CN115452286A - High-frequency dynamic characteristic test method for rubber suspension of electric automobile - Google Patents

Abstract

The invention relates to a high-frequency dynamic characteristic test method of an electric vehicle rubber suspension, belonging to the technical field of vehicle suspension tests, which can find out main influence factors of the high-frequency dynamic characteristic by analyzing boundary conditions of the suspension dynamic characteristic test, and identify the corresponding relation and influence rule of the dynamic characteristic and the main factors so as to expand the guiding principle of design and optimization of the electric vehicle suspension and a bracket thereof; the method comprises the following steps: s1, designing a clamp for fixing a rubber suspension; s2, respectively taking the suspension stiffness, the clamp mode and the rubber suspension mode as single variables, and respectively performing high-frequency dynamic characteristic tests to obtain the influence rule of each variable on the vibration peak value under the three frequency bands of 1000Hz-1200Hz, 1500Hz-1650Hz and 1900Hz-2300 Hz.

Description

High-frequency dynamic characteristic test method for rubber suspension of electric automobile

Technical Field

The invention relates to the technical field of automobile suspension tests, in particular to a high-frequency dynamic characteristic test method for an electric automobile rubber suspension.

Background

Currently, reduction of fossil energy consumption has become an international trend. Under the trend, clean energy such as wind, light and water and a battery energy storage technology are rapidly developed, and new energy automobiles enter the lives of people due to the environment-friendly characteristic of the new energy automobiles, so that the new energy automobiles rapidly become the key point of research and development of the automobile industry.

Compared with a hybrid electric vehicle, the electric vehicle does not need the design and development of a very complicated control strategy, has relatively simple architecture and structure, and becomes a product trend of a new energy vehicle. The NVH performance of the electric automobile is the dynamic quality of the whole automobile with the most obvious passenger perception degree, the power of the electric automobile is different from that of a traditional fuel oil automobile, and due to the lack of the masking effect of an engine, although the noise level is reduced, the noise frequency is obviously improved, so that passengers can more easily perceive the change of the sound quality of the whole automobile, and higher requirements are provided for the development and control of the NVH high-frequency performance.

The highest frequency of the conventional electro-hydraulic servo type suspension dynamic characteristic testing equipment is only 500Hz, and the test of the rubber suspension higher frequency dynamic characteristic is limited by the equipment and lacks research, so that the high frequency dynamic characteristic of the rubber suspension is less understood.

Accordingly, there is a need to develop a method for testing high frequency dynamic characteristics of rubber suspensions of electric vehicles to overcome the deficiencies of the prior art and to solve or alleviate one or more of the problems described above.

Disclosure of Invention

In view of the above, the invention provides a high-frequency dynamic characteristic test method for a rubber suspension of an electric vehicle, which can find out main influence factors of the high-frequency dynamic characteristic by analyzing boundary conditions of a suspension dynamic characteristic test, and identify the corresponding relation and influence rule of the dynamic characteristic and the main factors, thereby expanding the guiding principle of design and optimization of the suspension and a bracket of the electric vehicle.

In one aspect, the invention provides a high-frequency dynamic characteristic test method for an electric vehicle rubber suspension, which comprises the following steps:

s1, designing a clamp for fixing a rubber suspension;

s2, respectively carrying out high-frequency dynamic characteristic tests by taking the suspension rigidity, the clamp mode and the rubber suspension mode as single variables to obtain the influence rule of each variable on the vibration peak value under the three frequency ranges of 1000Hz-1200Hz, 1500Hz-1650Hz and 1900Hz-2300 Hz.

The above-described aspects and any possible implementations further provide an implementation in which the suspension stiffness is 800N/mm, 630N/mm, or 475N/mm. When the suspension stiffness is taken as a single variable, the values of the suspension stiffness are sequentially selected from 800N/mm, 630N/mm and 475N/mm from large to small, and high-frequency dynamic characteristic tests are respectively carried out; when the clamp mode or the rubber suspension mode is taken as a single variable, the suspension rigidity is selected from any one of 800N/mm, 630N/mm and 475N/mm and is kept unchanged.

The above aspect and any possible implementation further provides an implementation, wherein the clamp includes an upper clamp and a lower clamp; the active end bracket of the rubber suspension is fixed on the upper clamp, and the passive end bracket of the rubber suspension is fixed on the lower clamp; the upper clamp and the lower clamp are fixedly connected with two testing ends of the m + p electromagnetic high-frequency testing equipment respectively;

the upper clamp is made of aviation aluminum and has the weight of 2.248Kg;

the lower clamp is made of aviation aluminum and has the weight of 2.272Kg.

The above aspect and any possible implementation manner further provide an implementation manner, where the upper fixture includes a square plate at an upper end, and a left ear fork and a right ear fork fixed below the square plate, and lower ends of the two ear forks are each provided with a first sample fixing hole; and the active end bracket of the rubber suspension is fixed between the two ear forks through bolts.

In accordance with the above-mentioned aspects and any possible implementation manner, there is further provided an implementation manner, in which the lower fixture includes a circular plate located at a lower end and a hemipyramid platform fixedly arranged on the circular plate, a groove with an upper surface and a side surface both open is arranged on a side wall of the hemipyramid platform, and a plurality of second sample fixing holes are arranged on a side wall of the groove; and the passive end bracket of the rubber suspension is fixed on the second sample fixing hole through a bolt.

The above-described aspect and any possible implementation further provide an implementation that takes the clamp mode as a single variable, specifically: and sequentially adding weights with different weights to the upper clamp or the lower clamp.

The above-described aspect and any possible implementation further provide an implementation that takes the clamp mode as a single variable, specifically: weights of different weights are sequentially added to the side edges of the ear forks.

The above-described aspect and any possible implementation manner further provide an implementation manner that the rubber suspension mode is a single variable, specifically: and sequentially adding heavy objects with different weights at the round pipe shell of the rubber suspension driven end bracket.

The above-described aspects and any possible implementations further provide an implementation in which the weights of different weights are weights of, in particular, 0g, 45g, and 90 g.

In accordance with the above-described aspects and any possible implementations, there is further provided an implementation in which the ear fork has a symmetrical structure with two inclined planes, i.e., a wide top and a narrow bottom, and the inclined planes have a slope of 18 degrees. The inclined plane is the side of the ear fork for attaching different weights.

Compared with the prior art, one of the technical schemes has the following advantages or beneficial effects: the invention is based on the updating and upgrading of equipment, the upper limit of the frequency of a rubber suspension dynamic characteristic test is greatly improved from the traditional 500Hz to 3000Hz, and in order to reduce the influence of a clamp mode on the suspension dynamic characteristic test, a clamp design reference is provided;

another technical scheme in the above technical scheme has the following advantages or beneficial effects: the method is based on the dynamic characteristic test result, discusses main influence factors of three peak values of high-frequency dynamic stiffness, and provides a method for identifying through schemes of different stiffness and different additional mass, so as to draw a conclusion;

another technical scheme in the above technical scheme has the following advantages or beneficial effects: the invention is based on dynamic characteristic test results, and combines modal analysis of test boundary conditions to obtain the guidance principle of electric vehicle suspension and bracket design and optimization: the suspension stiffness and the passive end mass change obviously affect the suspension high-frequency dynamic characteristic, the initial stiffness of the suspension is reduced, or the additional mass of the passive end bracket is added, the peak value of the suspension dynamic stiffness can be effectively reduced, and the structural noise transmission is further reduced.

Of course, it is not necessary for any one product in which the invention is practiced to achieve all of the above-described technical effects simultaneously.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic diagram of a front electric drive assembly rear right bushing type rubber suspension assembly according to one embodiment of the present invention;

FIG. 2 is a diagram of a m + p suspension high-frequency dynamic characteristic test bed provided in an embodiment of the present invention;

FIG. 3 illustrates a suspended sample and clamp assembly provided in accordance with an embodiment of the present invention;

FIG. 4 is a diagram illustrating modal analysis results of a suspended high frequency test fixture according to an embodiment of the present invention; wherein, (a) is a first-order graph, (b) is a second-order graph, and (c) is a third-order graph;

FIG. 5 is a graph illustrating the results of a suspension dynamics test provided by one embodiment of the present invention;

FIG. 6 is a schematic diagram of the location of the added mass provided by one embodiment of the present invention;

FIG. 7 is a graph illustrating the results of a dynamic characteristic test of suspensions of different initial stiffness provided by one embodiment of the present invention;

FIG. 8 is a graph illustrating dynamic characteristics of various additional masses of a passive end bracket according to an embodiment of the present invention;

FIG. 9 is a graph illustrating the dynamic characteristics of the upper clamp according to various additional masses provided by an embodiment of the present invention.

Detailed Description

In order to better understand the technical scheme of the invention, the following detailed description of the embodiments of the invention is made with reference to the accompanying drawings.

It should be understood that the described embodiments are only some embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The purpose of the invention can be realized by the following technical scheme:

the test object comprises four suspensions of a front electric drive assembly and a suspension system thereof, which are bushing type rubber suspensions, and the right rear suspension of the test object is used as a high-frequency test research object, and the structure of the test object is shown in figure 1. The structure of the right rear suspension comprises an active end bracket and a passive end bracket. The whole driving end bracket (namely the suspension bracket) is in a horizontal cylindrical shape and comprises an internal mandrel, a rubber main spring arranged on the periphery of the mandrel and an aluminum alloy outer tube arranged on the periphery of the rubber main spring. The mandrel is of a hollow structure and is used for enabling a bolt to penetrate through to realize the suspension and fixation of the whole suspension sample piece. The passive end support is arranged below the suspension support, the whole passive end support is a groove shape, the cross section of a groove opening of the groove shape is square, the side surface of the groove shape is a triangle, and the triangle is different from a common triangle in that one side of the joint of the similar triangle and the cylindrical active end support is arc-shaped. Four threaded holes are formed in the passive end support and used for being fixed with the test equipment, and the arrangement direction of the threaded holes is perpendicular to the axial surface of the active end support.

Test equipment: the test adopts novel m + p electromagnetic type high frequency test equipment, the test frequency range is 50-3000Hz, and the preloading is 5000N at most. The suspension dynamic characteristic test bed is shown in figure 2.

Designing a clamp: the test highest frequency is 3000Hz, the clamping mode is limited, and the mode of the clamp is not easy to be much higher than the test frequency. In order to reduce the influence of the clamp mode on the suspension dynamic characteristic test, the first-order mode frequency of the clamp needs to be improved as much as possible. 7075 aviation aluminum alloy material with light weight, large specific stiffness and good formability is selected for designing and manufacturing the clamp. The mounting of the suspended sample piece and the fixture is as shown in fig. 3. The fixture is designed for the test object and the test equipment as shown in fig. 3. The clamp comprises an upper clamp and a lower clamp (the upper clamp and the lower clamp are made of aviation aluminum), and the suspension sample piece is arranged between the upper clamp and the lower clamp. The upper end of the upper clamp is of a square thick plate structure, a fork-shaped structure (ear fork) is arranged below the square thick plate structure, namely, the two ends of the square thick plate structure are respectively and fixedly provided with downward ear forks for fixing the suspension driving end, and the two ear forks are oppositely arranged in parallel; the ear fork and the square thick plate are preferably integrally formed so as to ensure the connection strength between the ear fork and the square thick plate; the lower tip of both ears fork all is equipped with first sample fixed orifices, and the initiative end through bolt and nut with the suspension appearance piece is fixed on last anchor clamps. The thickness of the square thick plate of the upper clamp is 0.029m, the ear fork is wide at the upper part and narrow at the lower part and is provided with a left inclined surface and a right inclined surface, and the inclination of the two inclined surfaces of the ear fork is 18 degrees. The overall weight of the upper clamp is 2.248Kg. The lower extreme of anchor clamps is circular thick plate structure down, and circular thick plate structure is last to be equipped with half frustum structure, and this half frustum structure is whole to be along the frustum axial cut nearly half structure (the shared radian of frustum is 214 degrees), is equipped with the recess in tangent plane department, supplies the type square structure of suspension appearance piece bottom to put into, has four second sample fixed orificess on the recess wall, fixes the type square structure of bottom of suspension appearance piece in the anchor clamps recess down through bolt and nut. The weight of the lower clamp is 2.272Kg. The square thick plate structure of the upper clamp and the round thick plate structure of the lower clamp are both provided with a plurality of clamp fixing holes, and are respectively fixedly connected with the upper test end and the lower test end of the m + p electromagnetic type high-frequency test equipment through bolts and nuts so as to perform a high-frequency dynamic characteristic test.

To investigate the influence of the clamp mode, a mode analysis of the clamp was performed. During analysis, the upper clamp and the lower clamp and the mounting bolt are reserved, the suspension and the passive end support of the suspension are simplified into a linear spring and equivalent mass, the analysis result is shown in fig. 4, a three-order clamp mode exists within 3000Hz, the first-order mode is mainly a Z-direction mode, namely, the positions of the suspension mandrel and the bolt for connecting the mandrel with the upper clamp; the second-order mode mainly comprises X-direction swing, namely an upper clamp ear fork part, and the maximum displacement point is near the connection point of the bolt and the clamp, namely the end part of the ear fork; the third-order mode is mainly that the lower clamp swings in the Y direction. The above three-order mode is shown in the test result of 3000Hz dynamic characteristic of the rubber suspension.

Under the condition that the influence of the clamp mode on the high-frequency dynamic characteristic cannot be avoided, the main influence factors of the suspension high-frequency dynamic characteristic are three: suspension stiffness, clamp mode and suspension bracket mode (the suspension bracket is the upper half part of the suspension sample piece, the active end bracket). The above factors interact with each other and jointly influence the test result of the suspension dynamic characteristics.

Test protocol: based on the test equipment and the clamping system, a test scheme is designed, the suspension sample piece and the clamp are assembled and installed on the high-frequency test equipment, as shown in figure 2, the upper end Z direction is pre-pressed to 350N, the lower end is an actuating end, the equal-amplitude acceleration excitation of +/-3 g is applied, and the frequency sweeping speed is 2Oct/min. The force signal at the upper end was measured and the suspension cross-point dynamic stiffness was calculated therefrom, the results being shown in fig. 5.

In order to discuss the main influence factors of the three peaks (as shown in fig. 5) of the high-frequency dynamic stiffness, the three peaks are identified by schemes of different stiffness and different additional mass. Single variables were controlled, tested one by one, and then compared for study. The test scheme and purpose are shown in table 1, the initial dynamic stiffness of the three suspension sample pieces at 50Hz is respectively 800, 630 and 475N/mm, and the initial dynamic stiffness is sequentially reduced and numbered as 1#, 2#, and 3#.

TABLE 1 experimental study scheme and purpose of influence factors of suspension high-frequency dynamic characteristics

Firstly, the rigidity of a suspension sample piece is changed by adjusting the hardness of rubber, and a high-frequency dynamic characteristic test is carried out. The initial dynamic stiffness of the three suspension sample pieces at 50Hz is respectively 800N/mm, 630N/mm and 475N/mm, and the initial dynamic stiffness is sequentially reduced and numbered as 1#, 2#, and 3#. The remaining test conditions were unchanged and the test results are shown in fig. 7. The result shows that the suspension stiffness has great influence on the full-band dynamic characteristic, and the full-band dynamic stiffness is reduced along with the reduction of the initial stiffness; particularly, the peak value and the frequency of the vibration peak value near 1200Hz (the vibration peak value in the frequency range of 1000Hz-1200 Hz) are gradually reduced, which shows that the peak value frequency is positively correlated with the suspension rigidity; the 1500Hz peak (vibration peak of 1500Hz-1650Hz frequency band) has no change; the peak value of 2000Hz (the vibration peak value in the frequency range of 1900Hz-2300 Hz) has no obvious gradient law along with the change of rigidity.

Secondly, for the suspension sample 1# and the suspension sample 2# respectively, 0g (i.e. no additional mass), 45g and 90g of additional mass are adhered to the circular tube shell of the suspension passive end bracket, the rest test conditions are unchanged, and the measured dynamic stiffness result is shown in fig. 8, wherein (a) is the test result of the suspension sample 1# and (b) is the test result of the suspension sample 2 #. The result shows that the additional mass added by the passive end bracket has no influence on the peaks of 1200Hz and 1500 Hz; but with the added mass increase, the dynamic stiffness peak value and the frequency thereof near 2000Hz are gradually reduced, and the gradient regularity is more obvious. The position of the additional mass of the No. 1 sample piece is slightly different from that of the No. 2 sample piece, wherein the additional mass of the No. 2 sample piece is arranged in the middle of the circular tube structure of the support, and the additional mass of the No. 1 sample piece is arranged on the upper part of the circular tube structure. The peak value of the dynamic stiffness and the frequency variation trend of the sample No. 2 in the vicinity of 2000Hz are more obvious, which shows that the dynamic characteristic is sensitive to the position of the additional mass of the passive end.

Thirdly, on the basis of the high-frequency dynamic characteristic test of the No. 1 sample without any additional mass, the upper clamp has the two sides with the maximum modal displacement and the total additional mass of 90g, the rest test conditions are unchanged, and the dynamic characteristic test result is shown in fig. 9. The results show that the additional mass at the upper clamp has little effect on the full-band dynamics, with only the 1500Hz peak and its frequency slightly reduced. In fact, the test results of the scheme of the two samples 2# and 3# are the same, and the consistency is good.

Based on the dynamic characteristic test result, the influence rule of each factor on the dynamic characteristic is summarized in combination with the modal analysis of the test boundary condition as shown in table 2.

TABLE 2 influence rule of various factors on suspension dynamic characteristics

The above conclusions are applied to the engineering of the whole vehicle, and the analysis is as follows because the boundary conditions change.

1200Hz peak: in a dynamic characteristic test, the additional mass of the upper clamp and the suspension passive end bracket has no influence on the dynamic characteristic test, the suspension rigidity is reduced, and the peak value and the frequency thereof are obviously reduced; and judging the mode caused by the Z-direction mode of the mandrel and the bolt thereof by combining the simulation analysis result. In the state of the whole vehicle, the mode corresponds to the mode of suspending the active end bracket. Tests show that the modal frequency of the active end support is positively correlated with the initial suspension stiffness, so that the initial suspension stiffness needs to be reduced within a reasonable range in order to improve the full-band vibration isolation and noise reduction capability of the suspension. The excitation frequency of the electric vehicle is high (for example, the order frequency of the main reducer can reach 1000 Hz), and in order to avoid the deterioration caused by the structural noise, the mode of the active end bracket needs to be further improved.

Peak at 1500 Hz: the initial rigidity change of the suspension and the additional mass of the passive end bracket have no influence on the peak value, and the peak value and the frequency are slightly reduced only after the additional mass of the upper clamp, and the peak is caused by the X-direction mode of the upper clamp. In a dynamic characteristic test, the excitation direction is approximately orthogonal to the X-direction mode of the upper clamp, and the radial dynamic characteristic is slightly influenced by the axial structure mode. In the state of the whole vehicle, the restraint of the suspension active end is generally weaker than that of a clamp on a test, and the modes are not necessarily orthogonal, so that corresponding structural noise can be caused.

Peak at 2000 Hz: the peak value and the frequency thereof are negatively related to the additional mass of the passive end bracket, the gradient rule is obvious, and the peak is judged to be caused by the mode of the round head part of the passive end bracket. According to the obvious inhibiting effect of the additional mass on the dynamic characteristic, the mass can be added at the vibration peak value of the suspension passive end, and the transmission of the peak value vibration is reduced. In the whole vehicle state, the rigidity of the vehicle body structure connected with the passive end bracket is weaker than that of the clamp under the test, and the modal frequency of the vehicle body structure is lower than 2000Hz.

And then obtain the electric motor car suspension and the guidance principle of support design and optimization: the suspension stiffness and the passive end mass change obviously affect the suspension high-frequency dynamic characteristic, the initial stiffness of the suspension is reduced, or the additional mass of the passive end bracket is added, the peak value of the suspension dynamic stiffness can be effectively reduced, and the structural noise transmission is further reduced.

According to the invention, an M + P high-frequency experiment table is required to be selected on test equipment, and in order to reduce the influence of clamp mode on the suspension dynamic characteristic test, the first-order mode frequency of the clamp is improved as much as possible by improving the strength of the clamp and reducing the weight of the clamp in the design of the clamp. 7075 aviation aluminum alloy material with light weight, large specific stiffness and good formability is selected for designing and manufacturing the clamp.

The method for testing the high-frequency dynamic characteristics of the rubber suspension of the electric vehicle provided by the embodiment of the application is described in detail above. The above description of the embodiments is only for the purpose of helping to understand the method of the present application and its core ideas; meanwhile, for a person skilled in the art, according to the idea of the present application, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present application.

Claims (10)

1. A high-frequency dynamic characteristic test method for an electric vehicle rubber suspension is characterized by comprising the following steps:

s1, designing a clamp for fixing a rubber suspension;

s2, respectively taking the suspension rigidity, the clamp mode and the rubber suspension mode as single variables, and performing a high-frequency dynamic characteristic test to obtain the influence rule of each variable on the vibration peak value under three frequency bands of 1000Hz-1200Hz, 1500Hz-1650Hz and 1900Hz-2300 Hz.

2. The method for testing high frequency dynamic characteristics of rubber suspensions of electric vehicles according to claim 1, wherein the suspension stiffness is 800N/mm, 630N/mm or 475N/mm.

3. The method for testing high-frequency dynamic characteristics of the rubber mount of the electric automobile according to claim 1, wherein the jig comprises an upper jig and a lower jig; the active end bracket of the rubber suspension is fixed on the upper clamp, and the passive end bracket of the rubber suspension is fixed on the lower clamp; the upper clamp and the lower clamp are fixedly connected with two testing ends of the m + p electromagnetic high-frequency testing equipment respectively;

the upper clamp and the lower clamp are both made of aviation aluminum, and the weight of the upper clamp is 2.248Kg; the weight of the lower clamp is 2.272Kg.

4. The method for testing the high-frequency dynamic characteristic of the rubber suspension of the electric automobile according to claim 3, wherein the upper clamp comprises a square plate at the upper end and a left ear fork and a right ear fork which are fixedly arranged below the square plate, and the lower end parts of the two ear forks are provided with first sample fixing holes; and the active end bracket of the rubber suspension is fixed between the two ear forks through bolts.

5. The method for testing the high-frequency dynamic characteristic of the rubber suspension of the electric automobile according to claim 3, wherein the lower clamp comprises a circular plate at the lower end and a semi-cone platform fixedly arranged on the circular plate, the side wall of the semi-cone platform is provided with a groove with an opening on the upper surface and an opening on the side surface, and a plurality of second sample fixing holes are formed in the side wall of the groove; and the passive end bracket of the rubber suspension is fixed on the second sample fixing hole through a bolt.

6. The method for testing the high-frequency dynamic characteristic of the rubber suspension of the electric automobile according to claim 3, wherein the clamp mode is taken as a single variable, and specifically comprises the following steps: and sequentially adding weights with different weights to the upper clamp or the lower clamp.

7. The method for testing the high-frequency dynamic characteristic of the rubber suspension of the electric automobile according to claim 5, wherein the clamp mode is taken as a single variable, and specifically comprises the following steps: weights of different weights are sequentially added to the side edges of the ear forks.

8. The method for testing the high-frequency dynamic characteristic of the rubber suspension of the electric automobile according to claim 1, wherein the rubber suspension mode is taken as a single variable, and specifically comprises the following steps: and sequentially adding heavy objects with different weights at the circular tube shell of the rubber suspension driven end bracket.

9. Method for testing high frequency dynamic characteristics of rubber suspensions for electric vehicles according to any one of claims 6 to 8, characterized in that the weights of different weights are weights of 0g, 45g and 90 g.

10. The method for testing high frequency dynamic characteristics of rubber suspensions of electric vehicles according to claim 4, wherein the ear forks are of a symmetrical structure with a wide top and a narrow bottom and a left inclined surface and a right inclined surface, and the inclination of the inclined surfaces is 18 degrees.

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