A bench test method for thermal equivalent durability of oil-gas springs

Abstract

This invention discloses a thermal equivalent durability bench test method for gas springs, belonging to the field of vehicle gas suspension, and includes the following steps: Step 1, obtaining the oil equilibrium temperature of the gas spring through actual sports car testing; Step 2, adjusting the parameters of the sinusoidal excitation of the bench to ensure that the oil temperature of the gas spring during the durability bench test meets the oil equilibrium temperature; This invention can accurately reflect the actual sports car mileage on the test bench using sinusoidal excitation durability.

Description

Technical Field

[0001] This invention relates to the field of vehicle hydropneumatic suspension, and more specifically to a bench test method for the thermal equivalent durability of hydropneumatic springs. Background Technology

[0002] A gas spring is a vibration damping device that integrates elastic and damping elements, using gas as the elastic medium and liquid as the force transmission medium. The elastic medium in a gas spring is typically an inert gas such as nitrogen, while the force transmission medium is usually liquid oil. It exhibits good nonlinear characteristics and, compared to other elastic elements, can significantly improve vehicle maneuverability, comfort, and handling stability, making it widely applicable in heavy-duty trucks, large buses, and military off-road vehicles. However, its reliability and durability have consistently been somewhat lacking, which has severely hindered the large-scale adoption of gas springs. From a forward design perspective, the main reason for this situation is the lack of a cost-effective, easy-to-operate, and accurate durability testing method. For example, consider a common test scheme involving sinusoidal excitation:

[0003] A common durability testing method involves applying sinusoidal displacement excitation using a hydraulic test bench. This method defines the durability of the gas spring by the number of times or duration the sinusoidal excitation is completed without failure. It is the most commonly used method in current gas spring component-level durability testing because it is relatively simple and easy to implement, avoiding the high costs of actual sports car testing or the demanding equipment requirements for applying actual displacement excitation. However, because the excitation experienced by the gas spring during actual sports car testing is random, there is a lack of scientific correlation between random excitation and sinusoidal excitation in durability assessment. This leads to test results that differ significantly from actual sports car mileage, resulting in inaccurate durability test results. Summary of the Invention

[0004] In view of this, the present invention provides a test method for the thermal equivalent durability of oil-gas springs on a test bench, which can accurately reflect the actual mileage of a sports car by using sinusoidal excitation durability on a test bench.

[0005] To solve the above-mentioned technical problems, the present invention is implemented as follows:

[0006] A bench test method for the thermal equivalent durability of a gas spring includes the following steps:

[0007] Step 1: Obtain the fluid equilibrium temperature of the gas spring through actual sports car testing.

[0008] Step 2: By adjusting the parameters of the sinusoidal excitation of the test bench, the oil temperature of the gas spring during the durability test is made to meet the oil equilibrium temperature.

[0009] Preferably, the parameters of the bench sinusoidal excitation include amplitude and frequency; the amplitude is related to the road surface grade, and the frequency is related to the average vehicle speed.

[0010] Preferably, step two is as follows:

[0011] The oil temperature of the gas spring was measured during the durability bench test.

[0012] According to the oil equilibrium temperature Adjust the parameters;

[0013] When the oil temperature is lower than the oil equilibrium temperature When the oil temperature is higher than the oil equilibrium temperature, increase the amplitude and / or frequency. At that time, reduce the amplitude and / or frequency.

[0014] Preferably, the parameter adjustment specifically involves:

[0015] At set time intervals t0, the oil temperature and the oil equilibrium temperature are monitored. Compare;

[0016] When the oil temperature is lower than the oil equilibrium temperature At this time, the amplitude of the sinusoidal excitation is increased by a set value 'a', and the frequency is increased by a set value 'b', and the experiment and temperature measurement are continued.

[0017] When the oil temperature is higher than the oil equilibrium temperature When a set value x is above a certain value, the frequency of the sinusoidal excitation is first reduced by b, and the test and temperature measurement are continued. If the oil temperature continues to rise, the amplitude of the sinusoidal excitation is reduced by a, and the test and temperature measurement are continued. If the oil temperature continues to rise, the excitation frequency and amplitude are reduced alternately in this way.

[0018] When the oil temperature is higher than the oil equilibrium temperature And lower than Meanwhile, continue the experiment and temperature measurement while maintaining the current excitation frequency and amplitude.

[0019] Preferably, the set time t0 = 200s, the set value x = 5℃, a = 0.005m, and b = 0.05Hz.

[0020] Preferably, the road surface grade and average vehicle speed are obtained through the road surface condition and vehicle speed in the actual sports test; the initial value of amplitude is obtained according to the correspondence between road surface grade and amplitude, and the initial value of frequency is obtained according to the correspondence between average vehicle speed and frequency.

[0021] Preferably, the correspondence is as follows:

[0022]

[0023] The road surface roughness is described by eight road surface grades A to H, which are classified according to power spectral density, and each grade corresponds to an initial value of sinusoidal excitation amplitude and an initial value of sinusoidal excitation frequency corresponding to the average vehicle speed.

[0024] Preferably, the oil equilibrium temperature of the gas spring is obtained. For example, during actual sports car testing, when the change in oil temperature within a set time t1 is less than a set value y, the highest temperature within this time t1 is called the oil equilibrium temperature.

[0025] Preferably, the set time t1 = 360s and the set value y = 1℃.

[0026] Preferably, the adjustment has a temperature rise grace period with a set time t2. During the grace period after the start of the test, if the oil temperature is lower than the equilibrium temperature, no adjustment is made and the temperature is allowed to rise. If the oil temperature is higher than the equilibrium temperature, the parameter adjustment is performed.

[0027] The present invention has the following beneficial effects:

[0028] (1) This invention establishes the correspondence between sinusoidal displacement excitation and actual random excitation, and obtains more accurate oil-gas spring durability test results through the test scheme of hydraulic test bench with sinusoidal displacement excitation.

[0029] (2) The correspondence between amplitude and road surface grade, frequency and average vehicle speed in this invention makes the actual running process, which is difficult to analyze and simulate due to the randomness of real excitation, possible to be simulated by a simple sinusoidal excitation process.

[0030] (3) By making the oil temperature approximately equal to the equilibrium temperature, this invention can achieve a durability test effect equivalent to random real excitation by simply adjusting two simple parameters: the amplitude and frequency of the sinusoidal excitation of the durability test bench.

[0031] (4) In the process of trying to reduce the oil temperature, the present invention selects a design that first reduces the frequency and then alternately reduces the amplitude, so that the durability test is more consistent and the adjustment operation is simpler, since changing the frequency of the sinusoidal excitation does not require stopping the equipment.

[0032] (5) The preferred values ​​of the set parameters in this invention further simplify the adjustment operation of the durability test and make the durability test of the gas spring more accurate.

[0033] (6) The initial value of the sinusoidal excitation parameter obtained from the parameters obtained from the actual sports car test further improves the accuracy of the fitting degree of the sinusoidal excitation applied by the test bench to the random excitation of the actual sports car test.

[0034] (7) The present invention makes the fitting relationship of the initial value more accurate by optimizing the data correspondence relationship and reduces the complexity of adjustment in subsequent experiments.

[0035] (8) By obtaining the oil balance temperature of the oil spring, the present invention enables the actual random excitation process, which is originally difficult to analyze, to be reflected by a definite temperature value.

[0036] (9) The present invention optimizes the parameter values ​​for oil equilibrium temperature, taking into account both the simplicity and accuracy of the test process.

[0037] (10) The heating grace period set in this invention reduces the complexity of subsequent adjustments and simplifies the test procedure. Attached Figure Description

[0038] Figure 1 The randomness of the road surface roughness function;

[0039] Figure 2 The sinusoidal displacement excitation that the test bench can provide;

[0040] Figure 3 The measured oil temperature rise curve for the gas spring durability test in a sports car;

[0041] Figure 4 A flowchart for collecting relevant parameters during actual sports car testing;

[0042] Figure 5 This is a flowchart for the equivalent durability test of a gas spring test bench. Detailed Implementation

[0043] The durability testing method of the present invention will be further described below with reference to the accompanying drawings.

[0044] As a shock absorber, the durability of a gas spring is significantly affected by the road surface conditions. In the field of suspension systems, the change q(I) in the height q of the road surface relative to the reference plane along the road's length I is usually referred to as the road surface roughness function, such as... Figure 1As shown, this exhibits randomness. Qualitative analysis reveals that at the same vehicle speed, the worse the road surface and the higher the unevenness, the greater the impact load on the gas spring, and the lower its lifespan, and vice versa. Conversely, under the same road conditions, the higher the vehicle speed, the more impacts the gas spring experiences per unit time, resulting in a greater impact load and a lower lifespan, and vice versa. Therefore, the lifespan of the gas spring is related to road unevenness and vehicle speed. Road unevenness affects the magnitude of the impact load on the spring, while vehicle speed affects the number of impacts. Road unevenness, as a random excitation, acts on the wheels or tracks, causing the impacts and loads experienced by the gas spring to also have randomness, making it theoretically difficult to predict accurately. Furthermore, during excited operation, the gas spring's temperature rises due to the conversion of mechanical energy into internal energy; the oil temperature of the gas spring indirectly reflects the intensity of its operation.

[0045] The experimental method provided by this invention is to adjust the parameters of the sinusoidal displacement excitation of the test bench to make the oil-gas explosive...

[0046] The oil temperature of the air spring meets the oil equilibrium temperature of the air spring obtained through actual sports car tests. (℃), establish the correspondence between sinusoidal displacement excitation and actual random excitation, and then obtain more accurate oil-gas spring durability test results through the test scheme of hydraulic test bench with sinusoidal displacement excitation.

[0047] Existing durability testing benches for gas springs or vibration dampers can provide, for example Figure 2 The diagram illustrates sinusoidal displacement excitation. In sinusoidal excitation, the amplitude affects the load magnitude; a larger amplitude results in a larger load. The frequency affects the number of impacts; a higher frequency results in more impacts. It is evident that the amplitude of the sinusoidal excitation corresponds to the parameter of road surface unevenness in simulating the use of a gas spring, and the frequency of the sinusoidal excitation corresponds to the parameter of vehicle speed in simulating the use of a gas spring. By adjusting the durability bench test parameters, including the test environment temperature and the sinusoidal excitation parameters, the amplitude and frequency of the sinusoidal excitation are optimally selected to simulate actual sports car tests. It is this correspondence that allows the actual sports car process, which is difficult to analyze and simulate due to the randomness of real excitation, to be simulated by a simple sinusoidal excitation process.

[0048] When a gas spring is energized and operates, the temperature of the oil will rise as heat is generated. Figure 3This is a curve showing the temperature change of the hydraulic fluid in a gas spring over time during a constant-speed test at a test track. It can be seen that in the initial stage of the test, the hydraulic fluid temperature rises rapidly. As time progresses, the slope of the temperature increase decreases, eventually reaching thermal equilibrium and maintaining a stable temperature. In this invention, this stable temperature is referred to as the hydraulic fluid equilibrium temperature. Specifically, during the actual gas spring test, within a set time t1, when the change in hydraulic fluid temperature is less than a set value y, the highest temperature within this time t1 is called the hydraulic fluid equilibrium temperature. For example... Figure 3 The equilibrium temperature of the hydraulic fluid in a gas spring is approximately 125℃. By obtaining the equilibrium temperature of the hydraulic fluid in the gas spring, the random excitation process in actual operation, which was originally difficult to analyze, can be reflected by a definite temperature value.

[0049] Based on the results of multiple experiments, the optimal values ​​were t1 = 360s and y = 1℃. These optimal values ​​for the oil equilibrium temperature parameters balanced simplicity and accuracy during the experimental process.

[0050] After obtaining the oil equilibrium temperature, during the durability bench test, the corresponding parameters are adjusted to ensure that the oil temperature of the gas spring during the test is approximately equal to the aforementioned oil equilibrium temperature. Specifically, the oil temperature of the gas spring is measured in real time during the bench test. When the oil temperature is lower than the equilibrium temperature, the amplitude or frequency is increased; when the oil temperature is higher than the equilibrium temperature, the amplitude or frequency is decreased, until the oil temperature is approximately equal to the equilibrium temperature. Through this approximate relationship achieved by adjusting the parameters, a durability test effect equivalent to random real excitation can be obtained by simply adjusting the amplitude and frequency of the sinusoidal excitation on the durability bench.

[0051] The present invention will be further described in detail below with reference to an embodiment.

[0052] Step 1: Conduct actual sports car tests using gas springs.

[0053] Figure 4 This is a flowchart of a real-world test of a gas spring in a sports car. In this embodiment, the real-world test requires determining two parameters: one is the oil equilibrium temperature. Second, the initial value of the sinusoidal excitation that needs to be adjusted.

[0054] For oil equilibrium temperature The method for determining this temperature is as follows: every 30 seconds, the temperature of the hydraulic spring fluid is collected. Once the fluid reaches thermal equilibrium and stabilizes at a certain temperature, the equilibrium temperature of the fluid is recorded. (°C).

[0055] The initial value of the sinusoidal excitation is determined as follows: the initial value of the sinusoidal excitation to be adjusted includes both amplitude and frequency. Based on the correspondence between road surface grade and the amplitude of the sinusoidal excitation, and between average vehicle speed and the frequency of the sinusoidal excitation, parameters such as road surface grade and average vehicle speed should be determined for durability bench testing. Road surface grade and average vehicle speed... The speed (km / h) can be obtained through actual sports car testing, or it can be set based on design specifications or experience. In this invention, actual sports car testing is preferred. The road surface grade of the test track is determined and recorded by measuring on-site or reading test track information, and the average speed of the sports car is calculated based on the driving time and mileage. (km / h). After determining the road surface grade and average vehicle speed, the initial amplitude value is obtained based on the correspondence between road surface grade and amplitude, and the initial frequency value is obtained based on the correspondence between average vehicle speed and frequency. The initial values ​​of the sinusoidal excitation parameters obtained from the actual sports test further improve the accuracy of the fitting of the sinusoidal excitation applied by the test bench to the random excitation of the actual sports test.

[0056] Based on the results of multiple experiments, the initial value correspondences between road surface grade and amplitude, and between average vehicle speed and frequency were optimized and are shown in Tables 1 and 2.

[0057] Road surface grade A B C D E F G H <![CDATA[Corresponding amplitude A0 (m)]]> 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08

[0058] Table 1

[0059]

[0060] Table 2

[0061] The road surface roughness is described using eight road surface grades, A to H, based on power spectral density, with each grade corresponding to an initial sinusoidal excitation amplitude A0 (m). The average vehicle speed is used as the criterion for grading. The vehicle speed is described by (km / h), and each corresponds to an initial value f0 (Hz) of the sinusoidal excitation frequency. By optimizing the data correspondence, the fitting relationship of the initial values ​​is made more accurate, and the complexity of adjustment in subsequent experiments is reduced.

[0062] Step 2: Conduct a sinusoidal excitation durability test on the test bench.

[0063] After collecting relevant actual sports car test data, the initial value of the sinusoidal excitation amplitude A0(m) was set as the initial amplitude A of the sinusoidal excitation applied by the test bench. i (m)(i=1), set the initial value of the sinusoidal excitation frequency f0 (Hz) to the initial frequency f of the sinusoidal excitation applied by the test bench. i (Hz)(i=1). Using x(t)=A i sin(2πf iPerform a durability bench test on the oil-gas spring with a sinusoidal excitation of x(t) = A sin(2πft), where t (s) is the test time.

[0064] During the test, the oil temperature T (°C) of the oil-gas spring is collected every set time t0 and compared with the average oil temperature (°C), that is, to judge whether it holds, and there are the following three situations:

[0065] ① That is, the current oil temperature T (°C) has not yet reached the oil equilibrium temperature (°C). At this time, judge whether the test time t (s) exceeds a set grace period with a duration of t2, that is, a grace period for waiting for the oil to heat up is given within a period of time after the start of the test. If t < t2, continue to perform the durability bench test on the oil-gas spring with a sinusoidal excitation of x(t) = A i sin(2πf i t) (i = 1). If t > t2, but the oil temperature T (°C) still has not reached the equilibrium temperature (°C), then the excitation amplitude is increased by a set value a, that is, A i+1 = A i + a, and the excitation frequency is increased by a set value b, that is, f i+1 = f i + b, and continue to perform the bench test with a sinusoidal excitation of x(t) = A i sin(2πf i t) (i = i + 1).

[0066] The significance of setting the grace period is that the oil-gas spring will continuously heat up to reach thermal equilibrium within a period of time after the start of the durability test. During this period, it is meaningless to adjust the amplitude or frequency to control the oil temperature. Setting the grace period can better reduce the complexity of adjustment and simplify the test plan.

[0067] ② That is, when the oil temperature T (°C) is higher than the oil equilibrium temperature (°C) by more than a set value x, first reduce the excitation frequency by b, that is, f i+1 = f i - b, and continue to perform the bench test with a sinusoidal excitation of x(t) = A i sin(2πf i t) (i = i + 1); if the equilibrium temperature continues to rise, then reduce the excitation amplitude by a, that is, A i+1 = A i - a, and continue to perform the bench test with a sinusoidal excitation of x(t) = A i sin(2πf iA bench test is conducted using t)(i=i+1). If the oil temperature continues to rise, the excitation frequency and amplitude are alternately reduced until the oil temperature drops to t)(i=i+1). Up to (°C) or below.

[0068] In the process of trying to reduce the oil temperature, since changing the frequency of the sinusoidal excitation does not require stopping the equipment, the design of first reducing the frequency and then alternately reducing the amplitude makes the durability test more consistent and the adjustment operation simpler.

[0069] ③ That is, the oil temperature T (°C) is higher than the oil equilibrium temperature. (°C), but below When (°C), maintain the current excitation frequency and amplitude, and continue to excite with sinusoidal x(t) = A. i sin(2πf i t) Conduct bench tests. When the oil temperature T (°C) meets this condition, it is said to meet the oil equilibrium temperature. (°C).

[0070] The set times and values ​​are optimized based on multiple tests as follows: t0 = 200s, x = 5℃, a = 0.005m, b = 0.05Hz. These optimized values ​​further simplify the adjustment operation of the durability test and make the durability test of the gas spring more accurate.

[0071] Figure 5 This is a flowchart for the equivalent durability test of the oil-gas spring test bench. The oil temperature T (°C) is collected and adjusted according to the three conditions described above to maintain the oil temperature T (°C) at a constant level. Within a certain range. In practice, under different temperature ranges, it is also possible to adjust only one of the parameters, amplitude and frequency, but the adjustment efficiency is slightly weaker.

[0072] By recording the test time t(s) from the durability test bench, combined with the average vehicle speed (km / h), calculate the equivalent test mileage s (km), we have:

[0073]

[0074] By analyzing the wear level and failure time of the gas springs during the test, the corresponding equivalent test mileage can be calculated. Finally, by applying sinusoidal excitation to the gas springs on the test bench, an approximate result of random excitation in actual sports car tests can be obtained. By testing various types of gas springs using the above-mentioned thermal equivalent durability bench test scheme and comparing the results with actual sports car tests, it was found that the actual wear level and failure mileage of the gas springs were close to the estimates from the equivalent test, indicating that this method is feasible.

[0075] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A bench test method for the thermal equivalent durability of a gas spring, characterized in that, Includes the following steps: Step 1: Obtain the fluid equilibrium temperature of the gas spring through actual sports car testing. ; Step 2: By adjusting the parameters of the sinusoidal excitation of the test bench, the oil temperature of the gas spring during the durability test is made to meet the oil equilibrium temperature. ; The parameters of the sinusoidal excitation on the test bench include amplitude and frequency; the amplitude is related to the road surface grade, and the frequency is related to the average vehicle speed. Step two is as follows: The oil temperature of the gas spring was measured during the durability bench test. According to the oil equilibrium temperature Adjust the parameters: Every set time interval t 0. Oil temperature and the oil equilibrium temperature Compare; When the oil temperature is lower than the oil equilibrium temperature At that time, the amplitude of the sinusoidal excitation is increased by a set value. a The frequency increases by a set value. b Continue conducting experiments and temperature measurements; When the oil temperature is higher than the oil equilibrium temperature A set value x When doing the above, first reduce the frequency of the sinusoidal excitation. b Continue the experiment and temperature measurement. If the oil temperature continues to rise, reduce the amplitude of the sinusoidal excitation. a Continue the experiment and temperature measurement. If the oil temperature continues to rise, continue to alternately reduce the excitation frequency and amplitude. When the oil temperature is higher than the oil equilibrium temperature And lower than + x Meanwhile, continue the experiment and temperature measurement while maintaining the current excitation frequency and amplitude.

2. The method for thermal equivalent durability bench testing of oil-gas springs as described in claim 1, characterized in that, The set time t 0 = 200s, the set value x =5℃, a =0.005m, b =0.05Hz.

3. The bench test method for thermal equivalent durability of oil-gas springs as described in claim 1 or 2, characterized in that, The road surface grade and average vehicle speed are obtained from the road surface condition and vehicle speed in the actual sports test; the initial value of amplitude is obtained according to the correspondence between road surface grade and amplitude, and the initial value of frequency is obtained according to the correspondence between average vehicle speed and frequency.

4. The bench test method for thermal equivalent durability of oil-gas springs as described in claim 3, characterized in that, The specific correspondence is as follows: The road surface roughness is described by eight road surface grades A to H, which are classified according to power spectral density, and each grade corresponds to an initial value of sinusoidal excitation amplitude and an initial value of sinusoidal excitation frequency corresponding to the average vehicle speed.

5. The method for thermal equivalent durability bench testing of oil-gas springs as described in claim 1, characterized in that, The oil equilibrium temperature of the gas spring is obtained. For: During actual sports car testing, the gas spring, at a set time t Within 1, when the change in oil temperature is less than a set value y At that time, this time t The highest temperature within 1 is called the oil equilibrium temperature.

6. The bench test method for thermal equivalent durability of oil-gas springs as described in claim 5, characterized in that, The set time t 1 = 360s, the set value y =1℃.

7. The method for thermal equivalent durability bench testing of oil-gas springs as described in claim 1, characterized in that, The adjustment has a set time period. t The temperature rise grace period 2 refers to the period after the start of the test. If the oil temperature is lower than the equilibrium temperature, no adjustment is made and the temperature is allowed to rise. If the oil temperature is higher than the equilibrium temperature, the parameters mentioned above are adjusted.

Images