Combined rigidity-adjustable liquid elastic vibration isolator and rigidity adjusting method thereof

Abstract

The invention provides a combined rigidity-adjustable liquid elastic vibration isolator and a rigidity adjusting method thereof, and relates to the technical field of liquid elastic vibration isolators. Required elastic rigidity is provided through a composite elastic system formed by combining rubber and an air spring; an electronic controller (ECU controller) is used for collecting and processing signals from an inner cylinder displacement sensor, an outer cylinder displacement sensor and a pressure sensor, the signals are compared and analyzed with preset target displacement difference signals of the inner cylinder and the outer cylinder, and then the duty ratio of output pulse width modulation signals is dynamically adjusted based on the comparison result. The opening and closing of an electromagnetic valve in the air spring assembly are controlled, so that the rigidity of the air spring is adjusted, and rigidity reduction caused by aging of a rubber material is compensated. According to the control scheme, the stability of the vibration isolation frequency of the liquid elastic vibration isolator is effectively maintained, and the performance reliability of the vibration isolation system in the long-term operation process is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid elastic vibration isolators, and particularly to a combined stiffness adjustable liquid elastic vibration isolator and its stiffness adjustment method. Background Art

[0002] In the study of helicopter dynamics, the inherent vibration excitation is identified as an important influencing factor on the performance and structural integrity of the aircraft. In particular, the rotor system, as the key vibration source of the helicopter, the alternating aerodynamic load it receives leads to the generation of hub excitation force, which has specific frequency characteristics and affects the fuselage structure through the transmission path connecting the main reduction gearbox and the fuselage. As a helicopter main reduction gearbox vibration isolation device with high vibration isolation efficiency and compact structure, the liquid elastic vibration isolator has the characteristics of high static stiffness and low dynamic stiffness near the vibration isolation frequency, and is widely used in foreign new helicopters.

[0003] The liquid elastic vibration isolator adopts the principle of dynamic anti-resonance. Its working principle is that through the shearing action of the inner and outer cylinders on the rubber layer, the rubber layer provides the necessary elastic stiffness. At the same time, the reciprocating motion of the liquid in the inertia channel causes the pressure change in the upper and lower liquid cavities, thereby effectively offsetting the external excitation force. At the designed target vibration isolation frequency, this system can achieve a significant vibration isolation effect. However, during the continuous operation of the liquid elastic vibration isolator, the temperature of the rubber layer gradually increases due to the long-term shear force. In addition, the time-dependence of the rubber material leads to the occurrence of creep behavior. Under the combined action of these factors, the stiffness performance of the rubber layer degrades, and then the vibration isolation frequency of the vibration isolator decreases, and it cannot accurately isolate all the vibrations transmitted from the hub and the main reduction gearbox to the fuselage. Therefore, the effectiveness of the liquid elastic vibration isolator in isolating the helicopter hub vibration weakens and cannot meet the strict requirements of the helicopter for vibration reduction. Summary of the Invention

[0004] Aiming at the problem that the stiffness performance of the rubber layer mentioned in the above background art degrades, and then the vibration isolation frequency of the vibration isolator decreases, and it cannot accurately isolate all the vibrations transmitted from the hub and the main reduction gearbox to the fuselage, the present invention proposes a combined stiffness adjustable liquid elastic vibration isolator and its stiffness adjustment method. This solution fixes multiple liquid elastic vibration isolators on the main shock-absorbing support rod through the base. In addition, a composite elastic system combining rubber and air spring is adopted to provide the required elastic stiffness. By utilizing the reciprocating motion of the liquid in the inertia channel, the pressure fluctuation in the upper and lower liquid cavities is induced, thereby offsetting the external excitation force, ensuring high-efficiency vibration isolation performance within the predetermined vibration isolation frequency range, so as to achieve the goal of isolating the vibration transmitted from the main reduction gearbox to the fuselage.

[0005] In addition, the present invention introduces a PID control system to adjust the duty cycle of the pulse-width modulation signal output by the electronic controller (ECU controller), thereby controlling the opening and closing state of the solenoid valve, realizing the adjustment of the air spring stiffness, and compensating for the stiffness decrease caused by the aging of the rubber material. This control method effectively maintains the stability of the vibration isolation frequency of the liquid spring vibration isolator and ensures the performance reliability of the vibration isolation system during long-term operation.

[0006] To achieve the above object, the present invention adopts the following technical solutions: In a first aspect of the present invention, a combined stiffness-adjustable liquid spring vibration isolator is provided, including: a liquid spring vibration isolator body and an air spring assembly. The liquid spring vibration isolator body includes an inner cylinder assembly, rubber, and an outer cylinder assembly; The outer cylinder assembly includes an upper outer cylinder assembly and a lower outer cylinder assembly. The inner wall of the upper outer cylinder assembly is firmly connected to the upper part of the inner cylinder assembly through a rubber vulcanization process. The lower end of the inner cylinder assembly is connected to the lower outer cylinder assembly and extends to the bottom end inside the lower outer cylinder assembly; An inertial channel for sealing liquid is provided in the center of the inner cylinder assembly, and an upper liquid replenishing cavity and a lower liquid replenishing cavity are attached to the inertial channel; The air spring assembly is arranged inside the lower outer cylinder assembly and is distributed around the lower part of the inner cylinder assembly. An air chamber is provided in the air spring assembly, and the charging and discharging of the air chamber are controlled by a semi-active control system to realize the pressure regulation in the air chamber, thereby continuously controlling the stiffness of the air spring assembly and further realizing the continuous dynamic adjustment of the stiffness of the vibration isolator.

[0007] As a further description of the present invention, the air spring assembly includes a solenoid valve and an airbag; The solenoid valve is assembled on the charging and discharging port of the airbag, and the charging and discharging port is connected to a gas storage tank through a gas guide pipe, so that the solenoid valve can control the inflation and deflation in the airbag.

[0008] As a further description of the present invention, the semi-active control system includes an electronic controller, an inner cylinder displacement sensor, an outer cylinder displacement sensor, and a pressure sensor; The pressure sensor is used to collect the pressure change signal in the air chamber in real time. The inner cylinder displacement sensor is used to collect the displacement signal of the inner cylinder assembly in real time. The outer cylinder displacement sensor is used to collect the displacement signal of the outer cylinder assembly in real time; The electronic controller is used to collect and process the signals from the inner cylinder displacement sensor, the outer cylinder displacement sensor, and the pressure sensor, compare and analyze them with the preset target displacement difference signal between the inner and outer cylinders, and then dynamically adjust the duty cycle of the output pulse-width modulation signal based on the comparison result to control the opening and closing of the solenoid valve in the air spring assembly, thereby realizing the continuous dynamic adjustment of the stiffness of the vibration isolator.

[0009] As a further description of the present invention, the inner cylinder assembly includes an inner cylinder and a first flange disposed on the outer periphery of the inner cylinder. The inner wall of the upper outer cylinder assembly is firmly connected to the upper part of the inner cylinder through a rubber vulcanization process. The upper end of the lower outer cylinder assembly is fixedly connected to the first flange, thereby forming a receiving cavity for containing the air spring assembly.

[0010] As a further description of the present invention, the pressure sensor is disposed on the airbag. The inner cylinder displacement sensor is located below the first flange of the inner cylinder, and the outer cylinder displacement sensor is located at the lower end of the lower outer cylinder assembly.

[0011] As a further description of the present invention, a waist ring made of rubber is attached to the waist of the airbag. The upper end of the airbag is connected to the first mounting groove at the lower part of the first flange through an elastic coupling, and the lower end of the airbag is connected to the second mounting groove in the lower outer cylinder assembly.

[0012] As a further description of the present invention, the upper outer cylinder assembly includes an integrally formed outer cylinder upper end cover and an upper outer cylinder. The lower outer cylinder assembly includes an integrally formed outer cylinder lower end cover and a lower outer cylinder. The upper end of the lower outer cylinder is fixedly connected to the first flange; The outer cylinder upper end cover and the outer cylinder lower end cover are used to be connected to the helicopter fuselage to fix it to the helicopter fuselage; The outer wall of the inner cylinder assembly is fixedly connected to the base through a fixture, realizing effective coupling between the liquid spring isolator and the helicopter main reducer.

[0013] In a second aspect of the present invention, a stiffness adjustment method for the above-mentioned combined stiffness adjustable liquid spring isolator is provided, including the following process: Determine the target isolation frequency of the combined stiffness adjustable liquid spring isolator; Calculate the sum of the initial stiffnesses of the air spring assembly and the rubber according to the target isolation frequency, denoted as the target stiffness of the isolator; Calculate the target displacement difference between the outer cylinder assembly and the inner cylinder assembly according to the target stiffness of the isolator; During the use of the isolator, monitor the real-time displacement difference between the outer cylinder assembly and the inner cylinder assembly. When it is monitored that the real-time displacement difference is less than the target displacement difference, control the inflation of the air cavity of the air spring assembly through a semi-active control system until the real-time displacement difference is equal to the target displacement difference.

[0014] As a further description of the present invention, the relationship between the isolation frequency of the combined stiffness adjustable liquid spring isolator and the sum of the stiffnesses of the air spring assembly and the rubber is: ; Wherein, represents the isolation frequency of the combined stiffness adjustable liquid spring isolator, represents the stiffness of the isolator rubber, represents the stiffness of the air spring assembly, represents the mass of the liquid in the inertia channel of the liquid - elastic isolator, represents the magnification ratio of the combined liquid - elastic isolator.

[0015] As a further illustration of the present invention, the relationship between the target displacement difference and the sum of the initial stiffnesses of the air spring assembly and the rubber is: ; wherein, is the target displacement difference, is the maximum static load received by the combined stiffness - adjustable liquid - elastic isolator, and respectively represent the displacement of the inner cylinder assembly and the outer cylinder assembly when the rubber is not aged, and respectively represent the initial stiffness of the rubber and the initial stiffness of the air spring assembly.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention utilizes the PID control strategy and adopts an elastic stiffness element composed of a rubber material and an air spring assembly to continuously and real - time adjust the stiffness of the combined stiffness - adjustable liquid - elastic isolator, ensuring that the combined liquid - elastic isolator can still maintain the stability of its vibration isolation frequency under the condition of rubber material aging, thereby improving the long - term reliability and efficiency of the vibration isolation system.

[0017] Other features and advantages of this technical solution will be described in the subsequent specification, and part of them will become obvious from the specification or be understood by implementing this technical solution. The objectives and other advantages of this technical solution can be achieved and obtained through the structures specifically pointed out in the written specification and the drawings.

[0018] The following further describes the technical solution of this technical solution in detail through the drawings and embodiments. Description of the Drawings

[0019] The drawings are used to provide a further understanding of this technical solution, and constitute a part of the specification. They are used together with the embodiments of this technical solution to explain this technical solution and do not constitute a limitation to this technical solution.

[0020] Figure 1 is the overall structural schematic diagram of the combined stiffness - adjustable liquid - elastic isolator provided by the present invention.

[0021] Figure 2 is the disassembled schematic diagram of the combined stiffness - adjustable liquid - elastic isolator provided by the present invention.

[0022] Figure 3 Front cross-sectional view of the combined stiffness-adjustable liquid spring vibration isolator provided by the present invention.

[0023] Figure 4 Left cross-sectional view of the combined stiffness-adjustable liquid spring vibration isolator provided by the present invention.

[0024] Figure 5 Schematic structural diagram of the air spring assembly provided by the present invention.

[0025] Figure 6 Schematic diagram of the force on the combined stiffness-adjustable liquid spring vibration isolator provided by the present invention.

[0026] Figure 7 Schematic diagram of the principle of the semi-active control air spring provided by the present invention.

[0027] In the drawings: 1 - Liquid spring vibration isolator body; 101 - Upper liquid replenishing cavity; 102 - Inner cylinder; 103 - Inertial channel; 104 - First flange; 105 - Bolt; 106 - Lower liquid replenishing cavity; 107 - Outer wall of the inner cylinder; 108 - First installation groove; 109 - Rubber; 110 - Inner cylinder displacement sensor; 111 - First installation hole; 2 - Air spring assembly; 201 - Elastic coupling; 202 - Waist ring; 203 - Airbag; 204 - Solenoid valve; 205 - Air cavity; 206 - Pressure sensor; 3 - Outer cylinder; 301 - Upper end cover of the outer cylinder; 302 - Second installation groove; 303 - Second installation hole; 304 - Upper outer cylinder; 305 - Lower end cover of the outer cylinder; 306 - Lower outer cylinder; 307 - Third installation hole; 308 - Electronic controller (ECU controller); 309 - Outer cylinder displacement sensor; 310 - Fourth installation hole; 401 - Gas storage tank; 402 - Air duct. Detailed implementation manners

[0028] The following describes the preferred embodiments of the present technical solution with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present technical solution and are not used to limit the present technical solution.

[0029] As Figures 1-5As shown in the figure, the present invention first provides a combined stiffness-adjustable liquid-spring vibration isolator, comprising: a liquid-spring vibration isolator body 1 and an air spring assembly 2. The liquid-spring vibration isolator body 1 includes an inner cylinder assembly, rubber 109 and an outer cylinder assembly 3; the outer cylinder assembly 3 includes an upper outer cylinder assembly and a lower outer cylinder assembly. The inner wall of the upper outer cylinder assembly is firmly connected to the upper part of the inner cylinder assembly through the rubber 109 vulcanization process. The lower end of the inner cylinder assembly is connected to the lower outer cylinder assembly and extends to the inner bottom end of the lower outer cylinder assembly; an inertia channel 103 for sealing liquid is provided at the center of the inner cylinder assembly, and an upper liquid replenishing cavity 101 and a lower liquid replenishing cavity 106 are attached to the inertia channel 103; the air spring assembly 2 is arranged inside the lower outer cylinder assembly and is distributed around the lower part of the inner cylinder assembly. An air cavity 205 is provided inside the air spring assembly 2. The air charging and discharging of the air cavity 205 is controlled by a semi-active control system to realize the pressure regulation in the air cavity 205, thereby continuously controlling the stiffness of the air spring assembly 2, and further realizing the continuous dynamic adjustment of the stiffness of the vibration isolator.

[0030] In an implementable manner, the air spring assembly 2 includes an electromagnetic valve 204 and an airbag 203. The electromagnetic valve 204 is assembled on the air charging and discharging port of the airbag 203. The air charging and discharging port is connected to a gas storage tank 401 through a gas conduit 402, so that the electromagnetic valve 204 can control the inflation and deflation of the airbag 203. The design of the gas conduit 402 here is used to connect the gas storage tank 402 with the electromagnetic valve 204 of the air spring assembly 2, thereby realizing the continuous air charging and discharging function of the air spring assembly 2. The electromagnetic valve 204 is connected to the gas conduit 402, thereby realizing the function of adjusting the air cavity pressure to adapt to different working requirements.

[0031] In an implementable manner, the semi-active control system includes an electronic controller 308, an inner cylinder displacement sensor 110, an outer cylinder displacement sensor 309 and a pressure sensor 206; the pressure sensor 206 is used to collect the pressure change signal in the air cavity 205 in real time, the inner cylinder displacement sensor 110 is used to collect the displacement signal of the inner cylinder assembly in real time, and the outer cylinder displacement sensor 309 is used to collect the displacement signal of the outer cylinder assembly 3 in real time; the electronic controller 308 is used to collect and process the signals from the inner cylinder displacement sensor 110, the outer cylinder displacement sensor 309 and the pressure sensor 206, and at the same time output a pulse width modulation signal to control the opening and closing of the electromagnetic valve 204 in the air spring assembly 2, thereby realizing the continuous dynamic adjustment of the stiffness of the vibration isolator.

[0032] In an implementable manner, the inner cylinder assembly includes an inner cylinder 102 and a first flange 104 arranged on the outer periphery of the inner cylinder 102. The inner wall of the upper outer cylinder assembly is firmly connected to the upper part of the inner cylinder 102 through the rubber 109 vulcanization process. The upper end of the lower outer cylinder assembly is fixedly connected to the first flange 104, thereby forming a receiving cavity for accommodating the air spring assembly 2.

[0033] In an achievable manner, the pressure sensor 206 is disposed on the airbag 203. The inner cylinder displacement sensor 110 is located below the first flange 104 of the inner cylinder 102, and the outer cylinder displacement sensor 309 is located at the lower end of the lower outer cylinder assembly. The air spring assembly 2, the air storage tank 401, the air duct 402, and the electronic controller 308 are all located in the accommodation cavity of the outer cylinder below the first flange 104 of the inner cylinder 102.

[0034] In an achievable manner, a waist ring 202 made of rubber is attached to the waist of the airbag 203. The upper end of the airbag 203 is connected to the first installation groove 108 below the first flange 104 through an elastic coupling 201, and the lower end of the airbag 203 is connected to the second installation groove 302 in the lower outer cylinder assembly. Among them, the design of the waist ring 202 can play a role in limiting; the cooperation of the elastic coupling 201 and the first installation groove 108 can ensure the stability of the connection and the transmission efficiency.

[0035] In an achievable manner, the upper outer cylinder assembly includes an integrally formed outer cylinder upper end cover 301 and an upper outer cylinder 304. The lower outer cylinder assembly includes an integrally formed outer cylinder lower end cover 305 and a lower outer cylinder 306. The upper end of the lower outer cylinder 306 is fixedly connected to the first flange 104 through a fourth installation hole 310 by bolts. The outer cylinder upper end cover 301 and the outer cylinder lower end cover 305 are used to be connected to the helicopter fuselage to fix it to the helicopter fuselage. Specifically, the outer cylinder upper end cover 301 and the outer cylinder lower end cover 305 are connected to the helicopter fuselage through the second installation hole 303 and the third installation hole 307 to fix it to the helicopter fuselage. The outer wall 107 of the inner cylinder is fixedly connected to the base through a fixture to achieve effective coupling between the liquid spring vibration isolator and the helicopter main reducer. The outer wall of the inner cylinder of the combined stiffness adjustable liquid spring vibration isolator provided by the present invention is fixedly connected to the base through a special fixture, and then the coupling with the helicopter main reducer is realized; its outer cylinder upper end cover and outer cylinder lower end cover are connected to the helicopter fuselage through the second installation hole and the third installation hole to fix it to the helicopter fuselage. This installation method is used to transmit the exciting force generated by the vibration of the main reducer.

[0036] In an achievable manner, rubber sealing rings are provided between the upper liquid replenishing cavity 101 and the outer cylinder upper end cover 301, and between the lower liquid replenishing cavity 106 and the outer cylinder lower end cover 305 to ensure the sealing performance and prevent liquid leakage.

[0037] The working principle of the combined stiffness adjustable liquid spring vibration isolator provided by the present invention is as follows: In the initial use stage of the liquid spring isolator, when there are no obvious signs of aging in the rubber material, the liquid spring isolator performs vibration isolation operations based on the principle of dynamic anti-resonance. At this time, the rubber layer and the air spring work together to provide the required elastic stiffness. When the combined liquid spring isolator is subjected to the exciting force from the main reducer, the rubber layer and the air spring will generate acting forces. At the same time, the liquid in the inertia channel is squeezed and flows up and down in the inertia channel to generate an inertial force, which cancels out the acting force generated by the elastic element, thus playing a role in vibration isolation.

[0038] As the rubber material ages, the relative displacement between the inner cylinder and the outer cylinder of the isolator shows a gradually increasing trend. In order to maintain the performance indicators of the vibration isolation system, a proportional-integral-differential (PID) closed-loop control strategy is adopted. This strategy involves using the displacement signals collected by the displacement sensors installed on the inner and outer cylinders to compare and analyze with the preset target displacement signal. Based on this comparison result, the electronic controller dynamically adjusts the duty cycle of the output pulse width modulation (PWM) signal to control the opening and closing states of the solenoid valves in the air spring assembly, thereby realizing the real-time dynamic adjustment of the stiffness of the isolator.

[0039] The present invention also provides a stiffness adjustment method for the above-mentioned combined stiffness-adjustable liquid spring isolator, including the following steps: Step 1: Determine the target vibration isolation frequency of the combined stiffness-adjustable liquid spring isolator.

[0040] The theoretical model of the present invention can be equivalently Figure 6 as shown. In this model, represents the mass of the vibration-isolated part composed of the helicopter rotor and the main reducer and the inner cylinder, represents the mass of the fuselage and the outer cylinder base, represents the mass of the liquid in the inertia channel of the liquid spring isolator, represents the cross-sectional radii of the upper and lower liquid cavities of the liquid spring isolator, represents the cross-sectional radius of the inertia channel, represents the stiffness of the isolator rubber, represents the stiffness of the air spring, is the length of the inertia channel. represents the periodic exciting force acting on the inner cylinder of the liquid spring isolator, respectively represent the displacements of the inner cylinder and the outer cylinder under the action of the external exciting force, represents the displacement of the inertial liquid in the inertia channel of the isolator, are the pressures in the upper and lower liquid cavities respectively. Let the damping of the isolator be are the cross-sectional areas of the upper and lower liquid cavities, is the cross-sectional area of the inertia channel.

[0041] In the theoretical analysis of liquid-elastic vibration isolators, the following basic assumptions are proposed to simplify the model: (1) Ignore the physical state of the liquid density and rubber during the operation of the liquid-elastic vibration isolator. The impact of changes in work status; (2) The change of rubber stiffness is a linear process; (3) The liquid-elastic vibration isolator always maintains an axial motion state.

[0042] Based on the theoretical analysis of the above liquid-elastic vibration isolator, the vibration isolation frequency of the combined stiffness adjustable liquid-elastic vibration isolator is determined, specifically: The dynamic equation of the combined liquid-elastic vibration isolator system is as follows:

[0043] Define the ratio of the cross-sectional area of ​​the upper and lower liquid chambers of the combined liquid-elastic vibration isolator to the cross-sectional area of ​​the inertial channel is the amplification ratio of the combined liquid-elastic vibration isolator. According to the liquid mass continuity equation in the inertial channel, we can get:

[0044] Combining the above equations, the dynamic equation of the combined liquid-elastic vibration isolator can be simplified to:

[0045] Depend on The resonant frequency of the combined liquid-elastic vibration isolator is obtained as:

[0046] Therefore, the force transmission rate of the combined liquid-elastic vibration isolator can be defined as the ratio of the force transmitted to the fuselage through the vibration isolator to the amplitude of the external exciting force: ; in: ; ; ; The force transmission rate of the combined liquid-elastic vibration isolator , then the relationship between the vibration isolation frequency of the combined stiffness adjustable liquid-elastic vibration isolator and the sum of the stiffness of the air spring assembly and the rubber is: ; in, It represents the vibration isolation frequency of the combined stiffness adjustable liquid-elastic vibration isolator. represents the stiffness of the isolator rubber, Indicates the stiffness of the air spring assembly, Represents the mass of the liquid in the inertia channel of the liquid spring isolator. Represents the magnification ratio of the combined liquid spring isolator.

[0047] Step 2: Calculate the sum of the initial stiffnesses of the air spring assembly and the rubber according to the target vibration isolation frequency, denoted as the target stiffness of the isolator.

[0048] According to the relationship between the vibration isolation frequency of the above combined stiffness adjustable liquid spring isolator and the sum of the stiffnesses of the air spring assembly and the rubber, it can be known that when the mass of the liquid in the inertia channel of the liquid spring isolator and the magnification ratio of the combined liquid spring isolator are both known constants, the sum of the initial stiffnesses of the air spring assembly and the rubber can be calculated according to the known target vibration isolation frequency.

[0049] Step 3: Calculate the target displacement difference between the outer cylinder assembly and the inner cylinder assembly according to the target stiffness of the isolator.

[0050] Since the vibration isolation frequency is fixed (the target vibration isolation frequency is known), and the rubber will age during use, resulting in a decrease in stiffness. Therefore, it is necessary to inflate the air spring to supplement the stiffness lost by the rubber. In this application, the displacement sensors are used to detect the displacements of the inner and outer cylinders and compare them with the target displacements to determine whether the stiffness will change.

[0051] The relationship between the target displacement difference and the sum of the initial stiffnesses of the air spring assembly and the rubber is: ; Wherein, is the target displacement difference, is the maximum static load borne by the combined stiffness adjustable liquid spring isolator, and respectively represent the displacements of the inner cylinder assembly and the outer cylinder assembly when the rubber is not aged, and respectively represent the initial stiffness of the rubber and the initial stiffness of the air spring assembly. The target displacement difference of the system is determined by the maximum static load and the initial overall stiffness of the system.

[0052] Step 4: During the use of the isolator, monitor the real-time displacement difference between the outer cylinder assembly and the inner cylinder assembly. When the monitored real-time displacement difference is less than the target displacement difference, control the inflation of the air chamber of the air spring assembly through the semi-active control system until the real-time displacement difference is equal to the target displacement difference.

[0053] The theoretical calculation formula for the stiffness of the air spring is: ; Wherein, is the air chamber pressure, is the atmospheric pressure, is the volume of the air spring, is the effective area of the air spring, is the polytropic index of the gas, generally taken as . is the vertical deformation of the air spring, is the effective area change rate, which depends on the structure of the air spring and is a constant in this system.

[0054] Through the above theoretical calculation formula of the stiffness of the air spring, it can be known that the stiffness of the air spring changes with the change of the air chamber pressure of the air spring, that is, by changing its air chamber pressure , the control of the stiffness of the air spring can be realized.

[0055] During the use of the combined stiffness adjustable liquid spring vibration isolator, the real-time displacement difference calculation expression in the ECU controller is as follows: ; Among them, is the real-time displacement, and are the inner and outer cylinder displacement signals detected in real time.

[0056] Since during use, the rubber will age and cause the stiffness to decrease, that is, decreases. To maintain the constant vibration isolation frequency of the system, it is necessary to increase the stiffness of the air spring . In this application, the change of the system stiffness is adjusted by means of the change of the displacement signal. When the displacement signal input into the ECU controller, the ECU controller outputs a control signal to drive the solenoid valve to open. At this time, the air spring is inflated to adjust the stiffness to increase. When , the system reaches the specified vibration isolation frequency and the solenoid valve closes.

[0057] In addition, in order to ensure the safety of the combined stiffness adjustable liquid spring vibration isolator system, the maximum pressure threshold of the air spring assembly is used as the safety constraint of this PID control framework. Given that the volume of the air spring in this system remains unchanged, in order to ensure the safe operation of the system, the pressure sensor located on the air spring assembly is responsible for monitoring and maintaining the internal pressure of the air spring not exceeding the preset maximum threshold , and determining the maximum threshold of the internal pressure of the air spring chamber is as shown in the following formula.

[0058] ; In this PID control framework, the introduction of the maximum pressure threshold acts as a key safety constraint, and its function is: (1)Limit the internal pressure of the air spring to prevent structural damage or system failure caused by overpressure.

[0059] (2)Provide a feedback signal to the PID controller to ensure that control actions are performed within the safe operating range.

[0060] (3)Optimize the regulation of the air spring stiffness by adjusting the PID control parameters while ensuring that the system stability is not affected.

[0061] Obviously, those skilled in the art can make various changes and modifications to this technical solution without departing from the spirit and scope of this technical solution. Thus, if these modifications and variations of this technical solution fall within the scope of the claims of this technical solution and its equivalent technologies, then this technical solution is also intended to include these changes and modifications.

Claims

1. A combined stiffness adjustable liquid-elastic vibration isolator, characterized in that: include: A liquid-elastic vibration isolator body (1) and an air spring assembly (2), wherein the liquid-elastic vibration isolator body (1) comprises an inner cylinder assembly, rubber (109) and an outer cylinder assembly (3); The outer cylinder assembly (3) comprises an upper outer cylinder assembly and a lower outer cylinder assembly, the inner wall of the upper outer cylinder assembly being firmly connected to the upper part of the inner cylinder assembly by a rubber (109) vulcanization process, the lower end of the inner cylinder assembly being connected to the lower outer cylinder assembly and extending to the inner bottom end of the lower outer cylinder assembly; An inertial channel (103) for sealing liquid is arranged at the center of the inner cylinder assembly, and the inertial channel (103) is provided with an upper liquid replenishing chamber (101) and a lower liquid replenishing chamber (106); The air spring assembly (2) is arranged in the lower outer cylinder assembly and distributed on the outer periphery of the lower part of the inner cylinder assembly. An air cavity (205) is provided in the air spring assembly (2). The semi-active control system controls the inflation and deflation of the air cavity (205) to achieve pressure regulation in the air cavity (205), thereby continuously controlling the stiffness of the air spring assembly (2), and further achieving continuous dynamic regulation of the stiffness of the vibration isolator.

2. The combined stiffness adjustable liquid-elastic vibration isolator according to claim 1, characterized in that: The air spring assembly (2) comprises a solenoid valve (204) and an air bag (203); The solenoid valve (204) is mounted on the air charging and discharging port of the airbag (203), and the air charging and discharging port is connected to the air storage tank (401) via an air guide tube (402), so that the solenoid valve (204) can control the inflation and deflation of the airbag (203).

3. The combined stiffness adjustable liquid-elastic vibration isolator according to claim 2, characterized in that: The semi-active control system comprises an electronic controller (308), an inner cylinder displacement sensor (110), an outer cylinder displacement sensor (309) and a pressure sensor (206); The pressure sensor (206) is used to collect the pressure change signal in the air cavity (205) in real time, the inner cylinder displacement sensor (110) is used to collect the inner cylinder component displacement signal in real time, and the outer cylinder displacement sensor (309) is used to collect the outer cylinder component (3) displacement signal in real time; The electronic controller (308) is used to collect and process signals from the inner cylinder displacement sensor (110), the outer cylinder displacement sensor (309) and the pressure sensor (206), and compare and analyze the signals with the preset target displacement difference signals of the inner and outer cylinders, and then dynamically adjust the duty cycle of the output pulse width modulation signal based on the comparison result to control the opening and closing of the electromagnetic valve (204) in the air spring assembly (2), thereby realizing continuous dynamic adjustment of the stiffness of the vibration isolator.

4. The combined stiffness adjustable liquid-elastic vibration isolator according to claim 2, characterized in that: The inner cylinder assembly comprises an inner cylinder (102) and a first flange (104) arranged on the outer periphery of the inner cylinder (102); the inner wall of the upper outer cylinder assembly is firmly connected to the upper part of the inner cylinder (102) through a rubber (109) vulcanization process; the upper end of the lower outer cylinder assembly is fixedly connected to the first flange (104), thereby forming a receiving chamber for containing the air spring assembly (2).

5. The combined stiffness adjustable liquid-elastic vibration isolator according to claim 4, characterized in that: The pressure sensor (206) is arranged on the airbag (203), the inner cylinder displacement sensor (110) is located at the lower part of the first flange (104) of the inner cylinder (102), and the outer cylinder displacement sensor (309) is located at the lower end of the lower outer cylinder assembly.

6. The combined stiffness adjustable liquid-elastic vibration isolator according to claim 4, characterized in that: The airbag (203) has a rubber waist ring (202) attached to its waist, the upper end of the airbag (203) is connected to the first mounting groove (108) at the lower part of the first flange (104) via an elastic coupling (201), and the lower end of the airbag (203) is connected to the second mounting groove (302) in the lower outer cylinder assembly.

7. The combined stiffness adjustable liquid-elastic vibration isolator according to claim 1, characterized in that: The upper outer cylinder assembly comprises an outer cylinder upper end cover (301) and an upper outer cylinder (304) formed in one piece, and the lower outer cylinder assembly comprises an outer cylinder lower end cover (305) and a lower outer cylinder (306) formed in one piece, and the upper end of the lower outer cylinder (306) is fixedly connected to the first flange (104); The outer cylinder upper end cover (301) and the outer cylinder lower end cover (305) are used to be connected to the helicopter fuselage so as to be fixed to the helicopter fuselage; The outer wall (107) of the inner cylinder assembly is fixedly connected to the base via a clamp, thereby achieving effective coupling between the liquid-elastic vibration isolator and the main reducer of the helicopter.

8. A method for adjusting the stiffness of a combined type liquid-elastic vibration isolator with adjustable stiffness according to any one of claims 1 to 7, characterized in that: The process includes the following: Determine the target vibration isolation frequency of the combined stiffness adjustable liquid-elastic vibration isolator; The sum of the initial stiffness of the air spring assembly and the rubber is calculated according to the target vibration isolation frequency and recorded as the target stiffness of the vibration isolator; According to the target stiffness of the vibration isolator, a target displacement difference between the outer cylinder assembly and the inner cylinder assembly is calculated; During the use of the vibration isolator, the real-time displacement difference between the outer cylinder assembly and the inner cylinder assembly is monitored. When it is detected that the real-time displacement difference is smaller than the target displacement difference, the semi-active control system is used to control the inflation into the air cavity of the air spring assembly until the real-time displacement difference is equal to the target displacement difference.

9. The stiffness adjustment method of the combined stiffness adjustable liquid-elastic vibration isolator according to claim 8, characterized in that: The relationship between the vibration isolation frequency of the combined stiffness adjustable liquid-elastic vibration isolator and the sum of the stiffness of the air spring assembly and the rubber is: ； in, It represents the vibration isolation frequency of the combined stiffness adjustable liquid-elastic vibration isolator. represents the stiffness of the isolator rubber, Indicates the stiffness of the air spring assembly, It represents the mass of the liquid in the inertial channel of the liquid-elastic isolator. Indicates the amplification ratio of the combined liquid-elastic vibration isolator.

10. The stiffness adjustment method of the combined stiffness adjustable liquid-elastic vibration isolator according to claim 8, characterized in that: The relationship between the target displacement difference and the sum of the initial stiffness of the air spring assembly and the rubber is: ； in, is the target displacement difference, is the maximum static load on the combined stiffness adjustable liquid-elastic vibration isolator, and They represent the displacement of the inner cylinder assembly and the outer cylinder assembly when the rubber is not aged. and They represent the initial stiffness of the rubber and the initial stiffness of the air spring assembly respectively.

Images