JPH0444851Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to a knocking control device for an internal combustion engine such as an automobile, and particularly to a knocking control device intended to prevent torque reduction during knocking control.

(Conventional technology) Knocking is mainly caused by compression ignition of unburned gas, and should be avoided as it can cause energy loss (lower output), shock to various parts of the engine, and lower fuel efficiency if it occurs violently. is desirable.

Suppression of such knocking is generally achieved by retarding the ignition timing. For example, when the occurrence of knocking is detected, the ignition timing is sequentially retarded to suppress the knocking, and when knocking no longer occurs, the ignition timing is retarded. is gradually advanced to maintain an appropriate combustion state. In this case, if the retardation and advance speeds of the ignition timing are fixed at constant values, the knocking phenomenon changes depending on the operating conditions of the engine, resulting in the following problems.

That is, in general, the knocking phenomenon has a high probability of occurring when the engine is under high load, and is less likely to occur when the engine is under light load. And 1
Considering the degree of influence on the engine, such as pre-ignition, the required retard amount required for engine knocking may be smaller as the load is lighter. If the amount of retardation is increased when the load is light, the drive feeling during steady running will deteriorate. Furthermore, when the load is light, there are many erroneous knock judgments due to noise caused by mechanical vibration.

Therefore, as a device that takes into account the correction of such defects, there are conventional devices described in, for example, Japanese Patent Application Laid-Open No. 59-43975 and Japanese Patent Application Laid-Open No. 58-70455.
The former device changes the amount of retardation and advance angle per knocking occurrence depending on the engine load, while the latter device increases the advance speed when knocking does not occur after a predetermined period of time, improving drivability. It is intended to increase the

(Problem to be solved by the invention) However, in such conventional knocking control devices, the retardation speed of the ignition timing during knocking control was a constant value, so the final ignition timing at the time of knocking There was a problem that, depending on the period, a large drop in torque occurred.

This will be explained based on FIG. 15. FIG. 15 is a graph showing the relationship between the magnitude of knocking and the shaft torque with respect to the ignition timing. It is known that engine knocking becomes more likely to occur as the ignition timing advances. Furthermore, it is known that even if the ignition timing is the same, the higher the load, the more likely it is to occur.

That is, as shown in FIG. 15, at low load, knocking starts to occur at an advance angle of 20° BTDC or more, whereas at high load, knocking starts to occur at a retard angle side of 20° BTDC or more.
Knock begins to occur above 10° BTDC. Hereinafter, the area around 10° BTDC will be referred to as the retard side relative to 20° BTDC, and conversely, the area around 20° BTDC will be referred to as the advance side relative to 10° BTDC.

On the other hand, if we look at the degree of change in shaft torque on the retard side and the advance side, we see that near the advance side there is an almost constant torque transition, but on the retard side there is a fairly large change. For example, ΔT is shown as the amount of torque change when the ignition timing is changed by 2 degrees.

This means that when retardation correction (knocking control) is performed by about 2 degrees on the advance side, the torque will not decrease so much, but on the retard side, a large torque decrease equivalent to ΔT will be felt and the driving condition will be affected. It is meant to make things worse.

Therefore, in conventional systems, the retardation speed of the ignition timing during knocking control was a constant value, so the torque drop was large especially when the ignition timing was on the retard side, which worsened drivability. There was a problem.

(Purpose of the invention) Therefore, the purpose of the present invention is to avoid the drop in torque due to knocking control and improve drivability.

(Structure of the invention) The knocking control device for an internal combustion engine according to the invention has an operating state detection means a for detecting the operating state of the engine, as shown in FIG.
a knock detection means b for detecting knocking occurring in the engine; a basic advance angle setting means c for setting a basic advance angle value based on the operating condition; a correction amount calculating means d for calculating a retard angle correction amount to be corrected to the retard side; an advance angle setting means e; a retardation speed setting means f for setting the retardation speed to a larger value as the retardation correction amount becomes smaller or the final advance value becomes larger; ignition means g for igniting the fire, which improves both the responsiveness and control accuracy of the knocking control.

(Example) Hereinafter, the present invention will be explained based on the drawings.

2 to 10 are diagrams showing a first embodiment of the present invention.

First, the configuration will be explained. In FIG. 2, reference numeral 1 denotes a cylinder pressure sensor, and the cylinder pressure sensor 1 is formed as a washer for a spark plug 3 screwed onto a cylinder head 2 of an engine, and is fastened together with the washer. The cylinder pressure sensor 1 converts the combustion pressure in the cylinder into an electric charge using a piezoelectric element, and outputs an electric charge output _S1 . The sensor output S ₁ is converted into a voltage signal S ₂ by a charge amplifier 4 and input to a multiplexer (MPX) 5 . Note that the cylinder pressure sensor 1 and the charge amplifier 4 are arranged for each cylinder.

The multiplexer 5 receives the switching signal Sc output from the microcomputer 6 at each predetermined timing.
In synchronization with , the signal _S2 from the charge amplifier 4 arranged corresponding to each cylinder is selectively switched for each cylinder in a time-division manner and output as the signal _S3 to the bandpass filter (BPF) 7. do. This is because the timing must be set to cover the in-cylinder pressure and knocking occurrence timing for each cylinder. The bandpass filter 7 is arranged in a frequency band corresponding to knocking vibration (for example, 5KH to 5KH) of the signal _S3 .
20KHz) and outputs it to the rectifier 8 as a signal _S4 , and the rectifier 8 performs full-wave rectification (half-wave rectification is also acceptable) of the signal _S4 , and outputs it to the integrator ₉ as a rectified signal S5.

The integrator 9 also receives an integral interval signal S _K from the microcomputer 6, and the integrator 9
integrates the rectified signal S ₅ only while this integral interval signal S _K is input, and outputs it to the microcomputer 6 as an integral value S corresponding to a physical quantity related to combustion vibration energy. The integral interval signal S _K is output, for example, in a range of 10° to 45° after compression top dead center (TDC). Therefore, the integrator 9 starts integrating the rectified signal _S5 at 10° ATDC, stops the integration at 45° ATDC, and resets the integral value S.

The reason why the integration processing section of the rectified signal _S5 is limited is as follows. If ignition noise, seating vibration of valves in other cylinders, switching noise of multiplexer 5, etc. are similar to vibrations caused by knocking, such noises will be regarded as vibrations caused by knocking, so regular knocking can be expected to occur. The influence of noise is eliminated by limiting the integration processing interval to only the interval in which the calculation is performed.

In the cylinder pressure sensor 1, a charge amplifier 4, a multiplexer 5, a bandpass filter 7, a rectifier 8 and an integrator 9 constitute a knock detection means 10.

The microcomputer 6 is further inputted with a signal S ₆ from the operating state detection means 11, and the operating state detection means 11 receives parameters representing the operating state of the engine (for example, throttle valve opening, intake air amount Q _a ,
(rotational speed N, cooling water temperature, etc.) and outputs the above signal _S6 .

The microcomputer 6 is a basic advance angle setting means,
It has the functions of a correction amount calculation means, a final advance angle setting means, and a retardation speed setting means, and is composed of a CPU 12, a memory 13, an I/O port 14, and an A/D converter 15. The A/D converter 15 A/D converts the output (integral value) S of the integrator 9 and sends it to the CPU.
12, and the CPU 12 outputs the output to I/O port 1 according to the program written in the memory 13.
4 and the A/D converter 15, and while exchanging data with the memory 13, it calculates and processes the processing values necessary for ignition timing control, and as necessary. The processed data is output to the I/O port 14. A signal S ₆ from the operating state detection means 11 is input to the I/O port 14, and a switching signal Sc, an integral interval signal _SK , and an ignition signal Sp are output from the I/O port 14. The memory 13 stores an arithmetic program for the CPU 12, and also stores data used in the arithmetic operations in the form of a map or the like. ignition signal
Sp is input to the ignition means 16, and the ignition means 16 is connected to the ignition coil 17 and the distributor 1.
8. Consists of a spark plug 3 and a transistor Q1. The ignition means 16 controls the transistor Q1 on/off based on the ignition signal Sp to generate a high voltage in the ignition coil 17, and sequentially distributes this high voltage to the spark plugs 3 of each cylinder by the distributor 18. Ignite the mixture.

Next, the action will be explained.

FIG. 3 shows an example of signal waveforms at each part. That is, the output signal _S2 of the charge amplifier 4 changes in proportion to the in-cylinder pressure, and includes a unique vibration component when knocking occurs. This voltage signal S ₂ becomes a signal S ₃ which is synthesized for each cylinder by a multiplexer ₅ as shown in FIG. Only the vibration component is extracted and becomes the signal _S4 . Next, the signal S ₄ is rectified by the rectifier 8 to become the signal S ₅ as shown in d of the figure, and this signal S ₅ is integrated over a predetermined interval by the integrator 9 to obtain the integral value S as shown in e of the figure. .

Next, the contents of the program executed by the microcomputer 6 will be explained.

4 to 6 are flowcharts showing the knocking control program written in the memory 13, and Pi (i=1, 2, 3, . . . ) in the drawings indicates each step of the flow.

FIG. 4 is a flowchart showing the initialization routine.

First, the stored contents of the ROM of the memory 13 are cleared at _P1 , and other arithmetic processing unrelated to knocking control is performed at _P2 , but the details are omitted here. Next, back ground job (BGJ) after P ₃
to move to. At P ₃ , rotation speed N and basic injection amount Tp
Calculate the basic advance angle value ADV based on . this is,
For example, the appropriate optimum value is looked up from a predetermined table map using N and Tp as parameters. Next, after correcting the basic advance angle value ADV based on the cooling water temperature in _P4 , other arithmetic processing is performed again in _P5 . In this way, the execution of BGJ continues.

FIG. 5 is a flowchart showing the interrupt routine.

First, other arithmetic processing is performed in _P11 , and it is determined in _P12 whether the crank angle θ is 50 degrees after top dead center (ATDC). When the crank angle θ is 50° ATDC, an interrupt is applied and the necessary processing values for ignition timing control are calculated in P ₁₃ (details will be described in the subroutine), and then other calculation processing is performed in P ₁₄ . end the routine. Also, the crank angle θ is 50°ATDC
If not, proceed to P ₁₅ , and in P ₁₅ the crank angle θ is
Determine whether it is 10° ATDC. When the crank angle θ is 10° ATDC, the integrator 9 is set (that is, the integral interval signal _SK is output) in _P16 , and the process proceeds to _P14 , and when it is not 10° ATDC, the process directly proceeds to _P14 .

FIG. 6 is a flowchart showing a subroutine for calculating the ignition timing, and this subroutine corresponds to the process of step _P13 in FIG. 5 described above.

First, determine the cylinder by determining the cylinder number n in P ₂₁ ,
At _P22 , the integral value S representing the knock level is A/D converted. Next, in P ₂₃ , the retard angle correction amount for correcting the advance angle value to the retard side is calculated from the table map shown in FIG.
Look up the retardation speed K1 of ADVn. _P24
Now, the slice level SL for knock determination is calculated using the rotational speed N and the retardation speed K1 as parameters. In this calculation, first, a function K corresponding to the retardation speed K1 is determined from the table map shown in FIG. 8, and a basic slice level SL1 corresponding to the rotation speed N is determined from the table map shown in FIG. Then, the slice level SL is determined according to the following formula:
Calculate.

SL=SL1×K...Next, in _P25 , the integral value S that has been A/D converted this time is compared with the slice level SL. When S>SL, it is determined that knocking has occurred, and in P ₂₆ the retard angle correction amount ADVNn for the n cylinder is retarded according to the following formula, and the process proceeds to P ₂₇ .

ADVNn=ADVNn'+K1... However, ADVNn': Previous retard angle correction amount Also, when S≦SL, it is determined that knocking has not occurred, and in P ₂₆ , the retard angle correction amount ADVNn is calculated according to the following formula. Correct the lead angle and proceed to page ₂₇ .

ADVNn=ADVNn′−K2... However, K2: Advance angle speed, for example, K2=0.1°/1 judgment level In this way, depending on the presence or absence of knocking,
ADVNn is corrected appropriately. In P ₂₇ , it is determined whether the retard angle correction amount ADVNn is smaller than the lower limit level of zero, and if ADVNn<0, it is determined in P ₂₉ .
Set the lower limit by setting ADVNn=0 and proceed to _P30 . Further, when ADVNn≧0, the process directly proceeds to P ₃₀ . At P ₃₀ , ADVNn is compared with the upper limit level UL, and when ADVNn > UL, ADVNn = UL at P ₃₁ .
Set the _upper limit as
If ≦UL, proceed directly to page ₃₂ . At _P32 , the final advance angle value ADVn is calculated according to the following formula.

ADVn = ADV - ADVNn ... However, ADV is the basic advance value obtained in the initialization routine, and the value obtained by correcting the water temperature. This allows the final advance value to be set at the next ignition timing.
The ignition signal Sp is output at a timing corresponding to ADVn, and the air-fuel mixture is ignited. Then, at _P33 , the integrator 9 is reset (that is, the integration interval signal Sk
(stops the output of), and switches the multiplexer 5 to the sensor output for the next combustion cylinder at P ₃₄ (that is, outputs the switching signal Sc for the next combustion cylinder).
Finish this routine.

The specific operation of the above-mentioned program is shown in FIGS. 10a and 10b, which show changes in ignition timing and generated torque when only specific cylinders are controlled. In the figure, E and E' are waveforms when knocks are difficult to occur, and F and F' are waveforms when knocks are easy to occur.

In other words, the final advance angle value at the time of knock occurrence is
When the BTDC is around 20°, the retard speed is set to be large (advanced angle in the conventional example), while when the final advance value is around 10° BTDC (the retarded angle in the conventional example) side), the retardation speed is set to be smaller.

As a result, the degree of change in shaft torque is large.
It is possible to avoid a drop in torque around 10° BTDC. To explain this with a diagram, in Fig. 15, when a knock occurs around 10° BTDC, the retardation speed is set to a smaller value (for example, 2°).
By setting it to a value smaller than ΔT, it is possible to suppress the decrease in shaft torque to a value smaller than ΔT, thereby allowing the torque to decrease while preventing the driver from feeling the drop in torque.

In this embodiment, as described in step _P23 above, the retard angle speed K1 is determined based on the magnitude of the final advance angle value ADVn, and its range is [1° to 5°/1 notch determination]. Therefore, as shown in Fig. 10a, when the ignition timing is advanced, the retardation speed K1 becomes large, and when it is delayed, it becomes small, but as shown in Fig. 10b, the generated torque changes in both cases. is smaller and more stable than before. Also,
In this case, the level of notsking also becomes stable at a moderate level. In this way, the responsiveness of the knocking control can be improved, and the control precision can also be made high.

In addition, in this example, the retardation speed K1 is [1° to 5°/
Since the advance angle speed K2 is set to [0.1°/1 non-knock judgment], when the angle is retarded by 1°, a knock is judged and controlled on average once every 10 times. Become. Therefore, with cumulative frequency
Control is performed at 10%, and the difference in sensor output due to knocking when knocking is likely to occur is clear from FIG. 16, so it can be said that the accuracy of knocking judgment is sufficient. Further, for example, when the angle is retarded by 5 degrees, the cumulative frequency is 2%, and even when knocking is unlikely to occur, a sufficient difference in sensor output can be obtained. Therefore, for example, Fig. 17a
After eliminating the problem shown by curve D, the advance angle speed K2 can be set to [0.1°/1 notch judgment] or higher.

11 and 12 are diagrams showing a second embodiment of the present invention, in which the retardation speed K1 is determined based on the retardation correction amount ADVNn.

That is, in the program shown in FIG.
After completing _P22 , in step _P41 , the retardation speed K2 is looked up from the table map shown in FIG. 12 based on the previous retardation correction amount ADVNn for n cylinders.
Proceed to page ₂₄ . The rest is the same as the first embodiment.
The retard angle correction amount ADVNn also becomes the final advance angle value.
ADVn is determined, and therefore, in this embodiment as well, the same effects as in the first embodiment can be obtained. Here, the above retardation correction amount ADVNn
generally represents the amount of retard from the basic ignition timing. For example, in the case of an ignition timing control system that matches the basic ignition timing to near the top of the engine torque curve (see the shaft torque curve in Figure 15) (where torque fluctuations are small), the larger the amount of retard from the basic ignition timing, the more In other words, the larger the retardation correction amount ADVNn is, the steeper the slope of the torque curve becomes, so the drop in torque becomes larger. Therefore, in such a system,
If the retardation speed K1 is made smaller as the retardation correction amount ADVNn increases, a drop in torque can be avoided.

FIGS. 13 and 14 are diagrams showing a third embodiment of the present embodiment, in which the rotation speed N is also used as a parameter for determining the retarded angular velocity K1.

That is, as shown in the omitted part of the program in FIG. 13, when _P22 is completed, in step _P51 , the table map shown in FIG. Look up the retardation speed K1 from , and proceed to _P24 . The rest is the same as the first embodiment. Therefore, this embodiment also provides the same effect as the first embodiment, but since the rotation speed N is also one of the parameters, the difference in torque characteristics as shown in FIG. 15 due to the difference in rotation speed N is caused. It has the advantage that it can also be modified. This makes it possible to minimize torque fluctuations and maintain them at a constant level even under a wide range of operating conditions.

Although the integral value S is used as the knock signal in each of the above embodiments, the knock signal is not limited to this, and for example, the integral value S minus its average value (S-) can be used.
may be used as a knock signal. In this way, there is no need to greatly change the rice level SL in accordance with the retardation speed K1, and knocking can be controlled with higher precision.

Furthermore, the slice level SL is calculated based only on the rotational speed N, and does not necessarily need to be corrected using the retardation speed K1, but it is better to perform such correction in order to control the size of the knock more accurately. . However, if the ignition timing is advanced too much, there are concerns about the durability of the engine, so if the ignition timing is advanced further, it is better to suppress knocking to a small level, and in that case, correction using the retardation speed K1 may not be necessary. .

Note that if this correction is not made, the knocking level will be controlled to be small when the angle is advanced.

(Effects) According to the present invention, it is possible to improve the responsiveness and control accuracy of knocking control while minimizing torque fluctuations due to the retard angle for suppressing knocking, and improve engine drivability.

[Brief explanation of the drawing]

Fig. 1 is a basic conceptual diagram of the present invention, Figs. 2 to 10 are diagrams showing the first embodiment of the invention, Fig. 2 is its overall configuration diagram, and Fig. 3 a to e are signals of each part. 4 is a flowchart showing the initialization routine, FIG. 5 is a flowchart showing the interrupt routine, FIG. 6 is a flowchart showing the ignition timing calculation subroutine, and FIG. 7 is a flowchart showing the ignition timing calculation subroutine. is a diagram showing the relationship between the final advance value and the retardation speed, FIG. 8 is a diagram showing the relationship between the retardation speed and the function K, and FIG. 9 is a diagram showing the relationship between the rotation speed and the basic slice level. , FIGS. 10a and 10b are timing charts for explaining the operation, the first
1 and 12 are diagrams showing a second embodiment of the present invention, FIG. 11 is a flowchart showing a subroutine for calculating the ignition timing, and FIG. 12 is a diagram showing the relationship between the retardation correction amount and the retardation speed. 13 and 14 are diagrams showing a third embodiment of the present invention, FIG. 13 is a flowchart showing part of a subroutine for calculating the ignition timing, and FIG. 14 is a retardation correction for the retardation speed. Diagrams showing the relationship between quantity and rotation speed, Nos. 15 to 17
15 is a diagram showing a conventional knocking control device for an internal combustion engine, and FIG.
FIG. 6 is a diagram showing the relationship between the magnitude of the knock signal and the cumulative frequency, and FIGS. 17a and 17b are timing charts for explaining the effect. 6... Microcomputer (basic advance angle setting means, correction amount calculation means, final advance angle setting means, retardation speed setting means), 10... Knock detection means, 11...
...Operating state detection means, 16...Ignition means.

Claims (1)

[Scope of Claim for Utility Model Registration] a) Operating state detection means for detecting the operating state of the engine; b) Knock detection means for detecting knocking occurring in the engine; c) A basic advance angle value based on the operating state. d) correction amount calculation means for calculating a retard angle correction amount for correcting the basic advance value to the retard side at a predetermined retard speed when knocking occurs; and e) a basic advance angle. Correct the value according to the retardation correction amount,
final advance angle setting means for determining a final advance angle value and outputting an ignition signal; f) setting the retard angle speed to be larger as the retard angle correction amount becomes smaller or as the final advance angle value becomes larger; A knocking control device for an internal combustion engine, comprising: a retarding speed setting means; and g) an ignition means for igniting an air-fuel mixture based on an ignition signal.