JP3218959B2 - Engine blow-by gas recirculation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a blow-by gas recirculation device for an engine.

[0002]

2. Description of the Related Art Gas flowing from a combustion chamber to a crank chamber through a gap between a piston and a cylinder (blow-by gas).
Is returned to the intake passage to prevent air pollution due to blow-by gas.
No. 413).

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

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

[0005]

By the way, unburned gas is generated due to flame extinguishing near the top land of the piston and near the bore wall immediately after the engine is warmed up immediately after starting at a low temperature. For example, since the amount of gas flowing into the crankcase as blow-by gas is small, most of the unburned gas is directly discharged as HC into the exhaust pipe.
At this time, if the catalyst provided in the exhaust pipe is not activated yet, the exhaust performance deteriorates due to a decrease in the conversion performance of the catalyst.

In view of the above, an object of the present invention is to reduce the amount of HC discharged to an exhaust pipe at a time of cooling by shutting off a fresh air introduction passage under conditions in which combustion gas extinguishes near a top land and a bore wall of a piston. And

[0007]

According to a first aspect of the present invention, there is provided a blow-by gas recirculation passage communicating between an engine internal chamber (for example, a crank chamber) through which blow-by gas blows from a combustion chamber and an intake pipe downstream of an intake throttle valve; In a blow-by gas recirculation system for an engine having an intake pipe upstream of a throttle valve and a fresh air introduction passage communicating with the engine internal chamber, an opening / closing means for opening and closing the fresh air introduction passage is provided, and a top land and a bore of the piston are provided. Under the condition that the combustion gas extinguishes near the wall, the opening / closing means closes the fresh air introduction passage regardless of the engine load, and opens under other conditions .

[0008] In the second invention, in the first invention, the switching means is open valves der the fresh air introduction passage
You .

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

[0010] In a fourth aspect based on the first or second aspect, the condition that the combustion gas extinguishes 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, a condition that combustion gas extinguishes near the top land and the bore wall of the piston before a predetermined time elapses after the start.

In a sixth aspect based on the first or second aspect, the condition that combustion gas extinguishes near the top land and the bore wall of the piston before traveling a predetermined distance after starting is set.

[0013]

In the first aspect of the invention, when the fresh air introduction passage is closed, only the blow-by gas is introduced into the intake pipe downstream of the throttle valve via the blow-by gas recirculation passage. The negative pressure in the engine internal chamber, into which the intake negative pressure is guided, greatly develops, especially at low loads, and the fresh air introduction passage is not closed due to this greatly developed negative pressure. The unburned gas and the combustion gas in the combustion chamber become blow-by gas more and blow through to the engine internal chamber as compared with the case. That is, by forcibly blowing the unburned gas extinguished near the top land and the bore wall of the piston into the engine interior chamber, the amount of HC discharged to the exhaust pipe can be reduced.

According to the third aspect of the present invention, the exhaust gas is forcedly blown into the crank chamber as blow-by gas as the blow-by gas by the unburned HC generated by the extinction of the combustion gas near the top land of the piston and near the bore wall immediately after the start of the engine and at the time of 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 in a state where 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,
5 is a piston, 6 is a combustion chamber, and 7 is a crank chamber.

In order to guide fresh air to the crank chamber 7, a fresh air introducing passage 11 diverging from the upstream of the air cleaner 2 and opening substantially at the center of the rocker cover 8 is provided in the engine body 1.
And a fresh air passage 12 communicating the upper part of the valve operating chamber 9 covered by the rocker cover 8 and the crank chamber 7,
It is provided along one side wall (left side in the figure) of the cylinder block.

In addition, blow-by gas (unburned gas or combustion gas in the combustion chamber) blown from the combustion chamber 6 into the crank chamber 7 through the gap between the piston 5 and the cylinder (for example, the opening of the piston ring and the side of the ring groove) during combustion. To the intake pipe 3 downstream of the throttle valve 4 for combustion processing, the blow-by passage 13 communicating the crank chamber 7 and the upper part of the valve operating chamber 9.
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 part (located at the upper left corner in the figure) of the valve operating chamber 9 and the intake air downstream of the throttle valve 4. A blow-by gas recirculation passage 14 communicating with the pipe 3 is provided.

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

By the way, unburned gas is generated by extinction near the top land of the piston 5 and near the bore wall immediately after the cold start and before the engine is warmed up. Crank chamber 7
Most of the unburned gas is directly discharged as HC into the exhaust pipe 18 because the amount of gas flowing through the exhaust pipe is small. At this time,
Before the catalyst provided in the exhaust pipe 18 (for example, a three-way catalyst) is activated, the exhaust performance deteriorates due to a decrease in the conversion performance of the catalyst.

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, and when a condition occurs in which the flame extinction occurs near the top land of the piston 5 and the bore wall, the control unit 22 transmits The valve 21 is closed by the signal of (1).

The contents of the 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 the 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 being warmed up, and the valve 21 is closed in step 3 to cut off the introduction of fresh air. At this time, since no fresh air is introduced through the fresh air introduction passage 11, the blow-by gas blown into the crank chamber 7 flows to the oil separator 16 through the blow-by passage 13 as shown in FIG. The blow-by gas is guided to another oil separator 17 through the fresh air passage 12 and the oil mist is separated by each oil separator. The blow-by gas is separated into the intake pipe 3 downstream of the throttle valve 4 through the blow-by gas recirculation passage 14. Introduced,
The combustion processing 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 via the blow-by gas recirculation passage 14, and fresh air flowing through the fresh air introduction passage 11 is not included. When 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 low, the load is greatly developed. Compared to after the engine is warmed up (water temperature 40 ° C or higher) to cancel the fresh air introduction cut
The unburned gas and the combustion gas in the combustion chamber 6 become more blow-by gas and flow into the crank chamber 7. The amount of HC discharged to the exhaust pipe 18 can be reduced by forcibly blowing the unburned gas generated by the quenching of the combustion gas near the top land and the bore wall of the piston into the crank chamber 7 at the time of cooling. is there.

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

On the other hand, when the cooling water temperature Tw becomes equal to or higher than 40 ° C., it is determined that the warming-up of the engine has been completed, and the routine proceeds to step 4, where the valve 21 is opened to cancel the cut of the fresh air introduction.
Since the catalyst is substantially 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.

In this way, in the present invention, by blocking the fresh air introduction passage, it is possible to develop a negative pressure in the crankcase at a low load, so that the large negative pressure can be used immediately after the engine is started and The amount of HC discharged to the exhaust pipe can be reduced by forcibly blowing unburned HC generated by the extinction of the combustion gas around the top land of the piston and near the bore wall as a blow-by gas into the crank chamber at the time of cooling. .

FIG. 3 is a flowchart of the second embodiment.
FIG. Steps 11 and 12 differ from FIG.
The same steps as those in FIG. 2 are denoted by the same step numbers.

In the second embodiment, whether or not the catalyst 19 (see FIG. 1) provided in the exhaust pipe 18 is in an active state is determined.
The new air cut is released after the catalyst has been activated, and the amount of HC discharged from the exhaust pipe can be reduced.
The time for purifying the wastewater can be shortened.

Specifically, at step 11, the catalyst temperature T detected by the temperature sensor provided at the catalyst outlet is read, and
This catalyst temperature T is compared with the minimum value (for example, 300 ° C.) of the temperature at which the catalyst is activated in step 12.
If the catalyst temperature T is lower than 300 ° C., it is determined that the activity of the catalyst is insufficient and it is necessary to reduce the amount of HC discharged to the exhaust pipe. 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 equal to or higher than 300 ° C., the catalyst is in the active state, and it is determined that the HC is sufficiently purified by the catalyst. In step 4, the valve 21 is opened to cancel the fresh air introduction cut.

The flowcharts of FIGS. 4 and 5 are a third embodiment and a fourth embodiment, respectively, which both correspond to FIG. FIG. 4 is different from FIG. 2 in steps 21, 22, 23, and 24, in which the introduction of fresh air is cut off until a certain time has elapsed after the start, and the fresh air is FIG. 5 shows a configuration in which the introduction cut is ended, and FIG. 5 shows a configuration in which the fresh air introduction is cut until the vehicle travels a certain distance after the start, and the cut of the fresh air introduction is completed after the vehicle travels a certain distance. is there. Also in these embodiments, it is possible to effectively reduce HC in a cold state without deteriorating the durability of an oil seal or the like and suppressing oil deterioration.

Referring to FIG. 4, in detail, at step 21, the signals of the key switch and the crank angle sensor are read, and at step 22, it is determined whether or not the engine has been started based on these signals. If the engine has been started, the routine proceeds to step 23, where the internal time of the control unit 22 is used to count the elapsed time after the start.
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 introduction of fresh air. On the other hand, if the elapsed time after starting in step 24 is 60 seconds or more, it is determined that the engine has been warmed up to some extent,
In step 4, the valve 21 is opened. Before the engine is started, the process proceeds from step 22 to step 4.

In FIG. 5, steps 31, 32, 3
3 is different from that of FIG. 4. The difference will be mainly described. In step 31, a signal from a vehicle speed sensor is read, and a running distance after starting is counted in step 32 based on the signal from the vehicle speed sensor. 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 0.5km,
In step 3, the valve 21 is closed. When the running distance after starting is 0.5 km or more, it is determined that the engine is slightly warmed up, and in step 4, the valve 21 is opened.

In the embodiment shown in FIG. 5, the state in which the fresh air introduction passage is shut off even though the engine has been completely warmed up has an adverse effect on oil seals and oil deterioration. There is (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 the unburned gas extinguished near the top land and the bore wall of the piston into the engine interior chamber. be able to.

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

In the fourth aspect, H discharged from the exhaust pipe
The amount of C can be reduced, and the time for purifying HC in a state where 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 according to a first embodiment.

FIG. 2 is a flowchart for explaining valve opening / closing control according to the first embodiment;

FIG. 3 is a flowchart for explaining valve opening / closing control according to a second embodiment;

FIG. 4 is a flowchart for explaining valve opening / closing control according to a third embodiment;

FIG. 5 is a flowchart for explaining valve opening / closing control according to a fourth embodiment;

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine main body 3 Intake pipe 4 Intake throttle valve 5 Piston 7 Crank chamber (engine internal chamber) 11 Fresh air introduction passage 14 Blow-by gas recirculation passage 21 Opening / closing valve 22 Control unit

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Koji Hiratani 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd. (56) References JP-A-6-212939 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) F01M 13/00

Claims (6)

(57) [Claims] A blow-by gas recirculation passage communicating between an engine internal chamber through which blow-by gas flows 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. A blow-by gas recirculation device for an engine having a fresh air introduction passage that opens and closes the fresh air introduction passage , and the combustion gas is extinguished near the top land and bore wall of the piston regardless of the engine load. By the opening and closing means
Ri closed fresh air introduction passage, the blow-by gas recirculation system for an engine, characterized in that the opening other than the condition. Wherein said opening and closing means, the blow-by gas feedback device for an engine according to claim 1, characterized in that the fresh air introduction passage open valve the. 3. The blow-by gas for an engine according to claim 1, wherein the condition that the combustion gas is extinguished near the top land and the bore wall of the piston is set when the cooling water temperature is lower than a predetermined value. Reflux device. 4. The method according to claim 1, wherein the condition that the combustion gas is extinguished near the top land and the bore wall of the piston is set when the temperature of the catalyst provided in the exhaust pipe is lower than a predetermined value. A blow-by gas recirculation device for the engine as described in the above. 5. The blow-by gas recirculation of an engine according to claim 1, wherein a condition that combustion gas extinguishes near a top land and a bore wall of the piston before a predetermined time elapses after the engine is started. apparatus. 6. The blow-by gas recirculation of an engine according to claim 1, wherein a condition that combustion gas is extinguished near a top land and a bore wall of the piston before traveling a predetermined distance after starting is set. apparatus.