JPS59543A - Cylinder number controlled engine - Google Patents

Abstract

PURPOSE:To stablilize combustion and to suppress the fluctuation of engine cycle by a method wherein oxygen sensors are provided in exhaust gas passages and when the multicylinder engine performing an air-fuel ratio control is operated with partial cylinders, the density of a air-fuel mixture supplied into the operating cylinders is made higher than the theoretical air- fuel ratio. CONSTITUTION:Calatysts 14 and 15 are provided in the exhaust passage 6 and the downstream side of a junction of the exhaust passages 6 and 7 on the operating side of the multicylinder engine comprising the non-operating side cylinders D-F and the operating side cylinders A-C and the O2 sensors 16 and 17 are provided in the exhaust passages 6 and 7, respectively, so that the signals of the O2 sensors are inputted to a control device 19 which transmits an injection pulse to fuel injection valves (a-f) on the bases of the quantity of sucked air, the engne r.p.m. and the like. When the engine is operated with the partial cylinders, a cotrol means 20 corrects sharply the pulse width of the injection pulse signal by a predetemined ratio and the density of the air-fuel mixture supplied to the operating cylinders is made somewhat higher than the theoretical air-fuel ratio so that the actual air-fuel ratio does not become lower than the theoretical air-fuel ratio even when a hunting phenomenon takes place and it is possible to control the fluctuation of engine cycle irrespective of the lengths of combustion intervals among the cylinders A-C, to thereby improve the operation characteristic of the engine.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a cylinder number control engine that performs partial cylinder operation by suspending the operation of some cylinders in a light engine load range or the like.

In general, fuel efficiency tends to improve when an engine is operated under a high load. For this reason, in a multi-cylinder engine, fuel supply to some cylinders is cut to stop operation when the engine load is light. An engine with controlled number of cylinders was devised that relatively increases the load on the remaining active cylinders by that amount, thereby improving overall fuel efficiency in the light load range. (Japanese Unexamined Patent Publication No. 55-131540, etc.) In this type of engine, which was previously filed by the present applicant, as shown in FIG.
Corresponding to F, the intake passage 2 is divided downstream of the throttle valve 1 into a working side intake passage 3 and a resting side intake passage 4, and the exhaust passage 5 is also divided halfway into a working side exhaust passage 6 and a resting side exhaust passage 7. It is divided into.

When stopping the operation of cylinders and F when the engine is under light load or no load, for example, the air 70-meter 8
Based on the intake air amount signal from the ignition coil 9 and the rotational speed signal from the ignition coil 9, the control device 10 turns on the cylinder, cuts the fuel supply by switching the fuel injection valve d~ft-total ft- corresponding to F, and stops the fuel injection valve. The shutoff valve 11 installed at the upstream side of the side intake passage 4 is closed, and at the same time, the valve 13 of the fresh air supply passage 12 that bypasses the air flow meter 8 and the throttle valve 1 is opened to supply fresh air on the upstream side to the rest side. Sufficiently supplies cylinders D-F.

As a result, partial cylinder operation is performed while reducing the pumping loss in the cylinders on the idle side.

However, in this case, in order to keep the engine output the same as when operating all cylinders, the fuel injection valve axc in the operating cylinders A and -C is
is switched so that the injection constant is doubled.

By the way, in this engine, during full-cylinder operation, the active cylinders A, C and the idle cylinders, F, emit combusted exhaust gas in the same way, but during partial cylinder operation, the active cylinders A, C Similarly, combustion gas flows from the cylinder on the idle side,
Fresh air at relatively low temperature (almost room temperature) is directly discharged from -F.

Therefore, when using a three-way catalyst as this exhaust treatment device, as shown in the figure, the first catalyst 14 purifies only the exhaust from the active cylinders A and -C, and the inactive cylinder mainly when all cylinders are operated. A second catalyst 15 for purifying the exhaust gas from F is separately installed downstream of the working side exhaust passage 6 and downstream of the confluence of both exhaust passages 6 and 70.

Furthermore, oxygen sensors (0, sensor) 16 and 17 are installed upstream of these catalysts 14- and 15, respectively, and their air-fuel ratio detection signals are sent to the control device 10 described above.

During partial cylinder operation, the first oxygen sensor 1
In response to the detection signal of the second oxygen sensor 17, the injection amount of the fuel injection valves a to C is corrected, and during all-cylinder operation, the injection amount of all the fuel injection valves a to f is corrected in accordance with the detection signal of the second oxygen sensor 17. The air-fuel ratio is corrected and controlled to reach the stoichiometric air-fuel ratio. For this,
Conversion efficiency with catalyst 14°15 is increased.

Note that the basic injection amount of the fuel injection valves a to f is also controlled by the control device 10 based on the intake air amount signal, the rotation speed signal, etc.

However, in such a conventional cylinder number controlled engine, the air-fuel ratio of the active cylinders A and C is feedback-controlled according to the detection signal from the oxygen sensor 16 even during partial cylinder operation. During operation, the combustion interval between cylinders A and C becomes long, resulting in a delay in response to oxygen concentration detection.

Due to feedback control, the air-fuel mixture changes slightly from the stoichiometric air-fuel ratio and repeats richness and leanness, but the detection information of this richness and leanness is delayed due to the small number of combustion cylinders. It ends up. Therefore, during partial cylinder operation, there is a problem in that the air-fuel ratio of the combustion mixture becomes larger than during full cylinder operation, cycle fluctuations increase, and drivability deteriorates.

This invention was made by focusing on such conventional problems, and by setting the mixture ratio of the active cylinder to be somewhat rich during partial cylinder operation, hunting of the air-fuel ratio can be avoided and the active cylinder The objective is to provide an engine with controlled number of cylinders that stabilizes overall combustion, suppresses cycle fluctuations, and improves drivability.

Hereinafter, the present invention will be explained based on the drawings.

FIG. 2 shows an embodiment of the present invention. In this embodiment, the inactive cylinder D-F stops operating (stops combustion) during light loads, etc., and the operating cylinder A continues to operate at all times. , C are interchanged with those in FIG.

In addition, axc\i is a fuel injection valve corresponding to the operating cylinders A and -C, d and f are fuel injection valves corresponding to the idle cylinder and F, and oxygen sensors 16 and 17 detect the oxygen concentration in the exhaust gas.
are installed in the active side exhaust passage 6 and the idle side exhaust passage 7 upstream of the catalysts 14 and 15 (three-way catalyst), respectively.

A signal from an air flow meter 8, a signal from an ignition coil (not shown), and a throttle valve switch 18.
Signals from etc. are input to the control device 19, and based on these signals, when the engine is under light load or no load, the control device 19 keeps the fuel injection valves d and f fully closed, and closes the fuel injection valves d and f to switch to the idle cylinder and F. At the same time, the shutoff valve 11f upstream of the intake passage 4 on the idle side is closed, and the valve 13 of the fresh air supply passage 12 that bypasses the air flow meter 8 and throttle valve 1 is opened to operate cylinders D-F. Stop, working cylinder A, -
Perform partial cylinder operation by operating only C.

On the other hand, when the engine is not under light load or when there is no load, the control device 19 issues a command opposite to the above, and the cylinder pressure is...=F.
operation is restored and all-cylinder operation is performed.

During this all-cylinder operation, the corresponding fuel injection valves arc are activated in response to detection signals from the oxygen sensors 16 and 17 that are fed back to the control device 19.

The injection amounts of d and f are corrected, and each cylinder A, C, and D to F are controlled so that a mixture at the stoichiometric air-fuel ratio is obtained.

On the other hand, during partial cylinder operation, based on the detection signal of the oxygen sensor 16, the fuel injection valve ax corresponding to the operating cylinders A and CK is
The injection amount of c is corrected and the air-fuel ratio is controlled, but
At this time, a control means 2° is provided for setting the air-fuel mixture to be somewhat richer than the stoichiometric air-fuel ratio.

The block configuration of this control means 20 is shown in FIG.
Reference numeral 1 denotes a cylinder number detection section in the control device 19, which outputs a full cylinder operation signal and a partial cylinder operation signal according to the operating state.

The fuel injection pulse width calculation section 2z calculates the appropriate pulse width of the pulse signal that drives the fuel injection valve axc, according to the signals from the air flow meter 8 and the oxygen sensor 16 that are input together with these signals.

This drive pulse signal is given to the fuel injection valves a-C via the injection valve drive section n to control the injection amount in the working cylinders A, -C. While the operation signal is being output, the control means 2
The fuel increase circuit 24 as 0 operates to instruct the pulse width of the drive pulse signal to be increased by a predetermined ratio.

As a result, the amount of injection from the fuel injection valves a and -C is increased to make the air-fuel mixture supplied to the active cylinders A to C during partial cylinder operation somewhat richer than the stoichiometric air-fuel ratio.

In this case, the air-fuel ratio is set to a level that does not significantly affect combustion.

In addition, in FIG. 2, 25 indicates an exhaust gas recirculation passage, and 26 indicates an EGR valve.

With this configuration, during partial cylinder operation, the slightly richer air-fuel mixture supplied to the active cylinders A and C is exhausted after being well combusted, and NO! The amount of (nitrogen oxides) becomes extremely small.

Then, this exhaust gas passes through the operating side exhaust passage 6t to the catalyst 1.
Leads to 4.

Therefore, in order to always aim for a slightly richer air-fuel ratio,
Even if hunting occurs, the air-fuel ratio will almost never become leaner than the stoichiometric air-fuel ratio, and as a result, even if the combustion interval of cylinders A, , = C is long, cycle fluctuations during partial cylinder operation can be sufficiently suppressed, and the operation can improve sexual performance.

In addition, since there is a reducing atmosphere inside the catalyst 14, the NOx in the exhaust gas is completely reduced when it passes through the catalyst 14, and then it joins the fresh air discharged from the idle cylinder and the downstream catalyst. 15.

Therefore, an oxidizing atmosphere is created within the catalyst 15, and CO (-carbon oxide) and HC (hydrocarbons) in the exhaust gas are sufficiently purified, making it possible to obtain exhaust gas that is much cleaner than K.

By setting a slightly rich air-fuel mixture to avoid this, it is possible to maintain stable combustion in the active cylinders A and C, thereby ensuring smooth operation of the engine while purifying the exhaust gas.

In addition, during all-cylinder operation, the pressure of each cylinder A, .
, C, D, and F can all be controlled to the stoichiometric air-fuel ratio to maintain good engine performance and exhaust performance.

FIG. 4 shows another embodiment of the present invention, in which feedback control of the air-fuel ratio is performed according to the signal from the oxygen sensor 27 only during full cylinder operation, and the air flow meter 8 is used during partial cylinder operation.
The injection amount of fuel injection valves a to c is increased by a predetermined amount in response to signals from the fuel injection valves a to c, and the opening control is performed.

In this case, as shown in FIG. 5, the control means 28 increases the pulse width of the drive pulse signal calculated by the fuel injection pulse width calculation section 22 based only on the signal of the air flow meter 8 by a predetermined ratio, and of course During partial cylinder operation, the mixture is always controlled to be slightly rich in the active cylinders A to C. However, according to this, hunting of the air-fuel ratio can be prevented and cycle fluctuations can be suppressed, and since only one control system is required, costs can be reduced.

In each example, since the amount of NOx generated by combustion is extremely small, exhaust gas recirculation can be reduced and engine performance can be maintained at a high level.

As explained above, according to the present invention, in an engine in which the operation of some cylinders is suspended in a light load range etc. to perform partial cylinder operation, the air-fuel mixture to the active cylinder is adjusted to the stoichiometric air-fuel ratio during partial cylinder operation. By making the exhaust gas a little richer, even if there is some hunting in the air-fuel ratio, when an oxygen sensor is installed in the exhaust gas to control the air-fuel ratio, it can be maintained almost on the rich side.
It is possible to maintain stable combustion and reduce cycle fluctuations during partial cylinder operation. In addition, due to excessively rich mixture, NOx
This has the effect of suppressing the generation of CO and HC, and also sufficiently reducing CO and HC due to the fresh air discharged from the cylinders on the idle side joining together at the catalyst, thereby improving driving performance and exhaust performance.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the configuration of a conventional example, FIG. 2 is a sectional view of the configuration of an embodiment of the present invention, FIG. 3 is a block configuration diagram of its control means, and FIG. 4 is a sectional view of another embodiment of the present invention. A cross-sectional diagram showing the configuration,
FIG. 5 is a block diagram of the control means. 1... Throttle valve, 6... Working side exhaust passage, 7... Pause 41111 exhaust passage, 8... Air flow meter, 14
．． 15... Touch 11.16.17... Oxygen sensor, 1
8... Throttle valve switch, 19... Control device, 20...
- Control means, 27...Oxygen sensor, 28...Control means. Patent applicant Nissan Motor Co., Ltd.

Claims (1)

[Claims] It is equipped with a dormant cylinder that stops operating when the fuel supply is cut off when the engine is under light load or no load, and an active cylinder that is constantly supplied with fuel and fresh air and continues to operate. In a multi-cylinder engine in which the exhaust passage is divided halfway according to the cylinders, and a catalyst is installed in the working side exhaust passage and the combined exhaust passage, the air-fuel mixture to the working side cylinder is changed to the stoichiometric air-fuel ratio when the fuel is shut off. An engine with a controlled number of cylinders, characterized in that it is equipped with a control means for setting the richness to be more or less rich.