JPS63208610A - Exhaust device for serial four cylinder four cycle engine - Google Patents

Abstract

PURPOSE:To prevent occurrence of two or more output troughs in the ranges of middle to high speed rotation as practical rotation by setting ratio of length of each exhaust tube connected with each gas cylinder and of a collecting tube for gathering the exhaust tubes in one in a certain range. CONSTITUTION:An exhaust device of a serial four cylinder four cycle engine ignited at an interval of 180 deg. of a crank angle is composed of exhaust tubes 1-4 each connected with each cylinder and a collecting tube 5 for gathering the back of the exhaust tubes 1-4 in one. The back of the collecting tube 5 is connected to a muffler 6, and the inside of the collecting tube 5 is parted by a separator 7 into two collecting parts 8, 9, and each collecting part 8, 9 has two exhaust tubes 1, 4 and 2, 3 each shifting by 360 deg. from each other respectively. In this case, where length of each exhaust tube 1-4 is l1, and length of the collecting part 5 is l2, ratio of length given by l2/(l1+l2) shall be set within the range of 0.26-0.46.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to the improvement of an exhaust system for a four-cylinder engine used in a motorcycle or the like in which it is difficult to provide a sufficiently long exhaust pipe length, and in particular, The present invention relates to an exhaust system suitable for an engine capable of high rotation and high output.

[Prior Art] In an in-line 4-cylinder 4-cycle engine used for motorcycles, etc., which explodes at crank angle intervals of 180°, the rear ends of the four exhaust pipes extending from the exhaust holes of each cylinder are In some cases, an exhaust system is used in which the exhaust pipes are combined into one and connected to the front end of a collecting pipe, and the rear end of the collecting pipe is further connected to a muffler (hereinafter, this type is referred to as a 4-1 set). However, in such an exhaust system, the exhaust gases coming from each cylinder in the collecting pipe may interfere with each other, resulting in a trough where the output decreases, especially in the middle rotation range.

In such a case, the countermeasure for the 4-1 set is complicated, so a separator is provided that divides the inside of the collecting pipe into two in the radial direction to define two collecting parts in the collecting pipe, and the front end of each collecting part is There is a system in which two exhaust pipes each having a phase shift of 360 degrees are connected to each other to prevent exhaust interference between the exhaust pipes having a phase shift of 180 degrees (hereinafter, this type is referred to as a 4-2 set). If the 4-2 set is adopted, valley countermeasures can be easily taken using separators or the like. An example of this is disclosed in Japanese Utility Model Application Publication No. 57-120201.

In addition, in the present invention, 4000 rpm is a low rotation range, and 4000~
8000rpm is a medium rotation range, 8000~1200Orp
m is defined as a high rotation range, and those exceeding 12,000 rpm are defined as an ultra-high rotation range.

[Problems to be solved by the invention] By the way, even if the above 4-2 set is used, if the structure is used as it is in an unprecedented ultra-high-speed, high-output engine, it will not be possible to achieve practical speeds at medium to high speeds. It was found that multiple troughs in the output occur in the region. Therefore, the present invention aims to provide an exhaust system having a 4-2 type collecting pipe that can prevent the occurrence of these multiple valleys even when used in an unprecedentedly high-speed, high-output engine. do.

[Means for solving the problem] The exhaust system for an in-line 4-cylinder 4-stroke engine that fires at 180° intervals according to the present application has four exhaust pipes connected to each cylinder, and a rear part of these exhaust pipes that is connected to one another. It consists of a collecting pipe and a collecting pipe. The inside of this collecting pipe is divided into two parts in the radial direction to form two collecting parts, and two exhaust pipes each having a 3600 phase shift are connected to the front end side of each collecting part. - It is of two-set format. In this exhaust system, the first invention provides a structure in which, when the length of the exhaust pipe is 1 and the length of the gathering part is 2,
) is set in the range of 0.26 to 0.46.

Further, a second invention according to the present application provides an opening for communicating between two collecting parts formed in the collecting pipe set to the length ratio according to the first invention, When the cross-sectional area of the opening is 31 and the cross-sectional area of the passage at the rear of the collecting pipe of the collecting pipe is 82, the cross-sectional area ratio given by a1/a2 is set in the range of 0°015 to 0.44. It is characterized by this.

[Operation of the Invention] In the 4-2 collecting pipe used in the exhaust system for an in-line 4-cylinder 4-cycle engine according to the present application, the first invention provides a 4-2 collecting pipe formed in the exhaust pipe and the collecting pipe. The length ratio between the two collecting parts is configured to be within a predetermined range. Therefore, among the troughs of output reduction that occur in the middle and high speed range, which is the practical speed range, when this engine is operated to ultra-high speeds, the occurrence of the troughs in the middle speed range is particularly suppressed.

Further, in the second invention, in addition to the above, by providing an opening having a predetermined cross-sectional area ratio and communicating the two gathering parts, the occurrence of valleys is further suppressed up to a high rotation range.

[Example] An example of the present invention will be described based on FIGS. 1 and 2. Figure 1 shows an in-line 4-cylinder, 4-cycle motorcycle engine that explodes at intervals of 180 degrees at the crank angle (not shown).
Fig. 2 is a schematic diagram of an exhaust system used for the exhaust system, and Fig. 2 shows its performance curve. In this exhaust system, the rear ends of exhaust pipes 1, 2, 3, and 4 connected to the exhaust holes of each cylinder of the engine are connected to a collecting pipe 5, respectively. In this embodiment, each exhaust pipe has an inner diameter of 30 mm. Further, the rear part of the collecting pipe 5 is connected to a muffler 6. Inside the collecting pipe 5,
A flat separator 7 is arranged in the front-rear direction on the front half side. This separator 7 is attached within the collecting pipe 5 by suitable means such as welding, thereby dividing the inside of the front half of the collecting pipe 5 into two in the radial direction and defining two collecting parts 8.9. Therefore, the front half of the collecting pipe 5 constitutes a 4-2 set. (However, since they are combined into one at the rear of the collecting pipe 5, the exhaust system as a whole is a 4-2-1 set, but for convenience, we include this type of 4-2-1 set.
There are two sets. ) The ignition order of the engine is shown by the code of the exhaust pipe corresponding to each cylinder: exhaust pipe 1 → exhaust pipe 2 → exhaust pipe 4 → exhaust pipe 3. The misaligned exhaust pipes 1 and 4 are connected,
Similarly, exhaust pipes 2 and 3, which are out of phase by 360 degrees, are arranged in the gathering part 9.
is connected. Note that an opening 10 is formed in the separator tough to communicate the gathering parts 8 and 9. In this embodiment, the diameter of the opening 10 is 10 mm.

Next, the length ratio (R4) and cross-sectional area ratio (Ra) of the collecting pipe 5 will be explained. First, the length ratio (RJI) is defined as R4=42/(S+f:L2), where the length of each exhaust pipe is □ and the length of the gathering part, that is, the separator is 2. In addition, the cross-sectional area ratio (Ra) is the opening area of the opening 10 a
1. If the passage cross-sectional area at the rear of the collecting part of the collecting pipe 5 is a2, it is defined as Ra''a1/a2.

In this example, R sentence=0.37 (sentence,=670
mm, sentence 2 = 400 mm), Ra = 0.08 (a
,=177mm2 (φ15mm), a2=2205m
m2 (φ53 mm)). However, this numerical example is just an example, and the length ratio (R1) is 0.26 to 0.
．． It has been found that the effect described below can be obtained by setting the value in the range of 46. For example, 500mm, 700mm
, 800mm, and 900mm, the length ratio (R4
It has been found that similar effects can be obtained by setting 2 so that ) falls within the above range.

Similarly, the cross-sectional area ratio (Ra) is 0.15 to 0.44.
(For example, when a2 is φ53mm, ao is φ5~35
It has been found that it is sufficient to set the distance within the range of mm).

Further, if the length from the front part of the collecting pipe 5 to the center of the opening 10 is 23, then 3/2=Q, preferably in the range of about 075 to 0.875. In this example, the sentence, 7 sentences 2 =
0.2, fL3=80 mm. However, it is not necessary to make this ratio too 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 the size of the opening 10 responds to the sense of convergence.

Note that the symbol a3 in the figure indicates the passage cross-sectional area of the collecting portions 8 and 9. It is preferable to set a3=1.4a to 1.5a2.

Next, the output characteristics of an engine using the exhaust system of this embodiment will be explained based on FIG. 2. The performance curve of this example is shown by a solid line X. For reference, the performance curve of the conventional 4-1 set is shown by a broken line Y. Further, the performance curve of the 4-2 set configured outside the range of the length ratio (R sentence) according to the present invention is shown by a chain double-dashed line Z.

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

Next, according to this embodiment shown by a solid line X, these valleys A and B
occurrence is prevented. It was found that the occurrence of valley A among these depends on the length ratio (R4). That is, the length ratio (
If RJI) is outside the above-mentioned numerical range, this valley A will occur.

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 (R4) is within the above range, if the opening 10 is not formed or the opening 1
Even if 0 is formed, this valley B will still occur if the cross-sectional area ratio (Ra) is outside the range other than the above-mentioned range.

Therefore, if only the length ratio (R4) is within the above range,
The output characteristics in the middle rotation range are improved, and if the cross-sectional area ratio (Ra) is set within the above range, the output characteristics in the high rotation range are also improved.

Furthermore, if the opening 10 is too large and the value of the cross-sectional area ratio (Ra) is outside the predetermined range, not only will the occurrence of the valley B not be eliminated, but the length will be substantially shortened to a considerable extent. It was also found that the length ratio (R4) substantially changed and went out of range, making it impossible to eliminate the valley A.

[Effects of the Invention] By setting the length ratio within a predetermined range in the 4-2 collection pipe according to the present invention, it is possible to eliminate the trough of output reduction in the middle rotation range. Further, an opening having a cross-sectional area ratio within a predetermined range is formed, and two openings are defined within the collecting pipe.
By connecting the two collecting parts, it is possible to eliminate the plurality of valleys in the high rotation range without affecting the output in the medium rotation range. Therefore, according to the present invention, it is possible to provide an ultra-high rotation, high output engine that reduces the occurrence of a decrease in output in the medium rotation range or high rotation range and has smooth output characteristics.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of an exhaust system that is an embodiment of the present invention;
The figure shows the performance curve of an engine using this exhaust system. (Explanation of symbols) 1.2.3.4...Exhaust pipe, 5...Collecting pipe, 6...
・Silencer, 7...Separator, 8.9...Collection part,
10...Aperture, A, B...Output valley.

Claims (2)

[Claims] (1) An exhaust system for an in-line 4-cylinder 4-stroke engine that fires at 180° intervals, consisting of 4 exhaust pipes connected to each cylinder and a collecting pipe that brings together the rear parts of these exhaust pipes. The inside of the collecting pipe is divided into two in the radial direction to define two collecting parts, and each collecting part has a 360 mm diameter on the front end side.
°In an exhaust pipe in which two exhaust pipes are connected out of phase, when the length of the exhaust pipe is l_1 and the length of the gathering part is l_2, the length ratio is given by l_2/(l_1+l_2). An exhaust system for an in-line 4-cylinder 4-cycle engine, characterized in that the is set to a range of 0.26 to 0.46. (2) An exhaust system for an in-line 4-cylinder 4-cycle engine that fires at 180° intervals, consisting of 4 exhaust pipes connected to each cylinder and a collecting pipe that brings together the rear parts of these exhaust pipes, The inside of the collecting pipe is divided into two in the radial direction to define two collecting parts, and each collecting part has a 360 mm diameter on the front end side.
°In an exhaust pipe in which two exhaust pipes are connected out of phase, when the length of the exhaust pipe is l_1 and the length of the gathering part is l_2, the length ratio is given by l_2/(l_1+l_2). is in the range of 0.26 to 0.46, and an opening is provided to communicate between the two collecting parts, the cross-sectional area of the opening is a_1, and the cross-sectional area of the passage at the rear of the collecting pipe of the collecting pipe is a_2. An exhaust system for an in-line four-cylinder four-cycle engine, characterized in that the cross-sectional area ratio given by a_1/a_2 is set in a range of 0.015 to 0.44.