JPH0463223B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio control device for an engine, which is equipped with closed-loop control means for feedback controlling the air-fuel ratio and open control means for controlling the air-fuel ratio in an open manner. This engine operates at the critical point where knocking occurs in the range where knocking is likely to occur at low speeds (hereinafter referred to as the "knocking range"), and at the same time automatically compensates for air-fuel ratio deviations due to aging. The present invention relates to an engine air-fuel ratio control device including a loop control means.

Various attempts have been made to compensate for variations in air-fuel ratio due to aging in automobile engines equipped with electronically controlled fuel injection devices.

For example, the one proposed in Japanese Patent Application Laid-Open No. 55-96339 is one example.

This system operates a microcomputer to perform learning control within the so-called feedback region, and is based on the output signal of the O ₂ sensor, which detects oxygen concentration from exhaust gas components, depending on the engine operating state. The preset fuel injection amount is corrected by a minute amount, and when the air-fuel ratio is changing to the richer side than the preset value, the fuel injection amount is reduced to correct the air-fuel ratio toward the lean direction, and the air-fuel ratio is When the change is toward the lean side, the fuel injection amount is increased to correct this toward the rich side.

However, in such a control device, in the so-called enrichment region where the air-fuel ratio must be enriched and the engine must be operated at high load,
The air-fuel ratio could not be accurately controlled, making it difficult to expect the engine to always operate under proper fuel conditions.

Therefore, in order to solve such inconveniences, the present applicant proposed in Japanese Patent Application Laid-Open No. 164698/1982 that learning control is performed also within the enrichment region based on the basic control value within the feedback region adjacent to the enrichment region. I am proposing something that can be done.

However, this proposal also had difficulty in accurately controlling the air-fuel ratio in the enriched region as required.

In other words, since the air-fuel ratio in the enrichment region is corrected based on the learning value obtained in the feedback region, the correction is based on expectations and the correction as requested has been achieved. It is difficult to say that this is the case, and especially in areas where knocking is likely to occur, such as high load and low rotation even within the enrichment area, if the air-fuel ratio is not set as required, knocking will occur and appropriate engine output will not be obtained. A serious problem had arisen.

The present invention was developed to solve the above-mentioned problems, and focuses on the fact that there is a correlation between the air-fuel ratio and knocking. By dividing the area into a knock area where knocking occurs and an unknocking area where knocking does not occur, and performing control appropriate to each area, the air-fuel ratio is always corrected to an appropriate level even in the enriched area, and changes over time are prevented. It is an object of the present invention to provide an air-fuel ratio control device for an engine that can compensate for variations caused by such factors.

An embodiment of the present invention will be described below, but before going into its detailed description, the principle of adjusting the air-fuel ratio within the knock region of the open loop control means of the present invention will be outlined.

In general, it is well known that the more advanced the engine's ignition timing is in the knock region, the higher the output the engine can obtain, and the more advanced the ignition timing is, the more likely knocking will occur.

Similarly, if we consider the relationship between knocking and air-fuel ratio under the same operating conditions, the richer the air-fuel ratio, the less likely knocking will occur, and conversely, the leaner the air-fuel ratio, the more likely knocking will occur. There is a tendency.

Therefore, if we now consider the case where the ignition timing critical point has shifted somewhat later than it initially was due to aging, when the engine is operated at that ignition timing, the air-fuel ratio should be set at the initial setting value. In the opposite case, the deviation is in the lean direction, and in the opposite case, the deviation is in the rich direction.

In other words, by comparing the knocking critical points of the ignition timing, it is possible to determine the direction of deviation in the air-fuel ratio due to aging, etc., and by repeatedly correcting this deviation, the engine can be operated under optimal conditions within the knocking region. It becomes possible to drive.

Here, in the air-fuel ratio control device for an engine according to the present invention, an open-loop control means that performs open-loop control based on a learning correction coefficient detects whether knocking occurs in the engine and determines whether knocking occurs. An ignition timing adjustment means that sometimes corrects the reference value of ignition timing to the retarded side, but corrects the reference value of the ignition timing to the advanced side when no knocking occurs to operate the engine at the optimum ignition timing, and this ignition timing adjustment. The optimum ignition timing obtained by the means is compared with a reference value set in advance and stored according to the operating condition, and based on the comparison result, when the optimum ignition timing is on the lag side than the reference value, the engine is activated. The learning correction coefficient during open-loop control is stored by increasing the learning correction coefficient during loop control, while decreasing the learning correction coefficient during open-loop control when the optimum ignition timing is on the advance side of the reference value.・Since the system includes an air-fuel ratio learning means for updating, the ignition timing can be moved to the critical point where knocking occurs in the knocking region where blind control was conventionally performed, and high-output operation can be achieved. Not only can this be done, but if the critical point fluctuates relative to a preset reference value,
By storing and updating the learning correction coefficient and using the updated learning correction coefficient the next time you move to the enrichment area, it is possible to compensate for variations such as changes in the air-fuel ratio over time, even after many years have passed. , the engine can be operated at high output at the critical point where knocking occurs.

Next, with reference to FIG. 1, the basic configuration of the open loop control means that constitutes the main part of the present invention will be explained.

1 is a knocking detection means including a knocking sensor that detects whether knocking occurs in the engine 6; 2 is an ignition timing adjustment that adjusts the ignition timing in a direction to suppress knocking based on the knocking detection means 1; Means 3 is an air-fuel ratio correction means for setting the fuel injection amount by specifying the pulse width of the fuel injection pulse that energizes the fuel injection valve; 4 is a reference value for the ignition timing set in advance according to the operating state; 5 is a comparison means for comparing the reference value stored in the storage means 4 with the optimum ignition timing set by the ignition timing adjustment means 2, and as a result of the comparison, a deviation is determined. When the deviation exists, the above-mentioned air-fuel ratio correcting means is controlled according to the deviation, thereby increasing or decreasing the fuel injection amount and issuing a command to correct the air-fuel ratio.

The ignition timing adjustment means 2 is the knocking detection means 1.
When the engine detects the occurrence of knocking, it reduces the ignition timing control amount (delays the ignition angle) that is given in advance according to the operating condition using a map, etc., so that the engine is always at the optimum ignition timing, that is, just as close as possible to the occurrence of knocking. operate at the critical point.

On the other hand, within the knock region, the air-fuel ratio correction means 3 determines that the optimum ignition timing set by the ignition timing adjustment means 2 is set in advance by the comparison means 5 according to the above-mentioned principle, which is read out from the storage means 4. When it is determined that the optimum ignition timing is on the delayed side from the reference value set, the basic fuel injection amount given in advance according to the operating condition is increased using a map, etc., and the comparison means 5 reads out the optimum ignition timing from the storage means 4. When it is determined that the fuel injection amount is on the advance side from the reference value, the basic fuel injection amount is decreased and the air-fuel ratio correction means 3 is controlled.

FIG. 2 is a schematic configuration diagram of the present invention using a microcomputer.
1 is a schematic configuration diagram constructed by combining known closed-loop control means.

The microcomputer 9 inputs the outputs of sensors 1, 10, 11, 13, 15, and 17, which will be described later, provided to know the operating state of the engine 6, and inputs the outputs to the ignition timing adjusting means 2 and the air-fuel ratio correcting means 3. Equipped with an I/O interface for outputting control signals, a central processing unit (CPU), read-only memory (ROM), and random access memory (RAM), which are connected by a data bus and an address bus. It has a basic structure.

In each address of the read-only memory, information regarding the fuel injection amount and ignition timing, which are set based on the engine speed ne and intake pressure P, is recorded as a so-called basic control map. The means 4 also consist of a read-only memory.

On the other hand, in each address of the random access memory, correction information that defines the amount of correction for the above-mentioned basic control amount is stored in the form of a correction coefficient.
This correction information includes a feedback correction coefficient (F _F/B ) that increases or decreases the fuel injection amount used during feedback control according to the zone determination result by the computer 9, and an advance angle that is used within the knock region during open loop control. A knock correction coefficient (K _K ) that increases or decreases the fuel injection amount, and a learning correction coefficient (K _L ) that increases or decreases the fuel injection amount used during learning control within the knock region are each stored in an updatable manner.

The ignition timing adjustment means 2 includes an ignition coil that ignites the spark plug and a driver 2 that energizes the ignition coil.
1 and a timer T ₂ 22 for setting the time until ignition by this driver 21,
The time until this ignition is ignited is defined by the advance angle based on the piston and TDC, that is, the set time _t3 of the timer _T2 .

The other air-fuel ratio correction means 3 includes a fuel injection valve, a driver 31 that energizes this injection valve, and a timer T ₁ 32 that defines the operating time of this driver 31, and the fuel injection amount is determined based on the fuel injection amount. This is done by defining the pulse width of the injection pulse, that is, the set time _t2 of the timer _T1 .

Here, each sensor that detects the operating state of the engine will be explained.

That is, the exhaust gas disposed within the exhaust manifold 7
The O ₂ sensor 15 is activated only during feedback control, but the rotation output sensor 10, the intake air temperature sensor 11 installed in the intake pipe 8, the water temperature sensor 13 installed in the cooling pipe, and the The installed intake pressure sensor 17 is operated during any control to set the basic control amount of fuel injection amount and ignition timing, and the correction amount for intake temperature and cooling water temperature. 9 is constantly being sent information.

On the other hand, the knocking detection means 1 including the knocking sensor is used to adjust the ignition timing when the engine operating range is in the knocking range, and is therefore an essential part of the open-loop control means. It is a configuration condition.

Next, a control program used to control the device of the present invention will be explained.

This program uses the previously described sensors 10, 11, 13, 15, 1 to know the operating state of the engine.
Starting from reading out information necessary for control from step 7, zone discrimination of the control areas shown in FIG. 3 is performed, and control is performed according to each control area. This zone determination is performed based on the following conditions.

(1) Feedback region This operating region is performed when the conditions that the intake pressure P of the engine 6 is lower than a predetermined value P _O and the cooling water temperature W is higher than a predetermined value W _O are satisfied, and the operating state of the engine 6 is The basic correction for the basic control amount of the fuel injection amount according to the amount, that is, the correction coefficients K _FA and K _FU for intake air temperature and cooling water temperature, and the basic correction for the ignition timing, that is, the correction number K _SA for intake air temperature and cooling water temperature. , K _SW is calculated, and O ₂
The sensor 15 determines whether the air-fuel ratio is lean or rich.

Then, based on the determination result by the O ₂ sensor 15, the feedback correction coefficient K _F/B of the fuel injection amount is increased or decreased by a small amount to control the air-fuel ratio. (Step 1000→…1013→1014→
(Refer to 1015→1016a or 1066b→1017→1018→1002) (2) Open loop region If the intake pressure P becomes a high load exceeding the predetermined value P _O ,
This will be the area. This region is an unlock region when the engine 6 rotation speed ne is higher than a predetermined rotation speed no, and an unlock region when the engine 6 rotation speed ne is higher than a predetermined rotation speed no.
It is divided into a knock area during high load and low rotation when ne is smaller than a predetermined number of times no, and the latter knock area is further divided into a learning area that uses a control map that specifies the correction amount of fuel injection amount, and a learning area that uses such a control map. It is divided into non-learning areas and non-learning areas that do not use.

In the unchecked region, the engine is ignited at the ignition timing _t3 determined by the basic correction coefficient calculated in steps 1011 and 1012, and the fuel injection amount is controlled by the previous learning control in addition to the basic correction described above. A correction corresponding to the learning correction coefficient K _L determined in is added. (step
1000→…1013→1019→1020→1027→1002) On the other hand, in the knock region (region where the conditions of P≧P _O and ne≦no are satisfied), when the knocking detection means 1 does not detect the occurrence of knocking, , the knock correction coefficient K _K is increased, and conversely, when the occurrence of knocking is detected, the knock correction coefficient K _K is decreased to operate the engine 6 at the critical point where knocking occurs.

Then, within this knock area, within the learning area, it is further determined whether the knock correction coefficient K _K has become larger or smaller than a predetermined value (reference value) K _K 〓, and the learning correction coefficient K _L is ΔK _L
will be increased or decreased by

In this way, the optimal value of the ignition timing is set within the knock region, and it is further determined whether or not it is in the learning region, and if it is, the fuel injection amount is adjusted to the basic correction based on the knock correction coefficient K _K. In addition to the amount, the amount is also corrected by the learning correction coefficient K _K , and if it is not in the learning area, no new correction is made to the basic correction amount of the fuel injection amount, and the value learned in the previous learning area is used as is. (Step 1000→…→
1013→1019→1021→1022a or 1022b→1023
→1024…→1002 or 1026…→1002) Here, the learning area satisfies the following conditions.

n ₁ ≦ne≦n ₂ ＜no Po≦P ₁ ≦P≦P ₂ Wo＜W ₁ ≦W≦W ₂ A ₁ ≦A≦A ₂ (A indicates the intake air temperature) Next, in Fig. 4, While referring to the flowchart,
The control procedure of the device of the present invention will be explained.

Starting from step 1000, after initial settings are made in step 1001, in step 1002,
When it is detected that the piston has reached the top dead center, the process moves to step 1003, where the main timer built into the computer 9 reads TDC time _t1 .

In step 1004, the injection time t2 is set in the timer _T1 in the air-fuel ratio correction means ₃ to start injection ( _t2 means the injection time of the fuel injector, that is, the pulse width of the fuel injection pulse; is completed at _t2 .) Then, in step 1005, the timer T2 of the ignition timing adjustment means ₂ is set to the time _t3 until ignition. In step 1006, the rotational speed ne is calculated from the difference between the previous TDC time t ₀ and the above-mentioned time t ₁ , that is, t ₁ - t ₀ .
is calculated. Then, in step 1007, t ₀ is changed to t ₁
Update to.

After that, in step 1008, the intake pressure P is read, and in step 1009, the fuel injection time t ₄ is calculated from the control map stored in the read-only memory in the computer based on the rotational speed ne and the intake pressure P.
Then, the ignition timing _t5 is read as the basic control variable.

Then, proceed to step 1010, and set the cooling water temperature W.
The intake air temperature A is read, and in step 1011, the intake air temperature correction coefficient for the fuel injection amount is calculated.
The basic correction for the basic fuel injection amount is performed by calculating the cooling temperature correction coefficient K _FU of K _FA , and further, in step 1012, the intake temperature correction coefficient K _SA and the cooling water temperature correction coefficient K _SW for the ignition timing are calculated. A basic correction is made to the basic ignition timing.

In this way, basic corrections are made to the basic control variables according to the engine operating condition, and the step
Moving to step 1013, when the engine intake pressure P, that is, the engine load condition is determined, the zone determination described above is performed.

That is, in step 1013, the predetermined value of the intake pressure P is
The magnitude relative to P _O is determined, and if the condition P≧P _O is satisfied, the process moves to step 1019, and if this condition is not satisfied, the process moves to step 1014. In step 1014, it is further determined whether the engine cooling water temperature is higher than the reference value W _O or not. If this condition is satisfied, it is confirmed that the engine is in the feedback region and feedback control is performed.

Feedback control begins at step 1015 in which the output of the O ₂ sensor 15 disposed in the exhaust manifold 7 is determined, and if it is determined in step 1015 that the air-fuel ratio is rich, the process continues.
The process proceeds to step 1016a, and if it is determined that it is lean, the process proceeds to step 1016b, where the feedback correction coefficient K _F/B is increased or decreased by a minute amount, that is, ΔK _F/B . Then, in step 1017, the fuel injection amount _t2 is calculated, and in step 1018, the ignition timing _t3 is further calculated, and known feedback control is performed.

On the other hand, in step 1013, if the condition P≧P _O that the engine 6 is in the high-load operating region is satisfied, the process moves to step 1019, where the rotational speed ne of the engine 6 is greater than the critical point no at which knocking occurs. It is determined whether the When the condition ne≦no in step 1019 is satisfied, it is confirmed that the area is in the knocking area, and the process proceeds to step 1021.
Go to one of 1022b.

That is, the ignition timing is corrected by the ignition timing adjusting means 2, and if knocking occurs, the process proceeds to step 1022a, and if knocking does not occur, the process proceeds to step 1022b, where the knock correction coefficient _K is increased or decreased. Ru.

Here, the knocking correction coefficient K _K defines the amount of advance of the ignition timing, and when the knocking detection means 1 detects the occurrence of knocking, the knocking correction coefficient K _K
is increased by a minute amount ΔK _K to increase the amount of ignition timing delay, and in the opposite case, it is decreased by a minute amount ΔK _K to reduce the amount of ignition timing delay. and,
In step 1023, the engine speed ne,
Various information such as intake pressure P, water temperature W, and intake air temperature A is read to determine whether the engine is within the learning range.

Then, if it is determined in step 1023 that it is within the learning area, the updated knock correction coefficient K _K is determined in step 1022a or step 1022b.
is the predetermined value stored in the basic map in the learning area.
It is further determined whether or not K _K 〓 is greater than K _{K 〓} .
K _K = In other words, when the amount of correction by knocking correction becomes large (meaning that the amount of delay in ignition timing becomes large), the learning correction coefficient K _L is increased by a minute amount ΔK _L , and K _K ≦ K _K = In other words, when the correction amount by knocking correction becomes smaller (meaning that the amount of delay in ignition timing becomes smaller), K _L is decreased by a minute amount ΔK _L to increase or decrease the fuel injection amount.

In step 1026, thus steps 1022a,
Alternatively, in step 1027, where the ignition timing t ₃ is determined according to the knock correction coefficient K _K obtained in step 1022b, the injection amount t ₂ to which the learning correction coefficient K _L is added is calculated. On the other hand, proceed from step 1013 to step 1019 and
If it is determined that the condition ≦no is not satisfied, it is confirmed that the engine is in the unlock region, and the process proceeds to step 1020, where the ignition timing _t3 is calculated, and at step 1027, the fuel injection time _t4 is set. Ru.

Also, moving from step 1013 to step 1014,
Here, even if it is confirmed that the condition W≧W _O is not satisfied, the same control as in the unlock area is performed.

Thereafter, information corresponding to the operating state of the engine is supplied from each sensor to the computer 9 from time to time, the operating range of the engine is determined, and the ignition timing adjusting means 2 and the air-fuel ratio correcting means are adjusted according to the same procedure as above. 3 is performed.

As detailed above, according to the engine air-fuel ratio control device of the present invention, when the engine operating state is in the feedback region, the air-fuel ratio can be corrected by learning based on the output signal of the O ₂ sensor. Of course, in the enrichment region where such learning correction of the air-fuel ratio cannot be performed, the presence or absence of knocking is detected, and when knocking occurs, the reference value of the ignition timing is set to the retarded side, and the ignition timing is set to the retarded side. When no knocking occurs, the reference value of the ignition timing is corrected to the advanced side, and the engine is operated at the optimum ignition timing, that is, the critical point at which knocking occurs, and high output can be obtained. Moreover, if the critical point fluctuates with respect to the preset reference value, the learning correction coefficient can be stored and updated, and the next time the area moves to the enrichment area, the updated learning correction coefficient can be used. This method has the remarkable effect of accurately compensating for variations in the air-fuel ratio due to aging, etc., and allowing the engine to operate at high output at the critical point where knocking occurs even after many years have passed.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the basic configuration of the open loop control means, Fig. 2 is a schematic diagram showing an embodiment of the device of the present invention, and Fig. 3 shows the relationship between engine rotation speed and engine intake pressure. FIG. 4 is a flowchart showing the control procedure of the apparatus of the present invention. (Explanation of symbols), 1... Knocking detection means,
2... Ignition timing adjustment means, 3... Air-fuel ratio correction means, 4... Memory means, 5... Comparison means.

Claims (1)

[Scope of Claims] 1. Closed loop control means for feedback controlling the air-fuel ratio of the intake air-fuel mixture supplied to the engine when the engine operating state is in the feedback region; An air-fuel ratio control device for an engine, comprising: an open-loop control means for open-loop controlling the air-fuel ratio of an intake air-fuel mixture supplied to the engine based on a learning correction coefficient, the open-loop control means comprising: (a) an engine; a knocking detection means including a knocking sensor for detecting the occurrence of knocking; (b) a storage means storing a reference value of ignition timing set in advance according to the operating condition; and (c) an engine. Ignition timing adjustment means that corrects the reference value of ignition timing to the retarded side when knocking occurs in the engine, and corrects the reference value of the ignition timing to the advanced side when no knocking occurs to operate the engine at the optimum ignition timing. (d) means for comparing the optimum ignition timing obtained by the ignition timing adjustment means with a reference value stored in the storage means; (e) determining the optimum ignition timing based on the comparison result of the comparison means; When the timing is behind the above reference value, the learning correction coefficient during open-loop control is increased, while when the above-mentioned optimum ignition timing is ahead of the above-mentioned reference value, the learning correction coefficient during open-loop control is decreased. 1. An air-fuel ratio control device for an engine, comprising an air-fuel ratio learning means for storing and updating a learning correction coefficient during open-loop control.