in the first working state, a first oil port of the hydraulic control one-way valve and a control oil port of the first pressure limiting valve are both communicated with an oil outlet of the pump source through the reversing valve; an oil inlet of the first pressure limiting valve is communicated with the first oil cavity, and an oil outlet of the first pressure limiting valve is communicated with an oil return tank through the reversing valve;

in a second working state, the oil inlet of the first one-way valve and the control oil port of the hydraulic control one-way valve are both communicated with the oil outlet of the pump source through the reversing valve, and the oil outlet of the first one-way valve is communicated with the first oil cavity; a first oil port of the hydraulic control one-way valve is communicated with the oil return tank through the reversing valve;

and a second oil port of the hydraulic control one-way valve is communicated with the second oil cavity through a first oil way, and the pressure regulating valve group is arranged on the first oil way.

According to the lifting hydraulic system provided by the invention, the pressure regulating valve group comprises a second pressure limiting valve, an oil inlet of the second pressure limiting valve is communicated with the first oil way, and an oil outlet of the second pressure limiting valve is communicated with the oil return tank.

According to the lifting hydraulic system provided by the invention, the lifting hydraulic system further comprises a first flow limiting valve;

and a first oil port of the first flow limiting valve is communicated with the reversing valve, and a second oil port of the first flow limiting valve is communicated with a first oil port of the hydraulic control one-way valve.

According to the lifting hydraulic system provided by the invention, the pressure regulating valve group comprises a pressure reducing valve and a second one-way valve;

an oil inlet of the pressure reducing valve is communicated with a second oil port of the hydraulic control one-way valve, and an oil outlet of the pressure reducing valve is communicated with the second oil cavity;

the second check valve is connected with the pressure reducing valve in parallel, an oil inlet of the second check valve is communicated with the second oil cavity, and an oil outlet of the second check valve is communicated with a second oil port of the hydraulic control check valve.

According to the lifting hydraulic system provided by the invention, the lifting hydraulic system further comprises a second flow limiting valve;

an oil inlet of the second flow limiting valve is communicated with the reversing valve, and an oil outlet of the second flow limiting valve is communicated with a control oil port of the first pressure limiting valve.

According to the lifting hydraulic system provided by the invention, the lifting hydraulic system further comprises a third flow limiting valve;

an oil inlet of the third flow limiting valve is communicated with the reversing valve, and an oil outlet of the third flow limiting valve is communicated with a control oil port of the hydraulic control one-way valve.

According to the lifting hydraulic system provided by the invention, the lifting hydraulic system further comprises an overflow valve, an oil inlet of the overflow valve is communicated with the reversing valve, and an oil outlet of the overflow valve is communicated with the oil return tank.

According to the lifting hydraulic system provided by the invention, the hydraulic actuating element is an oil cylinder or a motor.

The invention also provides a working machine comprising the lifting hydraulic system.

According to the working machine provided by the invention, the working machine comprises a fire truck, a bucket arm truck, a concrete pump truck or a crane.

The invention provides a lifting hydraulic system which comprises a hydraulic execution element, a reversing valve, a first check valve, a hydraulic control check valve, a first pressure limiting valve and a pressure regulating valve group, wherein the hydraulic execution element is provided with a first oil cavity and a second oil cavity, the pressure regulating valve group is arranged on a first oil way through which a second oil port of the hydraulic control check valve is communicated with the first oil cavity, the pressure regulating valve group can enable part of hydraulic oil in the second oil cavity to flow back to an oil return box, the pressure in the second oil cavity is guaranteed to be maintained in a normal range, and the control oil port of the first pressure limiting valve is communicated with the reversing valve, so that the pressure in the first oil cavity is guaranteed to be maintained in the normal range.

Drawings

In order to more clearly illustrate the technical solutions of the present invention or the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 is a hydraulic diagram of a prior art lift hydraulic system;

FIG. 2 is one of the hydraulic diagrams of the lift hydraulic system provided by the present invention;

FIG. 3 is a second hydraulic diagram of the hydraulic lift system provided by the present invention;

reference numerals:

1: a pump source; 2: a three-position four-way reversing valve; 3: a balancing weight;

4: a first oil chamber; 5: a second oil chamber; 6: a turntable main body;

7: fixing the bolt; 8: an overflow valve; 9: a first pressure limiting valve;

10: a first check valve; 11: a hydraulic control check valve; 12: a second pressure limiting valve;

13: a first flow limiting valve; 14: a pressure reducing valve; 15: a second one-way valve;

16: a second flow limiting valve; 17: a third flow limiting valve; 18: a third pressure limiting valve;

19: and a third one-way valve.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Fig. 1 shows a prior art hydraulic lifting system, which includes a hydraulic actuator having a first oil chamber 4 and a second oil chamber 5, a three-position four-way selector valve 2, a first pressure limiting valve 9, a first check valve 10, a third pressure limiting valve 18, and a third check valve 19.

The hydraulic actuating element can be a counterweight cylinder, a first oil chamber 4 of the counterweight cylinder is defined as a rod chamber, a second oil chamber 5 of the counterweight cylinder is defined as a rodless chamber, and the using process of the counterweight cylinder is described below.

In the process of extending the counterweight oil cylinder, hydraulic oil conveyed from the pump source 1 sequentially passes through the oil inlet of the three-position four-way reversing valve 2, the second working oil port of the three-position four-way reversing valve 2 and the third one-way valve 19 to enter the rodless cavity, and the hydraulic oil in the rod cavity flows back to the oil return tank through the first pressure limiting valve 9.

In the process of retracting the counterweight oil cylinder, hydraulic oil conveyed from the pump source 1 sequentially passes through the oil inlet of the three-position four-way reversing valve 2, the first working oil port of the three-position four-way reversing valve 2 and the first check valve 10 to enter the rod cavity, and the hydraulic oil in the rodless cavity flows back to the oil return tank through the third pressure limiting valve 18.

In the process that the counter weight hydro-cylinder stretches out, because do not set up the device that can carry out the pressure regulation to the pressure of no pole intracavity, when the counter weight hydro-cylinder stretches out to target in place soon, because factors such as assembly error or manufacturing error, take place the extrusion between the lug of counter weight hydro-cylinder and the lug of the structure of being connected with it, when the counter weight hydro-cylinder continues to stretch out, can lead to the pressure of no pole intracavity too big, the structure top fracture of being connected with the counter weight hydro-cylinder will be easily.

The existing solution is to add a travel switch, but the reliability of the travel switch is limited, the operation of the counterweight oil cylinder is limited due to damage or false alarm, or the pressure entering a rodless cavity is reduced, but the pressure is too low, so that a first pressure limiting valve 9 communicated with the rod cavity cannot be opened, oil return cannot be caused, and the operation of the counterweight oil cylinder is influenced.

In order to solve the above problems, the hydraulic lifting system of the present invention will be described below with reference to fig. 2 to 3.

As shown in fig. 2, the lifting hydraulic system provided in the embodiment of the present invention includes: the hydraulic control device comprises a hydraulic actuating element, a reversing valve, a first one-way valve 10, a hydraulic control one-way valve 11, a first pressure limiting valve 9 and a pressure regulating valve group, wherein the hydraulic actuating element is provided with a first oil cavity 4 and a second oil cavity 5;

the reversing valve has a first working state and a second working state, and in the first working state, a first oil port of the hydraulic control one-way valve 11 and a control oil port of the first pressure limiting valve 9 are both communicated with an oil outlet of the pump source 1 through the reversing valve; an oil inlet of the first pressure limiting valve 9 is communicated with the first oil cavity 4, and an oil outlet of the first pressure limiting valve 9 is communicated with the oil return tank through a reversing valve;

in a second working state, an oil inlet of the first check valve 10 and a control oil port of the hydraulic control check valve 11 are communicated with an oil outlet of the pump source 1 through a reversing valve, and an oil outlet of the first check valve 10 is communicated with the first oil chamber 4; a first oil port of the hydraulic control one-way valve 11 is communicated with the oil return tank through a reversing valve;

a second oil port of the hydraulic control one-way valve 11 is communicated with the second oil cavity 5 through a first oil way, and a pressure regulating valve group is arranged on the first oil way.

The reversing valve can be a three-position four-way reversing valve 2, and the three-position four-way reversing valve 2 is provided with four oil ports which are respectively defined as an oil inlet, an oil outlet, a first working oil port and a second working oil port.

Specifically, an oil inlet of the three-position four-way reversing valve 2 is communicated with an oil outlet of the pump source 1, and an oil outlet of the three-position four-way reversing valve 2 is communicated with an oil return tank.

An oil inlet of the first pressure limiting valve 9 is communicated with the first oil cavity 4, an oil outlet of the first pressure limiting valve 9 is communicated with a first working oil port of the three-position four-way reversing valve 2, and a control oil port of the first pressure limiting valve 9 is communicated with a second working oil port of the three-position four-way reversing valve 2; the first check valve 10 is connected with the first pressure limiting valve 9 in parallel, an oil inlet of the first check valve 10 is communicated with a first working oil port of the three-position four-way reversing valve 2, and an oil outlet of the first check valve 10 is communicated with the first oil cavity 4.

The first oil port of the hydraulic control one-way valve 11 is communicated with the second working oil port of the three-position four-way reversing valve 2, the second oil port of the hydraulic control one-way valve 11 is communicated with the first oil cavity 4 through a first oil path, a pressure regulating valve group is arranged on the first oil path, and the control oil port of the hydraulic control one-way valve 11 is communicated with the first working oil port of the three-position four-way reversing valve 2.

When the hydraulic execution element is in a first working state, hydraulic oil conveyed from the pump source 1 sequentially passes through an oil inlet of the three-position four-way reversing valve 2, a second working oil port of the three-position four-way reversing valve 2, a first oil port of the hydraulic control one-way valve 11 and a second oil port of the hydraulic control one-way valve 11 to enter the second oil cavity 5; the control oil port of the first pressure limiting valve 9 is communicated with the second working oil port of the three-position four-way reversing valve 2, the first pressure limiting valve 9 is opened, and the hydraulic oil in the first oil cavity 4 sequentially flows back to the oil return tank through the first pressure limiting valve 9 and the three-position four-way reversing valve 2.

When the hydraulic execution element is in a second working state, hydraulic oil conveyed from the pump source 1 sequentially passes through an oil inlet of the three-position four-way reversing valve 2, a first working oil port of the three-position four-way reversing valve 2, an oil inlet of the first check valve 10 and an oil outlet of the first check valve 10 to enter the first oil cavity 4; the control oil port of the hydraulic control one-way valve 11 is communicated with the first working oil port of the three-position four-way reversing valve 2, and hydraulic oil in the second oil cavity 5 sequentially flows through the second oil port of the hydraulic control one-way valve 11, the first oil port of the hydraulic control one-way valve 11 and the three-position four-way reversing valve 2 and then flows back to the oil return tank.

An oil path communicated with the hydraulic control one-way valve 11 and the second oil chamber 5 is defined as a first oil path, an oil path communicated with a control oil port of the first pressure limiting valve 9 and a second working oil port of the three-position four-way reversing valve 2 is defined as a second oil path, and an oil path communicated with the control oil port of the hydraulic control one-way valve 11 and the first working oil port of the three-position four-way reversing valve 2 is defined as a third oil path.

When the hydraulic execution element is in the first working state, because the pressure regulating valve group is arranged on the oil path communicated with the hydraulic control one-way valve 11 and the second oil chamber 5, when the pressure in the second oil chamber 5 is too high, part of hydraulic oil in the second oil chamber 5 can flow back to the oil return tank through the pressure regulating valve group, so that the pressure in the second oil chamber 5 is maintained in a normal range. The pressure regulating valve group is arranged on an oil path communicated with the hydraulic control one-way valve 11 and the second oil chamber 5, the pressure in the second oil path is not influenced, when the pressure in the second oil path reaches the threshold value of the first pressure limiting valve 9, the first pressure limiting valve 9 is opened, the hydraulic oil in the first oil chamber 4 flows back to the oil return tank through the first pressure limiting valve 9, and therefore the pressure in the first oil chamber 4 is maintained in a normal range. Thereby, the pressures in the first oil chamber 4 and the second oil chamber 5 are both maintained within the normal range.

In the embodiment of the invention, the pressure regulating valve group is arranged on the first oil path communicated with the second oil cavity 5 and the second oil port of the hydraulic control one-way valve 11, the pressure regulating valve group can enable part of hydraulic oil in the second oil cavity 5 to flow back to the oil return tank, so that the pressure in the second oil cavity 5 is maintained in a normal range, and the control oil port of the first pressure limiting valve 9 is communicated with the second working oil port of the three-position four-way reversing valve 2, so that the pressure in the first oil cavity 4 is maintained in a normal range.

In an optional embodiment, the pressure regulating valve group comprises a second pressure limiting valve 12, an oil inlet of the second pressure limiting valve 12 is communicated with the first oil path, and an oil outlet of the second pressure limiting valve 12 is communicated with the oil return tank.

When the hydraulic execution element is in the first working state, if the pressure in the second oil chamber 5 is too high and the pressure in the first oil path exceeds the threshold value of the second pressure limiting valve 12, the second pressure limiting valve 12 is opened, at this time, part of the hydraulic oil in the second oil chamber 5 enters the oil inlet of the second pressure limiting valve 12 along the first oil path and then flows back to the oil return tank through the oil outlet of the second pressure limiting valve 12, so that the pressure in the second oil chamber 5 is maintained in the normal range.

When the hydraulic actuator is in the second working state, if the pressure in the second oil chamber 5 is too high, part of the hydraulic oil in the second oil chamber 5 may also flow back to the oil return tank through the second pressure limiting valve 12, and the oil return mode is similar to that when the hydraulic actuator is in the first working state, and will not be described herein again.

In the embodiment of the present invention, the oil inlet of the second pressure limiting valve 12 is communicated with the first oil path, the oil outlet of the second pressure limiting valve 12 is communicated with the oil return tank, and a part of hydraulic oil in the second oil chamber 5 can be returned to the oil return tank through the second pressure limiting valve 12, so that the pressure in the second oil chamber 5 is maintained within a normal range.

In an optional embodiment, the hydraulic lifting system further includes a first flow limiting valve 13, a first oil port of the first flow limiting valve 13 is communicated with a second working oil port of the three-position four-way reversing valve 2, and a second oil port of the first flow limiting valve 13 is communicated with a first oil port of the pilot-controlled check valve 11.

Specifically, the oil passage communicated with the second working oil port of the three-position four-way reversing valve 2 is divided into two branches, which are respectively called a second oil passage and a fourth oil passage, the second working oil port of the three-position four-way reversing valve 2 is communicated with the control oil port of the first pressure limiting valve 9 through the second oil passage, the second working oil port of the three-position four-way reversing valve 2 is communicated with the first oil port of the hydraulic control one-way valve 11 through the fourth oil passage, and the first flow limiting valve 13 is arranged on the fourth oil passage.

When the hydraulic execution element is in the first working state, hydraulic oil conveyed from the pump source 1 sequentially passes through the oil inlet of the three-position four-way reversing valve 2, the second working oil port of the three-position four-way reversing valve 2, the first flow limiting valve 13, the first oil port of the hydraulic control one-way valve 11 and the second oil port of the hydraulic control one-way valve 11 to enter the second oil chamber 5, the flow of the hydraulic oil entering the second oil chamber 5 can be controlled through the first flow limiting valve 13 according to actual use conditions, and the pressure of the second oil chamber 5 is maintained within a normal range.

When the hydraulic execution element is in the second working state, the hydraulic oil in the second oil chamber 5 sequentially flows back to the oil return tank through the second oil port of the hydraulic control one-way valve 11, the first flow limiting valve 13 and the three-position four-way reversing valve 2, the flow of the hydraulic oil output from the second oil chamber 5 can be controlled through the first flow limiting valve 13 according to the actual use condition, and the pressure of the second oil chamber 5 is maintained within the normal range.

In the embodiment of the present invention, the fourth oil path is provided with the first flow limiting valve 13, the first oil port of the first flow limiting valve 13 is communicated with the second working oil port of the three-position four-way reversing valve 2, the second oil port of the first flow limiting valve 13 is communicated with the first oil port of the hydraulic control one-way valve 11, the flow rate of the hydraulic oil entering the second oil chamber 5 and the flow rate of the hydraulic oil flowing out of the second oil chamber 5 are controlled by the first flow limiting valve 13, and the pressure of the second oil chamber 5 is maintained within a normal range.

In an alternative embodiment, as shown in fig. 3, the pressure regulating valve group comprises a pressure reducing valve 14 and a second check valve 15;

an oil inlet of the reducing valve 14 is communicated with a second oil port of the hydraulic control one-way valve 11, and an oil outlet of the reducing valve 14 is communicated with the second oil chamber 5;

the second check valve 15 is connected with the pressure reducing valve 14 in parallel, an oil inlet of the second check valve 15 is communicated with the second oil chamber 5, and an oil outlet of the second check valve 15 is communicated with a second oil port of the hydraulic control check valve 11.

When the hydraulic execution element is in the first working state, hydraulic oil conveyed from the pump source 1 sequentially passes through the oil inlet of the three-position four-way reversing valve 2, the second working oil port of the three-position four-way reversing valve 2, the hydraulic control one-way valve 11, the oil inlet of the reducing valve 14 and the oil outlet of the reducing valve 14 to enter the second oil chamber 5, and the pressure of the hydraulic oil entering the second oil chamber 5 can be adjusted through the reducing valve 14, so that the pressure in the second oil chamber 5 is maintained within a normal range.

When the hydraulic execution element is in the second working state, the hydraulic oil in the second oil chamber 5 sequentially flows back to the oil return tank through the second check valve 15, the second oil port of the hydraulic control check valve 11, the first oil port of the hydraulic control check valve 11 and the three-position four-way reversing valve 2.

In the embodiment of the present invention, the second check valve 15 is connected in parallel with the pressure reducing valve 14, an oil inlet of the pressure reducing valve 14 is communicated with the second oil port of the pilot operated check valve 11, an oil outlet of the pressure reducing valve 14 is communicated with the second oil chamber 5, and the pressure entering the second oil chamber 5 is adjusted by the pressure reducing valve 14, so that the pressure in the second oil chamber 5 is maintained within a normal range.

In an optional embodiment, the lifting hydraulic system further includes a second flow limiting valve 16, an oil inlet of the second flow limiting valve 16 is communicated with a second working oil port of the three-position four-way reversing valve 2, and an oil outlet of the second flow limiting valve 16 is communicated with a control oil port of the first pressure limiting valve 9.

Specifically, a second flow limiting valve 16 is arranged on the second oil path, an oil inlet of the second flow limiting valve 16 is communicated with a second working oil port of the three-position four-way reversing valve 2, and an oil outlet of the second flow limiting valve 16 is communicated with a control oil port of the first pressure limiting valve 9.

When the hydraulic execution element is in the first working state, hydraulic oil conveyed from the pump source 1 sequentially flows to the control oil port of the first pressure limiting valve 9 through the oil inlet of the three-position four-way reversing valve 2, the second working oil port of the three-position four-way reversing valve 2, the oil inlet of the second flow limiting valve 16 and the oil outlet of the second flow limiting valve 16, the second flow limiting valve 16 can control the oil quantity of the hydraulic oil in the second oil path, and the speed of controlling the valve core of the first pressure limiting valve 9 to open is further achieved, so that the pressure of the first oil chamber 4 is maintained within a normal range.

In the embodiment of the invention, the second oil path is provided with the second flow limiting valve 16, the oil inlet of the second flow limiting valve 16 is communicated with the second working oil port of the three-position four-way reversing valve 2, the oil outlet of the second flow limiting valve 16 is communicated with the control oil port of the first pressure limiting valve 9, the oil quantity of hydraulic oil in the second oil path is controlled through the second flow limiting valve 16, the speed of opening the valve core of the first pressure limiting valve 9 is further controlled, and the pressure of the first oil chamber 4 is maintained within a normal range.

In an optional embodiment, the lifting hydraulic system further includes a third flow limiting valve 17, an oil inlet of the third flow limiting valve 17 is communicated with the first working oil port of the three-position four-way reversing valve 2, and an oil outlet of the third flow limiting valve 17 is communicated with the control oil port of the hydraulic control one-way valve 11.

Specifically, a third flow limiting valve 17 is arranged on the third oil path, an oil inlet of the third flow limiting valve 17 is communicated with a first working oil port of the three-position four-way reversing valve 2, and an oil outlet of the third flow limiting valve 17 is communicated with a control oil port of the hydraulic control one-way valve 11.

When the hydraulic execution element is in the second working state, hydraulic oil conveyed from the pump source 1 sequentially flows to the control oil port of the hydraulic control one-way valve 11 through the oil inlet of the three-position four-way reversing valve 2, the first working oil port of the three-position four-way reversing valve 2, the oil inlet of the third flow limiting valve 17 and the oil outlet of the third flow limiting valve 17, the oil amount of the hydraulic oil in the third oil path is controlled through the third flow limiting valve 17, the speed of controlling the reverse conduction of the hydraulic control one-way valve 11 is further achieved, namely the hydraulic oil flows from the second oil port of the hydraulic control one-way valve 11 to the first oil port, and therefore the hydraulic oil in the second oil chamber 5 sequentially flows back to the oil return tank through the second oil port of the hydraulic control one-way valve 11, the first oil port of the hydraulic control one-way valve 11 and the first flow limiting valve 13, and the pressure of the second oil chamber 5 is maintained within a normal range.

In the embodiment of the invention, the third oil path is provided with the third flow limiting valve 17, an oil inlet of the third flow limiting valve 17 is communicated with the first working oil port of the three-position four-way reversing valve 2, an oil outlet of the third flow limiting valve 17 is communicated with the control oil port of the hydraulic control one-way valve 11, the oil quantity of hydraulic oil in the third oil path is controlled through the third flow limiting valve 17, the speed of controlling the reverse conduction of the hydraulic control one-way valve 11 is further reached, the reverse conduction of the hydraulic control one-way valve 11 is further realized, and the pressure of the second oil chamber 5 is maintained within a normal range.

In an optional embodiment, the lifting hydraulic system further comprises an overflow valve 8, an oil inlet of the overflow valve 8 is communicated with an oil inlet of the three-position four-way reversing valve 2, and an oil outlet of the overflow valve 8 is communicated with an oil return tank.

Specifically, an oil inlet of the three-position four-way reversing valve 2 is communicated with an oil outlet of the pump source 1 through a fifth pipeline, an oil inlet of the overflow valve 8 is communicated with the fifth pipeline, and an oil outlet of the overflow valve 8 is communicated with the oil return tank. If the oil quantity of the hydraulic oil conveyed from the pump source 1 to the oil inlet of the three-position four-way reversing valve 2 is too large, part of the hydraulic oil in the fifth pipeline can sequentially flow back to the oil return tank through the oil inlet of the overflow valve 8 and the oil outlet of the overflow valve 8, so that the oil quantity of the hydraulic oil entering the first oil chamber 4 or the second oil chamber 5 is maintained within a normal range.

In the embodiment of the invention, the oil inlet of the overflow valve 8 is communicated with the oil inlet of the three-position four-way reversing valve 2, the oil outlet of the overflow valve 8 is communicated with the oil return tank, and part of hydraulic oil conveyed from the pump source 1 to the oil inlet of the three-position four-way reversing valve 2 can sequentially flow back to the oil return tank through the oil inlet of the overflow valve 8 and the oil outlet of the overflow valve 8, so that the oil amount of the hydraulic oil entering the first oil chamber 4 or the second oil chamber 5 is maintained within a normal range.

In alternative embodiments, the hydraulic actuator is a cylinder or a motor.

As shown in fig. 2, the hydraulic actuator may be a counterweight cylinder, the first oil chamber 4 of the counterweight cylinder is defined as a rod chamber, and the second oil chamber 5 of the counterweight cylinder is defined as a rodless chamber, and the operation process of the counterweight cylinder will be described below.

When the counterweight oil cylinder is in a first working state, namely when the counterweight oil cylinder extends out, hydraulic oil conveyed from the pump source 1 sequentially passes through the oil inlet of the three-position four-way reversing valve 2, the second working oil port of the three-position four-way reversing valve 2, the first flow limiting valve 13, the first oil port of the hydraulic control one-way valve 11 and the second oil port of the hydraulic control one-way valve 11 to enter the rodless cavity; the control oil port of the first pressure limiting valve 9 is communicated with the second working oil port of the three-position four-way reversing valve 2 through a second oil path, the pressure in the second oil path reaches the threshold value of the first pressure limiting valve 9, the first pressure limiting valve 9 is opened, and the hydraulic oil in the rod cavity sequentially flows through the first pressure limiting valve 9 and the three-position four-way reversing valve 2 and then flows back to the oil return tank.

The structural member connected with the counterweight oil cylinder is taken as the rotary table main body 6 for explanation, in the process of extending the counterweight oil cylinder, when the counterweight oil cylinder extends to a position quickly, due to factors such as assembly errors or manufacturing errors, extrusion may occur between the lifting lugs of the counterweight oil cylinder and the lifting lugs of the rotary table main body 6, when the counterweight oil cylinder continues to extend, the pressure in the rodless cavity can be increased, the pressure in the rodless cavity is continuously increased, and the rotary table main body 6 is cracked. Because the second pressure-limiting valve 12 is communicated with the first oil path, when the pressure in the first oil path reaches the threshold value of the second pressure-limiting valve 12, part of the hydraulic oil in the rodless cavity flows to the oil inlet of the second pressure-limiting valve 12 through the first oil path and flows to the oil return tank through the oil outlet of the second pressure-limiting valve 12, so that the pressure in the rodless cavity is maintained within a normal range, and the turntable main body 6 is protected from being damaged. After the counterweight oil cylinder extends in place, the fixing bolt 7 penetrates through the mounting hole of the lifting lug of the counterweight oil cylinder and the mounting hole of the lifting lug of the rotary table main body 6, and the counterweight oil cylinder and the rotary table main body 6 are assembled.

When the counterweight oil cylinder is in a second working state, namely when the counterweight oil cylinder retracts, the counterweight oil cylinder drives the counterweight block 3 to move upwards, and hydraulic oil conveyed from the pump source 1 sequentially passes through an oil inlet of the three-position four-way reversing valve 2, a first working oil port of the three-position four-way reversing valve 2, an oil inlet of the first check valve 10 and an oil outlet of the first check valve 10 to enter the rod cavity; the control oil port of the hydraulic control one-way valve 11 is communicated with the first working oil port of the three-position four-way reversing valve 2, the hydraulic control one-way valve 11 is conducted reversely, and hydraulic oil in the rodless cavity sequentially flows through the second oil port of the hydraulic control one-way valve 11, the first flow limiting valve 13 and the three-position four-way reversing valve 2 and then flows back to the oil return tank. The hydraulic oil in the rodless chamber can also flow back to the oil return tank through the second pressure limiting valve 12.

In summary, the hydraulic lift system ensures that the pressure in the rodless chamber and the pressure in the rod chamber are maintained within normal ranges during extension and retraction of the counterweight cylinder.

The embodiment of the invention also provides the working machine, and the working machine comprises the lifting hydraulic system.

Specifically, since the working machine includes the lifting hydraulic system, the specific structure of the lifting hydraulic system refers to the above embodiment, and since the working machine adopts the technical solution of the above embodiment, at least all the beneficial effects brought by the technical solution of the above embodiment are achieved, and no further description is given here.

The operation machine disclosed by the embodiment of the invention comprises a fire fighting truck, a bucket arm truck, a concrete pump truck or a crane.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present 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 still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.