JP2002030993A - Intake structure of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an EGR rate difference between cylinders and to inhibit a generation of NOx and soot in an engine having a pair of banks. SOLUTION: An EGR gas taken out from exhaust passages 144, 146 of both banks 120, 122 is once merged at an EGR chamber 160. Thereafter, it is recirculated at EGR openings 162, 164 formed on a pair of branched suction pipes 132, 134. A communication pipe 170 for communicating a pair of branched suction pipes 132, 134 with a downstream side than the EGR openings 162, 164 of the branched suction pipes 132, 134 is provided. Thereby, a dispersion of a period and an amplitude of an exhaust pressure and an intake pressure is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an intake structure of an engine having a pair of banks.

[0002]

2. Description of the Related Art FIG. 4 shows an example of an intake structure used in a conventional V-type eight-cylinder engine. Conventionally, as shown in FIG. 4, an intake passage 23 of an engine 18 having a pair of banks 20, 21 such as a V-type engine has an upstream end connected to an air cleaner (not shown) and a downstream side from the air cleaner. Are divided into a pair of branch intake pipes 27 and 29 and connected to the intake sides 31 and 33 of the banks 20 and 21 respectively. The exhaust sides 35 and 37 of both banks 20 and 21 of the engine 18 are provided to discharge exhaust gas generated during combustion of the engine 18.
Exhaust passages 39 and 41 are provided, respectively. Further, between the exhaust passages 39 and 41 and the above-described intake passage 23, exhaust gas recirculation passages (hereinafter, EGR passages) 45 and 46 are provided.
Are formed, and a part of the exhaust gas discharged into the atmosphere via the exhaust passages 39 and 41 is recirculated to the intake passage 23 side.

That is, both bank exhaust sides 3 of the engine 18
EGR gas outlets 47 and 49 are opened in exhaust pipes 39 and 41 provided in the exhaust pipes 5 and 37, and one ends of the EGR passages 45 and 46 are communicated with the exhaust pipes 39 and 41.
The openings 51 and 52 at the other end are connected to the intake passage 23.

[0004] For this reason, the EGR from the exhaust passages 39, 41
The EGR gas taken out through the gas outlets 47 and 49 mixes with fresh air sucked from the upstream side of the intake passage 23 near the EGR gas openings 51 and 52, and the combustion chamber of the engine 18 at the time of intake of the engine 18 Incorporated in. As a result, the combustion of the engine 18 is slowed down to lower the combustion temperature, and the generation of a large amount of nitrogen oxide (NOx) generated in a high combustion temperature range is suppressed.

However, in the intake structure described in the conventional example, since the EGR gas openings 51 and 52 are provided on the upstream side of the branch portion 25 formed in the intake passage 23, the EGR gas openings 51 and 52 are provided in the intake passage 23. After the EGR gas flows and mixes with the fresh air, a pair of branch intake pipes 27, 2
It will be divided into nine. Therefore, when the flow of the intake gas in which the EGR gas and the fresh air are mixed is disturbed due to the influence of the shape of the intake passage 23 and the like, the branch intake 25 connected to the pair of banks 20 and 21 in the branch portion 25 formed downstream. Tube 27,
29, the intake gas is not evenly distributed, and both banks 20,
There is a possibility that the ratio between the EGR gas and fresh air flowing into the combustion chamber 21 (hereinafter, EGR rate) may be biased.

As a result, the EG of the intake gas flowing into the cylinder
The difference between the cylinder with the highest R rate and the cylinder with the lowest EGR rate of the intake gas (hereinafter, the difference between the EGR rate cylinders) increases,
In a cylinder having a high EGR rate, sufficient combustion is not performed, and soot is generated. On the other hand, in a cylinder having a low EGR rate, there is a problem that a combustion temperature becomes high, and generation of NOx may be relatively increased.

To solve such a problem, FIG.
It is conceivable that the EGR gas openings 53 and 55 are located downstream of the branch portion 25 formed in the intake passage 23 as shown in FIG. However, even in this case, the variation in the cycle and amplitude of the intake pressure and the exhaust pressure becomes large due to the influence of the one-bank unequally spaced ignition, and it is difficult to sufficiently reduce the cylinder-to-cylinder difference in the EGR rate.

That is, as shown in FIG. 6, for example, in a V8 engine having a bank angle of 90 °, the cylinders of the first bank 20 are the first, third, fifth and seventh cylinders, and the cylinders of the second bank 21 are the second cylinder. When the numbers are assigned to the fourth, sixth, and eighth cylinders, ignition is generally performed in the order of the first, second, seventh, third, fourth, fifth, sixth, and eighth cylinders. At this time, looking only at the second bank 21,
The ignition is performed in the order of 2 → 4 → 6 → 8, and the ignition interval is 270 ° between the second cylinder and the fourth cylinder in terms of the crank angle and between the fourth cylinder and the sixth cylinder. 180 °, 90 ° between the 6th and 8th cylinders, and 180 ° between the 8th and 2nd cylinders, resulting in unequally spaced ignition. As a result, the intake pressure generated at the position X of the intake branch pipe 29 connected to the second bank 21 and the exhaust pressure at the position Y of the EGR passage 46 communicated with the exhaust passage 41 of the second bank 21 have a cycle of: Since the amplitudes vary, the intake and exhaust gases such as the EGR rate are high in the cylinder in the intake stroke when the exhaust pressure is high and the intake pressure is low, and the EGR rate is low in the cylinder in the intake stroke when the exhaust pressure is low and the intake pressure is high. There is a concern that the difference between the EGR rate cylinders may increase due to the influence of the pressure fluctuation.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to reduce the difference in EGR rate between cylinders in an engine having a pair of banks with a relatively simple configuration. .

[0010]

In order to solve the above-mentioned problems, according to the present invention, there are provided a pair of independently formed branch exhaust passages connected to an exhaust manifold and an EGR outlet of each of the branch exhaust passages. An exhaust gas recirculation passage that is communicated with the exhaust gas recirculation passage at the junction, an exhaust recirculation branch passage that communicates the EGR opening of each of the branch intake passages that communicates with the junction and the intake manifold, and an EGR opening of the branch intake passage. A communication pipe which is located downstream of the section and connects the two branch intake passages to each other is provided, so that the deviation of the EGR rate between the banks due to the branch of the intake passage is small, and the one-bank structure is provided by the junction and the communication pipe. Variations in the cycle and amplitude of the exhaust pressure and the intake pressure due to the effects of unequally spaced ignition are suppressed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIGS.

As shown in FIG. 1, the engine of this embodiment is a V-type eight-cylinder having a first bank 120 and a second bank 122 constituted by cylinder rows, and has a bank angle of nine.
It is set to 0 °. Intake passage 12 of engine 118
4 has a branch portion 130 having an upstream end 126 connected to the air cleaner 128 and a downstream side of the air cleaner 128.
, A pair of branch intake pipes 132 and 134 are provided, and the first branch intake pipe 132 and the second branch intake pipe 134 are disposed on the intake side of the first bank 120 and the second bank 122, respectively. , 137. A pair of banks 120, 1 of the engine 118
A pair of exhaust manifolds 14 are provided on each exhaust side.
0 and 142 are disposed, and the exhaust passages 144 and 14 are respectively provided.
6 is connected. And the exhaust manifold 140,
The exhaust passage 142 and the exhaust passages 144 and 146 form an independent branch exhaust passage for each bank. The exhaust passage 14
Exhaust pipe flow passages (hereinafter, EGR passages) 150 and 151 are formed between the intake passages 4 and 146 and the intake passage 124.

More specifically, an exhaust passage 144 in which exhaust pipes extending from the cylinders of the first bank 120 are gathered and integrated.
The first EGR gas outlet 152 is opened, and the second EGR gas outlet 1 is inserted into an exhaust passage 146 in which exhaust pipes extending from the cylinders of the second bank 122 are integrated.
54 is open. And the first EGR gas outlet 1
A first EGR valve 156 is provided in the EGR passage 150 connected to the second bank 52, and the EGR valve 156 is taken out from the first bank 120.
The amount of GR gas is adjusted, and the second EGR passage 151 extending to the second EGR gas outlet 154 is located downstream of the second EGR gas outlet 151.
An EGR valve 158 is provided to adjust the amount of EGR gas extracted from the second bank 122. Downstream sides of the first EGR valve 156 and the second EGR valve 158 disposed in the two EGR passages 150 and 151 are connected to an EGR chamber 160 having a predetermined volume, and EGR extracted from the first bank 120 and the second bank 122. A merging portion for once merging the gas is formed.

The EGR chamber 160 is provided in the intake passage 12.
The EGR openings 162 and 164 are formed in the first branch intake pipe 132 and the second branch intake pipe 134 which are disposed immediately below the intake passage 4 and downstream of the branch part 130 of the intake passage 124, respectively.

The E of the branch intake pipes 132 and 134 is
A pair of the first branch intake pipe 132 and the second branch intake pipe 134 are communicated further downstream of the GR openings 162 and 164 and near the connection between the banks 120 and 122 with the intake manifolds 136 and 137. The communication pipe 170 is open. In this embodiment, the communication pipe 170 is provided integrally with the intake passage 124, and the cross-sectional area of the communication pipe 170 is set substantially equal to the first branch intake pipe 132 and the second branch intake pipe 134. .

In the embodiment of the present invention having such a configuration, both the banks 120 and 12 are driven by the combustion of the engine 118.
Exhaust gas discharged from each exhaust manifold 14
0, 142 and the exhaust passages 144, 146, and are partially released into the atmosphere.
46, the first EGR gas outlet 152 formed respectively.
And the EGR passage 1 via the second EGR gas outlet 154
50, 151. The EGR gas taken into the EGR passage 150 from the first EGR gas outlet 152 is supplied to the EGR gas through the first EGR valve 156.
The EGR gas flowing into the GR chamber 160 and taken into the EGR passage 151 from the second EGR gas outlet 154 passes through the second EGR valve 158 to the EGR chamber 1.
Flow into 60. As a result, the EGR gas extracted from the exhaust passage 144 of the first bank 120 and the second bank 12
EGR gas extracted from the second exhaust passage 146
Merge once in the R room 160.

As described above, the exhaust gas generated by the first bank 120 and the second bank 122 is transferred to the EGR chamber 160.
And then recirculates to the intake passage 124, so that variations in the cycle and amplitude of the exhaust pressure are suppressed. That is, as described above, when the cylinders of the engine 118 are numbered 1 to 8, for example, in the second bank 122, the crank angle between the second cylinder and the fourth cylinder is 270 °, 4 °. 180 between cylinders # 6 and # 6
゜, 90 ° between 6th and 8th cylinder, 8th cylinder and 2
An interval of 180 ° is set between the cylinder and the cylinder, and ignition proceeds at irregular intervals. For this reason, at the position b in the EGR passage 151 which is affected only by the ignition interval of the second bank 122, the variation in the cycle and the amplitude of the exhaust pressure becomes large.

However, when the exhaust gases discharged from the first bank 120 and the second bank 122 are combined in the EGR chamber 160, the two banks 120, 122
The ignition interval affects Therefore, considering the entire engine 118 including the first bank 120 and the second bank 122, the order of 1 → 2 → 7 → 3 → 4 → 5 → 6 → 8 → 1 is as follows.
Ignition proceeds at regular intervals of 90 ° in crank angle. Therefore, as shown in FIG. 2, the exhaust pressure at the position c in the EGR chamber 160 has peaks at approximately equal intervals of 90 ° in terms of the crank angle, and the amplitude also becomes small.

The EGR gas, in which the variation of the cycle and the amplitude of the exhaust pressure is suppressed as described above, flows from the EGR openings 162 and 164 formed in the pair of branch intake pipes 132 and 134 of the intake passage 124 to the intake side. 136, 137
Refluxed. At this time, the branch 1 in the intake passage 124
EGR is added to branch intake pipes 132 and 134 downstream of
Since the openings 162 and 164 are provided, there is little deviation in the EGR rate between banks due to the branch of the intake passage 124.

The EGR openings 162, 164
The EGR gas recirculated from the EGR gas is mixed with fresh air from the upstream side of the intake passage 124 and is taken into the intake sides 136 and 137 of the first bank 120 and the second bank 122. At this time, as described above, the pair of branch intake pipes 132, 13
The communication pipe 170 that communicates the four with the EGR opening 16
Since the opening is located downstream of 2, 164, the variation in the cycle and amplitude of the intake pressure is also suppressed by the same mechanism as the method for suppressing the variation in the cycle and amplitude of the exhaust pressure described above.

That is, the first bank 120 or the second bank 1
In the case of being affected by the ignition interval of only 22, as described above, the variation of the cycle and the amplitude of the intake pressure becomes large due to the influence of the one-bank unequally spaced ignition.
Is provided, for example, at the position d in the second branch intake pipe 134, the ignition interval between the two banks 120 and 122 is affected. Therefore, as shown in FIG. 2, at the position d, the peak of the intake pressure appears at substantially equal intervals of 90 ° in terms of the crank angle, and the amplitude also decreases.

Further, when the cylinders of the first bank 120 are in the intake stroke, fresh air and E
The intake gas mixed with the GR gas flows into the first bank 120, and the communication pipe 17 also flows from the second branch intake pipe 134.
The intake gas flows into the first bank 120 via the zero. When the cylinders of the second bank 122 are in the intake stroke,
The intake gas in which fresh air and EGR gas are mixed flows from the second branch intake pipe 134 into the second bank 122 and
Intake gas also flows into the second bank 122 from the branch intake pipe 132 via the communication pipe 170. For this reason, the region where the fresh air from the upstream of the intake air and the EGR gas recirculating from the EGR openings 162 and 164 formed in the branch intake pipes 132 and 134 are mixed is substantially equal to the volume of the communication pipe 170. The fresh air and the EGR gas are mixed well, and the deviation of the EGR rate is reduced.

As described above, when the variation in the cycle and amplitude of the exhaust pressure and the intake pressure is suppressed, or when the deviation of the EGR rate is reduced, as shown in FIG. Is small, and the intake gas to be taken in has a substantially constant EGR rate regardless of the intake timing of each cylinder. For this reason, the intake gas E
The difference between the cylinders having the highest GR rate and the cylinder having the lowest EGR rate of the intake gas, which is the difference between the EGR rate cylinders, is reduced. Therefore, in the cylinder where the EGR rate of the intake gas is the highest, if the amount of the recirculated EGR gas is increased to the extent that soot is not generated due to the excessive EGR rate, the EGR rate becomes higher as a whole cylinder and the combustion temperature becomes lower. Since the high temperature is prevented, the generation of NOx is suppressed.

In this embodiment, the communication pipe 170 for connecting the pair of branch intake pipes 132 and 134 is configured to be integrated with the intake passage 124. However, the present invention is not limited to this. It may be configured to be welded to the branch intake pipe, or may be configured to be fixed with bolts.

The cross-sectional area of the communication pipe 170 is substantially the same as that of the intake passage 124. However, the present invention is not limited to this. The cross-sectional area is set to such an extent that variations in the cycle and amplitude of the intake pressure can be suppressed. It is good to do.

[0026]

As described above in detail with the embodiments, in the intake structure of the engine according to the present invention, the exhaust pipe flow passage which is communicated with the EGR outlets of the pair of branch exhaust passages and joined at the junction is provided. , The EGR of the junction and each branch intake passage
An exhaust gas recirculation branch passage communicating with the opening and a communication pipe located downstream of the EGR opening of the branch intake passage and communicating the two branch intake passages with each other are provided. There is no deviation between the banks, and the merging portion and the communication pipe suppress variations in the cycle and amplitude of the exhaust pressure and the intake pressure due to the influence of the one-bank unequally-spaced ignition, and reduce the difference in the EGR rate between the cylinders.

[0027]

[Brief description of the drawings]

FIG. 1 is an overall view of an intake structure of an engine according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram of a crank angle and an exhaust pressure and an intake pressure according to the embodiment of the present invention.

FIG. 3 shows a crank angle and EG according to the embodiment of the present invention.
It is a characteristic diagram with R rate.

FIG. 4 is an overall view of an intake structure of a conventional engine.

FIG. 5 is an overall view of an intake structure of a conventional engine.

FIG. 6 is a diagram showing an ignition sequence in a V8 engine.

[Explanation of symbols]

 118 engine 120 first bank 122 second bank 124 intake passage 130 branch 132 first branch intake pipe 134 second branch intake pipe 150 EGR passage 160 EGR chamber 162 first EGR opening 164 second EGR opening 170 communication pipe

Claims (1)

[Claims] An engine having a pair of banks, a pair of intake manifolds disposed on the intake side of each bank, an air cleaner disposed at an upstream end, and a downstream end branched from a collecting portion to form a pair of intake manifolds A pair of branch intake passages communicated with the manifold, a pair of exhaust manifolds disposed on the exhaust side of each of the banks, and a pair of branch exhaust passages independently formed while communicating with the exhaust manifold; An exhaust gas recirculation passage communicating with an EGR outlet of each of the branch exhaust passages and merging at a merging portion; an exhaust gas recirculation branch passage communicating the merging portion with an EGR opening of each of the branch intake air passages; An intake device for an engine, comprising a communication pipe located downstream of an EGR opening of the passage and communicating the two branch intake passages with each other.