JP2585568B2 - Exhaust system for in-line 4-cylinder 4-cycle engine - Google Patents

Description

The present invention relates to an improvement in an exhaust system of a four-cylinder engine used for a motorcycle or the like, in which it is difficult to take a sufficiently long exhaust pipe, and more particularly, to an exhaust system exceeding 15,000 rpm. The present invention relates to an exhaust device suitable for an engine capable of obtaining high output by enabling high rotation.

[Prior Art] In an in-line four-cylinder four-cycle engine used for motorcycles and the like, which explodes at a crank angle of 180 °, rear ends of four exhaust pipes extending from exhaust holes of each cylinder. May be combined and connected to the front end of the collecting pipe, and an exhaust device may be used that connects the rear end of the collecting pipe to the muffler (hereinafter, this type is referred to as a 4-1 set). However, in such an exhaust system, the exhaust gas coming from each cylinder in the collecting pipe may interfere with each other, causing a valley whose output is reduced particularly in a middle rotation range.

In such a case, in the case of the 4-1 assembly, the countermeasure becomes complicated. Therefore, a separator that divides the inside of the collecting pipe into two in the radial direction is provided, and two collecting sections are defined in the collecting pipe. There is a type in which two exhaust pipes each having a phase shift of 360 ° are connected to each other so as to prevent exhaust interference caused by one another with a phase shift of 180 ° (hereinafter, this type is referred to as a 4-2 set). When the 4-2 set is adopted, a valley countermeasure can be easily taken by a separator or the like. One such example is disclosed in Japanese Utility Model Laid-Open No. 57-120201.

Japanese Patent Publication No. Sho 62-501022 discloses that the rear end portions of the collecting pipes of the above-mentioned 4-2 are combined into one and the entirety is made as 4-2.
-1 A set of exhaust devices is shown, and it is also shown that the output characteristics of the engine are changed by appropriately setting the length of the exhaust pipe and the length of the collecting pipe. The medium rotation range, 8000 to 12000 rpm is referred to as a high rotation range, and the one exceeding 12000 rpm is referred to as an ultra high rotation range.

[Problems to be Solved by the Invention] By the way, even if the above-mentioned 4-2-1 assembly is used as it is in a conventional high-speed or ultra-high-speed high-power type engine, a practical rotation In the area
It was found that multiple valleys of output occurred in the high rotation range.

This valley is caused by the positive pressure generated by two open-end reflections in the 4-2 collecting portion P2, as shown in FIG. 4 which is a conceptual diagram of the 4-2-1 set. That is, the in FIG. 3, the pressure wave W ₀ of the exhaust gas when (EO) generating the exhaust valve opens, as shown by the solid line arrows, the exhaust valve side in the negative pressure W ₁ by the open reflection in one round of P2 And back again
When reflected open end at P2 return to the exhaust valve side in positive pressure W _2. The positive pressure W ₂ is just back at the timing overlap when the exhaust valve opens (EO), residual gas in the combustion chamber because the valley of the output remaining intake air amount is reduced occurs.

This valley is particularly pronounced in high speed engines with overlap where the intake valve opens before the exhaust valve closes. Therefore, the present invention provides an exhaust device having a 4-2-1 collective type collecting pipe capable of preventing the occurrence of the plurality of valleys even when used in an unprecedented ultra-high-speed, high-power engine. Aim.

[Means for Solving the Problems] The exhaust system for an in-line four-cylinder four-cycle engine according to the present invention, which ignites at 180 ° intervals, includes four exhaust pipes connected to each cylinder and a rear part of the exhaust pipes. It consists of a collecting pipe to be put together. This collecting pipe is divided into two collecting parts by dividing its inside into two parts in the radial direction, and two exhaust pipes each having a phase shift of 360 ° are connected to the front end side of each of these collecting parts. A 4-2 set is formed, and the rear end of each 4-2 set is united into a single 2-1 set to form a 4-2-1 set form as a whole. In this exhaust device, the present invention provides that the length of the exhaust pipe is 1 and 4
The length ratio given by l2 / (1 + 12) is set to be in the range of 0.26 to 0.46, where the length of the -2 gathering portion is l2.

[Effect of the Invention] In the 4-2-1 collecting pipe used in the exhaust system for the in-line 4-cylinder 4-cycle engine according to the present application, two reflections at the 4-2 collecting section P2 in FIG. Positive pressure W ₂
Returns to the exhaust valve side when the exhaust valve is open (EO) and the intake valve is open, and at the same time, 2-1 in FIG.
When open end reflections first in the set portion P1 is returned to the exhaust valve side, the reflection is as shown in FIG. 3, the positive pressure W ₂ and overlap becomes negative pressure W _3, abolished the positive pressure W _2, The valley of the output can be eliminated.

Conditions under which such a phenomenon occurs include the length of the pressure wave in the exhaust pipe length 1 for two reciprocations, and the exhaust pipe lengths 1 and 4-2.
That is, the length of the pressure wave in the total length (1 + l2) of the length l2 of the gathering portion coincides with the length of one reciprocation. Therefore, theoretically, since (1) × 2 = (1 + l2), the length ratio 12 / (1 + l2) is 0.5.

However, in practice, the exhaust gas temperature decreases toward the downstream side, and as a result, the sound speed decreases. Therefore, it is appropriate that the actual value of the length ratio l2 / (1 + l2) is in the range of 0.26 to 0.46.

[Embodiment] An embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows an in-line 4-cylinder 4-cycle motorcycle engine that explodes at crank angle intervals of 180 ° (not shown).
FIG. 2 is a schematic view of an exhaust device used in the present invention, and FIG. 2 is a performance curve thereof.

In this exhaust device, the rear ends of the exhaust pipes 1, 2, 3, and 4 connected to the exhaust holes of each cylinder of the engine are connected to the collecting pipe 5, respectively. In this embodiment, each exhaust pipe has an inner diameter of 30 mm. The rear part of the collecting pipe 5 is connected to a silencer 6.

Inside the collecting pipe 5, a flat separator 7 is disposed in the front-rear direction on the front half side. This separator 7
Is attached by a suitable means such as welding in the collecting pipe 5, whereby the inside of the front half side of the collecting pipe 5 is divided into two in the radial direction, thereby defining two collecting parts 8 and 9.

Therefore, the first half of the collecting pipe 5 forms a 4-2 set. However, at the rear part of the collecting pipe 5,
−1 assembly is formed, so that the exhaust system as a whole is 4
-2-1 set.

The ignition sequence of the engine is represented by the exhaust pipe 1 → exhaust pipe 2 → exhaust pipe 4 → exhaust pipe 3 as indicated by the reference numeral of the exhaust pipe corresponding to each cylinder.
The exhaust pipes 1 and 4 out of phase by 360 ° are connected to the collecting section 8, and the exhaust pipes 2 and 3 out of phase by 360 ° are connected to the collecting section 9. . The separator 7 has an opening 10 for communicating the collecting portions 8 and 9. In this embodiment, the hole diameter of the opening 10 is φ10 mm.
And

Next, the length ratio (Rl) and the cross-sectional area ratio (Ra) of the collecting pipe 5 will be described. First, the length ratio (Rl) is defined as Rl = l2 / (1 + l2), where the length of each exhaust pipe is 1, and the length of the separator, ie, the length of the separator is l2. The cross-sectional area ratio (Ra) is defined as Ra = a1 / a2, where a1 is the opening area of the opening 10 and a2 is the cross-sectional area of the passage at the rear of the collecting portion of the collecting pipe 5.

In this embodiment, Rl = 0.37 (1 = 670 mm, l2 = 4
00mm), Ra = 0.08 (a1 = 177mm ² (φ15mm), a2 = 2205mm
² (φ53mm). However, this numerical example is merely an example, and it has been found that the effect described later can be obtained when the length ratio (Rl) is in the range of 0.26 to 0.46.

When 1 is set to, for example, 500 mm, 700 mm, 800 mm, or 900 mm, l2 is adjusted so that the length ratio (Rl) falls within the above range.
It has been found that the same effect can be obtained by setting.

Similarly, it was found that the cross-sectional area ratio (Ra) should be set in the range of 0.15 to 0.44 (for example, when a2 is φ53 mm, a1 is φ5 to 35 mm).

Further, if the length from the front part of the collecting pipe 5 to the center of the opening 10 is l3, the range of l3 / l2 = 0.075 to 0.875 is preferable. In this embodiment, l3 / l2 = 0.2 and l3 = 80 mm. However, this ratio does not need to be very strict, but it has been found that the closer the position of the opening 10 is to the inlet of the collecting pipe, the more sensitively it reacts to the size of the opening 10.

It is to be noted that reference numeral a3 in the drawing denotes the passage cross-sectional area of the collecting portions 8 and 9, and it is preferable that a3 = 1,4a1 to 1.5a2.

Next, output characteristics of an engine using the exhaust device of the present embodiment will be described with reference to FIG. The performance curve of the present embodiment is shown by a solid line X. For reference, the performance curve of the conventional 4-1 set is indicated by a broken line Y. Further, the performance curve of the 4-2 set constituted outside the range of the length ratio (Rl) according to the present invention is indicated by a two-dot chain line Z.

First, in the 4-2 set of the two-dot chain line Z, it can be seen that valleys A and B of output reduction occur in the middle rotation range of 5000 to 7000 rpm and the high rotation range of 8000 to 9500 rpm, respectively.

Next, according to the present embodiment shown by a solid line X, these valleys A,
The occurrence of B is prevented. Of these, the occurrence of valley A was found to depend on the length ratio (Rl). That is, if the length ratio (Rl) is set within the above-mentioned numerical range, the length ratio shown in FIG.
Also -2 positive pressure W ₂ by open end two reflections in the set portion P2 is returned to the third open exhaust valve as shown in FIG. (EO) and the exhaust valve side during intake valve opening overlap, at the same time Figure 4 as shown in Figure 3 is the open end reflections first in 2-1 collection portion P ₁ shown in, since overlapping the positive pressure W ₂ back a negative pressure W _3, abolished the positive pressure W _2, the output Valley A can be erased. Further, at this time, in this embodiment, 1> l2, and by shortening the collecting pipe side where the exhaust gas temperature decreases, a practical configuration for obtaining the above-described phenomenon is obtained. The valley A occurs if the value is outside the numerical range.

It was also found that the valley B depends on the cross-sectional area ratio (Ra) of the opening 10. Therefore, even if the length ratio (Rl) is within the above-described range, if the opening 10 is not formed, or if the cross-sectional area ratio (Ra) is out of the range other than the above even if the opening 10 is formed, This valley B occurs.

Therefore, if only the length ratio (Rl) is within the above range,
The output characteristics in the middle rotation range are improved. In addition, if the cross-sectional area ratio (Ra) is set in the above range, the output characteristics in the high rotation range are also improved.

If the opening 10 is too large and the numerical value of the cross-sectional area ratio (Ra) is out of the predetermined range, the generation of the valley B will not be eliminated,
Since the length l2 is substantially the same as the length l3, the length ratio (Rl) is substantially changed to be out of the range, and the valley A cannot be eliminated.

[Effect of the Invention] In the exhaust device of the 4-2-1 assembly type according to the present invention, if the length ratio is in the range of 0.26 to 0.46, the positive pressure due to the two open-end reflections in the 4-2 assembly portion is reduced. Return, 2-1
The return of the negative pressure due to the first open-end reflection at the gathering portion causes interference, and the positive pressure can be eliminated. As a result, 4-
Since the valley of the output that may occur in the middle rotation range of the high-speed engine employing the 2-1 set type can be eliminated, the occurrence of the output decrease in the middle rotation range or the high rotation range is reduced, and the output is smooth. A high-speed or ultra-high-speed high-output engine having characteristics can be provided. Moreover, by shortening the collecting pipe side where the exhaust temperature drops,
The above phenomenon can be reliably realized.

[Brief description of the drawings]

FIG. 1 is a schematic view of an exhaust device according to an embodiment of the present invention.
The figure shows a performance curve of an engine using this exhaust device.
FIG. 3 is a diagram showing a pressure waveform on the exhaust valve side due to open-end reflection, and FIG. 4 is a conceptual diagram of a 4-2-1 assembly. (Explanation of reference numerals) 1, 2, 3, 4 ... exhaust pipe, 5 ... collecting pipe, 6 ... silencer, 7 ... separator, 8, 9 ... collecting part, 10 ... opening, A, B: Output valley.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Osamu Kudo 1-4-1 Chuo, Wako-shi, Saitama Pref. Honda Technical Research Institute Co., Ltd. (56) References Special Table 62-501022 (JP, A)

Claims (1)

(57) [Claims] An exhaust system for an in-line four-cylinder four-stroke engine that ignites at 180 ° intervals, comprising four exhaust pipes connected to each cylinder, and a collecting pipe integrating the rear portions of the exhaust pipes. The inside of the collecting pipe is divided into two in the radial direction,
4-2 collecting sections, two exhaust pipes each having a phase shift of 360 ° are connected to the front end of each 4-2 collecting section, and the rear end of each of these 4-2 collecting sections. Are combined into a 2-1 gathering part, and in a 4-2-1 gathering form, when the length of the exhaust pipe is 1 and the length of the 4-2 gathering part is l2 , L2 / (1 + l
An exhaust device for an in-line four-cylinder four-cycle engine, wherein the length ratio given in 2) is in the range of 0.26 to 0.46.