JPS58144644A - Engine capable of changing number of operative cylinders - Google Patents

Abstract

PURPOSE:To obtain an optimal air-fuel ratio at the time of full-cylinder operation and also at the time of partial-cylinder operation of an engine, by providing an O2-sensor respectively in an exhaust passage for cylinders that are always kept in operation and in an exhaust passage for cylinders that can be rendered inoperative, and controlling the air-fuel ratio for these two sets of cylinders independently according to the output signals of the two O2-sensors. CONSTITUTION:An exhaust passage 1 connected to both of cylinder-group #1-#3 that can be rendered inoperative by stopping fuel supply in a low-load region and cylinder- group #4-#6 that are alway kept in operation is divided into an exhaust passage 2 for the cylinders #1-#3 and an exhaust passage #4-#6 at an intermediate portion of the passage 1. A first catalyst 7 is disposed in the exhaust passage 3 while a second catalyst 8 is disposed on the downstream side of the position where the two exhaust passages 2 and 3 are joined. Further, a first O2-sensor 9 is disposed in the exhaust passage 3 at the position on the upstream side of the first catalyst 7 while a second O2-sensor 10 is disposed in the exhaust passage 2. During the operation of an engine, the air-fuel ratio of the cylinders #1-#3 and that for the cylinders #4-#6 are controlled independently from each other by furnishing the output signals of the two sensors 9, 10 to a control means.

Description

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

Generally, when an engine is operated under a high load condition, fuel efficiency tends to improve.For this reason, in a multi-cylinder engine, fuel supply to some cylinders is cut to stop operation when the engine load is low. An engine with a controlled number of cylinders was devised that relatively increases the load on the remaining active cylinders by this amount, thereby improving overall fuel efficiency in the light load range. (See Japanese Patent Application No. 53-72849.) In this type of engine, which was previously filed by the present applicant, cylinder wells 1 to #3 on the idle side and cylinder wells #4 to #6 on the operating side are shown in Fig. Correspondingly, the exhaust passage 1 is divided halfway into a rest exhaust passage 2 and an active exhaust passage 3.

When stopping the operation of cylinders #1 to #3 in a light load range of the engine, a control device (not shown) is operated based on, for example, an intake air amount signal from an air flow meter (not shown) or a rotation speed signal from an ignition coil, etc. The fuel injection valves (not shown) installed in the intake ports corresponding to cylinders #1 to #3 are held fully closed to cut off the fuel supply, and the fuel is introduced through the throttle valve 4 in the intake passage 5. Only fresh air is supplied to the idle cylinders #1 to #3. As a result, partial cylinder operation is performed by operating only the active cylinder wells 4 to #6 while reducing the pumping loss in the idle cylinders #1 to #3.

By the way, in this engine, during normal operation (when all cylinders are operated), combusted exhaust gas is discharged from each cylinder #1 to #6 in the same way, but during partial cylinder operation, the combusted exhaust gas is discharged from cylinder wells 4 to #6 on the operating side. Similarly, combustion gas from 6 flows into the idle side cylinders #1 to #3.
Fresh air is directly discharged from the

Therefore, when using a three-way catalyst as this exhaust treatment device 6, as shown in the figure, the first catalyst 7 purifies only the exhaust from the operating cylinders #4 to #6, and the A second catalyst 8 for purifying exhaust gas from side cylinders #1 to #3 is located downstream of the working side exhaust passage 3 and in both exhaust passages 2.3.
It will be divided into two parts: downstream of the confluence and downstream of the confluence.

Furthermore, oxygen sensors 9 and 10 are installed upstream of these contacts 117 and 8, respectively, and their air-fuel ratio detection signals are sent to the aforementioned control device.

During partial cylinder operation, the injection amount of the corresponding fuel injector is corrected according to the detection signal of the first oxygen sensor 9 so that a mixture at the stoichiometric air-fuel ratio is obtained in the active cylinders #4 to #6. During all-cylinder operation, the injection amounts of all fuel injection valves are corrected according to the detection signal of the second oxygen sensor 10, and all cylinders #1 to #6 are controlled to have the stoichiometric air-fuel ratio.

This increases the conversion efficiency in the first and second cylinders [7, 8] and the corresponding cylinders #1 to #3. The reaction with the exhaust gas from #4 to #6 is promoted to purify the exhaust gas.

However, in this way, when all cylinders are operated, the idle side and active side cylinders #1 to #3. If the air-fuel ratios of #4 to #6 are controlled only by the signal from the second oxygen sensor 10, for example, due to differences in the shape of the intake system, fuel injection valves, etc. Since variations tend to occur in the intake air amount and fuel injection amount between cylinders #4 to #6, it is difficult to obtain a mixture with the optimum air-fuel ratio for both cylinders, which deteriorates the combustion state and adversely affects driving performance. It may cause harm.

Therefore, conventionally, when all cylinders are operated, the idle cylinders #1 to #3 are
It has been proposed to separately control the air-fuel ratio of the operating cylinders #4 to #6 in accordance with the detection signal of the second oxygen sensor 10 and the air-fuel ratio of the operating cylinders #4 to #6 in accordance with the detection signal of the first oxygen sensor 9. There is. (Refer to JP-A-55-131540) However, even if the air-fuel ratio is controlled in this way, the second oxygen sensor 10 is installed downstream of the confluence of the idle side and active side exhaust passages 2.3. , the detected value is influenced by the exhaust gas from the active cylinder wells 4 to #6. For example, when the exhaust cylinders #4 to #6 on the operating side become rich when the cylinder is operated, the oxygen concentration is low), and the air-fuel ratio is made lean in the cylinders #4 to #6 in accordance with the signal from the first oxygen sensor 9. However, the detected value of the second oxygen sensor 10 changes accordingly, and the air-fuel ratio of the cylinders #1 to #3 on the idle side is also instructed to be reduced.

For this reason, the air-fuel ratio of the idle cylinders #1 to #3 cannot be optimally controlled, resulting in poor combustion and impeding the purification function of the second catalyst-8, making it impossible to obtain a good exhaust composition. There was a problem with it disappearing.

This invention was made by focusing on such conventional problems, and the first oxygen sensor and the first catalyst are installed in the active side exhaust passage, while the second catalyst is installed in the idle side exhaust passage. The above problem can be solved by installing a second oxygen sensor in each of the exhaust passages on the idle side downstream of the confluence of the cylinders, and controlling the air-fuel ratio of the corresponding cylinders on the active side and idle side according to the detection signals of these sensors. The purpose of the present invention is to provide a cylinder number control engine that solves the above problems.

Hereinafter, the present invention will be explained based on the drawings. As shown in FIG. 2, cylinders #1 to #3 are cylinders on the idle side where fuel is supplied only in the light load range of the engine and only fresh air is supplied.
On the other hand, cylinder wells 4 to #6 are active cylinders that are constantly supplied with fuel and fresh air and continue to operate.

The exhaust passage 1 that connects to the idle cylinder wells 1 to #3 and the active cylinder wells 4 to #6 is divided into an idle exhaust passage 2 and an active exhaust passage 3 correspondingly. .

Among these, the working side exhaust passage 3 has working side cylinders #4 to ##.
A first catalyst 7 that purifies only the exhaust gas from cylinders #1 to #6 on the idle side is located downstream of the confluence with the exhaust passage 2 on the idle side.
A second catalyst 8 is installed to purify the exhaust gas from 3. A three-way catalyst is used as the autocatalyst 7.8.

A first oxygen sensor 9 for detecting the oxygen concentration in the exhaust gas from the active cylinders #4 to #6 is installed in the active exhaust passage 3 upstream of the first catalyst 7, and a first oxygen sensor 9 is installed in the idle side exhaust passage 2 to detect the oxygen concentration in the exhaust gas from the active cylinders #4 to #6. Cylinder #1
A second oxygen sensor 10 for detecting the oxygen concentration in the exhaust gas of #3 to #3 is installed, respectively. These sensor detection signals are a control device! Sent to 11.

The control device 11 is configured as shown in FIG. 3, where 12 is an air meter 70 upstream of the comparison valve 4, 13 is an ignition coil, and 14 is a fuel corresponding to cylinders #1 to #3 on the idle side. Injection valve 15 indicates a fuel injection valve corresponding to operating cylinders #4 to #6.

First, the control device f11 includes an air flow meter 1.
Intake air amount signal from 2 and ignition coil 13
The engine rotational speed signal is input to the basic pulse generation circuit 16. (17 is a waveform shaping circuit, 18 is a frequency conversion circuit.) The basic pulse generation circuit 16 generates a pulse signal with a period and width according to these signals, and sends the signal to the fuel control circuit 19.20. .

Based on this pulse signal, the fuel control circuit 19.20 calculates a basic fuel injection formula using a calculation unit 21.22, corrects this using a fuel correction signal to be described later, and generates fuel (pulse).
A signal is commanded to control the opening time, that is, the injection amount, of the corresponding fuel injection valve 15, 14 via the power amplifiers 23, 24.

In this case, in a light load range where the amount of intake air is small compared to the engine speed due to the width of the fuel signal, etc., the cylinder number control circuit 25 operates to control the fuel injection valves corresponding to the idle cylinders #1 to #3. 14 is held fully closed, and the fuel supply is cut off. At this time, in the working cylinders #1 to #6, the throttle valve 4 is opened so that the output is approximately twice as compared to that immediately before, and the injection amount from the fuel injection valve 15 is increased according to the increasing amount of intake air. is increased.

As a result, while the cylinders #1 to #3 are deactivated, the load on the active cylinders #4 to #6 is relatively increased to perform partial cylinder operation.

In addition, the above-mentioned 1. The detection signals of the second oxygen sensors 9 and 10 are transmitted to the air-fuel ratio control circuit 26 in the control device 11, respectively.
．． 27.

The air-fuel ratio control circuits 26.27 detect respective fuel correction signals in response to these detection signals, and send these to the corresponding increase correction sections 28.29 in the fuel control circuits 19.20.

Then, the fuel control circuits 19 and 20 each correct the basic fuel injection amount calculated based on the pulse signal from the basic pulse generation circuit 16 in accordance with the correction signal. During partial cylinder operation, the optimum air-fuel ratio is set in the active cylinders #4 to #6 so that a mixture with the optimum air-fuel ratio (stoichiometric air-fuel ratio) can be obtained in both the side cylinders #4 to #6 and the idle cylinders #1 to #3. The injection amount of the fuel injection valves 14 and 15 is controlled so that a mixture with the appropriate fuel ratio is obtained.

In other words, in both full-cylinder operation and partial cylinder operation, the active cylinder #
4 to #6, the air-fuel ratio is controlled according to the detection signal of the first oxygen sensor 9, and in the idle cylinders #1 to #3, the air-fuel ratio is controlled according to the detection signal of the second oxygen sensor 10 when all cylinders are in operation. It controls the air-fuel ratio.

In addition, in FIG. 3, there is an engine start switch, 36 is a throttle valve switch, and 37 is a water temperature sensor, and these detection signals are sent to the fuel control circuit 19, 20 to increase the fuel amount via the respective fuel increase correction circuits 38, 39, and 40. It is input to the correction section 28, 29 and 1. The amount of fuel supplied to each cylinder #1 to #6 is increased at the time of starting, idling, and depending on the water temperature state, so that an air-fuel ratio suitable for the operating state can be obtained. Also, 41
42 and 43 indicate a battery, and 42 and 43 indicate a power supply voltage correction circuit.

With this configuration, air-fuel ratio control is performed accurately in the operating cylinders #4 to #6, and
This prevents the exhaust gas from affecting the detected value of the second oxygen sensor 10 installed in the idle side exhaust passage 2.

Therefore, from the second oxygen sensor 10 to the idle cylinder #1
The oxygen concentration in the exhaust gas of the cylinders #1 to #3 can be accurately detected, and therefore the air-fuel ratio of the cylinders #1 to #3 on the inactive side can also be appropriately controlled.

As a result, the combustion state of all cylinders #1 to #6 can be maintained in good condition to increase the output, and the conversion efficiency of the first and second catalysts 7 and 8 can be maintained at the best level to improve exhaust performance. can.

FIG. 4 shows another embodiment of the present invention, which is an engine in which intake air is introduced directly from the intake passage 5 upstream of the air meter 12 to the cylinder valves 1 to #3 on the idle side during partial cylinder operation. , performs the air-fuel ratio control described above.

However, like the exhaust passage 1, the intake passage 5 is divided from the middle into a rest-side intake passage 30 and an active-side intake passage 31 corresponding to the cylinder valves 1 to #3 on the rest side and the cylinders #4 to #6 on the working side. , pause, a cutoff valve 32 is installed at the upstream side of the side intake passage 30, and a fresh air supply valve 34 is installed at the bypass passage 33 that connects the intake side passage 30 and the intake passage 5 upstream of the air 70-meter 12. .

During partial cylinder operation, the cutoff valve 32 is closed and the fresh air supply valve 34 is opened.

Further, the working side exhaust passage 31 has a first oxygen sensor 9 and a first contact tIIA7, and the resting side exhaust passage 2 has a second oxygen sensor 10. A second catalyst 8 is installed downstream of the confluence of both exhaust passages 2.3, and the air-fuel ratio of each cylinder #1 to #6 is controlled by the control device 11 shown in FIG. 3 in the same manner as in the previous embodiment. Ru.

In this embodiment, with almost the same load, there is little variation in the amount of intake air passing through the air flow meter 12 between full-cylinder operation and partial-cylinder operation, so the air-fuel ratio control is highly accurate and more effective.

As explained above, according to the present invention, in a multi-cylinder engine in which only fresh air is supplied to the cylinder on the idle side during partial cylinder operation in a light engine load range, the exhaust passage can be arranged to correspond to the cylinder on the idle side and the cylinder on the active side. The first oxygen sensor and the first catalyst are installed in the active exhaust passage, the second oxygen sensor is installed in the idle exhaust passage, and the second catalyst is installed downstream of the confluence of both exhaust passages. , and the air-fuel ratios of the corresponding active and idle cylinders were controlled separately according to the sensor detection signals, so that the optimum air-fuel ratio was maintained for each cylinder regardless of whether all cylinders were operating or partial cylinders were operating. This has the effect of increasing the conversion efficiency of the catalyst, maintaining a good exhaust composition, and improving engine performance.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view of a conventional device, FIG. 2 is a schematic plan view showing an embodiment of the present invention, FIG. 3 is a block diagram showing a W control device of the present invention, and FIG. 4 is a schematic plan view of an embodiment of the present invention. FIG. 2 is a schematic plan view showing an embodiment of the invention. 1...Exhaust passage, 2...Stopping side exhaust passage, 3...
Operating side exhaust passage, 4... Throttle valve, 5... Intake passage,
7... First catalyst, 8... Second catalyst, 9... First oxygen sensor, 10... Second oxygen sensor, 11.
...Control device, 12...Air 70-meter, 13...
・Ignition coil, 14.15...Fuel injection valve.

Claims (1)

[Claims] In a multi-cylinder engine, there are two cylinders: a cylinder on the idle side to which fuel supply is cut off and only fresh air is supplied in the light load range of the engine, and an active cylinder to which fuel and fresh air are constantly supplied and operation continues. The exhaust passage is divided halfway into a cylinder on the idle side and a cylinder on the active side, and a first oxygen sensor and a first catalyst are installed in the active side exhaust passage, and a second sensor is installed in the exhaust side exhaust passage.
A second catalyst is installed downstream of the confluence of both exhaust passages, and a control device is provided that separately controls the air-fuel ratio of the corresponding working side cylinder and stop side cylinder according to these sensor detection signals. Features a cylinder number control engine.