JPS6155355A - Exhaust gas reflux device for multicylinder engine - Google Patents

Abstract

PURPOSE:To secure good exhaust emission control power, by branching an EGR passage off to branch EGR passages at the downstream side of an EGR valve, while setting the length and diameter of each these branch EGR passages to the specified condition. CONSTITUTION:Each of branch suction passages 5 and 6 is connected to the upstream side of both first and second suction manifold parts 3 and 4 and interconnected to a convergent passage 7. One end part of an EGR passage 11 is connected to a second exhaust pipe 10, and the other end part of the EGR passage 11 is branched off into branch EGR passages 11a and 11b. Each length of these branch suction passages 5 and 6 is set down to L while the passage width to D, respectively, and when each length of these branch EGR passages 11a and 11b is set down to l while the passage width to d, it should be set so as to satisfy the condition of d/l<1/2D/L<1/2>. Thus, exhaust gas is uniformly distributed and fed to each cylinder and good exhaust gas emission control power is securable.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an exhaust gas recirculation bag 2 for a multi-cylinder engine that is designed to improve output through dynamic effects of the 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 column vibration system on the upstream side of the collecting section is utilized. The intake device is, for example, Machi 7N Sho 56-115818M, Japanese Patent Application Laid-open Sho 57-51.
No. 910.

Therefore, when a part of the exhaust gas is recirculated from the exhaust system to reduce NOx in the above-mentioned intake system, in order to recirculate the exhaust gas to the metal cylinder, both the intake air 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 608 passage to the above-mentioned intake air collecting part, both the intake air collecting parts will be communicated through the 608 passage.
This will impair the resonance supercharging effect in the intake device.

In other words, when both intake air gathering parts are gathered by a branch intake passage on the upstream side with passage length and diameter, the tuned frequency of the air column vibration applied to this intake system is o/-/T. It is proportional to . This resonance supercharging effect has a large torque improvement effect in the relatively low and medium rotation range, and in order to set the tuned rotation speed in this low and medium rotation range, the diameter of the branch intake passage must be made small. Or, it is necessary to increase the passage length L.

When the 608 passage connects both the intake air collecting parts over a short length with respect to an intake system in which the tuned rotation speed is set as described above, the tuned rotation speed due to the 608 passage becomes higher than the tuned rotation speed. However, the resonance at this high tuned rotational speed becomes dominant, and there is a problem in that it is impossible to obtain an output improvement effect due to the resonant supercharging effect at a predetermined rotational speed.

(Objective of the Invention) In view of the above circumstances, an object of the present invention is to provide an exhaust gas recirculation device for a multi-cylinder engine that eliminates the influence of the 608 passage on the supercharging effect.

(Structure of the Invention) The exhaust gas recirculation device of the present invention has both intake collecting portions gathered together with a predetermined passage length and diameter by a branched intake passage on the upstream side, one end of which is connected to the exhaust passage. 6
08 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-mentioned intake collecting parts, respectively, and the passage length 9J and diameter d of this branch EGR passage are as follows: d
/(Ding<o/(TZ).

(Effects of the Invention) According to the present invention, when the 608 passage is connected to the intake air gathering part to recirculate the exhaust gas, the connection of the 608 passage is made such that the resonant supercharging effect of the intake device is not inhibited. By setting the path diameter d and the path length difference λ, a predetermined synchronized rotation is achieved in order to obtain a resonant supercharging effect by setting the path diameter and path length of the branch intake path upstream from the intake gathering section. It is possible to obtain a predetermined output improvement effect by increasing the number of cylinders, and it is possible to obtain good exhaust gas purification performance by equally distributing and supplying exhaust gas to each cylinder.

(Example) Hereinafter, the present invention will be explained in detail 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.

The in-line six-cylinder engine 1 has the first cylinder 1A to the sixth cylinder 1.
The ignition order of F, that is, the intake stroke order is 1st→4th→2nd→5th.
→The cylinders are set in the order of 3 → 6 cylinders. And each cylinder 1
The independent intake passages 2a to 2f connected to A to 1F are two cylinders 7 whose intake strokes do not substantially overlap! It is connected to the first intake air collecting section 3 (first surge tank) or the second intake air collecting section 4 (second surge tank). That is, the independent intake passages 2a, 2b, 2c of the first to third cylinders 1A, 1B and IC are gathered in the first intake collecting part 3, and the fourth to sixth cylinders ID,
IE, 1F independent intake passages 2d, 2e.

2f are collected in the second intake collecting portion 4.

Furthermore, one branch intake passage 5°6 is connected to the first and second intake collecting portions 3 and 4 on the upstream side thereof,
Both branch intake passages 5 and 6 are provided to be gathered together and communicated with a merging passage 7. Further, a throttle valve 13. which opens and closes in synchronization is located downstream of both branched intake passages 5.6.
14 are interposed respectively.

On the other hand, an independent exhaust passage 8a connected to each cylinder 1A to 1F
-8f are divided into two parts corresponding to the above-mentioned cylinder groups, and are respectively connected to the first exhaust pipes 9.-8f. B and the second exhaust pipe 10.

One end of the EGR passage 11 is connected and opened to the second exhaust pipe 1o, and the other end of the 608 passage 11 is branched into two branch EGR passages 11a and 11b, which are connected to the first and second intake pipes, respectively. It is connected to the gathering part 3.4. Further, an EGR valve 12 is interposed upstream of the branching part of the EGR passage 11, and when the EGR valve 12 is opened, exhaust gas from the exhaust pipe 10 is transferred to both intake collecting points of the intake system. 3.4, each independent intake passage 2a to 2f
The air is then supplied to the customer air@1A to 1F.

In the above-mentioned intake system, in the intake system upstream of the intake collecting portion 3.4, the intake valve period is generally 24.
At 0°, ignition is carried out in each cylinder sequentially with a 120° shift, and since the intake strokes occur alternately at 120° and 240° in the first intake collecting section 3 and the second intake collecting section 4, the intake stroke There is no stroke overlap, and the pressure fluctuations occur continuously, and the pressure fluctuations in the first intake collecting section 3 and the second intake collecting section 4 are out of phase with each other by 120 degrees. Therefore, 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
The pressure fluctuation at 3.4 becomes a valley value, and the branched intake passages 5.6 that connect both the intake air collection parts 3.4 vibrate each other, and the air column vibration system on the upstream side of the intake air collection parts 3.4 resonates. When I did,
A large resonance supercharging effect can be obtained. The resonance point of the pressure J vibration of the air column vibration system on the upstream side of the intake collecting parts 3 and 4, that is, the tuned rotation speed, is equal to the length of the branched intake passage 5.6 from the intake collecting parts 3 and 4 to the merging part. , when the passage diameter is D, it is proportional to o/(d). Since this resonant supercharging effect has good characteristics in the low and medium speed rotation range, the above tuning speed is It is set according to the required characteristics of the engine in this low-medium speed rotation range.

On the other hand, the above-mentioned intake collecting section 3.4 is also communicated with the branched EGR passages 11a and 11b of the EGR passage 11 of the exhaust gas rapid flow device. When the length of the branched EGR passages 11a and 11b is 21 and the passage diameter is d, similar to the above, a resonance effect occurs based on the tuned rotation speed proportional to d/(τ, but due to this EGR passage 11, The tuned rotational speed is set to a value lower than the tuned rotational speed due to the branch intake passages 5 and 6, that is, to satisfy the condition d/JT<o/(r).

The reason for this is that the synchronized rotation speed by the EGR passage 11 is
If the rotation speed is set higher than the synchronized rotation speed of the branch intake passage 5.6, that is, if the EGR passage 11 has a relatively large diameter or a relatively short passage length, the branch intake passage At the synchronized rotation speed of 5.6, the pressure fluctuations in the intake air gathering parts 3 and 4 are attenuated through the EGR passage 11, and the pressure fluctuations are reduced, so that a sufficient resonance supercharging effect cannot be obtained. In other words, the resonance effect of the resonance system that communicates the intake air gathering portions 3.4 with each other is dominated by the high tuned rotation speed side, and the tuned rotation speed by the EGR passage 11 is tuned by the branched intake passage 5.6. By setting the rotation speed to be lower than the rotation speed, the influence caused by this can be reduced.

At that time, the branch EGR passage 11a in the EGR passage 11
, 11b has a minimum diameter set to a certain extent in order to supply the required amount of exhaust gas t, and depending on the passage diameter d regulated by this condition,
Set the passage length relatively long and adjust the synchronized rotation speed to EGR.
The passage 11 is set to be lower than when it is not connected.

According to the exhaust gas flow device as in the above embodiment, EGR
One EGR valve 12 installed on the upstream side of the branching part of the branched EGR passages 11a and 11b of the passage 11 opens and closes the recirculating exhaust gas or controls the flow of the recirculating exhaust gas, so that four predetermined exhaust gases are transferred from the exhaust system to the intake system. This is to prevent the resonant supercharging effect of the intake system from being affected by the reflux.

In this case, since there is only one E-GR valve 12, it is easy to control and the uniformity of distribution to the intake air gathering portion 3.4 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 these upstream ends are open to an air cleaner or the like, the intake air collecting parts 3 and 4 may When synchronized with the resonance point of the air column vibration system on the upstream side, a resonant supercharging effect is obtained.
This is the length of 6.

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.
.

11b, and the diameter and length 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 drawings]

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 to 2f...Independent intake passage 3.4...Intake gathering section 5.6...Branch intake passage 8a to 8f...Independent exhaust passage 9.10...Exhaust pipe 11...E
GR passage 11a, 11b...Branch EGR passage 1
2...EGR valve

Claims (1)

[Claims] (1) Two groups of cylinders whose intake order is not consecutive are gathered into each intake collecting part by independent intake passages, and both intake collecting parts are brought together by a branched intake passage on the upstream side with a predetermined passage length L and diameter D. In a multi-cylinder engine, an 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 ends thereof are respectively connected to both the intake collecting parts, and this branch An exhaust gas recirculation device for a multi-cylinder engine, characterized in that a passage length l and a diameter d of an EGR passage are set to satisfy the following condition: d/√l<D/√L.