A two-stage relief valve, control method and hydraulic system

Abstract

The present application relates to a kind of double-stage overflow valve, control method and hydraulic system, double-stage overflow valve includes main valve, pilot valve, connecting module and electronic control unit, connecting module includes n parallel branch, n>1, the two ends of branch are respectively communicated main valve and pilot valve, dynamic pressure feedback hole and electromagnetic switch valve are equipped on branch, the size of dynamic pressure feedback hole on each branch is different, and electronic control unit is connected with electromagnetic switch valve on each branch.Compared with prior art, the present application improves the pressure instability problem of overflow valve under wide temperature range working condition.In the process of pressure regulation, temperature factor is considered, after temperature changes, switch to the dynamic pressure feedback hole of corresponding size to carry out oil flow, so that the overflow valve keeps stable pressure regulating state under the working condition that temperature change leads to oil viscosity change, can be applied to more kinds of extreme temperature change working environment and stable work, to solve the pressure instability problem of overflow valve under wide temperature range working condition.

Description

Technical Field

[0001] This invention relates to the fields of mechanical parts and transmission devices and fluid control technology in mechanical engineering, and in particular to a two-stage relief valve, control method and hydraulic system suitable for wide temperature range operating conditions. Background Technology

[0002] Hydraulic transmission technology features high force density, high standardization, and easy overload protection, and is widely used in aerospace, shipbuilding, port machinery, and construction machinery. Stable pressure in the hydraulic system is crucial for the safe operation and precise execution of the hydraulic power system. Relief valves are typically used for pressure control in hydraulic power systems; they are essential components for pressure control.

[0003] Relief valves can be classified into two types according to their structure: direct-acting relief valves and pilot-operated relief valves. Direct-acting relief valves are single-stage structures with fast response times and are generally used as the pilot stage in safety valves and pilot-operated relief valves. Pilot-operated relief valves were first designed by Harry Vickers in 1931 (Harry Vickers. Liquid Relief Valve [P]. US2043453, USA, 1931). They exhibit good performance under high-pressure and high-flow conditions and are widely used. However, both direct-acting and pilot-operated types experience problems such as pressure regulation instability and high-frequency vibration during use, significantly affecting the reliability of hydraulic systems. Scholars have conducted extensive research on this topic. For example, Hayashi from Japan proposed a method for analyzing the stability and nonlinear characteristics of pilot-operated relief valves and their hydraulic circuits (S. Hayashi. Instability of poppet valve circuit. JSME International Journal, 1995, 38(3): 357-366); K. Dasgupta from India introduced a modeling and simulation method for the dynamic characteristics of pilot-operated relief valves (K. Dasgupta, R. Karmakar. Dynamic analysis of pilot operated pressure relief valve. Simulation Modeling Practice and Theory. 2002(10): 35-49); and Johnston N from Italy used frequency domain analysis to study the stability of relief valves from the perspective of flow resistance (Johnston N, Edge KA and Brunelli M. Impedance and stability characteristics of a relief valve. Proceedings of the Institution of Mechanical Engineers Part I: Journal of Systems and Control). Engineering 2002; 216(5):371-382.); American Merrit proposed using a reasonable match between a damping throttle and the liquid capacity to improve the dynamic performance of the relief valve (HEMerrit. Hydraulic control systems[M]. John Willy & Sons, 1967). Since the 1980s, Chinese scholars have begun to study the dynamic performance of relief valves and the generation mechanism of valve vibration, and explore how to solve the problem of large pressure stabilization deviation of relief valves.The Shanghai Aerospace Bureau studied a direct-acting relief valve with a balance piston at the end of the valve core. The results showed that the single-stage relief valve with a fixed throttle valve and a balance piston has a three-in-one comprehensive function of vibration reduction, noise reduction and pressure stabilization, and can achieve precise pressure control (Yin Yaobao. Mechanism and characteristic analysis of single-stage relief valve with fixed throttle valve and balance piston. Shanghai Aerospace, 1995, 3:14-17). Tongji University proposed a stability criterion for an extremely small-sized double-stage relief valve and pointed out that when the volume of the main valve spring cavity and the mass of the pilot valve core cannot be increased due to space size and processing level, a damping orifice of appropriate size can be designed between the pilot valve and the main valve to improve its stability (Yin Yaobao, Yuan Jiayang, Fu Junyong. Characteristics of a new type of double-stage relief valve with a damping orifice added to the front cavity of the pilot valve. Journal of Jilin University, 2017, 47(01):129-136). Huaqiao University proposed a relief valve using a magnetorheological pilot valve. It uses a magnetorheological fluid as the working medium of the pilot valve. The opening pressure of the relief valve is controlled by adjusting the current intensity in the magnetorheological pilot valve coil and the preload of the pilot valve spring. This achieves the purpose of real-time, automated, and intelligent control and increases the pressure regulation range. It also has the characteristics of rapid response (Liu Xiaomei, Li Hongyou. A relief valve using a magnetorheological pilot valve: China, CN104633233B[P]. 2017-10-20).

[0004] Chinese patent application 202310083477.X discloses a two-stage relief valve with a structure of three consecutive series-connected throttling orifices. This two-stage relief valve comprises a main valve and a pilot valve, and its structure is as follows: Figure 2 As shown, the pilot valve controls the opening and closing of the main valve, and the main valve controls the system pressure. To enhance the stability of the two-stage relief valve, a damping orifice (13) of suitable size is added between the main valve and the pilot valve. The damping orifice (13), together with the main valve core throttling orifice and the pilot valve fixed throttling orifice, forms a three-series throttling orifice structure, enabling the improved two-stage relief valve to operate stably at the rated flow rate, thereby improving the dynamic performance of the two-stage relief valve. However, when the hydraulic system is in an extreme high-low temperature transition environment, the viscosity of the oil will also change with the change in ambient temperature. At this time, the flow capacity of the damping orifice (13) between the main valve (4) and the pilot valve (5) will change, and its hydraulic resistance will also change, thereby affecting the pressure regulation stability of the relief valve and causing the hydraulic system pressure regulation to become unstable. Therefore, for the working conditions of extreme high-low temperature transition, it is necessary to improve the pressure regulation scheme of the hydraulic system. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art and provide a two-stage relief valve, control method and hydraulic system suitable for wide temperature range operating conditions.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] According to a first aspect of the present invention, a two-stage relief valve is provided, comprising a main valve, a pilot valve, a connecting module, and an electronic control unit. The connecting module comprises n parallel branches, n>1, with the two ends of each branch connected to the main valve and the pilot valve, respectively. Each branch is provided with a dynamic pressure feedback port and a solenoid valve, the dynamic pressure feedback port on each branch having a different size. The electronic control unit is connected to the solenoid valve on each branch.

[0008] Furthermore, it also includes a temperature sensor connected to the electronic control unit, the temperature sensor being configured to measure the temperature of the oil.

[0009] Furthermore, the temperature sensor is installed in the oil tank and immersed in the oil.

[0010] Furthermore, the electronic control unit includes system circuitry, drive circuitry, and input / output interfaces.

[0011] Furthermore, the electronic control unit sends a first signal or a second signal to each electromagnetic switch valve, and the electromagnetic switch valve is configured to: receive the first signal and be in an on state, and receive the second signal and be in an off state.

[0012] Furthermore, the diameters of the dynamic pressure feedback holes on each branch are different.

[0013] According to a second aspect of the present invention, a control method for a two-stage relief valve is provided, based on the two-stage relief valve as described in the first aspect of the present invention, comprising:

[0014] The two-stage relief valve is pre-set to operate in different working conditions. In each working mode, the solenoid valve on one branch is in the connected state while the solenoid valves on the other branches are in the disconnected state.

[0015] The electronic control unit acquires real-time operating condition information, determines the operating mode based on the real-time operating condition information, and controls the two-stage relief valve to enter the corresponding operating mode.

[0016] Furthermore, the different operating conditions refer to different oil temperature ranges, and the real-time operating condition information refers to the real-time oil temperature.

[0017] Furthermore, in the preset multiple operating modes, as the oil temperature range of the operating condition increases, the size of the dynamic pressure feedback orifice on the branch where the electromagnetic switch valve is in the connected state decreases.

[0018] A hydraulic system characterized by comprising a two-stage relief valve as described in the first aspect of the invention.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) This invention improves the pressure regulation instability problem of relief valve under wide temperature range conditions. Temperature factors are considered during the pressure regulation process. When the temperature changes, the oil flow is switched to the corresponding size dynamic pressure feedback hole. This allows the relief valve to maintain a stable pressure regulation state under the condition that the oil viscosity changes due to temperature changes. It can be applied to a wider range of extreme temperature change working environments and work stably, thereby solving the pressure regulation instability problem of relief valve under wide temperature range conditions.

[0021] (2) The oil temperature is regarded as one of the factors affecting the pressure regulation dynamic characteristics of the relief valve, and targeted improvements are made. This greatly reduces the application limitations of the relief valve in a wide temperature range, enabling the relief valve to work stably in environments with extreme high and low temperature changes.

[0022] (3) Theoretically, any number of branches and dynamic pressure feedback holes greater than zero can be set to improve the pressure regulation stability of the hydraulic system in a wide temperature range, and it has strong scalability.

[0023] (4) The present invention can also adopt the structure of a cartridge-type integrated valve block to improve space utilization.

[0024] (5) The present invention can be easily transformed into a relief valve pressure regulation method suitable for another variable by adjusting the sensor type and relief valve model, such as multiple flow and pressure conditions. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the two-stage overflow valve pressure regulation scheme in an embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of a common overflow valve pressure regulation scheme in an embodiment of the present invention;

[0027] Figure 3 The output pressure curve of the two-stage relief valve pressure regulation provided by the present invention under wide temperature range conditions;

[0028] Figure 4 This is the output pressure curve of a common overflow valve pressure regulation scheme under wide temperature range conditions.

[0029] Explanation of markings in the diagram:

[0030] 1. Hydraulic pump; 2-1. Relief valve pressure regulating module of the present invention; 2-2. Ordinary relief valve pressure regulating module; 3. Hydraulic system load; 4. Main valve; 5. Pilot valve; 6. Electronic control unit; 7. Temperature sensor; 8. Main valve pressure control chamber; 9. Main valve core; 10. Differential pressure throttling orifice; 11. Main valve spring chamber; 12. Main valve spring; 13. Dynamic pressure feedback orifice / damping orifice between the main valve and the pilot valve (including 13-1, 13-2...13-n, each damping orifice has the same length but different diameters); 14. Electromagnetic switch valve (including 14-1, 14-2...14-n); 15. Pilot valve pressure control chamber; 16. Pilot valve core; 17. Pilot valve spring; 18. Hydraulic oil tank. Detailed Implementation

[0031] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are implemented based on the technical solutions of the present invention, providing detailed implementation methods and specific operating procedures. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them, and the scope of protection of the present invention is not limited to the following embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0032] In the accompanying drawings, components with the same structure are indicated by the same numerical designation, and components with similar structures or functions are indicated by similar numerical designations. The dimensions and thicknesses of each component shown in the drawings are arbitrary, and the present invention does not limit the dimensions and thicknesses of each component. To make the illustrations clearer and show the mating relationships between the components, some parts in the drawings have been appropriately scaled down, and the distances between the components have been increased or decreased.

[0033] In the description of the embodiments of this application, it should be understood 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, or the orientation or positional relationship commonly placed when the product of this application is used, or the orientation or positional relationship commonly understood by those skilled in the art. They are only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the device or component 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 application.

[0034] In the description of the embodiments of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set," "install," "connect," and "link" 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; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0035] Example 1:

[0036] The structural principle of the two-stage relief valve (ordinary relief valve) proposed in Chinese patent application 202310083477.X is as follows: Figure 2 As shown, in a typical relief valve pressure regulating scheme, 1 represents the hydraulic pump, 2-2 represents the typical relief valve pressure regulating module, and 3 represents the hydraulic system load. The typical relief valve pressure regulating module 2-2 includes a main valve 4 and a pilot valve 5. When the oil flows into the main valve's front chamber (main valve pressure control chamber 8), it enters the pilot valve pressure control chamber 15 through the differential pressure throttling orifice 10, and then flows into the main valve spring chamber 11 through the damping orifice 13 between the main valve 4 and the pilot valve 5. When the pressure p in the pilot valve pressure control chamber 15... c When the pressure is increased sufficiently to overcome the preload of the pilot valve spring 17, the pilot valve 5 opens and generates an overflow flow Q. x This causes a pressure difference (p) to be generated at both ends of the main valve core (9) under the throttling effect of the differential pressure throttling orifice 10. B -p A When this pressure difference reaches a level sufficient to overcome the preload of the main valve spring 12, the main valve 4 opens and generates an overflow flow Q. y This achieves the purpose of regulating system pressure. However, this pressure regulation method uses only one dynamic pressure feedback port 13. The size of the dynamic pressure feedback port 13 is fixed, but the oil viscosity decreases as the temperature rises and increases as the temperature falls. Therefore, the flow performance differs at different temperatures, and it cannot adjust the structural parameters of the components involved in pressure regulation according to temperature changes. The problem with this two-stage relief valve is that under wide temperature range conditions, the temperature rise leads to a decrease in oil viscosity, making the relief valve system an unstable control system. This causes large fluctuations in system pressure during pressure regulation, severely reducing the stability of the hydraulic system.

[0037] Based on this, the present invention provides a two-stage relief valve, including a main valve 4, a pilot valve 5, a connecting module and an electronic control unit 6. The connecting module includes n parallel branches, n>1, and the two ends of the branches are respectively connected to the main valve 4 and the pilot valve 5. The branches are provided with dynamic pressure feedback holes 13 and electromagnetic switching valves 14. The dynamic pressure feedback holes (13-1 to 13-n) on each branch have different sizes. The electronic control unit 6 is connected to the electromagnetic switching valves (14-1 to 14-n) on each branch.

[0038] A control method for a two-stage relief valve includes:

[0039] The two-stage relief valve is pre-set to operate in different working conditions. In each working mode, the solenoid switch valve 14 on one branch is in the connected state and the solenoid switch valve 14 on the other branches is in the cut-off state.

[0040] The electronic control unit 6 acquires real-time operating condition information, determines the working mode based on the real-time operating condition information, and controls the two-stage relief valve to enter the corresponding working mode.

[0041] In this application, such as Figure 1 As shown, a connection module is provided between the main valve 4 and the pilot valve 5. The connection module includes n parallel branches, each branch is provided with a dynamic pressure feedback port 13 of different sizes, and each branch is provided with an electromagnetic switch valve 14. The working state of each electromagnetic switch valve 14 is controlled by the electronic control unit 6, so that the branch with different sizes of dynamic pressure feedback port 13 can be selected to be connected under different working conditions, so that the size of the damping orifice between the main valve 4 and the pilot valve 5 can be adjusted to ensure pressure stability.

[0042] It is understood that this application is essentially an improvement on an existing ordinary relief valve. The size of the damping orifice 13 between the main valve 4 and the pilot valve 5 can be adjusted by controlling the state of the solenoid switch valve 14. The structure or model of the relief valve itself does not affect the effect. In fact, this application can be applied to two-stage relief valves of different models and structures, as long as the branch connecting the main valve 4 and the pilot valve 5 is provided with dynamic pressure feedback orifices 13 of different sizes that can be controlled by the solenoid switch valve 14. For ease of explanation, this embodiment uses... Figure 1 and Figure 2 The two-stage overflow valve structure shown illustrates the working principle of the present invention.

[0043] The electronic control unit 6 includes system circuitry, drive circuitry, and input / output interfaces. External control signals can be input to the electronic control unit 6, which then switches the operating state of the electromagnetic valve 14 based on these signals. Alternatively, a temperature sensor 7 can be installed, connected to the electronic control unit 6. The temperature sensor 7 is configured to measure the oil temperature and send the real-time oil temperature to the electronic control unit 6. The electronic control unit 6 has a built-in control program that switches the operating state of the electromagnetic valve 14. In this embodiment, the temperature sensor 7 is installed in the oil tank 18 and immersed in the oil.

[0044] It is understandable that different operating conditions correspond to different oil temperature ranges, and real-time operating condition information is the real-time oil temperature. Depending on the required control accuracy and cost, multiple temperature ranges can be set, along with a corresponding number of branches. Each size of the dynamic pressure feedback port 13 corresponds to a temperature range. Within this temperature range, the branch corresponding to the dynamic pressure feedback port 13 is in a conducting state (the solenoid valve 14 on this branch is in a connected state), while other branches are in a disconnected state (the solenoid valve 14 on this branch is in a cut-off state). The main valve 4 and the pilot valve 5 exchange oil through the dynamic pressure feedback port 13. When the temperature changes, the flow switches to the corresponding size of the dynamic pressure feedback port 13, thus ensuring that the relief valve maintains a stable pressure regulation state under wide temperature range conditions, thereby solving the problem of pressure regulation instability of the relief valve under wide temperature range conditions.

[0045] In this embodiment, the dynamic pressure feedback holes 13 on each branch have the same length but different diameters. In other embodiments, the dynamic pressure feedback holes (13-1 to 13-n) can also be made to have different sizes by adjusting other parameters.

[0046] The electronic control unit 6 is used to control the on / off state of the solenoid valves 14. The electronic control unit sends a first signal or a second signal to each solenoid valve 14. The solenoid valve 14 is configured to: receive the first signal and be in an on state, and receive the second signal and be in an off state. In this embodiment, the output current of the electronic control unit 6 has two states, corresponding to the first signal and the second signal respectively: ① zero current, at which time the pressure port and working port of the solenoid valve 14 are in an on state, so that its corresponding dynamic pressure feedback port 13 is connected to the overflow valve pressure regulating circuit to participate in controlling the opening and closing of the main valve 4; ② positive current, at which time the pressure port and working port of the solenoid valve 14 are in an off state, so that its corresponding dynamic pressure feedback port 13 cannot be connected to the overflow valve pressure regulating circuit and does not participate in controlling the opening and closing of the main valve 4.

[0047] The specific applications of this application are as follows:

[0048] like Figure 1 As shown, in the two-stage relief valve pressure regulating scheme provided by this invention, 1 is a hydraulic pump, 2-1 is a two-stage relief valve pressure regulating module, and 3 is the hydraulic system load. The two-stage relief valve pressure regulating module 2-1 includes a main valve 4, a pilot valve 5, a connection module, and an electronic control unit 6. First, the temperature sensor 7 detects the oil temperature in the oil tank 18, and then converts the detected temperature information into a current signal and transmits it to the electronic control unit 6. After receiving the current signal from the temperature sensor 7, the electronic control unit 6 compares and judges it, and then outputs the corresponding control current to each solenoid valve (14-1, 14-2...14-n) according to the judgment result, thereby controlling a certain dynamic pressure feedback port 13 to connect to the pressure regulating oil circuit.

[0049] In the preset multiple operating modes, as the oil temperature range of the operating condition increases, the size of the dynamic pressure feedback port 13 on the branch where the solenoid switch valve 14 is in the connected state decreases. When the electronic control unit 6 receives a high-temperature current signal from the temperature sensor 7, it sends a connection current signal to the solenoid switch valve (14-i) corresponding to the smaller diameter dynamic pressure feedback port (13-i), so that the dynamic pressure feedback port 13 is connected to the overflow valve pressure regulating circuit to participate in controlling the opening and closing of the main valve 4; at the same time, it sends a cut-off current signal to the solenoid switch valves (14-n, n=1, 2...i-1, i+1...n) corresponding to the other dynamic pressure feedback ports (13-n, n=1, 2...i-1, i+1...n), so that the other dynamic pressure feedback ports (13-n, n=1, 2...i-1, i+1...n) do not participate in controlling the opening and closing of the main valve 4; Conversely, when the electronic control unit 6 receives a high-temperature current signal from the temperature sensor 7, it sends a connection current signal to the solenoid valve (14-i) corresponding to the smaller diameter dynamic pressure feedback port (13-i), so that the dynamic pressure feedback port is connected to the overflow valve pressure regulating circuit to participate in controlling the opening and closing of the main valve 4; at the same time, it sends a cut-off current signal to the solenoid valves (14-n, n=1, 2...i-1, i+1...n) corresponding to the other dynamic pressure feedback ports (13-n, n=1, 2...i-1, i+1...n), so that the other dynamic pressure feedback ports (13-n, n=1, 2...i-1, i+1...n) do not participate in controlling the opening and closing of the main valve 4.

[0050] When the oil flows into the main valve front chamber (main valve pressure control chamber 8), it enters the pilot valve pressure control chamber 15 through the differential pressure throttling orifice 10, and then flows into the main valve spring chamber 11 through the dynamic pressure feedback orifice 13 between the main valve 4 and the pilot valve 5. When the pressure p in the pilot valve pressure control chamber 15... c When the pressure is increased sufficiently to overcome the preload of the pilot valve spring 17, the pilot valve 5 opens and generates an overflow flow Q. x This causes a pressure difference (p) to be generated at both ends of the main valve core (9) under the throttling effect of the differential pressure throttling orifice 10. B -p A When this pressure difference reaches a level sufficient to overcome the preload of the main valve spring 12, the main valve 4 opens and generates an overflow flow Q. y This achieves the purpose of regulating system pressure.

[0051] This invention addresses the problem of pressure regulation instability in relief valves under wide temperature range conditions. Temperature is considered during the pressure regulation process, ensuring stable pressure regulation of the relief valve even when temperature changes cause variations in oil viscosity. At lower temperatures, the larger-diameter dynamic pressure feedback port 13 is connected to the pilot valve's pressure regulation circuit to control the opening and closing of the main valve 4, while the remaining dynamic pressure feedback ports 13 remain open. At higher temperatures, the smaller-diameter dynamic pressure feedback port 13 is connected to the pilot valve's pressure regulation circuit to control the opening and closing of the main valve 4, while the remaining dynamic pressure feedback ports 13 remain open. This invention solves the problem of pressure regulation instability in relief valves under wide temperature range conditions by setting multiple temperature range judgment programs in the electronic control unit 6 and coordinating them with a corresponding number of dynamic pressure feedback ports 13.

[0052] The output pressure curve of the two-stage relief valve pressure regulation scheme provided in this application under wide temperature range conditions is as follows: Figure 3 As shown, the data comes from dynamic numerical simulation of an electromagnetic relief valve pressure regulation method applicable to a wide temperature range, with an input flow rate of 220 L / min and 46# hydraulic oil. The figure shows the output pressure curves of the hydraulic system applying this application at temperatures of 0℃, 20℃, 40℃, 60℃, and 80℃. Figure 3 As can be seen, within the temperature range of 0℃ to 80℃, after the system begins to build up pressure, the system pressure exhibits a fluctuating state of energy decay after overshoot, and after a short period of adjustment, the system pressure stabilizes. This demonstrates that the present invention can output stable pressure under wide temperature range conditions without affecting the normal operation of the hydraulic system.

[0053] The output pressure curve of a conventional electromagnetic overflow valve pressure regulation scheme under wide temperature range conditions is as follows: Figure 4 As shown, the data comes from dynamic numerical simulation of a common relief valve pressure regulation method, with an input flow rate of 220 L / min and 46# hydraulic oil. The figure shows the output pressure curves of the common scheme applied at temperatures of 0℃, 20℃, 40℃, 60℃, and 80℃. Figure 4 As can be seen, at 0℃, after the system starts to build up pressure, the system pressure exhibits a fluctuating state of energy decay after overshoot, and then stabilizes after a short period of adjustment. However, at temperatures of 20℃, 40℃, 60℃, and 80℃, the system pressure exhibits a continuous fluctuation after overshoot, and the amplitude of this fluctuation increases with increasing temperature. When the temperature reaches 80℃, the fluctuation amplitude can reach 7.14MPa. This shows that the ordinary relief valve pressure regulation scheme cannot output stable pressure under wide temperature range conditions. The fluctuating system pressure is detrimental to the normal operation of the hydraulic system, reducing its reliability and safety.

[0054] In summary, this invention enables more precise and stable pressure regulation of the relief valve over a wide temperature range, making it applicable to various flow and pressure conditions. Therefore, compared to existing relief valve pressure regulation solutions, this application is suitable for working environments with more extreme temperature variations.

[0055] The present invention also provides a hydraulic system including the aforementioned two-stage relief valve. The hydraulic system includes at least one two-stage relief valve, which can be configured according to actual needs. The size of the damping orifice in the two-stage relief valve of the hydraulic system is determined based on the parameters of the hydraulic system, the main valve, and the pilot valve.

[0056] Example 2:

[0057] This application achieves multi-level control by setting multiple branches with dynamic pressure feedback holes 13 of different sizes and electromagnetic switching valves 14 on the on / off branches. Example 1 uses temperature as the control variable, thereby stabilizing the pressure of the hydraulic system within a set range in environments with extreme high and low temperature transitions, which has the advantage of improving the reliability of the hydraulic system over a wide temperature range. In this example, the sensor type and relief valve model are adjusted to transform the relief valve pressure regulation scheme suitable for other variables, such as flow rate and pressure conditions. The basic principle is the same and will not be repeated here, as those skilled in the art will understand.

[0058] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A two-stage relief valve, characterized in that, It includes a main valve, a pilot valve, a connecting module, and an electronic control unit. The connecting module includes n parallel branches, n>1. The two ends of each branch are connected to the main valve and the pilot valve, respectively. Each branch is provided with a dynamic pressure feedback port and a solenoid switch valve. The dynamic pressure feedback port on each branch has a different size. A temperature sensor is configured to measure the temperature of the oil. An electronic control unit is connected to the solenoid valves on each branch and the temperature sensor, and is configured to control the opening and closing of each solenoid valve according to the real-time oil temperature measured by the temperature sensor. The electronic control unit has multiple preset operating modes corresponding to different oil temperature ranges. In each operating mode, only one branch of the electromagnetic switch valve is in the connected state while the electromagnetic switch valves on the other branches are in the disconnected state. Furthermore, as the oil temperature range increases, the size of the dynamic pressure feedback orifice on the branch where the electromagnetic switch valve is in the connected state decreases to compensate for the effect of oil viscosity changes caused by temperature changes on hydraulic resistance.

2. A two-stage relief valve according to claim 1, characterized in that, The temperature sensor is installed in the oil tank and immersed in the oil.

3. A two-stage relief valve according to claim 1, characterized in that, The electronic control unit includes system circuits, drive circuits, and input / output interfaces.

4. A two-stage relief valve according to claim 1, characterized in that, The electronic control unit sends a first signal or a second signal to each electromagnetic switch valve, and the electromagnetic switch valve is configured to: receive the first signal and be in an on state, and receive the second signal and be in an off state.

5. A two-stage relief valve according to claim 1, characterized in that, The diameters of the dynamic pressure feedback holes on each branch are different.

6. A control method for a two-stage relief valve, characterized in that, Based on the two-stage relief valve as described in any one of claims 1-5, comprising: The two-stage relief valve is pre-set to operate in different working conditions. In each working mode, the solenoid valve on one branch is in the connected state while the solenoid valves on the other branches are in the disconnected state. As the oil temperature range increases, the size of the dynamic pressure feedback orifice on the branch where the electromagnetic switch valve is in the connected state decreases to compensate for the effect of oil viscosity change caused by temperature change on liquid resistance. The real-time temperature of the oil is obtained, and the corresponding target working mode is determined according to the preset temperature range to which the real-time temperature of the oil belongs. The on / off state of each electromagnetic switch valve is controlled so that the two-stage relief valve enters the target working mode.

7. A hydraulic system, characterized in that, Includes the two-stage relief valve as described in any one of claims 1-5.

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