JP3169593B2 - Ignition control system for lean-burn internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to an ignition control device for a lean-burn internal combustion engine that improves fuel efficiency, with the object of optimizing the ignition advance angle in accordance with air-fuel ratio correction at the time of high accelerator opening. In an ignition control device for a lean-burn internal combustion engine, the air-fuel ratio of the mixture supplied to the internal combustion engine is controlled in a region leaner than the stoichiometric air-fuel ratio by using a correction coefficient that is calculated from the relationship between the engine speed and the throttle opening. The ignition control is performed by using an advance value which is calculated from the relationship between the rotational speed and the throttle opening degree.

[Industrial applications]

The present invention relates to an ignition 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.

In the ignition control, a maximum torque (MBT) can be generated by optimally setting the ignition timing on the advance side from the top dead center.

[Conventional technology]

In conventional lean burn systems, generally, the rotational speed NE and the negative pressure
While the air-fuel ratio is corrected to the lean side using a correction coefficient KAF that is map-calculated from PM, ignition control is performed using an advance value that is separately calculated with the same parameters. (Refer to Japanese Patent Application Laid-Open No. 60-237166) However, when the throttle opening is high, there is no change in PM.
With KAF, the torque does not increase much. That is, as shown in FIG. 5, the throttle opening TA is changed from fully closed to IDL (idle SW) O
When N → constant value x 値 → VL (power SW) ON → fully open, when TA <x ゜, the negative pressure PM changes corresponding to TA, so the torque changes, but TA> x Negative pressure PM when ゜
Therefore, the change in torque cannot be expected because the change is not so large (see FIG. 2 for the negative pressure PM). In this state, if the driver has an intention to accelerate, the accelerator pedal is further depressed, so that VL (power SW) is turned on. When VL ON, the fuel is forcibly increased and the torque increases. However, a shock occurs in which the change is sharp.

In order to improve this point, the present inventors have set the throttle opening
Air-fuel ratio correction coefficient KAFT calculated from TA and rotational speed NE
A was separately proposed.

Since the correction coefficient KAFTA increases with an increase in TA, using this will increase the torque even if TA> x ゜ as shown in FIG. 5, and will not cause a shock when VL is turned on.

[Problems to be solved by the invention]

By the way, using KAFTA calculated by NE and TA, as shown in FIGS. 5 and 2, TA> x ゜ and the air-fuel ratio A / F
Since MBT starts to decrease, the MBT also changes as shown in FIG. However, when TA> x ゜, the PM does not change as shown in FIG. 2, so that the conventional advance value that is calculated by NE and PM is maintained at a constant value. As a result, MBT cannot be realized.

The present invention seeks to improve this point by introducing an advance value ATA that is map-calculated with the same parameters as KAFTA.

[Means for Solving the Problems] According to the present invention, an air-fuel ratio of 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 is provided. When the first air-fuel ratio control is performed using the first air-fuel ratio correction coefficient determined by the engine speed and the intake negative pressure so that the engine speed substantially reaches the lean limit, the engine speed is set so that the ignition timing becomes the target ignition timing. The first ignition timing control is performed using the first ignition timing correction coefficient determined by the number and the intake negative pressure, and the first ignition timing is determined by the engine speed and the throttle opening so that the air-fuel ratio decreases as the throttle opening increases. When the second air-fuel ratio control is performed using the air-fuel ratio correction coefficient of 2, the second ignition timing correction determined by the engine speed and the throttle opening so that the ignition timing becomes the target ignition timing. The second ignition timing control is performed using the coefficient, and the first ignition timing control is performed without using the third ignition timing correction coefficient determined by the engine speed and the atmospheric pressure. The second ignition timing control is performed using the coefficient.

[Operation] Regardless of whether the first air-fuel ratio control is performed or the second air-fuel ratio control is performed, the ignition timing is optimally maintained regardless of the atmospheric pressure.

〔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 throttle opening TA obtained from the throttle sensor, and the E / G (engine) rotation. Injection control using several NEs, starter status, vehicle speed, etc. as inputs
It performs ignition control, no-load rotation control, and the like.

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 IG (ignition) coil, and a distributor.

Before describing the embodiment of the present invention, control using KAFTA proposed by the present inventors will be described first. FIGS. 6A and 6B are flowcharts showing two embodiments. 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 for calculating a map of the correction coefficient KAFTA using the rotation speed NE and the throttle opening TA as parameters. When the two kinds of correction coefficients KAF and KAFTA are calculated in this way, the two are compared in step S3, and steps S4 and S5
Stores the larger value in the control memory KAFM.

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. 6 (a), but the second embodiment of FIG. As described above, after determining that TA> x ゜ in the first step S6, only one of the KAF calculation and the KAFTA calculation may be performed in step S1 or S2. 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 executed so as to achieve the air-fuel ratio. 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 equal to or greater than x ゜, there is a margin between the air-fuel ratio set by the correction coefficient KAFTA and the lean limit. 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 when the throttle opening is x ゜ changes depending on the operating state, simply switching the correction coefficient when the throttle opening becomes x ゜ requires the air-fuel ratio. There is a problem that a step occurs and drivability deteriorates. In order to prevent this, the example shown in FIG. 6A has the above-described configuration. In the example shown in FIG. 6 (b), since step S6 is introduced instead of step S3 in FIG. 6 (a), step S5 is executed after step S1, and step S4 is executed after step S2. To end. However, at the time of open loop, KAF becomes KAF + α.

As an improvement of FIGS. 6 (a) and 6 (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 revolutions
Since it differs depending on the NE, it is preferable to set KAFTA <KAF when TA <x ゜.

Since the correction coefficient KAFTA increases as the throttle opening TA increases as shown in FIG. 7, the torque (KAFTA) shown in FIG.
A) can be increased even when TF> x ゜. And VL ON
Since the torque has risen enough just before
Almost no shock occurs.

When TA> x ゜, the air-fuel ratio (KAFTA) is the throttle opening T
It decreases inversely with 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.

FIG. 1 is a flowchart showing an embodiment of the present invention, and step S1 is a determination of an accelerator high opening degree control determination flag XK. The flag XK is set to 1 when the correction coefficient KAFTA is used in the air-fuel ratio control, and is set to 0 otherwise (when the correction coefficient KAF is used).

If XK = 1, a TA-advance value ATA is map-calculated in step S2. The following table is an example of the ATA map. NE is rpm, TA is
deg and ATA are ゜ CA.

The next step S3 is a map calculation of the atmospheric pressure correction value ATAPA. Atmospheric pressure correction can be realized at high altitudes even at advanced altitudes where knock occurs at low altitudes and MBT cannot be obtained at low altitudes because knock margin is larger than at low altitudes (atmospheric pressure is high) at low altitudes Paying attention, ATAPA is a correction value to be added to ATA. This ATAPA has an atmospheric pressure PA and a rotational speed NE
From the map and increases as PA decreases, as shown in the table below.

However, if PA is more than 730mmHg, there is a risk of knocking even at a slight advance angle under high load.
Set to 0. ATA and ATAPA calculated in this way
Are added in step S4, and the sum is stored in the memory in step S5.

On the other hand, if XK = 0 is determined in step S1, step S6
Calculates the normal PM-advanced lead angle value ABSE by map calculation. This ABSE
Is an advance value using the negative pressure PM and the rotation speed NE as parameters, and when the air-fuel ratio correction coefficient is KAF, the ABSE is stored in the memory in step S5 and used.

[Effects of the Invention] As described above, according to the present invention, regardless of whether the first air-fuel ratio control or the second air-fuel ratio control is performed, and regardless of the atmospheric pressure, the ignition timing Can be optimally maintained.

[Brief description of the drawings]

 FIG. 1 is a flowchart of an embodiment of the present invention, FIG. 2 is a characteristic diagram of an air-fuel ratio depending on a throttle opening, FIG. 3 is a characteristic diagram of an MBT air-fuel ratio, FIG. FIG. 5 is a control characteristic diagram of lean burn, FIG. 6 is a flowchart of an embodiment of the present invention, and FIG. 7 is a characteristic diagram of a correction coefficient of the present invention.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hirofumi Yamazaki 1-2-2, Goshodori, Hyogo-ku, Kobe City, Hyogo Prefecture Inside Fujitsu Ten Co., Ltd. (72) Inventor Keisuke Tsukamoto 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor (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) Reference Document JP-A-56-96132 (JP, A) JP-A-61-167134 (JP, A) JP-A-63-124865 (JP, A)

Claims (1)

(57) [Claims] An ignition 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. When the first air-fuel ratio control is performed using the first air-fuel ratio correction coefficient determined by the engine speed and the intake negative pressure, the first air-fuel ratio control determined by the engine speed and the intake negative pressure so that the ignition timing becomes the target ignition timing. The first ignition timing control is performed using the ignition timing correction coefficient, and the second ignition timing control is performed using the second air-fuel ratio correction coefficient determined by the engine speed and the throttle opening so that the air-fuel ratio decreases as the throttle opening increases. When the air-fuel ratio control of 2 is performed, the second ignition timing correction coefficient determined by the engine speed and the throttle opening is used so that the ignition timing becomes the target ignition timing.
The first ignition timing control is performed without using the third ignition timing correction coefficient determined by the engine speed and the atmospheric pressure, and the second ignition timing control is performed using the third ignition timing correction coefficient. An ignition control device for a lean-burn internal combustion engine, which controls the ignition timing of the engine.