JPH03185245A - Fuel injection control device for 2-cycle internal combustion engine - Google Patents

Abstract

PURPOSE:To correct an adequate fuel injection amount regardless of the variation of the fuel injection timing by dividing the learning area into plural areas responding to the fuel injection timings, and correcting the fuel injection amount from a responding fuel injection valve with the learning value learned in the learning area. CONSTITUTION:In a two-cycle engine furnishing a fuel injection valve 9 to feed a pressured fuel from a fuel feeding system to each cylinder respectively, a suction passage 2 furnishing a scavenging pump 10 to feed a fresh air to each cylinder, and an exhaust passage 11 furnishing a ternary catalyst for purifying exhaust gas, the fuel injection valve 9 is controlled by a control circuit 6 depending on various parameters to indicate the engine operation condition. And in the control circuit 6, plural divided learning areas are set responding to the fuel injection timings of the fuel injection valve 9, and the learning values learned in the plural learning areas respectively are used, and thereby the fuel injection amount is corrected in the operation condition responding to each learning area.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel injection control device for a two-stroke internal combustion engine, and more particularly to a fuel injection control device for a two-stroke internal combustion engine that changes fuel injection timing according to operating conditions.

[Conventional technology]

For example, in a two-stroke internal combustion engine, a control device is already known that attempts to prevent fuel blow-out and improve fuel atomization by changing the timing of fuel injection from a fuel injection valve depending on the operating state ( JP-A No. 63-500322).

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 two-stroke internal combustion engine that changes the fuel injection timing as described above, the amount of fuel blown into the exhaust system changes depending on the fuel timing. Therefore, if it is attempted to perform feedback control as described above in such an engine, the amount of unburned fuel in the exhaust gas will change due to the change in the amount of fuel blowout, which will affect the reaction speed of the 02 sensor. Therefore, even in learning control using the output signal of the 02 sensor, the learning conditions differ depending on the injection timing. For example, if the value learned at a certain injection timing is used to correct the fuel injection amount at another injection timing, the atrium will change the fuel amount. Therefore, there is a problem in that the accuracy of correcting the injection amount deteriorates.

In view of such problems, the present invention provides a two-stroke internal combustion engine in which the injection timing of the fuel injector is changed according to operating conditions, and when executing learning control of the injected fuel, the atrium takes into account changes in the amount of fuel. It is an object of the present invention to provide a fuel injection control device that does not deteriorate its correction accuracy.

[Means to solve the problem]

According to the present invention, for the above purpose, there is provided a means for controlling the timing of fuel injection from a fuel injection valve according to the operating state, and a means for learning a value based on an output signal from an oxygen sensor provided in the exhaust system of the engine. A fuel injection control device for a two-stroke internal combustion engine, comprising: means for correcting a fuel injection amount; A fuel injection control device for a two-stroke internal combustion engine is provided, comprising means for correcting a fuel injection amount during an operating state corresponding to each learning region using each learning value learned in each learning region. .

[For production]

The learning area is subdivided into multiple parts according to the fuel injection timing set according to the driving condition, and during actual driving, when the injection timing corresponds to the set learning area, the learning value learned in this learning area is used. Since the fuel injection amount from the corresponding fuel injection valve is corrected, the fuel injection timing changes and even if the fuel amount in the atrium changes, the fuel injection amount can be accurately corrected.

〔Example〕

The present invention will be described below with reference to the drawings, taking as an example a two-stroke internal combustion engine in which the fuel injection timing is switched over two ranges.

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 l.

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 sent 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. Pressurized fuel from a fuel supply system (not shown) is supplied by a fuel injection valve 9 provided for each cylinder, and a scavenging pump IO is also provided in the intake passage 2 to supply fresh air to each cylinder. For example, a three-way catalyst 12 is provided in each exhaust passage 11 to purify the exhaust gas, and oxygen (02) is provided on the upstream side of the three-way catalyst 12 in the exhaust gas.
A sensor 13 is provided. This 02 sensor 13 determines whether the exhaust air-fuel ratio is lean or rich with respect to the stoichiometric air-fuel ratio according to the oxygen concentration in the exhaust gas, and supplies different output voltages to the input port a of the control circuit 6 accordingly. . still,
On the exhaust upstream side of this 0□ sensor 13, in order to prevent the blown air from staying around the 02 sensor 13,
For example, an air consumption means represented by the combustor 14 such as an oxidation catalyst or a thermal reactor may be provided.

The control circuit 6 is configured as a microcomputer, for example, and includes, in addition to the input ports a and Pt16b described above, an output port C that outputs a drive signal to the fuel injection valve 9 of each cylinder, a memory 6d, and a memory 6d. It is provided with a bus 6e for connection.It should be noted that the input port 1- of this control circuit 6 is
In addition to the output signal described above, 6a also includes a fuel injection I which will be described later.
Cooling water temperature T for correction amount used for TAU calculation
HW, intake air temperature TA, etc. are inputted via AD converters 5b, 5c, . . . .

The control circuit 6 takes in the parameters representative of the engine operating conditions described above, calculates the final fuel injection amount (time) TAU using the following formula, and transmits the final fuel injection amount (time) TAU from the output port C to the fuel injection valve 9, which will be described later. A drive signal is output at a predetermined injection timing.

TAU = -Q/NXKXFTRXFAFXFG [where, k: constant, Q: intake air flow rate detected by air flow meter, N: engine rotation speed detected by crank angle sensor, K: determined by cooling water temperature, intake air temperature, etc. FTR: fresh air capture 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 2 shows the main In the embodiment, an example of two fuel injection timings that can be set is illustrated, and injection timing A is:
The injection end timing (crank angle: θAE) is set slightly ahead of the overlap period between the engine's intake valve and exhaust valve, that is, the end of the scavenging period in a two-stroke internal combustion engine, and It is intended to improve the atomization of
The amount of fuel vented will be large.

On the other hand, injection timing B is such that the injection end timing (θ, 2) is set to approximate the closing timing of the intake valve, and the intention is to reduce the amount of fuel vented.

FIG. 3 shows an example of a map for selecting one of the above-mentioned two injection timings A and B based on the operating state of the engine. In this embodiment, engine load Q/N and engine rotational speed N are used as parameters for detecting the operating state, and the operating region in which learning control is performed, that is, the learning region, corresponds to two fuel injection timings. They are provided correspondingly. Regarding this map setting, the higher the load and rotation of the engine becomes in the - class, the more the fuel injection timing is set to the beginning of the scavenging period, and the amount of fuel blowout increases, but the fuel injection timing increases. It is preferable to improve the atomization of.

FIG. 4 shows a flowchart for calculating the amount of fuel injected from the fuel injection valve 9 in a two-stroke internal combustion engine with the injection timing set as described above. It is executed at every predetermined crank angle. First, in step 41, the intake air amount Q1, engine speed N, cooling water temperature THW, intake air temperature TA, etc. are read. Next, in step 42, a map calculation of the fresh air capture coefficient FTR is performed using the read Q and N. This fresh air capture coefficient FTR 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 Memo 'J6d stores FTR data for the illustrated Q/NN.

Next, in step 43, the cooling water temperature THW and the intake air temperature TA are
A correction coefficient K is calculated from the above, and in step 44, FAF calculated by another program is read in accordance with the current operating conditions.

In step 45 following step 44, it is determined whether the current operating state read in step 41 is in region 1 in the map shown in FIG. It is determined whether or not the vehicle is in an operating state with a large amount of fuel. Note that this map is stored in advance in the memo 'J6d of the control circuit 6. 3rd in step 45
If it is determined that the area is in region 1 (injection timing B) in the figure, the process proceeds to step 46 and the fuel injection amount (time) is adjusted to TAU=-Q/NX.
KXFTIxFAFxFG1 (FGl: area 1
In step 47, the flag F for area setting is set to 1, and this routine ends.

On the other hand, if it is determined in step 45 that the area is 0 (injection timing A), that is, if it is determined that the fuel vent is in an operating state where the amount of fuel is small, then in step 48 the fuel injection amount is TAU=
-Q/NXKXFTRXFAFXFGO (However, FG
O: learning value in area O), and in step 4, the area setting flag F is set to 0 and this routine ends.

Figure 5 shows the fuel injection amount TAU calculated as above.
shows a flowchart for executing fuel injection from the fuel injection valve 9, and like the previous routine, this routine is also executed at every predetermined crank angle.

First, in step 51, it is determined whether or not the area setting flag F explained in the previous routine is currently set (F=1). If F=1, the process advances to step 52, and the area setting flag F, which corresponds to injection timing B, is determined. The injection start timing θBS is calculated by subtracting the TAU (in this case, TAU is the fuel injection time) calculated in step 46 of the routine shown in FIG. Then, in the following step 53, the current crank angle θ is set to θ0. Determine whether it is equal to θ
−θ6. Only in this case, the process proceeds to step 54 and fuel is injected using the above TAU. Step 52 mentioned above
The processing from 54 to 54 is the same even in the case of No in step 51, that is, F=O, and in step 55 the injection timing A
Step 48 in Fig. 4 from the injection end timing θAE corresponding to
After subtracting the TAU of and calculating the injection start time θ, ,
In step 56, it is determined whether θ=θ, . . . If YES, in step 57, fuel injection corresponding to TAU is executed.

Figure 6 shows the control of the air-fuel ratio correction coefficient FAF and the learned value FG.
This is the control routine for O, FG 1. Note that this routine is a time interrupt routine, for example, 4 m5ec
Interrupts are processed every time. This routine will be described below with reference to FIG. 7, which shows an FAF change model corresponding to the 02 sensor output.

First, in step 61, it is determined whether the current operating conditions are in the air-fuel ratio feedback region. For example, feedback control is not normally executed when the cooling water temperature THW is low, when the 0□ sensor 13 is inactive, or when increasing the amount of water at a high temperature, so if it is determined that it is not in the feedback region (No
), the process proceeds to step 62 and FAF is fixed at 1.0.

On the other hand, if it is determined in step 61 that it is in the feedback region (Yes), the process proceeds to step 63, where the current output of the 02 sensor 13 is checked and it is determined whether or not a rich signal is being output. If the rich signal is currently being output (Yes), the process proceeds to step 64, where it is compared with the 02 sensor signal from the previous flow execution, and is compared to the 02 sensor signal from the previous flow execution.
It is determined whether the signal of the sensor 13 has been inverted, that is, whether there has been an inversion from a lean signal to a rich signal. If the result in step 64 is No, that is, the rich signal has been output continuously since the previous flow execution, this corresponds to, for example, progressing from point a to point i shown in the model in FIG. , a process is performed in which a predetermined value α is subtracted from FAF. On the other hand, if it is determined in step 64 that the 02 sensor signal has been inverted (corresponding to progress from point C to point d), the process proceeds to step 66, and the FAFA
V is calculated. This FAFAV is the current value FAF,
Value FA immediately before skip at the previous 02 sensor reversal
The average value with FO, i.e. (FAF + FAFO) /
2, which is for estimating the degree of deviation from the control center value of FAF. Then, in the subsequent step 67, the current FAF is replaced with FAFO as the value immediately before skipping in order to calculate FAFAV when the next 02 sensor signal is inverted, and the process proceeds to step 58, where the current FAF Therefore, a process of subtracting the lean side skip amount R3L is performed. The processing from step 64 to step 65 described above is the same when inverting a rich signal to a lean signal, and if the determination is No in step 63, the rich signal is inverted to a lean signal in step 69. It is determined whether or not there was. If it has not been reversed (NO), a process of adding a predetermined value β to FAF is executed in step 70, and if it has been reversed, steps 71 to 73 are followed by steps 66 to 68.
Similarly, FAFAv is calculated, and processing is performed to skip FAF 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 74 following step 68 or step 73, 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 75 and checks whether FAFAV is below the center lower limit value of control (for example, 0.998), that is, in the case of FAFAV.
It is determined whether FAV<0.998, and FAVAV
>0.998, the routine ends as is. That is, in this case, FAF is included within the predetermined control range and the learning values FGO and FGI are not updated. In step 74, FAPAv>1. For QO2, step 7
6, it is determined whether the flag F set by executing the arithmetic routine shown in FIG. 4 is 1 or not. Mo and F2l
When F=O, a predetermined correction value (0.002 in this embodiment) is added to the previously learned value FGI in step 77 to update it.
0.002 is added to GO. Further, in step 75, when FAFAV < 0.998, it is determined in step 79 whether F=1, as in step 76, and when F=1, 0.002 is subtracted from FGI in step 80, F
If =0, 0.002 is subtracted from FGO in step 81, and this routine ends.

In this way, in the learning routine described above, the learning value F
When updating GI and FGO, when fuel is injected at injection timing B shown in Figure 2, that is, when the fuel vent is in an operating state with a large amount of fuel, only FGI is updated, and the injection timing is When fuel is being injected with A, that is, when the amount of fuel vented is low, only FGO is updated.

These learned values FGI and FGO are based on changes in atmospheric density and injector 9.
Changes due to changes in fuel injection amount due to changes over time, etc.
It compensates for atmospheric density, changes in the injection valve over time, etc. Also,
Since these learned values FGI and FGO are updated by the output signal of the 02 sensor 13, they are also influenced by the amount of fuel flowing through the exhaust system.

Therefore, even if the same learned value is updated under operating conditions in which the amount of fuel flowing through the exhaust system is different, that is, the fuel injection timing is different, it is not possible to accurately compensate for atmospheric density, changes in the injection valve over time, etc. Furthermore, if the fuel injection timing when these learning values FGI and FGO are updated and the fuel injection timing when correcting the fuel injection amount using these learning values FGI and FGO are different, the accuracy of correcting the fuel injection amount will decrease. do. However, in this embodiment, the amount of fuel venting is different under different operating conditions.
In other words, the learning value FGI is set for each learning area where the fuel injection timing is different.
Learn (update) FGQ, and each learned value FGI, F
The fuel injection timing during GO learning and the fuel injection timing during fuel correction match. Therefore, the accuracy of correcting the fuel injection amount based on the learned value is improved without being affected by changes in the amount of fuel flowing through the exhaust system.

Incidentally, it is preferable that the boundary line between region 1 and region 0 in the map shown in FIG. 3 actually have hysteresis to prevent the hunting phenomenon of the injection timing near the injection timing switching point.

The present invention has been described above using as an example a two-stroke internal combustion engine in which the fuel injection timing is varied over two stages depending on the operating condition, but the present invention is not limited to the above-mentioned embodiments, and the fuel injection timing can be varied in multiple stages. It is also applicable to engines that are variable stepwise or linearly within a certain crank angle range. In this case, the learning area to be set is divided into a plurality of areas A, B, and C according to the injection timing (injection end timing or injection start timing), for example, as shown in FIG. It is preferable to select which region to learn based on a combination of other expressed parameters (for example, engine rotational speed N) and the set injection timing. Therefore, as a calculation program for the fuel injection amount in this case, the above-mentioned fourth
Following step 35 of the flowchart shown in the figure, the operating conditions (
A process of calculating the fuel injection timing from Q/N, N, etc.) and a process of searching for which area the calculated fuel injection timing is included in, for example, as shown in FIG. 8, are executed.

If it is in either B or C, the learning value FGA, FG corresponding to the learning area A, B or C is determined in the following step.
TAtJ will be calculated using B or FCC. Also regarding the learning value control routine in this case,
Corresponding to steps 76 to 81 in the flowchart of FIG. 6 mentioned above, the learning value FG of the learning area according to the current injection timing is
Processing to update A, FGB, and FGC will be executed.

〔effect〕

As explained above, according to the present invention, in a two-stroke internal combustion engine in which the fuel injection timing is variable depending on the operating state, the atrium is different in the operating range where the fuel injection timing is different, that is, the atrium is different in the operating range where the fuel amount is different. Having independent learning values improves the accuracy of correcting the injection amount in the learning area.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a two-stroke internal combustion engine equipped with a fuel injection control device according to the present invention; FIG. 2 shows a scavenging period of the engine shown in FIG. 1 and two fuel injection timings that can be set in the engine. Figure; Figure 3 shows a map for determining injection timing based on operating conditions and the corresponding learning area; Figure 4 is a flowchart for calculating the injection amount from the fuel injection valve; Figure 5 is a flowchart for executing fuel injection from the fuel injection valve; FIG. 6 is a flowchart for controlling the air-fuel ratio correction coefficient and learning value; FIG. 7 is a diagram showing a change model of the air-fuel ratio correction coefficient corresponding to the 02 sensor output signal. ; FIG. 8 is a map diagram for setting a learning area different from that in FIG. 3 as another example. ■...Engine body, 6...Control circuit, 9...
-Fuel injection valve, 13...Oxygen (02) sensor.

Claims (1)

[Claims] 1. Means for controlling the timing of fuel injection from a fuel injection valve according to operating conditions, and fuel injection by learning a value based on an output signal from an oxygen sensor provided in the exhaust system of the engine. In a fuel injection control device for a two-stroke internal combustion engine, the fuel injection control device for a two-stroke internal combustion engine includes means for setting a plurality of learning areas according to the fuel injection timing of the fuel injector; A fuel injection control device for a two-stroke internal combustion engine, comprising means for correcting a fuel injection amount during an operating state corresponding to each learning region using learned values.