JPH02272327A - Engine knocking detector - Google Patents

Abstract

PURPOSE:To reduce the component parts and to constitute with low cost by calculating a knock decision level in the manner of adding an offset value to the population mean of vibration waveforms outputted from a knock sensor and deciding the existence of a generation of knocking. CONSTITUTION:A signal from the knock sensor 6 is converted into digital data with a sampling cycle set by sampling cycle setting means 21 in the period set by detection period setting means 22, in A/D conversion means 20 to output it to knocking level calculating means 23 and knock decision level calculating means 24. On the knock decision level calculating means 24, the specified offset value is added to the population mean of the vibrations to calculate the knock decision level (PKN). In the knock decision means 25, the knock level (P2) calculated by the knock level calculating means 23 and the knock decision level (PKN) are compared, and it decides no occurrence of knocking when P2<PKN, while the occurrence of knocking is decided when P2>=PKN, then the result of knock decision is transmitted to a main control circuit 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an engine knock detection device that directly converts the output waveform of a knock sensor into digital data to detect knocking.

[Problems to be solved by conventional technology and the invention] Recently, technology has been widely adopted in which a knock sensor detects the initial knock caused by abnormal combustion in the engine, and the ignition timing is controlled to avoid the occurrence of knock. ing. This makes it possible to control ignition timing at the knock limit, greatly improving engine output performance.

The knock sensor detects abnormal combustion pressure vibration due to abnormal combustion of the air-fuel mixture or mechanical motion transmitted to the cylinder block, etc., and outputs the vibration waveform as an electrical signal.

For example, the above-mentioned knock sensor determines whether knock has occurred.
JP-A-58-30477, JP-A-61-8472
As disclosed in the @publication, the knock component is selected by band-limiting the signal from the above-mentioned knock sensor through a filter circuit, the peak value of the waveform is held by the peak bold circuit, and this peak value is converted into an analog/digital signal. Convert. Then, the analog/digital converted peak value is compared with a predetermined level calculated by a microcomputer or the like to determine whether knocking has occurred.

However, in general, in analog circuits such as the filter circuit and peak hold circuit in the above-mentioned prior art, circuit elements such as resistors and capacitors used have tolerances, and errors due to circuit constants are unavoidable. Accurately setting these circuit constants requires a great deal of man-hours, such as making individual adjustments, and this, combined with the large number of circuit elements used in the analog circuits mentioned above, causes an increase in costs. Ta.

Furthermore, the circuit elements described above deteriorate over time, causing changes in circuit characteristics. Therefore, when a signal from a knock sensor is subjected to waveform processing by an analog circuit, there is a problem in that reliability deteriorates due to aging.

[Object of the Invention] The present invention has been made in view of the above circumstances, and it is possible to process the vibration waveform output from a knock sensor without relying on analog circuits, and to reduce the number of component parts. It is an object of the present invention to provide an engine knock detection device that can be constructed at low cost.

[Means and Effects for Solving the Problems 1] The engine knock detection device according to the present invention is an analog/digital system that directly converts a vibration waveform output from a knock sensor into digital data at a sampling period that allows the vibration waveform to be reproduced. a conversion means; a knock determination level output means for estimating a population average for the average value of the output of the analog/digital conversion means for each predetermined interval, and calculating a knock determination level by adding an offset value to this population average; The apparatus further includes knock determination means for comparing the average value of the output of the analog/digital conversion means during the knock period with the knock determination level to determine whether or not a knock has occurred.

That is, when the engine is detected by the knock sensor, the vibration waveform output from the knock sensor is converted into zero contact digital data by the analog/digital conversion means at a sampling period that allows the vibration waveform to be reproduced. converted.

Next, the average value of the output of the analog/digital conversion means in a certain predetermined period is further averaged for several cycles,
The population mean is estimated.

Then, an offset value is added to this population average to calculate a knock determination level, which is compared by the knock determination means with the average value of the output of the analog/digital conversion means during the knock period to determine whether or not a knock has occurred. be done.

[Embodiments of the invention] Hereinafter, the present invention will be described in detail with reference to the drawings.

The drawings show an embodiment of the present invention, in which Fig. 1 is a functional block diagram of a knock detection device, Fig. 2 is a circuit configuration diagram, Fig. 3 is a flow chart showing a knock detection procedure, and Fig. 4 is a flow chart showing a knock detection process. This is a timing chart.

(Configuration) The symbol @1 in Fig. 2 is a main control unit consisting of a microcomputer, to which various sensors such as a crank position sensor 2 are connected via a waveform shaping circuit 2a.
Further, an actuator drive circuit such as an ignition circuit 3 is connected. In addition, the main control unit 1 includes:
A knock detection unit 4 is connected to the knock detection unit 4, and the crank position sensor 2 and the knock sensor 6 are connected to the knock detection unit 4 via the waveform shaping circuit 2a and the amplifier 15, respectively.

The knock detection unit 4 includes a CPU 7, a ROM 8,
RAM9,
I)10. analog/digital (A/D) converter 11,
Timer TH1, T)12. TH3, TH4, and an input/output (Ilo>interface 12) are connected to each other via a path line 13.

The crank position sensor 2 is connected to the input port of the I10 interface 12 via the waveform shaping circuit 2a, and the knock sensor 6 is connected to the amplifier 5.
It is connected to the A/D converter 11 via.

The crank position sensor 2 is composed of an electromagnetic pickup or the like that detects a protrusion (or slit) on a rotor 2b that is linked to the crankshaft of the engine, and when the protrusion provided on the rotor 2b approaches and moves away from the crank position sensor 2, An alternating current output is generated due to the change in magnetic flux, and is converted into a pulse by the waveform shaping circuit 2a.

For example, in the case of a 6-cylinder engine, the above-mentioned crank position sensor is set every 30°C from 10° before top dead center (BTDC) to the compression top dead center (T, D C) of each cylinder, which exists every 120° CA. 2 outputs a crank angle signal. Zunawara, BTDCI O', BTDC40'', BTDC
70'', BTDC100' crank angle signals are input to the main control unit 1 to calculate ignition timing, etc., and when a predetermined ignition timing is reached based on these 30' CA signals, an ignition signal is sent to the ignition circuit 3. Output.

Note that the signal of the BTDC 10' is a fixed ignition angle signal at the time of starting the engine.

Further, from the crank position sensor 2 to the knock detection unit 4, for example, BTDC70° and BTDC10
' signals are input at intervals of 60'CΔ, and interrupt processing is activated.

In addition, the above-mentioned knock sensor 6 is connected to the resistor R from the power supply VCC.
This is a resonant knock sensor that consists of a vibrator with approximately the same natural frequency as the knock vibration, and a piezoelectric element that detects the acceleration of this vibrator and converts it into an electrical signal. Detects the vibrations transmitted to the cylinder block etc. during the combustion pressure wave during the explosion stroke,
The vibration waveform is output as an electrical signal.

After this electric signal is amplified to a predetermined level by the amplifier 5, it is sent to the A/D converter 1 of the knock detection unit 4.
1, it is A/D converted to digital data. During this A/D conversion, sampling is performed at high speed in order to faithfully convert the vibration waveform.

The CPU 7 activates internal interrupt processing by the timers Tl, TH2, TH3, and TH4 based on the signal from the crank position sensor 2, and detects the knock sensor in a predetermined period according to the knock detection processing program stored in the ROM 8. The signal from 6 is subjected to high-speed A/D conversion by the A/D converter 11. Then, it is determined whether or not knocking has occurred,
The judgment result is sent to the main control unit 1 by the SCI 1.
0 etc.

When the main control unit 1 receives a message from the knock detection unit 4 indicating that knocking has occurred, the main control unit 1 immediately delays the ignition timing of the relevant cylinder to avoid knocking.

(TL function configuration) The knock detection unit 4 includes an A/D conversion means 20, a sampling period setting means 21, a detection period setting means 22,
knock level calculation means 23, determination level calculation means 24,
It is composed of knock determination means 25, and performs a function dedicated to knock detection processing at high speed.

In the A/D conversion means 20, the signal from the knock sensor 6 is converted into digital data by the A/D converter 11 at the sampling period set by the sampling period setting means 21 in the period set by the detection period setting means 22. , and outputs it to the knock level calculation means 23 and the knock judgment level exclusion means 24.

In the sampling period I91 setting means 21, in the interval set by the detection interval setting means 22, the above-mentioned A/D
The sampling period of A/D conversion in the conversion means 20 is set and outputted to the A/D conversion means 201, the knock level calculation means 23, and the knock determination level output means 24. This sampling period is a time period of 11TS that can faithfully reproduce the vibration waveform from the knock sensor 6, for example, T3.
= set in timer TH4 at a cycle of 30 m.

Based on the signal from the crank position sensor 2, the detection interval setting means 22 sets a knock determination level detection interval and a knock detection interval for the non-knock occurrence period and the knock occurrence target period, respectively, and performs the above-mentioned Δ/D conversion. Means 20
, the sampling period setting means 21, the knock level calculating means 23, and the knock determination level calculating means 24.

The above-mentioned knock judgment level detection section and knock detection section are as follows:
The signal from the crank position sensor 2 is set directly or by interpolation according to the engine rotation speed N [from a preset map, etc., and the timer
Old and TH2 are the start time TIS of the knock judgment level detection section and the start time T2S of the knock detection section, respectively.
is set, and each end time TI is set in timer TH3.
E and T2E are set.

The knock level calculation means 23 calculates the A/D in the knock detection period set by the detection period setting means 22.
The imaging width center value PO of the vibration waveform is subtracted from the digital data Pi for each sampling period TS converted by the converting means 20, and the value is added for each sampling period Ts.

After the A/D conversion in the knock detection section is completed, the average value P2 is calculated by dividing by the sampling number S.

That is, P2=-Σ 1pi-POI (1) The average value P2 of the knock detection section is calculated, and this average value P2 is output to the knock determination means 25 as a knock level.

The knock determination level calculation means 24 calculates the average value P1 in the knock determination level detection interval set by the detection interval setting means 22 in the same way as the knock level calculation means.
Calculate.

P1=-Σ1Pi-Pot...(2) Next, estimate the population mean of the above average value P1, and add a predetermined offset value p0FFSET to this population mean to determine the knock judgment level PKN.
Calculate.

That is, when the A/D conversion in a knock judgment level detection section in a certain cycle N is completed, the average value P1 of that section is calculated. Next, the consecutive (N-1) until the previous time
By integrating the average value PIAVE' in the cycle, adding the current average value P1 to this cumulative brightness value, and dividing by the number of cycles N, the average value PIAVE of the N cycles up to this time is obtained.
Calculate E and use it as the population mean.

PIAVE=-((N-1)XPIAVE--1-Pi
)... (3) Then, the current knock determination level PKN is calculated by adding a predetermined offset value P 0FFSET to this average value p IAVE and output to the knock determination means 25 .

P KN= P IAVE+ P0FFSET-(4
) The knock determination means 25 compares the knock level P2 calculated by the knock level calculation means 23 with the knock determination level PKN calculated by the knock determination level calculation means 24, and determines that if P2 < PKH, no knocking occurs;
If P2≧PKH, it is determined that knocking has occurred, and the knocking determination result is sent to the main control unit 1 via the 5C110.
Send to.

(Knock Judgment Level Detection Procedure) Each of the above-mentioned processes is performed by timer TH1 as shown in FIG.
, TH2, TH3, and TH4. First, the knock determination level detection procedure will be explained according to the flowchart of FIG.

First, step 510 of the main routine of FIG. 3(a)
1, the interrupt vector, various flags, registers, etc. of the knock detection unit 4 are initialized.

Next, when the process proceeds to step 5102, interrupts are permitted, and the process proceeds to step 5103, where the process transitions to an idle task.
The CPU 7 is placed in a standby state and an interrupt is generated.

Next, in the case of a six-cylinder engine, for example, as shown in Fig. 5, when a signal of a crank angle of 70° CA is input from the crank position sensor 2, an external interrupt occurs, and as shown in Fig. 3(b).
At step 5151 shown in FIG.
An elapsed time T30 corresponding to 0″CΔ is calculated.

Next, the process proceeds to step 5152, and the step 515 described above is performed.
The engine speed NE is determined from the value of T2O calculated in step 1, and the process proceeds to step 5153.

In step 5153, the start time of the sampling period of the signal from the knock sensor 6, that is, the start time TIS of the knock determination level detection period, is set in the timer TH1 based on the engine rotation speed N [calculated in step 5152, and step Proceed to 5154.

In step 5154, the interrupt of the above-mentioned timer ■old is enabled, and the process proceeds to step 5155, where the above-mentioned engine rotation speed NE is
Based on this, the time width AOI of the knock judgment level detection section is calculated, and the process returns to the main routine.

Next, when an internal interrupt is generated by the above-mentioned timer ■old at time TIS, in step 5201 of FIG. TH3, and then in step 5202, interrupts of the timer TH3 are enabled.

Next, the process proceeds to step 5203, and the sampling period TSI of A/D conversion is set in timer TH4, and in step 5204, the interrupt of the above-mentioned timer ■ old is enabled, and the A/[) by A/[) converter 11 is set. Start the conversion immediately and return to the main routine.

That is, when the interrupt of timer TH4 is permitted in step 5204, the interrupt routine shown in FIG. A/ in vessel 11
D conversion is performed.

Then, in step 251, the digital data of the vibration waveform from the knock sensor 6 converted by the A/D converter 11 is read, and the process proceeds to step 5252, where the digital data Pi of the vibration waveform read in the step 5251 and the vibration The difference between the amplitude center value PO of the waveform, that is, the knock intensity (lPi-POI) is calculated.

Next, in step 5253, the current knock intensity calculated in step 5252 is added to the knock intensity integrated value KNP up to the previous sampling to calculate the knock intensity integrated value KNP up to the current sampling.KNP=KNP+
l Pi −POl ), proceed to step 5254.

Proceeding to step 5254, 1 is added to the sampling number S up to the previous time, and the sampling number S up to this time (S=
S+1) is calculated, and in step 5255, the next sampling timing is set in the A/D converter 11, the routine is ended, and the steps 8251 to 5255 are repeated again at the next sampling timing.

Here, step 5 of interrupt processing using the above timer
When the knock determination level detection section end time HE set in step 201 is reached, an internal interrupt is generated by the timer TH3 as shown in FIG. 3(f).

In the interrupt by the timer TH3, step 5401
In step 5402, the interrupt of the timer TH4 is prohibited to stop the sampling of the output signal from the knock sensor 6, and in step 5402, it is determined whether the flag F[^G is O or not. When calculating the knock determination level, since the flag is set to "1AG=O", the process advances to step 5403 and calculates the average value PI (-KNP/S) for the knock intensity integrated value KNP in the knock level detection section. After calculation, the process proceeds to step 5404.

In step 5404, the average value P1^VE= of each section in consecutive (N1) cycles up to the previous time is integrated,
The current average value P1 is added to the integrated value, and the average value PIAVE of N cycles up to this time is calculated using the above equation (3), PIAVE-1 ((N-1)XPIAVE'+P1).

Next, proceed to step 3405, and proceed to step 5404 described above.
An offset value p 0 is added to the average value P IAVE calculated by
Calculate the knock judgment level PKN by adding FFSET (PKN=PIAVE+P0FFSET
).

Then, in step 8406, the flag is set to FLAG=1, and the process proceeds to step 5412, where the values of the knock intensity integrated value KNP and the sampling number S are cleared, and the process returns to the main routine, thereby ending the detection of the knock determination level.

(Knock Detection Procedure) Next, when an interrupt signal with a crank angle of 10° CA indicating fixed ignition timing is input from the crank position sensor 2,
An external interrupt shown in FIG. 3(e) occurs, and step 53
51, based on the engine rotation speed NE calculated in the processing using the interrupt signal of the crank angle 70''CA, the sampling start time of the signal from the knock sensor 6, that is, the knock level detection start time T2S is set, and the timer TH2 is set. , and the process proceeds to step 5352.

In step 5352, the interrupt of the timer TH2 is permitted, and the process proceeds to step 5353, where the engine rotation speed N
The time width TA02 of the knock level detection section is calculated based on E, and the process returns to the main routine.

Then, when time T2S is reached, an internal interrupt is generated by timer TH2, similar to the knock determination level detection described above, and the knock detection sampling period end time T2E and sampling period TS2 are set in timer TH3 and timer TH4, respectively. A sampling process of the A/D converted value of the vibration waveform from the knock sensor 6 is executed by the timer TH4.

Here, the sampling period TS2 is, for example, 30J.
Js, and is set so that the captured waveform from the knock sensor 6 can be faithfully digitized.

In addition, with respect to the sampling period TS2, the sampling period TS1 in the knock determination level detection section is appropriately set, and the sampling period TSI and the sampling period TS2 may be the same period. In addition, the above timer TN
The interrupt processing by 2 and 184 is similar to the knock determination level detection procedure described above (TH1 interrupt, TH4 interrupt), so the explanation thereof will be omitted.

Next, the knock determination process by timer TH3 shown in FIG. 3(f) will be explained.

In step 5401, when interrupting the sampling processing of the A/D conversion value by timer TH4 is prohibited, step S
Proceeding to 402, it is determined whether the flag is set to O. In this case, since the previous 183 interrupt routine was for calculating the knock determination level, the flag was set to FLAG=1 in step 8406 of the previous routine, so the process advances from step 5402 to step 5407, and the knock intensity integration in the knock detection section is performed. Calculate the average value P2 (=KNP/S) of the value KNP, and perform step 8
Proceed to 408.

In step 8408, the average value P2 (knock level) in the knock detection section calculated in step 5407 is compared with the knock judgment level PKN calculated in the knock judgment level detection section described above, and when P2<PKH, step The process proceeds to step 5409, where it is determined that no knock has occurred, and the process proceeds to step 5411. On the other hand, when P2≧PKH, the process proceeds to step 8410, where it is determined that a knock has occurred, and a knock signal is transmitted to the main control unit 1 via the 5CIIO, and the process proceeds to step 5411.

Then, proceeding to step 5411, the flag is set to F[^G
← is set to O, the process proceeds to step 5412, the values of the knock intensity product sieve value KNP and the sampling number S in the knock detection section are cleared, and the process returns to the main routine.

According to the above procedure, the vibration waveform output from the knock sensor 6 is taken into the knock detection unit 4, and the presence or absence of knock occurrence is determined. For example, when it is determined that a knock has occurred and a knock signal is sent to the main control unit 1, the ignition signal output from the main control unit 1 to the ignition circuit 3 is immediately retarded to avoid knocking.

In this embodiment, an example has been described in which the knock detection process is performed by the knock detection unit 4, but the present invention is not limited to this, and the knock detection process is performed by the main control unit 1. good.

Furthermore, the knock sensor 6 is not limited to a co-molded sensor, and can detect vibration waveforms such as combustion pressure and vibration sound, as well as mechanical imaging of the engine transmitted to the cylinder block etc. It's good to have.

[Effects of the Invention] As described above, according to the present invention, the vibration waveform output from the knock sensor is directly converted into digital data by the analog/digital conversion means at a sampling period at which the vibration waveform can be reproduced.

Then, the knock determination level calculation means estimates a population average for the average value of the output of the analog/digital conversion means for each predetermined interval, adds an offset value to this population average to obtain a knock determination level, and determines the knock determination level. Since the means compares the average value of the output of the analog/digital conversion means during the knock period with the knock determination level to determine whether knock has occurred, the vibration waveform output from the knock sensor depends on the analog circuit. This improves the reliability of knock detection without being affected by changes in circuit characteristics due to aging of the circuit elements of the analog circuit.

Further, it is not necessary to set constants for the circuit elements of the analog circuit, and there is no error in circuit constants, so that knock detection can be performed accurately. Furthermore, it is possible to reduce the number of circuit element parts.
Excellent effects such as cost reduction can be achieved.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, in which Fig. 1 is a functional block diagram of a knock detection device, Fig. 2 is a circuit configuration diagram, Fig. 3 is a flowchart showing a knock detection procedure, and Fig. 4 is a knock detection procedure. Processing timing chart. 6... Knock sensor, 20... Analog/digital conversion means, 24... Knock judgment level calculation means, 25... Knock judgment means, 1"s... Sampling period, Pl, P2... Average value, PKN...Knock judgment level, P0FFSET...Offset value. (a) (b) 3121st (C) (d) (e)

Claims (1)

[Scope of Claims] Analog/digital conversion means for directly converting the vibration waveform output from the knock sensor into digital data at a sampling period at which the vibration waveform can be reproduced; a knock detection level calculating means for estimating a population average for the average value of the output, and calculating a knock detection level by adding an offset value to the population average; 1. A knock detection device for an engine, comprising: knock determination means for comparing the knock determination level with a knock determination level to determine whether knock has occurred.