Method for measuring friction force of hydro-pneumatic spring

Abstract

The invention discloses a hydro-pneumatic spring friction force measurement method, which comprises the following steps: firstly, constructing an equivalent model from the structure of a hydro-pneumatic spring, then decomposing different test states of the hydro-pneumatic spring and carrying out friction force measurement, and then carrying out a characteristic test according to the different test states of the hydro-pneumatic spring. Finally, the friction force change conditions of the hydro-pneumatic spring in different states are analyzed and used for determining the friction force characteristics of all dynamic sealing parts in the spring, and then optimal design and application of the hydro-pneumatic spring are guided. Friction force is decomposed into a combined state of a single friction pair or a plurality of friction pairs, a plurality of precise and controllable friction force influence factors are combined, a control variable method is adopted to carry out orthogonal experiment design, test data obtained under different test working conditions are extracted, data fitting is carried out, and a curve diagram is formed. The hydro-pneumatic spring can conveniently adjust a proper friction pair combination scheme in real time according to actual use requirements, the service life of the hydro-pneumatic spring is effectively prolonged, and the related performance of the hydro-pneumatic spring is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle oil-gas suspension, and more particularly to a method for measuring the friction force of an oil-gas spring. Background Art

[0002] A gas spring is a suspension component that uses liquid as a force transmission medium and gas as an elastic medium, combining the functions of an elastic element and a shock absorber. Depending on the air chamber, gas springs can be divided into single-chamber gas springs, dual-chamber gas springs, and gas springs with a back-pressure chamber. Compared to single-chamber gas springs, dual-chamber gas springs have the characteristic of variable stiffness. The working front end of a dual-chamber gas spring is the same as that of a single-chamber gas spring. When the load reaches a certain limit and is within a reasonable range, the overall stiffness of the spring decreases, resulting in a reduction in stiffness in the second half of the stroke. Gas springs with a back-pressure chamber have the function of preventing suspension breakdown at the compression endpoint. Gas springs can change the static equilibrium position height of the suspension by filling or releasing oil to adapt to driving requirements on different road conditions. The elastic medium in a gas spring is typically an inert gas like nitrogen, while the force transmission medium is typically oil. These springs exhibit excellent nonlinear characteristics and, compared to other elastic components, can significantly improve vehicle maneuverability, comfort, and operational stability. They have broad application prospects in heavy-duty vehicles, large buses, and military off-road vehicles. Due to the unique structure of gas springs, they are highly dependent on the performance of their sealing structure. Ensuring the sealing performance of gas springs while reducing internal friction and their cost has become a key issue in the development of suspension systems.

[0003] Experimental methods are generally used to measure the performance of gas springs. Currently, common testing methods often consider the friction within the gas spring as a whole, without focusing on the composition of the friction within the spring. This means they fail to analyze the specific impact of different friction pairs within the spring on friction, and thus fail to provide clear guidance for optimizing the friction of the gas spring. Without the ability to quickly and effectively determine the friction characteristics of different friction pairs within the spring, it is impossible to tailor the seal type to the actual requirements of dynamic sealing between different media. This can ultimately lead to a decrease in the overall sealing efficiency and seal life of the gas spring, as well as an increase in the thermal equilibrium temperature. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the object of the present invention is to provide a method for measuring the friction force of an oil-gas spring to solve one or more of the above-mentioned problems.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for measuring the friction force of an oil-gas spring, the working steps are as follows:

[0007] Step 1: Based on the structural characteristics of the oil and gas spring,

[0008] Construct an equivalent test model;

[0009] Step 2: Based on the constructed equivalent test model,

[0010] Decompose the different test states of the oil-gas spring and measure the friction force of the oil-gas spring under different test states;

[0011] Step 3: Based on the oil-gas springs under different test conditions, combined with the controllable factors that affect the friction of the oil-gas springs, carry out characteristic tests.

[0012] After the test, the output force and piston position indicator curves are obtained in compression and tension states respectively;

[0013] Step 4: Based on the power curve,

[0014] Extract the test data obtained under different test conditions and analyze the data to form the elastic force curve.

[0015] Combined with the indicator curve and elastic force curve, it guides the optimal design and application of gas springs.

[0016] Furthermore, in step 1, the position and number of friction pairs of the oil-gas spring are determined.

[0017] A decoupling test was conducted on the friction force of the oil-gas spring, and an equivalent model was established accordingly.

[0018] Furthermore, for the friction pair acting on the cylinder,

[0019] Replace the cylinder and floating piston with an accumulator that has no friction pair and meets the test stroke requirements.

[0020] It is regarded as eliminating the influence of the friction pair at this location.

[0021] Furthermore, according to the maximum volume V of the cylinder before replacement q and initial inflation pressure P q , combined with the volume V of the accumulator x and gas polytropic coefficient m, calculate the initial charging pressure P of the accumulator according to the formula x ,

[0022]

[0023] Adjust the initial charging pressure P of the accumulator x , keeping the internal gas energy consistent before and after replacement.

[0024] Furthermore, for the friction pair acting on the guide sleeve,

[0025] Remove the guide sleeve.

[0026] It is regarded as eliminating the influence of the friction pair at this location.

[0027] Furthermore, in step 2, based on the friction pair that can eliminate the influence,

[0028] Install equivalent replacement parts and several stop valves on the oil and gas springs.

[0029] Directly remove the components involved in the friction and / or adjust the stop valve to eliminate the components causing friction and load equivalent replacement components.

[0030] Decompose the different test states of the oil and gas spring,

[0031] And friction force measurement was carried out.

[0032] Furthermore, in step 3, the oil-gas springs in different test states are installed on the spring characteristic test bench and characteristic tests are carried out.

[0033] By using different initial inflation pressures or adjusting the test equilibrium position, the spring pressure can be accurately and quantitatively controlled. By using different excitation inputs, the relative motion linear velocity of the friction pair can be accurately and quantitatively controlled.

[0034] The output force value and piston position of the oil-gas spring under the corresponding test state are measured to form a power curve.

[0035] Further, it is divided into static characteristic test and dynamic characteristic test.

[0036] By adopting appropriate sinusoidal excitation, the actuator end of the test bench can accurately and quantitatively control the relative motion linear velocity of the friction pair.

[0037] Furthermore, according to the oil-gas spring bench performance test method, the static friction force was measured with a sinusoidal excitation frequency of 0.01 Hz and an amplitude of ±50 mm;

[0038] The dynamic friction force was set with a sinusoidal excitation frequency of 0.33 Hz and an amplitude of ±50 mm.

[0039] Furthermore, in step 4, based on the results of the characteristic test, the indicator curves of the static characteristic test and the dynamic characteristic test are analyzed and processed.

[0040] Extract the characteristic points of friction balance position, tensile limit position and compression limit position from the compression working condition curve and tensile working condition curve and fit the elastic force curve of the oil-gas spring.

[0041] The friction conditions at different points can be obtained by taking the difference between the three curves.

[0042] After judgment, select the best friction pair combination and adjust the sealing form.

[0043] In summary, the present invention has the following beneficial effects: by decoupling the friction pairs of the oil-gas springs, it is easy to grasp the friction conditions corresponding to each friction pair, and to design test methods and data analysis methods for friction forces in various states, which helps to optimize the combination of friction pairs according to actual needs and adjust the sealing scheme, which is beneficial to improving the overall sealing efficiency, sealing life and thermal equilibrium temperature of the oil-gas springs. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 A flowchart of an embodiment of the present invention;

[0045] Figure 2 A schematic diagram of the distribution of friction pairs in one embodiment of the present invention;

[0046] Figure 3 A schematic structural diagram of an oil-gas spring in one embodiment of the present invention;

[0047] Figure 4 A schematic diagram of an equivalent replacement structure in an embodiment of the present invention;

[0048] Figure 5 A structural diagram of a friction pair in state 1 in an embodiment provided by the present invention;

[0049] Figure 6 A structural diagram of a friction pair in state 2 in an embodiment provided by the present invention;

[0050] Figure 7 A structural diagram of a friction pair in state 3 in an embodiment provided by the present invention;

[0051] Figure 8 A structural diagram of a friction pair in state 4 in an embodiment provided by the present invention;

[0052] Figure 9 A structural diagram of a state 1 bench test in an embodiment of the present invention;

[0053] Figure 10 A structural diagram of a state 2 bench test in an embodiment of the present invention;

[0054] Figure 11 A structural diagram of a state 3 bench test in an embodiment of the present invention;

[0055] Figure 12 A structural diagram of a state 4 bench test in an embodiment of the present invention;

[0056] Figure 13 A static characteristic test indicator diagram in an embodiment of the present invention;

[0057] Figure 14 This is a dynamic characteristic test indicator diagram in an embodiment of the present invention.

[0058] In the figure: 1. Upper hinge; 2. Cylinder; 3. Main piston; 4. Guide sleeve; 5. Main piston rod; 6. Damping valve; 7. First stop valve; 8. Second stop valve; 9. Friction pair F1; 10. Friction pair F2; 11. Friction pair F3; 12. Cylinder; 13. Floating piston; 14. Charging valve; 15. Accumulator. DETAILED DESCRIPTION

[0059] Example:

[0060] The following is combined with Figure 1-14 The present invention is described in further detail.

[0061] A method for measuring the friction force of an oil-gas spring, such as Figure 1 As shown, the work steps include constructing an equivalent test model, decomposing the different test states of the oil-gas spring, conducting characteristic tests for the different test states of the oil-gas spring, and analyzing the test data to determine the changes in friction force under different states. This embodiment uses a dual-cylinder swing oil-gas spring as an example to allocate these four steps.

[0062] Step 1: Construct an equivalent model based on the structural characteristics of the gas spring. The basic principle is to decouple the friction force within the gas spring to guide subsequent experimental design.

[0063] like Figure 2 and Figure 3 As shown, first determine the position and number of friction pairs inside the oil-gas spring: in a twin-cylinder swing oil-gas spring, there are typically friction pairs F1 between the main piston and the cylinder barrel, F2 between the main piston rod and the guide sleeve, and F3 between the floating piston and the inner wall of the cylinder. The total friction force f of the twin-cylinder swing oil-gas spring is 总 =f F1 +f F2 +f F3 Where, f 总 is the total friction force of the twin-cylinder swing oil-gas spring, f F1 is the friction force caused by the friction pair F1, f F2 is the friction force caused by the friction pair F2, f F3 It is the friction force caused by friction pair F3.

[0064] like Figure 4 As shown, the friction pair F3 acting on the cylinder can be equivalently replaced with an accumulator, and the cylinder and the floating piston in the cylinder can be completely replaced with an accumulator without a friction pair, thereby eliminating the influence of the friction pair F3 during the test phase.

[0065] Among them, the accumulator must be a standard accumulator without friction pairs that meets the test stroke. The volume of the accumulator is recorded as V x According to the performance table of the gas spring, the maximum volume of its cylinder is recorded as V q , the volume of the accumulator V x Need to be larger than the maximum volume V of the oil and gas spring cylinder q The initial filling pressure of the cylinder is measured and recorded as P q If the external environment remains unchanged, the gas multivariate coefficient m is considered to be non-existent, but this variable needs to be considered in the calculation and setting of the initial charging pressure of the accumulator. The initial charging pressure P of the accumulator is calculated according to the formula x ,

[0066]

[0067] Adjust the initial charging pressure P of the accumulator x , to ensure that the work done by the gas in the cylinder and the gas in the accumulator on the outside world is consistent before and after the accumulator replaces the cylinder.

[0068] Furthermore, for the friction pair F2 acting on the guide sleeve, the guide sleeve can be directly removed so that there is no contact between the main piston rod and the guide sleeve, thereby eliminating the influence of the friction pair F2 during the test phase.

[0069] Step 2: Based on the equivalent test model constructed in step 1, different test states of the oil-gas spring are decomposed, and the friction force of the oil-gas spring under different test states is measured.

[0070] Remove the damping valve between the oil cylinder and the air cylinder in advance to reduce the damping force f generated by the oil passing through the damping valve c Influence.

[0071] An accumulator that meets the requirements is additionally connected to the oil cylinder of the double-cylinder swing oil-gas spring, a first stop valve is added between the oil cylinder and the air cylinder, and a second stop valve is added between the accumulator and the oil cylinder. By opening and closing the two stop valves and retaining or removing the guide sleeve, four test conditions are formed to measure the friction force.

[0072] like Figure 1 As shown, open the first stop valve, close the second stop valve, keep the guide sleeve, and when the oil-gas spring is working, all three friction pairs are involved. The friction force measured at this time is the total friction force f 总 , recorded as state 1; such as Figure 2 As shown, close the first stop valve, open the second stop valve, remove the guide sleeve, and when the oil-gas spring is working, only the friction pair F1 is involved. The friction force measured at this time is the friction force f between the main piston and the cylinder barrel. F1 , recorded as state 2; such as Figure 3As shown, close the first stop valve, open the second stop valve, keep the guide sleeve, and when the oil-gas spring is working, both the friction pair F1 and the friction pair F2 are involved. The friction force measured at this time is the combined friction force f F1 +f F2 , recorded as state 3; Figure 4 As shown, open the first stop valve, close the second stop valve, remove the guide sleeve, and when the oil-gas spring is working, both the friction pair F1 and the friction pair F3 are involved. The friction force measured at this time is the combined friction force f F1 +f F3 , recorded as state 4.

[0073] The test status table is summarized in Table 1:

[0074] Table 1 Test status table

[0075]

[0076] Step 3: Based on the oil-gas springs under different test conditions and combined with the controllable factors that affect the friction of the oil-gas springs, carry out orthogonal tests on the characteristics, such as Figure 9 As shown in Figure 12, after the test, the output force value and the main piston position indicator curves in the compression state and the tension state are obtained respectively.

[0077] The main factors affecting twin-cylinder swinging gas springs include interface temperature, lubrication conditions, spring pressure, sealing material, and relative velocity of the friction pair. Three of these factors can be accurately and quantitatively controlled through tension and compression testing on a gas spring characteristic test bench. The spring pressure and relative velocity of the friction pair can be guided by data analysis, while the sealing material can be controlled directly by replacing the seals. No data modeling or analysis is required; instead, the four existing states are simply fixed values ​​for similar states and set as state variables. Gas springs with different state variables are installed on the spring characteristic test bench and subjected to characteristic testing. The spring pressure can be adjusted by the initial inflation pressure or the spring test equilibrium position, the relative velocity of the friction pair can be adjusted by varying the excitation input, and the sealing material can be adjusted by replacing different seals. The friction force variations of the gas springs under different state variables are measured. During the relevant tests, the initial inflation pressure, test equilibrium position, and component materials remain unchanged; the spring pressure and sealing material are considered to be quantitatively involved. The linear velocity of the relative motion of the friction pair is mainly controlled by the input excitation at the actuator end of the test bench. Generally, sinusoidal excitation is used to measure the output force value of the oil-gas spring and the position of the piston extension and compression under the test state to form a work curve.

[0078] Since friction is divided into static friction and dynamic friction, and the two are generally not equal, static friction and dynamic friction are set according to the performance test method of oil-gas spring bench and measured through static characteristic test and dynamic characteristic test respectively: Generally, the static characteristic test is set with a sinusoidal excitation frequency of 0.01Hz and an amplitude of ±50mm; the dynamic characteristic test is set with a sinusoidal excitation frequency of 0.33Hz and an amplitude of ±50mm.

[0079] Because the damping force is related to the oil flow rate, further increasing the sinusoidal excitation frequency and amplitude may introduce additional damping force, causing heating of the oil-gas spring, and affecting the test progress and accuracy. Therefore, the relative motion linear velocity variable of the friction pair only considers the relevant changes in the static and dynamic characteristic tests.

[0080] Step 4: Based on the power curve, such as Figure 13 As shown in Figure 14, the elastic force curve of the oil-gas spring is obtained after extracting the characteristic points and fitting. Combined with the work curve and the elastic force curve, it can guide the optimization design and application of the oil-gas spring, such as determining the most suitable sealing form.

[0081] After the characteristic test, the output force value and the main piston position indicator curve of the compression and tension working conditions are obtained. The indicator curve is analyzed according to the ideal state to eliminate the influence of the damping force. It can be found that the indicator diagram is mainly composed of two parts: one is the change in elastic force caused by the pressure change caused by the expansion and compression of the gas spring under the tension and compression conditions; the other is the friction resistance caused by the relevant friction pair under the corresponding conditions, which is usually considered to be equivalent to the friction force of the relevant friction pair or friction pair combination. For the data processing of the indicator diagram, the indicator curve is generally divided into two working conditions: compression and tension. Figure 13 and Figure 14 The compression working condition curve of the listed dynamometer diagram is on the top, and the tension working condition curve is on the bottom. Since the data obtained from the test bench is a discrete curve, the compression working condition and the tension working condition are generally fitted separately during data processing to obtain a continuous compression working condition function curve F 压 And tensile working condition function curve F 拉 Ideally, the output force F of the gas spring in compression conditions is 压 is the elastic force F of the oil-gas spring 弹 And the friction resistance f at this time 压 The sum of the output force F of the oil-gas spring in the tensile condition 拉 is the elastic force F of the oil-gas spring 弹 And the friction resistance f at this time 拉 The difference between the two conditions is generally considered to be equal, and because the friction values ​​of compression and tension conditions are generally considered to be equal, that is, f 压 =f 拉 It is not difficult to conclude that at the same main piston stretching position, half of the difference in output force between the two working conditions is the elastic force F of the oil-gas spring at the current position. 弹 The value point of F弹 =(F 压 +F 拉 ) / 2, f=f 压 =f 拉 =(F 压 -F 拉 ) / 2, the elastic force and friction force curves of the gas spring can be obtained. Further analysis, combining the static and dynamic working conditions' indicator curves with the gas spring's elastic force curve, reveals the changes in friction resistance (and, in other words, friction force) under different working conditions corresponding to changes in the main piston position. This provides a scientific and reliable experimental and data processing method for identifying friction in gas springs.

[0082] In summary, through the analysis of the structure and state of the friction pair, the first orthogonal test was carried out to obtain the analysis data under ideal conditions. However, there are actually many external influencing factors, so variables such as the relative motion linear velocity of the friction pair were introduced, and a second orthogonal test was carried out by means of controlling variables to analyze data samples that are more in line with the actual situation. Based on the above method, engineering means are used to quickly and effectively obtain the friction characteristics of different internal friction pairs for different types of oil and gas springs through experimental means, and the sealing form is adjusted in a targeted manner according to the actual use requirements of dynamic seals between different media, that is, to select the appropriate friction pair or combination of friction pairs. This method has good operability and engineering significance, can reduce the overall friction of the oil and gas spring, improve sealing efficiency and sealing life, and reduce the thermal equilibrium temperature, providing a new idea for the identification and extraction of oil and gas spring friction, and providing scientific guidance for the optimization of oil and gas spring friction characteristics.

[0083] It should be noted that this specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to this embodiment as needed, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A method for measuring friction force of an oil-gas spring, characterized in that: The working steps are as follows: Step 1: Based on the structural characteristics of the oil and gas spring, Construct an equivalent test model; Step 2: Based on the constructed equivalent test model, Decompose the different test states of the oil-gas spring and measure the friction force of the oil-gas spring under different test states; Step 3: Based on the oil-gas springs under different test conditions, combined with the controllable factors that affect the friction of the oil-gas springs, carry out characteristic tests. After the test, the output force and piston position indicator curves are obtained in compression and tension states respectively; Step 4: Based on the power curve, Extract the test data obtained under different test conditions and perform data fitting to form the elastic force curve of the oil-gas spring. Combined with the indicator curve and elastic force curve, it guides the optimal design and application of gas springs.

2. The method for measuring friction force of a gas spring according to claim 1, characterized in that: In step 1, determine the position and number of friction pairs of the oil-gas spring. A decoupling test was conducted on the friction force of the oil-gas spring, and an equivalent model was established accordingly.

3. The method for measuring friction force of an oil-gas spring according to claim 2, characterized in that: For the friction pair acting on the cylinder, Replacing the cylinder and floating piston with an accumulator that has no friction pair and meets the test stroke requirements is considered to eliminate the influence of the friction pair at this location.

4. The method for measuring friction force of an oil-gas spring according to claim 3, characterized in that: According to the maximum volume V of the cylinder before replacement q and initial inflation pressure P q , combined with the volume V of the accumulator x and gas polytropic coefficient m, calculate the initial charging pressure P of the accumulator according to the formula x , Adjust the initial charging pressure P of the accumulator x , keeping the internal gas energy consistent before and after replacement.

5. The method for measuring friction force of an oil-gas spring according to claim 2, characterized in that: For the friction pair acting on the guide sleeve, Remove the guide sleeve. It is regarded as eliminating the influence of the friction pair at this location.

6. The method for measuring friction force of a gas spring according to claim 2, characterized in that: In step 2, based on the friction pair that can eliminate the influence, Install equivalent replacement parts and several stop valves on the oil and gas springs. Directly remove the components involved in the friction and / or adjust the stop valve to eliminate the components causing friction and load equivalent replacement components. Decompose the different test states of the oil and gas spring, And friction force measurement was carried out.

7. The method for measuring friction force of a gas spring according to claim 1, characterized in that: In step 3, the oil-gas springs in different test states are installed on the spring characteristic test bench and the characteristic test is carried out. By using different initial inflation pressures or adjusting the test equilibrium position, the spring pressure can be accurately and quantitatively controlled. By using different excitation inputs, the relative motion linear velocity of the friction pair can be accurately and quantitatively controlled. The output force value and piston position of the oil-gas spring under the corresponding test state are measured to form a power curve.

8. The method for measuring friction force of a gas spring according to claim 7, characterized in that: It is divided into static characteristic test and dynamic characteristic test. By adopting appropriate sinusoidal excitation, the actuator end of the test bench can accurately and quantitatively control the relative motion linear velocity of the friction pair.

9. The method for measuring friction force of a gas spring according to claim 8, characterized in that: The static friction force was measured according to the performance test method of the oil-gas spring bench, with a sinusoidal excitation frequency of 0.01 Hz and an amplitude of ±50 mm. The dynamic friction force was set with a sinusoidal excitation frequency of 0.33 Hz and an amplitude of ±50 mm.

10. The method for measuring friction force of a gas spring according to claim 8, characterized in that: In step 4, based on the results of the characteristic test, the power curves of the static characteristic test and the dynamic characteristic test are analyzed and processed. Extract the characteristic points of friction balance position, tensile limit position and compression limit position from the compression working condition curve and tensile working condition curve and fit the elastic force curve of the oil-gas spring. The friction conditions at different points can be obtained by taking the difference between the three curves. After judgment, the best friction pair combination is selected to guide the adjustment of the sealing form.

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