JP2998459B2 - Exhaust gas recirculation system for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation device for an internal combustion engine for recirculating exhaust gas and guiding the exhaust gas to each cylinder.

[0002]

2. Description of the Related Art Exhaust gas recirculation reduces the combustion temperature in a combustion chamber and reduces the amount of NOx generated by the heat capacity of an inert gas which is a main component of the exhaust gas. Although the recirculation of the exhaust gas involves some deterioration in combustion, in the recent improved internal combustion engine, it becomes possible to recirculate a large amount of the exhaust gas at the time of an engine middle load that does not require a high torque. Not only the effect is improved, but also the pumping loss of the piston is reduced, and the fuel efficiency can be improved.

[0003] A general exhaust gas recirculation device recirculates exhaust gas from an exhaust passage between a surge tank in an intake passage and a throttle valve. If a large amount of exhaust gas is recirculated by this device, a large amount of exhaust gas will remain in the large capacity surge tank when the exhaust gas recirculation is stopped due to high engine load requiring high torque. As a result, the supply of exhaust gas to the combustion chamber cannot be stopped immediately, resulting in poor responsiveness.In addition, when a large amount of exhaust gas is recirculated, the surge tank through which the exhaust gas passes is heated by the heat. Since the surge tank has a relatively large heat capacity, the temperature of the intake air passing through the surge tank rises for a while and the charging efficiency decreases, and in either case, the desired high torque operation can be performed immediately. It cannot be realized. Furthermore, there is a throttle valve near the exhaust gas supply section in the intake passage, and when a large amount of exhaust gas recirculation is performed, a large amount of carbon and the like contained in the exhaust gas adheres to the throttle valve in the long term. As a result, the throttle valve may stick.

[0004] Japanese Patent Application No. 2-333622 discloses an exhaust gas recirculation device that recirculates exhaust gas for each cylinder to an intake manifold downstream of a surge tank. According to this device, even if a large amount of exhaust gas is recirculated, the exhaust gas does not pass through the surge tank having a large capacity and heat capacity located upstream, and the throttle valve is further upstream of the surge tank. Due to the location, the above-mentioned problem does not occur.

[0005]

Generally, a control valve is provided in an exhaust gas recirculation passage to control the amount of exhaust gas to be recirculated depending on the operation state. When the amount of recirculated exhaust gas is large, it does not matter, but when the amount is small, in the exhaust gas recirculation device described above, the length of the exhaust gas recirculation passage from the control valve to each supply unit of the intake manifold is different. As the exhaust gas recirculation length becomes shorter, the closer the cylinder is to the control valve, the more exhaust gas is supplied and the same amount of exhaust gas cannot be supplied to each cylinder.

Accordingly, it is an object of the present invention to improve the responsiveness immediately after a large amount of exhaust gas recirculation is stopped, and to provide an exhaust gas recirculation system for an internal combustion engine capable of distributing the same amount to each cylinder during a small amount of exhaust gas recirculation. It is to provide.

[0007]

According to the first aspect of the present invention, an exhaust gas recirculation system for an internal combustion engine according to the present invention is configured such that an exhaust gas recirculated to each cylinder is once gathered, and the gathering portion and each cylinder are substantially equal. A plurality of passages respectively connected with fluid resistance are provided, a first exhaust gas recirculation passage passing through the collecting portion and the respective passages, and a second exhaust gas passing through the respective passages without passing through the collecting portion. A recirculation passage, wherein the exhaust gas is recirculated by the first exhaust gas recirculation passage by reducing the amount of exhaust gas to be recirculated at a low load when combustion is unstable, and the load is higher than the low load and stable combustion is specified. At the time of load, the amount of exhaust gas to be recirculated is increased and the exhaust gas is recirculated through the second exhaust gas recirculation passage.

According to a second aspect of the present invention, there is provided the exhaust gas recirculation device for the first internal combustion engine, wherein the collecting portion of the first exhaust gas recirculation passage comprises a surge tank. The plurality of passages include a plurality of intake ports communicating with the respective cylinders downstream of the surge tank.

[0009]

The exhaust gas recirculation device of the first internal combustion engine is
At a low load where combustion is unstable, a small amount of exhaust gas to be recirculated to each cylinder is once collected in a collecting portion in order to reduce the amount of exhaust gas to be recirculated and to recirculate the exhaust gas through the first exhaust gas recirculation passage. The same amount is surely distributed to each cylinder through a plurality of passages that respectively connect the collecting portion and each cylinder with substantially equal fluid resistance. Also, at a specific load where the load is higher than at a low load and combustion is stable, a large amount of exhaust gas is circulated to each cylinder in order to recirculate the exhaust gas through the second exhaust gas recirculation passage with a large amount of exhaust gas being recirculated. The fluid is returned to each cylinder through a plurality of passages without passing through any part.

The above-described second exhaust gas recirculation system for an internal combustion engine uses the first exhaust gas recirculation passage to recirculate the exhaust gas by reducing the amount of the exhaust gas to be recirculated at a low load when combustion is unstable. A small amount of exhaust gas to be recirculated to the cylinders is once collected in a surge tank and reliably distributed to each cylinder through multiple intake ports that connect the surge tank and each cylinder with substantially equal fluid resistance. Is done. Further, at a specific load where the load is higher than at the time of low load and the combustion is stable, the amount of exhaust gas to be recirculated is increased and the second
In order to recirculate exhaust gas through the exhaust gas recirculation passage, a large amount of exhaust gas recirculated to each cylinder is returned to each cylinder through a plurality of intake ports without passing through a surge tank.

[0011]

FIG. 1 is a schematic view showing a first embodiment of an exhaust gas recirculation system for an internal combustion engine according to the present invention. In the figure, 1 is a four-cylinder engine, 2 is an intake passage, and 3 is an exhaust passage. The intake passage 2 includes a surge tank 2a, a single intake pipe 2b having an upstream throttle valve 4, and intake ports 2c, 2d, 2e, and 2f communicating with the downstream cylinders. 2c, 2d, 2e, and 2f are configured to have substantially the same fluid resistance in order to make the intake air amount supplied to each cylinder the same.

A recirculating main exhaust gas passage 5 branched from the exhaust passage 3 is connected to each of the intake ports 2c, 2d, 2e, and 2f in sequence, and a first upstream of a connection portion with the intake port 2c is provided.
A control valve 6 is provided. The upstream of the first control valve 6 and the downstream of the throttle valve 4 of the intake pipe 2b are connected by a recirculation auxiliary exhaust gas passage 7, and a second control valve 8 is provided in the passage 7.

In this exhaust gas recirculation device, when the amount of recirculated exhaust gas determined by the operating state of the engine is small, the first control valve 6 is closed and the second control valve 8 is supplied with an appropriate amount of exhaust gas. The opening is controlled so as to be recirculated. Thereby,
A first exhaust gas recirculation passage is formed by the recirculation main exhaust gas passage 5 upstream of the first control valve 6, the recirculation sub-exhaust gas passage 7, the surge tank 2a, and the intake ports 2c, 2d, 2e, 2f. And an appropriate amount of recirculated exhaust gas is
a, and is distributed and supplied to each cylinder in the same amount through each of the intake ports 2c, 2d, 2e, and 2f having a substantially equal fluid resistance together with the intake air.

If the second control valve 8 is closed when the engine operation state changes and the recirculation of the exhaust gas is stopped, the amount of the exhaust gas remaining in the surge tank 2b is small. Is stopped, and the small amount of exhaust gas supplied to the surge tank 2b is cooled by the intake air, so that the surge tank 2b is maintained at a low temperature without being heated.

When the amount of recirculated exhaust gas determined by the operating state of the engine is large, the opening of the first control valve 6 is controlled so that an appropriate amount of exhaust gas is recirculated, and the second control valve 8 is controlled. Is closed. As a result, a second exhaust gas recirculation passage is formed by the recirculation main exhaust gas passage 5 and each of the intake ports 2c, 2d, 2e, 2f. The same amount of exhaust gas can be supplied to each cylinder without passing through the exhaust gas collecting portion such as the tank 2b.

If the first control valve 6 is closed when the engine operation state changes and the recirculation of the exhaust gas is stopped, the exhaust gas passes through the surge tank 2b having a relatively large capacity at this time. Therefore, the supply of the exhaust gas to each cylinder is immediately stopped, and the surge tank 2b having a relatively large heat capacity is not heated by the large amount of the exhaust gas.

As described above, according to the exhaust gas recirculation apparatus of the present embodiment, good responsiveness when stopping the recirculation of the exhaust gas is guaranteed, and at this time, the intake gas is heated by heating the surge tank 2b with the exhaust gas. It is prevented that the temperature rises, the filling efficiency decreases and the desired torque cannot be obtained,
Further, since the exhaust gas does not frequently pass near the throttle valve 4 and the amount of the exhaust gas passing therethrough is small, the possibility that carbon or the like in the exhaust gas adheres to the throttle valve 4 is low. In addition, the throttle valve 4 does not stick even for long-term use.

FIG. 2 is a schematic diagram showing a second embodiment of the exhaust gas recirculation system for an internal combustion engine according to the present invention. This embodiment is different from the first embodiment shown in FIG. 1 in that the second control valve 8 is omitted, and a third control valve 9 is provided instead of the first control valve 6 at a branch portion of the sub-recirculation exhaust gas passage 7. In particular, the recirculating main exhaust gas passage 5 is thick so as to allow a large amount of exhaust gas to pass therethrough, and the recirculating sub-exhaust gas passage 7 is thin so that only a small amount of exhaust gas can pass therethrough.

The third control valve 9 has a first position in which both exhaust gas passages 5 and 7 are simultaneously closed, a second position in which only the recirculation auxiliary exhaust gas passage 7 is opened, and only a recirculation main exhaust gas passage 5. Can be selected from a third position at which to open. Thus, when the recirculation of the exhaust gas is stopped, the first position is set to the first position, and the recirculation of the exhaust gas is stopped. When the small amount of exhaust gas is recirculated, the second position is set, thereby forming the first exhaust gas recirculation passage. Since the recirculation sub-exhaust gas passage 7 is so narrow that only a small amount of exhaust gas can pass, a desired small amount of exhaust gas is recirculated. When the large amount of exhaust gas is recirculated, the second exhaust gas recirculation passage is formed by setting the third position, and the recirculation main exhaust gas passage 5 is made thick to allow a large amount of exhaust gas to pass therethrough. , A desired amount of exhaust gas recirculation is performed. Thus, the same effect as in the first embodiment can be obtained by using only a single third control valve 9. Further, even if the third position is a position where both exhaust gas passages 5 and 7 are simultaneously opened, most of the exhaust gas has a small fluid resistance when the large amount of exhaust gas is recirculated. A similar effect can be obtained for passing through.

FIG. 3 is a schematic diagram showing a third embodiment of the exhaust gas recirculation system for an internal combustion engine according to the present invention. The difference between this embodiment and the first embodiment shown in FIG. 1 is that the second control valve 8 is omitted, and in particular, the recirculation sub-exhaust gas passage 5 has a recirculation main exhaust passage that allows a large amount of exhaust gas to pass. Compared with the exhaust gas passage 5, even if a negative pressure in the surge tank 2b is used, only a small amount of exhaust gas can pass therethrough.

In general, the recirculated exhaust gas amount control is set to a small amount at a low load where combustion is relatively unstable and a large amount at a medium load, taking into consideration that some combustion deterioration occurs at the time of exhaust gas recirculation. Further, the exhaust gas recirculation is stopped at the time of a high load requiring a high torque. In the exhaust gas recirculation apparatus of the present embodiment, by controlling the opening and closing of only the first control valve 6 in the same manner as in the first embodiment, the exhaust gas recirculation device of the present embodiment can perform such a small amount of exhaust gas recirculation, At the time of load, the first control valve 6 is closed to form the above-described first exhaust gas recirculation passage. At this time, the opening degree of the throttle valve 4 is small, and the degree of negative pressure in the surge tank 2b is large,
Utilizing this negative pressure, a small amount of exhaust gas is recirculated through the sub exhaust gas passage 7 for recirculation.

When a large amount of exhaust gas is recirculated, that is, when the engine is under medium load, the opening of the first control valve 6 is controlled so that an appropriate amount of exhaust gas is recirculated, and the above-described second exhaust gas recirculation passage is formed. You. At this time, the first exhaust gas recirculation passage is also formed, but the degree of the negative pressure in the surge tank 2b is reduced with the increase in the opening of the throttle valve 4, and the exhaust gas is recirculated to the sub exhaust gas passage for recirculation. The gas is returned only through the main exhaust gas passage 5 for recirculation without passing through the passage 7, and only the above-mentioned second exhaust gas recirculation passage is used. When the exhaust gas recirculation is stopped, that is, when the engine is under a high load, the first control valve 6 is closed to form only the first exhaust gas recirculation passage. At this time, the pressure in the surge tank 2b becomes almost atmospheric pressure. The exhaust gas does not pass through the sub exhaust gas passage 7 for recirculation,
Exhaust gas recirculation is stopped.

FIG. 4 is an enlarged sectional view of the vicinity of a throttle valve showing a fourth embodiment of the exhaust gas recirculation system for an internal combustion engine according to the present invention. In the present embodiment, a negative pressure valve 10 is added to the sub-recirculation exhaust gas passage 7 of the third embodiment shown in FIG. The negative pressure valve 10 has a first pressure chamber 10b communicating with the surge tank 2b by a connection pipe 10a, a second pressure chamber 10c opened to the atmosphere, and a diaphragm 10d serving as a boundary between the two pressure chambers 10b, 10c. A spring 10e for urging the diaphragm 10d toward the second pressure chamber 10c is provided in the first pressure chamber 10b, and the spring 10e is airtightly extended outside the second pressure chamber 10c on the second pressure chamber 10c side of the diaphragm 10d. The existing valve member 10f is connected.

When the pressure in the surge tank 2b is close to the atmospheric pressure, the pressure difference between the two pressure chambers 10b and 10c is small, and the tip of the valve member 10f is pressed by the diaphragm 10d urged by the spring 10e. Recirculation auxiliary exhaust gas passage 7
To close. On the other hand, when the negative pressure in the surge tank 2b reaches a predetermined value, the differential pressure between the two pressure chambers 10b and 10c increases and balances with the urging force of the spring 10e. The diaphragm 10d is deformed in a convex shape toward the first pressure chamber 10b, and the distal end of the valve member opens the auxiliary exhaust gas passage 7 for recirculation.

By providing such a negative pressure valve 10, when the small amount of exhaust gas is recirculated, that is, when the engine is under a low load, the opening of the throttle valve 4 is small and the negative pressure in the surge tank 2b becomes less than a predetermined value. , The recirculation sub-exhaust gas passage 7 is automatically opened to form the above-described first exhaust gas recirculation passage in the same manner as in the third embodiment. A small amount of exhaust gas is recirculated using negative pressure. At other times, the opening of the throttle valve 4 becomes large, the negative pressure in the surge tank 2b becomes greater than or equal to a predetermined value, and the recirculation exhaust gas passage 7 is automatically closed.
Thereby, at the time of executing a large amount of exhaust gas recirculation in the third embodiment, that is, at the time of medium engine load, and at the time of exhaust gas recirculation
That is, when the engine is under a high load, the auxiliary exhaust gas passage 7 for recirculation can be completely closed, and at this time, the first exhaust gas recirculation passage is not formed. Reliability for obtaining the effect of (1) can be improved.

The opening of the first control valve 6 used in the first, third and fourth embodiments is controlled so that the amount of exhaust gas can be controlled when a large amount of exhaust gas is executed. If it is not necessary to control the amount of exhaust gas, valve opening or valve closing control may be performed.

In all of the embodiments described above, in order to simplify the structure, the first exhaust gas recirculation passage used at the time of executing the small amount of exhaust gas recirculation includes the surge tank 2b and the intake ports 2c, 2d, 2e, 2f. However, it is also possible to separately provide a collecting portion in which the recirculated exhaust gas temporarily collects, and a plurality of passages from the collecting portion to each cylinder with substantially the same fluid resistance. Further, it is apparent that the present invention is not limited to the four-cylinder engine, but can be applied to other multi-cylinder engines.

[0028]

As described above, according to the exhaust gas recirculation apparatus for an internal combustion engine according to the present invention, the exhaust gas is recirculated by the first exhaust gas recirculation passage with a small amount of the exhaust gas recirculated at a low load when combustion is unstable. Therefore, a small amount of exhaust gas to be recirculated to each cylinder is uniformly distributed in the collecting section,
After that, the same amount is distributed to the respective cylinders through a plurality of passages respectively connecting the collecting portion and each of the cylinders with substantially equal fluid resistance, and supplied to the respective cylinders. Also, at a specific load where the load is higher than at a low load and combustion is stable, a large amount of exhaust gas is circulated to each cylinder in order to recirculate the exhaust gas through the second exhaust gas recirculation passage with a large amount of exhaust gas being recirculated. The exhaust gas is recirculated to each cylinder through a plurality of passages without passing through the section, and a large amount of exhaust gas is stored in the collecting section and does not heat the collecting section. Problem is solved. Also,
The structure of the exhaust gas recirculation device can be simplified by using the surge tank as the collecting portion and using the intake ports downstream of the surge tank as the plurality of passages.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a first embodiment of an exhaust gas recirculation device for an internal combustion engine according to the present invention.

FIG. 2 is a schematic view showing a second embodiment of an exhaust gas recirculation device for an internal combustion engine according to the present invention.

FIG. 3 is a schematic view showing a third embodiment of an exhaust gas recirculation device for an internal combustion engine according to the present invention.

FIG. 4 is a sectional view showing the vicinity of a throttle valve according to a fourth embodiment of the exhaust gas recirculation system for an internal combustion engine according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Four-cylinder engine 2 ... Intake passage 2a ... Intake pipe 2b ... Surge tank 2c, 2d, 2e, 2f ... Intake port 3 ... Exhaust passage 4 ... Throttle valve 5 ... Recirculation main exhaust gas passage 6 ... 1st control valve 7 ... recirculation auxiliary exhaust gas passage 8 ... second control valve 9 ... third control valve 10 ... negative pressure valve

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F02M 25/07 580 F02M 25/07 570 F02M 35/10 F02M 35/10 311

Claims (2)

(57) [Claims] A collection portion for once collecting exhaust gas to be recirculated to each cylinder; and a plurality of passages respectively connecting said collection portion and each cylinder with substantially equal fluid resistance. And a first exhaust gas recirculation passage through the respective passages, and a second exhaust gas recirculation passage through the respective passages without passing through the collecting portion. The first
The exhaust gas is recirculated by the exhaust gas recirculation passage, and the exhaust gas is recirculated by the second exhaust gas recirculation passage with a large amount of the recirculated exhaust gas at a specific load where the load is higher than the low load and the combustion is stable when the load is stable. An exhaust gas recirculation device for an internal combustion engine. 2. The method according to claim 1, wherein the collecting portion of the first exhaust gas recirculation passage comprises a surge tank, and the plurality of passages comprise a plurality of intake ports communicating with the respective cylinders downstream of the surge tank. The exhaust gas recirculation device for an internal combustion engine according to claim 1.