JP2009216510A - Abnormal noise inspection method of on-vehicle antivibration device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inspect whether abnormal noise is produced in a vehicle compartment before attaching an antivibration device to the vehicle, and to enable identification of the cause for the abnormal noise. <P>SOLUTION: This method has an input step (S1, 2) for applying a predetermined input to the antivibration device 1 mounted on a vibration exciting apparatus 3, a measurement step (S3, 4) for measuring a transmission force, and a determination step (S5, 6) for performing FFT processing of time series measurement data of the transmission force to perform its frequency resolving, extracting data in a specific frequency band and performing its reverse FFT processing after that to return it to time series data, and then based on data values in a specific time section of this data, determining whether or not abnormal noise will be produced in the vehicle compartment attached with the antivibration device 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for inspecting an anti-vibration device mounted on a vehicle, and in particular, whether or not abnormal noise is generated in a vehicle interior due to a transmission force from the anti-vibration device by using the anti-vibration device alone before being mounted on the vehicle. It relates to the inspection method.

  2. Description of the Related Art Conventionally, in vehicles such as automobiles, various types of vibration isolators such as engine mounts and suspension bushes are used in order to reduce engine vibration and transmission of road surface input to the interior of the vehicle and improve comfort. However, abnormal noise may occur in the passenger compartment due to minor problems such as variations in dimensions and shapes of parts of the vibration isolator and assembly errors.

  In this regard, for example, Patent Documents 1 and 2 disclose that an inspector in a vehicle interior determines whether or not an abnormal sound is generated while a completed vehicle is simulated, and a sound in the vehicle interior is detected by a microphone. There is also an inspection method for detecting the presence or absence of abnormal noise, but in this way, if the anti-vibration device is assembled in the vehicle, the result is that the anti-vibration device found defective is a good product. It takes a lot of time and money to replace it.

Accordingly, the inventors of the present application measured the transmission force to the vehicle body side by vibrating the vibration isolator alone before being assembled to the vehicle, and frequency-analyzed the measurement data, thereby differentiating the vehicle interior in the vehicle interior. A method for inspecting whether or not sound is generated has been developed (for example, Japanese Patent Application No. 2007-108287). That is, if the in-vehicle state inspection as in the above-mentioned patent document is performed in advance and the frequency band of the transmission force that causes abnormal noise in the passenger compartment is specified, the measured value data of the transmission force in this frequency band can be obtained. Based on this, OK / NG can be determined.
Japanese Patent No. 2623884 JP 2006-329879 A

  According to the invention according to the prior application, the vibration isolator can be inspected as a single unit, which is more efficient than the conventional completed vehicle inspection and requires work such as replacing the vibration isolator that has become NG. Therefore, it is possible to greatly reduce the cost burden, but it is not possible to distinguish the malfunction of the vibration isolator that causes abnormal noise in the vehicle interior.

  That is, for example, in the case of a general liquid seal type as an engine mount, when the liquid pressure greatly fluctuates due to an external input larger than a predetermined value, the movable plate housed in the member that partitions the main liquid chamber and the sub liquid chamber is partitioned It is well known that this impact is transmitted to the vehicle body and causes abnormal noise, but when the liquid chamber becomes a negative pressure close to vacuum due to a larger external input, bubbles are generated due to cavitation. In the process of disappearing, an impact is generated, and as a result, an abnormal noise is generated in the passenger compartment as described above.

  The abnormal noise generated in the passenger compartment is very similar to “Poco Poko”, which is caused by the collision of the movable plate and that caused by cavitation, and has peaks in almost the same frequency band. In the inspection by frequency analysis as in the invention according to the application, detection is possible in any case, but the two cannot be distinguished. Therefore, even if the NG product can be removed, effective measures cannot be taken in the manufacturing process based on the inspection result.

  The present invention has been made in view of such a point, and an object of the present invention is to determine whether or not abnormal noise is generated in the passenger compartment due to the transmission force from the in-vehicle vibration isolator. This makes it possible to inspect the cause of abnormal noise.

  In order to achieve the above object, the present inventor has intensively studied the difference between the abnormal noise caused by the collision of the movable plate and the abnormal noise caused by cavitation in the above-described liquid seal mount, and as a result, the timing at which they are generated is clarified. The differences were found and the present invention was completed.

  That is, the invention according to claim 1 is a vehicle-mounted vibration isolator for inspecting whether or not abnormal noise is generated in the vehicle interior due to the transmission force from the vibration isolator interposed between the vehicle body and the supported body. The sound inspection method is an object, and an input step of attaching a vibration isolator before being assembled to a vehicle to the vibration exciter and applying a predetermined input to the mounting portion on the supported body side of the vibration isolator, and the input A measurement step for measuring the transmission force output from the mounting portion on the vehicle body side of the vibration isolator, and time-series data of the transmission force thus measured are subjected to FFT processing to perform frequency decomposition, and data in a frequency band specified in advance is obtained. The data extraction step to be extracted, and the frequency band data thus extracted are subjected to inverse FFT processing to return to time-series data, and the vibration isolator differs depending on the data value of the time interval specified in advance in this data. sound Shall have, a determining step of determining whether or not the cause.

  In this inspection method, first, the vibration isolator before being assembled to the vehicle is attached to the vibration exciter, and a predetermined input is applied to the mounting portion on the supported body side of the vibration isolator. At this time, if the output from the mounting portion on the vehicle body side of the vibration isolator is measured, when the vibration isolator is assembled to the vehicle, it is transmitted from the supported body such as an engine to the vehicle body side via the vibration isolator. The transmitted force is measured. If the time series data of the measured transmission force is subjected to FFT processing and frequency decomposition, data in a specific frequency band can be easily extracted.

  Therefore, if the in-vehicle state inspection as in the conventional example (Patent Documents 1 and 2) is performed in advance and the frequency band of the transmission force that causes abnormal noise in the vehicle interior is specified, this vibration isolation It is possible to extract transmission force data in a specific frequency band that causes abnormal noise in the vehicle interior due to the transmission force from the device. Specifically, a test vibration isolator sample is assembled into a vehicle, input is made, time series data of vehicle interior sound is acquired by a microphone installed in the vehicle interior, and an inspector in the vehicle interior detects abnormal noise. What is necessary is just to verify the presence or absence of occurrence, specify the frequency of the abnormal sound by frequency analysis of the time-series data when abnormal noise occurs, and set a specific frequency band of the transmission force to include this frequency (Claim 2).

  The frequency band data thus extracted is subjected to inverse FFT processing to return to time-series data, and whether this vibration isolator causes noise when assembled on a vehicle based on the data value of the time interval specified in advance. Determine whether or not. If it carries out like this, about the abnormal noise which generate | occur | produces like the abnormal noise derived from the movable plate and the abnormal noise derived from cavitation in the said liquid seal mount, it can distinguish and detect NG goods according to those causes.

  In other words, the time-series data of the transmission force from the vibration isolator acquired by the vibration exciter is frequency-resolved, narrowed down to data in a specific frequency band that causes abnormal noise, and then returned to time-series data again. Thus, it is possible to distinguish and detect the occurrence of unusual noises that cannot be distinguished in the original time-series data.

  Here, the specific time interval can be set as follows, for example. In other words, a vibration isolator sample whose cause of abnormal noise is known in advance is attached to the vibration exciter, and a predetermined input is applied to the supported body side mounting portion, whereby the transmission force output from the vehicle body side mounting portion Measure. Then, the time series data of the measured transmission force is subjected to FFT processing and frequency-decomposed, and data of a specific frequency band is extracted and then subjected to inverse FFT processing to return to time series data. Since the peak of the transmission force that generates abnormal noise can be clearly identified, the time interval may be specified so as to include this peak (Claim 3).

  As described above, according to the inspection method according to the present invention, it is possible to inspect whether or not it causes an abnormal noise in the vehicle interior without assembling the vibration isolator to the vehicle, and for example, like a collision of a movable plate or cavitation The cause can also be distinguished. Therefore, it is possible to take effective measures on the production line based on the inspection result.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the following description of the preferred embodiment is merely illustrative in nature, and is not intended to limit the present invention, its application, or its use.

(Engine mount configuration)
FIG. 1 shows an engine mount 1 as an in-vehicle anti-vibration device, which is an object to be inspected for the occurrence of abnormal noise in this embodiment. The engine mount 1 includes a connecting bracket 12 (vehicle body side mounting portion) connected to the vehicle body side in a substantially cylindrical case 11 integrally formed with a connection portion 15 (supported body side mounting portion) connected to the engine side. ) And the mount main body portion 10 are accommodated. The mount main body 10 includes a rubber elastic body 13 that is interposed between the case 11 and the connection fitting 12 so as to be relatively displaceable.

  The connecting bracket 12 is formed in a substantially conical shape with the upper portion narrowed upward with a flange extending outward in the radial direction, and the lower portion formed in a substantially cylindrical shape. The lower end of the rubber elastic body 13 is connected to the cylindrical lower portion, and the lower part of the columnar shape is inserted into a hole 11 b formed in the bottom of the case 11. A bolt hole is opened at the lower end surface of the lower portion of the connecting metal 12, and although not shown, the connecting metal 12 is fixed to the vehicle body side by a bolt screwed into the bolt hole. A stopper rubber 13a is provided on the flange portion of the connecting fitting 12 so as to cover it.

  The rubber elastic body 13 is formed in a mortar shape that opens upward as shown in the figure, and the outer peripheral surface of the upper portion thereof is bonded to the inner peripheral surface of the case 11. A substantially cylindrical reinforcing plate 14 is embedded in an upper portion of the rubber elastic body 13, and an upper end portion of the rubber elastic body 13 protrudes radially outward from the outer peripheral surface of the rubber elastic body 13. The upper portion of the rubber elastic body 13 is fixed to the case 11 by being caulked by the caulking portion 11 a at the upper end.

  A rubber diaphragm 16 is disposed on the top of the mount main body 10 so as to cover the opening at the upper end of the rubber elastic body 13 to form a liquid chamber 17 in which a buffer solution is enclosed. Further, the diaphragm 16 is fitted with a metal orifice plate 18 so that the liquid chamber 17 is divided into a pressure receiving chamber 17a on the rubber elastic body 13 side and an equilibrium chamber 17b on the diaphragm 16 side. .

  An annular metal fitting 19 is embedded in a portion near the outer periphery of the diaphragm 16, and a lower end thereof projects radially outward from the outer peripheral surface of the diaphragm 16, together with an upper end portion of the reinforcing plate 14 of the mount main body 10. It is caulked to the caulking portion 11 a of the case 11. Thus, the orifice plate 18 is sandwiched between the diaphragm 16 fixed to the case 11 and the rubber elastic body 13. Reference numeral 22 denotes a cover for protecting the diaphragm 16.

  The orifice disc 18 includes a main body portion 18a having a spiral orifice passage 21 formed on the outer peripheral portion thereof, and a disc-shaped lid portion 18b disposed on the upper portion of the main body portion 18a. A concave portion 18c for accommodating the rubber movable plate 20 is formed in the central portion on the upper surface side of the main body portion 18a, and a plurality of through holes penetrating in the vertical direction are formed in the bottom wall of the concave portion 18c. Is formed. Further, in the lid portion 18b, a plurality of through holes penetrating in the vertical direction are formed in the central portion corresponding to the position of the concave portion 18c as well as the bottom wall of the concave portion 18c.

  The pressure receiving chamber 17a and the equilibrium chamber 17b defined by the orifice plate 18 having such a configuration are communicated with each other by an orifice passage 21 formed in a spiral shape on the periphery of the orifice plate 18. In the engine mount 1, When the buffer solution in the pressure receiving chamber 17a and the equilibrium chamber 17b flows through the orifice passage 21, vibrations of low frequency and large amplitude acting on the pressure receiving chamber 17a from the rubber elastic body 13 are attenuated. At this time, the diaphragm 16 is deformed so as to absorb the volume change of the equilibrium chamber 17b accompanying the flow of the buffer solution.

  Further, the high-frequency / small-amplitude vibration acting on the pressure receiving chamber 17a from the rubber elastic body 13 is attenuated by the movement of the movable plate 20 accommodated in the recess 18c. The orifice passage 21 is in a so-called clogged state against such high-frequency / small-amplitude vibration.

  FIG. 1 shows a no-load state in which the weight of the engine or the like (supported body) is not applied to the mount body 10. In this state, the stopper rubber 13 a of the mount body 10 and the bottom of the case 11 Are close together. On the other hand, although not shown, in the 1G state where the engine mount 1 is attached to the vehicle body and the weight of the engine or the like is applied to the mount main body 10, the rubber elastic body 13 is bent and the case 11 is relatively displaced downward. Thus, a predetermined gap is formed between the bottom portion and the stopper rubber 13a.

(Generation mechanism of abnormal noise)
FIG. 2 schematically shows a mechanism when abnormal noise is generated in the vehicle interior due to the transmission force from the engine mount 1. For example, when a large displacement is dynamically input to the engine mount 1 when traveling on a rough road or the like, a large fluid pressure fluctuation occurs in the engine mount 1, and the recess 18 c and the lid 18 b in the main body 18 a of the orifice board 18 The movable plate 20 accommodated in between collides with the main body portion 18a and the lid portion 18b.

  In particular, when the vehicle body side, that is, the mount main body 10 moves upward due to the thrust from the road surface, the hydraulic pressure in the pressure receiving chamber 17a suddenly rises, and the movable plate 20 that has received this is deformed while rapidly moving upward. Collides with the lid 18b. The shock at this time is transmitted to the vehicle body from the connecting bracket 12 through the rubber elastic body 13 and the case 11 of the engine mount 1 as shown in the figure, and is transmitted through the structural members of the vehicle body to vibrate the air in the vehicle interior, that is, to make a sound. Will be generated.

  Thus, the volume of sound generated in the passenger compartment by the transmission force from the engine mount 1, that is, the sound pressure level, can be expressed by the following formula: “Sound pressure level in the passenger compartment” = “body sensitivity” × “transmission force”. it can. That is, the sound pressure level in the passenger compartment is the product of the transmission force and the vehicle body sensitivity. If the frequency component having a high vehicle body sensitivity is greater than a predetermined value in the transmission force, this causes a part of the vehicle body panel to resonate in the vehicle body. An abnormal noise “Pokopoko” is generated.

  On the other hand, even if the transmission force from the engine mount 1 is large as a whole, if the frequency component with high vehicle body sensitivity is not so large, the sound pressure level of abnormal noise due to the resonance of the vehicle body panel as described above becomes low. For this reason, it is not recognized as an abnormal noise by the passenger. Therefore, if the transmission force from the engine mount 1 is measured and subjected to frequency analysis, it can be predicted with sufficient accuracy whether or not the “poco-poco” abnormal noise is generated in the passenger compartment.

  Such an inspection can be performed by itself without attaching the engine mount 1 to the vehicle. In this embodiment, the engine mount 1 is vibrated by the vibration device 3 (see FIG. 3) as described below. However, when the transmission force is measured and the engine mount 1 is assembled to the vehicle based on the measurement data, it is inspected whether this causes the “poco-poco” noise in the passenger compartment. .

  By the way, it is not only when the movable plate 20 collides with the orifice plate 18 in the engine mount 1 as described above that the noise is generated in the vehicle interior. For example, when a sudden fluid pressure fluctuation occurs in the fluid chamber 17 due to an excessive input, and this is temporarily in a negative pressure state close to a vacuum, an impact is generated in the process where bubbles are generated and disappear due to cavitation. It has been found that this impact is transmitted to the vehicle body through the same route as described above, and an abnormal noise is generated in the vehicle interior.

  The abnormal noise generated by the cavitation in the passenger compartment is a “poco-poco” abnormal noise having a sound quality very similar to that caused by the collision of the movable plate 20 and has a peak in substantially the same frequency band. Thus, even if frequency analysis is performed, the two cannot be distinguished, and moreover, it is difficult to distinguish them by a sensory test of an inspector in the passenger compartment.

  On the other hand, the inventor of the present application pays attention to the fact that the timing at which the transmission force increases is slightly different between the one caused by the collision of the movable plate 20 and the one caused by cavitation because the generation mechanism is different. did. That is, in this embodiment, as will be described in detail below, the transmission force measurement data (time-series data) from the engine mount 1 acquired by the vibration device 3 as described above is frequency-resolved to generate abnormal noise. After extracting only the data of the specific frequency band that is the cause of occurrence, it was converted back to time-series data, and the cause of the abnormal noise was identified from the timing at which the transmission force peaked.

(Configuration of inspection system)
FIG. 3 shows a block diagram of an abnormal sound inspection system used when the abnormal sound inspection method according to this embodiment is performed. This system includes a vibration device 3 that vibrates the engine mount 1 and measures a transmission force by the vibration, a hydraulic unit 41 that supplies hydraulic pressure for vibration input to the vibration device 3, and the vibration device 3. And a main control panel 42 that controls the hydraulic unit 41, and a computer 5 that performs predetermined processing on the measured transmission force data and determines whether or not abnormal noise due to the engine mount 1 has occurred. I have.

  The vibration exciter 3 includes a main body portion 31 and a cross head portion 32 that can move up and down relatively. The main body portion 31 is provided with a hydraulic cylinder 33 for inputting vibration to the engine mount 1, while the crosshead portion 32 has a measurement for measuring the transmission force output from the engine mount 1. A portion 34 is provided.

  The hydraulic cylinder 33 includes a stage 35 that is displaced in the vertical direction, and the hydraulic pressure supplied to the hydraulic cylinder 33 is controlled in accordance with the servo valve 36 being controlled by the main control panel 42. And move up and down in a predetermined pattern.

  The cross head portion 32 is configured to be movable up and down by a lifting cylinder (not shown). The measurement unit 34 is fixed to the lower surface of the crosshead unit 32 and includes a fixed part to which the coupling fitting 12 of the engine mount 1 is fixed, and measures a load acting on the fixed part. It has a load cell. The load cell detection signal is input to the computer 5 via the main control panel 42.

  The vibration mount 3 is attached with the engine mount 1 in a posture in which the top and bottom are reversed. That is, the case 11 is fixed to the stage 35 of the main body 31, while the connection fitting 12 is fixed to the measuring unit 34 of the crosshead 32. When the engine mount 1 is inspected, the control signal from the main control panel 42 in a state where the crosshead portion 32 is moved downward and a static load is applied so that the engine mount 1 is in the 1G state. Accordingly, the hydraulic cylinder 33 is driven.

  As a result, the stage 35 is displaced up and down in a predetermined pattern, and the vibration of the predetermined pattern is input to the case 11 of the engine mount 1. In this way, the load acting on the connection fitting 12 during the vibration of the case 11 is detected by the load cell of the measuring unit 34, and the detection signal is input to the computer 5 via the main control panel 42.

  FIG. 4 shows a configuration of a processing block realized by executing a predetermined program in the computer 5. The time series data acquisition unit 51 acquires time series data of the transmission force input from the vibration device 3 via the main control panel 42 as described above, and the data sampling unit 52 adds the acquired time series data to the time series data. On the other hand, sampling is performed at a predetermined frequency.

  The frequency analysis unit 53 includes an FFT processing unit 53a, a data extraction unit 53b, and an inverse FFT processing unit 53c. First, in the FFT processing unit 53a, a discrete time series of transmission forces sampled by the data sampling unit 52 is provided. Fast Fourier transform is applied to the data to calculate the power spectrum of the transmission force. The data extraction unit 53b stores a specific frequency band set in advance as described in detail below, and extracts transmission force data (in the frequency domain) in the specific frequency band. The frequency domain transmission force data thus extracted is subjected to inverse FFT processing in the inverse FFT processing unit 53 c and returned to time-series data, and is input to the determination unit 54.

  The determination unit 54 stores a time interval and an evaluation threshold specified in advance as described in detail below. In the time series data of the transmission force input from the inverse FFT processing unit 53c of the frequency analysis unit 53, When the data value is larger than the evaluation threshold value based on the data value (for example, peak value, averaged value, integrated value, etc.) of the specific time section, the engine mount 1 causes an abnormal noise (NG ). The result output unit 55 outputs the determination result to, for example, a display screen.

(Setting inspection conditions)
The inspection conditions in the inspection system will be described below. First, the vibration conditions of the engine mount 1 by the vibration device 3 and the frequency band extracted from the transmission force data in the frequency analysis unit 53 of the computer 5 will be described with reference to FIG. These are set based on the results of the actual vehicle running test.

  First, a plurality of test engine mounts 1 (samples) are prepared, each of which is assembled to a vehicle, and the input displacement (the displacement input to the case 11 in relation to the relative displacement between the vehicle body and the engine) can be measured. In addition, a microphone is installed in the passenger compartment. Then, the vehicle is driven under predetermined conditions (for example, driving on a predetermined road surface such as rough road driving, constant speed driving and acceleration driving, etc.), and time series data of input displacement to the engine mount 1 during this period, Sound time-series data is acquired.

  By reproducing the in-vehicle sound from the time series data obtained in this way, the time interval including the timing at which the abnormal noise appears to have occurred in the time series data is specified (see the dotted box), and the time series of this interval is determined. By analyzing the frequency of the data, the frequency of abnormal noise is specified. Then, the frequency band extracted from the transmission force data is specified so as to include the frequency of this abnormal sound, and this is stored in the frequency analysis unit 53 (data extraction unit 53b) of the computer 5.

  On the other hand, also in the time series data of the input displacement of the engine mount 1, frequency analysis is performed in a range corresponding to the generation timing of the abnormal noise (see the dotted box). As a result, the input displacement of the engine mount 1 when abnormal noise is generated in the vehicle interior is specified. Based on this, the appropriate vibration condition of the vibration device 3, that is, from the defective engine mount 1 is determined. It is possible to determine the frequency and amplitude of the vibration input that causes abnormal noise in the vehicle interior due to the transmission force. In this example, the excitation input is sinusoidal vibration.

  Next, the specific time interval and the evaluation threshold relating to the determination in the determination unit 54 of the computer 5 will be described with reference to FIGS. These are set from the results of the following tests performed in advance using the inspection system.

  As a sample of the engine mount 1, a sample in which abnormal noise was generated and a sample in which abnormal noise was not generated in the above-mentioned actual vehicle running test were prepared. Acquire transmission force data while oscillating under the conditions set in. An example of this data is as shown in FIG. 6A, and a sinusoidal transmission force (shown by a broken line) is similarly output from the engine mount 1 by a sinusoidal excitation input.

  The time-series data thus obtained is input to the computer 5, and the frequency analysis unit 53 performs the FFT processing and data extraction as described above to extract only the data of the specific frequency band of the abnormal sound, and then When the time series data is restored by the inverse FFT processing, data as shown in FIG. From this figure, it can be seen that the displacement due to the vibration input (vibration displacement) is a negative value, that is, the transmission force shows a peak in a predetermined time interval T1 while the pressure receiving chamber 17a is in a state of being expanded.

  Here, as shown by the broken line graph in FIG. 7 (a), the hydraulic pressure in the pressure receiving chamber 17a of the engine mount 1 fluctuates in synchronization with the vibration input, and compared with FIG. 6 (b), It can be seen that the time interval T1 corresponds to an interval in which the hydraulic pressure is positive. From this, it is considered that the peak of the transmission force appearing in FIG. 6 (b) is due to the movable plate 20 colliding with the lid portion 18b under the liquid pressure of the pressure receiving chamber 17a that has rapidly increased as described above. When this is larger than a predetermined value, an abnormal noise is generated in the passenger compartment. The hydraulic pressure graph is separately measured by attaching a hydraulic pressure sensor to the pressure receiving chamber 17a of the engine mount 1.

  Subsequently, the same test is performed on the sample in which no abnormal noise was generated. At this time, cavitation is generated in the pressure receiving chamber 17a of the engine mount 1 by changing the vibration condition and giving a larger input. For this purpose, a special engine mount that allows the inside of the pressure receiving chamber 17a to be observed from the outside is manufactured, and the oscillating device 3 vibrates while taking a picture with a high-speed camera, so that cavitation occurs. Check it.

  Then, the transmission force data is obtained by applying the excitation input in which cavitation occurs as described above to the sample in which no abnormal noise was generated in the actual vehicle running test, and this data is input to the computer 5 as described above. When only the data in the specific frequency band is extracted and then returned to time series data, data as shown in FIG. From this data, it can be seen that the transmission force has a positive value in a predetermined time interval T2 in which the excitation displacement is a positive value, that is, the pressure receiving chamber 17a is in a contracted state.

  Compared with FIG. 7 (a), the time interval T2 corresponds to the timing when the hydraulic pressure in the pressure receiving chamber 17a of the engine mount 1 reaches the peak on the negative pressure side, and appears in FIG. 7 (b). The peak of the transmission force is considered to be due to the impact generated in the process where bubbles are generated and disappear by cavitation as described above. If the impact due to the cavitation increases and the peak of the transmission force as shown in FIG. 7B becomes higher than a predetermined value, abnormal noise is generated in the passenger compartment.

  The noise caused by the collision of the movable plate 20 and the cavitation are very similar to each other in the sound quality of the abnormal noise generated in the passenger compartment, and cannot be distinguished by frequency analysis alone. As described above, it was found that the peak timing of the transmission force from the engine mount 1 is shifted, and peaks are shown in the specific time sections T1 and T2, respectively.

  Therefore, based on the data value of the transmission force in each of the time intervals T1 and T2, for example, the peak value, an averaged value, or an integrated value is used as an evaluation determination value, which is a predetermined evaluation threshold. When the value is larger than the value, it can be said that the engine mount 1 causes abnormal noise. The evaluation threshold value may be determined based on the sensory evaluation as described above or the measured level of abnormal noise.

(Engine mount abnormal noise inspection procedure)
Next, the procedure for inspecting the engine mount 1 in the abnormal sound inspection system of this embodiment will be described with reference to the flowchart shown in FIG. First, in step S1, vibration input (vibration) to the engine mount 1 attached to the vibration device 3 is started. In subsequent step S2, it is determined whether or not the vibration is stable. When it is not stable (NO), step S2 is repeated, while when it is stable (YES), the process proceeds to step S3. These steps 1 and 2 correspond to the input steps.

  In step S3, the signal from the load cell is taken in and the transmission force is measured. In subsequent step S4, the measurement data (time series data of transmission force) is transferred from the main control panel 42 to the computer 5. These steps S3 and S4 correspond to measurement steps.

  In step S5, as described above, the computer 5 extracts the data of the specific frequency band from the time series data of the transmission force, and then calculates the evaluation determination value from the data of the time intervals T1 and T2, for example. The presence / absence of abnormal noise is determined in step S6 by comparing the calculated evaluation determination value with the evaluation threshold value. These steps S5 and 6 correspond to a data extraction step and a determination step.

  When the determination result is OK, that is, when it is determined that no abnormal noise is generated, the process proceeds to step S7, and OK display is performed on a predetermined display (not shown), while the determination result is NG, that is, abnormal noise is generated. If it is determined, the process proceeds to step S8, and NG is displayed on the display. Then, the vibration input is finished in step S9, and the inspection is finished.

  Note that the excitation condition, the specific frequency band, and the specific time section in the inspection of the engine mount 1 are set in advance by the above-described experiment, and the type of the engine mount 1 to be inspected and the assembly thereof. It is preferable that it can be easily changed and set in accordance with the type and specifications of the vehicle to be used.

  Therefore, according to the inspection method for the on-vehicle vibration isolator according to this embodiment, the engine mount 1 can be inspected alone without being assembled to the vehicle, and it is predicted whether this will cause abnormal noise in the vehicle interior. Therefore, the inspection efficiency can be improved, and the cost burden can be greatly reduced without the need to replace the engine mount 1 as a result of the inspection.

  In addition, it is possible to distinguish the cause of abnormal noise in the vehicle interior, such as abnormal noise caused by the collision of the movable plate 20 in the liquid seal type engine mount 1 and abnormal noise caused by cavitation. Effective measures can be taken in the manufacturing process based on the inspection result. Of course, if there is a cause of abnormal noise other than the collision of the movable plate 20 and cavitation, this can also be identified and detected.

  In the embodiment described above, the object to be inspected for abnormal noise is the engine mount 1 in which the mounting portion on the vehicle body side and the mounting portion on the engine side are arranged substantially vertically. For example, the mounting portion on the engine side The so-called bush-type engine mount 1 in which the mounting portion on the vehicle body side is on the outside can be the inspection object.

  Further, the inspection target is not limited to the liquid-filled mount 1 and is not limited to the engine mount. In addition, the present invention can be widely applied to an on-vehicle vibration isolator used for supporting suspensions, exhaust pipes, and the like.

  As described above, the present invention can inspect whether or not it causes abnormal noise in the vehicle interior without assembling the vibration isolator to the vehicle, and the cause of the abnormal noise can be identified. This is extremely useful as a method for inspecting abnormal noise of a vehicle vibration isolator.

It is sectional drawing of the engine mount used as the object of the abnormal noise test | inspection which concerns on embodiment. It is a figure explaining the mechanism of abnormal noise generation. It is a block diagram of a system used for abnormal sound inspection. It is a block diagram which shows the process performed in a computer. It is explanatory drawing of the procedure which determines the vibration conditions etc. of an engine mount. It is a graph of transmitted force data, (a) shows the measured time-series data in comparison with the excitation input, and (b) shows the result of extracting a predetermined frequency band. (a) is a graph showing the relationship between excitation input and hydraulic pressure fluctuation, and (b) is a diagram corresponding to FIG. 6 (b) showing the transmission force by cavitation. It is a flowchart which shows the test | inspection procedure of an engine mount.

Explanation of symbols

1 Engine mount (on-vehicle vibration isolator)
12 Connecting bracket (vehicle body side mounting part)
14 Connecting part (Supported body side mounting part)
3 Exciter

Claims (3)

An abnormal noise inspection method for an in-vehicle vibration isolator for inspecting whether or not an abnormal noise is generated in a vehicle interior by a transmission force from a vibration isolator interposed between a vehicle body and a supported body,
An input step of attaching a vibration isolator before assembly to the vehicle to the vibration exciter and applying a predetermined input to the support side of the vibration isolator,
A measurement step of measuring a transmission force output from a mounting portion on the vehicle body side of the vibration isolator by the input;
A data extraction step of performing FFT processing on the time series data of the measured transmission force and performing frequency decomposition to extract data of a frequency band specified in advance;
The extracted frequency band data is subjected to inverse FFT processing to return to time-series data, and whether or not the vibration isolator causes noise generation based on a data value of a predetermined time interval in the data. An abnormal sound inspection method for an on-vehicle vibration isolator having a determination step. A test vibration isolator sample is assembled into the vehicle, input is made, and time series data of the vehicle interior sound is acquired by a microphone installed in the vehicle interior, and the inspector in the vehicle interior verifies whether or not abnormal noise has occurred. And
The abnormal noise according to claim 1, wherein the frequency of the time series data when abnormal noise occurs is analyzed to identify the frequency of the abnormal noise, and the specific frequency band of the transmission force is set so as to include this frequency. Inspection method. Attach a vibration isolator sample whose cause of abnormal noise is known in advance to the vibration exciter, apply a predetermined input to the support side mounting part, and measure the transmission force output from the body side mounting part And
The time series data of the measured transmission force is subjected to FFT processing to perform frequency decomposition, data of a specific frequency band is extracted, and then inverse FFT processing is performed to return to time series data. The abnormal sound inspection method according to claim 1 or 2, wherein a time interval of the generated transmission force is specified.

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