DE19826714A1 - Knock detector for internal combustion engine - Google Patents

Abstract

The knock detector has an ion current detector(17) which detects an ion current immediately after the occurrence of an ignition spark from an ignition plug(12) in the engine's frequency band from the ion current. A knock identification device(30) determines that a knock signal is present when a parameter of the extracted signal is at least at a threshold level and when the ratio of parameters extracted by the first signal extraction device and the second signal extraction device is at least at a defined level.

Description

The disclosure of the japani filed on June 16, 1997 patent application no. HEI 9-158224 with description, Drawings and summary are here in their entirety included as a reference document.

The invention relates to a knock detection device device for an internal combustion engine and on a knock detection method, wherein a knock condition using an in the spark plug arranged in the internal combustion engine is detected.

In a known knock detection device for an internal combustion engine, a spark plug disposed in a combustion chamber is used for detecting a knock condition based on an ion current that flows through the combustion chamber immediately after generating an ignition spark of the spark plug. In such a knock detection device shown in FIG. 6, a detected ion current signal is converted by a masking circuit 23 into a signal occurring substantially only within a masking interval determined based on a timing signal of a microcomputer 30 . The mask interval signal is then processed by a band pass filter (BPF) 24 to obtain a signal within a frequency band containing a knock signal. The filtered signal is then processed by a peak hold circuit 25 by a peak hold operation within a gate interval set based on a timing signal of the microcomputer 30 to obtain a gate interval signal. After the gate interval signal has been A / D converted by an A / D converter 26 , the signal is input to the microcomputer 30 . If the magnitude of the signal is greater than a predetermined value, the microcomputer 30 determines that there is a knock condition.

The voltage applied to the spark plug is approximately 100 V is the size of the immediately after the occurrence of a Ignition spark generated in the combustion chamber low ion, in  of the order of µA, and therefore susceptible to different Sources of interference. For the purpose of detecting the occurrence of a Knock condition without interference from a fault is in Japanese Patent Laid-Open No. SHO 61-57830 a Technology proposed according to which many during one Knocking containing frequency components occurring Band from another ent, many other frequency components holding band separated and the relationship between the off output signals in the two bands with a reference level is compared to determine if a knock condition, i. H. a combustion abnormality has occurred.

In such a case only based on the issue ratio The determining factor is the size of the knock signal not considered. Therefore, the aforementioned tech technology does not accurately detect the occurrence of a knock stands.

Accordingly, it is an object of the present invention a knock detection device for an internal combustion engine to provide an accurate detection of a knock condition without interference from a fault.

The object is achieved by a knocker Detection device for an internal combustion engine, wherein, under Use one in a combustion chamber of the internal combustion engine arranged spark plug, one immediately after the occurrence of a spark flowing ion current through an ion current detection device is detected, characterized by a first signal extraction device for extracting a Signals within a knock frequency band from the ions electricity; a second signal extraction device for extra purposes signal outside the knock frequency band from the Ion current; and a knock determination device for determination men that there is a knock condition when a size of by the first signal extractor extracted signal has at least the size of a predetermined size value and a ratio between the size of the Si  signal extractor extracted signal to a size ß of the extra by the second signal extraction device here signal at least the size of a predetermined ver ratio.

According to the knock determining device determines that there is a knock condition in the internal combustion engine when the Size of the extra by the first signal extraction device here signal in the knock frequency band is greater than or equal to is a predetermined value and the ratio between the Size of the signal in the knock frequency band and the size of the extracted by the second signal extractor Signal outside the knock frequency band at least the size has a predetermined value. Because the knock determination device both the size of the knock signal and that Output ratio between the knock signal and the interference signal taken into account, enables the knocking fiber according to the invention solution device a very precise detection of the occurrence knock condition in the internal combustion engine without interference by a disturbance.

The knock detection device according to the invention can further contain a spark retard control device to determine that a knock condition exists when the Size of the extra by the first signal extraction device here signal is greater than a predetermined value and that Ratio of the size of the signal extraction by the first signal extracted to the size of the device second signal extraction device extracted signal has at least a predetermined value, and wherein a Ignition timing control of the internal combustion engine is performed when there is a knock condition. thats why it is possible to knock on the basis of the without influencing knock condition precisely detected by a disturbance To control or to control ignition timing retardation wrestle.  

The knock detection device according to the invention can further include a delay control prevention direction to determine that there is a fault, and, follow Lich, to prevent the ignition timing from being carried out delay control when the size of the first Si gnaletraktionseinrichtung extracted signal larger than is a predetermined value and the ratio of the size of the Si extracted by the first signal extraction device gnals to the size of the by the second signal extraction direction extracted signal less than a predetermined Is worth. Knock detection is determined by this structure device the presence of a fault and prevents the Execution of the ignition timing retard control of the ver internal combustion engine if the size of the signal within the Knock frequency band is greater than a predetermined value and the ratio of the size of the signal in the knock frequency band to the size of the signal outside the knock frequency band is less than a predetermined value. By that on this Achieved accurate distinction of the occurrence of a Knocking condition from the occurrence of a disturbance it is possible improve the reliability of the knock control system that the ignition advance / retard control of the Carries out internal combustion engine.

The knock detection device for an internal combustion engine may also contain one between the ion currents solution device and the combination of the first signal extract tion device and the second signal extraction device arranged filter device. The filter device extra essentially only signals from the ion current within a above a predetermined frequency Chen frequency band. Such a filter device, the essentially just signals within one over one transmits predetermined frequency band, the extraction of the characteristic waveforms of the sturgeon signals and the knock signal upstream, so Kompo of the ion current in the below the predetermined Frequency located frequency band within which the knock  signal and the interference signal essentially the same waveform men before the extraction of the knock signal and the interference signals removed. Therefore, through the knock detection device a more precise determination of whether a Knocking condition or a fault is present, which means that the ver Reliability of the knock control system is improved.

The invention is based on a preferred Aus management example with reference to the drawings explained. Show it:

Fig. 1 is a schematic diagram of a knock detection apparatus according to the invention for an internal combustion engine;

FIG. 2 is a characteristic diagram with frequency components of the ion current signal detected in the knock detection device according to the invention for an internal combustion engine;

Fig. 3 is a map for indicating an output distribution for use in the knock detection device according to the invention for an internal combustion engine;

Fig. 4 is a flowchart showing a determination of a knocking condition performed by the knock detecting device of the present invention for an internal combustion engine;

Fig. 5 is a flowchart showing an ignition timing control executed by the knock detection device according to the invention for an internal combustion engine; and

Fig. 6 is a schematic diagram of a knock detection device for an internal combustion engine according to the prior art.

A preferred embodiment follows Example of the present invention with reference on the attached drawings.  

Fig. 1 shows a schematic diagram of a knocking detection device for an internal combustion engine according to an embodiment of the invention. Components of the knock detection device according to this exemplary embodiment, which are comparable to those of the prior art described with reference to FIG. 6, are identified by the same reference numerals. Fig. 2 shows a characteristic diagram showing frequency components of the ion current detected in the knock detection apparatus for an internal combustion engine according to the embodiment of the present invention.

Referring to Fig. 1 comprises an ignition coil 10 having a primary winding 10a and a secondary winding 10 b on. A spark plug 12 is arranged in a combustion chamber of an internal combustion engine (not shown). The primary winding 10 a of the ignition coil 10 is connected to a switching element 11 . If an ignition signal IGt is input from an electronic control unit (ECU) (not shown) into the control gate of the switching element 11 so that the switching element 11 is switched on, the primary winding 10 a of the ignition coil 10 becomes a primary current I ₁ from a battery power supply + B fed.

A current path on the side of the secondary winding 10 b of the ignition coil 10 , through which a secondary current I ₂ circulates, is formed by the spark plug 12 , the secondary winding 10 b of the ignition coil 10 , a Zener diode 13 and a further Zener diode 14 . The Zener diode 14 is connected in the forward direction with respect to the flow direction of the secondary current I ₂ (current of the secondary circuit). The Zener diode 13 is connected to charge egg nes connected as an ion current detection current source capacitor 15 , which is connected in parallel to the Zener diode 13 . A resistor 16 is connected in parallel to the Zener diode 14 .

The ion current is detected as follows. An ion current I _ION flows from the capacitor 15 via the secondary winding 10 b of the ignition coil 10 to the spark plug 12 . Furthermore, the ion current I _{ION flows} from the inverted terminal (-) of an operational amplifier 20 via an ion current detection resistor 17 . The ion current I _ION is _detected by the ion current detection resistor 17 . A resistor 21 connected between the inverting terminal (-) and an output terminal of the operational amplifier 20 is a gain resistor for setting a gain of the operational amplifier 20 .

An ion current signal SI _ION , ie an output signal of the operational amplifier 20 based on the ion current I _ION , shows a characteristic knock signal curve in a frequency band, for example in the range 6 kHz, as indicated by the dash-dotted line in FIG. 2 when a knock condition is present. If a disturbance such as a spike disturbance or a burning disturbance occurs, a characteristic disturbance signal appears in a frequency band, for example in the range of 4 kHz, in the ion current signal SI _ION , as indicated by a broken line in FIG. 2. In Fig. 2 is the waveform of the Ionenstromsi gnals SI _ION in a range below a frequency band around 3 kHz by a solid line angege ben, wherein neither an error nor a knocking condition is present. To extract these characteristic waveforms of the ion current signal SI _ION , the ion current signal SI _ION first passes through a high-pass filter (HPF) 22 with a cut-off frequency of 3 kHz, so that a signal is obtained in a frequency band above 3 kHz in which the knock signal or the interference signal are contained are. Since the frequency band below 3 kHz, in which the knock signal and the interference signal have essentially the same waveform, is initially removed from the ion current signal SI _ION , the occurrence of a knock condition or a disturbance can be determined with greater accuracy.

Thereafter, the signal passed through the HPF 22 is input to a masking circuit 23 , whereby the signal is processed into a signal occurring only within a masking interval set based on a timing signal of a microcomputer 30 described below. The guided by the mask circuit 23 signal is both in a bandpass filter (BPF, or a bandpass filter with specific frequency) 24 with, for example, 6 kHz, for detecting the occurrence of a knocking condition, as well as in a bandstop filter (BEF, or a bandstop filter with specific frequency) 27 , for example 6 kHz, for detecting the occurrence of a disturbance.

The signal filtered by the BPF 24 including the knock signal (the frequency band in the 6 kHz range) is input to a peak hold circuit 25 , thereby maintaining a peak value of the signal in a gate interval set based on the timing signal of the microcomputer 30 becomes. The peak value of the signal is then digitized by an A / D converter 26 A / D-converted (analog / digital converted). The converted digital value is input into the microcomputer 30 as a BPF output value. On the other hand, the signal filtered by the BEF 27 , in which the interference signal (the frequency band in the range of 4 kHz) is contained, is input to a peak hold circuit 28 , whereby a peak value of the signal is set in a gate interval based on the timing signal of the microcomputer 30 will keep. The peak value is then A / D converted by an A / D converter 29 . The digital value is then input to the microcomputer 30 as a BEF output value. The microcomputer 30 is designed as a logic circuit which contains a central processor unit (CPU) for performing various operations, a ROM storing control programs, a RAM storing various data, an auxiliary RAM, an input / output circuit, Bus lines and the like

Fig. 3 shows a map for indicating an output distribution of the BPF output value (mV) obtained by sequentially processing the ion current signal SI _{ION of} the operational amplifier 20 by the HPF 22 , the masking circuit 23 and the circuit path starting with the BPF 24 and thereafter in is input to the microcomputer 30 , and the BEP output value (mV) obtained by sequentially processing the ion current signal SI _{ION of} the operational amplifier 20 by the HPF 22 , the mask circuit 23, and the circuit path starting at the BEF 27 , and then into the microcomputer 30 is entered.

As is apparent from the above description, the occurrence of a knock condition leads to an increase in the BPF output value, and the occurrence of a disturbance leads to an increase in the BEF output value. Therefore, based on the input BPF output value and BEF output value, the microcomputer 30 can detect the occurrence of a knock condition as shown in the flowchart of FIG. 4. The following is a description of the determination operation regarding the detection of a knock condition with reference to the flowchart of FIG. 4. The determination operation performed as shown in FIG. 4 constitutes a knock determination means.

In step S100, the microcomputer 30 resets a knock flag F1 (to 0) that is set when a knock condition is detected in the determination operation, and also a fault flag F2 (to 0) that is set when the occurrence of a fault is detected. Thereafter, the microcomputer 30 accepts the input of a BPF output value and a BEF output value in step S102. In step S102, it is determined whether the BPF output value is within a range in which the BPF output value is greater than or equal to a previously set predetermined value α ( FIG. 3). If this determination condition is true (YES), it is then determined in step S103 whether the combination of the BPF output value and the BEF output value is within a range in which the ratio between them is greater than or equal to a predetermined value β, shown in the map of FIG. 3 as a gradient, ie (BPF output value) / (DIF output value) ≧ β, in particular a schattier in this case, on the basis of solid lines in Fig. 3 ter area. If this determination condition is true (YES), the microcomputer 30 determines that there is a knock condition in the engine and sets the knock flag F1 to "1" in step S104. Based on the result of this determination, the microcomputer 30 performs ignition timing retard control of the internal combustion engine. The following is a description of the ignition timing retard control with reference to FIG. 5.

If it is determined in step S102 that the BPF output value is smaller than the predetermined value α (NO), the microcomputer 30 determines that there is neither knocking nor failure, and ends the knocking state determination operation. It is determined in step S102 that the BPF output value is greater than or equal to the predetermined value α (YES), and in step S103 that the combination of the BPF output value and the BEF output value is within a range in which the relationship between this is less than the predetermined value β, ie (BPF output value) / (BEF output value) <β, in particular an area (NO) shaded in this case by the dashed lines in FIG. 3, the microcomputer 30 determines that there is a fault and sets the fault identifier F2 to "1". In this case, the microcomputer 30 prevents the ignition timing control of the internal combustion engine because there is no knocking condition.

The following is a description of the ignition timing retard control performed for the internal combustion engine upon detection of a knock condition with reference to FIG. 5. The control performed as shown in the flowchart of FIG. 5 constitutes an ignition timing retard control means.

In step S200, the microcomputer 30 accepts the input of data about operating states of the internal combustion engine (not shown), for example the engine speed NE and the intake air quantity Q, which are detected by a known speed sensor and a known intake air flow sensor.

Then, a reference ignition timing θB is calculated based on the engine speed NE and the intake air amount Q. The calculation of the reference ignition timing θB only serves to calculate an optimal ignition timing in accordance with the operating conditions of the internal combustion engine and is not described in more detail here. In step S202, it is determined whether the fault identifier F2 is "1", that is, whether the occurrence of a fault has been detected. If it is determined that the failure flag F2 is not "1" (NO), the flow advances to step S203, where it is determined whether the knock flag F1 is "1", that is, whether the occurrence of knocking has been detected. If it is determined that the knock flag F1 is "1" (YES), the flow advances to step S204, where an ignition timing θ is calculated by subtracting a predetermined quantity Rθ from the reference ignition timing θB calculated in step S201. Based on the ignition timing θ thus calculated, the microcomputer 30 performs the ignition timing control. In summary, the knocking when knocking occurs is controlled by retarding the ignition timing to the value obtained by subtracting the predetermined quantity Rθ from the reference ignition timing θB.

It is determined in step S202 that the failure flag F2 "1" is (YES), i.e. H. a malfunction has been or is being detected found in step S203 that the knock flag F1 is "1" carries (NO), d. H. the occurrence of a knock condition is detected the process proceeds to step S205 where the ignition Timing control based on the computed in step S201 neten reference ignition timing θB is performed.

In the knock detection device for an internal combustion engine according to this embodiment, various devices are formed by the above-described elements. An ion current detection device for detecting an ion current I _ION flowing in a combustion chamber of the internal combustion engine immediately after the occurrence of an ignition spark generated by the spark plug 12 as the ion current signal SI _ION is formed by the capacitor 15 , the secondary winding 10 b of the ignition coil 10 , the spark plug 12 Ion current detection resistor 17 , the operational amplifier 20 and the like. The BPF 24 forms a first signal extraction device for extracting a signal in the range of 6 kHz, ie in a knock frequency band, from the ion current signal SI _ION detected by the ion current detection device. The BEF 27 forms a second signal extraction device for extracting essentially all signals outside the knocking frequency band in the range of 6 kHz, from the ion current signal SI _ION detected by the ion current detection device. A knock determination device is implemented by the microcomputer 30 to determine that there is a knock condition, provided that the BPF output value based on the signal extracted by the BPF 24 is greater than or equal to the predetermined value α and that the ratio of the BPF output values to the BEF output value based on the signal extracted by the BEF 27 is greater than or equal to the predetermined value β.

In summary, the microcomputer 30 determines that there is a knock condition in the internal combustion engine when the knock determining device 60 determines that the BPF output value obtained by the BPF 24 is greater than or equal to the predetermined value α and that the ratio of the BPF- Output values for the BEF output value obtained by the BEF 27 are greater than or equal to the predetermined value β. Since the knock determination device takes into account both the size of the knock signal and the output ratio between the knock signal and the interference signal, the occurrence of a knock condition in an internal combustion engine can be detected with high accuracy without being influenced by the occurrence of interference.

The knock detection device for an internal combustion engine according to this embodiment further includes a deceleration control prevention device implemented by the microcomputer 30 . If the BPF output value based on the signal extracted by the BPF 24 is greater than or equal to the predetermined value α and, moreover, the ratio of the BPF output value to the BEF output value based on the signal extracted by the BEF 27 is less than the predetermined value Value β, the delay control preventing means determines that there is a trouble, and prevents the ignition timing control of the internal combustion engine.

In summary, the microcomputer 30 determines that there is a malfunction and prevents the ignition timing control of the internal combustion engine when the microcomputer 30 serving as the deceleration control preventing device determines that the BPF output value obtained by the BPF 24 is greater than or equal to the predetermined value α and that the ratio of the BPF output value to the BEF output value obtained by the BEF 27 is less than the predetermined value β.

Because of the exact differences between The knock condition and the malfunction can make it reliable speed of the knock control system can be improved, the ignition timing advance / delay control of combustion motor according to the occurrence of a knock condition carries out.

The knock detection device for an internal combustion engine according to this embodiment further includes a filter device formed by the HPF 22 with a cutoff frequency of 3 kHz. The filter device is between the capacitor 15 , the secondary winding 10 b of the ignition coil 10 , the spark plug 12 , the ion current detection resistor 17 , the operational amplifier 20 and the like ge ion current detection device and the combination of the first signal extraction device formed by the BPF 24 and the device by the BEF 27 formed second signal extraction device. The filter device formed by the HPF 22 essentially extracts only signals of a frequency band located above a predetermined frequency from the ion current signal SI _{ION of} the ion current detection device.

By means of the HPF 22 arranged upstream of the extraction of the signal curves characteristic of the knock signal and the interference signal, ie the filter device, the knock detection device according to this exemplary embodiment removes signal components in the frequency band below 3 kHz before the extraction of the knock and interference signal, within which the knock signal and the interference signal show essentially the same signal profile, from the ion current signal SI _ION . Therefore, the knock detection device according to this embodiment enables more accurate determination of whether there is a knock condition or a malfunction, thereby improving the reliability of the knock control system.

Although the first signal extraction device in the aforementioned embodiment is formed by the BPF 24 for extracting a signal within a knocking frequency band in the range of 6 kHz, the invention is not limited to this structure. According to the invention, it is essential that the extraction frequency band of the first signal extraction device is selected in accordance with the knock frequency band properties of the internal combustion engine for which the invention is used.

In the aforementioned embodiment, the second extraction device is formed by the BEF 27 for extracting essentially all signals outside the band in the range of 6 kHz, which is defined as the knock frequency band in this embodiment. Therefore, a shift of the interference frequency band from the range of 4 kHz depending on the engine speed of the internal combustion engine does not have any significant influence on the effectiveness of the extracted signal. As a result, the knock detection device for an internal combustion engine according to the aforementioned embodiment enables an excellent and reliable separation of the occurrence of a knock condition from a malfunction, and thus an accurate determination of the occurrence of a knock condition.

Although the peak holding circuits 25 , 28 have been used in the aforementioned embodiment, the invention is not limited to such a structure. For example, instead of this, integration circuits can be used for integrating the output signals of the BPF 24 and the BEF 27 accordingly.

In a knock detection device for an internal combustion engine gate becomes a in a combustion chamber immediately after generation a spark by means of a spark plug flowing ions current detected using an operational amplifier. The ion current signal passes through a bandpass filter (BPF) to Providing a knock frequency band covering BPF out given. In another circuit path, this goes through Ion current signal to provide a bandstop filter (BEF) len one essentially all frequency bands except of the knock frequency band covering BEF output value. The BPF and BEF output values are input to a microcomputer ben, which is both the size of the BPF output value and that Ratio of the BEF output value to the BEF output value below is looking for. The knock detection device therefore enables one accurately detect the occurrence of a knock condition in the Internal combustion engine without interference from a fault.

Claims (13)

1. Knock detection device for an internal combustion engine, wherein, using a spark plug ( 12 ) arranged in a combustion chamber of the combustion engine, an ion current flowing immediately after the occurrence of a spark is detected by an ion current detection device ( 17 ), characterized by

• a) a first signal extraction device ( 24 ) for extracting a signal located within a knock frequency band from the ion current;
• b) a second signal extraction device ( 27 ) for extracting a signal outside the knock frequency band from the ion current; and
• c) a knock determination device ( 30 ) for determining that a knock condition exists when a size of the signal extracted by the signal extraction device ( 24 ) has at least the size of a predetermined size value and a ratio between the size of the signal extraction device ( 24 ) extracted signal and a size of the signal extracted by the second signal extraction device ( 27 ) has at least the size of a predetermined ratio.

2. A knock detection device for an internal combustion engine according to claim 1, characterized by an ignition timing retard control means ( 30 ) for performing ignition retard control of the internal combustion engine when a knock condition is detected. 3. A knock detection device for an internal combustion engine according to claim 1, characterized by a delay control preventing means ( 30 ) for determining that there is a failure and for preventing ignition timing retard control from being performed when the size of the signal extracted by the first signal extracting means ( 24 ) is at least the size has a predetermined size value and the ratio between the size of the signal extracted by the first signal extracting device ( 24 ) and the size of the signal extracted by the second signal extracting device ( 27 ) is less than a predetermined ratio. 4. Knock detection device for an internal combustion engine according to claim 1, characterized in that the ion current is detected via the spark plug ( 12 ). 5. Knock detection device for an internal combustion engine according to claim 1, characterized in that the first signal extraction device contains a bandpass filter ( 24 ). 6. Knock detection device for an internal combustion engine according to claim 1, characterized in that the second signal extraction device contains a band-stop filter ( 27 ). 7. knock detection device for an internal combustion engine according to claim 1, characterized by a between the ion current detection means ( 17 ) and the first and second signal extraction means ( 24 , 27 ) GE switched filter ( 22 ) so that the filter ( 22 ) filters the ion current to prevent input of ion current components within a frequency band below a predetermined frequency into the first and second signal extraction devices ( 24 , 27 ). 8. A method of detecting a knock condition in an internal combustion engine, comprising the steps of generating a spark within a combustion chamber of the engine, detecting an ion current flowing in the combustion chamber of the engine immediately after generating the spark within the combustion chamber, characterized by

• a) extracting a knock component from a signal corresponding to the detected ion current, the knock component being within a predetermined knock frequency band;
• b) extracting an interference component from the signal corresponding to the detected ion current, the interference component being outside the predetermined knock frequency band;
• c) calculating a knock / interference ratio between a size of the knock component and a size of the interference component; and
• d) determining whether there is a knock condition based on the size of the knock component and the knock / noise ratio.

9. Knock detection method for an internal combustion engine according to claim 8, characterized in that the presence of a knock condition is determined when the Size of the knock component at least a predetermined value and the knock / sturgeon ratio at least a predetermined ratio ent speaks. 10. Knock detection method for an internal combustion engine according to claim 8, characterized in that the knock component is extracted by passing the the signal corresponding to the ion current through a bandpass fil ter in which the knock frequency band is passed. 11. Knock detection method for an internal combustion engine according to claim 8, characterized in that the interference component is extracted by passing the the signal corresponding to the ion current through a bandstop filter in which the knock frequency band is blocked. 12. Knock detection method for an internal combustion engine according to claim 8, marked by, the step of filtering, before extracting the knock and interference component, a component of the ion current speaking signal, in which the knock and interference component are indistinguishable from each other. 13. Knock detection method for an internal combustion engine according to claim 8, characterized in that  a step of retarding an ignition timing of the engine is performed when it is determined that a knock condition is present.