JPH07133730A - Air-fuel ratio control device for number of operating cylinder controlled engine - Google Patents

Abstract

PURPOSE:To suppress NOx so as to prevent much NOx from discharging by preventing an air-fuel ratio in an operating cylinder from transferring to its lean side. CONSTITUTION:In an ECU 25, air mixture is shut out from being supplied to a part of cylinders #1 to #8 at the time of a light load of an engine 1, and a part of the cylinders #1 to #8 are placed in halt so as to control the reduced number of the cylinder. When the reduced number of the cylinder is controlled by the ECU 25, air-fuel ratio feed back control is invalidated in the ECU 25. When air-fuel ratio feed back control is invalidated, a basic injection amount taubse calculated by the ECU 25 is corrected by the ECU 25 so as to transfer an air-fuel ratio to rich side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder number control engine, and more particularly, to a cylinder number control for controlling an air-fuel ratio when a cylinder cutoff control is performed by providing idle cylinders so that fuel is not supplied to some cylinders. The present invention relates to an air-fuel ratio control device for an engine.

[0002]

2. Description of the Related Art Conventionally, when an engine is generally operated under a high load, fuel consumption tends to be good. for that reason,
In a multi-cylinder engine, when the engine load is small (light load range), the fuel supply to some cylinders is cut off and the engine is stopped, and the load on the remaining operating cylinders is relatively increased by that amount, There is a cylinder number control engine designed to improve fuel efficiency in the light load region of the engine.

There is also an engine equipped with an EGR device for reducing NOx contained in exhaust gas. This EGR
The device recirculates part of the exhaust gas from the exhaust system to the intake system. That is, a flow rate control valve (EGR valve) is provided in the exhaust gas recirculation path connecting the intake system and the exhaust system of the engine.
Is provided, and the EGR valve is opened / closed according to the operating state of the engine. Therefore, the recirculation amount (EGR flow rate) in which the exhaust gas is recirculated to the intake system via the exhaust gas recirculation path is controlled.

[0004]

By the way, there is a cylinder number control engine in which an EGR device is mounted on a cylinder number control engine and a cylinder cutoff control is performed by suspending the cylinder without supplying fuel to some cylinders. In this engine, when the EGR valve is controlled and the EGR control is performed while the cut-off cylinder control is performed, the air discharged from the idle cylinder is returned to the intake system via the exhaust gas recirculation path. However, the fuel injection amount supplied to the operating cylinder is calculated based on the air amount measured by the air flow meter, the engine speed, and the like. Therefore, since the air recirculated from the exhaust gas recirculation path is further mixed with the mixture of the air and the fuel supplied from the intake system,
The air-fuel ratio of the air-fuel mixture supplied to the operating cylinders shifts to the lean side, and a large amount of NOx is exhausted.

It is also conceivable to simply stop the air-fuel ratio hood back control when the cylinder number control engine is operated in a reduced cylinder condition without controlling the EGR valve of the EGR device.
However, if the air-fuel ratio of the operating cylinder is near the stoichiometric air-fuel ratio and the air-fuel ratio of the operating cylinder shifts to the lean side from the theoretical air-fuel ratio due to engine operating conditions, temperature conditions and environmental conditions, NOx
Will be discharged in large quantities.

On the contrary, if the air-fuel ratio shifts to the rich side of the stoichiometric air-fuel ratio for some reason, the catalyst purification rate decreases and H
A large amount of C and CO are discharged. The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to prevent the air-fuel ratio of the operating cylinder from shifting to the lean side, and to make NO.
An object of the present invention is to provide an air-fuel ratio control device for a cylinder number control engine that suppresses a large amount of x.

[0007]

In order to achieve the above object, in the invention according to claim 1, a plurality of cylinders provided in the engine and a plurality of cylinders for supplying fuel to the plurality of cylinders are provided. An injection nozzle, a rotation speed sensor that detects the rotation speed of the engine, an intake air amount sensor that detects the amount of intake air taken into the intake system of the engine, and an exhaust gas that is exhausted to the exhaust system of the engine. An oxygen sensor for detecting the amount of oxygen to be generated, a basic injection amount calculation means for calculating a basic injection amount based on the detection signal from the rotation speed sensor and the detection signal from the intake amount sensor, and the detection signal from the oxygen sensor. An air-fuel ratio feedback control means for correcting the basic injection quantity calculated by the basic injection quantity calculation means on the basis of the basic injection quantity calculation means to perform air-fuel ratio feedback control. In the ratio control device, when the engine is lightly loaded, a cylinder cut-off control means for performing cylinder cut-off control by shutting off the cylinder so as not to supply the air-fuel mixture to the cylinders, and reducing the cylinder by the cylinder cut-off control means. When the cylinder control is performed, the invalidation means for invalidating the air-fuel ratio feedback control means, and the basic injection amount calculation means when the air-fuel ratio feedback control means is invalidated by the invalidation means The gist of the present invention is to include a basic injection amount correction unit that corrects the basic injection amount and shifts the air-fuel ratio to the rich side.

According to a second aspect of the present invention, a plurality of cylinders provided in the engine and an exhaust gas recirculation path connecting the exhaust system and the intake system of the engine are arranged, and a part of the exhaust gas is An air-fuel ratio control device for a cylinder number control engine, comprising: a flow rate control valve that recirculates to an intake system; and an opening degree control unit that controls an opening degree of the flow rate control valve when the engine has a light load. At times, the cylinder is cut off so as not to supply the air-fuel mixture to some cylinders and the cylinders are deactivated to perform cylinder reduction control, and when the cylinder reduction control is executed by the cylinder reduction control, The gist of the present invention is to include opening degree control invalidating means for invalidating the opening degree control of the flow rate control valve controlled by the degree control means.

[0009]

According to the first aspect of the present invention, the basic injection amount calculation means uses the detection signals from the rotation speed sensor and the intake amount sensor to supply the air-fuel mixture to each cylinder of the engine to control the operation of all cylinders. The basic injection amount is calculated based on this. Further, the air-fuel ratio feedback control means corrects the basic injection amount calculated by the basic injection amount calculating means based on the detection signal from the oxygen sensor provided in the exhaust system of the engine, and based on the corrected basic injection amount. Air-fuel ratio feedback is performed by supplying the air-fuel mixture to each cylinder.

When the engine is in a light load state,
The cut-off cylinder control means cuts off the air-fuel mixture so as not to supply it to some of the cylinders, and deactivates the cylinders to perform the cut-off cylinder control. When the cut-off cylinder control means performs the cut-off cylinder control, the invalidation means invalidates the air-fuel ratio feedback control means. And
When the invalidation unit invalidates the air-fuel ratio feedback control unit, the basic injection amount correction unit corrects the basic injection amount calculated by the basic injection amount calculation unit so that the air-fuel ratio becomes rich.

Therefore, since the air-fuel ratio of the operating cylinder shifts to the rich side, it becomes possible to suppress a large amount of NOx from being discharged. According to the second aspect of the present invention, when the engine is in a light load state in a state where the air-fuel mixture is supplied to each cylinder of the engine and the all-cylinder operation control is performed, the opening degree control means changes the opening degree of the flow control valve. Control. Therefore, the exhaust gas based on the opening degree of the flow control valve is recirculated from the exhaust system to the intake system via the exhaust gas recirculation path.

When the engine is lightly loaded, the cylinder cut-off control means cuts off the air-fuel mixture so as not to supply it to some of the cylinders, and deactivates the cylinders to perform the cylinder cut-off control. When the cylinder reduction control means performs the cylinder reduction control, the opening degree invalidation control means invalidates the opening degree control of the flow rate control valve controlled by the opening degree control means.

Therefore, since the exhaust gas is not recirculated from the exhaust system to the intake system, the air-fuel ratio is prevented from shifting to the lean side. Therefore, it is possible to suppress the NOx from being discharged in a large amount.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an air-fuel ratio control device in which the present invention is applied to a V8 gasoline engine equipped with an EGR device will be described in detail below with reference to FIGS.

As shown in FIG. 1, the engine 1 is provided with eight cylinders # 1 to # 8. Each cylinder # 1 to #
An intake passage 2 forming a part of the intake system and an exhaust passage 3 forming a part of the exhaust system are respectively connected to 8.

The engine 1 supplies to each of the cylinders # 1 to # 8 a mixture of intake air taken into the intake passage 2 and fuel injected from the fuel injection nozzles 4a to 4h. An ignition plug (not shown) is provided for each of the cylinders # 1 to # 8 of the engine 1, and the ignition voltage distributed by the distributor 5 is applied to the ignition plug.

The distributor 5 is an igniter 6
The high voltage output from the igniter 6 is used to distribute the high voltage output from the igniter 6 to each ignition plug in synchronization with each crank of the engine 1. Then, the engine 1 explodes the air-fuel mixture in each of the cylinders # 1 to # 8 by a spark plug to obtain a driving force, and then discharges the exhaust gas to the exhaust passage 3.

A surge tongue 7 for suppressing pulsation of intake air is provided on the upstream side of the intake passage 2. On the upstream side of the surge tank 7, there is provided a throttle valve 8 which is opened / closed in conjunction with the operation of an accelerator pedal (not shown), and the intake passage 2 is opened by opening / closing the throttle valve 8.
The intake air amount to the air is adjusted.

A throttle sensor 9 for detecting the opening of the throttle valve 8 is provided near the throttle valve 8. or,
On the upstream side of the throttle valve 8, an air flow meter 10 as an intake amount sensor for detecting the intake air amount.
Also, an air cleaner 11 is provided. In this embodiment, the air flow meter 10 is the intake amount sensor,
In addition to this, a Kalman type inhalation amount sensor may be applied.

On the other hand, the exhaust passage 3 is composed of a first exhaust passage 12a and a second exhaust passage 12b, and the first exhaust passage 12a is connected to cylinders # 1 to # 4 of the engine 1.
The second exhaust passage 12b is connected to the cylinders # 5 to # 8 of the engine 1. The first exhaust passage 12a and the second exhaust passage 12b are connected on the downstream side.

In order to purify the exhaust gas, an oxygen sensor 13 for detecting the oxygen concentration in the exhaust gas is provided downstream of the exhaust passage 3 to which the first exhaust passage 12a and the second exhaust passage 12b are connected. The three-way catalytic converter 14 is provided.

Between the intake passage 2 and the exhaust passage 3,
An EGR device 15 for recirculating exhaust gas in the exhaust passage 3 to the intake passage 2 side for exhaust gas recirculation is provided. That is, from the exhaust passage 3 to which the first and second exhaust passages 12a and 12b are connected, E as an exhaust gas recirculation passage is formed.
The GR pipe 16 is branched, and the other end is connected to the intake passage 2 between the surge tank 7 and the throttle valve 8. In the middle of the EGR pipe 16, an E as a flow control valve is provided.
A GR valve 17 is provided.

In this EGR valve 17, a step motor 18 rotates in response to a pulse signal, and the step motor 18
The so-called step motor type in which the lift amount of the valve element 19 provided in the valve changes and the opening area of the valve changes,
By controlling the opening degree of the EGR valve 17, the amount of exhaust gas recirculated to the intake passage 2 is controlled.

In addition to the throttle sensor 9, the air flow meter 10 and the oxygen sensor 13 described above, a distributor 5 is installed in the engine 1 to detect its operating condition.
A rotation speed sensor 20 for detecting the rotation speed of the engine 1 from the rotation of the rotor 5a and a water temperature sensor 21 for detecting the cooling water temperature of the engine are attached.

The various sensors are electrically connected to an electronic control unit (hereinafter simply referred to as "ECU") 25.
In addition, each fuel injection nozzle 4a-4h, igniter 5 and E
The GR valve 17 is electrically connected to the ECU 25.

The ECU 25 is a central processing unit (hereinafter referred to as CP
U) 26 and read-only memory (hereinafter ROM)
27 and a random access memory (hereinafter, RA)
28).

The CPU 26 executes various arithmetic processes according to a preset control program, and the ROM 27 stores C
A control program and initial data necessary for executing arithmetic processing in the PU 26 are stored in advance. In addition, RAM28
Temporarily stores the calculation result of the CPU 26.

In the ROM 27, as shown in FIG.
Upper limit and lower limit regions β1 and β2 defined in the relationship between the engine speed NE and the intake air amount QN per engine revolution are stored in advance as a two-dimensional map.
That is, the upper limit region β1 shows a characteristic that the negative pressure in the exhaust passage 2 becomes low, and the exhaust gas from the exhaust passage 3 is not sucked into the intake passage 2 via the EGR pipe 16 and has a high load.
Further, the lower limit region β2 shows a characteristic in which the engine 1 at the light load state has a limit value at which the engine speed NE does not misfire.

Therefore, when the intake air amount QN per engine revolution with respect to the engine speed NE at that time is between the upper and lower limit regions β1 and β2, the EGR device 15
It is a permission area where you can control. The engine 1 with respect to the engine speed NE at that time
The intake air amount QN per rotation is in the upper and lower limit region β1,
When it is not within the range of β2, the EGR device 15 is not controlled and the prohibited region is set.

Further, when the cylinder cut-off control in which fuel is not supplied to the cylinders # 1 to # 8 of the engine 1 by the fuel injection nozzles 4a to 4h is performed, a correction coefficient for calculating a correction coefficient for correcting the basic injection amount is calculated. The calculation formula is previously stored in the ROM 27 as follows.

F1 = 1 + f0-α where f0 = N / M N: number of idle cylinders in which fuel is not supplied from the injection nozzle in the same exhaust passage M: number of cylinders in the same exhaust passage α: exhaust state (emission), fuel consumption However, 0 ≦ α ≦ f0 and the cylinder # in operation when the cut-off cylinder control is performed
The correction injection amount calculation formula for calculating the injections 1 to # 8 is the ROM 2
7 is stored in advance as follows.

Τ = τbse × f1 τbse: basic injection amount calculated based on the engine speed NE and the air intake amount Q. Also, when the engine 1 is started, the CPU 26 of the ECU 25 outputs the detection signal from the water temperature sensor 21. Based on this, it is determined whether the cooling water temperature THW is equal to or higher than the set temperature γ. And
If the cooling water temperature THW does not exceed the set temperature γ, CP
U26 does not control the step motor 18 of the EGR device 15. That is, the exhaust gas is not recirculated from the exhaust passage 3 to the intake passage 2 via the EGR pipe 16.

When the cooling water temperature THW exceeds the set temperature γ, the CPU 26 determines the engine speed N based on the detection signals from the speed sensor 20 and the air flow meter 10.
The intake air amount QN per one revolution of the engine with respect to E is calculated.

The CPU 26 determines whether or not the intake air amount QN exists between the upper and lower limit regions β1 and β2 of the map stored in the ROM 27. That is, it is determined here whether or not the engine 1 is in a state of not causing a misfire and whether or not the engine 1 is in a high load state.

If this condition is not satisfied, the CPU 26 does not control the step motor 18 of the EGR device 15. That is, the exhaust gas is not recirculated from the exhaust passage 3 to the intake passage 2 via the EGR pipe 16.

When the intake air amount QN per engine revolution with respect to the engine speed NE exists between the upper limit and lower limit regions β1 and β2 of the map stored in the ROM 27, the CPU 26 causes the step motor of the EGR device 15 to operate. It is determined that the EGR control in which the exhaust gas is recirculated from the exhaust passage 3 to the intake passage 2 through the EGR pipe 16 by controlling 18 is performed can be performed. Similarly, the CPU 26 causes the fuel injection nozzles 4a to 4a of some of the cylinders # 1 to # 8 of the engine 1 to be connected.
It is determined that the cylinder cut-off control can be performed by shutting off the fuel so that the fuel is not supplied from 4h.

Further, when the intake air amount QN per engine revolution with respect to the engine speed NE exists between the upper limit and lower limit regions β1 and β2 of the map, the CPU 26 performs the cut-off cylinder control or the EGR control. When the cylinder control is performed, the CPU 26 immediately stops the EGR control of the EGR device 15 and corrects the exhaust gas from the exhaust passage 3 so as not to flow back to the intake passage 2 via the EGR pipe 16.

When the cut-off cylinder control is performed, the CPU 26
Determines how many cylinders # 1 to # 8 should be deactivated based on the load of the engine 1 and the state of the engine speed NE. And which cylinder # 1 to # 8
Is set as a deactivated cylinder, that cylinder # 1 to # 8
The fuel from the fuel injection nozzles 4a to 4h corresponding to is cut off.

Next, the same exhaust path, that is, the first exhaust path 1
CPU2 determines how many idle cylinders are in 2a, and how many idle cylinders are also in the second exhaust passage 12b.
6 is to be searched. Then, the CPU 26 calculates the cylinder-reduction rate f0a in the first exhaust passage 12a and calculates the cylinder-reduction rate f0b in the second exhaust passage 12b. Then, the CPU 26 calculates the cylinder removal rate f0a corresponding to the first exhaust passage 12a and the cylinder removal rate f0b corresponding to the second exhaust passage 12b. The CPU 26 reads out α stored in advance in the ROM 27 based on the detection signal of the oxygen sensor 13 and adjusts the numerical values of the cylinder cut-off ratios f0a and f0b so as not to increase the emission contained in the exhaust gas and reduce the fuel consumption. It has become.

Then, the CPU 26 calculates the reduced cylinder rate f.
0a and f0b are multiplied by the basic injection amount τbse calculated based on the engine speed NE and the air intake amount Q at that time to obtain the corrected injection amounts τ1 and τ2 of the operating cylinders # 1 to # 8. Has become.

Next, the operation of the air-fuel ratio control device configured as described above will be described. As shown in FIG. 3, after starting the engine 1, the CPU 26 of the ECU 25 determines whether or not the cooling water temperature THW is equal to or higher than a predetermined temperature γ based on the detection signal from the water temperature sensor 21 (STEP).
1, hereinafter, STEP is simply referred to as S). When the cooling water temperature THW is equal to or lower than the predetermined temperature γ, the CPU 26 causes the EGR
The step motor 18 of the device 15 is not controlled (S2).
That is, the exhaust gas in the exhaust passage 3 does not flow back to the intake passage 2 via the EGR pipe 16.

When the cooling water temperature THW is equal to or lower than the predetermined temperature γ, the CPU 26 calculates the intake air amount QN per engine revolution based on the engine speed NE and the intake air amount Q at that time (S3). Then, the CPU 26 determines whether or not the intake air amount QN per engine revolution with respect to the engine speed NE falls within a region between the upper limit region β1 and the lower limit region β2 of the map stored in the ROM 27 (S4). .

If the intake air amount QN per engine revolution with respect to the engine speed NE does not exist between the upper limit region β1 and the lower limit region β2, the CPU 26 makes a STEP.
After shifting to 2, the EGR device 15 is not controlled as in the above. When the intake air amount QN per engine revolution with respect to the engine speed NE exists between the upper limit region β1 and the lower limit region β2, the cut-off cylinder control of the engine 1 or E
The CPU 26 determines that the RG control can be performed.

At that time, the CPU 26 determines whether or not the cut-off cylinder control of the engine 1 is being performed (S).
5). If the cylinder reduction control of the engine 1 is being performed, the CPU
26 shifts to STEP 2 and the EGR device 15 is not controlled.

When the cylinder cut-off control of the engine 1 is not performed, the CPU 26 drives and controls the step motor 17 of the EGR device 15 to adjust the lift amount of the valve body 19,
The opening amount of the R valve 17 is adjusted. And the exhaust passage 3
The exhaust gas from is recirculated to the intake passage 2 via the EGR pipe 16.

On the other hand, when the cylinder reduction control of the engine 1 is performed,
As shown in FIG. 4, the CPU 26 controls the intake air amount Q per engine revolution with respect to the engine revolution speed NE at that time.
It is determined whether N exists between the upper limit region and the lower limit region β1 and β2, and the reduced cylinder control can be performed (S10).

If the intake air amount QN per engine revolution with respect to the engine speed NE at that time is between the upper and lower limit regions β1 and β2, the CPU 26
Determines that the cylinder reduction control can be performed. Then, the CPU 26 determines which of the cylinders # 1 to # 8 should be deactivated and how much to idle based on the load state of the engine 1 and the state of the engine speed NE. Here, for example, deactivated cylinders # 2, # 4, # 6
Then, the operating cylinders are set to # 1, # 3, # 5, # 7, and # 8 (S11).

Next, the CPU 26 causes the cylinder removal rate f0a in the same exhaust passage 12a and the cylinder removal rate f in the same exhaust passage 12b.
Calculate 0b. In this case, the number M of cylinders connected to the same exhaust path 12a, 12b is 4, respectively. Therefore,
The reduced cylinder ratios are f0a = 2/4 = 0.5 and f0b = 1/4, respectively.
= 0.25 (S12). Further, the CPU 26 stops the air-fuel ratio feedback control based on the detection signal from the oxygen sensor 13 provided in the exhaust passage 3 (S13).

The correction coefficients f1a and f1b are stored in the ROM 27.
It is calculated based on the correction coefficient calculation formula stored in. In this case, the correction coefficient f1a is f1a = 1 + 0.5-α, and the correction coefficient f1
1b becomes f1b = 1 + 0.25-α. Further, the CPU 26 sets α based on the load state of the engine 1, the temperature of the air, etc. at that time so as not to lead to an increase in emissions contained in the exhaust gas and a decrease in fuel consumption. Then, α in the correction coefficient f1a is adjusted within 0 ≦ α ≦ 0.5, and α in the correction coefficient f1b is adjusted within 0 ≦ α ≦ 0.25 (S14). Incidentally, if the correction coefficients f1a and f1b are always set appropriately, α may be eliminated.

Then, the CPU 26 multiplies the calculated correction coefficient f1a and the basic injection amount τbse calculated based on the engine speed NE and the intake air amount Q at that time to calculate the corrected injection amount τ1. The CPU 26 controls the fuel injection nozzles 4a and 4d to supply the corrected injection amount τ1 to the operating cylinders # 1 and # 3. Similarly, the calculated correction coefficient f
The CPU 26 multiplies 1b and the basic injection amount τbse calculated based on the engine speed NE and the intake air amount Q at that time to calculate the corrected injection amount τ2. The CPU 26 controls the fuel injection nozzles 4e, 4g, 4h to correct the injection amount τ2.
Is supplied to the operating cylinders # 5, # 7, and # 8 (S1
6).

Further, in STEP 10, when the reduced cylinder control of the engine 1 cannot be performed, the correction coefficients f1a, f
1a is set to f1a = f1a = 1 (S17). And STE
The process shifts to P15, and the same processing as above is performed. In this case, fuel injection control is performed based on the basic injection amount τbse.

Therefore, when the cylinder reduction control of the engine 1 is performed, the CPU 26 does not control the EGR device 15, so that the air exhausted from the idle cylinders # 1 to # 8 to the exhaust passage 3 is removed from the EGR pipe 16. Do not recirculate to the intake passage 2 via. Therefore, the air-fuel mixture supplied to the operating cylinders # 1 to # 8 is not diluted by the air recirculated from the EGR pipe 16.

As a result, the air-fuel ratio of the air-fuel mixture supplied to the operating cylinders # 1 to # 8 can be prevented from shifting to the lean side, and a large amount of NOx can be prevented from being discharged.

When the cylinder cut-off control of the engine is performed, CP
U26 stops the air-fuel ratio feedback control and calculates the corrected injection amount based on the injection amount correction calculation formula. With this corrected injection amount, the air-fuel ratio of the operating cylinders # 1 to # 8 can be made rich. Therefore, the exhaust gas passing through the three-way catalytic converter 14 can be made into an oxidizing atmosphere. As a result, CO and HC can be suppressed from being discharged in large amounts.

Further, since the air-fuel ratios of the operating cylinders # 1 to # 8 are shifted to the rich side, it is possible to suppress a large amount of NOx discharged. In this embodiment, the EGR control and the cut-off cylinder control are performed when the engine 1 is in a light load state. In this case, to determine whether the load of the engine 1 is a light load state or a high load state, it is determined based on the opening degree of the throttle valve 8 or based on the intake air amount Q and the engine speed NE. be able to.

In the present embodiment, the step motor 18
The ERG device 15 in which the lift amount of the valve body 19 is adjusted by adjusting the opening amount of the EGR pipe 16 is realized. Instead of the step motor 18, an electromagnetic valve type that operates by utilizing the negative pressure of the intake passage 2 can be used for the EGR device 15.

The first and second exhaust passages 12a and 12b are also provided.
Although the exhaust passage 3 is configured by, the air-fuel ratio control device can be applied to the engine 1 in which one exhaust passage 3 is connected to all the cylinders # 1 to # 8. In this case, when the eight-cylinder engine 1 is used, the reduced cylinder ratio f0 is f0 = N / 8.
(N: number of idle cylinders).

Further, in this embodiment, the EGR device 1
It was embodied in a cylinder number control engine 1 equipped with 5
In a cylinder number control engine in which the GR device 15 is not installed, the air-fuel ratio control device is installed to correct the air-fuel ratio of the air-fuel mixture supplied to the operating cylinders # 1 to # 8 to the rich side during the cylinder cut-off control. You may control.

Further, fuel injection nozzles 4a to 4h are provided for the cylinders # 1 to # 8, respectively. In addition to this, for example, an engine in which fuel injection nozzles 4a to 4d are associated with every two cylinders,
The engine in which the fuel injection nozzles 4a and 4b are associated with each four cylinders, and in the six-cylinder engine, the air-fuel ratio control device is mounted in the engine in which the fuel injection nozzles 4a and 4b are associated with each three cylinders. Is also possible.

In this embodiment, the cylinder # to be deactivated
The fuel is not injected into the fuel injection nozzles 4a to 4h corresponding to 1 to # 8. In addition to this, an opening / closing valve is provided on the intake passage 2 side of each of the cylinders # 1 to # 8 or a predetermined number of cylinders # 1 to # 8.
No cylinders # 1 to # 8 so that the air-fuel mixture is not supplied to
May be provided.

In this embodiment, the eight-cylinder engine is embodied, but it may be embodied in a multi-cylinder engine such as a six-cylinder engine or a four-cylinder engine. In the present embodiment, when the reduced-cylinder operation is performed, the air-fuel ratio of the operating cylinder is corrected and the control of the ERG device 15 is prohibited. In addition to this, when the reduced-cylinder operation is performed, it is possible to perform the air-fuel ratio control so as to prevent only the control of the EGR device 15 and prevent the mixture from leaning.

[0062]

As described above in detail, according to the present invention, there is an excellent effect that the air-fuel ratio of the operating cylinder does not shift to the lean side and NOx is prevented from being discharged in a large amount. .

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an outline of mounting an EGR device on a cylinder number control engine according to the present invention.

FIG. 2 is a map for determining whether the air intake amount per engine revolution with respect to the engine speed is present between an upper limit region and a lower limit region.

FIG. 3 is a flowchart diagram when performing EGR control.

FIG. 4 is a flow chart diagram when performing cut-off cylinder control.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Intake passage which comprises an intake system, 3 ... Exhaust passage which constitutes an exhaust system, 10 ... Air flow meter as an intake amount sensor, 13 ... Oxygen sensor, 20 ... Rotation speed sensor, 25 ... Basic injection amount E as the calculation means, the air-fuel ratio feedback control means, the cut-off cylinder control means, the invalidation means, the basic injection amount correction means, the opening control means and the opening control invalidation means
CU, 16 ... EGR pipe as exhaust gas recirculation path, 17 ...
EGR valve as a flow control valve, NE ... Engine speed, Q ... Air intake amount, τbse ... Basic injection amount, # 1 to # 8
…cylinder

Claims (2)

[Claims] 1. A plurality of cylinders provided in an engine, a rotation speed sensor for detecting a rotation speed of the engine, an intake amount sensor for detecting an intake air amount taken into an intake system of the engine, and the engine. An oxygen sensor that detects the amount of oxygen contained in the exhaust gas discharged to the exhaust system, and a basic injection that calculates the basic injection amount of fuel based on the detection signal from the rotation speed sensor and the detection signal from the intake amount sensor. Number of cylinders provided with an amount calculation means and an air-fuel ratio feedback control means for correcting the basic injection amount calculated by the basic injection amount calculation means based on a detection signal from the oxygen sensor to perform air-fuel ratio feedback control In an air-fuel ratio control device for a control engine, a cut-off cylinder control is performed by shutting off some of the cylinders so as not to supply the air-fuel mixture to the cylinders when the engine is lightly loaded, and deactivating the cylinders. Reducing cylinder control means for performing, and a reducing means for invalidating the air-fuel ratio feedback control means when the reducing cylinder control means performs the reducing cylinder control; and the invalidating means for invalidating the air-fuel ratio feedback control means. And a basic injection amount correction unit that corrects the basic injection amount calculated by the basic injection amount calculation unit to shift the air-fuel ratio to the rich side, the air-fuel ratio of the cylinder number control engine. Control device. 2. A flow rate control for arranging a plurality of cylinders provided in an engine and an exhaust gas recirculation path connecting an exhaust system and an intake system of the engine to recirculate a part of exhaust gas to the intake system. In an air-fuel ratio control device for a cylinder number control engine, which comprises a valve and an opening control means for controlling the opening of the flow control valve when the engine is lightly loaded, a mixture of some cylinders is performed when the engine is lightly loaded. A cylinder cut-off control means for performing cylinder cut-off control by shutting off the cylinder so as not to supply air and deactivating the cylinder, and when the cylinder cut-down control is executed by the cylinder cut-off control means, the opening degree control means controls An air-fuel ratio control apparatus for a cylinder number control engine, comprising: an opening degree control invalidating means for invalidating an opening degree control of a flow control valve.