Method for accelerated life testing of silicone fluid clutch solenoid

Abstract

The present application relates to a kind of silicone oil clutch solenoid life acceleration test method, which can be according to the life index of customer, by algorithm to obtain a set of acceleration test method for verifying solenoid reliability or life according to the Coffin-Manson model;The reliability or life index of solenoid is evaluated by using the method of acceleration test, and the index after evaluation can be used to guide the positive development of solenoid;The present application can evaluate the reliability of solenoid according to the reliability requirement of whole vehicle OEM, according to the road spectrum of whole vehicle and the proportion of different states of silicone oil clutch fan, and obtain the simulation results equivalent to long-term fatigue conditions in a relatively short period of time, save a lot of time cost, save verification cost.

Description

Technical Field

[0001] The present invention relates to the technical field of automobile thermal management systems, and in particular to a silicone oil clutch solenoid life acceleration test method. Background Art

[0002] As the sole electronically controlled component in an electronically controlled silicone oil clutch, the solenoid performs the following functions: First, it receives the pulse width modulation (PWM) signal from the ECU and, depending on the PWM duty cycle, induces magnetic fields of varying strengths within the clutch. This magnetic field drives the control valve stem in the oil reservoir, adjusting the amount of silicone oil in the working chamber to deliver varying torques and regulate the fan speed. Second, the solenoid converts the fan's real-time speed into high and low voltage signals and feeds them back to the ECU. The ECU continuously adjusts the desired speed based on the deviation between the fan's real-time speed and the desired speed represented by the PWM signal, thereby forming a PID closed-loop control system that rapidly brings the fan's real-time speed close to the desired speed. In summary, whether the solenoid is functioning properly can significantly impact the clutch fan's functionality, such as speed control stability and even clutch life.

[0003] Estimating the reliability of a solenoid requires considering numerous parameters, making it difficult to establish a reliability model. As a key component of an electronically controlled silicone oil clutch fan, the solenoid faces extremely high reliability requirements from vehicle OEMs. Furthermore, given the high failure rate of solenoids in the aftermarket, establishing a suitable solenoid life assessment mechanism during the design phase is imperative. Consequently, an increasing number of fan manufacturers are beginning to address this issue.

[0004] Currently, major fan manufacturers lack understanding of the reliability or life indicators of solenoids, and their design schemes or selected materials are also different. For example, when a commercial vehicle OEM proposes a specific solenoid life indicator, the fan manufacturer will not adopt different design schemes or materials based on the different life indicators. At the same time, the accelerated verification method is also applied to the existing verification method without adaptive modification. Specifically, there are many varieties of solenoids on the market, and the accelerated endurance test standards of different solenoids are also different. It is impossible to confirm whether the test standards can meet the reliability requirements of the whole vehicle; secondly, if the reliability requirements of the whole vehicle change, it is impossible to confirm whether these changes will lead to changes in the accelerated test standards of the solenoids; finally, different vehicle models, such as engineering vehicles and tractors, cannot confirm whether a test standard is reasonable. These doubts have hindered the evaluation of the reliability or life indicators of the solenoids. Summary of the Invention

[0005] To solve the above problems, the present invention provides a method for accelerating the life of a silicone oil clutch solenoid. The method can evaluate the reliability of the solenoid according to the reliability requirements of the vehicle OEM, the vehicle's road spectrum, and the proportion of different states of the silicone oil clutch fan.

[0006] The technical solution adopted by the present invention is: a silicone oil clutch solenoid life accelerated test method, characterized in that it includes the following steps:

[0007] S1. Vehicle life analysis

[0008] The collected parameters include: B10 design life mileage L, average speed V, B10 design life time T, average number of working days per year D2, average number of rest days per year D3 and daily driving time on working days T1;

[0009] The parameters to be calculated include: the total number of working days in the lifespan Total number of rest days in life D4 = D3 × Y1, total number of working days + rest days D = D1 + D4, total number of working days in life and B10 design life years

[0010] S2. Solenoid heat load data collection: Collect the following parameters in actual use: ambient temperature Ta, operating time, engine speed, fan speed, solenoid maximum temperature Ts and its proportion; then, the actual temperature change ΔT1 = Ts - Ta, the temperature distribution proportion in a day A, the number of temperature changes in a day n, and the actual number of cycles at different temperatures N1 = D1 × A × n;

[0011] Based on the collected actual ambient temperature Ta, operating time, engine speed, and fan speed, the clutch fan status is reproduced on the test bench and the highest solenoid temperature Ts and its proportion are collected on the test bench.

[0012] S3. Determination of solenoid bench accelerated test parameters: Design the number of cycles N2 required for the bench test based on the Coffin-Manson model

[0013]

[0014] The formula can be changed to obtain the number of cycles N2 required for the bench test

[0015]

[0016] Where AFcm is the model acceleration factor; N1 is the number of temperature cycles of the solenoid during vehicle use; N2 is the number of temperature cycles of the solenoid during bench testing; ΔT1 is the temperature change of the solenoid during vehicle use; ΔT2 is the temperature change of the solenoid during bench testing; and α is the Coffin-Manson exponent, which is the acceleration rate constant of temperature change.

[0017] Preferably, the temperature at the highest point of the solenoid is the highest, and the temperature at the highest point of the solenoid is collected by arranging a thermocouple at the highest point of the solenoid.

[0018] Preferably, α is 2.

[0019] The present invention has the following beneficial effects: Based on the Coffin-Manson model, the present invention can derive a set of accelerated test methods for verifying the reliability or life of a solenoid through an algorithm based on the customer's life indicators; the reliability or life indicators of the solenoid are evaluated using an accelerated test method, and the evaluated indicators can be used to guide the forward development of the solenoid; the present invention can evaluate the reliability of the solenoid according to the reliability requirements of the vehicle OEM, based on the vehicle's road profile and the proportion of different states of the silicone oil clutch fan; the present invention has the following advantages:

[0020] 1. Evaluating the fatigue properties of materials during product development often takes a long time, and in some cases, the evaluation results are unsatisfactory. However, the present invention can obtain simulation results equivalent to those under long-term fatigue conditions in a shorter period of time through accelerated testing methods, saving a lot of time and verification costs.

[0021] 2. Different acceleration parameters can be formulated according to the different working conditions of the solenoid to effectively evaluate whether the solenoid products meet the life requirements. This avoids the problem of using the same acceleration parameters for different customers and different road conditions, which may lead to inaccurate evaluation results. It can effectively reduce after-sales quality problems or cost increases caused by product over-design;

[0022] 3. The invention proposed the principle of accelerated life test for solenoids for the first time, filling the gap in domestic accelerated testing and providing fan manufacturers with a way to evaluate the life indicators of solenoids, saving development costs and time. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the solenoid assembly;

[0024] Figure 2 The temperature test curves of different positions of the solenoid are shown;

[0025] Figure 3 This is the solenoid temperature cycle test curve;

[0026] Figure 4 This is the temperature change percentage of the solenoid coil when the vehicle is driving;

[0027] In the figure: 1. Coil seat; 2. Electromagnetic coil; 3. Bearing; 4. Bearing seat; 5. Plastic housing; 6. Wiring harness; 7. Speed ​​sensor; 8. Silicone oil; 9. Control valve stem. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to the accompanying drawings.

[0029] like Figure 1 As shown, the silicone oil clutch solenoid primarily consists of an electromagnetic coil 2, a bearing 3, a coil holder 1, a bearing seat 4, a plastic housing 5, a wiring harness 6, and a speed sensor 7. First, when the silicone oil clutch fan is operating, the electromagnetic coil 2 in the solenoid receives periodic high and low level control signals from the ECU, causing it to periodically switch on and off. For example, when the electromagnetic coil 2 is on, it generates heat and induces a magnetic field. This magnetic field drives the control valve stem 9 inside the clutch, causing the solenoid temperature to rise. When the electromagnetic coil 2 is de-energized, the induced magnetic field disappears, the control valve stem 9 stops moving, and the solenoid temperature drops. Second, the silicone oil 8 inside the clutch converts the engine's mechanical energy into the fan's mechanical energy through its own shear force. Some of this lost energy is converted into heat energy in the silicone oil 8, resulting in a relatively high temperature. This heat is then radiated to the solenoid, transferring heat. Third, changes in ambient temperature, such as lower temperatures in the morning and evening and higher temperatures at noon, can also affect the solenoid temperature. In summary, the solenoid is always under the action of temperature alternation, and the Coffin-Manson Model is very suitable. The Coffin-Manson Model is used to describe the life characteristics of materials under temperature fatigue loads and is generally suitable for the accelerated model of temperature shock tests.

[0030] The thermal fatigue test method of the present invention for accelerating the life of a silicone oil clutch solenoid introduces the Coffin-Manson model into the thermal fatigue test of the solenoid, and comprises the following steps:

[0031] S1. Vehicle life analysis

[0032] The collected parameters include: B10 design life mileage L, average speed V, B10 design life time T, average annual working days D2, average annual rest days D3, and daily driving time on weekdays T1. The parameters to be calculated include: total working days D1, total rest days D4, total working days + rest days D (i.e., lifespan), total working days Y1, and B10 design life Y2. Specific definitions are shown in the table below.

[0033]

[0034] S2, solenoid heat load data collection: such as Figure 2 As shown, the temperature at the highest point of the solenoid is the highest. A thermocouple is arranged at this position (the temperature at the enameled wire of the coil of the solenoid is the best. The temperature collected here by the thermocouple can represent the temperature at the highest point of the solenoid). The solenoid is assembled on the whole vehicle. Then, according to the vehicle model: for example, tractor, engineering vehicle and mining vehicle, etc., and the vehicle application scenario: such as highway, mountainous area and urban road sections, the following parameters are collected: ambient temperature Ta, running time, engine speed, fan speed, the temperature at the highest point of the solenoid temperature Ts and its proportion; then, the actual temperature change ΔT1 = Ts-Ta, the temperature distribution proportion A in one day, the number of temperature changes in one day n, the actual number of cycles used at different temperatures N1 = D1×A×N; if the temperature and proportion of the solenoid cannot be detected on the whole vehicle, the state of the clutch fan can be reproduced on the test bench according to the collected actual ambient temperature Ta, running time, engine speed and fan speed, and the temperature at the highest point of the solenoid temperature Ts and its proportion on the test bench can be collected;

[0035] S3. The B10 design life of commercial vehicles is usually greater than 1 million kilometers. Calculated at an average speed of 40 km / h, the B10 design life is greater than 25,000 hours. During product development, if 25,000 hours of testing is used for verification, the test cycle will be long and costly, and it will not meet the project milestones. Therefore, it is necessary to design appropriate accelerated tests to save development costs. Based on the Coffin-Manson model, a bench test is designed to calculate the number of test cycles required:

[0036]

[0037] The formula can be changed to obtain the number of cycles N2 required for the bench test

[0038]

[0039] Where AFcm is the model acceleration factor; N1 is the number of temperature cycles of the solenoid during vehicle use; N2 is the number of temperature cycles of the solenoid during bench testing; ΔT1 is the temperature change of the solenoid during vehicle use; ΔT2 is the temperature change of the solenoid during bench testing; and α is the Coffin-Manson exponent, which is the acceleration rate constant of temperature change.

[0040] Example:

[0041] 1. Analysis of vehicle life requirements

[0042] For example, a certain vehicle model, B10, has a lifespan of L = 1.6 million kilometers. Based on a speed of V = 60 km / h, the design lifespan of B10 is calculated to be T = 26,667 hours. Assuming a daily driving time of T1 = 12 hours on weekdays, the total number of working days D1 = 2,222 days. Assuming an annual working day of D2 = 320 days and an average annual rest day of D3 = 45 days, the total number of working days Y1 = 6.94 years. The total number of rest days D4 = 313 days, and the total number of working days + rest days D = 2,535 days. Based on this model, the solenoid has a service life of Y2 = 6.94 years. The specific process is shown in the table below:

[0043]

[0044] 2. Solenoid thermal load data collection

[0045] There are two types of solenoid thermal loads: when the vehicle is moving and when it is stationary.

[0046] 2.1 Vehicle Driving

[0047] A silicone oil clutch fan equipped with a thermocouple was installed on the aforementioned B10 vehicle with a lifespan of L = 1.6 million kilometers. Assuming the vehicle's driving profile is: 18% mountain roads, 72% highways and flat roads, 1.6% mountain roads on secondary highways, 6.4% flat roads on secondary highways, 0.4% mountain roads in urban conditions, and 1.6% flat roads in urban conditions. By calculating the vehicle's driving time, engine speed, actual fan speed, solenoid coil temperature, and ambient temperature, the number of solenoid temperature cycles during driving is calculated. The specific process is shown in the table below:

[0048]

[0049]

[0050] Through data analysis, the change of solenoid temperature (Ts) relative to ambient temperature (Ta) during vehicle driving is ΔT1 = Ts-Ta = 70℃~110℃, and the temperature distribution in one day accounts for A (such as Figure 4 The number of temperature changes in one day is n=1. According to the above life calculation, the number of working days D1=2222 days. Therefore, the number of cycles at different temperatures N1=D1×A×n is: 70℃, 1777 times; 80℃, 222 times; 90℃, 111 times; 110℃, 111 times. See the table below for data.

[0051]

[0052] 2.2 Vehicle is stationary

[0053] The solenoid temperature is the same as the ambient temperature when the vehicle is stationary, and the ambient temperature varies within a day, so the effect of the ambient temperature variation within a day on the solenoid temperature needs to be considered. The maximum and minimum solenoid temperature variation ΔT1 within a day is defined as 20°C, and the number of ambient temperature variations n within a day is 2, and the specific number of variations is determined according to the working condition and the use region. Because the total number of working days and rest days is D = 2535 days, the number of solenoid temperature cycles when stationary is N1 = D x n = 2535 (times), and the data are shown in the following table.

[0054]

[0055] The number of solenoid temperature cycles within the life cycle is obtained by adding the number of solenoid temperature cycles when the vehicle is running and when the vehicle is stationary, and is N1 = 1777 + 222 + 111 + 111 + 5070 = 7291 (times).

[0056] 3. Determination of solenoid bench accelerated test parameters

[0057] The last step needs to confirm the number of solenoid temperature cycles in the test bench, and the specific process is as follows:

[0058] Taking the maximum proportion of 70°C, 1777 times above as an example; that is, the solenoid temperature varies by 70°C, and the life cycle is 1777 times, and the number of cycles required for testing is calculated. For example, the minimum temperature of the selected environmental chamber is -20°C, and the maximum temperature is 140°C. According to the Coffin-Manson model, the actual number of cycles N1 = 1777, the actual temperature variation ΔT1 = 70°C, the temperature variation ΔT2 = 140-(-20) = 160°C in the test, and the acceleration rate constant ɑ = 2 is taken. The ɑ parameter is related to the solenoid material, and the calculation can obtain the number of cycles N2 = 340 required for testing. It is defined that one cycle is performed per hour, and the cycle time of N2 is 340 hours, and the calculation method is as follows:

[0059]

[0060] Other temperature points can be obtained by continuing this method, and the test cycle number and time are 55 times for 80°C, 35 times for 90°C, 52 times for 110°C, and 40 times for 20°C. A total of 522 cycles need to be tested, and the summary is shown in the following table:

[0061]

[0062]

[0063] Figure 3This is the solenoid temperature cycle test curve. According to the empirical parameters, we take the lowest temperature of -20℃ and the highest temperature of +140℃ in the solenoid test, the holding time tLimit = 30min, the temperature change slope grade = 3~10℃ / min, and the number of cycles of the stand is calculated to be N2, which is 562.

[0064] The above illustrates and describes the basic principles and main structural features of the present invention. The present invention is not limited to the above examples. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for accelerating the life of a silicone oil clutch solenoid, characterized in that: The following steps are involved: S1. Vehicle life analysis The collected parameters include: B10 design life mileage L, average speed V, B10 design life time T, average number of working days per year D2, average number of rest days per year D3 and daily driving time on working days T1; The parameters to be calculated include: total number of working days in the service life, total number of rest days in the service life D4=D3×Y1, total number of working days + rest days D=D1+D4, total number of working days in the service life and B10 design life years; S2. Solenoid heat load data collection: Collect the following parameters in actual use: ambient temperature Ta, operating time, engine speed, fan speed, solenoid maximum temperature Ts and its proportion; then, the actual temperature change in use, the temperature distribution proportion A in a day, the number of temperature changes in a day n, and the actual number of cycles used at different temperatures N1 = D1 × A × n; Based on the collected actual ambient temperature Ta, operating time, engine speed, and fan speed, the clutch fan status is reproduced on the test bench and the highest solenoid temperature Ts and its proportion are collected on the test bench. S3. Determination of solenoid bench accelerated test parameters: According to the Coffin-Manson model, the number of cycles N2 required for the bench test is designed. ; The formula can be changed to get the number of cycles N2 required for the bench test, Where: AFcm is the model acceleration factor; N1 is the number of temperature cycles of the solenoid during vehicle use; N2 is the number of temperature cycles of the solenoid during bench testing; ∆T1 is the temperature change of the solenoid during vehicle use; ∆T2 is the temperature change of the solenoid during bench testing; α is the Coffin-Manson exponent, which is the acceleration rate constant of temperature change.

2. The accelerated life test method for a silicone oil clutch solenoid according to claim 1, characterized in that: The temperature at the highest point of the solenoid is the highest. A thermocouple is arranged at the highest point of the solenoid to collect the temperature at the highest point of the solenoid.

3. The accelerated life test method for a silicone oil clutch solenoid according to claim 1, characterized in that: α is set to 2.

Images