JPS62247176A - Ignition timing controller for multicylinder internal combustion engine - Google Patents

Abstract

PURPOSE:To obtain the max. combustion efficiency of an engine as a whole by allowing the spark plug in each cylinder to be ignition-timing-controlled independently, in the engine equipped with the cylinders for lean combustion and the cylinders for rich combustion. CONSTITUTION:The first cylinders 11-13 which are operated by the supply of the mixed gas in the vicinity of a theoretical air-fuel ratio and the second cylinder 14 into which the mixed gas in lean state is supplied in the low load operation and which is operated by the supply of the mixed gas in the vicinity of a theoretical air-fuel ratio in the operation other than the low load operation are provided. In such an engine, the spark plugs 51-54 installed onto the respective cylinders 11-14 are connected with a distributor 55, and supplied with the high voltage supplied from an ignition coil 56 controlled by the ignition instruction signal supplied from an ECU 60. Said ECU 60 is installed to allow the first cylinders 11-13 and the second cylinder 14 to perform the ignition timing control independently on the basis of the advance map memorized for the cylinder in each group according to the output of a cylinder discriminating sensor 57.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an ignition timing control device for a multi-cylinder internal combustion engine.

[Conventional technology]

Conventionally, IC, CO and NOx in engine exhaust gas
An exhaust purification system using a three-way catalyst to purify three components simultaneously is known. However, as shown in Figure 3, the range of air-fuel ratios that can simultaneously purify these three components is narrow, so in exhaust purification systems for engines with electronically controlled fuel injection devices, the
If the air-fuel ratio deviates to the rich or lean side due to deterioration of the 8 sensor, etc., there is a problem in that the amount of NOx or IC released increases.

In order to solve this problem, the applicant has already filed the patent application No.
No. 5819, the cylinder is a first cylinder that is operated by being supplied with an air-fuel mixture near the stoichiometric air-fuel ratio during engine operation;
A second cylinder is supplied with a lean air-fuel mixture during low-load operation of the engine, and a second cylinder is operated with a mixture near the stoichiometric air-fuel ratio during operations other than low-load operation, and the fuel injection valves are installed in each cylinder. We have proposed an exhaust purification device in which a catalyst device having a three-way catalyst and an oxidation catalyst is installed in the exhaust passage. The fuel injection valve corresponding to the second cylinder is configured to inject fuel during the intake stroke of that cylinder during low-load operation, and the intake boat opening to the second cylinder has a shape that generates an intake swirl. has. Further, in the catalyst device, a three-way catalyst is arranged upstream of the oxidation catalyst, and the exhaust gas from the first cylinder passes through the three-way catalyst and then the oxidation catalyst, and the exhaust gas from the second cylinder passes through the oxidation catalyst. Exhaust gas is configured to be directed upstream of the oxidation catalyst.

That is, in this proposed device, rich combustion is always performed in the first cylinder, lean combustion is performed in the second cylinder during low load operation, and rich combustion is performed at other times. Further, the ignition timing is controlled in the same way for all cylinders.

[Problem that the invention seeks to solve]

Rich combustion and lean combustion differ in the required ignition timing to achieve the best combustion efficiency, and as shown in FIG. 4, combustion is generally slower in lean combustion and the ignition timing must be advanced. Therefore, in a configuration in which the ignition timing of each cylinder is the same as in the proposed device, when lean combustion is performed in the second cylinder, the actual ignition timing in either the first or second cylinder is This causes a problem that the ignition timing deviates from the required ignition timing, making it impossible to obtain the best combustion efficiency for the engine as a whole.

Furthermore, when the intake boat of the second cylinder has a shape that generates an intake swirl as in the proposed device, combustion in the second cylinder is fast during full-load operation, and the ignition timing needs to be delayed. If the ignition timing is the same as that of the first cylinder, knocking will occur.

[Means for solving problems]

In order to solve the above problems, the ignition timing control device for a multi-cylinder internal combustion engine according to the present invention provides a first cylinder that is operated by being supplied with an air-fuel mixture near the stoichiometric air-fuel ratio during engine operation, and a first cylinder that is operated by being supplied with an air-fuel mixture near the stoichiometric air-fuel ratio during engine operation. Sometimes a lean mixture is supplied,
In a multi-cylinder internal combustion engine comprising a second cylinder that operates by being supplied with an air-fuel mixture near the stoichiometric air-fuel ratio during operation other than low-load operation, and a spark plug provided for each of these cylinders, the first It is characterized in that the ignition timing of the cylinder's ignition plug and the second cylinder's ignition plug are controlled independently of each other.

〔Example〕

The present invention will be explained below with reference to illustrated embodiments.

FIG. 1 shows an engine to which an embodiment of the present invention is applied.
The engine body 10 has cylinders #1 to #4, 11 and 12.
, 13 and 14 are provided, among which the first cylinder 1
1, 12, and 13 are cylinders that operate by being supplied with an air-fuel mixture near the stoichiometric air-fuel ratio, and the second cylinder 14 is supplied with a lean air-fuel mixture during low-load operation, and operates at a lean air-fuel ratio during operation other than low-load operation. This is a cylinder that operates by being supplied with an air-fuel mixture near the air-fuel ratio.

Each branch pipe of the intake manifold 15 connected to each cylinder 11 , 12 , 13 , 14 is provided with a fuel injection valve 21 , 22 , 23 , 24 corresponding to each cylinder. Intake bow 1 that communicates each of these branch pipes with each cylinder
−1st cylinder 1 among 31, 32, 33, and 34
1゜Intake boats 31 and 32 connected to 12 and 13
, 33 have a straight shape, and the intake boat 34 communicating with the second cylinder 14 is a swirl boat such as a helical boat for generating intake swirl. An intake pipe 16 connected to the base of the intake manifold 15 is provided with a throttle valve 17, an air flow meter 18 is provided upstream of the throttle valve 17, and an air cleaner 19 is provided most upstream. The air that is metered by the air flow meter 18 and guided into the intake pipe 16 via the air cleaner 19 is regulated by the throttle valve 17, and then distributed to each branch pipe in the intake manifold 15. , 34
It is supplied to each cylinder 11, 12, 13, and 14 through.

An exhaust manifold 25 is connected to the exhaust boats of the first cylinders 11, 12, and 13, and an 02 sensor 26 is provided at the base of the exhaust manifold 25. The downstream opening of the front exhaust pipe 27 connected to this base is connected to the artificial part 41 of the catalyst device 40, and the outlet part 42 of the catalyst device ii1.40 is connected to the muffler 2.
8 is connected to the upstream opening of the rear exhaust pipe 29. The catalyst device 40 includes a three-way catalyst 43 and an oxidation catalyst 4
4, the three-way catalyst 43 is disposed near the population section 41, and the oxidation catalyst 44 is disposed near the outlet section 42. Thus, a space 45 is formed between these catalysts 43 and 44. On the other hand, an exhaust pipe 36 is connected to the exhaust boat 35 of the second cylinder 14 , and the downstream opening of the exhaust pipe 36 opens into the space 45 of the catalyst device 40 .

Therefore, the exhaust gas from the first cylinders 11 , 12 , 13 passes through the three-way catalyst 43 and then passes through the oxidation catalyst 44 and is discharged to the rear exhaust pipe 29 . On the other hand, the second
Exhaust gas from the cylinder 14 is introduced into the space 45, passes through the oxidation catalyst 44, and is discharged to the rear exhaust pipe 29.

Each cylinder 11, 12, 13, 14 is provided with a spark plug 51, 52, 53, 54, respectively. These spark plugs 51 , 52 , 53 , 54 are electrically connected to a distributor 55 , and the distributor 55 is electrically connected to an ignition coil 56 . The ignition coil 56 receives an ignition command signal from an electronic control unit (ECU>60) equipped with a microcomputer, and supplies high voltage current to the distributor 55 based on this signal.

A distributor 55 distributes this high voltage current to each spark plug 5.
Power is distributed to the spark plugs 51, 52, 53, and 54 in a predetermined order.

A cylinder discrimination sensor 57 is attached to the distributor 55 to discriminate which cylinder should be ignited next.

The ECU 60 determines the amount of fuel injected from the fuel injection valves 21, 22, 23, and 24 based on the intake air amount and the oxygen concentration in the exhaust gas. Therefore, the signal from the air flow meter 18 and the signal from the 08 sensor 26 are input to the ECU 60. Further, the ECU 60 determines the ignition timing according to the engine load, engine speed, and air-fuel ratio for each cylinder to be ignited. Therefore, a signal from the cylinder discrimination sensor 57 and a signal from the rotational speed sensor 58 are further input to the ECU 60 .

FIG. 2 shows a flow chart of the ignition control routine program. This program is interrupted by a cylinder discrimination signal input from the cylinder discrimination sensor 57. In step 101, the intake air amount and engine speed are read.
In step 102, the content of the cylinder discrimination signal is read, and in step 103, it is determined whether or not the #4 cylinder 14 (second cylinder) will be ignited next. Step 103
When an affirmative determination is made in step 104, the EC
The ignition timing is determined from the advance angle map for #4 cylinder stored in advance in U60. On the other hand, when a negative determination is made in step 103, the process proceeds to step 105, and #1 to #3
Determine the ignition timing from the advance angle map for the cylinder. These advance angle maps are based on the ratio Q/N of intake air amount and engine speed,
It stores changes in ignition timing with respect to engine speed N1 and air-fuel ratio, and the advance angle map for #4 cylinder includes data that advances the ignition timing during lean combustion and retards the ignition timing during full-load operation. remembered. In step 106, ignition is performed according to the ignition timing determined in steps 104 and 105.

The device of this embodiment operates as follows.

During low load operation of the engine, the second cylinder 14 is operated by the ECU 60.
under the control of the first cylinders 11 and 12.

It operates by being supplied with a smaller amount of fuel than that supplied to No. 13, that is, by being supplied with a lean air-fuel mixture (air-fuel ratio of 20 or more). At this time, the intake air introduced into the combustion chamber of the second cylinder 14 is generating a swirl flow by the intake boat 34, and the timing of fuel injection by the fuel injection valve 24 is set to coincide with the intake stroke of this cylinder 14. Coupled with this, the air-fuel mixture in the combustion chamber is stratified,
Furthermore, the ignition timing is set on the advanced side as shown in FIG. 4, so that stable combustion is achieved.

The exhaust gas from the second cylinder 14 is guided to the space of the catalyst unit W140 via the exhaust pipe 36, purified of IIC and CO by the oxidation catalyst 44, and discharged to the rear exhaust pipe 29. Note that the amount of NOx in the exhaust gas from the second cylinder 14 is small because the air-fuel ratio is lean, and there is no problem even if it is not purified by the catalyst.

Also, during this low load operation, the first cylinders 11, 1.2.

13 is feedback-controlled by the ECU 60 to supply an air-fuel mixture near the stoichiometric air-fuel ratio (slightly rich state), and operates with the ignition timing set to the delayed side as shown in FIG. These first cylinders 11.

Exhaust gas from 12 and 13 is discharged to the exhaust manifold 25 and then to the front exhaust pipe 27.
is introduced into the inlet portion 41 of the catalyst device 40 via the catalytic converter. This exhaust gas is also in a slightly rich state since the air-fuel ratio of the air-fuel mixture is in a slightly rich state, and first passes through the three-way catalyst 43 to be purified of NOx. However,
Although combustion of NOx in the exhaust gas is slow due to the ignition timing being set to the delayed side, the amount of NOx in the exhaust gas is reduced compared to normal. When this exhaust gas passes through the three-way catalyst 43, HC and CO in the exhaust gas are not sufficiently purified, but this exhaust gas is diluted by the exhaust gas from the first cylinder 14 in the space 45, Since it is in a lean state and guided to the oxidation catalyst 44, the l in this exhaust gas is
fc and CO are sufficiently purified by this oxidation catalyst 44.

On the other hand, when the engine is operated with a load higher than a predetermined value, the control for operating the second cylinder 14 in a lean state is canceled,
The amount of fuel supplied to all cylinders 11, 12, 13, and 14 is increased so that all cylinders operate in a rich state. At this time, the ignition timing of the second cylinder 14 is set to the delayed side, and combustion is prevented from being accelerated due to intake by the swirl boat. Therefore, the second
There is no risk of non-king occurring in the cylinder 14, and sufficient engine output can be obtained.

In addition, in the above embodiment, the present invention is applied to a 4-cylinder engine,
Although the first cylinder has three cylinders and the second cylinder has one cylinder, for example, the first and second cylinders may each have two cylinders, and the present invention is also applicable to a six-cylinder engine. Needless to say, it will happen.

〔Effect of the invention〕

As described above, according to the present invention, the ignition timing of lean combustion cylinders can be relatively advanced and the ignition timing of rich combustion cylinders can be relatively delayed, and the best combustion efficiency can be obtained for the entire engine. It becomes possible. Additionally, if some cylinders have an intake boat that generates intake swirl, the ignition timing of that cylinder can be relatively delayed during full-load operation to prevent combustion from becoming too rapid and prevent non-king from occurring. It becomes possible.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an engine to which an embodiment of the present invention is applied, Fig. 2 is a flowchart of the ignition timing control routine program, and Fig. 3 shows the purification rates of NOx, HCl, and CO with respect to the air-fuel ratio. Graph FIG. 4 is a graph showing the required ignition timing with respect to the air-fuel ratio. 11, 12, 13...first cylinder 14...second cylinder
Cylinders 51, 52, 53, 54... Spark plugs 55...
distributor

Claims (1)

[Claims] 1. The first cylinder operates by being supplied with an air-fuel mixture near the stoichiometric air-fuel ratio during engine operation, and the first cylinder is supplied with a lean air-fuel mixture during low-load operation of the engine and operates at a near-stoichiometric air-fuel ratio during operations other than low-load operation. The second engine is supplied with a mixture of
In a multi-cylinder internal combustion engine, the spark plug of the first cylinder and the spark plug of the second cylinder are controlled independently of each other. An ignition timing control device for a multi-cylinder internal combustion engine, characterized in that: