JPH0721440B2 - Knocking detection device for internal combustion engine - Google Patents

Description

The present invention relates to a knocking detection device for an internal combustion engine.

[Conventional technology]

It is well known that in knock detection devices for internal combustion engines, the knock detector signal increases exponentially in proportion to the engine speed. Therefore, conventionally, the knocking detector signal does not become too small in the low speed region, and the amplification factor is controlled by the knocking detector signal output or the rotation speed so as not to exceed the maximum input voltage of the AD converter even in the high speed region. A means for switching or switching the maximum input voltage of the AD converter has been considered. (For example,
60-35238).

[Problems to be solved by the invention]

However, in the above-mentioned conventional one, the amplification factor is uniformly changed over all cylinders when the engine speed becomes equal to or higher than a predetermined value as shown in FIG. 2, so that a cylinder with a high knocking detector signal (A in FIG. ) And a small cylinder (B in FIG. 2) do not change the output of the knocking detector signal, and the cylinder with a small detector signal (B in FIG. 2) has a low resolution, which makes knocking detection difficult. There was a problem of becoming.

Therefore, conventionally, as described in JP-A-59-126929, the signal level after amplification becomes substantially uniform among the cylinders according to the knocking vibration transmissibility from each cylinder of the internal combustion engine to the knocking detector. Thus, it is considered to set the amplification factor to a different value for each cylinder.

However, even in this case, the output difference of the knocking detector signal between the cylinders is reduced because the amplification factor is set to a different value for each cylinder, but the value is set to a fixed value according to the knocking vibration transmissibility. Therefore, it is not possible to deal with the increase of the knocking detector signal with the increase of the engine speed, and the different amplification factor is set for each cylinder. JPA
Even if it is applied to a configuration in which the amplification factor is switched according to the engine speed as described in JP-A-60-35238, when the engine speed becomes a predetermined value or more, the amplification factor of each cylinder is determined according to the knocking vibration transmissibility. Even if such a combined configuration is conceived, it is possible to think of a combined configuration in which different values are simultaneously switched, and even with such a combined configuration, the magnitude of the knocking detector signal corresponding to each cylinder is unique depending on the engine speed and the knocking vibration transmissibility. However, it is not possible to eliminate the influence of the output difference of the knocking detector signal of each cylinder sufficiently because it does not depend on the mutual influences, aging and other reasons. First, when the magnitude of the knocking detection signal fluctuates greatly in accordance with the change in the operating state of the internal combustion engine, the knockin of each cylinder input to the A / D conversion means. There is a problem that it is difficult to keep the detection signal within a predetermined range.

Therefore, the present invention is not affected by the output difference of the knocking detector signal between the cylinders, and the A-D conversion is performed even if the magnitude of the knocking detection signal greatly varies with the change of the operating state of the internal combustion engine. The knocking detection signal input to the means can be kept within a predetermined range of the dynamic range without being too large or too small, and enables highly accurate knocking detection.

[Means for solving problems]

Therefore, as shown in FIG. 1, the present invention, as shown in FIG. 1, has knocking detection means smaller in number than the number of cylinders for detecting knocking occurring in a plurality of cylinders of an internal combustion engine, filter means for removing noise from the output of the knocking detection means, and Amplification means having a plurality of amplification factors for amplifying or attenuating the output of the filter means, and output detection means for each cylinder that detects the magnitude of the output from the knocking detection means after passing through the amplification means, for each cylinder, According to the knocking detection means output for each cylinder detected by the output detection means for each cylinder, when the output of each cylinder is larger than a predetermined upper limit value, the amplification factor of the amplification means is lowered stepwise, Amplification for each cylinder, which is set to a value smaller than the upper limit specified value and is independently switched for each cylinder in a direction in which the amplification factor is gradually increased when it is smaller than a predetermined lower limit value. A switching unit, an A / D converting unit for A / D converting the output of the amplifying unit, and a knocking determining unit for determining knocking of the internal combustion engine based on the signal A / D converted by the A / D converting unit. A knocking detection device for an internal combustion engine is provided.

[Action]

Thus, depending on the knocking detection means output after passing through the amplification means for each cylinder detected by the output detection means for each cylinder, when the output of each of these cylinders is larger than the predetermined value of the upper limit, the lower limit is set to the lower limit. When the value is smaller than the predetermined value, it increases in the high direction by the amplification factor switching means for each cylinder,
In addition, the amplification factor is switched independently for each cylinder, and the knocking detection means output of each cylinder after passing through the amplification means input to the A-D conversion means is in a range between a predetermined upper limit value and a predetermined lower limit value. It can be put in as much as possible.

〔Example〕

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

In the block diagram of FIG. 4, 41 is an in-line 4-cylinder internal combustion engine, 42 is a knocking detector that detects vibrations, sounds, etc. due to knocking of the engine 41, and 54 is a knocking-specific frequency among the detection signals of the knocking detector 42. A filter circuit that passes only the components, 55 to 57 are amplifiers with different amplification factors,
The amplification factor is G (1)> G (2)> G (3). 52
Is an AD converter that converts the output signals of the amplifiers 55 to 57 from analog signals to digital signals, and has analog input ports AN1 to AN3 corresponding to the amplifiers 55 to 57. Reference numeral 53 is a microcomputer equipped with a central processing unit (CPU), a storage device (ROM, RAM), an input / output device (I / O), etc.
A timing signal for starting A / D conversion is given in response to a signal from the comparison function for the accompanying threshold level of the converter 52, and the output signal (digital signal) of the A / D converter 52 is averaged to set the knocking determination level. Along with the calculation, the value of the digital signal within a predetermined period is compared with the knocking determination level to determine whether knocking has occurred, and the determination result is determined based on an ignition signal from an ignition timing control device (not shown). Output to. A well-known oscillator 43, a power-on reset circuit 44, and a power supply circuit 45 are connected to a one-chip microcomputer 47 containing the A / D converter 52 and the microcomputer 53. Also, the ignition signal (iGt) from the ignition timing control device (not shown)
Through the circuit of 1, collector resistance 49, transistor 50, 1
It is connected to the interrupt terminal iRQ of the chip microcomputer 47. The output resistance ladder 48 from the one-chip microcomputer 47 is DA converted, and the voltage-current converter 46 is supplied.
Is supplied to an ignition timing control device (not shown).

Next, a method of switching the amplification factor for each cylinder independently according to the output of the detection signal of the knocking detector 42 in the above configuration will be described. FIG. 5 is a flow chart showing the basic program flow of the first embodiment. Step 1
Which analog input port (AN1 to AN3) is selected as the initial amplification factor of each cylinder for A-D conversion of the detection signal of the knocking detector 42, and Vmean determination level GLEV1 to GLEV3 (GLEV1 for switching amplification factor) <GLEV2 <GLEV3) is initialized, and in step 2, the cylinder number corresponding to the timing of generation of the detection signal of the knocking detector 42 is set in the cylinder counter i.

Here, the amplification factor switching Vmean determination levels GLEV1 to GLEV3 will be described. GLEV2 is an average value Vmean described later.
When (i) becomes smaller than GLEV2, the average value Vmean
(I) means a predetermined lower limit value to be compared with the average value Vmean (i) in order to further increase the amplification factor so that GLEV2 is equal to or more than GLEV2, and GLEV3 is an average value Vmean described later.
When (i) becomes larger than GLEV3, the average value Vmean
In order to lower the amplification factor so that (i) becomes GLEV3 or less, it means a predetermined upper limit value that is compared with the average value Vmean (i), and GLEV1 increases the average value Vmean (i). Mean value Vmean
When (i) is smaller than GLEV1, it means a judgment level to be compared with the average value Vmean (i) in order to quickly increase the amplification factor.

Further, in the present embodiment, since the internal combustion engine has four cylinders, it goes without saying that the cylinder counter i is sequentially set to a value of 1 to 4 corresponding to each cylinder.
i in parentheses of n (i) also corresponds to the value of the cylinder counter i. In addition, the initial setting in step 1 is to repeat the processing of step 2 and subsequent steps after the internal combustion engine is started, regardless of what amplification factor is set. Since the amplification factor of each cylinder will be set appropriately, the analog input port and the amplification factor switching Vmean determination level corresponding to the preset default amplification factor should be any predetermined ones. Of course, if the initialization is performed (for example, the analog input port corresponding to the same amplification factor G (1) for all cylinders and the amplification factor switching Vmean determination level are initialized), there is no problem.

Then, in the next step 3, the average value Vmean of the detection signals of the knocking detector in the previous combustion cycle of the corresponding cylinder
It is determined by comparing with (i) whether or not it is rising, and if it is rising, the process proceeds to step 4. In this step 4, Vmean (i)
And the auxiliary decision level GLEV1 are compared, and Vmean (i) is
If it is smaller than GLEV1, it is judged that the knocking detection signal output is too small even when Vmean (i) rises,
Switch the analog input port selected in step 5 to the one with a higher amplification factor and proceed to step 6, where Vmean (i) is GLEV1.
In the above case, the process proceeds from step 4 to step 6. Next, in step 6, Vmean (i) is compared with the upper limit judgment level GLEV3, and if Vmean (i) is larger than GLEV3, the analog input port selected in step 7 is switched to the one with a lower amplification factor. 10. If Vmean (i) is GLEV3 or less, proceed to step 10 from step 6. On the other hand, when it is determined in step 3 that Vmean (i) is not rising, the process proceeds to step 8 and Vmean (i) and the lower determination level GLEV2
If Vmean (i) is smaller than GLEV2, switch the analog input port selected in step 9 to the one with higher amplification factor and proceed to step 10. If Vmean (i) is GLEV2 or more, step 8 To Go to Step 10. Step
Since the number of analog input ports of the A / D converter 52 at 10 is three, AN1 to AN3, even if the analog input port No. switched at steps 5, 7, and 9 is a value other than 1 to 3 Set the analog input port number to 1 ≤ n so that it falls within 1-3.
Guard with ≤3, then step 11 during knocking determination period
16 to 16, the knocking detection signal is taken into the AD converter 52 from the finally selected analog input port, and each peak of the detection signal waveform is AD-converted every other peak (step 11). Each A-D conversion value Vmean is subjected to weighted addition averaging with the average value Vmean (i) of the knocking detection signals of the corresponding cylinder before one ignition, and steps 3, 4, 6 in the next combustion cycle of the corresponding cylinder. , V for the new knocking detection signal of the corresponding cylinder V'mean
Calculate (i) (step 12). At the same time, the average value Vmean (i) and the constant K in the previous combustion cycle of the cylinder concerned
And the offset Vos are added to calculate the knocking determination level VLEV of the corresponding cylinder (step 13).
Compared with the converted value VANn (step 14), when VANn> VLEV, a knock pulse signal is output. And step 16
If it is in the knock determination section, the process returns to step 11, and if the knock determination section is completed, the process proceeds to step 2 to control the next cylinder. Then, the ignition timing of the next relevant cylinder is retarded according to the number of knock pulses in the determination section. The above steps are repeated for each cylinder.

In this way, immediately after the internal combustion engine is started, the amplification factor of the preset initialization (for example, the analog input port and the amplification factor switching corresponding to the same amplification factor G (1) for all cylinders) is set by the initialization of step 1. Since the Vmean determination level is set, there is a possibility that an amplification factor different from the actually required amplification factor will be initialized, but after that, by repeating the processing from step 2 onwards, the second combustion of each cylinder After the cycle, each cylinder is independently switched to an appropriate amplification factor according to the output of the knocking detection signal.

Therefore, although the magnitude of the knocking detection signal is different for each cylinder, depending on the magnitude of the detected output signal (average value Vmean (i)) for each cylinder after amplification, as shown in FIG. When the knocking signal (average value Vmean (i)) of each cylinder after amplification is larger than a predetermined upper limit value (GLEV3), a small amplification factor is set. When it is smaller than a predetermined lower limit value (GLEV2), a large amplification factor is set. It is switched step by step for each cylinder, and is not affected by the difference in the magnitude of the knocking detection signal between the cylinders, and the magnitude of the knocking detection signal fluctuates greatly with the change in the operating state of the internal combustion engine. Also, the knocking detection signal of each cylinder input to the AD converter 52 does not become too large or too small, and it can be contained within a predetermined dynamic range as much as possible, and effective AD conversion is possible. Becomes possible , Can accurately detect knocking. Here, FIG. 3 shows the knocking output voltage (average value Vmean) of the maximum output cylinder after passing through the amplifier.
(I)) The characteristics of A and the knocking sensor output voltage (average value Vmean (i)) B of the minimum output cylinder are shown corresponding to the engine speed.

Steps 2 to 10 in FIG. 5 correspond to the amplification factor switching means for each cylinder of the present invention, steps 11 and 12 correspond to the output detection means for each cylinder of the present invention, and steps 11 to 16 detect knocking detection of the present invention. Corresponds to a signal.

〔The invention's effect〕

As described above, in the present invention, the magnitude of the output signal of the knocking detection signal is different for each cylinder,
Depending on the magnitude of the detected output signal for each cylinder after amplification, a small amplification factor is set when the knocking signal of each cylinder after amplification is larger than a predetermined upper limit value, and a large amplification factor is smaller than a predetermined lower limit value. , It is switched step by step for each individual cylinder, and is not affected by the difference in the magnitude of the knocking detection signal between the cylinders, and the magnitude of the knocking detection signal increases as the operating state of the internal combustion engine changes. Even if it fluctuates,
The knocking detection signal of each cylinder input to the A-D conversion means can be kept within a predetermined range of the dynamic range without being too large or too small, and effective A-D conversion becomes possible. There is an excellent effect that knocking can be detected accurately.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to the scope of claims of the present invention, and FIGS. 2 and 3 are engine rotational speeds in a conventional device and the device of the present invention.
FIG. 4 is a knock sensor output voltage characteristic diagram, FIG. 4 is a block diagram showing a first embodiment of the device of the present invention, and FIG. 5 is a flow chart for explaining the operation of the device shown in FIG. 41 …… Internal combustion engine, 42 …… Knocking detector, 52 …… AD
Converter, 53 ... Microcomputer, 54 ... Filter circuit, 55 ~ 57 ... Amplifier.

Continuation of front page (56) Reference JP-A-60-35238 (JP, A) JP-A-58-155281 (JP, A) JP-A-59-126929 (JP, A) JP-B-61-1630 (JP , B2)

Claims (2)

[Claims] 1. A knocking detection means having a number smaller than the number of cylinders for detecting knocking occurring in a plurality of cylinders of an internal combustion engine, a filter means for removing noise from the output of the knocking detection means, and an output of the filter means is amplified. Alternatively, amplification means having a plurality of amplification factors for damping, cylinder-by-cylinder output detection means for detecting the magnitude of output from the knocking detection means after passing through the amplification means, and cylinder-by-cylinder output detection means According to the knocking detection means output for each cylinder detected by the above, when the output of each cylinder is larger than a predetermined upper limit value, the amplification factor of the amplification means is gradually decreased to be smaller than the predetermined upper limit value. A cylinder-by-cylinder amplification factor switching means for independently switching each cylinder in a direction in which the amplification factor is gradually increased when the value is smaller than a predetermined lower limit value. An A / D converting means for A / D converting the output of the width means, and a knocking determining means for determining knocking of the internal combustion engine for each cylinder based on the signal A / D converted by the A / D converting means. Knocking detection device for internal combustion engine. 2. The amplification means comprises a plurality of amplifiers having different amplification factors, and the amplification factor switching means for each cylinder independently outputs the output signal of any one of the amplifiers for each cylinder.
The knocking detection device for an internal combustion engine according to claim 1, wherein whether the A-D conversion is performed by the -D conversion means is selected.