JPH0518282A - Air-fuel ratio control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent the occurrence of erroneous learning and lowering of an injection amount owing to choking of an injector by counting how many times a learning value of air-fuel ratio feedback control produces an abnormal time and computing a fundamental injection time and a correction amount at an abnormal period when the number of times exceeds a reference range. CONSTITUTION:In an internal combustion engine using two kinds of mixture fuel, feedback control of an air-fuel ratio is effected by using a given learning value. In this case, an operation condition is detected by a means I, a learning value responding to the detected operation condition is computed by a means II, and it is counted by a means III how many times a computed learning value produces an abnormal value outside a given range. When the counted number of times of an abnormal value exceeds a reference value, a fundamental injection time responding to a learning value is computed by a means IV. The computed fundamental injection time is corrected by means of other correction factor and a correction amount at an abnormal period is computed by a means V. A fundamental injection time on some operation condition is corrected by a means VI by adding a correction amount at an abnormal period.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio control system for an internal combustion engine which uses a mixed fuel, and more particularly to an air-fuel ratio control system which improves the durability of an injector in an internal combustion engine which uses a mixed fuel of alcohol and gasoline. Regarding

[0002]

2. Description of the Related Art Conventionally, internal combustion engines for automobiles are roughly classified into a spark type engine that uses gasoline as a fuel and a compression ignition type engine that uses light oil. As a fuel, it has been attempted to use another fuel in gasoline, for example, a mixed fuel in which alcohol is mixed.

As described above, in an engine that can use a fuel in which alcohol is mixed with gasoline, an alcohol concentration sensor is provided in the fuel path to the engine so that the engine can be operated regardless of the proportion of alcohol mixed with gasoline. There has already been proposed a system for detecting the alcohol concentration in the fuel and controlling the fuel injection amount and the ignition timing according to the alcohol concentration (for example, Japanese Patent Laid-Open No. 56-66424 and Japanese Patent Laid-Open No. 6-42424).
56-98540). A vehicle that can run regardless of the proportion of alcohol mixed with gasoline is called a flexible fuel vehicle (FFV).

By the way, even in an engine using a mixed fuel of alcohol and gasoline, feedback control of the air-fuel ratio using an O ₂ sensor is performed, and as the control of the air-fuel ratio by learning correction during feedback of the air-fuel ratio, There are the following suggestions. (1) A method for judging an abnormality of an O ₂ sensor by comparing an average value of learning values with a reference value (Japanese Utility Model Laid-Open No. 2-56837). (2) A method for judging the abnormality of the O ₂ sensor by comparing the current and past learning correction counts (Japanese Patent Laid-Open No. 2-86937).

[0005]

However, in the conventional air-fuel ratio control system for an internal combustion engine which uses a mixed fuel of alcohol and gasoline, there is no consideration for the decrease in the flow rate of the fuel due to the clogging of the injector, and the clogging of the injector occurs. If this occurs, there was a problem that drivability deteriorates, such as stall of the engine. That is,
Compared to gasoline, alcohol is more likely to have an adhesive deposit on the valve seat inside the injector,
Further, with alcohol, it is difficult to dissolve and wash away the deposit, so the deposit increases the time from the ON signal of the injector to the actual start of fuel injection, and the dynamic injection amount is greatly reduced. For this problem,
Even if the learning function of the A / F in the conventional O ₂ sensor feedback control system is used, the flow characteristic deteriorates beyond the correction limit.

Therefore, the present invention prevents the erroneous learning due to the clogging of the injector in the engine using the conventional mixed fuel and changes the fuel injection time map according to the learning value to reduce the dynamic injection amount. An object of the present invention is to provide an air-fuel ratio control device for an internal combustion engine that can be prevented.

[0007]

FIG. 1 shows the structure of an air-fuel ratio control system for an internal combustion engine according to the present invention which achieves the above object. As shown in FIG. 1, the air-fuel ratio control device for an internal combustion engine is
An air-fuel ratio control device for an internal combustion engine, which uses two kinds of mixed fuels and performs feedback control of an air-fuel ratio using a learned value, the operating condition detecting means detecting an operating condition, and the detected current operating condition. Learning value calculation means for calculating a learning value according to the above, learning value abnormality number counting means for counting the number of times the calculated learning value becomes an abnormal value other than within a predetermined range, and a learning value under a certain operating condition is abnormal. When the number of times exceeds a reference value, a basic injection time calculating means for calculating a basic injection time, which is a correction value of the reference injection time corresponding to the learning value, every time the number of abnormalities of the learning value exceeds a predetermined number. An abnormal time correction amount calculation means for calculating the abnormal time correction amount by correcting the basic injection time every time the basic injection time is calculated, and the basic injection time under a certain operating condition, To add Ri composed of an abnormal basic injection time correction means for correcting.

[0008]

According to the air-fuel ratio control system for an internal combustion engine of the present invention,
When the injector is clogged, the number of times the learning value of the air-fuel ratio feedback control exceeds the reference range is counted, and every time the number of times exceeds the reference value, the correction value TPBSEADJi of TPBASE corresponding to the learning value is Calculated and TPBS
Every time EADJi is calculated, it is corrected by another correction coefficient to calculate the abnormal correction amount, and the basic injection time under that operating condition is corrected by adding the abnormal correction amount. Becomes longer depending on the clogging of the injector, improving the durability of the injector and
The engine operates normally.

[0009]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 2 schematically shows an electronically controlled fuel injection type internal combustion engine equipped with an embodiment of the air-fuel ratio control apparatus for an internal combustion engine of the present invention. In this figure, an engine 10 has, for example, four cylinders, and its piping and ignition system are adjusted so that a mixed fuel of gasoline and alcohol can be used.

A piston 13 is reciprocally housed in a cylinder bore 12 formed in the cylinder block 11,
A combustion chamber 15 is formed between the piston 13 and the cylinder head 14. The intake port 16 and the exhaust port 17 provided in the cylinder head 14 are opened and closed by an intake valve 18 and an exhaust valve 19, respectively. Inside the intake passage 21 of the engine 10, a throttle valve 23 interlocked with an accelerator pedal is provided, an air cleaner 24 is arranged at the most upstream side of the intake passage 21, and an air flow meter 25 and a throttle valve are provided at the downstream side thereof. 23 are provided in this order. At the downstream side of the throttle valve 23, there is a pressure sensor 30 for detecting the intake pipe internal pressure as a means for detecting the intake air amount.
A fuel injection valve 26 that injects fuel into each cylinder is attached to the most downstream side of 21 to inject fuel into the intake port 16 of each cylinder. As the pressure sensor 30, for example, a SAW sensor using a surface acoustic wave that causes a propagation phase delay due to strain proportional to pressure is used, and a pressure signal is extracted at an oscillation frequency that is inversely proportional to this phase delay time.

A mixed fuel of gasoline and alcohol in a fuel tank 27 is sent to each fuel injection valve 26 by a pump 28 through a fuel pipe 20. An alcohol concentration sensor 29 for detecting the alcohol concentration in the fuel sent to the fuel injection valve 26 is provided in the middle of the fuel pipe 20. Also,
The fuel pipe 20 on the downstream side of the pump 28 is branched into two, one of which is connected to the fuel injection valve 26 and the other of which is connected to a pressure regulator 9 for adjusting the pressure of the mixed fuel in the fuel pipe 20.

The pressure regulator 9 can change the pressure of the mixed fuel by controlling a solenoid diaphragm valve by a pulse signal or a voltage signal output from a control circuit 41 described later. As the pressure regulator 9, a control system using the intake pipe pressure can also be used. Then, the fuel surplus due to the pressure adjustment in the pressure regulator 9 is returned to the fuel tank 27 through the return pipe 8.

On the other hand, in the exhaust passage 31 of the engine 10, an air-fuel ratio sensor 32 for detecting the oxygen concentration in the exhaust gas is attached. The distributor 33 is fixed to the cylinder block 11, and the distributor 33 is provided with a rotation speed sensor 34 for detecting the engine rotation speed. The rotation speed sensor 34 includes a crank angle sensor that generates a reference position detection pulse signal for each 180 ° CA and a crank angle sensor that generates a reference position detection pulse signal for each 30 ° CA. Composed.

The control circuit 41 is composed of, for example, a microcomputer, and has an input port 42 having an analog input circuit, an input / output interface, an A / D converter, etc., a pressure control signal to the pressure regulator 9 and a fuel injection valve. 26
Output port 43 for outputting the injection signal to RAM, RAM or RO
A memory 44 for M and the like, a micro processing unit (MPU) 45 for controlling, and the like are provided, and these are interconnected by a bus 46.

Signals from the alcohol concentration sensor 29, the pressure sensor 30, the air-fuel ratio sensor 32, and the rotation speed sensor 34 are input to the input port 42 of the control circuit 41, and the control circuit 41 outputs the fuel based on these signals. The injection amount is determined by calculation. In addition to the above configuration, detection signals from an intake air temperature sensor, an oxygen concentration sensor, a vehicle speed sensor provided on a speedometer cable from a transmission, etc. (all not shown) are sent to the control circuit 41. However, since these are not directly related to the present invention, description thereof will be omitted.

Next, the operation of the above-mentioned control circuit 41 will be described with reference to the flow charts of FIGS. 3 and 4, but it is assumed that this routine is executed as an interrupt routine every predetermined time, for example, every 4 ms. In step 301, pressure sensor 30
The value of the intake pipe pressure PM is read from step 302.
Then, the value of the engine speed Ne from the engine speed sensor 34 is read. Then, in step 303, a learning value KGi corresponding to the operating state i at that time is calculated from the read value of the intake pipe pressure PM and the value of the engine speed Ne. This calculation can be obtained from a map stored in the memory 44 in advance.

FIG. 4 shows the basic injection time correction routine. In step 401, the learning value KGi in the operating state i calculated in step 303 is within the range between the lower limit value αi and the upper limit value βi in the operating state i. Or not. If αi ≤KGi ≤βi (YES), go to step 40.
If not (NO), proceed to step 402. In step 402, the number of times the learned value KGi falls outside the range between the lower limit value αi and the upper limit value βi in the operating state i is counted by the counter Ci, and in step 403, the number of times Ci is counted.
Is greater than or equal to the reference value NCi.

If Ci <NCi (NO) in step 403, this routine is terminated. If Ci ≥NCi,
If (YES), the process proceeds to step 404, the value of the counter Ci is cleared, and the value of the correction value TPBSEADJi is calculated in step 405. This calculation is performed by the following formula TPBSEADJi = TPBASEi × (KGi−1). In this formula, TPBASEi is the reference injection time in the operating state i.

After calculating the correction value TPBSEADJi in this way, the process proceeds to step 406, the alcohol concentration correction coefficient KALCL in the operating state i is reset (= 1), and the value of another counter ji is incremented by 1 in step 407. Increase. Step 408 is to calculate the abnormal correction amount Aji of the injection time, which is performed by the following formula Aji = TPBSEADJi × KALCL × COEFi. The abnormal correction amount Aji is calculated for each count of the other counter ji described above.

In step 409, the basic injection amount is calculated, and after step 408 is completed, or
If YES in 401, the basic injection amount TPi in the operating state i is calculated by the following formula TPi = (TPBASEi + TPSUBi) × KGi × COEFi × KALCL + ΣAji + Di. Here, TPSUB is a correction value of the reference injection time TPBASE, COEFi is various correction coefficients other than the learning value KG, for example, an air-fuel ratio feedback correction coefficient, an intake air temperature correction coefficient, KALCL is an alcohol concentration correction coefficient, and D is a start. It is an hour injection time or an asynchronous injection time. The alcohol concentration correction coefficient KALCL is calculated, for example, by the following formula.

KALCL = (A / Fst85) ÷ (A / Fstr) where A / Fst85 is, for example, the theoretical air-fuel ratio of 85% alcohol, and A / Fstr is the theoretical air-fuel ratio of the fuel component judged by the alcohol sensor. is there. When this step 409 ends, this routine ends, and after a predetermined time, the procedure described above is repeated. Therefore, if the progress of clogging of the injector continues, the correction value Aji in step 408 increases, so the added value in step 409 increases and the injection time is corrected to be longer.

FIG. 5 shows the transition of the actual injection time of the injector when the clogging of the injector continues to occur. The point of changing the map in FIG. 5 is when the abnormal correction amount Aji is changed. By repeating the procedure as described above, in the present invention, the map value of the injection time is corrected so that the injection time of the injector falls within the correction range of the learning value even when the injector continues to be clogged. Therefore, problems such as engine stalls do not occur. On the other hand, FIG. 6 shows the transition of the actual injection time of the injector when the injector continues to be clogged in the conventional air-fuel ratio control system for an internal combustion engine.
In the conventional device, if the injector continues to be clogged, the injection time of the injector is reduced and exceeds the correction range of the learning value, so that problems such as engine stall occur.

[0023]

As described above, according to the present invention,
It is possible to provide an air-fuel ratio control device for an internal combustion engine that can prevent erroneous learning due to clogging of an injector in an engine that uses a mixed fuel and that can prevent a decrease in injection amount by changing a fuel injection time map according to a learned value. effective.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an air-fuel ratio control device for an internal combustion engine of the present invention.

FIG. 2 is a configuration diagram of an internal combustion engine equipped with the device of the present invention.

FIG. 3 is a flowchart showing the operation of the control circuit of FIG.

FIG. 4 is a flowchart showing injection time correction of the control circuit of FIG.

FIG. 5 is a diagram showing changes in injection time when the injector is clogged according to the present invention.

FIG. 6 is a diagram showing a transition of injection time when a conventional injector is clogged.

[Explanation of symbols]

 8 ... Return pipe 9 ... Pressure regulator 10 ... Engine 20 ... Fuel pipe 26 ... Fuel injection valve 27 ... Fuel tank 28 ... Fuel pump 30 ... Alcohol concentration sensor 41 ... Control circuit.

Claims (1)

Claim: What is claimed is: 1. An air-fuel ratio control device for an internal combustion engine, which uses two types of mixed fuel and performs feedback control of an air-fuel ratio using a learned value, the operating condition detecting an operating condition. Detecting means, learning value calculating means for calculating a learning value according to the detected current operating condition, and learning value abnormality number counting means for counting the number of times the calculated learning value becomes an abnormal value outside a predetermined range When the number of times the learned value becomes abnormal under a certain operating condition exceeds the reference value, the basic injection time that is the correction value of the reference injection time corresponding to this learned value is set to A basic injection time calculating means for calculating each time the basic injection time is exceeded, and an abnormal time correction amount calculating means for calculating an abnormal time correction amount by correcting the basic injection time with another correction coefficient every time the basic injection time is calculated. Basic injection time The abnormality correction air-fuel ratio control apparatus for an internal combustion engine, characterized by comprising, an abnormality when the basic injection time correction means for correcting by adding.