JPS5898639A - Engine capable of changing number of cylinder to be operated - Google Patents

Abstract

PURPOSE:To enable to execute proper feedback control on the air-fuel ratio for both of operative cylinders and inoperative cylinders of an engine capable of changing the number of cylinders to be operated, by separating the exhaust passage for operative cylinders and that for inoperative cylinders from each other to a position just before a catalyst, and providing an air-fuel ratio sensor in each of the exhaust passages. CONSTITUTION:In low-load operation of an engine, fuel injection valves (a)-(c) stop fuel supply to cylinders #1-#3 that are to be rendered inoperative. At the same time, a fresh-air supply valve 10 is opened by the instruction of a control circuit 12, and an intake passage 2 for the cylinders #1-#3 is closed by a fresh-air stop valve 11, so that the cylinders #1-#3 are rendered inoperative. Further, an exhaust passage 5 for the inoperative cylinders #1-#3 and an exhaust passage 6 for operative cylinders #4-#6 are separated from each other to a position just before a catalyst 15, and air-fuel ratio sensors 13, 14 are provided respectively in the exhaust passages 5, 6. The output signals of the two air-fuel ratio sensors 13, 14 are furnished to the control circuit 12 and used for feedback control of the air-fuel ratio for the inoperative cylinders #1-#3 and operative cylinders #4-#6.

Description

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

Generally, fuel efficiency tends to improve when an engine is operated under a high load. Therefore, in a multi-cylinder engine, fuel supply to some cylinders is cut to stop operation when the engine load is low. An engine with cylinder number control has been devised that relatively increases the load on the remaining active cylinders by this amount and improves overall fuel efficiency in the light load range.

(Japanese Unexamined Patent Publication No. 55-37581) Conventionally, in this type of engine, the intake passage and the exhaust passage are divided into two systems, each corresponding to the cylinder on the idle side and the cylinder on the operating side. When the fuel supply is cut, partial cylinder operation is performed by sufficiently supplying fresh air from the intake passage on the idle side to the cylinder on the idle side. In addition, the engine loss in the cylinder on the idle side has been reduced to further improve fuel efficiency.

By the way, in such an engine, during normal operation (when operating all cylinders), both the idle and active cylinders burn and emit exhaust gas in the same way, but during partial cylinder operation, exhaust gas is emitted from the active cylinder as well. but.

Fresh air is directly discharged from the cylinder on the idle side.

Therefore, when attempting to feedback-control the air-fuel ratio by correcting the amount of fuel supplied to each cylinder based on the oxygen concentration in the exhaust gas, the air-fuel ratio sensor that detects the oxygen concentration should be connected to the operating side cylinder. It was necessary to install it in the exhaust gas of the engine, that is, in the operating side exhaust passage. By modifying this, it is possible to detect the oxygen concentration in the combustion exhaust gas during both full-cylinder operation and partial cylinder operation, and feedback control of the air-fuel ratio in each cylinder can be performed.

However, while this allows accurate feedback control of the air-fuel ratio in the active cylinder, feedback control in the idle cylinder is performed according to the air-fuel ratio in the active cylinder, so The accuracy cannot be said to be good, and there is a problem in that it is difficult to maintain the air-fuel ratio at the optimum level in the cylinder on the idle side as in the cylinder on the active side.

This invention was made with attention to such problems, and a fuel-fuel ratio sensor is installed in each of the exhaust passage on the operating side and the exhaust passage on the idle side, and the exhaust gas of the operating side cylinder and the idle side cylinder is The purpose of this invention is to provide a cylinder number control engine that enables feedback control of the optimum air-fuel ratio for each cylinder by separately detecting the oxygen concentration in gas.

Embodiment 1r of the present invention will be described below based on the drawings.

1, each cylinder φ1 to +6 of the engine is divided into inactive cylinders 1 to 3, whose operation is suspended by cutting fuel supply from fuel injection valves a to c in a light load range, and cylinders φ1 to 3, which are inactive in the light load range, and continuous fuel injection valves d- f
Correspondingly, the intake passage 1 and the exhaust passage 4 are divided into working side cylinders 4 to +6 to which fuel is supplied from the inactive side intake passage 2 and the working side intake passage 3. It is divided into a rest side exhaust passage 5 and an active side exhaust passage 6.

In this engine, during normal operation, when all cylinders are operated, fuel is supplied to each cylinder 1 to 6, and intake air is evenly introduced through the throttle valve 7.

Therefore, the cylinder on the idle side ÷ 1 ~ ÷ 3 and the cylinder on the operating side φ
Exhaust gas after combustion is discharged from the exhaust gases 4 to 6, respectively.

On the other hand, during partial cylinder operation in which the fuel supply to the idle cylinders φl to 3 is cut in the light load range, the operating cylinders φl to φ3 are cut off.
Fuel and intake air are supplied to φ6 to perform combustion, but fresh air is supplied to the cylinders +1 to +3 on the idle side from the air supply path 9 connecting the intake passage 2 on the idle side and the intake passage 1 upstream of the air flow meter 8. is introduced as a W-contact. Therefore, at this time, the exhaust gas after combustion is discharged from the operating side exhaust passage 6, and fresh air is discharged from the idle side exhaust passage 5.

However, there is a fresh air supply valve 10 in the middle of the fresh air supply passage 9.
A fresh air cutoff valve 11 is interposed in the upstream part of the intake passage 2 on the idle side, and opens the fresh air supply passage 9 during partial cylinder operation in response to a command from the control path 12, thereby shutting down the intake passage 2 on the idle side. It is configured to close the passage 2.

In this embodiment, air-fuel ratio sensors 13 and 1 are provided in the middle of the idle-side exhaust passage 5 and the working-side exhaust passage 6 of this engine, respectively.
4 is installed to separately detect the oxygen concentration in the exhaust gas of the idle cylinders 1 to 3 (when all cylinders are in operation) and the oxygen concentration in the exhaust gas of the operating cylinders 4 to 6. The detection signal is input to the control circuit 12.

Based on the intake air amount signal from the air flow meter 8 and the engine rotation speed signal from a rotation sensor (not shown), the control circuit 12 controls each cylinder from 1 to φ6 during all-cylinder operation.
The basic fuel injection amount is calculated and corrected according to the detection signal of the corresponding air-fuel ratio sensor 13. The fuel injection amount of each of the fuel injection valves a to f is feedback-controlled to obtain the desired amount. As a result, each cylinder
In addition to obtaining optimum combustion in the exhaust passages 5 and 6, the exhaust gas purification efficiency is maintained at a good level at the catalyst (three-way catalyst) 15 provided downstream of the exhaust passages 5 and 6 on the idle side and the active side.

Furthermore, in the engine light load range, the control circuit 12Fi closes the fresh air cutoff valve 11 as described above, opens the fresh air supply valve 10, and closes the fuel injection valves a to c, judging from the intake air amount signal, for example. The cylinder φ1 on the idle side is controlled to remain closed.
- Cut O fuel supply to φ3 to stop operation and perform partial cylinder operation.

In this case, by closing the shutoff valve 11, all of the fresh air that has passed through the throttle 9P7t will be inhaled into the operating open cylinders 4 to 6, and the amount of intake air in each cylinder will be smaller than that immediately before. is 2
Since the fuel injection volume is doubled, the injection amount from the fuel injection tank d-f is correspondingly doubled.
The injection constant is switched.

At this time, the basic fuel injection in the working side cylinders 4 to 6 is corrected according to the detection signal of the air-fuel ratio sensor 14 installed in the working side exhaust passage 9, and the fuel injection valve is adjusted to the stoichiometric air-fuel ratio. The injection amount of df is feedback-controlled. That is, the load on the operating cylinders 4 to 6 is relatively increased to operate in an operating range with excellent fuel efficiency and to maintain optimal combustion.

In this embodiment, the air-fuel ratio sensors 13 and 14 are installed in each of the idle-side exhaust passage 5 and the active-side exhaust passage 6, and the air-fuel ratio sensors 13 and 14 are installed in the idle-side exhaust passage 5 and the active-side exhaust passage 6, and the cylinders on the idle side are connected in accordance with the detection signals of these air-fuel ratio sensors 13 and 14. Since the air-fuel ratios in φ1 to 3 and active cylinders +4 to +6 are controlled separately and independently, accurate feedback control of the air-fuel ratio is possible, and the optimum air-fuel ratio for both φ3 and φ3 is achieved depending on the operating conditions. The fuel ratio can be obtained.

This improves the combustion state, further improving fuel efficiency and drivability, and also improves the purification efficiency of the catalyst 15 and reduces its burden, thereby further improving the exhaust composition.

As described above, according to the present invention, the air-fuel ratio of the active cylinder is determined according to the detection signal of the air-fuel ratio sensor installed in the active exhaust passage, and the air-fuel ratio of the idle cylinder is determined according to the detection signal of the air-fuel ratio sensor installed in the idle exhaust passage. Since the air-fuel ratio is controlled separately according to the detection signal of the air-fuel ratio sensor, accurate feedback control of the air-fuel ratio is performed in each cylinder, and the optimum air-fuel ratio can be maintained.

[Brief explanation of drawings]

The figure is a cross-sectional view showing an embodiment of the present invention. 2... Intake passage on the idle side, 3... Intake passage on the operating side, 5
...Stopping side exhaust passage, 6...Working wJII exhaust passage,
7... Throttle valve, 8... Air 70-meter, 9... Fresh air supply passage, 10... Fresh air supply valve, 11... Fresh air cutoff valve, 12... Control (ro ) Road, 13.14... Air-fuel ratio sensor, 15... Catalyst. Patent applicant Nissan Motor Co., Ltd.

Claims (1)

[Claims] In a multi-cylinder engine with a deactivated cylinder whose fuel supply is cut off in the light load range of Ennon, and an operational II cylinder which is constantly supplied with fuel, both exhaust paths are connected to the deactivated cylinder and the operational cylinder. Correspondingly, the air-fuel ratio sensor is divided up to just before the catalyst, and air-fuel ratio sensors are installed in the idle-side exhaust passage on the upstream side of the catalyst. A cylinder number control engine characterized by being equipped with a control circuit that separately controls the air-fuel ratio of the side cylinder and the active side cylinder.