Accelerated test method for life of solenoid of silicone oil clutch

Abstract

The invention relates to a silicone oil clutch solenoid service life acceleration test method, which is characterized in that a set of acceleration test method for verifying the reliability or service life of a solenoid can be obtained through an algorithm according to a Cofen-Mansen model and a service life index of a customer; the reliability or life index of the solenoid is evaluated in an accelerated test mode, and the evaluated index can be used for guiding forward development of the solenoid; the reliability of the solenoid can be evaluated according to the reliability requirement of the OEM of the whole vehicle and the proportions of the road spectrum of the whole vehicle and the silicone oil clutch fan in different states, a simulation result equivalent to a simulation result under a long-term fatigue condition can be obtained in a short time, a large amount of time cost is saved, and verification cost is saved.

Description

Technical Field

[0001] The 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 only electronically controlled part in the electronically controlled silicone oil clutch, the solenoid plays the following roles: on the one hand, it receives the pulse width modulation signal (PWM for short) sent by the ECU and induces magnetic fields of different strengths inside the clutch according to the different duty cycles of PWM, and uses the magnetic field force to drive the control valve stem movement in the oil storage chamber, adjust the amount of silicone oil in the working chamber, so as to transmit different torques and adjust the fan speed; on the other hand, the solenoid converts the real-time fan speed into high and low voltage signals and feeds them back to the ECU. The ECU continuously corrects the required speed based on the deviation between the real-time fan speed and the required speed represented by the PWM signal, thereby forming a PID closed-loop control, so that the real-time fan speed quickly approaches the required speed. In summary, whether the solenoid works properly will greatly affect the function of the clutch fan, such as the speed control stability and even the life of the clutch.

[0003] At present, the working environment of domestic commercial vehicles is relatively harsh and the working conditions are complex. The reliability estimation of solenoids needs to take into account many parameters, and it is difficult to establish a reliability model. As a key component of the electronically controlled silicone oil clutch fan, the reliability requirements of the vehicle OEM are extremely high. Considering that the failure rate of solenoids in the after-sales market is also high, it is imperative to establish a suitable solenoid life assessment mechanism in the design stage. More and more fan manufacturers have also begun to pay attention to the reliability issues of solenoids.

[0004] At present, major fan manufacturers have insufficient understanding of the reliability or life indicators of solenoids, and the design schemes or selected materials are not the same. 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 also applies the existing verification methods without adaptive modifications. Specifically: First, 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 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 solenoid. Summary of the invention

[0005] To solve the above problems, the present invention provides a silicone oil clutch solenoid life acceleration test method, which can evaluate the reliability of the solenoid according to the reliability requirements of the vehicle OEM, based on the road spectrum of the vehicle 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 acceleration test method, characterized in that it includes the following steps: 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: the total number of working days in the life span , 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 ; S2. Solenoid heat load data collection: collect the following parameters actually used: ambient temperature Ta, operating time, engine speed, fan speed, solenoid maximum temperature Ts and proportion; then, the actual temperature change , the temperature distribution ratio in one day is A, the number of temperature changes in one day is n, and the number of cycles actually used at different temperatures is 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: Design the number of cycles required for the bench test according to the Coffin-Manson model N2

[0007] The formula can be changed to obtain the number of cycles N2 required for bench test

[0008] 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 in bench testing; ∆T1 is the temperature change of the solenoid during vehicle use; ∆T2 is the temperature change of the solenoid in bench testing; α is the Coffin-Manson index, which refers to the acceleration rate constant of temperature change.

[0009] 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.

[0010] Preferably, α is 2.

[0011] The beneficial effects achieved by the present invention are as follows: the present invention is based on the Coffin-Manson model, and can obtain a set of accelerated test methods for verifying the reliability or life of the solenoid through an algorithm according to the customer's life index; the reliability or life index of the solenoid is evaluated by an accelerated test method, and the evaluated index 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, the road spectrum of the vehicle and the proportion of different states of the silicone oil clutch fan; the present invention has the following advantages: 1. It often takes a long time to evaluate the fatigue properties of materials during product development, and in some cases, the evaluation results are not satisfactory. However, the present invention can obtain simulation results equivalent to those under long-term fatigue conditions in a shorter time through accelerated testing methods, saving a lot of time costs and verification costs; 2. Different acceleration parameters can be formulated according to different working conditions of the solenoid and effectively evaluate whether the solenoid products meet the life requirements, avoiding the use of the same acceleration parameters for different customers and different road spectra, which leads to inaccurate evaluation results. It can effectively reduce the cost increase caused by after-sales quality problems or product over-design; 3. The invention proposed the principle of accelerated life test for solenoids for the first time, filling the gap in domestic accelerated testing, providing fan manufacturers with a way to evaluate the life indicators of solenoids, and saving development costs and time. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic diagram of the solenoid assembly; Figure 2 It is the temperature test curve diagram of different positions of the solenoid; Figure 3 It is the solenoid temperature cycle test curve; Figure 4 This is the temperature change ratio of the solenoid coil when the vehicle is running; In the figure: 1. Coil seat; 2. Electromagnetic coil; 3. Bearing; 4. Bearing seat; 5. Plastic shell; 6. Wiring harness; 7. Speed ​​sensor; 8. Silicone oil; 9. Control valve stem. DETAILED DESCRIPTION

[0013] The present invention will be further described below in conjunction with the accompanying drawings.

[0014] like Figure 1As shown, the silicone oil clutch solenoid is mainly composed of electromagnetic coil 2, bearing 3, coil seat 1, bearing seat 4, plastic shell 5, wiring harness 6 and speed sensor 7. First, when the silicone oil clutch fan is working, the electromagnetic coil 2 in the solenoid will receive the periodic high and low level control signal of the ECU, and the electromagnetic coil 2 will be periodically turned on and off. For example, when the electromagnetic coil 2 is turned on, it will heat up and induce a magnetic field. The magnetic field drives the control valve stem 9 inside the clutch to move, and the temperature of the solenoid rises due to power on; when the electromagnetic coil 2 is powered off, the induced magnetic field disappears, the control valve stem 9 does not move, and the temperature of the solenoid decreases due to power off. Secondly, the silicone oil 8 inside the clutch can convert the mechanical energy of the engine into the mechanical energy of the fan through its own shear force, and part of the lost energy will be converted into the heat energy of the silicone oil 8. Therefore, the temperature of the silicone oil 8 is often relatively high, and then the solenoid is thermally radiated and heat is transferred. Thirdly, changes in ambient temperature, such as lower temperatures in the morning and evening and higher temperatures at noon, will also affect the temperature of the solenoid. In summary, the solenoid is always under the action of temperature alternation, and is very suitable for the Coffin-Manson Model. The Coffin-Manson Model is used to describe the life characteristics of materials under temperature fatigue loads and is generally suitable for accelerated models of tests under temperature shock.

[0015] Combination Figure 2-4 As shown, the temperature fatigue test of the silicone oil clutch solenoid life acceleration test method of the present invention introduces the Coffin Manson model into the temperature fatigue test of the solenoid, comprising the following steps: 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 life D1, total number of rest days in the life D4, total number of working days + rest days D (i.e. life days), total number of working days in the life Y1 and B10 design life Y2. The specific definitions are shown in the table below;

[0016] S2, solenoid heat load data collection: such as Figure 2 As shown in the figure, 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 solenoid coil 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 vehicle, and then according to the vehicle model: such as tractor, engineering vehicle and mining vehicle, etc., the vehicle application scenario: such as highway, mountainous area and urban road section, etc., collect the following parameters: ambient temperature Ta, running time, engine speed, fan speed, temperature Ts at the highest point of the solenoid temperature and its proportion; then, the actual temperature change amount used , the temperature distribution ratio in one day is A, the number of temperature changes in one day is n, and the number of cycles actually used at different temperatures is N1=D1×A×N; if the temperature and ratio 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 Ts and ratio of the highest temperature of the solenoid on the test bench can be collected; S3. The design life of commercial vehicle B10 is usually greater than 1 million kilometers. Calculated at an average speed of 40 km / h, the design life of B10 is greater than 25,000 hours. If the test verification is carried out according to 25,000 hours during product development, the test cycle is long and the cost is high, which cannot meet the project node. Therefore, it is necessary to design a suitable accelerated test to save development costs; according to the Coffin-Manson model, the bench test is designed to calculate the number of cycles required for testing:

[0017] The formula can be changed to obtain the number of cycles N2 required for bench test

[0018] 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 in bench testing; ∆T1 is the temperature change of the solenoid during vehicle use; ∆T2 is the temperature change of the solenoid in bench testing; α is the Coffin-Manson index, which refers to the acceleration rate constant of temperature change. Example

[0019] 1. Analysis of vehicle life requirements For example, the life mileage of a certain model B10 is L=1.6 million kilometers. According to the speed V=60km / h, the design life of B10 is T=26667h; assuming that the driving time is T1=12h every day on weekdays, the total number of working days D1=2222 days is obtained; assuming that the number of working days per year is D2=320 days, and the average number of rest days per year is D3=45 days, the total number of working days is calculated to be Y1=6.94 years, and the total number of rest days is D4=313 days, and the total number of working days + rest days D=2535 days. According to this model, this solenoid has a service life of Y2=6.94 years. The specific process is shown in the table below:

[0020] 2. Solenoid heat load data collection There are two types of solenoid heat loads, when the vehicle is moving and when it is stationary.

[0021] 2.1 Vehicle driving The silicone oil clutch fan with thermocouple is installed on the above B10 vehicle with life mileage L=1.6 million kilometers. Assuming that the road spectrum of the vehicle is: mountain road 18%, highway flat road 72%, secondary highway mountain road 1.6%, secondary highway flat road 6.4%, urban road mountain road 0.4%, urban road flat road 1.6%, by calculating the vehicle driving time, engine speed, actual fan speed, solenoid coil temperature and ambient temperature, the number of solenoid temperature cycles in the life cycle during driving is obtained. The specific process is shown in the table below:

[0022] 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.

[0023] 2.2. Vehicle is stationary When the vehicle is stationary, the solenoid temperature is the same as the ambient temperature. The ambient temperature also changes during the day, so it is necessary to consider the impact of the ambient temperature change on the solenoid temperature. Define the maximum and minimum temperature changes of the solenoid in a day as ∆T1, which is 20°C. The number of ambient temperature changes in a day is n=2. The specific number of changes depends on the working conditions and the area of ​​use. 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×n=2535 (times). See the table below for the data:

[0024]

[0025] The number of temperature cycles of the solenoid during vehicle driving and vehicle stationary is added together to obtain the number of temperature cycles of the solenoid during its life cycle N1=1777+222+111+111+5070=7291 (times).

[0026] 3. Determination of solenoid bench accelerated test parameters The final step is to confirm the number of solenoid temperature cycles in the test bench. The specific process is as follows: Take the above-mentioned highest percentage of 70℃, 1777 times as an example; that is, the solenoid temperature changes by 70℃, and the life cycle is 1777 times, and calculate the number of cycles required for the test. For example, the lowest temperature of the selected environmental chamber is -20℃, and the highest temperature is 140℃. According to the Coffin-Manson model, the actual number of cycles used is N1=1777, the actual temperature change, the temperature change in the test, the acceleration rate constant ɑ=2 of the temperature change, the ɑ parameter is related to the material of the solenoid, and the number of cycles required to be tested is calculated to be N2=340. It is defined as one cycle per hour, and the cycle time of N2 is 340 hours. The calculation method is as follows:

[0027] Continuing in this way, the test cycle times and times for other temperature points can be obtained: 80°C: 55 times, 90°C: 35 times, 110°C: 52 times, 20°C: 40 times. A total of 522 cycles need to be tested, as summarized in the following table:

[0028] Figure 3 This is the solenoid temperature cycle test curve. According to the empirical parameters, we take the lowest temperature -20℃ and the highest temperature +140℃ in the solenoid test, the holding time tLimit=30min, the temperature change slope grade=3~10℃ / min, and calculate the number of cycles of the rack N2 as 562.

[0029] The above shows and describes the basic principles and main structural features of the present invention. The present invention is not limited to the above examples. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached 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: the total number of working days in the life span , 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 ; S2. Solenoid heat load data collection: collect the following parameters actually used: ambient temperature Ta, operating time, engine speed, fan speed, solenoid maximum temperature Ts and proportion; then, the actual temperature change , the temperature distribution ratio in one day is A, the number of temperature changes in one day is n, and the number of cycles actually used at different temperatures is 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: Design the number of cycles required for the bench test according to the Coffin-Manson model N2 2. The formula can be changed to obtain the number of cycles N2 required for bench test 3. 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 in bench testing; ∆T1 is the temperature change of the solenoid during vehicle use; ∆T2 is the temperature change of the solenoid in bench testing; α is the Coffin-Manson index, which refers to the acceleration rate constant of temperature change.

4. 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. By arranging a thermocouple at the highest point of the solenoid, the temperature at the highest point of the solenoid is collected.

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

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