JPH0681926B2 - Knotting control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention detects the occurrence state of knocking (hereinafter referred to as knock) occurring in an engine, and determines the ignition timing or air-fuel ratio,
The present invention relates to a knock control device (hereinafter, referred to as a knock control system) that controls a knock control factor such as intake pressure.

[Conventional technology]

In general, a knock control system detects the vibration of the engine body caused by knock by a knock sensor, and advances or retards the ignition timing according to the detection result, so that the ignition timing is always near the knock limit. It controls and improves the engine output and fuel consumption.

In such a knock control system, as shown in, for example, Japanese Patent Laid-Open No. 58-7538, it is very important how to accurately detect the knock from the knock sensor.

Currently, mass-produced knock control systems mainly use knock sensors of the type that detect vibration of the engine body in terms of cost and reliability. Since a knock sensor of this type is affected by mechanical vibration noise of the engine, the SN ratio is deteriorated in a high speed rotation range where the vibration noise is large, so that detection of a high speed knock becomes very difficult.

Further, the sensor output characteristics change due to manufacturing tolerance of the knock sensor and its change over time, and the vibration transmission characteristics of the engine change due to individual difference of the engine and its change over time, resulting in large variations in sensor output.

Therefore, it is difficult to detect a high speed knock in consideration of the variation of the engine or the sensor and their changes over time, and the current situation is that knock control is cut substantially in the high speed range.

In the low-medium speed range, even if a very large knock that damages the engine can be detected, the knocking noise during control varies greatly due to the above-mentioned variations and changes over time, which causes driver discomfort. There was also a case where a loud knocking sound that gave a sound was generated.

In order to solve the above-mentioned problems, it is a well-known fact that sensors aiming for a high SN ratio, such as in-cylinder pressure sensors and combustion light sensors, are being studied at the laboratory level. It is true that such sensors are now very costly and still have many reliability problems. However, even if the cost and reliability issues are resolved,
Sensor fabrication tolerances and aging issues remain.

In addition, since such a sensor does not receive mechanical vibration noise of the engine in principle, it is expected that the SN ratio in the high speed range will be improved, but the vibration noise generated by the engine is not limited to mechanical noise. There are also many pressure vibration noises and combustion light noises caused by combustion.

Since these combustion noises naturally change due to individual differences in the engine, basically variations in the engine,
Inevitably affected by changes over time. That is, the above problems cannot be fundamentally addressed even if such a sensor is used.

[Problems to be solved by the invention]

In view of the above problems, the present invention automatically compensates the knock determination level to accurately detect and control the knock without being affected by variations in the knock sensor or the engine, changes over time, and the like. An object of the present invention is to provide a knock control device capable of preventing hunting due to compensation and reducing occurrence of many knocks due to difference in octane number of fuel.

[Outline of Invention]

In view of the above problems, the present inventors previously proposed Japanese Patent Application No. 59-9989.
In method 8, some methods are proposed. This Japanese Patent Application Sho 59
In No. -99898, when the maximum peak value V _MAX in a predetermined section of the knock sensor is sampled in large numbers without knocking, one substantially logarithmic normal distribution is formed, and when sampled with knocking, they are mutually similar. The focus is on the combination distribution of two approximately lognormal distributions with different variances.

The present inventors do not necessarily have to detect the maximum peak value V _MAX, and the frequency component peculiar to knock (generally about 6 to 9 KHz, but depending on the structure of the engine, it may be on the lower frequency side. It may be present or may be present on the higher frequency side of 10 KHz or more.) That indicates the strength of the knock vibration component, including, for example, a value obtained by integrating the knock vibration output or a predetermined value with the knock vibration output. It has been discovered that the number of pulses of a pulse train obtained when comparing with the level, the integrated value thereof, or the effective value of the knock vibration output (hereinafter referred to as knock intensity value V) may be detected.

Furthermore, by comparing the distributive properties of these knock intensity values, we found more general properties common to these knock intensity values. The nature of these knock intensity values V will first be described by taking the maximum peak value V _MAX as an example.

In FIG. 1, (1) is a knock sensor signal when only the frequency component of 6 to 9 KHz is extracted from the vibration of the engine body. Within the engine combustion section of this signal (eg
When the maximum peak value V _MAX at 10 ° to 90 ° ATDC) is sampled in multiple combustion cycles, a frequency distribution as shown in Fig. 2 is obtained. When this V _MAX is logarithmically transformed and the frequency distribution is drawn again, when sampling is performed in the absence of knocking, the distribution becomes a distribution close to a normal distribution as shown in (3), and knocking occurs to some extent. When sampling is performed in this state, the distribution deviates from the normal distribution on the high output side as shown in FIG.

In order to show this more clearly, a lognormal probability paper will be used for explanation. Generally, if the frequency distribution is a normal distribution, the cumulative frequency distribution will be an S-shaped curve having an inflection point at the cumulative 50% point as shown in FIG. The paper in which the S-shaped curve peculiar to the normal distribution is precisely graduated so that the S-shaped curves line up on a straight line when plotted is the normal probability paper as shown in FIG. Such a normal probability paper (when the characteristic value is a logarithmic value, it is called a logarithmic normal probability paper) itself is already known in the field of statistical analysis, so a detailed description of the paper will be omitted. Only the properties of the paper that are directly relevant to the description are described here.

The vertical axis of the normal probability paper, that is, the scale of cumulative frequency, becomes farther away from the 50% point as it goes to the scale at both ends with respect to the 50% point (for example, the interval between the 70% and 60% scales is 60 % And 50% longer than the graduation interval), but 50%
The scale is vertically symmetrical with respect to the scale. (For example, the 10% scale and the 90% scale are equidistant from the 50% scale, and in general, the α% scale and the (100−
The α)% scale is equidistant from the 50% scale. ) Another important property of normal probability paper is that the slope of the straight line when plotted on this paper matches the reciprocal of the standard deviation σ (ie 1 / σ). Therefore, it means that the distribution is greater as the straight line lays sideways as it sleeps.

Now, when the distribution of the maximum peak value V _MAX without knocking is plotted on this log-normal probability paper, (2) in FIG.
It becomes one straight line as shown by "no knock" in the figure. This means that the maximum peak value V _MAX without knock forms one lognormal distribution.

On the other hand, the distribution of knocked states that occur at a certain frequency (that is, knocked cycles and non-knocked cycles are mixed together at a certain ratio) has a distribution of “knocked” in FIG. As shown by ", it becomes a polygonal line where the slope changes halfway.

That is, the lognormal distribution with a small variance formed on the relatively low output side and the lognormal distribution with a large variance formed on the relatively high output side overlap.

Now, the examples of the knock intensity values V having a property that the knock intensity values V other than the maximum crest value V _MAX can be approximated to approximately one log-normal distribution in the state without knock are listed as follows.

The first is a value obtained by rectifying and integrating the vibration output in a predetermined section (for example, 10 ° to 90 ° ATDC). This value is obtained by changing the time constant of the integrator,
Alternatively, it represents the integral value of the vibration output of the cycle, and in any case, it is a value corresponding to the intensity of vibration of the cycle.

The second is the number of pulse trains generated when the vibration output in a predetermined section is compared with a certain threshold value (for example, a level slightly above the vibration center), or the integrated value of the pulse trains.
This value is also a value corresponding to the vibration intensity of the cycle.
This intensity value is slightly inferior in accuracy because its range of change is limited as compared with the range of the maximum peak value V _MAX , but it has the advantage of being easy to handle.

The third example is the effective value (RMS) of the vibration output in the predetermined section. In this RMS, the vibration level at time t is X (t), and the time length of the predetermined section is T This value also corresponds to the vibration intensity of the cycle.

From the above three examples, the strength value V that generally corresponds to the vibration strength
For, it is natural and rational to think that the distribution in the state without knock is a nearly logarithmic distribution. For example, if a certain intensity value V can be approximated by a relationship of approximately V = a · (V _MAX ) ⁿ (a, n is any real number) with respect to the maximum peak value V _MAX which is a member of the same intensity value, becomes logV = loga + nlog V _MAX, as with log V _MAX, log V also a normal distribution (i.e. V is log-normal distribution) it is clear that becomes.

The inventors next investigated what a distributional difference these intensity values V have with and without knocking.

FIG. 3 shows an example of distribution when an in-cylinder pressure sensor is attached to one cylinder of the engine and the integrated value ∫V given as the first example is extracted from this signal. Of the signal from the in-cylinder pressure sensor, only the frequency component (6 to 9 KHz) peculiar to knock is taken out by a bandpass filter, which is 10 ° after half-wave rectification.
It is a value that is integrated at a time constant of 5 msec from ATDC and taken in at a timing of 90 ° ATDC. As can be seen from FIG. 3, the distribution in the state without knock is represented by one straight line on the lognormal probability paper. That is, it forms one lognormal distribution. On the other hand, the distribution with knocking is certainly a straight line on the low value side, but at a certain point it is a curved curve. This difference in distribution is compared with the difference in distribution of the maximum peak value V _MAX of vibration of the engine body.

FIG. 4 is a distribution when the maximum peak value V _MAX of the vibration of the engine body is sampled under the same conditions as in FIG. That is, the signal from the piezoelectric knock sensor mounted on the engine block has a center frequency of 7.5 KHz and a bandwidth Q = 20 dB.
Of this signal after filtering with a bandpass filter of
It is a distribution when the maximum peak value V _MAX between 10 ° to 90 ° ATDC is sampled only for the cylinder to which the in-cylinder pressure sensor is attached. Since the data sampling is performed by the in-cylinder pressure sensor and the vibration sensor at the same time, the knock state is exactly the same.

Comparing FIG. 3 and FIG. 4 reveals the following.
First, the in-cylinder pressure sensor integrated value ∫V in FIG. 3 is
The way of bending is clearer than the maximum peak value V _MAX of the vibration sensor in FIG. 4, and secondly, the integral value ∫V of the in-cylinder pressure sensor.
Is curved in the higher output side, whereas the maximum peak value V _MAX of the vibration sensor is curved in a substantially straight line. As will be described later in detail, this phenomenon means that the in-cylinder pressure sensor has a higher ability to distinguish between noise and knock, that is, the SN ratio is higher.

However, the most important point in the comparison between Fig. 3 and Fig. 4 is that even if the bending percentages are ∫V, V
Almost no change in _MAX (about 70% in this example)
That's what it means. This shows that the cumulative percentage corresponding to the bending point can be a very effective and universal index for identifying knock states. This is because, even though knock sensors of completely different types were used and different knock intensity values were taken out, the cumulative% of bending points
Are almost equal.

That is, the knocked state can be accurately detected by paying attention to the cumulative percentage of bending on the lognormal probability paper.
If this property is well devised, it can be regarded as a more general property.

In other words, the essence of the fact that the distribution with knocks bends sharply on a log-normal probability paper is that the distribution has a relatively low output value, and most of them have a distribution estimated from only data that can be regarded as a noise group. On the other hand, the data on the high output side deviates from the estimated value in such a way that it does not belong to the population of the distribution. By knowing from which point the distribution deviates, the knocking state can be accurately detected. That is, the distribution does not necessarily have to be approximated as a substantially logarithmic distribution.

Now, it is very easy to realize the method described above as a laboratory device (for example, a knock monitor measuring instrument). It is not necessary to explain that the function of sampling the data, the function of logarithmically converting the data, and the function of obtaining the cumulative percentage of bending by revising the cumulative frequency distribution can be realized by using the microcomputer.

However, in order to apply the present invention to an actual knock control system, it is necessary to further devise.
That is, in the actual engine, it is necessary to detect the knocked state earlier, and moreover, it is necessary to put the control algorithm in the limited ROM and RAM of the vehicle-mounted microcomputer. For that purpose, it is desired to more easily obtain the cumulative percentage at which the bending occurs without intentionally sampling a large number of data and without performing logarithmic conversion.
The following is an example of such a scheme. Of course, various other schemes can be considered.

The method will be described below with reference to FIG.

FIG. 5 (1) shows the cumulative distribution of logV (illustrated on the lognormal probability paper in the upper part) and the frequency distribution at that time (illustrated in the lower part) when the knock is smaller than the control target. On the contrary, FIG. 2B shows the cumulative distribution and the frequency distribution in the knock state larger than the control target.
Now, the state in which knock is occurring at a frequency of 10% in all cycles (hence the remaining 90% is a non-knock cycle) is the knock state of the control target. At this time, the distribution of the cumulative frequency in the knock state smaller than the target bends on the output side higher than the cumulative 90% point on the log-normal probability paper as shown in the upper part of Fig. (1). Therefore, it can be regarded as one straight line (that is, one lognormal distribution) on the output side lower than the 90% point.

Therefore, suppose a cumulative 50% point on the lognormal probability paper, that is, a median value M of the frequency distribution, and consider two threshold values V _L and V _H that are vertically equidistant to this M on the logarithmic axis. . Equidistant on the logarithmic axis has a geometrical relation on the axis (logV _H −logM = logM−logV _L , that is, V _H / M
= M / V _L ). At this time, the knock frequency of the control target is 10%
It is assumed that the lower threshold value V _L is set so that the knock intensity value falls below V _L by the frequency of the same numerical value. Ie cumulative
Suppose _VL is set at the 10% point. Then, when the knock state is smaller than the target value as shown in FIG. 5 (1), the upper threshold value V _H is set due to the property of the lognormal probability paper.
Corresponds to the cumulative 90% point. Therefore, when knocking is less than the target has a frequency of knock intensity values V is below the threshold V _L lower, the frequency of exceed the upper led value V _H equal. (10% in this case) However, in the knock condition larger than the target as shown in (2) of the figure, the curve bends at a percentage lower than 90% cumulative, so the upper threshold V _H becomes 90% cumulative. No match, corresponding to lower cumulative%. That is, the frequency of exceeding the upper threshold V _H increases. (2) If it is shown in the upper diagram of the figure, the frequency increases by the amount of the double arrow. Therefore,
When the knock is larger than the target, the frequency at which the knock frequency value V exceeds the upper threshold value V _H becomes greater than the frequency at which the knock frequency value V falls below the lower threshold value V _L.

From what has been said above, the number of times that knocking intensity value V is monitored for a predetermined cycles exceeded the number N _L and an upper threshold value V _H of the V falls below the threshold V _L of the lower _NH
By comparing with, it is possible to determine whether the knock state is larger or smaller than the target.

The remaining challenge is to set V _L and V _H. The setting method will be described below.

Now, consider obtaining the approximate value V _M of the cumulative 50% point M without data sampling. The cumulative 50% point M is a point at which the probability that the knock intensity value V exceeds the M is equal to the probability that the knock intensity value V will fall. Therefore, every time the knock intensity value V is input, the V is compared with a certain value V _M. If V is larger, V _M is increased by ΔV _M. Conversely, if it is smaller, V _M is the same. if sequentially updated V _M to decrease by an amount [Delta] V _M V _M converges to cumulative 50% point M. That is, the cumulative 50% point M can be obtained without sampling the data to obtain the distribution.

Next, consider obtaining the lower threshold value V _L. Since V _L is a cumulative 10% point, the probability that the knock intensity value V will fall below V _L is 1/10, and conversely, the probability that it will exceed V _L is 9/10. That is, each probability is 1: 9. Therefore, let us consider obtaining the cumulative 50% point M by the same method as that used for obtaining. Every time the knock intensity value V is input, the V is compared with a certain value V _L. If V is larger, V _L is increased by ΔV _L , and conversely V is smaller.
_If V _L is sequentially updated so as to decrease _L by 9 times ΔV _L , which is 9 · ΔV _L , V _L converges to a cumulative 10% point. This is because the expected value for increasing / decreasing V _L becomes 0 only at the actual cumulative 10% point (9/10 × Δ
V _L −1 / 10 × 9 · ΔV _L = 0). That is, by changing the ratio between the increase amount and the decrease amount, in principle, the value can be converged to an arbitrary cumulative% point.

Thus we have been able to determine the threshold _{V L} of cumulative 50% point _{V M} and lower, upper threshold _{V H} is, _{V M} / _{V L}
= A, V _H = V _M · A (= V _M ² / V _L ) can be easily obtained.

With the method described above, it is possible to easily obtain the cumulative percentage points of bending without data sampling and without logarithmic conversion, and it is possible to detect a knock state.

In the present invention, for example, as described above, the average knock state is detected, and the knock determination level (for example, rectification and integration of the knock sensor signal) is automatically compensated. The following inconvenience may occur. That is, first, the knock control factor and the determination level hunt.

This hunting phenomenon will be described using the model of the ignition timing θig in FIG. For example, knock determination level Vr
It is assumed that the automatic compensation of the determination level is started from the state (A) where ef is too small and is most retarded. Since there is no knock, Vref
Is determined to be too small, Vref is raised, and θig starts advancing when reaching a certain value, but during (B), the knock is extremely small, so Vref is excessively corrected. When θig advances and crosses the trace knock point, which is a light knock, Vref is lowered to make it easier to detect the knock sensor signal by automatic compensation, but the knock is large even if it exceeds the proper value, so it is corrected too small. (C). Therefore, θig is retarded from the trace knock point, and after that, the state becomes the same as that in (B) again, and Vref is excessively corrected (D). By repeating the above, hunting occurs between θig and Vref.

Next, as a disadvantage of automatic compensation of the knock determination level, the determination level may be overcorrected due to the difference in octane number of fuel, for example, gasoline. That is, for example, since knocking is less likely to occur during operation with gasoline having a high octane number (high-octane gasoline) than in the case of gasoline having a low octane number (regular gasoline), the ignition timing, which is a knock control factor, is corrected to the advance side. At the same time, the knock determination level Vref is corrected so as to be gradually increased to make it difficult to detect the knock sensor signal. afterwards,
If it is operated with regular gasoline, knocking is likely to occur, the ignition timing is corrected in the retard direction, and the knocking determination level Vref is gradually lowered,
Since it is difficult to detect the knock sensor signal until the determination level falls to an appropriate value for regular gasoline, knock may occur frequently.

The present invention solves the above-mentioned inconvenience.

[Means for solving problems]

In order to achieve the above object, the present invention, as shown in FIG. 7, includes a knock sensor for detecting an engine knock and a knock determination level creating means for creating a knock determination level for determining the knock. A knock determination means for determining knock according to the knock determination level and a signal from the knock sensor; knock intensity value detection means for extracting a knock intensity value V from the signal from the knock sensor; and knock performed by the knock determination means. Of knock determination situation detecting means for detecting the determination situation, knock generation state determination means for determining the knock generation state from the distribution shape obtained when multi-cycle sampling of the knock intensity value, and the knock determination state and the knock Knock determination level correction means for correcting the knock determination level according to the occurrence state,
And a control unit that controls the value of the knock control factor of the engine in accordance with the knock determination result of the knock determination unit.

〔Example〕

Hereinafter, the device of the present invention and its operation will be described in detail according to embodiments.

FIG. 8 is a block diagram showing an embodiment of the present invention. In the figure, 1 is a 4-cylinder 4-cycle engine, 2 is a reference angle sensor for detecting a reference crank angle position (for example, top dead center) of the engine, and a crank angle sensor for generating an output signal at every constant crank angle of the engine. A distributor 3 having a built-in power supply is an igniter and a coil that receives an ignition timing control signal output from the control circuit 10 and cuts off energization to the ignition coil.

4 is a knock sensor for detecting the vibration of the engine gorok corresponding to the knock phenomenon of the engine by a piezoelectric element or the like, 5 is an air flow meter for detecting the intake air amount of the engine, and outputting a signal corresponding thereto, 6 is A throttle valve connected to the throttle angle sensor, 7 is an injector for injecting fuel into the intake manifold based on the fuel injection timing and the fuel injection period determined by the control circuit 10, 8
Is a turbocharger for supercharging, 9 is an O ₂ sensor that generates an output signal according to whether the exhaust gas air-fuel ratio is richer or leaner than the stoichiometric air-fuel ratio, and 10 is from each of the above sensors. Is a control circuit for controlling the ignition timing and the air-fuel ratio of the engine in accordance with the input signal state of.

Next, the detailed configuration and operation of the control circuit 10 will be described with reference to FIG. In FIG. 9, reference numeral 10-1 is a central processing unit (CPU) for calculating the ignition timing and the fuel injection amount, which uses an 8-bit microprocessor. 10-2 is a read-only storage unit (ROM) for storing control programs and control constants necessary for calculation, and 10-3 is a CPU
Reference numeral 10-1 is a temporary storage unit (RAM) for temporarily storing operation data during operation according to a program. 10-4
And 10-5 are output signals of the reference angle sensor 2-1 and the crank angle sensor 2-2 built in the distributor 2 (a magnetic pickup is used in this embodiment).
Is a waveform shaping circuit for shaping the waveform.

10-6 is an interrupt control unit for causing the CPU to perform interrupt processing by an external signal or an internal signal, and 10-7 is configured so that the count value is increased by one for each clock cycle that is the basic cycle of CPU operation. It is a 16-bit timer. The engine speed and the crank angle position are fetched into the CPU by the timer 10-7 and the interrupt controller 10-6 as follows. That is, the CPU reads the count value of the timer each time an interrupt is generated by the output signal of the reference angle sensor 2-1. The count value of the timer is the clock cycle (for example, 1
μs), the time interval of the reference angle sensor signal, that is, the engine 1 is calculated by calculating the difference between the count value at the present interruption and the count value at the previous interruption.
The time required for rotation can be measured. In this way, the engine speed is obtained.

In addition, the crank angle position is determined based on the top dead center signal of the reference angle sensor 2-1 because the signal of the crank angle sensor 2-2 is output at every constant crank angle (for example, 30 ° CA). Can be known in 30 ° CA units. This crank angle signal for every 30 ° CA is used as a reference point for generating the ignition timing control signal.

10-8 is analog by switching multiple analog signals at appropriate times.
It is a multiplexer for leading to the digital converter (A / D converter) 10-9, and the switching timing is controlled by the control signal output from the output port 10-12. In this embodiment, an intake air amount signal from the air flow meter 5, a knock intensity value signal from the knock intensity detection circuit 10-10, etc. are input as analog signals. (In addition, the water temperature sensor signal,
Battery voltage etc. are input. ) 10-9 is A / for converting analog signal to digital signal
It is a D converter. Reference numeral 10-10 is a knock intensity value detection circuit for receiving the signal from the knock sensor 4 and extracting the knock intensity value V for each cycle. Reference numeral 10-11 is an input port for a digital signal, and a rich lean signal from the O ₂ sensor 9, an idle signal from the throttle sensor 6 and a power signal are input to this port.

10-12 are output ports for outputting digital signals. From this output port, an ignition timing control signal for the igniter 3, a fuel injection control signal for the injector 7, and a control signal for the multiplexer 10-8 are output. Reference numeral 10-13 is a CPU bus. The CPU puts a control signal and a data signal on this bus signal line to control peripheral circuits and send and receive data.

Next, the knock intensity value detection circuit 10-10 will be described with reference to FIG. In FIG. 10, 10-10-1 is a filter such as a band pass or a high pass for selecting and extracting only knock frequency components from the output signal of the knock sensor 4, 10-10
-2 is a rectifier for half-wave or full-wave rectification of the output of this filter, 10-10-3 is an integrator for integrating the output of the rectifier to obtain a knock intensity value for each cycle,
Reference numeral 10-10-4 is a gate circuit for controlling the integration interval of the integrator.

The operation of this knock intensity value detection circuit will be described with reference to FIG. FIG. 11 (1) shows the knock sensor output after passing through the filter, and FIG. 11 (2) shows the output obtained by half-wave rectifying the knock sensor output by the rectifier 10-10-2. (3) The figure shows the output signal of the gate circuit 10-10-4 which operates according to the control signal output from the output port 10-12 in the control circuit 10. Ie about 10
It rises at ゜ ATDC, and knock strength is CPU10-at about 90 ゜ ATDC
1 is a signal that falls immediately after being taken in, and this determines the integration section of the integrator 10-10-3. (4) The figure shows the integrator set and reset by the gate circuit 10-10-3
Is the output signal of.

The time constant of the integrator in this embodiment is adjusted to about 5 msec. The rising of the gate circuit starts integration of the signal after half-wave rectification (Fig. (2)), and the falling resets the integrated value. The gate circuit is CPU10-1
Falls immediately after the integrated value is fetched through the multiplexer 10-8 and the A / D converter 10-9, so that the integrated value for each cycle, that is, the knock intensity value, is successively fetched by the CPU.

Next, the knock detection and the operation of the knock control system will be described in detail with reference to the flowcharts of FIGS.

FIG. 12 is an interrupt routine for setting the ignition timing and the fuel injection time in the timer of the microcomputer. Interrupt 100
Therefore, in step 200, first, the basic ignition timing θ
_BSE and basic injection timing τ _BSE are calculated. The basic ignition timing θ _BSE and the basic injection time τ _BSE are proportional to the engine load, which is obtained by dividing the engine speed N and the engine additional A / N (the intake air amount Q measured by the air flow meter by the engine speed N). ) Is stored in the ROM of the microcomputer as a two-dimensional map. Then, in step 200, at the same time, the ignition timing and the injection time are corrected by various sensor signals other than the knock sensor. For example, the ignition timing and the injection time are corrected by the water temperature, or the injection time is corrected by the battery voltage (considering the invalid injection time).

Next, at step 300, it is judged if the current operating condition is the knock control execution condition. For example, it is generally known that when the load of the engine is light, knocking hardly occurs, and if the light load is forcibly controlled to knock, the output, fuel consumption and the like are rather lowered. Therefore, in this embodiment, the knock control is executed only when the engine load (which can be determined by Q / N) is equal to or greater than a predetermined value. (Otherwise, it is conceivable to set a limit based on the engine speed.) If it is determined that the knock control execution condition is satisfied, in step 400, the ignition timing and the injection time are corrected by the knock control. The correction amount of the ignition timing by the knock control (in the present embodiment, the retard amount R from the basic ignition timing θ _BSE ) is calculated by another routine described later, but the final ignition timing θ is determined in this step 400.
Then, θ = θ _BSE −R is obtained.

Further, the correction amount of the fuel injection time is determined based on this retardation amount R. That is, when the retard amount R is large, the ignition timing is retarded, so the exhaust temperature may become too high. Therefore, in this case, it is necessary to prolong the injection time so as to make the air-fuel ratio rich. For example, the correction amount of the injection time may be determined so as to be proportional to the retard amount R.
The final ignition timing θ and the final injection time τ thus determined are set in the timer of the microcomputer in step 500. After being set, the program returns to the main routine (step 600).

FIG. 13 shows a knock state detection and knock control routine. In the case of this embodiment, this interrupt routine is executed near the top dead center (TDC) of the engine for each ignition cycle.

When the interrupt routine is entered at step 700,
Step 800 for detecting an average knock condition over a relatively large number of cycles, in a manner as described in the operation of the invention.
To execute. Details of this step 800 will be described later. Next, in step 900, it is determined whether or not the current knock control execution condition is present. If not, the process directly returns in step 1400.

If it is under the knock control execution condition, in step 1000, a knock determination level Vref for determining the presence or absence of knock for each cycle is calculated. Although the knock state can be separately detected by the method of the present invention, since a relatively multicycle period is required to detect it,
Considering the case where knocks occur frequently within a very short period of time, such as when the engine is suddenly accelerated, the conventional knock control system method of determining the knock for each cycle and retarding the ignition timing for each cycle is also used. I did it.

The knock determination level Vref is _(a value that converges to the median of the frequency distribution, which will be described in detail later) V _M obtained for each cylinder at step 800 and the constant K (but which also set for each cylinder, the The value is also corrected in an appropriate direction in the step described later.) And Vref = K ·
It is created in relation to V _M. Therefore, although the knock determination level differs for each cylinder, this allows the knocks of all the cylinders to be detected with high accuracy. The initial value of K is stored in the ROM as a two-dimensional map of engine speed N and cylinders.

Next, at step 1100, the knock intensity value V fetched as the value of the immediately preceding ignition cycle and the knock determination level Vref are compared in magnitude to perform knock determination for each ignition. Step 1200 for calculating the ignition retard amount R in accordance with the result is 1200 (details will be described later). Next, in step 1300, it is determined whether or not the current knock determination level is appropriate, and this is always corrected in an appropriate direction (details will be described later). After this, the process returns at step 1400.

Next, the step 800 for detecting the knock state will be described in detail with reference to FIG. In step 801,
The knock intensity value V fetched this time is compared with the upper threshold value V _H corresponding to the cylinder. If V> V _H , the number of times N _H is exceeded is incremented by one (step 80).
2). In other cases, the routine proceeds to step 803, this time the knock intensity value V is compared with the lower threshold value _VL . V <V
_In the case of _L , the number of rounds is increased by one (step 804) and the process proceeds to step 805. Otherwise, go directly to step 805. Then in step 805,
Updates the value V _M of the cumulative 50% point. The update method is as described above. That is, when the knock intensity value V exceeds the current V _H corresponding to the cylinder (V> V _M ), V _M
Was increased by [Delta] V _M, only the same amount of [Delta] V _M and V _{<V M} if _{V M} conversely decrease. By doing this, V _M
Is constantly updated to follow the cumulative 50% point.

Next, in step 806, it is checked whether or not it is time to detect a knock state. That is, the knock state is detected at predetermined intervals. In this embodiment, this interval is set to about 0.7 sec. There are two reasons why the interval is not the cycle number but the time interval. The first reason is that the knocking state is detected as close to human sensory evaluation as possible. Generally, when a person evaluates a knock state, it is determined by how many knocks occur in a certain time. In other words, the engine cycle progress is an unrelated concept for the driver of a car, and only the time between them is the evaluation standard that the driver can know. In this way, by detecting the knocking state on an hourly basis, it is possible to bring out the best output and fuel efficiency without making the driver of the vehicle uncomfortable.

The second reason relates to the subsequent updating of the thresholds V _L , V _M. As described above, in order to check whether the knock state is larger or smaller than the target value, it is necessary to set the lower threshold value V _L to the cumulative percentage point of the same% as the knock occurrence frequency in the target knock state. There is. However, in general, the target knock state is usually set smaller as the engine speed increases. Even if a relatively large amount of knock occurs in the low speed range of the engine, the engine will not be damaged and the output and fuel efficiency will be improved. However, in the high-speed range, preignition may be induced and the engine may be damaged even in a relatively infrequently knocked state. For this reason, it is necessary to suppress the knock state to a relatively small value in the high speed range. Therefore, it is desirable to set the lower threshold value _VL to a smaller% accumulation point as the speed increases. In order to set this V _L to a small%, it is sufficient to increase the number C of updating cycles of V _L as already described in the operation. If the updating of V _L is executed every hour, the number of cycles C during that time increases as the speed increases, and thus the above-mentioned object can be achieved.

Next, in step 807, it is checked if the engine conditions have changed suddenly during the detection interval. That is, it is checked whether the engine speed and the engine load have changed by a predetermined value or more within 0.7 seconds. In this embodiment, for example, the allowable change in engine speed is ± 300 rpm, and the allowable change in engine load is ± 15 in terms of pressure.
It is set to 0 mmHg. If it is determined in step 807 that it is in the normal state, the knock state is detected in step 808.

The knocking state is detected by comparing the number of times N _H and N _L for each cylinder. Ie N _H and N _L
Is approximately equal, it is determined that the knocking state of the cylinder is smaller than the target value. If N _H is larger than _NL even if the error is taken into consideration, it is determined that the knocking state is larger than the target value. To be done. The detected knock state is stored as a flag for each cylinder, and a knock state detection completion flag indicating that the knock state is detected is set.

Next, at step 800, the upper threshold value V _H and the lower threshold value V _L are updated. The update method is as follows. First, V _H and V _L are V _H / V _M
= V _M / V _L. Let this geometric ratio be A (V _H
/ V _M = V _M / V _L = A), V _H and V _L can be updated by updating A. Since V _L = V _M / A, the knock intensity value V is V _L during this detection interval.
If it is lower than even once (that is, if N _L counted in step 804 is 1 or more), A is ΔA.
By decreasing V _L by ΔV _L ,
When N _L = 0, V is reduced by decreasing A by ΔA.
Increase _L by ΔV _L. By doing this, V _L
Can be set to the required cumulative percentage point. And the upper side of the threshold _{V H} can be made of _V H = A · _{V M.}
V _H, V _L is updated in this way for each cylinder.

Next, in step 810, N _H and N _L are cleared (N _H =
After 0, N _L = 0), the counter that creates the detection interval of 0.7 sec is cleared (step 811).

Next, with reference to FIG. 15, a method for calculating the ignition retard amount R in step 1200 of FIG. 13 will be described in detail.

First, if the knock intensity value V exceeds the knock determination level K · V _M at step 1201, the cycle increases the retard amount R from the basic ignition timing is regarded as a knock cycles only [Delta] R ₁₎ Step 1202). This ΔR ₁ is also used for general knock control,
Although it is about 0.5 ° to 2 ° CA, it is set to 1 ° CA in this embodiment. Next, at step 1203, the counter for the number of knock determinations is incremented. This counts the number of times regarded as a knock cycle, and is used as a judgment material for the knock judgment level correction described later.

In step 1201, if the V ≦ K · V _M considered non knock cycle proceeds to step 1204. Step
In 1204, R is limited to the case where it is regarded as a non-knock cycle and continues for a predetermined time (generally about 1 second).
The ignition timing is corrected by advancing the ignition timing by reducing ΔR ₁ . In other cases, the current retardation amount R is retained as it is.

Next, at step 1205, it is checked by the knock state detection completion flag at step 808 in FIG. 14 whether or not the average knock state is detected. If not yet detected (ie during the detection interval mentioned above)
The process proceeds to step 1213, but if the detection completion flag is set, the size of the knocked state is checked in step 1206. That is, if the flag that the knock state is larger than the target value is set, the retard amount R is increased by ΔR ₂ in step 1207. This ΔR ₂ is different from ΔR ₁ in which the knock is determined and retarded for each cycle described above, and it is a correction amount for correcting the ignition timing depending on the average state of the knocks, so a value smaller than ΔR ₁ , for example, 0.5 ° CA
The degree is good. As a result, the retard amount R is slowly corrected according to the average knocking state, and is also corrected in small increments centering on this to quickly avoid knocking depending on whether knocking occurs in each cycle.

When the retard amount R is set for each cylinder (that is, in the case of the ignition timing control for each cylinder), the retard amount R of the cylinder may be increased or decreased according to the knock state of the cylinder as described above. In the case of uniform ignition timing control for all cylinders, there is only one retard angle amount R, and at this time, the knocking state of each cylinder may be comprehensively determined and increased or decreased. For example, in the case of a four-cylinder engine, it is possible to determine that the knocking state is large when the knocking state is large in two or more cylinders.
Alternatively, the above N _L and N _H are not classified for each cylinder, and one N
It is also possible to directly know the knock state of the whole by counting the number with _L and N _H.

Even in this case, two thresholds V _L and V _H are set for each cylinder,
Comparison is also performed for each cylinder and only the comparison result (that is, N _L , N _H
Only) it is desirable to use the common for all the cylinders, if the expense of some accuracy of detecting knocking state, it is also possible to common V _L, a V _H on all cylinders.

Next, at step 1208, the retard amount R is set to the maximum retard amount limit Rm.
Compare with ax. Generally, the retard amount R is usually limited to avoid excessive ignition timing fluctuation due to knock control and to prevent exhaust temperature rise.
This limit value Rmax was a predetermined fixed value. However, in this example, this is learned by the average knock state. That is, the retard amount R is kept within the range of the minimum retard amount limit Rmin and the maximum retard amount limit Rmax so that the ignition timing is not unnecessarily advanced or conversely retarded. Then, we will learn how to absorb changes in seasons, differences in gasoline properties, and engine variations. If the ignition timing is retarded too much (that is, if R becomes too large), the exhaust temperature rises and becomes a problem, but if the knocking is frequent, the engine will be damaged unless retarded further. There is a fear. In this case, engine protection is prioritized. It is also possible to detect this state and turn on the abnormal lamp.

Step 1208 is a step for determining whether or not the control range of the retard amount R should be corrected in the retard direction. That is, when R is required to be larger than the maximum retardation amount Rmax and the average knocking state is large, Rmax is set to ΔRmax (for example, about 0.2 ° CA) in step 1209.
And at the same time increase Rmin to ΔRmin (also 0.2 ° C
By increasing only A), the limit range of R is corrected in the more retarded direction. This control range is preferably, for example, about 5 ° to 7 ° CA (Rmax-Rmin≈5 ° CA to 7 ° CA).

If it is determined in step 1206 that the knocked state is smaller than the target, the reverse operation described above is performed. That is, in step 1210, R is decreased (that is, corrected in the advance direction) due to the knocked state, and steps 1211 and 1
At 212, the control range of the retard amount R is corrected in the advance direction.

Thus, the process proceeds to step 1213, where the retard amount R is finally obtained.
Limit. That is, when R> Rmax, R = Rmax, and when R <Rmin, R = min.

Next, with reference to FIG. 16, a process of automatically correcting the knock determination level used for knock determination for each cycle in step 1300 of FIG. 13 which is a main part of the present invention in an appropriate direction will be described. .

First, at step 1301, it is checked by the knock state detection completion flag whether or not an average knock state is detected. If it is detected, the knock state is checked in step 1302. If it is determined that the knock condition is larger than the target, step 1303
In (12), the number of knock determinations (that is, frequency) for each cyggle as the knock determination status is checked (this number of determinations is counted in step 1203 in FIG. 15).

If the number of knock determinations is less than or equal to the predetermined value, it is determined that the knock determination level is too high, and K is decreased by ΔK to lower the knock determination level (step 1304). That is, when the knock state is large and the number of knock determinations is small, the knock determination level is too high and the knock determination is erroneous. In this case, if the number of knock determinations is relatively large, K is held as it is because the knock determination is normally performed.

If it is determined in step 1302 that the knock state is smaller than the target, it is checked in step 1305 whether the number of knock determinations is too large. If the number of knock determinations is too large, K is increased by ΔK in order to correct the knock determination level to a high value (step 1306).
That is, when the knock state is small and the number of knock determinations is too large, the knock determination level is too low and the noise cycle is erroneously determined as knock. If the number of knock determinations is small, this is only because the engine is not actually knocked, so the suitability of the knock determination level is unknown (may be appropriate or may be too high). Therefore, in this case, by keeping K as it is, it is possible to prevent the knock determination level from being excessively raised as described above, and to prevent the knock from occurring frequently due to a change in octane number.

The knock determination level is corrected for each cylinder.
That is, based on the knock state for each cylinder and the number of knock determinations for each cylinder, K corresponding to each cylinder is corrected in an appropriate direction. Of course, it is also possible to correct K as one common K without having it for each cylinder in the same way as described in the method of calculating the retardation amount R. Further, the determination of the number of knock determinations (steps 1303 and 1305) may be performed as "0" or "1" as if there was or was not a knock determination during that time.

Next, at step 1307, the knock determination count is cleared, and subsequently, the knock state detection completion flag is cleared (step 1308).

As described above, knock control is executed.

It should be noted that in the above-described embodiment, the detection of the knock determination situation is performed by the number of knock determinations (steps 1303 and 1305) in FIG. 16, but as shown in FIGS. It is also possible to determine that the value is changing in the direction in which knocking is likely to occur or in the direction in which knocking is less likely to occur, and set the knocking determination situation. That is, FIG. 17 shows a case where the ignition timing control is performed. In step 1303 ', it is judged whether or not the retard angle amount has decreased from a predetermined T seconds before, and in step 1305' it is determined whether or not the retard angle amount has increased. I am trying to determine whether
It is possible to prevent the above-mentioned ignition timing hunting and the like.

Further, although the ignition timing is treated as a factor for controlling the knock in the above-mentioned embodiment, this is due to the knock control factors such as the air-fuel ratio, the intake pressure (supercharging pressure such as turbo), the EGR, the anti-knock agent, etc. It can be widely applied. In this case, an immediate knock control factor such as ignition timing is controlled according to the knock determination result for each cycle, and an average knock occurrence such as boost pressure is generated according to the detection result of the average knock state. Various arrangements such as controlling the factors that influence the state are also possible. Of course, only one of the ignition timing, air-fuel ratio, intake pressure, EGR, anti-knock agent, etc. may be controlled.

Further, in the above-mentioned embodiment, the device which does not use the logarithmic converter is shown, but if the use of the logarithmic converter or the software for the logarithmic conversion instead thereof is allowed even if the constraint conditions such as the cost are taken into consideration. For example, various devices can be considered. For example, it is possible to detect the knock state by the magnitude relation between the average value and the median value of the logarithmic conversion value logV of the knock intensity value V. That is, when the knocked state is small, the distribution of logV is almost a normal distribution, and therefore the median and the mean of the normal distribution match. However, when the knock state becomes large, the average value becomes larger than the median value, so that the knock state can be identified.

Further, in the above embodiment, the type of sensor that detects the vibration of the engine block is used as the knock sensor,
As described in detail above, a microphone, an in-cylinder pressure sensor, a combustion light sensor, or the like can be used.

Also, as already explained, the assumed distribution is not limited to the lognormal distribution, and by applying appropriate conversion such as the binomial distribution and the gamma distribution, it can be treated practically as a lognormal distribution. With respect to such a distribution, the above-mentioned embodiment can be applied as it is, and the distribution becomes a normal distribution as it is instead of logarithm, and the handling becomes easier. In other words, the equivalence relation may be replaced with the equivalence relation.

〔The invention's effect〕

As described above in detail, according to the present invention, the knock shape value V, which has been difficult in the past, is detected by determining the distribution shape when the knock intensity value V is multi-cycle sampled to detect the average knock state. Alternatively, it is possible to detect a true knock state with high accuracy without being affected by engine variations and changes over time, and prevent hunting due to overcompensation of the knock determination level and knock due to difference in fuel octane number. Can be effectively reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing the maximum value of the knock signal and its distribution state, FIG. 2 is a diagram showing the cumulative distribution of the maximum value of the knock signal and this distribution on a log-normal probability paper, and FIG. 3 is a diagram showing the knock signal. The cumulative distribution of the integrated value is shown on a log-normal probability paper, and FIG. 4 is a graph showing the cumulative distribution of the maximum value of the knock signal on the log-normal probability paper in the same knock state as FIG. 3, and FIG. FIG. 6 is a diagram for comparing the distributions of knock intensity values when the knock is smaller and larger than the target, FIG. 6 is a diagram showing the hunting state of the ignition timing and the knock determination level, and FIG. 7 is a diagram showing the configuration of the present invention FIG. 8 is a block diagram for carrying out the invention, FIG. 8 is a block diagram showing an embodiment of the present invention, FIG. 9 is a detailed block diagram of the control circuit in FIG. 8, and FIG. 10 is a knock intensity value detection in FIG. Fig. 11 is a detailed circuit diagram of the circuit, and Fig. 11 is a signal wave used to explain the differential of the knock intensity value detection circuit. FIGS. 12 to 16 are flowcharts showing the procedure of knock detection and control in the control circuit, and FIG. 17 is a main part flowchart showing another embodiment of the present invention. 1 ...... engine, 3 ...... igniter, ignition coil, 4 ...... knock sensor, 7 ...... injector, 8 ...... turbocharger, 9 ...... O ₂ sensor, 10 ...... control circuit, 10-1 ...... CPU, 10-
2 ... ROM, 10-3 ... RAM, 10-10 ... knock intensity value detection circuit, 10-10-2 ... rectifier, 10-10-3 ... integrator.

Claims (4)

[Claims] 1. A knock sensor for detecting knock of an engine, a knock determination level creating means for creating a knock determination level for determining this knock, and a knock sensor according to the knock determination level and the signal of the knock sensor. Knock determination means for determining a knock, a knock intensity value detection means for extracting a knock intensity value V from a signal from the knock sensor, a knock determination situation detection means for detecting a knock determination situation by the knock determination means, and the knock Knock occurrence state determining means for determining a knock occurrence state from a distribution shape obtained when multi-cycle intensity values are sampled, and a knock determination level for correcting the knock determination level according to the knock determination status and the knock occurrence state. The correction means and the engine according to the knock determination result by the knock determination means. A knocking control device for an internal combustion engine, comprising: a control unit that controls a value of a knock control factor. 2. The knocking control device for an internal combustion engine according to claim 1, wherein the knocking determination status is detected based on a frequency of determination of the presence or absence of knocking. 3. The knocking control device for an internal combustion engine according to claim 1, wherein the knocking determination condition is detected by a change in a knocking control factor. 4. The internal combustion engine according to claim 1, wherein the knock determination level correction means corrects a constant K for creating the knock determination level. Knocking control device.