JP2003065142A - Engine misfire detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply and surely detect a misfire. SOLUTION: A gas engine 2 is provided with a vibration sensor 10. A band pass filter 11 selectively extracts component of a frequency band adjacent to a frequency corresponding to a natural frequency of the gas engine 2 from vibration detected from the gas engine 2 by the vibration sensor 10. An abnormality determination circuit 12 determines that a misfire abnormality occurs if signal level of the frequency band component corresponding to the natural frequency of the gas engine 2 gets greater than a value in a normal state. Since the frequency band component corresponding to the natural frequency has lower frequencies than that of noise component such as environmental noise, the band pass filter 11 eliminates noise and misfire abnormality is surely judged. When the gas engine 2 drives a generator at a fixed rotation speed, vibration component adjacent to a frequency corresponding to the rotation speed can be selected with a band pass filter 15 to detect abnormality of a rotation mechanism. Abnormality detection results can be remotely monitored by a monitoring device 21 via Internet 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine misfire detection device for detecting a fuel combustion failure in an engine used for various power sources.

[0002]

2. Description of the Related Art Conventionally, engines have been used as various power sources. For example, in a cogeneration facility with a relatively small capacity, a gas engine that uses city gas as a power source is used as a power source, and the generated mechanical work drives a generator to rotate, and exhaust gas is also used as a heat source. There is. A gas engine has a plurality of cylinders, and repeats the processes of intake and combustion of fuel and air as the piston reciprocates in each cylinder. Combustion is explosively carried out by ignition by a spark plug, and a piston rotates a crankshaft by combustion pressure and a rotational output can be taken out.

The spark plug ignites a mixture of fuel and air in the cylinder by electric discharge, and causes explosive combustion.
For this reason, the spark plug is exposed to a harsh environment, is damaged little by little each time it is ignited, and its performance deteriorates with continued use, which makes reliable ignition difficult. The extent to which the spark plug can be used can be predicted to some extent in advance as the life based on the acceleration test result and the like. Therefore, in the cogeneration equipment that is actually used, the spark plug is replaced when it reaches the end of its life, before the spark plug deteriorates and misfires occur.

Engine misfire may occur due to factors other than the spark plug. If the misfire occurs in a specific cylinder with the highest frequency, a biased load is applied to the crankshaft and the like, which may deform the crankshaft and prevent smooth rotation output. In an engine with multiple cylinders, even if the spark plugs are replaced in all cylinders at the same time, the life of each spark plug varies, and the lifespan of all cylinders does not end at the same time. It is possible that a misfire will occur in a shorter time. When the engine misfires, the fuel is discharged without being burned, the fuel is not used effectively, and air pollution may occur.

A prior art of a misfire detection device for directly detecting an engine misfire is disclosed in, for example, Japanese Patent Laid-Open No. 5-1131.
No. 49 publication. In this publication, a vibration sensor mounted on the engine detects engine vibration including a vibration component at the time of misfire. The vibration component at the time of misfire is taken out by a low pass filter, converted into a digital signal,
The digital filter extracts the misfire signal.

In the paragraph [0015], "The digital filter 4 is a bandpass filter that extracts only the misfire vibration component from the signal that has passed through the LPF 2, and its filter characteristic is mechanical noise included in the vibration sensor signal,
The lower cutoff frequency is 10 to 50 Hz, and the upper cutoff frequency is 50 to 10 to eliminate knocking vibrations.
It has a steep attenuation characteristic of 00 Hz. It is described that a digital filter is easier to realize than an analog filter in order to obtain a steep attenuation characteristic. ”

[0007]

In the prior art of the misfire detection device for detecting the misfire of the engine, Japanese Patent Laid-Open Publication No. Hei 5 (1998) -58200 is known.
FIG. 2 of Japanese Patent No. 113149 discloses a frequency analysis diagram of a vibration sensor, which is 30 in a frequency range of 25 Hz to 20 kHz.
It is shown that the signal level rises in the vicinity of Hz to 500 Hz at the time of misfire as compared with that at the time of normal ignition. However, this difference is relatively small and difficult to determine. With the electrical ignition waveform shown in FIG. 3 and the internal pressure sensor output waveform shown in FIG. 6, misfire determination is relatively easy. However, if these waveforms are detected and determined, a large amount of cost is required as compared with the case where the vibration sensor is installed.

An object of the present invention is to provide an engine misfire detection device which can detect misfire easily and reliably.

[0009]

SUMMARY OF THE INVENTION The present invention is an engine misfire detection device for detecting combustion failure in an engine that burns fuel in an engine to obtain mechanical work, and is a vibration sensor for detecting engine vibration. And a filter for selectively extracting the frequency band including the natural frequency component of the engine from the vibration detected by the vibration sensor, and the magnitude of the vibration component extracted by the filter is input, and the magnitude of the vibration component is An engine misfire, comprising: an abnormality determination unit that outputs a signal indicating a misfire abnormality when determining whether or not to respond when a misfire phenomenon occurs, and when determining that the magnitude of a vibration component corresponds to when a misfire phenomenon occurs. It is a detection device.

According to the present invention, from the vibration of the engine detected by the vibration sensor by the filter, the frequency range corresponding to the natural frequency within the frequency band including the natural frequency component of the engine, for example, the frequency band of 10 and several Hz or less. A range of 20% is selectively extracted. In an engine that burns fuel in the engine to obtain mechanical work, if a misfire, which is a combustion failure, occurs, the output from the cylinder in which the misfire occurred disappears, so the balance of the driving force between the cylinders is lost and It is equivalent to a state where a shock is applied to the. Therefore, the natural vibration of the engine is excited, and the vibration sensor detects the vibration in the frequency band in the vicinity thereof. Since the frequency band of the noise component is higher than the frequency corresponding to the natural vibration, the misfire can be effectively detected by removing the noise component.

Further, the present invention is characterized by further including remote monitoring means for remotely monitoring a signal indicating the misfire abnormality output from the abnormality determining means via a data communication network.

According to the present invention, the engine misfire abnormality is remotely monitored via the data communication network.
It is possible to intensively monitor the misfire abnormalities of the engines installed at multiple locations.

The present invention further includes a rotating mechanism abnormality determining means for determining an abnormality of the rotating mechanism by selectively extracting a vibration component having a frequency band different from that of the filter and corresponding to a predetermined rotating mechanism abnormality. It is characterized by

According to the present invention, not only the engine misfire abnormality but also the rotation mechanism abnormality can be effectively judged by selectively extracting the corresponding vibration component, and the use of the engine rotation output can be reliable. Can be done in high condition.

[0015]

1 shows a schematic system configuration of an engine misfire detection apparatus 1 according to an embodiment of the present invention. The engine misfire device 1 of this embodiment is used to detect a misfire phenomenon of the gas engine 2. The gas engine 2 uses, for example, city gas as a fuel and is used as a power source and a heat source of a cogeneration facility.
The gas engine 2 is a reciprocating internal combustion engine. The engine body 3 is provided with a plurality of cylinders 4, and each cylinder 4 is provided with an ignition plug 5. In the gas engine 2 used for the cogeneration facility, the number of the cylinders 4 may reach ten or more. Electric energy is supplied to the spark plug 5 at a predetermined timing, and a mixture of fuel and air drawn into the cylinder 4 is ignited by spark discharge. Since the spark plug 5 repeats spark discharge during use, the spark plug 5 is worn out little by little, and it becomes impossible to reliably ignite the air-fuel mixture. The engine misfire detection device 1 is arranged so that the spark plug 5 can be discharged before the life of the spark plug 5 is expired.
The purpose is to preventive maintenance such as replacement maintenance.

The engine misfire detection device 1 of this embodiment is
A vibration sensor 10, a bandpass filter 11, an abnormality determination circuit 12, an A / D conversion circuit 13, and a misfire abnormality signal output circuit 14 are included, and the vibration of the engine body 3 is detected to determine whether or not a misfire abnormality has occurred. judge. In addition, the bandpass filter 15, the abnormality determination circuit 16, the A / D conversion circuit 1
7 and the rotation mechanism abnormality signal output circuit 18, it is possible to detect rotation mechanism abnormality such as unbalance or misalignment of the rotation mechanism which is an abnormal phenomenon of the gas engine 2 other than the misfire phenomenon. The vibration sensor 10 is attached to the engine body 3 of the gas engine 2, detects mechanical vibration generated in the engine body 3, and converts the detected mechanical vibration into an electric signal. Such a vibration sensor 10
It is possible to convert vibration into an electric signal by utilizing a piezoelectric phenomenon or an electromagnetic phenomenon. The electrical output from the vibration sensor 10 is amplified by the signal amplification circuit 19 and input to the bandpass filters 11 and 15. Vibration sensor 10
Is mounted on the engine body 3, the vibration sensor 10 and the signal amplification circuit 19 are electrically connected by a signal cable or the like to separate the main part of the engine misfire detection device 1 from the vibration sensor 10. I'll do it.

The signals output from the misfire abnormal signal output circuit 14 and the rotating mechanism abnormal signal output circuit 18 of the engine misfire detection device 1 are transmitted from a public telephone line, a dedicated data communication line or the like through a data communication network such as the Internet 20. , Is input to the monitoring device 21 installed in a cogeneration facility management center or the like. Monitoring device 21
Is installed to monitor the operating status of multiple cogeneration facilities in a centralized manner and perform appropriate management. Once the gas engine 2 has started operation,
It is possible to continue operation without major problems. However,
When an abnormality occurs such as a misfire phenomenon due to the end of the life of the spark plug 5, it is necessary to take measures against the background of highly specialized technology. In the situation where cogeneration facilities are widespread and relatively small-scale facilities are distributed and distributed in various places, it is better to have a management center, etc. It is more efficient to install and manage multiple cogeneration facilities centrally.

Deterioration of the spark plug 5 gradually progresses, and the occurrence of the misfire phenomenon also gradually increases. If an initial misfire phenomenon can be remotely detected by the management center, an engineer is dispatched to the gas engine 3 in which misfire is detected, and the spark plug 5 is replaced to effectively maintain the gas engine 2. be able to.

FIG. 2 shows a vibration waveform that passes through the bandpass filter 11 of FIG. Shows the vibration waveform at the time of normal operation, and shows the vibration waveform at the time of misfire occurrence. The bandpass filter 11 selectively passes the frequency band of 5 to 8 Hz. The vibration waveform in this frequency band has a clear signal level difference between the normal state and the occurrence of misfire, as can be seen by comparing and. A / D conversion circuit 15 of FIG. 1 performs analog / digital conversion on the signal level having this clear difference,
The abnormality determination circuit 12 determines whether or not there is a misfire abnormality based on the signal level. In the abnormality determination circuit 12, a reference level is set so that the signal level in a normal state falls within the reference,
When the signal level is higher than this reference level, it is determined that a misfire abnormality has occurred. The misfire abnormality signal output circuit 14 outputs the determination result of the abnormality determination circuit 12 to the outside. The gas engine misfire detection device 1 is provided with an alarm lamp, a buzzer, etc., and when a "fault signal" indicating a misfire abnormality is output from the misfire abnormality determination circuit 12, a misfire abnormality signal output circuit 14
It is also possible to drive a lamp or a buzzer to warn of the occurrence of misfire abnormalities by light or sound.

FIG. 3 shows waveforms in the entire frequency band detected by the vibration sensor 10 of FIG. 1 from the engine body 3 in comparison between normal operation and misfire. And with (a)
Shows a time-varying waveform, and (b) shows a frequency spectrum. In the frequency spectrum shown in (b),
There is a peak at 5.525kHz during normal operation of
It can be seen that there is a peak at 5.550 kHz at the time of misfire, but it is not recognized that there is a significant difference with this alone. The level change in the entire frequency band as shown in (b) is also disclosed in Japanese Patent Laid-Open No. 5-113149 as FIG. In FIG. 2 of Japanese Patent Application Laid-Open No. 5-113149, a misfire and an ignition are distinguished by a solid line and a broken line,
Although they are displayed overlaid on the same graph and the differences are emphasized, it cannot be absolutely asserted that they are clearly different.

In FIG. 4, attention is paid to the fact that the frequency corresponding to the natural frequency of the gas engine 2 is 7.5 Hz, and the vicinity of this frequency is a frequency band within the range of ± 20% of 6 to.
It is selected at 9 Hz, and waveform changes are shown in comparison between normal and misfire. Similar to FIG. 3, (a) shows a time-varying waveform, and (b) shows a frequency spectrum. In the frequency spectrum shown in (b), it can be seen that there is a peak at 7.5 Hz corresponding to the natural vibration, and the signal level becomes large at the time of misfire. In the example shown in FIG. 2, the frequency band is set to 5 to 8 Hz, but the component of 7.5 Hz corresponding to this natural vibration is included. In the installation environment of the gas engine 2, noise components such as noise are extremely large. However, the frequency component corresponding to such natural vibration of the gas engine 2 is often less than 10 Hz, which is lower than the frequency band of the noise component, and the bandpass filter 11 effectively attenuates the noise component. be able to.

Further, in FIG. 1, the bandpass filter 11 is used.
Although the level of the signal that has passed through is converted into digital data by the A / D conversion circuit 13 and the abnormality determination circuit 12 determines whether or not there is a misfire abnormality, the level of the analog signal is normal without being converted into digital data. It is also possible to determine whether or not there is a misfire abnormality by comparing the signal level at that time with an analog comparator or the like. Furthermore, the output of the vibration sensor 10 or the output of the signal amplification circuit 19 is first converted into a digital signal,
A digital filter may be used in place of the analog signal filter such as the bandpass filter 11, and may be realized by a digital signal processor (DSP) including the abnormality determination circuit 12. When a digital signal processor is used, the characteristics of the filter, the abnormality determination standard, etc. can be easily changed by changing the program.

In the engine misfire detection device 1 of FIG. 1, the bandpass filter 15 selectively extracts the vibration component related to the rotation of the gas engine 2. The pass frequency band of the band pass filter 15 is ± 20 with the center frequency being the rotation frequency corresponding to the rotation speed of the gas engine 2 at a normal time.
Set to about%. Since the gas engine 2 used for the cogeneration facility drives the generator to rotate, the rotation speed is kept constant. Therefore, the pass frequency band of the bandpass filter 15 can also be set to be constant. The rotation mechanism abnormality detection by the abnormality determination circuit 16 is performed by analyzing the rotation frequency component, and particularly, the whirling phenomenon caused by the imbalance of the gas engine 2, misalignment, and abnormal bearing wear is detected. By making it possible to detect such a rotation mechanism abnormality, it is possible to reliably monitor the operating state of the gas engine 2. Since the misfire phenomenon and the rotation mechanism abnormality are monitored based on the detection output from the same vibration sensor 10, it is possible to suppress an increase in cost. It goes without saying that the gas engine misfire detection device 1 may only detect misfire abnormalities.

The engine misfire detection device 1 of this embodiment is
Gas engine 2 used for cogeneration equipment
Although the misfire is detected by, the concept of detecting the misfire from the frequency band component near the natural frequency of the engine according to the present invention can be applied to other engines. The invention can be applied not only to an engine used stationary, but also to an engine mounted on a moving body such as an automobile, a railroad vehicle, and a ship.

[0025]

As described above, according to the present invention, the frequency band including the natural frequency component of the engine is selectively extracted by the filter, and it is easy to determine whether or not a misfire, which is a combustion failure, has occurred. And it can be detected reliably. Since the frequency band of the noise component is higher than the frequency band corresponding to the natural frequency of the engine, misfire can be effectively detected by removing the noise component.

Further, according to the present invention, engine misfire abnormality can be remotely monitored via the data communication network.

Further, according to the present invention, it is possible to effectively determine not only the misfire of the engine but also the abnormality of the rotating mechanism, and the rotation output of the engine can be utilized with high reliability.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic system configuration of an engine misfire detection device 1 according to an embodiment of the present invention.

FIG. 2 is a graph showing vibration waveforms for determining whether or not there is a misfire abnormality in an abnormality determination circuit 12 of FIG. 1 in a normal state and in an abnormal state.

FIG. 3 is a graph showing changes in vibration frequency detected by the vibration sensor 10 of FIG. 1 and its frequency spectrum at all frequencies in a normal state and in an abnormal state.

FIG. 4 is a graph showing changes in a vibration waveform detected by the vibration sensor 10 of FIG. 1 and its frequency spectrum in the vicinity of a natural frequency in a normal state and an abnormal state.

[Explanation of symbols]

1 Engine misfire detection device 2 gas engine 5 spark plugs 10 Vibration sensor 11,15 bandpass filter 12, 16 Abnormality judgment circuit 14 Misfire abnormal signal output circuit 18 Rotation mechanism abnormality signal output circuit 20 Internet 21 Monitoring device

Continued front page    (72) Inventor Junzo Narano             4-1-2 Hirano-cho, Chuo-ku, Osaka-shi, Osaka Prefecture               Within Osaka Gas Co., Ltd. (72) Inventor Noboru Tsubakihara             4-1-2 Hirano-cho, Chuo-ku, Osaka-shi, Osaka Prefecture               Within Osaka Gas Co., Ltd. F term (reference) 3G084 AA05 BA33 DA27 DA28 EA02                       EB02 EB06 FA00 FA24                 3G301 HA22 HA27 JA23 JB09 JB10                       NA06 NB07 NB20 PE00Z

Claims (3)

[Claims] 1. An engine misfire detection device for detecting a combustion failure in an engine that burns fuel in an engine to obtain mechanical work, the vibration sensor detecting vibration of the engine, and the vibration detected by the vibration sensor. From which the frequency band including the natural frequency component of the engine is selectively extracted and the magnitude of the vibration component extracted by the filter is input, and whether or not the magnitude of the vibration component corresponds to the occurrence of the misfire phenomenon An engine misfire detection device, comprising: an abnormality determination unit that outputs a signal indicating a misfire abnormality when determining whether the magnitude of the vibration component corresponds to the occurrence of the misfire phenomenon. 2. The engine misfire detection according to claim 1, further comprising remote monitoring means for remotely monitoring a signal indicating the misfire abnormality output from the abnormality determination means via a data communication network. apparatus. 3. A frequency band different from that of the filter,
The engine misfire detection device according to claim 1 or 2, further comprising: a rotation mechanism abnormality determination means for selectively extracting a vibration component corresponding to a predetermined rotation mechanism abnormality to determine an abnormality of the rotation mechanism.