JP2887350B2 - Fuel injection control device for lean-burn internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a fuel injection control device for a lean-burn internal combustion engine that improves fuel efficiency, with the aim of improving drivability, in which the air-fuel ratio of the mixture supplied to the internal combustion engine is leaner than the stoichiometric air-fuel ratio. In a fuel injection control device for a lean-burn internal combustion engine controlled in a specific region, in a region where the throttle opening exceeds a predetermined value, fuel injection is performed using a correction coefficient that is map-calculated from the relationship between the engine speed and the throttle opening. It is configured to correct the amount.

[Industrial applications]

The present invention relates to a fuel injection control device for a lean-burn internal combustion engine that improves fuel efficiency.

Lean burn systems that make the air-fuel mixture burned in an internal combustion engine leaner than the stoichiometric air-fuel ratio
Enables driving at the desired speed while saving fuel consumption. The fuel injection control device determines the actual fuel injection amount by multiplying the basic injection amount by various correction coefficients. In a lean burn system, the fuel injection amount is controlled using a correction coefficient that makes the air-fuel ratio lean.

[Conventional technology]

An electronic fuel injection device controls the amount of fuel injected from an injector by the length of an intermittent fuel injection time. At this time, in the lean combustion system, the air-fuel ratio is controlled on the lean side using a lean sensor (lean mixture sensor) installed in the exhaust pipe to improve fuel efficiency. (JP 62-19994
[Problem to be solved by the invention] The air-fuel ratio of the conventional lean burn system is determined by the rotational speed NE and the negative pressure.
The correction is performed using the correction coefficient KAF calculated from the PM. This correction coefficient KAF is set within a range of 1.0 (the stoichiometric air-fuel ratio) or less when a multiplication term is added to the basic injection amount (time). Then, the correction coefficient FAF for feedback control is adjusted so that the lean sensor output (current) matches the target lean sensor output obtained from the KAF at that time to increase or decrease the fuel.

By the way, as shown in FIG. 5, the throttle opening TA is changed from fully closed to IDL (idle SW) ON → constant value x ° → VL (power SW) O
When changing from N to fully open, the negative pressure PM is TA
Changes in response to the
If> x °, the negative pressure PM does not change much, so that a change in torque cannot be expected. In this state, if the driver intends to accelerate, the accelerator is further depressed, and the VL (power SW) will be turned on soon. When VL is turned on, the fuel will be forcibly increased and the torque will increase. Therefore, a shock occurs.

Such irregularities in the torque change result from the fact that the negative pressure PM is used as a parameter of the correction coefficient KAF. That is,
This is because when TA> x °, the PM does not transmit a change in TA (acceleration will) to the control system.

The present invention uses the throttle opening degree as a parameter for air-fuel ratio correction.
The introduction of TA aims to improve the drivability of the lean burn system.

[Means for solving the problem]

The present invention relates to a fuel injection control device for a lean-burn internal combustion engine that controls an air-fuel ratio of an air-fuel mixture supplied to an internal combustion engine in a region leaner than a stoichiometric air-fuel ratio. The fuel injection amount is corrected using a correction coefficient that is calculated from the relationship between the engine speed and the intake pipe negative pressure, and in the region where the throttle opening exceeds a predetermined value, a map is calculated from the relationship between the engine speed and the throttle opening. The fuel injection amount is corrected by using a correction coefficient, and the fuel injection control device includes: a correction coefficient that is map-calculated from a relationship between an engine speed and a negative pressure in an intake pipe; The correction coefficient is compared with a correction coefficient that is calculated from the relationship between the number and the throttle opening, and the fuel injection amount is corrected using the larger correction coefficient.

[Action]

FIG. 1 is a characteristic diagram of the correction coefficient KAFTA of the present invention. This characteristic curve is drawn with a plurality of parameters using the engine speed NE as a parameter.
Has the property of increasing with the increase of If a plurality of such characteristic curves are collected by experiment and mapped, an optimal KAFTA can be obtained from NE and TA at each time point.

This KAFTA can be used unconditionally in place of the conventional KAF.However, use KAF and KAFTA separately at TA = x °, or always read KAF and KAFTA and select the larger one to use. You may make it. Either way, KAFT
When A is used, the fuel injection amount is corrected over almost the entire throttle opening TA, so that the change in torque becomes smooth and drivability is improved.

〔Example〕

FIG. 4 shows a lean burn system of an electronic fuel injection system.
The air that has passed through the throttle valve flows into the engine through the intake pipe. At this time, the fuel ejected from the injector (INJ) is atomized and mixed into the inflowing air to form a mixture having a desired air-fuel ratio. The air-fuel ratio of the air-fuel mixture is detected by a lean sensor (lean mixture sensor) installed in the exhaust pipe. The electronic control unit (ECU) uses a microcomputer, the engine cooling water temperature obtained from the water temperature sensor, the intake pipe negative pressure PM obtained from the pressure sensor, the slot opening TA obtained from the throttle sensor, and the E / G (engine) rotation. Injection control, ignition control, no-load rotation control, etc. are performed by inputting several NEs, starter status, vehicle speed, etc. The injection control is control of the valve opening time of the injector (INJ), and the ignition control is control of the ignition timing of a spark plug (not shown) through an igniter, an ignition coil (IG), and a distributor.

FIGS. 2A and 2B are flow charts showing two embodiments of the present invention. FIG. 7A shows a first embodiment, in which step S1 is a process for calculating a map of a conventional correction coefficient KAF using the rotational speed NE and the negative pressure PM as parameters. On the other hand, the next step S2 is a process of calculating a map of the correction coefficient KAFTA of the present invention using the rotation speed NE and the throttle opening TA as parameters. Thus, two kinds of correction coefficients KAF,
When KAFTA is calculated, the two are compared in step S3, and the larger value is stored in the control memory KAFM in steps S4 and S5.

The following is an example of a map for KAF and KAFTA. However, KAF is a value at the time of feedback control.

The calculation of the fuel injection amount is based on the following equation.

Injection amount = Basic injection amount * KAFM * Other correction coefficients KAFM in the above equation is KAFM = max {KAF, KAFTA} in the example of FIG. 2 (a), but the second embodiment of FIG. As described in the above, it is also possible to make only the KAF calculation or the KAFTA calculation in step S1 or S2 after judging that TA> x ° in the first step S6. Here, the reason for using the larger one of the two values will be described. The correction coefficient KAF is set so that the air-fuel ratio is near the lean limit at that time,
The feedback control is performed so that the air-fuel ratio is obtained. However, when the control is in an open loop, it is difficult to perform control with such an air-fuel ratio. Therefore, the correction coefficient KAF in the open loop is set to a value larger than the value in the feedback. On the other hand, in the region where the throttle opening is x ° or more, there is a margin between the air-fuel ratio set by the correction coefficient KAFTA and the lean limit, so the correction coefficient KAFTA has the same value in feedback and in open loop. It has become.

Thus, the correction coefficient KAF changes variously depending on the operation state. Therefore, since the magnitude relationship between the correction coefficient KAF and the correction coefficient KAFTA at the throttle opening of x ° also changes depending on the operating state, simply switching the correction coefficient when the throttle opening reaches X ° does not mean that the air-fuel ratio is high. There is a problem that a step occurs and drivability deteriorates. In order to prevent this, the present embodiment has the above-described configuration. In this example, step S6 is introduced instead of step S3 in FIG.
After step S2, step S4 is executed and the processing ends. However, at the time of open loop, KAF becomes KAF + α.

As an improvement of FIGS. 2 (a) and 2 (b), a constant hysteresis may be provided to stabilize the switching between KAF and KAFTA. The constant value x ° of the throttle opening TA is the number of rotations.
Since it differs depending on the NE, it is preferable to set KAFTA <KAF so that TA <x °.

FIG. 3 is a characteristic diagram of the air-fuel ratio and the torque, wherein (KAFTA) is a characteristic curve of the present invention using the correction coefficient KAFTA, and (KAF) is a conventional characteristic curve using the correction coefficient KAF.

Since the correction coefficient KAFTA of the present invention increases as the throttle opening TA increases as shown in FIG. 1, the torque (KAFTA) in FIG. 3 can be increased even when TA> x °. And V
Since the torque has risen enough just before L ON, VL
There is almost no shock even when turned ON.

When TA> x °, the air-fuel ratio (KAFTA) is the throttle opening T
Decreases in inverse proportion to A and approaches the stoichiometric air-fuel ratio (14.5),
Then, when VL is turned on, the air-fuel ratio becomes a rich state of about 12.5, and the power mode becomes a large torque mode.

〔The invention's effect〕

As described above, according to the present invention, the torque can be changed according to the throttle opening even in the lean burn system, and the shock at the time of shifting to the power mode can be reduced, so that the drivability can be improved as a whole. There are advantages.

[Brief description of the drawings]

 FIG. 1 is a characteristic diagram of a correction coefficient of the present invention, FIG. 2 is a flowchart showing an embodiment of the present invention, FIG. 3 is an operational characteristic diagram of the present invention, FIG. The figure is a conventional operating characteristic diagram.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Keisuke Tsukamoto 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Toshio Takaoka 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation ( 72) Inventor Takao Fukuma 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (56) References JP-A-61-167134 (JP, A) JP-A-58-59328 (JP, A) 3-944 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) F02D 41/04 330 F02D 41/14 310

Claims (4)

(57) [Claims] In a fuel injection control apparatus for a lean-burn internal combustion engine for controlling an air-fuel ratio of an air-fuel mixture supplied to an internal combustion engine in a region leaner than a stoichiometric air-fuel ratio, a throttle opening (TA) is set to a predetermined value (x °). ) In the following areas, the fuel injection amount is corrected using a correction coefficient (KAF) that is calculated from the relationship between the engine speed (NE) and the intake pipe negative pressure (PM), and the throttle opening (TA) is fixed. Value (x °)
In the region beyond the range, the correction coefficient (KAFT) calculated from the relationship between the engine speed (NE) and the throttle opening (TA) is calculated.
A fuel injection control device for a lean-burn internal combustion engine, wherein the fuel injection amount is corrected using A). 2. A fuel injection control apparatus for a lean-burn internal combustion engine for controlling an air-fuel ratio of an air-fuel mixture supplied to an internal combustion engine in a region leaner than a stoichiometric air-fuel ratio. PM) is compared with the correction coefficient (KAF) that is calculated from the relationship between the engine speed (NE) and the throttle opening (TA). A fuel injection control device for a lean-burn internal combustion engine, wherein the fuel injection amount is corrected by using a fuel injection control method. 3. An engine speed (NE) and a negative pressure (P) in an intake pipe.
There is a certain hysteresis in switching between the correction coefficient (KAF) calculated from the relationship of M) and the correction factor (KAFTA) mapped from the relationship between the engine speed (NE) and the throttle opening (TA). 3. The method according to claim 1, wherein
A fuel injection control device for a lean-burn internal combustion engine according to claim 1. 4. In a region where the throttle opening (TA) is equal to or less than a predetermined value (x °), a correction coefficient (KAFTA) that is map-calculated from the relationship between the engine speed (NE) and the throttle opening (TA).
The lean combustion is set to be smaller than a correction coefficient (KAF) that is map-calculated from the relationship between the engine speed (NE) and the intake pipe negative pressure (PM). A fuel injection control device for an internal combustion engine.