JPH0542615B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <<Industrial Application Field>> The present invention relates to an engine knocking detection device.

<Background of the Invention> It is well known to advance the ignition timing in order to improve engine output, but if the ignition timing is advanced too much, depending on the operating conditions, the engine may knock, causing unpleasant vibrations and engine failure. becomes.

However, it is known that fuel efficiency and output improve in slight knocking conditions, so the ignition timing is controlled while detecting engine knocking, and the engine is always operated at the best output condition while avoiding knocking. A system is being developed.
An example of a knocking detection device used in such a system is the one shown in FIG.

When knocking occurs in the combustion chamber 1 of the engine, vibrations are transmitted through the cylinder block 2 and reach the knock sensor 3. The knock sensor 3 extracts this vibration as an electric signal, and is composed of a magnetic core 4, a coil 5, and a permanent magnet 6. When force is applied to the core 4, which is held between plates 6a that bend when subjected to vibration, the internal The magnetic flux changes due to the strain, and a voltage is generated in the coil 5.

By the way, since the engine constantly vibrates, a signal is output even if knocking does not occur, but the vibration frequency of knocking is 6 to 8 KHz.
As a characteristic of the sensor itself, it has a resonance point of about 7 KHz, so when knocking occurs, the sensor 3 resonates, and the output signal from the sensor 3 increases.

The knock control unit 7 which receives such a signal from the knock sensor 3 is composed of a knock vibration detecting section 8, a knock strength determining section 9, and a retard control section 10.

In order to remove mechanical noise other than knocking from the signal from the knock sensor 3, the knock vibration detection section 8 filters and detects only the knocking signal having a frequency of about 7 KHz.

Then, the knocking strength determination section 9 discriminates the level of the detected knocking signal for each ignition to determine the knocking strength, and when the level of the knocking signal exceeds a predetermined knocking strength reference level, the knocking strength is determined. If so, it is determined that knocking has occurred, and further, the knocking strength is determined depending on the degree of exceeding the reference level.

When it is determined that knocking has occurred, a retard signal is supplied from the ignition timing control section 10 to the igniter 11 of the distributor, and the ignition timing is controlled to be delayed depending on the intensity of knocking. Note that 12 in the figure is an ignition coil.

Then, in the next combustion, if knocking is still occurring, the ignition timing is further delayed, or conversely, if it is determined that no knocking is occurring, a signal is output that advances the ignition timing. The aim is to improve output and fuel efficiency by keeping the output at a level with slight knocking. In addition, there are other publications such as Japanese Patent Publication No. 58-13749 and Japanese Patent Publication No. 51-46606.

However, although the conventional knocking detection device described above is configured to extract only the vibration frequency component of knocking, it is difficult to detect noise caused by mechanical vibrations generated by engine rotation or load combinations. If the above-mentioned knocking vibration frequency contains the same frequency component, this noise will be detected as a knocking signal, and the noise will be superimposed on the knocking signal, or the knocking will be affected by the relatively large vibrations that occur during ignition. There is a high risk of misidentification.

Furthermore, in addition to the above conventional example that uses a vibration sensor, a knocking detection device that uses a pressure sensor that detects changes in cylinder internal pressure has also been proposed, and if this pressure sensor is used, it is possible to pick up mechanical vibration components. Although this is not the case, electrical noise caused by the spark from the ignition plug is picked up, so there is still a risk that knocking may be mistakenly determined due to this ignition noise.

[Object of the Invention] This invention was made in view of the above circumstances, and its purpose is to eliminate the influence of noise components other than knocking, especially noise during ignition, and to detect knocking with high accuracy. An object of the present invention is to provide an engine knocking detection device capable of detecting engine knocking.

<<Structure of the Invention>> In order to achieve the above object, the present invention is configured as shown in the diagram corresponding to the claims shown in FIG. Frequency component extraction means 100; Crank angle detection means 101 for detecting the crank angle of the engine; Rotation speed detection means 102 for detecting the rotation speed of the engine; Ignition timing for detecting the ignition angle of the engine a detecting means 103; an integrating means 104 for sequentially accumulating the natural frequency components in a predetermined crank angle range from before the ignition angle to after the compression top dead center; Each integrated value (I ₃ , I ₄ ) at one crank angle position and each integrated value (I ₁ , I ₂ ) at two crank angle positions set at the time of ignition and immediately after ignition are calculated, and each integrated value Correction is made by subtracting the amount of increase in integrated value (I ₂ - I ₁ ) in ignition from (I ₃ , I ₄ ), and the correction results are (I ₃ - (I ₂ - I ₁ ), I ₄ - (I ₂
-I ₁ )) ratio K(={I ₄ -(I ₂ -I ₁ )}/{I ₃ -(I ₂ -
I ₁ )}); and a discriminator 106 that compares the value of the ratio K with a predetermined reference value determined by the rotational speed of the engine to determine the presence or absence of knocking. .

<<Description of Embodiments>> Embodiments of the present invention will be described in detail below with reference to FIG. 3 and the subsequent drawings.

FIG. 3 is a block diagram showing the structure of an embodiment of the engine knocking detection device according to the present invention.

In the figure, the pressure sensor 21 is a washer-type pressure sensor in which a piezoelectric element is formed into a washer shape, and the fourth
As shown in the figure, it is inserted into the mounting portion of the spark plug 13 in the same manner as a normal washer, and detects changes in cylinder internal pressure accompanying gas combustion.

The output S ₁ of the pressure sensor 21 is supplied to a charge amplifier 22 , converted into a voltage signal S ₂ , and then supplied to a BPF (band pass filter) 23 .

The BPF 23 is a filter that transmits only knocking frequency components having a knocking vibration frequency of 6 to 8 KHz, similar to the knocking vibration detecting section 8 in the conventional example shown in FIG.

The above-mentioned knocking frequency component S ₃ is transmitted to the rectifier circuit 24
After being rectified by , it is supplied to an integrating circuit 25 .

The crank angle sensor 26 uses a pulse generator (not shown) built into the distributor 11 shown in FIG. 1 to output a pulse signal corresponding to the rotation angle of the drive shaft of the distributor. , the 120° signal S ₅ generates one pulse every 120° of the crankshaft rotation, and the 120° signal S 5 generates one pulse every 2° of the crankshaft rotation.
2° signal S ₆ is output.

The drive shaft of the distributor is configured to rotate twice for each revolution of the crankshaft, and the 120° signal _S5 indicates that the crankshaft in a 6-cylinder engine is 70° before top dead center. The pulse is set to occur at an angular position.

The integration circuit 25 receives the 120° signal _S5 and the 2° signal
S ₆ is supplied, and based on these signals, the input signal S ₄ is
The system is configured so that the integral value is then reset up to 40 degrees after top dead center, and after this integral value is held until 45 degrees after top dead center.

Further, the counter 31 counts the pulses of the 2° signal S ₆ for a certain period of time, and supplies the count value for each certain period of time to the microcomputer 30 as engine rotational speed data D ₃ .

The microcomputer 30 includes a multiplexer 28 in addition to the engine rotational speed data _D3 .
and the A/D converter 29, the integral value data _D1 of the integrating circuit 25, and the air flow meter 2
The intake air amount data _D2 from 7 is input. Further, the 120° signal _S5 and the 2° signal _S6 are input as interrupt timing signals.

A timing signal _S7 is supplied from the microcomputer 30 to the multiplexer 28.
and ignition timing control data F are output. In addition, 3
2 is a memory composed of ROM, RAM, etc.

FIG. 5 shows the charge amplifier 22, BPF 23, rectifier circuit 24, and the rectifier circuit 24 when knocking occurs.
3 is a diagram showing each output S ₂ , S ₃ , S ₄ , and D ₁ of the integrating circuit 25. FIG. As shown in the figure, in addition to the large vibration output a caused by knocking, a relatively large vibration output b is also detected at the time of ignition.

6 to 8 are flowcharts showing the contents of the processing executed by the microcomputer 30. FIG.

The flowcharts in Figures 6a, b, and c are as follows:
This is an interrupt processing routine in which an interrupt is made when the crank angle reaches a predetermined value based on the 120° signal S ₅ and the 2° signal S ₆ , where a is the ignition time t ₁ and b is the after ignition time. The time points t ₂ and c when the crank angle has rotated 5 degrees are respectively interrupted at the time t ₃ when the crank angle has rotated 5 degrees after passing the top dead center. Then, integral value data I ₁ to I ₃ (shown in FIG. 5) at each point in time is read from the integrating circuit 25 and stored.

The process shown in the flowchart in Figure 7 is performed when the crank angle has rotated 400 degrees after passing the top dead center.
An interrupt is made at _t4 , and in steps (1) and (2), the integral value _I4 at that time point _t4 is sent from the integrating circuit 25.
The process of reading and storing is performed.

Then, in step (3), based on the integral values I ₁ to I ₄ read at the above four times t ₁ to t ₄ ,
Find the integral value increase amount (I ₂ - I ₁ ) at the time of ignition (from time t ₁ to t ₂ ) (this corresponds to the amount of noise at the time of ignition), and calculate the amount of increase in the integral value at the time t ₃ and t ₄ above. From the integral values I ₃ and I ₄ , increase amount at the time of ignition (I ₂ − _{I 1} )
This correction result I ₃ − (I ₂ − I ₁ ),
Ratio of I ₄ - (I ₂ - I ₁ ) (hereinafter referred to as knocking strength) K K = {I ₄ - (I _{2 -} I ₁ )}/{I ₃ - (I ₂ - I ₁ )}... (1
) is performed.

In this way, the knocking strength K obtained from the above equation (1) does not include the noise component at the time of ignition, and it is possible to obtain an accurate knocking strength. For example, only the intensity of the ignition noise increases,
Even if the output _D1 of the integrating circuit becomes as shown by the imaginary line in Fig. 5, by performing the above correction, the value of the knocking strength K obtained is the same as that shown by the solid line in the same figure. value.

Next, in step (4), the counter 31
The engine rotational speed data _D3 is read in, and in step (5), a reference value X corresponding to the engine rotational speed is determined based on the characteristic map stored in advance. This reference value X is set in consideration of changes in mechanical noise caused by increases and decreases in engine speed, changes over time in the crank angle range _t3 to _t4 , and the like.

Then, in step (6), the reference value X is compared with the knocking strength K, and if the comparison result is KX, it is determined that knocking has occurred, and in step (7) By reducing the advance angle correction value ΔA by a constant value α, data for retarding the ignition timing from the previous ignition timing is generated. Further, if K<X, in step (8), a constant value β is added to the advance angle correction value ΔA obtained in the previous process to form data for advancing the ignition timing from the previous ignition timing.

Next, the process shown in the flowchart of FIG.
An interrupt is made by the 120° signal _S5 , and the interrupt process is started when the crank angle is 70° before top dead center, that is, when the crank angle has rotated 50° after passing the previous top dead center.

First, in step (11), the intake air amount data _D2 from the air flow meter 27 and the counter 31 are
Read the engine speed data _D3 from
Based on a basic ignition timing characteristic map stored in advance, basic ignition timing data A corresponding to the engine speed and intake air amount is determined.

Next, in step (12), the advance angle correction value ΔA obtained in the process shown in FIG. 7 is added to the basic ignition timing data A to obtain ignition timing control data F.

Then, through the processing of steps (13) to (16), the upper and lower limits are cut so that the value of the ignition timing control data F falls within the range of O≦F≦70 (the value of F is the upper limit). , if the lower limit is exceeded, the value of F is set to the upper limit of 70.
or correcting it to the lower limit value 0), the ignition timing control data F is output in step (17).

The ignition timing control circuit 33 is composed of a register R, a comparator P, a counter C, etc. (all not shown), and the value of the counter C is preset to 70 by the pulse in the 120° signal _S5 . Thereafter, a countdown is performed by both the rising and falling edges of the pulse in the 2° signal _S6 (that is, every 1° of crank angle).

The register R stores the ignition timing control data F supplied from the microcomputer 30, and the comparator P compares the ignition timing control data F with the count value of the counter C (ignition timing control data F). = (count value), an ignition signal is output.

To explain specifically, if the ignition timing control data F is, for example, 40, the number of counts until the count value of the counter C reaches 40 is (70
−40) = 30, and the crank angle is 120° above signal S ₅
The point at which the point has been rotated by 30 degrees from the point at which
Ignition will occur 40 degrees before top dead center.

In the above embodiment, the pressure sensor 21 is used to detect the knocking frequency component, but a vibration sensor may also be used as in the conventional example shown in FIG. good.

<<Effects of the Invention>> As is clear from the above description, the engine knocking detection device according to the present invention sequentially detects the natural frequency components of knocking in a predetermined crank angle range from before the ignition angle to after the compression top dead center. Each integrated value (I ₃ , I ₄ ) at two crank angle positions set at a later angle than the ignition angle.
and each integrated value (I ₁ , I ₂ ) at two crank angle positions set at the time of ignition and immediately after ignition, and from each integrated value (I ₃ , I ₄ ), calculate the increase in the integrated value at ignition. The amount (I ₂ - I ₁ ) is subtracted and corrected, and the ratio K of the correction result (I ₃ - (I ₂ - I ₁ ), I ₄ - (I ₂ - I ₁ ))
Find (= {I ₄ − (I ₂ − I ₁ )}/{I ₃ − (I ₂ − I ₁ )}),
Since the value of the ratio K is compared with a predetermined reference value determined by the rotational speed of the engine to determine the presence or absence of knocking, it is possible to eliminate noise components other than knocking, especially the influence of ignition noise at the time of ignition. This has the effect that knocking can be detected with high accuracy.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a conventional knocking detection device, FIG. 2 is a configuration diagram of the present invention, FIG. 3 is a block diagram showing an embodiment of the engine knocking detection device according to the present invention, and FIG. is a sectional view showing how the pressure sensor used in the device is installed, FIG. 5 is a diagram showing the main waveforms in the device, and FIGS. This is a flowchart showing the contents of the process. 21...Pressure sensor, 23...Band pass
Filter, 25...Integrator circuit, 26...Crank angle sensor, 30...Microcomputer, 31
... Counter, 100 ... Knocking frequency component extraction means, 101 ... Crank angle detection means, 10
2...Rotational speed detection means, 103...Ignition timing detection means, 104...Integration means, 105...Arithmetic means, 106...Discrimination means.

Claims (1)

[Claims] 1. Detecting engine vibration or internal pressure change,
knocking frequency component extraction means for outputting a frequency component specific to knocking; crank angle detection means for detecting the crank angle of the engine; rotational speed detection means for detecting the rotational speed of the engine; and ignition angle of the engine. ignition timing detection means for detecting the ignition timing; integrating means for sequentially accumulating the natural frequency components in a predetermined crank angle range from before the ignition angle to after the compression top dead center; Each integrated value (I ₃ , I ₄ ) at the two set crank angle positions, and the two set at the time of ignition and immediately after ignition.
Each integrated value (I ₁ ,
I ₂ ) is corrected by subtracting the amount of increase in the integrated value (I ₂ − I ₁ ) in ignition from each integrated value (I ₃ , I ₄ ), and the correction result (I ₃ − (I ₂ − I ₁ ), I ₄ − (I ₂ −
I ₁ )) ratio K(={I ₄ −(I ₂ −I ₁ )}/{I ₃ −(I ₂ −I _{1 )}
)})
A knocking detection device for an engine, comprising: calculation means for calculating the ratio K; and discrimination means for comparing the value of the ratio K with a predetermined reference value determined by the rotational speed of the engine to determine whether or not knocking is present.