JPS63186949A - Knock control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To enhance the detecting accuracies both in knock and in fail in a simple and inexpensive constitution, by substantially invalidating the judgment of fail at the time when the amplification factor of knock detecting output is set on a smaller side. CONSTITUTION:A knock detecting means B which detects the knock generated in an internal combustion engine A, and an amplifying means C which amplifies the output of the knock detecting means B are provided respectively. And a means D by which the amplification factor of the amplifying means C is changed, and a discriminating means E which discriminates the condition of knock by the output of the amplifying means C in the amplification factor changed by the means D are provided respectively. Further, a means F which controls the knock controlling factor on the basis of the result judged by the discriminating means E is provided. On the other hand, a means G which generates the output of fail when the output of the amplifying means C is lower than the judging level of fall is provided. And a means H which substantially invalidates the judgment of fail when the amplification factor of the amplifying means C is changed on a smaller side is provided.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to an internal combustion engine that detects the state of knock occurring in an internal combustion engine and controls knock control factors such as ignition timing, air-fuel ratio, and intake pressure. The present invention relates to a knock control device for use in a vehicle.

[Prior Art] Conventionally, a knock detection means for detecting knock occurring in an internal combustion engine, an amplification means for amplifying the output of this knock detection means, and an amplification factor of this amplification means are changed according to the rotational speed of the internal combustion engine. an amplification factor variable means for determining the knocking state, a knock determination means for determining the state of knock based on the output of the amplification means at the amplification factor determined by the amplification factor variable means; Some devices are known that are equipped with knock control factor control means for controlling knock control factors such as air-fuel ratio and intake pressure (for example, Japanese Patent Application Laid-Open No. 60-35238). There are also known devices that generate a fail output when the output signal is lower than the fail judgment level (for example, Japanese Patent Application Laid-Open No. 1983-1999).
17336).

(Problems to be Solved by the Invention) However, in a system that simply combines the conventional former and latter methods described above, even when the knock sensor is normal, the sensor output in the low speed and light load range of the internal combustion engine is Since the error is very small, it is very difficult to distinguish this from sensor abnormalities such as sensor output deterioration.For this reason, special high-magnification fail detection amplifiers have been added, and safety measures have been taken. By making some sacrifices, it is possible to detect failures only in higher rotation ranges, or by giving up on abnormality detection due to sensor output deterioration and only detecting electrical connection states such as disconnections and short circuits in the sensor signal line. However, there is a problem in that it is not possible to achieve both cost and reliability.

Therefore, an object of the present invention is to achieve both cost and reliability.

[Means for solving problems]

Therefore, as shown in FIG. 1, the present invention includes a knock detection means for detecting knock occurring in an internal combustion engine, an amplification means for amplifying the output of this knock detection means, and amplification according to the output level of this amplification means. an amplification factor variable means for changing the amplification factor of the amplification factor; a knock determination means for determining the state of knock based on the output of the amplification means at the amplification factor determined by the amplification factor variable means; and a determination result of the knock determination means. a knock control factor control means for controlling knock control factors such as ignition timing, air-fuel ratio, and intake pressure according to the amplification means; a fail determination means for generating a fail output when the output of the amplification means is lower than a fail determination level; Provided is a knock control device for an internal combustion engine, comprising a fail judgment invalidation means for substantially invalidating the fail judgment of the fail judgment means when the amplification factor of the amplification means is set to a small side by the rate variable means. It is something.

[Effect]

Thereby, the fail judgment invalidation means substantially invalidates the fail judgment of the fail judgment means when the amplification factor of the amplification means is set to the small side by the amplification factor variable means.

〔Example〕

The present invention will be described below with reference to embodiments shown in the drawings.

In FIG. 2, 1 is a knock sensor serving as a knock detection means for detecting engine knock, 2 is an engine control electronic control unit (ECU) for controlling engine ignition timing, air-fuel ratio, etc., and 3 is an engine control electronic control unit (ECU). An igniter receives an ignition control signal from the ECU 2 and turns on/off the ignition coil. An injector 4 receives an air-fuel ratio control signal from the ECU 2 and injects fuel into the intake system of the engine.

Further, in the ECU 2, 21 is a filter circuit that passes only the knock-specific frequency component of the knock sensor output signal, and 22 is a part of an amplification means for amplifying or attenuating the signal after passing through the filter at a predetermined amplification factor. 23 is an amplifier that constitutes a part of amplification means for further amplifying or attenuating the output of the amplifier 22 by a predetermined amplification factor, 24 is a microcomputer with a built-in A/D converter, and 25 is various types of amplifiers. This is a host computer for controlling ignition timing, air-fuel ratio, etc. in response to knock detection results from the sensor and microcomputer 24.

The knock sensor 1 is a piezoelectric knock sensor that converts vibrations of the engine block caused by knocking into electrical signals. This electric signal passes through a bandpass filter 21 to remove noise components, and only the frequency component (for example, 8KH2) unique to knocking is inputted to the amplifier 22. The amplification factor of the amplifier 22 is determined by taking into account the output characteristics of the knock sensor used or the range of the A/D converter 24a, which will be described later. If the amplification factor of this amplifier 22 is set to G, then G1 may be greater than or equal to 1.

The output of the amplifier 22 is branched into two, one of which is connected to the microcomputer 24 (in this embodiment, M888413 manufactured by Fujitsu is used as a one-chip microcomputer).
The input signal is input to an analog input port ANI of an A/D converter 24a built in, and the other input is input to an amplifier 23.

The amplifier 23 is for further amplifying the output of the preceding amplifier 22, and its amplification factor is, for example, four times.

The output of this amplifier 23 is input to another analog input port AN2 of the A/D converter 24a. By doing this, the sensor signals that are relatively different by a factor of 4 are
It is simultaneously input to two bauds 1-ANI and AN2 of the D converter 24a (ANI is the amplification factor G, , AN2 is the amplification factor G
z=4×G+). Any value is possible for the amplification factor of the amplifier 23, but 2, 4, 8, .・・・・・・
・Or 1/2.1/4°1/8. It is desirable to set it to a power j of r2 such as . This is because the microcomputer 24 has sensor input ports ANI and A.
By appropriately selecting and using N2, the input gain of the knock sensor 1 is switched and controlled, but at that time, it is necessary to correct the calculated value, and if it is a relative ratio of a power of 2, the calculation is easy and the execution time is quick. This is because shift calculation processing can be used. Further, by using a power of 2, it can be widely applied to microcomputers without division or multiplication functions.

Note that the amplifier 23 is installed after the amplifier 22 in order to maintain high accuracy of the relative signal ratio (in this example, 4 times). That is, the output of the filter 21 is branched into two, inputted in parallel to the amplifiers 22 and 23, and the output is sent to the boat ANI.

Even if it is input to AN2, it is functionally the same. However, in this case, in order to maintain the accuracy of the relative signal ratio (for example, 11 times), the amplification factor G of the amplifier 22 and the amplification factor G of the amplifier 23 must be
It is necessary to increase the accuracy of both amplification factors G2 (in this case, G2/G+ is the relative signal ratio)
.

On the other hand, if the embodiment is used, the relative signal ratio is determined only by the amplifier 23, so errors can be reduced.

Now, the microcomputer 24 has an A/D
A converter 24a, and a central processing unit (CP) (not shown).
U), storage devices (ROM, RAM), input/output devices (Il
o), etc., and an analog capo-1-AN for A/D conversion.
Knock determination and knock sensor fail detection are executed based on the knock sensor signal value taken in from I and AN2. The knock judgment result and the knock sensor failure result are output from the output port of the microcomputer 24, and are sent to the engine control host computer 2 at an appropriate timing.
5 through its input port.

This host computer 25 is also a microcomputer, and it is preferable to use a relatively high-grade microcomputer such as an 8-bit microcomputer. As is well known, the engine control microcomputer 25 calculates basic ignition timing and basic injection time based on sensor signals from a rotation angle sensor, an intake air amount sensor (air flow meter), etc. (not shown).

The air-fuel ratio is controlled by adding correction values from various sensors (for example, water temperature sensor) to the basic injection time, or by feedback controlling the injection time using rich/lean signals from the oxygen concentration (02) sensor. achieved.

On the other hand, the ignition timing is always controlled near the knock limit by advancing or retarding the basic ignition timing in accordance with the knock determination result of the microcomputer 24. Further, when the microcomputer 24 detects a failure of the knock sensor 1, the engine control host computer 25 also executes measures such as setting the ignition timing to the maximum retardation. The host computer 25 also manages the reset signal of the microcomputer 24. That is, when the power of the host computer 25 is turned on, the host computer 25 first initializes itself, and then sends a reset signal to the knock detection microcomputer 24 to initialize it.

Next, the operation of this embodiment will be explained. FIG. 3 shows a timing chart of the microcomputer 24 for non-king detection, determination, sensor fail detection, and retard amount calculation output in this embodiment. Figure 4 shows the microcomputer 24
2 is a flowchart showing the basic program flow. In the main routine starting from the start step 220, the ignition layer rrxso is calculated using the built-in timer (step 221L) Based on the value, the delay time (masking time) TI until the start of A/D conversion, the time for performing the A/D conversion ( Judgment time) Calculation of a magnification (K value) determined experimentally in advance to multiply the average value of the knock sensor signal in order to obtain the judgment level to be compared with the A/Di conversion value (Step 2)
22) and calculation of a fail judgment level (VF) for knock sensor fail detection (step 223).

Interrupt start (I) output from the host computer 25
When the RQ) signal falls (211 in FIG. 3), the microcomputer 24 is interrupted (step 21 in FIG. 4).
1-1). In this example, before the top dead center of each cylinder of the engine (
BTDC)10' The host computer 25 lowers the IRQ signal at the CA timing. After starting the interrupt routine, following the interrupt processing (212 in Figure 3), the masking time T
1 (213 in FIG. 3), the microcomputer 24 waits for A/D conversion (step 213-1 in FIG. 4). After the masking time ends, the knock sensor signal input to the analog input port ANI or AN2 is repeatedly A-D converted for the period of the value of time T2 (FIG. 3 214).
Step 214-1 in Figure 4), after smoothing the A-D conversion value (Step 214-2 in Figure 4), each A/D conversion value ■AD and the cylinder-specific judgment level of the previous calculation V
LE, and if VLEV〈■AD, count up the knock pulse (step 214-3 in Fig. 4).
do. The A/D conversion value smoothing process in step 214-2 is performed as follows.

15 V MAD5-1+ ■＾D.

Vo. 5 = □ Here, V A Di is the current A/D conversion value, VNA
IB-1 is the result of annealing up to the previous time, and VMADi is the result of annealing this time.

Next, in step 214-4, data replacement for calculating the maximum value Vpemm is performed. In other words, this time A/
The D conversion value VADi is the maximum value until the previous time. .

If it is larger, replace ■pok with the current VA□,
V A D i is ■. , if it is smaller than the previous V,. , save the value as is. By repeating this during the T2 loop (step 214-5), the maximum wave height value V ppm@ within the knock determination section (T2) can be determined (see FIG. 8).

Furthermore, after the A/D conversion is completed, the average value of the A/D converter 24a is calculated at the timing 215 in FIG.
15-1.215-2).

Here, the average value calculation in step 215-1 is performed as follows.

where VNAI) is the final smoothing result calculated in step 214-2, VMEAM! -1 is the average value up to the previous cycle, and ■□ is the average value up to this time.

Further, the determination level V L[V in step 215-2 is calculated as follows.

VLEV = KX (VMEAN+VHos)
Here, VMO3 is a constant for correcting A/D conversion errors, arithmetic processing errors, etc., and is determined in advance through experiments.

Knock judgment level V LE obtained as above
V changes depending on engine conditions and also changes from cylinder to cylinder. In other words, i is the basis for calculating V LEV
VMIAN is a quantity corresponding to the average sensor output value of only that cylinder, so even if the value is constant for all cylinders, V
LEV changes for each cylinder.

The microcomputer 24 stores and updates determination levels for each cylinder (for example, four for four cylinders) in the RAM area.

Next, within the timing 215 of FIG. 3, the fail output is calculated in step 215-3 of FIG. 4 as follows.

b Here, V Fa i L r is the current fail output result, V FsiLi-1 is the previous fail output, ■. As already mentioned, □ is the maximum wave height value within the knock determination section. This V Fa i-th is calculated for each cylinder in the same way as V□AN.

Next, the selection of the A/D conversion port in step 215-4 in FIG. 4 within the timing 215 in FIG. 3 is performed as follows according to the flowchart shown in FIG.

First, when the microcomputer 24 is initialized, the A/D conversion port is preset to a port with a relatively large amplification factor, that is, AN2. Then, when engine conditions change, for example, when the engine speed increases, the sensor output increases and V%tAN increases. As a result, the knock judgment level V Ltv = K
X (V MEAM + VMos) is a predetermined value v, s
A cylinder with a relatively large output (j
As the engine speed increases, the knock determination level V LtV of the cylinder (assumed to be a cylinder) exceeds a predetermined value V MAX at a certain speed.

At this time, the microcomputer 24 switches the A/D conversion port at the timing of that cylinder to the ANI side with a lower amplification factor (steps 261 to 263), and for another cylinder, the knock judgment level V LEV of that cylinder is set to a predetermined value. When the value V WAX is exceeded, the A/D conversion port is switched to AN2.
(See the # cylinder in Figure 9), and for the cylinder where the boat was switched from AN2 to the ANI side, the corresponding cylinder ■MEAN+ ■□9 and V Fail are calculated by the relative signal density. (step 264). In this example, it is set to 1/4. At this time, if the ratio is set to a power of 2, high-speed processing can be achieved by shift calculation. In other words, in this case ■□□＊ ”LEV
By shifting +V F @ i L by 2 bits to the right, the value can be quickly corrected to 1/4. Now, conversely, when the engine speed decreases and VLEV falls below the predetermined value ■□8, the A/D conversion port is switched to the side with a larger amplification factor (i.e., the second step 261 switches from ANI to AN2 side, 265', 266), and VLEV, V□□, VF□ of that cylinder are shifted to the left by 2 bits (that is, 4 times the step 267). Therefore, for example, under a condition where the engine speed is constant, there may be a case where #jj cylinder is selected as a boat on the ANI side, and cylinder # is selected as a boat on the AN2 side. To explain this a little more, for example, in a 4-cylinder engine, the ignition order is #1.
#3゜#4. Assuming that the #2 cylinder is in this order, at the timing of the knock detection of the #1 cylinder, the A from the boat on the AN2 side is
The /D conversion value is taken in, and the A/D conversion value from the ANI side boat is taken in at the timing of the next knock detection for the #3 cylinder.

Through such operations, the amplification factor can be switched for each cylinder and in accordance with the output level of the sensor signal.

Note that if the ratio of the upper and lower switching thresholds V MAX and V MIN is set with a margin greater than or equal to the relative signal ratio (4 times in this example), hysteresis can be provided to the switching characteristics of the boat, and the switching Hunting of motion can be prevented (see FIG. 9(a)).

Next, a detailed operation explanation of the A/D conversion part and the knock determination output will be given using FIG. 5.6.7.

301 in FIG. 5 corresponds to one period of the non-king detection signal. As mentioned above, the detection signal is an 8KH2 sine wave. Referring to FIG. 6, when the A-D conversion program is started (step 320), the mode of the comparator, which is the comparison function in the one-chip microcomputer 24, is specified and the threshold level Th is set with respect to the O level. is set (step 321). Then, start the comparator (step 322L to detect the falling time TDO of the sine wave 301 from Th).step 323-1)
, the Th level is further confirmed for the purpose of preventing malfunction (step 323-2). After detecting the Th level, the routine moves to detecting the rise from the Th level (step 32).
5), the rising detection time TZ1 is delayed by a predetermined time ΔD (step 326), and the time TSI is reached. In addition, in the rising detection routine (step 325), judgments are arranged in series, and even if a rising edge is not detected, step 326 is finally executed.
This prevents the calculation process from falling into an infinite loop. Subsequently, the time to start A/D conversion from time TSI is set around the peak 310-1 of the sine wave 301.

At this time, the slope near the peak of the sine wave 301 is considered to be almost constant compared to the slopes of the rise and fall of the sine wave, and even if A/D conversion is performed by delaying the delay time ΔD to the vicinity of the peak. (Step 327) Sine wave 301
The peak value ■, is obtained. That is, the value V 51 given by the conversion start time TSI.

The value V f i given by the end time Tfi has a very small difference compared to the peak value . The obtained A/D conversion value is closer to ``31+Vfi''.The obtained conversion value is read into the memory (step 328) and is used in the next operation step 3.
Moving on to 29.

FIG. 7 is a more detailed flowchart of the pulse counting part (step 214-3 in FIG. 4) for determining the knock intensity.

The A/D converted value ■AD is the previously determined cylinder-specific determination level VLav (step 215 in Fig. 4).
-2) (step 331), and if the A/D conversion value is lower than the cylinder-specific determination level VLEV, the process moves to the next operation step 333. Judgment level V LEV for each cylinder
If it is determined that the knock pulse is larger than that, 1 is added to the knock pulse counter.
is added (step 332).

By repeating this pulse count during the knock determination period (step 414-50T2 loop in FIG. 4), 1
The total number of pulses during the firing period is determined. This total number of pulses corresponds to the knock intensity. For example, the knock intensity can be classified and determined such that a total number of pulses O to 1 means no knock, 2 to 5 means a small knock, 6 to 9 means a medium knock, and more than that means a large knock. The reason why the pulse number 1 is included in "no knock" is to prevent sharp electrical noise from being misjudged as a knock when it occurs.

The result of the knock strength determined in this manner is transmitted from the output port of the microcomputer 24 to the host computer 25 in step 216-1 of FIG. For example, if there are four types of knock strength: none, small, medium, and large, this can be transmitted to the host computer 25 using a 0.1 combination of two signal lines. The host computer 25 reads this information at an appropriate timing, calculates the advance or retardation of the ignition timing based on this information, and finally sends an ignition timing control signal to the igniter 3 to perform knock control.

Next, the fail judgment output in step 216-2 in FIG. 4, which is the main focus of the present invention, will be explained in detail with reference to the flowchart in FIG. 11.

As explained earlier, the detected signal of knock sensor failure is the maximum wave height value within the knock judgment section.■2. Annealed value V of □
1□4. are using. This V Fa i Li
is calculated for each cylinder (step 215-3), and this is determined as the fail judgment level ■ in step 216-2.

Compare with. To explain this using FIG. 9(b),
The fail judgment level (■) changes depending on engine conditions (for example, engine speed). This fail judgment level ■F may be changed for each cylinder, but
There is no particular problem in practical use even if the fail judgment level is common to all cylinders. This fail judgment level ■ and the detected signal V F
Compare m i L i every ignition (step 271)
. Then, only when this VFaili is smaller than the fail judgment level (2) and the amplification factor of that cylinder is on the large side (as determined in step 272), the fail counter is incremented by 1 (step 273).

Then, if an ignition cycle occurs where V F m i (i exceeds ■), or if a cylinder with a small amplification factor occurs, the fail counter is set to 0.
(step 274). In this way, when the count value of the fail counter reaches a predetermined value, for example, 3
When the fail counter is continuously incremented by 0 ignitions (determined in step 275), it is determined that the sensor has failed, and the host computer 2 is output from the digital output port.
5 (step 276). When the host computer 25 receives this signal, it takes safety measures such as setting the ignition time 1 to the most retarded angle.

Although the fail judgment level VF is an engine adaptation constant, a very small value cannot be used for reasons such as noise margin. In Figure 9(b), this lower limit is
7.7, the conventional system that detects failure without switching the amplification factor is N.

Fails can only be detected in the above rotation range. However, in the present invention, it is possible to detect this failure even at low rotation speeds (N2). Therefore, in this embodiment, it is determined in step 270 whether or not the engine speed is N2 or higher, and a rotation range of N2 or higher is set as the failure detection execution condition.

In addition, as in the above-mentioned embodiment, by setting the quantity related to the direct value of the maximum wave in the combustion section (knock judgment section) in which the sensor signal is relatively large as the fail judgment signal, the fail detection accuracy can be further improved. improves.

In addition, although the amplification factor was switched for each cylinder in the above-described embodiment, it may be switched commonly (simultaneously) for all cylinders. However, if this embodiment is followed, high-performance cylinder-specific gain switching can be achieved using only microcomputer software, so this embodiment is more desirable.

Further, in the above embodiment, the amplification factor is switched to two stages, but it is of course possible to switch to multiple stages of three or more stages. At this time, for example, set the amplification factors in descending order of G+, Gz
, G's..., then fail detection is detected only when G and G2, and fail detection is prohibited only when G3), and furthermore, the fail judgment level ■1 itself is set to G1 and G.
It is also possible to switch to 2.

Further, in the embodiment described above, the outputs of the amplifiers 22 and 23 are directly connected to the input ports ANI and A of the A/D converter 24a at the same time.
Although the signal is input to N2, it is also conceivable to selectively input the signal to the A/D converter 24a via the analog switch 26 as shown in FIG. At this time, switching control of the analog switch 26 can be executed by the digital port of the microcomputer 24.

Further, in the above-described embodiment, the 16 ignition annealed value V Fa i (i
However, ■p and □ can also be directly used as fail detection signals. However, this embodiment is preferable because the accuracy of fail detection is higher when using the raw value V F a i (i.
Although F m i L i is created for each cylinder, it may also be created in common for all cylinders.

Also, in this example, ■. Fails are detected using the rounded value of □, but ■□. It is also possible to detect failures using Fail determination can also be made using the distribution median value (cumulative 50% point) of V p*aw. ■
□, distribution median of ■,. is V 13 per ignition cycle
If mak is larger than ■5°, then V. =■,. +Δ■,.

, conversely, V plait is ■. If it is smaller than ■,
. =V,. -ΔV5° can be obtained by sequentially updating.

Furthermore, in the above-described embodiment, the amplification factor was switched based on the knock determination levels ■□ and V, but various amounts can be considered in response to the knock sensor output such as VME□.

In addition, in the embodiment described above, when the amplification factor is switched to the small side, the fail counter is cleared to 0 and fail detection is completely canceled, but when the amplification factor is small, the count value of the fail counter is held. can also be considered.

[Effects of the Invention] As described above, the present invention has the following advantageous effects.

■Fail detection is performed when the amplification factor is relatively high, increasing fail detection accuracy and allowing fail detection to occur even in low rotation and low load ranges.

■Since there is no need to add a special fail detection amplifier,
There is not much cost increase.

■Since the amplification factor is varied according to the output of the sensor, the relative signal ratio can be increased regardless of the tolerances of the sensor and engine, and therefore both knock detection accuracy and fail detection accuracy can be improved. .

[Brief explanation of the drawing]

FIG. 1 is a diagram corresponding to the claims of the present invention, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 is a timing chart of calculation output for explaining the operation of the device shown in FIG.
Figure 4, Figure 6, Figure 7, Figure 10 and Figure 11 are
FIG. 5 is a flowchart showing various processing procedures in the microcomputer of the device shown in FIG. 6. FIG. 8 is a diagram showing A/D conversion timing according to the flowchart shown in FIG. 6. FIG. 9 is a characteristic diagram showing the cylinder-by-cylinder discrimination output signal obtained from the knock sensor output in the device shown in FIG. 2 and the detected signal for fail judgment in response to the rotation speed, and FIG. 12 is a characteristic diagram of the present invention. FIG. 3 is a block diagram showing the configuration of main parts of another embodiment of the inventive device. 1... Knock sensor serving as knock detection means, 2...
Electronic control unit for engine control, 3... igniter, 4... injector, 22. 23... amplifier constituting amplification means, 24... microcomputer.

Claims (2)

[Claims] (1) Knock detection means for detecting knock occurring in an internal combustion engine, amplification means for amplifying the output of this knock detection means, and an amplification factor for changing the amplification factor of this amplification means according to the output level of this amplification means. a variable means, a knock discrimination means for discriminating the state of knock based on the output of the amplification means at the amplification factor determined by the amplification factor variable means; and ignition timing, air-fuel ratio,
knock control factor control means for controlling knock control factors such as intake pressure; fail determination means for generating a fail output when the output of the amplification means is lower than a fail determination level; and amplification of the amplification means by the amplification factor variable means. 1. A knock control device for an internal combustion engine, comprising: fail determination invalidation means for substantially invalidating fail determination by the fail determination means when a ratio is set to a small side. (2) The knock control device for an internal combustion engine according to claim 1, wherein a value related to the maximum peak value within the knock determination section among the outputs from the amplification means is used as the determined signal of the fail determination means.