JPS5974321A - Exhaust gas purifier for engine controlled of number of working cylinders - Google Patents

Abstract

PURPOSE:To keep the activity of a catalyst sufficiently high, by placing the first catalyst bed of a reducing catalyst converter in an exhaust passage for always working cylinders and providing a second catalyst bed surrounded by the first catalyst bed and placed in an exhaust passage for not always working cylinders, to maintain the temperature of the second catalyst bed. CONSTITUTION:A cylinder number control circuit 14 receives a negative pressure signal S3 from a negative pressure sensor 15 and a water temperature signal S4 from a water temperature sensor 16 so that the circuit acts to cut off injection pulses Pb, Pc to put a second and a third cylinders 2b, 2c at rest when the load on the engine is not higher than a prescribed level and its temperature is not lower than a prescribed level. An exhaust passage 4a for always working cylinders 2a, 2d communicates with a first catalyst bed 17a placed in the outer section of a reducing catalyst converter 17. An exhaust passage 4b for the not always working cylinders 2b, 2c communicates with a second catalyst bed 17b surrounded by the first catalyst bed 17a.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust purification device for an engine with controlled number of cylinders.

Generally, in internal combustion engines, during low-load operation, the pumping loss increases, leading to a decrease in fuel efficiency. A so-called cylinder number control engine is being considered, which aims to improve fuel efficiency by increasing the load on other operating cylinders.

One method of stopping the mixture supply to some cylinders as in the above method is to provide a dedicated fuel injection valve for each cylinder, as shown in, for example, Japanese Patent Application Laid-Open No. 158515/1983. Among these, a so-called fuel cut method is known in which fuel injection valves for some cylinders are stopped. In an engine in which the number of cylinders is controlled by such a fuel cut, only air is sent to the deactivated cylinders during partial cylinder operation in which some cylinders are deactivated.

On the other hand, in order to purify exhaust gas, a catalyst is often installed in the engine exhaust passage. Catalysts used in automobile engines and the like are generally classified into three types depending on the reaction: oxidation catalysts, reduction catalysts, and three-way catalysts, and these are of course widely used in engines with controlled number of cylinders as described above. However, among the above-mentioned catalysts, when a reduction catalyst or a three-way catalyst, in which a reduction reaction is used for exhaust purification, is used in the fuel cut-type cylinder number control engine, during partial cylinder operation, the idle cylinders are not used for combustion and are A problem arises in that the oxygen concentration in the exhaust gas increases due to the air that circulates and is discharged into the exhaust passage, destroying the reducing atmosphere and inhibiting exhaust gas purification.

Therefore, conventionally, the above-mentioned Japanese Patent Application Laid-Open No. 54-158515
As indicated in the publication, the exhaust passage on the side of the deactivated cylinder, which can be deactivated during partial cylinder operation, and the exhaust passage on the side of the active cylinder, which is always operated, are separated, and a reduction catalyst (including a three-way catalyst) is used. ) 2 converters separated from each other
An exhaust gas purification device has been considered which is formed from two catalyst beds and in which the two exhaust passages are separately communicated with these catalyst beds. In this way, excessive air will not be sent to the catalyst that purifies the exhaust gas on the operating cylinder side by a reduction reaction, and a stable exhaust gas purification device can be obtained.

However, in the above-mentioned catalytic converter, when the engine is in partial cylinder operation, high-temperature exhaust gas is not sent to the catalyst communicating with the idle cylinder, but only air that has simply passed through the idle cylinder is sent. will be cooled by outside air, wind from the vehicle, etc. The catalyst, which has been cooled to a low temperature, loses sufficient activity, and the next time the engine returns to full cylinder operation and exhaust gas is sent, it can immediately sufficiently purify the exhaust gas. Therefore, a problem arises in that the exhaust gas purification rate decreases until the catalyst is heated by the exhaust gas.

SUMMARY OF THE INVENTION An object of the present invention is to provide an exhaust gas purification device for an engine with controlled number of cylinders, which eliminates the above-mentioned problems.

As described above, the exhaust gas purification device for an engine with a controlled number of cylinders according to the present invention has two catalyst beds that are separated from each other and each independently communicates with the exhaust passage on the idle cylinder side and the exhaust passage on the active cylinder side. In the converter (including the original catalyst),
A catalyst bed (first catalyst bed) communicating with the working cylinder side exhaust passage is arranged around the converter, while a catalyst bed (second catalyst bed) communicating with the idle cylinder side exhaust passage is connected to the first catalyst bed. It is located in the center of the converter so that it is surrounded by the floor.

With the above configuration, during partial cylinder operation, the second catalyst bed communicating with the exhaust passage on the idle cylinder side is kept warm by the first catalyst bed through which high-temperature exhaust gas flows, and maintains sufficient catalytic activity. As soon as the engine returns to full cylinder operation and exhaust gas is sent, the exhaust gas is sufficiently purified.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a cylinder number controlled engine equipped with an exhaust purification device according to an embodiment of the present invention. 4 of the first cylinder 23 to fourth cylinder 2d formed in the cylinder block 1
Each cylinder has a first intake passage 33 to a fourth intake passage 3.
d are communicated with each other, and the exhaust passage 4 is also communicated with each other. A throttle valve 6 that is operated by an accelerator pedal or the like to control the amount of intake air is provided in the intake passage 5 upstream of the gathering part of the first intake passage 3a to the fourth intake passage 3d, and the throttle valve 6 is located at an upstream position. is provided with an air flow sensor 7 that detects the amount of intake air.

Each of the first to fourth intake passages 3a to 3d includes a fuel injection valve that injects fuel into the intake air flowing through the intake passages 33 to 3d to form an air-fuel mixture to be supplied to each cylinder 2a to 2d. 11a to lid are provided. These fuel injection valves 1
1a to Ild are formed and output by the fuel injection control circuit 13 based on the intake air amount signal S1 outputted by the button 7 yometer 7a of the airflow sensor 7 and the rotational speed signal S2 outputted by the engine rotational speed sensor 12. Injection pulse signal P
a to Pd, the cylinders 2a to 2d are driven to inject a predetermined amount of fuel commensurate with the amount of intake air in each cycle of each cylinder 2a to 2d.

As shown in FIG. 1, the injection pulse signal Pa-P
d is connected to each fuel injection valve 113 through the cylinder number control circuit 14.
It is set to be input to lid. Although this cylinder number control circuit 14 is conventionally known, the cylinder number control circuit 14 will be briefly explained below with reference to FIG. 2. The cylinder number control circuit 14 includes a negative pressure signal S output from a negative pressure sensor 15 that detects the intake negative pressure in the intake passage 5 on the downstream side of the throttle valve 6 to detect engine load, and engine cooling water. A water temperature signal vS4 output from a water temperature sensor 16 that indirectly detects the engine temperature from the temperature is input.

The negative pressure signal S3 outputted by the negative pressure sensor 15 is sent to the comparator circuit 20.
In the comparison circuit 20, the negative pressure signal S3 is compared with a set negative pressure signal S6, which is also generated by the set signal generating circuit 21 and carries a negative pressure corresponding to a predetermined engine load. The negative pressure signal S3 is the set negative pressure signal S.

When the engine load exceeds the predetermined value, that is, when the engine load is less than a predetermined value, the comparator circuit 20 outputs an output S7. Further, the water temperature signal S4 outputted from the water temperature sensor 16 is sent to the comparison circuit 22.
In the comparison circuit 22, the set water temperature signal S8, which is generated from the set signal generating circuit 23 and carries a water temperature corresponding to a predetermined engine temperature, is compared with the water temperature signal S4. When the water temperature signal S4 exceeds the set water temperature signal S8, that is, when the engine temperature is above a predetermined value, the comparison circuit 22 outputs an output S. The comparison circuits 20 and 22 are connected to gate circuits 25 and 26 via an AND gate 24. These gate times, @
25 and 26 are injection pulse signals Pb that drive the fuel injection valves 11b and 11C for the second and third cylinders 2b and 2C, respectively;
It passes through and blocks Pc, and the AND gate 2
When the output 810 is issued from 4, that is, when the engine load is below a predetermined value and the engine temperature has reached the predetermined temperature, the injection nozzle signal Pb.

Pc is cut off, and the signal Pb is used at other times.

Pass Pc. As described above, the injection pulse signal Pb,
When Pc is cut off, fuel injection from the fuel injection valve 11b and IIC is naturally stopped, and the second and third cylinders 2b and 2C are stopped. Therefore, during low load, the engine is operated only by the first and fourth cylinders 2a and 2d, and as described above, the pumping loss is reduced and fuel efficiency is improved. The reason why we do not operate two cylinders when the engine temperature is low is that when the engine temperature is low, fuel atomization is poor (and combustion is unstable), so we also run two cylinders to avoid engine malfunction. This is to prevent the stable state from increasing.

As described above, the reduction catalytic converter 17 that carries a reduction catalyst and purifies exhaust gas through the reduction reaction of the catalyst is disposed in the exhaust passage 4 of the engine that performs cylinder number control using a general fuel cut method. has been done. The exhaust passage 4 is connected to an active cylinder side exhaust passage 4a that communicates with the first and fourth cylinders 2a and 2d that are operated in all operating ranges, and an exhaust passage 4a that communicates with the second and third cylinders 2b and 2C that are inactive during a specific operation. It is divided into two systems, one being the inactive cylinder side exhaust passage 4b which communicates with the other.

Figure 3 and Figure 4, which is a sectional view taken along the line IV-IV of Figure 3.
As shown in detail in the figure, the catalytic converter 17 is monolithic with a honeycomb cross section, and the inactive cylinder side exhaust passage 4b is arranged such that the end portion of the pipe wall 4C is in contact with the center of the catalyst bed of the converter 17. It is connected to 17. The other active cylinder side exhaust passage 4a is installed around the inactive cylinder side exhaust passage 4b so as to communicate with the converter 17. The pipe wall 4C of the idle cylinder side exhaust passage 4b is connected to the upstream end of the catalyst bed of the converter 17 while maintaining airtightness between the inside and outside of the pipe wall 4C, so that the pipe wall 4C is connected to the upstream end of the catalyst bed of the converter 17, so that the pipe wall 4C is connected to the upstream end of the catalyst bed of the converter 17. The exhaust gas that flows through the outer cylindrical part of the converter partition wall 17c that aligns with the pipe wall 4C, and the exhaust gas sent to the converter 17 from the idle cylinder side exhaust passage 4b flows through the inner part of the partition wall 17c. It circulates through the center. In other words, the converter 17 is divided into an outer part (first catalyst bed) 17a and an inner part (second catalyst bed) 17b by the partition wall 17C.

As mentioned above, since the first catalyst bed 17a communicating with the active cylinders 2a, 2d and the second catalyst bed 17b communicating with the dormant cylinders 2b, 2C are completely separated, during partial cylinder operation, The air that has passed through the second and third cylinders 2b and 2C is
, the exhaust gas from the fourth cylinders 2a and 2d is not sent to the catalyst that purifies it (the exhaust gas is stably purified by the reduction reaction of the catalyst).

Then, during partial cylinder operation of the engine, the second catalyst bed 17b
No high-temperature exhaust gas is sent to the cylinder 2b, which is simply the idle cylinder 2b.
, 2C is fed into the second catalyst bed 17b, but as described above, even during this partial cylinder operation, the second catalyst bed 17b is surrounded by the first catalyst bed 17a into which high-temperature exhaust gas from the active cylinders 2a and 2d is fed. and the first catalyst bed 1
7a protects it from the outside air, the wind from the vehicle, etc., and keeps it warm. By receiving such heat insulation, the second catalyst bed 1
The catalyst 7b maintains its catalytic activity even during partial cylinder operation, and then the engine returns to full cylinder operation and the second and third cylinders 2b, 2
When the exhaust gas is sent from C, the exhaust gas is immediately sufficiently purified.

In the above embodiment, a monolith type catalytic converter 17 is used, but it is of course possible to use a pellet type catalytic converter, and in such a case, a cylindrical partition wall may be provided inside the converter. The catalyst bed may be divided into an inner part and an outer part.

As explained in detail above, the exhaust gas purification device for a cylinder number controlled engine of the present invention maintains the catalytic activity of the catalyst bed on the side of the idle cylinder at a sufficiently high level even when the engine is in partial cylinder operation. Therefore, it is possible to reliably prevent a transient decrease in the purification rate when the engine returns to full-cylinder operation.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing one embodiment of the present invention, Fig. 2 is a block diagram showing in detail the configuration of an electric circuit in the above embodiment, and Fig. 3 is a side cross section showing an enlarged part of the above embodiment. 4 is a sectional view taken along the line IV-IV in FIG. 3. 2a, 2b, 2C92d...Cylinder 3a, 3b
, 3c, 3d, 5... - Intake passage 4a... Working cylinder side exhaust passage 4b... Inactive cylinder side exhaust passage 11a, llb, lic, Ild... Fuel injection valve 14
... Cylinder number control circuit 17 ... Reduction catalytic converter

Claims (1)

[Claims] In a cylinder number control engine that allows air to flow through the idle cylinders even during partial cylinder operation, the exhaust passage is divided into two systems: an exhaust passage on the active cylinder side and an exhaust passage on the idle cylinder side, and the first catalyst is placed around the exhaust flow passage. The reduction catalytic converter is divided into a bed and a second catalyst bed surrounded by the first catalyst bed. This is an exhaust purification device for an engine that controls the number of cylinders and is arranged in a staggered manner.