JPH01138363A - Intake system muffler for internal combustion engine - Google Patents

Abstract

PURPOSE:To reduce the intake noise by forming an air capacity chamber having a relatively large diameter midway in an intake pipe and forming the flowing sectional area of an air cleaner side intake passage branched by the air capacity chamber smaller than that of a combustion chamber side intake passage. CONSTITUTION:An air capacity chamber 10 extending upwardly is formed in the intermediate part of an intake pipe 7 connected with an intake inlet 5 opened into a combustion chamber 4. A passage in the intake pipe 7 is branched into a combustion chamber side intake passage 11 and an air cleaner side intake passage 12 by the air capacity chamber 10. The flowing sectional area of the air capacity chamber 10 is formed larger than each intake passage 11, 12, and the capacity is set to about 25-150% of the engine exhaust quantity. Further, the flowing sectional area S1 of the air cleaner side intake passage 12 is formed smaller than the flowing sectional area S2 of the combustion chamber intake passage 11. Further, the length of the combustion chamber side intake passage 11 is set shorter so that the combustion chamber side open port part of the air capacity chamber 10 is set close to the intake inlet 5.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an intake system muffling device provided in an intake system between an intake port of a combustion chamber of an internal combustion engine and an air cleaner.

(Prior art) Generally, in the intake system of a reciprocating internal combustion engine, air is drawn into the combustion chamber intermittently by opening and closing the intake valve, which causes intake pulsation, which causes noise. There is. Particularly in the case of a single-cylinder internal combustion engine, intake noise due to changes in pulsating pressure is large, and there is a problem in that unpleasant noise (so-called bumping noise) is emitted from the air inlet of the air cleaner in a relatively low frequency range of 300 to 500 Hz. .

In order to reduce the above-mentioned intake noise, for example, as shown in FIG. 30 acts as an expansion chamber,
Intake silencers that attenuate negative pressure in an intake passage have been developed in the past.

However, in the past, only a volume chamber was provided, and no measures were taken to reduce noise in the intake pipe other than the air volume chamber.

(Object of the Invention) The present invention achieves the effect of reducing intake noise by devising the respective flow cross-sectional areas of the air cleaner side intake passage and the combustion chamber side intake pipe passage, which are separated by an air volume chamber, as well as the length of the combustion chamber side intake passage. The aim is to further improve the

(Technical Means for Achieving the Object) In order to achieve the above object, the present invention provides a method in which a flow cross-sectional area larger than the intake passage in the intake pipe is provided in the middle of the intake pipe connecting the air cleaner and the intake inlet of the combustion chamber. An air volume chamber having a flow cross-sectional area is formed, and the flow cross-sectional area of the intake passage on the air cleaner side than the air volume chamber is made smaller than the flow cross-section area of the intake passage on the combustion chamber side. The length of the combustion chamber side intake passage is shortened so that the opening is as close as possible to the combustion chamber intake port.

(Operation) Pulsating waves are generated by opening and closing the intake valve installed at the intake inlet of the combustion chamber, but these pulsating waves travel backwards through the intake passage on the combustion chamber side and enter the air volume chamber, where they expand and attenuate. .

Moreover, in the above-mentioned reverse movement process, since the intake passage on the combustion chamber side is formed as short as possible, the pulsating wave enters the air volume chamber immediately after being generated and is attenuated. The time taken is extremely short and the noise reduction effect can be achieved quickly.

In addition, since the cross-sectional area of the intake passage on the air cleaner side is made smaller than the cross-sectional area of the intake passage on the combustion chamber side, noise is efficiently prevented from being emitted from the air inlet of the air cleaner, thereby increasing the noise prevention effect. Improve further.

(Example) FIG. 1 shows an intake system silencer according to the present invention installed in a single-cylinder diesel engine, and in this FIG.
1 is a horizontal cylinder liner, 2 is a piston, 3 is a cylinder head, and 4 is a combustion chamber. An intake port 5 is formed on the side surface of the cylinder head 3, and the lower end of the intake pipe 7 is provided in the intake port 5. is connected.

An air volume chamber 10 extending upward is located in the middle of the intake pipe 7.
The air volume chamber 10 divides the passage in the intake pipe 7 into an intake passage 11 on the combustion chamber side and an intake passage 12 on the air cleaner side.

The combustion chamber side intake passage 11 is the lower opening 1 of the air volume chamber 10.
The air cleaner side intake passage 12 extends generally horizontally from 1a.
extends upward from the upper end of the air volume chamber 10. The flow cross-sectional area of the air volume chamber 10 is the same as that of any of the above-mentioned intake passages 1.
1.12, and the volume of the air volume chamber 10 is approximately 25% to 150% of the engine displacement.

An air cleaner 15 is connected to the upper end of the intake pipe 7. An inner cylinder 17 extending vertically is disposed in the center of the air cleaner 15, and an element 1 is arranged around the outer circumference of the inner cylinder 17.
8 is placed. That is, the upper end opening 17a of the inner cylinder 17
communicates with the air intake 20 via the element 18.

The lower end of the inner cylinder 17 is connected to the element side intake passage 12.
It is connected to the upper side of the intake passage 12 with the same inner diameter and the same center.

The flow cross-sectional area St of the air cleaner side intake passage 12 is formed to be smaller than the flow cross-sectional area S2 of the combustion chamber side intake passage 11, and specifically, it is formed in the following ratio.

That is, assuming that the inner diameter of the air cleaner side intake passage 12 with a circular cross-sectional shape and a cross-sectional area of 81 is di, and the combustion chamber-side intake passage 11 with a square cross-sectional shape is circular with a cross-sectional area of 82, its virtual diameter is In the case of d2, the inner diameter d1 is set to be 75 to 95% of the inner diameter d2.

In other words, the cross-sectional area ratio Sl:S2 is 752 to 952:1
It is set to 002.

The combustion chamber-side intake passage 11 extends in a generally straight line while maintaining approximately the same height as the intake population 5, and the entire intake pipe 7 is installed as close as possible to the opening 10a of the air volume chamber 10.
is formed short so that it approaches the intake population 5.

For example, the length of the intake passage on the combustion chamber side is approximately twice the inner diameter d2.
It is set to about 3 times.

The length of the air cleaner side intake passage 12 plus the passage inside the inner pipe 17, that is, the passage length of the inner diameter d1 above the air volume chamber 10 is set to be at least 2.5 times the inner diameter dl. has been done.

The relationship between the noise reduction effect and the engine output rate, etc. obtained by setting the intake passage diameters di and d2 and the passage length in the air cleaner 15 as described above will be explained using graphs of experimental results.

In Fig. 2, as the inner diameter ratio di/d2 decreases, the volume reduction tends to increase, that is, the noise tends to decrease, approximately 9
Experiments have proven that most of the harsh frequencies (particularly around 400 Hz) are on the positive side from around 5%. On the other hand, as shown in Fig. 3, the inner diameter ratio di
When /d2 is 75% or more, the engine output rate is reduced to 100%.
%, but when it becomes less than 75%, the engine output rate drops rapidly due to a decrease in the volumetric efficiency of intake air.

Based on the experimental results shown in Figures 2 and 3, in order to obtain an effective noise reduction effect within the range where the engine output rate can be maintained at 100%, the inner diameter ratio di/d2 must be set between 75% and 95%.
It is preferable to set it within a range of about 75%, and especially when it is set to about 75%, the best noise reduction effect can be obtained.

Figure 4 shows the relationship between the air cleaner central passage length L and noise, and it has been proven that the longer the passage length L, the lower the noise, and approximately up to about 2.5 times the inner diameter d1. It can be seen that the noise decreases rapidly between 1 and 2, and gradually decreases after that.

Therefore, by setting the passage length to approximately 2.5 times or more the inner diameter d1, a sufficient noise reduction effect can be obtained.

Figure 5 shows the amount of noise generated for each frequency (solid line) when the inner diameter ratio di/d2 is set to 75% and the length of the passage inside the air cleaner is set to 2.5 dl, and the amount of noise generated for each frequency (solid line) when the air cleaner and the intake This is a graph comparing the noise generation amount (virtual line) for each frequency when the entrance is connected, and the sound is reduced by about 6 dB to 12 dB at each frequency.

Figure 6 shows the overall noise level, and the solid line graph shows the amount of noise when the inner diameter ratio di/d2 is set to 75% and the air cleaner passage length is set to 2.5 dl. This graph is a graph obtained when the air cleaner and the intake inlet are simply connected through an intake pipe. (Another embodiment) (1) In Fig. 1, the inner pipe 17 inside the air cleaner is added to the air cleaner side intake passage 12, but the air cleaner side intake passage 12 itself is extended to the upper part of the air cleaner, and the inner pipe 17 is added to the air cleaner side intake passage 12. It may also have a structure that is inserted into a pipe.

(2) The combustion chamber side intake passage 11 can also have a circular cross-sectional shape.

(Effects of the Invention) As explained above, the present invention provides an air volume chamber 10 in the middle of the intake pipe 7 having a flow cross-sectional area larger than the flow cross-sectional areas S1 and S2 of the intake passages 11 and 12 in the intake pipe 7. form,
The flow cross-sectional area S1 of the intake passage 12 on the air cleaner side than the air volume chamber 10 is made smaller than the flow cross-section area S2 of the intake passage 11 on the combustion chamber side, and the combustion chamber side opening 10a of the air volume chamber 10 is made smaller than the flow cross section S2 of the intake passage 11 on the combustion chamber side. The length of the combustion chamber side intake passage 11 is shortened so that it comes as close as possible to the intake inlet 5, so that the following effects are achieved.

(1) The pulsating waves that are generated by the opening and closing of the intake valve and travel backwards are:
By entering the air volume chamber 10 and expanding, it is attenuated and the noise is reduced.

(2) In the reverse process of the pulsating waves, since the combustion chamber side intake passage 11 is formed short, the pulsating waves enter the air volume chamber 10 immediately after generation and are attenuated. The time required for the damping effect to be applied is extremely short, and a rapid noise reduction effect can be achieved.

(3) Since the flow cross-sectional area S1 of the air cleaner side intake passage 12 is made smaller than the flow cross-sectional area S2 of the combustion chamber side intake passage 11, noise is efficiently prevented from being emitted from the air inlet of the air cleaner 15. , This further improves the noise prevention effect.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view of a silencer to which the present invention is applied, Fig. 2 is a graph showing the relationship between the intake passage inner diameter ratio and the volume reduction, and Fig. 3 is a graph showing the relationship between the intake passage inner diameter ratio and the engine output rate. , Fig. 4 is a graph showing the relationship between the length of the air cleaner passage and noise, Fig. 5 is a graph showing the noise at each frequency, Fig. 6 is a graph showing the overall noise, and Fig. 7 is a longitudinal section of the conventional example. It is a front view. 5... Intake inlet, 7... Intake pipe, 10
... Air volume chamber, 11 ... Combustion chamber side intake passage, 12
... Air cleaner side intake passage, 15 ... Air cleaner patent applicant Yanmar Diesel Co., Ltd. Figure 4 Figure 6 Figure 5

Claims (1)

[Claims] An air volume chamber having a flow cross-sectional area larger than the flow cross-sectional area of the intake passage in the intake pipe is formed in the middle of the intake pipe that connects the air cleaner and the intake inlet of the combustion chamber, and the intake passage is closer to the air cleaner than the air volume chamber. The length of the combustion chamber side intake passage is made so that the flow cross-sectional area of the air volume chamber is smaller than that of the combustion chamber side intake passage, and the combustion chamber side opening of the air volume chamber is as close as possible to the combustion chamber intake port. An intake system silencer for an internal combustion engine characterized by a shortened structure.