JPH03145551A - Knock control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To suppress the unnecessary spark delay control by the post-knock detection and improve reliability by correcting the threshold value based on the knock level and noise level, comparing the threshold value and knock level after correction, and judging the presence of knock. CONSTITUTION:The peak level P of the output A is generated for every ignition timing by a peak holding circuit 2 from the output A of a knock sensor 1 for each cylinder. The preset threshold value TH and the peak value P are compared by a knock judging section 17, if P>TH, the spark delay quantity thetaR is calculated by a spark delay quantity calculating section 18 and outputted to an ignition timing controller 19. An operation state processing unit 12 determining the operation region D based on the outputs of a crank angle sensor 3 and a load sensor 11 is provided, and the threshold value corresponding to the operation state D is read out from the first ROM 13. This threshold value is corrected 20 by the noise level N corresponding to the operation region D read out from the second ROM 14, and the threshold value after correction is applied to the knock judging section 17.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to a control device that detects knock in an internal combustion engine such as an automobile gasoline engine and retards the cylinder ignition position. The present invention relates to a knock control device for an internal combustion engine that prevents erroneous knock detection due to variations.

[Prior Art] Generally, an internal combustion engine driven by multiple cylinders uses a microcomputer (E
CU) is used to control the ignition timing, fuel injection order, etc. for each cylinder according to load conditions and the like.

However, if the ignition position is controlled to be too advanced during high-speed operation, abnormal combustion may cause vibrations called knocking (hereinafter referred to as knocking), which may damage the cylinder. Occurrence of such knocking In order to suppress
Conventionally, when abnormal vibration is detected during ignition, the cylinder ignition position is corrected to the retarded side in accordance with the vibration.

FIG. 3 is a block diagram showing a conventional knock control device for an internal combustion engine.

In the figure, (1) is a knock sensor attached to one or each of the cylinders for driving the internal combustion engine, and is made of a piezoelectric element for detecting vibrations, and has a knock sensor with a frequency peculiar to the knock (for example, 7 k It It has a resonant characteristic that is tuned to z).

(2) is a peak hold circuit that generates the peak level P of the output signal A of the knock sensor (1) at each predetermined ignition timing, and (3) is a peak hold circuit that is attached to the crankshaft or camshaft of an internal combustion engine and is installed at a predetermined crank angle. A crank angle sensor that detects the position θ, (4) a timing signal generator that generates a timing signal T for resetting the peak hold circuit (2) based on the crank angular position θ, and (5) a crank angular position θ A rotation speed detector detects the rotation speed R of the internal combustion engine based on the rotation speed R, and (6) is a function generator that generates a threshold level TI-1 corresponding to the rotation speed R.

(7) is a knock discriminator consisting of a comparator etc.
The peak level P is compared with the threshold value TH, and in the case of ATH, a comparison output C of level "1" is output. (8) is a retard amount calculator that generates a retard amount θ for cylinder ignition position correction based on the comparison output C. (
9) is an ignition timing controller that controls the ignition timing (ignition position) of the cylinder, and the base advance value determined according to the rotation speed and load condition of the internal combustion engine is corrected by the retard amount θ8. ing.

Note that the timing signal T generated at each predetermined period corresponds to the reference position of the cylinder that is synchronized with the rotation of the internal combustion engine.
For example, it consists of a pulse that rises at the first reference position B75° of each cylinder and falls at the second reference position WB5°. Therefore, the peak hold circuit (2) is reset at the first reference position fiB75°, and the period from this first reference position B75° to the second reference position B5° is masked. Then, it is enabled and the peak level P is maintained from the second reference position B5'' of the next cylinder to the first reference position g B 75° of the next cylinder.

Next, the operation of the conventional internal combustion engine knock control device shown in FIG. 3 will be described with reference to the waveform diagram in FIG. 4 and the characteristic diagram in FIG. 5.

Normally, each cylinder is ignited near the second reference position WB5°, which is about 5° before TDC (Top Dead Center -0°).
The explosion of the air-fuel mixture occurs at a crank angle of about 10° to 60° past TDC] A1G” to A60°,
Knock due to abnormal combustion also occurs in synchronization with this explosion timing.

The knock sensor (1) is fixed to a cylinder or the like to detect vibrations, and when a knock occurs, it generates an output signal A (see Fig. 4) that has a large amplitude compared to other vibration levels. For example, if knock occurs in a cylinder consisting of
The output signal A of the knock sensor (1> is the crank angle position 1A)
The waveform has a periodically large amplitude around 10° to 60°.

The crank angle sensor (3) is a first crank angle sensor corresponding to the operation of the cylinder.
and generate a crank angular position θ indicating the second reference positions B75° and B5°, and based on this crank angular position θ,
A timing signal generator (4>) outputs a pulse-like timing signal T.

The peak hold circuit (2) detects the peak level P of the output signal A of the knock sensor (1) from the rising edge of the timing signal T (second reference position it B 5°), and uses this as the rising edge of the timing signal T. Down (first reference position B
75°) until reset.

The rotation speed detector (5) detects the rotation speed R of the internal combustion engine from the crank angular position θ, and generates a signal level corresponding to this rotation speed R. The function generator (6) is composed of, for example, a ROM table, and generates a threshold value T H that increases as the rotational speed R increases, as shown in FIG. Because the rotation speed R
This is because as P increases, the amount of vibration due to knocking and noise increases, and the amplitude of the peak level P increases overall. The characteristics of the threshold value T I-1 as shown in FIG.
It is set in advance in the ROM etc. in the function generator (6).

The knock discriminator (7) compares the peak level P with a threshold value τ11, determines that a knock has occurred when the peak level P exceeds the threshold value TH, and generates a comparison output C of the "1" level. The retard amount calculator (8) increases the retard amount θ8 by a predetermined value when the comparison output C is generated (when knock occurs), and when the comparison output C is not generated (knock does not occur). case), the retard amount θ8 is decreased by a predetermined value at predetermined intervals.

Ignition timing control H(9) corrects the base advance value using the retard amount θ8 and performs calculation control of the cylinder ignition position.

As a result, the ignition position of the cylinder to be controlled is retarded toward the knock suppression side, and knock no longer occurs.

However, while the threshold value TH is uniquely set for the operating condition, the noise level included in the peak level P is determined by the internal combustion engine or knock sensor (1) even if the operating condition is the same. It fluctuates due to variations in the characteristics of

Therefore, even if the peak level P is a noise level, there is a possibility that it exceeds the threshold f1αTH.

If noise is determined to be a knock and retard control is performed, the cylinder ignition position will be cumulatively retarded every time a knock is detected, resulting in a significant loss of cylinder control efficiency.

[Problem to be Solved by the Invention 1] As described above, the conventional knock control device for an internal combustion engine determines the peak level P using the threshold value T I-1 that is preset according to the operating condition. When the noise level at the peak level P fluctuates, the noise is likely to be erroneously detected as knocking, and the cylinder ignition position is continuously retarded, resulting in a significant loss of control efficiency.

This invention has been made to solve the above-mentioned problems, and provides a knock control device for an internal combustion engine that can prevent false detection of noise even if the peak level fluctuates due to variations in the engine or knock sensor. The purpose is to

"Means for Solving the Problems" A knock control device for an internal combustion engine according to the present invention includes a first storage means for storing a threshold value corresponding to the operating state, and a second storage means for storing a noise level corresponding to the operating state. storage means,
The sensor level corresponding to the output signal of the knock sensor and the second
a threshold correction calculation processing section that corrects the threshold read from the first storage means based on the noise level read from the storage means of the first storage means, and compares the sensor level with the correction threshold from the threshold correction calculation processing section. The system is designed to determine whether there is a knock or not.

[Operation] In the present invention, when the average value of the sensor level becomes larger than a preset noise level, the dark value is corrected to become larger, thereby suppressing unnecessary retard control due to noise.

“Example” An example of the present invention will be described below with reference to the drawings.
The figure is a block diagram showing one embodiment of the present invention.
) to (4) are the same as described above.

Moreover, (17) to (19) correspond to (7> to (9), respectively).

(10> is an AD that converts the peak level P into a digital value.
This converter is inserted between the peak hold circuit (2) and the knock discrimination processing section (17).

Reference numeral (11) denotes a load sensor that detects a load state as an operating state different from the rotational speed R, and is composed of a semiconductor or the like that detects an intake state caused by the accelerator, for example.

(12) is an operating state processing unit that determines the operating range divided into two dimensions based on the crank angular position θ and the load state, and a rotation speed detector ( 5) (see FIG. 3) and a load detector that detects the load level from the load condition fiL. (1
3) is a first ROM that stores the threshold value TH corresponding to each operating region as a three-dimensional map table, and the threshold value TH for each operating region is read out. (
14) is a second ROM that stores the average noise level N corresponding to each operating region, and the noise level N for each operating region is read out.

(20> is a threshold correction calculation processing unit that corrects the threshold TH based on the peak level P and noise level N, and an averaging processing unit (20) that averages the peak level P every predetermined period.
1), the average value pg from the averaging processing section (21) and the second
a division unit <22> that generates a correction coefficient K from the ratio with the noise level N read out from the ROM (14); and a first ROM
The multiplication unit (23) generates the corrected threshold THE by multiplying the threshold TH read from (13) by the correction coefficient K.

The knock discrimination processing unit (17) generates a comparison output C by comparing the peak level P passed through the AD converter (10) with the correction threshold value TH outputted from the threshold correction calculation processing unit (20). , the retardation amount 31 calculation processing unit (18) generates the retardation amount θ8 based on the comparison output C, and the ignition timing control unit (19)
The cylinder ignition position is retarded based on the retard amount θ8. These are the operating state processing section (12);
It is configured in a microcomputer together with the first R-OM (13), the second ROM (14), and the l value correction calculation processing section (20).

Next, while referring to the flowchart in FIG.
The operation of the embodiment of the present invention shown in the figure will be explained.

The peak bold time 1i'8 (2) is the output signal A of the knock sensor (1) according to the timing signal T as described above.
The AD converter (10) converts the peak level P into a digital value and inputs it to the knock discrimination processing section (17).

The operating state processing unit (12) classifies the rotational speed R and load level at the time of detection based on the crank angle position θ from the crank angle sensor (3) and the load state UL from the load sensor (11), and The threshold value TH corresponding to the dimensional driving region is read from the first T' (OM(13)).

At this time, the first ROM (13) stores in advance a threshold value TH corresponding to each operating range of rotation speed R and load level, and a high level threshold value is stored at light load when the noise level is relatively high. TH is read out, making it difficult to misjudge knocking.

The threshold correction calculation processing section (20> first initializes the rotation speed, load level, etc. corresponding to the time of knock detection, according to the threshold correction processing routine shown in FIG. 2) (step Sl).

Next, it is determined whether or not the set rotational speed at the time of knock detection is determined (step S2), and if the set rotational speed has been reached, further,
It is determined whether the set load level is reached (step S3).

If the set rotation speed and set load level for knock sheets have been reached, the averaging processing unit (21) calculates the average value of the current peak level P for one line (step S4).
.

Next, in step S5), the noise level N, which is preset corresponding to the current rotational speed and load level and corresponding to the average value pg, is read out from the second ROM (14), and the dividing unit 22) calculates the average value. A correction coefficient K is calculated from K=PX/N by taking the ratio of the value P and the noise level N (step S6).

After R, the threshold f! is read out from the first ROM (13) by the multiplier (23). Multiplying fTH by correction coefficient K, T
From H work = T I - I X K, correction r:
AMTH' is inputted to jH[L (sf7''S7), and the corner correction threshold T H1 is inputted to the reference terminal of the knock discrimination processing section (17).

On the other hand, if it is determined in step S2 or S3 that the set rotational speed or the set load level has not been reached, knock detection is not performed, so the threshold correction processing routine is not executed, and the process immediately returns and ends.

Due to the above threshold value correction process, the threshold value TH preset corresponding to the driving state is not used as it is as the reference level of the knock discrimination processing section (17), and the average value P of the peak level P at that time is corrected in response to fluctuations in

If the average value 1 quintillion is larger than the preset noise level N, the correction coefficient K becomes K>1, so the correction threshold TH8 becomes T H vehicle> T H , and the noise level is taken as the knock level. In order to suppress false detection, even if the peak level P fluctuates due to variations in the individual characteristics of the knock sensor (1), the fluctuation is absorbed by the threshold correction calculation processing section (20). Correction threshold T H that always corresponds to the peak level P
Accurate knock discrimination can be performed using this as a reference.

In the above embodiment, the sensor means for detecting the operating state includes a crank angle sensor (3) that detects the crank angle position θ corresponding to the rotation speed, and a load sensor that detects the load state corresponding to the load level. (11) is used, but other sensor means may be used, or one sensor means may be used as shown in FIG.

Further, although the peak level P is used as the level corresponding to the output signal A of the knock sensor (1), an integral level via an integrating circuit may be used.

Furthermore, although the knock discrimination processing section (17) is configured with a comparison circuit, it may also be configured with a comparison calculation circuit to obtain an output signal according to the input signal difference.

[Effects of the Invention] As described above, according to the present invention, the first storage means for storing the threshold value corresponding to the driving state, the second storage means for storing the noise level corresponding to the driving state, and the knock sensor a threshold correction calculation processing unit that corrects the threshold read out from the first storage means based on the sensor level corresponding to the output signal of the sensor level and the noise level read out from the second storage means; Since the presence or absence of knock is determined by comparing it with the correction threshold value from the correction calculation processing section, it is possible to suppress unnecessary retard control due to erroneous detection of knock, thereby improving reliability of knock for internal combustion engines. This has the effect of providing a control device.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a flowchart for explaining the operation of the threshold correction calculation processing section in Fig. 1, and Fig. 3 is a conventional knock control for internal combustion engine. FIG. 4 is a waveform diagram for explaining the operation of the device shown in FIG. 3, and FIG. 5 is a characteristic diagram showing the contents of the function generator in FIG. 3. (l...Knock sensor (3...Crank angle sensor (11-=fi load sensor (13)-1st ROM (14...
... 2nd n OM (17... Knock discrimination processing unit (20... Threshold correction calculation processing unit A... Knock sensor output signal θ... Crank angle position... Load state T H
・Threshold THL ・Correction threshold N ・Noise level P ・Peak level C ・Comparison output θ8 ・Amount of retardation Note that in the figures, the same symbols indicate the same or equivalent portions.

Claims (1)

[Scope of Claims] A knock sensor for detecting vibrations of an internal combustion engine; a sensor means for detecting an operating state of the internal combustion engine; a first storage means for storing a threshold value corresponding to the operating state; and a first storage means for storing a threshold value corresponding to the operating state. a second storage means for storing a noise level corresponding to the knock sensor; and a noise level read from the first storage means based on the sensor level corresponding to the output signal of the knock sensor and the noise level read from the second storage means. A knock for an internal combustion engine, comprising: a threshold correction calculation processing section that corrects the read threshold; and a knock determination means that compares the correction threshold from the threshold correction calculation processing section with the sensor level to determine whether there is knocking. Control device.