JPH03242463A - Ignition control device of lean burning internal combustion engine - Google Patents

Abstract

PURPOSE:To set ignition timing optimum in an advance timing side so as to always generate maximum torque by using an advance timing value, map- calculated from an engine speed and a throttle opening, to control ignition. CONSTITUTION:In this ignition system, air-fuel ratio of a mixture supplied to an internal combustion engine is controlled in a region leaner than theoretical air-fuel ratio by using a correction coefficient KAFTA map-calculated from a relation between an engine speed NE and a throttle opening TA. In this ignition system, ignition control is performed by using an advance timing value calculated from a relation between the engine speed NE and the throttle opening TA. Since the advance timing value of ignition timing is map-calculated with the throttle opening TA serving as a parameter in such a way as mentioned, maximum torque can be realized even in an accelerator high opening control region, where the air-fuel ratio is decreased in accordance with increase of the throttle opening TA, that is, in a relation where throttle opening TA > fixed value x deg.. This advance timing value is provided with a quality where the value is decreased according to increase of the throttle opening Ta accordingly decrease of the air-fuel ratio when the speed NE is fixed.

Description

[Detailed Description of the Invention] [Summary] Regarding an ignition control device for a lean-burn internal combustion engine that improves fuel efficiency, the present invention aims to optimize the ignition advance angle in conjunction with air-fuel ratio correction when the accelerator opening is high. In an ignition control device for a lean-burn internal combustion engine that controls the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine in a range leaner than the stoichiometric air-fuel ratio using a correction coefficient map calculated from the relationship between engine speed and throttle opening. , the ignition control is performed using an advance angle value that is map-calculated from the relationship between the rotational speed and the throttle opening.

[Industrial application field]

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

Lean burn systems, which make the air-fuel mixture burnt by the internal combustion engine leaner than the stoichiometric air-fuel ratio, allow the vehicle to travel at the desired speed while saving fuel consumption.

Ignition control optimally sets the ignition timing to the advanced side of top dead center to generate maximum torque (MBT).

[Prior art] In a conventional lean burn system, the air-fuel ratio is generally corrected toward the lean side using a correction coefficient KAF that is map-calculated from the rotational speed NE and negative pressure PM, while a map is calculated separately using the same parameters. Ignition control is performed using the advance angle value. (
(Refer to Japanese Patent Application Laid-open No. 60-237166.) However, when the throttle opening is high, there is no PM change (therefore, the torque does not increase much with KAF.

In other words, when the throttle opening TA is changed from fully closed to IDL (idle 5W) ON - constant value X - VL (power 5W) ON = fully open as shown in Figure 5, when TA < xo, the negative pressure PM Since TAG changes correspondingly, the change in torque also follows, but when TA>Xo, the negative pressure PM does not change much, so no change in torque can be expected (see FIG. 2 for negative pressure PM). In this state, if the driver has the intention of accelerating, he will step on the accelerator further, and eventually the VL (power SW)
) turns ON. When VL is turned ON, the amount of fuel is forcibly increased, so the torque increases, but this change is so sudden that a shock occurs.

In order to improve this point, the present inventors have developed a throttle opening T
Air-fuel ratio correction coefficient K map calculated from A and rotation speed NE
APTA was proposed separately.

Since the correction coefficient KAPTA increases as TA increases, if it is used, the torque will increase even when TA>x as shown in FIG. 5, and no shock will occur when VL is turned on.

[Problem to be solved by the invention]

By the way, when using KAFTA which is map-calculated with NE and TA, as shown in Fig. 5 and Fig. 2, the air-fuel ratio A/F starts to decrease when TA>x', so as shown in Fig. 3, MBT
also changes. However, when TA>x, PM
does not change, the conventional advance angle value calculated by map using NE and PM remains constant, and as a result, MBT cannot be realized.

The present invention attempts to improve this point by introducing an advance angle value ATA which is map-calculated using the same parameters as APTA.

[Means to solve the problem]

The present invention provides a lean-burn internal combustion engine that controls the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine in a region leaner than the stoichiometric air-fuel ratio using a correction coefficient map calculated from the relationship between engine speed and throttle opening. The ignition control device is characterized in that ignition is controlled using an advance angle value that is map-calculated from the relationship between the rotational speed and the throttle opening.

[Operation] The advance angle value ATA of the present invention is calculated using a map using the throttle opening degree TA as a parameter. Therefore, MBT can be achieved even in the high accelerator opening control region (TA >x'') where the air-fuel ratio decreases as the throttle opening TA increases. The value decreases as the air-fuel ratio increases and therefore the air-fuel ratio decreases.

〔Example〕

Figure 4 shows a lean burn system with electronic fuel injection, in which air passes through the throttle valve and flows into the engine through the intake pipe. At this time, the fuel injected from the injector (INJ) is atomized and mixed into the incoming air, forming an air-fuel mixture with a desired air-fuel ratio.

The air-fuel ratio of this 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 to control engine cooling water temperature obtained from a water temperature sensor, negative pressure PM in the intake pipe obtained from a pressure sensor, slot opening TA obtained from a throttle sensor, and E/G (engine) rotation. Injection control, ignition control, no-load rotation control, etc. are performed by inputting the number NE, starter status, vehicle speed, etc.

Injection control is control of the valve opening time of an injector (INJ), and 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 explaining the present invention in detail, control using KAFTA proposed by the above-mentioned inventors will be explained first. FIGS. 6(a) and 6(b) are flowcharts showing two embodiments. FIG. 5A shows a first embodiment, in which step Sl is a process of calculating a conventional correction coefficient KAF using the rotational speed NE and negative pressure PM as parameters. On the other hand, the next step S2 is a process of calculating a correction coefficient KAPTA using the rotational speed NB and throttle opening TA as parameters. After the two types of correction coefficients KAF and KAFTA are calculated in this way, step S
3, the two are compared, and step S4. In S5, the larger value is stored in the control memory KAFM.

An example map of KAF and KAFTA is shown below. However, K
Regarding AF, the values are those during feedback control.

Table 1 (KAF map) Table 2 (KAFTA map) The fuel injection amount is calculated using the formula below.

Injection amount - Basic injection amount * KAFM *Other correction coefficients The above formula 〇 KAFM is KAFM = max in the example of Fig. 6 (a)
(KAF, KAFTA), but the second
As in the embodiment, it is also possible to first determine that TA>x' in step S6, and then perform only one of the KAF calculation and KAFTA calculation in step Sl or S2.

Here, the reason for using the larger of both values will be described. Regarding the correction coefficient KAF, it is set so that the air-fuel ratio at that time is near the line limit, and feedback control is executed so that the air-fuel ratio is maintained at that air-fuel ratio. However, when the control becomes open loop, it becomes difficult to control with such an air-fuel ratio, so the correction coefficient KAF during open loop is set to a larger value than the value during feedback. On the other hand, the throttle opening is
Since there is a margin between the air-fuel ratio set by the correction coefficient KAPTA and the lean limit in the range of .degree. or more, the correction coefficient KAPTA has the same value during feedback and open loop.

In this way, the correction coefficient KAF changes variously depending on the driving state. Therefore, the magnitude relationship between the correction coefficient KAF and the correction coefficient KAFTA when the throttle opening reaches Xo also changes depending on the driving condition, so simply switching the correction coefficient when the throttle opening reaches Xo will cause a difference in air-fuel ratio. There is a problem that occurs and the drivability worsens. In order to prevent this, this embodiment employs the above-mentioned configuration. In this example, step S6 is introduced in place of step S3 in FIG.
Execute step 4 and exit. However, as an improved example of open loop Fig. 6 (a) and (b), KAF and KAF
TA (7) A certain hysteresis may be provided to stabilize switching. In addition, since the constant value X° of the throttle opening TA varies depending on the rotation speed NE, TA〈X''
', it is recommended to set it so that KAFTA<KAF.

The correction coefficient KAPTA is calculated based on the throttle opening T as shown in Fig. 7.
Since it increases as A increases, the torque (K
AFTA) can also be increased when TA>x'. Furthermore, since the torque has sufficiently increased just before VL ON, almost no shock occurs even when VL is turned ON.

When TA>x', the air-fuel ratio (KAFTA) decreases in inverse proportion to the throttle opening TA, and the stoichiometric air-fuel ratio (14, 5)
approach. Then, when VL is turned on, the air-fuel ratio is 12.
It becomes a rich state of about 5 and becomes a power mode with large torque.

FIG. 1 is a flowchart showing an embodiment of the present invention, and step S1 is determination of the accelerator high opening control determination flag XK. This flag XK is a correction coefficient KAPT in air-fuel ratio control.
It is set to l when A is used, and to O otherwise (when correction coefficient KAF is used).

When XK=1, the TA corresponding lead angle value ATA is set in step S2.
Calculate the map. The table below is an example of an ATA map.
is rpra, TA is deg, and ATA is “CA.”

Table 3 (ATA map) is large, so we focused on the fact that the advance angle that knocks occur at low altitudes and MBT cannot be obtained can be realized at high altitudes, and ATAPA is a correction value added to ATA. This ATAPA is map-calculated from the atmospheric pressure PA and the rotational speed NE, and increases as PA decreases as shown in the table below.

Table 4 (Map of ATAPA) The next step S3 is map calculation of the atmospheric pressure correction value ATAPA. Atmospheric pressure correction has a slight margin at high altitudes (low atmospheric pressure) compared to low altitudes (high atmospheric pressure).However, PA is 73
If it exceeds 0mmHg, there is a risk of knocking even with a slight advance angle under high load, so set ATAPA=O in this region. ATA and ATA map calculated in this way
PA is added in step S4 and the sum is stored in memory in step S5.

On the other hand, if it is determined in step S1 that XK=O, a normal PM corresponding lead angle value ^BSE is map-calculated in step S6. Since this ABSE is an advance angle value using negative pressure PM and rotational speed NE as parameters, when the air-fuel ratio correction coefficient is KAF, ABSE is stored in the memory and used in step S5.

〔Effect of the invention〕

As described above, according to the present invention, when the air-fuel ratio of the lean burn system is determined by the correction coefficient KAPTA using the throttle opening TA as a parameter, the ignition advance value AT
Since A is also calculated using the throttle opening TA as a parameter, there is an advantage that MBT can always be achieved.

[Brief explanation of drawings]

Fig. 1 is a flowchart of an embodiment of the present invention, Fig. 2 is a characteristic diagram of air-fuel ratio dependence on throttle opening, Fig. 3 is a characteristic diagram of air-fuel ratio dependence of MBT, Fig. 4 is a diagram showing constituent countries of the lean burn system, 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 the correction coefficient of the present invention. Applicant Toyota Motor Corporation

Claims (1)

[Claims] 1. Engine speed (NE) and throttle opening (TA)
In an ignition control system for a lean-burn internal combustion engine, which controls the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine in a region leaner than the stoichiometric air-fuel ratio using a correction coefficient (KAFTA) map-calculated from the relationship between rotation speed ( An ignition control device for a lean-burn internal combustion engine, characterized in that ignition control is performed using an advance angle value (ATA) that is map-calculated from the relationship between NE) and throttle opening (TA).