A hydraulic excavator spill control system and method

Abstract

The application provides a hydraulic excavator overflow pressure grading control system and method, which comprises a primary connection, a plurality of working connections connected with the primary connection, and feedback oil paths connected with the working connections respectively; one end of the high-pressure feedback oil path is communicated with the oil inlet of the high-pressure overflow valve and the oil pressure feedback port of at least one working connection of the plurality of working connections, and the other end is communicated with the oil pressure feedback port of the pump; one end of the low-pressure feedback oil path is communicated with the oil inlet of the low-pressure overflow valve and the oil pressure feedback port of the other working connection of the plurality of working connections, and the other end is communicated with the high-pressure feedback oil path through a pressure boosting valve; the pressure boosting valve can be switched to a state of bidirectional conduction of the first oil port and the second oil port or a state of unidirectional conduction of the first oil port to the second oil port. The system can improve the overflow pressure of part of actions during the operation of the excavator, so that the higher load operation requirement of part of actions can be met without affecting the working pressure of other actions.

Description

Technical Field

[0001] This invention belongs to the field of hydraulic technology, specifically relating to a hydraulic excavator overflow pressure graded control system and method. Background Technology

[0002] Excavator overflow pressure: To protect the excavator's hydraulic system and prevent damage to pipelines, pumps, or actuators due to overpressure, the overflow valve opens and releases excess hydraulic oil when the system reaches its maximum working pressure.

[0003] like Figure 1 As shown, in the existing technology of excavator load-sensitive hydraulic systems, an LS relief valve with a fixed pressure value is integrated on a multi-way valve as a device to limit the maximum working pressure of the hydraulic system, that is, the maximum allowable load pressure is the same for all operating conditions of the excavator.

[0004] However, excavators operate under complex conditions and face varying loads. A single, fixed LS relief valve setting to limit the maximum operating pressure of the entire system cannot meet the operational needs of diverse load conditions. While the LS relief valve's operating pressure setting is sufficient for most actions to overcome load requirements during excavator operation, certain actions require a higher LS relief valve operating pressure setting to overcome the load. Current solutions can only achieve this by increasing the LS relief valve setting, thus increasing the operating pressure of all actions.

[0005] Such a technical solution increases the working pressure of the entire system to meet the pressure requirements of a certain working condition. This not only creates pressure redundancy in low-load pressure demand conditions, but also increases the pressure resistance of low-load pressure hydraulic components, resulting in increased costs. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a hydraulic excavator overflow pressure graded control system and method, which can increase the overflow pressure of some actions during excavator operation, so as to meet the higher load construction operation requirements of some actions without affecting the working pressure of other actions.

[0007] To achieve the above objectives / to solve the above technical problems, the present invention is implemented using the following technical solution:

[0008] In a first aspect, the present invention provides a hydraulic excavator overflow pressure graded control system, comprising: a primary link, a plurality of working links connected to the primary link, and feedback oil circuits respectively connected to each working link.

[0009] The feedback oil circuit can select the oil pressure feedback port of the pump that is subject to the highest feedback pressure in the connected working circuit, so that the pump outputs the required flow rate of the system.

[0010] The working link can be connected to the actuator to drive the actuator to move.

[0011] The first section is equipped with a high-pressure relief valve, a low-pressure relief valve, and a pressure boosting valve.

[0012] The set pressure of the high-pressure relief valve is higher than that of the low-pressure relief valve.

[0013] The feedback oil circuit includes a low-pressure feedback oil circuit and a high-pressure feedback oil circuit.

[0014] One end of the high-pressure feedback oil circuit is connected to the oil inlet of the high-pressure relief valve and the oil pressure feedback port of at least one of the multiple working connections, and the other end is connected to the oil pressure feedback port of the pump.

[0015] One end of the low-pressure feedback oil circuit is connected to the oil inlet of the low-pressure relief valve and the oil pressure feedback port of other working connections in the multiple working connections, and the other end is connected to the high-pressure feedback oil circuit through a pressure boosting valve.

[0016] The pressure boosting valve is provided with a first oil port and a second oil port.

[0017] The first oil port of the pressure boosting valve is connected to the oil inlet of the low-pressure relief valve and the low-pressure feedback oil circuit, respectively.

[0018] The second oil port of the pressure boosting valve is connected to the oil inlet of the high-pressure relief valve and the high-pressure feedback oil circuit, respectively.

[0019] The pressure boosting valve can be switched to a state where the first oil port and the second oil port are bidirectionally connected, or a state where the first oil port is unidirectionally connected to the second oil port.

[0020] The above settings produce the following effect: When the pressure boosting valve is switched to a bidirectional state between the first and second oil ports, the oil can be bidirectionally connected between the high-pressure feedback oil circuit and the low-pressure feedback oil circuit. At this time, if one or more actuators operate, the high-pressure feedback oil circuit and the low-pressure feedback oil circuit select the highest feedback pressure in the working connection to act on the pump's oil pressure feedback port, so that the pump outputs the flow required by the system. At the same time, since the high-pressure feedback oil circuit and the low-pressure feedback oil circuit are connected to the inlet ports of the low-pressure relief valve and the high-pressure relief valve, the highest feedback pressure of both the high-pressure feedback oil circuit and the low-pressure feedback oil circuit is determined by the low-pressure relief valve, that is, the highest working pressure of the system is determined by the low-pressure relief valve.

[0021] When the first port is unidirectionally connected to the second port, the oil can only flow unidirectionally from the low-pressure feedback circuit to the high-pressure feedback circuit. At this time, if one or more actuators operate, the feedback circuit selects the highest feedback pressure to act on the pump, causing the pump to output the required flow rate of the system. Meanwhile, due to the presence of the check valve in the pressure boosting valve, the high-pressure feedback circuit is only connected to the inlet of the high-pressure relief valve. At this time, the highest feedback pressure of the high-pressure feedback circuit is determined by the high-pressure relief valve, which means that the highest working pressure of the working link connected to the high-pressure feedback circuit is determined by the high-pressure relief valve. On the other hand, the low-pressure feedback circuit is connected to both the inlet of the low-pressure relief valve and the inlet of the high-pressure relief valve. At this time, the highest feedback pressure of the low-pressure feedback circuit is determined by the low-pressure relief valve, which means that the highest working pressure of the working link connected to the low-pressure feedback circuit is determined by the low-pressure relief valve.

[0022] Furthermore, the maximum operating pressure of the working link connected to the high-pressure feedback oil circuit is higher than that of the working link connected to the low-pressure feedback oil circuit.

[0023] The effects of the above settings are as follows: Since high-pressure components are more expensive than low-pressure components and are used less frequently, it is only necessary to set the maximum working pressure of the working link connected to the high-pressure feedback oil circuit to that of the high-pressure component. This can effectively reduce costs, increase load levels, and at the same time reduce the use of high-pressure relief valves and high-pressure working links, thus reducing costs.

[0024] Furthermore, the system also includes a pump, an oil inlet circuit, and an oil return circuit.

[0025] The oil inlet end of the oil inlet circuit is connected to the oil outlet of the pump, and the oil outlet end of the oil inlet circuit is connected to the oil inlet of each working link. The oil outlet of each working link is connected to the oil return circuit.

[0026] The low-pressure relief valve outlet is connected to the return oil circuit. The high-pressure relief valve outlet is connected to the return oil circuit.

[0027] Furthermore, the working link includes a first working link, a second working link, a third working link, and a fourth working link.

[0028] Both the first working link and the second working link are connected to the high-pressure feedback oil circuit.

[0029] Both the third and fourth working connections are connected to the low-pressure feedback oil circuit.

[0030] Furthermore, the system also includes a controller connected to the control terminal of the pressure boosting valve. The controller is used to send control signals to the pressure boosting valve.

[0031] The above settings produce the following effect: Through an external controller, the automatic switching of the feedback oil circuit inside the system can be realized, thereby realizing the change of oil circuit overflow pressure.

[0032] Furthermore, the system also includes a high-pressure sensor connected to the high-pressure feedback oil circuit.

[0033] The high-pressure sensor is connected to the controller signal and is used to collect the high-pressure feedback oil circuit pressure in real time and feed it back to the controller.

[0034] The controller compares the pressure of the high-pressure feedback oil circuit with the preset low-pressure relief valve setting pressure.

[0035] If the pressure in the high-pressure feedback oil circuit is less than or equal to the preset low-pressure relief valve setting pressure, the controller controls the pressure boosting valve to switch to a bidirectional state between the first and second oil ports.

[0036] If the pressure in the high-pressure feedback oil circuit is greater than the preset low-pressure relief valve setting pressure, the controller controls the pressure boosting valve to switch to a state where the first oil port unidirectionally connects to the second oil port.

[0037] Furthermore, the system also includes a low-pressure sensor. The low-pressure sensor is used to acquire the pilot control pressure of the working link connected to the high-pressure feedback oil circuit and transmit it to the controller.

[0038] The controller compares the pilot control pressure of the working link connected to the high-pressure feedback oil circuit with the set pilot pressure.

[0039] If the pilot control pressure of the working link connected to the high-pressure feedback oil circuit is less than or equal to the set pilot pressure, the controller controls the pressure boosting valve to switch to a bidirectional state between the first and second oil ports.

[0040] If the pilot control pressure of the working link connected to the high-pressure feedback oil circuit is greater than the set pilot pressure, the controller controls the pressure boosting valve to switch to the state where the first oil port unidirectionally connects to the second oil port.

[0041] Furthermore, the pressure boosting valve is a two-position two-way valve with electromagnetic two-position two-way function.

[0042] When the two-position two-way valve is in the first position, the first oil port and the second oil port are bidirectionally connected, and the low-pressure feedback oil circuit and the high-pressure feedback oil circuit are bidirectionally connected.

[0043] When the two-position two-way valve is in the second position, the first oil port is unidirectionally connected to the second oil port, and the low-pressure feedback oil circuit and the high-pressure feedback oil circuit are unidirectionally connected.

[0044] Furthermore, the pressure boosting valve is bidirectionally oriented when in the right position and unidirectionally oriented when in the left position.

[0045] Furthermore, the controller can control the pressure boosting valve to be energized or de-energized.

[0046] When the pressure boosting valve is de-energized, the pressure boosting valve is in the first position.

[0047] When the pressure boosting valve is energized, it is in the second position.

[0048] In a second aspect, the present invention provides a method for graded control of overflow pressure in a hydraulic excavator, based on the graded control system for overflow pressure in a hydraulic excavator described in the first aspect, comprising the following steps:

[0049] Obtain the pressure of the high-pressure feedback oil circuit.

[0050] The pressure in the high-pressure feedback oil circuit is compared with the preset pressure of the low-pressure relief valve.

[0051] If the pressure in the high-pressure feedback oil circuit is less than or equal to the preset low-pressure relief valve setting pressure, the control pressure boosting valve switches to a bidirectional state between the first and second oil ports.

[0052] If the pressure in the high-pressure feedback oil circuit is greater than the preset low-pressure relief valve setting pressure, the control pressure boosting valve switches to a state where the first oil port unidirectionally connects to the second oil port.

[0053] Furthermore, the method also includes:

[0054] Obtain the pilot control pressure of the working link connected to the high-pressure feedback oil circuit.

[0055] The pilot control pressure of the working link connected to the high-pressure feedback oil circuit is compared with the set pilot pressure.

[0056] If the pilot control pressure of the working link connected to the high-pressure feedback oil circuit is less than or equal to the set pilot pressure, the control pressure boosting valve switches to a bidirectional state between the first and second oil ports.

[0057] If the pilot control pressure of the working link connected to the high-pressure feedback oil circuit is greater than the set pilot pressure, the control pressure boosting valve switches to a state where the first oil port unidirectionally connects to the second oil port.

[0058] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: (1) By setting the overflow pressure in stages in a hydraulic system, the construction conditions can be better met according to the pressure required by the load, thus solving the problem of poor adaptability to a single load.

[0059] (2) Example: In existing excavator hydraulic systems, increasing travel traction is often achieved by increasing system pressure. However, increasing system pressure will also increase the working pressure of other actions besides travel, requiring re-verification of the pressure resistance values ​​of other actuators, which may increase costs. With this technical solution, a high-pressure relief valve is used to limit travel conditions, and a low-pressure relief valve is used to limit other conditions. This allows for the increase of travel traction without affecting the use of other actions. Attached Figure Description

[0060] Figure 1 This is a schematic diagram of the existing technology.

[0061] Figure 2 This is a schematic diagram of one structure of the present invention.

[0062] Figure 3 This is another structural schematic diagram of the present invention.

[0063] Figure 4 This is a schematic diagram of a control system according to the present invention.

[0064] Figure 5 This is a flowchart of a control method according to the present invention.

[0065] Figure 6 This is a schematic diagram of the structure of the low-pressure sensor of the present invention.

[0066] Figure 7 This is a schematic diagram of another control system of the present invention.

[0067] Figure 8 This is a flowchart of another control method of the present invention.

[0068] In the diagram: 1. Oil inlet circuit. 2. High-pressure feedback circuit. 3. Low-pressure feedback circuit. 4. Oil return circuit. 5. Pressure boosting valve. 6. High-pressure relief valve. 7. Low-pressure relief valve. 8. First working connection. 9. Second working connection. 10. Third working connection. 11. Fourth working connection. 12. High-pressure sensor. 13. Low-pressure sensor. Detailed Implementation

[0069] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0070] In the description of this embodiment, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this embodiment and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this embodiment.

[0071] Example 1: like Figure 2 As shown, this embodiment provides a hydraulic excavator overflow pressure graded control system, including: a primary link, multiple working links connected to the primary link, and feedback oil circuits connected to each working link respectively.

[0072] The feedback oil circuit can select the oil pressure feedback port of the pump that is subject to the highest feedback pressure in the connected working circuit, so that the pump outputs the required flow rate of the system.

[0073] The work link can connect to the actuator and drive the actuator to move.

[0074] The first section is equipped with a high-pressure relief valve 6, a low-pressure relief valve 7, and a pressure boosting valve 5.

[0075] The set pressure of the high-pressure relief valve 6 is higher than that of the low-pressure relief valve 7.

[0076] The feedback oil circuit includes low-pressure feedback oil circuit 3 and high-pressure feedback oil circuit 2.

[0077] One end of the high-pressure feedback oil circuit 2 is connected to the oil inlet of the high-pressure relief valve 6 and the oil pressure feedback port of at least one of the multiple working connections, and the other end is connected to the oil pressure feedback port of the pump.

[0078] One end of the low-pressure feedback oil circuit 3 is connected to the oil inlet of the low-pressure relief valve 7 and the oil pressure feedback port of other working connections in multiple working connections, and the other end is connected to the high-pressure feedback oil circuit 2 through the pressure boosting valve 5.

[0079] The pressure boosting valve 5 is equipped with a first oil port and a second oil port.

[0080] The first oil port of the pressure boosting valve 5 is connected to the oil inlet of the low-pressure relief valve 7 and the low-pressure feedback oil circuit 3, respectively.

[0081] The second oil port of the pressure boosting valve 5 is connected to the oil inlet of the high pressure relief valve 6 and the high pressure feedback oil circuit 2, respectively.

[0082] The pressure boosting valve 5 can be switched to a state where the first oil port and the second oil port are bidirectionally connected, or a state where the first oil port is unidirectionally connected to the second oil port.

[0083] Implementation Principle: Generally, the maximum operating pressure of the working link connected to the high-pressure feedback oil circuit 2 is higher than that of the working link connected to the low-pressure feedback oil circuit 3. Since high-pressure components are more expensive and used less frequently than low-pressure components, it is sufficient to set the maximum operating pressure of the working link connected to the high-pressure feedback oil circuit to that of a high-pressure component. This effectively reduces costs, increases load capacity, and reduces the use of the high-pressure relief valve 6 and the high-pressure working link, further lowering costs.

[0084] When the pressure boosting valve 5 is switched to a bidirectional state between the first and second oil ports, the oil can be bidirectionally connected between the high-pressure feedback oil circuit 2 and the low-pressure feedback oil circuit 3. At this time, if one or more actuators operate, the high-pressure feedback oil circuit 2 and the low-pressure feedback oil circuit 3 select the highest feedback pressure in the working connection to act on the pump's oil pressure feedback port, so that the pump outputs the flow required by the system. At the same time, since the high-pressure feedback oil circuit 2 and the low-pressure feedback oil circuit 3 are connected to the inlet of the low-pressure relief valve 7 and the inlet of the high-pressure relief valve 6, the highest feedback pressure of both the high-pressure feedback oil circuit 2 and the low-pressure feedback oil circuit 3 is determined by the low-pressure relief valve 7, that is, the highest working pressure of the system is determined by the low-pressure relief valve 7.

[0085] When the first oil port is unidirectionally connected to the second oil port, the oil can only flow unidirectionally from the low-pressure feedback oil circuit 3 to the high-pressure feedback oil circuit 2. At this time, if one or more actuators operate, the feedback oil circuit selects the highest feedback pressure to act on the pump, so that the pump outputs the flow required by the system. At the same time, due to the presence of the check valve in the pressure boosting valve 5, the high-pressure feedback oil circuit 2 is only connected to the oil inlet of the high-pressure relief valve 6. At this time, the highest feedback pressure of the high-pressure feedback oil circuit 2 is determined by the high-pressure relief valve 6, that is, the highest working pressure of the working link connected to the high-pressure feedback oil circuit 2 is determined by the high-pressure relief valve 6. Meanwhile, the low-pressure feedback oil circuit 3 is connected to both the oil inlet of the low-pressure relief valve 7 and the oil inlet of the high-pressure relief valve 6. At this time, the highest feedback pressure of the low-pressure feedback oil circuit 3 is determined by the low-pressure relief valve 7, that is, the highest working pressure of the working link connected to the low-pressure feedback oil circuit 3 is determined by the low-pressure relief valve 7.

[0086] Example 2: This embodiment provides a hydraulic excavator overflow pressure graded control system. Using this overflow pressure graded control system, the overflow pressure of some actions can be increased during excavator operation, so as to meet the higher load construction operation requirements of some actions without affecting the working pressure of other actions.

[0087] refer to Figure 2 The present invention provides a hydraulic excavator overflow pressure graded control system, including: a pump, an oil inlet circuit 1, an oil return circuit 4, a primary connection, multiple working connections connected to the primary connection, and feedback circuits connected to each working connection respectively.

[0088] The inlet end of oil inlet circuit 1 is connected to the outlet of the pump, and the outlet end of oil inlet circuit 1 is connected to the inlet of each working link. The outlet of the working link is connected to the return oil circuit 4.

[0089] The outlet of the low-pressure relief valve 7 is connected to the return oil circuit 4. The outlet of the high-pressure relief valve 6 is connected to the return oil circuit 4.

[0090] The feedback oil circuit can select the oil pressure feedback port of the pump that is subject to the highest feedback pressure in the connected working circuit, so that the pump outputs the required flow rate of the system.

[0091] The work link can connect to the actuator and drive the actuator to move.

[0092] The first section is equipped with a high-pressure relief valve 6, a low-pressure relief valve 7, and a pressure boosting valve 5.

[0093] The set pressure of the high-pressure relief valve 6 is higher than that of the low-pressure relief valve 7.

[0094] The feedback oil circuit includes low-pressure feedback oil circuit 3 and high-pressure feedback oil circuit 2.

[0095] One end of the high-pressure feedback oil circuit 2 is connected to the oil inlet of the high-pressure relief valve 6 and the oil pressure feedback port of at least one of the multiple working connections, and the other end is connected to the oil pressure feedback port of the pump.

[0096] One end of the low-pressure feedback oil circuit 3 is connected to the oil inlet of the low-pressure relief valve 7 and the oil pressure feedback port of other working connections in multiple working connections, and the other end is connected to the high-pressure feedback oil circuit 2 through the pressure boosting valve 5.

[0097] The pressure boosting valve 5 is equipped with a first oil port and a second oil port.

[0098] The first oil port of the pressure boosting valve 5 is connected to the oil inlet of the low-pressure relief valve 7 and the low-pressure feedback oil circuit 3, respectively.

[0099] The second oil port of the pressure boosting valve 5 is connected to the oil inlet of the high pressure relief valve 6 and the high pressure feedback oil circuit 2, respectively.

[0100] The pressure boosting valve 5 can be switched to a state where the first oil port and the second oil port are bidirectionally connected, or a state where the first oil port is unidirectionally connected to the second oil port.

[0101] The maximum working pressure of the working link connected to the high-pressure feedback oil circuit 2 is higher than the maximum working pressure of the working link connected to the low-pressure feedback oil circuit 3.

[0102] Since high-pressure components are more expensive than low-pressure components and are used less frequently, it is only necessary to set the maximum working pressure of the working link connected to the high-pressure feedback oil circuit 2 to that of the high-pressure component. This can effectively reduce costs and increase the load level.

[0103] The system also includes a pump, an oil inlet circuit 1, and an oil return circuit 4.

[0104] The inlet end of oil inlet circuit 1 is connected to the outlet of the pump, and the outlet end of oil inlet circuit 1 is connected to the inlet of each working link. The outlet of the working link is connected to the return oil circuit 4.

[0105] The outlet of the low-pressure relief valve 7 is connected to the return oil circuit 4. The outlet of the high-pressure relief valve 6 is connected to the return oil circuit 4.

[0106] like Figure 2 and Figure 3 As shown, the working connections include a first working connection 8, a second working connection 9, a third working connection 10, and a fourth working connection 11. Both the first working connection 8 and the second working connection 9 are connected to the high-pressure feedback oil circuit 2. Both the third working connection 10 and the fourth working connection 11 are connected to the low-pressure feedback oil circuit 3.

[0107] The system also includes a controller connected to the control terminal of the pressure boosting valve 5. The controller is used to send control signals to the pressure boosting valve 5. Through the external controller, the automatic switching of the feedback oil circuit within the system can be realized, thereby achieving changes in the overflow pressure of the oil circuit.

[0108] This invention provides two types of relief valves: a high-pressure relief valve 6 and a low-pressure relief valve 7. The high-pressure relief valve 6 has a high set pressure rating. The low-pressure relief valve 7 has a low pressure rating.

[0109] Since the load-sensitive multi-way valve provided by the present invention includes a high-pressure feedback oil circuit 2 and a low-pressure feedback oil circuit 3, the feedback pressure of the first working link 8 and the second working link 9 acts on the pump through the high-pressure feedback oil circuit 2, and the feedback pressure of the third working link 10 and the fourth working link 11 acts on the pump through the low-pressure feedback oil circuit 3 via the electromagnetic pressure boosting valve 5.

[0110] Therefore, when the pressure boosting valve 5 is in the right position, the oil can be bidirectionally connected between the high-pressure feedback oil circuit 2 and the low-pressure feedback oil circuit 3. At this time, if one or more actuators are activated, the feedback oil circuit selects the highest feedback pressure in the working connection to act on the pump, so that the pump outputs the flow required by the system. At the same time, since the high-pressure feedback oil circuit 2 and the low-pressure feedback oil circuit 3 are connected to the inlet of the low-pressure relief valve 7 and the inlet of the high-pressure relief valve 6, the highest feedback pressure of both the high-pressure feedback oil circuit 2 and the low-pressure feedback oil circuit 3 is determined by the low-pressure relief valve 7. That is, the highest working pressure of the system is determined by the low-pressure relief valve 7.

[0111] When the pressure boosting valve 5 is in the left position, the oil can only flow unidirectionally from the low-pressure feedback oil circuit 3 to the high-pressure feedback oil circuit 2. At this time, if one or more actuators are activated, the feedback oil circuit selects the highest feedback pressure to act on the pump, so that the pump outputs the flow required by the system. At the same time, due to the presence of the check valve in the pressure boosting valve 5, the high-pressure feedback oil circuit 2 is only connected to the inlet of the high-pressure relief valve 6. At this time, the highest feedback pressure of the high-pressure feedback oil circuit 2 is determined by the high-pressure relief valve 6, that is, the highest working pressure of the first working link 8 and the second working link 9 is determined by the high-pressure relief valve 6. In addition, the low-pressure feedback oil circuit 3 is connected to both the inlet of the low-pressure relief valve 7 and the inlet of the high-pressure relief valve 6. At this time, the highest feedback pressure of the low-pressure feedback oil circuit 3 is determined by the low-pressure relief valve 7, that is, the highest working pressure of the third working link 10 and the fourth working link 11 is determined by the low-pressure relief valve 7.

[0112] refer to Figure 3 The hydraulic excavator overflow pressure graded control system and method provided by this technical solution can also automatically identify the action pressure. To achieve the above objectives, the present invention can also provide the following technical solutions:

[0113] like Figure 4 As shown, this embodiment also provides a controller, which is used to send a control signal to the control terminal of the pressure boosting valve 5 to control the pressure boosting valve 5 to be in the left or right position, so that the high pressure feedback oil circuit 2 and the low pressure feedback oil circuit 3 are unidirectionally or bidirectionally connected.

[0114] Preferably, the pressure boosting valve 5 is a two-position, two-way valve with electromagnetic two-position, two-way function. When the valve is in the first position, the first port and the second port are bidirectionally connected, and the low-pressure feedback oil circuit 3 and the high-pressure feedback oil circuit 2 are bidirectionally connected. When the valve is in the second position, the first port is unidirectionally connected to the second port, and the low-pressure feedback oil circuit 3 and the high-pressure feedback oil circuit 2 are unidirectionally connected. The pressure boosting valve 5 is bidirectionally connected when in the right position and unidirectionally connected when in the left position.

[0115] The controller can control the energization or de-energization of pressure boosting valve 5. When pressure boosting valve 5 is de-energized, it is in the first position. When pressure boosting valve 5 is energized, it is in the second position.

[0116] like Figure 5 As shown, this embodiment also provides an automatic identification and control method for graded overflow pressure in a hydraulic excavator, applied to the controller of a graded overflow pressure control system for a hydraulic excavator. The method includes: in automatic identification mode, determining whether the pressure in the pressure feedback oil circuit exceeds the pressure setting value in the controller program; if so, outputting a signal to the pressure boosting valve 5, causing the pressure boosting valve 5 to be in the left position, thus implementing the content of the previous solution. If not, the pressure boosting valve 5 is in the right position.

[0117] The key to this technical solution is to control the maximum working pressure of a certain load independently from the working pressure limit of the entire hydraulic system.

[0118] This system is equipped with a high-pressure sensor 12. The high-pressure sensor 12 is connected to the controller signal and is used to collect the pressure of the high-pressure feedback oil circuit 2 in real time and feed it back to the controller. The controller compares the pressure of the high-pressure feedback oil circuit 2 with the preset pressure set by the low-pressure relief valve 7. If the pressure of the high-pressure feedback oil circuit 2 is less than or equal to the preset pressure set by the low-pressure relief valve 7, the controller controls the pressure boosting valve 5 to switch to a bidirectional flow state between the first and second oil ports. If the pressure of the high-pressure feedback oil circuit 2 is greater than the preset pressure set by the low-pressure relief valve 7, the controller controls the pressure boosting valve 5 to switch to a unidirectional flow state between the first and second oil ports.

[0119] Since the load-sensitive multi-way valve provided by the present invention includes a high-pressure feedback oil circuit 2 and a low-pressure feedback oil circuit 3, the feedback pressure of the first working link 8 and the second working link 9 acts on the pump through the high-pressure feedback oil circuit 2, and the feedback pressure of the third working link 10 and the fourth working link 11 acts on the pump through the low-pressure feedback oil circuit 3 via the electromagnetic pressure boosting valve 5.

[0120] refer to Figure 6 , Figure 7 The present invention also provides a low-pressure sensor 13, which is connected to the pilot control oil circuit of the first working link 8 and the second working link 9.

[0121] refer to Figure 8 The present invention also provides a control program for a controller, wherein the control program determines the output of a control signal by comparing the set pressure of the program with the pilot control pressure of the first working link 8 and the second working link 9.

[0122] The low-pressure sensor 13 is used to acquire the pilot control pressure of the working link connected to the high-pressure feedback oil circuit 2 and transmit it to the controller. The controller compares the pilot control pressure of the working link connected to the high-pressure feedback oil circuit 2 with the set pilot pressure. If the pilot control pressure of the working link connected to the high-pressure feedback oil circuit 2 is less than or equal to the set pilot pressure, the controller controls the pressure boost valve 5 to switch to a bidirectional state where the first port and the second port are open. If the pilot control pressure of the working link connected to the high-pressure feedback oil circuit 2 is greater than the set pilot pressure, the controller controls the pressure boost valve 5 to switch to a unidirectional state where the first port is open to the second port.

[0123] The low-pressure sensor continuously collects the pilot control pressure of the first working link 8 and the second working link 9 and feeds it back to the controller.

[0124] When the control program determines that the pilot control pressure of the first working link 8 and the second working link 9 is less than the program-set pressure, it does not output a control signal to the pressure boosting valve 5, the pressure boosting valve 5 is de-energized, and the low-pressure feedback oil circuit 3 and the high-pressure feedback oil circuit 2 are bidirectionally connected.

[0125] When the control program determines that the pilot control pressure of the first working link 8 and the second working link 9 is greater than the program-set pressure, it outputs a control signal to the pressure boosting valve 5, which is energized, and the low-pressure feedback oil circuit 3 and the high-pressure feedback oil circuit 2 are unidirectionally connected.

[0126] By setting the overflow pressure in stages in a hydraulic system, the construction conditions can be better met according to the pressure required by the load, thus solving the problem of poor adaptability to a single load.

[0127] In existing excavator hydraulic systems, increasing travel traction is often achieved by increasing system pressure. However, increasing system pressure also increases the working pressure of other actions besides travel, requiring recalibration of the pressure resistance values ​​of other actuators, potentially leading to increased costs. This technical solution uses a high-pressure relief valve 6 to limit travel conditions and a low-pressure relief valve 7 to limit other conditions, allowing for increased travel traction without affecting other actions.

[0128] Example 3: This embodiment provides a graded control method for overflow pressure in a hydraulic excavator, based on the graded control system for overflow pressure in a hydraulic excavator described in Embodiment 2. The core objective of this method is:

[0129] Based on the actual working conditions of the excavator (mainly the intensity of operation of the high-pressure hydraulic circuit), the system intelligently switches the overflow pressure level (low-pressure mode / high-pressure mode) to achieve the following:

[0130] 1. Energy saving and consumption reduction: In low-pressure mode (such as fine control, light load operation), a lower overflow pressure is used, which significantly reduces the pump's output pressure and flow demand, reduces overflow loss and throttling loss, and reduces oil consumption.

[0131] 2. Enhanced performance: Provides higher overflow pressure in high-pressure modes (such as heavy digging and high-load operation) to ensure that high-load actuators can output sufficient force and speed.

[0132] 3. Protective components: Protect hydraulic pumps, valve assemblies, and actuators from excessive pressure shocks by precisely controlling the maximum working pressure.

[0133] The specific method steps in this embodiment include:

[0134] Step 1. System Initialization and Parameter Setting:

[0135] The controller is powered on or started.

[0136] Load preset parameters:

[0137] P1: The set pressure value of the low-pressure overflow valve 7.

[0138] P_high_set: The set pressure value of the high-pressure overflow valve 6.

[0139] P3: The pilot pressure setting threshold for the high-pressure working connection to trigger the high-pressure mode. This value needs to be calibrated according to the characteristics of the operating handle, system response, and operating habits.

[0140] Initialize the state of the pressure boosting valve 5 (usually initialized to the bidirectional conduction state - low-pressure mode).

[0141] Step 2. Real-time data acquisition:

[0142] As Figure 3 shown, collect the pressure (P2) of the high-pressure feedback oil circuit 2: Read the pressure value in real time through the high-pressure pressure sensor 12 installed on the high-pressure feedback oil circuit 2 (for example, located before the high-pressure feedback oil circuit 2 enters the pump feedback port or near the inlet of the high-pressure overflow valve 6).

[0143] Or, as Figure 6 shown, collect the high-pressure working connection pilot control pressure (P4) through the low-pressure pressure sensor 13: Read the operating handle input pressure of this working connection in real time through the pressure sensor installed on the pilot control oil circuit connected to the main spool of the high-pressure working connection. This pressure directly reflects the operator's operation intention and intensity for this working connection (such as boom lifting, stick digging).

[0144] As Figure 6 shown, the system may have multiple working connections connected to the high-pressure feedback oil circuit 2. Here, the pressure of one key working connection or their maximum value / average value is collected, depending on the design. Usually, the most commonly used or the working connection with the largest load is selected, such as the stick digging connection.

[0145] Step 3. Mode switching logic judgment:

[0146] Based on the collected data, the controller performs the following parallel and prioritized logic judgments, and can select Logic A and / or Logic B:

[0147] Logic A: Based on the pressure (P2) of the high-pressure feedback oil circuit 2:

[0148] Judgment condition A1: P2 < P1 + ΔP1 (ΔP1 is the set small hysteresis interval, such as 0.5 MPa, used to prevent mode jitter caused by frequent pressure fluctuations near the threshold).

[0149] Action A1: If condition A1 holds, control the pressure boosting valve 5 to switch to the state of "bidirectional conduction between the first oil port and the second oil port" (low-pressure mode).

[0150] Judgment condition A2: P2 >= P1 + ΔP1.

[0151] Action A2: If condition A2 holds, control the pressure boosting valve 5 to switch to the state of "unidirectional conduction from the first oil port to the second oil port" (high-pressure mode).

[0152] Design principle: This logic directly monitors the actual load pressure of the high-pressure oil circuit. When the load of the high-pressure oil circuit is very low (not reaching the set value of the low-pressure relief valve 7), the system does not require high-pressure capability and switches to the low-pressure mode for energy conservation. Once the load of the high-pressure oil circuit exceeds the low-pressure setting (even if the opening of the operating handle of the high-pressure working union is not large, but the load itself is large), the system immediately switches to the high-pressure mode to meet the pressure demand.

[0153] Logic B: As Figure 8 shown, based on the pilot control pressure (P4) of the high-pressure working union.

[0154] Judgment condition B1: P4 < P3 + ΔP2 (ΔP2 is the set small hysteresis interval, such as 0.2 MPa).

[0155] Action B1: If condition B1 holds, control the pressure boosting valve 5 to switch to the state of "bidirectional conduction between the first oil port and the second oil port" (low-pressure mode).

[0156] Judgment condition B2: P4 >= P3 + ΔP2.

[0157] Action B2: If condition B2 holds, control the pressure boosting valve 5 to switch to the state of "unidirectional conduction from the first oil port to the second oil port" (high-pressure mode).

[0158] Principle: This logic anticipates the operation intention. When the opening of the operating handle of the high-pressure working union by the operator (reflected as P4) exceeds the set threshold, it means that the operator intends to perform a powerful operation (such as deep digging). The system switches to the high-pressure mode in advance to prepare for the upcoming high load, avoiding the slow response or weakness of the actuator due to the delay in mode switching when the high-pressure demand suddenly appears. Even if P2 may not have increased at this time (because the load has not been established yet), the system is already ready for high-pressure capability.

[0159] Logic priority and integration:

[0160] Logic A and Logic B are in an "or" (OR) relationship. As long as any one of the conditions in Logic A or Logic B requires entering the high-pressure mode (Action A2 or B2), the system must switch to the high-pressure mode.

[0161] The system only switches back to low-voltage mode when both logic A and logic B require entering low-voltage mode (actions A1 and B1 are satisfied simultaneously).

[0162] Design Principles: The design of this invention ensures that:

[0163] When the load pressure is high (logic A is satisfied), the system can provide sufficient pressure regardless of the opening degree of the operating handle (safety and performance take priority).

[0164] When the operator explicitly requests high-pressure operation (logic B is satisfied), the system will provide high-pressure capability in advance (responsiveness and performance take priority), regardless of whether the current load pressure is high.

[0165] Switching to the energy-saving low-voltage mode only occurs when there is no high load demand (P2 low) and the operator has no intention of operating with excessive force (P4 low). This minimizes the "powerless" state of the system in low-voltage mode when high voltage is required.

[0166] Step 4. Pressure boosting valve 5 is controlled and executed:

[0167] Based on the output of the mode switching logic, the controller sends a corresponding control signal (current or switching quantity) to the electromagnet (usually a proportional electromagnet or a switching electromagnet) controlling the pressure boosting valve 5.

[0168] Low-pressure mode command: The control signal drives the valve core of pressure boosting valve 5 to move to the right position of "bidirectional conduction between the first oil port and the second oil port".

[0169] High pressure mode command: The control signal drives the pressure boosting valve 5 valve core to move to the left position of "first oil port unidirectionally opens to second oil port" (the one-way valve function is activated).

[0170] Step 5. System pressure feedback and pump flow control:

[0171] Regardless of the mode, the feedback circuit (including high-pressure feedback circuit 2 and low-pressure feedback circuit 3) always selects the highest load pressure (P_max_demand) among all working couplers through its internal selector valves (such as a shuttle valve network).

[0172] This maximum load pressure P_max_demand is applied to the hydraulic pump's oil pressure feedback port (LS port or similar function port).

[0173] The hydraulic pump (usually a load-sensitive variable pump) automatically adjusts its swashplate angle (displacement) according to P_max_demand, so that its output pressure is higher than P_max_demand by a constant pressure difference (called the pump's pressure difference control value ΔP_pump, usually 1.8-2.5MPa), and outputs a flow rate that meets the flow requirements of all actuators.

[0174] The impact of this mode on overflow protection:

[0175] Low-pressure mode (bidirectional flow): P_max_demand is limited to P1. If the pressure anywhere in the system (maximum load pressure) attempts to exceed P1, the low-pressure relief valve 7 will open to overflow and protect the system.

[0176] High voltage mode (one-way conduction):

[0177] The maximum load pressure (P_high_demand) of the working link connected to high-pressure feedback oil circuit 2 is limited to P_high_set. If P_high_demand attempts to exceed P_high_set, the high-pressure relief valve 6 opens to relieve pressure.

[0178] The maximum load pressure (P_low_demand) of the working link connected to the low-pressure feedback oil circuit 3 is still limited to P1. If P_low_demand attempts to exceed P1, the low-pressure relief valve 7 opens to overflow (because the low-pressure feedback oil circuit 3 is still connected to the inlet of the low-pressure relief valve 7 through the check valve side of the pressure boosting valve 5).

[0179] At this point, P_max_demand may be the maximum value of P_high_demand or P_low_demand, and the pump adjusts the output pressure according to this value (P_pump=P_max_demand+ΔP_pump).

[0180] Step 6. Continuous monitoring and dynamic adjustment:

[0181] The controller executes steps 2 to 5 in a loop (data acquisition -> logic judgment -> valve control), responding in real time to operator input and load changes.

[0182] The setting of the hysteresis interval (ΔP1, ΔP2) effectively avoids frequent mode switching (jitter) caused by small fluctuations in pressure or pilot pressure near the set value, thus improving system stability.

[0183] Explanation of the method and its principles:

[0184] 1. Load Sensitive Basis: The entire control method is based on the load sensitive (LS) system principle. The pump output always tracks the actuator's maximum load demand (P_max_demand) and maintains a constant pressure differential (ΔP_pump), which inherently offers energy-saving advantages (providing only the pressure needed to overcome the load, avoiding the throttling losses of a constant pressure system). This method extends the pressure rating based on this principle.

[0185] 2. The core of the pressure classification - the pressure boosting valve 5 - is the key hub connecting the high and low pressure feedback oil circuits 3 and the relief valve.

[0186] Low-pressure mode (bidirectional conduction): This is equivalent to "short-circuiting" the high-pressure feedback oil circuit 2 to the low-pressure relief valve 7. In this mode, regardless of the working load on the high-pressure feedback oil circuit 2, as long as the system's maximum pressure (P_max_demand) exceeds P1, the low-pressure relief valve 7 will open, preventing further pressure increases. The high-pressure relief valve 6 will not function at this time (because its inlet pressure is also clamped below P1).

[0187] High-pressure mode (one-way flow): Isolates the high-pressure oil circuit: In the one-way flow state (especially the check valve), the oil circuit from the high-pressure feedback oil circuit 2 to the low-pressure relief valve 7 is blocked. The high-pressure feedback oil circuit 2 is only connected to the inlet of the high-pressure relief valve 6.

[0188] Maintaining low-pressure oil circuit protection: Low-pressure feedback oil circuit 3 remains connected to the inlet of low-pressure relief valve 7. The check valve in pressure boosting valve 5 allows oil from the low-pressure oil circuit to flow to the high-pressure oil circuit (when the low-pressure oil circuit pressure is higher, but this is less common in graded systems), but prevents oil from the high-pressure oil circuit from flowing to the low-pressure oil circuit and low-pressure relief valve 7.

[0189] Result: The working link on high-pressure feedback circuit 2 is protected by high-pressure relief valve 6 (P_high_set) and can withstand higher load pressures (for heavy digging). The working link on low-pressure feedback circuit 3 is still protected by low-pressure relief valve 7 (P1) (for fine movements or low-load functions).

[0190] 3. The significance of double-trigger logic:

[0191] Pressure feedback trigger (P2): This is reactive logic. It ensures that when the high-pressure working link encounters a high load, the system can immediately provide sufficient overflow pressure protection and support. This is the last guarantee for system safety and a basic requirement for performance.

[0192] Pilot pressure triggering (P4): This is predictive logic. It switches to high-pressure mode in advance based on the operator's intentions. This brings significant performance improvements:

[0193] Eliminates response delay: This avoids the time required to switch from low-pressure mode to high-pressure mode (valve spool movement, oil circuit pressure build-up). When the operator pushes the handle forcefully for digging, the system is already in a high-pressure state, and the actuator can instantly output maximum force, resulting in a more direct and powerful operating experience.

[0194] Avoid "soft start": If you start operating at high pressure in low-pressure mode without prior warning, the system pressure can only rise to P1 in the initial stage, and the actuator will seem powerless. The power will only come up after the load pressure or logic trigger switches to high-pressure mode. This will lead to inconsistent operation and decreased efficiency.

[0195] The "OR" logic guarantees performance: the system provides high-voltage capacity as long as the load is high or the operational intent is strong. It only enters energy-saving mode when both are low. This prioritizes operational performance to the maximum extent possible.

[0196] 4. Energy saving and cost reduction principle:

[0197] Reduced constant pressure loss: In low-pressure mode, the system's maximum operating pressure (P_max_demand upper limit) is reduced from P_high_set (e.g., 32MPa) to P1 (e.g., 25MPa). According to the hydraulic power formula P_hydraulic=pQ, under the same flow rate (Q), the pump needs to output pressure (p) significantly reduced (pump output pressure P_pump=P_max_demand+ΔP_pump≈P1+ΔP_pump), greatly reducing pump drive power and engine fuel consumption.

[0198] Reduce overflow losses: In low-pressure mode, the overflow valve opens at a lower pressure, consuming less energy during overflow.

[0199] Reduce throttling losses: Although load-sensitive systems have relatively small throttling losses, in cases of complex operations and large load differences, the low-pressure mode limits the maximum pressure requirement of the high-pressure actuator, resulting in a lower overall pump output pressure and a corresponding reduction in pressure drop (throttling loss) through the valve port.

[0200] Since high-pressure components are more expensive than low-pressure components and are used less frequently, it is only necessary to set the maximum working pressure of the working link connected to the high-pressure feedback oil circuit 2 to that of the high-pressure component. This can effectively reduce costs and increase the load level.

[0201] 5. Application scenario examples:

[0202] Low-pressure mode is suitable for: travel, swing, and light-load fine adjustments of boom / stick / bucket (such as leveling, slope repair, and precise lifting), and when a single actuator is in operation and the load is not high.

[0203] High-pressure mode is suitable for: heavy-duty digging (boom digging and bucket digging with high loads), breaker operation, and when the boom or stick needs to quickly and forcefully lift heavy objects. When the operator pushes the digging or lifting handle all the way down (P4>P3), the system will enter high-pressure mode to prepare for high loads, regardless of whether the current load is already high.

[0204] The hydraulic excavator overflow pressure classification control method of this invention cleverly utilizes the pressure boosting valve 5 to switch the connection relationship between the high and low pressure feedback oil circuit 3 and different overflow valves, and combines this with dual monitoring of the actual high-pressure oil circuit load pressure (P2) and the high-pressure working operation intention (P4) (using "OR" logic to trigger the high-pressure mode), thus realizing intelligent classification of the system overflow pressure. It perfectly balances the contradictory demands of energy saving and consumption reduction (low-pressure mode) and high-performance output (high-pressure mode). Its core value lies in:

[0205] Significantly reduces fuel consumption: operates in low-pressure mode during most non-intensive working conditions.

[0206] Enhanced operational performance: Provides maximum hydraulic power instantaneously when needed (anticipated or under high actual load) to ensure digging force, speed, and responsiveness.

[0207] Protect the hydraulic system: Precisely control the maximum working pressure of different circuits.

[0208] Improve system adaptability: better meet the complex and ever-changing working conditions of excavators.

[0209] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature, and in the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0210] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection. They can refer to a mechanical connection or an electrical connection. They can refer to a direct connection or an indirect connection through an intermediate medium, or a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0211] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0212] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0213] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A hydraulic excavator overflow pressure graded control system, characterized in that, include: The first joint, multiple working joints connected to the first joint, and feedback oil circuits connected to each working joint respectively; The feedback oil circuit can select the oil pressure feedback port of the pump that is subject to the highest feedback pressure in the connected working link, so that the pump outputs the flow rate required by the system. The working link can be connected to the actuator to drive the actuator to move; The first section is equipped with a high-pressure relief valve, a low-pressure relief valve, and a pressure boosting valve; The set pressure of the high-pressure relief valve is higher than that of the low-pressure relief valve; The feedback oil circuit includes a low-pressure feedback oil circuit and a high-pressure feedback oil circuit; One end of the high-pressure feedback oil circuit is connected to the oil inlet of the high-pressure overflow valve and the oil pressure feedback port of at least one of the multiple working connections, and the other end is connected to the oil pressure feedback port of the pump. One end of the low-pressure feedback oil circuit is connected to the oil inlet of the low-pressure relief valve and the oil pressure feedback port of other working connections in the multiple working connections, and the other end is connected to the high-pressure feedback oil circuit through the pressure boosting valve. The pressure boosting valve is provided with a first oil port and a second oil port; The first oil port of the pressure boosting valve is connected to the oil inlet of the low-pressure relief valve and the low-pressure feedback oil circuit, respectively. The second oil port of the pressure boosting valve is connected to the oil inlet of the high-pressure relief valve and the high-pressure feedback oil circuit, respectively. The pressure boosting valve can be switched to a state where the first oil port and the second oil port are bidirectionally connected, or a state where the first oil port is unidirectionally connected to the second oil port. The system also includes a controller connected to the control terminal of the pressure boosting valve; the controller is used to send control signals to the pressure boosting valve. The system also includes a high-pressure sensor connected to the high-pressure feedback oil circuit; The high-pressure sensor is connected to the controller for real-time acquisition of the high-pressure feedback oil circuit pressure and feedback to the controller. The controller compares the pressure in the high-pressure feedback oil circuit with the preset low-pressure relief valve setting pressure. If the pressure in the high-pressure feedback oil circuit is less than or equal to the preset low-pressure relief valve setting pressure, the controller controls the pressure boost valve to switch to a bidirectional state between the first and second oil ports. If the pressure in the high-pressure feedback oil circuit is greater than the preset low-pressure relief valve setting pressure, the controller controls the pressure boosting valve to switch to a state where the first oil port unidirectionally connects to the second oil port.

2. The hydraulic excavator overflow pressure graded control system according to claim 1, characterized in that, The system also includes a pump, an oil inlet circuit, and an oil return circuit; The oil inlet end of the oil inlet circuit is connected to the oil outlet of the pump, and the oil outlet end of the oil inlet circuit is connected to the oil inlet of each working link; the oil outlet of the working link is connected to the oil return circuit. The low-pressure relief valve outlet is connected to the return oil circuit; the high-pressure relief valve outlet is connected to the return oil circuit.

3. The hydraulic excavator overflow pressure graded control system according to claim 1, characterized in that, The working link includes a first working link, a second working link, a third working link, and a fourth working link; Both the first and second working connections are connected to the high-pressure feedback oil circuit; Both the third and fourth working connections are connected to the low-pressure feedback oil circuit.

4. The hydraulic excavator overflow pressure graded control system according to claim 1, characterized in that, The system also includes a low-pressure sensor; the low-pressure sensor is used to acquire the pilot control pressure of the working link connected to the high-pressure feedback oil circuit and transmit it to the controller; The controller compares the pilot control pressure of the working link connected to the high-pressure feedback oil circuit with the set pilot pressure; If the pilot control pressure of the working link connected to the high-pressure feedback oil circuit is less than or equal to the set pilot pressure, the controller controls the pressure boosting valve to switch to a bidirectional state between the first oil port and the second oil port. If the pilot control pressure of the working link connected to the high-pressure feedback oil circuit is greater than the set pilot pressure, the controller controls the pressure boosting valve to switch to the state where the first oil port unidirectionally connects to the second oil port.

5. The hydraulic excavator overflow pressure graded control system according to claim 1 or 4, characterized in that, The pressure boosting valve is a two-position two-way valve with electromagnetic two-position two-way function. When the two-position two-way valve is in the first position, the first oil port and the second oil port are bidirectionally connected, and the low-pressure feedback oil circuit and the high-pressure feedback oil circuit are bidirectionally connected. When the two-position two-way valve is in the second position, the first oil port is unidirectionally connected to the second oil port, and the low-pressure feedback oil circuit and the high-pressure feedback oil circuit are unidirectionally connected.

6. The hydraulic excavator overflow pressure graded control system according to claim 5, characterized in that, The controller can control the pressure boosting valve to be energized or de-energized. When the pressure boosting valve is de-energized, the pressure boosting valve is in the first position; When the pressure boosting valve is energized, it is in the second position.

7. A method for graded control of overflow pressure in a hydraulic excavator, based on the graded control system for overflow pressure in a hydraulic excavator according to any one of claims 1-6, characterized in that, Includes the following steps: Obtain the pressure of the high-pressure feedback oil circuit; The pressure in the high-pressure feedback oil circuit is compared with the preset pressure of the low-pressure relief valve. If the pressure in the high-pressure feedback oil circuit is less than or equal to the preset low-pressure relief valve setting pressure, the control pressure boosting valve switches to a bidirectional state between the first and second oil ports. If the pressure in the high-pressure feedback oil circuit is greater than the preset low-pressure relief valve setting pressure, the control pressure boosting valve switches to a state where the first oil port unidirectionally connects to the second oil port.

8. The hydraulic excavator overflow pressure graded control method according to claim 7, characterized in that, The method further includes: Obtain the pilot control pressure of the working link connected to the high-pressure feedback oil circuit; Compare the pilot control pressure of the working link connected to the high-pressure feedback oil circuit with the set pilot pressure; If the pilot control pressure of the working link connected to the high-pressure feedback oil circuit is less than or equal to the set pilot pressure, the control pressure boosting valve switches to a bidirectional state between the first oil port and the second oil port. If the pilot control pressure of the working link connected to the high-pressure feedback oil circuit is greater than the set pilot pressure, the control pressure boosting valve switches to a state where the first oil port unidirectionally connects to the second oil port.

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