Hydraulic swing system, swing device and working machine

Abstract

The application relates to the field of engineering machinery and provides a slewing hydraulic system, a slewing device and a working machine, which comprise a hydraulic motor, a main reversing valve, a slewing buffer valve and a pilot oil pipeline. The main reversing valve is used for switching the rotating direction of the hydraulic motor. The slewing buffer valve comprises two two-stage pressure boost overflow valves, the overflow valve oil inlets of the two two-stage pressure boost overflow valves are respectively connected to the hydraulic oil pipelines between the main reversing valve and the hydraulic motor. The pilot oil pipeline is respectively connected to the overflow valve pilot ports of the two two-stage pressure boost overflow valves. When starting, the pilot oil pipeline controls the opening pressure of the two-stage pressure boost overflow valve on the oil inlet side to reach a first opening pressure, and the opening pressure of the two-stage pressure boost overflow valve on the oil return side is kept at a second opening pressure. Since the first opening pressure is large, a larger starting torque can be provided for the hydraulic motor. When slewing braking, since the second opening pressure is small, low-pressure buffering can be provided for the stop of the hydraulic motor.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of engineering machinery, in particular to a slewing hydraulic system, a slewing device and a working machine. BACKGROUND

[0002] At present, in the slewing device of engineering machinery equipment, a large number of hydraulic circuits with buffering function are applied, such as excavator slewing device, crane slewing device, aerial working vehicle slewing device, manipulator slewing device and forestry machinery slewing device, and the slewing buffering plays an important role in the slewing hydraulic system.

[0003] In the prior art, the slewing buffering system is generally connected to the working oil port of the hydraulic motor through the overflow valve and the check valve to realize the buffering function. When the slewing device rotates at high speed, the system pressure value is very high, and when the slewing device rotates at idle speed, the system pressure value is very low. In order to meet the two working conditions, the set pressure of the overflow valve is based on the required pressure when rotating at high speed. However, when braking, the hydraulic motor rotates at idle speed, the system impact pressure is not enough to overcome the opening pressure of the overflow valve, resulting in that the overflow valve is always closed, and the buffering function cannot be effectively realized. SUMMARY

[0004] The present application provides a slewing hydraulic system, a slewing device and a working machine, which solve the defect that the set pressure of the overflow valve in the prior art is based on the required pressure when rotating at high speed, resulting in that the opening pressure is large, and the system impact pressure cannot open the overflow valve when the hydraulic motor rotates at idle speed, and the buffering function cannot be effectively realized, and the effect that the opening pressure of the overflow valve is controllable is realized.

[0005] The present application provides a slewing hydraulic system, comprising: a hydraulic motor; a main reversing valve, two working oil ports of the main reversing valve are in one-to-one correspondence with two motor working oil ports of the hydraulic motor; a slewing buffering valve, the slewing buffering valve comprises two secondary pressure increasing overflow valves, overflow valve inlet ports of the two secondary pressure increasing overflow valves are connected on two hydraulic oil pipelines between the main reversing valve and the hydraulic motor respectively; a pilot oil pipeline, the pilot oil pipeline is connected with overflow valve hydraulic control ports of the two secondary pressure increasing overflow valves respectively; when the overflow valve hydraulic control port is communicated with the pilot oil pipeline, the opening pressure of the corresponding secondary pressure increasing overflow valve is a first opening pressure, when the overflow valve hydraulic control port is disconnected with the pilot oil pipeline, the opening pressure of the corresponding secondary pressure increasing overflow valve is a second opening pressure, wherein the first opening pressure is greater than the second opening pressure.

[0006] According to the rotary hydraulic system provided by the application, the pilot oil pipeline comprises: two reversing valves, each of which is provided with a pilot oil inlet, a pilot oil return and a pilot oil outlet; a pilot oil inlet pipeline in communication with the pilot oil inlets of the two reversing valves; a pilot oil return pipeline in communication with the pilot oil returns of the two reversing valves; and a pilot oil outlet pipeline in communication with the pilot oil outlets of the two reversing valves and the overflow valve pilot ports of the two secondary pressure boost valves one by one.

[0007] According to the rotary hydraulic system provided by the application, the main reversing valve is a hydraulic control reversing valve, and the two pilot oil outlet pipelines are in communication with the two hydraulic control ports of the main reversing valve one by one.

[0008] According to the rotary hydraulic system provided by the application, the main reversing valve is an electric control reversing valve.

[0009] According to the rotary hydraulic system provided by the application, the main reversing valve is a three-position four-way reversing valve, when the three-position four-way reversing valve is in the first working position and the second working position, the oil supply directions of the three-position four-way reversing valve are opposite, and when the three-position four-way reversing valve is in the third working position, the oil supply and return of the three-position four-way reversing valve are both cut off.

[0010] According to the rotary hydraulic system provided by the application, the rotary hydraulic system further comprises a supplementary oil pipeline, two oil outlet ends of the supplementary oil pipeline are in communication with the two motor working oil ports of the hydraulic motor, and the supplementary oil pipeline can selectively supply oil to one of the motor working oil ports of the hydraulic motor.

[0011] According to the rotary hydraulic system provided by the application, the supplementary oil pipeline comprises: a main supplementary oil pipeline, an oil inlet end of the main supplementary oil pipeline is in communication with a hydraulic oil source; two sub-supplementary oil pipelines, oil inlet ends of the two sub-supplementary oil pipelines are in communication with an oil outlet end of the main supplementary oil pipeline, oil outlet ends of the two sub-supplementary oil pipelines are in communication with the two motor working oil ports of the hydraulic motor, and a one-way valve is connected to each of the sub-supplementary oil pipelines, and the flow direction of the one-way valve is from the oil inlet end to the oil outlet end of the sub-supplementary oil pipeline.

[0012] According to the rotary hydraulic system provided by the application, the number of the hydraulic motors is two or more, and the two or more hydraulic motors are connected in parallel.

[0013] The application further provides a rotary device comprising the rotary hydraulic system according to any one of the above.

[0014] The application further provides a working machine comprising the rotary hydraulic system according to any one of the above or comprising the rotary device according to the above.

[0015] The rotary hydraulic system provided by the application comprises a hydraulic motor, a main reversing valve, a rotary buffer valve and a pilot oil line. Two working oil ports of the main reversing valve are in one-to-one correspondence with two motor working oil ports of the hydraulic motor. The main reversing valve is used for controlling the start and stop of the hydraulic motor and switching the rotation direction of the hydraulic motor. The rotary buffer valve comprises two secondary pressure boost relief valves. Relief valve oil inlets of the two secondary pressure boost relief valves are connected to hydraulic oil lines between the main reversing valve and the hydraulic motor. The pilot oil line is connected to relief valve pilot ports of the two secondary pressure boost relief valves. In operation, the main reversing valve controls the oil inlet and oil return of the hydraulic motor. The pilot oil line controls the opening pressure of the secondary pressure boost relief valve on the oil inlet side to reach a first opening pressure, and the opening pressure of the secondary pressure boost relief valve on the oil return side is still maintained at a second opening pressure. Since the first opening pressure is large, the oil pressure on the oil inlet side is large, and a large starting torque can be provided for the hydraulic motor. During rotary braking, since the second opening pressure is small, the oil return on the oil return side can overcome the second opening pressure, and the oil return on the oil return side can be discharged through the secondary pressure boost relief valve on the oil return side, so as to provide a buffer for the stop of the hydraulic motor, and the hydraulic motor can be smoothly braked at low pressure. The rotary hydraulic system provided by the application uses the secondary pressure boost relief valve which can be controlled by the pilot oil line, and controls the opening pressure of the secondary pressure boost relief valves on the oil inlet side and the oil return side through the pilot oil line, so that the hydraulic motor can be started at a large torque and can be smoothly braked at low pressure.

[0016] Further, in the rotary device and the working machine provided by the application, since they both have the rotary hydraulic system as described above, they have the same advantages as described above. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0018] Figure 1 is a schematic diagram of the rotary hydraulic system provided by the application;

[0019] Reference signs:

[0020] 100: swing buffer valve; 110: first secondary pressure relief valve; 120: second secondary pressure relief valve; 200: hydraulic motor; 300: main directional valve; 400: pilot oil line; 410: first directional valve; 420: second directional valve; 430: pilot oil inlet line; 440: pilot oil return line; 450: first pilot oil outlet line; 460: second pilot oil outlet line; 510: main oil supplement line; 520: sub oil supplement line; 521: check valve; P: oil inlet; T: oil return; A: first working oil port; B: second working oil port; a: first hydraulic control port; b: second hydraulic control port; C1: first motor working oil port; C2: second motor working oil port; e1: first pressure relief valve hydraulic control port; e2: second pressure relief valve hydraulic control port; P1: first pressure relief valve oil inlet; P2: second pressure relief valve oil inlet. DETAILED DESCRIPTION

[0021] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be described clearly and completely below with reference to the drawings in the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0022] The present application will be described below with reference to the drawings. Figure 1 The present application provides a swing hydraulic system, a swing device and a working machine.

[0023] The present application provides a swing hydraulic system, a swing device and a working machine.

[0024] The hydraulic motor 200 is used to drive the rotation of the rotating part of the swing device, for example, can drive the rotation of the rotating disc of the excavator, crane, aerial work platform, manipulator or agricultural and forestry machinery and the like. The number of hydraulic motors 200 can be one, two or more than two, and the increase in the number of hydraulic motors 200 can increase the torque, and by increasing or decreasing the number of hydraulic motors 200, the swing requirements under various working conditions can be met.

[0025] The hydraulic motor 200 includes two motor working oil ports, which can be a first motor working oil port C1 and a second motor working oil port C2. When the number of hydraulic motors 200 is greater than or equal to two, the first motor working oil ports C1 of the plurality of hydraulic motors 200 are connected to one point, and similarly, the second motor working oil ports C2 of the plurality of hydraulic motors 200 are also connected to one point, in other words, the plurality of hydraulic motors 200 are connected in parallel.

[0026] The rotary cushion valve 100 described above comprises two two-stage pressure boost overflow valves, which can be a first two-stage pressure boost overflow valve 110 and a second two-stage pressure boost overflow valve 120 respectively. Referring to Figure 1 The two-stage pressure boost overflow valve on the left side in the figure is the first two-stage pressure boost overflow valve 110, and the two-stage pressure boost overflow valve on the right side is the second two-stage pressure boost overflow valve 120.

[0027] The overflow valve inlet of the first two-stage pressure boost overflow valve 110 is a first overflow valve inlet P1, which is in communication with a first motor working oil port C1 of the hydraulic motor 200. The overflow valve inlet of the second two-stage pressure boost overflow valve 120 is a second overflow valve inlet P2, which is in communication with a second motor working oil port C2 of the hydraulic motor 200.

[0028] The two-stage pressure boost overflow valve described above is further provided with an overflow valve pilot port. The overflow valve pilot port on the first two-stage pressure boost overflow valve 110 can be a first overflow valve pilot port e1, and the overflow valve pilot port on the second two-stage pressure boost overflow valve 120 can be a second overflow valve pilot port e2.

[0029] The pilot oil line 400 can be connected to the first overflow valve pilot port e1 and the second overflow valve pilot port e2 respectively, and can supply pilot oil to the first overflow valve pilot port e1 or the second overflow valve pilot port e2 respectively. When the pilot oil line 400 supplies pilot oil to the first overflow valve pilot port e1, the opening pressure of the first two-stage pressure boost overflow valve 110 reaches a first opening pressure, which is relatively large and can meet the starting requirements of the hydraulic motor 200. When there is no pilot oil supply in the first overflow valve pilot port e1, the opening pressure of the first two-stage pressure boost overflow valve 110 is a second opening pressure, which is relatively small and can make the hydraulic motor 200 brake smoothly at this pressure. As for the second two-stage pressure boost overflow valve 120, its control mode is the same as that of the first two-stage pressure boost overflow valve 110, which will not be described here.

[0030] The two working oil ports of the main reversing valve 300 are in one-to-one correspondence with the two motor working oil ports of the hydraulic motor 200, for switching the flow direction of the hydraulic oil in the hydraulic motor 200, thereby controlling the forward rotation or reverse rotation of the hydraulic motor 200, and at the same time, the main reversing valve 300 can also block the oil supply to the hydraulic motor 200 and the return of the hydraulic oil of the hydraulic motor 200.

[0031] The main reversing valve 300 described above can be a pilot-operated reversing valve, which can be a three-position four-way reversing valve, provided with an inlet port P, a return port T, two working oil ports, and two pilot ports. Among them, the two working oil ports are a first working oil port A and a second working oil port B, and the two pilot ports are a first pilot port a and a second pilot port b.

[0032] Referring to Figure 1 , the left side of the bottom of the main reversing valve 300 is the oil inlet port P, the right side of the bottom of the main reversing valve 300 is the oil return port T, the left side of the top of the main reversing valve 300 is the first working oil port A, the right side of the top of the main reversing valve 300 is the second working oil port B, the left side of the main reversing valve 300 is the first hydraulic control port a, and the right side of the main reversing valve 300 is the second hydraulic control port b.

[0033] When connected, the first pilot oil outlet pipeline 450 communicates with the second hydraulic control port b, the second pilot oil outlet pipeline 460 communicates with the first hydraulic control port a, the oil inlet port P communicates with the hydraulic oil source, the oil return port T communicates with the hydraulic oil tank, the first working oil port A communicates with the first motor working oil port C1 of the hydraulic motor 200, and the second working oil port B communicates with the second motor working oil port C2 of the hydraulic motor 200.

[0034] When the main reversing valve 300 is in the third working position, i.e., in the middle position, the oil inlet port P, the oil return port T, the first working oil port A, and the second working oil port B are all blocked. When the main reversing valve 300 is in the first working position, i.e., in the left position, the oil inlet port P communicates with the first working oil port A, and the second working oil port B communicates with the oil return port T, and the hydraulic oil in the hydraulic motor 200 flows from the first motor working oil port C1 to the second motor working oil port C2. When the main reversing valve 300 is in the second working position, i.e., in the right position, the oil inlet port P communicates with the second working oil port B, and the first working oil port A communicates with the oil return port T, and the hydraulic oil in the hydraulic motor 200 flows from the second motor working oil port C2 to the first motor working oil port C1.

[0035] Of course, the above-mentioned main reversing valve 300 can also be an electrically controlled reversing valve or a manually controlled reversing valve, and the reversing effect of the main reversing valve 300 can still be achieved.

[0036] The rotary hydraulic system provided by the application uses a liquid-controllable two-stage pressure relief valve for the rotary buffer valve 100, and the opening pressure of the two two-stage pressure relief valves is controlled through the pilot oil pipeline 400, so that the opening pressure of the two-stage pressure relief valve on the oil supply side is maintained at a first opening pressure, and the opening pressure of the two-stage pressure relief valve on the oil return side is maintained at a second opening pressure, thereby achieving large-torque starting of the hydraulic motor 200 and smooth braking of the hydraulic motor 200.

[0037] In an embodiment of the application, the pilot oil pipeline 400 includes two reversing valves, a pilot oil inlet pipeline 430, a pilot oil return pipeline 440, and a pilot oil outlet pipeline.

[0038] Among them, the two reversing valves can be a first reversing valve 410 and a second reversing valve 420, referring to Figure 1The first directional valve 410 is located on the left side, and the second directional valve 420 is located on the right side. Both of the directional valves can be electrically controlled directional valves, and the electrically controlled directional valve can be a two-position three-way directional valve.

[0039] The pilot oil inlet, the pilot oil return and the pilot oil outlet are arranged on both of the directional valves. The pilot oil inlet pipeline 430 is in communication with the pilot oil source at the oil inlet end, and is in communication with the pilot oil inlets of both of the directional valves at the oil outlet end. The pilot oil return pipeline 440 is in communication with the pilot oil returns of both of the directional valves at the oil inlet end.

[0040] The pilot oil outlet pipeline includes two, which can be a first pilot oil outlet pipeline 450 and a second pilot oil outlet pipeline 460. The first pilot oil outlet pipeline 450 is in communication with the pilot oil outlet of the first directional valve 410 at the oil inlet end, and is in communication with the second overflow valve hydraulic control port e2 of the second two-stage overflow valve 120 at the oil outlet end. The second pilot oil outlet pipeline 460 is in communication with the pilot oil outlet of the second directional valve 420 at the oil inlet end, and is in communication with the first overflow valve hydraulic control port e1 of the first two-stage overflow valve 110 at the oil outlet end.

[0041] When the first directional valve 410 is powered on, the first directional valve 410 connects the pilot oil inlet pipeline 430 and the first pilot oil outlet pipeline 450, at this time, the pilot oil is supplied to the second overflow valve hydraulic control port e2 of the second two-stage overflow valve 120, so that the opening pressure of the second two-stage overflow valve 120 reaches the first opening pressure. When the first directional valve 410 is powered off, the first directional valve 410 cuts off the communication between the pilot oil inlet pipeline 430 and the first pilot oil outlet pipeline 450, and the second overflow valve hydraulic control port e2 of the second two-stage overflow valve 120 is depressurized, and the opening pressure returns to the second opening pressure.

[0042] Since the two directional valves are directional valves of the same structure, only the working process of the first directional valve 410 is described here, and the working process of the second directional valve 420 is the same as that of the first directional valve 410, which will not be described here. However, only one of the first directional valve 410 and the second directional valve 420 is powered on during the working process.

[0043] In an embodiment of the present application, the rotary hydraulic system further comprises a supplement pipeline, the supplement pipeline includes two oil outlet ends, the oil outlet end located on the left side is in communication with the first motor working oil port C1 of the hydraulic motor 200, and the oil outlet end located on the right side is in communication with the second motor working oil port C2 of the hydraulic motor 200, and the supplement pipeline can selectively supplement oil to one of the motor working oil ports of the hydraulic motor 200.

[0044] Specifically, the oil supplement pipeline includes a main oil supplement pipeline 510 and two sub oil supplement pipelines 520. The oil inlet end of the main oil supplement pipeline 510 is in communication with the hydraulic oil source, the oil inlet ends of the two sub oil supplement pipelines 520 are in communication with the oil outlet end of the main oil supplement pipeline 510, the sub oil supplement pipeline 520 on the left side is in communication with the first motor working oil port C1 of the hydraulic motor 200, and the sub oil supplement pipeline 520 on the right side is in communication with the second motor working oil port C2 of the hydraulic motor 200. A one-way valve 521 is further arranged on each sub oil supplement pipeline 520, and the flow direction of the one-way valve 521 is from the oil outlet end of the main oil supplement pipeline 510 to the oil outlet end of the sub oil supplement pipeline 520. Alternatively, the flow direction of the one-way valve 521 on the left sub oil supplement pipeline 520 is leftward, and the flow direction of the one-way valve 521 on the right sub oil supplement pipeline 520 is rightward.

[0045] When the oil supply to the hydraulic motor 200 is stopped, the hydraulic motor 200 will continue to rotate under the action of the moment of inertia, and in the rotating process, the hydraulic oil will continue to flow, and the oil supplement pipeline can continuously supplement the oil to the oil inlet end of the hydraulic motor 200, thereby avoiding the suction of the hydraulic motor 200.

[0046] The working principle of the rotary hydraulic system will be described below, and the case where the main reversing valve 300 is in the right position will be described.

[0047] When the hydraulic motor 200 needs to be started, the first reversing valve 410 is energized, the second reversing valve 420 remains in a de-energized state, the pilot oil inlet pipeline 430 is in communication with the first pilot oil outlet pipeline 450 through the pilot oil inlet port of the first reversing valve 410, and the pilot oil is supplied to the second pilot port b of the main reversing valve 300 and the second overflow valve pilot port e2 of the second two-stage pressure boost overflow valve 120.

[0048] At this time, the right side pressure of the valve core of the main reversing valve 300 is greater than the left side pressure, the valve core is pushed to the right position, the oil inlet port P of the main reversing valve 300 is in communication with the second working oil port B, and the first working oil port A is in communication with the oil return port T. Since the second overflow valve pilot port e2 of the second two-stage pressure boost overflow valve 120 has oil pressure, the opening pressure of the second two-stage pressure boost overflow valve 120 is increased to the first opening pressure. The first overflow valve pilot port e1 of the first two-stage pressure boost overflow valve 110 has no oil pressure, and thus the opening pressure of the first two-stage pressure boost overflow valve 110 remains at the second opening pressure.

[0049] When the oil inlet P of the main reversing valve 300 is supplied with oil, the hydraulic oil is supplied to the second motor working oil port C2 of the hydraulic motor 200 through the second working oil port B of the main reversing valve 300, and in the process of oil supply, the hydraulic oil passes through the second overflow valve inlet P2 of the second two-stage pressure boosting overflow valve 120, so that the hydraulic oil pressure supplied to the second motor working oil port C2 of the hydraulic motor 200 is equal to the first opening pressure, and since the first opening pressure is large, the hydraulic motor 200 can be started with large torque.

[0050] The hydraulic oil flows to the first motor working oil port C1 through the second motor working oil port C2 of the hydraulic motor 200, and finally returns to the oil return port T through the first working oil port A of the main reversing valve 300.

[0051] When the hydraulic motor 200 is braked, the first reversing valve 410 is de-energized, the second reversing valve 420 remains in the de-energized state, the second pilot port b of the main reversing valve 300 loses oil pressure, and the spring of the main reversing valve 300 pushes the valve core back to the neutral position, at this time, the oil inlet P, the oil return port T, the first working oil port A and the second working oil port B are all cut off.

[0052] At this time, the hydraulic motor 200 continues to rotate under the action of the moment of inertia, and at the same time, the hydraulic motor 200 drives the hydraulic oil to continuously flow from the second motor working oil port C2 to the first motor working oil port C1. However, at this time, the hydraulic system has stopped supplying oil to the hydraulic motor 200 through the oil inlet P of the main reversing valve 300, in order to prevent the hydraulic motor 200 from being sucked empty, the oil supplement pipeline can be opened, and the hydraulic oil is supplied to the second motor working oil port C2 of the hydraulic motor 200 through the right sub-oil supplement pipeline 520.

[0053] At this time, since the oil return of the hydraulic motor 200 cannot return from the oil return port T of the main reversing valve 300, the pressure on the oil return side increases. Since the opening pressure of the first two-stage pressure boosting overflow valve 110 is the second opening pressure, the second opening pressure is low, so the hydraulic oil pushes open the first two-stage pressure boosting overflow valve 110 to unload and release pressure, so that the hydraulic motor 200 can be braked smoothly under low oil pressure.

[0054] In the prior art, since the opening pressure of the overflow valve on the oil return side is large, the pressure on the oil return side is high, and the hydraulic motor 200 is forced to stop, which causes the hydraulic motor 200 to be subjected to large hydraulic impact. The rotary hydraulic system provided by the present application can reduce the oil pressure on the oil return side and achieve smooth braking.

[0055] The above is the working condition of driving the hydraulic motor 200 to start and brake when the main reversing valve 300 is located at the right position, and similarly, when the reversing valve is located at the left position, the hydraulic motor 200 can be driven to reverse, and the working principle is the same, so this place will not be described in detail.

[0056] The present invention also provides a slewing device, which can be an excavator slewing device, a crane slewing device, an aerial work platform slewing device, a robot arm slewing device, and an agricultural and forestry machinery slewing device, etc. Since they are all equipped with the slewing hydraulic system described above, they have the same advantages as those described above.

[0057] The present invention also provides a working machine, which can be an excavator, crane, aerial work platform, robot, agricultural and forestry machinery, etc., with a slewing device. Since they all have the slewing hydraulic system or slewing device as described above, they have the same advantages as described above.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A rotary hydraulic system, characterized in that, include: Hydraulic motor; The main directional valve has two working ports that are connected one-to-one with the two motor working ports of the hydraulic motor. A rotary buffer valve, comprising two secondary pressure-boosting relief valves, wherein the oil inlets of the two secondary pressure-boosting relief valves are respectively connected to two hydraulic oil lines between the main directional valve and the hydraulic motor; A pilot oil line is connected to the hydraulic control ports of the two secondary booster relief valves respectively. The main directional valve is a hydraulically controlled directional valve, and the pilot oil line is connected to the two hydraulic control ports of the main directional valve respectively. When the overflow valve's hydraulic control port is connected to the pilot oil line, the opening pressure of the corresponding secondary booster overflow valve is the first opening pressure. When the overflow valve's hydraulic control port is disconnected from the pilot oil line, the opening pressure of the corresponding secondary booster overflow valve is the second opening pressure. The first opening pressure is greater than the second opening pressure. The first opening pressure is used to start the hydraulic motor, and the second opening pressure is used to brake the hydraulic motor.

2. The rotary hydraulic system according to claim 1, characterized in that, The pilot oil line includes: Two directional valves, each of which is provided with a pilot oil inlet, a pilot oil return port and a pilot oil outlet; A pilot oil inlet line is connected to the pilot oil inlet ports of the two directional valves respectively; Pilot oil return line, wherein the pilot oil return line is connected to the pilot oil return port of each of the two directional valves; The pilot oil outlet pipeline connects the pilot oil outlet ports of the two directional valves to the hydraulic control ports of the two secondary booster relief valves in a one-to-one correspondence.

3. The rotary hydraulic system according to claim 2, characterized in that, The two pilot oil outlet lines are connected one-to-one with the two hydraulic control ports of the main directional valve.

4. The rotary hydraulic system according to claim 3, characterized in that, The main directional valve is a three-position four-way directional valve. When the three-position four-way directional valve is in the first working position and the second working position, the oil supply direction of the three-position four-way directional valve is reversed. When the three-position four-way directional valve is in the third working position, both the oil supply and return are cut off.

5. The rotary hydraulic system according to claim 1, characterized in that, It also includes an oil replenishment line, the two oil outlets of which are respectively connected to the two motor working oil ports of the hydraulic motor, and the oil replenishment line can selectively replenish oil to one of the motor working oil ports of the hydraulic motor.

6. The rotary hydraulic system according to claim 5, characterized in that, The replenishment pipeline includes: The main oil supply pipe has its inlet end connected to the hydraulic oil source; Two sub-oil supply pipes are provided, with the inlet ends of both sub-oil supply pipes connected to the outlet end of the main oil supply pipe. The outlet ends of the two sub-oil supply pipes are respectively connected to the two working oil ports of the hydraulic motor. Each sub-oil supply pipe is connected to a one-way valve, with the flow direction of the one-way valve from the inlet end of the sub-oil supply pipe to the outlet end.

7. The rotary hydraulic system according to claim 1, characterized in that, The hydraulic motor is provided with at least two, and the hydraulic motors are connected in parallel.

8. A rotary device, characterized in that, Includes the rotary hydraulic system as described in any one of claims 1 to 7.

9. A type of operating machinery, characterized in that, It includes the rotary hydraulic system as described in any one of claims 1 to 7 or the rotary device as described in claim 8.

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