JPH0569982B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an exhaust gas recirculation device for a multi-cylinder engine that aims to improve output through dynamic effects of an intake system.

(Prior Art) Conventionally, in a multi-cylinder engine, the intake passages connected to each cylinder are connected to an intake collecting part so that the intake order is not consecutive to each other, and intake interference in this collecting part is prevented, and
The above-mentioned intake collecting section is collected by a branch intake passage on the upstream side, and the supercharging effect (hereinafter referred to as resonance supercharging effect) accompanying pressure vibration due to the influence of the air injection vibration system on the upstream side of the collecting section is utilized. Such intake devices have been proposed, for example, in Japanese Patent Application Laid-Open Nos. 56-115818 and 57-51910.

Therefore, in the above-mentioned intake system, when a part of exhaust gas is recirculated from the exhaust system to reduce NOx, in order to recirculate this exhaust gas to all cylinders, it is necessary to It is necessary to recirculate the exhaust gas to the collecting part to improve distribution.

However, if the exhaust gas is recirculated by simply connecting the downstream end of the EGR passage to the above-mentioned intake air collecting section, both intake air collecting parts will be communicated through the EGR passage, and resonance in the intake system will occur. This will impair the supercharging effect. That is, when both intake air gathering parts are gathered by the upstream branch intake passage with passage length L and diameter D, the harmonic frequency of air column vibration in this intake system is proportional to D/√. This resonance supercharging effect has a large torque improvement effect in a relatively low and medium rotation range, and in order to set the tuned rotation speed in this low and medium rotation range, the diameter D of the branch intake passage is made small. Or, it is necessary to increase the passage length L.

For an intake system in which the tuned rotational speed is set as described above, when both intake air collecting parts are communicated with each other through a short length through the EGR passage, the tuned rotational speed due to this EGR passage is lower than the tuned rotational speed above. get high,
Resonance at this high tuning speed becomes dominant,
This has the disadvantage that it is not possible to obtain an output improvement effect due to the resonance supercharging effect at a predetermined rotation speed.

(Object of the Invention) In view of the above-mentioned circumstances, an object of the present invention is to provide an exhaust gas recirculation device for a multi-cylinder engine that eliminates the negative influence of the EGR passage on the supercharging effect.

(Structure of the Invention) The exhaust gas recirculation device of the present invention has a predetermined passage length L between both intake collecting portions by an upstream branch intake passage.
and a diameter D, the EGR passage whose one end is connected to the exhaust passage is branched into a branch EGR passage on the downstream side of the EGR valve, and the end thereof is connected to both the above-mentioned intake collecting parts, respectively, This branch
This is characterized in that the passage length l and diameter d of the EGR passage are set to satisfy the condition d/√<D/√.

(Effects of the Invention) According to the present invention, when the EGR passage is connected to the intake collecting part to recirculate exhaust gas, this
By setting the passage diameter d and the passage length l so that the connection of the EGR passage does not impede the resonance supercharging effect of the intake system, the passage diameter D of the branch intake passage upstream from the intake gathering part It is possible to obtain a predetermined output improvement effect at a predetermined synchronized rotation speed to obtain a resonant supercharging effect by setting and passage length L, and exhaust gas is evenly distributed and supplied to each cylinder. Good exhaust gas purification performance can be obtained.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an in-line six-cylinder engine showing the basic configuration of the present invention.

In the inline six-cylinder engine 1, the ignition order, that is, the intake stroke order of the first cylinder 1A to the sixth cylinder 1F is set in the order of the first cylinder, the fourth cylinder, the second cylinder, the fifth cylinder, the third cylinder, and the sixth cylinder. The independent intake passages 2a to 2f connected to the cylinders 1A to 1F are each divided into two groups of cylinders whose intake strokes do not substantially overlap. 2 is connected to the intake air collecting section 4 (second surge tank). That is, the first to third cylinders 1
A, 1B, 1C independent intake passages 2a, 2b, 2c
are collected in the first intake collecting part 3, and the fourth to sixth
Independent intake passages 2d, 2 for cylinders 1D, 1E, 1F
e, 2f are collected in the second intake collecting portion 4.

Further, the first and second intake collecting portions 3, 4
has one branch intake passage 5 on its upstream side,
6 are connected, and both branch intake passages 5 and 6 are collectively provided to communicate with a merging passage 7. Furthermore, throttle valves 13 and 14, which open and close in synchronization, are interposed in the downstream portions of both branched intake passages 5 and 6, respectively.

On the other hand, the independent exhaust passages 8a to 8f connected to the cylinders 1A to 1F are divided into two parts corresponding to the cylinder groups, and a first exhaust pipe 9 and a second exhaust pipe 1 are respectively divided into two.
It is connected to 0 and aggregated.

Then, an EGR passage 11 is connected to the second exhaust pipe 10.
One end is opened for connection, and the other end of the EGR passage 11 is branched into two branched EGR passages 11a and 11b, which are opened for connection to the first and second intake air collecting parts 3 and 4, respectively. Also, above
The EGR valve 1 is located upstream of the branch part of the EGR passage 11.
2 is interposed, and when this EGR valve 12 is open, the exhaust gas from the exhaust pipe 10 is returned to both the intake collecting parts 3 and 4 of the intake system, and each independent intake passage 2
It is supplied to each cylinder 1A to 1F via a to 2f.

In the above-mentioned intake system, in the intake system upstream of the intake collecting parts 3 and 4, the opening period of the intake valve is generally 240°, and ignition is performed in each cylinder sequentially with a 120° shift. In the collecting part 3 and the second intake collecting part 4, the intake strokes occur alternately by 120° and 240°, so there is no overlap in the intake strokes and the pressure fluctuation occurs continuously, and the first intake collecting part 3 The pressure fluctuations at the second intake collecting portion 4 and the second intake collecting portion 4 are out of phase with each other by 120°. Then,
When the pressure fluctuation in one intake collecting part 3 or 4 is at the peak value, the pressure fluctuation in the other intake collecting part 4 or 3 is at the trough value, and the branched intake that communicates both the intake collecting parts 3 and 4 When the passages 5 and 6 vibrate each other and the air column vibration system on the upstream side of the intake air collecting sections 3 and 4 resonates, a large resonant supercharging effect can be obtained. The resonance point of the pressure vibration of the air column vibration system on the upstream side of the intake collecting parts 3, 4, that is, the tuned rotation speed, is determined by the length L of the branched intake passages 5, 6 from the intake collecting parts 3, 4 to the merging part. When the passage diameter is D, it is proportional to D/√. Since this resonant supercharging effect has good characteristics in a low-medium speed rotation range, the tuning rotation speed is set in accordance with the required characteristics of the engine in this low-medium speed rotation range.

On the other hand, the intake collecting parts 3 and 4 are also communicated by the branch EGR passages 11a and 11b of the EGR passage 11 of the exhaust gas recirculation device, and the branch EGR passages from the intake collecting parts 3 and 4 to the branching part are connected to each other. Passage 1
When the length of 1a and 11b is l, and the passage diameter is d, as in the above, a resonance effect occurs based on the number of tuned circuits proportional to d/√, but the tuned rotation speed due to this EGR passage 11 teeth,
It is set to a value lower than the synchronized rotation speed by the branch intake passages 5 and 6, that is, to satisfy the condition d/√<D/√.

The reason for this is that if the tuned rotation speed by the EGR passage 11 is set to a higher rotation speed than the tuned rotation speed by the branch intake passages 5 and 6, that is,
If the passage diameter D of the EGR passage 11 is set relatively large or the passage length l is set short, pressure fluctuations in the intake collecting parts 3 and 4 will be caused by the EGR Because it is attenuated through the passage 11 and its pressure fluctuation is reduced,
A sufficient resonance supercharging effect cannot be obtained. In other words,
The resonance effect of the resonant system that interconnects the intake air gathering parts 3 and 4 is dominated by the high tuned rotation speed side, and the tuned rotation speed by the EGR passage 11 is reduced to the tuned rotation speed by the branched intake passages 5 and 6. By setting the rotation speed to a lower value, the influence caused by this can be reduced.

At this time, in order to supply the necessary amount of exhaust gas, the minimum diameter of the passage diameter d of the branched EGR passages 11a and 11b in the EGR passage 11 has a certain limit, and depending on this condition, According to the regulated passage diameter d, the passage length l is set to be relatively long, and the tuned rotation speed is set to be lower than when the EGR passage 11 is not connected.

According to the exhaust gas recirculation device as in the above embodiment,
One EGR valve 12 interposed on the upstream side of the branch part of the branch EGR passages 11a and 11b of the EGR passage 11
A predetermined amount of exhaust gas is recirculated from the exhaust system to the intake system by opening/closing or metering the recirculating exhaust gas, and the recirculation is made so as not to impede the resonance supercharging effect of the intake system. ing. In this case, since there is only one EGR valve 12, its control is easy and the uniformity of distribution to the intake air collecting parts 3 and 4 is improved.

In FIG. 1, the branched intake passages 5 and 6 on the upstream side of the intake air collecting parts 3 and 4 are arranged to merge, but even if the upstream ends of these passages are open to an air cleaner or the like, this air collecting part When synchronized with the resonance point of the air column vibration system on the upstream side, a resonant supercharging effect can be obtained. This is the result.

Furthermore, the present invention is applicable not only to in-line engines but also to V-type engines. In that case, the intake order of each cylinder is not continuous in the left and right banks, and there is no overlap in the intake strokes, so it can be applied to V-type engines. An intake system is constructed by collecting independent intake passages and further collecting them at a branch intake passage on the upstream side.The branch EGR passages 11a and 11a of the EGR passage 11 are connected to the overlapping part of this intake system, respectively.
11b, and the passage diameter D and passage length L of this branched EGR passage are set in the same manner as described above.

Furthermore, the present invention can be applied not only to six-cylinder engines but also to multi-cylinder engines that can obtain a resonance supercharging effect.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a multi-cylinder engine according to an embodiment of the present invention. 1...Engine, 1A~1F...Cylinder, 2a~
2f...Independent intake passage, 3, 4...Intake gathering part,
5, 6... Branch intake passage, 8a to 8f... Independent exhaust passage, 9, 10... Exhaust pipe, 11... EGR passage, 11a, 11b... Branch EGR passage, 12...
...EGR valve, l, L...passage length, d, D...passage diameter.

Claims (1)

[Scope of Claims] 1. Two groups of cylinders whose intake order is not consecutive are collected in each intake collecting part by independent intake passages, and both intake collecting parts are connected to a predetermined passage by an upstream branch intake passage. In a multi-cylinder engine that has a length L and a diameter D, one end is connected to the exhaust passage.
The EGR passage is branched into a branch EGR passage on the downstream side of the EGR valve, and the ends thereof are connected to both the above intake collecting parts, respectively, and the passage length l and diameter d of this branch EGR passage are expressed as d/√< An exhaust gas recirculation device for a multi-cylinder engine, characterized in that it is set to satisfy the condition of D/√.