Hydraulic pump and pressure control device therefor

Abstract

The application discloses a hydraulic pump and a pressure control device thereof, and belongs to the technical field of hydraulic pump control, wherein the pressure control branch circuit comprises a three-position electromagnetic reversing valve; the oil pressure of the pressure control branch circuit and the oil pressure of a main working oil circuit and opening and closing are adjusted through switching of working positions of the three-position electromagnetic valve, so that the minimum control pressure of a pump port of the hydraulic pump is maintained, the lubricating effect of a sliding shoe pair in the pump is ensured, and the minimum pump control pressure is provided for an oil-operated actuator.

Description

Technical Field

[0001] This invention relates to the field of hydraulic pump control technology, and more specifically, to a hydraulic pump and its pressure control device. Background Technology

[0002] As the core power transmission and control unit of modern engineering machinery, mining equipment, and industrial equipment, the reliability of the hydraulic system directly determines the working efficiency and service life of the entire machine. In the hydraulic system, the variable pump (such as the axial piston variable pump: V32G pump, which can automatically match the output pressure according to the pressure required by the load) serves as the power source. The key friction pairs inside, such as the piston pair, slipper pair, and distributor plate pair, all operate under high pressure and high speed conditions, relying on a continuous and stable oil film for lubrication and support.

[0003] Current technologies generally lack adequate lubrication and pressure management during the startup and standby phases of hydraulic pumps, directly leading to significant problems such as accelerated pump wear, shortened service life, and excessive system energy consumption. In common existing hydraulic systems, hydraulic pumps often directly enter a load-bearing pressure-building state after startup. That is, once the hydraulic pump starts, its output oil circuit is directly connected to the working load, and the pump outlet pressure rises from zero to a high-pressure value determined by the load in a very short time, typically reaching hundreds of bar. During this process, the friction pairs inside the hydraulic pump have not yet established an effective lubricating oil film, and are in a state of boundary friction or even dry friction. The instantaneous establishment of high pressure causes the slipper to be violently pressed against the swashplate, and the plunger end and distributor plate to experience severe extrusion, which can easily cause early failure phenomena such as slipper burn-out, distributor plate plowing, and plunger scoring. Especially under conditions of low ambient temperature and high hydraulic oil viscosity, cold oil has poor fluidity and cannot quickly penetrate and fill the tiny friction gaps, making the above-mentioned dry friction phenomenon more serious, directly leading to the accumulation of initial damage to the pump body, and significantly reducing the reliability and lifespan of the pump.

[0004] In summary, existing hydraulic systems lack effective low-pressure preheating and prelubrication methods, failing to establish safe isolation on the load side during pump startup and unable to forcibly establish an oil film protection for the internal friction pairs of the pump before high-pressure loading. This results in persistent problems such as damage to the hydraulic pump upon startup, shortened lifespan, and poor equipment reliability. Therefore, how to provide a hydraulic control method for pre-lubricating pump components under low pressure has become a technical problem urgently needing to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a hydraulic pump and its pressure control device to solve the aforementioned technical problems.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A pressure control device for a hydraulic pump, comprising: Main working oil circuit and pressure control branch; One end of the main working oil circuit is connected to the output end of the hydraulic pump, and the other end is connected to the oil-using actuator. A pressure control valve is provided in the middle of the main working oil circuit. The pressure control valve is configured to open when the oil pressure at the pressure control valve is greater than or equal to the third preset pressure, thereby opening the main working oil circuit and supplying high-pressure oil to the oil-using actuator, which hydraulically drives the oil-using actuator. When the oil pressure at the valve is less than the third preset pressure, the pressure control valve closes, cutting off the main working oil circuit. The pressure control branch includes a three-position solenoid directional valve and a return oil line. The three-position solenoid directional valve has a high-pressure inlet P, a first working port A, and a second working port B. When the three-position solenoid directional valve is in the first working position, P and B are connected, and both are cut off from the other ports of the valve. When it is in the neutral position, all ports of the valve are closed, and any two ports of the valve are cut off from each other. When it is in the second working position, P and A are connected, and both are cut off from the other ports of the valve. Port B of the solenoid directional valve is connected to the inlet end of the return oil line, and port A of the solenoid directional valve is connected to the inlet end of the return oil line through a second relief valve. The oil outlet of the return oil pipeline is connected to the oil tank. The second relief valve is a normally closed valve. When the oil pressure at the second relief valve is greater than or equal to the second preset pressure, the A of the solenoid directional valve and the return oil pipeline are opened, thereby allowing the oil at point A to overflow back to the oil tank. The output end of the hydraulic pump is connected to the inlet end of the return oil pipeline through the first relief valve. The P of the solenoid directional valve is connected between the first relief valve and the output end of the hydraulic pump. The first relief valve is a normally closed valve. When the oil pressure at the first relief valve is greater than or equal to the first preset pressure, the output end of the hydraulic pump and the return oil pipeline are opened, thereby allowing the oil output by the hydraulic pump to overflow back to the oil tank. The first preset pressure > the third preset pressure > the second preset pressure > 0.

[0007] Optionally, the three-position solenoid directional valve is a three-position four-way solenoid directional valve, which is provided with a high-pressure oil inlet P, a low-pressure oil return port T, a first working oil port A, and a second working oil port B. When the solenoid directional valve is in the first working position, P and B are connected, and A and T are connected. When it is in the middle position, P, T, A, and B are all closed, and any two oil ports are cut off from each other. When it is in the second working position, P and A are connected, and B and T are connected.

[0008] Optionally, the pressure control branch also includes a cartridge relief valve, which is a normally closed pressure-controlled valve. One end of the cartridge relief valve is connected between the hydraulic pump output and the first relief valve, and the other end is connected to the return oil line or the oil tank. When the control pressure is greater than or equal to the first preset pressure, the hydraulic pump output and the return oil line are opened, thereby allowing the oil output by the hydraulic pump to overflow back to the oil tank. The control pressure is the inlet pressure of the cartridge relief valve itself or the pilot control pressure introduced by the external control oil circuit. The pressure tap of the external control oil circuit is connected between the hydraulic pump output and the first relief valve, and the control end of the external control oil circuit is connected to the pilot control interface of the cartridge relief valve.

[0009] Optionally, the pressure control device for the hydraulic pump also includes a pressure sensor, the pressure tap of which is connected between the output of the hydraulic pump and the first relief valve.

[0010] Optionally, a pressure test connector is also provided between the pressure sensor and the oil inlet of the cartridge relief valve for measuring oil pressure.

[0011] Optionally, the main working oil circuit is also equipped with a check valve to allow the hydraulic pump to output oil to the hydraulic actuator and to cut off the oil flowing back to the hydraulic pump.

[0012] Optionally, the pressure control valve is a normally closed valve, which is configured such that when the oil pressure at the pressure control valve is greater than or equal to a third preset pressure, the pressure control valve opens, thereby opening the main working oil circuit and supplying high-pressure oil to the oil-using actuator.

[0013] Optionally, the pressure control valve is a sequence valve.

[0014] According to another aspect of the present invention, a hydraulic pump is provided, which is equipped with the above-described pressure control device.

[0015] As is well known, once the low-pressure direct-flow oil circuit is connected in the control circuit, the oil will spontaneously prioritize returning to the oil tank via the lower pressure and less flow resistance circuit. Components in other high-pressure circuits (such as the first and second relief valves in the first operating position, and the first relief valve in the second operating position) cannot form a sealed cavity and cannot accumulate back pressure, thus losing the conditions required for high-pressure branch establishment. In other words, during the low-pressure drain circuit's operation, the high-pressure control circuit is forcibly locked and cannot be put into operation, forming a control logic that prioritizes the low-pressure circuit and excludes high- and low-pressure operating conditions.

[0016] The main working oil circuit and the pressure control branch are both connected to the common pressure oil source at the output end of the hydraulic pump and are interconnected, forming a parallel oil circuit structure. As is well known, in the parallel oil circuit structure of a hydraulic valve group, multiple functional branches share the same common pressure oil source and are interconnected. Based on the principle of balanced pressure transmission throughout the closed fluid domain, the medium pressure in the same connected cavity is equal everywhere, and the reference pressure of each parallel branch is completely synchronized and unified.

[0017] When multiple pressure control branches with different opening thresholds are connected in parallel, the hydraulic pressure will preferentially match the operating condition of the branch with the lowest set opening pressure. The low-pressure branch will reach the conduction condition first and form a continuous venting path, continuously releasing the system medium pressure. Due to the constraint of the normal flow and pressure relief of the low-pressure branch, the common pressure header cannot be sealed and stored, making it difficult to accumulate and establish a higher level of working pressure. The other control branches with higher pressure thresholds will remain in a normally closed state for a long time because they can never reach their own valve opening critical pressure. Therefore, in the parallel architecture of multiple pressure level branches, the steady-state working pressure of the entire system is uniquely defined by the branch with the lowest opening pressure. The high-pressure control branch is constrained by the pressure clamping effect of the low-pressure unloading circuit and cannot independently build pressure to start operation.

[0018] An electrical signal is sent to the three-position solenoid directional valve, energizing the corresponding electromagnet to maintain the valve in its first operating position. The hydraulic pump is then started. At this point, the hydraulic pump output flows to the P port of the solenoid directional valve. Because the P port of the solenoid directional valve is connected to its B port in the first operating position, the hydraulic pump output flows from the P port to the B port. Since the B port of this valve is connected to the return oil line to the oil tank, the hydraulic pump output flows directly back to the oil tank through this circuit. The pressure control branch circuit is unloaded, and the oil pressure approaches 0 bar. However, the minimum pressure required to open the main working oil circuit (the third preset pressure) is greater than 0 bar. Therefore, the main working oil circuit is shut off, the hydraulic pump operates without load, and the pressure control branch is opened to drain oil.

[0019] The hydraulic pump lubricates itself by running without load for a preset time as described above. Then, an electrical signal is sent to the three-position solenoid directional valve, energizing the corresponding electromagnet to maintain the valve in its second operating position. At this time, the hydraulic pump output flows to port P of the solenoid directional valve. Because ports P and B are closed and ports P and A are open in the second operating position, port P cannot connect to port B of the valve, allowing for direct no-load return flow. The oil flows from port P to port A of the valve, creating a closed cavity that accumulates back pressure in the second relief valve. When the pressure build-up condition is met, the pressure accumulates until the accumulated oil pressure at the second relief valve is greater than or equal to the second preset pressure. At this point, port A of the solenoid directional valve and the return oil line are opened, and the oil flows back to the oil tank through the return oil line. The first relief valve requires a higher pressure to open, so the high-pressure build-up condition is not yet met. Therefore, the oil output from the hydraulic pump flows directly back to the oil tank through the circuit containing the second relief valve. The pressure control branch operates under low load, maintaining the oil pressure at the second preset pressure. Because the second preset pressure is still lower than the third preset pressure, the main working oil circuit remains in the off state. The low-pressure circulation of the pressure control branch is coordinated with the on / off control of the oil load branch (main working oil circuit), ensuring that the load branch remains off during the low-pressure circulation lubrication preheating period. This prevents the load branch from being open at low pressure, which would cause the oil to exert thrust on the load, resulting in non-targeted creep or drift (affecting equipment safety, increasing unnecessary energy consumption, and impacting lubrication effect and speed). At this time, the hydraulic pump is in low-pressure circulation and standby mode, ready to open the load branch as needed. The standby hydraulic pump can quickly respond when oil needs to be output to the load, while simultaneously meeting the pump body's lubrication requirements.

[0020] When the electrical load needs to operate normally, the electrical signal is changed so that both electromagnets on both sides of the three-position solenoid directional valve are de-energized, and the solenoid valve is in the neutral position. At this time, the hydraulic pump output flows to port P of the solenoid directional valve. Because all ports of the solenoid directional valve are cut off in the neutral position, port P cannot connect to port B of the valve for direct no-load return, nor can it flow to port A to connect to the circuit where the second relief valve is located. The hydraulic pump output to the pressure control branch can only flow to the first relief valve. The first relief valve forms a closed cavity to accumulate back pressure. When the pressure build-up condition is met, and the accumulated oil pressure at the first relief valve is greater than or equal to the third preset pressure, the load branch is opened to supply oil to the electrical load. The accumulation continues until the accumulated oil pressure at the first relief valve is greater than or equal to the first preset pressure, at which point the hydraulic pump output end and the return oil line are opened, and the oil flows back to the oil tank through the return oil line. When the oil pressure is too high, it overflows, directly limiting the maximum oil pressure of the pressure control branch, thereby indirectly limiting the maximum oil pressure of the load branch, protecting the hydraulic pump and the oil-using load.

[0021] Compared to existing technologies, the hydraulic pump and its pressure control device provided by this invention can operate without load during pump startup, actively establish and maintain a low-pressure lubrication process during pump standby, and switch to high-pressure load drive after the oil film is fully established. The pump pressure gradually increases until the main working oil circuit is opened to supply oil to the oil-using actuators. On the one hand, it lubricates the pump body components under low pressure in advance, and on the other hand, it provides the minimum pump pressure for the oil-using actuators, meeting the minimum pump pressure requirements of some oil-using actuators. This hydraulic control and drive method can reduce and delay pump body wear, extend the service life of the hydraulic pump, and reduce unnecessary energy consumption. Attached Figure Description

[0022] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention, but do not constitute an undue limitation of the invention. Obviously, the drawings described below are merely some embodiments, and those skilled in the art can obtain other drawings based on these drawings without creative effort. In the drawings: Figure 1 This is a schematic diagram of the structure of a hydraulic pump provided in one embodiment of this application; Figure 2 for Figure 1 A partial enlarged view of the embodiment; Figure 3 for Figure 1 A partial enlarged view of the embodiment; Figure 4 for Figure 3 A structural diagram of the three-position electromagnetic directional valve in the embodiment when it is switched to the first working position; Figure 5 for Figure 3 A structural diagram of the three-position solenoid directional valve in the embodiment when it switches to the second working position.

[0023] Reference numerals: 1. Motor; 2. Hydraulic pump; 3. Check valve; 4. Sequence valve; 5. Three-position solenoid directional valve; 6. Second relief valve; 7. First relief valve; 8. Cartridge valve; 9. Pressure sensor; 10. Pressure test connector; 11. Oil tank; 12. Main working oil circuit; 13. Core control valve group integration; 14. Layer boundary line; 15. Pressure tap of external control oil circuit; 16. Pilot control terminal; 17. Return oil line. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0025] See Figures 1-5This invention provides a pressure control device for a hydraulic pump, comprising a main working oil circuit 12 and a pressure control branch circuit. Wherein: One end of the main working oil circuit 12 is connected to the output end of the hydraulic pump 2, and the other end is connected to the oil-using actuator. A pressure control valve is provided in the middle of the main working oil circuit 12. The pressure control valve is configured such that when the oil pressure at the pressure control valve is greater than or equal to the third preset pressure, the pressure control valve opens, allowing the main working oil circuit 12 to be open and supplying high-pressure oil to the oil-using actuator, thus hydraulically driving the oil-using actuator; when the oil pressure at the valve is less than the third preset pressure, the pressure control valve closes, cutting off the main working oil circuit 12, and the hydraulic pump 2 no longer supplies high-pressure oil to the oil-using actuator, thus no longer hydraulically driving the oil-using actuator.

[0026] The pressure control branch includes a three-position solenoid directional valve 5 and a return oil line 17. The three-position solenoid directional valve 5 has a high-pressure inlet P, a first working port A, and a second working port B. In the three-position solenoid directional valve 5: when the three-position solenoid directional valve 5 is in the first working position, P and B are connected, and both are cut off from the other ports of the valve; when it is in the neutral position, all ports of the valve are closed, and any two ports of the valve are cut off from each other; when it is in the second working position, P and A are connected, and both are cut off from the other ports of the valve.

[0027] Outside the solenoid directional valve 5: B of the solenoid directional valve 5 is connected to the oil inlet end of the return oil line 17, A of the solenoid directional valve 5 is connected to the oil inlet end of the return oil line 17 through the second relief valve 6, and the oil outlet end of the return oil line is connected to the oil tank 11. The second relief valve 6 is a normally closed valve. When the oil pressure at the second relief valve 6 is greater than or equal to the second preset pressure, A of the solenoid directional valve 5 and the return oil line 17 are opened, thereby overflowing the oil at A back to the oil tank 11. The output end of the hydraulic pump 2 is connected to the oil inlet end of the return oil line 17 through the first relief valve 7. P of the solenoid directional valve 5 is connected between the first relief valve 7 and the output end of the hydraulic pump 2. The first relief valve 7 is a normally closed valve. When the oil pressure at the first relief valve 7 is greater than or equal to the first preset pressure, the output end of the hydraulic pump 2 and the return oil line 17 are opened, thereby overflowing the oil output by the hydraulic pump 2 back to the oil tank 11. The first preset pressure > the third preset pressure > the second preset pressure > 0.

[0028] As is well known, once the low-pressure direct oil circuit is connected in the loop, the oil will spontaneously prioritize returning to the oil tank 11 via the lower pressure and less flow resistance connecting circuit. Components in other high-pressure circuits of the control loop (such as the first relief valve 7 and the second relief valve 6 in the first operating position, and the first relief valve 7 in the second operating position) cannot form a sealed cavity and cannot accumulate back pressure, thus losing the high-pressure establishment conditions required for the high-pressure branch. In other words, during the period when the low-pressure drain path is open, the high-pressure control loop is forcibly locked and cannot be put into operation, forming a control logic that prioritizes the low-pressure path and excludes high and low pressure operating conditions.

[0029] The main working oil circuit 12 and the pressure control branch are both connected to the common pressure oil source at the output end of the hydraulic pump 2 and are interconnected, forming a parallel oil circuit structure. As is well known, in the parallel oil circuit structure of a hydraulic valve group, multiple functional branches share the same common pressure oil source and are interconnected. Based on the principle of balanced pressure transmission throughout the closed fluid domain, the medium pressure in the same connected cavity is equal everywhere, and the reference pressure of each parallel branch is completely synchronized and unified.

[0030] When multiple pressure control branches with different opening thresholds are connected in parallel, the hydraulic pressure will preferentially match the operating condition of the branch with the lowest set opening pressure. The low-pressure branch will reach the conduction condition first and form a continuous venting path, continuously releasing the system medium pressure. Due to the constraint of the normal flow and pressure relief of the low-pressure branch, the common pressure header cannot be sealed and stored, making it difficult to accumulate and establish a higher level of working pressure. The other control branches with higher pressure thresholds will remain in a normally closed state for a long time because they can never reach their own valve opening critical pressure. Therefore, in the parallel architecture of multiple pressure level branches, the steady-state working pressure of the entire system is uniquely defined by the branch with the lowest opening pressure. The high-pressure control branch is constrained by the pressure clamping effect of the low-pressure unloading circuit and cannot independently build pressure to start operation.

[0031] An electrical signal is sent to the three-position solenoid directional valve 5, energizing the corresponding electromagnet to maintain the valve in its first operating position. Then, motor 1 drives hydraulic pump 2, starting it. At this point, the oil output from hydraulic pump 2 flows to port P of solenoid directional valve 5. Because port P of solenoid directional valve 5 is connected to port B in the first operating position, the oil output from hydraulic pump 2 flows from port P to port B. Since port B of this valve is connected to the return oil line 17 to the oil tank 11, the oil output from hydraulic pump 2 flows directly back to the oil tank 11 through this circuit. The pressure control branch circuit is unloaded, and the oil pressure approaches 0 bar. Since the minimum pressure (third preset pressure) of the main working oil circuit 12 is greater than 0 bar, the main working oil circuit 12 is shut off, hydraulic pump 2 operates without load, and the pressure control branch is opened to drain oil.

[0032] Hydraulic pump 2 lubricates the system by running without load for a preset time as described above. Then, it sends an electrical signal to the three-position solenoid directional valve 5, energizing the corresponding electromagnet to maintain the valve in its second operating position. At this time, the oil output from hydraulic pump 2 flows to port P of solenoid directional valve 5. Because ports P and B of solenoid directional valve 5 are closed and ports P and A are open in the second operating position, port P cannot connect to port B of the valve for direct no-load return flow. The oil flows from port P to port A of the valve, and the second relief valve 6 forms a closed cavity to accumulate back pressure. The pressure establishment condition is met, and the oil accumulates until the accumulated oil pressure at the second relief valve 6 is greater than or equal to the second preset pressure. Then, port A of solenoid directional valve 5 and return oil line 17 are opened, and the oil flows back to the oil tank 11 through the return oil line. The first relief valve 7 requires a higher pressure to open, and the high-pressure establishment condition is still not met. Therefore, the oil output from hydraulic pump 2 flows directly back to the oil tank 11 through the circuit containing the second relief valve 6. The pressure control branch operates under low load, and the oil pressure is maintained at the second preset pressure. Because the second preset pressure is still less than the third preset pressure, the main working oil circuit 12 remains in the off state. The low-pressure circulation of the pressure control branch is coordinated with the on / off control of the oil load branch (main working oil circuit 12), ensuring that the load branch remains off during the low-pressure circulation lubrication preheating period. This prevents the load branch from being open at low pressure, which would cause the oil to exert thrust on the load, resulting in non-targeted creep or drift (affecting equipment safety, increasing unnecessary energy consumption, and impacting lubrication effect and speed). At this time, the hydraulic pump 2 is in low-pressure circulation and standby mode, ready to open the load branch as needed. The standby hydraulic pump 2 can quickly respond when oil needs to be output to the load, while simultaneously meeting the pump body's lubrication requirements.

[0033] When the electrical load needs to operate normally, the electrical signal is changed so that the electromagnets on both sides of the three-position solenoid directional valve 5 are de-energized, and the solenoid valve is in the neutral position. At this time, the oil output from the hydraulic pump 2 flows to port P of the solenoid directional valve 5. Because all the oil ports of the solenoid directional valve 5 are cut off in pairs in the neutral position, port P cannot connect with port B of the valve for direct no-load return, nor can it flow to port A to connect with the circuit where the second relief valve 6 is located. The oil output from the hydraulic pump 2 to the pressure control branch can only flow to the first relief valve 7. The first relief valve 7 forms a closed cavity to accumulate back pressure. When the pressure establishment condition is met, and the accumulated oil pressure at the first relief valve 7 is greater than or equal to the third preset pressure, the load branch is opened to supply oil to the electrical load. The accumulation continues until the accumulated oil pressure at the first relief valve 7 is greater than or equal to the first preset pressure, at which point the output end of the hydraulic pump 2 and the return oil line 17 are opened, and the oil flows back to the oil tank 11 through the return oil line. When the oil pressure is too high, it overflows, directly limiting the maximum oil pressure of the pressure control branch, thereby indirectly limiting the maximum oil pressure of the load branch and protecting the hydraulic pump 2 and the oil-using load.

[0034] Compared to existing technologies, the hydraulic pump 2 and its pressure control device provided by this invention can operate without load when the pump starts. When the pump switches to standby, it can actively establish and maintain a low-pressure lubrication process during standby. After the oil film is fully established, it switches to high-pressure load drive, and the pump pressure gradually increases until the main working oil circuit is opened to supply oil to the oil-using actuators. On the one hand, it lubricates the pump body components with low pressure in advance, and on the other hand, it provides the minimum pump pressure for the oil-using actuators, meeting the minimum pump pressure requirements of some oil-using actuators. This hydraulic control and drive method can reduce and delay pump body wear, extend the service life of the hydraulic pump 2, and reduce unnecessary energy consumption.

[0035] This application does not specify whether the three-position solenoid directional valve 5 is a three-position or multi-port solenoid directional valve, as long as it can achieve the above-mentioned opening and closing purposes in the above-mentioned position states. It can be selected as a three-position three-way solenoid directional valve, with only P, A, and B ports; it can also be selected as a three-position four-way solenoid directional valve 5. For example: In one possible implementation, the three-position solenoid directional valve 5 is a three-position four-way solenoid directional valve, equipped with a high-pressure inlet port P, a low-pressure return port T, a first working port A, and a second working port B. When the solenoid directional valve 5 is in the first working position, P and B are connected, and A and T are connected. When it is in the neutral position, P, T, A, and B are all closed, and any two ports are cut off from each other. When it is in the second working position, P and A are connected, and B and T are connected. In addition to the solenoid directional valve 5, port T of the solenoid directional valve 5 is also connected to the return oil line 17 (this connection is optional and can be flexibly set according to user habits and actual conditions).

[0036] In one possible implementation, the pressure control branch also includes a cartridge valve 8, which is a pressure-responsive normally closed control valve. One end of the cartridge valve 8 is connected to the (common pressure) oil circuit between the output end of the hydraulic pump 2 and the first relief valve 7, and the other end is connected to the return oil line 17 or the oil tank 11. When the control pressure is greater than or equal to the first preset pressure, the output end of the hydraulic pump 2 and the return oil line 17 are opened, thereby allowing the oil output by the hydraulic pump 2 to overflow back to the oil tank 11. Optionally, the cartridge valve 8 is a cartridge-type relief valve. Further optionalally, the control pressure is the inlet pressure of the cartridge valve 8 itself, and the cartridge valve 8 is a direct-acting cartridge valve, with the inlet pressure directly acting on the main valve core. Alternatively, to accommodate large flow rates, cartridge valve 8 can be selected as a pilot-operated cartridge valve. The pressure tap of the external control oil circuit is connected to the (common pressure) oil circuit between the output of hydraulic pump 2 and the first relief valve 7. The oil outlet (which is also its control end) of the external control oil circuit is connected to the pilot control interface of the cartridge valve 8. The oil pressure at the pressure tap 15 of the external control oil circuit is the pilot control pressure introduced by the external control oil circuit, which is also the aforementioned control pressure. It acts on the pressure-bearing end face of the main valve core at the pilot control end 16 through the external control oil circuit. When the oil pressure at the pressure tap 15 is greater than or equal to the first preset pressure, the hydraulic control pressure overcomes the valve core spring preload, pushes the main valve core to open, and connects the output of hydraulic pump 2 to the return oil line 17, thus completing the system depressurization.

[0037] In one possible implementation, the pressure control device of the hydraulic pump further includes a pressure sensor 9, with the pressure tap of the pressure sensor 9 connected between the output of the hydraulic pump 2 and the first relief valve 7. By installing the pressure sensor 9 in the common pressure oil circuit at the output of the hydraulic pump 2, this invention can acquire real-time and accurate system oil pressure parameters, dynamically monitor pressure changes under all working conditions including zero-pressure unloading, low-pressure standby, and high-pressure operation, and accurately identify the critical switching nodes of the first preset pressure, second preset pressure, and third preset pressure. This provides closed-loop data support for the electronic control switching of the three-position electromagnetic directional valve 5 and the precise control of low-pressure lubrication time, avoiding pressure switching lag or malfunction, and ensuring the stability and reliability of the graded pressure control logic.

[0038] Optionally, a pressure testing connector 10 is also provided between the pressure sensor 9 and the oil inlet of the cartridge-type relief valve 8 for measuring oil pressure. This invention adds a pressure testing connector 10 to accommodate external testing instruments for on-site pressure calibration, valve group pressure adjustment, and troubleshooting, facilitating the quick disassembly, repair, and replacement of external testing instruments. With the pressure sensor 9 already installed, the core purpose of the external measuring instrument at the pressure testing connector 10 is for offline pressure calibration and on-site adjustment. There is no need for long-term installation of mechanical pressure measuring instruments; offline pressure measuring equipment (such as a mechanical pressure gauge) is only connected when needed to perform on-site calibration and adjustment of the system pressure. The focus is on verifying the accuracy of the preset opening pressures of the first relief valve 7 and the second relief valve 6, correcting pressure deviations, and avoiding system low-pressure anomalies, high-pressure overloads, or load malfunctions caused by inaccurate relief valve pressure settings, ensuring that pressure control accuracy meets design requirements. The pressure testing connector 10 facilitates the quick disassembly, repair, and replacement of external measuring instruments, and also makes it convenient for staff to load, unload, and maintain the equipment, further improving the safety and maintainability of the device and reducing the equipment failure rate and subsequent maintenance costs.

[0039] In one possible implementation, the main working oil circuit 12 is also provided with a check valve 3, which is used to allow the oil output from the hydraulic pump 2 to the oil-using actuator, and to cut off the oil flowing back to the hydraulic pump 2 in the reverse direction.

[0040] In one possible implementation, the pressure control valve is a normally closed valve, configured such that when the oil pressure at the pressure control valve is greater than or equal to a third preset pressure, the pressure control valve opens, thereby connecting the main working oil circuit 12 and supplying high-pressure oil to the oil-using actuator. Optionally, the pressure control valve is a sequence valve 4.

[0041] exist Figure 1 In this embodiment, the pressure control device of the hydraulic pump is equipped with all the above-mentioned components. The oil flow direction in the oil circuit is as shown by the arrow. The electromagnetic reversing valve 5, the first relief valve 7 and the second relief valve 6 form the core control valve group integration 13. The third preset pressure is 35 bar, the second preset pressure is 30 bar, and the first preset pressure is 315 bar. Figure 1 A magnified view of the part is as follows Figure 2 As shown. It should be noted that, Figure 2 The middle section consists of interlayer boundary lines distinguishing pressure levels and busbars connecting to the oil ports of the electromagnetic directional valve 5 across layers. It should not be understood as a physical structure, much less as an actual component of the oil circuit. To better illustrate the invention, the following is provided: Figure 2 The oil circuit structure diagram after removing interlayer boundaries and some invalid busbars is as follows: Figure 3 As shown. Figure 1-3 In this embodiment, both electromagnets a and b are de-energized, and the electromagnetic reversing valve 5 is in the neutral position. This invention also provides... Figure 4 This embodiment shows a partial oil circuit structure diagram when electromagnet a is energized and solenoid directional valve 5 is in the first working position (left position); it also provides... Figure 5 This diagram shows a portion of the oil circuit structure of this embodiment when the electromagnet b is energized and the electromagnetic directional valve 5 is in the second working position (right position).

[0042] According to another aspect of the present invention, a hydraulic pump 2 is provided, which is equipped with the pressure control device of the aforementioned hydraulic pump.

[0043] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A pressure control device for a hydraulic pump, characterized by comprising: include: Main working oil circuit and pressure control branch; One end of the main working oil circuit is connected to the output end of the hydraulic pump, and the other end is connected to the oil-using actuator. A pressure control valve is provided in the middle of the main working oil circuit. The pressure control valve is configured to open when the oil pressure at the pressure control valve is greater than or equal to the third preset pressure, thereby opening the main working oil circuit and supplying high-pressure oil to the oil-using actuator to hydraulically drive the oil-using actuator. When the oil pressure at the valve is less than the third preset pressure, the pressure control valve closes, cutting off the main working oil circuit. The pressure control branch includes a three-position solenoid directional valve and a return oil line. The three-position solenoid directional valve has a high-pressure inlet P, a first working port A, and a second working port B. When the three-position solenoid directional valve is in the first working position, P and B are connected, and both are cut off from other ports of the valve. When it is in the neutral position, all ports of the valve are closed, and any two ports of the valve are cut off from each other. When it is in the second working position, P and A are connected, and both are cut off from other ports of the valve. Port B of the solenoid directional valve is connected to the inlet end of the return oil line, and port A of the solenoid directional valve is connected to the inlet end of the return oil line through a second relief valve. One end of the pipeline is connected to the oil tank. The second relief valve is a normally closed valve. When the oil pressure at the second relief valve is greater than or equal to the second preset pressure, the A end of the solenoid directional valve and the return oil line are opened, thereby allowing the oil at point A to overflow back to the oil tank. The output end of the hydraulic pump is connected to the inlet end of the return oil line through the first relief valve. The P end of the solenoid directional valve is connected between the first relief valve and the output end of the hydraulic pump. The first relief valve is a normally closed valve. When the oil pressure at the first relief valve is greater than or equal to the first preset pressure, the output end of the hydraulic pump and the return oil line are opened, thereby allowing the oil output by the hydraulic pump to overflow back to the oil tank. The first preset pressure > the third preset pressure > the second preset pressure > 0.

2. The pressure control device for the hydraulic pump according to claim 1, characterized in that, The three-position solenoid directional valve is a three-position four-way solenoid directional valve, which is provided with a high-pressure oil inlet P, a low-pressure oil return port T, a first working oil port A, and a second working oil port B. When the solenoid directional valve is in the first working position, P and B are connected, and A and T are connected. When it is in the middle position, P, T, A, and B are all closed, and any two oil ports are cut off from each other. When it is in the second working position, P and A are connected, and B and T are connected.

3. The pressure control device of the hydraulic pump according to claim 1, characterized by The pressure control branch also includes a cartridge valve, which is a normally closed pressure-controlled valve. One end of the cartridge valve is connected between the hydraulic pump output and the first relief valve, and the other end is connected to the return oil line or the oil tank. When the control pressure is greater than or equal to the first preset pressure, the hydraulic pump output and the return oil line are opened, thereby allowing the oil output by the hydraulic pump to overflow back to the oil tank. The control pressure is the inlet pressure of the cartridge relief valve itself or the pilot control pressure introduced by the external control oil line. The pressure tap of the external control oil line is connected between the hydraulic pump output and the first relief valve, and the control end of the external control oil line is connected to the pilot control interface of the cartridge relief valve.

4. The pressure control device of the hydraulic pump according to claim 1, characterized by It also includes a pressure sensor, the pressure sensor’s pressure tapping end of which is connected between the hydraulic pump output end and the first relief valve.

5. The pressure control device of the hydraulic pump according to claim 4, wherein A pressure testing connector is also provided between the pressure sensor and the oil inlet of the cartridge-type relief valve for measuring oil pressure.

6. The pressure control device of the hydraulic pump according to claim 1, wherein The main working oil circuit is also equipped with a check valve, which is used to allow the hydraulic pump to output oil to the hydraulic actuator and to cut off the oil flowing back to the hydraulic pump.

7. The pressure control device of the hydraulic pump according to claim 1, wherein The pressure control valve is a normally closed valve, and it is configured such that when the oil pressure at the pressure control valve is greater than or equal to a third preset pressure, the pressure control valve opens, thereby opening the main working oil circuit and supplying high-pressure oil to the oil-using actuator.

8. The pressure control device of a hydraulic pump according to claim 7, wherein The pressure control valve is a sequence valve.

9. A hydraulic pump characterized by, The hydraulic pump is equipped with the pressure control device as described in any one of claims 1-8.

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