JPH03185242A - Fuel injection controller of internal combustion engine - Google Patents

Abstract

PURPOSE:To secure a proper fuel injection quantity all the time by setting a learning range in response to respective using ranges of a fuel injection valve, and compensating the fuel injection quantity from the fuel injection valve which corresponds, with a learning value learned in the learning range, during operation range which corresponds to the set learning range. CONSTITUTION:An inter-cylinder fuel injection valve 9 which supplies pressurized fuel from a fuel supply system to cylinders and a port fuel injection valve 10 arranged inside an intake port 11 are provided on every cylinder. Fuel injection is performed by the inter-cylinder fuel injection valve 9 for whole operation range, and a fuel quantity which is an amount exceeding the maximum injection quantity of the fuel injection valve 9 is injected from the port fuel injection valve 10. In such an internal combustion engine, a value based on the output signal of an O2 sensor 15 in a control circuit 6 is learned so as to compensate the fuel injection. In addition, a plurality of learning ranges are set in response to using conditions of respective fuel injection valves 9, 10, respective learning values learned in respective learning ranges are used so as to compensate the fuel injection quantity at the time of operation condition corresponding to the learning range.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a fuel injection control device for an internal combustion engine, and particularly to a fuel injection control device for an internal combustion engine, which is equipped with a plurality of fuel injection valves per cylinder and is capable of controlling overload in a wide load range from idle to high load. The present invention relates to a fuel injection control device for an internal combustion engine that supplies required fuel without shortage.

[Conventional technology]

For example, in a two-stroke internal combustion engine, the intake port is divided into two and a fuel injection valve is installed in each.The number of injectors used can be changed depending on the engine load to prevent fuel from flowing through and to ensure the amount of fuel injected at high loads. An organization that attempted to achieve both is already known (Japanese Patent Application Laid-Open No. 63-9627).

In addition, in air-fuel ratio feedback control to maintain the air-fuel ratio at a target air-fuel ratio (for example, stoichiometric air-fuel ratio),
A value (learning correction amount) based on the output signal of an oxygen sensor installed in the engine exhaust system is learned in advance, and the fuel injection amount is corrected using the learning correction amount that corresponds to the actual operating conditions, thereby adjusting the air-fuel ratio. Learning control devices that attempt to improve the accuracy of feedback control are also already known.

[Problem to be solved by the invention]

By the way, in the case where the fuel injection amount is corrected by learning the value based on the output signal of the oxygen sensor as described above, it goes without saying that the learned value is also affected by variations (individual differences) in the fuel injection valves installed in the engine. This is one of the influencing factors, and in actual fuel injection control, this individual difference is also corrected. Therefore, if such learning control is applied to an internal combustion engine having multiple fuel injection valves as described above, the amount of fuel injected from the multiple fuel injection valves will be corrected using the learned values stored in a specific operating range. However, if the fuel injector used in the operating area (learning area) in which learning is performed is different from the fuel injector used when correcting the fuel injection amount using the learned value, the installed There was a problem in that the accuracy of correcting the injection amount deteriorated due to individual differences between the fuel injection valves. In view of such problems, an object of the present invention is to provide a fuel injection control device that does not deteriorate the correction accuracy when executing learning control of injected fuel in an internal combustion engine equipped with a plurality of fuel injection valves per cylinder. shall be.

[Means to solve the problem]

For the above purpose, according to the present invention, in a fuel injection control device for an internal combustion engine having a plurality of fuel injection valves per cylinder, fuel injection from the plurality of fuel injection valves is controlled according to the operating state. means for correcting the fuel injection amount by learning a value based on an output signal from an oxygen sensor installed in the exhaust system of the engine; and a means for correcting the fuel injection amount during an operating state corresponding to each learning area using each learning value learned in each of the learning areas. An injection control device is provided.

[For production]

A learning area is set corresponding to the usage range of each fuel injector, and during actual operation, when the operating state corresponds to the set learning area, the corresponding fuel is adjusted using the learning value learned in this learning area. In order to correct the fuel injection amount from the injection valve, individual differences between the fuel injection valves are corrected, and an appropriate injection amount can be obtained.

〔Example〕

The present invention will be described below with reference to the drawings, taking a two-stroke internal combustion engine as an example.

FIG. 1 is an overall schematic diagram of a two-stroke internal combustion engine according to the present invention. In this figure, an air flow meter 3 is provided in an intake passage 2 of an engine body 1.

The air flow meter 3 directly measures the amount Q of intake air taken in from the outside via the air cleaner 4, has a built-in potentiometer, and generates an analog voltage output signal proportional to the amount Q of intake air. This output signal is input to the control circuit 6 via the A/D converter 5a.
is supplied to. In addition, in the distribution tough,
In order to detect the engine rotational speed N, a crank angle sensor 8a that generates a pulse signal for detecting a reference position and a crank angle sensor 8b that generates a pulse signal for detecting an angular position are provided. The pulse signals of these crank angle sensors 8a and 8b are supplied to the input port a of the control circuit 6, and the output of the crank angle sensor 8b is supplied to the interrupt terminal of CP[I6b.

By the way, generally in a two-stroke internal combustion engine, the second
As shown in the figure, it is desirable to perform in-cylinder injection as much as possible in order to prevent fuel from flowing into the exhaust system due to the blow-through that occurs during the opening period of the intake valve and the exhaust valve, that is, during the scavenging period. However, in order to inject fuel from idle to high load with one fuel injection valve within the short fuel injection period of this two-stroke internal combustion engine, the width of the injection amount,
That is, an injection valve with a wide dynamic range is required, and it is difficult to manufacture an injection valve with such a wide dynamic range. Therefore, in the case of this embodiment, which takes a two-stroke internal combustion engine as an example, as shown in FIG. A port fuel injection valve 10 disposed inside the boat 11 is provided for each cylinder, so that fuel is injected by the in-cylinder fuel injection valve 9 over the entire operating range, and the maximum injection amount of the in-cylinder fuel injection valve 9 is controlled. By injecting the excess amount of fuel using the port fuel injection valve ■0, it is possible to achieve both fuel blow-through and ensuring the amount of fuel to be injected during high loads.

In this embodiment, the intake passage 2 is further provided with a scavenging pump 12 for supplying fresh air to each cylinder, and the exhaust passage 13 is provided with, for example, a three-way catalyst 14 for purifying exhaust gas. Furthermore, oxygen (0
2) A sensor 15 is provided. This 02 sensor 15 determines whether the exhaust air-fuel ratio is on the lean side or rich side with respect to the stoichiometric air-fuel ratio according to the oxygen concentration in the exhaust gas, and outputs a different output voltage to the input capacitor (6a) of the control circuit 6 accordingly. supply

Note that a combustor 16 such as an oxidation catalyst or a thermal reactor is installed on the exhaust upstream side of the 02 sensor 15 in order to prevent the blown air from staying around the 02 sensor 15.
An air consumption means typified by: may be provided.

The control circuit 6 is configured, for example, as a microcomputer, and includes, in addition to the aforementioned CPU 6a and CPU 6b, an output port c for outputting drive signals to each fuel injection valve 9, 10, etc., a memory 6d, and a memory 6d. It is equipped with a bus 6e for connecting. In addition to the above-mentioned output signals, the input capacitor (6a) of this control circuit 6 receives AD conversion signals such as the cooling water temperature THW and the intake air temperature TA for the correction amount used for calculating the fuel injection amount TAU, which will be described later. The signals are inputted via devices 5b, 5c, . . . .

The control circuit 6 takes in the parameters representative of the engine operating conditions described above, calculates the final fuel injection amount TAU using the following formula, and calculates the final fuel injection amount TAU from the output port C.
．． A drive signal is output to 11.

TAU=k-Q/NXKXFTIXFAF XF
G [where, k: constant, Q: intake air flow rate detected by air flow meter, N: engine rotation speed detected by crank angle sensor, K: correction amount determined by cooling water temperature, intake air temperature, etc., : Fresh air acquisition coefficient calculated according to the operating conditions (Q/N, N), FAF: Air-fuel ratio correction coefficient that increases or decreases depending on the 02 sensor output, FG: Learned value] Figure 3 shows the fuel injection with the above configuration. In the control device, a flowchart is shown for controlling fuel injection from each fuel injection valve 9.10, and this routine is executed at every predetermined crank angle in the cpo 6b based on a signal from the crank angle sensor 8b.

First, in step 31, the intake air amount Q, the engine rotation speed N,
Read the cooling water temperature THW, intake air temperature TA, etc. next,
In step 32, a map calculation of the fresh air capture coefficient FTR is performed using the read Q and N. This fresh air capture coefficient FTi1 is a correction factor for the fuel injection amount related to the proportion of fresh air involved in combustion itself, with the air volume subtracted from the Q measured by the air flow meter 3, and the control circuit 6 The memory 6d has Q/ as shown in the figure.
FTR data for NH is stored. Next, in step 7, a correction coefficient K is calculated from the cooling water temperature THW and the intake air temperature TA, and in step 34, FAF calculated by another program is read in accordance with the current operating conditions.

By the way, in an internal combustion engine having a plurality of fuel injection valves per cylinder, the fuel injection valve to be used is determined in advance depending on the operating condition, as described above, and in this example,
For example, as shown in Fig. 4, the fuel injector used is loaded (Q
A map divided according to the relation: /N>one rotational speed (N) is stored in advance in the memory 6d of the control circuit 6.

In this figure, region 1 indicates an operating condition range in which the required fuel is supplied only by the in-cylinder fuel injection valve 9, and region 0 indicates an operating condition range in which fuel is supplied by two fuel injectors 9 and 10. .

Therefore, in step 35 following step 34 in FIG. 3, the current operating state read in the previous step 31 is
It is determined whether or not it is in area 1 in the map shown in the figure. If it is determined in step 35 that the area is in the area l (in-cylinder injection only) shown in FIG.
U = k Q / N X K X F T +1
It is calculated as
1 as TAU, and the fuel injection amount TAU Q of the other port fuel injection valve 10 as 0.

On the other hand, in step 35, area 0 (in-cylinder injection + boat injection)
If it is determined that the fuel injection amount is TAU=
kQ/NXKXFt++XFAFXFGO (However, FG
O: learned value in region 0), the region setting flag F is set to O in step 40, and the injection amount TAII 1 of the in-cylinder fuel injection valve 9 is set to TALI in the subsequent step 41.
3, and the injection ITALI O of the port fuel injection valve 10 is TAU-TAU 31. : Set. Note 1. : Iron TA
[l 3c. The maximum injection amount of the in-cylinder fuel injection valve 9 determined by the engine rotational speed N (decreases as the speed N increases) to a predetermined value (for example, the effective minimum of the port fuel injection valve ■0) This is the value obtained by subtracting the injection amount).

Then, in step 42 following step 38 or 41,
As is well known, the fuel of TAU 1 is injected from the in-cylinder fuel injection valve 9 and the fuel of TAXI O is injected from the port fuel injection valve 10, and this routine ends.

Figure 5 shows the control of the air-fuel ratio correction coefficient FAF and the learned value FG.
This is a control routine for O, FGI. Note that this routine is a time interrupt routine, and interrupt processing is performed every 4 m5ec, for example. This routine will be described below with reference to FIG. 6, which shows an FAF change model corresponding to the 02 sensor output.

First, in step 51, it is determined whether the current operating conditions are in the air-fuel ratio feedback region. For example, feedback control is normally not executed when the coolant temperature THW is low, when the 02 sensor 15 is inactive, or when increasing the amount of water at a high temperature.
), the process proceeds to step 52 and FAF is fixed at 1.0.

On the other hand, if it is determined in step 51 that it is in the feedback region (Yes), the process proceeds to step 53, where the current output of the 02 sensor 15 is checked and it is determined whether or not a rich signal is being output. If the rich signal is currently being output (Yes), then the process advances to step 54, where it is compared with the 02 sensor signal from the previous flow execution and the 02 sensor signal is output for the first time.
It is determined whether the signal of the sensor 15 has been inverted, that is, whether there has been an inversion from a lean signal to a rich signal. If the result in step 54 is NO1, that is, if the rich signal has been output continuously since the previous flow execution, this corresponds to, for example, progress from point a to point i shown in the model of FIG. 6, so the process proceeds to step 55. A process of subtracting a predetermined value α from FAF is executed. On the other hand, if it is determined in step 54 that the 02 sensor signal has been reversed (corresponding to progress from the fifth garden point C to point d), the process proceeds to step 56, and the FAFA
V is calculated. This FAFAV is the current value FAF,
Value FA immediately before skip at the previous 02 sensor reversal
Average value with FQ, i.e. (FAF+FAF O)/2
This is for estimating the degree of deviation from the control center value of FAF. Then, in step 57, in order to calculate FAFAv at the time of the next 02 sensor signal inversion, the current FAF is set as the value immediately before skipping and the FAF O
Then, the process proceeds to step 58, where a process of subtracting the lean side skip amount R3L from the current FAF is performed as shown in FIG. The processing from step 54 to step 55 described above is the same when inverting a rich signal to a lean signal, and if the determination is No in step 53, the rich signal is inverted to a lean signal in step 59. It is determined whether or not there was. If it is not reversed (NO), in step 60, the FAF
A process of adding a predetermined value β to
8, FAFAV is calculated and FAF is skipped to the rich side by R3R.

Once FAFAv is calculated as described above, a process is then performed to control the learning values FGO and FGI based on the magnitude. That is, in step 64 following step 58 or step 63, it is determined whether the calculated FAFAv exceeds a predetermined central upper limit value (for example, 1.002) of FAF control.

When FAFAV < 1.002, that is, in the case of No, the process proceeds to step 65, and it is determined whether or not FAFA'V falls below the control central lower limit value (for example, 0.998), that is, in the case of FAFAV
It is determined whether FAv<0.998, and FAFAv>0.
．． If the number is 998, the routine ends as is. That is, in this case, FAF is included within a predetermined control range, and learning values FGO and FGl are not updated. Step 64
If FAFAV>1.002, the process proceeds to step 66, where it is determined whether the flag F set by the execution of the control routine shown in FIG. 3 is 1 or not. When F=1, a predetermined correction value (in this embodiment, 0.002) is added to the previously learned value FG1 in step 67 to update it, and on the other hand, when F=0, step 67 68 and 0 to FGO
．． 002 is added. Also, in step 65, FAF
When Av<0.998, it is determined in step 69 whether or not F=1 in the same way as step 66, and when F=1, 0.002 is subtracted from FGI in step 70, and when F=0, In step 71, 0.002 is subtracted from FGO,
This routine ends.

In this way, in the learning routine described above, the learning value F
When updating G 1 and FGO, when only the in-cylinder injection valve 9 is used, only the FGI is updated, and when both the in-cylinder injection valve 9 and the port injection valve 10 are used, only the FGO is updated. is updated. Also, this learning value FG
I and FGQ change due to changes in atmospheric density, individual differences between the injection valves 9 and 10, changes over time, etc. Therefore, if the injector used when the learned values FG 1 and FG O are updated (learning area) and the injector used when the fuel injection amount is corrected using the learned values FGI and FGO, If the learning value FGI differs, the accuracy of correcting the fuel injection amount will decrease, but the learned value FGI in this embodiment.

As shown in the flowchart of FIG. 3, the FGO is used when the usage status of each fuel injection valve 9, 10 is the same as during learning, and corrects the fuel injection amount. Therefore, the accuracy of correcting the fuel injection amount based on the learned value is improved.

Incidentally, it is actually preferable to provide hysteresis to the boundary line between region 1 and region 0 in the map shown in FIG. 4 to prevent hunting phenomenon of the injection form near the injection valve switching point.

The present invention has been described above by taking as an example a two-stroke internal combustion engine having an in-cylinder fuel injection valve and a port fuel injection valve per cylinder. The present invention is similarly applicable to internal combustion engines having two or more fuel injection valves per cylinder.

Furthermore, regarding the injection form, as shown in Fig. 7, operating ranges in which each fuel injector is used alone and in combination are set respectively, and learning values are set to correct the fuel injection amount in accordance with the ranges A, B, and C. FGA, FGB, and FGC may be provided respectively, and this learning area may not only be made to correspond only to the injection form, but may also be further subdivided by taking other conditions into account.

[Effect] As explained above, according to the present invention, in an internal combustion engine having a plurality of fuel injection valves per cylinder, the fuel injection amount is determined using the fuel injection valves used in the learning area and the learning value. The accuracy of correcting the injection amount is improved because the injection valves used are the same when correcting the injection amount.

Accordingly, the followability of the air-fuel ratio is improved and exhaust emissions are improved. Furthermore, since the error from the target air-fuel ratio is reduced, even if the air-fuel ratio is set to the lean side, the possibility of misfire can be reduced and fuel efficiency can be improved.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of a two-stroke internal combustion engine equipped with a fuel injection control device according to the present invention; Fig. 2 is a diagram showing the scavenging period and fuel injection timing of the engine shown in Fig. 1; Fig. 3 is a diagram showing the fuel injection timing of the engine shown in Fig. 1; Flowchart for executing fuel injection from the injection valve: 4th
The figure is a map that is used in the routine shown in Figure 3 and determines the fuel injection valves to be used depending on the operating condition; Figure 5 is a flowchart for controlling the air-fuel ratio correction coefficient and learning value; Figure 6 is a flowchart for controlling the air-fuel ratio correction coefficient and learning value; A diagram showing a change model of an air-fuel ratio correction coefficient corresponding to a sensor output signal; FIG. 7 is a map diagram for setting a learning area different from that in FIG. 4 as another embodiment. 1... Engine body, 9... In-cylinder fuel injection valve, 15... Oxygen (02) sensor. 6...Control circuit, 10...Port fuel injection valve, TDC (Top dead center)

Claims (1)

[Scope of Claims] 1. In a fuel injection control device for an internal combustion engine having a plurality of fuel injection valves per cylinder, means for controlling fuel injection from the plurality of fuel injection valves according to operating conditions; Means for correcting the fuel injection amount by learning a value based on an output signal from an oxygen sensor installed in an exhaust system of an engine, and setting a plurality of learning areas corresponding to usage conditions of the plurality of fuel injection valves. and means for correcting the fuel injection amount during the operating state corresponding to each learning area using each learning value learned in each of the learning areas. Device.