JPS6282242A - Air-fuel ratio controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent a degree of drivability and an exhaust characteristic from getting worse, by installing a device, which makes responsiveness vary according to a difference between a fuel fundamental quantity and the responsiveness delay operating value, in a control device controlling this fundamental quantity upon compensation. CONSTITUTION:A load detecting device M2 detecting the load of an internal combustion engine M1 and a control device M3 calculating a fuel fundamental quantity while controlling this fundamental quantity upon compensation both are installed there. A responsiveness altering device M4 is installed in this control device M3, and according to a difference between the fundamental quantity and the responsiveness delay operating value, responsiveness of the responsiveness delay operating value is lowered in proportion as the difference becomes smaller, while the responsiveness is made to go up in proportion as the difference becomes larger. Accordingly, even in the case where a load variation occurs, a fuel injection supply can be increased or decreased and a compensated in the wake of delicate variations in a driving state of the internal combustion engine M1. And, even at the time of load variation occurrence, such air-fuel ratio control that favorably keeps the driving state of the engine M1 is performable without entailing any damage to drivability.

Description

OBJECTS OF THE INVENTION [Industrial Field of Application] The present invention relates to an air-fuel ratio control device for an internal combustion engine, and more particularly to an air-fuel ratio control device for an internal combustion engine that is effective during load fluctuations of the internal combustion engine.

[Prior Art] When load fluctuations occur in an internal combustion engine, for example, when acceleration or deceleration is performed, control is performed for the purpose of compensating for fluctuations in the air-fuel ratio of the air-fuel mixture that contributes to combustion in the internal combustion engine. An air-fuel ratio control device for an internal combustion engine has been developed. For example, by predicting the amount of fuel that will adhere to the intake pipe wall surface such as the intake boat wall or intake valve based on information indicating the load state and warm-up state of the engine, and correcting the amount of supplied fuel accordingly. , ``Air-fuel ratio control method and device'' (Japanese Patent Application Laid-Open No. 57-24426), etc., have been proposed to satisfactorily compensate for fluctuations in the air-fuel ratio of the air-fuel mixture that contributes to direct combustion in this engine.

[Problems to be Solved by the Invention] This prior art air-fuel ratio control device for an internal combustion engine has the following problems. That is, (1) The amount of fuel supplied to the internal combustion engine when there is a load change is corrected based on the difference between the load parameter of the internal combustion engine and the value obtained by filtering the load parameter using a predetermined filter function. It was being done. However, the filter constant of the predetermined filter function is set constant, and no consideration is given to load fluctuations of the internal combustion engine, such as acceleration/deceleration states. Therefore, there has been a problem in that it is difficult to correct the fuel supply amount in accordance with subtle changes in the operating state of the internal combustion engine.

(2) In addition, as a countermeasure for the problem in (1) above, if the filter constant is set large, the amount of correction at the beginning of load fluctuation will be too large and the exhaust characteristics will deteriorate; on the other hand, if the filter constant is set small Another problem is that the time for correcting the fuel supply amount becomes too short, resulting in large torque fluctuations in the internal combustion engine and deterioration of drivability.

SUMMARY OF THE INVENTION An object of the present invention is to provide an air-fuel ratio control device for an internal combustion engine that appropriately corrects the fuel supply amount in accordance with subtle changes in the operating state of the internal combustion engine when load fluctuations occur in the engine.

Configuration of the Invention [Means for Solving the Problems] In order to solve the above problems, the present invention adopts the configuration shown in FIG. 1. FIG. 1 is a basic configuration diagram showing the content of the present invention. As shown in FIG. 1, the present invention includes a load detection means M2 for detecting the load of the internal combustion engine M1, and a basic amount of fuel to be supplied to the internal combustion engine M1 according to the detected load. In the air-fuel ratio control device for an internal combustion engine, the control means M3 corrects and controls the basic quantity with a correction amount according to the difference between the basic quantity and its responsiveness delay processing value, further comprising the control means M3. , Depending on the difference between the basic quantity and its responsiveness delay processing value, the smaller the difference, the lower the responsiveness of the responsiveness delay processing value, and the larger the difference, the more the responsiveness is increased. The gist of the present invention is an air-fuel ratio control device for an internal combustion engine, which is characterized in that it is configured to include a responsiveness changing means M4.

The load detection means M2 detects the load of the internal combustion engine M1. For example, the pressure in the intake pipe of the internal combustion engine M1 may be detected by a pressure sensor, and the load may be detected from the rotational speed of the internal combustion engine M1 and the pressure in the intake pipe. Further, the load on the internal combustion engine M1 may be detected based on the numbing value of the basic fuel injection amount to the internal combustion engine M1. Further, the amount of intake air of the internal combustion engine M1 is detected by an air flow meter, and the amount of intake air and the amount of intake air of the internal combustion engine M1 are detected.
The load may be detected from the rotation speed of 1. Alternatively, the load may be detected from the throttle valve opening degree of Ml.

The control means M3 calculates the basic fuel supply amount based on the load detected by the load detection means M2, and
Control is performed to increase or decrease the basic fuel supply amount in accordance with the difference between the basic fuel supply amount and its responsiveness delay processing value. For example, the basic fuel injection amount is calculated by dividing the intake air amount of the internal combustion engine M1 by the rotational speed and multiplying it by a constant, and then calculates the basic fuel injection amount by dividing the intake air amount of the internal combustion engine M1 by the rotational speed.
It is also possible to calculate the fuel injection amount by correcting it based on values such as the cooling water temperature and the throttle valve opening. Note that the responsiveness delay processing value may be, for example, a weighted average value of past basic quantities, or may be, for example, an integral value of past basic quantities. Furthermore, various calculated values can be used, such as a value calculated from the basic quantity by a filter function having a predetermined delay constant.

The responsiveness changing means M4 reduces the responsiveness of the responsiveness delay processing value as the difference between the basic amount of fuel supplied to the internal combustion engine M1 and its responsiveness delay processing value becomes smaller;
The larger the difference, the higher the responsiveness. For example, a configuration may be considered in which the constant of a predetermined function for calculating the responsiveness delay processing value is changed.

The control means M3 and the responsiveness changing means M4 can also be realized as independent discrete logic circuits. In addition, centering on the well-known CPU, ROM, RA
M and other peripheral circuit elements may be configured as a logical operation circuit, and both of the above means may be realized according to a predetermined processing procedure.

[Operation] As shown in FIG. 1, the air-fuel ratio control device for an internal combustion engine according to the present invention has
The control means M3 calculates the basic amount of fuel according to the load, and further corrects the basic amount with a correction amount according to the difference between the basic amount and the response delay processing value. Means M4 acts to reduce the responsiveness of the responsiveness delayed processing value as the difference between the basic quantity and its responsiveness delayed processing value becomes smaller, and to increase the responsiveness as the difference becomes larger. .

That is, when load fluctuation occurs, the response changing means M4
As the difference between the basic quantity and its responsiveness delayed processing value becomes smaller, the responsiveness of the responsiveness delayed processing value decreases, so that the followability of the control for correcting the basic quantity by the control means M3 is improved. That's why I'm here.

Therefore, the air-fuel ratio control device for an internal combustion engine according to the present invention operates to quickly correct the fuel supply amount when a load change occurs in the internal combustion engine M1. The technical problems of the present invention are solved by each component of the present invention acting as described above.

[Example] Next, a preferred example of the present invention will be described in detail based on the drawings.

An engine air-fuel ratio control device that is an embodiment of the present invention includes:
The system configuration is as shown in Figure 2.

As shown in FIG. 2, the engine 1 has a combustion chamber 5 formed by a cylinder 2, a piston 3, and a cylinder head 4.
A spark plug 6 is disposed in the combustion chamber 5.

The intake system of the engine 1 includes an intake valve 7 in the combustion chamber 5.
an intake manifold 8 that communicates with the intake manifold 8, a fuel injection valve 9 that injects fuel into the intake manifold 8, an intake pipe 10 that communicates with the intake manifold 8, a surge tank 11 that absorbs pulsation of intake air, a throttle valve 12, It is made up of Acrylee 13. Further, the exhaust system of the engine 1 includes an exhaust manifold 15 that communicates with the above-mentioned combustion chamber 5 via an exhaust valve 14. moreover,
The engine 1 includes an igniter 16 that outputs a high voltage necessary for ignition, and a distributor 17 that is linked to a crankshaft (not shown) and distributes the high voltage generated by the igniter 16 to the spark plugs 6 of each cylinder.

The engine 1 includes a water temperature sensor 20 provided in the cooling system of the engine 1 to detect the temperature of the cooling water, an intake temperature sensor 21 provided in the air cleaner 13 to detect the temperature of the intake air sent to the engine 1, and a throttle sensor. a throttle position sensor 22 that detects the opening of the throttle valve 12 in conjunction with the valve 12; an intake pipe pressure sensor 23 that communicates with the intake pipe 10 and measures the pressure inside the intake pipe;
an oxygen concentration sensor 24 that is provided in the exhaust manifold 15 and detects the residual oxygen concentration in the exhaust gas as an analog signal;
Every 1/24 rotation of the camshaft of the distributor 17 installed in the distributor 17,
In other words, a rotation angle sensor 2 that also serves as a rotation speed sensor outputs a rotation angle signal every integer multiple of the crank angle 0° to 30'.
5. Each cylinder is provided with a cylinder discrimination hinge 26 which outputs a reference signal once for each revolution of the camshaft of the distributor 17, that is, for every two revolutions of the crankshaft (not shown).

The signals detected by each of the above sensors are input to an electronic control unit (hereinafter simply referred to as ECU) 30, and ECU 3O drives the fuel injection valve 9 and igniter 16 described above based on each signal to control the engine 1. Do the following.

Next, the configuration of the ECU 3O will be explained based on FIG. 3. ECU3O inputs and calculates each signal detected by each sensor mentioned above according to a control program, and also performs processing for controlling each device mentioned above.
The PU 30a, the ROM 30b in which the above control program and initial data are stored in advance, the RAM 30c in which various signals input to the ECU 3O and data necessary for arithmetic control are temporarily stored, and the key switch of the engine 1 are turned off by the driver. It is configured as a logic operation circuit centered around a backup RAM 30d backed up by a battery so that it can store and hold various data necessary for controlling the engine 1 from then on. It is connected to the input port 30C1 and the output port 30h to perform input/output with external equipment.

The ECU 3O includes the intake pipe internal pressure sensor 23, the water temperature sensor 20, the intake air temperature sensor 21, and the variation of output signals from the throttle 1 to position sensor Fj22.
A multiplexer 30n that selectively outputs the output signal of each sensor to the CPU 30a, and an A/D converter 30p that converts an analog signal into a digital signal are also provided. . Each of these signals is input to the CPU 30a via the input/output port 30f. In addition, the ECU 3O includes a buffer 30q for the output signal of the oxygen concentration sensor 24 described above, and a buffer 30q for the output signal of the oxygen concentration sensor 24 described above.
A comparator 30r that outputs a signal when the output voltage of Q exceeds a predetermined voltage, and the cylinder discrimination sensor 2 described above.
6. It has a waveform shaping circuit 30S that shapes the waveform of the output signal of the rotation angle sensor 25. Each of these signals is input to the CPU 30a via the input port 3pC1. Further, the ECU 3O includes a drive circuit 30t that supplies a drive current to the fuel injection valve 9 and the igniter 16 described above.

30u, and the CPU 30a outputs control signals to both of the drive circuits 30t and 30u via the output port 30i. In addition, ECU3O includes CPU30a and ROM30b.
, RAM 30c, etc., is also provided with a clock circuit 30V that sends a clock signal serving as a control timing at predetermined intervals.

Next, the correction coefficient calculation process executed by the ECU' 30 will be explained based on the flowchart shown in FIG. This correction coefficient calculation process is started every 360 degrees of crank angle of the engine 1, and is repeatedly executed in synchronization with the rotation of the engine 1.

First, in step 100, a process is performed in which the intake pipe pressure PM is detected from the intake pipe pressure sensor 23 and the cooling water temperature THW is detected from the water temperature sensor 20. In subsequent step 110, based on the cooling water temperature THW detected in step 100, a water temperature correction coefficient KTC used when calculating the actual fuel injection amount and a weighted average value PMDi, which will be described later, are calculated. A process of calculating a constant switching determination value LTC to be used is performed. Here, there is a relationship as shown in FIG. 5 between the cooling water temperature THW and the water temperature correction coefficient KTC. That is, the cooling water temperature THW
As the water temperature correction coefficient KTC decreases, the water temperature correction coefficient KTC increases. ECU
3O is a map that defines the relationship between the cold water temperature THW and the water temperature correction coefficient KTC as shown in Fig. 5.
It is stored in a predetermined area within M30b. When the coolant temperature THW is detected, the ECU 3O calculates the water temperature correction coefficient KTC based on the above map. Further, there is a relationship as shown in FIG. 6 between the cooling water temperature THW and the constant switching determination value LTC. That is, as the cooling water temperature THW decreases, the constant switching determination value LTC increases. ECU3
O stores in advance in the ROM a map that defines the relationship between the cooling water temperature THW and the constant switching judgment value LTC, as shown in FIG.
It is stored in a predetermined area within 30b. Cooling water temperature T
When HW is detected, the ECU 3O calculates a constant switching determination value LTC based on the above map.

Next, the process proceeds to step 120, where the previously calculated difference ΔPMi- between the intake pipe internal pressure PM and its weighted average value PMD
It is determined whether the absolute value of 1 exceeds the constant switching determination value LTC calculated in step 110 above. Above difference Δ
If the absolute value of PMi-1 exceeds the constant switching determination value LTC, the process proceeds to step 130, where the constant N is set to 4, and then the process proceeds to step 150. On the other hand, if the absolute value of the difference ΔPM i-1 is less than or equal to the constant switching determination value LTC, the process proceeds to step 140, where the constant N is set to 8, and then the process proceeds to step '150. In step 150, the weighted average value pv of the intake pipe internal pressure PM
A process is performed to calculate o; as shown in the following equation (1).

PDMi = (PMDi-I x (N-1) 10 PM)/N...
(1) However, pMD;-t is the weighted average value of the intake pipe internal pressure calculated last time.

N is the constant PM set in step 130 or 140, and in step 160, the weight of the intake pipe pressure PM detected in step 100 and the intake pipe pressure PM calculated in step 150. Difference △PM between mean value pMD;
A process is performed to calculate i as shown in the following equation (2).

ΔPMi = PM−PMDi (2
) In the subsequent step 170, the difference ΔPMi calculated in the above step 160 is determined as the acceleration determination value α (10 [
mmHg] ) is determined. Difference ΔPM
If i exceeds the acceleration determination value α, the process proceeds to step 180. In step 180, a process is performed to calculate the increase correction coefficient FTCI as shown in the following equation (3).

FTC1=ΔpM; XKTC...(3) However, ΔP
Mi...Difference KTC calculated in step 160 above...Water temperature correction coefficient calculated in step 110 above.Then, proceed to NEXT and end this process.

On the other hand, if the difference ΔPM1 is less than or equal to the acceleration determination value α in step 170, the process proceeds to step 190. In step 190, the difference ΔPM calculated in step 160 above is
i is the deceleration judgment value β (-10 [mmHQ] in this example)
) is determined. If the difference ΔPMi is less than the deceleration determination value β, the process proceeds to step 200.

In step 200, the weight loss correction coefficient FT02 is calculated using the following formula (4
) is calculated as follows.

FTC2=ΔpMr XKTC...(4) However, ΔP
Mi...Difference calculated in step '160 above KTC...Water temperature correction coefficient calculated in step 110 above After that, the process goes to NEXT and ends this process. Note that if the difference ΔPM1 is equal to or greater than the deceleration determination value β in step 190, the process can be directly proceeded to NEXT and the process ends. This correction coefficient calculation process is activated and repeatedly executed every 360 degrees of crank angle. The increase correction coefficient FTC1 or the decrease correction coefficient FTC2 calculated in this process is used when correcting the basic injection amount tJJ to calculate the actual injection amount in the fuel injection amount calculation process (not shown). Fuel corresponding to the calculated actual injection amount is supplied from the fuel injection valve 9 to the engine 1, and the engine 1 is operated.

Next, as an example of the above-mentioned control, a description will be given based on the timing chart shown in FIG. 7, which expresses changes in various quantities over time when load fluctuation occurs due to acceleration. Acceleration begins at time t1. Then, the intake pipe internal pressure PM rapidly increases and approaches atmospheric pressure. on the other hand,
The weighted average value PMD of the intake pipe internal pressure also increases accordingly.

In this case, the case where the constant N is set to 4 is shown by a dashed line, and the case where the constant N is set to 8 is shown by a broken line. The difference ΔPM between the intake pipe internal pressure PM and its weighted average value PMD reaches a maximum at time t2. Weighted average value P of the intake pipe internal pressure between time t1 and time t2
There is no significant difference in MD whether the constant N is set to 4 or 8. The difference ΔPM that reached the maximum value at the time t2 decreases and falls below the constant switching determination value LTC at the time t3.

From this time t3, the intake pipe internal pressure weighted average value PMD
The case where the constant N used to calculate is set and fixed at 4 as in the conventional case is shown by a dashed line in FIG. That is, the difference ΔP between the intake pipe internal pressure PM and its weighted average value PMD
M decreases rapidly from time t3, and the difference ΔPM becomes zero at time t4. Therefore, the fuel increase correction coefficient FTCI determined based on the difference ΔPM decreases from time t3 and reaches O at time t4, so that sufficient fuel increase correction is not performed during acceleration. As a result, the air-fuel ratio shifts from the stoichiometric air-fuel ratio to the lean side (1-ean) from time t3 to time t5, as shown by the two-dot chain line in FIG. It became.

On the other hand, when the constant N for calculating the weighted average value PMD of the intake pipe internal pressure from time t3 is changed from 4 to 8 as in the case of this embodiment, the weighted average value PMD of the intake pipe internal pressure is changed from 4 to 8. The value PMD changes as shown by the broken line in FIG. That is, the difference ΔPM between the intake pipe internal pressure PM and its weighted average value PMD gradually decreases from time t3, and reaches zero at time t5. Therefore, the increase correction coefficient FTC1 determined based on the above difference ΔPM is:
Since it gradually decreases from time t3 to time t5, sufficient fuel increase correction is performed during acceleration. the result,
Since the air-fuel ratio takes a value close to the stoichiometric air-fuel ratio from time t3 to time t5, as shown by the solid line in FIG. 7, the operating state of the engine 1 is stable.

In addition, even if load fluctuation occurs due to deceleration, the difference ΔP
At the time when the absolute value of M falls below the constant switching determination value LTC, the constant is changed from 4 to 8.

Therefore, since the reduction correction coefficient FT02 gradually decreases, the fuel decreases with deceleration, and the air-fuel ratio does not move away from the stoichiometric air-fuel ratio to the rich side (Rich), but instead approaches the stoichiometric air-fuel ratio. controlled by.

Note that in this embodiment, the engine 1 is replaced by the internal combustion engine M1,
The intake pipe pressure sensor 23, the ECU 3O, and the ffi! executed by the ECU 3O. (Step 100) corresponds to the load detection means M1, and the ECU 3O corresponds to the control means M3. In addition, the ECU 3O and the processing executed by the ECU 3O (
Step 120゜130.140) is responsiveness changing means M
Functions as 4.

As explained above, in this embodiment, when the absolute value of the difference ΔPM between the intake pipe internal pressure PM and its weighted average value PMD is equal to or less than the constant switching judgment value LTC, the weighted average value PMD
The constant N for outputting @% is changed from 4 to 8 to calculate the increase correction coefficient FT01 or the decrease correction coefficient FT02. Therefore, when the engine 1 shifts to an acceleration state, the constant N is changed from 4 to 8 when the difference ΔPM becomes less than or equal to LTC, so that PM is gradually reduced to the above difference. , increase correction coefficient FTCI
Since the increase correction of the actual fuel injection amount is continued through the correction based on , the air-fuel ratio is controlled to be close to the stoichiometric air-fuel ratio, and torque fluctuations of the engine 1 do not occur, making it possible to maintain good acceleration performance.

Furthermore, when the engine 1 shifts to a deceleration state, the constant N is similarly changed from 4 to 8, so the reduction correction coefficient F
Since the correction based on TC2 continues to reduce the actual fuel injection amount, the air-fuel ratio is controlled to be close to the stoichiometric air-fuel ratio,
It becomes possible to maintain good exhaust characteristics of the engine 1.

In this embodiment, the intake pipe internal pressure PM detected by the intake pipe internal pressure sensor 23 and its weighted average value PMD
It is configured to calculate the weight increase correction coefficient FTC1 and the weight loss/increase correction coefficient FTC2 based on the following. However, for example,
Instead of the intake pipe internal pressure PM, increase or decrease correction coefficients FTC1, FT are based on the throttle valve opening obtained 1q from the throttle position sensor 22 or the basic fuel injection amount tjJ calculated from the load and rotational speed.
Even if the configuration is such that C2 is calculated, the effects of the present invention can still be achieved.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and it goes without saying that it can be implemented in various forms without departing from the gist of the present invention. .

Effects of the Invention As detailed above, in the internal combustion engine control device of the present invention, the control means calculates the basic amount of fuel to be supplied to the internal combustion engine based on the load detected by the load detection means, and
When performing control to correct the basic amount with a correction amount corresponding to the difference between the basic amount and its responsiveness delay processing value, the responsiveness changing means adjusts the basic amount so that the difference between the basic amount and its responsiveness delay processing value is small. Indeed, the responsiveness of the responsiveness delay processing value is reduced,
On the other hand, the larger the difference, the higher the responsiveness. Therefore, even when load fluctuations occur in the internal combustion engine, an excellent effect is achieved in that the fuel injection supply amount can be increased or decreased in accordance with subtle changes in the operating state of the internal combustion engine.

Moreover, even when load fluctuations occur in the internal combustion engine, air-fuel ratio control can be performed to maintain the operating condition of the internal combustion engine in a good condition without impairing drivability or deteriorating exhaust characteristics.

[Brief explanation of drawings]

FIG. 1 is a basic configuration diagram showing the contents of the present invention, FIG. 2 is a system configuration diagram of an engine air-fuel ratio control device according to an embodiment of the present invention, and FIG.
Fig. 4 is a flowchart of the processing executed by the ECU, Fig. 5 is a graph showing a map defining the relationship between the water temperature correction coefficient and the cooling water temperature, and Fig. 6 is a flowchart of the process executed by the ECU. A graph showing a map defining the relationship between the switching determination value and the cooling water temperature, and FIG. 7 is a timing chart showing changes in various quantities over time. Ml... Internal combustion engine M2... Load detection means M3... Control means M4... Response changing means 1... Engine 20... Water temperature sensor 22... Throttle position sensor 23... Intake Pipe pressure sensor

Claims (1)

[Scope of Claims] 1. Load detection means for detecting the load of an internal combustion engine, calculating a basic amount of fuel to be supplied to the internal combustion engine according to the detected load, and calculating the basic amount and its response delay. In an air-fuel ratio control device for an internal combustion engine, the air-fuel ratio control device for an internal combustion engine includes: a control means for correcting and controlling the basic quantity with a correction amount according to a difference from a processed value; Responsiveness changing means is configured to reduce the responsiveness of the delayed responsiveness processed value as the difference becomes smaller, and increase the responsiveness as the difference becomes larger, according to the difference between the processed value and the processed value. An air-fuel ratio control device for an internal combustion engine, characterized in that: