JP3461088B2 - Knock detection method for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention
The generation of knock in the engine is detected in the combustion chamber after ignition.
Knock detection method for internal combustion engine that detects ion current
About. [0002] 2. Description of the Related Art Conventionally, knock generated in an internal combustion engine is detected.
For this purpose, a vibration knock sensor is used.
Knock based on the signal output from the knock sensor
A configuration for detecting occurrence is known. like this
In the knock detection device, the output signal from the knock sensor
Among them, a signal of a predetermined frequency band is extracted and the extracted
It is configured to process the signal to detect knock. In addition, knock is detected by using ion current.
For example, Japanese Patent Application Laid-Open No. 58-7536 discloses
Corresponding to the detected ion current, as in the method described in
Knock is detected (determined) from the amplitude and width of the ion signal.
Things are known. Even in this example, Sparkno
To prevent the noise from being superimposed on the ion signal.
Signal detection is performed after a predetermined time delay from ignition.
You. And even in the case of such an ion current,
As in the case of the above knock sensor, a predetermined value of the ion current
Peak hole signal in frequency band (knock frequency component)
There is known an apparatus which performs signal processing by applying a signal. [0004] By the way, the vibration type knock
In the knock detection method that uses the
Measure the output signal of the knock sensor during rotation and measure
The average value of the specified output signal is used as the reference level for knock determination.
Output signal measured after the reference level and ignition.
Signal level, and based on the comparison result,
There is known a method of detecting occurrence of a lock. like this
The knock detection method is based on the knock detection using ion current.
Attempts have also been made to use the
Since measurement can be performed only during the period, the above-mentioned reference level is set.
Signal level where no knock occurs.
Can be difficult to determine. The present invention solves such a problem.
And for the purpose. [0006] SUMMARY OF THE INVENTION The present invention provides such an eye.
The following measures have been taken to achieve
You. That is, a knock detection method for an internal combustion engine according to the present invention
Suppresses fluctuations in the reference signal level for knock detection.
Of the measured ion current
Signal level exceeding the judgment level based on the
This is excluded from the bell setting process. in this way,
From the reference signal level of the ion current signal level
Do not be involved in setting the reference signal level
Therefore, fluctuations in the reference signal level can be kept small.
Wear. As a result, the knock signal relative to the reference signal level is
The determination becomes easier, and the knock detection accuracy is improved. [0007] DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a combustion chamber of an internal combustion engine.
Measure the signal level of the ion current generated for each fire, and
Knock generated in the internal combustion engine based on the measured signal level
A knock detection method for an internal combustion engine for detecting a knock,
Reference signal level for knock detection based on signal level
And set the threshold based on the reference signal level.
An excessive signal level exceeding a certain level is detected, and the detected
Processing for setting the large signal level to the reference signal level
Exclude fromAnd the engine speed
Set to be larger as the number gets higherFeatures
Knock detection method for an internal combustion engine. [0008] An embodiment of the present invention will be described below with reference to the drawings.
explain. The engine 100 schematically shown in FIG.
It is of a three-cylinder type for a motor vehicle and its intake system 1 is not shown.
Throttle valve 2 that opens and closes in response to the accelerator pedal
Is provided, and a surge dunk 3 is provided downstream thereof.
ing. Near one end communicating with surge tank 3
Is further provided with a fuel injection valve 5, and the fuel injection valve 5
5 is independently injected for each cylinder by the electronic control unit 6.
We are trying to control as much as possible. The exhaust system 20 has an exhaust system.
O for measuring oxygen concentration in gaseous gas_TwoSensor 21
Is installed in the pipeline leading to the muffler (not shown).
It is attached at a position upstream of the two-dimensional catalyst 22. The electronic control unit 6 includes a central processing unit 7
, A storage device 8, an input interface 9, and an output interface.
Interface 11 and an A / D converter 10
Mainly composed of a microcomputer system
Have been. The input interface 9 has a surge tank
Output from intake pressure sensor 13 for detecting pressure in 3
Detected intake pressure signal a, and detects the rotation state of engine 100
Output from the cam position sensor 14 for
The cylinder discrimination signal G1, the crank angle reference position signal G2, and the engine
Vehicle speed sensor 1 for detecting gin rotation speed signal b and vehicle speed
5, the vehicle speed signal c output from the throttle valve 2
Output from idle switch 16 for detecting closed state
LL signal d to detect the engine coolant temperature
The water temperature signal e output from the water temperature sensor 17 of FIG.
O_TwoThe current signal h output from the sensor 21 is input.
You. On the other hand, from the output interface 11, the fuel injection
The fuel injection signal f is supplied to the valve 5 and the spark plug 1
8 so that the ignition pulse g is output
Has become. This spark plug 18 has a high pressure
Bias for measuring the ion current through the node 23
Power supply 24 is connected. This bias power supply 24
Circuit 25 for measuring ion current and its measuring method
As such, various methods known in the art can be used.
You. Note that, in this embodiment, the ion current
Is detected, and therefore, knock detection for each cylinder
Can be done. The electronic control unit 6 includes an intake pressure sensor 13
Pressure signal a output from the cam position sensor 14
And the rotation speed signal b output from the
Based on various correction factors determined according to the operating state of the
The main injection time is corrected and the fuel injection valve opening time,
Jector final energization time T is determined, and the determined energization
The fuel injection valve 5 is controlled according to the time to respond to the engine load.
Program for injecting the same fuel into the intake system 1
It is stored. In addition, the operation of the engine 100 is
Control while detecting the ion current flowing for each ignition.
The electronic control unit 6 detects the program
I have That is, to detect knock,
For knock detection based on the signal level of the
Set the signal level and set based on the reference signal level.
If an excessive signal level exceeding the specified judgment level is detected,
The output excessive signal level is used for setting the reference signal level.
Exclude from processingWith the judgment level
Set to increase as the rotation speed increasesBlog
And the reference signal level thus set.
Signal level that exceeds the set detection level.
The program that detects the occurrence of knock when
It is built into the device 6. The knock detection program based on the ion current
The outline of the system is as shown in FIGS. FIG.
Is a background level BGN which is a reference signal level.
FIG. 3 is a flowchart for setting KNK, and FIG.
Is based on the set background level BGNKNK.
Is a flowchart for detecting the occurrence of knocking.
Note that, in this embodiment, the knock detection is detected for each cylinder.
The cylinder is determined prior to knock detection.
No, the knock detection process is executed for each determined cylinder.
It is. The processing routine for each cylinder is as shown in FIG.
The cylinder discrimination output from the cam position sensor 14
The first cylinder is determined based on the signal G1 (step S21),
If it is the first cylinder, the processing of the first cylinder is executed (step
(Step S22) If it is not the first cylinder, it is determined whether or not it is the second cylinder.
(Step S23), if it is the second cylinder, the second cylinder
The second eye processing is executed (step S24), and it is not the second cylinder
In this case, the processing of the third cylinder is executed assuming that the cylinder is the third cylinder.
(Step S25). Setting of background level BGNKNK
First, in step S1, the detected ion voltage
A / D conversion of the knock signal from the stream and the conversion result
Is the signal level NIONKNK. The knock signal is one
Generally, when the combustion starts and the maximum combustion pressure is exceeded
Is known to occur,
The ion current signal during that period.
It detects from the bell. In step S2,
The background level BGNKNK at this time _n-1Second
Multiplied by one coefficient K1, and the calculation result is determined as a judgment level LVL
BGN1. The first coefficient K1 is equal to a second coefficient described later.
In both cases, as shown in FIG. 5, the engine speed NE is high.
It is set to be as large as possible. Step S3
Now, this time signal level NIONKNK_nIs the judgment level
It is determined whether or not it exceeds LVLBGN1. Stay
In step S4, the current signal level NIONKNK_nage
And the background level BG obtained by the previous calculation
NKNK_n-1Apply In step S5, n points
Signal level NI based on ion current detected in fire
Calculate the moving average of ONKNK and calculate the background
Wind level BGNKNK_nIs calculated. BNGKNK_n = (NIONKNK₀ +… + NIONKNK_i +… + N
IONKNK_n) / N In step S6, the current background
Dlevel BGNKNK_nIs set within a predetermined range, that is,
Between the lower limit BGNMIN and the upper limit BGNMAX
To verify that. Lower limit value BGNMIN and upper limit value BGN
MAX increases as the engine speed NE increases.
(Fig. 6). This predetermined range
Exceeded, that is, below the lower limit BGNMIN or upper limit
If the value is greater than or equal to BGNMAX,
Dlevel BGNKNK_nDo not adopt. This background
The round level BGNKNK is set for each cylinder.
It is. Next, in FIG.
Is the background BGNNK set last time_n-1To
By multiplying by the second coefficient K2, the detection level for occurrence of knock is detected.
Set LVLBGN2. The second coefficient K2 is the first coefficient
It is set to be larger than the number K1 and the ion
Set to distinguish between flow fluctuations and others
You. In step S12, the current signal level NIONK
NK_nIs higher than the detection level LVLBGN2?
Is determined. In step S13, knock occurs.
Knock detection flag XKNKEX is set
(= 1). In step S14, knock occurs.
Reset, knock detection flag XKNKEX is reset.
(= 0). Now, while the engine 100 is operating,
Ion current is detected at each ignition in the cylinder, and the
The knock signal is A / D converted from the
Dlevel BGNKNK_nSet, for example, combustion
It becomes unstable and the signal level NIO
NKNK becomes excessive, but knocks occur
State, but not above the judgment level LVLBGN1
Let's say it is big. In this case, the program
Step S1 → S2 → S3 → S4 → S5 → S6
The signal level NIONKNK obtained by A / D conversion this time
Is the background level BGNKNK_nFrom the setting process of
Excluded, previous background level BGNKNK_n-1
Is the current signal level NIONKNK_nAs the buck
Land level BGNKNK_nMake the settings for On the other hand, a signal level NION of a normal magnitude
In the case of KNK, steps S1 → S2 → S3 → S5 → S6
And the signal level NIO obtained by the A / D conversion this time
Background level BGNKN by adopting NKNK
K_nMake the settings for Even in this case, the calculation
Background level BGNKNK_nIs the lower limit BG
If NMIN or more and BGNMAX or less,
Ground level BGNKNK_nAlso set as
Therefore, if it exceeds this range, it will not be adopted and the previous calculation
It is kept on what was issued. Knock is signal level NIONKNK_nBut
Abnormally large, exceeding the detection level LVLGGND2
The program detects that
Ground level BGNKNK_n-1Detection based on
Do. That is, step S11 → S12 → S13
And sets knock detection flag XKNKEX to
Detects the occurrence of a lock. On the other hand, the judgment level LVLBGN
Even if signal level NIONKNK exceeds 1
If the level does not exceed LVLBGN2, the program
Is executed in steps S11 → S12 → S14, and
The knock detection flag XKNKEX is reset to
It is determined that no occurrence has occurred. Therefore, the background average is calculated by the moving average value.
Level BGNKNK_nIs calculated, but excessive,
However, the signal level is not due to knocking.
NIONKNKi (i = 0 to n) and when knock occurs
Background level by one signal level NIONKNK
The level BGNKNK does not change. As a result,
Background level BGNKNK increases
The knock detection level LVLBGN2 correspondingly rises
Ascending and actually knocking,
Because it does not exceed the detection level LVLBGN2,
The problem that the occurrence of a lock cannot be detected is eliminated.
And the knock signal of the ion current partially becomes excessive.
Even if there were no such fluctuations,
The knock signal can be determined under almost the same conditions.
The occurrence of a lock can be reliably detected. Also this
As in the embodiment, the background level BGN is set for each cylinder.
If KNK is set to detect knock,
The background level BGNKNK is different for each cylinder
Also, it is possible to prevent the knock from being detected by mistake. The present invention is limited to the above-described embodiment.
It is not specified. In the above embodiment,
Signal level NIONKNK_nIs the judgment level LVLBGN
When the signal level exceeds 1, the current signal level NIONKNK
_nThe background level BGNKN previously calculated as
K_n-1Is set (step S4).
Has a background level BGNKNK_nArithmetic processing
(Indicated by a dotted line in FIG. 2).
Therefore, the current signal level NIONKNK _nIs
Ground level BGNKNK_nExcluded from arithmetic processing
Is what is done. Also, the background level BGNKNK
Is the movement of the signal level NIONKNK in n ignitions
Although the calculation based on the average value has been described, for example,
It is calculated by performing a smoothing calculation as shown in
You may. BGNKNK_n = BGNKNK_n-1 + (BGNKNK_n-1 + BGNKNK_n) / m In addition, the configuration of each unit is not limited to the illustrated example.
Various modifications are possible without departing from the spirit of the present invention.
is there. [0021] As described above, according to the present invention, the ion
When detecting knock based on the current, the knock
Minimize fluctuation of reference signal level as detection reference level
Can be obtained. As a result, signal level fluctuation
Knock detection under almost the same conditions regardless of
Detection accuracy and reliability are improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration explanatory view showing one embodiment of the present invention. FIG. 2 is a flowchart showing a schematic control procedure of a routine for setting a background level according to the embodiment; FIG. 3 is a flowchart showing a schematic control procedure of a knock detection routine according to the embodiment; FIG. 4 is a flowchart illustrating a schematic control procedure of a routine for performing cylinder-specific processing according to the embodiment. FIG. 5 is a graph showing a relationship between first and second coefficients of the embodiment and an engine speed; FIG. 6 is a graph showing a relationship between an engine speed and an upper limit value and a lower limit value of the embodiment. FIG. 7 is an operation explanatory view of the embodiment. [Description of Signs] 6 ... Electronic controller 7 ... Central processing unit 8 ... Storage device 9 ... Input interface 10 ... A / D converter 11 ... Output interface 18 ... Spark plug

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F02P 17/12 F02D 45/00 F02P 5/152 F02P 5/153

Claims (1)

(57) Claims 1. A signal level of an ionic current generated at each ignition in a combustion chamber of an internal combustion engine is measured, and a knock generated in the internal combustion engine is detected based on the measured signal level. A knock detection method for an internal combustion engine, comprising: setting a reference signal level for knock detection based on the signal level; detecting an excessive signal level exceeding a determination level set based on the reference signal level; with exclude excessive signal levels from processing for setting the reference signal level, increase the determination level as the engine rotational speed is higher
A knock detection method for an internal combustion engine, characterized in that: