JPH09184415A - Blowby gas recirculation device of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an HC quantity discharged in an exhaust pipe during cooling operation of an engine. SOLUTION: An engine blowby gas recirculation device is provided with such constitution that a blowby gas recirculation passage 14 for giving communication between an engine inside chamber 7 in which blowby gas flows through from a combustion chamber 6 and an intake air pipe 3 located downstream from an intake air throttle valve 4 and a fresh air introducing passage 11 for giving communication between an air intake pipe located upstream from the intake air throttle valve 4 and the engine inside chamber 7 are provided. In this case, such a means 21 as closing the fresh air introducing passage 11 under such a condition as blowing out the flame of combustion gas near the top land of a piston 5 and a bore wall is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine blow-by gas recirculation system.

[0002]

2. Description of the Related Art Gas blown from a combustion chamber into a crank chamber through a gap between a piston and a cylinder (blow-by gas)
There is a system in which the air is returned to the intake passage to prevent air pollution due to blow-by gas (Actual No. Sho 62-29).
413).

To explain this, when the load is low, as shown in FIG. 6 (A), the fresh air upstream of the air cleaner 2 passes through the fresh air introduction passage 11 and the fresh air passage 12 to the crank chamber 7.
The blow-by gas blown from the combustion chamber 6 into the crank chamber 7 is introduced into the oil separator 16 above the valve operating chamber 9 through the blow-by passage 13 by the fresh air, and the oil mist in the blow-by gas is introduced there. Are separated. The blow-by gas from which the oil mist has been separated passes through the blow-by gas recirculation passage 14 together with the fresh air, and then the throttle valve 4
It is introduced into the intake pipe 3 on the downstream side and burned in the combustion chamber 6.

On the other hand, since the amount of blow-by gas increases under high load, unlike the case of low load, blow-by gas moves with fresh air through the crank chamber 7 and fresh air passage 12 as shown in FIG. 6B. After rising to the valve chamber 9 and the oil mist is separated by the oil separator 17, it is introduced into the intake passage 3 through the fresh air introduction passage 11.

[0005]

By the way, unburned gas is generated due to the extinction of the piston near the top land and the bore wall immediately after the cold start and before the engine is warmed up. For example, since the amount of gas blown into the crank chamber as blow-by gas is small, most of the unburned gas is directly discharged to the exhaust pipe as HC.
At this time, before the catalyst provided in the exhaust pipe is activated, the conversion performance of the catalyst is deteriorated and the exhaust performance is deteriorated.

In view of the above, the present invention aims to reduce the amount of HC discharged to the exhaust pipe during cooling by cutting off the fresh air introduction passage under the condition that the combustion gas is extinguished near the top land and the bore wall of the piston. And

[0007]

According to the first aspect of the invention, a blow-by gas recirculation passage that connects an engine internal chamber (for example, a crank chamber) through which blow-by gas blows out from a combustion chamber and an intake pipe downstream of an intake throttle valve, and the intake air In a blow-by gas recirculation device for an engine, which includes an intake pipe upstream of a throttle valve and a fresh air introduction passage that communicates with the internal chamber of the engine, the fresh air under the condition that the combustion gas extinguishes near the top land and the bore wall of the piston A means for closing the introduction passage was provided.

In a second aspect based on the first aspect, the means for closing the fresh air introducing passage comprises a valve capable of opening and closing the fresh air introducing passage, and means for instructing the valve to be closed.

According to a third aspect of the present invention, in the first or second aspect of the invention, the condition that the temperature of the cooling water is lower than a predetermined value is a condition for quenching the combustion gas near the top land and the bore wall of the piston.

According to a fourth aspect of the present invention, in the first or second aspect of the present invention, the condition that the combustion gas is extinguished near the top land and the bore wall of the piston when the temperature of the catalyst provided in the exhaust pipe is lower than a predetermined value. And

According to a fifth aspect of the present invention, in the first or second aspect of the invention, a condition is set before the predetermined time elapses after the start of combustion gas extinction near the top land and the bore wall of the piston.

In a sixth aspect of the present invention, in the first or second aspect of the present invention, the condition before the traveling of a predetermined distance after the start is the condition that the combustion gas extinguishes near the top land and the bore wall of the piston.

[0013]

In the first aspect of the invention, when the fresh air introduction passage is closed, only the blowby gas is introduced into the intake pipe downstream of the throttle valve through the blowby gas recirculation passage, and the fresh air introduction passage is introduced. Since all the fresh air is not included, the negative pressure of the engine internal chamber, which is guided by the suction negative pressure, greatly develops at the time of low load, and when the newly developed negative pressure does not close the fresh air introduction passage. Compared with the above, more unburned gas and combustion gas in the combustion chamber become blow-by gas and blow through to the engine internal chamber. That is, the amount of HC discharged to the exhaust pipe can be reduced by forcibly blowing out the unburned gas extinguished near the top land and the bore wall of the piston into the engine internal chamber.

In the third aspect of the present invention, the unburned HC generated by the extinction of the combustion gas near the top land of the piston and near the bore wall is forcedly blown as blow-by gas into the crank chamber immediately after the engine is started and during cooling. The amount of HC discharged to the pipe can be reduced.

In the fourth aspect of the invention, H discharged from the exhaust pipe
The amount of C can be reduced, and the time for purifying HC while the conversion efficiency of the catalyst is reduced can be shortened.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, 1 is an engine body, 2 is an air cleaner, 3 is an intake pipe, 4 is an intake throttle valve,
Reference numeral 5 is a piston, 6 is a combustion chamber, and 7 is a crank chamber.

In order to introduce the fresh air into the crank chamber 7, the fresh air introduction passage 11 that branches from the upstream side of the air cleaner 2 and opens near the center of the rocker cover 8 is provided in the engine body 1.
And a fresh air passage 12 that communicates the upper part of the valve operating chamber 9 covered by the rocker cover 8 with the crank chamber 7,
It is provided along one side wall (left side in the figure) of the cylinder block.

Further, at the time of combustion, blow-by gas (unburned gas or combustion gas in the combustion chamber) blown from the combustion chamber 6 through the gap between the piston 5 and the cylinder (for example, the joint of the piston ring and the side surface of the ring groove) into the crank chamber 7. Is introduced into the intake pipe 3 downstream of the throttle valve 4 for combustion processing, so that the blow-by passage 13 that connects the crank chamber 7 and the upper portion of the valve operating chamber 9 is communicated.
Is opened along the other side wall (right side in the figure) of the cylinder block, and from the rocker cover 8 at the highest portion (positioned at the upper left corner in the figure) of the valve operating chamber 9 and the intake air downstream of the throttle valve 4 is opened. A blow-by gas recirculation passage 14 communicating with the pipe 3 is provided.

In this case, the blow-by gas blown into the crank chamber 7 contains oil mist. Therefore, in order to separate this oil mist, the blow-by passage 13 is separated at the outlet (at the upper right corner of the valve operating chamber 9 in the figure). An oil separator (consisting of a baffle plate) 16 is provided in communication with
An oil separator 17 is also provided immediately below the connection between the blowby gas recirculation passage 14 and the valve operating chamber 9.

By the way, immediately after the engine is warmed up at a low temperature and before the engine is warmed up, unburned gas is generated due to the extinction of the piston 5 in the vicinity of the top land and the bore wall. Crank chamber 7
Since the amount of gas blown into the exhaust gas is small, most of the unburned gas is directly discharged to the exhaust pipe 18 as HC. At this time,
Before the catalyst (for example, a three-way catalyst) provided in the exhaust pipe 18 becomes active, the conversion performance of the catalyst deteriorates, and the exhaust performance deteriorates.

In order to cope with this, in the present invention, a normally open electromagnetic valve 21 is provided in the fresh air introduction passage 11 so that the control unit 22 causes the control unit 22 to operate under the condition that extinction occurs near the top land and the bore wall of the piston 5. Signal to close this valve 21.

The contents of this control executed by the control unit 22 will be described with reference to the flowchart of FIG.

First, in step 1, a cooling water temperature Tw is read from a water temperature sensor (not shown), and this cooling water temperature Tw is read.
Is compared with a predetermined value (for example, 40 ° C.) in step 2. When Tw is less than 40 ° C., it is determined that the engine is in the process of warming up, and the valve 21 is closed in step 3 to cut off the introduction of fresh air. At this time, since fresh air is not introduced through the fresh air introduction passage 11, the blow-by gas blown into the crank chamber 7 passes through the blow-by passage 13 to the oil separator 16 as shown in FIG. While being introduced, the blow-by gas introduced into another oil separator 17 via the fresh air passage 12 and separated from the oil mist by each oil separator is introduced into the intake pipe 3 downstream of the throttle valve 4 via the blow-by gas recirculation passage 14. Was introduced,
The combustion process is performed in the combustion chamber 6.

In this case, only the blow-by gas is introduced into the intake pipe 3 downstream of the throttle valve 4 through the blow-by gas recirculation passage 14, and fresh air through the fresh air introduction passage 11 is not included. , The negative pressure in the crank chamber 7 to which the suction negative pressure is guided through the blow-by gas recirculation passage 14 and the passages 12 and 13 inside the engine is greatly developed when the load is low, and by this large developed negative pressure, Compared to after the engine has warmed up (water temperature of 40 ° C or higher) to cancel the fresh air introduction cut,
A larger amount of unburned gas and combustion gas in the combustion chamber 6 becomes blow-by gas and blows into the crank chamber 7. Since the unburned gas generated by the extinction of the combustion gas near the top land and the bore wall of the piston at the time of cooling is forcedly blown into the crank chamber 7, the amount of HC discharged to the exhaust pipe 18 can be reduced. is there.

If the fresh air introduction through the fresh air introduction passage 11 is cut off only when the cooling water temperature Tw is lower than 40 ° C., the negative pressure in the crank chamber 7 is increased. Since it can be done in a short time, it is possible to suppress deformation of the oil seal and the like and deterioration of the oil due to a large negative pressure in the crank chamber 7.

On the other hand, when the cooling water temperature Tw becomes 40 ° C. or higher, it is judged that the engine warm-up is completed and the routine proceeds to step 4 where the valve 21 is opened and the cut of fresh air introduction is released.
Since the catalyst is almost activated when the cooling water temperature is around 40 ° C., HC can be effectively reduced even if the unburned gas in the combustion chamber 6 is discharged.

As described above, in the present invention, by blocking the fresh air introduction passage, the negative pressure in the crank chamber can be developed at the time of low load. Therefore, by utilizing this large negative pressure, immediately after starting the engine and It is possible to reduce the amount of HC discharged to the exhaust pipe by forcibly blowing the unburned HC generated by the extinction of the combustion gas around the top land of the piston and near the bore wall into the crank chamber as blow-by gas during cooling. .

The flowchart of FIG. 3 is a second embodiment,
It corresponds to FIG. Steps 11 and 12 are different from FIG.
Therefore, the same step numbers are given to the same parts as in FIG.

In the second embodiment, it is checked whether the catalyst 19 (see FIG. 1) provided in the exhaust pipe 18 is in the active state, and the fresh air introduction is cut before the catalyst becomes the active state.
This is designed to release the fresh air introduction cut after the catalyst has become active, so that the amount of HC discharged from the exhaust pipe can be reduced and the HC conversion efficiency can be reduced in the state where the catalyst conversion efficiency is lowered.
It is possible to shorten the time for purifying.

Specifically, in step 11, the catalyst temperature T detected by the temperature sensor provided at the catalyst outlet is read,
This catalyst temperature T is compared with the minimum temperature (for example, 300 ° C.) at which the catalyst becomes active in step 12.
If the catalyst temperature T is lower than 300 ° C., it is judged that the catalyst activity is insufficient and it is necessary to reduce the HC discharged to the exhaust pipe, and in step 3, the valve 21 is closed to cut off the introduction of fresh air. . On the other hand, when the catalyst temperature T is 300 ° C. or higher, it is determined that the catalyst is in the active state, and HC is sufficiently purified by the catalyst, and in step 4, the valve 21 is opened to release the fresh air introduction cut.

The flowcharts of FIGS. 4 and 5 are the third embodiment and the fourth embodiment, respectively, both of which correspond to FIG. FIG. 4 is different from FIG. 2 in steps 21, 22, 23, and 24. Regardless of the operating state after the start, the fresh air introduction is cut until a fixed time elapses after the start, and after the fixed time elapses. The introduction cut is terminated, and FIG. 5 shows that the introduction of fresh air is cut until the vehicle runs a certain distance after the start, and the cutting of fresh air is finished after the vehicle has run a certain distance. is there. Also in these embodiments, it is possible to effectively reduce HC during cold engine operation without impairing the durability of the oil seal or the like and suppressing oil deterioration.

Referring to FIG. 4, in detail, in step 21, the signals of the key switch and the crank angle sensor are read, and based on these signals, it is checked in step 22 whether the engine has started. When the engine has started, the routine proceeds to step 23, where the internal timer of the control unit 22 counts the elapsed time after startup, and at step 24 the elapsed time after startup is set to a predetermined value (for example, 60
Seconds). If the elapsed time after the start is less than 60 seconds, the valve 21 is closed in step 3 to cut off the fresh air introduction. On the other hand, if the elapsed time after the start is 60 seconds or more in step 24, it is determined that the engine has been warmed up to some extent,
In step 4, the valve 21 is opened. Further, before starting the engine, the process proceeds from step 22 to step 4.

In FIG. 5, steps 31, 32 and 3 are shown.
Since 3 is different from FIG. 4, this different part will be mainly described. In step 31, the signal of the vehicle speed sensor is read, and in step 32, the traveling distance after starting is counted based on the signal of this vehicle speed sensor, and this starting is performed. The subsequent traveling distance is compared with a predetermined value (for example, 0.5 km) in step 33. If the mileage after starting is less than 0.5 km,
In step 3, the valve 21 is closed, and when the mileage after the start becomes 0.5 km or more, it is determined that the engine is warmed up to some extent, and the valve 21 is opened in step 4.

In the embodiment shown in FIG. 5, the engine seal has been warmed up but the fresh air introduction passage remains blocked, which may adversely affect the oil seal and the oil deterioration. However (for example, if the idling state after starting for a long time and then driving),
This can be avoided in the other three embodiments.

[0035]

According to the first aspect of the present invention, the amount of HC discharged to the exhaust pipe is reduced by forcibly blowing out the unburned gas extinguished in the vicinity of the top land and the bore wall of the piston into the engine internal chamber. be able to.

According to the third aspect of the invention, the unburned HC generated by the extinction of the combustion gas near the top land of the piston and near the bore wall is forcedly blown as blow-by gas into the crank chamber immediately after the engine is started and during cooling. The amount of HC discharged to the pipe can be reduced.

In the fourth invention, H discharged from the exhaust pipe
The amount of C can be reduced, and the time for purifying HC while the conversion efficiency of the catalyst is reduced can be shortened.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an engine of a first embodiment.

FIG. 2 is a flow chart for explaining opening / closing control of the valve of the first embodiment.

FIG. 3 is a flowchart for explaining opening / closing control of a valve of the second embodiment.

FIG. 4 is a flow chart for explaining opening / closing control of a valve of a third embodiment.

FIG. 5 is a flowchart for explaining opening / closing control of a valve of a fourth embodiment.

FIG. 6 is a configuration diagram of a conventional engine.

[Explanation of symbols]

 1 engine body 3 intake pipe 4 intake throttle valve 5 piston 7 crank chamber (engine internal chamber) 11 fresh air introduction passage 14 blowby gas recirculation passage 21 on-off valve 22 control unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Hiratani 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd.

Claims (6)

[Claims] 1. A blow-by gas recirculation passage that connects an engine internal chamber where blow-by gas blows out from a combustion chamber and an intake pipe downstream of an intake throttle valve, and an intake pipe upstream of the intake throttle valve and the engine internal chamber. In a blow-by gas recirculation system for an engine having a fresh air introduction passage, a means for closing the fresh air introduction passage is provided under the condition that the combustion gas is extinguished near the top land and the bore wall of the piston. Blow-by gas recirculation device. 2. The engine according to claim 1, wherein the means for closing the fresh air introduction passage comprises a valve capable of opening and closing the fresh air introduction passage, and means for instructing to close the valve. Blow-by gas recirculation device. 3. The blow-by gas for an engine according to claim 1, wherein when the cooling water temperature is lower than a predetermined value, the combustion gas is extinguished near the top land and the bore wall of the piston. Reflux device. 4. The condition for extinguishing combustion gas in the vicinity of the top land and bore wall of the piston when the temperature of the catalyst provided in the exhaust pipe is lower than a predetermined value is set as a condition. Blow-by gas recirculation system for the engine described. 5. The blow-by gas recirculation of an engine according to claim 1, wherein the combustion gas is extinguished near the top land and the bore wall of the piston before a predetermined time has elapsed after the start. apparatus. 6. The blow-by gas recirculation for an engine according to claim 1 or 2, wherein the condition before combustion of the combustion gas extinguishes in the vicinity of the top land and the bore wall of the piston is made before traveling a predetermined distance after starting. apparatus.