Automobile vibration characteristic testing method

Abstract

This invention provides a non-destructive and rapid vibration characteristic testing method for automobiles that can detect structural differences from a standard automobile structure. [Solution] The automobile vibration characteristic test method according to the present invention involves inputting sinusoidal vibrations with the same frequency but a phase difference to two vibration input points 111a and 111b on the automobile body 100 to be tested, and measuring the response waveform of the vibration generated in the excited automobile body 100 in synchronization with the input waveform of the vibration input to the vibration input points 111a and 111b. The amplitude of the measured response waveform and the phase difference of the input waveform of the vibration input to the vibration input points 111a and 111b are determined as the response characteristics of the excited automobile body. The response characteristics obtained for the automobile body 100 to be tested are compared with the response characteristics when a standard structure automobile body 100 is excited with a phase difference, thereby detecting the structural differences between the automobile body 100 to be tested and the standard structure automobile body 100.

Description

[Technical Field]

[0001] This invention relates to a method for testing the vibration characteristics of an automobile, which involves inputting vibrations into the automobile and detecting structural differences in the vibration transmission path of the automobile. [Background technology]

[0002] Vibration characteristic tests, which measure vibrations and cabin noise felt by occupants during vehicle operation, are conducted through actual vehicle driving tests of completed vehicles and bench tests in which completed vehicles are placed on a vibration platform and vibrations are input to the wheels. Furthermore, Patent Document 1 discloses a technology for reproducing the vibration states excited on the vehicle body under road surface conditions and vehicle driving conditions during actual vehicle operation, and for determining the vibration characteristics such as vibrations and noise generated on the vehicle body. It is stated that this technology makes it possible to determine changes in the vibration characteristics of the vehicle body due to changes in the vehicle body structure and materials. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2000-88697 [Overview of the project] [Problems that the invention aims to solve]

[0004] In the automobile manufacturing process, inspections are conducted to detect structural changes (abnormalities) in the vehicle body due to the quality of the joints between body parts (quality of welding and adhesive application). Furthermore, the quality of the joints during the assembly of the automobile body is typically guaranteed by process assurance, which assumes that the quality is maintained unless there are any particular problems in the manufacturing process, except for initial production models of new models and periodic sampling inspections.

[0005] Sampling inspections are carried out using destructive testing methods, such as testing the strength of joints by driving jigs like chisels into the joints where vehicle body parts are joined, or visually inspecting the joint surfaces after destroying the adhesive-bonded joints. However, destructive testing is very costly in terms of both time and money, so its implementation has been limited.

[0006] As mentioned above, the method described in Patent Document 1 allows for the evaluation of the influence of the vehicle body structure on the vibration characteristics of the vehicle body. Therefore, if the influence of the vehicle body structure, such as the quality of the joints of the vehicle body parts, is evident in the vibration characteristics of the vehicle obtained by the method described in Patent Document 1, it is considered possible to detect structural differences from a vehicle with a standard structure that has no problems with the joint quality, etc., non-destructively and in a short time. However, no technology for detecting structural differences in a vehicle through such vibration characteristic testing has been reported to date.

[0007] This invention was made to solve the above-mentioned problems and aims to provide a vibration characteristic test method for automobiles that can detect structural differences from a standard automobile structure non-destructively and in a short time. [Means for solving the problem]

[0008] (1) The vibration characteristics test method for an automobile according to the present invention involves inputting vibration to the automobile to be tested and detecting structural differences from the automobile with a standard structure, A phase difference excitation process is performed by applying sinusoidal vibrations of the same frequency but with a phase difference to two vibration input points on the automobile to be tested, thereby exciting the automobile. A response waveform measurement step, which measures the response waveform of vibrations generated in the excited automobile in synchronization with the input waveform of vibrations input to the vibration input part, A response characteristic acquisition step is performed to determine the response characteristics of the excited automobile by taking the amplitude of the response waveform measured in the response waveform measurement step and the phase difference of the input waveform of the vibration input in the phase difference excitation step, With respect to the aforementioned automobile of the reference structure, a reference structure response characteristic acquisition step is performed to acquire the response characteristics obtained by carrying out the phase difference excitation step, the response waveform measurement step, and the response characteristic acquisition step, similar to the aforementioned automobile to be tested. The method is characterized by including a structural difference detection step, which involves comparing the response characteristics obtained for the vehicle under test with the response characteristics obtained for the vehicle with a standard structure, and detecting the structural differences between the vehicle under test and the vehicle with the standard structure.

[0009] (2) The vibration characteristics test method for an automobile according to the present invention involves inputting vibration to the automobile to be tested and detecting structural differences from the automobile with a standard structure, A phase difference excitation process is performed by applying sinusoidal vibrations of the same frequency but with a phase difference to two vibration input points on the automobile to be tested, thereby exciting the automobile. A response waveform measurement step, which measures the response waveform of vibrations generated in the excited automobile in synchronization with the input waveform of vibrations input to the vibration input part, The steps include: the ratio of the maximum amplitude to the minimum amplitude in the response waveform measured in the response waveform measurement step; the phase lag of the response waveform with respect to the phase difference of the input waveform of the vibration input in the phase difference excitation step; and the step of acquiring response characteristics to be determined as the response characteristics of the excited automobile. With respect to the aforementioned automobile of the reference structure, a reference structure response characteristic acquisition step is performed to acquire the response characteristics obtained by carrying out the phase difference excitation step, the response waveform measurement step, and the response characteristic acquisition step, similar to the aforementioned automobile to be tested. The method is characterized by including a structural difference detection step, which involves comparing the response characteristics obtained for the vehicle under test with the response characteristics obtained for the vehicle with a standard structure, and detecting the structural differences between the vehicle under test and the vehicle with the standard structure.

[0010] (3) In the case of the items described in (1) or (2) above, In the response waveform measurement step, a microphone is installed in the automobile, and the sound pressure waveform of the noise generated from the vibrated automobile is measured as the response waveform. This is the gist of the invention.

Advantages of the Invention

[0011] According to the present invention, it is possible to detect the structural differences between the test target automobile and the reference structure automobile non-destructively and in a short time.

Brief Description of the Drawings

[0012] [Figure 1] It is a flowchart for explaining the processing flow in the vibration characteristic test method of an automobile according to an embodiment of the present invention. [Figure 2] In an embodiment of the present invention, it is a diagram showing the method of supporting the automobile body to be tested and two vibration input sites set on the automobile body. [Figure 3] It is a diagram showing the configuration of a vibration characteristic test device used in an embodiment of the present invention. [Figure 4] In an embodiment of the present invention, it is a diagram for explaining a specific mode of applying a phase difference to two vibration input sites set on the automobile body and vibrating. [Figure 5-1] It is a graph obtained by obtaining the response waveform at the vibration measurement point by formula (1), assuming the case where phase difference excitation is performed by continuously changing the phase of one vibration when vibrating by inputting vibrations of a constant frequency of 36 Hz to two vibration input sites ((a) A = 1.​​​​​​ [Figure 6] This graph shows the frequency response characteristics of the cabin noise in a completed vehicle subjected to frequency-swept excitation in Example 1. [Figure 7] This graph shows the relationship between the phase difference of the input waveform of the completed vehicle, which was excited by phase difference vibration at each frequency in Example 1, and the amplitude intensity of the noise inside the vehicle. [Figure 8] This graph shows the relationship between the phase lag and amplitude ratio of the in-cabin noise obtained by phase difference excitation of a modified automobile body in Example 3. [Modes for carrying out the invention]

[0013] The vibration characteristic test method for an automobile according to an embodiment of the present invention (hereinafter simply referred to as the "vibration characteristic test method") involves inputting vibration to an automobile body 100 and detecting structural differences in the vibration transmission path of the automobile body 100, as shown in Figure 2. The vibration characteristic test method according to this embodiment includes a phase difference excitation step S1, a response waveform measurement step S3, a response characteristic acquisition step S5, a reference structure response characteristic acquisition step S7, and a structural difference detection step S9, as shown in Figure 1. In the following, we will describe the process of implementing the vibration characteristics test method according to this embodiment using the vibration characteristics test apparatus 1 shown in Figure 3. After describing the automobile body 100 and the vibration characteristics test apparatus 1, we will explain each of the above steps.

[0014] <Automobile body> The automobile body 100 is the so-called vehicle frame (white body), which does not include the chassis frame, suspension components, drivetrain components, interior components, etc. In the automobile body 100 shown in Figure 2, the body floor 109 is supported by being loaded onto four air cushions 211 installed on the floor surface 201. Therefore, when vibration is input to the automobile body 100, the body floor 109, which is supported by the air cushions 211, is not restrained, and the automobile body 100 can be excited. Furthermore, the support points and support methods for the automobile body 100 are not limited to those described above, and may be appropriately selected according to the vibration characteristics to be evaluated.

[0015] <Vibration Characteristics Testing Equipment> The vibration characteristic testing apparatus 1 inputs vibration to the automobile body 100 to excite it, measures the response waveform of the vibration generated in the automobile body 100, and determines the response characteristics of the automobile body 100 to the vibration input to the automobile body 100.

[0016] As shown in Figure 3, the vibration characteristic test apparatus 1 comprises an excitation device 10, a response waveform measuring device 20, and a response characteristic acquisition device 30. The configuration and operation of the excitation device 10, the response waveform measuring device 20, and the response characteristic acquisition device 30 will be specifically described in the phase difference excitation process S1, the response waveform measurement process S3, and the response characteristic acquisition process S5 of the vibration characteristic test method according to this embodiment.

[0017] <Phase difference excitation process> In the phase difference excitation process S1, sinusoidal vibrations with the same frequency but a phase difference are input to two vibration input points 111a and 111b on the automobile body 100 to be tested, as shown in Figure 2, thereby exciting the automobile body 100 (also referred to as "phase difference excitation" in this application).

[0018] The vibration input point 111a is located on the bumper reinforcement 105, which is positioned between a pair of left and right front side members 101 at the front of the automobile body 100. On the other hand, the vibration input point 111b is located on the rear floor cross member 107, which is positioned between a pair of left and right rear side members 103 at the rear of the automobile body 100.

[0019] In the phase difference excitation process S1, vibrations are input to the vibration input points 111a and 111b using the excitation device 10 shown in Figure 3. The vibration exciter 10 includes a plurality of vibrators 11 (11a, 11b), a function generator 13, a delay processing device 15, and a plurality of vibrator control devices 17 (17a, 17b).

[0020] The vibrator 11 inputs and vibrates the vibration input part 111 set on the vehicle body 100 of the automobile. In the present embodiment, as shown in FIG. 2, a vibrator 11a and a vibrator 11b for inputting vibration to the front vibration input part 111a and the rear vibration input part 111b of the vehicle body of the automobile are provided respectively.

[0021] As shown in FIG. 2, the vibrators 11a and 11b are installed on the floor surface 201 via vibration isolation rubber 203 and are connected to the vibration input parts 111a and 111b via a steel vibration rod 19 respectively.

[0022] As the vibrator 11, a dynamic electric vibrator can be exemplified, but the present invention is not limited thereto.

[0023] The function generator 13 generates a reference signal P of a sine wave vibration input to the front vibration input part 111a of the vehicle body 100 of the automobile A and a delay signal Q of a sine wave vibration input to the rear vibration input part 111b B and has a signal generation device 13a and a delay processing device 15.

[0024] The signal generation device 13a generates a reference signal P A and a reference signal P B serving as a reference for the delay signal Q B and. The delay processing device 15 delays one of the two reference signals P A and P B generated by the signal generation device 13a to generate a delay signal Q B B B and.

[0025] The vibrator control device 17 drives and controls the vibrator 11 and has a vibrator control device 17a for driving and controlling the vibrator 11a and a vibrator control device 17b for driving and controlling the vibrator 11b. When a dynamic electric vibrator is used as the vibrator 11, the vibrator control device 17 generates an input power pattern of the power input to the dynamic electric vibrator.

[0026] In the phase difference excitation process S1, the automobile body 100 is excited by a phase difference using the excitation device 10 according to the following procedure.

[0027] First, the signal generator 13a of the function generator 13 generates two reference signals P A and P B Generates the reference signal P. A and P B The two signals are sine waves with the same frequency and phase. Then, the generated reference signal P A and P B Of these, the delay processing unit 15 controls the reference signal P B The delay is applied to the signal Q, which has a phase angle that is continuously changed from 0° to 360° at a constant sweep rate. B Generates.

[0028] Next, as shown in Figure 4, the reference signal P A The signal is input to the vibrator control device 17a to drive and control the vibrator 11a, and vibration is input to the vibration input point 111a set in front of the automobile body 100. Furthermore, as shown in Figure 4, the delayed signal Q has a continuously changing phase angle. B The vibration is input to the vibrator control device 17b to drive and control the vibrator 11b, and the vibration is input to the vibration input site 111b set at the rear of the automobile body 100. As a result, the vibration exciter 10 can input sinusoidal vibrations with the same frequency but different phases to two vibration input points 111a and 111b, thereby enabling phase-difference excitation of the automobile body 100.

[0029] <Response waveform measurement process> In the response waveform measurement step S3, the response waveform of vibrations occurring in the automobile body 100 is measured using the response waveform measurement device 20 shown in Figure 3, in synchronization with the input waveform of vibrations input to the vibration input part 111.

[0030] The response waveform measuring device 20 includes an accelerometer 21 and a data logger 23. The accelerometer 21 measures the vibration acceleration generated in the excited automobile body 100 and is installed at vibration measurement points set on the automobile body 100. The vibration measurement points can be set on body frame components, panel components, etc., which can be appropriately selected according to the vibration characteristics and vibration transmission path to be tested, and multiple locations on the automobile body 100 may be set.

[0031] The data logger 23 records the vibration acceleration of the automobile body 100 measured by the accelerometer 21 and the reference signal P generated by the function generator 13. A Then, the delayed signal Q processed by the delay processing unit 15 B And, are retrieved synchronously.

[0032] <Response characteristics acquisition process> The response characteristic acquisition step S5 determines the response characteristics of the automobile body 100 excited in the phase difference excitation step S1 by taking the amplitude of the response waveform measured in the response waveform measurement step S3 and the phase difference of the input waveform of the vibration input in the phase difference excitation step S1.

[0033] In the response characteristic acquisition process S5, the response characteristics of the automobile body 100, which has been excited with a phase difference, can be determined by following the procedure below.

[0034] First, the time history data of the response waveform at the vibration measurement point of the automobile body 100, measured in the response waveform measurement process S3, is divided into multiple sections at predetermined time intervals. Then, for each divided section, the time history data of the response waveform is Fourier transformed to calculate the frequency response characteristics of the response waveform. Next, for each divided section, the amplitude with the same frequency as the input waveform of the vibration input to the automobile body 100 (excitation frequency) is extracted from the calculated frequency response characteristics. Next, the time intervals of each section obtained by dividing the time history data of the response waveform are replaced with the phase angles of the delayed signal, and the relationship between the phase difference of the input waveform of the vibration input to the vibration input section 111 (= phase angle of the delayed signal) and the amplitude of the same frequency as the excitation frequency is determined.

[0035] In addition, in the response characteristic acquisition step S5, as the response characteristics of the automobile body 100 that has been excited with a phase difference, the ratio of the maximum amplitude to the minimum amplitude in the response waveform and the phase lag of the response waveform with respect to the phase difference of the input waveform may be determined, as will be explained in Example 3 below.

[0036] <Process for obtaining reference structural response characteristics> In the standard structure response characteristic acquisition process S7, the response characteristics obtained are acquired by performing the phase difference excitation process S1, the response waveform measurement process S3, and the response characteristic acquisition process S5 on the standard structure automobile body 100, in the same manner as the automobile body 100 to be tested.

[0037] <Structural difference detection process> The structural difference detection step S9 compares the response characteristics of the test vehicle body 100 obtained in the response characteristic acquisition step S5 with the response characteristics of the standard structure vehicle body 100 when it is excited with a phase difference. Then, the structural difference detection step S9 detects the structural differences between the test vehicle body 100 and the standard structure vehicle body 100.

[0038] <Reasons why structural differences can be detected> The reason why the vibration characteristic test method for automobiles according to this embodiment can detect structural differences between the automobile under test and the automobile with a standard structure will be explained below. In the following explanation, as shown in Figure 2 above, the case in which vibration input points 111a and 111b (111) are provided at two locations on the front and rear of the automobile body 100 and phase difference excitation is performed will be used as an example.

[0039] When vibration is applied to the vibration input points 111 of the automobile body 100 to excite it, a vibration transmission path is formed in the automobile body 100 through which the vibration is transmitted from the vibration input points 111 to the vibration measurement point. When sinusoidal vibrations with the same frequency but a phase difference are applied to the two vibration input points 111a and 111b, the vibration response waveform at the vibration measurement point is thought to be a waveform that is a composite of the input waveforms of the vibrations applied to the two points. For example, when the vibration input waveforms applied to two vibration input points 111a and 111b are in phase (phase difference 0°), the two input waveforms are amplified, and the amplitude of the response waveform is maximized. In contrast, when the input waveforms are out of phase (phase difference 180°), the two input waveforms are attenuated by interference, and the amplitude of the response waveform is minimized.

[0040] Furthermore, the vibration response waveform at the vibration measurement point is thought to differ from the amplitude and phase of the input waveform depending on the structure of the vibration transmission path and the length of the vibration transmission path (distance from the vibration input point to the vibration measurement point).

[0041] Therefore, when the automobile body 100 is excited by phase difference vibration, the response waveform measured at the vibration measurement point is the sum of the phase difference of the input waveform and the phase delay due to structural differences in the vibration transmission path from the vibration input parts 111a and 111b to the vibration measurement point.

[0042] When vibration is input to two vibration input points 111 with a phase difference, the response waveform measured at the vibration measurement point can be expressed by equation (1).

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[0043] The inventor used equation (1) to calculate how the amplitude of the response waveform Fsyn(t) changes with respect to the phase difference p of the input waveform, and investigated the effects of A and d in equation (1) on the amplitude of the response waveform.

[0044] Figure 5-1 is a graph showing the response waveform at the vibration measurement points, calculated using equation (1), assuming a case where a constant frequency vibration of 36 Hz is applied to two vibration input points, and the phase of one of the vibrations is continuously changed at a phase sweep rate of 0.1 deg / ms to perform phase difference excitation. In Figure 5-1, (a) is A=1.0, d=0, and (b) is A=0.6, d=12 ms, with the phase difference p at time t indicated on the horizontal axis.

[0045] Figure 5-1 shows that when the phase difference changes continuously with time, the amplitude of the response waveform at the vibration measurement point changes with time (phase difference), and the maximum and minimum values ​​of the amplitude, as well as the position (phase difference) where the amplitude is maximum or minimum, change depending on A and d.

[0046] Figure 5-2 shows the response waveform at the vibration measurement point, calculated using equation (1), assuming a case where a constant frequency vibration of 100 Hz is input to two vibration input points, and the phase of one of the vibrations is continuously changed at a phase sweep rate of 9.0 deg / s to perform phase difference excitation. In Figure 5-2, (a) is A=1.0, d=0.0 ms, (b) is A=0.8, d=5.0 ms, and (c) is A=0.2, d=2.5 ms, with the phase difference p at time t indicated on the horizontal axis of (c).

[0047] From the graphs shown in Figures 5-1 and 5-2, it can be seen that the amplitude of the response waveform represented by equation (1) shows that when d=0, the amplitude of the response waveform Fsyn(t) shows a minimum value at a phase difference p=180° and a maximum value at a phase difference p=0°. Furthermore, the graphs in Figures 5-1 and 5-2 show that the positions of the maximum and minimum amplitudes change depending on the phase delay d. From this, it is thought that the phase delay d can be estimated by determining the difference between the position where the amplitude shows a minimum (or maximum) value in the response waveform measured for a vehicle that has actually undergone phase sweep excitation, and the position where the amplitude shows a minimum (or maximum) value when the phase delay d is assumed to be 0.

[0048] Furthermore, the amplitude ratio A is correlated with the difference between the maximum and minimum amplitudes of the response waveform and can be estimated from the ratio of the response amplitude to the amplitude when A=1.0. Also, the minimum amplitude of the response waveform Fsyn(t) when A=1.0 is zero, as shown in Figures 5-1 and 5-2. From these, the amplitude ratio A can be determined by finding the minimum amplitude Fmin and maximum amplitude Fmax from the response waveform measured for a vehicle excited by phase difference vibration, and substituting these into the following equation (2).

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[0049] Figure 5-3 is a graph showing the amplitude of the response waveform in relation to the phase difference when A and d in equation (1) are changed in various ways, as shown in Figures 5-2(a) to (c). As shown in Figure 5-3, the amplitude ratio A of the input waveform corresponds to the ratio of the maximum value Fmax to the minimum value Fmin of the amplitude of the response waveform at the vibration measurement point, calculated by equation (2). It was found that the phase difference p when the amplitude reaches its maximum value is 2πd / T, that is, the phase difference corresponding to the phase delay d in the vibration transmission path.

[0050] This finding suggests that by organizing the amplitude changes of the response waveform measured at vibration measurement points of a vehicle excited with a phase difference using the phase difference of the input waveform, and identifying the positions of the maximum and minimum amplitudes of the response waveform, the phase difference between the input waveform and the response waveform (phase lag) can be determined.

[0051] The phase delay in the response waveform changes depending on the frequency of the input waveform, the vibration measurement point, and the location of the vibration input site. If there are no differences in the vibration transmission path and structure, the phase delay in the response waveform does not change.

[0052] Furthermore, if the vibration input points are the same in the vehicle under test and the vehicle with the standard structure, the vibration response characteristics are determined by the frequency of the input waveform and the position of the vibration measurement point. Assuming that the response characteristics of the vehicle with the standard structure are known, if there are structural differences in the vehicle under test, its response characteristics will differ from those of the vehicle with the standard structure.

[0053] Furthermore, structural differences refer to structures equivalent to dampers and springs in terms of vibration transmission characteristics, and are assumed to be differences in the rigidity of the components that make up the automobile and the structure of the connections between components (joining method, shape, and quality, etc.). When there are structural differences in an automobile, the resulting differences in its response characteristics (amplitude and phase difference of the response waveform) are thought to be due to the influence of rigidity, etc., in the parts where the structural differences exist.

[0054] For example, when vibrations input to a vibration input point are transmitted along the vibration transmission path, differences in stiffness can cause differences in vibration damping and transmission speed, resulting in a decrease in amplitude or a delay in vibration transmission. This can lead to changes in the ratio of maximum to minimum amplitude in the response waveform, as well as a phase lag in the response waveform.

[0055] Therefore, by comparing the response characteristics of the vehicle under test and a vehicle with a standard structure, and identifying the differences between the two, it becomes possible to detect structural differences in the vehicle under test.

[0056] <Effects and Effects> In the vibration characteristic test method according to this embodiment, the automobile body 100 is excited by inputting sinusoidal vibrations of the same frequency but with a phase difference to two vibration input points 111a and 111b. Then, the response waveform of the vibration generated in the automobile body 100 is measured in synchronization with the input waveform of the vibration input to the vibration input points 111a and 111b, and its response characteristics are determined. Furthermore, the response characteristics obtained for the automobile under test are compared with the response characteristics of a reference automobile. This makes it possible to detect structural differences between the automobile under test and a reference automobile non-destructively and in a short time.

[0057] In particular, the vibration characteristic test method according to this embodiment does not require a special environment such as an anechoic chamber for the phase difference excitation of the automobile body 100 in the phase difference excitation process S1 and the measurement of the response waveform in the response waveform measurement process S3, and therefore can be carried out on the line side of the manufacturing process.

[0058] In the phase difference excitation process S1 according to this embodiment, the phase angle of the delayed signal was continuously changed. However, if the correspondence between the difference in response characteristics at a specific frequency and phase angle and the structural differences is known in advance, the present invention may also determine the response characteristics by performing phase difference excitation on the vehicle under test at the specific frequency and phase angle. In this case as well, the presence or absence of structural differences in the vehicle under test can be detected by comparing it with the response characteristics of a vehicle with a standard structure.

[0059] In the present invention, the phase difference excitation process is not limited to generating a reference signal and a delayed signal using the excitation device 10 configured as shown in Figure 3 in order to input vibration with a phase difference. It is sufficient to input a sinusoidal wave vibration that has been delayed by a predetermined phase angle to one of the vibration input points.

[0060] This embodiment describes a case where an automobile body 100 was used as the test subject, but the present invention may also be applied to a completed vehicle. In the case of a completed vehicle, it is advisable to set two vibration input points on the vehicle parked on a horizontal floor. The vibration input points can be set as appropriate, such as the front and rear axles of the completed vehicle or the area around the connection between the chassis frame and the vehicle body.

[0061] When a car is in motion, vibrations from the road surface are input to the area around the axle, and are transmitted to various parts of the car mainly through the body frame components, and then to the occupants through the steering wheel and seats. Furthermore, vibrations transmitted to panel components such as the roof, floor, and doors, as well as trim components and the windshield, become radiated sound, which contributes to cabin noise.

[0062] Therefore, although this embodiment measured the response waveform of vibration acceleration occurring in the automobile body 100, the present invention may also measure the sound pressure waveform of noise generated from the excited automobile as the response waveform by installing a microphone in the automobile. In this case, the microphone may be installed, for example, inside the automobile.

[0063] In-cabin noise is sound radiated into the cabin as air vibrations due to membrane vibrations of panel components and other parts. Therefore, the sound pressure waveform measured by a microphone includes all the sound radiated from various parts of the automobile, which differs from measuring vibration acceleration generated in the automobile body using an accelerometer.

[0064] However, even when measuring the sound pressure waveform of noise from a vibrated finished vehicle as a response waveform, it can be treated in the same way as the response waveform of vibration acceleration measured by an accelerometer.

[0065] In particular, measuring noise from a finished vehicle involved measuring a mixed waveform of sound radiated simultaneously from multiple body parts, raising concerns that the effects of phase differences in the input waveform might be latent. However, similar to the response waveform measured by an accelerometer, the effects of phase differences in the input waveform can be clearly detected. This is presumed to be because each body part has a different vibration resonance frequency, and the noise level emitted from a vibrated finished vehicle is dominated by the sound pressure generated from the part that experiences the most dominant vibration.

[0066] Furthermore, when measuring the sound pressure waveform of noise using a completed vehicle as the test subject, the vibration frequency input to the completed vehicle should be selected from resonant frequencies with high noise levels or frequencies that pose challenges in actual vehicle driving tests. Furthermore, even when measuring the sound pressure waveform of noise by vibrating a finished vehicle or automobile body, a test building with low noise levels can be used as the test environment, and a special environment such as an anechoic chamber is not required.

[0067] In the phase difference excitation process, the frequency of the vibration input to the vibration input point should be selected from the resonant frequency of the response waveform measured at the vibration measurement point. This is expected to allow for more appropriate detection of structural differences from a standard automobile structure.

[0068] Note that the input vibration frequency is not limited to those mentioned above. For example, in actual vehicle driving tests, the frequency of the dominant response waveform for the input vibration may be selected, or if the frequency of the target or problematic frequency is predetermined, a frequency other than the resonant frequency may be selected.

[0069] Furthermore, if the target of the investigation or the frequency of the problem has not been determined, or if the resonant frequency is unknown, the excitation frequency can be determined as follows: First, vibrations with an input waveform that continuously changes frequency without changing the phase difference are input to two vibration input points on the automobile to be tested, and the frequency response characteristics are determined in advance from the response waveform at the vibration measurement points. Then, the frequency at which the peak occurs in the determined frequency response characteristics is taken as the frequency of the input waveform in phase difference excitation. This allows for the appropriate determination of the excitation frequency in phase difference excitation. [Examples]

[0070] To verify the vibration characteristics test method for automobiles according to the present invention, the response characteristics of vibration and cabin noise in an automobile excited with a phase difference will be determined in Examples 1 and 2, and the difference in response characteristics with a standard structure automobile will be verified in Example 3.

[0071] <Example 1> In Example 1, a completed automobile was used as the test subject. The response waveform of the cabin noise of the automobile, which was excited by applying a phase difference, was measured using a microphone, and the response characteristics were determined.

[0072] The vehicle used for the test was a commercially available compact car (vehicle length 4.0m, vehicle weight 1.0t). The completed vehicle was parked on the horizontal floor inside the test building, and the connection points between the chassis frame and the vehicle body at two locations, the front and rear, under the vehicle floor were used as vibration input points. Each of these vibration input points was then fixedly connected to an electrodynamic vibrator via a steel vibration rod, and the electrodynamic vibrator was driven and controlled by a function generator and a vibrator control device to input vertical vibrations to the vibration input points, thereby exciting the completed vehicle with a phase difference.

[0073] A microphone was placed at headrest height between the driver's and passenger's seats inside the interior of a completed vehicle. The sound pressure waveform of the noise inside the vibrated vehicle was measured, and its frequency response characteristics were determined.

[0074] First, a sinusoidal vibration with continuously varying frequency was applied only to the vibration input area at the front of the completed vehicle (frequency sweep excitation), and the frequency response characteristics of the cabin noise of the excited completed vehicle were determined. In the frequency sweep excitation, the input vibration frequency was set to 30-2000 Hz, and the sweep speed was a logarithmic sweep of 30 s / octave. Then, the noise peak frequency was extracted from the obtained frequency response characteristics. Figure 6 is a graph showing the frequency response characteristics of the cabin noise of a completed vehicle subjected to frequency-swept excitation. From the frequency response characteristics shown in Figure 6, 62.6 Hz, 200 Hz, 400 Hz, 586 Hz, 670 Hz, and 985 Hz were extracted as noise peak frequencies.

[0075] Next, the extracted noise peak frequency was used as the excitation frequency, and phase difference excitation was performed by inputting a sinusoidal wave vibration with a continuously changing phase to the vibration input points at the front and rear. The time history data of the response waveform was measured using a microphone installed inside the vehicle. In phase difference excitation, the sweeping phase angle range was set to 0° to 360°, and the sweep speed was set to 1.0 deg / s. The sampling frequency for the time history data of the response waveform was set to 10 kHz.

[0076] Then, the time history data of the measured response waveform was divided into 0.4096s intervals, and the time history data for each divided interval was Fourier transformed to obtain the frequency response characteristics (amplitude of each frequency component).

[0077] Furthermore, the time intervals of each time-divided section were converted to the corresponding phase angles in phase difference excitation, and the amplitude of the frequency component corresponding to the excitation frequency was extracted from the frequency response characteristics of each section. The relationship between the phase difference and amplitude was then determined as the response characteristics of the completed vehicle subjected to phase difference excitation.

[0078] Figure 7 shows the response characteristics of the completed vehicle subjected to phase difference excitation at each excitation frequency. The results shown in Figure 7 indicate that the noise level excited inside the vehicle cabin by phase difference excitation changes under the influence of the phase difference of the input waveform, and that the response characteristics (pattern of the response waveform) differ for each excitation frequency.

[0079] <Example 2> In Example 2, a vehicle body was subjected to phase difference excitation, and the response waveform of the vibration generated on the vehicle body was measured using an accelerometer to determine the response characteristics.

[0080] The vehicle body used for the test was the same as the completed vehicle used in Example 1, but with the floor, roof, and side door interior trim parts removed. The vibration input points were the two connection points between the chassis frame and the vehicle body at the front and rear of the underbody. As in Example 1, vertical vibration was applied to the vibration input points, and the vehicle body was excited by a phase difference. The response waveforms of vibrations generated in the automobile body were measured using single-axis accelerometers installed on the floor panel and roof panel, which are panel components.

[0081] To determine the response characteristics of a vehicle body subjected to phase difference excitation, frequency sweep excitation was first performed by applying vibrations with continuously changing frequencies only to the vibration input points at the front of the vehicle body, and the frequency response characteristics of the floor panel and roof panel were determined. As a result, the floor panel showed a resonance peak in the 400-500Hz range. In contrast, the roof panel showed a peak in the 100-300Hz range.

[0082] Next, phase difference excitation was performed by continuously changing the phase difference at the same frequency band in which a resonance peak was observed during frequency sweep excitation. Then, time history data of the vibration acceleration generated in each panel component of the automobile body subjected to phase difference excitation was measured, and, as in Example 1, frequency response characteristics were calculated for each time-divided section of the time history data, and the relationship between phase difference and amplitude was determined.

[0083] The response characteristics of the floor panel were similar to the response characteristics of the in-cabin noise obtained in Example 1 in the same frequency band (Figure 7(c)). Similarly, the response characteristics of the roof panel were similar to the response characteristics of the in-cabin noise obtained in Example 1 in the same frequency band as the resonant frequency of the roof panel (Figure 7(b)). In-cabin noise caused by vehicle body vibration is largely due to vibrations transmitted through the frame components to panel components, and there is a high correlation between the frequency characteristics of the sound radiated from the panel components and the vibrations. Therefore, the sound radiated from the panel components, i.e., the in-cabin noise, tends to be louder at the vibration resonance frequency of the panel components.

[0084] Thus, it was confirmed that even when using an automobile body as the test subject and measuring the response waveform with an accelerometer, the response characteristics when a phase difference is applied and vibration is detected can be determined.

[0085] <Example 3> In Example 3, a commercially available small car body was subjected to phase difference excitation, and the response characteristics of the noise characteristics of the excited car body were determined. The difference from the response characteristics of the noise characteristics when a standard structure car body was excited was verified.

[0086] The vehicle body used for the test remained with its doors, hoods, and other body parts, as well as the windshield, attached. It was loaded and supported by four air mounts installed on the horizontal floor of the test building. Two vibration input points were designated at the connection points between the vehicle body and the chassis frame at the front and rear, and electrodynamic vibrators were connected to these points via steel vibration rods. Vertical vibrations with the same frequency but a phase difference were applied to these two vibration input points, thereby exciting the vehicle body with a phase difference.

[0087] The vibration input waveform to be input to the vibration input site was generated by a function generator and a delay processor. The reference signal generated by the function generator and the delayed signal generated by the delay processor were input to the exciter control device, which then drove and controlled the electrodynamic exciter.

[0088] Furthermore, in this test, a microphone was placed at headrest height between the driver's seat and the passenger seat inside the vehicle's interior, and the sound pressure waveform of the noise generated from various parts of the vibrated vehicle body was measured, and its frequency response characteristics were determined.

[0089] The test subjects were automobile bodies whose structure had been modified by partially altering the joints of the dash crossmember or rear floor crossmember, which are presumed to be the main vibration transmission paths from vibration input points in the automobile body. The response characteristics of the modified automobile body were then compared with the response characteristics of the automobile body with the standard structure before the modification was made, and it was investigated whether it was possible to detect structural differences.

[0090] The method and conditions for vibration of the automobile body, as well as the method for determining the frequency response characteristics and response characteristics, were the same as in Example 1. Furthermore, the response characteristics included the ratio of the maximum amplitude to the minimum amplitude in the response waveform (amplitude ratio) and the phase delay of the response waveform relative to the input waveform.

[0091] Figure 8 is a graph showing the relationship between amplitude ratio and phase lag obtained from vibration characteristic tests of the test subject and the reference structure of an automobile body. The response characteristics of the test vehicle body with modified dash cross joints showed almost no difference from the vehicle body with the standard structure before the modification. In contrast, the response characteristics of the vehicle body with modified rear floor cross member joints showed a larger phase lag and a lower amplitude ratio compared to the response characteristics of the vehicle body with the standard structure. Thus, it was found that in the test vehicle body with modifications to the joints, the behavior of in-cabin noise with respect to phase difference changed, and the position showing the amplitude extremum, i.e., the phase lag caused by the structure of the vibration transmission path, increased or decreased.

[0092] The difference in response characteristics is thought to be due to the distance from the vibration transmission path. Since the dash cross is located far from the vibration transmission path, modifications to its joints have little effect on phase delay. In contrast, since the rear floor cross member is located close to the vibration transmission path, modifications to its joints have a significant effect on phase delay.

[0093] In summary, the present invention suggests that it is possible to determine the normal range or range of variation in structural differences from a standard automobile structure non-destructively and in a short time, and to detect structural differences. Based on these results, it is considered effective to apply the present invention to quality inspections on the manufacturing line to manage trends in structural differences of manufactured automobiles. [Explanation of Symbols]

[0094] 1. Vibration characteristics testing apparatus 10. Vibration device 11. Vibrator 11a Shaker 11b Shaker 13 Function Generator 13a Signal generator 15 Delay Processing Unit 17. Vibrator control device 17a Vibrator control device 17b Vibrator control device 19 Vibration rod 20 Response waveform measuring device 21 Accelerometer 23 Data Loggers 30 Response characteristic acquisition device 100 automobile body 101 Front Side Member 103 Rear side member 105 Bumper Reinforcement 107 Rear Floor Cross Member 109 Car body floor 111 Vibration input site 111a Vibration input site 111b Vibration input site 201 Floor 203 Vibration-damping rubber 211 Air Cushion

Claims

1. A method for testing the vibration characteristics of an automobile, which involves inputting vibrations into the automobile under test and detecting structural differences between the automobile and a reference structure, A phase difference excitation process is performed by applying sinusoidal vibrations of the same frequency but with a phase difference to two vibration input points on the vehicle being tested, thereby exciting the vehicle. A response waveform measurement step, which measures the response waveform of vibrations generated in the excited automobile in synchronization with the input waveform of vibrations input to the vibration input part, A response characteristic acquisition step is performed to determine the response characteristics of the excited automobile by taking the amplitude of the response waveform measured in the response waveform measurement step and the phase difference of the input waveform of the vibration input in the phase difference excitation step, With respect to the aforementioned automobile of the reference structure, a reference structure response characteristic acquisition step is performed to acquire the response characteristics obtained by carrying out the phase difference excitation step, the response waveform measurement step, and the response characteristic acquisition step, similar to the aforementioned automobile to be tested. A method for testing the vibration characteristics of an automobile, comprising a structural difference detection step of comparing the response characteristics obtained for the automobile to be tested with the response characteristics obtained for the automobile with a reference structure, and detecting a structural difference between the automobile to be tested and the automobile with the reference structure.

2. A method for testing the vibration characteristics of an automobile, which involves inputting vibrations into the automobile under test and detecting structural differences between the automobile and a reference structure, A phase difference excitation process is performed by applying sinusoidal vibrations of the same frequency but with a phase difference to two vibration input points on the vehicle being tested, thereby exciting the vehicle. A response waveform measurement step, which measures the response waveform of vibrations generated in the excited automobile in synchronization with the input waveform of vibrations input to the vibration input part, The steps include: the ratio of the maximum amplitude to the minimum amplitude in the response waveform measured in the response waveform measurement step; the phase lag of the response waveform with respect to the phase difference of the input waveform of the vibration input in the phase difference excitation step; and the step of acquiring response characteristics to be determined as the response characteristics of the excited automobile. With respect to the aforementioned automobile of the reference structure, a reference structure response characteristic acquisition step is performed to acquire the response characteristics obtained by carrying out the phase difference excitation step, the response waveform measurement step, and the response characteristic acquisition step, similar to the aforementioned automobile to be tested. A method for testing the vibration characteristics of an automobile, comprising a structural difference detection step of comparing the response characteristics obtained for the automobile to be tested with the response characteristics obtained for the automobile with a reference structure, and detecting a structural difference between the automobile to be tested and the automobile with the reference structure.

3. The method for testing the vibration characteristics of an automobile according to claim 1 or 2, characterized in that, in the response waveform measurement step, a microphone is installed on the automobile and the sound pressure waveform of the noise generated from the excited automobile is measured as the response waveform.

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