Method for detecting fastening performance of wheel fastener

Abstract

The invention provides a method for detecting the fastening performance of a wheel fastener. The method comprises the following steps: carrying out a standing test on a vehicle; carrying out dynamic site testing on the vehicle; carrying out reinforced bad road test on the vehicle; and performing high and low temperature test on the vehicle. The testing device has the advantages that through the most harsh working condition combined by four harsh working conditions, a typical extreme driving mode enabling the wheel fastener to be easy to loosen is truly simulated, and the fastening performance of the wheel fastener can be comprehensively, directly and accurately tested; evaluation standards are set for the test in each stage, and the test can be stopped in time once the evaluation standards are not met, so that the test cost is effectively saved.

Description

Technical Field

[0001] The invention relates to the technical field of automobile wheel fastening performance testing, in particular to a method for testing the fastening performance of a wheel fastener. Background Art

[0002] Generally, the wheels of a car are fixed to the wheel bearings of the car through 5 wheel bolts, and all the forces between the car and the ground are borne by the wheel assembly. If the tightening performance of the wheel bolts does not meet the standards, it will cause the car to lose control and threaten the personal safety of passengers. If the tightening performance of the wheel bolts is relatively poor, there will be problems with the coordination between the wheel bolts, wheels and hub bearings. It is very likely that the bolts will loosen or even the wheels will suddenly loosen under extreme use by the user, leading to serious accidents. There are indeed many similar cases in reality. According to our tests and statistics, after the wheel is pre-tightened, some extreme driving actions are directly performed, such as heavy braking below 100km / h, full acceleration, turning with large lateral acceleration of different turning radii, large turning radius around poles, and high-frequency vibrations generated by passing different bad roads and bumpy sections at a certain speed, which will have a great impact on the tightening performance of the bolts. The tightening performance test of the wheel bolts is related to whether the wheel bolts and wheels can operate stably during the dynamic movement of the vehicle, and is an important aspect of the safety of the whole vehicle.

[0003] In order to verify the tightening performance of wheels and wheel bolts, OEMs and suppliers of wheels and wheel bolts basically use road test, bench test, or field abuse extreme driving method to test the tightening characteristics of wheel bolts. Among them, the road test method cannot meet the most demanding driving assessment conditions. The bench test cannot truly simulate the driving conditions of extreme drivers and lacks authenticity. The field abuse extreme driving method currently has no fixed route, test quantity and standard. It is just a random test condition that is considered to be harsh in an open field, lacking standardization and consistency.

[0004] In summary, a highly demanding, standardized field test method that can simulate real extreme driving styles is needed to test the tightness performance of wheels and wheel bolts to ensure the safety of the vehicle and the driver. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for testing the tightening performance of wheel fasteners. Through a combined testing method of four typical extreme working conditions, namely static test, dynamic test, enhanced bad road test and high and low temperature test, extreme driving conditions are truly simulated, thereby conducting a standardized and rigorous inspection of the tightening performance of wheel fasteners.

[0006] The present invention solves the technical problem by adopting the following technical solution:

[0007] A method for testing the fastening performance of a wheel fastener, the method comprising a first round of testing, the first round of testing comprising the following steps:

[0008] Step 1, performing a static test on the vehicle, measuring the fastening performance parameters of the wheel fasteners before and after the static test, comparing the change rate Δ1 of the fastening performance parameters with the first threshold value P1, and continuing the test when Δ1≤P1; and ending the test when Δ1>P1, and determining that the fastening performance is unqualified;

[0009] Step 2, performing a dynamic field test on the vehicle, measuring the fastening performance parameters of the wheel fasteners before and after the dynamic field test, comparing the change rate Δ2 of the fastening performance parameters with the second threshold value P2, and continuing the test when Δ2≤P2; and ending the test when Δ2>P2, and determining that the fastening performance is unqualified;

[0010] Step 3, performing an enhanced bad road test on the vehicle, measuring the fastening performance parameters of the wheel fasteners before and after the enhanced bad road test, comparing the change rate Δ3 of the fastening performance parameters with the third threshold value P3, and continuing the test when Δ3≤P3; and ending the test when Δ3>P3, and determining that the fastening performance is unqualified;

[0011] Step 4, perform high and low temperature tests on the vehicle, measure the fastening performance parameters of the wheel fasteners before and after the high and low temperature tests, compare the change rate Δ4 of the fastening performance parameters with the fourth threshold value P4, when Δ4≤P4, end the test and determine that the fastening performance is qualified; when Δ4>P4, end the test and determine that the fastening performance is unqualified.

[0012] Further, when the fastening performance of the first round of testing is qualified, the method further includes a second round of testing, and the second round of testing includes the following steps:

[0013] Step 5: Make the fasteners old and tight;

[0014] Step 6: Repeat the first round of testing.

[0015] Furthermore, the method of performing a static test on a vehicle includes:

[0016] Step 11, obtaining the initial axial force F of the wheel fastener before the static test;

[0017] Step 12: Place the vehicle on a horizontal surface at room temperature, and measure the axial force F′ after the vehicle has been stationary for a period of time t;

[0018] Step 13, compare the attenuation degree Δ1 of the axial force with the first threshold value P1, when Δ1≤P1, continue the test; when Δ1>P1, end the test and determine that the fastening performance is unqualified, wherein Δ1=(FF′) / F×100%.

[0019] Furthermore, the method for performing dynamic field testing on a vehicle includes:

[0020] Step 21, obtaining the initial axial force F of the wheel fastener before the dynamic field test;

[0021] Step 22, a dynamic slalom test is performed at the S1 test site. After the vehicle has traveled M1 mileage, the axial force F′ of the wheel fastener after cooling is measured;

[0022] Step 23, compare the attenuation degree Δ2 of the axial force with the second threshold value P2, where the second threshold value P2 is the melting zone threshold value P2′, and when Δ2≤P2′, continue the test; when Δ2>P2′, end the test and determine that the fastening performance is unqualified, wherein Δ2=(FF′) / F×100%;

[0023] Step 24, after the vehicle has traveled M2 mileage, the axial force F″ of the wheel fastener after cooling is measured;

[0024] Step 25, compare the attenuation degree Δ2 of the axial force with the second threshold value P2, where the second threshold value P2 is the steady-state threshold value P2″. ​​When Δ2≤P2″, continue the test; when Δ2>P2″, end the test and determine that the fastening performance is unqualified, wherein Δ2=(FF″) / F×100%.

[0025] Furthermore, the method for performing enhanced bad road testing on a vehicle includes:

[0026] Step 31, obtaining the initial axial force F of the wheel fastener before the enhanced bad road test;

[0027] Step 32: At the S2 test site, drive the vehicle through each road section at a predetermined speed to perform a cycle test;

[0028] Step 33, continuously repeating step 32 to perform multiple cycle tests;

[0029] Step 34, measuring the axial force F′ of the wheel fastener after cooling;

[0030] Step 35, compare the attenuation degree Δ3 of the axial force with the third threshold value P3, when Δ3≤P3, continue the test; when Δ3>P3, end the test and determine that the fastening performance is unqualified, wherein Δ3=(FF′) / F×100%.

[0031] Furthermore, the method for performing high and low temperature testing on a vehicle includes:

[0032] Step 41, obtaining the initial axial force F of the wheel fastener before the high and low temperature test;

[0033] Step 42, placing the vehicle in a low temperature environment for cooling, and then placing it in a normal temperature environment, and measuring the axial force F' of the wheel fastener;

[0034] Step 43, compare the attenuation degree Δ4 of the axial force with the fourth threshold value P4, at this time the fourth threshold value P4 is the low temperature threshold value P4′, when Δ4≤P4′, continue the test; when Δ4>P4′, end the test and judge that the fastening performance is unqualified, wherein Δ4=(FF′) / F×100%;

[0035] Step 44, placing the vehicle in a high temperature environment to increase the temperature, and then placing it in a normal temperature environment to measure the axial force F″ of the wheel fastener;

[0036] Step 45, compare the attenuation degree Δ4 of the axial force with the fourth threshold value P4, where the fourth threshold value P4 is the high temperature threshold value P4″. When Δ4≤P4″, the test is terminated and the fastening performance is determined to be qualified; when Δ4>P4″, the test is terminated and the fastening performance is determined to be unqualified, wherein Δ4=(FF″) / F×100%.

[0037] Further, the first threshold value P1 is one of 3%-8%, the second threshold value P2 is one of 20%-30%, the third threshold value P3 is one of 3%-8%, and the fourth threshold value P4 is one of 20%-30%; preferably, the first threshold value P1 is 5%, the melting zone threshold value P2′ is 25%, the steady-state threshold value P2″ is 30%, the third threshold value P3 is 5%, the low temperature threshold value P4′ is 20%, and the high temperature threshold value P4″ is 25%.

[0038] Furthermore, the method also includes: when performing dynamic field testing and enhanced bad road testing on the vehicle, measuring the wheel fastener angle β, comparing the wheel fastener angle β with a preset angle threshold β0, and when the wheel fastener angle β≤the preset angle threshold β0, continuing the test; when the wheel fastener angle β>the preset angle threshold β0, ending the test and determining that the fastening performance is unqualified; preferably, the preset angle threshold β0 is 25°-30°.

[0039] Furthermore, the method also includes: when the vehicle is subjected to dynamic field testing and enhanced bad road testing, the wheel temperature is measured using a temperature sensor, and the real-time axial force of the wheel fasteners is monitored using an ultrasonic axial force measuring instrument, and the temperature sensor is electrically connected to the ultrasonic axial force measuring instrument; the ultrasonic axial force measuring instrument is provided with a temperature threshold T0 and an axial force alarm threshold Q0, and when the axial force Q collected by the ultrasonic axial force measuring instrument is ≤ the axial force alarm threshold Q0, and the wheel temperature T collected by the temperature sensor is ≤ the temperature threshold T0, the ultrasonic axial force measuring instrument issues an alarm reminder; preferably, the temperature threshold T0 includes 60°C, and the axial force alarm threshold Q0 includes 20kN.

[0040] Furthermore, the method further includes preparing the vehicle before the first round of testing, and pre-tightening the initial torque of the wheel fastener to 75%-90% of the rated torque.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] (1) This method uses the most demanding working condition of the four harsh working condition combinations to truly simulate the typical extreme driving mode that makes the wheel fasteners easy to loosen, and can conduct a comprehensive, direct and accurate test on the tightening performance of the wheel fasteners. Moreover, evaluation criteria are set at each stage of the test. Once the evaluation criteria are not met, the test can be stopped in time, effectively saving the test cost.

[0043] (2) The axial force of the test bolt is used to determine the tightening performance. The tightening force of the wheel bolt can be accurately measured. At the same time, the bolt stress condition can be maintained during the measurement process, so that the bolt is not affected by the external force during the measurement and maintains the real state, so that each test and assessment can be carried out continuously without affecting the test process.

[0044] (3) The ultrasonic axial force measuring instrument is used to measure the axial force of the bolt in real time without destroying the bolt torque and thread tightness. The test results are more real and accurate, with strong continuity, monitorability and test standardization. It can monitor the looseness of the bolt in real time and issue safety prompts in time, which has a higher safety factor and economy for the driver. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 The present invention is a flow chart for testing the fastening performance of wheel fasteners.

[0046] Figure 2 This is a schematic diagram of the S1 test site of the present invention.

[0047] Figure 3 This is a schematic diagram of the S2 test site of the present invention.

[0048] In the figure: 100-S1 test site; 101-pile point; 200-S2 test site. DETAILED DESCRIPTION

[0049] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0050] In the description of the present invention, it should be noted that the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In addition, in the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0051] The tightening performance test of wheel bolts is related to whether the wheel bolts and wheels can operate stably during the dynamic movement of the vehicle, and is an important aspect of vehicle safety. At present, OEMs and suppliers of wheels and wheel bolts generally adopt the endurance road test method with wheel bolts, the test bench simulation method, and the simple simulation of rough driving by extreme users in the dynamic square for testing. The above methods all have various shortcomings:

[0052] Road test method: The road test method is to install the test wheel bolts on the road test vehicle, mark them, and regularly observe whether the mark position changes. After the road test, the torque of the bolts is measured with a torque meter to examine their tightening performance. This road test method is not extreme and intense, and cannot simulate extreme user driving conditions under extreme driving conditions where the bolts are loose. In fact, it is very likely that the assessment intensity of the wheel bolts for extreme driving of tens of kilometers will be higher than the assessment intensity of thousands of kilometers in road tests. Moreover, the road test method is to observe the rotation of the bolt marking scale and finally measure the reduction of torque with a torque meter. This method belongs to the torque measurement method, which only approximately indicates the looseness of the bolts, not directly indicates the tightening force, so it is not accurate. Moreover, this method can only be measured once and cannot be monitored. After the measurement, the assessment of the bolts is interrupted, and other types of test assessments cannot be continued.

[0053] Bench test method: The bench test method includes a bench torque test method and a bench axial force test method. The bench torque test method is to measure the torque attenuation of the bolts after tightening and loosening the bolts multiple times on the bench. The bench axial force test method is to measure the axial force attenuation after tightening and loosening the bolts multiple times on the bench. The actual force on the wheel bolts is very complex. This method is only a simple tightening and loosening of the bolts to test the bolt torque or axial force, and the degree of simulation is poor. The bench test cannot perform targeted simulation of the most demanding key working conditions of bolt loosening, and cannot perform bench simulation of the complex force changes of real wheel bolts. The test through the actual vehicle field test method is the most realistic and accurate.

[0054] The dynamic square simply simulates the rough driving method of extreme users: Some manufacturers will send drivers to do various extreme actions in a wide square to simulate the driving methods of extreme users with fierce driving actions. However, this method does not have clear test item items, test standards and processes, and the driving actions are not targeted, so it is difficult to ensure the repeatability, strength and difficulty of the test. This method lacks standardization and cannot guarantee the consistency of test strength. Moreover, because the large loosening and force attenuation of wheel bolts are caused by many special working conditions, not just a single working condition, it is far from enough to just do a single test on the site.

[0055] Therefore, in response to the above problems, the present invention provides a method for testing the tightening performance of wheel fasteners, with the aim of providing a highly demanding, standardized field test method that can simulate real extreme driving styles of drivers, so as to test the tightening performance of wheel bolts and ensure the safety of the vehicle and the driver.

[0056] The fastening performance of the wheel fastener can be tested on the bolt or the nut. For the convenience of description, the following embodiments only illustrate the method by taking the bolt as an example. It is understandable that the method can also be applied to fasteners of other vehicle parts.

[0057] refer to Figure 1 As shown, it shows a flow chart of the present invention for testing the tightening performance of wheel fasteners, and the method includes a first round of testing, and the first round of testing includes steps 1 to 4. Due to the influence of the stiffness and elasticity of the metal material, and the contact condition of the friction contact surface of the bolt will change after pre-tightening, so the tightening force of the bolt after pre-tightening will decay with time. Step 1 can measure the attenuation of the tightening force after a certain time after pre-tightening, and examine and measure the matching characteristics, dimensions and material properties between parts. The dynamic field test in step 2 and the enhanced bad road test in step 3 can simulate the typical extreme driving style of extreme users that really makes the bolts easy to loosen. The vehicle will be in different ambient temperatures when in use. Pre-tightening and measurement under different temperature conditions will also cause the tightening force of the bolt to have a more obvious change. Step 4 can examine the change in the tightening force of the bolt under different temperature conditions. Static test, dynamic field test, enhanced bad road test and high and low temperature test are four harsh working conditions for testing the tightening performance of bolts. This method combines the four harsh working conditions into the most harsh working condition, truly simulating the typical extreme driving style that makes the wheel fasteners easy to loosen, and can conduct a comprehensive, direct and accurate test on the tightening performance of the wheel fasteners.

[0058] Before the test, the vehicle can be prepared as required to make the vehicle state reach the most demanding, such as filling the vehicle with oil, checking tire pressure, setting it to maximum load, etc. The first round of testing can be carried out on new bolts, assembling new wheels, new wheel fasteners, new wheel hub bearings, brake discs and other related supporting parts, and the bolts can be pre-tightened with a torque meter. Preferably, the initial torque of the wheel bolts is pre-tightened to 75%-90% of the rated torque. For example, the initial torque can be pre-tightened to 75%, 80%, 85%, 90%, etc. of the rated torque to simulate the harsh situation of not fully tightening the bolts.

[0059] The first round of tests has evaluation criteria set for each stage of the test. Once the attenuation of the bolt's tightening force at any stage exceeds the corresponding threshold, the bolt tightening performance is judged to be unqualified, and the test can be stopped in time. Omitting subsequent tests can effectively save test costs. When the attenuation of the bolts at each stage of the first round of tests is qualified, the tightening performance of the first round of tests can be judged to be qualified.

[0060] Carry out the tests in the order of steps 1 to 4. When the tightening performance of the first round of tests is qualified, the second round of tests can be carried out. The second round of tests is for old bolts that have been loosened and tightened many times to simulate the tightening characteristics after the user has replaced the wheel assembly many times. After completing the first round of tests, make the bolts loose and old. For example, you can use a torque wrench to loosen the original car bolts (less than 10Nm), and then pre-tighten them, complete 5 times each, the pre-tightening torque is the rated torque, and then loosen it again (less than 10Nm), and then pre-tighten it to 85% of the rated torque. After the aging is completed, repeat steps 1 to 4, repeat the first round of tests, and when the tightening performance of the second round of tests is also qualified, it can be determined that the tightening performance of the bolts is qualified. After the second round of tests, the test can be ended and an inspection report can be issued. Combining the first and second rounds of tests can verify the tightening performance of the bolts throughout their life cycle.

[0061] It needs to be understood that the wheels are fixed to the wheel bearings of the automobile by multiple wheel bolts. When testing the tightening performance of the wheel bolts, it is necessary to test the tightening performance of each wheel bolt at the same time. If the tightening performance of all wheel bolts is qualified, then the tightening performance of the wheel bolts of this batch is qualified. If the tightening performance of some wheel bolts is unqualified, then the tightening performance of the wheel bolts of this batch is unqualified.

[0062] At present, the method for measuring the tightening performance of wheel bolts is usually to measure the torque of wheel bolts with a torque wrench, so that the torque value is used as the basis for judging the bolt clamping force. At present, except for the bench test method of axial force measurement, other test methods are torque measurement methods. The torque measurement method cannot directly express the tightening characteristics of the bolt in terms of accuracy, but only approximates it, so it is not very accurate. Moreover, the torque method can only measure the torque of the bolt once and does not have the ability to monitor continuously. The most direct indicator of the tightening performance (tightening degree) of the bolt is the axial tightening force (axial force) of the bolt. The tightening performance parameter of the bolt can use the axial force. Scientifically controlling the size of the axial force of the bolt is of great significance to the safe operation of the equipment and improving the life of the equipment. The tightening performance parameters of the bolt can also use the strain of the bolt. Using parameters such as axial force and strain to evaluate the tightening performance of the bolt can not interrupt the test process, and will not apply external force to change the stress condition of the bolt, so that the bolt can maintain a real state and each test assessment can be carried out continuously.

[0063] It is understandable that the attenuation of the axial force at each stage can be compared with the axial force F' of the wheel bolt after the test at that stage and the initial axial force F of the wheel bolt before the test at that stage as a benchmark. The attenuation of the axial force can be obtained according to Δ=(FF') / F×100%, or according to Δ=F' / F×100%. Accordingly, various thresholds can be set. Preferably, the attenuation of the axial force Δ=(FF') / F×100%, the first threshold P1 is one of 3%-8%, the second threshold P2 is one of 20%-30%, the third threshold P3 is one of 3%-8%, and the fourth threshold P4 is one of 20%-30%.

[0064] As an embodiment of the present invention, a method for performing a static test on a vehicle includes steps 11 to 13, and preferably, the first threshold value P1 is set to 5%. In step 11, the initial axial force F of the wheel bolts before the static test is obtained, and the axial force of each bolt to be tested can be measured using an ultrasonic axial force measuring instrument. In step 12, the vehicle can be placed on a horizontal ground in a room temperature environment, and the axial force F' after the vehicle has been stationary for 3 hours is measured. According to Δ1=(FF') / F×100%, the attenuation degree of the axial force Δ1 is calculated, and then step 13 is performed to compare the attenuation degree of the axial force Δ1 with 5%. When Δ1≤5%, the test can be continued, and steps 11-13 are repeated to measure the attenuation degree of the axial force after the vehicle has been stationary for more time. When Δ1>5%, the test is terminated and the fastening performance is determined to be unqualified. The stationary time of the vehicle can be set to 6h, 12h, etc.

[0065] After the static test, field testing will be carried out, and tests will be conducted on fixed routes to simulate extreme driving conditions of special users, standardize and normalize the test operations, and improve the test intensity and consistency of test results.

[0066] As an embodiment of the present invention, the method for performing dynamic field testing on a vehicle includes steps 21 to 25. The test at this stage can be performed at the S1 test field 100. Referring to the coordinates of the pile point 101 shown in Table 1, the S1 test field 100 is formed Figure 2 The route shown. In step 21, the initial axial force F of the wheel bolts before the dynamic field test is obtained. The axial force of each bolt to be tested can be measured by an ultrasonic axial force measuring instrument before the dynamic field test, or the last measurement result of the static test can be used. After several miles of extreme driving, the galvanized layer on the surface of the new wheel bolts will melt, forming a melting zone, which will affect the friction performance of the contact surface between the wheel bolts and the wheel, and the contact surface with the threaded hole of the steering knuckle assembly. The torque changes nonlinearly during the engagement and tightening process between the wheel bolts and the inner threaded hole of the wheel hub bearing, and the axial force of the wheel bolts will be greatly attenuated. In step 22, according to Figure 2As shown, the test vehicle follows a clockwise route (direction indicated by "→" in the figure) from 1# pile point 101-66# pile point 101-1# pile point 101, completes 3 laps of test mileage at the maximum possible speed and in the shortest time, then cools to ambient temperature, measures the axial force F' of the wheel bolts after cooling, and then calculates the axial force attenuation Δ2 according to Δ2 = (FF') / F × 100%. Preferably, the melting zone threshold P2' is set to 25%. When Δ2 ≤ 25%, the melting zone tightening performance is qualified and step 24 can be continued; when Δ2 > 25%, the test is terminated and the tightening performance is determined to be unqualified. In step 24, the test vehicle continues to follow Figure 2 The vehicle is driven along the route and in the direction shown in the figure, and 11 test laps are completed in the shortest time at the maximum possible speed. The vehicle is then cooled to ambient temperature, and the axial force F″ of the wheel bolts after cooling is measured. The axial force attenuation Δ2 is calculated according to Δ2=(FF″) / F×100%. After the melting zone, the dynamic field test is continued. The axial force attenuation of the wheel bolts is small, and a steady-state zone is formed. Preferably, the steady-state threshold value P2″ is set to 30%. When Δ2≤30%, the bolt tightening performance is qualified and the test can continue. When Δ2>30%, the test is terminated and the tightening performance is judged to be unqualified.

[0067] Table 1S1 Test site stake point coordinates

[0068] Pile point number Pile point coordinate x Pile point coordinate y Pile point number Pile point coordinate x Pile point coordinate y Pile point number Pile point coordinate x Pile point coordinate y 1 17.4 149.5 23 52.2 33.1 45 118.1 182.5 2 24.1 158.6 24 71.9 6.9 46 130 154 3 26.3 166.5 25 83 5.4 47 141.5 147.9 4 21.9 181.1 26 93.1 7.2 48 149.7 151.2 5 46.1 195.5 27 104.5 14.3 49 152.3 173.9 6 72.5 178.5 28 112.1 18 50 157.1 184.3 7 64.9 154 29 117.4 20 51 159.3 192 8 54.2 156.1 30 127.8 21.6 52 174 196.5 9 44.9 161.6 31 136.5 30.2 53 194.9 175.9 10 38.6 155 32 155.1 35.5 54 186 151.9 11 44.1 144.1 33 168.2 58.1 55 154.2 121.8 12 43.6 136.2 34 184.1 58.1 56 157.2 120.7 13 44.1 130 35 192.2 67.7 57 116.2 74 14 28.2 115.1 36 125.2 110.8 58 119 55.1 15 25.3 105.2 37 126.8 113.2 59 111.1 45.8 16 28.2 95.1 38 74.5 135.3 60 84.7 50.7 17 54.1 79.9 39 68.8 142.5 61 57.9 43.2 18 59.1 70.3 40 75.1 151.9 62 59.8 40.8 19 56.3 65.1 41 90.2 142.5 63 33.5 25.5 20 43.5 56.9 42 99.8 145 64 11.2 34.4 21 37.2 49.4 43 94.1 161.1 65 5.2 56.2 22 50.1 31.2 44 97.6 182.3 66 14.3 83.7

[0069] When a vehicle passes through some bad roads and bumpy roads, high-frequency vibrations of different amplitudes will cause the wheel bolts to be subjected to alternating forces, thereby attenuating the axial force. In extreme cases, the wheel bolts will become loose. The typical working condition test of strengthening bad roads can accurately simulate the working conditions of the vehicle on bad roads and bumpy roads. As an embodiment of the present invention, the method for strengthening bad road testing of a vehicle includes steps 31 to 35. This stage of testing can be performed at the S2 test site 200, refer to Figure 3As shown, the reinforced bad road of the S2 test site 200 includes at least one of the following sections: stone road, billy stone road, washboard road (wavelength includes 0.3m), goose warm stone road, fish scale pit road, and the length of each section of bad road route includes 260m. In step 31, the initial axial force F of the wheel bolt before the reinforced bad road test is obtained. The axial force of each bolt to be tested can be measured using an ultrasonic axial force measuring instrument before the reinforced bad road test, or the last measurement result of the dynamic field test can be used. According to the setting order of each section of the S2 test site 200, the test vehicle drives through each reinforced bad road section at a speed of 50km / h in turn, drives a cycle, drives continuously for 12 cycles, and then cools to ambient temperature, measures the axial force F′ of the wheel bolt after cooling, and then calculates the attenuation degree Δ3 of the axial force according to Δ3=(FF′) / F×100%. Preferably, the third threshold value P3 is set to 5%. When Δ3≤5%, the tightening performance of the reinforced bad road test bolt is qualified and the test can be continued; when Δ3>5%, the test is terminated and the tightening performance is determined to be unqualified.

[0070] As an embodiment of the present invention, a method for performing high and low temperature tests on a vehicle includes steps 41 to 45. The test at this stage can be performed in an environmental chamber. In step 41, the initial axial force F of the wheel bolts before the high and low temperature tests is obtained. The axial force of each bolt to be tested can be measured using an ultrasonic axial force measuring instrument before the high and low temperature tests, or the measurement results of the enhanced bad road test can be used. Compared with being placed in a high temperature environment, the axial force of the wheel bolts will be more obviously attenuated after being placed in a low temperature environment. Preferably, when performing high and low temperature tests on the wheel bolts, a low temperature test is first performed and then a high temperature test is performed, so that the axial force of the wheel bolts is obviously attenuated. In step 42, the vehicle is placed in an environment of -20°C to cool, and then placed in a normal temperature environment of 10-15°C to measure the axial force F′ of the wheel bolts, and then the attenuation degree Δ4 of the axial force is calculated according to Δ4=(FF′) / F×100%. Preferably, the low temperature threshold value P4′ is set to 20%. When Δ4≤20%, the low temperature test fastening performance of the bolt is qualified, and step 44 can be continued; when Δ4>20%, the test is ended and the fastening performance is judged to be unqualified. In step 44, the vehicle is placed in an environment of 35°C for heating, and then placed in a normal temperature environment of 10-15°C to measure the axial force F″ of the wheel bolts, and then the attenuation degree Δ4 of the axial force is calculated according to Δ4=(FF″) / F×100%. Preferably, the high temperature threshold value P4″ is set to 25%. When Δ4≤25%, the test is ended and the fastening performance is judged to be qualified; when Δ4>25%, the test is ended and the fastening performance is judged to be unqualified.

[0071] As an embodiment of the present invention, when a vehicle is subjected to a dynamic field test and an enhanced bad road test, it is also necessary to evaluate the tightening performance in combination with the bolt angle β, especially for split bolts. While comparing the axial force attenuation of the bolts, it is also necessary to measure the wheel bolt angle β. The wheel bolt angle β is compared with the preset angle threshold β0. When the wheel bolt angle β ≤ the preset angle threshold β0, the test can continue; when the wheel bolt angle β>the preset angle threshold β0, the test ends and the tightening performance is judged to be unqualified. For example, the preset angle threshold β0 is 30°. When the axial force attenuation is qualified and the wheel bolt angle β ≤ 30°, the bolt tightening performance at the corresponding stage can be judged to be qualified.

[0072] The safety of the test is the most important issue faced in conducting real vehicle tests. Since the test itself is extremely risky, and once the fastening performance of the wheel and the wheel bolt is not up to standard, the wheel bolt becomes loose, and the driver is unaware of it, there is a high possibility that the wheel bolt will be completely loose, or even the wheel assembly will be detached, and the vehicle will lose control. Therefore, it is crucial to monitor the loosening of the fastening force in real time. In order to improve the safety of the test process, the method also includes: when the vehicle is subjected to dynamic field testing and enhanced bad road testing, the wheel temperature is measured using a temperature sensor, and the real-time axial force of the wheel bolt is monitored using an ultrasonic axial force measuring instrument, and the temperature sensor is electrically connected to the ultrasonic axial force measuring instrument. For example, the temperature sensor can use an infrared temperature sensor, and then use wireless data transmission, such as Bluetooth, WIFI, etc., to send the temperature signal collected by the temperature sensor and the axial force signal collected by the ultrasonic axial force measuring instrument probe to the ultrasonic axial force measuring instrument host arranged in the vehicle, so that the driver can understand the attenuation of the bolt fastening force in real time. When using an ultrasonic axial force measuring instrument to measure the axial force of the bolt, it is necessary to pre-process both ends of the bolt so that the roughness of the two end faces of the bolt meets the test requirements of the ultrasonic axial force measuring instrument.

[0073] Since the ultrasonic measurement of bolt axial force measurement results is greatly affected by temperature, and the high temperature generated by friction plates and tire friction during driving sometimes makes the real-time monitoring feedback value inaccurate, the ultrasonic axial force measuring instrument is provided with a temperature threshold T0 and an axial force alarm threshold Q0. Preferably, the temperature threshold T0 includes 60°C, and the axial force alarm threshold Q0 includes 20kN. When the temperature T collected by the temperature sensor is ≤60°C, the data collected by the ultrasonic axial force measuring instrument is valid data; when the temperature T collected by the temperature sensor is >60°C, the data collected by the ultrasonic axial force measuring instrument is invalid data, which can be filtered or marked on the data display device of the ultrasonic axial force measuring instrument. When the axial force Q collected by the ultrasonic axial force measuring instrument is ≤20kN, and the wheel temperature T collected by the temperature sensor is ≤60°C, the bolt may be loose, and the ultrasonic axial force measuring instrument issues an alarm reminder, such as a voice broadcast reminder, prompting the driver to stop driving to ensure safety. After stopping driving, the axial force can be measured after the wheel temperature cools down. If the axial force is ≥20kN and the attenuation of the axial force is less than or equal to the corresponding stage threshold, the test can continue. Otherwise, the test needs to be terminated and the result is judged as unqualified. This ensures the safety of the driver and avoids subsequent meaningless test processes by terminating the test in time.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for testing the fastening performance of a wheel fastener, characterized in that: The method includes a first round of testing, which includes the following steps: Step 1, performing a static test on the vehicle, measuring the fastening performance parameters of the wheel fasteners before and after the static test, comparing the change rate Δ1 of the fastening performance parameters with the first threshold value P1, and continuing the test when Δ1≤P1; and ending the test when Δ1>P1, and determining that the fastening performance is unqualified; Step 2, performing a dynamic field test on the vehicle, measuring the fastening performance parameters of the wheel fasteners before and after the dynamic field test, comparing the change rate Δ2 of the fastening performance parameters with the second threshold value P2, and continuing the test when Δ2≤P2; and ending the test when Δ2>P2, and determining that the fastening performance is unqualified; Step 3, performing an enhanced bad road test on the vehicle, measuring the fastening performance parameters of the wheel fasteners before and after the enhanced bad road test, comparing the change rate Δ3 of the fastening performance parameters with the third threshold value P3, and continuing the test when Δ3≤P3; and ending the test when Δ3>P3, and determining that the fastening performance is unqualified; Step 4, perform high and low temperature tests on the vehicle, measure the fastening performance parameters of the wheel fasteners before and after the high and low temperature tests, compare the change rate Δ4 of the fastening performance parameters with the fourth threshold value P4, when Δ4≤P4, end the test and determine that the fastening performance is qualified; when Δ4>P4, end the test and determine that the fastening performance is unqualified.

2. The method according to claim 1, characterized in that When the fastening performance of the first round of testing is qualified, the method further includes a second round of testing, and the second round of testing includes the following steps: Step 5: Make the fasteners old and tight; Step 6: Repeat the first round of testing.

3. The method according to claim 1, characterized in that Methods for stationary testing of vehicles include: Step 11, obtaining the initial axial force F of the wheel fastener before the static test; Step 12: Place the vehicle on a horizontal surface at room temperature, and measure the axial force F′ after the vehicle has been stationary for a period of time t; Step 13, compare the attenuation degree Δ1 of the axial force with the first threshold value P1, when Δ1≤P1, continue the test; when Δ1>P1, end the test and determine that the fastening performance is unqualified, wherein Δ1=(FF′) / F×100%.

4. The method according to claim 3, characterized in that: Methods for dynamic field testing of vehicles include: Step 21, obtaining the initial axial force F of the wheel fastener before the dynamic field test; Step 22, a dynamic slalom test is performed at the S1 test site. After the vehicle has traveled M1 mileage, the axial force F′ of the wheel fastener after cooling is measured; Step 23, compare the attenuation degree Δ2 of the axial force with the second threshold value P2, where the second threshold value P2 is the melting zone threshold value P2′, and when Δ2≤P2′, continue the test; when Δ2>P2′, end the test and determine that the fastening performance is unqualified, wherein Δ2=(FF′) / F×100%; Step 24, after the vehicle has traveled M2 mileage, the axial force F″ of the wheel fastener after cooling is measured; Step 25, compare the attenuation degree Δ2 of the axial force with the second threshold value P2, where the second threshold value P2 is the steady-state threshold value P2″. ​​When Δ2≤P2″, continue the test; when Δ2>P2″, end the test and determine that the fastening performance is unqualified, wherein Δ2=(FF″) / F×100%.

5. The method according to claim 4, characterized in that Methods for conducting enhanced bad road testing on vehicles include: Step 31, obtaining the initial axial force F of the wheel fastener before the enhanced bad road test; Step 32: At the S2 test site, drive the vehicle through each road section at a predetermined speed to perform a cycle test; Step 33, continuously repeating step 32 to perform multiple cycle tests; Step 34, measuring the axial force F′ of the wheel fastener after cooling; Step 35, compare the attenuation degree Δ3 of the axial force with the third threshold value P3, when Δ3≤P3, continue the test; when Δ3>P3, end the test and determine that the fastening performance is unqualified, wherein Δ3=(FF′) / F×100%.

6. The method according to claim 5, characterized in that Methods for high and low temperature testing of vehicles include: Step 41, obtaining the initial axial force F of the wheel fastener before the high and low temperature test; Step 42, placing the vehicle in a low temperature environment for cooling, and then placing it in a normal temperature environment, and measuring the axial force F' of the wheel fastener; Step 43, compare the attenuation degree Δ4 of the axial force with the fourth threshold value P4, at this time the fourth threshold value P4 is the low temperature threshold value P4′, when Δ4≤P4′, continue the test; when Δ4>P4′, end the test and judge that the fastening performance is unqualified, wherein Δ4=(FF′) / F×100%; Step 44, placing the vehicle in a high temperature environment to increase the temperature, and then placing it in a normal temperature environment to measure the axial force F″ of the wheel fastener; Step 45, compare the attenuation degree Δ4 of the axial force with the fourth threshold value P4, where the fourth threshold value P4 is the high temperature threshold value P4″. When Δ4≤P4″, the test is terminated and the fastening performance is determined to be qualified; when Δ4>P4″, the test is terminated and the fastening performance is determined to be unqualified, wherein Δ4=(FF″) / F×100%.

7. The method according to claim 6, characterized in that The first threshold value P1 is one of 3%-8%, the second threshold value P2 is one of 20%-30%, the third threshold value P3 is one of 3%-8%, and the fourth threshold value P4 is one of 20%-30%; preferably, the first threshold value P1 is 5%, the melting zone threshold value P2′ is 25%, the steady-state threshold value P2″ is 30%, the third threshold value P3 is 5%, the low temperature threshold value P4′ is 20%, and the high temperature threshold value P4″ is 25%.

8. The method according to any one of claims 1 to 7, characterized in that: The method further includes: when performing dynamic field testing and enhanced bad road testing on the vehicle, measuring the wheel fastener angle β, comparing the wheel fastener angle β with a preset angle threshold β0, and continuing the test when the wheel fastener angle β≤the preset angle threshold β0; when the wheel fastener angle β>the preset angle threshold β0, ending the test and determining that the fastening performance is unqualified; preferably, the preset angle threshold β0 is 25°-30°.

9. The method according to claim 1, characterized in that: The method also includes: when performing dynamic field testing and enhanced bad road testing on the vehicle, using a temperature sensor to measure the wheel temperature, and using an ultrasonic axial force measuring instrument to monitor the real-time axial force of the wheel fasteners, the temperature sensor is electrically connected to the ultrasonic axial force measuring instrument; the ultrasonic axial force measuring instrument is provided with a temperature threshold T0 and an axial force alarm threshold Q0, when the axial force Q collected by the ultrasonic axial force measuring instrument is ≤ the axial force alarm threshold Q0, and the wheel temperature T collected by the temperature sensor is ≤ the temperature threshold T0, the ultrasonic axial force measuring instrument issues an alarm reminder; preferably, the temperature threshold T0 includes 60°C, and the axial force alarm threshold Q0 includes 20kN.

10. The method according to claim 1, characterized in that The method further includes preparing the vehicle before the first round of testing by pre-tightening the initial torque of the wheel fasteners to 75%-90% of the rated torque.

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