Checking and testing method for assembling torque of automobile bolt connection pair

Abstract

The invention discloses an automobile bolt connection pair assembly torque checking and testing method, which belongs to the technical field of vehicle engineering, and is characterized in that the minimum tightening force required by a bolt connection pair is calculated in combination with CAE simulation analysis, the initial value of the assembly torque is obtained through theoretical calculation, and bolt axial force detection is carried out in combination with whole vehicle reliability verification. The bolt axial force attenuation rate is monitored, and verification is carried out through combination of theories and practice, so that the test method is relatively sufficient. The connecting reliability of the automobile bolt pair can be improved, the safe driving performance of an automobile is further improved, and customer complaints caused by abnormal sound due to bolt looseness can be reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle engineering, and more specifically, to an assembly torque checking and testing method for an automobile bolt connection pair. Background Art

[0002] Bolt connections are common and critical fasteners in automobile connections. Reasonable assembly torque can provide sufficient axial force to prevent abnormal noise caused by torque attenuation, while improving the strength and reliability of bolt connections. Currently, mainstream automobile manufacturers mainly use two methods to set the assembly torque of bolted connections: one is the disassembly benchmarking method, which is to purchase a benchmark car and disassemble it for reference. This method has a large error; the other is the theoretical calculation method, which uses empirical formulas and has poor accuracy. After the torque is set, it can only be verified by the vehicle reliability test. The verification cycle is long and it is easily disturbed by the driver's subjective feelings, causing some details to be ignored, which in turn causes risks such as abnormal vehicle noise and bolt breakage, causing customer dissatisfaction.

[0003] The existing assembly torque verification and test methods mainly use benchmarks or empirical formulas to determine the torque setting value according to the bolt specifications, and then verify it with the help of vehicle reliability tests. The rationality of the bolt assembly torque is judged by checking whether the connection pair has abnormal noise, bolt breakage and other failure modes. This existing technology has the following defects:

[0004] 1. The initial value of the torque is selected based on the disassembly benchmark method or empirical formula combined with the bolt specifications. The initial value setting error is large, lacks rigor, and has the risk of trial and error.

[0005] 2. After the torque is set, it can only be verified through the vehicle durability test. The verification cycle is too long, there are serious inadequacies, and it is easily affected by the driver's subjective feelings, thus missing some key details.

[0006] In summary, there is still no accurate and systematic test and judgment method to accurately set the assembly torque of the bolt connection to ensure that the axial force generated by the connection meets the required minimum tightening force requirement, how to combine theory with practice to carry out the verification of the assembly torque and torque attenuation, and whether the bolts can still provide sufficient axial force after attenuation. Summary of the invention

[0007] An object of the present invention is to provide a method for checking and testing the assembly torque of an automobile bolt connection, so as to solve the problems that the initial value of the torque is set according to the disassembly benchmark method or the empirical formula, resulting in a large initial value setting error, the risk of trial and error, and the torque can only be verified through the durability test of the whole vehicle after setting, the verification cycle is long, there are serious insufficiencies, and it is easy to be affected by the subjective feelings of the driver.

[0008] According to the present invention, a method for checking and testing the assembly torque of an automobile bolt connection pair is provided, comprising the following steps:

[0009] Step S1: extract the load of the bolt connection point by CAE simulation analysis, and calculate the tightening force required for the bolt connection pair;

[0010] Step S2: determining the calculated tightening force as the minimum axial force required to be provided by the bolt connection pair, and calculating the initial value of the assembly torque for the bolt connection pair to provide the minimum axial force;

[0011] Step S3: tightening the axial force detection bolt according to the initial value of the assembly torque;

[0012] Step S4: using a bolt axial force ultrasonic detection system to detect the axial force generated by the current bolt connection pair;

[0013] Step S5: Perform the test at a preset interval distance, calculate the axial force attenuation rate according to the initial value of the assembly torque and the axial force generated by the current bolt connection pair, and perform reliability verification according to the axial force attenuation rate.

[0014] Optionally, before step S1, the method further includes:

[0015] Step S0: Confirm the temperature and humidity of the test environment and the test sample to determine whether they meet the test specifications.

[0016] Optionally, in step S2, the initial value M of the assembly torque for providing the minimum axial force of the bolt connection pair is calculated according to the following formula: A :

[0017] ;

[0018] Among them, M A is the initial value of the assembly torque, unit: N·mm;

[0019] F min The minimum tightening force required for the bolt connection pair, unit: N;

[0020] p is the pitch of the bolt, unit: mm;

[0021] d2 is the median diameter of the bolt's external thread, unit: mm;

[0022] μ G is the friction coefficient of the bolt;

[0023] μ k is the end surface friction coefficient;

[0024] D km It is the effective friction surface diameter of the bolt connection pair, unit: mm.

[0025] Optionally, in step S3, a fixed value torque wrench is used according to the initial assembly torque value M. A Tighten the bolts.

[0026] Optionally, in step S4, a sensor is attached to the end face of the axial force detection bolt, and the sensor is connected to the bolt axial force ultrasonic detection system via a data cable.

[0027] Optionally, in step S4, a bolt axial force acquisition curve graph is generated using the detected axial force generated by the current bolt connection pair.

[0028] Optionally, in step S5, the formula for calculating the axial force attenuation rate is:

[0029] Axial force attenuation rate = (initial value of assembly torque - axial force detected by the current bolt connection pair) / initial value of assembly torque × 100%.

[0030] Optionally, when the axial force attenuation rate is less than 20%, it is determined that the torque setting of the bolt connection pair is reasonable.

[0031] Optionally, the automobile bolt connection assembly torque verification and test method further includes:

[0032] Step S6: Check the reliability road test bolt connection pair test results, and if there is no need to optimize the tightening torque, output the test conclusion;

[0033] Step S7: If the tightening torque needs to be optimized, the strength theory check is performed on the bolt connection pair after the optimized torque, and the reliability road test verification is carried out again.

[0034] The automobile bolt connection assembly torque verification and testing method disclosed in the present invention has the following technical effects:

[0035] The method of the present invention integrates theoretical CAE simulation analysis methods to accurately extract the load information borne by the connecting bolts, and determines the tightening force value required for the bolt connection pair after in-depth analysis and calculation. With the help of actual vehicle testing, the axial force of the bolt connection pair during the bolt tightening process is measured, and the attenuation of the axial force after the tightening operation is completed is monitored. Through the above operation, the rationality of the torque setting of the bolt connection pair can be efficiently verified, and then the precise tightening process parameters of the bolt connection can be obtained, providing a key basis and strong support for the optimization and quality improvement of the bolt connection process.

[0036] Further features and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments of the present invention with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

[0038] Figure 1 A schematic diagram of a flow chart of a method for checking and testing an assembly torque of an automobile bolt connection pair provided by an embodiment of the present invention;

[0039] Figure 2 A hardware connection diagram for checking and testing the assembly torque of an automobile bolt connection pair provided by an embodiment of the present invention;

[0040] Figure 3 A bolt axial force acquisition curve diagram in the assembly torque verification and test method of an automobile bolt connection pair provided by an embodiment of the present invention;

[0041] Figure 4 A schematic diagram of a bolt axial force attenuation curve in an assembly torque verification and test method for an automobile bolt connection pair provided in an embodiment of the present invention.

[0042] The following are marked in the figure:

[0043] 1. Assembly nut; 2. First assembly component; 3. Second assembly component; 4. Axial force detection bolt; 5. Sensor; 6. Data cable; 7. Bolt axial force ultrasonic detection system. DETAILED DESCRIPTION

[0044] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention unless otherwise specifically stated.

[0045] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

[0046] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered as part of the specification.

[0047] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0048] The present invention provides an embodiment of a method for checking and testing the assembly torque of an automobile bolt connection pair. Specifically, Figure 1 As shown, the following steps are included:

[0049] Step S1: Use CAE (Computer Aided Engineering) simulation analysis to extract the load of the bolt connection point and calculate the tightening force F required for the bolt connection pair min Specifically, for bolt connection points, by accurately modeling and applying corresponding boundary conditions and load conditions, the magnitude and direction of the force on the bolt connection points can be simulated, and then these load data can be extracted. Based on the extracted load data, combined with mechanical principles and related structural analysis algorithms, CAE simulation software is used to calculate and obtain the minimum tightening force F that the bolt connection pair needs to achieve to ensure reliable and stable connection. min The minimum clamping force F min It is an important basic parameter for the subsequent calculation of assembly torque and evaluation of connection performance. It ensures that the bolt can withstand the expected force in actual use without loosening or other problems.

[0050] Step S2: Determine the calculated tightening force as the minimum axial force required to be provided by the bolt connection pair, and calculate the initial value M of the assembly torque for the bolt connection pair to provide the minimum axial force. A Specifically, the tightening force F min It is equivalent to the minimum axial force that the bolt connection needs to provide, because this force is the key force to maintain the reliability of the bolt connection and enable the bolt connection point to resist external loads.

[0051] Step S3: tighten the axial force detection bolt 4 according to the initial value of the assembly torque;

[0052] Step S4: Use the bolt axial force ultrasonic detection system 7 to detect the axial force generated by the current bolt connection pair; it should be noted that the connection relationship between the bolt axial force ultrasonic detection system 7 and the corresponding detected component is as follows: Figure 2 As shown, the assembly nut 1 and the axial force detection bolt 4 are threadedly connected to form a bolt connection pair, and the bolt connection pair is used to fasten the first assembly component 2 and the second assembly component 3. A sensor 5 is attached to the end face of the axial force detection bolt 4, and the sensor 5 is connected to the bolt axial force ultrasonic detection system 7 through a data line 6. The bolt axial force ultrasonic detection system 7 uses ultrasonic technology to detect the axial force of the bolt. The propagation characteristics of the ultrasonic wave in the bolt are closely related to the stress state of the bolt. When the bolt is subjected to axial force, the propagation speed, frequency and other parameters of the ultrasonic wave will change. The detection system can capture and analyze these changes to infer the current axial force of the bolt, and then draw a curve of the axial force changing with time, working conditions and other factors, providing a basis for judging the reliability of the bolt connection pair.

[0053] Step S5: Test at a preset interval distance, calculate the axial force attenuation rate based on the initial value of the assembly torque and the axial force generated by the current bolt connection pair, and perform reliability verification based on the axial force attenuation rate; specifically, as the vehicle mileage increases and the repeated action under various complex working conditions, the axial force of the bolt will decay. Through a 5,000-kilometer reliability verification, the axial force of the bolt is tested regularly (every 1,000 kilometers), and the axial force attenuation rate is calculated based on the collected data using the corresponding calculation formula, such as Figure 4 As shown in the figure, the calculated axial force attenuation rate value can objectively reflect the change in the fastening performance of the bolt connection during actual use. If the attenuation rate is too large, it means that the bolt connection may gradually loosen, affecting the connection reliability.

[0054] In the embodiment of the present invention, before step S1, the method further includes:

[0055] Step S0: Confirm the temperature, humidity and test samples of the test environment to determine whether they meet the test specifications. It should be noted that temperature and humidity will affect the physical properties and friction coefficient of the material. At the same time, the specifications and quality of the test samples themselves also need to meet the established test specifications. Only by ensuring that these environmental factors are within a reasonable range and the samples are qualified, the subsequent test and analysis results will be reliable and accurate.

[0056] In the embodiment of the present invention, in step S2, the initial value M of the assembly torque providing the minimum axial force of the bolt connection pair is calculated according to the following formula: A :

[0057] ;

[0058] Among them, M A is the initial value of the assembly torque, unit: N·mm;

[0059] F min The minimum tightening force required for the bolt connection pair, unit: N;

[0060] p is the pitch of the bolt, unit: mm;

[0061] d2 is the median diameter of the bolt's external thread, unit: mm;

[0062] μ G is the friction coefficient of the bolt;

[0063] μ k is the end surface friction coefficient;

[0064] D km It is the effective friction surface diameter of the bolt connection pair, unit: mm.

[0065] It should be noted that these parameters reflect the geometric characteristics of the axial force detection bolt 4 itself and the friction characteristics of the connection part. Different parameter combinations will result in different assembly torque requirements. A It is crucial for the subsequent correct tightening of the bolts, as it determines how much torque should be applied in actual operation to enable the axial force detection bolt 4 to generate an axial force that meets the requirements.

[0066] In the embodiment of the present invention, in step S3, a fixed value torque wrench is used to adjust the initial value of the assembly torque M. A Tighten the bolts. It should be noted that a fixed-value torque wrench is a tool that can accurately control the magnitude of the applied torque. Use this fixed-value torque wrench to tighten the bolts according to the set value to ensure that each bolt can be applied with a relatively accurate torque, so that the bolt connection pair can reach the expected initial tightening state, laying the foundation for subsequent performance testing and verification. If the torque is not applied accurately, too large a torque may cause the bolt to be over-tightened and damaged (such as bolt stretching deformation, thread damage, etc.), and too small a torque may not provide sufficient axial force, which may easily cause the bolt to loosen in subsequent use.

[0067] In the embodiment of the present invention, in step S4, a sensor 5 is attached to the end face of the axial force detection bolt 4, and the sensor 5 is connected to the bolt axial force ultrasonic detection system 7 through a data line 6. It should be noted that the sensor 5 is a strain sensor 5 or a piezoelectric sensor 5, and the sensor 5 senses the magnitude of the bolt axial force and converts it into an electrical signal, and then transmits the signal to the bolt axial force ultrasonic detection system 7 through the data line 6. The bolt axial force ultrasonic detection system 7 uses the correlation between the propagation characteristics of ultrasonic waves in the bolt and the axial force to process and analyze the electrical signal, thereby accurately measuring the actual axial force generated by the current bolt connection pair.

[0068] In the embodiment of the present invention, in step S4, the bolt axial force acquisition curve diagram is generated by using the detected axial force generated by the current bolt connection pair. Figure 3 As shown, the horizontal axis of the graph is the rotation angle, and the vertical axis is the tightening force and total torque. When the tightening angle is 400 degrees, the corresponding total torque is 113.738Nm and the tightening force is 54.076kN. This curve can intuitively reflect the changes in the axial force of the bolt at different times and under different working conditions, which is convenient for subsequent analysis of the performance change trend of the bolt connection pair and evaluation of its stability.

[0069] In the embodiment of the present invention, in step S5, the formula for calculating the axial force attenuation rate is:

[0070] Axial force attenuation rate = (initial value of assembly torque - current axial force detected by bolt connection pair) / initial value of assembly torque × 100%. This axial force attenuation rate value can objectively reflect the change in the tightening performance of the bolt connection pair during actual use, and is one of the important indicators to measure whether the torque setting is reasonable.

[0071] In the embodiment of the present invention, Figure 4 The figure shows a schematic diagram of the bolt axial force attenuation curve. When the axial force attenuation rate is less than 20%, it is determined that the torque setting of the bolt connection pair is reasonable. The specified attenuation rate is less than 20%, which means that within this range, the bolt connection pair can maintain good connection performance during the entire 5,000-kilometer reliability verification process, and the torque setting is basically reasonable.

[0072] In an embodiment of the present invention, the automobile bolt connection assembly torque verification and testing method further includes:

[0073] Step S6: Check the reliability road test bolt connection test results. If the tightening torque does not need to be optimized, the test conclusion is output; it should be noted that after completing the 5,000-kilometer reliability verification, the entire bolt connection test results are comprehensively checked and evaluated. If the axial force attenuation rate indicators all meet the requirements, it means that the currently set assembly torque is appropriate and does not need to be adjusted and optimized. At this time, the test conclusion can be output, indicating that the torque setting of the bolt connection has passed the verification; on the contrary, if it is found that there is a situation that does not meet the requirements (such as the axial force attenuation rate exceeds the limit range), it is necessary to enter step S7 to optimize the torque, etc. to improve the performance of the bolt connection.

[0074] Step S7: If the tightening torque needs to be optimized, the strength of the bolt connection pair after the optimized torque is theoretically checked, and the reliability road test verification is carried out again. It should be noted that after the tightening torque is optimized and adjusted, the bolt connection pair needs to be checked from a theoretical level according to mechanical principles, material strength, etc., including the calculation and evaluation of the tensile strength, shear strength and overall strength of the bolt, to ensure that the optimized torque will not cause insufficient strength of the bolt (such as plastic deformation due to exceeding the yield strength of the material) or other reliability problems caused by torque changes, and to ensure that the bolt can still work safely and reliably under the new torque and corresponding axial force. By testing the bolt axial force and other indicators under actual driving conditions again, it is further verified whether the optimized bolt connection pair truly meets the requirements for long-term reliable operation of the vehicle. Only by passing the verification again can it be finally determined that the optimized torque setting is reasonable and effective.

[0075] The assembly torque verification and test method of automobile bolt connection provided by the present invention combines CAE simulation analysis to calculate the minimum tightening force required for the bolt connection, obtains the initial value of the assembly torque through theoretical calculation, and has relatively high accuracy. Combined with the reliability verification of the whole vehicle, the bolt axial force detection is carried out to monitor the bolt axial force attenuation rate, and the verification is carried out by combining theory with practice. The test method is relatively sufficient, which can improve the safe driving performance of the vehicle and reduce customer complaints due to loose bolts and abnormal noises.

[0076] The above describes in detail the structure, features and effects of the present invention based on the embodiments shown in the drawings, but the above is only a preferred embodiment of the present invention. It should be noted that the technical features involved in the above embodiments and their preferred methods can be reasonably combined and matched into a variety of equivalent schemes by those skilled in the art without departing from or changing the design ideas and technical effects of the present invention; therefore, the present invention is not limited to the scope of implementation shown in the drawings, and all changes made in accordance with the concept of the present invention, or modifications to equivalent embodiments with equivalent changes, which still do not exceed the spirit covered by the specification and drawings, should be within the protection scope of the present invention.

Claims

1. A method for checking and testing the assembly torque of an automobile bolt connection pair, characterized in that: The following steps are involved: Step S1: extract the load of the bolt connection point by CAE simulation analysis, and calculate the tightening force required for the bolt connection pair; Step S2: determining the calculated tightening force as the minimum axial force required to be provided by the bolt connection pair, and calculating the initial value of the assembly torque for the bolt connection pair to provide the minimum axial force; Step S3: tightening the axial force detection bolt according to the initial value of the assembly torque; Step S4: using a bolt axial force ultrasonic detection system to detect the axial force generated by the current bolt connection pair; Step S5: Perform the test at a preset interval distance, calculate the axial force attenuation rate according to the initial value of the assembly torque and the axial force generated by the current bolt connection pair, and perform reliability verification based on the axial force attenuation rate.

2. The method for checking and testing the assembly torque of a bolt connection pair for an automobile according to claim 1, characterized in that: Before step S1, the method further includes: Step S0: Confirm the temperature and humidity of the test environment and the test sample to determine whether they meet the test specifications.

3. The method for checking and testing the assembly torque of a bolt connection pair for an automobile according to claim 1, characterized in that: In step S2, the initial value MA of the assembly torque for providing the minimum axial force of the bolt connection pair is calculated according to the following formula: ； Among them, M A is the initial value of the assembly torque, unit: N·mm; F min The minimum tightening force required for the bolt connection pair, unit: N; p is the pitch of the bolt, unit: mm; d2 is the median diameter of the bolt's external thread, unit: mm; μ G is the friction coefficient of the bolt; μ k is the end surface friction coefficient; D km It is the effective friction surface diameter of the bolt connection pair, unit: mm.

4. The method for checking and testing the assembly torque of an automobile bolt connection according to claim 3 is characterized in that: In step S3, a fixed value torque wrench is used to set the initial assembly torque M. A Tighten the bolts.

5. The method for checking and testing the assembly torque of a bolt connection pair for an automobile according to claim 1, characterized in that: In the step S4, a sensor is attached to the end surface of the axial force detection bolt, and the sensor is connected to the bolt axial force ultrasonic detection system via a data line.

6. The method for checking and testing the assembly torque of a bolt connection pair for an automobile according to claim 5, characterized in that: In step S4, a bolt axial force acquisition curve graph is generated using the detected axial force generated by the current bolt connection pair.

7. The method for checking and testing the assembly torque of a bolt connection pair for an automobile according to claim 1, characterized in that: In step S5, the formula for calculating the axial force attenuation rate is: Axial force attenuation rate = (initial value of assembly torque - axial force detected by the current bolt connection pair) / initial value of assembly torque × 100%.

8. The method for checking and testing the assembly torque of a bolt connection pair for an automobile according to claim 7, characterized in that: When the axial force attenuation rate is less than 20%, it is determined that the torque setting of the bolt connection pair is reasonable.

9. The method for checking and testing the assembly torque of a bolt connection pair for an automobile according to claim 1, characterized in that: Also includes: Step S6: Check the reliability road test bolt connection pair test results, and if there is no need to optimize the tightening torque, output the test conclusion; Step S7: If the tightening torque needs to be optimized, the strength theory check is performed on the bolt connection pair after the optimized torque, and the reliability road test verification is carried out again.

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