JPS63309724A - Exhaust device for multi cylinder engine with supercharger - Google Patents

Abstract

PURPOSE:To unify the exhaust pressure of every cylinder by providing a plurality of independent exhaust passages which lead exhaust from an engine to the turbine portion of a turbosupercharger and at the same time, forming at the turbine portion a plurality of scrolls which correspond to respective independent exhaust passages. CONSTITUTION:In a 6-cylinder engine, the 1st and 2nd exhaust manifolds 13, 14 which are independent exhaust passages are provided corresponding to the 1st and 2nd cylinder groups which respectively consist of 3 cylinders and in which an exhaust stroke does not overlap. The lower stream portions of respective manifolds 13, 14 are connected to the turbine portion 6 of a turbosupercharger 7. In this case, the turbine portion 6 is formed so as to have two scroll portions 15, 16, which are respectively connected with respective exhaust manifolds 13, 14. Also, when A is the cross sectional area of an exhaust inflow portion, and R is the distance from the center of this cross sectional to the shaft center of the turbine portion 6, the A/R of the turbine portion 6 is set larger for the exhaust manifold 13 having a larger exhaust resistance than for the exhaust manifold 14 having a smaller exhaust resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an exhaust system for a supercharged multi-cylinder engine, and particularly to one improved to equalize exhaust resistance for all cylinders.

[Prior Art] For example, as described in Japanese Patent Application Laid-Open No. 61-8421, twin engines are used to prevent exhaust interference and effectively utilize the kinetic energy of exhaust gas in a multi-cylinder engine with a turbocharger. A scroll-type turbo supercharger is adopted, and one scroll section introduces exhaust gas from the cylinder group corresponding to half of the cylinders whose exhaust strokes do not overlap, and the other scroll section introduces exhaust gas from the cylinder group corresponding to half of the cylinders whose exhaust strokes do not overlap. A system is known in which exhaust gas is introduced from a group of cylinders corresponding to half of the cylinders.

In this way, all the cylinders are grouped into cylinder groups with the same number of cylinders to form the exhaust passage from the engine to the turbine, so the same amount of flow goes to the pair of scrolls in the turbine of the turbocharger. Exhaust gas is now being introduced. Therefore, the cross-sectional areas of the exhaust gas inflow portions of both scroll portions are generally set to be approximately equal, and the distances from both exhaust gas flow portions to the axis of the turbine portion are also generally set to be approximately equal.

For reference, A/R is a parameter representing the performance of radial turbines used in automobile turbochargers.
is used.

That is, as shown in FIG. 6, a turbine wheel 102 is disposed within a housing 101 of a radial turbine 100, and a spiral scroll portion 104 connected to an exhaust inflow portion 103 is formed outside the turbine wheel 102. , the flow of exhaust gas accelerated at the exhaust inflow section 103 is further accelerated at the scroll section 104 and flows into the turbine wheel 102.
flows towards.

When the cross-sectional area of the exhaust gas inflow section 103 connected to the scroll section 104 is A, and the distance from the axis of the turbine wheel 102 to the center of the cross-sectional area A is R, the smaller A/R is, the more the turbine wheel 102 rotates. It is known that as the number of turbines increases, the turbine front pressure increases due to the increased resistance of the turpin.

[Problems to be Solved by the Invention] When providing the exhaust passages for each cylinder group from the engine to the turbine section as described above, it is common to set the passages so that their resistances are as equal as possible. However, due to restrictions on the arrangement of equipment attached to the engine such as a turbo supercharger, the passage lengths of the two exhaust passages mentioned above are different, and the curvature of the curved part is different, so in reality the two exhaust passages are different. The resistance will be different.

Therefore, the pressure in front of the turbine in the exhaust passage differs for each cylinder group, and the exhaust pressures among the cylinder groups are not averaged, resulting in large variations.

As a result, due to the variation in exhaust efficiency among cylinders, the variation in air-fuel ratio becomes large, and the range of fluctuation in torque also becomes large.

Further, in cylinders with low exhaust capacity and cylinders with high filling efficiency, knocking is likely to occur, and ignition timing retardation to prevent non-king causes problems such as a decrease in output.

SUMMARY OF THE INVENTION An object of the present invention is to provide an exhaust system for a multi-cylinder engine with a supercharger that can make the exhaust pressure of each cylinder as uniform as possible, equalize the air-fuel ratio, improve output, and prevent torque fluctuations. .

[Means for solving problems]

An exhaust system for a multi-cylinder engine with a weekly charger according to the present invention is an exhaust system for a multi-cylinder engine equipped with a turbo supercharger, and includes a plurality of independent exhaust passages for guiding exhaust gas from the engine to a turbine section of the turbo supercharger. The turbine section is provided with a plurality of scroll sections corresponding to the plurality of independent exhaust passages, and the cross-sectional area of the exhaust inflow part from the independent exhaust passage to the scroll section is A, and the axis of the turbine section is set from the center of the cross-sectional area to A. It is characterized in that, when the distance to the center is R, the A/R is set to be larger as the independent exhaust passage has a larger exhaust resistance.

[Effect]

In the exhaust system for a supercharged multi-cylinder engine according to the present invention, exhaust from the multi-cylinder engine is guided to the turbine section of the turbocharger via a plurality of independent exhaust passages, and the exhaust from each independent exhaust passage is flows into the corresponding scroll section of the turbine section through the exhaust inlet section.

Then, when the cross-sectional area of the exhaust inflow section is A, and the distance from the center of the cross-sectional area to the axis of the turbine section is R,
The setting is such that the A/R increases as the independent exhaust passage has greater exhaust resistance.

The above A/R is a parameter that indicates the resistance at the turbine section, and the larger the A/R (as the resistance at the turbine section becomes smaller, the more it acts to lower the exhaust pressure in the independent exhaust passage. Therefore, the exhaust gas Independent exhaust passages with high resistance reduce resistance at the turbine section, so the exhaust pressure becomes uniform across all of the multiple independent exhaust passages.In this way, the exhaust pressure becomes uniform, so Variations in exhaust efficiency and air filling amount between cylinders are reduced, and the air-fuel ratio is made more uniform.
Output is improved and torque fluctuation is reduced.

〔Effect of the invention〕

According to the exhaust system for a supercharged multi-cylinder engine according to the present invention, as explained above, the air-fuel ratio between the cylinders is This makes it possible to improve engine output and improve torque fluctuations while suppressing the occurrence of knocking.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic configuration of the intake system and exhaust system of a vertical in-line six-cylinder engine equipped with a turbo supercharger. A cylinder block 1 is provided with first to sixth cylinders C1 to C6, The ignition order is, for example, C3 → C5 → C4 → C6 → C2
→The order is C4.

In the intake passage 2, from the upstream side, there is an air cleaner 3, a compressor section 5 of the turbo supercharger 7. An ink cooler 8, a throttle valve 9, and a surge tank 10 are provided, and branch intake pipes 10a are connected from the surge tank 10 to intake boats 11 of each cylinder C1 to C6.

The above six cylinders C8 to C6 are arranged in the first to third cylinders so that their exhaust strokes do not overlap (that is, the exhaust strokes are not adjacent).
The first cylinder group is cylinder 01 to C3, and the fourth to sixth cylinder C4
~C6 forms a second cylinder group, and a first exhaust manifold 13 (independent exhaust passage) corresponding to the first cylinder group and a second exhaust manifold 14 (independent exhaust passage) corresponding to the second cylinder group are provided. Each branch exhaust pipe 13a of the first exhaust manifold 13 connects to the exhaust port 1 of the corresponding cylinder C1 to C8.
2, and each branch exhaust pipe 14a of the second exhaust manifold 14 is connected to the exhaust port of the corresponding cylinder C4 to C6.

The downstream part of the first exhaust manifold 13 merges into one passage and is connected to the turbine section 6 of the turbocharger 7, and the downstream part of the second exhaust manifold 14 merges into one passage and is connected to the turbine section 6 of the turbocharger 7. It is connected to the turbine section 7.

The turbine section 6 of the turbocharger 7 is of a twin scroll type having first and second scroll sections 15 and 16, and the downstream end of the first exhaust manifold 13 is connected to the exhaust inflow section 15a of the first scroll section 15. The downstream end of the second exhaust eyebrow board 14 is connected to the exhaust inflow section 16a of the second scroll section 16.

A merging exhaust passage 17 extends from the turbine portion 6, and a common waste gate passage 18 that branches from the pair of exhaust inflow portions 15a and 16b extends to the waste gate portion 19 of the merging exhaust passage 17. A wastegate valve 20 is interposed at the end, and the wastegate valve 20 is opened and closed by an actuator 20a into which intake pressure on the downstream side of the compressor section 5 is introduced, and is opened when the intake pressure exceeds a predetermined pressure. It has become.

Here, since the turbine section 6 is arranged slightly toward the sixth cylinder 06 side with respect to the central part in the longitudinal direction of the cylinder block 1, point A of the first exhaust manifold 13
The length between the point 8 and the point 8 is longer than the length between the point 8 of the second exhaust manifold 14 and the point 8. Therefore, the exhaust resistance (passage resistance) of the first exhaust manifold 13 is greater than the exhaust resistance of the second exhaust manifold 14.

In this way, when the exhaust resistance of the first exhaust manifold 13 is greater than the exhaust resistance of the second exhaust manifold 14,
The exhaust pressure of the first exhaust manifold 13 becomes higher than the exhaust pressure of the second exhaust manifold 14, and the first to
The exhaust performance of the third cylinders C7 to C3 becomes lower than the exhaust performance of the fourth to sixth cylinders 04 to C1 of the second cylinder group, and the filling efficiency of the former becomes lower than that of the latter.

The filling efficiency differs among the first to third cylinders 01 to C3 of the first cylinder group or the fourth to sixth cylinders 04 to C6 of the second cylinder group due to differences in exhaust resistance.

In this way, due to variations in exhaust performance between cylinders C8 to C6 and variations in exhaust performance between exhaust manifolds 13 and 14, large variations occur in the intake air filling amount between all cylinders C1 to C6, and knocking occurs. This may cause torque fluctuations.

In the exhaust system of the present application, at least the exhaust manifold 13
・In order to eliminate fluctuations in exhaust resistance during the 14-hour period, the following measures have been taken.

That is, in the first exhaust manifold 13 having a large exhaust resistance, the A/R of the turbine section 6 is set larger than in the second exhaust manifold 14 having a small exhaust resistance.

That is, as shown in FIG. 2, the first exhaust manifold 1
A1 is the narrowest cross-sectional area of the exhaust inflow part 15a to which
Exhaust inlet 16 to which the second exhaust manifold 14 is connected
The narrowest cross-sectional area of a is A2, and the distance from the center of the cross-sectional area A to the axis 21a of the turbine shaft 21 (however, the distance l in the direction perpendicular to the inflow direction of exhaust gas is RI, and the cross-sectional area A is
If the distance from the center of 2 to the axis 21a of the turbine shaft 21 is R2, it is set as AI/R1>AZ/R2.

However, in the case of this example, since R,=R2, AI
>A2.

In this way, as explained in the [Prior Art] section, A/R is a parameter that represents the performance of the turbine section 6, and the larger A/R is, the smaller the resistance in the turbine section 6 becomes, and the Pressure or exhaust gas inflow portions 15a and 16
Since the exhaust pressure of a decreases, the first exhaust manifold 13
This has the effect of lowering the exhaust pressure inside.

That is, since the exhaust resistance of the first exhaust manifold 13 is greater than the exhaust resistance of the second exhaust manifold 14, the exhaust pressure in the first exhaust manifold 13 is higher than the exhaust pressure in the second exhaust manifold 14. However, as mentioned above, by setting the A/R larger for the passage with greater exhaust resistance, the first and second exhaust manifolds 13
・The exhaust pressure inside 14 can be made as uniform as possible. Thereby, the exhaust performance of the cylinders C5 to C3 of the first cylinder group and the cylinders 04 to C6 of the second cylinder group can be made as uniform as possible, and the intake air filling amount can be made as uniform as possible.

In this way, by optimizing the air-fuel ratio in each cylinder to improve combustibility, and by promoting uniformity of intake air filling across all cylinders, the engine prevents knocking and reduces output due to knocking. Torque fluctuation can be reduced.

Incidentally, as shown in FIG. 3, the first exhaust manifold 13
If A1 corresponding to the second exhaust manifold 14 is approximately equal to A2 corresponding to the second exhaust manifold 14, the scroll portion 15
- Inflow direction line 15b from 16 to turbine wheel 22
・The smaller the intersection angle α1 between 16b and the axis 21a, the smaller the resistance in the turbine section 6. Therefore, the first exhaust manifold 13, which has a large exhaust resistance, is set to the smaller intersection angle α1.
It is assumed that the scroll section 15 is connected to the scroll section 15 corresponding to the scroll section 15.

2, since the crossing angle α is also a parameter representing the resistance in the turbine section 6, the first and second The scroll portions 15 and 1 of the turbine portion 6 are
It is desirable to set it to 6.

In the above embodiment, the six cylinders CI-Cb are made up of cylinders C1 to C3 and cylinders C4 to C6, each of which has a non-overlapping exhaust stroke, and one independent exhaust manifold 13, 14 is provided for each cylinder group. However, in the case of the above ignition order, 3 cylinders such as the first and second cylinders C3 and C2, the third and fourth cylinders C3 and C4, and the fifth and sixth cylinders C5 and C6
The cylinders may be grouped into three cylinder groups, and the turbine section 6 may have three scroll portions corresponding to each cylinder group.

Further, although it is desirable that the exhaust strokes of cylinders included in the same cylinder group do not overlap, they may overlap.

z For example, set the first to fourth cylinders of a vertical 4-cylinder in-line engine to 0.
1 to C4, and the ignition order is C2→C3→C4→C2, the first cylinder group is the first and second cylinders C1 and C2, and the second
A cylinder group is formed by third and fourth cylinders C3 and C4, and an exhaust manifold corresponding to each cylinder group is provided.

In this case, although exhaust interference occurs,
By connecting the exhaust branch pipes 1 to C4 through a communication path,
Countermeasures against exhaust interference can be taken, and the structure of the exhaust manifold is less complicated and the exhaust resistance of the exhaust manifold is reduced by using the cylinder group as described above.

The exhaust system of the present invention can be applied not only to multi-cylinder in-line engines with six or more cylinders, but also to multi-cylinder ■-type engines and multi-cylinder rotary engines.

Next, an exhaust system for a turbocharged three-cylinder rotary piston engine according to another embodiment will be described with reference to FIGS. 4 and 5.

This rotary engine has first to third cylinders C8 to C3, and first to third independent exhaust passages 24a to 24c corresponding to each cylinder CI''C't are provided.

Further, the turbine section 6A of turbocharging @IA includes scroll sections 25a to 25c corresponding to the first to third independent exhaust passages.
are provided, and the first to third independent exhaust passages 24a to 2
4c, the second independent exhaust passage 24b has the smallest exhaust resistance, and the first and third independent exhaust passages 24
The exhaust resistances of a and 24c are approximately equal.

And the first to third independent exhaust passages 24a, 24b, 24
When the intersection angle between the direction of inflow from the scroll portions 25a, 25b, and 25c corresponding to c into the turbine wheel 22 and the axis 21a of the turbine shaft 21 is α8 ·α, ·α0, α8<αb<α. Therefore, scroll section 25
When the cross-sectional area of a~25C is Aa-AC, Am <
It is set so that Ab<AC or A, =Ab<AC, and the cross-sectional area of the exhaust gas inflow part corresponding to these scroll parts 25a to 25c is also set to have the same relationship as above.

Even in the case of A<Ah, α1<α, so the turbine front pressure of the scroll portion 25b is greater than the turbine front pressure of the scroll portion 25a.

The operation of the exhaust device described above is substantially the same as that described above, so a description thereof will be omitted.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a configuration diagram of the intake system and exhaust system of a 6-cylinder in-line engine, and FIG. 2 is an explanatory diagram illustrating A/R of the turbine section of a turbocharger. , 3rd
The figure is an explanatory diagram explaining the direction of inflow from the scroll part to the turbine wheel, Figure 4 is a cross-sectional plan view of the main parts of the 3-cylinder rotary piston engine and turbocharger, and Figure 5 is the
A sectional view taken along the line V-V in FIG. 6 is an explanatory diagram illustrating the A/R of a general radial turbine. 7, 7A... Turbo supercharger, 6, 6A... Turbine section, 13, 14... 1st and 2nd exhaust manifold (independent exhaust passage), 15, 16... 1st and 2nd scroll section, 21a ...Axis center, 24a to 24c...First to third independent exhaust passages, 25a to 25c...First to third scroll portions. Patent Applicant: Mazda Motor Corporation Figure 6 A-A, A1

Claims (1)

[Claims] (1) In an exhaust system for a multi-cylinder engine equipped with a turbocharger, a plurality of independent exhaust passages are provided to guide exhaust gas from the engine to a turbine section of the turbocharger, and the turbine section has a plurality of independent exhaust passages. A plurality of scroll parts are provided corresponding to each of the scroll parts, and when the cross-sectional area of the exhaust inflow part from the independent exhaust passage to the scroll part is A, and the distance from the center of the cross-sectional area to the axis of the turbine part is R, An exhaust system for a multi-cylinder engine with a supercharger, characterized in that the independent exhaust passage having a greater exhaust resistance is set to have a greater A/R.