JPS6278480A - Ignition timing control of internal combustion engine - Google Patents

Abstract

PURPOSE:To securely prevent knocking from occurring regardless of varied octane numbers of gasoline used, by sensing the change in the knocking occurrence level characteristics against the amount of advance/retard angle of the ignition timing, and by computing according to such a change the maximum limit of the retard angle of the ignition timing. CONSTITUTION:Presence of knocking is judged by a knocking level decision means B based on signals from a knock sensor A which senses fluctuation of combustion pressure or vibration caused by combustion of the internal combustion engine. When knocking is produced, the ignition timing is corrected to retard by means of a retard angle control means C and when knocking is not produced, the ignition timing is corrected to advance by means of an advance angle control means D. Here, a characteristic change sensing means F is provided to detect change in characteristics of the knocking occurrence level against the advance angle amount of the ignition timing so that the maximum limit of the ignition retard angle to be performed by a retard angle control means C according to the characteristic change detected can be computed by means of a maximum retard angle limit computing means G.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This U-mei is designed to determine whether or not knocking has occurred in an internal combustion engine based on a detection signal from a knock sensor, and to suppress the non-king level to a predetermined value or less. This invention relates to an ignition VJ control device that controls ignition timing.

[Conventional technology]

This is a conventional ignition timing control device.

For example, there are those found in Japanese Patent Publication No. 57-61897 or Japanese Patent Application Laid-Open No. 59-3175.

Various types of knocking control using knock sensors have been known in the past, but when considering the case where an engine has multiple cylinders, there are two types: one in which all cylinders are controlled simultaneously and one in which each cylinder is controlled independently.

Generally, knocking occurs due to differences in compression ratio, air-fuel ratio, combustion chamber wall temperature, etc. between cylinders. Since the engine timing differs from cylinder to cylinder and is not the same, better output performance can be obtained by detecting the knocking level for each cylinder and performing control to delay the ignition timing only in the cylinder in which knocking occurs.

In that case, conventionally, the basic (base) ignition timing common to each cylinder is determined according to the operating conditions, and the advance side is within a range in which the ignition timing is not advanced beyond this basic ignition timing.

In addition, on the retard side, the sensor output increases due to variations in knock sensor sensitivity, noise, and mechanical vibration, and it may be determined that knocking is occurring and retard the angle more than necessary, resulting in a significant torque drop. In order to prevent this, [ignition timing that gives a slight knocking condition (so-called 1 to race knock)] -α°.

Or M B T (MinimuIIadvance
For Re5t, Torgue) point is on the retard side than the trace knock point.

A limit value on the retard side is set in advance at the point MBT-α° (α = 5° to 6° is appropriate), and within a range that does not retard more than this limit value, advance or advance the angle relative to the knocking level. Retard angle control is performed.

That is, first, ignition is performed based on the basic ignition timing,
When knocking occurs, the ignition timing is delayed in accordance with the non-knocking level in order to avoid the knocking, resulting in a slight knocking condition. 'When knocking no longer occurs due to this retardation operation, the ignition timing is considered to have been retarded more than necessary and is advanced again to maintain a slight non-knocking condition.

However, if this advance operation causes the ignition timing to advance beyond the basic ignition timing, the ignition timing is regulated to the basic ignition timing.

This basic ignition timing is set to the ignition timing that provides the maximum torque below the slight knocking level of the applied engine.

Under low engine load conditions, the relationship between 1 ignition timing and the generated 1-lux becomes as shown by the broken line in Figure 7, and the ignition timing that provides the maximum torque point is higher than the ignition timing that provides the slight knocking level shown at point A. (MBT) is on the retarded side, but under high load conditions, the relationship between ignition timing and generated torque becomes as shown by the solid line in the figure, and when low octane gasoline is used, the slight knocking level shown at point B occurs. The ignition timing that gives this is retarded than MBT.

When fuel with a high octane rating is used, the ignition timing that provides a slight knocking level will be as shown at point C in Figure 7, and there are operating conditions (especially at high speeds) where the MBT will be on the retarded side.

Therefore, the basic ignition timing is MBT at low loads.

At high loads, a slight non-king level or MBT ignition timing is set.

[Problem that the invention seeks to solve]

However, such conventional ignition timing control devices are designed not to retard the ignition timing beyond a predetermined limit value. Point C in Figure 7
As shown in the figure, the ignition timing that gives a slight non-king is MB.
It is near T, and M B T will be adopted as the basic ignition timing.

The retard side limit value at that time is M B T-α (α=5~
6°), and is located approximately midway between points B and C in FIG. 7 (point D).

In this way, engines designed to use high-octane gasoline have the advantage of being less likely to knock, allowing the engine's compression ratio to be increased, and improving fuel efficiency under partial load.

However, even if high-octane gasoline is sold on the assumption that it will be used, users may use cheaper gasoline with a lower octane rating, and in that case the trace knock point will be delayed to point B shown in Figure 7. However, as a result of controlling the ignition timing by setting the retard limit value as described above, the ignition timing is retarded only until the ignition starts.

For example, when using gasoline with an octane number of about 90 RON, the octane number is 98 RO.
The difference in ignition timing of MBT (or trace knock point) C when using gasoline with about N is 10 to 15 degrees CA.
(crank angle) also available, octane rating 90RON
There was a problem in that the knocking level when using about 300 liters of gasoline became a heavy knock, and the knocking sound became significantly louder.

On the other hand, it is necessary to set the above-mentioned ignition timing retard limit value, and while setting such a limit value, knocking control that corresponds to changes in the octane number of the fuel has become necessary.

, this invention is similar to conventional ignition II,? JIJ
The purpose of this invention is to solve problems in the I Ftll control device and stably control the fuel to a slight non-king level even if the octane number of the fuel used changes.

[Means for solving problems]

An ignition timing control device for an internal combustion engine according to the present invention.

In order to solve the above problems, as shown in the functional block diagram in FIG. knocking level determination means B that determines whether or not knocking has occurred based on knocking; retard control means C that retards the ignition timing when knocking occurs; and advance control means that advances the ignition timing when knocking does not occur. 1. An ignition timing control device for controlling the generation timing of the ignition signal by the ignition signal generating means E, comprising: a characteristic change detecting means F for detecting a characteristic change in the knocking occurrence level with respect to the amount of advance of the ignition timing;

A maximum retard limit value calculating means G is provided for calculating the maximum limit value of the ignition retard amount by the retard control means C in accordance with the characteristic change detected by the characteristic change detecting means F.

[For production]

Based on the characteristic change in the knocking occurrence level with respect to the amount of advance of the ignition timing detected by the characteristic change detection means F, it is determined, for example, whether the gasoline used is regular gasoline or high-octane gasoline, and the maximum retard limit value calculation means G is retarded. The maximum limit value of the ignition retard amount by the angle control means C is calculated to the optimum value according to the determination result, and while the occurrence of knocking is determined by the knocking level determination means B, the ignition timing is adjusted up to the maximum limit value. to keep the knock level at an appropriate level.

〔Example〕

Embodiments of the present invention will be described with reference to FIG. 2 and subsequent figures of the accompanying drawings.

FIG. 2 is a block diagram of essential parts of an internal combustion engine showing an embodiment of the present invention, in which 1 is a cylinder block of the engine, and 2 is a knock sensor attached to the cylinder block 1. In FIG.

The knock sensor 2 is a well-known device that is composed of, for example, a piezoelectric element or an electromagnetic element, and converts mechanical vibrations caused by combustion phenomena of an internal combustion engine into electrical amplitude fluctuations and detects them.

Further, an in-cylinder pressure sensor may be attached as a washer for the spark plug 3 attached to each cylinder and used as a knock sensor, in which case vibrations in combustion pressure are detected.

4 is a distributor, and this distributor 4
are provided with crank angle sensors 5 to 7.

The crank angle sensor 5 is for cylinder discrimination, and this engine is 6
If it is a cylinder, each revolution of the distributor shaft, that is, every two revolutions of the crankshaft (720'C
One pulse is generated for each A). The occurrence position is set to 1, for example, the top dead center of the first cylinder.

The crank angle sensor 6 generates 6 pulses during one revolution of the distributor shaft, and therefore a crank angle of 120°.
Generates one pulse every time.

Further, the crank angle sensor 7 generates a pulse every 2 degrees of crank angle, and the pulse is used to count the rotation angle of the crankshaft.

Electric signals from these knock sensors 2 and crank angle sensors 5 to 7 are input to a control circuit 10. The control circuit 10 also receives a signal representing the intake air flow rate from an air flow sensor 12 provided in an intake passage 11 of the engine.

On the other hand, the control circuit 10 outputs an ignition signal to the igniter 13, and the spark current generated by the igniter 13 is distributed to the spark plugs 3 of each cylinder via the distributor 4.

An internal combustion engine is normally provided with various other sensors that detect operating state parameters, and the control circuit 10 also controls the smoke injection valve 14, but these are not directly related to this invention. , all of these will be omitted in the following explanation.

FIG. 3 is a block diagram showing an example of the configuration of the control circuit 10 of FIG. 2. In FIG.

In this control circuit 10, a voltage signal from an air flow sensor 12 is input to an analog multiplexer 21 via a buffer 20, selected according to an instruction from a microcomputer 30, and sent to an A/D converter 22 as a digital signal (2 After being converted into a forward signal), it is taken into the microcomputer 30 from the input/output port 31.

Pulses at every 720° crank angle from the crank angle sensor 5, pulses at every 120” crank angle from the crank angle sensor 6, and pulses at every 2° crank angle from the crank angle sensor 7 are input via the shaping circuit 23. It is input to the output port 32.

The detection signal from the knock sensor 2 is sent to the input circuit 24 and the A/
It is converted into a digital signal via the D converter 25 and input to the input/output port 32.

The A/D conversion of the A/D converter 25 starts at the input/output port 3.
This is performed by an A/D conversion activation signal applied from the microcomputer 30 via signal #2 and signal #26.

When the A/D conversion is completed, the A/D converter 25 notifies the microcomputer 30 of the completion of the A/D conversion via the signal a27 and the input/output capos 1 to 32.

On the other hand, from the microcomputer 30, the output port 33
When an ignition signal is output to the drive circuit 28 via the ignition signal, it is converted into a drive signal to energize the igniter 13, and ignition control is performed according to the duration and duration of the ignition signal.

The microcomputer 30 has the above-mentioned input/output capo-1-3.
1, 32, 33, and microprocessor (MPU) 34
, a random access memory (RAM) 35, a read-only memory (ROM) 36, a clock generation circuit 37, and a bus 38 that connects these.
Various processes are performed according to the control program stored in M36.

Here, before explaining a specific operation program for performing ignition timing control according to the present invention using this control circuit 10, the background and basic operation of the ignition timing control according to the present invention will be explained with reference to FIG. explain.

Figure 4 shows the case when regular gasoline with a low octane number (91RON) is used (dashed line) and the case where regular gasoline with a high octane number (91RON) is used (dashed line).
98RON) When using high-octane gasoline (solid line)
This figure shows the characteristics of generated torque with respect to ignition timing under high load.

In the case of regular gasoline, knocking is likely to occur, so slight knocking (trace knock) occurs on the retard side (indicated by point B) compared to MBT. If you advance the ignition timing further, the MBT will rise.

The knocking becomes more intense and the torque eventually decreases.

The ignition timing at which trace knock occurs varies depending on changes in intake air temperature and humidity, so in systems that do not have a means for determining knocking, it is normal to set the base ignition timing on the retarded side to allow some margin. However, in a device that is equipped with a knock determining means and performs retard control, the basic ignition timing is set at the very edge of the ignition timing (point B) at which trace knock occurs. By doing so, we try to increase the output torque as much as possible.

In the case of high-octane gasoline, knocking is less likely to occur, so the ignition timing at which trace knock occurs (indicated by point C) is near MBT or on the advanced side of MBT.

For engines designed to use high-octane gasoline, when the trace knock point is on the advance side of MBT, MB
T, if it is on the retard side, give the trace knock point as the basic ignition timing.

If regular gasoline with a low octane number is put into an engine with such specifications, knocking worse than heavy knock will occur at the ignition timing near MBT, so it will immediately retard and retard the ignition to the retard limit value, point D, but at point D. So 4.
Approximately medium knocking occurs. - When using non-high octane gasoline, there is no knock at point D, so the output level of the knock sensor at point D is significantly different.

Therefore, if the output level of the knock sensor at the retard limit point is equal to or higher than a predetermined value, it is determined that regular gasoline is being used, and the retard limit A is set to point E, which is on the retard side of point B. change.

This point E may be a preset value, but if it is given as a function of the knock sensor output level at point D, stable control can be achieved not only in the case of regular gasoline with an octane number of 91 RON, but also in the case of various octane numbers.

Next, the ignition timing control function according to the present invention by the microcomputer '50 of the control circuit 10 of FIG. 3 mentioned above will be explained with reference to the flowchart of FIG. Note that this is an example of controlling the ignition timing for each cylinder.

In the case of a six-cylinder engine, the routine shown in FIG. 5 is processed every 12° signal at about 80' before top dead center.

First, in step 1, it is determined whether there is a high load condition. 29 may be determined based on the accelerator opening degree or the amount of intake air.

Under low load conditions, knocking does not occur and the effect of controlling the ignition timing for each cylinder is small.

All-cylinder-specific ignition timing Bo is set only by table lookup (step 29.30).

In the case of high load conditions, cylinder discrimination is performed in step 2. A well-known method is to identify the cylinder number from a 72° signal and a signal every 120''.

Next, in step 3, it is determined whether or not the first cylinder (#1 cyl) is present, and if it is determined that the ignition timing of the first cylinder is to be processed, the process proceeds to step 4.

Below, we will discuss the ignition timing control for the first cylinder.

In step 4, a table giving the basic ignition timing B of the first cylinder is looked up using the engine rotational speed N and the engine load Q.

B I=func (N, Q) Furthermore, in step 5, the level (knocking level) of the knocking vibration frequency component in the output of the knock sensor of the first cylinder is detected, and it is set as .

Then, in step 6, the trace knock level TI of the first cylinder is calculated or looked up in a table.

This trace knock level is determined by the engine rotation speed (N)
Since the vibration components detected by the knock sensor differ depending on the type of knock, the sensor output level also differs even for the same 1-race knock.

T I =func (N) Also, if a knock sensor is not installed in each cylinder (for example, a block type knock sensor).

The detection level corresponding to trace knock varies depending on the distance between the knock sensor and the combustion chamber.

If a knock sensor is installed in each cylinder, T
Even if the calculation of 1 is common to each cylinder, a large G mismatch will not occur.

Next, in step 7, and T1 are compared so that 5 has 1≧
If T, it is determined that there is knocking and the process proceeds to step 88. If K<T, it is determined that there is no knocking and the process proceeds to step 25.

In step 8, the retard angle correction furl at the time of knock is set to r 4
=func (Kl −T+).

The functional form or table data of this rl is common to each cylinder.

Then, in step 9, the previous correction amount d is subtracted by rl, and (d+-rt) is stored as a new dl.

Step]0 sets the output ignition timing A1 to A,=B.

Calculated as 10d. A, ,B are on the advanced side than TDC, that is, B 'I' D C(B
Set the ignition timing of A T D C (A T D C) to a positive value.
The ignition timing of DC) is treated as a negative value and treated as a signed quantity.

dl is also signed. Then, it is determined whether the AI value is too retarded or not using the following routine.

In step 11, ttlcyl corresponding to point D in FIG.
, the retard limit value ignition timing LiMiTr (referred to as L I+) is looked up in the table.

LiMiTl = func (N r Q) [N: engine speed, Q: load (intake air amount or fuel injection view)
].

In step 12, it is determined whether the output ignition timing A is on the retarded side than the limit value L11 obtained in step 11. If Yes, the octane number of the fuel is determined by the following routine. If No, that is, Al)L, then the ignition timing A is output as is in step 31.

If A, ≦Ll+, there is a possibility that regular gasoline is being used, so in step 13, a parameter C1 is calculated to determine whether or not the characteristics of the knocking occurrence level with respect to the amount of advance of the ignition timing have changed. .

C1=fun (Adv, N); Adv is the ignition timing. This CI is a slightly inflated (offset) characteristic of the detection level by the knock sensor with respect to the ignition timing when using high-octane gasoline. This is shown by the dashed line in Figure 6. Note that the solid line indicates the lowest level of knocking level characteristics when regular gasoline is used.

Next, in step 14, and C1 are compared, and K1≧C1
If so, it can be determined that regular gasoline is being used, so proceed to step 16 and set the second retard limit value LiM.
Calculate iT2 (assumed to be L 21). This A21 is a value corresponding to point E in FIG.

In step I7, it is determined whether or not A1 is on the retard side than A21. If it is on the retard side, in step 18, the value of A1 is set to A2.
1 is adopted.

If it is determined in step 17 that A1≧L2+, then in step 31, A is directly output as the ignition timing.

In step 14, if <C, it can be determined that high-octane gasoline is being used, so in step 15 the AI
=1-11, and in step 31, Ll+ is output as the ignition timing.

If it is determined in step 7 that Kl <T, then step 2
In step 5, it is determined whether or not there is a failure in the knocking detection system.

For example, if a piezoelectric type sensor is used as the knock sensor and a charge amplifier type is used in the input circuit 24 in Fig. 3, if a failure such as an open or short circuit occurs in the signal line of the knock sensor, electric charge will flow into the charge amplifier. Therefore, the output voltage of the input circuit 24 becomes almost zero or a noise level. Therefore, K r < T
When it is 1, it is necessary to determine whether there is a failure or not.

If the determination in step 25 is NO, it can be determined that there is no knocking, and therefore control is performed to the advance side.

First, in step 19, the advance angle correction amount a1 is set as a 1 = f
Calculated by unc (T I-K + ).

These eight function forms or table data are common to each cylinder.

Next, in step 20, al is added to the previous correction amount d, and (d+10a+) is stored as a new dl.

Then, in step 21, the output ignition timing A1 is calculated using A, =B, +d, and it is determined in steps 22 and 23 whether or not this A1 is too advanced.

In step 22, #1cy1. Maximum advance angle limit value LiM
iT3 (assumed to be L 31), L 31=func
Calculate or table lookup by (N t Q).

Then, in step 23, A1 and A31 are compared, and A+>
If L3+, A H=L 3+ is set in step 24. If AI≦L31, A is output as is in step 31.

On the other hand, if Yes in step 25, that is, it is determined that there is a failure in the knocking level detection system, in step 27,
Let the correction amount d1=-α.

a=func CN+Q), which corresponds to the difference between point B in FIG. 4 and the basic ignition timing (near MBT).

Then, in step 28, the output ignition timing is set to A.

=B, +d, and output as 31 as is.

Furthermore, if it is determined that the partial load is present in step 1, a table lookup is performed for the ignition timing BO common to each cylinder in step 29, and in step 30, the output ignition timings A1 to A6 of the 1st to 6th cylinders are all set to BO. .

, and outputs it in step 31.

When it is determined in step 3 that the cylinder is not number 1, it is determined in step 32 whether or not it is cylinder number 2 (#2cy1.). If it is the second cylinder, the same processing as steps 4 to 28 for the first cylinder is performed for the second cylinder.

If it is determined in step 32 that it is not the second cylinder, it is determined in step 33 whether it is the third cylinder (#3cy1.). The same procedure is repeated up to the 6th cylinder.

〔Effect of the invention〕

As explained above, according to the present invention.

Its configuration is such that it detects the characteristic change in the knocking occurrence level with respect to the amount of advance and retardation of the ignition timing, and calculates the maximum limit value of the amount of retardation of the ignition timing in accordance with that change. It is possible to prevent the sensor output from increasing due to variations in detection sensitivity or noise or mechanical vibration, which may cause knocking to occur, thereby preventing the engine from retarding the engine unnecessarily and causing a significant drop in torque. .

Even if the octane number of the gasoline used changes, the effect of reducing knocking to a slight level can be obtained.

[Brief explanation of drawings]

FIG. 1 is a functional block diagram showing the basic configuration of an ignition timing control device according to the present invention, FIG. 2 is a configuration diagram of main parts of an internal combustion engine showing an embodiment of the present invention, and FIG. 6 is a control circuit in FIG. 2. FIG. 1 is a block diagram showing a configuration example of 1o. FIG. 4 is a diagram showing the relationship between ignition timing, generated i-lux, and knock level to explain the background and basic operation of this invention. FIG. A flowchart showing the ignition timing control program according to the present invention. FIG. 6 shows an example of parameters for determining whether or not the characteristics of the knocking occurrence level have changed with respect to the amount of advance of the ignition timing calculated in step 13 of FIG. FIG. 7 is a diagram showing the relationship between ignition timing and generated torque under high load conditions and low load conditions, for explaining the problems to be solved by the present invention. A, 2...Knock sensor B...Knocking level discrimination means C...Retard angle control means D...Advance angle control means E
... Fish large signal generation means F ... Characteristic change detection means G ... Maximum retard limit value calculation means 1 ... Cylinder block 3 ... Spark plug 4.
...Distributor 5-7...Crank angle sensor 10...Control circuit 12...Air flow sensor 13...Igniter 14...Fuel injection valve 3
0... Microcomputer Figure 1 Figure 2 Figure 4 Figure 77' Late Ignition timing Advance Figure 6 Figure 7 Slow Ignition timing Advance

Claims (1)

[Scope of Claims] 1. A knock sensor that detects vibrations caused by combustion phenomena in an internal combustion engine or vibrations in combustion pressure, knocking level determining means that determines whether or not knocking has occurred based on a detection signal of the knock sensor, and An ignition timing control device for an internal combustion engine, comprising a retard control means for retarding the ignition timing when knocking occurs, and an advance control means for advancing the ignition timing when knocking does not occur, comprising: advancing or retarding the ignition timing; characteristic change detection means for detecting a characteristic change in the knocking occurrence level with respect to the amount of knocking; 1. An ignition timing control device for an internal combustion engine, comprising: angle limit value calculation means.