JPH08121235A - Misfire detection system by spectrum and its method - Google Patents

Abstract

PURPOSE: To provide a misfire detection system of internal combustion engines that can detect a wide range of misfire states precisely even in a transient operational phase. CONSTITUTION: The system and method for detecting misfire states via an analysis of spectral activities employs devices 309 and 313 for measuring acceleration characteristics indicative of the performance of an engine in operation. According to acceleration signals 317 from the acceleration measuring devices 309 and 313, a programmable filter depending on engine speed as at 335 provides filtered acceleration signals. A spectrum discriminator 319 produces a normal ignition signal 321 corresponding to spectrum energy in a normal ignition state and a misfire signal 323 corresponding to spectrum energy in a misfire state. A comparator 325 provides a misfire state command 327 when the misfire signal 323 exceeds the normal ignition signal 321 in magnitude.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to the field of misfire detection in internal combustion engines,
And more particularly, a method and corresponding apparatus for determining misfire during a combustion event in an engine by interpreting the spectral activity of the engine during operation.

[0002]

BACKGROUND OF THE INVENTION Various systems have been used on engines to detect misfires in combustion events. If a cylinder repeatedly misfires, fuel to that cylinder is typically shut off. This prevents a large amount of unburned fuel from passing over the exhaust catalyst. This is done to prevent degradation of the performance and useful life of the catalyst.

One type of system is coupled to an ignition system to detect misfires associated with ignition. This mechanism is capable of detecting only ignition-related misfire conditions, which is a subset of possible misfire conditions, and thus lacks the full functionality required to accurately determine misfire over a wide range of operating conditions. It is not convenient because

Another mechanism is to measure the temperature of the exhaust gas flow from the engine. It is also possible to determine the misfire state by detecting the contents of carbon monoxide and hydrocarbons. Both of these mechanisms suffer from the slow response speed of the sensor system and the limited durability of the sensor in adverse vehicle environments.

Another mechanism monitors the average angular velocity of the engine crankshaft. In an attempt to predict misfire conditions, a signature analysis was performed for this average engine crankshaft speed.
s) is performed. Other mechanisms rely on measuring average engine crankshaft acceleration. Both of these mechanisms are inaccurate because they rely on the average of multiple combustion cycles. This means that these mechanisms are subject to transient operating conditions and strong combustion variability.
It is a problem because it is inaccurate and unreliable during other states with a lity). Combustion variability occurs in a number of forms, including the effects of crankshaft torsion due to the resonance characteristics of the crankshaft, and the effects of various engine accessories such as alternators, air conditioner compressors, fans, and others.

In addition, the misfire component of the sensed signal varies considerably in amplitude and frequency over the entire operating range of the engine. Since the averaging mechanisms rely on predicting changes from steady state, they are inherently inaccurate under these transient operating conditions. These effects are typically attributable to reciprocating inertial torque and engine load torque fluctuations caused by crankshaft torsional vibrations.

Another mechanism uses pressure transducers to measure variations in pressure or flow in the exhaust path of a combustion chamber. By sign analysis, the output of this pressure transducer is compared to a predetermined signal to detect a misfire condition.

Other systems contemplate analysis of audio output from the engine. It relies on analyzing the ignition performance of the engine by coupling an audio sensor to the output of the exhaust system to measure the frequency spectrum of the exhaust noise.

[0009]

This mechanism, and the exhaust measurement mechanism described above, also have a number of drawbacks. For example, it substantially depends on the properties of the coupling medium, in this case in the exhaust system. The exhaust system includes an exhaust manifold coupled to an exhaust pipe, the exhaust pipe is coupled to a catalytic converter, the catalytic converter is coupled to a silencer, and the silencer is coupled to an exhaust stack. Because of such a structure, this configuration is susceptible to interference from audio noise sources that are unrelated to engine performance, including engine and vehicle vibrations coupled to the exhaust system. The resonance of this coupling medium can increase the harmonic spectrum provided by the engine. Also, because of its large volume size, the exhaust system acts like a low pass filter that reduces the available signal, thus affecting the accuracy of the measurement. In addition, the propagation time of the audio output from the engine changes as the exhaust system heats up or cools down. Further, accuracy under transient engine operating conditions is compromised by the time lag associated with the length of the exhaust system. Therefore, synchronous tuning of the engine cannot be guaranteed. Also, the length that the audio output of an individual cylinder travels varies from cylinder to cylinder, due to the different exhaust runner lengths of the exhaust manifold. This changes the delay from when the exhaust valve opens to when it is detected. This variable length coupling from each cylinder to the sensor means may also shift the harmonic spectrum provided by the engine. This is due to the reflection of the pressure wave caused by the different amount of time the pressure pulse requires to travel from the exhaust valve to the audio sensor in different cylinders. Additionally, the engine exhaust system is tuned for optimum engine performance. The use of this mechanism makes this tuning even more complicated, since it requires the extra consideration of having an audio sensor in the tuning path. Also, the audio sensor has a limited durability.

In summary, prior art misfire detection mechanisms are inaccurate, slow to respond to transient engine operating conditions, and lack the ability to detect the wide range of misfire conditions possible in an operating engine. Perfect.

Accordingly, it is also an object and need of the present invention to be accurate, capable of responding to transient engine operating conditions, and capable of detecting a wide range of misfire conditions possible in an operating engine. SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved system for detecting misfire in an internal combustion engine that requires only minimal configuration and is easily applicable to different engine families.

[0012]

SUMMARY OF THE INVENTION In accordance with the present invention, there is provided a device for improving signal fidelity in a misfire detection system of an operating engine, the device comprising the operating engine. Acceleration measuring means for providing an acceleration signal indicative of the acceleration behavior of the vehicle, means for determining the speed of the operating engine, and programmable filtering means depending on the speed of the operating engine. And a filtering means for providing a filtered acceleration signal in response to the acceleration signal provided by the acceleration measuring means.

Furthermore, the normal ignition signal is provided in response to the behavior of the acceleration, which receives the filtered acceleration signal provided by the filter means and which is due to a part of the composite signal representing the normal ignition state. And at the same time as providing the normal ignition signal, an acceleration discriminating means for providing a misfire signal in response to the behavior of acceleration by the other part of the composite signal representing the misfire state, and together with the acceleration. For receiving the normal ignition signal and the misfire signal provided by a discriminating means and providing a misfire indication when the magnitude of the misfire signal exceeds the magnitude of the normal ignition signal. Comparison means can be provided.

Such an arrangement provides a system for detecting the presence of a misfire condition by monitoring spectral activity through measuring motion associated with acceleration characteristics indicative of the performance of the combustion process of an operating engine. The disadvantages of the prior art are eliminated.

[0015]

The preferred embodiment describes a system for detecting the presence of a misfire condition by monitoring the spectral activity of an operating engine. In this preferred embodiment, certain characteristics, preferably acceleration characteristics, of the operating engine that indicate the performance of the combustion process,
The spectrum related to is considered. A number of different means for measuring this characteristic produce suitable information for determining misfire conditions. For example, by accelerometers means of measuring engine vibrations, optical means, ionization or ionization means, pressure means for measuring combustion phenomena in cylinders, or any movement related to acceleration characteristics indicative of the combustion process. Means for doing so are useful. One of ordinary skill in the art will recognize other similar means and methods that can be substituted for these means without departing from the spirit of this disclosure.

The charts of FIGS. 1 and 2 show the combustion performance of an operating engine in cycle / cycle.
3 shows the spectral behavior of acceleration in the s / revolution) region. The expression in the cycle / rotational region is convenient, because combustion, engine imbalances, and variations in acceleration due to engine accessories (such as alternators, air conditioner compressors, fans, etc.) are independent of engine speed. This is because they remain at the same cycle / rotation generation frequency.

FIG. 1 shows the engine ignition spectrum of a 4-stroke 6-cylinder engine under normal ignition conditions. The output of acceleration fluctuation is especially 3 (10
Notable in series starting with 1), 6 (103), and 9 (105) cycles / rev. Of course higher harmonics or partials (p
arteries) are in the series, but they are insignificant when compared to the noise of the whole tissue. Also note the strong response indicated by reference numeral 107. This represents the spectral response that results directly from the crankshaft twisting effect. The normal ignition spectrum phenomenon is independent of engine speed in the cycle / rotation region, and the spectrum of torsional vibrations is cycle / cycle, given that the torsional vibrations have a constant frequency behavior.
It should be noted that it can vary in the region of rotation.

FIG. 2 shows the engine ignition spectrum for a misfired condition where one cylinder is not ignited. The output is not only particularly pronounced in the series starting at 3 (101 '), 6 (103'), and 9 (105 ') cycles / rev, but also at 1/2 (20
1), 1 (203), 3/2 (205), 2 (2
It should be noted that it is also significant at 07), and 5/2 (209) cycles / revolution. The behavior of this sub-harmonic series shows that only one cylinder is misfiring. If a pair of cylinders misfires, significant energy will appear in the series starting with 1 and 2 cycles / revolution. This behavior is quite common and is due to the failure of the shared ignition coil typically found in today's ignition systems.

Of course, in engine configurations with different numbers of cylinders, the misfired ignition pairs will be different, but will also have predictable spectral behavior. Furthermore, in a non-even ignition engine, the spectral behavior of the acceleration characteristic has a correspondingly predictable spectral behavior.

Whether it is 2 or 4 strokes,
The basic or lowest order ignition frequency for all engines can be expressed by the relationship:

F = 360 / Δθ [cycle / revolution] In this case, 360 = degree / revolution (degrees / rev)
solution and uniform ignition (even)
For firing engines, Δq = frequency between cylinder firings, and uneven firing
For firing engines, Δq = the number of iterations in the firing pattern.

The basic or lowest order misfire frequency for all uniform ignition engines can be expressed as:

[Formula 2] f _{2 stroke} = 1 cycle / revolution

[Formula 3] f _{4 stroke} = 1/2 cycle / revolution

The entire series for the spectral relationships given above can be deterministically approximated as follows. The torque on the crankshaft of the engine due to the gas pressure for a single cylinder engine can be approximated by the equation:

[Equation 4] In this case, T _p = instantaneous pressure torque T _m = average torque of the engine W _n , f _n = coefficient varying with engine type and operating conditions n = harmonic order q = engine rotational position.

For a typical four-stroke engine with uniform or uniform ignition intervals, the torque vector increases when n is a multiple of the number of cylinders divided by two, and under normal operating conditions. Cancel for all other values of n in. However, FIG.
, And as previously mentioned, when a single cylinder misfires, all low orders (n = 1/2,
1,3 / 2,2, ...) are present in addition to the normal ignition order. If in the ignition order a misfire occurs in pairs with respect to the opposite stroke, then only the higher order exists, as mentioned previously. Therefore, misfire detection can be achieved by observing the presence of spectra in the series n = 1 / 2,1,3 / 2,2, .... This is valid for all engine loads and speeds.

A chart showing the characteristic frequencies for a four stroke, uniform ignition engine for different cylinder configurations is given as follows.

Table 1 Number of cylinders Ignition (lower than ignition) Additional frequency vs. Ignition frequency 1 Cylinder misfire Misfire ------------------------- −−−−−−−−−− 4 n = 2,4,6, ... n = 1 / 2,1,3 / 2, n = 1 ... 6 n = 3,6,9, ... n = 1 / 2,1,3 / 2, n = 1,2 ... 8 n = 4,8,12, ... n = 1 / 2,1,3 / 2, n = 1,2,3 ... Where n = cycles / revolution (cycles / revol)
)).

The spectrum resulting from a misfire condition will therefore be located at a fixed spectral distance below the spectrum associated with a normal ignition condition.

A system for recognizing behavior as described above is coupled to an operating engine and is spectral sensing means for providing a spectral signal representative of the spectral activity of the operating engine and indicative of engine performance. including. In the preferred embodiment, a crankshaft position sensor is used to measure the angular displacement, and is then conditioned to provide a composite signal representative of the acceleration of the crankshaft. Other embodiments, described in detail below, include other sensing mechanisms for measuring motion associated with acceleration characteristics that is indicative of the performance of the combustion process of an operating engine.

Spectral discriminating means receives the composite signal provided by said measuring means and provides a normal ignition signal corresponding to the spectral energy attributable to a portion of the composite signal representative of a normal ignition condition. If a misfire condition exists, the spectral discrimination means provides a misfire signal corresponding to the spectral energy due to the other portion of the composite signal representing the misfire condition of the engine that is still operating. A misfire indication is then provided if the amplitude of the misfire signal exceeds the amplitude of the ignition signal by a predetermined rate or amount.

FIG. 3 shows a system block diagram of a misfire detection system that applies this behavior recognition strategy to enable improved detection of misfire conditions in an operating engine. In the preferred embodiment, a 6 cylinder, 4 stroke engine is used. In the preferred embodiment, a discrete time signal processing element is used to configure the central element for detecting misfire conditions.

Alternatively, those skilled in the art will be aware of other equivalent embodiments, such as those using traditional continuous time signal processing elements, including traditional analog circuits. Discrete time signal processing was chosen because of the advantages it has over continuous time signal processing elements. These advantages include fewer components, stable decision performance, no aging, no drift, no adjustments, easy tuning for different engines, high noise immunity, and self-testing. Including the possibility.

As mentioned previously, a crankshaft displacement sensor is used to measure the angular displacement, which produces a composite signal representative of the crankshaft acceleration due to the performance of the combustion process in the engine that is to operate next. Prepared to provide. To make that measurement, FIG.
In, the sensor 301 is a rotating wheel 305 mounted on the crankshaft of an operating engine.
The upper passing tooth 303 is measured. This method of using toothed wheels on the crankshaft is commonplace in the field of engine control.
Of course, those skilled in the art will recognize numerous other, substantially equivalent means and methods for measuring angular displacement. An engine angular displacement signal 307 is provided by sensor 301. In the preferred embodiment, the angular displacement signal 307 is provided by the sensor 301 in response to engine operation.
Is a signal of a logic level that transits when the tooth 303 and the succeeding interval portion 311 are detected. Therefore, depending on the combustion process in the engine that operates, as the toothed wheel 305 rotates, the angular displacement signal 307 is substantially angular velocity, or a rectangular waveform that is a function of engine speed.

This angular displacement signal 307 is provided to element 309. Element 309 determines the acceleration of the crankshaft of the operating engine. Those skilled in the art will be aware of several means and methods for this. In the preferred embodiment, the elapsed time intervals between adjacent transitions of the square wave 307 are compared to determine crankshaft acceleration. It is preferable to filter this determined acceleration to remove any torsional vibrations or other acceleration effects that are not associated with misfire behavior. This will be described later.

The acceleration information is then provided to element 313. In the preferred embodiment, element 313 samples the acceleration information synchronously with the angular displacement of the engine. As mentioned previously, the spectral phenomenon of the acceleration information of interest, which is for detecting engine ignition and misfire spectra, is independent of engine speed if synchronous sampling of the engine is used. . Therefore, in this embodiment, element 313 is simply a gate controlled by the angular displacement signal 307. Element 313
Is a composite signal, or captured (a) that represents the engine's spectral emissions related to the combustion performance of the operating engine.
cquisitioned) The engine crankshaft acceleration signal 317 is output.

As mentioned previously, the preferred embodiment relies on discrete time signal processing elements. Element 315 represents a digital signal processor, or DSP. Elements of the system level block diagram of the components shown within element 315 represent microcoded hardware means with appropriate software routines. In this case, a Motorola DSP56001 is used as device 315.
Motorola's DSP56001 has 10 million (te
It has the ability to execute more than n million instructions and provides a dynamic range of 144 dB over a 24-bit wide data path. Of course, one of ordinary skill in the art will be aware of other equivalently useful DSP devices, or hardwired or other microcoded approaches having substantially the same function.

The key elements of this configuration include the digital filter represented by element 319. This filter is shown in Figure 7.
It consists of three separate filters detailed in

Referring to FIG. 7, this filter 319 is a noise filtering means arranged to remove any effect from the crankshaft torsional spectral components,
Alternatively, the notch filter 701 is included. The noise filtering means 701 or the noise spectrum discriminating means receives the composite spectrum signal, which in this case is the captured engine crankshaft acceleration signal 317, and is free of the predetermined noise component of the composite spectrum signal. A corrugated signal 703 is provided. In this case, the predetermined noise component is crankshaft torsional vibration. This filter 701 must be tuned in synchronism with engine speed because the cycles / revolution region is used in this embodiment and because the torsional vibrational spectral components are constant in the frequency domain. Therefore, the element 333
Determines the engine speed and provides an output variable 335 corresponding to the speed of the engine crankshaft measuring devices 301, 303, 305, 311 and 307.

Tuning of filter 701 is accomplished by obtaining a variable filter coefficient that corresponds to engine speed. This is especially true for the Motorola DSP56001
Convenient and alternative
ve) This is achieved by the use of a look-up table with filter coefficients. Alternatively, the recalculation of the filter coefficients causes the filter 7 to
01 can effectively be used for tuning.
Those skilled in the art will also be aware of how to resample the data into the frequency domain, apply a fixed filter, and, alternatively, resample into the cycle / rotation domain. The filter 701 is an ignition filter bank 70.
7 and the misfire filter bank 709 provide a noise filtered signal 703.

As described above for notch filter 701, filters 705 and 707 are also designed to account for spectral energy in the cycle / rotation domain. In other embodiments, some of which are described herein, these filters 701, 705, and 707 are designed to operate on data in the frequency domain.

The ignition filter bank 707 is 3, 6,
And to extract the expected spectral energy from the noise filtered signal 703 associated with normal ignition at 9 cycles / rev. Alternatively, if a lower accuracy is acceptable, the ignition filter bank 7
07 can directly extract the expected spectral energy from the composite spectral signal 317. The ignition filter bank 707 provides a normal ignition signal 321 that corresponds to the spectral energy, or output, attributable to the portion of the noise filtered signal 703 that represents the energy caused by the normal ignition conditions of the operating engine. To do.

The misfire filter bank 705 is 1/2,
It is designed to extract the expected spectral energy from the noise filtered signal 703 associated with misfire at 1,3 / 2,2,2 and 5/2 cycles / rev.
The filter bank 705 provides a misfire signal 323 corresponding to the spectral energy attributable to another portion of the composite signal that is representative of the misfire condition of the engine during operation.

Note that in the preferred embodiment, a six cylinder, four stroke engine is used. If other engine configurations were used, the appropriate spectral relationships would be those shown in Table 1.

Of course, one of ordinary skill in the art will appreciate that other notch filters 701 include cancellation of other unwanted systematic noise, such as due to force imbalances, road disturbances, and noise associated with engine accessories. You will recognize the uses of. Multiple notches, or differently tuned stopbands, can be used to filter out some of these other phenomena.

The digital filters 701, 705, 7
07 is configured as a finite impulse response or FIR filter. Alternatively, an infinite impulse response, or IIR filter can be used. A significant amount of today's excellent literature is available on the subject of digital filter design. This document contains McGraw-HillIn
c. Published in 1979 by Andreas
Written by Antoniou, "DIGITAL
FILTERS: ANALYSIS AND DES
Includes a textbook entitled "IGN". Pren
ice Hall Inc. Another outstanding publication published in 1990 by the company is "DESIGNAL SIGN".
AL PROCESSING IN VLSI ". In the described embodiment, the DSP 5 is implemented to implement these digital filters.
The device 315 of 6001 is programmed. F
IR filters are very commonly designed using this DSP 315.

In the preferred embodiment, and in some of the others described below, the fact that the spectral phenomenon of interest is independent of engine speed in the cycle / rev region makes it convenient to apply to synchronous sampling of engines. Has become a good one. To do this, for normal ignition at 3, 6, and 9 cycles / rev, and 1/2, 1, 3/2, 2, and 5
The coefficients of the digital filter for misfire at / 2 cycles / rev are sampled according to Nyquist theory in the cycle / rev domain, or specified in terms of data, rate. Therefore, when the engine changes speed, the coefficient of the digital filter has a fixed relationship to the sampling rate, so the phenomenon of interest remains constant in the cycle / rotation region, and the filters 701, 705, 707 Virtually follow.

After filtering, the normal ignition signal 321 and misfire signal 323 are converted to digital filters 705 and 707.
To element 325. Element 325 provides a misfire indication signal 327 when the amplitude of misfire signal 323 exceeds the amplitude of fire signal 321 by a predetermined rate or amount. This predetermined rate, etc., is preferably adjustable for different engine families.

Misfire indication signal 327 is preferably provided to element 329 which blocks the transfer of fuel to the misfiring cylinder. The misfire indication signal 327 can also be provided external to the system for reporting misfire conditions to other engine controls or diagnostics.

Element 331 is provided to identify the particular cylinder that matches the misfire indication signal 327.
Element 331 is the angular displacement signal 307 and the TDC marker signal 3 to calculate the cylinders currently in the combustion process.
Consider 33. Other sensors 335 and teeth
h) 337 is attached to the crankshaft of the engine and is used to provide the TDC, or cylinder identification, marker signal 333. Once the daunting task of accurately identifying misfires has been completed, numerous devices and methods for identifying and disabling misfiring cylinders are well known to those skilled in the art of engine design.

In accordance with the techniques described in the preferred embodiment above, the measured acceleration characteristics associated with ignition and misfire combustion performance are represented by the operating engine embodied by the toothed wheel 305 and the sensor 301. It should be noted that it does not depend on the measurement path length to and from the sensor system. This also applies in multi-cylinder designs. Furthermore, having free space as a coupling medium, as in prior art systems that rely on coupling medium, which inevitably bears an unbearable burden,
It does not load the engine and does not substantially affect the measured characteristics.

The elegance of this embodiment
e) includes fixed, stable spectral discrimination means depending on the input data rate obtained directly by the engine speed, or the sample rate. This engine-synchronized sampling technique is not possible with the tuned analog filter arrangement used in the prior art, but is more convenient with digital filters. Also, because a single point of the engine is used to measure combustion performance, the measurement is independent of measurement path length and shape, and thus does not introduce measurement path coupling or multipath error as in the prior art. .

Another embodiment is shown in FIGS. 4, 5 and 6. In FIG. 4, the same crankshaft sensing system is used with a digital filter associated with the frequency domain rather than the cycle / rotation domain.

Element 313 'inputs the crankshaft acceleration information provided by element 309 at a fixed sampling rate. Of course, this fixed sampling rate is chosen to be high enough to meet the requirements of Nyquist theory to ensure that aliasing does not occur. Element 313 'is constructed using gates controlled by a clocking oscillator, and outputs 317' at constant sample rate, element 319 '.
To provide.

Referring to FIG. 8, this filter 319 '
Is shown in detail in FIG.
Has substantially the same structure as found in. However, since this approach uses a fixed sampling rate in time, the data represented by 317 'is in the frequency domain. Therefore, the digital filter 7
01 'can be fixed and digital filters 705' and 707 'must be tunable to track engine speed. This is because the digital filter 701 'can be fixed because the sampling rate is fixed and the torsional vibration spectrum phenomenon is fixed in the frequency domain. Also, the ignition and misfire spectral phenomena of interest do not remain constant in the frequency domain as they did in the embodiment in the cycle / rotation domain, and thus these filters 705 ',
The 707 'must be tuned to track engine speed. In this example, the engine speed variable 33
5 is provided to tune filters 705 'and 707'.

As mentioned in the preferred embodiment, the filter 701 'is preferably designed as a notch filter, but here the filter coefficients are fixed and specified in the frequency domain. In particular, the filter 70
1 corresponds to 4.5 cycles / revolution at 3,210 RPM 2
It is fixedly tuned to 40 hertz (Hz). It is noted that this filter is fixed, since the effective crankshaft torsional vibration effect is fixed in the frequency domain.

The output 703 'of this filter 701', or the noise-filtered signal, is output to another filter 705 ',
And 707 'provide a torsion-free signal.

Filter 707 'is constructed as a digital multi-passband filter having a response that discriminates the spectrum corresponding to frequencies representing 3, 6, and 9 cycles / rev at known engine speeds. The coefficients of the digital filter 707 'are variable and specified in the frequency domain. In particular, the filter 707 'has 3,210
It is tuned to 160, 320 and 480 Hertz for RPM engine speeds. If the engine speed is reduced by 50% to 1,605 RPM,
As before, the new filter coefficients are looked up and the filter 707 'is correspondingly 80 Hz, 16
It is tuned to 0 and 240 hertz.

The filter 705 'also has 1/2, 1, 3 /
Configured as a digital multi-passband filter with a response that discriminates the spectrum corresponding to frequencies representing misfires at 2, 2, and 5/2 cycles / revolution. The coefficients of the digital filter 705 are variable and defined in the frequency domain. In particular, the filter 705 is 27 Hertz, 5 for an engine speed of 3,210 RPM.
It is tuned to 3 Hertz, 80 Hertz, 106 Hertz, and 160 Hertz. If the engine speed is 1,605RP
If you reduce M to 50%, the new filter coefficient becomes
As previously mentioned, the lookup and filter 7
05 is tuned accordingly to 13 Hertz, 27 Hertz, 40 Hertz, 53 Hertz, and 80 Hertz.

These filters 707 'and 705'
Each output a corresponding signal 321 'and 323' to indicate the spectral energy located at the expected ignition and misfire frequencies, respectively. The other elements operate as previously described in the description of FIG.

In FIG. 5, an accelerometer 501 mounted on the engine, conveniently the same one that can be used for knock detection, is used to measure combustion performance. Apart from the replacement of the sensor means, this embodiment operates in the same way as the preferred embodiment.

Although FIG. 5 is shown using the engine-synchronous sampling technique common for measurements in the cycle / rotation domain, the fixed sampling rate, or frequency domain, technique may be applied instead. In addition to the previously mentioned advantages, this approach shares the sensor with that provided for the knock detection function. This makes sense for cost savings, ease of factory installation and field repair, and field reliability. further,
This method is insensitive to torsional vibration of the crankshaft.

In FIG. 6, an in-cylinder sensor 601 is used to measure the combustion performance. Various types of sensors can be used. A subset of these include optical, pressure, and ionization sensors. Also, a sensor can be used for each of the cylinders. If sensors are provided for multiple cylinders, their outputs are preferably combined and input to the misfire detection system. Alternatively, each sensor can be analyzed individually. FIG. 6 shows a method in the frequency domain.

Element 313 'inputs the combustion information provided by in-cylinder sensor 601 at a fixed sampling rate. This element 313 'is the same as the element described in FIG. Sampled data 31
7'is provided to the filter 319 '. The filter 31
9'is designed to operate similarly to the filter described in FIG. The other elements operate as previously described in the description with respect to FIG.

Alternatively, if the cylinders are analyzed individually, the digital filter will be 1 /
Tuned to detect two (one-half) cycles / rev, lack of ignition or significantly attenuated ignition energy at 1/2 cycle / rev indicates misfire.

Of course, a sampling method synchronized with the engine can be used instead. In addition to the advantages previously mentioned, this technique is not affected by extraneous system noise sources, such as crankshaft torsion effects, which directly measure the combustion process and affect other sensing techniques. .

[0063]

In conclusion, a system is presented for detecting the presence of a misfire condition by monitoring spectral activity through measuring motion related acceleration characteristics indicative of the performance of the combustion process of an operating engine. It was
The preferred and alternative embodiments overcome the significant disadvantages of the prior art. These improvements include more accurate detection of misfire conditions because the measurement path is direct, improved insensitivity to external influences, single measurement path that is not affected by errors caused by multipath, And this technique involves avoiding any inaccuracy due to averaging multiple cycles. The system is also more stable and more predictable due to the digital filter configuration. Moreover, this approach responds better to transient engine operating conditions because multiple cycle averaging is not used. This approach is also independent of the energy radiated and does not create load problems on the measured engine as occurs in prior art systems. Since all engines exhibit misfire behavior in the known spectrum, this system requires minimal calibration and is easily applicable to different engine families.

Although the embodiments proposed herein depend on a particular systemic approach, it is clear that numerous other systems and methods (along with other devices) can be devised to produce the same advantages as this approach. is there.

[Brief description of drawings]

FIG. 1 is a graph showing an ignition spectrum of an engine in a normal ignition state in which all cylinders are ignited as designed.

FIG. 2 is a graph showing an ignition spectrum of an engine in a misfired state in which one cylinder is not igniting as designed.

FIG. 3 is a system block diagram of an ignition detection system according to a preferred embodiment of the present invention.

FIG. 4 is a system block diagram of a misfire detection system including spectrum analysis means responsive to engine speed according to another embodiment of the present invention.

FIG. 5 is a system block diagram of a misfire detection system including an engine-mounted accelerometer according to another embodiment of the present invention.

FIG. 6 is a system block diagram of a misfire detection system including an in-cylinder sensor according to another embodiment of the present invention.

FIG. 7 is a system block diagram of a digital filter used in embodiments of the present invention to extract torsional crankshaft vibration, ignition-related spectrum, and misfire-related spectrum, all in the cycle / rotation region.

FIG. 8 is a system block diagram of a digital filter used in embodiments of the present invention to extract torsional crankshaft vibration, ignition-related spectrum, and misfire-related spectrum, all in the frequency domain.

[Explanation of symbols]

301 Sensor 303 Wheel Teeth 305 Wheel 307 Engine Angular Displacement Signal 309 Crankshaft Acceleration Determining Element 311 Gap 313 Captured Engine Spectrum Radiating Element 315 Digital Signal Processor 317 Captured Engine Crankshaft Acceleration Signal 319 Spectral Analysis of Ignition and Misfire Related Spectra Element 321 Normal ignition signal 323 Misfire signal 325 Misfire instruction element 327 Misfire instruction signal 329 Fuel cutoff element 331 Working cylinder identification element 333 Engine speed determination element 335 Other sensor 337 Teeth

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor John F. Folly Wixom Road, Novi 48374, Michigan, USA 24930 (72) Inventor David Francowski Michigan, USA 48116, Wood Haven, Bellwood Drive 21848 (72) Inventor Stephen Elple 2226 Pine Hollow, Bryton, Michigan, Michigan, USA 2226

Claims (21)

[Claims] 1. An apparatus for improving signal fidelity in a misfire detection system of an operating engine, the acceleration measuring means for providing an acceleration signal indicative of the behavior of acceleration of the operating engine. Means for determining the speed of said operating engine, and a filter means programmable depending on the speed of said operating engine, said filter means comprising an acceleration signal provided by said acceleration measuring means. An apparatus for improving signal fidelity in a misfire detection system of an operating engine, comprising: providing a filtered acceleration signal in response to the. 2. A normal ignition signal, which further receives the filtered acceleration signal provided by the filter means, and which corresponds to the behavior of acceleration due to a part of a composite signal representing a normal ignition state. And at the same time as providing the normal ignition signal, the acceleration discriminating means for providing the misfire signal in response to the behavior of acceleration by the other part of the composite signal representing the misfire state, and together. A misfire indication is provided when the normal ignition signal and the misfire signal provided by the acceleration discriminating means are received and the magnitude of the misfire signal exceeds the magnitude of the normal ignition signal. A device according to claim 1, characterized in that it comprises: 3. The apparatus of claim 2 wherein said acceleration measuring means comprises means for measuring the angular acceleration of the engine corresponding to the angular displacement of said engine during operation. 4. An apparatus according to claim 2, wherein said acceleration measuring means comprises means for measuring an acceleration corresponding to the vibration of the engine during operation. 5. The acceleration measuring means comprises means for measuring an in-cylinder combustion phenomenon that depends on the behavior of acceleration of the operating engine.
An apparatus according to claim 1. 6. The apparatus of claim 2 further comprising means for shutting off fuel to a cylinder in response to providing the misfire indication. 7. The normal ignition acceleration discriminating means responsive to spectral energy attributable to a portion of a composite signal representative of a normal ignition condition, and the spectrum attributable to a portion of a composite signal representative of a misfire condition. An energy responsive misfire signal acceleration discriminating means comprising spectrally discriminating a predetermined fixed spectral distance lower than said normal ignition spectral discriminating means. The apparatus according to 2. 8. The misfire signal spectral discriminating means is one of the salient spectral positions of the normal ignition spectral discriminating means.
8. Apparatus according to claim 7, characterized in that it comprises a multi-spectral discriminating means which is significantly responsive to frequencies located at / 2,1, and 3/2 cycles / revolution. 9. Further comprising means for providing a synchronization signal representative of the speed of said operating engine, said acceleration measuring means of said operating engine being provided by said means for providing said synchronization signal. 9. The apparatus according to claim 8, wherein the acceleration is measured at a sample rate according to the applied synchronization signal. 10. The device according to claim 7, wherein the salient spectral position of the acceleration discriminating means is tunable. 11. A means for providing a synchronization signal representative of the speed of said operating engine, said significant spectral position of said acceleration discriminating means being provided by means for providing said synchronization signal. 11. Device according to claim 10, characterized in that it is tuned in response to the applied synchronization signal. 12. The acceleration measuring means is independent of the measurement path length between the acceleration related motion indicative of the performance of the combustion process of the operating engine and the means for measuring the acceleration. The device according to claim 2, wherein the device measures acceleration. 13. The acceleration measuring means measures the acceleration in a multi-cylinder engine without depending on a measurement path length between the measuring means and the operating engine. The apparatus according to 2. 14. The coupling medium used by the acceleration measuring means does not load the engine and has no substantial effect on the measured acceleration. apparatus. 15. An apparatus for detecting a misfire condition by interpreting the acceleration activity of an operating engine, the apparatus being coupled to the operating engine and providing a signal representative of the acceleration activity of the operating engine. An acceleration sensing means for providing and for providing a composite signal accordingly; an acceleration resulting from a portion of said composite signal receiving said composite signal provided by said acceleration sensing means and representing a normal ignition condition. A misfire, which corresponds to the behavior of the acceleration signal, and which at the same time as the provision of the normal ignition signal, corresponds to the behavior of acceleration due to the other part of the composite signal representing the misfire condition. Acceleration discriminating means for providing a signal, and providing an indication of a misfire condition when the magnitude of the misfire signal exceeds the magnitude of the ignition signal by a predetermined percentage or amount. Apparatus for detecting a misfire condition by interpreting acceleration activity of the engine during operation, characterized in that it comprises because of means. 16. The apparatus of claim 15 wherein said acceleration sensing means comprises an accelerometer coupled to said operating engine. 17. The apparatus of claim 15, wherein the acceleration sensing means comprises means for sensing acceleration of a crankshaft coupled to the operating engine. 18. The acceleration sensing means further comprises speed sensing means for providing a synchronization signal representative of the speed of the operating engine, wherein the acceleration discriminating means is the composite signal representative of a normal ignition condition. Frequency tunable normal ignition acceleration filtering means responsive to the behavior of acceleration due to a portion of the same, and frequency tunable misfire responsive to the behavior of acceleration due to a portion of said composite signal representative of a misfire condition. Signal acceleration filtering means, wherein the frequency tunable misfire signal acceleration filtering means is spectrally located lower than the frequency tunable normal ignition acceleration filtering means by a predetermined fixed spectral distance, And both the frequency tunable normal ignition acceleration filtering means and the frequency tunable non-ignition acceleration filtering means are provided by the speed sensing means. Apparatus according to claim 15, characterized in that the spectrally tuned in response to the synchronization signal. 19. The frequency tunable misfire signal acceleration filtering means comprises 1/2, 1, and 3/2 cycles / of the significant spectral position of the normal ignition spectrum discriminating means.
19. The apparatus of claim 18, comprising a plurality of acceleration filtering means responsive to a rotationally located acceleration spectrum. 20. A method of detecting a misfire condition by interpreting the acceleration of an operating engine, the method comprising providing an acceleration signal indicative of the behavior of acceleration of the operating engine. Determining the speed of the vehicle, providing an acceleration signal dependent on the speed of the operating engine determined in the determining step, and providing an acceleration signal filtered in response to the step, and providing in the measuring step. And spectrally discriminating the composite signal and providing a normal ignition signal corresponding to spectral energy due to a portion of the composite signal representative of a normal ignition condition of the operating engine, and
At the same time as providing the normal ignition signal, providing a misfire signal corresponding to spectral energy due to another portion of the composite signal representative of a misfire condition in the operating engine, and together with the measuring step. Comparing the normal ignition signal and the misfire signal, and providing a misfire indication when the magnitude of the misfire signal exceeds the magnitude of the normal ignition signal. A method of detecting a misfire condition by interpreting the acceleration of an operating engine, the method comprising: 21. An apparatus for detecting a misfire condition by interpreting the spectral activity of an operating engine, the characteristic being indicative of the performance of the combustion process of the operating engine, and Means for providing a composite spectral signal representative of performance, receiving the composite spectral signal provided by means for measuring the characteristic, and noise filtered without a predetermined noise component of the composite spectral signal. Noise spectrum discriminating means for providing a signal, a portion of the composite signal receiving the noise filtered signal provided by the noise spectrum discriminating means and representative of a normal ignition condition in the operating engine. To provide a normal ignition signal in response to the spectral energy due to A spectral discrimination means for providing a misfire signal, the magnitude of said misfire signal corresponding to the spectral energy due to the other part of said composite signal representing the misfire condition, Means for providing an indication of a misfire condition when a predetermined percentage or amount is exceeded, a device for detecting a misfire condition by interpreting the spectral activity of an operating engine.