JP6373012B2 - Engine diagnostic device - Google Patents

Description

  The present invention relates to an engine diagnostic apparatus that diagnoses deterioration of engine components constituting an engine using acoustic emission.

  Patent Document 1 describes an EGR cooler breakage diagnosis device that diagnoses breakage of an EGR cooler for cooling exhaust gas recirculating through an EGR passage communicating with an exhaust passage and an intake passage of an engine. The breakage diagnosis apparatus includes an acoustic emission sensor that is disposed in the EGR cooler and outputs a detected acoustic emission signal, and a control unit that diagnoses breakage of the EGR cooler based on a signal from the acoustic emission sensor. It has been. The control means has a memory for storing in advance an acoustic emission signal pattern generated in a crack state generated when the EGR cooler is cracked, and the waveform pattern of the acoustic emission signal output from the acoustic emission sensor is cracked. It is determined that a crack has occurred in the EGR cooler when it matches the acoustic emission signal waveform pattern in the state.

JP 2004-360546 A (FIGS. 1 and 5)

  In the damage diagnosis apparatus according to Patent Document 1, when the waveform pattern of the acoustic emission signal output from the acoustic emission sensor matches the signal pattern at the time of occurrence of the crack stored as the reference pattern, a crack is generated in the constituent member of the EGR cooler. Therefore, there is an advantage that this can be detected when a crack occurs. However, since the acoustic emission signal includes vibrations from various vibration sources (sound sources), the waveform shape is complicated, and also changes depending on the state of cracks. A highly accurate waveform pattern matching is required. However, increasing the accuracy of waveform pattern matching increases the cost of the control means. For this reason, a simpler and more accurate engine diagnostic device is desired.

An engine diagnostic apparatus according to the present invention includes a receiving element that detects an acoustic emission wave emitted from an engine component during engine operation and outputs a sound wave signal, and a predetermined time region of the sound wave signal for each measurement period. A maximum amplitude value calculating unit for calculating a maximum amplitude value, an evaluation value calculating unit for calculating an evaluation value based on a plurality of the maximum amplitude values obtained over a plurality of measurement cycles, and the evaluation value being preset. And an evaluation unit that compares the threshold value with each other to determine abnormality of the engine component. The engine component is a bearing metal of a crankshaft, and a solid propagation sound from the bearing metal reaches the engine housing. The receiving element is mounted on the outer surface corresponding to the cylinder, and an evaluation result for each cylinder is output.

  According to this configuration, the plurality of maximum amplitude values obtained by calculating the maximum amplitude value in the predetermined time region of the sound wave signal transmitted from the receiving element for each measurement period perform abnormality determination of the engine constituent member. The basic value of Further, when the evaluation value calculated based on the plurality of maximum amplitude values is compared with a preset threshold value and the evaluation value exceeds (or falls below) the threshold value, the engine component member Is determined to be abnormal. Here, the maximum amplitude value of a sound wave signal that can be easily obtained in terms of signal processing is adopted as a basic value for abnormality determination, and is calculated based on a plurality of maximum amplitude values obtained by repeating such measurement. An excellent point of view of the present invention is that the abnormality determination of the engine component can be performed only by comparing the evaluation value with the threshold value as the determination criterion. In addition, using the maximum amplitude value of the sound wave signal that can be easily calculated as a basic value leads to simplification and cost reduction of the measurement configuration.

The threshold value serving as a determination criterion can be obtained by statistical processing of experimental results, and the accuracy of abnormality evaluation can be further improved by correcting it with an empirical value obtained through actual diagnosis work. For this reason, in a preferred embodiment of the present invention, the evaluation unit determines abnormality of the engine component from the evaluation value using a threshold value obtained from a statistical value of a result of an experiment performed in advance as an evaluation condition. . In one more preferred embodiment, the threshold value is configured to be changeable depending on measurement conditions such as measurement timing and measurement location.
Further, the inventor has found that an evaluation method in which the maximum value among a plurality of maximum amplitude values is an evaluation value is particularly effective for damage occurring in the bearing metal of the engine crankshaft and its surrounding area. It is confirmed from the experimental results. For this reason, in the engine diagnostic apparatus according to the present invention, the engine constituent member to be diagnosed is a bearing metal of a crankshaft. With such an engine diagnostic device according to the present invention that uses acoustic emission, the quality determination of the bearing area of the crankshaft, which is one of the important maintenance and inspection items for engines used in private power generators, etc. is highly reliable. You can do it. At that time, for quick diagnosis of a multi-cylinder engine, a receiving element is mounted on the outer surface of the engine housing where solid sound propagates from the bearing metal arranged corresponding to each cylinder. And diagnosed with multi-channel.

The acoustic emission wave is attenuated according to the distance between the engine constituent member to be diagnosed and the receiving element, that is, the propagation distance of the acoustic emission wave. Since this attenuation directly affects the amplitude value, if the amplitude values of acoustic emission waves having different propagation distances are adopted as they are, accurate abnormality evaluation cannot be performed. In addition, since the engine has various vibration sources (sound sources), the sound wave signal output from the receiving element includes a so-called noise vibration component that is propagated from such a vibration source. If it is adopted, accurate abnormal evaluation cannot be performed. For this reason, in a preferred embodiment of the present invention, the engine component and the receiving element to be diagnosed based on the sound wave attenuation of the engine component with respect to the sound wave signal output from the receiving element, And a signal pre-processing unit that performs high-pass filter processing on the sound wave signal that has been processed by the pre-amplifier . The reason why the high-pass filter processing is performed is that the noise vibration component has a lower frequency than the frequency component of the acoustic emission wave generated based on the abnormality of the engine component that is the subject of the present invention. Based on the findings of

  In particular, since it has also been found that what should be removed as noise vibration is vibration frequency due to engine speed and combustion sound frequency due to engine combustion, in one of the preferred embodiments of the present invention, the high-pass In the filter processing, a high-pass filter having a frequency exceeding the vibration frequency due to the engine speed and the combustion sound frequency due to engine combustion is used.

  As an evaluation value calculated from a plurality of maximum amplitude values, from an experimental finding, a maximum value among a plurality of maximum amplitude values and an average value or an intermediate value of the plurality of maximum amplitude values are the engines targeted by the present invention. It has been found that the evaluation value is appropriate as the value to be evaluated when the abnormality of the structural member is judged. In particular, the correlation between the maximum value of the plurality of maximum amplitude values and the occurrence of abnormality is good. For this reason, in one of the preferred embodiments of the present invention, the evaluation value calculation unit calculates the maximum value among a plurality of maximum amplitude values as the evaluation value.

It is a schematic diagram explaining the basic principle of this invention. It is a functional block diagram which shows one of the embodiments of the engine diagnostic apparatus by this invention. It is a schematic diagram which shows the example of arrangement | positioning of the receiving element with respect to an engine housing. It is a wave form diagram which shows an example of the sound wave signal after pre-processing. It is a graph which shows the processing result of the sound wave waveform as a list at the time of the diagnosis performed with respect to the bearing metal of various states.

Before describing a specific embodiment of the engine diagnosis apparatus according to the present invention, the basic principle of the present invention will be described with reference to FIG. This engine diagnostic device is an inspection device that uses acoustic emission (hereinafter abbreviated as AE), and generates elastic waves (vibration, sound waves) that are generated when the material structure cracks or develops. By detecting and processing the detection signal, normality or abnormality is determined.
A receiving element 2 that is an AE sensor is attached to a location where an AE wave emitted from an engine component to be diagnosed in the engine 1 can be received. The receiving element 2 is an ultrasonic transducer that converts an elastic wave into a sound wave signal, and a piezoelectric element is generally used.

  The sound wave signal output from the receiving element 2 is subjected to signal processing after being subjected to attenuation correction and amplification as necessary. Diagnosis of a specific engine component is performed by signal processing on a plurality of sound wave signals acquired sequentially (every measurement period). In FIG. 1, n sound wave signals acquired in different time regions S1... Sn (depending on the sampling repetition frequency) are handled. In this signal processing, first, the maximum amplitude value in the sound wave signal in each time domain is calculated. Here, the maximum amplitude value in each time domain is indicated by MA1... MAn.

Next, an evaluation value suitable for diagnosis is derived from the calculated n maximum amplitude values. The calculation method for deriving the evaluation value is determined in advance through experiments or the like. Here, G represents a function for deriving the evaluation value. That is, if the evaluation value is V, this evaluation value: V is
V = G (MA1,..., MAn)
Calculated by
One of the suitable evaluation value derivation functions is a function for obtaining the maximum value of a specified numerical group (argument), and if the function is described as Gmax,
V = Gmax (MA1,..., MAn)
It is expressed. That is, the maximum of the n maximum amplitude values is used as the evaluation value.
Another one of the evaluation value derivation functions is arithmetic average, and if the function is described as Gave,
V = Gave (MA1,..., MAn) = (MA1 +... + MAn) / n
It is expressed. That is, an average value of n maximum amplitude values is used as the evaluation value. Of course, it is also included in the present invention to use other functions that derive representative values from a plurality of numerical value groups used in statistical calculations.

  The evaluation value derived using the adopted evaluation value derivation function was created based on the evaluation value group calculated using the evaluation value derivation function in the experiment of the normal sample and the abnormal sample performed in advance. Compared with the normal / abnormal threshold value. When the evaluation value exceeds this threshold value (below depending on the type of evaluation value derivation function employed), it is determined that an abnormality has occurred in the diagnosis target location.

  Next, one specific embodiment of the engine diagnostic apparatus according to the present invention will be described. FIG. 2 is a functional block diagram of the engine diagnostic apparatus. A constituent member of the engine 1 to be diagnosed by the engine diagnostic device is a bearing metal 12 of the crankshaft 11. In order to detect an AE wave generated based on an abnormality such as wear or crack of the bearing metal 12, the receiving element 2 is mounted on the outer peripheral surface of the engine housing 13 at a location close to the bearing metal 12 and easily accessible. ing. As schematically shown in FIG. 3, the engine 1 is a 6-cylinder gas engine, and seven receiving elements 2 are mounted at positions where each cylinder is removed. Operates with no signal input.

  Each receiving element 2 is provided with a preamplifier 3, and a sound wave signal, which is an AE signal output from the receiving element 2, is amplified at an appropriate level. The sound wave signal sent to the processing unit 5 through the preamplifier 3 is subjected to preprocessing including filter processing in the signal preprocessing unit 51. Further, the signal preprocessing unit 51 processes the input sound wave signal into a signal form suitable for the subsequent signal processing. In the filter processing, a 100 kHz high-pass filter is used, and an example of a sound wave signal after the filter processing is shown in FIG.

  In addition to the signal preprocessing unit 51, the processing unit 5 includes a maximum amplitude value calculation unit 52, an evaluation value calculation unit 53, an evaluation unit 54, a threshold value setting unit 55, and these as functional units particularly related to the present invention. A processing management unit 50 that manages the operation of the functional units is constructed. Furthermore, a data output unit 56 for outputting the evaluation result by the processing management unit 50, the processing data used for the evaluation, the input sound wave signal, and the like to the outside is also provided.

  The maximum amplitude value calculation unit 52 calculates the maximum amplitude value in the sound wave signal in the predetermined time region (about 200 msec in this embodiment) preprocessed by the signal preprocessing unit 51. Since several tens of such sound wave signals are captured in the diagnosis of one measurement location, several tens of maximum amplitude values are calculated. If the processing time of the sound wave signal is not in time for generation of the sound wave signal, the sound wave signal is temporarily recorded in the buffer memory.

  In this embodiment, the evaluation value calculation unit 53 is configured to calculate the maximum of the n maximum amplitude values calculated by the maximum amplitude value calculation unit 52 as an evaluation value. Therefore, the threshold value setting unit 55 is set with a threshold value that is obtained as a normal / abnormal judgment condition for the bearing metal 12 of the engine 1 through an experiment that employs the maximum of the maximum amplitude value as the evaluation value. The evaluation unit 4 compares this threshold value with the evaluation value calculated by the evaluation value calculation unit 53 (maximum maximum amplitude value for each sound wave signal captured a plurality of times). When the evaluation value exceeds the threshold value, it is determined that there is an abnormality in the bearing metal 12 specified from the mounting position of the receiving element 2 of the corresponding measurement channel.

  The data output unit 56 connects the evaluation result of the evaluation unit 54, the raw sound wave signal (waveform data) input to the processing unit 5, the sound wave signal (waveform signal) processed by the processing unit 5, and the like. Output in a format suitable for the data format of the external device. As external devices, a media recorder 61, a monitor 62, a printer 63, an alarm device 64, a communication device 65, and the like are connected to the processing unit 5 or can be connected. The media recorder 61 records waveform data, diagnosis results, and the like together with identification codes of engine components that have been diagnosed and date / time data for history management. The monitor 62 and printer 63 visually output various data. The alarm device 64 alerts an operator when it is considered that an abnormality has occurred, and a buzzer, a lamp, or the like is used. Various data relating to diagnosis for performing analysis over time is stored in the database of the management center, and the communication device 65 is used for such data transmission. Further, by using this communication device 65, it is possible to monitor this diagnosis online from the outside.

  FIG. 5 is a graph showing the processing results at the time of diagnosis performed on the bearing metal in various states. The horizontal axis of this graph represents the signal channel (see FIG. 3) of the receiving element mounted on the outer peripheral surface of the engine housing 13 that receives the AE wave from the region of the bearing metal 12 corresponding to each cylinder of the 6-cylinder engine 1. Represents. The vertical axis represents the amplitude (V) of the sound wave waveform. The maximum value of the maximum value in each signal channel (that is, the sound wave waveform detected by each receiving element 2) is connected and indicated by a line graph. Different states of the gas engine 1 to be diagnosed are shown by three line graphs. A line graph indicated by a one-dot chain line represents a diagnosis result of the gas engine 1 in a new state. A line graph indicated by a dotted line represents a diagnosis result in the gas engine 1 in a slightly damaged state in a simulated manner. A line graph indicated by a solid line represents a diagnosis result in the gas engine 1 used severely. For this reason, a slight wear or damage does not give a diagnostic result that makes it possible to make a significant distinction. However, it seems that wear and damage must be considered under severe use and overhaul. Under such circumstances, it can be understood that the normal / abnormal determination, that is, the determination of whether or not the overhaul needs to be performed, is sufficiently possible. In particular, an evaluation value that a sound signal that is an AE wave that is emitted due to damage generated in the bearing metal of the engine crankshaft and its surrounding region has a good S / N ratio is obtained from a plurality of sound wave signals. It has been found that it is optimal to use the largest of the maximum amplitude values as the evaluation value. That is, the bearing metal 12 of the crankshaft 11 that requires overhaul can be estimated by evaluating the maximum value among the maximum amplitude values of the sound wave signal detected a plurality of times from the location.

  In FIG. 5, the value of the comma number V is shown as a threshold value for normal / abnormal determination. This threshold value is obtained from on-site sample experiments, but it can be overhauled fairly accurately by making corrections in consideration of diagnostic data obtained through repeated on-site diagnostic work. It becomes possible to determine the implementation period.

[Another embodiment]
(1) In the above-described embodiment, the diagnosis target is the bearing metal 12 of the gas engine 1, but other engine components such as an exhaust pipe, an intake pipe, a cylinder housing, a cylinder head, and the like may be the diagnosis target. it can.
(2) In the above-described embodiment, the maximum of a plurality of maximum amplitude values is adopted as the evaluation value. However, as described in the explanation of the basic principle using FIG. Various methods for calculating the representative values used in the statistics of can be adopted.
(3) In the above-described embodiment, a configuration in which multipoint inspection is performed at the same time by the multichannel method is adopted. However, in a simpler apparatus, a configuration in which diagnosis is performed for each place by a single channel method is adopted. Also good.

  The present invention can be applied to diagnosis of engine components by AE, in particular, determination of repair timing.

1: Engine 12: Bearing metal (diagnosis target area)
2: receiving element 50: processing management unit 51: signal preprocessing unit 52: maximum amplitude value calculation unit 53: evaluation value calculation unit 54: evaluation unit 55: threshold setting unit

Claims (5)

A receiving element that senses an acoustic emission wave emitted from an engine component during engine operation and outputs a sound wave signal;
A maximum amplitude value calculation unit for calculating a maximum amplitude value included in a predetermined time region of the sound wave signal for each measurement period;
An evaluation value calculation unit that calculates an evaluation value based on a plurality of the maximum amplitude values obtained over a plurality of measurement periods;
An evaluation unit that compares the evaluation value with a preset threshold value to determine abnormality of the engine component,
The engine component is a bearing metal of a crankshaft, and the receiving element is attached to the outer surface of the engine housing where the solid propagation sound from the bearing metal reaches, corresponding to the cylinder, and an evaluation result for each cylinder is output. Engine diagnostic device. A process including attenuation correction corresponding to the distance between the engine constituent member to be diagnosed and the receiving element is performed on the sound wave signal output from the receiving element based on the sound wave attenuation of the engine constituent member. A preamplifier,
The engine diagnostic apparatus according to claim 1, further comprising: a signal preprocessing unit that performs high-pass filter processing on the sound wave signal that has been processed by the preamplifier. The engine diagnostic apparatus according to claim 2, wherein in the high-pass filter process, a high-pass filter having a frequency that exceeds a vibration frequency caused by engine speed and a combustion sound frequency caused by engine combustion is used. The engine diagnostic apparatus according to any one of claims 1 to 3, wherein the evaluation value calculation unit calculates a maximum value among the plurality of maximum amplitude values as the evaluation value. The said evaluation part performs abnormality determination of the said engine structural member from the said evaluation value by making into an evaluation condition the threshold value calculated | required from the statistical value of the experimental result performed beforehand. Engine diagnostic device.

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