JPH0842375A - Controller of multi-cylinder internal combustion engine - Google Patents

Abstract

PURPOSE:To improve emission, so as to improve fuel consumption by switching the fuel injection timing and the ignition timing by means of a cylinder having the rich air-fuel ratio and a cylinder having the lean air-fuel ratio when the air fuel ratios of respective cylinders are sequentially switched in switching of the target air-fuel ratio. CONSTITUTION:While an engine E is operated, in an electronic control unit U, the target air-fuel ratio is map-retrieved on the basis of the detected signals of a throttle opening sensor 5 and an engine speed sensor 7. The target air-fuel ratio is set to stoichiometric, namely, the theoretical air-fuel ratio in the normal operating range of the engine E, and the target air-fuel ratio is set to the lean side in the specific operating range like in decelerating of the engine E to improve fuel consumption. In switching of the air-fuel ratio, the fuel injection timing is set during the exhaust stroke of the cylinder having the rich air-fuel ratio and during the intake stroke of the cylinder having the lean air-fuel ratio, while, the ignition timing is delay-controlled for the rich cylinder and advance- controlled for the lean cylinder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention increases the air-fuel ratio of each cylinder by increasing or decreasing the fuel injection amount from a fuel injection valve provided for each cylinder at the time of switching the target air-fuel ratio. The present invention relates to a control device for a multi-cylinder internal combustion engine that sequentially switches.

[0002]

2. Description of the Related Art As such a multi-cylinder internal combustion engine, Japanese Patent Laid-Open No.
The one described in Japanese Patent Publication No. 295151/1990 is known.

As shown by the broken line in FIG. 3, the target air-fuel ratio is changed from rich (A / F = 14.7) to lean (A / F = 22.
When continuously switched to 0), the output torque of the engine changes smoothly, but there is a problem that the emission amount of NO _X from the exhaust gas purification catalyst sharply increases at the intermediate air-fuel ratio. To avoid this, the target air-fuel ratio can be instantaneously switched from rich to lean to avoid a sudden increase in NO _X emissions, but a sudden change in engine torque causes shock and drivability. A problem that aggravates.

Therefore, in the conventional multi-cylinder internal combustion engine, when the target air-fuel ratio is switched from rich to lean, the fuel injection amount of the fuel injection valve provided in each cylinder exceeds the intermediate air-fuel ratio at which the emmission deteriorates. As described above, it is sequentially decreased at a predetermined interval. This avoids the torque shock that occurs when the fuel injection amounts of all the cylinders are reduced all at once, and improves the drivability while preventing the deterioration of emissions.

[0005]

However, in the conventional multi-cylinder internal combustion engine, the cylinder having a rich air-fuel ratio and the cylinder having a lean air-fuel ratio have the same fuel injection timing and ignition timing.
There was room for further improvement in fuel efficiency and emissions.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to further improve fuel consumption and emission in the above-described multi-cylinder internal combustion engine.

[0007]

In order to achieve the above object, the invention described in claim 1 sets a predetermined amount of fuel injection from a fuel injection valve provided for each cylinder at the time of switching the target air-fuel ratio. In a control device for a multi-cylinder internal combustion engine that sequentially switches the air-fuel ratio of each cylinder by increasing or decreasing with a time difference of, the fuel injection timing and the ignition are different between the cylinder with a rich air-fuel ratio and the cylinder with a lean air-fuel ratio. It is characterized by having a control means for changing the time.

In addition to the structure of claim 1, the invention described in claim 2 sets the fuel injection timing of a cylinder having a rich air-fuel ratio during the exhaust stroke and also has a lean air-fuel ratio. The fuel injection timing of is set during the intake stroke.

In addition to the structure of claim 1, the invention described in claim 3 retards the ignition timing of a cylinder having a rich air-fuel ratio and sets the ignition timing of a cylinder having a lean air-fuel ratio. It is characterized by advancing.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

1 to 6 show an embodiment of the present invention, FIG. 1 is an overall configuration diagram of a control system for a multi-cylinder internal combustion engine, and FIG. 2 is a diagram for explaining an air-fuel ratio switching sequence of each cylinder. 3, FIG. 3 is a graph showing changes in the NO _X emission amount and output torque due to switching of the target air-fuel ratio, FIG. 4 is a graph showing the relationship of the Pmi fluctuation rate with respect to the fuel injection timing during lean, and FIG. 5 is the fuel during rich. FIG. 6 is a graph showing the relationship between the HC emission amount and the injection timing, and FIG. 6 is a graph showing the relationship between the MBT and the air-fuel ratio.

As shown in FIG. 1, an intake passage 1 of a four-cylinder internal combustion engine E (hereinafter simply referred to as engine E) is connected via an intake manifold 2 to four cylinders 3 _{1 to} 3 ₄ of # 1 to # 4. Connected respectively. The intake passage 1 is provided with a throttle valve 4 which is connected to an accelerator pedal (not shown) to open and close. A signal from a throttle opening sensor 5 which is connected to the throttle valve 4 and detects a throttle opening is electronically controlled. Input to the unit U. An intake air amount sensor 6 including an air flow meter for detecting the intake air amount is provided in the intake passage 1 upstream of the throttle valve 4, and a signal from the intake air amount sensor 6 is input to the electronic control unit U. . An engine speed sensor 7 for detecting the engine speed based on the rotation of a crankshaft (not shown) is provided inside the engine E, and a signal from the engine speed sensor 7 is supplied to the electronic control unit U.
Is input to

The intake manifold 2 has four cylinders 3 ₁ ...
_Four fuel injection valves 8 ₁ to 8 ₄ are provided corresponding to 3 ₄ respectively. Each of the fuel injection valves 8 ₁ to 8 ₄ is connected to the electronic control unit U, and the fuel injection amount and fuel injection timing are controlled. 4 corresponding to each of the _four cylinders 3 _{1 to} 3 4
Spark plugs 9 _{1 to} 9 ₄ are provided. Each of the spark plugs 9 _{1 to} 9 ₄ is connected to the electronic control unit U, and its ignition timing is controlled.

Next, the operation of the embodiment of the present invention will be described.

The electronic control unit U determines the switching of the target air-fuel ratio based on the operating state of the engine E. That is,
The electronic control unit U searches the map for the target air-fuel ratio based on the throttle opening detected by the throttle opening sensor 5 and the engine speed detected by the engine speed sensor 7. There are two types of target air-fuel ratios, and the target air-fuel ratio is set to stoichiometry, that is, the stoichiometric air-fuel ratio (A / F = 14.7) in the normal operating region of the engine E, and the specification when the engine E is decelerating, etc. In the operating region of, the target air-fuel ratio is set to lean (for example, A / F = 22.0) in order to improve fuel efficiency.

The fuel injection valve 8 ₁ is used to switch the target air-fuel ratio.
It is performed by controlling the fuel injection quantity from 8 _4. When the target air-fuel ratio is the stoichiometric air-fuel ratio, the fuel injection time corresponding to the air intake amount detected by the intake air amount sensor 6 and the engine speed detected by the engine speed sensor 7 so that the stoichiometric air-fuel ratio is obtained. Is set. on the other hand,
When the target air-fuel ratio is made leaner than the stoichiometric air-fuel ratio, the fuel injection time is set so that the leaned target air-fuel ratio is obtained.

As shown in FIG. 2, the air-fuel ratios of the square cylinders 3 _{1 to} 3 ₄ are not switched at the same time, but are constant with a predetermined time difference at both the stoichiometric → lean switching and the lean → stoichi switching. Order (for example, # 1 cylinder 3 ₁ → # 3 cylinder 3 ₃ → # 4 cylinder 3 ₄ → # 2
Cylinder 3 ₂ order).

As described above, when the target air-fuel ratio is switched, the air-fuel ratios of the four cylinders 3 _{1 to} 3 ₄ are sequentially switched with a predetermined time difference, so that NO _{x as} shown by the solid line in FIG. The torque shock of the engine E can be minimized while avoiding a sharp increase in the emission amount of the engine.

In this embodiment, the air-fuel ratio of each cylinder 3 _{1 to} 3 ₄ is changed, and at the same time, the fuel injection timing and ignition timing are controlled at the same time. Hereinafter, the control of the fuel injection timing and the ignition timing will be specifically described. Fuel injection timing As shown in FIG. 4, the variation rate of the indicated mean effective pressure Pmi of the engine with respect to the end timing of fuel injection (hereinafter referred to as fuel injection timing) when the air-fuel ratio is lean is shown as follows. The crank angle is around 100 °)
It has the property of increasing before and after that. Therefore, when the air-fuel ratio is in the lean state, the fuel consumption can be improved by setting the fuel injection timing near the crank angle of 100 ° after TDC.

On the other hand, as shown in FIG. 5, the HC emission amount with respect to the fuel injection timing when the air-fuel ratio is in the stoichiometric state becomes maximum during the intake stroke and during the exhaust stroke (around 120 ° crank angle before TDC). It has the characteristic of being the minimum. Therefore, when the air-fuel ratio is in the stoichiometric state, the emission can be improved by setting the fuel injection timing near the crank angle of 120 ° before TDC.

Thus, the fuel injection timing is set during the intake stroke when the air-fuel ratio is in the lean state, and the fuel injection timing is set during the exhaust stroke when the air-fuel ratio is in the stoichiometric state. It is possible to achieve both the improvement of the emission and the improvement of the emission. Ignition Timing As shown in FIG. 6, the MBT (minimum ignition advance angle for obtaining the maximum output torque of the engine) with respect to the air-fuel ratio is the crank angle 50 before TDC when the air-fuel ratio is lean.
When the air-fuel ratio is in the stoichiometric state, the crank angle is around 28 ° before TDC. Therefore, by setting the switching aforementioned MBT according to the ignition timing of each cylinder 3 ₁ to 3 ₄ air-fuel ratio, i.e., relatively ignition timing rich time along with the relatively advancing the ignition timing during lean By retarding, the fuel efficiency can be improved.

As described above, when the target air-fuel ratio is switched, the air-fuel ratio of each cylinder is sequentially switched at a predetermined interval to prevent the deterioration of emission while preventing the occurrence of torque shock. Since the fuel injection timing and the ignition timing are also controlled in accordance with the switching of the fuel ratio, it is possible to achieve further improvements in emission and fuel efficiency.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various design changes can be made.

For example, the specific fuel injection timings and ignition timings shown in the embodiments are merely examples, and may be appropriately changed according to the characteristics of the engine.

[0025]

As described above, according to the invention described in claim 1, when the target air-fuel ratio is switched, the fuel injection amount from the fuel injection valve provided for each cylinder is increased with a predetermined time difference. In a control device for a multi-cylinder internal combustion engine that sequentially switches the air-fuel ratio of each cylinder by decreasing the control, the fuel injection timing and the ignition timing are switched between a cylinder with a rich air-fuel ratio and a cylinder with a lean air-fuel ratio. Since the means is provided, it is possible to set the optimum fuel injection timing and ignition timing according to the air-fuel ratio of each cylinder to improve emissions and fuel efficiency.

According to the invention described in claim 2,
By setting the fuel injection timing of the cylinder with a rich air-fuel ratio during the exhaust stroke and setting the fuel injection timing of the cylinder with a lean air-fuel ratio during the intake stroke, the emission is improved when the air-fuel ratio is rich It is possible to achieve both the improvement of fuel efficiency when the air-fuel ratio is lean.

According to the invention described in claim 3,
By retarding the ignition timing of the cylinder with a rich air-fuel ratio and advancing the ignition timing of the cylinder with a lean air-fuel ratio, optimum ignition is achieved both when the air-fuel ratio is rich and when it is lean. It is possible to improve fuel efficiency at the right time.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a control device for a multi-cylinder internal combustion engine.

FIG. 2 is a diagram for explaining the order of switching the air-fuel ratio of each cylinder.

FIG. 3 is a graph showing changes in NO _X emission amount and output torque due to switching of target air-fuel ratio.

[Fig. 4] Pmi with respect to fuel injection timing at lean time
Graph showing the relationship of volatility

FIG. 5 is a graph showing the relationship between the HC emission amount and the fuel injection timing at the rich time.

FIG. 6 is a graph showing the relationship between MBT and air-fuel ratio.

[Explanation of symbols]

3 _{1 to} 3 ₆ cylinders 8 ₁ to 8 ₄ fuel injection valve U electronic control unit (control means)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location F02D 43/00 301 EB J F02P 5/15

Claims (3)

[Claims] 1. When switching the target air-fuel ratio, each cylinder (3 _{1 to} 3)
₄ ) The air-fuel ratio of each cylinder (3 _{1 to} 3 ₄ ) is sequentially switched by increasing or decreasing the fuel injection amount from the fuel injection valve (6 _{1 to} 6 ₄ ) provided for each cylinder with a predetermined time difference. the control apparatus for internal combustion engine, air-fuel ratio exiting the cylinder is rich (3 ₁ to 3 ₄₎ air-fuel ratio is lean cylinder and (3 ₁ to 3 _4), changing has fuel injection timing and ignition timing control A control device for a multi-cylinder internal combustion engine, comprising a means (U). 2. A cylinder (3 _1- ) having a rich air-fuel ratio
3. The fuel injection timing of 3 ₄ ) is set during the exhaust stroke, and the fuel injection timing of the cylinders (3 _{1 to} 3 ₄ ) having a lean air-fuel ratio is set during the intake stroke. A control device for a multi-cylinder internal combustion engine as described. 3. An air-fuel ratio is rich cylinder (3 ₁ -
3 ₄ with retarding the ignition timing), characterized in that the air-fuel ratio advances the ignition timing of the cylinder (3 ₁ to 3 ₄₎ is lean, the control of a multi-cylinder internal combustion engine according to claim 1, wherein apparatus.