Method for evaluating NVH (Noise Vibration and Harshness) attenuation performance of vehicle chassis bushing

Abstract

The invention discloses a method for evaluating the NVH attenuation performance of a vehicle chassis bushing, and the method comprises the steps: obtaining Fs curves of a durable bushing in three directions, and converting the Fs curves in the three directions into stiffness curves of the durable bushing in the three directions; determining the rigidities of the durable bushing in the three directions based on the rigidity curves of the durable bushing in the three directions; and evaluating the NVH attenuation performance of the durable bushing according to the rigidities of the durable bushing in the three directions and the rigidities of the new bushing in the three directions. According to the method, the stress of the bushing is divided into the radial solid direction, the radial hollow direction and the axial direction and is converted into the rigidity in the corresponding direction, the elastic condition of the bushing can be quantitatively and visually expressed through rigidity conversion, and the NVH attenuation performance of the bushing is conveniently reflected to the rigidity attenuation resistance of the bushing and the rigidity attenuation condition of the bushing. The method is simple and efficient, the evaluation result is more accurate, and meanwhile, the mileage of the vehicle cannot be changed.

Description

Technical Field

[0001] The invention belongs to the field of automobile technology, and in particular relates to a method for evaluating the NVH attenuation performance of a vehicle chassis bushing. Background Art

[0002] As the domestic automobile market becomes more and more mature, modern consumers have higher requirements for automobile performance and quality. New energy vehicles do not have traditional fuel engines, and the overall electric drive noise is relatively small, so the contribution of vehicle road noise to the comfort of the whole vehicle is increasing. Fig. 9 As shown in the figure, the main excitation source of vehicle road noise is the rough asphalt road surface excitation tire through the chassis bracket path to cause the rumbling sound inside the car. The front bracket of the vehicle is softly connected to the triangular arm through the bushing, and the rear bracket is softly connected to the body through the bushing. Automobile bushings can reduce vibration and noise, significantly improve the comfort and driving experience of the vehicle, and automobile bushings play a vital role in improving the NVH performance of the vehicle. NVH performance refers to noise, vibration and harshness.

[0003] At present, for new cars that have been stored for a long time, the NVH attenuation performance of the bushing is tested by driving the vehicle for a certain mileage, detecting the noise conditions of the road surface inside the vehicle during driving, and judging the NVH attenuation performance of the bushing based on the noise conditions. This method will change the vehicle mileage. Summary of the invention

[0004] The purpose of the present invention is to solve the deficiencies of the above-mentioned background technology and to provide a method for evaluating the NVH attenuation performance of a vehicle chassis bushing.

[0005] The technical solution adopted by the present invention is: a method for evaluating the NVH attenuation performance of a vehicle chassis bushing, obtaining Fs curves in three directions of a durable bushing, and converting the Fs curves in three directions into stiffness curves in three directions of the durable bushing respectively;

[0006] Determine the stiffness of the durable bushing in three directions based on the stiffness curves of the durable bushing in three directions;

[0007] The NVH attenuation performance of the durable bushing is evaluated based on the stiffness of the durable bushing in three directions and the stiffness of the new bushing in three directions.

[0008] Furthermore, the Fs curves of the durable bushing in three directions are obtained through the bushing stand, and the three directions are radial hollow direction, radial solid direction and axial direction respectively.

[0009] Furthermore, the process of converting the Fs curves in three directions into the stiffness curves of the durable bushing in three directions is as follows:

[0010] The Fs curve is discretized according to the set distance resolution to obtain a plurality of discrete points, the stiffness of each discrete point is calculated, and the stiffness of all discrete points is fitted to obtain the stiffness curve.

[0011] Furthermore, the stiffness of the discrete points is calculated by the following formula:

[0012]

[0013] in, is the stiffness of the ith discrete point, is the force magnitude of the i+1th discrete point, is the force magnitude of the ith discrete point, To set the distance resolution.

[0014] Furthermore, before converting the stiffness curve of the radial hollow direction of the durable bushing, the point on the Fs curve of the radial hollow direction of the durable bushing where the force fluctuation change is greater than a set threshold is taken as the inflection point, and the Fs curve of the radial hollow direction of the durable bushing is filtered based on the inflection point, and the range segment after the inflection point on the curve is filtered out, and the stiffness curve of the radial hollow direction of the durable bushing is converted based on the filtered Fs curve.

[0015] Further, the process of determining the stiffness of the durable bushing in three directions based on the stiffness curves of the durable bushing in three directions is:

[0016] Calculate the average stiffness of all discrete points on the stiffness curve, and use the average stiffness as the stiffness of the durable bushing in the corresponding direction.

[0017] Further, the process of evaluating the NVH attenuation performance of the durable bushing according to the stiffness of the durable bushing in three directions and the stiffness of the new bushing in three directions is:

[0018] The stiffness of the durable bushing in three directions is divided by the stiffness of the new bushing in three directions to obtain the improvement ratio of the durable bushing in three directions. The total reduced stiffness of the durable bushing is determined based on the improvement ratio and the set ratio. The total reduced stiffness of the durable bushing is compared with the total reduced stiffness of the new bushing. The NVH attenuation performance of the durable bushing is evaluated based on the comparison results.

[0019] Furthermore, the total reduced stiffness of the durable bushing is determined by the following formula:

[0020]

[0021] in, is the total reduced stiffness of the durable bushing, , , are the improvement proportions of the durable bushing in radial hollow direction, radial solid direction and axial direction respectively. A, B and C are the set proportions of the durable bushing in radial hollow direction, radial solid direction and axial direction respectively. A+B+C=the total reduced stiffness of the new bushing.

[0022] Furthermore, the process of comparing the total reduced stiffness of the durable bushing with the total reduced stiffness of the new bushing and evaluating the NVH attenuation performance of the durable bushing according to the comparison result is as follows:

[0023] The total reduced stiffness of the durable bushing is divided by the total reduced stiffness of the new bushing to obtain the attenuation value, and the NVH attenuation performance of the durable bushing is evaluated based on the attenuation value.

[0024] Furthermore, the process of evaluating the NVH attenuation performance of the durable bushing according to the attenuation value is as follows:

[0025] If the attenuation value is less than the first set value, it is determined that the NVH attenuation performance of the durable bushing is good;

[0026] If the attenuation value is greater than or equal to the first set value and less than the second set value, it is determined that the NVH attenuation performance of the durable bushing is qualified;

[0027] If the attenuation value is greater than or equal to the second set value, it is determined that the NVH attenuation performance of the durable bushing is unqualified and the bushing needs to be replaced.

[0028] The beneficial effects of the present invention are:

[0029] The present invention divides the bushing force into three directions: radial solid direction, radial hollow direction and axial direction, and converts them into stiffness in corresponding directions respectively. The bushing elasticity can be quantitatively and intuitively expressed through stiffness conversion, which is convenient for evaluating the bushing NVH attenuation performance. The bushing NVH attenuation performance is evaluated by comparing the stiffness of the durable bushing with the stiffness of the new bushing. The method is simple and efficient, the evaluation result is more accurate, and it will not change the vehicle mileage.

[0030] The present invention sets the ratio of the stiffness of the bushing in each direction according to different calibrations of the importance of road noise, performs ratio conversion according to the set ratio, compares the converted stiffness with the converted height of the new bushing, and performs NVH attenuation evaluation through the ratio-converted stiffness, with higher evaluation accuracy.

[0031] The present invention filters the Fs curve in the radial hollow direction of the durable bushing, and filters out the range segment on the Fs curve where the force fluctuation is greater than a set threshold, that is, eliminates some parameters that have no effect on road noise, and only uses the remaining parameters to transform and calculate the stiffness curve, so that the final evaluation result is more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a flow chart of the present invention.

[0033] Figure 2 Schematic diagram of the bushing structure.

[0034] Figure 3 This is the Fs curve diagram of the radial hollow direction of the durable bushing of the present invention and the new bushing (before filtering).

[0035] Figure 4 The stiffness curve diagram of the durable bushing of the present invention and the new bushing in the radial hollow direction (before filtering).

[0036] Figure 5 It is the Fs curve diagram of the durable bushing of the present invention and the new bushing in the radial solid direction.

[0037] Figure 6 It is a stiffness curve diagram of the durable bushing of the present invention and the new bushing in the radial solid direction.

[0038] Figure 7 It is the Fs curve diagram of the durable bushing of the present invention and the new bushing in the axial direction.

[0039] Figure 8 The stiffness curve diagram of the durable bushing of the present invention and the new bushing in the axial direction.

[0040] Fig. 9 Schematic diagram of the transmission relationship between road noise and road surface, tires, and bushings. DETAILED DESCRIPTION

[0041] The specific embodiments of the present invention are further described below in conjunction with the accompanying drawings. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0042] like Figure 1 As shown, the present invention provides a method for evaluating the NVH attenuation performance of a vehicle chassis bushing, obtaining Fs curves of a durable bushing in three directions, and converting the Fs curves in three directions into stiffness curves of the durable bushing in three directions respectively; the Fs curve of the bushing is a force-displacement curve, which is a curve drawn by plotting the pressing force and pressing displacement data collected during the press-fitting process, and it reflects the force and deformation of the bushing during the press-fitting process;

[0043] Determine the stiffness of the durable bushing in three directions based on the stiffness curves of the durable bushing in three directions;

[0044] The NVH attenuation performance of the durable bushing is evaluated based on the stiffness of the durable bushing in three directions and the stiffness of the new bushing in three directions.

[0045] The present invention converts the Fs curves of the three directions of the bushing into the stiffness of the corresponding directions respectively. The stiffness conversion can quantitatively and intuitively express the elasticity of the bushing, which is convenient for evaluating the NVH attenuation performance of the bushing. The stiffness attenuation of the bushing is evaluated by comparing the stiffness of the durable bushing with the stiffness of the new bushing. The attenuation of the bushing stiffness reflects the NVH attenuation performance of the bushing, and then the NVH road noise attenuation performance of the vehicle model can be quickly judged. The method is simple and efficient, the evaluation result is more accurate, and it will not change the vehicle mileage.

[0046] In the above scheme, the Fs curves of the durable bushing (i.e., the durable sample) and the new bushing (new sample) in three directions are obtained through the bushing test bench. The three directions are radial hollow direction, radial solid direction, and axial direction, respectively. Figure 3 , Figure 5 , Figure 7 As shown, the Fs curves of the bushing in radial hollow direction, radial solid direction and axial direction respectively.

[0047] In the above scheme, the process of converting the Fs curves in three directions into the stiffness curves of the durable bushing in three directions is as follows: discretizing the Fs curve according to the set distance resolution to obtain a number of discrete points, calculating the stiffness of each discrete point, fitting the stiffness of all discrete points to obtain the stiffness curve, and the converted stiffness curve is as follows: Figure 4 , Figure 6 , Figure 8 The distance resolution is set according to the bushing structure size, and the range is 0.02mm-0.1mm. In this embodiment, it is preferably 0.02mm, 0.03mm, 0.04mm or 0.05mm.

[0048] In the above scheme, the stiffness of the discrete points is calculated by the following formula:

[0049]

[0050] in, is the stiffness of the ith discrete point, i starts from 1, is the force magnitude of the i+1th discrete point, is the force magnitude of the ith discrete point, To set the distance resolution.

[0051] The vehicle chassis bushings include the rear bushings of the triangle arm and the front and rear bushings of the rear bracket. The bushing Fs curve generally shows a smooth growth trend, but due to the presence of openings in the radial direction of the bushing, such as Figure 2 As shown in Figure 2, when it is subjected to force, there will be a sudden change, resulting in an inflection point in the Fs curve, such as Figure 3As shown in the figure, the range after the inflection point is caused by the large deformation of the bushing due to the opening. The curve in this range cannot reflect the actual stress deformation of the bushing. Therefore, in the subsequent stiffness calculation, the range after the inflection point is not included in the calculation. The processing for this is that before converting the stiffness curve of the radial hollow direction of the durable bushing, the point where the force fluctuation change on the Fs curve of the radial hollow direction of the durable bushing is greater than the set threshold is used as the inflection point, and the Fs curve of the radial hollow direction of the durable bushing is filtered based on the inflection point, and the range after the inflection point on the curve is filtered out, and the stiffness curve of the radial hollow direction of the durable bushing is converted based on the filtered Fs curve.

[0052] The present invention filters the Fs curve in the radial hollow direction of the durable bushing, and filters out the range segment on the Fs curve where the force fluctuation is greater than a set threshold, that is, eliminates some parameters that have no effect on road noise, and only uses the remaining parameters to transform and calculate the stiffness curve, so that the final evaluation result is more accurate.

[0053] In the above scheme, the process of determining the stiffness of the durable bushing in three directions based on the stiffness curve of the durable bushing in three directions is: calculating the average stiffness of all discrete points on the stiffness curve, and taking the average as the stiffness of the durable bushing in the corresponding direction. The present invention takes the average stiffness value of each point on the bushing stiffness curve as the stiffness in the corresponding direction, which can better reflect the stiffness level of the bushing when it is subjected to torsional force.

[0054] In the above scheme, the process of evaluating the NVH attenuation performance of the durable bushing according to the stiffness of the durable bushing in three directions and the stiffness of the new bushing in three directions is: the stiffness of the durable bushing in three directions is divided by the stiffness of the new bushing in three directions to obtain the improvement ratio of the durable bushing in three directions, the total converted stiffness of the durable bushing is determined based on the improvement ratio and the set ratio, the total converted stiffness of the durable bushing is compared with the total converted stiffness of the new bushing, and the NVH attenuation performance of the durable bushing is evaluated according to the comparison result. The present invention sets the ratio of the stiffness of the bushing in each direction according to different calibrations of the importance of road noise, performs ratio conversion according to the set ratio, compares the converted stiffness with the converted height of the new bushing, and performs attenuation evaluation through the stiffness converted by the ratio, so that the evaluation accuracy is higher.

[0055] In the above scheme, the total reduced stiffness of the durable bushing is determined by the following formula:

[0056]

[0057] in, is the total reduced stiffness of the durable bushing, , , A, B, and C are the ratios of the radial hollow direction, radial solid direction, and axial direction of the durable bushing, respectively. A, B, and C are the ratios of the radial hollow direction, radial solid direction, and axial direction of the durable bushing, respectively, which are equal to the corresponding direction contribution multiplied by one hundred, that is, the total reduced stiffness of the new bushing is 100, then A+B+C=100. The present invention finally calculates with the reduced stiffness, and the calculation process is more convenient and quick.

[0058] The stiffness results of the chassis bushing in three directions are different in size, and their importance to road noise is also different. Among them, the axial stiffness is the most important, but its value is the smallest. The radial hollow direction is the second most important, and the radial solid direction is the third most important. According to the importance, it can be distributed according to the 60%, 25%, and 15% method, that is, A=25, B=15, C=60 mentioned above. According to product requirements, other distribution ratios can also be set. The calculation results are shown in Table 1 below. The improvement ratio in Table 1 is the stiffness of the corresponding direction of the durable bushing divided by the stiffness of the corresponding direction of the new bushing. The contribution amount is the importance of the three directions to road noise. Setting the ratio according to the contribution amount can more accurately characterize the correlation between the stiffness attenuation of the bushing and the vehicle NVH road noise.

[0059] Table 1 Vehicle durability bushing stiffness calculation table

[0060]

[0061] The total reduced stiffness of the above-mentioned durable bushing is compared with the total reduced stiffness of the new bushing, that is, the total reduced stiffness of the durable bushing is divided by the total reduced stiffness of the new bushing to obtain the attenuation value, and the NVH attenuation performance of the durable bushing is evaluated according to the attenuation value:

[0062] If the attenuation value is less than the first set value, it is determined that the NVH attenuation performance of the durable bushing is good;

[0063] If the attenuation value is greater than or equal to the first set value and less than the second set value, it is determined that the NVH attenuation performance of the durable bushing is qualified;

[0064] If the attenuation value is greater than or equal to the second set value, it is determined that the NVH attenuation performance of the durable bushing is unqualified and the bushing needs to be replaced.

[0065] The first set value and the second set value are calibrated according to actual needs. In this embodiment, the first set value is set to 10% and the second set value is set to 28%. Therefore, the final calculated attenuation value is judged to be good if it is between 0-10%, qualified if it is between 10-28%, and needs to be replaced if it is above 28%.

[0066] Through the above evaluation process, for vehicles that have been placed overseas for a long time, the bushing of a single vehicle can be analyzed to determine the NVH attenuation performance of the bushings of all vehicles in the batch, thereby quickly determining the NVH road noise performance of all vehicles. This method is simple, efficient and highly reliable.

[0067] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in the field.

Claims

1. A method for evaluating the NVH attenuation performance of a vehicle chassis bushing, characterized in that: Obtain the Fs curves of the durable bushing in three directions, and convert the Fs curves in three directions into stiffness curves of the durable bushing in three directions respectively; Determine the stiffness of the durable bushing in three directions based on the stiffness curves of the durable bushing in three directions; The NVH attenuation performance of the durable bushing is evaluated based on the stiffness of the durable bushing in three directions and the stiffness of the new bushing in three directions.

2. The NVH attenuation performance evaluation method of a vehicle chassis bushing according to claim 1, characterized in that: The Fs curves of the durable bushing in three directions are obtained through the bushing bench, and the three directions are radial hollow direction, radial solid direction and axial direction.

3. The NVH attenuation performance evaluation method of a vehicle chassis bushing according to claim 1, characterized in that: The process of converting the Fs curves in three directions into the stiffness curves in three directions of the durable bushing is as follows: The Fs curve is discretized according to the set distance resolution to obtain a plurality of discrete points, the stiffness of each discrete point is calculated, and the stiffness of all discrete points is fitted to obtain the stiffness curve.

4. The NVH attenuation performance evaluation method of a vehicle chassis bushing according to claim 3, characterized in that: The stiffness of the discrete points is calculated by the following formula: ， in, is the stiffness of the ith discrete point, is the force magnitude of the i+1th discrete point, is the force magnitude of the ith discrete point, To set the distance resolution.

5. The NVH attenuation performance evaluation method of a vehicle chassis bushing according to claim 3, characterized in that: Before converting the stiffness curve of the radial hollow direction of the durable bushing, the point on the Fs curve of the radial hollow direction of the durable bushing where the force fluctuation change is greater than the set threshold is taken as the inflection point, and the Fs curve of the radial hollow direction of the durable bushing is filtered based on the inflection point, and the range segment after the inflection point on the curve is filtered out, and the stiffness curve of the radial hollow direction of the durable bushing is converted based on the filtered Fs curve.

6. The NVH attenuation performance evaluation method of a vehicle chassis bushing according to claim 1, characterized in that: The process of determining the stiffness of the durable bushing in three directions based on the stiffness curve of the durable bushing in three directions is as follows: Calculate the average stiffness of all discrete points on the stiffness curve, and use the average stiffness as the stiffness of the durable bushing in the corresponding direction.

7. The NVH attenuation performance evaluation method of a vehicle chassis bushing according to claim 1, characterized in that: The process of evaluating the NVH attenuation performance of the durable bushing according to the stiffness of the durable bushing in three directions and the stiffness of the new bushing in three directions is as follows: The stiffness of the durable bushing in three directions is divided by the stiffness of the new bushing in three directions to obtain the improvement ratio of the durable bushing in three directions. The total reduced stiffness of the durable bushing is determined based on the improvement ratio and the set ratio. The total reduced stiffness of the durable bushing is compared with the total reduced stiffness of the new bushing. The NVH attenuation performance of the durable bushing is evaluated based on the comparison results.

8. The NVH attenuation performance evaluation method of a vehicle chassis bushing according to claim 7, characterized in that: The total reduced stiffness of the durable bushing is determined by the following formula: ， in, is the total reduced stiffness of the durable bushing, , , are the improvement proportions of the durable bushing in radial hollow direction, radial solid direction and axial direction respectively. A, B and C are the set proportions of the durable bushing in radial hollow direction, radial solid direction and axial direction respectively. A+B+C=the total reduced stiffness of the new bushing.

9. The NVH attenuation performance evaluation method of a vehicle chassis bushing according to claim 7, characterized in that: The process of comparing the total reduced stiffness of the durable bushing with the total reduced stiffness of the new bushing and evaluating the NVH attenuation performance of the durable bushing according to the comparison result is as follows: The total reduced stiffness of the durable bushing is divided by the total reduced stiffness of the new bushing to obtain the attenuation value, and the NVH attenuation performance of the durable bushing is evaluated based on the attenuation value.

10. The NVH attenuation performance evaluation method of a vehicle chassis bushing according to claim 9, characterized in that: The process of evaluating the NVH attenuation performance of the durable bushing according to the attenuation value is as follows: If the attenuation value is less than the first set value, it is determined that the NVH attenuation performance of the durable bushing is good; If the attenuation value is greater than or equal to the first set value and less than the second set value, it is determined that the NVH attenuation performance of the durable bushing is qualified; If the attenuation value is greater than or equal to the second set value, it is determined that the NVH attenuation performance of the durable bushing is unqualified and the bushing needs to be replaced.

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