JPH0792415B2 - Knocking detection device for internal combustion engine - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine knocking detection device, and more particularly, to an improved knocking detection method, which uses a cylinder pressure change waveform to determine a crank cycle of each cycle. The present invention relates to a knocking detection device that calculates heat generation with respect to a corner, obtains a ratio of heat generation due to normal combustion and heat generation due to knocking, and determines the strength of knock by this value.

(Prior art) Since electronic control technology for vehicles and engines has been widely used, approaches to knocking have been diversified. In addition to improvements such as flow and reduction of combustion by increasing the octane number, the ignition timing is advanced to the limit where slight knocking occurs to the extent that human ears do not feel it depending on the running condition. Knocking control technology is being used in mass-produced vehicles to control and to obtain the best fuel economy and power performance with those conditions regardless of differences in fuel properties and changes in engine octane number over time. There is. Recently, the knocking control technology has been applied to each cylinder of a six-cylinder engine. Also, in recent on-board knock control by electronic control, knock detection and quantification technology is important.

Knocking detection methods that can be installed in vehicles for automobiles are classified according to the physical quantity to be detected, and there are various methods such as cylinder pressure, engine vibration, combustion light, knocking sound, and ion current in cylinder.

Among them, a typical conventional knocking detection device for an internal combustion engine is, for example, one described in "Automotive Technology" 1986 Vol. 40 NO11. In this device, an in-cylinder pressure sensor is attached to the spark plug, a high-frequency component near the knocking frequency is detected in the pressure change waveform of the combustion chamber based on the output of the in-cylinder pressure sensor, the vibration strength is quantified, and statistically processed knocking The level has been decided.

(Problems to be Solved by the Invention) However, in such a conventional knocking detection device for an internal combustion engine, the vibration detected by the in-cylinder pressure sensor is affected by the mounting position, sensor type, sensor type, and detection cylinder. However, it is necessary to adapt the knock detection logic for each engine model, which causes an increase in man-hours and cost, and there is a problem that the detection accuracy is deteriorated when the logic is not sufficiently adapted.

Further, the in-cylinder pressure sensor used in the conventional knocking detection method does not require special processing of the engine,
Although it is highly effective, in addition to combustion pressure, it also includes mechanical vibration due to engine vibration and rotation. Therefore, in the method that uses the high-frequency signal component obtained from the sensor output, the vibration component that causes noise is separated. Have difficulties, and therefore
There is a problem that the regular knock component cannot be detected accurately and the detection accuracy is not sufficient.

For example, at high rotations, high-frequency vibration components increase, and it becomes difficult to separate a particular knock component.

In this case, it is conceivable to cut the high frequency component corresponding to the noise in the knock vibration region, but electrical noise and mechanical noise superimposed on the in-cylinder pressure signal are different from knock vibration. Noise remains in the in-cylinder pressure signal, and an operation based on this data is not an effective solution.

(Object of the invention) Therefore, the present invention calculates heat generation for a crank angle for each cycle from a pressure change waveform obtained by cutting a high frequency component of the combustion chamber pressure detected by a sensor, for example, heat generation due to normal combustion and heat due to knocking. By taking the generation ratio and determining the strength of knock by this value, the effect of noise can be effectively removed regardless of the engine model and the individual difference of the sensor output, and without changing the logic, the man-hours and cost can be reduced. Is intended to be reduced and the detection accuracy is improved.

(Means for Solving the Problems) In order to achieve the above object, the knocking detection device for an internal combustion engine according to the present invention, as shown in the basic conceptual diagram of FIG. 1, shows a combustion pressure or a signal that changes in proportion to the combustion pressure. A pressure detecting means a for outputting, a removing means b for removing a predetermined high frequency component from the output of the pressure detecting means a, an operating state detecting means c for detecting an operating state of the engine, and a crank angle for detecting a crank angle of the engine. The total heat generation for the crank angle in one cycle is calculated based on the detecting means d, the pressure change waveform obtained by removing the high frequency component of the combustion pressure detected by the pressure detecting means a, and the operating state of the engine, and the read prohibition command is issued. Then, the reading of the combustion pressure is stopped, and during that time, the total heat calculation means e for calculating the total heat generation using the combustion pressure estimated by the estimation means g and the pressure Force detection means a
And a prohibition command means f for instructing the reading prohibition on the basis of one or more of the high frequency components extracted from the output of the above, and the level of the high frequency components being a predetermined value or more or the crank angle being a predetermined value. When the pre-reading prohibition is instructed, the estimation means g for estimating the combustion pressure during the prohibition instruction period from the values before and after the combustion pressure during that period and the starting point of heat generation due to knocking in one cycle are specified. The starting point specifying means h for calculating the heat generation due to knocking in one cycle is calculated, and when the reading prohibition is instructed, the reading of the combustion pressure is stopped during that time as in the case of the total heat calculating means e, and is estimated. Knock heat calculation means i for calculating heat generation using the combustion pressure, and one or more of heat generation or total heat generation by normal combustion in one cycle and knocking. Calculating a ratio of the heat generation, and a, a knock intensity determining unit j determining the intensity of knocking on the basis of this ratio.

(Operation) In the present invention, the heat generation for the crank angle for each cycle is calculated from the pressure change waveform obtained by cutting the high frequency component of the combustion chamber pressure detected by the pressure detection means. in this case,
When the predetermined high frequency component of the combustion pressure exceeds a predetermined value, or when one or more conditions at a predetermined crank angle are satisfied, the reading of the combustion pressure is prohibited, and the combustion pressure is changed from the previous and next values during that period. The heat generation is estimated and calculated.

Then, the ratio of heat generation due to normal combustion (or total heat generation may be used) and heat generation due to knocking is obtained, and the knock strength is determined based on this ratio.

Therefore, unlike the conventional method of digitizing vibration intensity, it is based on the change in heat generation with respect to the crank angle, so it does not require logic changes regardless of the engine model and sensor output differences. It is possible to detect knocking with high accuracy. Further, the influence of noise is effectively removed, and knocking can be detected with extremely high accuracy.

(Example) Hereinafter, the present invention will be described with reference to the drawings.

2 to 12 are diagrams showing a first embodiment of a knocking detection device for an internal combustion engine according to the present invention, and are diagrams showing an example in which the present invention is applied to a combustion control device.

First, the configuration will be described. FIG. 2 is an overall configuration diagram of the combustion control device, in which 1 is an engine, intake air is supplied from an air cleaner 2 to each cylinder through an intake pipe 3, and fuel is injected by an injector 4 based on an injection signal Si. Is jetted. The air-fuel mixture in the cylinder explodes and burns due to the discharge action of the ignition plug 5 based on the ignition signal Sp, becomes exhaust gas, and is exhausted from the exhaust pipe 6.

The air flow rate Qa drawn into the engine 1 is the air flow meter 7
And is controlled by the throttle valve 8 in the intake pipe 3. The intake negative pressure (boost) in the intake pipe 3 is detected by an intake pressure sensor 9, and the crank angle of the engine 1 is detected by a crank angle sensor (crank angle detecting means) 10. The engine speed N is calculated by counting the output pulses of the crank angle sensor 10.

The oxygen concentration in the exhaust gas is detected by the oxygen sensor 11 provided in the exhaust pipe 6, and the temperature of the cooling water flowing through the water jacket is detected by the water temperature sensor 12. Further, the combustion pressure (cylinder pressure) of each cylinder is measured by a cylinder pressure sensor (pressure detecting means) 13
The in-cylinder pressure sensor 13 is tightened and fixed as a washer of the ignition plug 5. If a signal that changes in proportion to the combustion pressure is generated, the cylinder pressure sensor
Not limited to 13, the main body of the ignition plug 5 may have a pressure-sensitive element incorporated therein.

The air flow meter 7, the crank angle sensor 10, the oxygen sensor 11 and the water temperature sensor 12 constitute an operating state detecting means 14, and the outputs from the operating state detecting means 14 and the cylinder pressure sensor 13 are input to the control unit 20. . The control unit 20 is composed of a microcomputer and an electronic circuit, calculates a processing value necessary for knocking detection and knock suppression control and other combustion control based on the detection result, and outputs the injection signal Si and the ignition signal Sp. .

Here, among the functions of the control unit 20, the configuration of the part particularly related to knocking detection is shown in FIG. In FIG. 3, the output signal of the in-cylinder pressure sensor 13 is input to the high frequency cut filter 21 to remove a predetermined high frequency component, and then A / D converted by the A / D converter 22 and input to the read inhibit circuit 23. It The read prohibition circuit 23 prohibits the output of the A / D converter 22 from being read into the knock intensity calculation circuit 25 when the output of the comparator 24 is at “H” level, and does not read when the output is at “L” level. Tolerate. Here, the high frequency component is cut by using the high frequency cut filter 21 in order to effectively remove the noise component when detecting knocking, and the cutoff frequency for cutting the high frequency component is as shown in FIG. Is changed in proportion to the engine speed N. Specifically, the engine speed N is calculated based on the output of the crank angle sensor 10, and the filter selection circuit 26 selects the optimum cutoff frequency from the characteristics shown in FIG. To that effect, and the high frequency cut filter 21 cuts off the high frequency components of the selected frequency band.

As the high frequency cut filter 21, for example, an analog filter is used. This filter is a combination of elements in which the resistance component has frequency dependency, and allows the attenuation ratio of the input signal to have frequency dependency, so that it passes or blocks an arbitrary frequency range. There are Bessel filters and Butterworth filters.
The high frequency cut filter 21 and the filter selection circuit 26
Constitutes the removing means 27. High frequency cut filter
The filter 21 is not limited to the analog filter, and other filters such as a filter using Fourier transform may be used. This filter expands the input signal into a Fourier series, where each term is a polynomial corresponding to each frequency, calculates the polynomial in which the terms corresponding to the frequency range to be cut off are deleted, and from this equation It is a filter that transmits or blocks an arbitrary frequency range by reconstructing a signal.

On the other hand, the output of the in-cylinder pressure sensor 13 is branched in the middle and is also input to the high-pass filter 28, and the high-pass filter 28 passes only a predetermined high-frequency component from the pressure vibration signal and outputs it to the comparator 24. A predetermined reference value is input to the other input terminal of the comparator 24, and the comparator 24 reads the “H” level signal when the high frequency component of the pressure vibration signal, that is, the predetermined high frequency vibration exceeds the reference value. It is output to the inhibition circuit 23 and the cylinder pressure estimation circuit 29. The in-cylinder pressure estimation circuit (corresponding to the estimation means) 29, when the output of the comparator 24 is at the “H” level,
The in-cylinder pressure during the read prohibition command period is estimated from the values before and after the in-cylinder pressure (combustion pressure) and output to the knock intensity calculation circuit 25. In addition to the signals from the in-cylinder pressure estimation circuit 29 and the read prohibition circuit 23, signals from the crank angle sensor 10 and the operating state detection means 14 are also input to the knock intensity calculation circuit 25, and the knock intensity calculation circuit 25 calculates heat generation. Department (corresponding to total heat calculation means) 3
0, knocking heat generation start point detection section (corresponding to start point specifying means) 31, knock part heat generation calculation section (corresponding to knock heat calculation means) 32, and knock strength calculation section (corresponding to knock strength determination means) 33 To be done.

The heat generation calculation unit 30 calculates the total heat generation for the crank angle during one cycle based on the operating state of the engine 1 from the pressure change waveform obtained by removing the high frequency component of the combustion pressure detected by the in-cylinder pressure sensor 13, and reads it. When the prohibition is commanded, the reading of combustion pressure is stopped, and the cylinder pressure estimation circuit
Calculation of heat generation is performed using the combustion pressure estimated by 29. Knocking heat generation start point detection unit 31 identifies a starting point of heat generation due to knocking in one cycle. Further, the knock part heat generation calculation unit 32 calculates the heat generation due to knocking in one cycle, and the knock strength calculation unit 33 calculates the ratio between the total heat generation during one cycle and the heat generation due to knocking. The strength of knocking is determined based on the determination result, and the determination result is output to the knock intensity signal output circuit 34.
Knock strength signal output circuit 34 generates a knock strength signal corresponding to the determination result, and this signal is used for knock suppression control information. In addition to knocking control, it may be used as input data to a knock intensity input meter as data for detecting knocking, for example. The read prohibition circuit 23, the comparator 24, and the high-pass filter 28 together constitute prohibition command means 35.

Next, the operation will be described.

When the engine 1 starts operating, the combustion pressure in the combustion chamber of each cylinder changes, and a peak of the combustion pressure appears every cycle. As shown in FIG. 5, the calculation of heat generation in this case is such that the value of the combustion pressure signal from which the high frequency component has been removed is a function of the fuel basic injection amount Tp or the intake negative pressure (boost) or the intake air amount in the knock detection state. It starts from the point where the calculated values Po and Po = func (Tp or Boost) are exceeded.

The calculation of heat generation amount is executed in step S ₁₅ described below,
For convenience of explanation, this will be described first, specifically, as follows. Now, as shown in FIG. 6, the cylinder 36
About stroke volume VST, combustion chamber volume V
C, the connecting rod length is CL, and the radius is r, the compression ratio r
c is And the total volume V (θ) at a certain crank angle (θ) as shown in FIG. It is expressed by Also, as shown in Fig. 7, the polytropic index PN is calculated from the combustion pressure waveforms during the compression stroke from the combustion pressures P ₁ and P ₂ corresponding to 60 ° and 44 ° before TDC and the volumes V ₁ and V _{2 at} that point. Calculate as. Further, in actuality, the combustion pressure P (I) and the volume V (I) for each unit crank angle are sequentially calculated to obtain the total heat generation amount, but the calculation for each unit crank angle is performed by, for example, FIG. P (I), V as shown in a)
In contrast to (I), P (I + 1), V (I
+1), and the breakdown of such a pressure change is as shown in FIG. 8B, at the timing t ₁ (corresponding to I) and the timing t ₂ (corresponding to I + 1), the pressure increase due to combustion and the piston Both increased pressure due to exercise is included. Then, calculate one coefficient F _K necessary for calculation of heat generation amount. However, if Cv: constant volume specific heat R: gas constant and the stroke volume at the compression start point is V (1) = VST, the total heat generation Q _A is It is calculated by

Next, the calculation of the heat generation portion due to knocking is performed. The heat generation portion due to knocking is the portion shown by hatching in FIG. In this case, the inflection point of the heat generation change with respect to the crank angle as the starting point of the heat generation part due to knocking is the midpoint between the heat generation start point and the end point, or the inflection point delayed from the compression top dead center (or ignition timing). Is used as the starting point of heat generation by knocking. By determining the knock start point by such a method, the start point can be specified with high accuracy in accordance with the actual combustion state. On the other hand, as the end point of heat generation due to knocking, a point at which heat generation with respect to the crank angle becomes 0 is used. Then, the heat generation amount Q _B due to knocking is
The knock start point and end point are connected by a straight line, and the heat generation portion (hatching portion) that exceeds this straight line is obtained.

When the heat generation amounts Q _A and Q _B are calculated in this way, the knock strength calculation unit 33 then calculates the ratio S between the total heat generation Q _A and the heat generation Q _B due to knocking. The knock strength is determined based on this ratio S.

Next, a program for knock determination processing including an estimated portion of heat generation calculation processing, which is a feature of the present invention, will be described with reference to the flowchart in FIG. The program shown in the figure is executed in synchronization with the 2 ° crank angle signal.

First, in step S ₁ , the crank angle θ is read from the output of the crank angle sensor 10, and in step S ₂ , the combustion pressure P is detected. Next, in step S ₃ , it is determined whether or not the crank angle θ this time satisfies the relationship of θ ₁ ≦ θ ≦ θ ₂ . θ ₁ and θ ₂ are predetermined crank angles that are considered to cause knocking, for example θ
It is set to ₁ = 0 ° ATDC and θ ₂ = 50 ° ATDC. Step S ₃
In to determine the value of the flag FN in step S ₄ when the YES, NO
If so, jump to step S ₆ . Flag FN is a comparator
When the output of 24 is "H", FN = 1, and when it is "L", FN = 0
The output of the in-cylinder pressure sensor 13 is so noisy that the reading of the combustion pressure P is prohibited. That is, as shown by the change waveform of the combustion pressure P in FIG. 11, in addition to the disturbance due to knocking, the waveform has disturbance due to ignition noise and mechanical vibration noise. This is extracted by the high-pass filter 28, and when the level exceeds the reference value, the output of the comparator 24 becomes "H" and the flag FN becomes FN = 1. Then, reading of the combustion pressure P is prohibited during the period of FN = 1, and the combustion pressure P is estimated during this period.

Return to the program of FIG. 10 again, and in step S ₄ , FN = 1
If so, the detected value of the combustion pressure P is set to P = ∞ in step S ₅ , and the process proceeds to step S _{6. If} FN = 0, the process jumps to step S ₆ . In step S ₆ , the combustion pressure P of the corresponding crank angle θ is stored in each memory, and the routine ends. The fact that P = ∞ means that, during this period, it is not used as the data of the combustion pressure, and eventually the acquisition of the raw data is stopped.

FIG. 12 is a flowchart showing a knock intensity determination program. This program is executed once for every predetermined crank angle corresponding to the timing when one combustion cycle ends.

First, the combustion pressure P stored in step S ₁₁ is searched from the memory, and it is determined in step S ₁₂ whether P = ∞. When there is P = ∞, it is determined that it is the period in which the reading prohibition of P is instructed, and the pressure values immediately before and immediately after P = ∞ are searched from the memory in step S ₁₃ , and the pressure values are searched in step S ₁₄ . The pressure at P = ∞ is estimated by interpolation calculation from the two pressure values, the estimated value is stored in the corresponding memory, and the process proceeds to step S ₁₅ . On the other hand, step S
_If there is no P = ∞ in ₁₂ , jump directly to step S ₁₅ . In step S ₁₅ calculates the heat generation in the manner described above, to determine the knock intensity from the ratio S at step S _16, further terminates the routine outputs a knock intensity signal corresponding thereto in step S ₁₇ .

As described above, in the present embodiment, unlike the conventional case where the vibration intensity is digitized to detect knocking, it is based on the change in heat generation with respect to the crank angle,
It is possible to detect knocking with high accuracy regardless of the engine model, the mounting position of the cylinder pressure sensor 13, the individual difference in sensor output, and the like without requiring a change in the detection logic.

In addition, the reading of combustion pressure is stopped during the period when noise is generated, and the pressure value is estimated from the values before and after that period, so the effect of noise is effectively removed, and extremely high precision knocking detection can be performed. You can This is because unlike the conventional method where high frequency components are cut (combustion pressure is still being read), the pressure signal itself is not cut and is not read. The detection accuracy is improved.

In particular, even if the high-frequency vibration component increases in the high rotation range, the regular knock component can be separated by the heat generation analysis, and the detection accuracy improves. As a result, the number of knock detection steps is reduced,
The cost can be reduced.

In the above embodiment, the ratio S is calculated using the total heat generation Q _A as the denominator, but the present invention is not limited to this. For example, heat generation due to normal combustion (Q _A −Q _B ) is calculated and this is used as the denominator. As The ratio S may be obtained from the following equation.

Next, FIGS. 13 to 17 are views showing a second embodiment of the present invention. In this embodiment, masking is carried out in advance during the noise generation period. FIG. 13 is a block diagram of the main part,
In the figure, the output of the crank angle sensor 10 is further input to a mask timing setting circuit (corresponding to prohibition command means) 41, and the mask timing setting circuit 41 outputs a combustion pressure signal at a predetermined crank angle to be masked. Such a period is set, and the result is output to the A / D converter 22 and the pressure estimation circuit 42. When the mask period is reached, the A / D converter 22 masks the output signal of the high frequency cut filter 21 and stops the output to the knock intensity calculation circuit 25. A pressure estimation circuit (corresponding to estimation means) 42 estimates the pressure value in the mask period from the pressure before and after the mask and outputs it to the knock intensity calculation circuit 25 during the mask period. Others are the same as those in the first embodiment.

In the above configuration, FIG. 14 is a flow chart showing a program for combustion pressure detection, and this program is executed once every 2 ° of the crank angle. First, read the ignition timing T _adv in step S _21. Next, in step S ₂₃ , the mask timing θ ₃ is θ ₃ = T _adv −α ₀ where α ₀ is calculated as a predetermined value. Similarly, in step S ₂₄ , the mask timing θ ₄ is θ ₄ = T _adv + β _0, where β ₀ : Calculate as a predetermined value. As shown in FIG. 15, the mask timings θ ₃ and θ ₄ are for masking the ignition noise at the ignition timing T _adv (to create a mask signal), and the intake of the combustion pressure P is prohibited during this mask period. It Then calculates the valve jumping end time alpha ₁ from the function as α ₁ = func (N) becomes equation of the engine speed N at the time of closing the intake valve at step S _25. This is because the value of α ₁ differs depending on the rotation speed N. The valve jumping end time beta ₁ at the time of closing the exhaust valve in the same manner in step S ₂₆
Is calculated as a function of the engine speed N from the formula β ₁ = func (N). Next, in step S ₂₇ , the mask timing θ ₂ is calculated as θ ₂ = θ ₁ + α _1, where θ ₁ is the crank angle corresponding to the intake valve closing timing, and in step S ₂₈ , the mask timing θ ₆ is θ ₆ = θ ₅ + β ₁ However, θ ₅ is calculated as the crank angle corresponding to the exhaust valve closing timing. These masking timings θ ₂ and θ ₆ are for masking mechanical noise when the intake / exhaust valve is closed, as shown in FIG. 16, and represent the timing in terms of crank angle. Note that the timing is expressed in time in FIG. 15, and the period when the intake valve is closed is Tin
~Tin + α (where, theta ₁ corresponding to Tin), the exhaust valve is a closed period Tex~Tex + β (where, theta ₅ corresponding to the Tex) as, these periods are inhibited uptake combustion pressure P.

Since the period during which the intake of the combustion pressure P is prohibited is determined in advance by the above processing, the present crank angle is compared with θ ₁ to θ _{6 in} steps S _{29 to} S ₃₄ , respectively, and the crank angle θ becomes ₁ through? _2] is not performed uptake combustion pressure P is immediately terminated the routine at this time when it is between [theta ₃ through? _4] [theta ₅ through? _6]. On the other hand, the crank angle θ is θ
When it is equal to any one of _{1 to} θ ₆ , the A / D conversion value of the combustion pressure P is taken in as P _{1 to} P ₆ in steps S _{35 to} S ₃₉ , respectively, in order to obtain the detection value immediately before and immediately after the mask period, and thereafter.
With respect to P ₁ , P ₃ , and P ₅ , the pressure value of the corresponding crank angle θ is stored in each memory in step S ₄₀ , and the routine ends. Further, for the pressure values P ₂ , P ₄ , and P ₅ , in steps S _{41 to} S ₄₃ , the mask period [θ ₁ to
Pressure value P at θ ₂ ], [θ _{3 to} θ ₄ ], and [θ _{5 to} θ ₆ ].
Estimate (θ). This estimation is performed, for example, by calculation of temporary interpolation or quadratic interpolation.

P (θ) (θ _{1 to} θ ₂ ) = func (P ₁ , P ₂ ) P (θ) (θ _{3 to} θ ₄ ) = func (P ₃ , P ₄ ) P (θ) (θ _{5 to} θ ₆ ) = Func (P ₅ , P ₆ ) Then, after the estimation, the process proceeds to step S ₄₀ . On the other hand, θ
When <θ ₁ , θ ₂ <θ <θ ₃ , θ ₄ <θ <θ ₅ and θ> θ ₆ are both satisfied, the combustion pressure P is A / D converted and fetched in step S ₄₄ , and then the process proceeds to step S ₄₀ . .

Next, the knock strength judgment is performed by the program of FIG.
This program is executed in synchronization with the timing when one combustion cycle ends after a predetermined crank angle, for example, θ ₆ . The content is similar to that of the first embodiment, and step S ₅₁
Calculate heat generation as described above in step _S52.
The knock intensity is determined from the ratio S in step S, and further step S
_{At 53} , a knock intensity signal corresponding to this is output and the routine ends.

As described above, in this embodiment, the period of noise generation is examined in advance, the masking process is performed for this period, and the pressure value is obtained by estimation, so that the error of combustion pressure detection due to ignition noise and mechanical noise is eliminated. Therefore, the accuracy of knocking detection can be improved more effectively.

(Effect) According to the present invention, knocking can be detected accurately regardless of the engine model, the mounting position of the sensor, the individual difference in the sensor output, and the like without requiring a change in the detection logic. It is possible to reduce man-hours and costs.

In addition, when there is a noise component in the combustion pressure, the intake is stopped and the detected value is estimated during that period, so the adverse effect of noise can be avoided and the calculation accuracy of heat generation can be improved, and knocking detection accuracy can be significantly improved. And can be improved.

[Brief description of drawings]

FIG. 1 is a basic conceptual diagram of the present invention, FIGS. 2 to 12 are diagrams showing a first embodiment of a knocking detection device for an internal combustion engine according to the present invention, FIG. 2 is an overall configuration diagram thereof, and FIG. Is a block configuration diagram of its main part, FIG. 4 is a diagram showing characteristics of its cutoff frequency, FIG. 5 is a diagram explaining a starting point of its heat generation calculation, and FIG. 6 is a diagram showing calculation of its compression ratio. Schematic diagram, No. 7
The figure shows a part of the combustion pressure waveform, and FIG. 8 (a).
(B) is a diagram for explaining the increase in combustion pressure, FIG. 9 is a diagram for explaining the calculation of heat generation, FIG. 10 is a flow chart showing a program for determining the knock intensity, and FIG. 11 is a diagram showing its combustion pressure waveform. FIG. 12 is a diagram showing the relationship of the read prohibited section, FIG. 12 is a flowchart showing the program for the knock strength determination,
13 to 17 are diagrams showing a second embodiment of the knocking detection device for an internal combustion period according to the present invention. FIG. 13 is a block configuration diagram of a main part thereof, and FIG. 14 is a combustion pressure detection program thereof. FIG. 15 is a flowchart showing the relationship between the combustion pressure waveform and the mask period, FIG. 16 is a view showing the relationship between the combustion pressure waveform and the mask period, and FIG. 17 is a flowchart showing the knock intensity determination program. Is. 1 ... Engine, 4 ... Injector, 5 ... Spark plug, 7 ... Air flow meter, 9 ... Intake pressure sensor,
10 …… Crank angle sensor, 13 …… Cylinder pressure sensor, 14 ……
Operating state detection, 20 ... Control unit, 21 ... High frequency cut filter, 22 ... A / D converter, 23 ... Read prohibition circuit, 24 ... Comparator, 25 ... Knock strength calculation circuit, 26
...... Filter selection circuit, 27 …… Removal means, 28 …… Bypass filter, 29 …… Cylinder pressure estimation circuit (estimation means), 30 ・ ・ ・
… Heat generation calculation unit (total heat calculation unit), 31 …… Knocking heat generation start point detection unit (start point identification unit), 32 …… Knocking heat generation start point detection unit (knock heat calculation unit), 33 …… Knock Strength calculation unit (knock strength determination means), 34 ... Knock strength signal output circuit, 35 ... Prohibition command means, 41 ... Mask timing setting circuit (prohibition command means), 42 ... Pressure estimation circuit (estimation means).

Claims (1)

[Claims] 1. A) pressure detecting means for outputting a combustion pressure or a signal that changes in proportion thereto; b) removing means for removing a predetermined high frequency component from the output of the pressure detecting means; and c) operating condition of the engine. Based on the pressure change waveform and the engine operating state from which the high frequency component of the combustion pressure detected by the pressure detecting means is removed, and d) the crank angle detecting means for detecting the crank angle of the engine. And calculates the total heat generation for the crank angle during one cycle, and stops reading the combustion pressure when the reading prohibition is instructed, and during that time, calculates the total heat generation using the combustion pressure estimated by the estimating means. Total heat calculation means for performing: f) extracting a predetermined high frequency component from the output of the pressure detecting means, and when the level of the high frequency component is a predetermined value or more, or crank Is a predetermined value, the prohibition command means for instructing the above-mentioned read prohibition based on one or more items; and g) When the pre-read prohibition is instructed, the period is from the value before and after the combustion pressure. The estimation means for estimating the combustion pressure inside, h) the starting point specifying means for specifying the starting point of heat generation due to knocking in one cycle, and the i) calculation and reading of the heat generation due to knocking during one cycle When the prohibition is instructed, the reading of the combustion pressure is stopped during that time, like the total heat calculation means.
Knock heat calculation means for calculating heat generation using the estimated combustion pressure, and j) a ratio of one or more of heat generation due to normal combustion or total heat generation in one cycle and heat generation due to knocking. A knocking detection device for an internal combustion engine, comprising: knocking strength determination means that calculates and determines the strength of knocking based on this ratio.