JPS5951666B2 - cylinder number control engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cylinder number control engine that performs partial cylinder operation in which operation of some cylinders is stopped when the engine is under light load.

In general, fuel efficiency tends to improve when an engine is operated under a high load. Therefore, in a multi-cylinder engine, when the engine load is low, fuel supply to some cylinders is cut to stop operation, and the fuel consumption is reduced. An engine with controlled number of cylinders was devised that relatively increases the load on the remaining operating cylinders, thereby improving overall fuel efficiency in the light load range.

Conventionally, in this engine, as shown in FIG. 1, a cutoff valve 2 provided downstream of a throttle valve 1 is closed during partial cylinder operation to cut off the supply of fresh air to the idle cylinders, and at the same time, an exhaust recirculation valve 3 is closed. When opened, exhaust gas at approximately atmospheric pressure is recirculated from the exhaust passage 4a on the idle cylinder side to the exhaust gas recirculation passage 5 to the intake system of the idle cylinder, reducing pumping loss in the idle cylinder when the working body is inactive, further improving fuel efficiency. We are trying to

In addition, both exhaust passages 4a and 4b on the operating cylinder side and the idle cylinder side
An air-fuel ratio sensor 6 is disposed downstream of the confluence point 4C of The fuel injection amount determined based on the fuel injection amount is feedback-corrected via the control circuit 8, thereby increasing the conversion efficiency of the three-way catalyst 9 and achieving the best purification of exhaust gas, and at the same time further improving fuel efficiency.

By the way, in such a conventional engine, during partial cylinder operation, the amount of NOx produced in the operating cylinders increases due to the relative increase in load, while the low-temperature recirculated exhaust gas discharged from the idle cylinders increases. This leaks into the three-way catalyst 9, lowering the temperature of the catalyst 9 and reducing its conversion efficiency, resulting in a problem that the degree of purification of exhaust gas deteriorates.

The present invention has been made in view of the above, and an object of the present invention is to obtain a cylinder number controlled engine that can satisfactorily purify exhaust gas even during partial cylinder operation.

This will be explained below with reference to the drawings.

FIG. 2 shows an embodiment of the present invention.

10 is an air introduction pipe (air gear) for introducing air into the exhaust system on the side of the idle cylinder, and a check valve 11 is interposed in the middle, and three secondary air introduction pipes corresponding to the number of cylinders are installed downstream of the check valve 11. Pipes 12a, 12b, 12C
is connected.

Taking the pipe 12a as an example, each pipe block 12a, 12b, 12C has an exhaust port 1-' as shown in FIG.
It opens in the center near the exit 1 of 13a.

In FIG. 3, 14a is an exhaust valve, 15a is an intake port, 16a is an intake valve, 17a is a branch of the exhaust passage 4a on the side of the idle cylinder, and 18a is a piston.

The rest of the structure is the same as in FIG. 1, and the same members are given the same reference numerals.

By the way, during partial cylinder operation, the cylinders are inactive, so high-pressure combustion exhaust gas is not discharged, and therefore each secondary air introduction pipe 12a, 12b, 12C
The pressure at the open 1'' portion is relatively reduced compared to when all cylinders are operated.

Also, during this partial cylinder operation, although the exhaust gas at approximately atmospheric pressure is recirculated, in reality, each pipe 12a, 12b, 1
The pressure at the opening of 2C periodically fluctuates above and below approximately atmospheric pressure in accordance with the opening and closing of the valve and the movement of the piston.

For this reason, the pressure in the opening mentioned above sometimes becomes negative pressure periodically in synchronization with the rotation of the clamp, and the magnitude of the negative pressure is also larger than when operating all cylinders because there is no pressure increase during the explosion stroke. After all, during partial cylinder operation, a relatively large amount of air is introduced into the exhaust passage 4a on the idle cylinder side through the air gear gallery 10 and the pipes 12a, 12b, 12C, compared to when the full cylinder operation is performed.

This introduced large amount of air mixes with the combustion exhaust discharged from the active cylinder side and dilutes it at the confluence point 4C of both the exhaust passages 4a, 4b on the active cylinder side and the idle cylinder side.

When this diluted exhaust gas flows into the air-fuel ratio sensor 6, the sensor 6 outputs a weaker air-fuel ratio detection signal by the amount of dilution, so the fuel injection amount in the operating cylinder increases in order to enrich the air-fuel ratio. As a result, during partial cylinder operation, a rich air-fuel mixture is supplied to the active cylinders in accordance with the dilution of the exhaust gas.

Therefore, the amount of NOx generated, which is highest when the air-fuel ratio is stoichiometric, is reduced by enriching the air-fuel mixture.

In addition, the rich mixture combustion exhaust from the operating cylinders contains a rich amount of unburned substances, and after a large amount of oxygen is added from the diluted air, this flows into the three-way catalyst 9, so it is diluted with air. Even with such exhaust gas whose temperature has decreased due to oxidation, etc., an oxidation reaction easily occurs in the three-way catalyst 9, and the catalyst 9 is maintained at a high temperature by the reaction heat.

On the other hand, in response to the dilution of the exhaust gas, the air-fuel mixture is enriched so that the exhaust gas becomes the combustion exhaust gas at the stoichiometric air-fuel ratio. It corresponds to combustion exhaust.

As a result, combined with the above-mentioned high temperature of the catalyst 9, the catalyst 9
The conversion efficiency was maintained extremely well, and the above-mentioned NO
In addition to the reduction in production volume, the exhaust gas is sufficiently purified even during partial cylinder operation.

Note that the amount of air flowing in from each of the pipes 12a, 12b, and 12C significantly depends on the internal cross-sectional area, etc. of each pipe, so it is necessary to determine the internal cross-sectional area, etc., so as to obtain the optimum inflow amount.

Furthermore, the check valve 11 functions to prevent backflow of exhaust gas.

By the way, during all-cylinder operation, as mentioned above, the amount of air flowing in from each pipe 12a, 12b, 12C is very small, and the air-fuel mixture is accurately feedback-controlled to the stoichiometric air-fuel ratio. In order to
A valve may be provided to shut off the

As explained above, according to the present invention, exhaust gas can be sufficiently purified even during partial cylinder operation by simply providing a simple mechanism for introducing air into the exhaust system on the idle cylinder side during partial cylinder operation. becomes possible.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing a conventional engine, FIG. 2 is a schematic sectional view showing main parts of an embodiment of the engine of the present invention, and FIG. "]
It is a sectional view showing a part in detail. ]...Finger valve, 2...Shutoff valve, 3...Exhaust recirculation valve, 4a, 4b...Exhaust passage, 4C...Confluence point, 5...
...Exhaust recirculation passage, 6...Air-fuel ratio sensor, 7...Air flow meter, meter...Control circuit, 9...Three-way catalyst,
10...Air gear rally, 11...Check valve,
12a, 12b, 12C...Secondary air introduction pipe, 1
3a...Exhaust port, 14a...Exhaust valve, 15a...
... Intake port, 16a... Intake valve, 17a... Exhaust passage branch, 18a... Screws 1 to 1.

Claims (1)

[Scope of Claims] 1. Means for performing partial cylinder operation by cutting off fuel supply to some cylinders to stop operation when the engine is under light load, and detection by an air-fuel ratio sensor provided in the exhaust passage downstream of the exhaust port. In a multi-cylinder engine having a means for feedback controlling the fuel supply amount so that the air-fuel mixture reaches the stoichiometric air-fuel ratio according to the air-fuel ratio sensor, and a three-way catalyst disposed in the exhaust passage downstream of the air-fuel ratio sensor, This engine is equipped with an air introduction pipe having one end open to the exhaust port of the cylinder whose operation is stopped during cylinder operation and the other end communicating with the atmosphere, and a check valve interposed in the air introduction pipe. 2. The cylinder number control engine according to claim 1, wherein the air introduction pipe is provided with a cutoff valve that opens only during partial cylinder operation upstream of the check valve.