Exhaust air leakage inspection device of vehicle and method

Abstract

To inspect the presence or absence of the leakage of exhaust air in a joint portion of an exhaust system in a short time in a completed car inspection step.SOLUTION: In a state that an engine 1 mounted on a vehicle is operated at an idle rotational speed, an outlet part opening face of an exhaust system is closed by a shutter 20, and exhaust passage resistance is raised. A high-frequency sound which is equal to or higher than 10 kHz corresponding to a leakage sound leaked from a clearance is extracted by a sound analysis part 11 from a sound acquired by a microphone 10 which is provided toward the exhaust system of the engine 1. When a lapse time after closing the shutter 20 and a rise of a sound pressure level of the high-frequency sound are correlated to each other, an exhaust air leakage sound determination part 30 determines the leakage sound from the exhaust system, and displays it on a display part 40.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an exhaust leak inspection device and method for inspecting for exhaust leaks from connections in an engine exhaust system based on leakage sounds during the finished vehicle inspection process or the like. [Background technology]

[0002] For example, in the finished vehicle inspection process, which is the final stage of an automobile production line, an inspector test drives the finished vehicle to be inspected on free rollers and inspects many items such as the engine, meters, brakes, horn, lights, etc. Generally, during this inspection process, the inspector checks for exhaust leaks from connections in the engine's exhaust system by listening for leak sounds, but the accuracy of such a sensory inspection by an inspector is relatively low.

[0003] Patent Document 1 discloses a technology for visually checking for exhaust leaks by applying soapy water to the connections of the exhaust system and then covering the tip of the exhaust pipe with a cap equipped with a relief valve that keeps the exhaust pressure approximately constant, thereby increasing the exhaust pressure. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Utility Model Application Publication No. 6-4322 Summary of the Invention [Problem to be solved by the invention]

[0005] The leak inspection method that involves applying soapy water as described above has the problem that it is necessary to apply soapy water to all of the multiple locations where leaks may occur, and it takes a long time to inspect each vehicle. [Means for solving the problem]

[0006] The vehicle exhaust leak inspection device according to the present invention comprises: A microphone for acquiring sounds from an exhaust system of an engine mounted on a vehicle; a passage resistance variable mechanism that changes an exhaust passage resistance at an outlet of the exhaust pipe; a sound analysis unit that extracts high-frequency sounds corresponding to sounds leaking from gaps from the sounds acquired by the microphone; an exhaust leakage noise determination unit that determines the presence or absence of leakage noise from an exhaust system based on an increase in sound pressure level of the high frequency sound when the exhaust passage resistance is increased by the passage resistance variable mechanism under a predetermined engine rotation speed; A display unit that displays the test results; The present invention is configured to include the following components:

[0007] When the exhaust passage resistance is increased by the passage resistance variable mechanism at a given engine speed, the exhaust pressure inside the exhaust system increases. If there is a small gap at the connection and exhaust is leaking, high-frequency sound is generated due to the exhaust leak, and the sound pressure level of this high-frequency sound increases with the increase in exhaust pressure. If there is no leak due to the gap, there is no increase in the sound pressure level of the high-frequency sound. Effect of the Invention

[0008] According to the present invention, there is no need for a preparatory treatment such as application of soapy water, and it is possible to inspect for the presence or absence of exhaust leaks in a short time, for example, during the finished vehicle inspection process. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a functional block diagram of a first embodiment in which the present invention is applied to leak inspection in a finished vehicle inspection process. [Diagram 2] 4 is a flowchart showing the flow of processing in the first embodiment. [Diagram 3] FIG. 4 is an explanatory diagram showing a display example on a display unit according to the first embodiment. [Figure 4] FIG. 11 is a functional block diagram of a second embodiment for estimating an exhaust leakage amount. [Diagram 5] 10 is a flowchart showing the flow of processing according to a second embodiment. [Figure 6] FIG. 11 is an explanatory diagram showing a display example on a display unit according to a second embodiment. [Figure 7] FIG. 11 is a functional block diagram of a third embodiment for estimating an exhaust leak location. [Figure 8] 13 is a flowchart showing the flow of processing according to a third embodiment. [Figure 9] FIG. 13 is an explanatory diagram showing a display example on a display unit according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An embodiment of the present invention applied to an exhaust leak inspection in a finished vehicle inspection process for automobiles will be described below. In general, in a finished vehicle inspection process, which is the final stage of an automobile production line, an inspector test drives the finished vehicle to be inspected on free rollers, and inspects a number of items including the engine, transmission, meters, horn, brakes, etc., according to a predetermined inspection sequence. The exhaust leak inspection in one embodiment is for determining whether there is any exhaust leak from a connection, etc., in the exhaust system (including multiple exhaust pipes, catalytic converter, muffler, etc.) of the engine mounted on the vehicle, based on the leakage sound. The leaks expected to be inspected can be caused, for example, by missing or damaged gaskets at the connection, defective welding, etc.

[0011] FIG. 1 shows a functional block diagram of an exhaust leak inspection device of a first embodiment. In FIG. 1, an exhaust system of an engine 1 is shown in schematic form, including a plurality of exhaust pipes 3 connected via joints 4 and a muffler 5. A catalytic converter and the like are omitted from the illustration. The engine 1 to be inspected for exhaust leaks is actually mounted on a vehicle. The operation or driving of the engine 1 is controlled by an engine control unit 2. As the engine control unit 2, an engine controller provided in the vehicle may be used as it is, or it may be provided as a part of the exhaust leak inspection device so as to remotely control the engine 1.

[0012] The exhaust leak inspection device of the first embodiment includes a microphone 10 for acquiring sounds from the exhaust system of the engine 1, a sound analysis unit 11 for analyzing the acquired sounds, a shutter 20 for covering the opening surface of the outlet of the tail pipe protruding from the silencer 5 as a passage resistance variable mechanism, an actuator unit 21 for driving the shutter 20 to open and close, an exhaust opening / closing control unit 22 for controlling the actuator unit 21 in cooperation with the engine control unit 2, an exhaust leakage sound determination unit 30 for determining the presence or absence of leakage sound from the exhaust system, a display unit 40 for displaying the inspection results, and a memory unit 50 for storing the inspection results and various data. The sound analysis unit 11, the exhaust opening / closing control unit 22, the exhaust leakage sound determination unit 30, the display unit 40, and the memory unit 50 are configured as parts of a so-called computer system.

[0013] The microphone 10 is one having an appropriate directivity in consideration of the layout of the target exhaust system and the installation position of the microphone 10. For example, an omnidirectional microphone or a shotgun-type directional condenser microphone may be used. A configuration in which a plurality of microphones are combined may be used. In addition, as for its frequency characteristics, it is desirable that the microphone 10 has sensitivity to sounds of a general frequency up to about 16 kHz. It is desirable that the microphone 10 is placed in a position where it can pick up sounds from each part of the exhaust system, especially the plurality of joints 4, and at the same time, where it is difficult to pick up sounds from the exhaust pipe outlet part covered by the shutter 20. For example, the inspection lane in the finished vehicle inspection process generally has a semi-underground pit in part of the floor, so that the microphone 10 is placed in this pit and the sound of the exhaust system can be collected from below the vehicle located so as to cover the pit. If no pit is provided, the microphone 10 may be placed on the floor.

[0014] In addition, the exhaust leakage sound may be acquired by using an existing microphone in the vehicle, such as a microphone for voice recognition provided in the vehicle's car navigation system or a microphone for mobile calls.

[0015] The sound analysis unit 11 performs frequency analysis of the audio signal output by the microphone 10 by signal processing such as STFT (short-time Fourier transform), and extracts high-frequency sounds corresponding to sounds leaking from minute gaps from the sounds acquired by the microphone 10 through a high-pass filter or a low-cut filter. For example, sounds of 10 kHz or higher are extracted. In a preferred embodiment, as described later, relatively low-frequency components, for example sounds of 6 kHz or lower, are filtered and extracted separately from high-frequency sounds in order to contrast with the behavior of high-frequency sounds of 10 kHz or higher.

[0016] The shutter 20 is moved by an actuator unit 21 consisting of an electric motor, a solenoid, etc., and opens and closes the opening surface of the outlet portion of the tail pipe during a leak test. In the illustrated example, it is depicted as a plate-like configuration that moves in a direction perpendicular to the longitudinal direction of the tail pipe, but the passage resistance variable mechanism may be of any type, such as an opening / closing mechanism combining multiple plates, or a cap-like configuration that moves in the axial direction of the tail pipe. In order to complete the leak test in a short time, it is desirable to minimize the passage area remaining when the outlet portion opening surface is closed, but the present invention is not limited to this, and a configuration that covers part of the opening surface may also be used.

[0017] Furthermore, in the case where the muffler 5 of the vehicle is equipped with a flow path switching mechanism for changing the exhaust resistance therein, this flow path switching mechanism may be utilized as the passage resistance variable mechanism.

[0018] The exhaust opening / closing control section 22 is connected to the engine control section 2 via an appropriate communication means, and controls the opening / closing ratio (passage opening area when closed), opening / closing speed, opening / closing timing, opening / closing time, etc. of the shutter 20 for leak testing, taking into consideration the state of the engine 1. In a preferred embodiment, the shutter 20 is fully closed for a predetermined time (for example, several seconds to several tens of seconds) to perform a leak test, on condition that the engine 1 has completed warming up and is at an idling speed. Note that, if the engine 1 is not idling properly due to an increase in exhaust pressure, it is desirable to configure the shutter 20 to open based on a signal from the engine control section 2.

[0019] The exhaust leakage sound determination unit 30 determines the presence or absence of leakage sound from the exhaust system based on the increase in the sound pressure level of the high-frequency sound when the exhaust passage resistance is increased by the shutter 20 under a predetermined engine rotation speed (e.g., idling speed). That is, when the front end outlet of the exhaust system is closed by the shutter 20, the pressure in the exhaust system increases with time. If a small gap (e.g., a gap of 1 mm or less) exists in the joint 4 of the exhaust system, gas flows out at high speed through the small gap as the pressure in the system increases, and leakage sound, i.e., high-frequency sound of 10 kHz or more, is generated. Moreover, the sound pressure level of this high-frequency sound increases as the pressure in the exhaust system increases, so there is a correlation between the time elapsed since the shutter 20 was closed, i.e., the pressure increase in the exhaust system, and the increase in the sound pressure level of the high-frequency sound. For example, if the pressure increases four times, the flow speed of the gas flowing through the gap increases twice, and the sound pressure level increases by 18 dB. On the other hand, if there is no leakage in the exhaust system, the high-frequency sound at the sound pressure level correlating with the pressure increase is not detected. Even if the surrounding noise during the finished vehicle inspection contains high frequency sounds, there is no correlation between the time that has passed since the shutter 20 was closed and the sound pressure level.

[0020] At idle speed, the basic amount of exhaust gas emitted from the engine 1 is small, so that it takes a few seconds for the pressure in the exhaust system to gradually increase, and the correlation with the increase in sound pressure level can be accurately determined.

[0021] The display unit 40 is a means for displaying acquired data, inspection results, and other information to relevant parties such as an inspector driving the vehicle and a manufacturing manager, and is composed of, for example, a liquid crystal display, an organic EL display, various indicator lights, etc. It is not limited to being a visual display, and may be a device that displays audio information, a haptic device that presents tactile information to the hand or arm, etc.

[0022] In addition, if the relevant parties are to be able to hear and confirm the leaking sound via the display unit 40, it is advisable to convert high frequency sounds of 10 kHz or more, which are difficult for the human ear to hear, into sounds of a frequency of about 3 to 5 kHz, which are easier for humans to hear, and then provide this from a speaker (not shown).

[0023] The storage unit 50 is a storage means including a HDD for storing voice data acquired through the microphone 10, control signals for the engine 1, data calculated for judging the leakage sound, judgment results, etc., and is configured by a server computer in the factory included in the finished vehicle inspection device, a cloud computer connected via a communication line, etc. The recorded past data is useful for ensuring the traceability of the inspection, and can also be used for future deep learning.

[0024] 3 is an explanatory diagram showing a display example on the display unit 40 of the first embodiment. In this example, in addition to the fact that it has been determined that there is sound leakage from the exhaust system being written in large letters at the top, a time chart is displayed on the left half, which contrasts the open / closed state of the shutter 20 ("exhaust end") with the sound pressure levels of high frequency sounds of 10 kHz or more and sounds of 6 kHz or less, and a characteristics diagram showing the frequency characteristics of the measurement sounds when the shutter 20 is closed is displayed on the right half.

[0025] In the example of Fig. 3, the sound pressure level of high frequency sounds of 10 kHz or more increases with the passage of time after the shutter 20 is closed (i.e., pressure increases), and it is determined that the increase in sound pressure level and the increase in pressure are correlated. It is also shown that the sound pressure level of sounds of 6 kHz or less is not affected by the increase in pressure. As shown in the frequency characteristics on the right side of Fig. 3, the respective sound pressure levels are evaluated by the integrated value of the sound pressure level of high frequency sounds of 10 kHz or more and the integrated value of the sound pressure level of sounds of 6 kHz or less.

[0026] The presence or absence of a correlation between the increase in sound pressure level of high-frequency sound of 10 kHz or more shown on the left side of Figure 3 and the passage of time (pressure increase) can be determined by calculating the correlation coefficient between the two using an appropriate method and comparing it with a predetermined threshold value.

[0027] In a preferred embodiment, it is determined that "sound leakage exists" when the following three conditions are met: there is a correlation between the increase in sound pressure level of high frequency sounds of 10 kHz or more and the passage of time (pressure increase), there is no correlation between the increase in sound pressure level of sounds of 6 kHz or less and the passage of time (pressure increase), and there is a difference between the sound pressure level of high frequency sounds of 10 kHz or more and the sound pressure level of sounds of 6 kHz or less when the shutter 20 is closed.

[0028] Although not shown in the example of Figure 3, information such as the vehicle identification number, vehicle model name, and vehicle specifications of the inspected vehicle, as well as information such as the inspection date and time, inspection status, inspector name and inspector number, weather, temperature, and humidity, may also be displayed.

[0029] Also, a button for playing an audio file may be displayed on the screen shown in Fig. 3, and the measured leak sound may be played back by operating this button. In this case, as described above, it is desirable to convert high frequency sounds of 10 kHz or more, which are difficult for the human ear to hear, into sounds of frequencies of about 3 to 5 kHz, which are easy for humans to hear, and play them back.

[0030] Next, Fig. 2 shows the process flow of the leak inspection device of the first embodiment as a flowchart. First, in step 1, sound data is acquired by the microphone 10 with the shutter 20 open. Next, in step 2, the shutter 20 is closed, and in step 3, sound data is acquired by the microphone 10 with the shutter 20 closed. Although not shown in the flowchart, as described above, high frequency sounds of 10 kHz or more (and sounds of 6 kHz or less if necessary) are extracted from the sound data, and their sound pressure levels are calculated. Then, in step 4, a correlation coefficient is calculated between the time elapsed since the shutter 20 was closed and the increase in sound pressure level.

[0031] The process of steps 1 to 4 may be repeated multiple times to obtain an average of the correlation coefficients, thereby improving accuracy.

[0032] In step 5, the value of the correlation coefficient thus obtained is compared with a predetermined threshold value. If the correlation coefficient is equal to or greater than the threshold value, the process proceeds to step 6, where it is determined that there is an exhaust leak, and if the correlation coefficient is less than the threshold value, the process proceeds to step 7, where it is determined that there is no exhaust leak. In either case, the process proceeds to step 8, where the inspection results are displayed as shown in FIG. 3 and are recorded in the memory unit 50.

[0033] In this way, the leak inspection device of the above embodiment can inspect for exhaust leaks from the exhaust system by increasing the pressure inside the exhaust system and collecting high frequency sounds with the microphone 10. Therefore, there is no need for a preparatory process such as applying soapy water, and it is possible to sequentially inspect for exhaust leaks in a short time, for example, during the finished vehicle inspection process.

[0034] In particular, since the judgment is based on the correlation between the increase in the sound pressure level of the high frequency sound and the elapsed time since closing the shutter 20, the judgment can be made more accurately without being affected by noise other than the leaking sound, compared to when the sound pressure level of the high frequency sound is simply compared to a threshold value. Moreover, by using the elapsed time as a parameter instead of the pressure value, a process of measuring the pressure in the exhaust system with a pressure sensor or the like is not required.

[0035] In addition, for a typical exhaust system volume, the exhaust pressure rise required for exhaust leak sound inspection can be obtained in a few seconds. Since this is a relatively short time, there is no adverse effect on the engine 1 due to the increase in exhaust pressure.

[0036] Next, a leak inspection device according to a second embodiment will be described with reference to Figures 4 to 6. The following mainly describes the differences from the first embodiment. The second embodiment is designed to not only determine the presence or absence of an exhaust leak, but also to estimate and display the amount of the leak if it is determined that an exhaust leak exists.

[0037] 4 shows a functional block diagram of the exhaust leak inspection device of the second embodiment. As in the first embodiment, the exhaust leak inspection device of the second embodiment is configured to include a microphone 10, a sound analysis unit 11, a shutter 20, an actuator unit 21, an exhaust opening / closing control unit 22, an exhaust leakage sound determination unit 30, a display unit 40, and a storage unit 50. In addition to the exhaust leakage sound determination unit 30, the second embodiment further includes an exhaust leakage amount estimation unit 31 that estimates the amount of exhaust leakage from gaps in the exhaust system. Like the exhaust leakage sound determination unit 30, the exhaust leakage amount estimation unit 31 is configured as a part of a so-called computer system.

[0038] The principle of exhaust leakage amount estimation is that the larger the exhaust leakage, the slower the pressure rise in the exhaust system when the shutter 20 is closed, and therefore the slower the rise in the sound pressure level of the high frequency sound. In order to estimate the exhaust leakage amount, the sound pressure level rise characteristics of the high frequency sound of a plurality of samples, for example, when there is no leakage, when there is 10% leakage, when there is 20% leakage, etc., are obtained in advance by experiment or simulation using the same vehicle model and exhaust system as the test object. For explanation, the sound pressure level rise characteristics of three samples are shown by dashed lines in the characteristic diagram at the bottom left of the display example of FIG. 6. The larger the leakage amount, the slower the pressure rise, and therefore the gradient of the sound pressure level rise becomes lower. Therefore, by comparing the sound pressure level rise characteristics of the high frequency sound when an exhaust leakage test is actually performed with the sound pressure level rise characteristics of the samples, it is possible to estimate the percentage of the leakage amount.

[0039] The exhaust leakage amount estimation unit 31 compares the sound pressure level rise characteristics of several pre-given samples with the sound pressure level rise characteristics of the high-frequency sound of the test subject obtained in the leak test, and performs interpolation calculations, etc. to estimate the leakage amount as a percentage, and further converts the leakage amount into a gas flow rate.

[0040] The sound pressure level rise characteristic of the sample can be obtained, for example, by changing the proportion of the opening surface of the outlet of the exhaust system covered by the shutter 20. For example, by leaving 10% of the opening area and covering the rest, it can be considered that the leakage amount is 10%.

[0041] In the display example of FIG. 6, it is determined that there is a leak sound from the exhaust system, and the value of the estimated exhaust leakage amount is written in large letters at the top. Then, as in the first embodiment, a time chart showing the open / closed state of the shutter 20 and the sound pressure level of high frequency sound of 10 kHz or more and sound of 6 kHz or less in comparison is displayed in the left half, and a characteristic diagram showing the frequency characteristic of the measured sound when the shutter 20 is closed is displayed in the right half. As described above, in the characteristic diagram of the sound pressure level on the left, the sound pressure level rise characteristic of the sample is shown by a broken line, and the characteristic of the test object is shown by a solid line. In this illustrated example, since the sound pressure level rise characteristic of the high frequency sound measured with the shutter 20 closed is close to the sample with 10% leakage, it is determined that the leakage amount is equivalent to 10%. Then, based on the displacement and idle speed of the engine 1, the leakage amount equivalent to 10% is displayed as a gas flow rate.

[0042] FIG. 5 is a flowchart showing the process flow of the leak test device of the second embodiment. First, in step 1, sound data is acquired by the microphone 10 with the shutter 20 open. Next, in step 2, the shutter 20 is closed, and in step 3, sound data is acquired by the microphone 10 with the shutter 20 closed. Although not shown in the flowchart, as described above, high frequency sounds of 10 kHz or more (and sounds of 6 kHz or less if necessary) are extracted from the sound data, and their sound pressure levels are calculated. Then, in step 4, a correlation coefficient is calculated between the time elapsed since the shutter 20 was closed and the increase in sound pressure level.

[0043] The processing of steps 1 to 4 may be repeated multiple times to calculate the average of the correlation coefficients, thereby improving accuracy.

[0044] In step 5, the value of the correlation coefficient thus obtained is compared with a predetermined threshold value. If the correlation coefficient is equal to or greater than the threshold value, the process proceeds to step 6, where it is determined that there is an exhaust leak. Then, in step 6A, the amount of exhaust leakage is estimated. If the processes in steps 1 to 4 are repeated multiple times, the average characteristics of the multiple increases in sound pressure level are compared with a sample to estimate the amount of leakage. The process then proceeds to step 8, where the inspection results are displayed as shown in FIG. 6, and are recorded in the memory unit 50.

[0045] If the correlation coefficient is less than the threshold in step 6, the process proceeds to step 7, where it is determined that there is no exhaust leak. In this case, the process also proceeds to step 8, where the inspection result is displayed and recorded in the memory unit 50.

[0046] In this way, according to the leak inspection device of the second embodiment, when it is determined that there is an exhaust leak based on the high frequency sound, the amount of the leak is further estimated and displayed. Knowing the amount of the leak in this way is useful for estimating where the leak is coming from, etc.

[0047] Next, a leak inspection device according to a third embodiment will be described with reference to Figures 7 to 9. The following mainly describes the differences from the first embodiment. In addition to determining whether or not there is an exhaust leak, the third embodiment estimates and displays the location of the leak when it is determined that there is an exhaust leak.

[0048] FIG. 7 shows a functional block diagram of the exhaust leak inspection device of the third embodiment. The exhaust leak inspection device of the third embodiment is configured to include a microphone 10, a sound analysis unit 11, a shutter 20, an actuator unit 21, an exhaust opening / closing control unit 22, an exhaust leak sound determination unit 30, a display unit 40, and a storage unit 50, as in the first embodiment. Here, the microphone 10 includes a plurality of microphones 10 for localizing the sound source. For example, in a form similar to general stereo recording, a first microphone 10L corresponding to the left channel and a second microphone 10R corresponding to the right channel are provided. In the third embodiment, in addition to the exhaust leak sound determination unit 30, an exhaust leak position estimation unit 32 that estimates the exhaust leak position, which is the position where the exhaust leak sound occurs, is further provided. The exhaust leak position estimation unit 32 is configured as a part of a so-called computer system, like the exhaust leak sound determination unit 30.

[0049] The exhaust leak position estimation unit 32 uses an appropriate general sound source localization method to identify the sound source position of a high frequency sound of 10 kHz or more acquired by the two microphones 10L, 10R. For example, the sound source position can be estimated by using the difference in arrival delay time of the sound to each microphone 10L, 10R, the difference in the attenuation amount of the phase or the amplitude of the sound, the change due to the incident angle of the sound to each microphone 10L, 10R, etc. Then, by superimposing the direction and distance estimated as the sound source on the layout of the exhaust system, it is possible to estimate from which part of the exhaust system the exhaust is leaking. Note that the number of microphones 10 (the number of channels) is not limited to two, and a microphone array including multiple microphones may be used. Furthermore, the method of sound source localization is not limited to simple trigonometry and may be any method.

[0050] 9 is an explanatory diagram showing a display example on the display unit 40 of the third embodiment. In this example, as in the first embodiment, it is written in large letters at the top that it has been determined that there is a leak sound from the exhaust system, and in the left half, a time chart is displayed that compares the open / closed state of the shutter 20 with the sound pressure levels of high frequency sounds of 10 kHz or more and sounds of 6 kHz or less, and in the right half, a characteristic diagram is displayed that shows the frequency characteristics of the measurement sound when the shutter 20 is closed. In the display example of the third embodiment, the configuration of the entire exhaust system is illustrated, and a red circle, for example, is displayed over the diagram of the exhaust system at the location that is estimated to be the exhaust leak location. The location surrounded by the circle indicates that it is the estimated exhaust leak location.

[0051] The leak location may be displayed in text using the part name instead of a diagram. For example, it may be displayed as "the connection part of the muffler" or "around the gasket of the joint part of the catalyst". In addition, since exhaust leaks generally occur at joints, if the middle position of the pipe is estimated as the exhaust leak location, the joint part closest to the estimated position may be presented as a candidate for the exhaust leak location. Furthermore, a graph showing the spatial probability as contour lines may be superimposed on the diagram of the exhaust pipe, or a color-coded display may be used to indicate the locations with high probability to low probability, such as "red → orange → green".

[0052] Furthermore, multiple sets of microphones may be used or multiple sound source localization methods may be applied to find multiple candidate leakage positions, and if the positions of these candidates match, the matching positions may be presented, and if the multiple candidates do not match, each candidate position may be switched and displayed in sequence.

[0053] FIG. 8 is a flowchart showing the process flow of the leak inspection device of the third embodiment. First, in step 1, sound data is acquired by the microphone 10 with the shutter 20 open. Next, in step 2, the shutter 20 is closed, and in step 3, sound data is acquired by the microphone 10 with the shutter 20 closed. Although not shown in the flowchart, as described above, high-frequency sounds of 10 kHz or more (and sounds of 6 kHz or less, if necessary) are extracted from the sound data, and their sound pressure levels are calculated. Then, in step 4, a correlation coefficient between the elapsed time after the shutter 20 is closed and the increase in sound pressure level is calculated. In the third embodiment, since sounds are acquired by the multiple microphones 10, for example, the sound pressure level of the high-frequency sound corresponding to a leak can be evaluated by calculating the sum of the integrated values ​​of the high-frequency sound components of 10 kHz or more.

[0054] The processing of steps 1 to 4 may be repeated multiple times to calculate the average of the correlation coefficients, thereby improving accuracy.

[0055] In step 5, the value of the correlation coefficient thus obtained is compared with a predetermined threshold value. If the correlation coefficient is equal to or greater than the threshold value, the process proceeds to step 6, where it is determined that there is an exhaust leak. Then, in step 6B, the exhaust leak position is estimated. When the processes of steps 1 to 4 are repeated multiple times, the exhaust leak position may be estimated from each sound data and a position with a high probability may be specified as the exhaust leak position, or the exhaust leak position may be specified from representative sound data among the multiple times. After the process of step 6B, the process proceeds to step 8, where the inspection results are displayed as shown in FIG. 9, and are recorded in the memory unit 50.

[0056] If the correlation coefficient is less than the threshold in step 6, the process proceeds to step 7, where it is determined that there is no exhaust leak. In this case, the process also proceeds to step 8, where the inspection result is displayed and recorded in the memory unit 50.

[0057] In this way, when the leak inspection device of the third embodiment determines that there is an exhaust leak based on the high frequency sound, it also estimates and displays the location of the leak, making it easier to take measures such as inspecting the gasket that may be causing the exhaust leak.

[0058] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and can be modified in various ways. In the above embodiment, an example in which the present invention is applied to the finished vehicle inspection process has been described, but the present invention can also be used in inspection and maintenance at a maintenance factory, for example. In addition, the passage resistance variable mechanism may be configured so that an operator manually opens and closes the mechanism. [Explanation of symbols]

[0059] 1. Engine 3...Exhaust pipe 10. Microphone 10L…1st microphone 10R…Second microphone 11...Sound analysis section 20...Shutter 21...Actuator section 22...Exhaust opening / closing control section 30…Exhaust leak sound detector 31…Exhaust leakage amount estimation section 32…Exhaust leak location estimation unit 40...Display section 50...Storage section

Claims

1. A microphone for acquiring sounds from an exhaust system of an engine mounted on a vehicle; a passage resistance variable mechanism that changes an exhaust passage resistance at an outlet of the exhaust pipe; a sound analysis unit that extracts high-frequency sounds corresponding to sounds leaking from gaps from the sounds acquired by the microphone; an exhaust leakage noise determination unit that determines the presence or absence of leakage noise from an exhaust system based on an increase in sound pressure level of the high frequency sound when the exhaust passage resistance is increased by the passage resistance variable mechanism under a predetermined engine rotation speed; A display unit that displays the test results; An exhaust leak inspection device for a vehicle comprising:

2. the exhaust leakage noise determination unit determines the presence or absence of leakage noise from the exhaust system based on a correlation between the elapsed time since the exhaust passage resistance was increased and an increase in the sound pressure level of the high-frequency noise.

2. The vehicle exhaust leak inspection device according to claim 1.

3. The exhaust leakage noise determination unit calculates a correlation coefficient between the elapsed time since the exhaust passage resistance was increased and the sound pressure level of the high-frequency sound, and determines that the high-frequency sound is a leakage noise when the correlation coefficient is equal to or greater than a predetermined threshold value.

3. The vehicle exhaust leak inspection device according to claim 2.

4. The sound analysis unit further extracts low-frequency sounds having relatively low frequencies from the sounds acquired by the microphone, The exhaust leakage noise determination unit determines that the low-frequency sound is a leakage noise based on a weighted condition that there is no correlation between the elapsed time since the exhaust passage resistance was increased and the sound pressure level of the low-frequency sound.

4. The vehicle exhaust leak inspection device according to claim 3.

5. The high frequency sound is a sound of 10 kHz or more.

2. The vehicle exhaust leak inspection device according to claim 1.

6. and an exhaust leakage amount estimation unit that estimates the amount of exhaust leakage based on the degree of increase in sound pressure level when the exhaust leakage sound determination unit determines that there is a leakage sound.

2. The vehicle exhaust leak inspection device according to claim 1.

7. Equipped with multiple microphones, and an exhaust leak position estimation unit that estimates an exhaust leak position by localizing a sound source using the multiple microphones.

2. The vehicle exhaust leak inspection device according to claim 1.

8. The passage resistance variable mechanism is a shutter mechanism for covering an opening surface of the exhaust pipe outlet.

2. The vehicle exhaust leak inspection device according to claim 1.

9. The passage resistance variable mechanism is a passage switching mechanism inside the muffler of the vehicle.

2. The vehicle exhaust leak inspection device according to claim 1.

10. The inspection is performed at the idle speed as the predetermined engine speed.

2. The vehicle exhaust leak inspection device according to claim 1.

11. When an engine mounted on a vehicle is operated at a predetermined engine speed, an exhaust passage resistance is increased at an outlet of the exhaust pipe, Sound from the engine's exhaust system is captured using a microphone, and high-frequency sounds corresponding to leaking sounds from gaps are extracted from the captured sounds. determining whether or not there is a sound leak from the exhaust system based on an increase in the sound pressure level of the high frequency sound when the exhaust passage resistance is increased; Display the test results, How to test a vehicle for exhaust leaks.

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