JPH0733808B2 - Knotting control device for internal combustion engine - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a knocking control device for an internal combustion engine, and more particularly, to a knocking control device for an internal combustion engine without being affected by background noise.
The present invention relates to a knocking control device for an internal combustion engine with improved responsiveness.

(Prior Art) Generally, a knocking control device for an internal combustion engine detects knocking caused by abnormal combustion of the engine by a knocking detection means such as a pressure sensor and compares the detection result with a predetermined comparison reference value. Whether or not knocking has occurred is determined. The purpose of this is to adjust the control elements such as the ignition timing based on the result of this determination to avoid knocking and to perform appropriate combustion.

In this case, the knocking detection means does not detect only the pure knocking component, but includes various background noises generated by the internal combustion engine, such as a change in cylinder pressure due to normal combustion and a change in pressure due to acceleration / deceleration. Such a background noise is accompanied by a change over time, and there are variations in the characteristics of the knocking detection means itself. How to accurately identify is an important issue for avoiding knocking.

Heretofore, as a proposal that focuses on this problem,
For example, the one described in JP-A-59-39972 is known. This knocking control device employs the average value of the output of the knocking detection means in a predetermined crank angle period as the background noise. Then, a value obtained by multiplying this background noise by k (constant) is used as a first reference value, and if the maximum value of the output of the knocking detection means in a predetermined crank angle period is larger than the first reference value, it is determined that knocking has occurred and ignition is performed. I try to delay the timing. Further, the maximum value of the output of the knocking detection means is compared with a second fixed reference value which is a predetermined fixed value (a value larger than the first comparative reference value), and when the maximum value is larger than the second comparative reference value, knocking occurs. The ignition timing is retarded when it is judged to have occurred. Therefore, the knocking can be detected while preventing the influence of the background noise, and the knocking detection is compared with the second comparison even when the average value adopted as the background noise rises and becomes too large. It can be performed based on the reference value.

In this case, the first comparison reference value is, for example,
It is set to a value that detects a relatively large knock that occurs approximately once every 20 to 500 cycles. this is,
Knocking control is intended to avoid knocking that is audible to the human ear or that adversely affects the engine, and small knocking is due to poor detection accuracy.

That is, one of the internal combustion engines detected by the knocking detection means
FIG. 12 shows the knocking intensity for each cycle (every explosion) and its cumulative frequency (that is, the output signal S of the knocking detecting means and its cumulative frequency) for each knocking intensity. In FIG. 12, the horizontal axis represents knocking strength,
The vertical axis is the cumulative frequency with respect to the knocking strength, which is 4
The characteristic lines of the book represent the respective operating states of strong knocking, medium knocking, weak knocking, and no knocking. When such knocking is judged by a comparison reference value (corresponding to a 15% cumulative frequency value) that detects one rotation in seven cycles, and knocking avoidance control is performed, knocking is controlled as shown in FIG. . In FIG. 13, the solid line shows the characteristic curve in the high engine speed region, and the broken line shows the characteristic curve in the low engine speed region. Therefore, 15%
When the knocking control is performed with the cumulative frequency value, the characteristic curve in the high rotation range has the small knocking characteristic shown in FIG. 12, but the characteristic curve in the low rotation range has the medium knocking characteristic, and some audible knocking appears.

Further, the sensitivity of the knocking detection means is, as shown in FIG. 14, from the 15% value of the cumulative frequency value shown in FIG. 12 (a value detected about once every 7 cycles) with respect to the magnitude of knocking. The 2% value (value detected about once every 50 cycles) is also larger, and the 2% value is also more resistant to circuit variations. Note that "high sensitivity" of the knocking detection means means a state in which background noise can be appropriately eliminated and only a necessary knocking component can be accurately detected. Specifically, the knocking signal (S) and the background signal can be detected. A state in which the ratio (S / N ratio) to the ground noise (N) is large.

For the above reasons, the above-mentioned conventional example is a comparative reference value corresponding to a value for detecting comparatively strong knocking that occurs approximately once every 20 to 500 cycles of the engine, that is, a cumulative frequency value of 5% to 0.2%. Is set, and the presence or absence of knocking is determined by comparing this comparison reference value with the output signal of the knocking detection means.

Therefore, if knocking is detected once every 20 to 500 cycles, control elements such as retarding the ignition timing are used to avoid knocking, and then 20 cycles later.
Controls such as advancing the ignition timing over 500 cycles are performed to restore the control elements to their original state.

(Problems to be Solved by the Invention) However, in such a conventional knocking control device for an internal combustion engine, a comparative reference value is raised to a higher value, specifically about once every 20 to 500 cycles. Set to a value that detects knocking, and the control element that detects and changes knocking was restored from the same 20 cycles to 500 cycles, so it is possible to accurately distinguish only strong knocking by a high comparison reference value and knock. However, it takes a very long time for the control elements such as ignition timing to change significantly due to the small advance rate, but the control response is poor during transient operation, and it is sufficient after knocking is avoided. There was a problem that it was not possible to generate a large torque.

That is, as shown in FIG. 15 showing the change of the advance amount when the ignition timing is controlled by the 15% cumulative frequency value and the 2% cumulative frequency value, as shown in FIG. c)) is smaller than the case where the advance speed after the retard control is the 15% cumulative frequency value (Fig. 15 (b)), and the ignition timing is long to advance to the original ignition timing after the retard control. It takes time. Where 2
The cumulative frequency value of% picks up knocking that occurs only about once every 50 cycles. Therefore, when advancing corresponding to this, the advance speed is as shown in Fig. 15 (c). Inevitably smaller. Conversely, if it is attempted to determine knocking at a frequency of about once every 50 cycles, the advance speed will have to be reduced. This is because if the same advance rate as the 15% cumulative frequency value is used,
This is because the angle of advance of knocking increases because the angle of advance advances greatly in a short time. Therefore, during transient operation, for example, when strong knocking once occurs and the ignition timing is retarded during acceleration operation, the advancing speed thereafter is slow and sufficient torque cannot be generated.

At this time, if the retard amount is increased, the advancing speed can also be increased, but since the torque fluctuation increases, it cannot be actually adopted.

(Object of the invention) Therefore, in the present invention, the comparison reference value is set low in an operating state in which knocking is likely to occur, and the comparison reference value is set in an operating state in which knocking is unlikely to occur, so that knocking detection accuracy is increased. The purpose is to improve the output torque by improving the responsiveness in the transient operation state while maintaining it.

(Structure of the Invention) As shown in the basic conceptual diagram of FIG. 1, the knocking control device for an internal combustion engine according to the present invention has a knocking detection means a for detecting knocking of the internal combustion engine and an output signal of the knocking detection means. A discriminating means b for discriminating knocking when exceeding one reference value, and a value which is larger than the first reference value and is higher when the engine speed is higher than the low engine speed. While setting the second reference value
When the output signal of the knocking detection means exceeds the second reference value, the reference value control means c for controlling the magnitude of the first reference value in the decreasing direction, and the determination means determine knocking. , And knocking avoiding means d for avoiding knocking.

According to this, the driving state in which knocking is likely to occur and the driving state in which knocking is unlikely to occur are discriminated using the second reference value, and in the driving state where knocking is likely to occur, the first reference value for knocking determination is lowered. In the operating state in which knocking is unlikely to occur, the first reference value is set higher to ensure sufficient engine output.

Further, the second reference value is corrected so as to increase as the engine speed increases. This is because the background noise in the knocking signal becomes higher as the engine speed becomes higher, and when the background noise is high, it is better to keep the first reference value for knocking determination higher. This is because the knocking signal can be detected accurately without being affected by Therefore, according to the above requirements, for example, when the vehicle runs at a constant speed while the engine speed is kept high, the knocking signal is accurately detected without being affected by the background noise.

(Example) Hereinafter, the Example of this invention is described based on drawing.

2 to 10 are views showing a first embodiment of the present invention,
The present embodiment is applied to a multi-cylinder internal combustion engine.

First, the structure will be described. In FIG. 2, reference numeral 1 denotes an ignition plug attached to a cylinder head 2 of an internal combustion engine for each cylinder, and each ignition plug 1 serves as knocking detection means between the ignition plug 1 and the cylinder head 2. Washer pressure sensor 3
Is sandwiched between. The pressure sensor 3 is formed of a piezoelectric element,
The change in cylinder pressure is output as a change in charge amount. The output of the pressure sensor 3 is input to the control unit 4, which controls the charge amplifier 5, the multiplexer 6, the bandpass filter 7, the rectifier 8 ,.
It is composed of an integrator 9 and a microcomputer 10.

The charge amplifier 5 includes, for example, a capacitor (for example, 0.01 μF) 11 and a resistor (for example, 1 M) as shown in FIG.
Ω) 12 and an op amp 13 and outputs a change in the amount of charge of the pressure sensor 3 as a voltage change. This charge amplifier 5 is provided in the number corresponding to the number of pressure sensors 3 provided for each cylinder.

The multiplexer 6 time-divisionally outputs a signal input from each charge amplifier 5 based on a signal from the microcomputer 10 and detected by each pressure sensor 3 for a predetermined crank angle period. The time is set so that knocking and background noise for each cylinder can be sufficiently detected (for example, a period from 70 ° before the compression top dead center to 50 ° after the compression top dead center).

The bandpass filter 7 is a bandpass filter of about 5 to 20 KKz, and separates only the signal due to knocking from the low-frequency pressure change due to combustion.

The rectifier 8 rectifies the signal that has passed through the bandpass filter 7.

The integrator 9 integrates the signal rectified by the rectifier 8 only for a predetermined crank angle period, and the start and end of the integration are controlled by the signal from the microcomputer 10. In this embodiment, the integration starts 10 ° after the top dead center and ends 50 ° after the top dead center. The charge amplifier 5, the multiplexer 6, the bandpass filter 7, the rectifier 8 and the integrator 9 together constitute a quantifying means 101 for quantifying the output of the pressure sensor 3 during a predetermined crank angle period.

The microcomputer 10 includes an A / D converter 14 and I / O port 1
5, CPU16, RAM17 and ROM18, it acts as a discrimination means, a reference value control means, and knocking avoidance means. The signal from the integrator 9 is input to the A / D converter 14, and the A / D converter 14 converts the integrated value into a digital signal and I
Output to / O port 15. The I / O port 15 takes in a signal from the A / D converter 14, takes in a signal indicating a crank angle from a crank angle sensor (not shown), and outputs a control signal to the multiplexer 6 and the integrator 9. . It also outputs an ignition signal to the power transistor 19 described later. The CPU 16 fetches the required external data from the I / O port 15 according to the program written in the ROM 18, and transfers the data to and from the RAM 17 while performing the arithmetic processing on the I / O port. Output to 15. The ROM 18 stores a program for controlling the CPU 16, and the RAM 17 is composed of, for example, a non-volatile memory and stores data used for calculation in the form of a map or the like, and retains the stored content even after the engine is stopped. To do. When the ignition signal is input from the control unit 4, the power transistor 19 is turned on and the primary current of the ignition coil 20 flows. The high voltage boosted by the ignition coil 20 by turning on and off the power transistor 19 is supplied to the ignition plug 1 of the cylinder selected by the distributor 21, and the air-fuel mixture of the cylinder is ignited.

Next, the operation will be described.

As shown in FIGS. 4 (a) and 4 (b), the output signal of the pressure sensor 3 has a high-frequency knocking waveform superimposed on the waveform of the in-cylinder pressure change associated with combustion. Therefore,
First, this high-frequency waveform must be extracted.
The knocking waveform must be identified from this background noise.

In this embodiment, a high-frequency waveform is extracted from a large waveform associated with combustion, and the first process for quantifying the waveform is performed by the quantifying means 101 from the charge amplifier 5 to the integrator 9, and the high-frequency waveform is backed up. The microcomputer 10 carries out a second process for controlling the ignition timing by discriminating knocking from the ground noise.

First, the first process will be described.

As shown in FIG. 4 (a), the output waveform of each pressure sensor 3 is such that a high frequency wave due to knocking or the like is superimposed on a low frequency wave associated with combustion, and this low frequency wave travels one stroke in the cylinder. Occurs once per hit. The charge amplifier 5 converts the output of the pressure sensor 3 into a voltage signal, and the multiplexer 6 follows an instruction from the microcomputer 10 for a predetermined crank angle period (for example, from 70 ° before compression top dead center to after compression top dead center).
The pressure sensor 3 of each cylinder is time-divided every (50 ° period),
The waveform of FIG. 4 (b) is obtained, then only the high frequency wave is taken out by the band pass filter 7 to obtain the waveform of FIG. 4 (c), and half-wave rectified by the rectifier 8 to obtain the waveform of FIG. 4 (d). Waveform. This rectified wave is integrated by the integrator 9 and is shown in FIG.
, And quantify high frequency components.

Therefore, it is possible to detect and quantify only the high-frequency pressure change due to knocking or the like from the large low-frequency pressure change due to combustion. Incidentally, FIG. 4 (c), (d)
A large pulse-like waveform appears inside, which is caused by a shock caused by switching in the multiplexer 6.

Next, the second processing will be described.

Since the second processing is performed in the microcomputer 10, it will be described with reference to the flowcharts shown in FIGS.

First, the initialization routine of FIG. 5 will be described.

When the ignition switch of the engine is turned on, the CPU 16 clears the RAM 17 and sets initial data in step M ₁ . Next, although description and step diagrams are omitted, the fuel injection amount is calculated and the basic ignition timing Ta is looked up from a data table stored in advance in the ROM 18 in step M ₂ . The basic ignition timing Ta is stored in advance in the ROM 18 with the engine speed and the basic fuel injection amount as parameters, for example. The basic ignition timing Ta in Step M ₃ is corrected based on the coolant temperature ignition timing Tav
Is calculated.

Next, the interrupt processing routine shown in FIG. 6 will be described. In step R ₁ , it is determined whether the crank angle is 50 ° after the compression top dead center. If it is 50 ° after the compression top dead center, in step R ₂ , it is 50 ° after the compression top dead center shown in FIG. 7. Execute the interrupt processing routine of. If the crank angle is not 50 ° after compression top dead center with switch R ₁ , it is determined in step R ₃ whether or not the crank angle is 10 ° after compression top dead center, and 10 ° after compression top dead center. If it is, in step R ₄ , the integrator 9
Is set and the signal from the rectifier 8 is integrated.

Next, the interrupt processing routine at 50 ° after the compression top dead center shown in FIG. 7 will be described.

In Step P _1, the signal from the crank angle sensor, determines whether there the 50 ° after the compression top dead center is what cylinder, i.e. performs cylinder discrimination, in step P _2, after the said compression dead center The output of the integrator 9 of the cylinder at 50 ° is output to the A / D converter 14 and converted into a digital value (A / D conversion). Step P
_{At 3} , the integration result S of the integrator 9 is stored in the address corresponding to the cylinder number n of the RAM 17 as the data Sn of the cylinder number n,
In step P ₄ , a smoothed value SAn, which will be described later, is subtracted from the data Sn to obtain a difference value DSn (DSn = Sn−SAn). Step P
_{At 5} , the first comparison reference value (first reference value) S / L1 is calculated by the calculation method described later. In step P ₆ , the difference value DSn is set to the first
The comparative reference value S / L1, when DSn ≦ S / L1 is, it is determined that the knocking has not occurred, in step P _7, the ignition timing of the cylinder compensation amount Tcn the Tcn = Tcn-k ₁ ( The ignition timing Tav is advanced by setting k ₁ to, for example, about 0.05 ° to 0.2 °.

In step P ₆ , when DSn> S / L, it is determined that knocking has occurred, and in step P ₈ , the ignition timing correction amount Tcn
Is set to Tcn = Tcn + k ₂ (k ₂ is, for example, about 1 °), and the ignition timing Tav is retarded a little. Therefore, the ignition timing Tav can be controlled by determining whether knocking has occurred.

If the ignition timing correction amount Tcn is a negative value in step P ₉ , the ignition timing correction amount Tcn is set to zero (Tcn = Tcn = Pcn) in step P _10.
In 0), when the knocking does not occur, it is prevented that the advance angle is too advanced and the fuel consumption is deteriorated and the exhaust performance is deteriorated. In step P ₁₁ , the ignition timing correction amount Tcn is compared with the upper limit value UL, and if Tcn> UL, in step P ₁₂ , Tc
By setting n = UL, it prevents excessive retardation. In addition,
Considering the influence on engine output etc. as the upper limit value UL, 10
Set about 20 to 20 degrees.

In step P _13, the smoothed value SAn, is calculated by the following equation.

SAn = Sn × (1/16) + SAn × (15/16) (1) As is clear from the formula (1), even if the data Sn at this execution is a large value (large knocking), Smooth value SA
Since n does not change significantly, in the high rotation range of the period,
Even if high-level background noise continues for a long time, the smoothed value SAn can be set low, and the difference value DSn calculated in step P ₄ and the first comparison reference value S / L calculated in step P ₅ can be set in step P. By comparing with ₆ , it is possible to accurately detect knocking.

In step P ₁₄ , the ignition timing Tavn of the cylinder is calculated by the following equation.

In step P ₁₅ , reset the integrator 9
_{At 16} , the multiplexer 6 is switched to the next cylinder, and this routine ends.

The above process is performed for each cylinder, and the ignition timing can be controlled for each cylinder.

Next, the calculation processing of the first comparison reference value will be described with reference to the flowchart shown in FIG.

In step S ₁ , the difference value DSn is changed to the peak hold value MD of the difference value DSn.
Compared to Sn, when the DSn ≦ MDSN, especially it is determined that a large knocking has not occurred, in step S _2, the peak hold value by the peak hold value MDSN calculated by the following equation
Attenuate MDSn, and proceed to step S ₁₆ .

MDSn = MDSn × 127/128 (1) In step S ₁ , when DSn> MDSn, in step S ₃ ,
The difference value DSn this time is adopted as the peak hold value MDSn, and the intermediate value AMDS of the increase of the peak hold value MDSn
Calculate n by the following formula.

AMDSn = (MDSn + DSn) / 2 (2) Next, in step P ₄ , the pulse width Tp of the basic fuel injection amount
Is 5 ms or less, and if the basic pulse width Tp is 5 ms or more and is within 5 s, it is determined whether or not a transient operation state is established, and Tp <5 ms or Tp ≧ 5 ms. Within 5 seconds, it is determined that knocking is unlikely to occur, or the transient operation is in progress, and it is determined to be immediately after that, and the process proceeds to step S ₁₆ . In step S ₄ , when Tp ≧ 5 ms has elapsed for 5 s or more, in step P ₅ , it is determined whether the gear position of the transmission is the first speed or the neutral position, and when the first speed or the neutral position, the engine speed is changed. Judging that it is a transition time during which the change is drastic, the process proceeds to step S ₁₆ . In step S _5, when the gear position is not the first speed or neutral, in step S _6, the ignition timing correction amount Tcn is determined whether or not less than 1 °, when Tcn <1 DEG unless a stable knock control in It is determined and the process proceeds to step S ₁₆ .
If Tcn ≧ 1 ° in step S ₆ , the second comparison reference value (S / L 2) is looked up from the memory in step S ₇ .
This second comparison reference value (S / L2) is stored in advance in the form of a data map in the ROM 18 with the engine speed as a parameter, and is a value larger than the first comparison reference value S / L1, for example, FIG. It is given in the form shown in. Step S
₈ compares the intermediate value AMDSn the second comparison reference value (S / L2), when AMDSn <S / L2, in step S _9, the correction value HSL1 the first comparison reference value S / L1 arithmetic Calculate by the following formula.

HSL1 = HSL1 + ISL ...... (3 ) where, ISL: in variate step S ₁₀ per one HSL1,
The correction value HSL1 is compared with the upper limit value HSL1m, and when HSL1> HSL1m, the correction value HSL1 is set to the upper limit value HSL1m and step S ₁₆
Proceed to. Therefore, it is possible to prevent the first comparison reference value S / L1 from becoming too large, and it is possible to reliably detect knocking.

When AMDSn ≧ S / L2 in step S _8, in step S _12,
The intermediate value AMDSn is compared with a value twice the second comparison reference value S / L2 (second reference value), and when AMDSn ≦ 2 × (S / L2), the first comparison reference value S / L1 is reduced. When it is determined that the knocking has not occurred so much, the process proceeds to step S ₁₆ . Step S
When AMDSn> 2 × the (S / L2) is _12, that is, when the output signal of the knocking detection means exceeds a second reference value, at step S _13, the correction value a correction value HSL1 by calculating the following equation HSL1 To reduce.

HSL1 = HSL-ISL (4) Then, the correction value HSL1 is compared with the lower limit value HSL1n, and HSL1 <HSL
When the 1n, the process proceeds to step S ₁₆ to set the correction value HSL1 the lower limit HSL1n. Therefore, the first comparison reference value S / L1 can be prevented from becoming too small, and knocking can be accurately discriminated from background noise.

In step S _16, a basic value BSL1 the first comparison reference value S / L1 lookup from the memory. This basic value BSL1 is stored in advance in the form of a data map in the ROM 18 with the engine speed as a parameter, and is given in the form as shown in FIG. 9, for example. In step S ₁₇ , the first comparison reference value S / L1
Is calculated by the following formula.

S / L1 = BSL1 + HSL1 (5) The above operation will be described with reference to the figure. In FIG.
FIG. 10 (a) shows the difference value DSn and the peak hold value MDSn of the difference value DSn on the horizontal axis, and at the same time, the first comparison reference value S / L1 and the second comparison reference value S / L2 and the doubled value 2 × (S / L2) of the second comparison reference value S / L2 are shown. Difference
When DSn exceeds the first comparison reference value S / L1, as shown in FIG. 10 (b), the ignition timing (ignition advance angle) ° BTDC is retarded,
After that, it is returned at a constant advance speed. At the same time, the peak hold value MDSn is
When a difference value DSn that exceeds Sn is generated, it is converted to that value, but after that, it gradually attenuates, and the peak hold value MD
When the difference value DSn that exceeds Sn is generated, the intermediate value AMDSn is calculated. When this intermediate value AMDSn exceeds the double value 2 × (S / L2) of the second comparison reference value S / L2 (for example, point A at 10 o'clock (a)), the first comparison reference value S / L1 becomes , As shown in FIG. 10 (a), it is set small so that the response after the transient operation can be improved. Therefore, the knocking level is
As shown in FIG. 10 (c), the output torque is reduced and the output torque is improved.

FIG. 11 is a diagram showing a second embodiment of the present invention. In this embodiment, the calculation process of the first comparison reference value of the first embodiment is changed, and the difference value exceeds the second comparison reference value. The first comparison reference value is set based on the ratio.

The calculation process of the first comparison reference value (first reference value) will be described below with reference to the flowchart of FIG.

Steps Q ₁ to Q ₄ are the same as steps S ₄ to S ₇ in FIG. That is, it is determined whether or not it is not appropriate to change the ignition timing during transient operation, etc., and when it is not appropriate to change the ignition timing,
In step Q ₅ , the counter CS and the counter CL are reset (CS = 0, CL = 0) and the process proceeds to step Q ₁₀ . Counter C
As for L, the difference value DSn is the second comparison reference value (second
When the difference value DSn is equal to or less than the second comparison reference value S / L2, the counter CL is a counter that is incremented by 1 when the reference value) S / L2 is exceeded. Is. In step Q ₄ , the second comparison reference value S / L2 that is looked up based on the engine speed is compared with the difference value DSn in step Q ₆ in the same manner as above, and DSn>
When the S / L2, in step Q _7, increments the count value of the counter CL by one. In step Q ₆ , DSn ≤ S
At / L2 is incremented in step Q _8, the count value of the counter CS by one. Then, in step Q ₉ , it is checked whether the total count value of the counters CS and CL has reached 256. If this total does not reach 256, it is assumed that there are not enough samples, and step Q
Proceeds to _10, when the total value reaches 256, at step Q _11, the count value of the counter CL is checked whether or not 2 or less. When it is 2 or less, the correction value HSL1 for calculating the first comparison reference value S / L1 is calculated by the above equation 3 in step Q ₁₂ , and when it is larger than 2, the count value of the counter CL is set to 10 in step Q _13. Compare. If CL> 10, determine that the vehicle is in a knocking-prone operating state, and proceed to step Q ₁₄
In the (4) calculates a correction value HSL1 by formula, when the CL ≦ 10 proceeds directly to step Q _15. Step Q
_15, by performing the same processing as performed in the step S _10, S ₁₁ and step S _14, S ₁₅ to the correction value HSL1, it sets an upper limit and a lower limit, in step Q _16, resets the counter CL, the CS . Step Q _10, in Q ₁₇ by performing the same processing as performed in the step S _16, S _17, a basic value of the first comparison reference value S / L1
The lookup of BSL1 and the calculation of the first comparison reference value S / L1 are performed by the equation (5).

Therefore, when the ratio of the difference value DSn exceeding the second comparison reference value S / L2 is (2/256) × 100 = 0.78% or less, the first comparison reference value S / L1 is largely corrected and this ratio becomes (11 / 256) x 10
When 0 = 4.3% or more, the first comparison reference value S / L1 is corrected to be small. As a result, the first comparison reference value S / L1 can be set small in an operating state in which knocking is likely to occur, and the responsiveness after transient operation can be improved. Therefore, it is possible to accurately detect knocking and improve the output torque after a transient operation or the like.

In each of the above embodiments, the ignition timing is controlled as a control element for avoiding knocking, but needless to say, the present invention is not limited to this.

(Effects) According to the present invention, in an operating state in which knocking is likely to occur, the first reference value for knocking determination can be set to a low value to improve the knocking detection accuracy.
In an operating state in which knocking is unlikely to occur, the first reference value can be set higher to secure a sufficient engine output.

Further, when the engine (engine) rotation speed becomes high, the second reference value is corrected so as to be increased. Therefore, for example, when running at a constant speed with the engine rotation speed kept high, it is affected by background noise. Without this, the knocking signal can be detected accurately.

[Brief description of drawings]

FIG. 1 is a basic conceptual diagram of a knocking control device for an internal combustion engine of the present invention. 2 to 10 are diagrams showing a first embodiment of the present invention, FIG. 2 is an overall configuration diagram thereof, FIG. 3 is a circuit diagram showing its charge amplifier, and FIG. 4 is its quantifying means. FIG. 5 to FIG. 8 are flow charts showing the action in FIG. 5, FIG. 5 is a flow chart of the initialization process, FIG. 6 is a flow chart of the interrupt process,
FIG. 7 is a flow chart of interrupt processing at 50 ° after compression top dead center, FIG. 8 is a flow chart of calculation processing of the first comparison reference value, and FIG. 9 is prestored in ROM of microcomputer as a parameter of engine speed. FIG. 10 is a diagram for explaining the operation of the present invention, which is a data table of the second comparison reference value and the basic value that has been created. FIG. 11 is a flow chart showing the operation of the second embodiment of the present invention. 12 to 15 are operation explanatory views of a conventional knocking control device for an internal combustion engine, FIG. 12 is a diagram showing a relationship between the knocking intensity and the cumulative frequency, and FIG. 13 is a 15% cumulative frequency value. FIG. 14 is a diagram showing the knocking intensity and cumulative frequency when knocking is controlled, FIG. 14 is a diagram showing the relationship between the knocking intensity and the detection sensitivity of the knocking detection means, and FIG. FIG. 7 is an operation explanatory view showing a difference when knocking control is performed with a cumulative frequency value. 3 ... Pressure sensor (knocking detection means), 10 ... Microcomputer (discrimination means, reference value control means, knocking avoidance means).

Claims (1)

[Claims] 1. A) knocking detection means for detecting knocking of an internal combustion engine, b) determination means for determining knocking when an output signal of the knocking detection means exceeds a first reference value, and c) the first. The second reference value is set such that the value is larger than the reference value and is larger at the high engine speed than at the low engine speed, and the output signal of the knocking detection means is set to the second value. Reference value control means for controlling the magnitude of the first reference value in a decreasing direction when the value exceeds two reference values; and d) when knocking is determined by the determination means,
A knocking control device for an internal combustion engine, comprising: knocking avoiding means for avoiding knocking.