JPH0742923B2 - 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.

[Prior Art] Generally, a knock control system detects a vibration of an engine body caused by a knock by a knock sensor, and the ignition timing is always advanced by advancing / retarding the ignition timing according to the detection result. It controls near the knock limit to improve engine output and fuel efficiency.

In such a knock control system, it is very important how accurately a knock sensor detects a knock as disclosed in Japanese Patent Laid-Open No. 58-7538.

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 deteriorates in the high speed rotation range where the vibration noise becomes large, so that detection of high speed knock becomes extremely difficult.

Further, the sensor output characteristics change due to the manufacturing tolerance of the knock sensor and its change over time, and the vibration transmission characteristics of the engine change due to the individual difference of the engine and its change over time, resulting in large variations in the 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 substantially cut 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 variations and changes over time as described above, which is not suitable for the driver. In many cases, a large knocking sound that gives a pleasant feeling 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 expensive and still have many problems in terms of reliability. However, even if the cost and reliability problems are solved, there still remain the problems of sensor manufacturing tolerance and aging. 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 provides a knock control device that accurately detects a knock without being influenced by variations in a knock sensor or an engine, aging, and the like, and controls a knock control factor according to the detection result. It is intended.

[Means for solving problems]

In order to achieve the above object, the present invention provides a knock sensor for detecting knock of an engine, a maximum peak value detecting means for extracting a maximum peak value V _MAX of this signal from the signal of the knock sensor, and this maximum wave. A determination means that determines whether the distribution shape obtained when high value V _MAX is sampled in multiple combustion cycles is a predetermined distribution shape, and that detects the average knock state over multiple cycles according to the determination result, and the knock sensor Knock determination means for determining the presence or absence of knock for each combustion cycle based on the signal, and control for controlling knock control factors such as engine ignition timing or air-fuel ratio intake pressure according to the knock determination result And means for limiting the control value range of the knock control factor in accordance with the detection result of the knock state.

[Action]

Hereinafter, the outline of the present invention and the technical basis of the present invention will be described in detail.

In order to solve the above problems, the present inventors previously proposed several methods and devices in Japanese Patent Application No. 59-99898. In this Japanese Patent Application No. 59-99898, when the maximum peak value V _MAX in a predetermined section of the knock sensor is sampled in large numbers without knocking, one substantially lognormal distribution is formed and sampling is performed with knocking. In this case, it is noted that in this case, a combined distribution of two approximately lognormal distributions having different variances is obtained.

The nature of this maximum peak value V _MAX will be briefly described. In Fig. 1, (1) shows 6 of the vibrations of the engine body.
It is a knock sensor signal when only the frequency component of ~ 9KHz is taken out. Within the engine combustion section of this signal (for example,
When the maximum peak value V _MAX in 10 ° to 90 ° ATDC) is sampled by multiple combustion cycles, the 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 knock, it becomes a distribution close to a normal distribution as shown in Fig. (3), and knock has occurred 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. Since such a normal probability paper (which is called a logarithmic normal probability paper when the characteristic value is a logarithmic value) itself is already known in the field of statistical analysis, a detailed description of the paper will be omitted. Only the properties of the paper that are directly related to the explanation of are described here.

The vertical axis of the normal probability paper, that is, the scale of the 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, longer than the interval between the 70% and 60% scales). ) Is a vertically symmetrical scale with respect to the 50% scale. (For example, a 10% scale and a 90% scale are equidistant from a 50% scale, and in general α
The% scale and the (100-α)% scale are equidistant to 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.

When plotted on this log-normal probability paper as the distribution of the maximum peak value V _{MAX in} the state without knocking, one straight line is obtained as shown by “without knocking” in (2) of FIG.
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 ", the line becomes a polygonal line whose slope changes.

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.

Here, as will be described later, the cumulative% corresponding to the bending point is the ratio of non-knock cycles (noise cycles) in all cycles, in other words, the remaining% (100% in this example).
(-70 = 30%) indicates the rate of knock cycles.

This will be described in detail with reference to FIG. Figure 1 (1)
The figure shows that the signal-to-noise ratio for knock detection is very high, and the maximum peak value V of knock cycle and non-knock cycle (noise cycle) V
_{When the MAX} can be completely separated, a frequency distribution corresponding to two knock states of large and small (illustrated in the upper row) and a cumulative frequency distribution corresponding to each of them on the normal probability paper (illustrated in the lower row) are drawn. Is. The horizontal axis is a logarithmic scale. In the upper group frequency distribution, the solid line shows a distribution of relatively small knock states in which the ratio of noise to knock is 90:10, that is, 10% of the total is knock cycle, and the broken line is 40% of total knock cycle. This is a relatively large knock state distribution. In actual engine knock, the frequency of knock increases as the knock increases, and the peak value itself also increases, so the distribution corresponding to the knock cycle in the distribution of the broken line actually shifts to the larger value. . However, when the knocking state becomes large, the frequency of knocking also increases, so even if we discuss only the knocking frequency, the essence is not lost at all.

The cumulative frequency distribution corresponding to each knock state in the upper row (that is, the distribution when the noise distribution and the knock distribution are regarded as one group and accumulated from the smaller value) is plotted on a log-normal probability paper. become that way. As can be seen from this figure, when viewed from the lower values, a curve is a straight line up to a certain point and a downward convex curve that sharply bends from that point. The cumulative% of the points where the bending occurs indicates the noise generation rate in any case. That is, the remaining% indicates the occurrence rate of knock.

Next, in the same knock condition, assume that the discrimination between knock and noise is very poor, that is, when a sensor with a low SN ratio is used or when a knock strength value with a poor SN ratio is selected. The solid line in (2) of Fig. 3 represents the distribution sampled by a sensor with a good SN ratio when the knock occurrence frequency is 10% (noise and knock ratio is 90:10).
The broken line shows the same knock condition, a sensor with a poor SN ratio, or
This is the distribution when a knock strength value with a poor SN ratio is selected.
The cumulative distributions corresponding to these are shown in the lower row. From this figure, it can be seen that the distribution of the sensor with a good SN ratio is curved from a certain point, but when the SN ratio is relatively poor, it can be approximated by two straight lines that are bent from the middle. It can be seen that in both cases, the cumulative percentage of occurrence of bending is almost the same. The cumulative% still indicates the noise generation rate, and therefore the remaining% indicates the knock generation rate.

In other words, even if a sensor or knock strength value with a slightly poor SN ratio is selected, or if a sensor or knock strength value with a relatively high SN ratio is selected, the cumulative% at which bending occurs will be accurate. It is possible to indicate the occurrence rate of, and thus the knock state.

For example, in the state where the noise distribution and the knock distribution are overlapped (that is, the state where the SN ratio is bad) like the frequency distribution indicated by the broken line in FIG. 3B, the maximum peak value of each overlapped portion is It is impossible to individually identify whether this is noise or knock. In other words, it is impossible to discriminate at all by the conventional method in which the threshold value of the maximum crest value is set to a threshold value, and when the output is higher than this, knock is generated, and when the output is lower than this, noise is generated. However, if attention is paid to the cumulative percentage of the bending points described here, the knocking state can be accurately detected even in such a case.

As described above, the knock state can be accurately detected by paying attention to the cumulative percentage of bending on the lognormal probability paper. Then, if the properties described above are carefully considered, this 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. Then, by knowing from which point of the distribution the data deviates, it is possible to accurately detect the knock state.
That is, the distribution does not necessarily have to be approximated as a substantially logarithmic distribution.

Of course, a state in which all the sampled data are knocked, that is, an oversized knock state in which all cycles are knocked cannot be identified by the method described above. However, such an oversized knock state can be sufficiently discriminated by a conventional method (for example, a method of determining a knock when the knock peak value exceeds a certain threshold value). It doesn't matter at all. Further, in such an oversized knock state, the dispersion of data becomes extremely large. Therefore, if a method of monitoring the dispersion is added, it is not necessary to use the conventional method in parallel.

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 calculating 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 methods can be considered.

The method will be described below with reference to FIG.

FIG. 4 (1) shows the cumulative distribution of logV _MAX (illustrated on the lognormal probability paper in the upper row) and the frequency distribution at that time (illustrated in the lower row) when 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 cumulative frequency distribution 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. Therefore, it can be regarded as one straight line (that is, one lognormal distribution) on the output side lower than the 90% point.

Therefore, assuming a cumulative 50% point on the lognormal probability paper, that is, the median value M of the frequency distribution, consider two thresholds 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 real axis (logV _H −logM = logM−logV _L , that is, V _H / M = M /
V _L ). At this time, 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 as the control target knock occurrence frequency of 10%. That is, V _{L at the} cumulative 10% point
Is set. Then, when the knocked state is smaller than the target value as shown in FIG. 4 (1), the upper threshold value V _H coincides with the cumulative 90% point due to the property of the lognormal probability paper. Therefore, when the knock is smaller than the target, the frequency at which the peak value V _MAX falls below the lower threshold V _L and the frequency above the upper threshold V _H become equal (in this case, 10
%).

However, in the knock condition larger than the target as shown in (2) of the same figure, the curve bends at a% lower than the cumulative 90%, so the upper threshold V _H does not match the cumulative 90%, and the lower cumulative _VH Corresponds to%.

That is, the frequency of exceeding the upper threshold value V _H increases. (2) The frequency increases by the amount of the double-headed arrow if it is shown in the diagram of the upper group in the figure. Therefore, when the knock is larger than the target, the maximum peak value V _MAX exceeds the upper threshold value V _H more frequently than the lower threshold value V _L.

From what has been said above, the maximum crest value V _MAX 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 By comparing with the number of times N _H , 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, let us consider obtaining the approximate value V _M of the cumulative 50% point M without data sampling. The cumulative 50% point M is the probability that the maximum peak value V _MAX exceeds that M, and the probability that it falls below the probability. Are equal. Therefore, every time the peak value V _MAX is input, the V _MAX is compared with a certain value V _M. If V _MAX is larger, V _M is increased by ΔV _M , and conversely, if it is smaller, V _M if the go by sequentially updating the V _M to decrease by the same 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 V _L. V _L is cumulative
Since it is a point of 10%, the maximum peak value V _MAX has a probability of falling below V _L by 1/10, and conversely it has a probability of rising above V _L of 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. Each time the peak value V _MAX is input, that V _MAX
If a certain value V _L is compared and if V _MAX is larger, V _L is updated by sequentially updating V _L by 9 times ΔV _L , which is 9 times ΔV _L , V _L becomes 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 × ΔV _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.

However, this is not a problem when finding a cumulative percentage point such that the amount of increase and the amount of decrease are approximately equal, such as the cumulative 50% point, but it is far from the cumulative 50% point (for example, 10%).
% Or 90% point), the ratio of the increase amount and the decrease amount becomes too large, and there is concern about hunting near the convergence value. Therefore, the present invention proposes another method for obtaining V _L.

Now, the maximum peak value V _{MAX and a} certain value V _L are continuously compared for a predetermined number of cycles C. And, if the peak value V _MAX falls below the V _L at least once in between the V _L is reduced by ΔV _L, the V _L only if the better of all the while V _MAX continued around above the V _L ΔV It is considered that V _L is sequentially updated every predetermined number of cycles C by increasing _L. Since the amount of increase / decrease is the same, V _L converges on the point of the following probability relationship. That is, the probability that the peak value V _MAX will fall below the convergent value of V _L is P, (1-P) ^C = 1- (1-P) ^C
Converge to the point indicated by the relationship. In order to converge V _L to the cumulative 10% point, P = 0.1 and the number of cycles C should be about 7 cycles. By this method, the value of the cumulative% point far from the cumulative 50% point can be accurately and sequentially obtained.

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 as V _H · A (= V _M ² / V _L ).

With the method described above, it becomes possible to easily obtain the cumulative percentage points of bending without data sampling and without logarithmic conversion.

〔Example〕

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

FIG. 5 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.

Reference numeral 4 is a knock sensor for detecting the vibration of the engine block 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 outputs a signal corresponding thereto, 6 is a throttle A throttle valve connected to the angle sensor, 7 is an injector for injecting fuel into the intake manifold based on the fuel injection timing and fuel injection time determined by the control circuit 10, 8
Is a turbocharger for supercharging, 9 is an O ₂ sensor that generates an output signal depending on whether the air-fuel ratio of exhaust gas is richer or leaner than the stoichiometric air-fuel ratio, and 10 is each of the above It is a control circuit for controlling the ignition timing and the air-fuel ratio of the engine according to the state of the input signal from the sensor.

Next, the detailed configuration and operation of the control circuit 10 will be described with reference to FIG. In FIG. 6, 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 an interrupt process by an external signal or an internal signal, and 10-7 is configured so that the count value is increased by one every 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. Since the count value of the timer increases every clock cycle (for example, 1 μs), by calculating the difference between the count value at the current interrupt and the count value at the previous interrupt, the reference angle sensor signal The time interval, that is, the time required for one revolution of the engine can be measured. In this way, the engine speed is obtained.

As for the crank angle position, since the signal of the crank angle sensor 2-2 is output at every constant crank angle (for example, 30 ° CA), the crank angle at that time is based on the top dead center signal of the reference angle sensor 2-1. You can know the angle in units of 30 ° CA. 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, the intake air amount signal from the air flow meter 5, the maximum peak value signal from the maximum peak value 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 for converting an analog signal to a digital signal.
It is an A / D converter. Reference numeral 10-10 is a maximum peak value detection circuit for receiving the signal from the knock sensor 4 and extracting the maximum peak value V _MAX 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, a control signal for the multiplexer 10-8, and a control signal for the maximum peak value detection circuit 10-10 are output. 10-13
Is a CPU bus, and the CPU puts control signals and data signals on this bus signal line to control peripheral circuits and send and receive data.

Next, the maximum peak value detecting circuit 10-10 will be described with reference to FIG. In FIG. 7, 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-
An amplifier 10-10-3 for amplifying the output of this filter is a peak hold circuit for peak-holding the output of the amplifier based on the signal from the output port, for example, by a capacitor.

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. 8 is an interrupt routine for setting the timer of the microcomputer for the ignition timing and the fuel injection time. Interrupt 100
Therefore, in step 200, first, the basic ignition timing θ
_BSE and basic injection time τ _BSE are calculated. The basic ignition timing θ _BSE and the basic injection time τ _BSE are the engine speed N and the engine load Q / (a value obtained by dividing the intake air amount Q measured by the air flow meter by the engine speed N is proportional to the engine load). It is stored in the ROM of the microcomputer as a two-dimensional map. And in this step 200, at the same time,
The ignition timing and 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 knocking hardly occurs when the engine load is light, and that if the light load is forcibly controlled to knock, the output, fuel consumption, etc. will rather decrease. . 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 view 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 timing 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. 9 is a knock state detection and knock control routine which is the main object of the present invention. In the present embodiment, this interrupt routine is executed at each ignition cycle near the top dead center (TDC) of the engine.

When the interrupt routine is entered at step 700,
Step 800 is performed to detect an average knock condition over a relatively large number of cycles, in a manner as described in the operation of the invention. 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.

This knock determination level Vref is V _M obtained for each cylinder in step 800 (a value that converges to the median of the frequency distribution, details will be described later) and a constant set for each cylinder (however, this value It is also created in relation Vref = K · V _M with gradually corrected properly to the appropriate direction.) in a later step. 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 maximum peak value V _MAX taken in 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, in step 800 of detecting the knock state, a detailed description will be given with reference to FIG. In step 801,
The maximum peak value V _MAX taken this time is compared with the upper threshold value V _H corresponding to the cylinder, and when V _MAX > V _H , the number of times N _H is exceeded is increased by one ( Step 802).

In other cases, the process proceeds to step 803, and this time the maximum peak value V _MAX is compared with the lower threshold value V _L. If V _MAX <V _L , increase the number of rounds by one (step 80
4) Go to step 805. Otherwise, step 805 is difficult as it is. Then in step 805, the cumulative 50
Update V _M of% points. The update method is as described above. That is, when the maximum peak value V _MAX exceeds the current V _M corresponding to the cylinder (V _MAX > V _M ), V _M is increased by ΔV _M , and conversely, if V _MAX <V _M, it is the same as V _M. Develop only ΔV _M amount. By doing so, V _M is constantly updated so as to always 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 a concept that is unrelated to a car driver, 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 _H. As mentioned above, the lower threshold value can be used to check if the knock condition is larger or smaller than the target value.
V _L is the same as the knock occurrence frequency in the target knock state%
It is necessary to set the cumulative percentage point of. 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 V _L to a smaller cumulative point of% as the speed increases. In order to set this V _L to a small%, it is sufficient to increase the number C of cycles for updating V _L , as already described in the operation.
If V _L is updated every hour, the number of cycles C during that period
Becomes larger 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. Ie
It is checked whether the engine speed and engine load have changed by more than a predetermined value within 0.7 seconds. In this embodiment, for example, the allowable change in the engine speed is ±
300 rpm, allowable change of engine load ± 150 mmH in pressure conversion
It is set to g. If it is considered to be quasi-stationary in step 807, 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. That is, if N _H and N _L are almost equal, it is judged that the knocking state of the cylinder is smaller than the target value, and if N _H is larger than N _L even if the error is taken into consideration, it is larger than the target value. It is determined to be knocked. 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 809, 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 have a relationship of V _H / V _M = V _M / V _L as described in the action. Let this geometric ratio be A (V _H / V _M ＝ V _M / V _L ＝
By updating A) and A, V _H and V _L can be updated. Since V _L = V _M / A, if the maximum peak value V _MAX falls below V _L even once during this detection interval (that is, if N _L counted in step 804 is 1 or more). Increases A by ΔA to decrease V _L by ΔV _L, and when N _L = 0, decreases A by ΔA to increase V _L by ΔV _L. This allows V _L to be set to the required cumulative percentage point.
Then, the upper threshold V _H can be made of V _H = A · V _M. In this way, V _H and V _L are updated for each cylinder.

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

Next, with reference to FIG. 11, a method of calculating the ignition timing retarding amount R in step 1200 of FIG. 9 will be described in detail.

First, if the maximum peak value V _MAX in step 1201 exceeds the knock determination level K · V _M, the retard amount from the basic ignition timing is regarded as the cycle is knocking cycles R
Is increased by ΔR ₁ (step 1202). This ΔR ₁ is also used for general knock control, and is usually 0.
Although it is about 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 cycle, and is used as a judgment material for the knock judgment level correction described later.

In the case of V _MAX ≦ K · V _M at step 1201 deemed non knock cycle proceeds to step 1204. Step 12
In 04, the ignition timing is corrected in the advance direction by decreasing R by ΔR ₁ only when the non-knock cycle is continued for a predetermined time (generally about 1 second). 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 of FIG. 10 whether or not the above-mentioned average knock state is detected. If it is not detected yet (that is, during the above-mentioned detection interval), the process moves to step 1213, but if the detection completion flag is set, the magnitude of the knock 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.

If the retard amount R is set for each cylinder (that is, the ignition timing for each cylinder), as described above, the retard amount R of the cylinder may be increased or decreased according to the knock state of the cylinder. In the case of uniform ignition timing control for all cylinders, there is only one retard angle amount R. At this time, it is sufficient to increase or decrease R by comprehensively judging the knocking state of each cylinder. 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, without the aforementioned N _L, the N _H each cylinder, one N _L,
It is also possible to directly know the knocking state of the whole by counting the number with one N _L , N _H without having N _H for each cylinder.

Even in this case, it is desirable to have two thresholds V _L and V _H for each cylinder, to perform comparison for each cylinder and use only the comparison result (that is, only N _L and N _H ) for all cylinders. if you sacrifice some accuracy of detection of the state, it is possible to V _L, a V _H in common for all the cylinders.

Next, at step 1208, the retard amount R is compared with the maximum retard amount Rmax. Generally, the retard amount R is usually limited in order to avoid excessive ignition timing fluctuation due to knock control and to prevent exhaust temperature rise, but conventionally, the limit value Rmax is a fixed value set in advance. there were. 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, unnecessarily 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
The control range of R is corrected in the more retarded direction by increasing the value by about A). 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,
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
If R <Rmin, R = Rmin.

Next, with reference to FIG. 12, the process of automatically correcting the knock determination level used for the knock determination in each cycle in step 1300 of FIG. 9 in the proper direction will be described.

First, in step 1301, it is checked by the knock state detection completion flag whether or not a knock state is detected. If it is detected, the knock state is checked in step 1302. When it is determined that the knock state is larger than the target, the number of knock determinations for each cycle up to now is checked in step 1303 (the number of determinations is counted in step 1203 in FIG. 14). If the number of knock determinations is less than or equal to a 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, the knock determination is normally performed, so K is held as it is.

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 the 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, K is held as it is.

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, with the same idea as described in the calculation method of the retardation amount R,
It is also possible to correct K as one common K without having K for each cylinder. 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, in step 1307, the knock determination count is cleared, and subsequently, the knock state detection completion flag is also cleared (step 1308).

As described above, knock control is executed.

In the above embodiment, the average knock state is detected, and thereby the ignition timing is manipulated, the ignition timing control range is corrected,
The knock determination level for knock determination is modified for each cycle, but these can all be effective alone. For example, for detection of knocking state, this can be directly applied to a knock monitoring device or a gasoline octane number detecting device. As an example applied to an actual automobile, it can also be used to display a warning light when nonque is likely to occur abnormally due to gasoline properties or some factor. For example, as shown in the flowchart of FIG. 13 for the main part, the octane number of gasoline is discriminated and displayed according to the magnitude of the retardation amount R obtained in FIG. That is, in step 1214, the set value RA for determining the octane number and the retardation amount R are compared to determine the magnitude of the octane number, and the determination results are displayed in steps 1215 and 1216. The retard amount R indicates the likelihood of knocking, and R
If is small, knocking is unlikely to occur, and it is determined that the octane number is large.

Further, regarding the operation of the ignition timing, in the above-described embodiment, the ignition timing is operated for each ignition according to the knock determination result for each cycle, and the ignition timing is operated in a longer circumference than that according to the average knock state. The double loop is adopted. This is because the transient state of the engine in which a sudden change in knock state is expected is taken into consideration. However, the average knock state is, for example, 1s as in this embodiment.
Since it can be calculated within ec, it is of course possible to correct this only by the knock state without modifying the ignition timing for each ignition. In this case, the knock determination level for determining the presence or absence of knock for each cycle becomes unnecessary.

It is also possible to configure a simple knock avoidance system that detects the knock state for a longer period of time, and switches the ignition timing characteristic to two or more stages using a plurality of maps. .

Further, although the ignition timing is dealt with as a factor for controlling knock in the above-mentioned embodiment, this is due to other knocks such as air-fuel ratio, intake pressure (for example, boost pressure of turbo), EGR, anti-knock agent, etc. It can be widely applied to control factors.
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.

Regarding the modification of the control range of the knock control factor such as the ignition timing, it is possible to perform only this in accordance with the knock state. That is, the control can be performed only according to the knock determination result for each cycle, and only the control range can be corrected according to the average knock state.

Further, regarding the correction of the knock determination level, it is not always necessary to commonly use the signal to be determined to be knocked for each cycle and the maximum peak value for detecting the knock state (that is, the maximum peak value in the embodiment). For example, the integrated value of the signal may be used as the signal to be judged to be knocked, and the maximum peak value may be used to detect the average knock state. However, it is more efficient to use them in common as in the above embodiment. In the above embodiment, the relationship between the two threshold values V _L and V _H is defined by the median value M of the distribution (5 of the cumulative distribution).
Although it is set to have a substantially equal relationship with respect to the 0% point), some error may occur in the approximate value V _M that should converge to the median value M, so V _L = V _M / A, _{V H = (a + D)} .V case it is better to put some of the offset D as also _M there. Since this offset D can be used as an element for finely adjusting the target knocking sound, either positive or negative sign can be taken, but essentially a positive value of D is desirable. Because, depending on the maximum crest value V _M to determine the V _M, but to converge to the median value M by increasing or decreasing the same amount [Delta] V _M, be converged around the central value M, the same amount variation To do. Therefore,
If you look at this on the logarithmic axis, the amount that deviates to the lower side inevitably increases. Therefore, it is desirable to make D positive in order to correct this. Or in order to correct this from the beginning, increase V _M by a little more than 50% cumulative (eg cumulative
It is possible to converge toward the position of 55%). In this case, the ratio of increase / decrease of V _M may be set to 55:45, for example.

Further, in the above embodiment, the lower threshold value _VL is corrected by feedback so that it becomes the cumulative percentage point of the same value as the knock occurrence frequency in the target knock state, but the distribution of the maximum peak value is A fixed value may be used when it can be predicted to some extent or when it is not necessary to detect the knock state with such accuracy. Therefore, in this case, V _H is also a fixed value, and it is not particularly necessary to find the median value M of the distribution. However, it is clear that the above embodiment is far superior.

In the above embodiment, the average knock state is detected by comparing the number of times the upper threshold value V _H is exceeded and the number of times the lower threshold value V _L is lowered, but In this way, the knock state can be detected. That is, the cumulative α% point Lα when accumulating from the lower value, the cumulative α% point Hα when accumulating from the higher value, and the median value V _{M of the} distribution are calculated, and _M / L [alpha, and by examining the magnitude of H-alpha / V _M, or knocking state than the target knock occurrence frequency alpha% is large, small or can be determined.

That is, in the small knock state in which the knock occurrence frequency is lower than α%, Lα, V _M , and α are aligned on a log normal probability paper. Therefore, in this case, since L [alpha and H-alpha become geometric relationship with respect to V _M, V _M / Lα and H-alpha / V _M is approximately equal. On the contrary, in a large knock state in which the knock occurrence frequency is higher than α%, this geometric relationship is broken, and _H α / V _M is V _M / V _M
It becomes larger than Lα. As will be apparent from the disclosure of the operation part of the invention, Hα and Lα are determined by comparing the maximum peak value V _MAX with Lα and Hα for a predetermined number of cycles C, and V is the predetermined value of Lα. When falling below the number of times, Lα
Is reduced by ΔLα, and α is reduced to Δ
Lα and Hα are desired by increasing Lα, and at the same time, increasing Vα by ΔHα when V _MAX exceeds Hα by a predetermined number of times or more, and decreasing Vα by ΔHα when V _MAX is less than the predetermined number of times. Converge to the cumulative% point of.

Further, in the above-described embodiment, although the logarithmic converter is not used and the device is shown, 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. Therefore, various methods and devices can be considered. For example, it is possible to detect the knock state by the magnitude relationship between the average value and the median value of the logarithmic conversion value logV _MAX of the maximum peak value V _MAX . That is, when the knock state is small, the distribution of logV _MAX is almost a normal distribution, and thus the median and the mean of the normal distribution match. However, as the knocked state becomes larger, the average value becomes larger than the median value, so that the knocked state can be identified.

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

Also, as already explained, the assumed distribution is not limited to a lognormal distribution, and by applying an appropriate transformation such as a binomial distribution or a gamma distribution, a distribution that can be treated as a lognormal distribution is practically acceptable. As for the above, the above-described embodiment can be applied as it is, and the distribution becomes a normal distribution as it is instead of the logarithm, and the handling becomes simpler. In other words, the equivalence relation may be replaced with the equivalence relation.

Further, if it is required to increase the calculation time and the cost of the device, it is possible to identify the knock state for any distribution. That is, it suffices to use only the relatively low value data to assume one knock-free distribution and to see where the higher data deviates from this distribution.

〔The invention's effect〕

As described above in detail, the present invention detects the average knock state by determining the distribution shape when multicycle sampling of the maximum peak value V _max , and the ignition timing and the air-fuel ratio according to the detection result. Since the knock control factors such as the intake pressure are controlled, the true knock state can be detected very accurately without being affected by the variation of the knock sensor or the engine, which has been difficult in the past, or the change over time. In addition, it is possible to suppress knocking satisfactorily.

Further, according to the present invention, the average knock state over a plurality of cycles is determined according to the determination result of whether or not the distribution shape obtained when the maximum peak value of the knock sensor signal is multicycle sampled is a predetermined distribution shape. Means, and the control means limits the control value range of the knock control factor such as ignition timing according to the detection result, so the control is suitable for the knock state determined according to the distribution shape of the knock sensor signal. It is possible to control knock control factors such as ignition timing by limiting to a value range, and the knock control factors can be changed to a knock state determined according to the distribution shape of the knock sensor signal according to the determination result of the knock determination means. There is an excellent effect that it is possible to prevent unnecessary change outside the suitable control value range.

[Brief description of drawings]

FIG. 1 is a diagram showing the maximum peak value of the knock signal and its distribution state, FIG. 2 is a diagram showing the cumulative distribution of the maximum peak value of the knock signal and this distribution on a log-normal probability paper, and FIG. The figure which shows the distribution state of a high-value knock cycle and a non-knock cycle, FIG. 4 is a figure for comparing the distribution of the maximum crest value when knock is smaller and larger than the target, FIG.
6 is a block diagram showing an embodiment of the present invention, FIG. 6 is a detailed block diagram of the control circuit in FIG. 5, FIG. 7 is a detailed block diagram of the maximum peak value detecting circuit in FIG. 6, and FIG. FIG. 13 to FIG. 13 are flowcharts showing knock detection and control procedures in the control circuit. 1 ...... engine, 3 ...... igniter, ignition coil, 4 ...... knock sensor, 6 ...... injector, 8 ...... turbocharger, 9 ...... O ₂ sensor, 10 ...... control circuit, 10-1 ...... CPU, 10-
2 ... ROM, 10-3 ... RAM, 10-10 ... Maximum peak value detection circuit, 10-10-3 ... Peak hold circuit.

Claims (8)

[Claims] 1. A knock sensor for detecting engine knock, and a maximum peak value V _{MAX of} this signal from the signal of this knock sensor.
Maximum peak value detecting means for extracting the maximum peak value VMAX, and whether or not the distribution shape obtained when the maximum peak value V _MAX is _subjected to multi-cycle sampling is a predetermined distribution shape, and an average knock over a plurality of cycles is determined according to the determination result. Discriminating means for detecting the state, knock determining means for determining the presence or absence of knock for each cycle based on the signal of the knock sensor, and the ignition timing of the engine, or the air-fuel ratio, intake air in accordance with the knock determination result. An internal combustion engine comprising: control means for controlling a knock control factor such as pressure; and limiting means for adding a limit to a control value range of the knock control factor according to a detection result of the determination means. Knocking control device. 2. The predetermined distribution is one distribution estimated from only the data of the maximum peak value V _{MAX which} is relatively small, and from which cumulative% the actual cumulative frequency distribution is relative to the cumulative frequency distribution of this distribution. The knocking control device according to claim 1, wherein the knocking state is detected by determining the distribution shape according to whether or not it has started to differ. 3. The knocking control device according to claim 1 or 2, wherein the predetermined distribution is a lognormal distribution. 4. The discriminating means is set to a relatively high first threshold value V _L and a relatively high value within a range of values that the maximum peak value V _MAX can take. Has a second threshold value V _H and has a maximum peak value V over a plurality of cycles.
_MAX is compared with each of the threshold values, and the maximum peak value V _MAX is below the first threshold value _VL and the maximum peak value V _MAX is above the second threshold value V _H. The knocking control device according to any one of claims 1 to 3, wherein the number of times is counted, and the distribution shape is substantially determined based on the magnitude relationship between the count values. 5. The side where the first threshold value V _L is smaller than the cumulative 50% point M with respect to the cumulative 50% point of the distribution obtained when the maximum peak value V _MAX is subjected to multi-cycle sampling. 5. The knocking control device according to claim 4, wherein the second threshold value V _H is set to be larger than the point M. 6. The discriminating means has means for estimating the cumulative 50% point M by the value of the maximum peak value V _MAX which is successively input, and the estimated value V _{M of the} point M is estimated. , The first
Of the threshold value V _L and the second threshold value V _H are almost equal (V _M / V _L ≈V _H / V _M ), or slightly larger than the ratio.
The knocking control device according to claim 4 or 5, characterized in that V _H is set such that V _M / V _L + D = V _H / V _M , D> 0). Wherein said estimated value V _M is a variable that will be sequentially updated for every cycle, V _MAX each time the maximum crest value V _MAX is input
When you bought more of the maximum peak value V _MAX is larger than the V _M and
If V _M is increased by ΔV _M , and if it is smaller, then V _M is increased by the same amount Δ
Sequentially updated to converge the V _M to the cumulative 50% point M by reducing by V _M, values and predetermined geometric number A of this V _M
By using the first threshold V _L as V _L = V _M / A and the second threshold V _H as V _H = V _M · A or V _H = V _M · (A + D)
The knocking control device according to claim 5 or 6, wherein the knocking control device is estimated in a relationship of (D> 0). 8. The geometrical ratio A is a variable that is updated every predetermined number of cycles C, and the maximum peak value V _MAX and the first threshold value V _L (= V) between the number of cycles C. _M / A), and when the maximum peak value V _MAX is lower than V _L a predetermined number of times or more, the geometrical ratio A is slightly increased to correct V _L to the lower side, When the number of times is less than the predetermined number, the geometrical ratio A is slightly decreased in order to correct V _L to a higher value, and the maximum peak value V _MAX is substantially lower than the first threshold V _L. 8. The knocking control device according to claim 7, wherein the geometric ratio A is adjusted so as to be substantially equal to a desired probability.