JPH08210175A - Knock detecting device for engine - Google Patents

Abstract

PURPOSE: To set a knock determination section by discriminating between a noise component and a knocking component contained in an ion current and make knock detection by means of an ionic current precisely practicable. CONSTITUTION: An ionic current between plug electrodes is detected by an ionic current detecting means 11, the peak time is detected by a peak time detecting means 12, and a knock frequency component is extracted by a filtering means 13. Corresponding to the peak time, a knock determination section is set by a knock determination time setting means 14, the knock level is set according to a filtered ionic current in the knock determination section by a knock level setting means 15, and the determination level is created by a knock determination level creating means 16. After the knock is detected by a knock detecting microcomputer 17, engine control corresponding to the knock detecting condition is executed by the engine control microcomputer 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine knock detection device for controlling knock control factors such as engine ignition timing, air-fuel ratio, intake pressure, etc., and in particular, based on an ion current flowing between spark plug gaps. .

[0002]

2. Description of the Related Art As a means for detecting the occurrence of knock in a cylinder of an engine, there is known a method of detecting an ion current flowing through a gap of a spark plug. For example, Japanese Patent Application Laid-Open No. 2-504307 discloses a technique relating to a method of detecting knocking in an engine using such an ion current, in which the level of the ion current flowing between the plug gaps is a predetermined threshold. After a fixed delay time after reaching the value, an output current from the filtering means for extracting a knock noise frequency component from the detected ion current, that is, a knock determination interval for sampling the filtered ion current is set. I am trying to set it.

However, when the knock determination section is set and the filtered ion current is sampled in this way, when the fixed delay time is too long, it is obtained in this way. A knock may occur earlier than the knock determination section. Also, if the fixed delay time is short, ignition noise or noise (residual energy noise) caused by energy remaining in the coil or high tension cord due to ignition may be mixed in the knock determination section, which may result in knock discrimination. It will be difficult.

Further, Japanese Patent Application Laid-Open No. 6-101562 relates to a knock detection method in which a knock determination section is set after a predetermined time corresponding to the operating state of an engine has elapsed with an ignition timing as a reference point. The technology is disclosed. In this detection method, the knock determination section is set according to the operating state of the engine, but since the residual energy noise changes due to engine manufacturing variations and changes over time, it is predetermined. In some cases, this delay cannot be dealt with only by the delayed time, and reliable knock detection cannot be performed.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and it is possible to accurately discriminate between a noise component and a knocking component included in an ion current, so that an optimal knock determination section can be obtained. It is an object of the present invention to provide a knock detection device for an engine in which knock detection by ion current can be performed with high accuracy.

[0006]

A knock detection device for an engine according to the present invention detects an ion current flowing through a plug gap of a spark plug from the start of combustion and detects a peak value of the detected ion current. Then, a peak timing detecting means for determining the peak timing is provided, and the knock determination interval setting means sets the knock determination interval in the time range set from the peak timing of the detected ion current. Then, the knock level creating means obtains a knock level based on the ion current in the knock judging section, and the knock occurrence is detected by comparing the knock level obtained by the knock level creating means with the set knock judgment level. I am trying to do it.

[0007]

In the engine knock detection device having such a configuration, the knock determination section is always set on the basis of the peak time of the ion current detected for each combustion. It is possible to avoid energy noise and set an optimal knock determination section that is not affected by engine manufacturing variations and aging. Therefore, engine knock detection is performed reliably and reliably, and highly accurate engine control is performed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First, FIG. 1 shows the basic configuration of the present invention, which is provided with an ion current detecting means 11 for detecting an ion current flowing between the plug gaps of the ignition plug. That is,
Ion current generated by combustion is detected,
The detected ionic current is input to the peak timing detection means 12 and the filtering means 13. In the peak time detection means 12, by detecting the change in the detected ionic current to detect the peak of the level of the ionic current, and inputting the result to the knock determination section setting means 14,
The knock determination section setting means 14 sets the knock determination section based on the detected peak time.

The filtering means 13 extracts only the frequency component of knock noise from the detected ionic current, and the filtered ionic current is the knock determination set by the knock determination interval setting means 14. It is output corresponding to the section and is input to knock level creating means 15. The filtered ionic current from the filtering means 13 is supplied to the knock determination level creating means 16.

The knock level created by the knock level creating means 15 and the knock judging level created by the knock judging level creating means 16 are input to the knock control microcomputer 17 to detect the knock, and based on the detection result. Then, the engine control microcomputer 18 controls the ignition timing, the air-fuel ratio and the like to control the engine so that the knocking is suppressed.

FIG. 2 shows the configuration of a more detailed embodiment, in which the ion current detection circuit 21 detects the ion current. The ion current detection circuit 21 employs various commonly known means, and is configured as shown in FIG. 3, for example. That is, based on the ignition signal A output from the engine control microcomputer, the transistor 211
Is controlled so that the primary coil of the ignition coil 212 is de-energized when the ignition signal A is in the off state, and a high voltage is generated in the secondary coil of the ignition coil 212.
Electric discharge occurs between the electrodes of 213 and the air-fuel mixture is burned. An ion current is generated along with the combustion of the air-fuel mixture, and the current is voltage-converted by the measurement bias power supply 214 and the resistor 215 by this ion, and detected and output as the charging voltage Vi of the capacitor 216.

The ion current thus detected is supplied to the 7 KHz bandpass filter 23 constituting the filtering means 13 together with the first multiplexer 22.
First multiplexer 22 is intended to be controlled based on a command from the knock control microcomputer 24, and outputs one of an output from the detected ion current Vi or band-pass filter 23 V _B, amplifier Enter for 25.

The output signal from the amplifier 25 is supplied to the second multiplexer 26. This second multiplexer 26 is also controlled by a command from the knock control microcomputer 25, and switches and supplies the output signal from the amplifier 25 to either the sample hold circuit 27 or the peak hold circuit 28. The output signal from the sample hold circuit 27 or the peak hold circuit 28 is converted into a digital signal in the A / D converter 29, and this signal is input to the knock control microcomputer 24.

The knock control microcomputer 24 detects a knock, and the knock detection result is supplied to an engine control ECU (electronic control unit) 30. Detection signals from various sensors 31 are supplied to the engine control ECU 30, and engine control including knock control such as engine ignition timing and air-fuel ratio is executed in the engine control ECU 30.

With this configuration, it becomes possible to configure a knock detection device based on an ion current, in which the knock determination section is set from the time point of the peak of the ion current detected for each combustion. An accurate knock determination section is set that is not affected by manufacturing variations and aging of a certain engine. Then, high-accuracy knock detection is executed, and highly reliable engine control is executed. The operation will be described in detail below.

FIG. 4 shows a flow of processing executed at each ignition timing. In step 401, a predetermined table is searched to set a mask time (TMASK). In the next step 402, the ignition timing to the mask time (TMAS
The ion current is detected after the passage of K), and the peak value thereof is detected. In step 403, the knock detection section is set from the time when this peak value is detected. And
In step 404, knock is detected and knock determination is performed in this knock determination section, and the determination result is output to the ECU that executes knock control in step 405.

FIG. 5 is a diagram for explaining the operating state in such knock determination processing. In response to an ignition signal as shown in FIG. 5 (A), an ion current as shown in FIG. 5 (B) is detected. To be done. Then, based on the time point of detecting the peak value of the ion current, as shown in FIG.
MASK) is set, and the knock component of the ion current is extracted as shown in FIG.

FIG. 6 shows the detailed processing flow of step 401. At step 411, the mask time (TMASK) is read from a predetermined table. The table used here is, for example, (A) or (B) in FIG.
As shown by, the engine speed and load, the engine speed and the ignition timing are provided as parameters, and a predetermined mask time (TMASK) is read based on these parameters. And step 412
Set the TMASK read on the timer at
In step 413, the end of this timer is checked. Then, this processing is ended by confirming the elapse of time of TMASK.

FIG. 8 shows the details of step 402 in the process flow shown in FIG. 4. In step 421, the first multiplexer 22 selects the ion current Vi from the ion current detection circuit 21, and the amplifier 25 Output to. In step 422, a command is given to the second multiplexer 26 to select the sample hold circuit 27, and the output from the amplifier 25 is sampled and held.

The ion current Vi held in the sample hold circuit 27 in this way is then supplied to the A / D converter 29 in step 423 and converted into a digital value. A obtained in
The / D conversion value Vi (i) is compared with the A / D conversion value Vi (i-1) in the previous processing. Then, when it is determined that the value in the previous processing is larger than the value obtained in the current processing, it is determined that the peak is detected in the previous processing, and Vi (i-1) is set to the peak value in step 425. This is output as Vpeak and this processing is terminated. In the flow of this process, steps 423 and 424 are repeatedly executed at every A / D conversion cycle (for example, 50 μsec).

FIG. 9 shows step 403 of the processing flow of FIG. 4 in detail. In step 431, the threshold value V _TH for determining whether to output the knock determination result in the knock control microcomputer 24 or not. Is calculated from the following equation.

V _TH (i) = {K + V _peak + 15 × V _TH (i-1)} / 16 K in the above equation is, for example, 1/2, so that the determination result is obtained when the peak is below what percentage. The value of K may be a fixed value or may be changed according to the operating conditions. Further, the number of rotations of the smoothing which expresses the denominator of this equation is not limited to "16", but a multiplier of "2" facilitates calculation in the microcomputer.

In the next step 432, the calculated threshold value V _TH is compared with the previously calculated peak V peak. When it is determined in step 432 that Vpeak is larger, the process proceeds to step 433, and the flag XKDL for validating the determination result is set to "1". Conversely, Vpeak
If it is determined that the flag XKDL is smaller, the process proceeds to step 434 to set the flag XKDL to "0".

When the flag XKDL is set in this way, the routine proceeds to step 435, where the first multiplexer 22 is controlled to select the output V _B from the band pass filter 23, and the second multiplexer 22 is supplied through the amplifier 25. Input to the multiplexer 26 of. Then, in step 436, the second multiplexer 26
To the peak hold circuit 28 so that the ion current V _B passing through the bandpass filter 23 is input to the peak hold circuit 28.

In step 437, TKNK is set to the timer to define the length of the knock determination section. The length TKNK of the knock determination section is, for example, 50
The value may be a fixed value such as ° CA, but may be a value that changes according to the operating state of the engine. Then, in step 538, the peak hold circuit 28 is set to peak-hold the ion current V _B that has passed through the bandpass filter 23. In step 439, the time corresponding to the length of the knock determination section is monitored. , Continue until TKNK is confirmed.

By performing such processing, ignition noise and residual energy noise can be avoided, and the knock determination section can be set from the peak of the ion current. A knock detection operation that is not affected by the above variation or secular change is executed.

When the knock determination section is set in this way, knock determination is performed in step 404 of FIG. 4, and the determination result is output to the ECU in step 405. In the knock determination, it is well known that the peak hold value within the set knock determination section is compared with the knock determination level calculated as the average value or integrated value of the peak hold values. The measures taken are taken.

The output of the knock detection (judgment) result is shown in the following table 1 according to the flag XKDL that defines the output and the detection result.
As shown in. Then, the engine control ECU 30
Therefore, when the flag XKDL is "0", the ignition timing, the air-fuel ratio, etc. are not operated.

[0029]

[Table 1]

By executing such processing, the knock determination section is continued from the time when the peak is detected in step 401 after the lapse of the noise mask period TMASK set in step 401. The knock determination section is always set at an optimum timing without depending on ignition noise, engine manufacturing variations, or secular change, and the knock is reliably detected.

Further, with this structure, it is possible to detect engine misfire. For example, the misfire can be detected by comparing the peaks of the unfiltered ion current with those of the threshold values for detecting the misfire that are obtained by a table according to the moderation of the peaks and the operating state. This kind of misfire detection method is a well-known means for detecting misfires due to fluctuations in engine speed when it is difficult to detect fluctuations in speed due to drive wheel idling during high engine speeds or running on rough roads. In addition, it is effective to use it supplementarily.

In the embodiment, the start timing of the processing routine shown in FIG. 4 may be the output start time of the ignition signal pulse output from the ECU 30, or may be the output end time. Further, in the embodiment, the change state of the ion current in the knock determination section is extracted by the peak hold circuit 28. However, even if this is an integrated value, it is repeatedly A / D converted and processed by the microcomputer. It may be a peak value determined by

Further, A / A is repeated within the knock determination section.
When the peak value is obtained by D conversion, the A / D converted value is, for example, small at the gate start and end, and large at the central portion in succession. Even if the noise period and the noise generation section are very close to each other in the compression engine and noise is mixed in the noise determination section, the influence of this noise can be minimized.

[0034]

As described above, according to the engine knock detection device of the present invention, the start time of the knock determination section is set from the time when the peak of the ion current is detected. The optimal knock determination section that avoids noise and does not depend on engine manufacturing variations and aging changes is set for each ignition, enabling accurate knock detection and ensuring optimum engine operation. Ignition timing control and the like are executed.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the basic configuration of the present invention.

FIG. 2 is a configuration diagram illustrating a knock detection device according to an embodiment of the present invention.

FIG. 3 is a circuit diagram showing an example of an ion current detection circuit.

FIG. 4 is a flowchart illustrating a flow of knock detection processing.

FIG. 5 is a signal waveform diagram for explaining the operation of the apparatus according to the above embodiment.

FIG. 6 is a flowchart illustrating the flow of mask time setting in FIG.

7A and 7B are diagrams showing examples of tables for setting mask times.

FIG. 8 is a flowchart illustrating the flow of peak value detection processing in FIG.

9 is a flowchart illustrating a flow of knock detection processing in FIG.

[Explanation of symbols]

11 ... Ion current detecting means, 12 ... Peak time detecting means,
13 ... Filtering means, 14 ... Knock judgment section setting means, 15 ... Knock level creating means, 16 ... Knock judgment level creating means, 17 ... Knock detection microcomputer, 18 ... Engine control microcomputer, 21 ... Ion current detection circuit, 22 , 26 ... Multiplexer, 23 ... 7 KHz bandpass filter, 24 ... Knock control microcomputer, 25 ... Amplifier, 27 ... Sample and hold circuit, 28 ... Heak world circuit, 29 ... A / D converter,
30 ... Engine control ECU, 31 ... Various sensors.

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location F02P 17/12 G01M 15/00 A

Claims (4)

[Claims] 1. An ion current detecting means for detecting an ion current flowing between a plug gap of an ignition plug from the start of combustion; a peak value of the detected ion current; and a peak timing at which this peak value is detected. Based on the ion current in the knock determination section, and a peak determination section that determines a knock determination section of a time range set from the peak timing of the detected ion current, An engine characterized by comprising knock level creating means for determining a knock level, wherein knock occurrence is detected by comparing the knock level obtained by the knock level creating means with a knock determination level to be set. Knock detection device. 2. The knock determination section setting means is supplied with an output signal from a filtering means for extracting a frequency component of knock noise from a detection signal from the ion current detecting means, and within the set knock determination section. The engine knock detection device according to claim 1, wherein the knock level in the knock level creating means is specified based on the signal level from the filtering means. 3. The knock detection device for an engine according to claim 1, wherein the peak timing detection means for the ion current executes the peak timing detection operation after a lapse of a predetermined time with the ignition timing as a reference point. 4. In a state where the peak value of the ion current detected by the peak timing detection means is determined to be a predetermined value or less,
4. The knock detection result is invalidated.
The knock detection device for the engine according to any one of 1.