JP2001055955A - Ignition timing sensing method for internal combustion engine and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ignition timing sensing method and device for an internal combustion engine which can estimate an ignition timing independently of an operation condition of the internal combustion engine. SOLUTION: An internal combustion engine has a pressure sensor for sensing inside pressure of a cylinder. In such an internal combustion engine, fluctuation of the inside pressure of the specified cylinder is sensed from a compression stroke to an explosion stroke, wavelet-conversion is carried out in respect to a signal indicating fluctuation of the pressure inside the cylinder, a characteristic peak is sensed from a spectrum of the signal which is wavelet-converted, and the sensed peak is determined as an ignition timing. In such a case, in order to suppress calculation work of the wavelet-conversion, the signal of the inside pressure of the cylinder is first divided into plural frequency bands which are continuously distributed from low to high bands. Wavelet-conversion is performed and an ignition timing is obtained in each frequency band. The ignition timing in the low frequency band is corrected by the ignition timing in the high frequency band, for improving accuracy of the ignition timing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for detecting an ignition timing of an internal combustion engine, and more particularly, to an internal combustion engine having no spark plug such as a diesel engine.
The present invention relates to a method and a device for detecting an ignition timing of an internal combustion engine capable of accurately detecting an ignition timing in a cylinder from a change in a cylinder pressure.

[0002]

2. Description of the Related Art Conventionally, in an internal combustion engine such as a diesel engine, it is important to detect the ignition timing of fuel in a cylinder in order to optimally control the timing of fuel injection into the cylinder. In general, the ignition timing of fuel in the cylinder can be detected from a change in the in-cylinder pressure waveform. Methods are known. Here, motoring refers to rotation in which a spark plug does not ignite in a cylinder in a gasoline engine, and rotation in which fuel injection is not performed in a diesel engine.

FIG. 1 (a) shows a first example of a conventional method for detecting the ignition timing of fuel in a cylinder. FIG. 1 (a) shows a waveform of a change in an in-cylinder pressure waveform in a cylinder of a predetermined cylinder of an internal combustion engine. 5 shows a difference waveform (combustion pressure waveform) obtained by subtracting the motoring waveform at this rotation speed. Since this differential waveform indicates an increase in combustion pressure due to ignition of fuel in the cylinder, conventionally, the ignition timing in the cylinder has been detected from a change point of the differential waveform.

FIG. 1 (b) shows a second example of a conventional method for detecting the ignition timing of fuel in a cylinder. A differential waveform obtained by differentiating a cylinder pressure waveform in a cylinder of a predetermined cylinder of an internal combustion engine is shown. It shows. Also, the waveform obtained by differentiating the motoring waveform shown in (a) becomes as shown by the broken line in (b), and then smoothly rises and then decreases smoothly. On the other hand, the differential waveform of the in-cylinder pressure waveform rises smoothly from the differential value of the motoring waveform due to an increase in combustion pressure due to the ignition of fuel in the cylinder, and then falls again to be lower than the differential value of the motoring waveform. It becomes a waveform. Conventionally, the ignition timing is detected by setting a certain portion of the differentiated waveform as a threshold. That is, the combustion state is detected by looking at the changing point of the differential value of the in-cylinder pressure.

[0005]

However, there is a problem that the noise of the diesel engine is large at the time of idling, and it is known that this noise is caused by the rise of the combustion waveform. There is an attempt to burn as smoothly as possible. Then, the change in the in-cylinder pressure waveform becomes slow as shown in FIG. 2 (a), and there is a problem that the conventional ignition timing detection method based on the change in the in-cylinder pressure waveform cannot be applied.

Further, when the fuel injection timing is advanced or retarded in a diesel engine to improve combustion,
At the time of advance, the peak point of the in-cylinder pressure due to combustion approaches the peak value of the compression pressure as shown in FIG. 2 (b), and at the time of retard the peak of the in-cylinder pressure due to combustion as shown in FIG. 2 (c). Since the point moves away from the peak value of the compression pressure, it has not been known which point is the peak due to combustion, that is, the ignition time.

Further, when pilot injection is performed before main injection of a diesel engine to improve combustion, the change in the in-cylinder pressure waveform becomes smooth as shown in FIG.
It was unknown where the ignition was going. As described above, in the conventional ignition timing detection method, since the change in the in-cylinder pressure waveform becomes small at the time of slow combustion, advance, retard, pilot injection, etc., the ignition timing detection accuracy is low. In some cases, the ignition timing cannot be detected due to disturbance noise.

[0008] Accordingly, the present invention provides a method for slow combustion, advance,
Alternatively, even when the change in the in-cylinder pressure waveform becomes small, such as when the valve is retarded or when pilot injection is performed, the ignition timing can be reduced by applying a wavelet transform to the analysis of the in-cylinder pressure waveform to make it easier to find discontinuous points. It is an object of the present invention to provide a method and an apparatus for detecting an ignition timing of an internal combustion engine, which can detect the combustion state accurately and make it possible to predict an outline of a combustion state.

Further, according to the present invention, when the wavelet transform is applied to the analysis of the combustion pressure waveform, the wavelet transform is realized by a simple circuit, and the configuration of the control circuit required for the analysis can be simplified. A second object is to provide a method and a device for detecting the ignition timing of an engine.

[0010]

The features of the present invention to achieve the above object are described below as first to ninth inventions. According to a first aspect of the present invention, there is provided a method for detecting an ignition timing in an internal combustion engine provided with a pressure sensor for detecting a pressure in a cylinder of the internal combustion engine. Detecting a change in pressure, performing a wavelet transform on a signal indicating a change in pressure in the cylinder, detecting a characteristic peak from the spectrum of the wavelet-transformed signal, and detecting the detected peak. Is determined as the ignition timing.

According to a second aspect of the present invention, there is provided a method for detecting an ignition timing in an internal combustion engine provided with a pressure sensor for detecting a pressure in a cylinder of the internal combustion engine. Detecting the change in the pressure in the cylinder, and dividing the signal indicating the change in the pressure in the cylinder into a plurality of frequency bands distributed continuously from a low frequency side to a high frequency side by dividing the signal at a predetermined frequency. Performing a high-speed wavelet transform on the signal of each divided frequency band, and determining an ignition timing for each frequency band from a spectrum of the signal subjected to the high-speed wavelet transform for each frequency band, The process of correcting the ignition timing determined in the lower frequency band by the ignition timing determined in the frequency band adjacent to the higher frequency band,
There is provided a step of sequentially repeating the operation from the lowest frequency side and a step of determining the ignition timing corrected with the ignition timing determined in the highest frequency band as the final ignition timing.

According to a third aspect of the present invention, in the second aspect, the step of determining the ignition timing for each frequency band from the spectrum of the signal subjected to the high-speed wavelet transform for each frequency band is performed in the cylinder. Sampling the signal indicating the change in pressure at every predetermined clock, and comparing the wavelet transform value of the in-cylinder pressure signal at the time of sampling with the wavelet transform value of the motoring value which is the cylinder pressure value at the time of non-ignition. And determining the ignition timing from the difference between the wavelet transform value and the wavelet transform value of the motoring value.

According to a fourth aspect of the present invention, in the third aspect, the ignition timing is determined using linear interpolation with reference to a map in which the relationship between the ignition timing and the difference value is set in advance. That's what I did. According to a fifth aspect of the present invention, in the third or fourth aspect, the sampling interval is longer in a low frequency band than in a high frequency band.

A structural feature of the sixth invention is that, in any one of the third to fifth inventions, the clock is a fixed clock having a fixed oscillation frequency. According to a seventh aspect of the present invention, in any one of the third to fifth aspects, the clock is a clock synchronized with the crank angle of the internal combustion engine. The constitutional features of the eighth invention are as follows.
The ignition timing detection device of the internal combustion engine is provided with a pressure sensor provided in at least one cylinder of the internal combustion engine and detecting a change in pressure in the cylinder during a compression stroke to an explosion stroke of the cylinder, and a signal from the pressure sensor. An engine control unit, a digital signal processor provided in the engine control unit and performing a wavelet transform on a signal indicating a change in pressure in the cylinder from the pressure sensor, and a digital signal processor provided in the engine control unit; A central processing unit is provided for detecting a characteristic peak from the spectrum of the wavelet-transformed signal and determining the detected peak as ignition timing.

A ninth aspect of the present invention is characterized in that an ignition timing detecting device for an internal combustion engine is provided in at least one cylinder of the internal combustion engine, and detects a change in pressure in the cylinder from a compression stroke to an explosion stroke of the cylinder. A pressure sensor to detect, an engine control unit to which a signal from the pressure sensor is input,
A signal, which is provided in the engine control unit and indicates a change in the pressure in the cylinder from the pressure sensor, is divided at a predetermined frequency and divided into a plurality of frequency bands continuously distributed from a low frequency side to a high frequency side. A digital signal processor that is provided in the engine control unit and performs a high-speed wavelet transform on the signal of each divided frequency band; and a digital signal processor that is provided in the engine control unit. The ignition timing is determined for each frequency band from the spectrum of the signal subjected to the high-speed wavelet transform every time, and the ignition timing determined in the lower frequency band is corrected by the ignition timing determined in the frequency band adjacent to the higher frequency band. The ignition timing corrected by the ignition timing determined in the highest frequency band in order from the lowest frequency band In the provision and determining central processing unit as the final ignition timing.

According to the method of the first invention and the apparatus of the eighth invention, by applying the wavelet transform to the signal indicating the change in the pressure in the cylinder, a peak is obtained from the spectrum of the wavelet-transformed signal. By detecting the ignition timing, the ignition timing can be reliably detected.
According to the method of the second to seventh inventions and the apparatus of the ninth invention, a signal indicating a change in pressure in a cylinder is separated into a plurality of frequency bands, and a high-speed wavelet transform is applied to each frequency band. Then, the ignition timing is detected, so that the configuration of the detection circuit can be simplified.

[0017]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 3 is a configuration diagram showing a configuration of an internal combustion engine to which the method for detecting an ignition timing of an internal combustion engine according to the first embodiment of the present invention is applied, and a configuration of an ignition timing detection device. The internal combustion engine shown in FIG. 3 is a diesel engine 1, and a sub-combustion chamber 3 is provided in a cylinder head 1 </ b> H, and a fuel injection valve 4 and a glow plug 5 are provided in the sub-combustion chamber 3. The high-pressure fuel pressurized by the fuel injection pump 8 is applied to the fuel injection valve 4, and the fuel injection valve 4 is opened by an electric signal from a driver 15 driven by an ECU (engine control unit) 10 described later. Then, high-pressure fuel is injected into the sub-combustion chamber 3. As such a fuel injection pump 8, a common rail type fuel injection pump which is a kind of a high pressure pump can be used. A glow plug relay 9 is connected to the glow plug 5. When the relay 9 is turned on by a signal from the ECU 10, a battery voltage is supplied to the glow plug 5.

Cylinder head I of diesel engine 1
Below H, there is a cylinder block 1B provided with a cooling water passage 7, and inside this cylinder block 1B is a main combustion chamber 2 in which a piston 6 slides. Cylinder block 1
B, a pressure sensor S for detecting the in-cylinder pressure in the main combustion chamber 2
P, a water temperature sensor ST for detecting a cooling water temperature, and a crank angle sensor SC for detecting a crank angle are provided. The signals detected by the pressure sensor SP, the water temperature sensor ST, and the crank angle sensor SC are input to the ECU 10 together with an accelerator opening signal and an engine speed signal from a sensor (not shown).

The ECU 10 of the first embodiment has a CPU
(Central processing unit) 11 and this CPU 11
An SP (digital signal processor) 12 is connected. The in-cylinder pressure signal from the above-described pressure sensor SP
The data is input to the CPU 11 via P12. The DSP 12 in the first embodiment detects the ignition timing in the main combustion chamber 2 based on the in-cylinder pressure in the main combustion chamber 2 detected by the pressure sensor SP, and inputs this ignition timing to the CPU 11. The ECU 10 calculates an appropriate fuel injection timing based on the ignition timing detected by the DSP 12, and outputs an injection signal to the driver 15 at the fuel injection timing. The driver 15 amplifies the injection signal and drives the fuel injection valve 4.

In the first embodiment, the DSP 12 provided in the ECU 10 performs a wavelet transform on the signal of the in-cylinder pressure in the main combustion chamber 2 detected by the pressure sensor SP, thereby igniting the ignition in the main combustion chamber 2. The time has been detected.
The wavelet transform is a new signal processing technique beyond the Fourier transform, and expresses the energy distribution of a signal on a plane using time and frequency as horizontal and vertical coordinate axes. When this energy distribution is integrated along the time axis, it becomes a power vector of the signal, when integrated along the frequency axis, it represents a change in signal strength over time, and when integrated over the entire time-frequency plane, It becomes the total energy of the signal.

In a diesel engine, the combustion pressure due to fuel combustion is a discontinuous component that is suddenly generated with respect to the motoring waveform. It is considered time. When such an in-cylinder pressure waveform is subjected to wavelet transform, if a discontinuous portion appears in the change in in-cylinder pressure, a characteristic peak appears in the waveform (white noise waveform) after the wavelet transform. Therefore, by detecting this peak, a discontinuous point in the in-cylinder pressure waveform, that is,
The ignition timing can be detected.

FIG. 4A shows a cylinder pressure waveform T when the fuel in the combustion chamber 2 of the diesel engine 1 of FIG. 3 is performing slow combustion, and a cylinder pressure waveform T during the slow combustion. The waveform W subjected to the wavelet transform is shown in comparison. Note that M in FIG. 4A indicates a motoring waveform. As can be seen from this figure, a characteristic peak P appears in a waveform W obtained by performing a wavelet transform on the in-cylinder pressure waveform T at a discontinuity point D between the in-cylinder pressure waveform T and the motoring waveform M. Therefore, the DSP 12 detects this peak P, determines this as the ignition timing, and outputs this to the CPU 11.

Similarly, FIG. 4 (b) shows the in-cylinder pressure waveform T when the fuel injection timing is advanced and the waveform W obtained by wavelet transforming the in-cylinder pressure waveform T. FIG. 4C shows the in-cylinder pressure waveform T when the fuel injection timing is advanced and the waveform W obtained by subjecting the in-cylinder pressure waveform T to a wavelet transform. Further, FIG. 4 (d) shows a comparison between the in-cylinder pressure waveform T when pilot injection is performed in the sub-combustion chamber 3 of the diesel engine 1 and the waveform W obtained by subjecting the in-cylinder pressure waveform T to a wavelet transform. is there. 4B to 4D, M is a motoring waveform, and P is a characteristic peak appearing in a waveform W obtained by performing a wavelet transform on the in-cylinder pressure waveform T. As described above, the waveform W obtained by wavelet transforming the in-cylinder pressure waveform T includes the motoring waveform of the in-cylinder pressure waveform T at any of the advancing, retarding, and pilot injection times of the fuel injection timing. It can be seen that a characteristic peak P appears at a discontinuous point D with M.

As described above, according to the first embodiment of the present invention, a characteristic peak P appears in the waveform W obtained by performing the wavelet transform on the in-cylinder pressure waveform T at the ignition timing regardless of the combustion state of the diesel engine 1. Therefore, this peak P is
By detecting the SP 12, the ignition timing in the main combustion chamber 2 can be accurately determined. When the ignition timing is known in this way, the injection timing can be controlled accordingly.

In the first embodiment described above, the DSP 1
2 performs a complete wavelet transform, so D
The calculation amount of the SP 12 and the CPU 11 is large, and the scale of these becomes large. Therefore, a DSP using a high-speed wavelet transform that simplifies the wavelet transform is used.
A second embodiment will now be described in which the amount of calculation by the CPU 12 and the CPU 11 can be reduced, and the ignition timing in the main combustion chamber 2 can be accurately determined while reducing the scale of these.

FIG. 5 is a block diagram showing a configuration of an internal combustion engine to which the method for detecting an ignition timing of an internal combustion engine according to a second embodiment of the present invention is applied, and a configuration of an ignition timing detection device. FIG.
Is also a diesel engine 1, and the configuration is exactly the same as the configuration of the diesel engine 1 described with reference to FIG. Therefore,
The same components are denoted by the same reference numerals, and the description thereof will be omitted.
Here, only the ECU 10 having a different configuration will be described.

The ECU 10 of the first embodiment includes a CPU 11
And the DSP 12 alone, and the in-cylinder pressure signal from the pressure sensor SP has been input to the CPU 11 via the DSP 12. On the other hand, the ECU 10 in the second embodiment has a DS
A filter group 13 is provided before P12, and a signal of the in-cylinder pressure in the main combustion chamber 2 detected by the pressure sensor SP is first divided into several continuous frequency bands by the filter group 13 in the ECU 10. You. Then, the DSP 12 performs high-speed wavelet transform on the in-cylinder pressure signal in the main combustion chamber 2 divided into several frequency bands.

FIG. 6A shows in detail the internal configuration of the filter group 13 and the DSP 12 of the ECU 10 of FIG.
In the second embodiment, the signal of the in-cylinder pressure in the main combustion chamber 2 detected by the pressure sensor SP is a low-pass filter (L
The frequency band is divided into four frequency bands (1) to (4) by a band pass filter (PF) 13A and three band pass filters (BPFs) 13B to 13D having different frequency bands. FIG. 6B is a characteristic diagram showing frequency pass characteristics of each of the filters 13A to 13D in the filter group 13 of FIG. The cutoff point on the high frequency side of the bandpass filter 13D that passes the highest frequency is about several KHz. Higher frequency components higher than this are not used because they cause noise.

Each filter 1 in the filter group 13
The frequency pass characteristics of 3A to 13D are examples, and the cutoff frequency of each of the filters 13A to 13D cannot be uniquely determined because noise is individual depending on each engine, and is a suitable element of each engine. I have. DSP
12, each divided into four frequency bands (1) to
There are multipliers 21 to 24 for multiplying the signal of (4) by a wavelet scale described later, respectively, and the wavelet scale is input from the wavelet scale generation circuit 20 to these multipliers 21 to 24. The clock signal from the clock generation circuit 25 is input to the wavelet scale generation circuit 20. The clock signal can be a signal generated as an internal clock in the ECU 10, but a clock signal synchronized with the crank angle of the engine can also be used.

Frequency band in each of the multipliers 21 to 24
The timing of multiplying the signals (1) to (4) by the wavelet scale is performed based on the clock signal from the clock generation circuit 25, but the timings are not all the same. This is because the signal component of the lowest frequency band (1) does not change much over time, so the conversion cycle may be slightly longer, but the signal component of the highest frequency band (4) changes over time. Is large, so that it is necessary to perform conversion in a short cycle.

Therefore, in the second embodiment, the multiplier 24 of the highest frequency band (4) multiplies the wavelet scale by the shortest cycle, for example, every cycle of the clock signal from the clock generation circuit 25. And the multiplier 23,
For the clock signals 22 and 21, the clock signal is set to 1/2, 1 /
The wavelet scale is multiplied every cycle of frequency division of 4, 1/8. Therefore, in this embodiment, the multiplication cycle of the signal in the frequency band (1) and the wavelet scale in the multiplier 21 is the longest.

In this manner, each of the frequency bands (1) to (4) multiplied by the wavelet scale at a predetermined cycle
Are the ignition timing detection circuits 31 to 31 for each band.
The ignition timing is input to each band and the ignition timing is detected for each band. The ignition timing detected by the first ignition timing detection circuit 31 based on the signal in the lowest frequency band (1) is not highly accurate (low in time resolution) and the ignition timing is detected by the signal in the high frequency band. The higher the time, the higher the accuracy. However, in the ignition timing detected by the fourth ignition timing detection circuit 34 based on the signal of the highest frequency band (4), a plurality of ignition timings may be detected due to the influence of noise. Therefore, in the second embodiment, the ignition timing that is not high in accuracy detected by the first ignition timing detection circuit 31 based on the signal in the lowest frequency band (1) is sent to the first ignition timing correction circuit 41. And the first ignition timing correction circuit 41
The ignition timing detected by the second ignition timing detection circuit 32 based on the signal in the frequency band (2) adjacent to the frequency band (1) is also input. Then, the first ignition timing correction circuit 41 corrects the ignition timing detected by the first ignition timing detection circuit 31 with the ignition timing whose accuracy detected by the second ignition timing detection circuit 32 is improved. I have.

In the second embodiment, the ignition timing corrected by the first ignition timing correction circuit 41 and the ignition timing detected by the third ignition timing detection circuit 33 are similarly corrected by the second ignition timing correction. The ignition timing input to the circuit 41 and corrected by the first ignition timing correction circuit 41 is corrected by the ignition timing with further improved accuracy detected by the third ignition timing detection circuit 33. Further, the ignition timing corrected by the second ignition timing correction circuit 42 and the ignition timing detected by the fourth ignition timing detection circuit 34 are input to a third ignition timing correction circuit 43, and the second ignition timing The ignition timing corrected by the correction circuit 42 is corrected by the highly accurate ignition timing detected by the fourth ignition timing detection circuit 34.

As described above, the ignition timing corrected by the third ignition timing correction circuit 43 is a highly accurate ignition timing, and the ignition timing whose accuracy has been enhanced by the correction is input to the CPU 11, It is used for calculating the fuel injection timing thereafter. FIG. 7A shows the operation timing in each frequency band of the high-speed wavelet transform in the DSP 12 of FIG. 6 together with the clock signal generated by the clock generation circuit 25. FIG. 7B shows the waveform of a simple wavelet generated by the wavelet scale generation circuit 20 of FIG.

As shown in FIG. 7A, the multiplier 24 of the highest frequency band (4) output from the band-pass filter 13D is synchronized with the period of the clock signal from the clock generation circuit 25 indicated by Then, the wavelet scale shown in FIG. 7B is multiplied. Then, at the point of time (sampling point) shown in FIG. 7A, the wavelet scale of FIG. 7B is multiplied by the scalar amount of the level shown by. Therefore, the fast wavelet transform in the second embodiment is equivalent to weighting the signal of each frequency band.

Similarly, the multiplier 23 of the frequency band (3) output from the band-pass filter 13C has a clock synchronized with the period of the signal obtained by dividing the clock signal from the clock generation circuit 25 by two. The wavelet scale shown in FIG. 7 (b) is multiplied. Further, the band-pass filter 13
The multiplier 22 of the frequency band (2) output from B includes:
7B is multiplied by the wavelet scale shown in FIG. 7B in synchronization with the period of the signal obtained by dividing the clock signal from the clock generation circuit 25 by 4. Further, the multiplier 21 of the frequency band (1) output from the low-pass filter 13A is synchronized with the period of the signal obtained by dividing the clock signal from the clock generation circuit 25 by 8 as shown in FIG. Is multiplied.

FIG. 8 shows an in-cylinder pressure waveform for each frequency band detected by the fast wavelet transform shown in FIG.
The ECU 10 measures in advance for each frequency band, and
3 shows a high-speed wavelet transform of the motoring waveform stored therein. This figure shows waveforms from the time when the piston 6 in FIG. 5 reaches the top dead center (TDC) to the time when the crank angle becomes about 30 ° CA. When the clock signal is an internal clock, the detection points from time t1 to t5 after TDC are at intervals of eight clocks of the clock signal in FIG. 7A. Therefore, the sampling point in the in-cylinder pressure waveform of each frequency band after the high-speed wavelet transform is determined by the time tDC after TDC in the in-cylinder pressure waveform of the lowest frequency band (1).
Only at each detection point from 1 to t5, it is twice as high in the next highest frequency band (2), 4 times in the next highest frequency band (3), and the highest frequency band ( In 4), there are eight times.

That is, in this embodiment, only the high-speed wavelet transform value of the signal of each frequency band shown in FIG.
Since the accuracy of detecting the ignition timing for each frequency band becomes low, the motoring waveform is previously stored in the filter group 13 having the same configuration.
, A motoring waveform for each frequency band is obtained in advance, and data obtained by high-speed wavelet transform of the motoring waveform for each frequency band is stored in the ECU 10 in the form of a map. FIG. 8 shows the high-speed wavelet transform values of the signals in each frequency band shown in FIG. 7 and the data obtained by performing the high-speed wavelet transform on the motoring waveform for each frequency band from the map and also shows them.

As described above, if the two values after the wavelet transform (actual measurement values and map values of the motoring waveform) are compared, the difference between the two starts from the discontinuous point, that is, the ignition timing. By observing, it becomes easy to determine the ignition timing. In other words, even if the difference between the two becomes large a little after the actual ignition timing, the time point of the actual ignition timing immediately before the difference can be calculated by linear interpolation. Therefore, by comparing the two after the wavelet transform, the accuracy of the ignition timing determination in the ignition timing detection circuits 31 to 34 is improved.

Thereafter, the accuracy of the ignition timing is further improved by sequentially correcting the low-frequency value of the ignition timing detected for each frequency band with the high-frequency value.
In this way, by calculating the ignition timing for each frequency band and performing the correction to calculate the final ignition timing, the amount of calculation is smaller than the normal wavelet transform of the DSP 12 in the first embodiment, The load on the CPU 11 is light, and the ignition timing can be quickly determined.

In the above-described embodiment, the case where the clock signal is the internal clock has been described. However, when the clock signal is the crank angle, the time from the time t1 to the time t1 in FIG.
5 is the crank angle (CA). When the internal clock is used as the clock signal, the interval between times t1 and t5 does not depend on the engine speed. Therefore, the signal lengthens as the engine speed decreases, so that the sampling number increases. If synchronized ones are used, the sampling interval will not change.

In the above embodiment, the diesel engine 1 provided with the sub-combustion chamber 3 has been described as an example. However, in the diesel engine 1, the fuel injection valve 4 and the glow plug 5 are directly connected to the main combustion chamber 2. It may be of the direct injection type attached to the device. In the embodiment described above, the wavelet transform of the in-cylinder pressure waveform in the diesel engine has been described. However, the present invention can be effectively applied to a gasoline engine.

[0043]

As described above, according to the method of the first invention and the apparatus of the eighth invention, the wavelet transform is applied to the signal indicating the change in the pressure in the cylinder, so that the wavelet transform is performed. By detecting the peak from the spectrum of the signal obtained, the ignition timing can be reliably detected.

Further, according to the method of the second to seventh inventions and the apparatus of the ninth invention, the signal indicating the change in the pressure in the cylinder is separated into a plurality of frequency bands, and each of the frequency bands is separated. Since the ignition timing is detected by applying the high-speed wavelet transform, there is an effect that the configuration of the detection circuit can be simplified.

[Brief description of the drawings]

1A is a waveform diagram showing a differential waveform obtained by subtracting a motoring waveform from an in-cylinder pressure waveform, and FIG. 1B is a waveform diagram showing a differential waveform obtained by differentiating an in-cylinder pressure waveform.

2 (a) is a waveform diagram showing a cylinder pressure waveform during slow combustion, FIG. 2 (b) is a waveform diagram showing an in-cylinder pressure waveform during advance, and FIG. 2 (c) is a cylinder pressure waveform during a retard angle. FIG. 7D is a waveform chart showing a cylinder pressure waveform at the time of pilot injection.

FIG. 3 is a configuration diagram showing a configuration of an internal combustion engine to which the method for detecting an ignition timing of an internal combustion engine according to the first embodiment of the present invention is applied, and a configuration of an ignition timing detection device.

FIG. 4 (a) is a waveform diagram showing a comparison between the in-cylinder pressure waveform during slow combustion and a signal indicating the ignition timing according to the present invention, and FIG. 4 (b) is an in-cylinder pressure waveform during advancement and the ignition timing according to the present invention. A waveform diagram showing the signal indicating the ignition timing according to the present invention in comparison with the in-cylinder pressure waveform at the time of retardation,
(d) is a waveform chart showing a comparison between the in-cylinder pressure waveform at the time of pilot injection and the signal indicating the ignition timing according to the present invention.

FIG. 5 is a configuration diagram showing a configuration of an internal combustion engine to which a method for detecting an ignition timing of an internal combustion engine according to a second embodiment of the present invention is applied, and a configuration of an ignition timing detection device.

6A is a block diagram showing the internal configuration of the ECU of FIG. 5 in detail, and FIG. 6B is a characteristic diagram showing the frequency characteristics of the filter group of FIG.

7A is an explanatory diagram showing the timing of high-speed wavelet transform in the DSP of FIG. 6 for each frequency band, and FIG. 7B is a waveform diagram showing a waveform of a simple wavelet generated by the wavelet scale generating circuit of FIG. 6; It is.

8 is a waveform diagram showing a comparison between an in-cylinder pressure waveform and a motoring waveform of a high-speed wavelet transform waveform for each frequency band detected by the high-speed wavelet transform shown in FIG. 7;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Diesel engine 1H ... Cylinder head 2 ... Main combustion chamber 3 ... Subcombustion chamber 4 ... Fuel injection valve 5 ... Glow plug 7 ... Cooling water passage 8 ... Fuel injection pump 10 ... ECU (engine control unit) 11 ... CPU 12 ... DSP (Digital Signal Processor) 13 ... Filter group 20 ... Wavelet scale generation circuit 21-24 ... Multiplication circuit 25 ... Clock generation circuit 31-34 ... Ignition timing detection circuit 41-43 ... Ignition timing correction circuit

Claims (9)

[Claims] 1. A method for detecting an ignition timing in an internal combustion engine provided with a pressure sensor for detecting a pressure in a cylinder of the internal combustion engine, the method comprising: detecting a change in pressure in the cylinder from a compression stroke to a power stroke of a predetermined cylinder. Detecting, performing a wavelet transform on a signal indicating a change in the pressure in the cylinder, detecting a characteristic peak from the spectrum of the wavelet-transformed signal, and setting the detected peak to an ignition timing. Determining the ignition timing of the internal combustion engine. 2. A method for detecting an ignition timing in an internal combustion engine provided with a pressure sensor for detecting a pressure in a cylinder of the internal combustion engine, the method comprising detecting a change in pressure in the cylinder from a compression stroke of a predetermined cylinder to an explosion stroke. Detecting, dividing a signal indicating a change in pressure in the cylinder at a predetermined frequency, and dividing the signal into a plurality of frequency bands continuously distributed from a low frequency side to a high frequency side; Performing a high-speed wavelet transform on the signal of each frequency band; and determining an ignition timing for each of the frequency bands from a spectrum of the signal subjected to the high-speed wavelet transform for each of the frequency bands. The process of correcting the ignition timing determined in the frequency band of the above by the ignition timing determined in the frequency band adjacent to the high frequency side is sequentially repeated from the lowest frequency side. Phase and, most high frequency side ignition timing detection method for an internal combustion engine, characterized in that it comprises a step of determining a final ignition timing of the ignition timing corrected by the ignition timing determined in the frequency band of. 3. A step of determining an ignition timing for each of the frequency bands from a spectrum of a signal subjected to the high-speed wavelet transform for each of the frequency bands, comprising the steps of: And comparing the wavelet transform value of the in-cylinder pressure signal at the time of the sampling with a wavelet transform value of a motoring value that is the in-cylinder pressure value when no ignition occurs, and the wavelet transform value 3. The ignition timing detection method for an internal combustion engine according to claim 2, further comprising: determining an ignition timing from a difference between the motoring value and a wavelet transform value. 4. The internal combustion engine according to claim 3, wherein the determination of the ignition timing is performed using linear interpolation with reference to a map in which the relationship between the ignition timing and the difference value is set in advance. Ignition timing detection method. 5. The ignition timing detection method for an internal combustion engine according to claim 3, wherein the sampling interval is longer in a lower frequency band than in a higher frequency band. 6. The ignition timing detecting method for an internal combustion engine according to claim 3, wherein the clock is a fixed clock having a fixed oscillation frequency. 7. The ignition timing detection method for an internal combustion engine according to claim 3, wherein the clock is a clock synchronized with a crank angle of the internal combustion engine. 8. A pressure sensor provided in at least one cylinder of the internal combustion engine, for detecting a change in pressure in the cylinder during a compression stroke to an explosion stroke of the cylinder, and an engine control to which a signal from the pressure sensor is input. A digital signal processor provided in the engine control unit and performing a wavelet transform on a signal indicating a change in pressure in the cylinder from the pressure sensor; and a digital signal processor provided in the engine control unit. A central processing unit that detects a characteristic peak from the spectrum of the wavelet-transformed signal and determines the detected peak as the ignition timing. 9. A pressure sensor provided in at least one cylinder of the internal combustion engine, for detecting a change in pressure in the cylinder during a compression stroke to an explosion stroke of the cylinder, and an engine control to which a signal from the pressure sensor is input. And a signal provided in the engine control unit and indicating a change in pressure in the cylinder from the pressure sensor.
A band-pass filter group divided into a plurality of frequency bands continuously distributed from a low frequency side to a high frequency side, divided by a predetermined frequency, and each of the divided frequency bands provided in the engine control unit. A digital signal processor for performing a high-speed wavelet transform on the signal of the signal, and an ignition timing for each of the frequency bands, based on the spectrum of the signal subjected to the high-speed wavelet transform for each of the frequency bands provided in the engine control unit. The process of correcting the ignition timing determined in the lower frequency band by the ignition timing determined in the frequency band adjacent to the higher frequency is sequentially repeated from the lowest frequency side, and in the highest frequency band. A central processing unit for determining an ignition timing corrected by the determined ignition timing as a final ignition timing. Ignition timing detection device for an internal combustion engine.